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2011

Manual for Railway Engineering

1

Volume 2 Structures Chapter 7

Timber Structures

Chapter 8

Concrete Structures and Foundations

Chapter 9

Seismic Design for Railway Structures

Chapter 15 Steel Structures General Subject Index

3

Copyright © 2011 by the AMERICAN RAILWAY ENGINEERING AND MAINTENANCE-OF-WAY ASSOCIATION All rights reserved No part of this publication may be reproduced, stored in an information or data retrieval system, or transmitted, in any form, or by any means—electronic, mechanical, photocopying, scanning, recording, or otherwise—without the prior written permission of the publisher. Photocopying or electronic reproduction and/or distribution of this publication is a violation of USA and International Copyright laws and is expressly prohibited. Correspondence regarding copyright permission should be directed to the Director of Administration, AREMA, 10003 Derekwood Lane, Suite 210, Lanham, MD 20706 USA. ISSN 1542-8036 - Print Version ISSN 1543-2254 - CD-ROM Version

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CHAPTER 7 TIMBER STRUCTURES1 FOREWORD

The material in this chapter is written with regard to typical North American Railroad Timber Trestles and other timber structures mentioned herein with • Spans up to 16 feet, • Standard Gage Track, • Normal North American passenger and freight equipment, and

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• Speeds of freight trains up to 80 mph and passenger trains up to 90 mph. Special provisions for longer spans and/or higher train speeds should be added by the company as necessary. This chapter is presented as a consensus document by a committee that comprises railroad engineers, engineers in private practice, engineers involved in research and teaching, and other industry professionals having substantial and broad-based experience designing, evaluating, and investigating timber structures used by railroads. The recommendations contained herein are based upon past successful usage and are periodically updated to ensure future successful usage. Therefore, as an ongoing concern, the recommendations printed herein are updated in response to changes in the operating environment, changes in the designations and availability of material and material systems, advances in design and maintenance practices, and advances in the state of knowledge overall. These recommendations have been developed and are intended for routine use and might not provide sufficient criteria for infrequently encountered conditions. Professional judgement must be exercised when applying the recommendations of this chapter as part of an overall solution to any particular problem. In general, this chapter is revised and printed anew on a calendar-year basis. The latest printed revision of the chapter should be used, regardless of the age of an existing structure. For purposes of determining historical recommendations under which an existing structure may have been built and maintained, it can prove useful to examine previous printed editions of the chapter. However, when historical recommendations differ from the recommendations contained in the latest printed revision of the chapter, the recommendations of the latest printed revision of the chapter should be used.

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The material in this and other chapters in the AREMA Manual for Railway Engineering is published as recommended practice to railroads and others concerned with the engineering, design and construction of railroad fixed properties (except signals and communications), and allied services and facilities. For the purpose of this Manual, RECOMMENDED PRACTICE is defined as a material, device, design, plan, specification, principle or practice recommended to the railways for use as required, either exactly as presented or with such modifications as may be necessary or desirable to meet the needs of individual railways, but in either event, with a view to promoting efficiency and economy in the location, construction, operation or maintenance of railways. It is not intended to imply that other practices may not be equally acceptable.

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TABLE OF CONTENTS Part/Section 1

Description

Page

Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Timber Bridge Ties and Recommendations for Fire-Retardant Coating for Creosoted Wood . . . . . . . . 7-1-1

1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8

Structural Grades of Softwood Lumber and Timber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Grading Rules for Hardwood Structural Timbers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Specifications for Engineered Wood Products (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ordering Structural Lumber, Timber and Engineered Wood Products . . . . . . . . . . . . . . . . . Specifications for Timber Piles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Specifications of Fasteners for Timber Trestles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Specifications for Timber Bridge Ties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Recommendations for Fire-Retardant Coating for Creosoted Wood (1963) R(2008) . . . . . . .

7-1-3 7-1-3 7-1-3 7-1-6 7-1-7 7-1-13 7-1-16 7-1-20

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Design of Wood Railway Bridges and Trestles for Railway Loading . . . . . . . . . . . . . . . . 2.1 Design of Public Works Projects. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 General Features of Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Loads, Forces and Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4 Designing for Engineered Wood Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 Allowable Unit Stresses for Stress-Graded Lumber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6 Details of Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7 Recommended Practice for Design of Wood Culverts (1962) . . . . . . . . . . . . . . . . . . . . . . . . . . 2.8 Recommended Practice for Simple Stress Laminated Deck Panels. . . . . . . . . . . . . . . . . . . . .

7-2-1 7-2-3 7-2-4 7-2-7 7-2-11 7-2-20 7-2-38 7-2-39 7-2-40

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Rating Existing Wood Bridges and Trestles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Rules for Rating Existing Wood Bridges and Trestles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-3-1 7-3-2

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Construction and Maintenance of Timber Structures. . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Handling of Material (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 Storage of Material (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 Workmanship for Construction of Pile and Framed Trestles . . . . . . . . . . . . . . . . . . . . . . . . . 4.5 Framing of Timber (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6 Substructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.7 Superstructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.8 Support, Repair, Preserve, or Replace Damaged Portions of the Structure (2010) . . . . . . . . 4.9 Methods of Fireproofing Wood Bridges and Trestles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.10 Use of Guard Rails and Guard Timbers (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.11 Typical Plans for Timber Railway Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-4-1 7-4-2 7-4-3 7-4-3 7-4-3 7-4-4 7-4-5 7-4-14 7-4-14 7-4-18 7-4-20 7-4-21

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Inspection of Timber Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1 General (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 Details of Inspection (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-5-1 7-5-1 7-5-2

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Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1 Materials Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 Design Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 Rating Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4 Construction and Maintenance Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5 Inspection Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-6-1 7-6-2 7-6-5 7-6-13 7-6-13 7-6-13

Chapter 7 Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-G-1

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AREMA Manual for Railway Engineering

TABLE OF CONTENTS (CONT) Part/Section

Description

Page

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-R-1

Appendix 1 - Contemporary Designs and Design Aids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-A1-1

Appendix 2 - Temporary Structures . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . .

7-A2-1

Appendix 3 - Legacy Designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-A3-1

INTRODUCTION The Chapters of the AREMA Manual are divided into numbered Parts, each comprised of related documents (specifications, recommended practices, plans, etc.). Individual Parts are divided into Sections by centered headings set in capital letters and identified by a Section number. These Sections are subdivided into Articles designated by numbered side headings. Page Numbers – In the page numbering of the Manual (7-2-1, for example) the first numeral designates the Chapter number, the second denotes the Part number in the Chapter, and the third numeral designates the page number in the Part. Thus, 7-2-1 means Chapter 7, Part 2, page 1.

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In the Glossary and References, the Part number is replaced by either a “G” for Glossary or “R” for References. Document Dates – The bold type date (Document Date) at the beginning of each document (Part) applies to the document as a whole and designates the year in which revisions were last made somewhere in the document, unless an attached footnote indicates that the document was adopted, reapproved, or rewritten in that year.

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Article Dates – Each Article shows the date (in parenthesis) of the last time that Article was modified. Revision Marks – All current year revisions (changes and additions) which have been incorporated into the document are identified by a vertical line along the outside margin of the page, directly beside the modified information. Proceedings Footnote – The Proceedings footnote on the first page of each document gives references to all Association action with respect to the document. Annual Updates – New manuals, as well as revision sets, will be printed and issued yearly.

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Part 1 Material Specifications for Lumber, Timber, Engi-

neered Wood Products, Timber Piles, Fasteners, Timber Bridge Ties and Recommendations for FireRetardant Coating for Creosoted Wood — 2011 — 1 TABLE OF CONTENTS Section/Article

Description

Page

1.1 Structural Grades of Softwood Lumber and Timber. . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.1 Grading Rules (2010). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.2 Preservative Treatments (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-1-3 7-1-3 7-1-3

1.2 Grading Rules for Hardwood Structural Timbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2.1 General (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-1-3 7-1-3

1.3 Specifications for Engineered Wood Products (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.1 Structural Glued Laminated Timber - Glulam (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-1-3 7-1-3

1.4 Ordering Structural Lumber, Timber and Engineered Wood Products . . . . . . . . . . . . 1.4.1 Inquiry or Purchase Order (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-1-6 7-1-6

1.5 Specifications for Timber Piles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.1 General Provisions (2007). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.2 Classification of Piles (2007). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.3 General Requirement for All Piles (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.4 Special Requirements for First-Class Piles (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.5 Special Requirements for Second-Class Piles (2007). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.6 Inquiries and Purchase Orders (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-1-7 7-1-7 7-1-7 7-1-10 7-1-11 7-1-12 7-1-13

1.6 Specifications of Fasteners for Timber Trestles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6.1 Material (2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6.2 Types of Fasteners (2009). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6.3 Use of Protective Coatings for Steel Fasteners on Timber Bridges (2008) . . . . . . . . . . . .

7-1-13 7-1-13 7-1-13 7-1-15

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Timber Structures

TABLE OF CONTENTS (CONT) Section/Article

Description

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1.7 Specifications for Timber Bridge Ties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7.1 Material (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7.2 Physical Requirements (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7.3 Design (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7.4 Inspection (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7.5 Delivery (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7.6 Shipment (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7.7 Dapping or Sizing Bridge Ties (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7.8 Bridge Tie Installation (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7.9 Preservative Treatment of Bridge Ties (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7.10 Spike or Bolt Holes (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7.11 Tie Plugs (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7.12 Tie Branding (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7.13 End Splitting Control Devices (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-1-16 7-1-16 7-1-16 7-1-16 7-1-16 7-1-17 7-1-17 7-1-17 7-1-18 7-1-19 7-1-19 7-1-19 7-1-20 7-1-20

1.8 Recommendations for Fire-Retardant Coating for Creosoted Wood (1963) R(2008) . 1.8.1 Scope (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.8.2 General Product Requirements (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.8.3 Application Requirements and Instructions (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.8.4 Testing (2011). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-1-20 7-1-20 7-1-20 7-1-21 7-1-22

LIST OF FIGURES Figure 7-1-1

Description

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Measurement of Short Crook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-1-12

LIST OF TABLES Table

Description

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7-1-1 Typical Net Finished Glulam Sizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1-4 7-1-2a Friction Piles – Specified Butt Circumference with Minimum Tip Circumferences for Coast Douglas Fir Piles and Other Species, Except Southern Yellow Pine (See Note 1) . . . . . . . . . . . . . . . . . . . . . 7-1-8 7-1-2b Friction Piles – Specified Butt Circumference with Minimum Tip Circumferences for Southern Yellow Pine (See Notes 1, 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1-9 7-1-3a End-Bearing Piles – Specified Tip Circumferences with Minimum Butt Circumferences for Piles of Coast Douglas Fir and Other Species Except Southern Yellow Pine (See Note 1) . . . . . . . . . . . 7-1-9 7-1-3b End-Bearing Piles – Specified Tip Circumferences with Minimum Butt Circumferences for Piles for Southern Yellow Pine Piles (See Notes 1, 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1-10

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Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Etc.

SECTION 1.1 STRUCTURAL GRADES OF SOFTWOOD LUMBER AND TIMBER1 1.1.1 GRADING RULES (2010) It is recommended that structural lumber and timber be purchased in accordance with the grading rules of the industry’s agency publishing rules for the species. For allowable stresses for stress graded lumber and timber generally used refer to Article 2.5.6.

1.1.2 PRESERVATIVE TREATMENTS (2010) Pressure preservative treatments are listed in American Wood Preservers Association (AWPA) Standards.2 Retention and penetration levels are specified in AWPA Standards (C2, C4, C14 or C24 as applicable) in units of pounds of retained perservative per cubic foot of wood and depth of penetration in inches. Creosote retentions in the range of 8 to 12 pcf are common in railroad applications. It is strongly recommended that all fabrication, trimming and boring of glulam members be performed prior to the pressure treating process. If field fabrication is needed, surface damage, cuts and holes must be field treated to protect any exposed wood. Field treatments in accordance with AWPA Standard M4 should be specified.

1 SECTION 1.2 GRADING RULES FOR HARDWOOD STRUCTURAL

TIMBERS3

1.2.1 GENERAL (2009) Hardwood structural timbers shall comply with the requirements of Northeastern Lumber Manufacturers Association, Inc. (NELMA), Chapter 6, Timber, Beams and Stringers, Posts and Timbers for the species and grades listed in Part 2 of this Manual.

SECTION 1.3 SPECIFICATIONS FOR ENGINEERED WOOD PRODUCTS4 (2006)

4

1.3.1 STRUCTURAL GLUED LAMINATED TIMBER - GLULAM (2006)5 1.3.1.1 General and Appearance a.

General For allowable stresses for Glued Laminated Timber generally used refer to Article 2.4.1.2.

b. Appearance Classifications6 1

See Part 6 Commentary. See Reference 7. 3 References, Vol. 65, 1964, pp. 393, 756; Vol. 89, 1988, p. 106. 4 References, Vol. 55, 1954, pp. 568, 1005; Vol. 56, 1955, pp. 641, 1071; Vol. 62, 1961, pp. 512, 848; Vol. 69, 1968, p. 362; Vol. 84, 1983, p. 81; Vol. 89, 1988, p. 106. See Part 6 Commentary. 5 See Part 6 Commentary. 2

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7-1-3

Timber Structures

For railway bridge stringer, pile cap, deck panel, and rail tie applications, the Industrial or Framing appearance classifications should be considered. Industrial Appearance: Voids appearing on the edges of laminations need not be filled. Loose knot holes appearing on the wide face of the laminations exposed to view shall be filled. Members are required to be surfaced on two sides only and the appearance requirements apply to these sides. Framing Appearance: The Framing appearance classification permits "hit or miss" surfacing to provide specialized finish widths of 3-1/2, 5-1/2 and 7-1/4 inches. This appearance classification may be suitable for pile caps or bridge deck panel applications. 1.3.1.2 Layup Combinations1 For glulam members stressed primarily in bending, such as for railroad bridge stringers, layups of graded Douglas fir (DF) and Southern pine (SP) lumber are used throughout the member depth based on the "Stress Groups" shown in Table 7-2-7, selected specifically for the most commonly used applications. Stress Group options for bending members shown in this table are defined by bending-stress/Modulus of Elasticity (MOE) categories selected specifically as "Balanced Combinations" for railroad applications. 1.3.1.3 Balanced These members are manufactured with symmetrical grade zones above and below mid-depth. Balanced beams are used in applications such as continuous stringer applications, where the top and bottom of the member is stressed in tension. Balanced beams are recommended for railroad use since preservatives may make it difficult to distinguish the tension side. 1.3.1.4 Hardwoods Hardwoods may be specified by special order in accordance with the Standard Specification For Structural Glued Laminated Timber Of Hardwood Species, AITC 119. 1.3.1.5 Adhesives Adhesives must be in conformance with specifications included in ANSI A190.1 for wet-use. Wet-use adhesives may be specified for all moisture conditions and are required when the in-service moisture content is 16 percent or higher for repeated or prolonged periods, or when the wood is treated with preservatives before or after gluing. 1.3.1.6 Finished Sizes2 Table 7-1-1. Typical Net Finished Glulam Sizes Nominal Width

3”

4”

6”

8”

10”

12”

Western Species

2-1/2”

3-1/8”

5-1/8”

6-3/4”

8-3/4”

10-3/4”

Southern Pine

2-1/2”

3”

5”

6-3/4”

8-3/4”

10-1/2”

Depths can be provided in multiples of nominal 1-1/2 inch for Western species or 1-3/8 inch for Southern Pine laminations, or for special depths to be compatible with existing solid sawn installations.

6

See Part 6 Commentary. See Part 6 Commentary. 2 See Part 6 Commentary. 1

© 2011, American Railway Engineering and Maintenance-of-Way Association

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AREMA Manual for Railway Engineering

Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Etc. 1.3.1.7 Preservative Treatments1 Pressure preservative treatments listed in American Wood Preservers Association (AWPA) Standard C28 for glulam include creosote, pentachlorophenol and waterborne inorganic arsenicals. Waterborne treatments such as ammoniacal copper arsenate (ACA) and chromated copper arsenate (CCA) are not recommended for western species but may be used to treat glulam manufactured with Southern Pine. Waterborne treatments are typically applied to lumber prior to the laminating process. Waterborne treatments applied to glulam after the laminating process can cause dimensional changes such as warping, and twisting, in addition to excessive checking as the result of the necessary re-drying process. Fire-retardant coatings may be used for glulam railroad structures in accordance with Part 6 Commentary. Species listed in AWPA Standard C28 for preservative treatment include Pacific Coast Douglas fir, Western hemlock, hem-fir and southern pine. Other species may also be available by specification in agreements with the glulam manufacturer. Retention and penetration levels are specified in AWPA Standard C28 in units of pounds of retained preservative per cubic foot of wood and depth of penetration in inches. Creosote retentions in the range of 8 to12 pcf are common in railroad applications. It is strongly recommended that all fabrication, trimming and boring of glulam members be performed prior to the pressure treating process. If field fabrication is needed, surface damage, cuts and holes must be field treated to protect any exposed wood. Field treatments in accordance with AWPA Standard M4 should be specified.

1

1.3.1.8 Fire-retardant coatings Fire-retardant coatings may be used for glulam railroad structures in accordance with Article 1.8. 1.3.1.9 Certification, Wrapping and Shipping When specified by the engineer or customer, Certificates of Conformance shall be supplied by the glulam manufacturer to indicate conformance with industry standard ANSI A190.1.

3

1.3.1.10 Storage and Handling Loading & Unloading: Glulam stringers are commonly loaded and unloaded with forklifts. Greater stability can be achieved when the sides of the beams rest on the forks. Moving long beams on their sides, however, can cause them to flex excessively increasing the risk of damage. If a crane with cable slings or chokers is used to load, unload, or install glulam members, adequate blocking shall be provided between the cable (or strap), and the members. Wooden cleats or blocking should be used to protect long edge corners. Use of spreader bars can reduce the likelihood of damage when lifting beams in excess of 30 feet in length. Storage: To minimize possible degradation that can result from excessive seasoning checks or splits (checks that develop into openings across the member width), glulam members should be stored off of the ground on blocks in a level, well-drained location and covered. If members are to be stacked, spacer blocks should be placed between members to allow for ventilation and to protect against water entrapment on surface areas.

1

See Part 6 Commentary.

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-1-5

4

Timber Structures

SECTION 1.4 ORDERING STRUCTURAL LUMBER, TIMBER AND ENGINEERED WOOD PRODUCTS See Commentary Article 6.1.4 for an Example.

1.4.1 INQUIRY OR PURCHASE ORDER (2010)1 An inquiry or purchase order for structural lumber or timber should clearly stipulate: a.

Quantity in board feet or number of pieces.

b. Thickness, width and length. c.

Whether rough or surfaced, and extent of surfacing.

d. Stress-grade. Use the complete designation as given in the rules. Paragraph or page numbers may be used as additional identification. e.

Species of wood.

f.

The name and date of the grading rule book and the name of the organization issuing it. It is preferable to use the most recent rule book but the designation “current grading rules” should not be used because confusion may result due to changes in grade names and/or paragraph or page numbers.

g.

Any exceptions to or modifications of the grading rules such as: (1) Lumber or timber to be free of wane. (2) Seasoning if desired, stating the method and acceptable moisture content. (Note that mills do not ordinarily season beam and stringer or post and timber sizes.) (3) Special heartwood requirements. (4) Special shear grades. (5) Special provisions to make joist and plank or beam and stringer grades suitable for continuous spans. (6) Special provisions to make joist and plank or beam and stringer grades suitable as columns or tension members. (7) Special inspection provisions. (8) Provisions for treatment.

1

See Part 6 Commentary.

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-1-6

AREMA Manual for Railway Engineering

Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Etc.

SECTION 1.5 SPECIFICATIONS FOR TIMBER PILES1 1.5.1 GENERAL PROVISIONS (2007) 1.5.1.1 Scope This specification covers the physical characteristics timber piles to be used either untreated or treated by approved preservative process. 1.5.1.2 Species of Wood Piles may be of any species which will satisfactorily withstand driving and support the superimposed loads.

1.5.2 CLASSIFICATION OF PILES (2007) 1.5.2.1 Classes Piles are classified in this specification under two general classes according to quality, First-Class Piles and Second-Class Piles. First-Class Piles are divided into two size groups as follows: 1.5.2.2 First-Class Piles a.

Butt Circumference – The butt circumference is specified and minimum tip circumferences are in accordance with Table 7-1-2a and Table 7-1-2b. (friction piles) .

1

b. Tip Circumference –The tip circumference is specified and minimum butt circumferences are in accordance with Table 7-1-3a and Table 7-1-3b. (end-bearing piles). 1.5.2.3 Second-Class Piles Piles which do not meet the requirements of First-Class Piles but which are suitable for use in cofferdams, falsework, temporary work and light foundations or other light construction. Second-Class Piles may also be specified by butt circumference or tip circumference.

3

1.5.2.4 Sizes a.

The ratio of “out of round” maximum to minimum diameter at the butt or the tip of any pile shall not exceed 1.2.

b. All circumference measurements must be taken under the bark. c.

1

The circumference at the butt may not exceed the circumference at 3 feet from the butt by more than 8 inches.

References, Vol. 10, 1909, part 1, pp. 541, 603; Vol. 29, 1928, pp. 506, 1301; Vol. 34, 1933, pp. 66, 760; Vol. 37, 1936, pp. 668, 1036; Vol. 40, 1939, pp. 376, 789; Vol. 406, 1945, pp. 185, 802; Vol. 54, 1953, pp. 945, 1329; Vol. 61, 1960, pp. 587, 1095; Vol. 89, 1988, p. 106.

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

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4

Timber Structures Table 7-1-2a. Friction Piles – Specified Butt Circumference with Minimum Tip Circumferences for Coast Douglas Fir Piles and Other Species, Except Southern Yellow Pine (See Note 1) Required Minimum Circumference, (inches), 3 feet from Butt

22

25

28

Length (feet)

31

35

38

41

44

47

50

57

Minimum Tip Circumference (inches)

20

16.0

16.0

16.0

18.0

22.0

25.0

28.0

30

16.0

16.0

16.0

16.0

19.0

22.0

25.0

28.0

16.0

17.0

20.0

23.0

26.0

29.0

16.0

17.0

19.0

22.0

25.0

28.0

60

16.0

16.0

18.6

21.6

24.6

31.6

70

16.0

16.0

16.0

16.2

19.2

26.2

80

16.0

16.0

16.0

16.0

21.8

90

16.0

16.0

16.0

16.0

19.5

100

16.0

16.0

16.0

16.0

18.0

16.0

16.0

40 50

110 120

16.0

Note 1: Where the taper applied to the butt circumferences calculates to a circumference at the tip of less than 16 inches, the individual values have been increased to 16 inches to ensure a minimum of 5 inches tip diameter for purposes of driving.

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-1-8

AREMA Manual for Railway Engineering

Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Etc. Table 7-1-2b. Friction Piles – Specified Butt Circumference with Minimum Tip Circumferences for Southern Yellow Pine (See Notes 1, 2) Required Minimum Circumference, (inches), 3 feet from Butt

22

25

28

Length (feet)

31

35

38

41

44

47

50

57

Minimum Tip Circumference (inches)

20

16

16

18

21

25

28

31

34

37

40

47

30

16

16

16

19

23

26

29

32

35

38

45

17

21

24

27

30

33

36

43

19

22

25

28

31

34

41

60

20

23

26

29

32

39

70

18

21

24

27

30

37

19

22

25

28

35

40 50

80

Note 1: Where the taper applied to the butt circumferences calculates to a circumference at the tip of less than 16 inches, the individual values have been increased to 16 inches to ensure a minimum of 5 inches tip diameter for purposes of driving. Note 2: Southern Yellow Pine piles are generally available in lengths shorter than 70 feet or girth of less than 50 inches at 3 feet from butt. A dark horizontal line in each column designates pile sizes (above the line) which are generally available. The purchaser should inquire as to availability of sizes below the lines.

1

Table 7-1-3a. End-Bearing Piles – Specified Tip Circumferences with Minimum Butt Circumferences for Piles of Coast Douglas Fir and Other Species Except Southern Yellow Pine (See Note 1)

3 Required Minimum Tip Circumference, (inches) Length (feet)

16

19

22

25

28

31

35

38

Minimum Circumferences 3 feet from Butt (inches)

20

21.0

24.0

27.0

30.0

33.0

36.0

40.0

43.0

30

23.5

26.5

29.5

32.5

35.5

38.5

42.5

45.5

40

26.0

29.0

32.0

35.0

38.0

41.0

45.0

48.0

50

28.5

31.5

34.5

37.5

40.5

43.5

47.5

50.5

60

31.0

34.0

37.0

40.0

43.0

46.0

50.0

53.0

70

33.5

36.5

39.5

42.5

45.5

48.5

52.5

55.5

80

36.0

39.0

42.0

45.0

48.0

51.0

55.0

58.0

90

38.5

41.5

44.5

47.5

50.5

53.5

57.5

60.5

100

41.0

44.0

47.0

50.0

53.0

56.0

60.0

110

43.5

46.5

49.5

52.5

55.5

58.5

120

46.0

49.0

52.0

55.0

58.0

4

Note 1: Piles purchased as “8-inch and natural taper” have a required minimum tip circumference of 25 inches and are available in lengths of 20 to 45 feet. © 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-1-9

Timber Structures Table 7-1-3b. End-Bearing Piles – Specified Tip Circumferences with Minimum Butt Circumferences for Piles for Southern Yellow Pine Piles (See Notes 1, 2)

Required Minimum Tip Circumference, (inches)

16

Length (feet)

19

22

25

28

31

35

38

Minimum Circumferences 3 feet from Butt (inches)

20

19

22

25

28

31

34

38

41

30

21

24

27

30

33

36

40

43

26

29

32

35

38

42

45

50

31

34

37

40

44

47

60

33

36

39

42

46

49

70

35

38

41

44

48

51

80

37

40

43

46

50

53

90

39

42

45

48

52

55

40

Note 1: Piles purchased as “8-inch and natural taper” have a required minimum tip circumference of 25 inches and are available in lengths of 20 to 45 feet. Note 2: Southern Yellow Pine piles are generally available in lengths shorter than 70 feet or girth of less than 50 inches at 3 feet from the butt. A dark horizontal line in each column designates pile sizes (above the line) which are generally available.

1.5.3 GENERAL REQUIREMENT FOR ALL PILES (2007) 1.5.3.1 General Quality Except hereinafter provided, all piles shall be of sound wood, free from defects which may impair their strength or durability as piles such as decay, red heart, marine borer attack, or insect attack. Cedar and cypress piles may have a pipe or stump rot hole not more than 1-1/2 inches in diameter. Cypress piles may have peck aggregating not more than the limitation for holes. Piles having sound turpentine scars not damaged by insects shall be permitted. Piles shall be cut above the ground swell and have continuous and reasonably uniform taper from butt to tip. 1.5.3.2 Knots1 a.

Sound knots shall be no larger than one sixth the circumference of the pile located where the knot occurs. Cluster knots shall be considered as a single knot, and the entire cluster cannot be greater in size than permitted for a single knot. The sum of knot diameters in any 1 foot length of pile shall not exceed one third of the circumference at the point where they occur. Knots shall be measured at a right angle to the length of the pile.

b. Piles may have unsound knots not exceeding half the permitted size of a sound knot, provided that the unsoundness extends to not more than a 1-1/2 inch depth, and that the adjacent areas of the trunk are not affected.

1

See Part 6 Commentary.

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-1-10

AREMA Manual for Railway Engineering

Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Etc. 1.5.3.3 Heartwood Piles specified to have high heartwood content, for use without preservative treatment, shall exhibit a heartwood diameter at the butt not less than eight-tenths the diameter of the pile. 1.5.3.4 Sapwood Piles for use with preservative treatment shall have sufficient sap wood to meet minimum penetration requirements. 1.5.3.5 Close Grain If close grain is specified for softwood piles, the pile shall show on the butt end not less than 6 annual rings per inch, measured radially over the outer 3 inches of the cross section. Douglas-fir and pine averaging from 5 to 6 annual rings per inch shall be accepted as the equivalent of close grain if having one-third or more summerwood. 1.5.3.6 Cutting and Trimming Butts and tips of piles shall be sawed square with the axis of the piles and shall not be out of square by more than 1/10 inch per inch of diameter. All knots and limbs shall be trimmed or smoothly cut flush with the surface of the pile. 1.5.3.7 Peeling a.

1

Piles are classified according to the extent of bark removal as clean-peeled, rough-peeled or unpeeled.

b. Clean peeled piles require the removal of all outer bark. In addition, at least 80 percent of the inner bark, well distributed over the surface of the pile shall be removed. Piles for preservative treatment shall have no strip of inner bark larger than 1 by 6 inches. c.

3

Rough-peeled piles require the complete removal of all outer bark.

d. Unpeeled piles require no bark removal. e.

The sapwood of piles shall not be unnecessarily scarred or injured in the process of peeling.

f.

Piles for preservative treatment shall be clean-peeled.

4

1.5.3.8 Lengths Piles shall be furnished cut to any of the following lengths as specified: 16 feet to 40 feet, incl., in multiples of 2 feet; over 40 feet in multiples of 5 feet. Individual piles may exceed the length specified as much as plus 1 foot in piles 40 feet and shorter, and plus 2 feet in piles over 40 feet. 1.5.3.9 Twist of Grain Spiral grain shall not exceed 180 degrees of twist when measured over any 20 foot section of the pile.

1.5.4 SPECIAL REQUIREMENTS FOR FIRST-CLASS PILES (2007) a.

A straight line from the center of the butt to the center of the tip of First-Class piles shall lie entirely within the body of the pile. First-Class piles shall be free from short crooks that deviate more than 2-1/2 inches from straightness in any 5 foot length (see Figure 7-1-1). © 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-1-11

Timber Structures b. Holes less than 1/2 inch in average diameter shall be permitted in First-Class piles provided that the sum of average diameters of all holes in any square foot of pile surface does not exceed 1-1/2 inch, and the depth of any hole does not extend to more than 1-1/2 inch and provided that holes are not caused by decay or marine borer attack. Internal holes or damage to the cross-section (bearing) surfaces caused by decay, marine borers, or insects are not permitted. c.

Splits in First-Class Piles shall not be longer than the butt diameter. The length of any shake or combination of shakes, measured along the curve of the annual ring, shall not exceed one-third the circumference of the butt of the pile.

Figure 7-1-1. Measurement of Short Crook

1.5.5 SPECIAL REQUIREMENTS FOR SECOND-CLASS PILES (2007) a.

A straight line from the center of the butt to the center of the tip of Second-Class piles may lie partly outside the body of the pile, but the maximum distance between the line and the pile shall not exceed 1/2 percent of the length of the pile or 3 inches, whichever is the smaller. Second-Class piles shall be free from short crooks that deviate more than 2-1/2 inches from straightness in any 5 foot length. (See Figure 7-1-1).

b. Holes less than 1/2 inch in average diameter shall be permitted in Second-Class piles provided that the sum of the average diameters of all holes in any square foot of pile surface does not exceed 3 inches and the depth of any hole does not extend to more than 1-1/2 inch and provided that the holes are not caused by decay, or marine borer attack. Internal holes or damage to the cross-section (bearing) surfaces caused by decay, marine borers, or insects are not permitted. c.

Splits in Second-Class piles shall not be longer than 1-1/2 times the butt diameter. This length of any shake or combination of shakes, measured along the curve of the annual ring, shall not exceed one half the circumference of the butt of the pile.

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-1-12

AREMA Manual for Railway Engineering

Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Etc.

1.5.6 INQUIRIES AND PURCHASE ORDERS (2007) Each inquiry or purchase order for piles purchased under this specification should clearly state: a.

The number of pieces of each length.

b. The species of wood. c.

Whether the piles shall conform to the requirements for First Class or Second Class piles.

d. Whether the piles shall be specified by butt circumference or tip circumference. e.

Whether the piles shall be clean-peeled, rough peeled, or unpeeled.

f.

If close grain is wanted (in softwood piles).

g.

If heartwood content is wanted.

h. Whether piles shall be treated or untreated, and if treated, the type of preservative and minimum penetration. i.

Any exceptions to this specification such as the entire removal of all inner bark for clean-peeled piles.

j.

Instruction for inspection, marking, acceptance and shipment.

1

SECTION 1.6 SPECIFICATIONS OF FASTENERS FOR TIMBER TRESTLES1

3

1.6.1 MATERIAL (2008) a.

Malleable Iron. Malleable iron castings shall conform to current ASTM Specifications, designation A47, Grade 35018, with minimum yield point of 35,000 psi.

b. Cast Iron. Cast iron shall conform to current ASTM Specifications, designation A48, Class No. 30. c.

4

Rolled Steel. Rolled steel plates, bars and shapes shall conform to current ASTM Specifications, designation A36.

d. Cast Steel. Cast steel shall conform to current ASTM Specifications, designation A27, Grade 65-35, full annealed with minimum yield point of 33,000 psi.

1.6.2 TYPES OF FASTENERS (2009) a.

1

Nails, Spikes and Drift Bolts. Nails, spikes and drift bolts shall be made of rolled steel, square or round, as called for on the plans. Where special heads are not specified, the manufacturer’s standard heads will be acceptable. Nails used for fastening timbers shall be of a type having grooved, barbed or otherwise deformed shanks for greater holding power.

References, Vol. 7, 1906, pp. 692, 719; Vol. 11, 1910, part 1, pp. 178, 228; Vol. 37, 1936, pp. 667, 1036; Vol. 48, 1947, pp. 386, 938; Vol. 54, 1953, pp. 942, 1329; Vol. 61, 1960, pp. 587, 1095; Vol. 89, 1988, p. 106.

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

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Timber Structures b. Through Bolts. Through bolts shall be made of rolled steel with U.S. standard square or hexagon heads and nuts unless otherwise specified on the plans. c.

Washers. (1) Ogee washers shall be made of cast iron and conform with ASTM A48.

.

A Bolt Size

Top Outside Diameter

1/2 5/8 3/4 7/8 1 1-1/8 1-1/4 1-1/2

1-3/8 1-5/8 1-7/8 2 2-1/2 2-1/2 2-1/2 3

B Bottom Outside Diameter 2-3/8 2-3/4 3 3-1/2 4 4-1/4 4-1/2 5-1/2

T Thickness 1/2 5/8 3/4 7/8 1 1-1/8 1-1/4 1-1/2

(2) Malleable cast iron round washers shall be made of malleable or cast iron. Finish may be black or hot dip galvanized.

Bolt Size 3/8 1/2 5/8 3/4 7/8 1 1-1/8 1-1/4 1-1/2

A

T

Outside Diameter

Thickness

2-1/2 2-1/2 2-3/4 3 3-1/2 4 4-1/2 5-1/2 6

1/4 1/4 5/16 7/16 7/16 1/2 1/2 9/16 3/4

(3) Round plate washers shall be made of rolled steel. Finish may be black or hot dip galvanized.

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-1-14

AREMA Manual for Railway Engineering

Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Etc.

Bolt Size 3/8 1/2 5/8 3/4 7/8 1 1-1/4 1-1/2

B

A

C

Outside Diameter 2 2-1/4 2-1/2 3 3-1/2 4 5 5

Inside Diameter 7/16 9/16 11/16 13/16 15/16 1-1/16 1-3/8 1-5/8

Thickness 3/16 3/16 1/4 1/4 5/16 3/8 3/8 3/8

d. Lag Screws. Lag screws, including steel drive dowels and spikes with spirally grooved shanks shall be made of rolled steel. Heads for lag screws shall be U.S. standard unless otherwise specified. e.

Special Castings. Special castings, including such parts as gib plates, angle blocks, etc., shall be made of cast or malleable iron. They shall be true to pattern, free from wind, without injurious defects and of the size and shape specified on the plans.

f.

Cap - Stringer Fasteners. These include such types of fastenings as shown on Appendix 3 - Legacy Designs; Figure 7-A3-64. They shall be made of rolled steel of the size and shape specified on the plans.

g.

1

Metal Joint Connectors. (1) Spiked grids, cast shear plates and claw plates shall be made of malleable iron. (2) Split rings, toothed rings, bull dog types, pressed shear plates and clamping plates shall be made of rolled steel.

3

(3) They shall be of the size and design specified on plan. h. Brace Plates and Washer Plates. Brace plates and washer plates or similar items shall be made of rolled steel to the size and details specified on the plan.

1.6.3 USE OF PROTECTIVE COATINGS FOR STEEL FASTENERS ON TIMBER BRIDGES (2008) a.

Plain iron or steel fastenings will ordinarily outlast untreated timber. Creosote oil, whether straight or in coal-tar or oil mixtures, will retard corrosion of embedded metal fastenings.

b. Galvanizing or other protective coating on iron or steel fastenings is not warranted if the fastenings are to be entirely embedded in untreated or creosote treated timber or if metal is to be exposed only to ordinary weathering. c.

When metal fastenings are not to be completely embedded and are to be exposed to salt water or an unusually corrosive atmosphere, consideration should be given to the use of galvanizing or to some other protective coatings on the exposed metal. As the limits within which protectively coated metal is economical are not well established, local experience should be investigated.

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

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4

Timber Structures

SECTION 1.7 SPECIFICATIONS FOR TIMBER BRIDGE TIES 1.7.1 MATERIAL (2009) 1.7.1.1 Kinds of Wood Before manufacturing ties, the railway or end user shall determine which species of wood are acceptable.

1.7.2 PHYSICAL REQUIREMENTS (2009) 1.7.2.1 General Quality The general quality of bridge ties shall conform to the appropriate grading rules. All ties shall be sawn from live, sound, straight timber free of defects that may impair strength or durability; such as decay, splits, shake, excessive slope of grain, or numerous holes or knots, bark, wane, etc.

1.7.3 DESIGN (2009) Also see Article 1.7.4. 1.7.3.1 Support Conditions Depending on the intended service conditions, bridge ties may be classified as structural or bearing ties. Structural ties are normally used for open deck bridges having steel girder spans. Under these conditions the strength of the ties is governed by flexure or horizontal shear. Bearing ties are normally used for open decks of timber trestle spans or on open decks of steel beam spans having multiple beams where the strength of ties is governed by bearing on the top of the stringer flange. 1.7.3.2 Dimensions a.

The minimum cross-section for structural and bearing type bridge ties shall be based on the applicable clauses of Chapter 7, Part 2.

b. The minimum width of bridge ties shall be eight (8) inches nominal. c.

When ties are dapped, the minimum depth of the tie shall be the net depth as calculated in Article 1.7.3.2a.

d. The minimum length of bridge ties shall be ten feet (nominal) or center-to-center of outer supports plus three times the depth of tie, whichever is greater.

1.7.4 INSPECTION (2009) 1.7.4.1 Place Before accepting ties for installation, the bridge ties shall be inspected at locations specified by the railway. 1.7.4.2 Manner Prior to treatment, inspectors shall make a close examination of the top, bottom, sides and ends of each bridge tie with regard to its manufacture and compliance with respect to the grading rules. Each bridge tie shall be judged independently, without regard to decisions on other ties in the same lot.

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Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Etc. 1.7.4.3 Handling Bridge ties are to be handled with care to prevent damage. Damaged ties will not be accepted. 1.7.4.4 Quality Bridge ties shall be treated No. 1 Grade in the following species: • Douglas Fir - Costal Species, Beams and Stringers, WCLIB, WWPA or NLGA. • Oak, Timbers - Beams and Stringers, NELMA. • Southern Yellow Pine, Timbers, SPIB. 1.7.4.5 Dimensions The following finished dimensional tolerances of sawn or machined bridge ties are to be followed unless otherwise specified by the railway. Depth: Sized or dapped areas: ± 1/16”

1.7.5 DELIVERY (2010) 1.7.5.1 Location

1

Bridge ties delivered for acceptance shall be stacked at suitable and convenient locations meeting individual railway safety requirements and as approved by the railway. Bridge ties delivered on the premises of a railway for inspection shall be stacked on blocking placed on firm ground. 1.7.5.2 Risk, Rejection

3

All bridge ties remain the property of the supplier until accepted. All rejected ties shall be removed from railway premises by the supplier at his expense within a time frame specified by the railway; for example within thirty (30) days after the date of rejection.

1.7.6 SHIPMENT (2009) Bridge ties shall be separated into bundles therein according to bridge locations for which they are intended, and also according to the location on the bridge spans, unless otherwise stipulated in the contract, on the railway order form or on the accompanying plans for the ties.

1.7.7 DAPPING OR SIZING BRIDGE TIES (2009) Dapping or sizing of ties is to be performed in a framing mill properly equipped to perform such work. Dapping or sizing is to be performed before treatment. a.

When dapped bridge ties are used, the width of dap shall be the width of flange plus 1/2 inch and the minimum depth of dap shall be 3/8 inch or such that the undapped portion will not bear on gusset plates, bracing, etc.

b. When sized ties are required, the railway may specify surfacing on 1 or more sides or edges.

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c.

On curved tracks, superelevation may be provided by tapered ties, which may be dapped or sized. An approved tie plan must be provided to the framing mill and the ties should be uniquely and individually numbered to identify ties having different dapped dimensions. The method of numbering shall comply with the requirements of the railway.

1.7.8 BRIDGE TIE INSTALLATION (2010) 1.7.8.1 Bridge Tie Spacing and Spacers a.

The maximum recommended nominal clear distance between ties shall be: • six (6) inches for structural ties, • six (6) inches for bearing ties on steel beams or girders and • eight (8) inches on timber stringers.

b. Bridge tie spacers may be a minimum 4" x 8" wood, or 3" x 5/8” steel bar having predrilled holes for fasteners, or of other design as specified by the railway. c.

A tie spacer shall be fastened to each bridge tie with 5/8” diameter drive spikes, lag screws or lag bolts and shall be long enough to engage a minimum of one half the depth of tie. To avoid splitting, it is recommended to pre-bore holes in the ties.

1.7.8.2 Rail Fastening The type of rail fasteners to be used will be determined by the railway. a.

For spikes refer to Chapter 5, Part 2.

b. For spiking refer to Chapter 5, Part 4. c.

For other fastening systems refer to manufacturer’s specifications.

1.7.8.3 Tie Plates a.

For tie plates refer to Chapter 5, Part 1.

b. Suitably sized double shouldered tie plates shall be used taking into consideration species of wood, axle loads, predominant train speeds, track curvature, etc. c.

The minimum recommended size of tie plates is: Main line bridge decks: 7¾” x 15" For other bridge decks: 7" x 12"

d. The railway may use tie plates of special design providing the requirements of Article 1.7.8.3c are met. 1.7.8.4 Bridge Tie Pads a.

Tie pads may be used to minimize plate cutting and to reduce impact and vibration effects on the bridge structures.

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b. Tie pads may be made of a plain or reinforced elastomeric material, impregnated fibrous material or any other suitable product, provided they are strong enough for the loading, are water repellent and stay firm in shape during service. c.

The size of tie pad shall conform to the tie plate used and shall be of suitable thickness.

d. Many special design tie plates do not permit the use of tie pads. The suitability of specific tie plates for use with bridge tie pads shall be verified with the tie plate manufacturer. e.

Refer to Chapter 30, Section 2.5 for material requirements and testing.

1.7.8.5 Bridge Tie Fastening a.

For fastening bridge ties to timber stringers, one of the following anchoring systems may be used: (1) Bolts or drive spikes. (2) Machine bolts with adequate washers and nuts. (3) A combination of (1) and (2).

b. For fastening bridge ties to steel beams and girders, one of the following anchoring systems may be used: (1) Machine bolts with a plate or spring washer and standard or lock type nut.

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(2) Hook bolts with a plate or spring washer and standard or lock type nut. (3) Machine bolts with a clip and plate or spring washer and standard or lock type nut. (4) Other systems may be used if approved by the railway. (5) Ties installed on the rivet or bolt heads of built-up girders should have the fasteners re-tightened after traffic has set the new deck down on the girder flange. c.

3

The size and the spacing of the anchoring system should be such as to provide adequate stability for the open deck considering the loads and forces as described in Chapter 7 and Chapter 15.

d. Refer to Chapter 7, Part 1 and Chapter 15, Section 8.3 of the latest revision of this Manual for additional guidelines.

1.7.9 PRESERVATIVE TREATMENT OF BRIDGE TIES (2009) Refer to Chapter 30, Section 3.6 and Section 3.7.

1.7.10 SPIKE OR BOLT HOLES (2009) Refer to Chapter 30, Part 3.

1.7.11 TIE PLUGS (2009) Refer to Chapter 30, Article 3.1.5.

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1.7.12 TIE BRANDING (2009) Refer to Chapter 30, Article 3.1.4.5.

1.7.13 END SPLITTING CONTROL DEVICES (2009) Refer to Chapter 30, Articles 3.1.6 and 3.1.7.

SECTION 1.8 RECOMMENDATIONS FOR FIRE-RETARDANT COATING FOR CREOSOTED WOOD1 (1963) R(2008) 1.8.1 SCOPE (1988) These recommendations are intended primarily for use with coatings of the film-forming classification, such as paints and mastics. Any material other than film-forming type shall conform to these recommendations except where film-forming qualities are required for fulfillment of the recommendations and apply to: a.

Performing requirements of fire-retardant coating compositions for use with wood treated with creosote or mixture of creosote with coal tar or petroleum, and

b. Methods for the acceptance testing of such fire-retardant coatings.

1.8.2 GENERAL PRODUCT REQUIREMENTS (1988) 1.8.2.1 Uniformity a.

All component raw materials of the product shall be thoroughly mixed and dispersed during its manufacture, unless the product is a multi-component system which sets or polymerizes rapidly and requires mixing immediately prior to application.

b. The formulation and quality of the product shall be maintained constant by the manufacturer and shall not be varied without notice. 1.8.2.2 Stability in Storage The product shall maintain stability at temperatures above 32 degrees F, shall not require unusual storage conditions, and shall conform to the requirements of the following: a.

In a freshly opened container the product shall reveal no curdling, livering, lumping, decomposition, gelling or any other objectionable characteristic within 12 months after delivery.

b. Separated, settled, caked or thickened materials shall be easily and adequately dispersible with a paddle without change in the quality or properties of the product. 1.8.2.3 Applied Coating A dry film of the product shall exhibit the following properties: 1

References, Vol. 64, 1963, pp. 374, 621; Vol. 89, 1988, p. 106.

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a.

Adhesion: The product shall be cohesive and shall adhere to the primary surface or to any secondary supporting surface.

b. Durability: The product shall resist water, brine, creosote, mixtures of creosote with petroleum or coal tar, sunlight, freezing and thawing, and general temperature extremes. c.

Foot Traffic: The product shall resist damage when applied on traffic areas.

d. Fire Retardancy: The product shall withstand heat or flames originated by miscellaneous heat sources, including ignited fusees, hot brake shoe splinters, sparks, hot coals or cinders, drops of molten metal, and burning debris. 1.8.2.4 Flammability of Wet Films a.

The evaporation of solvents or other materials from a wet film of the product shall cease to constitute a flammable hazard within 4 hours after application.

b. A film of the product, applied so as to achieve the minimum total dry thickness recommended by the manufacturer, shall cease to support combustion within 48 hours after application of the final coat. 1.8.2.5 Drying Time A film of the product, applied at the maximum wet thickness recommended by the manufacturer, within 36 hours after application and without forced drying, shall be hard enough to allow firm pressure of the thumb against the coated object without rupture of the film or adherence of coating to the thumb.

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1.8.3 APPLICATION REQUIREMENTS AND INSTRUCTIONS (1988) 1.8.3.1 Handling Instructions All precautions for storage and handling prior to and during application of the product shall be stated clearly in an accompanying instruction leaflet prominently displayed on each container, together with complete information and instructions for recommended equipment and materials for surface preparation, thinning, and application.

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1.8.3.2 Product Information All information and physical measurements not specified elsewhere in these recommendations, which might assist in the proper handling or testing of the product, shall accompany the instructions and shall include the following: a.

Specific gravity, and weight in pounds per gallon, or weight to the nearest 0.1 g of 1 pint of the coating.

b. Recommended maximum wet thickness and calculated coverage of a single-coat application of the coating, unthinned and thinned with recommended proportions of thinner. c.

Measured resultant dry thickness of the recommended maximum wet thickness of a single-coat application.

d. Recommended minimum dry thickness required for fire-retardancy effectiveness. e.

Drying time required between applications, thinned and unthinned.

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f.

Duration of solvent fire hazard during the drying lime of a single-coat application, thinned and unthinned.

g.

Drying or curing time required to attain maximum fire retardancy.

h. Recommended spray equipment (gun type, orifice size, spray pattern, pressure, etc.). i.

Solvents and materials which may be used to clean application equipment.

j.

Corrosiveness of product to container and spray equipment.

k. Toxicity to humans and animals of the product in the wet and dried conditions. 1.8.3.3 Working Properties a.

The product shall be applicable by brushing, spraying and, if it is a mastic, by trowelling, or it shall be adaptable for spraying, without loss of quality, by addition of a thinner recommended by the manufacturer.

b. A wet film of the product, when applied at the thickness recommended by the manufacturer, shall not show sagging, running, pinholing or other objectionable features. 1.8.3.4 Surface Preparation Timber surface preparation or treatment shall not be extensive and shall not require unusual equipment, materials or operations.

1.8.4 TESTING (2011) 1.8.4.1 Specimen Preparation a.

Wood Selection. The wood shall be selected from well-seasoned nominal 2 inches by 6 inches boards of Grade B & Btr edge-grained southern yellow pine containing no more than 10 percent heartwood, at least 14 feet in length, dressed on four sides and free from knots, stains, pitch pockets and bark. The maximum width of the annual growth rings shall be no greater than 1/16 inch. Edge-grained shall mean that at both ends of a board, where the wood has been cut cross sectionally, at least half of the acute angles between lines drawn tangential to the annual rings and lines drawn perpendicular to the broad surfaces of the board shall be no greater than 45 degrees.

b. Sectioning. The first 6 inches of the ends of each board shall be discarded, and the remainder shall be cut laterally into 18 inch sections. Each section shall be identified by the board number and by its own number from one end of the board. Each section shall be tested for moisture content at 6 inch intervals along its longitudinal axis with an electrical moisture meter employing metal probes which are no shorter than 1/4 inch. The moisture content of a section shall be greater than 8 percent and less than 15 percent. The sections shall be protected from checking or loss of moisture, preferably by storage in a cold, humidified atmosphere. A section which has checked shall not be used as a test specimen. c.

Preservative Treatment. The dimensions of an 18 inch section shall be measured to the nearest 0.01 inch and the volume calculated to the nearest 0.001 cubic foot. Each section shall be weighed to the nearest gram before preservative treatment. The creosote solutions and treating methods employed for impregnation of the sections shall be prescribed by the purchaser. After preservative treatment, each section shall be allowed to drain freely for 24 hour, wiped clean, and weighed to the nearest gram. The preservative retention shall be calculated in pounds per cubic foot to the nearest 0.01 lb per cubic foot,

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using the previously obtained dimensions and volume calculations, and the resultant figure shall be called “initial retention.” The treated sections shall be stored for a minimum of 30 days or a maximum of 60 days, at approximately 75 degrees F and 50 percent relative humidity, prior to a coating application or any form of testing. Immediately prior to preparation of a section for use in testing procedures, the section shall be weighed to the nearest gram, the net preservative retention shall be calculated: the resultant figure shall be called “test retention.” The test retention of any specimen shall be no less than 10 lb per cubic feet. All treated or untreated specimens used in a test shall be subjected to identical pretest storage conditions. 1.8.4.2 Fire Tests 1.8.4.2.1 Testing in Fire-Test Cabinet a.

Apparatus. The fire-test cabinet shall be a rectangular insulated chamber measuring 31 inches high, 10 inches wide and 12 inches deep. In order to suspend the specimen in the fire-test cabinet, a supporting rod shall be affixed horizontally 1 inch from the tops of opposite walls of the cabinet. For draft control, the 2-inch bottom section of the cabinet shall consist of louvers which can be raised 90 degrees. Two pairs of ungalvanized iron pipe with 3/8 inch internal diameter, each pair vertically parallel and separated by 3 inches between their longitudinal axes, shall be fastened to opposite sides of the cabinet. Orifices of 1/32 inch diameter shall be located in a straight line at 1-inch intervals, for 20 inches along each pipe, beginning at 1/2 inch from the cap (Figure 7-A3-1). The cabinet shall be equipped with a removable door fitted with viewing ports covered with mica sheet (Figure 7-A3-2). A pilot-flame orifice shall be installed at the bottom of one pipe at each side of the cabinet (Figure 7-A3-3 and Figure 7-A3-4).

b. Fuel. Bottled liquid-petroleum gas, with a minimum propane content of 95 percent, shall be supplied to the burner pipes at the rate of 0.4 cubic foot per minute or approximately 60,000 Btu per hour during the course of a specimen ignition. The flames shall extend approximately 4 inches horizontally from the orifices and shall be a definite yellow color. c.

Specimen Section and Position. The test specimen shall be selected by the procedures specified under Article 1.8.4.1a coated with a film of uniform thickness, allowed to dry or cure completely, and shall be suspended vertically in the fire-test cabinet at the initiation of the test. The broad faces of the specimen shall parallel the two pairs of burner pipes at a distance of 3 inches from the orifices, with the top end of the specimen on a level with the top orifices.

d. Test Procedure. A specimen shall be positioned in the fire-test cabinet with the door closed and the pilot flames lit. The ignition of the specimen shall be effective by quickly opening the fuel valve to the required setting and allowing the flames of the ignited gas to be directed against the specimen for 5 minutes. The duration of self-sustained flaming after ignition shall be recorded and designated as “freeburning time.” The period after which flaming has stopped and glowing occurs shall be recorded and designated as “glow time.” The free-burning interval shall be terminated for one of the following reasons: (1) A maximum free-burning time of 30 minutes shall have passed. (2) During the 30-minute free-burning period it is judged that the flames are merely flickering or flashing and constitute practical self-extinguishment, or that small flames are being sustained only at the ends of the specimen. If at the end of the 30-minute free-burning period, flaming continues at a rate requiring the use of an accessory extinguishing agent, the flames shall be extinguished with a fire-extinguishing gas.

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The test may be conducted in a well insulated laboratory fume hood or on a table placed under an insulated canopy. Both the fume hood and the canopy shall be equipped with efficient, safe, smokeexhaust fans. The exhaust fans shall be operating prior to ignition of the specimen. e.

Observations. The specimen shall be attentively observed during the ignition and the free-burning periods, and specimen appearance, coating condition and flame activity shall be recorded. Relative flame activity during the free-burning period and at its termination shall be described with the following terminology: (1) Vigorous – Entire specimen flaming with little or no apparent diminishment of combustion rate. (2) Very Strong – Approximately 75 percent of specimen flaming, with apparent combustion rate slowly decreasing. (3) Strong – Approximately 50 percent of specimen flaming, with apparent combustion rate decreasing. (4) Mild – Approximately 25 percent of specimen flaming, with apparent combustion rate decreasing rapidly. (5) Scattered – Areas of flaming where creosote wicking may be occurring or a heat trap may be located. (6) Torching – Flames occurring with jet-like activity at points of coating rupture or specimen checking. (7) Flickering – Small, virtually extinguished, flames at a few discrete points. (8) Flashing – Spontaneous extinguishment and reignition of an area. After the free-burning period, the specimen shall be allowed to remain in the fire-test cabinet, with the door removed, until glowing has ceased. The time required for the cessation of glowing shall be recorded as “glow time.” The burned specimen shall be weighed to the nearest gram, with the coating removed and wood char intact, not less than 24 nor more than 36 hours after the free-burning period. The specimen shall be cleaned of char immediately, without damage to the wood, and weighed again. The differences between the two weighings shall be recorded as the weight of the char, and shall be calculated in pounds per cubic foot of volume of the unburned specimen. The difference of weight of the specimen before burning and after being burned and cleaned shall be recorded as its total weight loss, and shall be calculated in pounds per cubic foot by volume of the unburned specimen. The thickness of the burned, cleaned specimen shall be measured to the nearest 1/64 inch on its longitudinal axis at a point 6 inches from the end which was topmost in the fire-test cabinet. The difference between the thickness of the specimen before and after cleaning shall be divided by two and recorded as char depth. Other observations which shall be recorded are: (1) Coating thickness and weight, wet. (2) All defects found in a coated or uncoated specimen before a fire test. (3) Blistering, fissuring, rupturing, intumescence, sloughing or other effects exhibited by a coating during a test and the elapsed time before their occurrence. (4) Relative extent of preservative bleeding during a fire test.

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(5) Relative amount of smoke production during a fire test. f.

Acceptance Criteria. The specimen shall be totally self-extinguished within the 30-minute free-burning period or shall exhibit only flickering flames. (1) The total weight loss of the specimen, with char removed, shall not exceed 30 percent, or 15 lb per cubic foot by volume of the unburned specimen. (2) The char depth shall not exceed 1/8 inch. The char shall be evenly distributed with no occurrence of cupped areas. (3) The quality of char shall not exceed 2.5 lb per cubic foot by volume of the unburned specimen. (4) Glowing shall cease within 1 hour after termination of the free-burning period. (5) The coating shall remain intact upon the specimen throughout the ignition, free-burning and glow periods, and shall exhibit no sloughing, spalling or peeling. (6) The performance of a minimum of three specimens, prepared in an identical manner, shall conform to the stipulations of the acceptance criteria.

1.8.4.2.2 Fusee Test a.

Construction. The fusee test apparatus shall consist of two specimens selected by the procedures specified under Article 1.8.4.1a and a section of gypsum or other fireproof insulating board measuring 18 inches by 16 inches by 1 inch. The two wood specimens shall be coated uniformly with the same thickness used for specimens tested in the fire-test cabinet, and allowed to dry or cure completely. The coated specimens shall be joined together lengthwise in the shape of an “L”, forming one side and the bottom of a flat-bottomed trough. The trough shall be completed in a “U” shape by joining the insulation board to the bottom specimen. The specimens need not be nailed or fastened together. The bottom specimen may be laid flat, with the other coated specimen and the insulation board standing on their edges and placed flush against the edges of the bottom specimen.

1

3

b. Procedure. The trough shall be situated in a laboratory fume hood, with the exhaust fan operating. A 10minute fusee shall be ignited and laid snugly in the corner formed by the junction of the two coated specimens. When the fusee has been consumed the duration and intensity of residual flame activity shall be recorded. c.

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Acceptance Criteria. (1) Flames shall be totally or virtually self-extinguished within 10 minutes after the fusee has stopped burning. (2) The coating shall not flake, peel, crumble, slough or exhibit any other effects which result in the exposure of the wood substrate. (3) Glowing shall have ceased within 30 minutes after flaming has stopped.

1.8.4.2.3 Accelerated Weathering Test a.

Apparatus and Specimens. When a coating shall have conformed to the standards of the first tests during initial testing, it shall be used to prepare five additional specimens which shall be approximately identical to those which had been tested. After thorough drying or curing, the specimens shall be exposed

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to artificial sunlight and simulated rainfall in a weathering device described in ASTM Specifications, designation E42. b. Procedure. Each specimen shall be positioned vertically in the weathering device, with one of its broad surfaces facing the light source. The same surface shall face the light throughout the test. The test shall be terminated after an accumulated light-exposure time of 1,000 hours or when, at any prior time, the coating is judged to have failed. The decision of apparent coating failure shall be subjective and shall be based on the appearance of excessive blistering or softening, or exposure of wood by sloughing, peeling, flaking, cracking or other effects. The test shall be conducted in accordance with the following program: (1) The specimen shall be exposed to artificial sunlight at all times during the operation of the weathering device, except for such time as shall be required for the restriking of the carbon arc. (2) The specimens shall be mounted, with a face-to-face diameter of 30 inches, on a circular rack which rotates at the rate of 1 rpm. A water spray in the weathering device shall operate for 18 minutes at intervals of 102 minutes, so that during each 2 hours of light radiation the specimens shall be exposed to water for 18 minutes. In this manner each specimen shall receive approximately 2.5–3.0 minutes direct water spray during each 2-hour radiation period. (3) Exposure in the artificial weathering device shall be undertaken daily, for a total of 90 hours within 5 days. At the end of each 90 hours of exposure, the specimens shall be allowed to cool at room temperature for a minimum of 2 hours and then placed for 65 hours in a cold chamber adjusted to maintain a temperature of –20 degrees F. At the end of the cold period, the specimens shall be observed during all handling and transfer operations involving a specimen so as not to modify its condition. c.

Acceptance Criteria. At the termination of the weathering program, if failure has not occurred, the specimens shall be subjected to the fire tests and shall be rated by the acceptance criteria of those tests.

1.8.4.2.4 Brine Resistance Tests a.

Apparatus. An assembly shall be arranged consisting of a stop-cock-controlled funnel and a small container equipped with an overflow outlet. The container shall measure 4 inches on all sides, with an overflow tube of a minimum 1/8 inch diameter leading out from a point 1 inch below the top edge, and shall be composed of waterproof and chemical-resistant materials, such as glass, rubber or plastics. The funnel shall be large enough to contain a minimum of 500 ml of liquid and shall be placed vertically over the container.

b. Specimen Selection and Preparation. An 18 inch preservative-treated specimen shall be selected by the procedures outlined under Article 1.8.4.1a discarding 4-1/2 inches of each end of the specimen. The remainder of the specimen shall be sawn laterally at 2 inch intervals, yielding four sections, each of which shall be weighed to the nearest 0.1 g. A uniform continuous coating film of the same thickness used for the fire-test specimens shall be applied to all surfaces of the section, beginning at a point 1 inch from one end. The thickness and weight of the wet coating application shall be recorded, and the coating shall be allowed to dry or cure completely. c.

Test Procedure. The container shall be filled to the overflow outlet with a 10 percent sodium chloride brine solution. The funnel also shall be filled with the brine solution. The test shall be conducted at room temperature, 75 to 80 degrees F, and the brine shall be maintained at that temperature throughout the test. The coated end of a specimen shall be immersed at approximately a 45 degree angle in the container, with the wider side facing upward, and with the uncoated area of the opposite side resting on the edge of the container. No more than 4 nor less than 3-1/2 inches of a coated side shall be below the surface of the solution. The tip of the funnel shall be positioned 1 inch above the center of the line between the coated and uncoated areas of the specimen. At the start of the test, the stop cock shall be © 2011, American Railway Engineering and Maintenance-of-Way Association

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opened sufficiently to allow drops of brine to fall at the rate of approximately 10 drops per minute, striking the specimen at the midpoint of the line between the coated and uncoated areas. Dripping and immersion shall be continuous for 300 hours. The effluent from the specimen container shall be collected in any suitable container and discarded. At the end of 300 hours, the brine solution in the specimen container shall be examined for discoloration and for materials which have separated from the coating. The specimen shall be observed for blistering, fissuring, crumbling or other effects. d. Acceptance Criteria. The specimen shall be examined immediately at the end of a test and at a time one week after the test. Fissures in the coating shall be no wider than hairline cracks. Blisters shall be no larger than 1/8 inch in diameter. Gentle teasing of the coating with knife point shall not result in easy dislodgement of coating particles. The dry thickness of the coating at any location on the specimen shall not have decreased by more than 1/4 of the original dry thickness. Discoloration of the brine solution and the presence of coating particles in the container shall indicate possible leaching or solvation of the fireretardant constituents of the coating. 1.8.4.2.5 Foot Traffic Test A specimen shall be selected and prepared in the same manner as the specimens used for the fire tests, with the same thickness of coating applied. The coating shall be allowed to dry or cure completely. a.

Procedure. The specimen shall be heated for 1 hour at 140 degrees F in an electric oven. The specimen shall then be removed from the oven and immediately laid flat on one of its broad surfaces on a protected area of the floor, The uppermost surface shall be stepped upon with one foot by a person weighing no less than 150 lbs. His entire weight shall be concentrated on the specimen for 1 minute, at the end of which time he shall execute a 45 degree twisting movement of the ball of his foot upon the coating and then step off the specimen.

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b. Acceptance Criteria. (1) The coating shall not exhibit tearing and shall not be lifted from the wood substrate by adhesion to the shoe used to exert pressure. Should these or other objectionable effects occur, the test shall be repeated, using mineral aggregate or similar material spread over the specimen surface while the coating is still wet.

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(2) When a surfacing material is used in conjunction with a coating, it shall not be sufficiently dislodged to require resurfacing the specimen.

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Part 2 Design of Wood Railway Bridges and Trestles for Railway Loading1 — 2011 — FOREWORD

This specification covers the design of wood structures subject to railway loading, and it assumes each structural member to carry its own load, competent design and fabrication, reliable stress grading of timber material, and adequate maintenance of structures.

1

TABLE OF CONTENTS Section/Article

Description

Page

2.1 Design of Public Works Projects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.1 General (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-2-3 7-2-3

2.2 General Features of Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.1 Materials (1988). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.2 Clearances (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.3 Stringers (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.4 Ties (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.5 Bents (1998) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.6 Piles and Post Footings (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.7 Contemporary and Legacy Designs and Design Aids (2010). . . . . . . . . . . . . . . . . . . . . . . . 2.2.8 Temporary Structures (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-2-4 7-2-4 7-2-4 7-2-5 7-2-6 7-2-6 7-2-7 7-2-7 7-2-7

2.3 Loads, Forces and Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.1 Loads and Forces (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.2 Dead Load (1988). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.3 Live Load (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.4 Centrifugal Force (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.5 Other Lateral Forces (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-2-7 7-2-7 7-2-7 7-2-8 7-2-8 7-2-9

1

References, Vol. 44, 1943, pp. 362, 670, 691; Vol. 51, 1950, pp. 433, 866; Vol. 52, 1951, pp. 428, 847; Vol. 58, 1957, pp. 676, 1169; Vol. 70, 1969, p. 219; Vol. 76, 1973, p. 232; Vol. 84, 1983, p. 88; Vol. 89, 1988, p. 106; Vol. 91, 1990, pp 57, 62.

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3

Timber Structures

TABLE OF CONTENTS (CONT) Section/Article

Description

Page

2.4 Designing for Engineered Wood Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4.1 Design Values for Glued Laminated Timber (Glulam) (2006) . . . . . . . . . . . . . . . . . . . . . . 2.4.2 Design Equations (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-2-11 7-2-11 7-2-17

2.5 Allowable Unit Stresses for Stress-Graded Lumber. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5.1 Working Unit Stresses (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5.2 Form Factor (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5.3 Deflection, Permanent Set (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5.4 Compression Parallel to Grain or Centrally Loaded Columns (2009) . . . . . . . . . . . . . . . . 2.5.5 Bearing (1988). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5.6 Allowable Unit Stresses for Stress-Graded Lumber (2010) . . . . . . . . . . . . . . . . . . . . . . . . 2.5.7 Bearing at Angle to Grain (1988). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5.8 Combined Axial and Bending Loads (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5.9 Horizontal Shear (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5.10 Notches (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5.11 Shearing Stress (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5.12 Bearing on Bolts (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5.13 Connectors (1988). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5.14 Round Sections (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-2-20 7-2-20 7-2-20 7-2-20 7-2-20 7-2-21 7-2-21 7-2-29 7-2-29 7-2-30 7-2-30 7-2-31 7-2-31 7-2-38 7-2-38

2.6 Details of Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6.1 General (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6.2 Net Section (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6.3 Bolted Connections (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6.4 Notched Beams (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-2-38 7-2-38 7-2-38 7-2-38 7-2-39

2.7 Recommended Practice for Design of Wood Culverts (1962) . . . . . . . . . . . . . . . . . . . . . 2.7.1 Wood Culverts (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7.2 General Notes (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7.3 Design Data (Tangent Track) (1988). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-2-39 7-2-39 7-2-39 7-2-40

2.8 Recommended Practice for Simple Stress Laminated Deck Panels . . . . . . . . . . . . . . . 2.8.1 Material (2000) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.8.2 Fabrication (2000). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-2-40 7-2-40 7-2-43

LIST OF FIGURES Figure 7-2-1 7-2-2

Description

Page

Tangent Track . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cooper E 80 Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-2-5 7-2-8

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-2-2

AREMA Manual for Railway Engineering

Design of Wood Railway Bridges and Trestles for Railway Loading

LIST OF TABLES Table 7-2-1 7-2-2 7-2-3 7-2-4 7-2-5 7-2-6 7-2-7 7-2-8 7-2-9 7-2-10 7-2-11 7-2-12 7-2-13 7-2-14 7-2-15 7-2-16 7-2-17

Description Lateral Clearance for Curved Track . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Centrifugal Force for Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Applicability of Adjustment Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Effective Column Length for Various End Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Specific Gravity of Lumber for Design of Connectors in Timber Structures . . . . . . . . . . . . . . . . . . Applicable Adjustment Factors to Fasteners for Trestle Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . Design Values for Structural Glued Laminated Softwood Timber - Railroad Applications. . . . . . . Design Values for Structural Glued Laminated Softwood Timber -- Railroad Applications . . . . . . Allowable Unit Stresses for Stress Graded Lumber – Railroad Loading (Visual Grading)1 . . . Unit Compression (Column) Stresses for Standard Stress Grades. . . . . . . . . . . . . . . . . . . . . . . Basic Unit Stresses for Bearing on Bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Percentage of Basic Stress for Various L/d Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bearing Value for Bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Spacing of Prestressing Bar, SP (Inches) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bulkhead Channel Sizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bearing Plates Sizes For Channel Bulkhead Anchorage Configuration . . . . . . . . . . . . . . . . . . . Bearing Plates Sizes For Bearing Plate Anchorage Configuration . . . . . . . . . . . . . . . . . . . . . . .

Page 7-2-5 7-2-9 7-2-12 7-2-14 7-2-16 7-2-17 7-2-18 7-2-19 7-2-22 7-2-28 7-2-31 7-2-32 7-2-33 7-2-41 7-2-42 7-2-42 7-2-43

1 SECTION 2.1 DESIGN OF PUBLIC WORKS PROJECTS 2.1.1 GENERAL (1990) a.

The design, plans, special provisions and specifications for railroad bridges to be built as a public works project and paid for with public funds administered by a public agency shall be prepared by the engineering staff of the railroad involved or by a consulting engineer whose selection has been mutually approved by the railroad and the public agency. The intention of this requirement is that if a consultant is selected, it shall be one who is familiar with the design of railroad bridges, and particularly with the special requirements and operating conditions of the railroad concerned so that the time involvement of the railroad’s engineering staff will be minimized.

b. If a consulting engineer is engaged, the contract for his services may be administered by the public agency or by the railroad if it so desires. In either case, the technical aspects of the work of the consulting engineer shall be under the direction of the railroad and the final plans and specifications must meet with the approval of the railroad. c.

Specifications and Recommended Practice for Overhead and Other Wood Highway Bridges (2009) It is recommended that the current edition of Standard Specifications for Highway Bridges adopted by the American Association of State Highway and Transportation officials be used as a guide for overhead and other wood highway bridges. Clearances, foundations, construction practices and details should be with approval and in accordance with individual railroad practice.

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AREMA Manual for Railway Engineering

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3

4

Timber Structures

SECTION 2.2 GENERAL FEATURES OF DESIGN1 2.2.1 MATERIALS (1988) a.

Wood piles shall conform to AREMA specifications see, Part 1, Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Timber Bridge Ties and Recommendations for Fire-Retardant Coating for Creosoted Wood.

b. Structural lumber shall be stress-grade and shall conform to AREMA specifications see, Part 1, Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Timber Bridge Ties and Recommendations for Fire-Retardant Coating for Creosoted Wood. c.

Where portions of the structure consists of structural steel, reinforced concrete or masonry, the current AREMA specifications relating to structures of these materials shall apply, with the allowance for impact provided for in those specifications.

2.2.2 CLEARANCES (1988) a.

The clearances on straight track shall be not less than those shown in Figure 7-2-1. On curved track, the lateral clearance each side of track centerline shall be increased 1-1/2 inches per degree of curvature. When the fixed obstruction is on tangent track, but the track is curved within 80 feet of the obstruction, the lateral clearance each side of track centerline shall be increased as shown in Table 7-2-1.

b. Where legal requirements specify greater clearances, such requirements shall govern. c.

1

The superelevation of the outer rail shall be specified by the Engineer. The distance from the top of rail to the top of tie shall be assumed as 8 inches, unless otherwise specified by the Engineer.

See Part 6 Commentary.

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-2-4

AREMA Manual for Railway Engineering

Design of Wood Railway Bridges and Trestles for Railway Loading

1 Figure 7-2-1. Tangent Track

3 Table 7-2-1. Lateral Clearance for Curved Track Distance from Obstruction to Curved Track in Feet

Increase per Degree of Curvature in Inches

0-21

1-1/2

21-40

1-1/8

41-60

3/ 4

61-80

3/ 8

4

d. Where there are plans for electrification, the minimum vertical clearance shall be increased to that specified in Chapter 28, Clearances. e.

The clearances shown are for new construction. Clearances for reconstruction work or for alterations are dependent on existing physical conditions and, where reasonably possible, should be improved to meet the requirements for new construction.

2.2.3 STRINGERS (2009) a.

The span length, for the purpose of computing bending stresses in the stringers, shall be assumed as the clear distance face to face of bearings plus 6 inches; except that, if continuity is figured on, the intermediate support shall be taken at the center of the support.

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Timber Structures

b. Stringers shall be selected to provide: (1) Depth, preferably, not less than one-twelfth of the span. (2) Width, not less than one-third of the depth. c.

Stringers shall comprise a group placed to effect, as nearly as practicable, equal distribution of track loads. On open deck timber bridges, each stringer chord shall be centered as nearly as practicable beneath the rail it supports.

2.2.4 TIES (2010)1 a.

Cross ties shall be of adequate size to distribute the track load to all stress-carrying stringers.

b. Each tie shall be designed to carry not less than one-third of the maximum axle load, as well as to provide sufficient stiffness to properly distribute loads to the stringers. Ties shall be secured against bunching, and the maximum clear space between them, on open deck timber bridges, shall be 8 inches. c.

On open deck timber bridges, timber bearing ties shall be selected to provide: (1) Depth, nominal, not less than the following, rounded to the nearest half-inch: The larger of: 8” or

( b – N ) 3 – 6t -------------------------------------6

(which can be approximated as 0.2887 (b - N) - t)

Where: b = total nominal width of a single stringer chord centered beneath a single rail, in inches. N = width of rail base, in inches. t = minimum thickness, in inches, of rail seat: i.e. the portion of the tie plate in direct contact with the rail base (2) Width, not less than 8 inches. (3) Length, not less than 10 feet.

2.2.5 BENTS (1998) a.

1

Bents shall consist of a sufficient number of piles or posts, so that no member in any bent will be overstressed under any condition of loading. For the purpose of computing stresses in the bents their spacing shall be considered as the distance center to center of caps thereon. An approximate analysis to determine the division of load among the several piles of a bent is given in Appendix 3 - Legacy Designs.

See Part 6 Commentary.

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-2-6

AREMA Manual for Railway Engineering

Design of Wood Railway Bridges and Trestles for Railway Loading

See Table 7-A3-1 thru Table 7-A3-4. The application of this analysis to bents of various typical dimensions is given in Appendix 3 - Legacy Designs. See Figure 7-A3-5 through Figure 7-A3-57.

2.2.6 PILES AND POST FOOTINGS (1988) Piles shall be driven to the required bearing capacity in accordance with AREMA specifications see, Part 4, Construction and Maintenance of Timber Structures and Part 5, Inspection of Timber Structures. Posts shall be provided with adequate foundation to support the loads superimposed upon them.

2.2.7 CONTEMPORARY AND LEGACY DESIGNS AND DESIGN AIDS (2010) See Appendix 1 - Contemporary Designs and Design Aids and Appendix 3 - Legacy Designs.

2.2.8 TEMPORARY STRUCTURES (2010) See Appendix 2 - Temporary Structures.

SECTION 2.3 LOADS, FORCES AND STRESSES1 2.3.1 LOADS AND FORCES (1988)

1

The following loads and forces should be considered: (1) Dead load. (2) Live load.

3

(3) Centrifugal force. (4) Lateral force due to wind load and nosing of locomotives. (5) Longitudinal force.

4

(6) Impact.

2.3.2 DEAD LOAD (1988) The dead load shall consist of the estimated weight of the structural member, plus that of the tracks, ballast and other portions of the structure supported thereby. The weight of material shall be assumed to be as follows: Track, rails, inside guard rails, and fastenings . . . . 200 lb per linear foot of track Ballast, including track ties. . . . . . . . . . . . . . . . . . . . 120 lb per cubic foot Timber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 lb per foot board measure Protective coverings. . . . . . . . . . . . . . . . . . . . . . . . . . Actual weight

1

See Part 6 Commentary.

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Timber Structures

2.3.3 LIVE LOAD (2010) a.

The recommended live load is Cooper E-80 loading with axle loads and axle spacing as shown in Figure 7-2-2. The Engineer shall specify the live load to be used, and such load shall be proportional to the recommended load, with the same axle spacing.

Figure 7-2-2. Cooper E 80 Load

b. On bridges with ballasted deck the live load shall be assumed as distributed laterally over a width equal to the length of track ties, plus twice the depth of ballast below the base of tie, unless deck planks are designed to effect greater distribution of the load. c.

For members receiving load from more than one track all tracks contributing load shall be assumed fully loaded.

2.3.4 CENTRIFUGAL FORCE (1988) a.

On curves, the centrifugal force in percentage of the live load is: 0.00117 S2 D where: S = Speed in miles per hour D = Degree of curve (Because of the limited duration of the loads, centrifugal force need not be considered in the design of stringers.)

b. It shall be assumed to act 6 feet above the rail. Table 7-2-2 gives the permissible speeds and the corresponding centrifugal force percentages for curves with the amounts of superelevation shown. It is based on a maximum speed of 100 mph and a maximum superelevation of 7 inches, resulting in a maximum centrifugal force of 17.5 percent.

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AREMA Manual for Railway Engineering

Design of Wood Railway Bridges and Trestles for Railway Loading

Table 7-2-2. Centrifugal Force for Curves D

E

S

C

D

E

S

C

0°-10¢

100

1.95

2°-30¢

7

77

17.5

0°-20¢

100

3.90

3°-0¢

7

71

17.5

0°-30¢

0.33

100

5.85

3°-30¢

7

65

17.5

0°-40¢

1.44

100

7.80

4°-0¢

7

61

17.5

0°-50¢

2.56

100

9.75

5°-0¢

7

55

17.5

1°-0¢

3.67

100

11.7

6°-0¢

7

50

17.5

1°-15¢

5.33

100

14.6

8°-0¢

7

43

17.5

1°-30¢

7

100

17.5

10°-0¢

7

39

17.5

1°-45¢

7

93

17.5

15°-0¢

7

32

17.5

2°-0¢

7

87

17.5

20°-0¢

7

27

17.5

2°-15¢

7

82

17.5 C = .00117 S2 D = 1.755 (E+3)

D = Degree of curve. E = Superelevation in inches.

2

S = Permissible speed in miles per hour.

2 E = --3

C = Centrifugal force in percentage of live load.

1500 S2 = ------------- ( E + 3 ) D

c.

S D C – 5.265 ------------- – 3 = ------------------------1000 1.755

1

If the conditions at the site restrict the speed to less than that shown in the table, the centrifugal force percentage shall be taken for the greatest speed expected.

3

d. The effect of centrifugal force may be reduced by the compensating effect of the actual amount of superelevation provided.

2.3.5 OTHER LATERAL FORCES (2009) 2.3.5.1 Wind on the Structure

4

The lateral force due to wind shall be assumed as 30 lb per square foot acting in any horizontal direction as a moving load: a.

on 1-1/2 times the vertical projection of the floor system for trestles.

b. for truss spans, on the vertical projection of the span, plus any portion of the leeward trusses not shielded by the floor system. c.

on the vertical projection of all bracing, posts, and piles of trestles and towers.

2.3.5.2 Wind on the Train The wind force on the train shall be taken as 300 lb per linear foot on the track applied 8 feet above the top of rail. This force shall be considered as a moving load acting in any horizontal direction.

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AREMA Manual for Railway Engineering

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Timber Structures 2.3.5.3 Nosing of the Locomotive a.

The lateral force due to the nosing of the locomotive shall be a moving concentrated load of 20,000 lb applied at the top of the rail in either horizontal direction at any point of the span. The resulting vertical forces shall be disregarded.

b. Because of the limited duration of the loads, the lateral forces from wind and nosing of the locomotive need not be considered in the design of stringers. c.

In computing the stability of towers and trestle bents, the structure shall be considered as loaded on the leeward track with a live load of 1200 lb per linear foot and subjected to a wind force of 300 lb per linear foot applied 8 feet above the top of rail.

2.3.5.4 Longitudinal Force1 a.

The effect of starting and stopping of trains shall be considered as a longitudinal force, acting 6 feet above top of rail, and taken as the larger of: • Force due to braking, equal to 15 percent of the live load. • Force due to traction, equal to 25 percent of weight on the driving wheels.

b. Design of bridges shall ensure the adequate transfer of longitudinal forces from the structure to ground. c.

For bridges where by reason of continuity or frictional resistance of rails and floor system, much (or all) of the longitudinal force will be carried directly to the abutments or embankment, longitudinal force need not be considered in the design of piles, posts or bracing of bents, (Such bracing is to be designed to give the necessary L/d stability to the posts).

d. The longitudinal forces shall be considered as being carried by the stringers and deck of the bridge to the abutments or embankment or other locations providing specifically designed restraint to transfer the longitudinal force from the bridge to the ground. Intervals of such restraint shall not exceed 550 feet for material meeting the requirements of Number 1 Douglas Fir or Number 1 Southern Yellow Pine or better. For other timber materials use 400-foot intervals of restraint to ground unless an evaluation shows that a larger interval may be used. The design shall ensure the adequacy of timber stringers and foundation materials to carry this load. 2.3.5.5 Combined Stresses For stresses produced by longitudinal force, wind or other lateral forces, or by a combination of these forces with dead and live loads and centrifugal force, the allowable working stresses may be increased 50 percent, provided the resulting sections are not less than those required for dead and live loads and centrifugal force. 2.3.5.6 Impact The dynamic increment of load due to the effects of speed, roll and track irregularities is not well established for timber structures. Its total effect is estimated to be less than the increased strength of timber for the short cumulative duration of loading to which railroad bridges are subjected in service, and is taken into consideration in the derivation of allowable working stresses for design.

1

See Part 6 Commentary.

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-2-10

AREMA Manual for Railway Engineering

Design of Wood Railway Bridges and Trestles for Railway Loading

SECTION 2.4 DESIGNING FOR ENGINEERED WOOD PRODUCTS1 2.4.1 DESIGN VALUES FOR GLUED LAMINATED TIMBER (GLULAM) (2006)2 Design values for glulam are derived based on ASTM D3737, Standard Practice for Establishing Allowable Properties for Structural Glued Laminated Timber, using data from ASTM D2555, Standard Test Methods for Establishing Clear Wood Strength Values, and full-scale bending and shear tests. 2.4.1.1 Allowable Stresses3 Selected Douglas fir and Southern pine layup combinations intended specifically for railroad stringer applications -- members to be stressed primarily in bending -- as balanced combinations, are provided in Table 7-2-7 (see Part 6 Commentary, Article 6.2.4.1.2). Properties for the selected Stress Groups are listed in Table 7-2-7 based on the loading direction as well as the specific gravity for connection design. Stresses are listed based on Bending about the X-X Axis, Bending about the Y-Y Axis, for Axially Loaded, and for Fasteners.

1

3 Bending About X-X Axis – The design values to be used when loads are applied perpendicular to the wide faces of laminations, causing bending about the X-X axis, are designated in Table 7-2-7 by the subscript X. For example the "Fbx" column in Table 7-2-7, lists allowable bending stresses when members are stressed primarily in bending with loads applied perpendicular to the wide faces of the laminations. For balanced layups, the allowable bending stress values with "Tension Zone Stressed in Tension (positive bending), Fbx+" and “Compression Zone Stressed in Tension (negative bending), Fbx-” are the same. Bending About Y-Y Axis – The design values to used when loads are applied parallel to the wide faces of laminations, causing bending about the Y-Y axis, are designated in Table 7-2-7 by the subscript Y. Glulam members stressed in the Y-Y orientation, such as for ballast deck panels, shall be designed using values with the Y subscript. Axial Loading – Glulam members to be designed as columns or truss members shall be designed using values Ft for tension loading, and Fc for compression loading, under the Axially Loaded heading. For lateral or eccentric loads on columns, either Fbx or Fby values may be applicable, depending on the loading direction. Layup combinations made up from all one grade of laminations are listed in Table 7-2-8. 1 2 3

See Part 6 Commentary. See Part 6 Commentary. See Part 6 Commentary.

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-2-11

4

Timber Structures

Fasteners -- For specialized applications including trestle designs, the specific gravity values shall be used in conjunction with the information in Sections 2.4.1.5 and 2.5.12. 2.4.1.2 Tabular Design Values1 [See Tables 7-2-7 & 7-2-8] 2.4.1.3 Adjustment Factors2 Design values tabulated in Tables 7-2-7 and 7-2-8 shall be adjusted based on the adjustment factors defined below. Table 7-2-3 indicates the applicability of the various factors to specific design properties. Railroad Application Adjustment Factors Table 7-2-3. Applicability of Adjustment Factors Note: Railroad Use and Wet-Use adjustments are included in Tables 7-2-7 and 7-2-8. Design Properties Temperature Beam CT Stability CL

Volume CV

Column Chemical Stability (fireCP retardants) CR -------------

Fb’ = Fb x

1.0

1.0

CV

none

none

Ft’ = Ft x

1.0

none

none

none

none

Fv’ = Fv x

1.0

none

none

none

none

Fc^’ = F^ x

1.0

none

none

none

none

Fc’ = Fc x

1.0

none

none

CP

none

E’ = E x

1.0

none

none

none

none

CRR: Railroad Use Factor: Tabular design values listed in Tables 7-2-7 and 7-2-8, except for Fv, E and Fc perp, include a 0.9 RR Use Factor. The shear values shown include adjustments that are not cumulative with the RR Use Factor. Note: The appropriate Railroad Use adjustment factor has been applied to the values listed in Tables 7-2-7 and 7-2-8 with the exceptions noted in this section and in footnotes to the tables. CM: Wet Service Factor Wet-use adjustment factors are applicable when glulam members are subject to in-service equilibrium moisture content of 16 percent or higher. Note: The appropriate Wet-Use adjustment factors have been applied to the values listed in Tables 7-2-7 and 7-2-8. CT: Temperature Factor 1 2

See Part 6 Commentary. See Part 6 Commentary.

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-2-12

AREMA Manual for Railway Engineering

Design of Wood Railway Bridges and Trestles for Railway Loading

Design values listed in Tables 7-2-7 and 7-2-8 need not be adjusted in railroad use for temperature effects unless glulam members are subject to sustained exposure to temperatures greater than 100oF (without cycling intermittently to lower values). Engineers must use judgment when considering the applicability of temperature adjustment factors (See Commentary). Cv: Volume Factor Allowable bending stresses of glulam are affected by geometry and size. Generally, larger sizes have a correspondingly lower allowable bending stress than smaller members. To account for this behavior, a volume factor, Cv, shall be applied. Cv shall not exceed 1.0 and is computed as follows: p

p

p

æ 5.125 ö æ 12 ö æ 21 ö Cv = ç ÷ ç ÷ ç ÷ £ 1.0 è b ø è dø è  ø where: b = width of bending member in inches. For multiple piece width layups, b = width of widest piece in the layup. For practical purposes, b £10.75 in. d = depth of bending member in inches  = length of bending member between points of zero moment in feet

1

p = 1/20 for Southern pine and 1/10 for other species Cp: Column Stability Factor Tabulated compressive stresses parallel to grain (Fc) shall be multiplied by the column stability factor, Cp. CP

=

ìï1 + ( F /F * ) cE c í 2c ïî

é1 + ( FcE /F * c ) ù ê ú 2c ë û

2

3

ü ( FcE /F * c ) ï ý c ïþ

where: Fc* = tabulated compression design value multiplied by all applicable adjustment factors except CP FcE = KcE E’/(e/d)2 KcE = 0.418 for glulam E’ = tabulated E value multiplied by all applicable adjustment factors e = effective column length in inches, which shall be determined in accordance with principles of engineering mechanics or using the unsupported column length multiplied by an appropriate buckling length coefficient as shown in Table 7-2-4 c = 0.90 for glulam

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-2-13

4

Timber Structures

Table 7-2-4. Effective Column Length for Various End Conditions

When a compression member is supported throughout the length to prevent lateral displacement in all directions, Cp = 1.0. In addition, the slenderness ratio, e/d, shall be based on the larger ratio in both directions, and shall not exceed 50 except that during construction e/d shall not exceed 75. CL: Beam Stability Factor The beam stability factor is not applicable when the compression edge of a bending member is supported throughout its length to prevent lateral displacement, and the end points of bearing have been laterally supported to prevent rotation. CL = 1.0 under these conditions. This condition is typical for stringer applications. The beam stability factor shall not apply simultaneously with the volume factor. Beam stability considerations for other conditions are beyond the scope of this document. The National Design Specification (NDS) includes information on special cases. CR: Chemical Treatment Factor Glulam industry standards do not specify reductions in "dry" design values for glulam preservative treated in accordance with AWPA Standard C28. Use of adjustments to account for wet-use in service conditions (moisture content of 16 percent or higher) are considered adequate to include possible effect from the treating process, including incising. Fire-retardant coatings that may be specified in accordance with Section 1.8 require no additional adjustment in design properties. Adjustment for the tabulated design values, including connection design values, may be necessary with some fire-retardant treatments. Values for these adjustments may be obtained from the company providing the treatment and redrying services. 2.4.1.4 Other Design Considerations

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-2-14

AREMA Manual for Railway Engineering

Design of Wood Railway Bridges and Trestles for Railway Loading

Notches and Holes Field modifications of glulam members such as notching, tapering or drilling not shown on the design or shop drawings shall be avoided and never done without a thorough understanding of their effects on the structural integrity of the members involved. This understanding shall include knowledge of how affected members are expected to perform in the design application. Notches: Notching of bending members shall be avoided whenever possible, especially on the tension faces, for both simple span and continuous span applications. Notching of bending members on the tension face results in stress concentrations that can induce tension perpendicular-to-grain stresses that can propagate into splits. Normal adjustments used to account for notching in building structures are not applicable to railway bridge applications. Horizontal Holes: Holes drilled through width of bending members should be limited to locations away from shear and moment critical zones as determined by the design engineer. Field-drilled horizontal holes shall not be used as attachment points for brackets or other load bearing hardware unless specifically designated in the design. Any horizontal holes required for support of significant weight, such as water mains, must be located above the neutral axis of the member in zones stressed to less than 50 percent of the design flexural stresses. Vertical Holes: Vertical holes drilled through the depth of a glulam beam cause a reduction in the capacity at that location directly proportional to the ratio of 1-1/2 times the diameter of the hole to the width of the beam. For example, a 2-inch vertical hole drilled in a 8-3/4 inch wide beam may be assumed to reduce the allowable capacity of the beam by approximately (2 x 1.5)/8.75 = 34%. For this reason when it is necessary to drill vertical holes in glulam bending members, the holes should be positioned in areas of the member stressed to less than 50 percent of design stress in bending.

1

Holes for Support of Suspended Equipment: Heavy equipment or piping suspended from glulam beams shall be attached such that loads are applied to the top to the member to avoid introducing tension perpendicular-to-grain stresses. Storage & Handling: Glulam members should be stored on evenly spaced blocks to minimize ground contact and to prevent warping or permanent-set in bending (Y-Y axis). Physical damage such as gouges and splits should be reviewed for possible structural significance by the Engineer of Record prior to installation. Also see Article 1.3.1.10.

3

2.4.1.5 Connections and Fasteners

4

Glulam Simple or Continuous Span Bridges and Bridge Decks Panels: Timber railway bridge components are generally designed to take high rail loads in full bearing as loads are transferred through bridge ties to stringers, pile caps and pile ends. Where connections are used to maintain alignment and resist lateral loads, stresses developed at the connections can be amplified by dimension changes inherent in structural components subject to in-service cyclic wetting and drying conditions. Structural performance and serviceability of any glulam or solid sawn timber structure is dependent on proper design of connections. Larger sizes and longer spans made possible with glulam components make the proper detailing of connections critical. Careful consideration of moisture related expansion and contraction characteristics of wood is essential in detailing glulam connections to prevent introducing tension perpendicular-to-grain stresses. Wood expands and contracts as a result of changes in its internal moisture content. While expansion in the direction parallel to the grain in a wood member may be slight, dimensional changes in the direction perpendicular to the grain can be significant and must be accounted for in connection design detailing. A 24 inch deep beam can decrease in depth through shrinkage by approximately 1/4 inch as it changes from 12 to 8

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-2-15

Timber Structures

percent in equilibrium moisture content. Connections should be detailed to allow for such changes by over sizing or slotting bolt holes in steel connectors. In addition to moisture-induced tension perpendicular-to-grain stresses, similar failures can result from a number of factors associated with poor connection detailing. Improper beam notching, application of eccentric (out of plane) loads, and loading beams in tension perpendicular to the wide face of the laminations can induce internal moments and tension perpendicular-to-grain stresses. The following seven basic principles will provide guidance for efficient, durable and structurally sound connections: a.

Transfer loads in compression/bearing whenever possible.

b. Allow for dimensional changes in the glulam due to potential in-service moisture cycling. c.

Avoid the use of details that induce tension-perpendicular-to-grain stresses.

d. Avoid moisture entrapment in connections. e.

Do not place glulam in direct contact with masonry or concrete (use steel plates at the interface).

f.

Avoid eccentricity in joint details.

g.

Minimize exposure of end grain.

Table 7-2-5 contains a partial list of specific gravity that may be used for connector design in accordance with the National Design Specification (NDS) published by the American Forest and Paper Association. Also tabulated in Table 7-2-5 are species groups for split ring and shear plate connectors. Table 7-2-5. Specific Gravity of Lumber for Design of Connectors in Timber Structures Species

Specific Gravity

Species Group for Split Ring and Shear Plate Connectors

Alaska Cedar

0.42

C

Douglas fir

0.50

B

Douglas fir (North)

0.49

B

Engleman Spruce-Lodgepole Pine

0.38

D

Hem fir

0.43

C

Hem fir (North)

0.46

C

Mixed Oak

0.68

A

Mixed Maple

0.55

B

Redwood (open grain)

0.37

D

Redwood (close grain)

0.44

C

Southern Pine

0.55

B

Spruce-Pine-Fir

0.42

C

Spruce-Pine-Fir (South)

0.36

D

Western Hemlock

0.47

C

Western Woods

0.36

D

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-2-16

AREMA Manual for Railway Engineering

Design of Wood Railway Bridges and Trestles for Railway Loading

Glulam Trestles: Details on connector and fastener design needed for glulam or timber trestle design require specialized application of connection design principles. This information is covered in detail in the National Design Specification (NDS), for Wood Construction available through the American Wood Council (www.awc.org). Details on design values for the use of bolts, screws, nails, spikes, shear plates and split rings are provided in the NDS. Consider the following items when determining design values for mechanically fastened joints in glulam or timber trestles: a.

Lumber species, specific gravity, dowel bearing strength

b. Critical section or net section c.

Angle of load with respect to the grain

d. On center spacing and pitch spacing of fastening groups e.

Edge and end distances

f.

Conditions of loading

g.

Eccentricity, and

1

h. Adjustment factors applied to tabular design values. Adjustment factors applicable to fasteners for trestle design may include: Table 7-2-6. Applicable Adjustment Factors to Fasteners for Trestle Design CD - Duration of load

CS - Spacing

CM - Moisture content

Cd - Depth of embedment

CT - Temperature

Cg - Group action

Ce - Edge distance

Cst - Steel sideplate

3

4

Cn - End distance The tabulated design properties for connection designs in wood are tied directly to specific gravity. Species groups and specific gravity values to be used in conjunction with the Tables 7-2-7 and 7-2-8 are given in Table 7-2-5.

2.4.2 DESIGN EQUATIONS (2006)1 Equations from Articles 2.5.7, 2.5.8, and 2.5.9 are applicable to the design of glued laminated timbers. Use appropriate design stresses from Tables 7-2-7 and 7-2-8.

1

See Part 6 Commentary.

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-2-17

Timber Structures

7-2-18

AREMA Manual for Railway Engineering

© 2011, American Railway Engineering and Maintenance-of-Way Association

See Part 6 Commentary. 1

1

Table 7-2-7. Design Values for Structural Glued Laminated Softwood Timber - Railroad Applications

1 See

Part 6 Commentary.

7-2-19

Design of Wood Railway Bridges and Trestles for Railway Loading

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

Table 7-2-8. Design Values for Structural Glued Laminated Softwood Timber -- Railroad Applications 1

Timber Structures

SECTION 2.5 ALLOWABLE UNIT STRESSES FOR STRESS-GRADED LUMBER1 2.5.1 WORKING UNIT STRESSES (1988) a.

Working unit stresses to be used for design shall be those shown in Table 7-2-9 for the appropriate condition of use and species.

b. In locations of more extreme exposure than “occasionally wet but quickly dried,” and where serious depreciation is more apt to occur, a further reduction in the working stresses for extreme fiber and compression should be made. c.

Where timber is treated by creosoting or other process rendering it decay resistant, the working stresses for continuously dry may be used except in compression perpendicular to the grain and for joists and planks continuously submerged.

2.5.2 FORM FACTOR (1988) The size and shape of a beam affects the modulus of rupture. This effect is called the form factor. A factor of 0.90 has been assumed in arriving at allowable stresses, so that for rectangular beams of ordinary size no form factor need be figured. The form factor for beams of all sizes and for round and box or I-section are given in the Wood Handbook.

2.5.3 DEFLECTION, PERMANENT SET (1988) The modulus of elasticity given in Table 7-2-9 gives the deflection which will occur immediately on application of load. Under long continued load there will be an additional sag or permanent set which will be approximately equal to the elastic deflection.

2.5.4 COMPRESSION PARALLEL TO GRAIN OR CENTRALLY LOADED COLUMNS (2009) a.

Stress values in Table 7-2-9 are to be used for posts and struts where the unsupported length is not greater than 11 times the least dimension, and for end bearing of compression members.

L b. For columns where ---- is more than 11, the allowed working stresses are: d 1 L 4 P ---- = c 1 – --- æ --------ö for L/d less than K 3 è Kdø A 0.274E P ---- = ------------------- for L/d greater than K A Lö 2 æ --è Dø E K = 0.641 ---c

p E K = --- -----2 6c

or

where: P = total load in pounds 1

See Part 6 Commentary.

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-2-20

AREMA Manual for Railway Engineering

Design of Wood Railway Bridges and Trestles for Railway Loading

A = area in square inches c = working unit stress in compression parallel to the grain for short columns L = unsupported length in inches d = least dimension in inches (also see Article 2.5.14) E = modulus of elasticity (Table 7-2-10) P Table 7-2-10, gives values of allowed ---A L Columns should be limited to ---- = 50 d

2.5.5 BEARING (1988) a.

The working stresses for compression perpendicular to grain apply to bearings 6 inches or more in length located anywhere in the length of a timber and to bearings of any length at the ends of beams or other members. For bearings shorter than 6 inches located 3 inches or more from the end of a timber the stresses may be increased in accordance with the following factors: Length of bearing, inches

1/ 2

1

1-1/2

2

3

4

6

Factor of increase

1.75

1.38

1.25

1.19

1.13

1.10

1.00

b. For stress under a washer or other round bearing area, the same factor may be taken as for a bearing whose length equals the diameter of the washer.

1

2.5.6 ALLOWABLE UNIT STRESSES FOR STRESS-GRADED LUMBER (2010) 2.5.6.1 Working Stresses (1990)

3

Recommended working unit stresses for most commercial stress-grades of lumber have been determined in accordance with the principles set forth in the ASTM D245 for several conditions of use. These stresses are shown in Table 7-2-9. For other conditions the stresses should be adjusted as recommended in Section 2.7, Recommended Practice for Design of Wood Culverts (1962).

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-2-21

Timber Structures Table 7-2-9. Allowable Unit Stresses for Stress Graded Lumber – Railroad Loading (Visual Grading)1 (See Notes) Railroad values wet conditions (over 19% MC) Grade

Size Classification

Fb psi

Ft psi

Fv psi

Fc^ psi

Fc psi

235

615

E ksi

Grading Agency Rules

Eastern Spruce Select Str. No. 1 Select Str. No. 1

Beams and Stringers Posts and Timbers

945

565

115

1400

810

385

115

235

510

1400

880

610

120

235

635

1400

720

495

120

135

555

1400

Select Str.

995

520

120

200

865

1170

No. 1

670

360

120

200

755

1080

595

315

120

200

720

990

345

180

120

200

520

900

670

360

120

200

865

900

385

205

120

200

720

810

460

250

120

200

565**

900

No. 2 No. 3 Construction Standard

2” to 4” thick by 2” and wider (use dimension lumber adjustment factors)

Stud

NELMA

Hem-Fir Select Str. No. 1 Select Str. No. 1

Beams and Stringers

1170

675

125

245

760

1300

945

475

125

245

615

1300

Posts and Timbers

1080

720

125

245

800

1300

880

585

125

245

695

1300

1070

835

130

245

1080

1440

Select Str. No. 1 & better

840

655

130

245

970

1350

750

565

130

245

970

1350

650

475

130

245

935

1170

385

270

130

245

655**

1080

750

540

130

245

1115

1170

Standard

420

295

130

245

935

1080

Stud

520

360

130

245

720**

1080

No. 1 No. 2 No. 3 Construction

1

2” to 4” thick by 2” and wider (use dimension lumber adjustment factors)

WCLIB WWPA

See Part 6 Commentary.

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-2-22

AREMA Manual for Railway Engineering

Design of Wood Railway Bridges and Trestles for Railway Loading Table 7-2-9. Allowable Unit Stresses for Stress Graded Lumber – Railroad Loading (Visual Grading)1 (Continued)

Railroad values wet conditions (over 19% MC) Size Classification

Grade

Fb psi

Ft psi

Fv psi

Fc^ psi

Fc psi

E ksi

Grading Agency Rules

Douglas Fir (See Note 4) Dense Select Structural

1710

990

150*

440

1065

1700

Select Struct.

1440

855

150*

380

900

1600 1700

Beams and Stringers

Dense No. 1

1395

700

150*

440

900

No. 1

1215

610

150*

380

760

1600

Dense Select Structural

1575

1035

150*

655

1215

1700

Select Struct.

1350

900

150*

565

1035

1600

1260

855

150*

655

1080

1700

No. 1

1080

745

150*

565

900

1600

Select Struct.

1150

900

155

380

1225

1710

No. 1 & better

920

720

155

380

1115

1620

765

610

155

380

1080

1530

690

520

155

380

970

1440

405

295

155

380

700**

1260

Dense No. 1

No. 1 No. 2 No. 3 Construction

Posts and Timbers

2” to 4” thick by 2” and wider (use dimension lumber adjustment factors)

765

585

155

380

1190

1350

Standard

440

340

155

380

1010

1260

Stud

535

405

155

380

610

1260

WCLIB WWPA NLGA

1

3

4

1

See Part 6 Commentary. © 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-2-23

Timber Structures Table 7-2-9. Allowable Unit Stresses for Stress Graded Lumber – Railroad Loading (Visual Grading)1 (Continued)

Railroad values wet conditions (over 19% MC) Size Classification

Grade

Fb psi

Ft psi

Fv psi

Fc^ psi

Fc psi

150*

395

990

1600 1500

E ksi

Grading Agency Rules

Southern Pine Dense Select Structural

1575

Select Struct. No. 1 Dense

5” x 5” and larger

No. 1

1350

900

150*

340

855

1395

945

150*

395

880

1600

1215

810

150*

340

745

1500

No. 2 Dense

880

585

150*

395

565

1300

No. 2

765

495

150*

340

475

1200

Dense Select Structural

2335

1485

135

400

1620

1710

Select Struct.

2180

1440

135

340

1510

1620

No. 1 Dense

1530

990

135

400

1440

1620

1415

945

135

340

1330

1530

1300

790

135

400

1330

1530

1150

745

135

340

1190

1440

2” to 4” thick and 2” to 4” wide

No. 1 No. 2 Dense No. 2 Nol 3 & stud

765

430

135

340

700

1260

Dense Select Structural

2065

1350

135

400

1550

1710

Select Struct.

1950

1260

135

340

1440

1620

No. 1 Dense

2” to 4” thick and 5” to 6” wide

No. 1 No. 2 Dense

1340

855

135

400

1370

1620

1260

810

135

340

1260

1530

1110

700

135

400

1260

1530

No. 2

955

655

135

340

1150

1440

Nol 3 & stud

675

385

135

340

665

1260

Dense Select Structural

1875

1215

135

400

1475

1710

Select Struct.

1760

1170

135

340

1370

1620

1260

790

135

400

1295

1620

1150

745

135

340

1190

1530

1070

610

135

400

1225

1530

No. 1 Dense

2” to 4” thick and 8” wide

No. 1 No. 2 Dense No. 2

920

585

135

340

1115

1440

Nol 3 & stud

630

360

135

340

630

1260

Dense Select Structural

1645

1080

135

400

1440

1710 1620

Select Struct.

1570

990

135

340

1330

No. 1 Dense

1110

700

135

400

1260

1620

995

655

135

340

1150

1530

2” to 4” thick and 10” wide

No. 1 No. 2 Dense No. 2

920

565

135

400

1190

1530

945

520

135

340

1080

1440

Nol 3 & stud

540

295

135

340

610

1260

Dense Select Structural

1570

990

135

400

1405

1710

Select Struct.

1455

945

135

340

1295

1620

No. 1 Dense

1035

655

135

400

1225

1620

955

610

135

340

1150

1530

1035

520

135

400

1150

1530

No. 2

880

495

135

340

1045

1440

Nol 3 & stud

520

295

135

340

745**

1260

No. 1 No. 2 Dense

1

1080

2” to 4” thick and 12” wide

SPIB

See Part 6 Commentary. © 2011, American Railway Engineering and Maintenance-of-Way Association

7-2-24

AREMA Manual for Railway Engineering

Design of Wood Railway Bridges and Trestles for Railway Loading Table 7-2-9. Allowable Unit Stresses for Stress Graded Lumber – Railroad Loading (Visual Grading)1 (Continued)

Railroad values wet conditions (over 19% MC) Grade

Size Classification

Fb psi

Ft psi

Fv psi

Fc^ psi

Fc psi

E ksi

Grading Agency Rules

Mixed Maple Select Str. No. 1 Select Str. No. 1

Beams and Stringers Posts and Timbers

Select Str. No. 1 No. 2 No. 3 Construction Standard

2” to 4” thick by 2” and wider (use dimension lumber adjustment factors)

Stud

890

590

145

375

615

710

485

145

375

530

1100 1100

890

590

145

375

615

1100

710

485

145

375

530

1100

765

540

170

540

630

1170

555

385

170

540

630**

1080

535

385

170

540

495**

990

305

225

170

540

295**

900

610

430

170

540

655**

990

345

250

170

540

520**

900

420

295

170

540

315**

900

NELMA

Red Oak Select Str. No. 1 Select Str. No. 1

Beams and Stringers Posts and Timbers

Select Str. No. 1 No. 2 No. 3 Construction Standard

2” to 4” thick by 2” and wider (use dimension lumber adjustment factors)

Stud

1215

720

140

495

675

1200

1035

495

140

495

575

1200

1125

765

140

495

715

1200

900

610

140

495

635

1200

880

610

150

495

720

1260

630

450

150

495

745**

1170

610

430

150

495

565**

1080

365

250

150

495

340**

990

710

495

150

495

610**

1080

400

270

150

495

585**

990

480

340

150

495

360**

990

1 NELMA

3

4

1

See Part 6 Commentary.

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-2-25

Timber Structures

Table 7-2-9. Allowable Unit Stresses for Stress Graded Lumber – Railroad Loading (Visual Grading)11 (Continued) * : 150 psi value was derived from AAR beam fatigue tests

Note 1:

Abbreviations used in this table are as follows: NELMA – Northeastern Lumber Manufacturers Association, Inc. NLGA - National Lumber Grades Authority SPIB – Southern Pine Inspection Bureau WCLIB – West Coast Lumber Inspection Bureau WWPA – Western Wood Products Association Fb – Unit Stress in Extreme Fiber in Bending Ft – Unit Stress in Tension Parallel to the Grain Fv – Unit Stress in Horizontal Shear Fc^ – Unit Stress in Compression Perpendicular to the Grain Fc – Unit Stress in Compression Parallel to the Grain E – Modulus of Elasticity Str. – Structural MC – Moisture Content

Note 2:

Conditions of use where the moisture content will not exceed 19%, the tabulated values above may be multiplied by the following factors: Dry use Factor: Cm for 5” and Thicker Lumber Fb

Ft

Fv

Fc^

Fc

E

1.00 1.00 1.00 1.49 1.10 1.00

for Nominal 2” to 4” Thick Lumber Fb

Ft

Fv

Fc^

Fc

1.18 1.00 1.03 1.49 1.25

E 1.11

do not adjust values with ** next to them

Note 3:

For Beams & Stringers, Posts & Timbers, and Southern Pine sections 5” and wider, when the depth of the member exceeds 12” the tabulated bending design stresses, Fb, shall be multiplied by the following size factor: Cr = (12/d)1/9

Note 4:

1 See

Douglas-Fir South, Inland Douglas Fir and Douglas Fir-Larch are not deemed appropriate for outdoor Railway use.

Part 6 Commentary.

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-2-26

AREMA Manual for Railway Engineering

Design of Wood Railway Bridges and Trestles for Railway Loading

Table 7-2-9. Allowable Unit Stresses for Stress Graded Lumber – Railroad Loading (Visual Grading)11 (Continued) Note 5:

For all species except Southern Pine, the tabulated bending, tension, and compression parallel to grain design values for dimension lumber 2” to 4” thick shall be multiplied by the following size factors: Size Factors: Cf Fb

Ft

Fc

Thickness Grade

Select Structural No. 1 & Btr. No. 1, No. 2 No. 3

Stud

Width

2” & 3”

4”

2”, 3” & 4”

1.5

1.5

1.5

1.15

5”

1.4

1.4

1.4

1.1

6”

1.3

1.3

1.3

1.1

8”

1.2

1.3

1.2

1.05

10”

1.1

1.2

1.1

1.0

12”

1.0

1.1

1.0

1.0

14” and up

0.9

1.0

0.9

0.90

2”, 3” & 4”

1.1

1.1

1.1

1.05

5” & 6”

1.0

1.0

1.0

1.0

8” and up Construction, Standard

Use No. 3 Grade design values and Cf

2”, 3” & 4”

1.0

1.0

1.0

1.0

1 Note 6:

The design values for dimension lumber 2” to 4” thick are based on edge-wise use. When such lumber is used flat-wise, the design values for extreme fiber in bending for all species may be multiplied by the following factors:

Width 2” & 3”

4 inch

2” & 3”

1.0

~

4”

1.1

1.0

5”

1.1

1.05

6”

1.15

1.05

8”

1.15

1.05

10” & up

1.2

1.1

Note 7:

1

Thickness

3

4

The design values for beams and stringers are based on edge-wise use. When such lumber is used flatwise, the design values for extreme fiber bending and modulus of elasticity for all species except Southern Pine shall be multiplied by the following factors:

Grade

Fb

E

Select Structural

0.86

1.00

No. 1

0.74

0.90

Note 8:

Grading restrictions for beams and stringers shall apply over the entire length of each piece. This will make each piece suitable for use in simple spans as well as over 2 or more continuous spans or under concentrated loads without the necessity of making special shear or other special stress requirements.

Note 9:

For normal conditions other than railroad loading, allowable unit stresses may be multiplied by 1.11 for Fb , Ft , Fv, Fc^, and Fc. E shall remain unchanged.

See Part 6 Commentary.

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-2-27

Short Column Stress 1300

1200

AREMA Manual for Railway Engineering

© 2011, American Railway Engineering and Maintenance-of-Way Association

1100

1000

900 800

Stress at Ratio of Length to Least Dimension (L/d)

Modulus of Elasticity

K

1,300,000

11

12

14

16

18

20

25

30

35

40

45

50

20.3

1300

1247

1203

1132

1032

892

570

396

291

223

176

142

1,600,000

22.5

1300

1265

1235

1190

1123

1030

701

487

358

274

216

175

1,200,000

20.3

1200

1151

1110

1045

953

823

526

365

268

206

162

132

1,300,000

21.1

1200

1158

1122

1068

989

827

570

396

291

223

176

142

1,500,000

22.7

1200

1169

1142

1102

1042

959

658

457

336

257

203

164

1,600,000

23.4

1200

1172

1148

1112

1060

986

701

487

358

274

216

175

1,200,000

21.2

1100

1063

1031

981

910

810

526

365

268

206

162

132

1,300,000

22.1

1100

1068

1041

999

938

854

570

396

291

223

176

142

1,500,000

23.7

1100

1076

1055

1024

978

914

658

457

336

257

203

164

1,600,000

24.4

1100

1078

1060

1032

991

935

701

487

358

274

216

175

1,200,000

22.2

1000

972

947

910

856

780

526

365

268

206

162

132

1,300,000

23.1

1000

976

955

923

877

813

570

396

291

223

176

142

1,500,000

24.8

1000

982

966

942

908

859

658

457

336

257

203

164

1,600,000

25.6

1000

984

970

948

918

876

697

487

358

274

216

175

1,000,000

21.4

900

870

845

806

750

674

438

304

224

171

135

110

1,200,000

23.4

900

879

861

834

795

740

526

365

268

206

162

132

1,600,000

27.0

900

888

878

863

841

810

680

487

358

274

216

175

1,000,000

22.7

800

779

762

734

694

639

438

304

224

171

135

110

Timber Structures

7-2-28

Table 7-2-10. Unit Compression (Column) Stresses for Standard Stress Grades

Design of Wood Railway Bridges and Trestles for Railway Loading

2.5.7 BEARING AT ANGLE TO GRAIN (1988) a.

Allowed bearing stresses on surfaces at an angle to the direction of the grain, may be taken from the following formula: PQ N = -----------------------------------------------P sin 2 q + Q cos 2 q where: N = Unit compressive stress in a direction at inclination with the direction of the grain P = Unit stress in compression parallel to the grain – Table 7-2-7 Q = Unit stress in compression perpendicular to the grain – Table 7-2-9 q = Angle between the grain and the normal to the inclined surface

b. The chart shown in Appendix 1 - Contemporary Designs and Design Aids, Figure 7-A1-3 gives a graphical solution.

2.5.8 COMBINED AXIAL AND BENDING LOADS (1988) a.

The general formulas for safe eccentric or combined bending and end loadings of square or rectangular wood columns are: P 6e zP P ---- æ ------ö + M ----- + ------- ---è ø A A d S A + --------------------------------------------- = 1 f C P 15e zP P ---- æ ---------ö + M ----- + ------- ---è ø A A 2d S A- -----------------------------------------------+ - = 1 c P f – ---A

1

L for columns with ---- of 11 or less, and d

3 L for columns with ---- of 20 or more d

where:

4 P ---- = average compressive stress induced by axial load. A M ----- = flexural stress induced by side loads. S z = ratio of flexural to average compressive stress when both result from the same loading, so that the ratio remains constant while the load varies. e = eccentricity of axial load. d = width of column, measured in the direction of side loads and eccentricity. This is the depth to use in computing the flexural stress. f = allowable working unit stress for extreme fiber in bending. c = allowable unit stress for the member if used as a centrally loaded column.

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-2-29

Timber Structures

L b. Stresses for columns with ---- between 11 and 20 are determined by straight-line interpolation between d L L the formula for a ---- of 11 and the formula for a ---- of 20. d d c.

Where side loads are such that maximum deflection and flexural stress do not occur at mid-length of the M column, it is generally satisfactory to consider ----- as the maximum flexural stress due to the load or S loads, regardless of its position in the length of the column.

d. A more detailed discussion may be found in U.S. Forest Products Laboratory Report No. R 1782, Formulas for Columns with Side Loads and Eccentricity.

2.5.9 HORIZONTAL SHEAR (2006) a.

The following procedure shall be used for horizontal shear at the neutral plane: 3V S = ----------2bh where: S = Maximum unit shear stress in pounds per square inch V = Maxiumum shear in pounds b = Breadth of beam in inches h = Height of beam in inches

b. The results obtained must not exceed the allowable unit shear stress. c.

In calculating the maximum shear, V, use the following rules: (1) V shall be calculated at a distance away from the face of support equal to the height of the beam. (2) Neglect all loads within the height of the beam from the face of the support. (3) Moving loads shall be placed such that they will produce the maximum value for V. (4) When a beam spans continuously over one or more supports, continuity shall be considered when calculating V. (5) Take into account any relief to the beam under consideration resulting from the loading being distributed to adjacent parallel beams by flooring or other members of the construction.

2.5.10 NOTCHES (1988) Notches with square corners should be avoided where possible because there will be a strong tendency for a check or split to result. If a square-cornered notch is used near the end of a piece, the effective depth in computing shear should be taken as 2

c ----d © 2011, American Railway Engineering and Maintenance-of-Way Association

7-2-30

AREMA Manual for Railway Engineering

Design of Wood Railway Bridges and Trestles for Railway Loading

where: c = the net depth at the notch d = total depth of the piece

2.5.11 SHEARING STRESS (1988) The allowable shearing stress for joint details shall be taken at 50 percent greater than the values for horizontal shear in Table 7-2-9.

2.5.12 BEARING ON BOLTS (1988) a.

Working unit stresses for timber bearing on bolts may be taken as the product of the following factors: • Basic unit stress for bearing, Table 7-2-11. • Factor based on L/d ratio of bolt, Table 7-2-12. • For bearing perpendicular to the grain only, a factor as follows: Diameter of bolt, inches

3/ 8 1 / 2 5 / 8 3 / 4 7 / 8

Diameter factor

1.95 1.68 1.52 1.41 1.33 1.27 1.19

1

1 ---1 /4 1 --- 1 / 2 1 --- 3 / 4 1.14

1 1. 0

2 2 --- 1/ 2 3 1.07 1.03

1

1

b. Bolts acting at an angle with the grain shall be allowed bearing values by the formula in Article 2.5.7, where P and Q are allowed bearing values computed for the L/d ratio of the bolt. Table 7-2-13 shows bearing values for bolts for the most common condition of exposure occasionally wet but quickly dried. For locations continuously dry, use 4/3 the values in the table, and for locations damp or wet most of the time, use 8/9 the values in the table.

3

Table 7-2-11. Basic Unit Stresses for Bearing on Bolts Basic Unit Stress Group

Species of Wood

Parallel with Perpendicular Grain to Grain

4

Softwoods (Conifers) 1

Hemlock, Eastern

800

150

2

Cedar, Port Orford and Western Red; Douglas Fir, Inland

1000

200

3

Cypress, Southern; Douglas Fir, Coast; Pine, Southern; Redwood

1300

275

Hardwoods (Broad Leaved) 1

Chestnut

925

175

2

Elm, soft; Gum, Black and Red; Tupelo

1200

250

3

Ash, white; Beech; Birch; Elm, Rock; Maple, hard; Oak, red, white

1500

400

Note:

Above values are for continuously dry location. For occasionally wet but quickly dried, use 3/4 of values in table. For damp or wet most of the time, use 2/3 of values in table. © 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-2-31

Timber Structures Table 7-2-12. Percentage of Basic Stress for Various L/d Values Parallel with Grain Length ---------------------------Diameter L --d Ratio

Common Bolts

Perpendicular to Grain

High Strength Bolts

Common Bolts

Conifers High HardConifers Group 3 woods Strength Group Group Group Group Group Group Group HardGroup Group Bolts All 1 2 3 1 2 3 1 woods 2 Groups 3 Group 2

1 to 2

100

100

100

100

100

100

100

100

100

100

100

3

100

100

99.0

100

100

100

100

100

100

100

100

4

99.5

97.4

92.5

100

100

99.0

100

100

100

100

100

5

95.4

88.3

80.0

100

99.8

96.0

100

100

100

100

100

6

85.6

75.8

67.2

100

95.4

89.5

100

100

100

96.3

100

7

73.4

65.0

57.6

95.8

88.8

81.0

100

100

97.3

86.9

100

8

64.2

56.9

50.4

39.3

81.2

73.0

100

96.1

88.1

75.0

100

9

57.1

50.6

44.8

82.5

74.2

66.4

94.6

86.3

76.7

64.6

97.7

10

51.4

45 5

40.3

75.8

68.0

60.2

85.0

76.2

67.2

55.4

90.0

11

46.7

41.4

36.6

69.7

61.9

54.8

76.1

67.6

59.3

48.4

81.5

12

42.8

37.9

33.6

64.0

56.7

50.2

68.6

61.0

52.0

42.5

73.6

13

39.5

35.0

31.0

59.1

52.4

46.3

62.2

55.3

45.9

37.5

66.9

Note:

The above values are for joints with metal plates. (View a) Where wood splice plates are used, each one-half of thickness of main timber, (View b) use 80 percent of tabular value for bearing parallel with grain; no reduction for bearing perpendicular to grain. Common bolts: yield point about 45,000 pounds per square inch. High strength bolts: yield point about 125,000 pounds per square inch. L = length of bolt in main timber in inches. d = diameter of bolt in inches.

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-2-32

AREMA Manual for Railway Engineering

Design of Wood Railway Bridges and Trestles for Railway Loading

Parallel to Grain, P

Perpendicular to Grain, Q

Parallel to Grain, P

Perpendicular to Grain, Q

Parallel to Grain, P

Perpendicular to Grain, Q

Parallel to Grain, P

Perpendicular to Grain, Q

Parallel to Grain, P

Perpendicular to Grain, Q

Parallel to Grain, P

3

Perpendicular to Grain, Q

2-5/8

Projected Area of Bolt, square inches

2

Hardwoods (Broad Leaved)

L/D

1-5/8

Softwoods (Conifers)

Diameter of Bolt, inches

Length of Bolt in Main Member L, inches

Table 7-2-13. Bearing Value for Bolts Allowable Load per Bolt for Timber Bearing on Common Bolts with Wood Side Plates (For timber occasionally wet but quickly dried.)

1 /2

3.3

0.813

150

390

200

480

280

620

180

450

260

580

410

710

5 /8

2.6

1.016

170

490

230

610

320

790

200

560

290

730

460

910

3 /4

2.2

1.219

190

590

260

730

350

950

230

680

320

880

520 1090

7 /8

1.9

1.422

210

680

280

850

390 1110

250

790

350 1020

570 1280

1

1.6

1.625

230

780

310

970

430 1270

270

900

390 1170

620 1460

1 /2

4.0

1.000

190

480

250

580

350

720

220

550

310

700

500

5 /8

3.2

1.250

210

600

280

750

390

950

250

690

360

900

570 1100

3 /4

2.7

1.500

240

720

320

900

440 1160

280

830

400 1080

630 1340

7 /8

2.3

1.750

260

840

350 1050

480 1360

310

970

440 1260

700 1570

1

2.0

2.000

290

960

380 1200

520 1560

330 1110

480 1440

760 1800

1 /2

5.3

1.313

250

580

330

670

450

780

290

670

410

650

5 /8

4.2

1.641

280

780

370

940

510 1150

330

900

470 1130

750 1320

3 /4

3.5

1.969

310

940

420 1170

570 1470

360 1090

520 1400

830 1700

7 /8

3.0

2.297

340 1100

460 1380

630 1770

400 1270

570 1650

920 2050

1

2.6

2.625

380 1260

500 1570

690 2040

440 1460

630 1890 1000 2350

1 /2

6.0

1.500

280

610

380

520

330

470

5 /8

4.8

1.875

320

870

430 1010

590 1210

370 1000

530 1220

860 1390

3 /4

4.0

2.250

360 1070

480 1310

650 1620

420 1240

590 1580

950 1870

7 /8

3.4

2.625

390 1260

520 1560

720 1970

460 1450

650 1870 1050 2280

1

3.0

3.000

430 1440

570 1800

790 2320

500 1660

710 2160 1140 2670

Group 1 Hemlock, Eastern

Group 2 Group 3 Cedar, Port Cypress, Orford and Southern; Western Douglas Fir, Red; Coast; Pine, Douglas Fir, Southern; Inland Redwood

680

790

Group 1 Chestnut

710

Group 3 Ash, White; Group 2 Beech, Elm, Soft; Birch, Elm, Gum, Black Rock; and Red; Maple, Tupelo Hard; Oak, Red, White

800

820

730

830

3

900

910

See Table 7-2-13 footnotes on Page 7-2-78

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

1

7-2-33

4

Timber Structures

Perpendicular to Grain, Q

Parallel to Grain, P

Perpendicular to Grain, Q

Parallel to Grain, P

Perpendicular to Grain, Q

Parallel to Grain, P

Perpendicular to Grain, Q

Parallel to Grain, P

Perpendicular to Grain, Q

Parallel to Grain, P

Perpendicular to Grain, Q

Parallel to Grain, P

4-1/2

Projected Area of Bolt, square inches

4

Hardwoods (Broad Leaved)

L/D

3-5/8

Softwoods (Conifers)

Diameter of Bolt, inches

Length of Bolt in Main Member L, inches

Table 7-2-13. Bearing Value for Bolts (Continued) Allowable Load per Bolt for Timber Bearing on Common Bolts with Wood Side Plates (For timber occasionally wet but quickly dried.)

1/ 2

7.3

1.813

340

610

450

680

590

790

400

710

540

820

760

910

5/ 8

5.8

2.266

390

950

520 1060

710 1230

450 1100

650 1280 1000 1420

3/ 4

4.8

2.719

430 1260

580 1470

790 1750

500 1450

720 1760 1150 2020

7/ 8

4.1

3.172

470 1510

630 1840

870 2260

550 1740

790 2200 1270 2610

1

3.6

3.625

520 1730

690 2140

950 2690

600 2010

860 2570 1380 3100

1/ 2

8.0

2.000

380

610

480

610

440

550

5/ 8

6.4

2.500

430

960

570 1070

780 1260

500 1120

700 1290 1060 1420

3/ 4

5.3

3.000

480 1330

630 1520

870 1770

560 1540

790 1830 1250 2060

7/ 8

4.6

3.500

520 1630

700 1930

960 2320

610 1890

870 2320 1400 2680

1

4.0

4.000

570 1910

760 2340 1050 2890

670 2210

950 2810 1520 3330

1/ 2

9.0

2.250

400

610

490

470

540

5/ 8

7.2

2.813

480

960

640 1070

840 1230

560 1120

770 1290 1080 1420

3/ 4

6.0

3.375

540 1390

710 1530

980 1770

620 1600

890 1840 1370 2060

7/ 8

5.1

3.938

590 1780

790 2060 1080 2440

690 2060

980 2470 1570 2790

1

4.5

4.500

640 2100

860 2510 1180 3040

750 2430 1070 3010 1710 3490

1-1/8

4.0

5.063

700 2420

930 2960 1280 3650

820 2800 1170 3550 1860 4220

Group 1 Hemlock, Eastern

Group 3 Group 2 Cedar, Port Cypress, Orford and Southern; Western Douglas Fir, Coast; Pine, Red; Douglas Fir, Southern; Redwood Inland

680

680

600

Group 1 Chestnut

790

790

710

710

Group 3 Ash, White; Group 2 Beech, Elm, Soft; Birch, Elm, Gum, Black Rock; and Red; Maple, Tupelo Hard; Oak, Red, White

820

820

760

730

910

910

See Table 7-2-13 footnotes on Page 7-2-78

5

1/ 2

10.0

2.500

400

610

480

5/ 8

8.0

3.125

530

960

670 1070

3/ 4

6.7

3.750

7/ 8

5.7

1 1-1/8

680

580

790

470

710

530

820

700

910

860 1230

620 1120

780 1290 1070 1420

590 1390

790 1540 1070 1770

690 1600

970 1840 1420 2060

4.375

650 1860

870 2090 1200 2400

760 2150 1090 2510 1700 2790

5.0

5.000

710 2290

950 2650 1310 3120

830 2650 1190 3180 1910 3600

4.4

5.625

780 2640 1040 3160 1430 3840

910 3060 1300 3800 2080 4430

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AREMA Manual for Railway Engineering

Design of Wood Railway Bridges and Trestles for Railway Loading

Perpendicular to Grain, Q

Parallel to Grain, P

6-1/2

Projected Area of Bolt, square inches

6

Hardwoods (Broad Leaved)

L/D

5-1/2

Softwoods (Conifers)

Diameter of Bolt, inches 5 /8

8.8

3.438

560

960

3 /4

7.3

4.125

650 1390

860 1540 1130 1770

760 1600 1030 1840 1450 2060

7 /8

6.3

4.813

720 1880

960 2090 1310 2400

840 2190 1190 2510 1800 2790

1

5.5

5.500

790 2390 1050 2710 1440 3150

920 2760 1310 3250 2060 3640

1-1/8

4.9

6.188

860 2850 1140 3310 1570 3920 1000 3290 1430 3980 2280 4520

5 /8

9.6

3.750

570

3 /4

8.0

4.500

710 1390

910 1540 1150 1770

830 1600 1050 1840 1430 2060

7 /8

6.9

5.250

790 1880 1050 2090 1410 2400

920 2190 1280 2510 1840 2790

1

6.0

6.000

860 2470 1140 2730 1570 3150 1000 2860 1430 3270 2200 3640

1-1/8

5.3

6.750

930 3000 1250 3420 1710 3980 1090 3460 1560 4110 2460 4630

5 /8

10.4

4.063

570

3 /4

8.7

4.875

740 1390

920 1540 1140 1770

860 1600 1030 1840 1400 2060

7 /8

7.4

5.688

850 1880 1120 2090 1460 2400

990 2190 1330 2510 1860 2790

1

6.5

6.500

930 2470 1240 2730 1680 3150 1080 2860 1530 3270 2270 3640

1-1/8

5.8

7.313 1010 3070 1350 3440 1860 3980 1180 3550 1690 4120 2620 4630

960

960

690 1070

690 1070

670 1070

850 1230

830 1230

820 1230

650 1120

660 1120

660 1120

Parallel to Grain, P

Perpendicular to Grain, Q

Parallel to Grain, P

Group 3 Ash, White; Group 2 Beech, Elm, Soft; Birch, Elm, Gum, Black Rock; and Red; Maple, Tupelo Hard; Oak, Red, White Perpendicular to Grain, Q

Parallel to Grain, P

Group 1 Chestnut

Perpendicular to Grain, Q

Parallel to Grain, P

Perpendicular to Grain, Q

Parallel to Grain, P

Group 1 Hemlock, Eastern

Group 3 Group 2 Cedar, Port Cypress, Orford and Southern; Western Douglas Fir, Coast; Pine, Red; Douglas Fir, Southern; Redwood Inland Perpendicular to Grain, Q

Length of Bolt in Main Member L, inches

Table 7-2-13. Bearing Value for Bolts (Continued) Allowable Load per Bolt for Timber Bearing on Common Bolts with Wood Side Plates (For timber occasionally wet but quickly dried.)

770 1290 1050 1420

760 1290 1010 1420

740 1290

7

5 /8

11.2

4.375

560

3 /4

9.3

5.250

760 1390

7 /8

8.0

6.125

920 1880 1170 2090 1480 2400 1070 2190 1350 2510 1830 2790

1

7.0

7.000 1000 2470 1330 2730 1780 3150 1170 2860 1620 3270 2320 3640

1-1/8

6.2

7.875 1090 3120 1450 3460 1990 3980 1270 3630 1810 4180 2740 4630

660 1070

790 1230

920 1540 1130 1770

650 1120

720 1290

940 1420

890 1600 1020 1840 1370 2060

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AREMA Manual for Railway Engineering

3

970 1420

See Table 7-2-13 footnotes on Page 7-2-78 960

1

7-2-35

4

Timber Structures

9-1/2

Group 3 Ash, White; Group 2 Beech, Elm, Soft; Birch, Elm, Gum, Black Rock; and Red; Maple, Tupelo Hard; Oak, Red, White

10.0

5.625

760 1390

7 /8

8.6

6.563

950 1880 1180 2090 1460 2400 1110 2190 1330 2510 1800 2790

1

7.5

7.500 1070 2470 1400 2730 1820 3150 1250 2860 1660 3270 2310 3640

1-1/8

6.7

8.438 1170 3120 1560 3460 2100 3980 1360 3630 1910 4180 2790 4630

5 /8

12.8

5.000

540

3 /4

10.7

6.000

750 1390

7 /8

9.1

7.000

980 1880 1190 2090 1450 2400 1140 2190 1320 2510 1780 2790

1

8.0

8.000 1140 2470 1460 2730 1850 3150 1330 2860 1680 3270 2290 3640

1-1/8

7.1

9.000 1250 3120 1650 3460 2200 3980 1450 3630 2000 4180 2850 4630

1-1/4

6.4 10.000 1340 3850 1780 4270 2430 4920 1560 4480 2210 5130 3300 5700

960

910 1540 1100 1770

640 1070

Parallel to Grain, P

Perpendicular to Grain, Q

Parallel to Grain, P

760 1230

640 1120

690 1290

Parallel to Grain, P

3 /4

650 1070

Perpendicular to Grain, Q

960

Parallel to Grain, P

550

Group 1 Chestnut

Perpendicular to Grain, Q

4.688

Perpendicular to Grain, Q

12.0

Parallel to Grain, P

5 /8

Group 1 Hemlock, Eastern

Perpendicular to Grain, Q

Parallel to Grain, P

Projected Area of Bolt, square inches

Group 3 Group 2 Cedar, Port Cypress, Orford and Southern; Western Douglas Fir, Coast; Pine, Red; Douglas Fir, Southern; Redwood Inland

Perpendicular to Grain, Q

8

Hardwoods (Broad Leaved)

L/D

7-1/2

Softwoods (Conifers)

Diameter of Bolt, inches

Length of Bolt in Main Member L, inches

Table 7-2-13. Bearing Value for Bolts (Continued) Allowable Load per Bolt for Timber Bearing on Common Bolts with Wood Side Plates (For timber occasionally wet but quickly dried.)

910 1420

880 1600 1000 1840 1320 2060

740 1230

630 1120

670 1290

880 1420

890 1540 1080 1770

870 1600

980 1840 1280 2060

3 /4

12.7

7.125

720 1390

7 /8

10.9

8.313

960 1880 1140 2090 1370 2400 1120 2190 1250 2510 1630 2790

1

9.5

860 1540

990 1770

850 1600

900 1840 1180 2060

9.500 1220 2470 1470 2730 1790 3150 1420 2860 1630 3270 2170 3640

1-1/8

8.4 10.688 1450 3120 1820 3460 2270 3980 1690 3630 2060 4180 2790 4630

1-1/4

7.6 11.875 1590 3850 2070 4270 2670 4920 1850 4480 2430 5130 3380 5700 See Table 7-2-13 footnotes on Page 7-2-78

10

7 /8 1

11.4

8.750

960 1880 1130 2090 1350 2400 1120 2190 1230 2510 1610 2790

10.0 10.000 1210 2470 1450 2730 1760 3150 1410 2860 1600 3270 2110 3640

1-1/8

8.9 11.250 1480 3120 1810 3460 2220 3980 1720 3630 2020 4180 2720 4630

1-1/4

8.0 12.500 1670 3850 2140 4270 2700 4920 1950 4480 2460 5130 3350 5700

1

11 5 11.500 1190 2470 1410 2730 1680 3150 1390 2860 1520 3270 1990 3640

11-1/2 1-1/8 10.2 12.938 1490 3120 1780 3460 2150 3980 1740 3630 1960 4180 2580 4630 1-1/4

9.2 14.375 1780 3850 2160 4270 2640 4920 2080 4480 2400 5130 3220 5700

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AREMA Manual for Railway Engineering

Design of Wood Railway Bridges and Trestles for Railway Loading

1 12

Parallel to Grain, P

Perpendicular to Grain, Q

Group 3 Ash, White; Group 2 Beech, Elm, Soft; Birch, Elm, Gum, Black Rock; and Red; Maple, Tupelo Hard; Oak, Red, White Parallel to Grain, P

Parallel to Grain, P

Group 1 Chestnut

Perpendicular to Grain, Q

Parallel to Grain, P

Perpendicular to Grain, Q

Parallel to Grain, P

Group 2 Group 3 Cedar, Port Cypress, Orford and Southern; Western Douglas Fir, Red; Coast; Pine, Douglas Fir, Southern; Inland Redwood Perpendicular to Grain, Q

Parallel to Grain, P

Group 1 Hemlock, Eastern

Hardwoods (Broad Leaved)

Perpendicular to Grain, Q

Softwoods (Conifers)

Perpendicular to Grain, Q

Projected Area of Bolt, square inches

L/D

Diameter of Bolt, inches

Length of Bolt in Main Member L, inches

Table 7-2-13. Bearing Value for Bolts (Continued) Allowable Load per Bolt for Timber Bearing on Common Bolts with Wood Side Plates (For timber occasionally wet but quickly dried.)

12.0 12.000 1180 2470 1390 2730 1630 3150 1370 2860 1490 3270 1940 3650

1-1/8 10.7 13.500 1470 3120 1750 3460 2110 3980 1710 3630 1920 4180 2520 4630 1-1/4

9.6 15.000 1780 3850 2150 4270 2610 4920 2080 4480 2380 5130 3160 5700

1

References, Vol. 51, 1950, p. 433; Vol. 52, 1951, pp. 428, 847. Table 7-2-13 tabulated values are for joints when two wood side plates are used, each side plate one-half the thickness of the main member: a. If either side plate is thicker than one-half the thickness of the main member, no increase in the tabulated value is permissible. b. When one or both side plates are thinner than one-half the thickness of the main member, use tabulated value indicated for a main member twice as thick as the thinnest side plate. c. When a joint consists of two members only (bolt in single shear) of equal thickness, use one-half the tabulated value for a main member twice the thickness of one of the members. d. When a joint consists of two members only of unequal thickness, use one-half the tabulated value for a main member twice as thick as the thinnest member.

3

4

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Timber Structures

2.5.13 CONNECTORS (1988) Where metal connectors are used, working values may be taken as those recommended in the National Design Specification.

2.5.14 ROUND SECTIONS (1988) a.

The strength, stiffness, and horizontal shearing value in bending of round timbers of any species may be assumed to be identical with that of square timbers of the same grade and cross-sectional area. Tapered timbers should be assumed as of uniform diameter, the point of measurement being one-third the span from the small end, but the diameter should not be assumed to be more than 1-1/2 times the small end diameter.

b. The strength of round columns may be considered the same as that of square columns of the same crosssectional area. In long tapered columns the strength may be assumed as identical with that of a square column of the same length, and of cross-sectional area equal to that of the round timber measured at a point one-third its length from the small end. The stress at the small end must not exceed the allowable stress for short columns.

SECTION 2.6 DETAILS OF DESIGN 2.6.1 GENERAL (1988) All members shall be framed, anchored, tied and braced to develop the strength and rigidity necessary for the purposes intended.

2.6.2 NET SECTION (1988) All stress computations shall be based on actual size of timbers. Where members are dapped or otherwise framed to materially reduce the effective size, the net section of the piece shall be used.

2.6.3 BOLTED CONNECTIONS (1988) a.

The center to center distance along the grain between bolts acting parallel with the grain shall be not less than four times the bolt diameter.

b. The tension area remaining at the critical section should be at least 80 percent of the total area in bearing under all bolts for coniferous woods; 100 percent for hardwoods. c.

In a tension joint, the distance from the end of the timber to the center of nearest bolt shall be not less than seven times the bolt diameter for coniferous woods; five times for hardwoods. For compression stress, this end distance need be only four times the bolt diameter.

d. For loads acting perpendicular to the grain, the distance between the edge toward which the bolt pressure is acting, and the center of the bolt nearest this edge, should be not less than four times the bolt diameter.

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7-2-38

AREMA Manual for Railway Engineering

Design of Wood Railway Bridges and Trestles for Railway Loading

2.6.4 NOTCHED BEAMS (1988) The allowable end reaction for beams with square-cornered notches at the ends shall be computed by the following formula: 2

2 bc q V = --- ------------d 3 where: b = Width c = Depth above the notch d = Total depth of beam q = Working unit stress in horizontal shear V = Allowable end reaction

SECTION 2.7 RECOMMENDED PRACTICE FOR DESIGN OF WOOD CULVERTS1 (1962)

1

(Reapproved with revisions 1962) 2.7.1 WOOD CULVERTS (1988) For the recommended practice for design of wood culverts refer to Figure 7-A3-79 and Table 7-A3-10 (See Appendix 3 - Legacy Designs).

3

2.7.2 GENERAL NOTES (1988) a.

Timber culverts should be constructed of pressure-treated timber conforming to AREMA specifications for structural timber.

b. Timbers with appreciable warp, particularly wall timbers should not be used. c.

4

Timbers should be cut to length and bored before treatment.

d. Surfaces of treated timber unavoidably cut or damaged in construction should be field treated with two coats of hot creosote oil and one coat of hot sealing compound or equal. Holes unavoidably bored in the field in treated timber should be thoroughly saturated with hot creosote oil and the fastener immediately placed.

1

e.

Protective coatings or galvanizing of metal fastenings should conform to recommendations for “use of protective coatings for iron and steel fastenings for wood bridges,” miscellaneous part, this chapter. Spikes or fasteners should be dipped in a preservative before driving.

f.

Lock nut or spring washer should be used on all bolts, and nuts tightened securely.

References, Vol. 52, 1951, pp. 436, 849; Vol. 53, 1952, pp. 635, 1023; Vol. 61, 1960, pp. 587, 1095; Vol. 63, 1962, pp. 455, 684; Vol. 89, 1988, p. 106.

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Timber Structures

g.

Backfilling of culverts should be built up uniformly on both sides, and embankment constructed in layers, well compacted in accordance with best practice.

2.7.3 DESIGN DATA (TANGENT TRACK) (1988) a.

Live Load. Cooper E72 Loading, Axle loads distributed uniformly over a distance of 5¢ -0² parallel to track, and uniformly over a distance equal to length of tie plus depth of fill under ties perpendicular to track.

b. Dead Load. Assumed weight of materials follows:

c.

Track rails and fastenings:

200 lb per linear foot of track

Earth fill and ballast:

120 lb per cubic foot

Timber:

60 lb per cubic foot

Lateral Earth Pressure. Active earth pressure equal to: 0.286w (h + h¢ ) where: w = 120 lb per cubic foot h = depth below base of rail h¢ = live load surcharge

d. Timber Sections. Full nominal dimensions without reduction for bolt holes. e.

Unit Working Stresses. For allowable unit working stresses for timber see specifications for design this Chapter.

SECTION 2.8 RECOMMENDED PRACTICE FOR SIMPLE STRESS LAMINATED DECK PANELS 2.8.1 MATERIAL (2000) 2.8.1.1 Wood Laminates a.

Shall be Douglas Fir, Southern Pine or Red Oak No. 2 or better as per AREMA Manual for Railway Engineering, Chapter 7, Timber Structures.

b. Shall be 5” thick or less, rough sawn to full size and surfaced on one side (S1S) to ensure uniform thickness throughout its length. c.

Laminate width shall equal the deck thickness, T in accordance with Table 7-A1-4 having selected the design Cooper’s E loading and the span length based on the allowable stresses for the material to be used.

d. Shall be predrilled for prestressing bars and trimmed prior to treatment. © 2011, American Railway Engineering and Maintenance-of-Way Association

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AREMA Manual for Railway Engineering

Design of Wood Railway Bridges and Trestles for Railway Loading

e.

Hole spacing (SP) shall be in accordance with the ranges shown on Table 7-2-14 having selected a deck thickness (T). Bar spacing should also consider conflicts with other structural components such as walkway support brackets. Table 7-2-14. Spacing of Prestressing Bar, SP (Inches) 1” DIA BAR (As=0.85 SQ.IN.)

THICKNESS OF PANEL, T

1-1/4” DIA BAR (As=1.25 SQ.IN.)

MAX.

MIN.

MAX.

MIN.

12”

74

44

--

--

14”

64

38

94

56

16”

56

33

82

49

Max. based on Ni=100psi SP = (As x 0.70 x Fpu)/(Ni x T)

(1)

Min. based on max. wood/steel ratio of 0.0016 SP = As/(T x 0.0016)

(2)

f.

Predrilled hole diameter shall be twice the diameter of the prestressing bar to be used, but shall not exceed 20% of the width of the laminates.

g.

Trimming shall be done in a way which would ensure maximum full face contact between laminate members.

h. Shall be treated with 100% creosote in a clean treatment process as per AREMA Manual for Railway Engineering, Chapter 30, Ties. i.

Additional material shall be procured to allow for rejection of unsuitable pieces (up to 5% of total).

j.

All field holes and cuts in treated wood must be treated with preservative.

2.8.1.2 Prestressing Bars a.

3

4

Shall be galvanized grade 150 ksi dywidag bars or approved equal in accordance with the latest issue ASTM A-722.

b. Shall be sized in accordance with Table 7-2-14 having selected the deck thickness, T and bar spacing, SP then checked for tensile strength. However, the steel-wood area ratio must not exceed 0.0016 (as per the Ontario Highway Bridge Design Code). c.

1

The required tensile load, P is determined by dividing the cross-sectional area of the bar, As into the required prestressing force Fps (i.e. P = Fps/As). Fps is the product of the initial lamination stress, Ni (from Table 7-A1-4) in psi and the bar spacing, SP and deck thickness, T both in inches (i.e. Fps – Ni x SP x T).

d. The required tensile load, P must not exceed 89,250 lbs and 131,250 lbs for 1” dia. And 1 ¼” dia. Bars respectively. If the required tensile load, P is greater than that permitted, a larger bar size or closer bar spacing must be used.

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AREMA Manual for Railway Engineering

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Timber Structures

e.

If bar ends are cut, they shall be coated with two coats of zinc rich paint or an approved equal.

f.

Do not weld on or near prestressing bars or use them as ground connections.

g.

Use nylon or rope slings for handling and transport of prestressing bars.

h. Do not use prestressing bars to lift or move the deck panel. i.

Bars damaged during shipment shall be rejected and replaced with new bars.

2.8.1.3 Anchorage System a.

Structural steel shall conform to the current ASTM A36 specifications.

b. Decks up to 16” in depth shall have a bulkhead channel or bearing plate anchorage configuration. Decks over 16” in depth shall have only a bearing plate anchorage configuration. c.

Channel sizes are to be in accordance with Table 7-2-15. Table 7-2-15. Bulkhead Channel Sizes THICKNESS OF PANEL, T

RECOMMENDED DEPTH OF (IMPERIAL) CHANNEL, Dc

Tw, WEB THICKNESS

11”

C10 X 25

10”

0.53”

12” – 14”

C12 X 30

12”

0.51”

15” – 16“

C15 X 40

15”

0.52”

d. Anchor plate sizes for bulkhead channel anchorage configurations shall be in accordance with Table 7-2-16.

Table 7-2-16. Bearing Plates Sizes For Channel Bulkhead Anchorage Configuration THICKNESS OF PANEL, T

WIDTH Wp

LENGTH Lp

THICKNESS Tp

12”

9”

9” – 18”

Lp/12

14”

9”

9” – 18”

Lp/12

16”

12”

12” – 24”

Lp/12

Select a plate length, then check that effective bearing area is sufficient to prevent crushing of the laminates (i.e. fc+ < F¢ c+ where F¢ c+ = 375 psi and + indicates perpendicular to the grain of the material). For Douglas Fir fc+ can be determined as follows: fc+ = (Ni x SP x T)/Dc(Lp+2Tw)(3) Where Ni, SP, T, Dc and Tw are all known from prior design steps. e.

Bearing plates sizes for bearing plate anchorage configurations shall be in accordance with Table 7-2-17.

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-2-42

AREMA Manual for Railway Engineering

Design of Wood Railway Bridges and Trestles for Railway Loading

Table 7-2-17. Bearing Plates Sizes For Bearing Plate Anchorage Configuration THICKNESS OF PANEL, T

WIDTH Wp

LENGTH Lp

THICKNESS Tp

12”

10”

10” – 20”

SEE BELOW

14”

12”

12” – 24”

“

“

16”

14”

14” – 28”

“

“

Select a plate length, then check that plate bearing area is sufficient to prevent crushing of the laminates (i.e. fc+ < F¢ c+ where F¢ c+ = 375 psi and + indicates perpendicular to the grain of the material). For Douglas Fir fc+ can be determined as follows fc+ = (Ni x SP x T)/(Lp x Wp)(4) Where Ni, SP and T are all known from prior design steps. Actual plate thickness, Tp is based on the use of a 6” x 6” x 1” anchorage plate and can be determined as follows: Tp = square root of [(3 x (Tn x SP x T) x k x k)/Fb](5) Where Ni, SP and T are all known from prior design steps, Fb – 24,200 psi for 44W steel and k is the greater of (Wp-6)/2 or (Lp-6)/2

1

f.

Channel bulkhead anchorage, bearing plates, high strength steel nuts and other fasteners to be hot dip galvanized to latest issue of ASTM 123 after fabrication.

3

2.8.1.4 Waterproofing a.

Waterproofing shall cover the entire top surface of each panel

b. Consideration shall be given to facilitate drainage to the curb sides. c.

4

The membrane shall be placed only after the second prestressing has occurred.

d. Coat all anchorage nuts to protect against corrosion. e.

Each panel shall be supplied with drain holes through its curb on each side at span one-third points.

2.8.2 FABRICATION (2000) 2.8.2.1 Panel Assembly a.

Panels may be assembled in a shop or on site in a staging area. In place assembly on active lines will not be permitted as a panel cannot be placed into service until after the second prestressing.

b. A temporary support shall be constructed from timber and blocking to provide a level plane on which the panel may be assembled.

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Timber Structures

c.

Laminates shall be oriented with their crown up, bottoms even at the bearing ends and the predrilled holes aligned. Alternate laminates shall be flipped and turned end for end to allow for the inaccuracy of milling. An 18” steel dowel, with a diameter larger than the selected prestressing bar diameter, can be used to align the holes. Laminates may be nailed together temporarily to hold their position prior to prestressing.

d. Prestressing bars shall be fed through the holes as assembly of laminates progresses thus ensuring passage of the bars through the laminates. e.

Once all laminates and bars are in place, bulkhead channels (when used), bearing anchor plates and nuts are applied at the ends of each bar.

f.

Stressing of the panel shall be from one side only. Bars are adjusted to project 5” on the anchored side and 12” or more on the stressing side to permit connection of the hydraulic jack(s).

g.

Tighten all anchorage nuts with a pipe wrench prior to prestressing.

h. Do not stress bars until all bars within a span have been installed complete with the selected anchorage system and tightened with hand tools. i.

Stressing operations must be supervised by a qualified individual.

2.8.2.2 Stressing Equipment a.

60 ton hydraulic hollow core jacks (single or multiple jacks) may be used for prestressing.

b. Appropriate pull coupler suited to the selected prestressing bar size (one per jack). c.

Prefabricated jack chair (one per jack) to allow tightening of the anchorage nut with an open end wrench.

d. Jack chairs and wrench are not required if the jack is equipped with a built-in ratchet. e.

Hydraulic pump with reservoir sufficient to supply all jacks that will be used simultaneously.

f.

Hoses and manifolds to connect all jacks to the hydraulic pumps.

2.8.2.3 Prestressing Procedures a.

Stressing Sequence (1) First stressing can be executed on completion of assembly. Stress the deck panel fully to 100% Ni, the initial design in psi for the panel as per Table 7-A1-4. After the first stressing, bar projections may be cut back using a cutoff saw to the minimum required to re-attach a jack but no shorter than 5”. (2) Second stressing to be conducted one week after the initial stressing. Again stress fully to 100% Ni. After second stressing and upon acceptance of the bars by the Engineer, apply corrosion protection material, grease caps and galvanize lock nuts. Water proofing membrane and curb timbers may now be applied. (3) Final stressing to be conducted 4 to 6 weeks after the second stressing (5 to 7 weeks after assembly). Again stress fully to 100% Ni. Do not stress while panel is under live load conditions.

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7-2-44

AREMA Manual for Railway Engineering

Design of Wood Railway Bridges and Trestles for Railway Loading

(4) Stress levels shall be periodically checked as part of an ongoing maintenance program. Bars shall be re-stressed when stress levels approach N, the minimum stress in pounds required for the panel to perform adequately per Table 7-A1-4. b. Prestressing force required (Fps) is the stress that is applied to each of the bars in order to stress the laminates fully to 100% Ni Fps = Ni x SP x T(6) Where SP is the selected spacing of bars, T is the selected deck thickness and Ni is the initial stress required between laminations as per Table 7-A1-4. c.

Stressing Methods (1) Single Jack Method • Attach the jack to the left most bar and stress the bar to the appropriate level using the pump. • Tighten the nut using an open end wrench through the opening of the jack chair or by using the built-in ratchet if so equipped. • Release pressure, remove jack and attach it to the next bar to the right. Repeat this procedure until all bars are stressed. • Starting again at the left most bar repeat the entire procedure three additional times to achieve a uniform stress throughout the panel.

1

(2) Multiple Jack Method 1 (number of jacks = number of bars in one panel) • Connect all jacks to one pump. • Attach one jack assembly to each bar and stress all bars to the appropriate level at the same time using the pump.

3

• Tighten each nut using an open end wrench through the opening of the jack chair or by using the built-in ratchet if so equipped.

4

• Release pressure, remove jacks, stressing is complete. (3) Multiple Jack Method 2 (number of jacks < number of bars in one panel) • Connect all jacks to one pump. • Attach one jack assembly to a bar starting from the left most bar in the panel and stress these bars to the appropriate level at the same time by using the pump. • Tighten each nut using an open end wrench through the opening of the jack chair or by using the built-in ratchet if so equipped. • Release pressure, remove all but the right most jack and move them to the bars on the right side of the jack remaining in place. Repeat the procedure until the entire span is stressed.

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AREMA Manual for Railway Engineering

7-2-45

Timber Structures 2.8.2.4 Stressing Record a.

Record date of each stressing.

b. Record elongation of bars resulting from stressing. 2.8.2.5 Stressing Safety a.

Pull couplers for stressing jack must be evenly and fully engaged to the bar projection prior to the application of stress.

b. When stressing above grade, a safety rope must be used to secure jack and pull rod to the structure. c.

A warning sign must be posted in the area affected by stressing.

d. Never stand behind a jack while stressing or while removing the jack from a stressed bar. Do not stand on hoses while stressing. e.

Pump must be connected to a proper power source with approved connection. Prior to stressing bars cycle jacks(s) several times to check for leaks and to eliminate air from the system.

2.8.2.6 Handling Panels a.

Handle the panels with extreme care to avoid damage to laminates and other components. Do not use steel chains or cables if possible.

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Part 3 Rating Existing Wood Bridges and Trestles — 2010 — TABLE OF CONTENTS

Section/Article

Description

3.1 Rules for Rating Existing Wood Bridges and Trestles . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.1 Classification (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.2 General (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.3 Carrying Capacity (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.4 Inspection (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.5 Computation of Stresses (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.6 Loads and Forces (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.7 Dead Load (1988). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.8 Live Load (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.9 Impact (1988). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.10 Centrifugal Force (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.11 Other Lateral Forces (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.12 Longitudinal Force (1988). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.13 Combined Stresses (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.14 Unit Stresses (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.15 Chord Deflection (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.16 Composite Trusses (1988). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.17 Action to be Taken (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Page 7-3-2 7-3-2 7-3-2 7-3-2 7-3-2 7-3-3 7-3-3 7-3-3 7-3-3 7-3-3 7-3-4 7-3-4 7-3-4 7-3-4 7-3-4 7-3-5 7-3-5 7-3-6

LIST OF TABLES Figure 7-3-1

Description Unit Stresses for Rating. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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3

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SECTION 3.1 RULES FOR RATING EXISTING WOOD BRIDGES AND TRESTLES1 3.1.1 CLASSIFICATION (1988) Wood railway bridges and trestles shall be classified according to their rated carrying capacity as determined by the rules specified herein. The work of classifying bridges shall be as described in Chapter 15, Steel Structures, Part 7, Existing Bridges.

3.1.2 GENERAL (1988) Except as otherwise provided in these rules, the recommendations in this part shall govern.

3.1.3 CARRYING CAPACITY (1988) The carrying capacity of a bridge shall be determined by the computation of stresses based on authentic records of the design, details, species and grade of wood, materials, workmanship, and physical condition, including data obtained by inspection. If deemed advisable, field determination of stresses shall be made and the results given due consideration in the final assignment of the carrying capacity. For a specific service the location and behavior under load shall be taken into account.

3.1.4 INSPECTION (2010) An inspection of the bridge shall be made to determine: a.

Whether the actual sections and details conform to the drawings. Where actual sections and details do not conform to the drawings the differences shall be noted in detail; of special importance are the number and spacing of piles, size of cap, height of bents, length of panels, size and number of stringers, positioning of stringer joints on caps, whether stringers are continuous over bents, size and spacing of ties, and size and location of sway and longitudinal bracing on bents, if any.

b. Any additions to the dead load not shown on the plan, such as heavier deck or rail, walks, pipelines, conduits, signal devices, and wire supports. c.

The position of the track with respect to the center line of the bridge.

d. Any loss of wood due to decay and wear. This determination should be made by increment borings. e.

The physical condition, noting such conditions as loose bolts and excessive checks or splits.

f.

The condition of all points of bearing.

g.

The condition of bents, especially at the ground line and cap connection.

h. An inspection of the bridge shall be made to determine evidence of excessive deflection (c.f. Article 3.1.15), lateral movement, or longitudinal movement that may necessitate immediate closure of the structure to traffic. Stability of the structure as a whole as well as its parts must be assured under live load.

1

References, Vol. 63, 1962, pp. 456, 687; Vol. 89, 1988, p. 106.

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3.1.5 COMPUTATION OF STRESSES (1988) The computation of stresses shall be made for the details as well as for the main members, giving particular attention to: a.

The increased load carried by a stringer, cap, floor member, or truss due to eccentricity of the load. This applies to bridges on tangent where the tracks are off center as well as to bridges on curves.

b. Spacing of bents. c.

Continuity occurring in stringers. Where the support under a rail consists of three or more stringers assembled as a chord, or otherwise acting in unison, and extending over two spans with staggered joints, a partially continuous beam action may be assumed to exist, and the computations may be made for stringers based on the average stress as determined from single beam analysis and that for a fully continuous condition.

3.1.6 LOADS AND FORCES (1988) Stresses shall be computed for the following loads and forces: a.

Dead Load.

b. Live Load.

1 c.

Impact.

d. Centrifugal force. e.

Other lateral forces.

f.

Longitudinal force.

3

3.1.7 DEAD LOAD (1988) The dead load shall be the weight of the bridge including the deck and track, together with any other fixed loads.

4

3.1.8 LIVE LOAD (1988) a.

The live load shall be one of the Cooper E series, other standard loading, or a load consisting of a specific locomotive or other equipment, depending on the purpose for which the rating is desired.

b. If the live load is to be a specific locomotive and cars (or other equipment), complete data shall be obtained, including the spacing of axles and the static load on each axle. This data shall be used to convert the specific locomotive and cars (or other equipment) to equivalent standard loading for the various span lengths of the bridges being rated.

3.1.9 IMPACT (1988) The dynamic increment of load due to the effects of speed, roll and track irregularities is not well established for timber structures. Its total effect is estimated to be less than the increased strength of timber for the short

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cumulative duration of loading to which railroad bridges are subjected in service, and is taken into consideration in the derivation of allowable working stresses for design.

3.1.10 CENTRIFUGAL FORCE (1988) Centrifugal force shall be determined as specified in Article 2.3.4.

3.1.11 OTHER LATERAL FORCES (1988) Other lateral forces shall be determined as specified in Article 2.3.5, except that the wind force shall be taken as not exceeding two-thirds of the forces shown and the nosing load shall be taken as 1/16 the weight of one locomotive without tender, both applied as stated. Due to their limited duration, wind forces may be ignored in the rating of pile or frame trestles where the bridge is geographically located in an area not normally exposed to winds of exceptional magnitude.

3.1.12 LONGITUDINAL FORCE (1988) Longitudinal force shall be determined as specified in Article 2.3.5.4.

3.1.13 COMBINED STRESSES (1988) For stresses produced by longitudinal or other lateral forces, or by a combination of these forces with dead and live loads and centrifugal force, the allowable rating stresses may be twice the working unit stress shown in Table 7-2-9, provided the stress resulting from dead and live loads and centrifugal force only does not exceed the rating unit stress established in Article 3.1.14.

3.1.14 UNIT STRESSES (2010) a.

Loading beyond Design Load without careful regular inspection is not recommended. Frequent loading beyond the Design Load shortens the useful life considerably. Recommendations in this Article assume the structural connections are tight and structure geometry is correct.

b. The permissible unit stresses for rating resulting from dead and live loads and centrifugal force for structures inspected in accordance with Article 3.1.4 are shown in Table 7-3-1, to be used without allowance for impact due to live load.

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Rating Existing Wood Bridges and Trestles Table 7-3-1. Unit Stresses for Rating

Description f=

unit stress in extreme fiber in bending, in pounds per square inch

All other unit stresses E=

modulus of elasticity, in thousands of pounds per square inch.

where: k= Fh =

Equipment or Regularly Assigned Locomotives Not Equipment or Regularly Assigned Locomotives 1.3 kFh

1.1 kFh

1.3 k

1.1 k

As shown in Table 7-2-9

Unit Stress for Structural Lumber Subject to Railway Loading, Section 2.5, Allowable Unit Stresses for Stress-Graded Lumber. depth factor. 2

=

H + 143 0.81 -----------------------2 H + 88 where:

c.

H is the depth of the beam. For H of 16 inches or less, Fh = 1 may be used.

For structures inspected with a full tactile inspection by qualified timber inspectors, the permissible stress for regularly assigned equipment or locomotives may be increased from 1.1 to 1.2 kFh for bending and 1.2k for all other stresses. This does not apply to caps or similar non-load sharing members, and does not apply to members with end splits.

1

d. If the actual section modulus or cross-section area is less than 75% of that for which the Rating was calculated, a new Rating using the revised properties must be made.

3

e.

For unit stress in compression parallel to grain for columns with L/d ratio greater than 11, see Article 2.3.2.

f.

Where the grade of timber actually in use in any structure is not definitely known, k shall be assumed as 1.0 times the minimum grade shown in Table 7-2-9 for the species used, for timbers usually used in stress grades.

g.

If a structure fails to qualify under the foregoing permissible stresses for equipment or locomotives not regularly assigned, then speed may be restricted to not to exceed 10 mph and the members recomputed with the k coefficient increased 15 percent.

4

3.1.15 CHORD DEFLECTION (2009) Measured net chord deflection (inches) under live load should not exceed L/250, where L is the span length in inches.

3.1.16 COMPOSITE TRUSSES (1988) For trusses composed of both wood and steel or iron members, the metal portions shall be rated using stresses as specified in the Rules for Rating Existing Steel Bridges, Chapter 15, Steel Structures; Part 7, Existing Bridges.

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3.1.17 ACTION TO BE TAKEN (1988) If the stresses exceed those permissible under these rules, the loading shall be restricted so that the permissible stresses will not be exceeded until the indicated remedial work has been done. The remedial work in general will consist of replacing defective parts, adding posts or piles to bents where required, or placing additional stringers. When the permissible stresses are closely approached, or when the physical condition of the main members or the details are not good, the bridge shall be kept under frequent inspection as long as it is continued in service.

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Part 4 Construction and Maintenance of Timber Structures — 2011 — TABLE OF CONTENTS

Section/Article

Description

Page

4.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1.1 Upgrading and Rehabilitating Timber Structures (1995). . . . . . . . . . . . . . . . . . . . . . . . . .

7-4-2 7-4-2

4.2 Handling of Material (1995). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-4-3

4.3 Storage of Material (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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4.4 Workmanship for Construction of Pile and Framed Trestles . . . . . . . . . . . . . . . . . . . .

7-4-3

4.5 Framing of Timber (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-4-4

4.6 Substructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6.1 Pile Posting, or Replacing Defective Portions of Piles (1995) . . . . . . . . . . . . . . . . . . . . . . 4.6.2 Driving Timber Piles (1984) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-4-5 7-4-5 7-4-6

4.7 Superstructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-4-14

4.8 Support, Repair, Preserve, or Replace Damaged Portions of the Structure (2010) . . 4.8.1 Control Moisture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.8.2 Field Application of Preservative Chemicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-4-14 7-4-18 7-4-18

4.9 Methods of Fireproofing Wood Bridges and Trestles . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.9.1 Foreword (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.9.2 Metal Protection (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.9.3 Coatings (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.9.4 Impregnation (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.9.5 Fire Alarm Systems (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.9.6 Housekeeping (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.9.7 Fire Barriers (2011). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-4-18 7-4-18 7-4-18 7-4-19 7-4-19 7-4-19 7-4-19 7-4-19

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TABLE OF CONTENTS (CONT) Section/Article

Description

Page

4.10 Use of Guard Rails and Guard Timbers (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.10.1 Field Side Guard or Spacer Timbers (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.10.2 Metal Gage Side Guard Rails (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.10.3 Combined Use of Guard Timbers and Guard Rails (1988). . . . . . . . . . . . . . . . . . . . . . . . .

7-4-20 7-4-20 7-4-20 7-4-21

4.11 Typical Plans for Timber Railway Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.11.1 Plans (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.11.2 General Notes (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-4-21 7-4-21 7-4-21

LIST OF FIGURES Figure 7-4-1 7-4-2 7-4-3 7-4-4 7-4-5 7-4-6 7-4-7 7-4-8 7-4-9

Description

Page

Schematic Diagram of Pile Posting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sample Pile Record Form . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Splicing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Scabbing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pile Restoration Using Cast in Place Reinforced Concrete Jacket. . . . . . . . . . . . . . . . . . . . . . . Filling Voids with Grout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Clamping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stitching. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Earth Fill Break in a Long Trestle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-4-6 7-4-13 7-4-14 7-4-14 7-4-15 7-4-16 7-4-17 7-4-17 7-4-20

LIST OF TABLES Table 7-4-1

Description

Page

Recommended Practice Plans. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-4-23

SECTION 4.1 GENERAL 4.1.1 UPGRADING AND REHABILITATING TIMBER STRUCTURES (1995) Replacement in kind must be adequate for current and anticipated traffic. a.

Existing timber members may be replaced with timber of increased section or strength. Additional timber members may be placed to increase capacity.

b. Timber Open Decks may be replaced by Timber Ballast Decks, in accordance with Part 2, Design of Wood Railway Bridges and Trestles for Railway Loading. c.

Timber bridges may be upgraded or rehabilitated by replacing caps, stringers or decking with concrete or steel in accordance with Chapter 8, Concrete Structures and Foundations or Chapter 15, Steel Structures respectively of this Manual while leaving existing timber piling in place for structure support.

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SECTION 4.2 HANDLING OF MATERIAL (1995) a.

All material should be handled to avoid structural damage or unnecessary disfiguring.

b. Piling or timber that has been treated with preservatives should be handled with extreme care in unloading and assembling to avoid damage to the timber which would expose untreated wood. These materials shall be preferably handled with rope slings. Sharp-pointed bars, peavies, hooks, tongs or similar tools shall not be used, except as approved by the Engineer.

SECTION 4.3 STORAGE OF MATERIAL (1995) a.

Materials should be stored at the site in a neat manner at proper clearance to operated tracks.

b. Care should be exercised to prevent fires in material held in storage. The ground underneath and in the vicinity of piling and lumber should be scalped and cleared of all weeds, rubbish and combustible material. c.

Treated lumber should be close-stacked in a manner that will prevent long timbers or preframed material from sagging or becoming crooked.

d. Untreated lumber should be open-stacked on suitable skids at least 1 foot above the ground and above possible high water; it should be piled in a manner to shed water and to prevent warping. When required, it shall be protected from the weather by suitable covering. e.

Piling should be stacked in a manner to prevent excessive bending.

f.

Hardware received at the job site should be protected from corrosion by storing under cover or by a protective coating.

SECTION 4.4 WORKMANSHIP FOR CONSTRUCTION OF PILE AND FRAMED TRESTLES1

Trestles constructed under this recommended practice should be built complete, ready for the laying of track rails, in a workmanlike manner, in strict accordance with the plans and the intent of this recommended practice.

b. It is presumed that the design of structures to which this recommended practice attaches is in accordance with prevailing practice, and, more specifically, in general accordance with, Part 2, Design of Wood Railway Bridges and Trestles for Railway Loading. c.

1

Nothing contained herein shall be construed as superseding details or notations shown on design drawings. Where this recommended practice conflicts with the drawings, the drawings will govern.

References, Vol. 8, 1907, pp. 397, 442; Vol. 35, 1934, pp. 998, 1176; Vol. 36, 1935, pp. 781, 1009; Vol. 54, 1953, pp. 942, 1329; Vol. 61, 1960, pp. 587, 1095; Vol. 89, 1988, p. 106.

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4

This section covers workmanship for the construction of pile or framed trestles carrying railway traffic. a.

1

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d. Workmanship should be of the best quality in each class of work. Competent bridge carpenters shall be employed and all framing shall be true and exact. No blocking or shimming will be permitted, except as otherwise provided herein. e.

On completion of the work, all surplus material or material salvaged from an existing structure should be removed from the premises as directed. Material not salvageable and other refuse should be properly disposed of. Premises shall be left in a clean, neat and orderly condition.

SECTION 4.5 FRAMING OF TIMBER (1988) a.

All cutting, framing, and boring of timbers to be treated, shall be done before treatment unless otherwise shown on the plans or specifically permitted by the Chief Engineer.

b. All cuts or abrasions made in or suffered by treated lumber shall be carefully trimmed and then field treated by the application of two saturating coats of hot creosote oil. All holes bored in treated material shall be field treated with hot creosote oil under pressure, using an approved type of bolt hole treater, in such a manner that the entire surface of the hole receives thorough penetration. All countersunk recesses for bolts which would form pockets to retain water shall be treated as for cuts and then filled with a suitable mastic after the bolt is placed. c.

Sills shall have a true and even bearing on foundation piles, timber grillages, mats or pedestals. All earth shall be removed from around sills so that there will be free air circulation around them.

d. Posts in framed bents shall be sawed to proper length (vertical or batter) and shall have an even bearing on caps and sills. e.

Caps shall be sized to a uniform depth and placed to a uniform and even bearing on piles or posts.

f.

Sash and sway bracing, tower bracing and girts shall bear firmly against the piles or timber to which secured. When necessary, filler shall be placed to avoid bending the bracing more than 1 inch out of line when the bracing bolts or other fastenings are drawn up tight. Built-up fillers will not be permitted and each filler shall be a single piece of creosoted lumber of like kind to that in the brace with a width of not less than 6 inches and a length of not less than 12 inches.

g.

Stringers shall be sized to provide a uniform depth and even bearing at supports. They shall be assembled in the structure according to plans.

h. Ties shall be sized and spaced in accordance with the plans. i.

Guard timbers shall be framed in accordance with the plans and laid to line and uniform top surface.

j.

Deck plank and ballast retainers on ballasted deck trestles shall be placed in accordance with the plans. Drainage shall be provided for in the manner specified.

k. Bulkheads at the ends of trestles shall be of sufficient height and width to retain properly the shoulders of embankments and to provide a berm sufficient to prevent loss of embankment from beneath the bulkhead. When necessary, special anchorage, such as bulkhead piles or dead-men buried in the embankment, shall be provided to support the bulkhead.

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l.

Refuse platforms, water barrels platforms, footwalks, motor car set-off or other special platforms shall be in accordance with the plans.

m. All fastenings, including bolts, dowels, lag screws, timber connectors and other type fastenings shall be placed in accordance with the plans, drawn up securely, and on completion of the structure shall be retightened. Unless otherwise shown on the plans, holes for dowels and drift bolts shall be bored 1/16 inch smaller than the nominal diameter of the dowel or bolt used; holes shall not be bored deeper than the length of the dowel or bolt. Holes for machine bolts and rods other than dowels and drift bolts shall be bored the same size as the nominal diameter of the bolt or rod used. Holes for lag screws shall be bored with a bit not larger than the body of the screw at the base of the thread. n. Screw-type fastenings shall be screwed into place for the entire length of the fastening. Driving with a maul or other tool will not be permitted. o.

Timber connectors shall be of the types specified on the plans. Split-ring and shear-plate connectors shall be installed in pre-cut grooves of the dimensions shown on the plans or as recommended by the manufacturer. Toothed-ring and spike-grid connectors, and clamping plates, shall be forced into the contact surfaces of the timbers joined by means of proper pressure tools; all connectors of these types at any joint shall be embedded simultaneously and uniformly.

SECTION 4.6 SUBSTRUCTURE

1

4.6.1 PILE POSTING, OR REPLACING DEFECTIVE PORTIONS OF PILES (1995) Pile Posting, or replacing defective portions of piles should be performed as follows: a.

Posting of the outside piles should not be permitted on bridges on curves where bents exceed 12 feet in height or on tangents where bents are over 23 feet in height.

3

b. Posting of 1 pile in a 4 pile bent, 2 piles in a 5 pile bent or 3 piles in a six or seven pile bent should be permitted. c.

No more than two posted piles should be adjacent to each other.

d. Bents should be framed or replaced in their entirety with suitable longitudinal and lateral bracing if more than the allowable number of piles or more than two consecutive piles need posting. e.

Posting may be accomplished per Figure 7-4-1.

f.

Where piles are decayed at the top, they may be cut off and double capped; a single pile may be corbeled.

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4

Timber Structures

Figure 7-4-1. Schematic Diagram of Pile Posting

4.6.2 DRIVING TIMBER PILES1 (1984) 4.6.2.1 Scope (1990) This specification covers the driving of wood piles in trestles, foundations, and for protection work.2 4.6.2.2 Tests (1990) In the absence of other reliable information to determine pile lengths, a thorough exploration shall be made at the site by borings, driving test piles, or by pile loading tests, prior to the selection of the length of piles for the work, and to determine characteristics incident to pile resistance and penetration. 4.6.2.3 Materials (1990) The kinds of wood, physical requirements, dimensions, and manufacture are specified in Part 1, Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Timber Bridge Ties

1

References, Vol. 12, 1911, part 1, pp. 279, 307; Vol. 16, 1915, pp. 894, 1181; Vol. 41, 1940, pp. 326, 864; Vol. 54, 1953, pp. 943, 1329; Vol. 62, 1961, pp. 513, 848; Vol. 89, 1988, p. 106; Vol. 91, 1990, p. 57. 2 For the driving of concrete piles and steel piles, and for information on loading tests, see Chapter 8, Concrete Structures and Foundations.

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and Recommendations for Fire-Retardant Coating for Creosoted Wood, under the subject title Specifications for Timber Piles. 4.6.2.4 Handling of Material (1990) a.

Treated piles shall be handled with rope slings, taking care to avoid dropping, bruising or breaking of outer fibers, or penetrating the surface with tools. Sharp pointed tools shall not be used in handling treated piles or turning them in the leads.

b. The surface of treated piles below cut-off elevation shall not be disturbed by boring holes or driving nails or spikes into them to support temporary material or staging. Staging may be supported in rope slings carried over the tops of piles or attached to pile clamps of an approved design. 4.6.2.5 Selection and Preparation of Piles (1990) 4.6.2.5.1 Size a.

The piles in each bent of a pile trestle shall be selected for uniformity of size to facilitate placing of the brace timbers.

b. It is presumed that piles will be furnished in approximately the lengths required to secure the desired penetration and bearing. In the event piles are found to be much in excess of the required lengths, they shall be shortened at the small end before driving, as may be directed by the engineer, in order to preserve the desired diameter of pile at the cut-off.

1

4.6.2.5.2 Pointing Under ordinary conditions points of piles shall be cut perpendicular to the axis of the pile; where necessary or desirable, points may be trimmed to form a truncated pyramid 4 inches to 6 inches square at the end and with length of trimming not to exceed twice the tip diameter of the pile.

3

4.6.2.5.3 Pile Shoes a.

Where the driving of a test pile or former experience at the site indicates that difficult driving will be encountered, metal shoes of an approved design may be attached to the tips of the piles.

b. Each pile point shall be carefully trimmed to fit the shoe and obtain full and uniform bearing, and to avoid displacement of the shoe or damage to the pile or shoe. 4.6.2.5.4 Collars Where the heads of piles tend to split when being driven, the heads shall be tightly wrapped with No. 12 gage annealed iron wire to form a band not less than 2 inches in width, held in place with staples, or shall be protected with strap-iron bands applied with a banding tool, or other effective means shall be used to prevent splitting. 4.6.2.5.5 Driving Cap The heads of piles shall be protected while being driven with a driving cap (bonnet) of approved design. The cap shall be shaped to fit over the head of the pile to provide lateral support, and to uniformly distribute the hammer blow. Pile heads shall be trimmed to fit snugly into the cap.

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Timber Structures 4.6.2.6 Types of Hammers (1988) a.

Pile driving shall not be started on any project until approval is secured from the engineer as to the type and weight of the hammer to be used.

b. Piles shall be driven with the heaviest hammer that, in the judgement of the engineer, can be used to secure maximum penetration without appreciable damage to the pile.1 c.

Where a drop hammer is used, the striking ram shall weigh not less than 3000 lbs. The fall shall be so regulated as to avoid injury to the pile.

d. Special care shall be used in choice of hammer where the shock to surrounding material may cause damage to an adjacent structure. 4.6.2.7 Driving (1988) 4.6.2.7.1 Leads Pile driver leads shall be constructed in such a manner as to afford freedom of movement of the hammer, and they shall be held in position by guys or stiff braces to insure support for the pile during driving. Inclined leads shall be used to drive batter piles. 4.6.2.7.2 Followers The use of followers shall be avoided if practicable and shall be used only with the written permission of the engineer. 4.6.2.7.3 Line Piles shall be driven as accurately as possible in the correct location, true to line both laterally and longitudinally, and to the vertical or batter lines as indicated on the plans. On sloping ground or under difficult conditions of driving, the pile shall be started in a hole or guiding template or other necessary means provided to insure driving in the proper location. In case a pile works out of line in driving, it shall be properly aligned before it is cut off or braced, and the distance that it may be pulled shall be determined by the engineer. 4.6.2.7.4 Jetting Jetting shall not be done unless specifically permitted by the engineer. When waterjets are used, the number of jets and the volume and pressure of water shall be sufficient to freely erode the material adjacent to the pile. The plant shall have sufficient capacity to deliver at least 100 psi pressure at two 3/4 inch nozzles. Before the desired penetration is reached, the jets shall be removed and the pile finally set under normal driving by at least 50 blows from a gravity or single-acting hammer or 200 blows from a double acting hammer. 4.6.2.7.5 Drilling a.

When it has been satisfactorily demonstrated to the engineer that piling cannot be driven in the regular manner or by jetting, holes may be drilled to facilitate the driving.

b. Where drilling is permitted, the holes drilled shall have a diameter not more than 1 inch larger than the tip diameter of the pile and the drilling will continue only through the strata of hard material obstructing the driving. Where the hard material extends below the desired penetration, the drilling 1

For a discussion of the proper relationship of weight of ram to weight of pile, and net effective energy of blow, in selecting pile driving hammers, reference is made to Vol. 37, 1936, AREMA Proceedings.

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shall be stopped above that penetration level and the pile finally set under normal driving in accordance to the bearing required. At least 50 blows from a gravity or single-acting hammer or 200 blows from a double-acting hammer shall be used if possible to do so without damaging the pile. 4.6.2.7.6 Drilling and Shooting Where it is impossible to drive, jet, or drill and drive the piles, the engineer will determine whether shooting the holes with explosives or redesign of the structure is necessary. Shooting will not be permitted except by written permission of the engineer. 4.6.2.7.7 Penetration It is expected that piles shall be driven, jetted or drilled and driven to the full penetration shown on the plans or as otherwise required. This shall not be construed to mean that driving may stop when such penetration as shown on the plans has been secured, but on the contrary, driving shall continue in every case until the total penetration obtained is satisfactory to the engineer, regardless of the fact that sufficient bearing capacity as determined by formula may be obtained at a lesser depth. 4.6.2.7.8 Bearing Capacity a.

Where possible, test piles shall be driven and loading tests made before construction is started, as referred to under Article 4.6.2.2. In the absence of such data, the following “Engineering News” formulas may be used to estimate the approximate safe bearing capacity of piles in most soils:

1

For drop hammers: P = FWh -------------S+1 For double-acting steam hammers:

3

Fh ( W + ap ) P = -------------------------------S + 0.1 For single-acting hammers:

4

FWh P = ----------------S + 0.1 where: P = safe load in pounds W = weight of hammer or ram in pounds h = fall of hammer or stroke of piston in feet S = average penetration in inches per blow, for the last 5 blows of a drop hammer or 20 blows of a single or double-acting hammer a = effective area of piston in square inches p = mean effective steam pressure in pounds per square inch F = 2 for piles driven to practical refusal in any material

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b. These formulas are applicable only when the hammer has a free fall, the head of the pile is not broomed or crushed, the penetration is reasonably uniform, and there is no appreciable bounce of the hammer. The character of the soil penetrated; conditions of driving; spacing, size and length of piles; and experience under similar conditions; shall be given due consideration in determining the value of piles by formula. c.

The formulas should not be applied to friction piles driving into such soils as silt, muck, peat, or plastic clays, nor to piles which act as end-bearing piles.

d. For jetted piles the same formulas will apply and the test shall be made when driving is resumed after removal of the jets. For piles driven in drilled holes, the tests shall be made after the tip of the pile has passed the bottom of the hole. 4.6.2.7.9 Delay When driving is interrupted before final preparation is reached, record for bearing capacity shall not be taken until at least 12 inches penetration or refusal has been obtained after driving has been resumed. 4.6.2.7.10 Overdriving When the point of refusal is reached, care shall be taken to avoid damaging the pile by overdriving. This condition is indicated when the hammer begins to bounce or when the energy of the blow is dissipated in the bending or kicking of the pile. 4.6.2.7.11 Replacing Any pile driving too far out of line, driven below cut-off elevation, or so injured in driving or straightening as to impair its structural value as a pile under the conditions of use, shall be pulled and replaced by a new pile. 4.6.2.8 Framing (1988) 4.6.2.8.1 Cut-Off The tops of piles shall be pulled into line if necessary, fixed in position, cut off to a true plane as shown on the plans, and at the elevation established by the engineer. Piles shall show a solid head at the plane of the cut off. 4.6.2.8.2 Treatment After the cut-off has been made, the tops of treated piles shall be saturated with hot preservative, followed by two coats of hot sealing compound. The sealing compound shall be a mixture of creosote coal-tar pitch, mixed to about the consistency of Vaseline, and brushed thoroughly into the wood. 4.6.2.8.3 Pile Covering a.

The treated pile cut-off may be covered with plastic cement used with or without a fabric layer and topped with a 1/4 inch neoprene pad if desired.

b. The use of roofing material or sheet metal to cover the cut-off has been found to retain moisture or increase wetting and is not recommended. 4.6.2.8.4 Placing Caps Caps shall be placed while the piles are held in correct position. Where drift bolts are used for making the connection, the caps and tops of piles shall be bored the same diameter as the drift bolt and to a depth of 3 © 2011, American Railway Engineering and Maintenance-of-Way Association

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inches less than its length. Where the connection is made with straps and bolts, see Article 4.6.2.8.6 for boring and treatment of holes. 4.6.2.8.5 Bracing Piling shall not be trimmed or cut to facilitate the framing of sway or longitudinal bracing. Where necessary, filler blocks shall be used between the pile and brace to establish the bracing in a true plane. 4.6.2.8.6 Holes for Bolts a.

Holes shall be bored the same diameter as the bolt and 1/8 inch less than the nominal diameter of drive spikes.

b. When holes are bored in treated piles, caps or bracing in the field, the entire hole shall be pressure treated or swabbed with hot preservative and sealing compound just before the bolt is placed. Bolts shall be cleaned of rust and scale, and dipped in hot sealing compound before placing. All unused holes shall be plugged at each end with tight fitting treated wooden plugs. 4.6.2.8.7 General Field Treatment Where it is necessary to disturb the surface of treated piles or timber, or where the surface has been damaged in handling, such surfaces shall be treated with a liberal quantity of hot preservative followed by two applications of hot sealing compound.

1

4.6.2.9 Foundation Piles (1990) a.

For the design of pile foundations, exploration at the site, and test pile loading, see Chapter 8, Concrete Structures and Foundations; Part 4, Pile Foundations.

b. The general specifications above shall apply to the driving of wood foundation piles. c.

3

Pile driving shall not be started until foundation excavation has been carried to plan depth.

d. After all of the piles are driven, tests shall be made to determine if any of the piles have raised due to driving of adjacent piles. Any piles that have raised shall be driven down again. e.

After driving is completed, the piles shall be cut off as shown on the plans and at the elevation established by the engineer. All loose and displaced materials down to the level of original excavation shall be removed from the foundation pit, leaving a clean solid surface on the piles, and bottom and walls of the pit.

4.6.2.10 Protection Work (1990) a.

The general specifications above shall apply to the driving of wood piles for protection work.

b. It is essential that protection work be constructed as securely as possible, accurately located as shown on the plans, and the piles driven to a fixed penetration or to refusal as may be determined by the engineer.

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Timber Structures 4.6.2.11 Pile Record (1988)1 a.

An accurate record shall be kept of all piles, as each is driven, to show the location in the structure, size of pile, penetration, resistance to driving and other essential data. See suggested form for reporting this information, Figure 7-4-2. Size can be 8-1/2² ´ 11² or 8² ´ 10-1/2².

b. The size and arrangement of pile driving record forms may be varied to adapt them to the convenience of user, method of filing, and use to be made of the data. The form found in Figure 7-4-2 embodies the minimum of information for a satisfactory record. Among additional items which may be desirable are: • reference to piles other than wood; • steam hammer blows per minute; • data on batter; • reference to jetting; • computed bearing value; and • other arrangement of data on length between butt, cut-off, ground and point of pile.

1

References, Vol. 12, 1911, part 1, pp. 278, 307; Vol. 52, 1951, pp. 426, 846; Vol. 62, 1961, pp. 514, 848; Vol. 89, 1988, p. 106.

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North and South Railroad Pile Record of Bridge: Location: Weight and Kind of Hammer:

Date: Avg. Last Blows (Note 3)

Size of Pile

Date

Bent No. of Kind of Base-rail Total No. Pile Cutoff Wood to Ground Penetration (Note 1) (Note 2) Tip Butt Length End End

Drop of Penetration Hammer

Kind of Remarks Soil

1

3

4

Note 1: Bents numbered in direction in which mile posts increase. Note 2: Piles numbered from left to right. Note 3: Five blows for drop hammers and 20 blows for single or double-acting hammers. Figure 7-4-2. Sample Pile Record Form

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SECTION 4.7 SUPERSTRUCTURE Under Development

SECTION 4.8 SUPPORT, REPAIR, PRESERVE, OR REPLACE DAMAGED PORTIONS OF THE STRUCTURE (2010) a.

Splicing provides additional material to support small structurally deficient areas. Sufficient connections must be provided for adequate load transfer. A structural analysis should be performed to verify stress distribution and adequacy. See Figure 7-4-3.

Figure 7-4-3. Splicing

b. Scabbing provides additional material to support large structurally deficient areas. Sufficient connections must be provided for adequate load transfer and support. Scabbing may also be used to increase capacity of a member and may be composed of timber or steel. A structural analyses should be performed to verify stress distribution and adequacy. See Figure 7-4-4.

Figure 7-4-4. Scabbing

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c.

Deteriorated pile may be restored by using a cast in place reinforced concrete jacket. The jacket must extend above and below the defective area to adequately support the loads. See Figure 7-4-5.

1

3

Figure 7-4-5. Pile Restoration Using Cast in Place Reinforced Concrete Jacket

4

d. Voids in pile may be filled with an epoxy or other suitable grout. See Figure 7-4-6.

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Timber Structures

Figure 7-4-6. Filling Voids with Grout e.

Splits or checks may be arrested by clamping, using steel assemblies to compress the member, or stitching, using through bolts to hold the member together. Configuration, number and size of fasteners should be determined on a case by case basis. Stitch bolt spacing should be determined by Part 2, Design of Wood Railway Bridges and Trestles for Railway Loading; Section 2.6, Details of Design, Article 2.6.3. Holes for stitch bolts should be sized in accordance with Article 4.5.m. Stitch bolts should only be tightened to the point where they begin to take tension. Splits or checks should not be closed as this may extend the defect to the other side of the clamp or stitched area. See Figure 7-4-7 and Figure 7-4-8.

f.

When individual caps, sills, braces or struts have become weakened beyond their ability to perform their intended function, replacing these members with similar sized members may be performed.

g.

Shimming of stringers to provide proper surface and cross level should be performed using a single hard wood shim under each chord or stringer. Shimming with stacked or multiple shims is to be avoided.

h. All bolts should be retightened during normal servicing of the structure.

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Figure 7-4-7. Clamping

1

3

Figure 7-4-8. Stitching

4

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Timber Structures

4.8.1 CONTROL MOISTURE The hazard of decay is reduced by controlling the amount of moisture present in timber bridges. Once visible wetting or high moisture contact areas are located, the following action is recommended: a.

Remove dirt and debris.

b. Provide adequate drainage from deck. c.

Ensure adequate support surface for tie plates.

d. Provide water proofing systems for ballast decks. e.

Ensure hardware is tight, sealing holes preventing moisture entrance.

f.

Plug any unused holes with treated wood plugs.

4.8.2 FIELD APPLICATION OF PRESERVATIVE CHEMICALS Timber decay can be arrested by field application of preservative chemicals which should be applied in accordance with manufacturer’s specifications. It is recommended they be used by qualified personnel with experience in treating structural timber. a.

Liquids are brushed, squirted or sprayed on the surface and may be injected into timber.

b. Semi-solids, greases or pastes are spread on the affected area. They are mostly used in ground line applications or treating fresh cuts. c.

Fumigants are normally injected into the wood. They originally are liquid and volatilize, creating a gas which permeates wood cells inhibiting decay.

d. Plugs or pastes containing salts, which, when combined with moisture release an active ingredient which permeates wood cells inhibiting decay.

SECTION 4.9 METHODS OF FIREPROOFING WOOD BRIDGES AND TRESTLES1 4.9.1 FOREWORD (1988) The following methods are used in providing fire protection for open-deck bridges and trestles:

4.9.2 METAL PROTECTION (1988) This method consists of covering the deck partially or completely with sheets of No. 24 gage galvanized iron fastened with 12d heavy galvanized barbed car nails with flat heads and diamond points.

1

References, Vol. 42, 1941, pp. 291, 868; Vol. 54, 1953, pp. 962, 1331; Vol. 62, 1961, pp. 514, 848; Vol. 63, 1962, pp. 453, 684; Vol. 89, 1988, p. 106.

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4.9.3 COATINGS (1988) Coatings of bituminous and non-bituminous materials with clean gravel embedded in them are showing promise of being fire resistant when applied on horizontal surfaces. Vertical surfaces require special treatment.

4.9.4 IMPREGNATION (1988) This method includes the use of various salt solutions applied at treating plants. The treated wood, in addition to being made fire resistant, is also given protection against decay and termite attack.

4.9.5 FIRE ALARM SYSTEMS (1988) a.

Under this method fusible-link detector systems are so connected with the signal and communication systems that in case of fire the block signals will show warning indications, and the nearest telegraph operator will receive notification so that maintenance of way forces may be assembled to combat the fire.

b. Special fire-fighting apparatus and watchmen are employed in unusual cases where conditions warrant.

4.9.6 HOUSEKEEPING (1988) NOTE:

a.

The following practices, applicable to both open- and ballasted-deck bridges and trestles, are being employed where conditions warrant.

Decks are kept clear of all combustible material, and decayed spots in exposed ties or timbers kept trimmed.

b. Brush and weeds are kept down for a distance of at least 25 feet from the bridge, both underneath and on the embankment at the ends of the bridge or trestle. Also, all sod is removed from under timber bridges and for a distance of 3 feet outside the timbers. This is accomplished by scalping or by the use of a soil sterilant. c.

NOTE:

4

Applicable to both open and ballasted-deck bridge and trestles.

Under this method long bridges and trestles are protected by introducing fire barriers at intervals of about 400 feet. This reduces the hazard by preventing loss of the entire structure in case of fire. Such barriers may be grouped by types of construction, as follows: Earth fill (see Figure 7-4-9).

b. Reinforced concrete piers or concrete pile bents (see Figure 7-A3-58). c.

3

Water barrels with buckets are installed on timber bridges, 1 barrel each for structures up to 50 feet long and 1 additional barrel for each additional 150 feet or fraction thereof. For creosoted structures, sand boxes with water-tight covers for keeping the sand dry are used, dry sand being more effective than water in extinguishing small fires on creosoted structures.

4.9.7 FIRE BARRIERS (2011)

a.

1

Facing bents with fire-resisting materials (see Figure 7-A3-59).

d. Application of mastic materials to open-deck structures (see Figure 7-A3-60).

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Timber Structures

Figure 7-4-9. Earth Fill Break in a Long Trestle

SECTION 4.10 USE OF GUARD RAILS AND GUARD TIMBERS1 (2004) 4.10.1 FIELD SIDE GUARD OR SPACER TIMBERS (1988) On all open-floor railway bridges, the ties should be held securely in their proper spacing; guard or spacer timbers fastened to every tie near its end are effective. If such continuous timbers are not placed, blocks or other suitable fastenings should be used for spacer timber attachment; on track where speed or other circumstances so indicate it may be advisable also to embed clamping plates or timber connectors between the timbers and ties. Such metal fastenings are more effective than dapping of the spacer timbers, because of the tendency of the wood to split off between daps.

4.10.2 METAL GAGE SIDE GUARD RAILS (2004) a.

Consideration should be given to the use of metal inner guard rails taking into account the alignment, train speed, deck type, density and type of traffic, as well as height and length of bridge.

b. It is recommended that the inner guard rails, when used, be steel track rails not higher than the running rails. If 5 inches or more in height they should not be more than 2 inches lower than the running rails. If less than 5 inches in height they should not be more than 1 inch lower than the running rails. Normally, they will consist of two rails, spaced about 10 inches inside the running rails (measured between near sides of head) spiked to every tie and spliced with joint bars, fully bolted. The inner guard rails may be tie plated when deemed advisable. They must not contact tie plates of tracks carrying electric signal circuits. Where they protect against a hazard on one side only, a single line of rails may be used, adjacent to the running rail further from the hazard.

1

References, Vol. 14, 1913, pp. 652, 1136; Vol. 15, 1914, pp. 402, 1036; Vol. 21, 1920, pp. 1285, 1434; Vol. 52, 1951, pp. 426, 847; Vol. 62, 1961, pp. 514, 848; Vol. 63, 1962, pp. 454, 684; Vol. 89, 1988, p. 106.

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c.

It is further recommended that where inner guard rails are used, they extend at least 50 feet beyond the end of the bridge or other structure. This distance may be increased where train speed, curves or other factors warrant the increase, and may be decreased on the leaving end where traffic is in one direction. The ends should run to the center of the track and be beveled, bent down or otherwise protected against direct impact. A filler block or plate should be provided at the meeting of the converging rails.

4.10.3 COMBINED USE OF GUARD TIMBERS AND GUARD RAILS (1988) Where both guard timbers and inner guard rails are used they should be so spaced that a derailed truck will strike the inner guard rail and not the timber.

1

SECTION 4.11 TYPICAL PLANS FOR TIMBER RAILWAY BRIDGES 4.11.1 PLANS (1988)

For aligning of plans for open-deck pile and framed trestles, multiple-story trestles, and ballasted deck pile and framed trestles refer to Table 7-4-1.

4.11.2 GENERAL NOTES (1988) a.

For various combinations of loading, panel lengths, number and size of stringers, number of piles and permissible working stresses, see Part 2, Design of Wood Railway Bridges and Trestles for Railway Loading.

1

b. All lumber and piles should be pressure treated in accordance with AREMA Chapter 30, Ties. All lumber should be framed and bored before treatment wherever possible. c.

Holes should be bored the same diameter as the bolt and 1/8 inch less than the nominal diameter of drive spikes.

3

d. Lumber cut after treatment should be painted with three coats of hot creosote oil. e.

Holes bored after treating should be treated with hot creosote oil applied with a pressure bolt hole treater.

f.

Each bolt should have a square head, suitable type lock nut and 2 “OG” washers, with a double-coil spring when shown on the plans.

g.

Trestles on curves should be built to follow the curve. Bents should be placed on radial lines and spaced to maintain standard panel lengths under the outside stringer.

h. Crushed-rock ballast should be hard, durable stone and should conform to size No. 4 of the National Bureau of Standards.

1

i.

For use of protective coating for hardware see Part 1, Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Timber Bridge Ties and Recommendations for Fire-Retardant Coating for Creosoted Wood, Section 1.6, Specifications of Fasteners for Timber Trestles.

j.

For use of inner guard rails see Section 4.10, Use of Guard Rails and Guard Timbers (2004).

References, Vol. 23, 1922, pp. 709, 1148; Vol. 24, 1923, pp. 773, 1196; Vol. 37, 1936, pp. 667, 704, 1036, 1038; Vol. 38, 1937, pp. 183, 624; Vol. 45, 1944, pp. 203, 596; Vol. 49, 1948, pp. 272, 672; Vol. 60, 1959, pp. 556, 1081; Vol. 63, 1962, pp. 455, 684; Vol. 89, 1988, p. 106. © 2011, American Railway Engineering and Maintenance-of-Way Association

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Timber Structures Table 7-4-1. Recommended Practice Plans Figure No.

Plan Name

Page No.

7-A3-61

Floor Plan for Open-Deck Trestles

7-A3-65

7-A3-62

Floor Plan for Ballasted-Deck Trestles

7-A3-48

7-A3-63

Bulkheads and Miscellaneous Details

7-A3-49

7-A3-64

Cap Stringer Fastening and Pile Top Protection

7-A3-50

7-A3-65

Bent Details for Open-Deck Pile Trestles

7-A3-51

7-A3-66

Bent Details for Ballasted-Deck Pile Trestles

7-A3-52

7-A3-67

Longitudinal Bracing

7-A3-53

7-A3-68

Details of Footings for Framed Bents

7-A3-54

7-A3-69

Multiple-Story Trestle Bents (6 Post Bent)

7-A3-55

7-A3-70

Multiple-Story Trestle Bents (5 Post Bent)

7-A3-56

7-A3-71

Walk and Handrail - Open-Deck Trestles (to be used where required)

7-A3-57

7-A3-72

Water Barrel and Refuge Platform - Open-Deck Trestles (to be used where required)

7-A3-58

7-A3-73

Track Car Platforms - Open-Deck Trestles (to be used where required)

7-A3-59

7-A3-74

Walk and Handrail - Ballasted-Deck Trestles (to be used where required)

7-A3-60

7-A3-75

Water Barrel and Refuge Platform - Ballasted-Deck Trestles (to be used where required)

7-A3-61

7-A3-76

Track Car Platform - Ballasted-Deck Trestles (to be used where required)

7-A3-62

7-A3-77

Recommended Practice for Creosoted Timber Pile Piers for Long Spans, E60 Loading-Pier for 150-foot and 80-foot Spans

7-A3-63

7-A3-78

Recommended Practice for Creosoted Timber Pile Piers for Long Spans, E60 Loading-Pier for 150-foot Span and Trestle Approach

7-A3-66

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7

Part 5 Inspection of Timber Structures — 2010 — TABLE OF CONTENTS

Section/Article

Description

Page

5.1 General (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-5-1

5.2 Details of Inspection (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.1 Identification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.2 Waterway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.3 Track . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.4 Superstructure. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.5 Substructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.6 Fire Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.7 Earthquakes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-5-2 7-5-2 7-5-2 7-5-3 7-5-3 7-5-3 7-5-4 7-5-4

3

FOREWORD It is the purpose of these instructions to describe the manner of inspecting a timber bridge; no attempt is made to set up the organization nor to fix the responsibility or the functioning of the various members of the organization.

SECTION 5.1 GENERAL (1988) The method of inspecting timber, regardless of its location in the structure, follows: a.

Make a careful surface inspection of each timber for cross grain, tension or horizontal shear failures that may have developed from uneven bearing, original defects, overstress or other causes. Note whether timber and piling are treated or untreated.

b. Test each timber and pile for soundness, especially at points of contact with other timbers, ground, or at low water line, and where end grain bears on a sill or cap. (1) For treated timber, test shall be made by sounding with the knob end of an inspection bar or lightweight hammer, using care to avoid injuring or disfiguring the fiber. If hollow or dead sound results,

© 2011, American Railway Engineering and Maintenance-of-Way Association

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determine nature and extent of the defect by boring, preferably with an increment borer. Bore holes, where possible, so water can drain, and carefully plug with treated wood. (2) For untreated timber, test may be made by sounding with the knob end of an inspection bar or lightweight hammer, also by probing with pointed end of inspection bar, using care to avoid any unnecessary injury or disfiguring of the wood. Note the feel and sound when struck by the bar, the appearance of the fiber, and of all decayed or otherwise unsound wood, which should be trimmed away to sound timber. c.

Make a careful surface inspection of the timber and adjacent ground surface for evidence of termites, carpenter ants, marine borers or other destructive insects.

d. Make inspection on new work, where timber is treated, of all field cuts for exposed untreated wood. e.

Make an outline of repairs based on information from Part 4 and Part 5. The inspector should determine the cause of the deterioriation of the structural component and suggest maintenance or repair measures that would correct existing deficiences and prevent their reoccurance.

SECTION 5.2 DETAILS OF INSPECTION (2002) The bridge inspector’s notes for each bridge shall be written while at the structure after a careful examination has been made covering the following points:

5.2.1 IDENTIFICATION a.

Division or subdivision. Name of inspector and members of inspection party. Date of inspection.

b. Bridge Number. Name of nearest station and mile-post location. Age and type of structure. Total length, height and number of panels. c.

Number of bents, towers, spans or panels in each bridge in the direction in which the mile post numbers increase, starting with the dump bent as No. 1. Number the piles in each bent or tower and the stringers in each panel from left to right, when facing in the direction in which the mile post numbers increase.

5.2.2 WATERWAY a.

Observe if the opening appears adequate for drainage area and if free of obstructions, such as drift, vegetation, displaced revetment stone, or old pile stubs. Note whether the channel is stable, filling, deepening or subject to scour, and if public improvements have altered the general condition in any way. Measure and record the distance from base of rail to ground line at each bent. Measure and record high water mark if obtainable. If heavy or accumulated drift is troublesome during high water, ascertain the type, such as logs, trees, ice, etc., and observe whether of such intensity as to force the bridge out of line and/or break piling.

b. Note if protection work is required or whether cleaning and straightening of the channel are necessary. Note whether bent alignment obstructs or deflects normal flow and if revetment or deflection dikes are needed. c.

Note evidence that would indicate the presence of any buried cable, conduit, tile or pipe lines crossing under the bridge, giving the panel location, together with size and use.

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Inspection of Timber Structures

5.2.3 TRACK a.

State whether track is level or on a grade, and if alignment is tangent or curved. If on a curve, note how superelevation is provided, whether by cutoff in the bents, taper in the caps or in the ballast section. Note location of track with reference to the chords for uniformity of loading.

b. Observe condition of embankment at the bridge ends for fullness of crown, steepness of slopes and depth of bulkheads. Note whether track ties are fully ballasted and well bedded. c.

Record the weight and condition of the track rails and inside guard rails; also the condition of the rail joints and fastenings. Note the size and condition of the tie plates.

d. Where track is out of line or surface, the location, amount and probable cause should be determined.

5.2.4 SUPERSTRUCTURE a.

Ascertain size, spacing and uniformity of bearing of the ties. Note condition as to soundness, mechanical wear, spike killing and other defects.

b. Determine the size, condition, and security of anchorage of the guard timber. c.

Inspect all walks, railings, and refuge bays, noting the condition as to soundness and security of fastening devices.

1 d. Note all members to determine if any are broken or have moved out of proper position and whether all fastening devices are functioning properly. On ballasted-deck trestles, note whether ballast is clean and in full section. e.

f.

Examine all stringers for soundness and surface defects. Note size and kind, and the number used in each panel. Note if bearing is sound and uniform, if all stringers are properly chorded and securely anchored, and if all shims and blocking are properly installed. Note whether packers or separators are used and the condition of all chord bolts. Note and report presence of any wires, cables, pipe lines or other attachments which are foreign to the bridge structure.

5.2.5 SUBSTRUCTURE a.

4

Make careful examination of all piles and posts for soundness, noting particularly the condition at points of contact with the caps, girts, bracing, sills, and at the ground or water line.

b. Examine all bents and towers for plumbness, settlement, sliding and churning, and give an accurate description of the nature and extent of any irregularities. Note particularly whether caps and sills have full and uniform bearing on the supports. c.

Record number and kind of piles or posts in the bents or towers. Note uniformity of spacing and the location of any stubbed or spliced members, especially if the bridge is on a curve or the bent is more than 15 feet in height.

d. Ascertain whether all bents and towers are properly sway, sash and tower braced, and if girts and struts are applied as needed. e.

3

Examine all fastening devices for physical condition and tightness.

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f.

Observe action of bridge under movement of trains, where practicable, in order to evaluate better the riding condition and soundness of the structure.

5.2.6 FIRE PROTECTION a.

Note whether surface of the ground around and beneath the structure is kept clean of grass, weeds, drift or other combustible material.

b. Where rust-resisting sheet metal is used as a fire protection covering for deck members, note condition of metal and fastenings. c.

Note if any other method of fire protection has been used, such as fire retardant salts, external or surface protective coatings, or fire walls. Record such apparent observations as are pertinent to the physical condition and effectiveness of such protective applications.

d. Where water barrels are provided, note the number, condition, if filled, and if buckets for bailing are on hand. If sand is used, note whether bins are full and in condition to keep the sand dry. e.

Note if timber, particularly top surfaces of ties and stringers in open deck bridges, is free from frayed fiber, punk wood, or numerous checks.

5.2.7 EARTHQUAKES In the occurrence of a seismic event refer to Chapter 9 of this manual.

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7

Part 6 Commentary — 2010 — TABLE OF CONTENTS

Section/Article

Description

Page

6.1 Materials Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.1 Structural Grades of Lumber and Timber and Method of Their Derivation (2010) . . . . . 6.1.3 Specifications for Engineered Wood Products (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.4 Examples for Inquiry or Purchase Order (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-6-2 7-6-2 7-6-2 7-6-5

6.2 Design Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.2 General Features of Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.3 Loads, Forces and Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.4 Designing for Engineered Wood Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.5 Notes on the Use of Stress-Graded Lumber . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-6-5 7-6-5 7-6-6 7-6-6 7-6-7

6.3 Rating Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-6-13

6.4 Construction and Maintenance Commentary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-6-13

6.5 Inspection Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-6-13

LIST OF FIGURES Figure 7-6-1

Description Chart Showing Relation of Design Stress to Duration of Load . . . . . . . . . . . . . . . . . . . . . . . . . .

Page 7-6-11

LIST OF TABLES Table 7-6-1

Description Derivation of listed values, using combination 16F-1.5E DF as an example . . . . . . . . . . . . . . .

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3

Timber Structures

SECTION 6.1 MATERIALS COMMENTARY 6.1.1 STRUCTURAL GRADES OF LUMBER AND TIMBER AND METHOD OF THEIR DERIVATION (2010) a.

Lumber, including structural lumber, is the product of the saw and planing mill not further manufactured than by sawing, resawing, passing lengthwise through a standard planing machine, cross cutting to length and working. After the lumber is produced, it is necessary to inspect each piece individually to determine its grade. Lumber which is so graded that working stresses can be assigned is called stress-graded or structural lumber.

b. Traditional design values for wood are based on testing of small clear samples; results summarized in ASTM D2555, and are developed in accordance with ASTM D245 with reductions applied to account for various wood defects. For a detailed explanation of the intial concepts see AREA Proceedings Vol. 30, 1929, pages 1206 to 1224. Starting in the 1980s, the coordinated Canadian and U.S. in-grade testing program started to develop properties based on full-sized structural tests of members (Madsen) using proof loading concepts. At present there is a large database for dimension lumber sizes in Douglas FirLarch, Hem-Fir and Spruce-Pine-Fir. As in-grade testing is expanded to timber sizes and other species, the values from this program will replace the results of tests done on small clear samples adjusted for defects.

LUMBER INDUSTRY ABBREVIATIONS (2007) a.

The same as American Softwood Lumber Abbreviations, as approved by the American Lumber Standards Committee.

b. These standard lumber abbreviations are commonly used for softwood lumber, although all of them are not necessarily applicable to all species. When used in the preparation or writing of contracts and other documents arising in transactions of purchase and sale of American Softwood Standard Lumber, these abbreviations shall be construed as provided therein.

NOMENCLATURE OF COMMERCIAL DOMESTIC HARDWOODS AND SOFTWOODS (2007) The standard commercial names for lumber cut from species or species groups of domestic hardwoods or softwoods are the same as those used in the current standard grading rules for the species

6.1.3 SPECIFICATIONS FOR ENGINEERED WOOD PRODUCTS (2006) 6.1.3.1 Structural Glued Laminated Timber - Glulam Glued laminated timbers (glulam) are manufactured by end jointing individual pieces of stress-graded lumber together with rigid structural adhesives to create long lamination lengths. The laminations are then face bonded to create the desired member depth in accordance with layup specifications. The manufacturing standard for the glulam industry is America National Standard - ANSI A190.1. Chapter 7 Sections 1.3.1 and 2.4 are to be used in conjunction with railroad design practices and design methodology provided in other sections of the chapter, and in conjunction with basic structural engineering equations. Glulam material properties to be used for design are available primarily from industry technical

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AREMA Manual for Railway Engineering

Commentary

trade associations. The values listed in Tables 7-2-7 and 7-2-8 are traceable to association sources and the glulam section of the National Design Specification (NDS). The glulam content in Chapter 7 has been heavily edited from building design and construction reference documents (such as the NDS), to serve the needs of railroad bridge designers. Content in Sections 1.3.1 and 2.4 has been arranged to simplify use of the material for design engineers that may not be familiar with glulam properties and recommended practices as they apply to the use of glulam in railroad bridge applications. The primary need for editing glulam design reference tables and design literature excerpts was to reduce the information by removing adjustment factors and design considerations commonly used in building construction, but not applicable to railroad bridge design. Decisions on options for this simplification process were guided primarily by committee members knowledgeable in railroad timber bridge design practices, input from glulam industry members on Committee 7, and through contact with the glulam industry technical trade associations. A number of modifications to basic glulam industry practice were included in this section to tailor the material for railroad bridge structure applications. For this reason, direct comparisons with common glulam industry standards and specifications will show differences. 6.1.3.1.1 Appearance Classifications b. Industry recommendations for finished appearance of glued laminated timber typically identify four classifications: Premium, Architectural, Industrial and Framing. Framing and Industrial appearance classifications are shown. Premium and Architectural appearance classifications are not applicable to railroad bridge applications.

1

It should be noted that appearance classifications are cosmetic in nature and do not affect the structural properties of glulam members. The glulam manufacturer should be contacted for details on Framing appearance classification. 6.1.3.1.2 Layup Combinations

3

Layup combinations listed in the reference design property tables (Tables 7-2-7 and 7-2-8) have been limited to bending "Stress Groups" that are most likely to be used for railroad bridge applications. Both Balanced and Unbalanced combinations are available in the respective stress groups. Only Balanced combinations are listed in Table 7-2-7 for the two major species (Douglas fir and Southern pine) used for railroad structures in North America.

4 A comprehensive list of all available layup combinations (for a variety of lumber species) is available from agencies, such as APA - The Engineered Wood Association (http://www.apawood.org) or American Institute of Timber Construction (AITC, http://www.aitc-glulam.org) certifyng glulam manufacturers. Glulam members may also be supplied with all laminations of a single grade, from the desired species. Combinations for this option are intended primarily for axial loading, such as columns. Combinations listed in Table 7-2-8 are for all one grade of given species. All one-grade combinations are identified by number designations that identify specific lumber grade categories within species groups. Grade Requirements Layup grade requirements may be achieved with the use of both visual and mechanically graded lumber sources in a variety of species. Glulam manufacturers have the option to use alternate sources of lumber as long as species criteria are maintained in layup grade requirements. Douglas fir and Southern pine species are generally available in the United States, with Spruces more common in Canada.

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Manufacturing specifications for layup combinations are generally not needed by the designer. Glulam industry manufacturing specifications are referenced in ANSI A190.1. Customized layup options are possible to meet specialized design requirements within the scope of industry standards for glulam manufacture. Bending Members Bending members are typically specified on the basis of the maximum allowable bending stress and modulus of elasticity of the member. For example, a 24F-1.8E designation indicates a member with an allowable bending stress of 2400 psi and a MOE of 1,800,000 psi. This “stress class” may be produced in a variety of different species, each with the same properties listed for the 24F-1.8E stress class. Table 7-2-7 is a simlified version of a stress class table listing only DF and SP balanced combinations. Glulam layup combinations are specified to provide the highest lumber grades int he zones of the member depth where bending stresses are highest. Layup stress group combinations for members stresses primarily in bending are listed in Table 7-2-7. Layup combinations may be provided based on selective grade zones through the member depth however only properties for balanced combinations are shown in Table 7-2-7. 6.1.3.1.3 Balanced Beams Balanced beams must be used in applications such as continuous stringer applications, where the top and bottom of the member is stressed in tension. 6.1.3.1.6 Finished Sizes Finished sizes are provided for typical bridge stringers, deck panels and pile caps only. Other sizes are available. Glulam can be manufactured in widths greater than 12-inch nominal widths through the use of laminations made up of multiple-pieces of lumber. Specifications for special order members of this type should be negotiated directly with the glulam manufacturer. Multiple-piece laminations may be used to develop glulam members in widths greater than nominal lumber widths. Where multiple-piece laminations are used, the allowable gap between laminations shall be limited to a maximum of 1/16 inch if a gap-filling structural adhesive is specified. Otherwise, multiple-piece laminations to be used for pile cap applications shall be edge-glued. Typical Net Finished Glulam Deck Panels: Depths (Thickness): 2-1/2 to 12-1/4-in. (hit & miss surfaces) Widths: 45 to 52 in. Lengths: 24 to 24 ft. Other sizes may be supplied for specific applications as required. Typical Net Finished Glulam Pile Caps: Depth: Width: Length:

14 in., 16 in. or deeper as required 12 in. (hit & miss), 11-3/4 in. finished Multiple-piece lams for 14 in., 16 in. or wider Stock lengths up to 60 ft.

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Commentary 6.1.3.1.7 Preservative Treatments In general, pressure preservative treatment processes commonly used for glulam do not affect the strength properties of glued laminated timbers. Information on the possible effects of specific treatment is available through the AWPA or the treatment provider. Waterborne Treatments Waterborne treatments are typically applied to lumber prior to the laminating process. Waterborne treatments applied to glulam after the laminating process can cause dimensional changes such as warping, and twisting, in addition to excessive checking as the result of the necessary re-drying process. 6.1.3.1.9 Certification, Wrapping and Shipping Glulam members may be supplied in virtually any length, limited only by treating facilities, shipping routes and jobsite handling capabilities. Glulam members to be pressure-treated with preservatives after manufacture may be supplied without cover depending on conditions, or load wrapped as needed. If wrapping is to be specified for environmental protection or for other reasons, members may be supplied either load wrapped, bundle wrapped or individually wrapped. 6.1.3.1.10 Storage and Handling Seasoning checks in glulam members may be excessive if members are stored flat and placed unprotected in an environment where changes in the relative moisture content of members is forced to change rapidly.

1

6.1.4 EXAMPLES FOR INQUIRY OR PURCHASE ORDER (2010) Example 1: 30,000 fbm 2 x 8 x 12 feet, S4S, Select Structural joist and plank, Bald Cypress, Grading for structural Cypress, Southern Pine Inspection Bureau (SPIB). Example 2: 120 pieces 3 x 12 x 20 feet, S4S, selected structural joists and planks, Douglas-fir, coast region, in accordance with Paragraph 123(a) Standard No. 17, Grading Rules for West Coast Lumber issued by West Coast Lumber Inspection Bureau, except to have 90% heartwood.

3

Example 3: 48 pieces 2 x 12 x 12 feet, rough, dense select structural, Southern Yellow Pine, in accordance with Paragraph 401.1 of Southern Pine Inspection Bureau’s Grading Rules, except to be free of wane.

4 SECTION 6.2 DESIGN COMMENTARY 6.2.2 GENERAL FEATURES OF DESIGN 6.2.2.3 Stringers (2009) An approximate analysis to determine the division of rail load to several stringers is given in the chart, Figure 7-A1-1, in Appendix 1 - Contemporary Designs and Design Aids.

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6.2.3 LOADS, FORCES AND STRESSES 6.2.3.5 Other Lateral Forces (2009) 6.2.3.5.4 Longitudinal Force d. Since longitudinal bracing in timber trestles is essentially there to provide L/d stability and geometrical constraint, the longitudinal forces are transferred through the stringer and deck system with some help from the rails in proportion to their axial stiffness. Where stringers are discontinuous, the load is likely transferred through the dowels to the cap and back to the next set of stringers. This load path needs to be adequate to do this. Traditionally this has been accomplished by the use of earth fill or similar fire barriers at 400-foot intervals but with the addition of Articles 2.3.5.4.b, c and d it is necessary to include this limitation, as some of these fire details would not transmit any appreciable force.

6.2.4 DESIGNING FOR ENGINEERED WOOD PRODUCTS 6.2.4.1 Design Values for Glued Laminated Timber (Glulam) (2006) Methods used to establish glulam design properties take into account basic lumber properties. Lumber properties published by the grading agencies for Douglas fir and Southern pine are derived from standard practices provided in ASTM D245 in conjunction with clear wood properties published in ASTM D2555. Basic lumber grade characteristics are adapted to a glulam beam design modeling method described in ASTM D3737 to establish glulam beam properties for the various layup "combinations" listed in Tables 7-2-7 and 7-2-8. Railroad bridge design applications require the use of basic structural engineering principles and design equations in conjunction with published glulam allowable stresses. 6.2.4.1.1 Allowable Stresses The National Design Specification (NDS) provides an "equation format" that may be used with the specialized equations and loading requirements specified in the AREMA Manual for Railway Engineering for design of bridge structures. Design methodology for connections is also included in the NDS. The allowable stresses included in Tables 7-2-7 and 7-2-8 may be used directly for glulam bridge design. Appropriate stress adjustment factors for typical railroad bridge applications described in the NDS and glulam industry design publications have been applied to these table values to simplify use of the values in basic engineering equations. Glulam beams are "engineered" to optimize grade characteristics of the lumber used to make the product. The highest lamination grades are used in the outer zones of the beam depth. The X-X, Y-Y and Axial orientations are defined here to explain the use of these terms as they are used in glulam product design. Fasteners: The design methodology provided in Section 2.4 is applicable to glulam products. In addition, the information provided in the NDS for fasteners in solid sawn members is applicable for glulam design. Fastener capacities for withdrawal, single shear, double shear, and fastener group patterns in glulam members are controlled by wood species and the specific gravity within species groups. Specific gravity values to be used with the stress groups listed in Tables 7-2-7 and 7-2-8 are provided. 6.2.4.1.2 Tabular Design Values See Appendix 1 - Contemporary Designs and Design Aids.

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Commentary 6.2.4.1.3 Adjustment Factors Adjustment factors for wet-use, cyclic loading and the RR Use as defined in this section have been applied to the appropriate values in Tables 7-2-7 and 7-2-8. Other factors that may be considered have been included in Table 7-2-3. In cases where factors are not applicable, "none" is entered in the table. If adjustment for a given condition may be considered, but has been judged to be not necessary for glulam applications, a value of 1.0 is noted in the table. For example the Beam Stability factor CL is 1.0 when the compression side of a bending member is supported throughout its length, and the ends at points of bearing have lateral support to prevent rotation. Temperature effects (CT) are reversible for normal day/night cycles even in climates where daytime temperatures may be extreme. The US Forest Service Handbook No. 72 indicates that potential temporary strength reductions due to temperatures above 120oF will be offset by low member moisture content common to arid climates. The depth of heat penetration in given members must also be recognized when considering the possible effect of temporary (daily) exposure to high temperatures on beam properties. The Railroad Use Factor as defined for use in Chapter 7 is a duration of load adjustment not applicable to the glulam shear stress values listed in Tables 7-2-7 and 7-2-8 since a compensating adjustment to account for cyclic loading has already been applied by glulam industry standard recommendations. A factor of 0.72 has been applied to the listed values to account for possible cyclic loading effects. The base value for glulam shear (prior to adjustment) is derived from full-scale beam test results using static loading. Base shear values used in Tables 7-2-7 and 7-2-8, prior to application of the wet use factor, are 265 psi for Douglas fir and 300 psi for southern pine. This base value is higher than values originally derived from small sample blocks shear tests and ASTM D245 adjustment factors. Design shear stresses may also require adjustment to account for seasoning checks when they are expected to exceed 15% of the member width in high shear zones --center half of the depth, in the end fourths of the member length, and mid depth over intermediate supports. Technical Notes on the evaluation of checking in glued laminated timbers are available from industry trade associations. The KcE factor to be used in the column stability equation (shown as 0.418 for glulam), is related to stiffness COV (Coefficient of Variation), and varies between products. The COV for glulam Modulus of Elasticity is assumed to be 10% for members with 6 or more laminations.

1

3

6.2.4.2 Design Equations (2006) In addition to basic structural design principles, the use of specialized design procedures and assumptions to account for loading conditions unique to railroad bridge structures, as presented in Section 2.5, may be applied for glulam design in conjunction with stresses listed in Tables 7-2-7 and 7-2-8.

4 Tables 7-2-7 and 7-2-8: To simplify use of these tables, basic adjustment factors that are to be applied generally for railroad bridge applications have been applied to the respective values listed in the tables. An explanation of the methodology used to derive the table values is provided below.

6.2.5 NOTES ON THE USE OF STRESS-GRADED LUMBER 6.2.5.1 Working Unit Stresses (1988) Introduction To make the most effective and efficient use of any material the designer should be familiar with the characteristics of that material. In the following, the important characteristics which affect the strength of lumber are discussed briefly. Other characteristics, such as durability, resistance to splitting, resistance to wear, hardness, holding power of nails, finishing characteristics, etc., are not discussed, although they may be important and must not be overlooked.

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Timber Structures

Basic Stress The term “basic stress” is used to denote the allowable working stress for lumber which is unchecked, straight grained, and clear, and which will be subject to maximum load for a long time and will be saturated all of the time. The basic stress is not a working stress for any commercial grade. It must be modified for the grade of the lumber and for actual loading and moisture conditions to obtain working unit stresses. For basic stresses and for the quantitative effect of lumber characteristics on strength, see the Wood Handbook. The stresses given in Table 7-2-9 take into account the characteristics permitted in the grading rules. Knots and Holes The distortion of the grain around a knot causes stresses across the grain which limit the allowable stress in tension and compression parallel to grain for fully intergrown knots the same as for loose knots and knot holes. The effect of knots and knot holes on compression perpendicular to the grain and on shear stress may ordinarily be disregarded. Holes from other causes, such as bored holes, have approximately the same effect as knots. If there are many holes or large holes or grooves made in the lumber during fabrication and erection, their effect on stress should not be disregarded. Slope of Grain Lumber is much stronger in both tension and compression along the grain than in any other direction, and since in a straight beam or post there will be a component of stress across the grain whenever the grain is not parallel to the axis of the beam or post, it is necessary to limit slope of grain. Ordinarily, grading rules limit the slope of grain throughout the length of posts, but only in the middle half of beams and joists, on the assumption that the slope of grain near the ends will not be much greater than the slope in the central part. If a beam or joist is to be used for continuous spans or a tension member, the slope of grain should be further limited (see Note 8, Table 7-2-9). Since the allowable slope of grain for posts is somewhat greater than for beams and joists, it is not considered necessary to limit specifically the slope of grain near the ends of beams or joists which are to be used as posts. Pitch and Gum Pockets, Seams and Streaks The effect of pitch or gum on the strength of wood may be disregarded, although it is sometimes associated with pockets or seams where the absence of wood may affect the strength. Wane Wane is permitted in most structural grades. Its effect on the strength of the piece in bending or compression parallel to grain is not great. Wane at a point of bearing perpendicular to grain has a proportional effect on bearing stress and, in addition, may cause eccentricity of load or support. Where bearing stresses are high or eccentricity is objectionable, the structure can be designed so that the wane will be removed in framing or the lumber can be ordered “to be free of wane.” Density Density has a large effect on the strength of lumber. For a few species a visual inspection method has been developed which will separate the lumber into two density classifications, but there is considerable overlap of actual densities in the two classifications. If a more accurate method of density segregation, economically applicable to commercial production, could be devised, a large increase in allowable stress could be made for most lumber.

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Commentary Warp, Cup, Bow Warp, cup and bow may cause eccentricity of loading and torsional stresses and difficulties in framing. For ordinary construction the stresses produced can be disregarded if the member is straight enough for easy framing. Checks, Splits, Shakes Some grading rules limit checks, splits and shakes throughout the length of structural lumber because of their effect on hazard of decay, appearance, etc., and these considerations are the primary ones in post grades. In beams and joists the checks, splits and shakes within the middle half of the height of the piece within a distance from each end equal to three times the height of the piece are limited because of their effect on shear stresses. Outside of these limits checks, splits or shakes large enough to cause a shear failure are unlikely. Mismanufacture Mismanufacture affects framing primarily. If the strength of the pieces is based on the smallest size permitted, mismanufacture may be disregarded. Moisture Content a.

The strength of lumber in tension, compression and shear is a function of the moisture content at the time and is practically independent of its previous condition. However, changes in moisture content produce checks, and enlarge checks and splits already present. The amount of checking will increase with an increase in the size of the piece and will vary with the method of seasoning and exposure to weather. In Table 7-2-9, assume the lumber has not become more severely checked, because of improper seasoning or severe exposure to weather, than contemplated by the grading rules.

b. Under most conditions lumber which has been installed when green or saturated will dry out in service, and prolonged exposure to moisture will be required to raise the moisture content very much. Lumber of joist and plank sizes and larger which is not submerged or framed to retain moisture will not acquire much moisture content in exposure to usual weather most places in the United States. Some contact surfaces, such as the bearing between stringers and caps of railway trestles, are conducive to the retention of moisture, and at such surfaces it is recommended that the stresses be limited to those applicable to green or saturated lumber. c.

1

3

Good timber preservatives do not affect the strength-moisture content relations.

Decay

4

Decay weakens wood. The decrease in strength may be very marked when the decay is barely perceptible, and since decay may spread rapidly, infected structural members should be inspected frequently until replaced. It is common practice to reduce the allowable stresses for untreated lumber subject to decay hazard to offset loss of strength due to undetected decay. Such reductions should not be relied on to compensate for loss of strength due to known decay. Good preservatives can protect wood against decay for many years, and if applied by modern treating processes, properly conducted, the damage to the wood by the treating process may be disregarded. Duration of Load The allowable load varies with the length of time the load is applied. Figure 7-6-1 shows graphically the approximate relation of allowable stress to time. If the load is removed before failure is reached, there will be some recovery, but so little is known about the amount of recovery that it should be disregarded, and the duration of load should be figured as the sum of all the lengths of time that the load is applied. If lumber is subjected to several different loads with different durations, each combination should be investigated, and if each alone is safe the lumber may be considered safe. © 2011, American Railway Engineering and Maintenance-of-Way Association

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Timber Structures

Temperature, Heat The stresses recommended in Table 7-2-9, and the provisions in these notes on the use of stress-graded lumber assume the lumber is to be used under ordinary conditions of temperature. If abnormal temperatures are anticipated, the designer should refer to the U.S. Forest Laboratory Report No. R 471, Effect of Heat on the Properties and Serviceability of Wood. 6.2.5.6 Allowable Unit Stresses for Stress-Graded Lumber (2010) 6.2.5.6.1 Working Stresses Table 7-6-1, Note 4: Inland Douglas Fir and Douglas Fir-Larch are deemed to be refractory and hence very difficult to treat. Douglas Fir South is not produced in sufficient quantities and is somewhat weaker; its suitability for Timber Railroad Bridges is questionable.

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Commentary

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3

4

Figure 7-6-1. Chart Showing Relation of Design Stress to Duration of Load

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Timber Structures

Table 7-6-1. Derivation of listed values, using combination 16F-1.5E DF as an example

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Commentary

SECTION 6.3 RATING COMMENTARY 6.3.1.3 Factor of Safety, Variability (1988) There are many factors affecting the strength of lumber for which no satisfactory, commercially applicable methods of evaluating the effects have been found. These factors produce a variability among pieces which otherwise seem to be alike. Since the allowable stresses of Table 7-2-9 are based on the strength of the weakest pieces that may occur in the grade and assume that each piece must carry its load, it follows that if a load is carried by several members, not independent of each other, the designer could reasonably allow somewhat higher stresses. Conversely, if the failure of a single member would cause unusually great damage, the allowable stress on that member should be reduced. An overload of 50 percent will cause failure in only rare cases, but if the load is doubled, failures will be frequent.

SECTION 6.4 CONSTRUCTION AND MAINTENANCE COMMENTARY

SECTION 6.5 INSPECTION COMMENTARY

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3

4

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Chapter 7 Glossary1

1. LUMBER INDUSTRY ABBREVIATIONS2 a.

The same as American Softwood Lumber Standard as developed by the National Bureau of Standards.

b. These standard lumber abbreviations are commonly used for softwood lumber although all of them are not necessarily applicable to all species when used in the construction of contracts and other documents arising in transactions of purchase and sale of American Softwood Standard Lumber, these abbreviations shall be construed as provided therein. c.

There are additional abbreviations applicable to a particular region or species which may be included in approved grading rules.

d. Abbreviations are commonly used in the forms indicated, but variations, such as the use of periods and other forms of punctuation, are optional.

2. NOMENCLATURE OF COMMERCIAL DOMESTIC HARDWOODS AND SOFTWOODS3

1

The standard commercial names for lumber cut from species or species groups of domestic hardwoods and softwoods are the same as those listed in the current standard grading rules for the species.

3. TERMS

3

The following terms are used in Chapter 7, Timber Structures, and are placed here in alphabetical order for your convenience.

Air Dried Seasoned by exposure to the atmosphere, in the open or under cover, without artificial heat.

All-heart Of heartwood throughout; that is, free of sapwood.

American Standard Lumber See American Softwood Lumber Standards.

Annual Ring Growth layer put on in a single growth year. 1

References, Vol. 42, 1941, pp. 253, 868; Vol. 54, 1953, pp. 960, 1330; Vol. 61, 1960, pp. 587, 1095; Vol. 89, 1988, p. 106. References, Vol. 28, 1927, pp. 333, 1425; Vol. 42, 1941, pp. 261, 868; Vol. 54, 1953, pp. 961, 1330; Vol. 61, 1960, pp. 587, 1095; Vol. 89, 1988, p. 106. 3 References, Vol. 22, 1921, pp. 494, 1062; Vol. 27, 1926, pp. 833, 1406; Vol. 28, 1927, pp. 323, 1425; Vol. 30, 1929, pp. 1147, 1456; Vol. 34, 1933, pp. 66, 760; Vol. 37, 1936, pp. 671, 1037; Vol. 42, 1941, pp. 253, 868; Vol. 54, 1953, pp. 960, 1330; Vol. 61, 1960, pp. 587, 1095; Vol. 89, 1988, p. 106. 2

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Bark Pocket Patch of bark partially or wholly enclosed in the wood; classified as are pitch pockets.

Board See American Softwood Lumber Standards.

Bow See Warp.

Boxed Pith When the pith is between the four faces on an end of a piece.

Bright (sapwood) Unstained.

Characteristics Distinguishing features which by their extent and number determine the quality of a piece of lumber.

Check Lengthwise grain separation, usually occurring through the growth rings as a result of seasoning. • Surface Check. • Small Surface Check. Perceptible opening not over 4 inches long and 1/32 inch wide. • Medium Surface Check. Not over 1/32 inch wide and over 4 inches, but not over 10 inches long. • Large Surface Check. Over 1/32 inch wide or over 10 inches long. • End Check. Occurs on an end of a piece. • Through Check. Extends from one surface through the piece to the opposite surface or to an adjoining surface.

Chipped Grain Area where the surface is chipped or broken out in very short particles below the line of cut. Not classed as torn grain and, as usually found, is not considered unless in excess of 25 percent of the surface involved.

Clear Free, or practically free, of all blemishes, characteristics or defects.

Compression Wood Abnormal wood that forms on the underside of leaning and coniferous tress. It is characterized aside from its distinguishing color by being hard and brittle and by its relatively lifeless appearance.

Corner The intersection of two adjacent faces.

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Glossary

Crook See Warp.

Cross Break Separation of the wood across the width, such as may be due to tension resulting from unequal shrinkage or mechanical stress.

Cup See Warp.

Cutting Resulting pieces after crosscutting and/or ripping.

Decay Disintegration of wood substance due to action of wood-destroying fungi. Also known as dote and rot. • Advanced or Typical Decay. Older stage of decay in which disintegration is readily recognized because the wood has become punky, soft, and spongy, stringy, shaky, pitted, or crumbly. Decided discoloration or bleaching of the rotted wood is often apparent. • Incipient Decay. Early stage of decay in which disintegration has not proceeded far enough to soften or otherwise change the hardness of the wood perceptibly. Usually accompanied by a slight discoloration or bleaching of the wood.

1

• Pocket Rot. Typical decay which appears in the form of a hole, pocket, or area of soft rot, usually surrounded by apparently sound wood. • Water Soak or Stain. Water-soaked area in heartwood, usually interpreted as the incipient stage of certain wood rots.

3

De-grades Pieces which on reinspection prove of lower quality than the grade in which they were shipped.

Discoloration

4

See Stain.

Double End Trimmed Trimmed reasonably square by saw on both ends.

Dry Seasoned, not green (for the purpose of this standard, dry lumber is defined as lumber which has been seasoned to a maximum moisture content of 19 percent or less).

Edge The narrow face of rectangular shaped lumber.

Edge Grain (Vertical Grain) Annual rings (so-called grain) which form an angle of 45 degrees or more with the surface of the piece.

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Firm Red Heart A stage of incipient decay characterized by a reddish color in the heartwood, which does not unfit the wood for the majority of yard purposes, not to be confused with the natural red heart of some species.

Flat Grain (Splash Grain) Annual rings (so-called grain) which form an angle of less than 45 degrees with the surface of the piece.

Free of Heart Centers (FOHC) Free of heart centers (f.o.h.c.). when the pitch is not enclosed within the four sides of the piece.

Green Not fully seasoned (for the purpose of this standard, green lumber is defined as lumber having a moisture content in excess of 19 percent).

Gum Pocket Openings between growth rings which usually contains or has contained resin or bark or both.

Gum Seam Check or shake filled with gum.

Gum Spot Accumulation of gumlike substance occurring as a small patch. May occur in conjunction with a bird-peck or other injury to the growing wood.

Gum Streak Well-defined accumulation of gum in more or less regular streak. Classified as are pitch streaks.

Heart Face Face side free of sapwood.

Heart Shake See Shake-pitch Shake.

Heartwood Inner core of the tree trunk comprising the annual rings containing nonliving elements; usually darker in color than sapwood.

Hit and Miss Series of surfaced areas with skips not over 1/16 inch deep between them.

Hit or Miss To skip or surface a piece for a part or the whole of its length, provided it is nowhere more tha 1/16 inch scant.

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Glossary

Holes Holes may extend partially or entirely through a piece and be from any cause. To determine the size of a hole, average the maximum and minimum diameters, unless otherwise specified. • Pin Hole. Not over 1/16 inch in diameter. • Medium Hole. Ove 1/16 inch but not over 1/4 inch in diameter. • Large Hole. Over 1/4 inch in diameter.

Honeycomb Honeycomb is indicated by large pits in the wood.

Kiln Dried Seasoned in a chamber by means of artificial heat.

Knot Branch or limb, embedded in the tree and cut through in the process of lumber manufacture; classified according to size, quality, and occurrence. To determine the size of a knot, average the maximum length and maximum width, unless otherwise specified.

Knot Quality

1

• Decayed Knot. Softer than the surrounding wood, and containing advanced decay. • Encased Knot. Its rings of annual growth are not intergrown with those of the surrounding wood. • Hollow Knot. Apparently sound, except that it contains a hole over 1/4 inch in diameter. • Intergrown Knot. Its rings of annual growth are completely intergrown with those of the surrounding wood.

3

• Loose Knot. Not held tightly in place by growth or position, and cannot be relied upon to remain in place. • Fixed Knot. Will hold its place in a dry piece under ordinary conditions; can be moved under pressure, though not easily pushed out. • Pith Knot. Sound knot except that it contains pith hole not over 1/4 inch in diameter. • Sound Knot. Solid across its face, as hard as the surrounding wood, shows no indication of decay and may vary in color from the natural color of the wood to reddish brown or black. • Star-checked Knot. Having radial checks. • Tight Knot. So fixed by growth or position as to retain its place. • Firm Knot. Solid across its face, but containing incipient decay. • Water-tight Knot. Its rings of annual growth are completely intergrown with those of the surrounding wood on one surface of the piece, and it is sound on that surface.

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Timber Structures

Knot Occurrence • Branch Knots. Two or more divergent knots sawed lengthwise and tapering toward the pith at a common point. • Corner Knot. Located at the intersection of adjacent faces. • Knot Cluster. Two or more knots grouped together, the fibers of the wood being deflected around the entire unit. A group of single knots is not a knot cluster. • Single Knot. Occurs by itself, the fibers of the wood being deflected around it. • Spike Knot. A knot sawed in a lengthwise direction.

Loosened Grain Small portion of the wood loosened but not displaced.

Machine Burn Darkening or charring due to overheating by machine knives.

Machine Gouge Groove due to the machine cutting below the desired line cut.

Mismanufacture Includes all defects or blemished produced in manufacturing. See Chipped Grain, Hit and Miss, Hit or Miss, Loosened Grain, Machine Burn, Machine Gouge, Mismatched Lumber, Raised Grain, Skip, Torn Grain, and Variation in Sawing.

Mismatched Lumber Worked lumber that does not fit tightly at all points of contact between adjoining pieces, or in which the surfaces of adjoining pieces are not in the same plane. • Slight Mismatch. Surface variation not over 1/64 inch. • Medium Mismatch. Surface variation over 1/64 inch, but not over 1/32 inch. • Heavy Mismatch. Surface variation over 1/32 inch.

Mixed Grain Any combination of edge grain and flat grain.

Moisture Content Weight of the water in wood expressed in percentage of the weight of oven-dry wood.

Peck Channeled or pitted areas or pockets as sometimes found in cedar and cypress.

Pecky Characterized by Peck.

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Glossary

Pitch Accumulation of resin in the wood cells in a more or less irregular patch. • Light Pitch. Lightly evident presence of pitch. • Medium Pitch. Trace of pitch slightly more evident than light pitch. • Heavy Pitch. Very evident presence of pitch showing by its color and consistency. • Massed Pitch. Clearly defined accumulation of solid pitch in a body by itself.

Pitch Pocket Well-defined opening between growth rings which usually contain or has contained resin or bark or both. Bark also may be present in the pocket. • Very Small Pitch Pocket. Not over 1/8 inch in width and not over 2 inches in length. • Small Pitch Pocket. Not over 1/8 inch in width and not over 4 inches in length; or not over 1/4 inch in width and not over 2 inches in length. • Medium Pitch Pocket. Not over 1/8 inch in width and not over 8 inches in length; or not over 3/8 inch, in width and not over 4 inches in length.

1

• Large Pitch Pocket. Width or length exceeds the maximum permissible for a medium pitch pocket. • Closed Pitch Pocket. Does not show an opening on both sides of the piece. • Open (through) Pitch Pocket. Is cut across on both sides of the piece.

Pitch Seam

3

Shake or check filled with pitch.

Pitch Streak Well-defined accumulation of pitch in a more or less regular streak. • Small Pitch Streak. Not over one-twelfth the width by one-sixth the length of the surface on which it occurs. • Medium Pitch Streak. Over one-twelfth, but not over one-sixth the width by over one-sixth but not over one-third the length of the surface on which it occurs. • Large Pitch Streak. Over one-sixth the width by one-third the length of the surface on which it occurs.

Pith Small soft core in the structural center of a log. • Boxed Pith. When the pith is within the four faces on an end of a piece.

Pith Fleck Narrow streak resembling pith on the surface of a piece, usually brownish, up to several inches in length, resulting from burrowing of larvae in the growing tissue of the tree. © 2011, American Railway Engineering and Maintenance-of-Way Association

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Timber Structures

Quarter Sawed See, Edge Grain.

Radial Coincident with a radius from the axis (pith) of the tree to the circumference.

Raised Grain Roughened condition of the surface of dressed lumber in which the hard summerwood is raised above the softer springwood, but not torn loose from it.

Sapwood Outer layers of growth in a tree, exclusive of bark, which contain living elements; usually lighter in color than heartwood. • Bright Sapwood. Unstained.

Saw Butted Trimmed by a saw on both ends.

Seasoning Evaporation or extraction of moisture from green or partially dried wood.

Shake A lengthwise separation between or through the growth rings and may be further classified as ring shake or pith shake. • Fine Shake. A barely perceptible opening. • Slight Shake. More than a perceptible opening, but not over 1/32 inch wide. • Medium Shake. Over 1/32, but not over 1/8 inch wide. • Open Shake. Over 1/8 inch wide. • Cup Shake. Does not completely encircle the pith. • Round Shake. Completely encircles the pith. • Shell Shake. When both ends of a shake which has been cut across occur on the face or edge of a piece. • Through Shake. Extending from one surface through the piece to the opposite surface or to an adjoining surface. • Pith Shake (Heart Check). Extends across the rings of annual growth in one or more directions from the pith toward, but not to the surface of a piece. Distinguished from season check by having its greatest width nearest the pith, whereas the greatest width of a season check is ordinarily at the surface of a piece, and when a piece has boxed pith the greatest width of a season check is farthest from the pith.

Side Cut When the pith is not enclosed within the four sides of the piece. © 2011, American Railway Engineering and Maintenance-of-Way Association

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Glossary

Skip Area on a piece that failed to surface, classified as follows: • Slight Skip. Area not over six times the width of the piece that the planer knife failed to surface smoothly. • Shallow Skip (Small). Area not over six times the width of the piece that the planer knife failed to touch by not over 1/32 inch. • Deep (Heavy) Skip. Area not over twelve times the width of the piece that the planer knife failed to touch by not over 1/16 inch.

Smoke Dried Seasoned in the open, exposed to the heat and smoke of a fire maintained beneath and within stacks of lumber.

Softwood One of the group of trees which have needle-like or scale-like leaves. The term has no reference to the softness of the wood.

Sound Free of decay.

1

Spiral Grain Fibers which extend spirally about, instead of vertically along, the hole of a tree.

Split Lengthwise separation of the wood extending from one surface through the piece to the opposite surface or to an adjoining surface.

3

• Short Split. Length does not exceed either the width of a piece or one-sixth its length. • Medium Split. Length exceeds the width of a piece, but does not exceed one-sixth its length. • Long Split. Length exceeds one-sixth the length of a piece.

4

Springwood More or less open and porous tissue marking the inner part of each annual ring, formed early in the period of growth.

Stain Discoloration on or in lumber, of any color other than its natural color of the piece on which it appears; classified as follows: • Light Stain. Slight difference in color which will not materially impair the appearance of the piece if given a natural finish. • Medium Stain. Pronounced difference in color which, although it does not obscure the grain of the wood, is customarily objectionable in a natural but not a painted finish. • Heavy Stain. Difference in color so pronounced as practically to obscure the grain of the wood. © 2011, American Railway Engineering and Maintenance-of-Way Association

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Timber Structures

Summerwood Denser fibrous outer portion of each annual ring, usually without conspicuous pores, formed late in the growing period, not necessarily in summer.

Torn Grain Part of the wood torn out in dressing; classified as follows; • Slight Torn Grain. Not over 1/32 inch in depth. • Medium Torn Grain. Over 1/32 inch, but not over 1/16 inch deep. • Heavy Torn Grain. Over 1/16 inch, but not over 1/8 inch deep. • Deep Torn Grain. Over 1/8 inch deep.

Unsound Decayed.

Variation in Sawing A deviation from the line of cut. Slight variation is not over 1/16 inch in 1 inch lumber, 1/8 inch in 2 inches, 3/16 inch in 3 to 7 inches, and 1/4 inch in 8 inches and larger.

Wane This is bark or the lack of wood from any cause, on the corner of a piece. • Slight Wane. Not over 1/4 inch wide on the surface on which it appears, for one-sixth the length and onefourth the thickness of the piece. • Medium Wane. Over 1/4 inch, but not over 1/2 inch wide on the surface on which it appears, for one-sixth the length and one-fourth the thickness of the piece. • Large Wane. Over 1/2 inch wide on the surface on which it appears, or over one-sixth the length and onefourth the thickness of the piece, or both.

Warp Any variation from a true or plane surface; includes bow, crook, cup, or any combination thereof. • Bow. Deviation flatwise from a straight line from end to end of a piece; measured at the point of greatest distance from the straight line. • Crook. Deviation edgewise from a straight line from end to end of a piece; measured at the point of greatest distance from the straight line, and classified as slight, small, medium, and large. Based on a piece 4 inches wide and 16 feet long, the distance from each degree of crook shall be: slight crook, 1 inch; small crook, 1-1/2 inches; medium crook, 3 inches; and large crook, over 3 inches. For wider pieces it shall be 1/8 inch less for each additional 2 inches of width. Shorter or longer pieces may have the same curvature. • Cup. Curve in a piece across the grain or width of a piece; measured at the point of greatest deviation from a straight line from edge to edge and classified as slight, medium, and deep. Based on a piece 12 inches wide, the distance for each degree of cup shall be; slight cup, 1/4 inch, medium cup, 3/8 inch, and deep cup, 1/2 inch Narrower or wider pieces may have the same curvature.

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7

References

The following list of references used in Chapter 7, Timber Structures is placed here in alphabetical order for your convenience. 1. American Institute of Timber Construction. Standard Specifications for Hardwood Glued Laminated Timber. AITC 119-76. 2. American Institute of Timber Construction. Standard Specifications for Structural Glued Laminated Timber of Douglas Fir, Western Larch, Southern Pine, and California Redwood, AITC 117-76. 3. American Institute of Timber Construction. Standard Specifications for Structural Glued Laminated Timber Using Visually Graded Lumber of Douglas-Fir, Southern Pine, Hem-Fir, and Lodgepole Pine. AITC 120-76. 4. American Institute of Timber Construction. Timber Construction Standards AITC 100-72. 5. American Society for Testing and Materials. Standard Method for Establishing Stresses for Structural Glued Laminated Timber (Glulam) Manufactured From Visually Graded Lumber. ASTM D3737-78.

1

6. American Wood-Preservers Association. Standards C20 and C28. 7. AWPA. 2007. Book of Standards. Birmingham, AL: American Wood Preservers Association.

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8. Current National Design Specification for Stress-Grade Lumber and Its Fastenings, National Forest Products Association. 9. Fry, G., “Rail-Stringer Interaction.” Presentation to AREMA Committee No. 7, 12 August 2008. 10. Madsen, Borg, “Structural Behaviour of Timber” Timber Engineering Ltd., 1992. 11. Timber Construction Manual, by American Institute of Timber Construction, John Wiley and Sons, Inc., 1973. 12. U.S. Department of Agriculture Technical Bulletin 1069, Fabrication and Design of Glued Laminated Wood Structural Members, by A.D. Freas and M.L. Selbo, Forest Products Laboratory. Available from American Institute of Timber Construction. 13. U.S. Department of Commerce, Voluntary Product Standard PS 56-73, Structural Glued Laminated Timber (available from Superintendent of Documents, U.S. Government Printing Office).

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Appendix 1 - Contemporary Designs and Design Aids — 2011 — TABLE OF CONTENTS Section/Article

Description

Page

A1.1 Introduction . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-A1-2

A1.2 Stringers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-A1-3

A1.3 Pile Design Aids . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-A1-4

A1.4 Hankinson Formula . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-A1-6

1

A1.5 Comparison of Unit Stresses in Timbers in Open and Ballasted-Deck Trestles (2009) 7-A1-6 A1.5.1 For Open-Deck Trestles, E-80 Loading (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-A1-6 A1.5.2 For Ballasted-Deck Trestles, E-80 Loading (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-A1-10 A1.6 Stress Laminated Decks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-A1-19 A1.6.1 Stress Laminated Panel Design Stresses, LL Deflection and Minimum Transverse Stressing Required for Various Span Lengths and Panel Thicknesses . . . . . . . . . . . . . . . . . . . . . . 7-A1-19 A1.6.2 Calculation of Deck Loads for Stress Laminated Decks . . . . . . . . . . . . . . . . . . . . . . . . 7-A1-28 A1.6.3 Allowable Unit Stresses for Stress Graded Lumber - Railroad Loading (Visual Grading) 7-A1-28 A1.6.4 Typical Design Example for a Simple Stress Laminated Lumber Deck Panel . . . . . . . . . 7-A1-29 A1.6.5 Tables for Simple Stress Laminated Lumber Deck Panel Design . . . . . . . . . . . . . . . . . . . 7-A1-31

LIST OF FIGURES Figure

Description

7-A1-1 7-A1-2 7-A1-3 7-A1-4

Distribution of Load to Stringers of Timber Trestles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Distribution of Load to Piles of Timber Trestles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Graphical Solution of Hankinson Formula . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Typical Design Example for a Simple Stress Laminated Lumber Deck Panel. . . . . . . . . . . .

© 2011, American Railway Engineering and Maintenance-of-Way Association

Page 7-A1-3 7-A1-4 7-A1-6 7-A1-30

7-A1-1

3

Timber Structures

LIST OF TABLES Table

Description

Page

7-A1-1 7-A1-2 7-A1-3 7-A1-4

Comparison of Unit Stresses in Open Deck Trestles, Cooper E 80 Loading, No Impact . . . . . 7-A1-7 Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 80 Loading, No Impact . . 7-A1-11 Comparison of Unit Stresses in Open Deck Trestles, E - 80 Cooper Loadings, No Impact . . . 7-A1-17 Stress Laminated Panel Design Stresses, LL Deflection and Minimum Transverse Stressing Required for Various Span Lengths & Panel Thicknesses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-A1-20 7-A1-5 Stress Laminated Panel Design Stresses, LL Deflection and Minimum Transverse Stressing Required for Various Span Lengths & Panel Thicknesses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-A1-22 7-A1-6 Stress Laminated Panel Design Stresses, LL Deflection and Minimum Transverse Stressing Required for Various Span Lengths & Panel Thicknesses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-A1-24 7-A1-7 Stress Laminated Panel Design Stresses, LL Deflection and Minimum Transverse Stressing Required for Various Span Lengths & Panel Thicknesses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-A1-26 7-A1-8 Tabulation of Deck Loads for Stress Laminated Decks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-A1-28 7-A1-9 Allowable Unit Stresses for Stress Graded Lumber - Railroad Loading (Visual Grading) . . . . 7-A1-29 7-A1-10Tables for Simple Stress Laminated Lumber Deck Panel Design . . . . . . . . . . . . . . . . . . . . . . . 7-A1-32

A1.1 INTRODUCTION This Appendix contains information useful in the design of Recommended Contemporary Structures.

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A1-2

AREMA Manual for Railway Engineering

Appendix 1 - Contemporary Designs and Design Aids

A1.2

STRINGERS

1

3

4

Figure 7-A1-1. Distribution of Load to Stringers of Timber Trestles

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A1-3

Timber Structures

A1.3 PILE DESIGN AIDS

Figure 7-A1-2. Distribution of Load to Piles of Timber Trestles

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A1-4

AREMA Manual for Railway Engineering

Appendix 1 - Contemporary Designs and Design Aids

1

3

4

Figure 7-A1-2. Distribution of Load to Piles of Timber Trestles (Continued)

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A1-5

Timber Structures

A1.4 HANKINSON FORMULA

Figure 7-A1-3. Graphical Solution of Hankinson Formula

A1.5 COMPARISON OF UNIT STRESSES IN TIMBERS IN OPEN AND BALLASTED-DECK TRESTLES (2009) A1.5.1 FOR OPEN-DECK TRESTLES, E-80 LOADING (2010) For Open-Deck Trestles, E-80 Loading refer to Table 7-A1-1.

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A1-6

AREMA Manual for Railway Engineering

Appendix 1 - Contemporary Designs and Design Aids

Table 7-A1-1. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 80 Loading, No Impact 12’, 13’ and 14’ Spans All loads in pounds per track. All moments in foot-pounds per track. Panel length C to C of bents

12’

13’

13’

14’

14’

Number and size of stringers

8-10” x 16”

8-9” x 18”

8-10” x 18”

8-10” x 18”

6-10” x 20”

Above stringers

500

500

500

500

500

Stringers-nominal size

535

540

600

600

500

Total dead load

1035

1040

1100

1100

1000

Dead load per foot of track

Reaction on bent in pounds Dead load

12420

13520

14300

15400

14000

Live load

186740

197030

197030

208690

208690

Total

199160

Kind of bent

Pile

Number of piles or posts Size of piles or posts Total area of piles or posts-sq. in.

924

Pile

6

6

14D

12x14

Unit bearing stress on piles and posts-psi 216 Average load in tons per pile or post

210550

Frame

211330

Frame

Pile

6

6

14D

12x14

224090

Frame

Pile

6

6

14D

12x14

222690

Frame

Pile

Frame

6

6

6

6

14D

12x14

14D

12x14

1008

924

1008

924

1008

924

1008

924

1008

198

228

209

229

210

243

222

241

221

16.6

17.5

17.6

18.7

18.6

1

Bearing-Stringers on caps for continuous butt type deck. Area sq.in.-14” cap

1120

1008

1120

1120

840

Bearing stress-psi- 14” cap

178

209

189

200

265

Area sq.in.-16” cap

1280

1152

1280

1280

960

Bearing stress-psi- 16” cap

156

183

165

175

232

16608

19764

20904

24432

22211

Bending in stringers Dead load moment-foot pounds per track

Live load moment-foot pounds per track

280000

327000

327000

387000

387000

Total load moment-foot pounds per track

297000

347000

348000

412000

410000

Section modulus-nominal size

3413

3888

4320

4320

4000

Bending stress-psi-nominal size

1044

1071

967

1144

1230

Section modulus-dressed size

3225

3676

4096

4096

3803

Bending stress-psi-dressed size

1105

1133

1020

1207

1294

18

20

Longitudinal shear-Standard formula- First driver at height of the beam from the support. Depth nominal c to c

16

18

18

12

13

13

14

14

L = (c to c) + 0.5 - 14/12

11.33

12.33

12.33

13.33

13.33

L’ ignore within d of face

8.17

8.83

8.83

9.83

9.50

a

10

10.83

10.83

11.83

11.67

b

5

5.83

5.83

c, if > d W Dead load = WL/2

6.83

6.67

1.83

1.67

10.5

1040

1100

1100

1000

4226

4593

4858

5408

4750

Live Load

102353

104865

104865

109000

107000

Total load

106579

109458

108723

114408

111750

1280

1296

1440

1440

1200

Cross section-sq. in.-nominal size

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A1-7

3

4

Timber Structures

Table 7-A1-1. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 80 Loading, No Impact 12’, 13’ and 14’ Spans (Continued) All loads in pounds per track. All moments in foot-pounds per track. Panel length C to C of bents

12’

13’

13’

14’

14’

Number and size of stringers

8-10” x 16”

8-9” x 18”

8-10” x 18”

8-10” x 18”

6-10” x 20”

Unit shear- psi- = 3R/2bh

125

127

114

119

140

Cross section-sq. in.-dressed size

1240

1260

1400

1400

1170

Unit shear- psi- = 3R/2bh

129

130

118

123

143

Assumptions: L = Distance C to C bents for bearing on caps in feet = Distance face to face of caps plus 0.5 foot for stringer bending and shear. (Assume 14² Cap) W = Total Dead Load per linear foot of track: Rail and fastenings = 200 pounds per linear foot Ties 8² ´ 8² ´ 10¢ @ 12² ctrs = 267 pounds per linear foot R = Total Reaction

h = Height of stringer in feet b = Breadth of stringers in feet P = Weight on one driving axle = 80000 pounds a = Distance from load P to support, in feet Dressed size = Nominal size less 1/2² in depth

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A1-8

AREMA Manual for Railway Engineering

Appendix 1 - Contemporary Designs and Design Aids

Table 7-A1-1. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 80 Loading, No Impact 15’ and 16’ Spans All loads in pounds per track. All moments in foot-pounds per track. Panel length C to C of bents

15’

15’

16’

16’

Number and size of stringers

8-10” x 18”

8-10” x 20”

8-10” x 20”

8-12” x 20”

Above stringers

500

500

500

500

Stringers-nominal size

600

667

667

800

Total dead load

1100

1167

1167

1300

Dead load

16500

17505

18672

20800

Live load

218740

218740

227430

227430

Total

235240

236245

246102

248230

Dead load per foot of track

Reaction on bent in pounds

Kind of bent

Pile

Frame

6

6

Size of piles or posts

14D

Total area of piles or posts-sq. in. Unit bearing stress on piles and postspsi

Number of piles or posts

Pile

Frame

Pile

Frame

Pile

Frame

6

6

6

6

6

6

12x14

14D

12x14

14D

12x14

14D

12x14

924

1008

924

1008

924

1008

924

1008

255

233

256

234

266

244

269

246

Average load in tons per pile or post

19.6

19.7

20.5

20.7

Area sq.in.-14”cap

1120

1120

1120

1344

Bearing stress-psi- 14” cap

210

211

220

185

Area sq.in.-16” cap

1280

1280

1280

1536

Bearing stress-psi- 16” cap

184

185

192

162

Dead load moment-foot pounds per track

28235

29955

34282

38189

Live load moment-foot pounds per track

447000

447000

506000

506000

Total load moment-foot pounds per track

476000

477000

541000

545000

Section modulus-nominal size

4320

5333

5333

6400

Bending stress-psi-nominal size

1322

1073

1217

1022

Section modulus-dressed size

4096

5071

5071

6111

Bending stress-psi-dressed size

1395

1129

1280

1070

1

Bearing-Stringers on caps for continuous butt type deck.

3

Bending in stringers

Longitudinal shear-Standard formula- First driver at height of the beam from the support. Depth nominal

18

20

20

20

c to c

15

15

16

16

L = (c to c) + 0.5 - 14/12

14.33

14.33

15.33

15.33

L’ ignore within d of face

10.83

10.50

11.50

11.50

a

13.08

13.08

14.00

14.00

b

8.08

8.08

9.00

9.00

c, if > d

3.08

3.08

4.00

4.00

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A1-9

4

Timber Structures

Table 7-A1-1. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 80 Loading, No Impact 15’ and 16’ Spans (Continued) All loads in pounds per track. All moments in foot-pounds per track. Panel length C to C of bents

15’

15’

16’

16’

Number and size of stringers

8-10” x 18”

8-10” x 20”

8-10” x 20”

8-12” x 20”

1100

1167

1167

1300

5958

6127

6710

7475

Live Load

126977

124313

131739

131739

Total load

132935

130313

138449

139214

Cross section-sq. in.-nominal size

1440

1600

1600

1920

Unit shear- psi- = 3R/2bh

138

122

130

109

Cross section-sq. in.-dressed size

1400

1560

1560

1872

Unit shear- psi- = 3R/2bh

142

125

133

112

W Dead load = WL/2

Assumptions: L = Distance C to C bents for bearing on caps in feet = Distance face to face of caps plus 0.5 foot for stringer bending and shear. (Assume 14² Cap) W = Total Dead Load per linear foot of track: Rail and fastenings = 200 pounds per linear foot Ties 8² ´ 8² ´ 10¢ @ 12² ctrs = 267 pounds per linear foot R = Total Reaction

h = Height of stringer in feet b = Breadth of stringers in feet P = Weight on one driving axle = 80000 pounds a = Distance from load P to support, in feet Dressed size = Nominal size less 1/2² in depth

A1.5.2 FOR BALLASTED-DECK TRESTLES, E-80 LOADING (2010) For Ballasted-Deck Trestles, E-80 Loading refer to Table 7-A1-2.

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A1-10

AREMA Manual for Railway Engineering

Appendix 1 - Contemporary Designs and Design Aids

Table 7-A1-2. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 80 Loading, No Impact 11.5’, 12’, and 12.5’ Spans All loads in pounds per track. All moments in foot-pounds per track Panel length C to C of bents

11.5’

12’

12’

12.5’

Number and size of stringers

10-8” x 16”

8-9” x 18”

10-9” x 16”

12-8” x 16”

Above stringers

2310

2310

2310

2310

Stringers-nominal size

530

540

600

640

Total dead load

2840

2850

2910

2950

Dead load per foot of track

Reaction on bent in pounds Dead load

32660

34200

34920

36875

Live load

180690

186740

186740

191890

Total

213350

220940

221660

228765

Kind of bent

Pile

Frame

Pile

Number of piles or posts Size of piles or posts

6

6

14D

12x14

Total area of piles or posts-sq. in.

924

Unit bearing stress on piles and posts-psi

231

Average load in tons per pile or post

Frame

Pile

6

6

6

6

6

6

14D

12x14

14D

12x14

14D

12x14

1008

924

1008

924

1008

924

1008

212

239

219

240

220

248

227

17.8

Frame

Pile

Frame

18.4

18.5

19.1

1

Bearing-Stringers on caps for continuous butt type deck. Area sq.in.-14” cap

896

756

1008

1120

Bearing stress-psi- 14” cap

238

292

220

204

Area sq.in.-16” cap

1024

864

1152

1280

Bearing stress-psi- 16” cap

208

256

192

179

41000

46000

47000

52000

3

Bending in stringers Dead load moment-foot pounds per track Live load moment-foot pounds per track

257000

280000

280000

310000

Total load moment-foot pounds per track

299000

327000

328000

363000

Section modulus-nominal size

2731

2916

3072

3413

Bending stress-psi-nominal size

1314

1346

1281

1276

Section modulus-dressed size

2563

2756

2883

3203

Bending stress-psi-dressed size

1400

1424

1365

1360

16

16

4

Longitudinal shear-Standard formula- First driver at height of the beam from the support. Depth nominal

16

18

c to c

11.5

12

12

12.5

L = (c to c) + 0.5 - 14/12

10.83

11.33

11.33

11.83

L’ ignore within d of face

7.67

7.83

8.17

8.67

a

9.5

9.83

10.00

10.50

b

4.5

4.83

5.00

5.50

2840

2850

2910

2950

c, if > d W

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A1-11

Timber Structures

Table 7-A1-2. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 80 Loading, No Impact 11.5’, 12’, and 12.5’ Spans (Continued) All loads in pounds per track. All moments in foot-pounds per track Panel length C to C of bents

11.5’

12’

12’

12.5’

Number and size of stringers

10-8” x 16”

8-9” x 18”

10-9” x 16”

12-8” x 16”

Dead load = WL/2

10887

11163

11883

12783

Live Load

99692

100000

102353

104789

Total load

110579

111163

114235

117572

Cross section-sq. in.-nominal size

1280

1296

1440

1536

Unit shear- psi- = 3R/2bh

130

129

119

115

Cross section-sq. in.-dressed size

1240

1260

1395

1488

Unit shear- psi- = 3R/2bh

134

132

123

119

Assumptions: L = Distance C to C bents for bearing on caps in feet = Distance face to face of caps plus 0.5 foot for stringer bending and shear. (Assume 14² cap) W = Total Dead Load per linear foot of track: Rail and fastenings = 200 pounds per linear foot Ballast = 120 pounds per cubic foot R = Total Reaction

h = Height of stringer in feet b = Breadth of stringers in feet P = Weight on one driving axle = 80000 pounds a = Distance from load P to support, in feet Dressed size = Nominal size less 1/2² in depth In calculating bearing, bending, and shear stresses outer stringers are considered as carrying no load.

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A1-12

AREMA Manual for Railway Engineering

Appendix 1 - Contemporary Designs and Design Aids

Table 7-A1-2. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 80 Loading, No Impact 13’ and 14’ Spans All loads in pounds per track. All moments in foot-pounds per track Panel length C to C of bents

13’

13’

13’

14’

14’

Number and size of stringers

10-10” x 16”

10-9” x 18”

12-9” x 16”

10-10” x 18”

8-10” x 20”

Above stringers

2310

2310

2310

2310

2310

Stringers-nominal size

670

680

720

750

670

Total dead load

2980

2990

3030

3060

2980

Dead load

38740

38870

39390

42840

41720

Live load

197030

197030

197030

208690

208690

Total

235770

235900

236420

251530

250410

Dead load per foot of track

Reaction on bent in pounds

Kind of bent

Pile

Frame

Pile

Frame

Pile

Frame

Pile

Frame

Pile

Frame

Number of piles or posts

6

6

6

6

6

6

6

6

6

6

Size of piles or posts

14D

12x14

14D

12x14

14D

12x14

14D

12x14

14D

12x14

Total area of piles or posts-sq. in.

924

1008

924

1008

924

1008

924

1008

924

1008

234

255

234

256

235

272

250

271

248

Unit bearing stress on piles and posts-psi 255 Average load in tons per pile or post

19.6

19.7

19.7

21.0

20.9

1

Bearing-Stringers on caps for continuous butt type deck. Area sq.in.-14” cap

1120

1008

1260

1120

840

Bearing stress-psi- 14” cap

211

234

188

225

298

Area sq.in.-16” cap

1280

1152

1440

1280

960

Bearing stress-psi- 16” cap

184

205

164

197

261

Dead load moment-foot pounds per track

57000

57000

58000

68000

66000

Live load moment-foot pounds per track

340000

340000

340000

400000

400000

398000

398000

399000

469000

467000

Section modulus-nominal size

3413

3888

3840

4320

4000

Bending stress-psi-nominal size

1399

1228

1247

1303

1401

Section modulus-dressed size

3203

3675

3604

4083

3803

Bending stress-psi-dressed size

1491

1300

1329

1378

1474

3

Bending in stringers

Total load moment-foot pounds per track

Longitudinal shear-Standard formula- First driver at height of the beam from the support. Depth nominal

16

18

16

18

20

c to c

13

13

13

14

14

L = (c to c) + 0.5 - 14/12

12.33

12.33

12.33

13.33

13.33

L’ ignore within d of face

9.17

8.83

9.17

9.83

9.50

a

11.00

10.83

11.00

11.83

11.67

b

6.00

5.83

6.00

6.83

6.67

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A1-13

4

Timber Structures

Table 7-A1-2. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 80 Loading, No Impact 13’ and 14’ Spans (Continued) All loads in pounds per track. All moments in foot-pounds per track Panel length C to C of bents

13’

13’

13’

14’

14’

Number and size of stringers

10-10” x 16”

10-9” x 18”

12-9” x 16”

10-10” x 18”

8-10” x 20”

1.83

1.67

c, if > d W

2890

2990

3030

3060

2980

Dead load = WL/2

13246

13206

13888

15045

14155

Live Load

107027

104865

107027

109000

107000

Total load

120273

118071

120915

124045

121155

Cross section-sq. in.-nominal size

1600

1620

1728

1800

1600

Unit shear- psi- = 3R/2bh

113

109

105

103

114

Cross section-sq. in.-dressed size

1550

1575

1674

1750

1560

Unit shear- psi- = 3R/2bh

116

112

108

106

116

Assumptions: L = Distance C to C bents for bearing on caps in feet = Distance face to face of caps plus 0.5 foot for stringer bending and shear. (Assume 14² cap) W = Total Dead Load per linear foot of track: Rail and fastenings = 200 pounds per linear foot Ballast = 120 pounds per cubic foot R = Total Reaction

h = Height of stringer in feet b = Breadth of stringers in feet P = Weight on one driving axle = 80000 pounds a = Distance from load P to support, in feet Dressed size = Nominal size less 1/2² in depth In calculating bearing, bending, and shear stresses outer stringers are considered as carrying no load.

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A1-14

AREMA Manual for Railway Engineering

Appendix 1 - Contemporary Designs and Design Aids

Table 7-A1-2. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 80 Loading, No Impact 15’ and 16’ Spans All loads in pounds per track. All moments in foot-pounds per track Panel length C to C of bents

15’

15’

15’

16’

16’

Number and size of stringers

12-9” x 18”

10-10” x 18”

12-10” x 18”

10-10” x 20”

10-12” x 20”

Above stringers

2310

2310

2310

2310

2310

Stringers-nominal size

810

750

900

830

1000

Total dead load

3120

3060

3210

3140

3310

Dead load

46800

45900

48150

50240

52960

Live load

218740

218740

218740

227430

227430

Total

265540

264640

266890

277670

280390

Dead load per foot of track

Reaction on bent in pounds

Kind of bent

Pile

Frame

Pile

Frame

Pile

Frame

Pile

Frame

Pile

Frame

Number of piles or posts

6

6

6

6

6

6

6

6

6

6

Size of piles or posts

14D

12x14

14D

12x14

14D

12x14

14D

12x14

14D

12x14

Total area of piles or posts-sq. in.

924

1008

924

1008

924

1008

924

1008

924

1008

263

292

263

289

265

241

221

303

278

Unit bearing stress on piles and posts-psi 287 Average load in tons per pile or post

22.1

22.1

22.2

23.1

23.4

1

Bearing-Stringers on caps for continuous butt type deck. Area sq.in.-14” cap

1260

1120

1400

1120

1344

Bearing stress-psi- 14” cap

211

236

191

248

209

Area sq.in.-16” cap

1440

1280

1600

1280

1536

Bearing stress-psi- 16” cap

184

207

167

217

183

Dead load moment-foot pounds per track

80000

79000

82000

92000

97000

Live load moment-foot pounds per track

460000

460000

460000

520000

520000

541000

540000

543000

613000

618000

Section modulus-nominal size

4860

4320

5400

5333

6400

Bending stress-psi-nominal size

1336

1500

1207

1379

1159

Section modulus-dressed size

4594

4083

5104

5070

6084

Bending stress-psi-dressed size

1413

1587

1277

1451

1219

3

Bending in stringers

Total load moment-foot pounds per track

Longitudinal shear-Standard formula- First driver at height of the beam from the support. Depth nominal

18

18

18

20

20

c to c

15

15

15

16

16

L = (c to c) + 0.5 - 14/12

14.33

14.33

14.33

15.33

15.33

L’ ignore within d of face

10.83

10.83

10.83

11.50

11.50

a

13.08

13.08

13.08

14.00

14.00

b

8.08

8.08

8.08

9.00

9.00

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A1-15

4

Timber Structures

Table 7-A1-2. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 80 Loading, No Impact 15’ and 16’ Spans (Continued) All loads in pounds per track. All moments in foot-pounds per track Panel length C to C of bents

15’

15’

15’

16’

16’

Number and size of stringers

12-9” x 18”

10-10” x 18”

12-10” x 18”

10-10” x 20”

10-12” x 20”

c, if > d

3.08

3.08

3.08

4.00

4.00

W

3120

3060

3210

3140

3310

Dead load = WL/2

16900

16575

17388

18055

19033

Live Load

126977

126977

126977

131739

131739

Total load

143877

143552

144364

149794

150772

Cross section-sq. in.-nominal size

1944

1800

2160

2000

2400

Unit shear- psi- = 3R/2bh

111

120

100

112

94

Cross section-sq. in.-dressed size

1890

1750

2100

1950

2340

Unit shear- psi- = 3R/2bh

114

123

103

115

97

Assumptions: L = Distance C to C bents for bearing on caps in feet = Distance face to face of caps plus 0.5 foot for stringer bending and shear. (Assume 14² cap) W = Total Dead Load per linear foot of track: Rail and fastenings = 200 pounds per linear foot Ballast = 120 pounds per cubic foot R = Total Reaction

h = Height of stringer in feet b = Breadth of stringers in feet P = Weight on one driving axle = 80000 pounds a = Distance from load P to support, in feet Dressed size = Nominal size less 1/2² in depth In calculating bearing, bending, and shear stresses outer stringers are considered as carrying no load.

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A1-16

AREMA Manual for Railway Engineering

Glued Laminated Sections Assume 24F-1.8E DF or SP Cooper Design Load

80

80

80

80

15' 0 10-6.75 x18

14' 0 10-6.75 x16.5

12' 6" 8- 6.75 × 16.5

500 506 1006

500 464 964

500 371 871

15094 218666 233760 Pile Frame 6 6 14" D 12 x 14 924 1008

13497 208571 222068 Pile Frame 6 6 14" D 12 x 14 924 1008

10891 192000 202891 Pile Frame 6 6 14" D 12 x 14 924 1008

80

Panel Length C to C of Bents 12' 6" 14' 0 8- 6.75 × 16 8-6.75x 18 Number and size of Stringers Dead Load per foot of track 500 500 Above Stringers 360 405 Stringers -nominal size 860 905 Total Dead Load Reaction on bent, pounds 10750 12670 Dead Load 192000 208571 Live Load 202750 221241 Total Pile Frame Pile Frame Kind of Bent Number of piles of posts 6 6 6 6 Size of piles or posts 14" D 12 x 14 14" D 12 x 14 Total Area of piles of posts, sq.-in. 924 1008 924 1008 Unit bearing stress on piles or posts, lb. per sq. 219 201 239 219 in. Average load in Tons per pile or post 17 17 18 18 Bearing-Stringers on caps for contineous Butt type Deck 756 756 Area sq. in. - 14" cap 268 293 Bearing stress - lb. Per sq. in. - 14" cap 864 864 Average sq. in. 16" cap 235 256 Bearing stress - lb. Per sq. in. - 16" cap Bending in Stringers 15053 20111 Dead Load Moment - foot pounds per track 310000 400000 Live Load Moments - foot pounds per track 325053 420111 Total Load Moment - foot pounds per track 2304 2916 Section Modulus-nominal size 1693 1729 Bending stress-lb per sq. in - nominal size Longitudinal shear-Standard formula - - First driver at height of the beam from the support 16 18 depth nominal

253

232

19

19

240 19

220 19

220 17

201 17

945 247 1080 216

945 235 1080 206

756 268 864 235

25841 460000 485841 3645 1599

21424 400000 421424 3063 1651

15250 310000 325250 2304 1694

18

16.5

16.5

7-A1-17

Appendix 1 - Contemporary Designs and Design Aids

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

Table 7-A1-3. Comparison of Unit Stresses in Open Deck Trestles, E - 80 Cooper Loadings, No Impact All loads in pounds per track. All moments in foot-pounds per track.

AREMA Manual for Railway Engineering

© 2011, American Railway Engineering and Maintenance-of-Way Association

c, if > d 810 W 3308 Dead load = WL'/2 71135 Live load 74443 Total load 768 Cross section - sq. in.-nominal size 145 Unit shear-lb per sq. in. = 3R/2bh 744 Cross section - sq. in.-dressed size 150 Unit shear-lb per sq. in. = 3R/2bh Assumptions: L = Distance C to C bents for bearing on caps in feet = Distance face to face of caps plus 0.5 foot for stringer bending and shear. (Assume 14 cap) W = Total Dead Load per linear foot of track: Rail and fastenings = 200 pounds per linear foot Ballast = 120 pounds per cubic foot R = Total Reaction

900 3675 89303 92978 960 145 930 150

905 3997 90446 94443 972 146 945 150

927 3552 95705 99257 1024 145 992 150

905 3545 91000 94545 972 146 945 150

950 3958 100997 104956 1080 146 1050 150

h = Height of stringer in feet b = Breadth of stringers in feet P = Weight on one driving axle = 72000 pounds a = Distance from load P to support, in feet Dressed size = Nominal size less 1/2 in depth In calculating bearing, bending, and shear stresses, outer stringers are considered as carrying no load.

950 4196 100801 104997 1080 146 1050 150

2.42 1000 5250 111767 117017 1200 146 1170 150

Timber Structures

7-A1-18

Table 7-A1-3. Comparison of Unit Stresses in Open Deck Trestles, E - 80 Cooper Loadings, No Impact (Continued) All loads in pounds per track. All moments in foot-pounds per track.

Appendix 1 - Contemporary Designs and Design Aids

A1.6 STRESS LAMINATED DECKS A1.6.1 STRESS LAMINATED PANEL DESIGN STRESSES, LL DEFLECTION AND MINIMUM TRANSVERSE STRESSING REQUIRED FOR VARIOUS SPAN LENGTHS AND PANEL THICKNESSES Ensure that the allowable stresses for the material you have selected are not exceeded by any of the design stresses tabulated for the particular span and panel thickness chosen.

1

3

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A1-19

Species: Douglas Fir Grade: No. 1

Allowable Stresses (psi) Wet Condition (> 19% M.C.)

Fb 1150 x Cls

1.5

Fv 80

1.33

x Cv

Fc+ 375 E

1750000

Fb’ 1725 Dead Load (includes: track, ballast, curb, Fv’ 106 protective cover, stressing system) 4128 lb/ft Variable Dead Load due to various panels’ thicknesses (per inch of panel thickness) 70 lb/ft

Timber Structures

7-A1-20

Table 7-A1-4. Stress Laminated Panel Design Stresses, LL Deflection and Minimum Transverse Stressing Required for Various Span Lengths & Panel Thicknesses

AREMA Manual for Railway Engineering

© 2011, American Railway Engineering and Maintenance-of-Way Association

Species: Douglas Fir - Larch Grade: No. 1

Allowable Stresses (psi) Wet Condition (> 19% M.C.)

Fb 1150 x Cls

1.5

Fv 80

1.33

x Cv

Fc+ 375 E

1750000

Fb’ 1725 Dead Load (includes: track, ballast, curb, Fv’ 106 protective cover, stressing system) 4128 lb/ft Variable Dead Load due to various panels’ thicknesses (per inch of panel thickness) 70 lb/ft

7-A1-21

Appendix 1 - Contemporary Designs and Design Aids

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

Table 7-A1-4. Stress Laminated Panel Design Stresses, LL Deflection and Minimum Transverse Stressing Required for Various Span Lengths & Panel Thicknesses (Continued)

Species: Southern Pine Grade: No. 1

Allowable Stresses (psi) Wet Condition (> 19% M.C.)

Fb 1075 x Cls

1.5

Fv 75

1

x Cv

Fc+ 340 E

1500000

Fb’ 1613 Dead Load (includes: track, ballast, curb, protective cover, stressing system) Fv’ 75 4128 lb/ft Variable Dead Load due to various panels’ thicknesses (per inch of panel thickness) 70 lb/ft

Timber Structures

7-A1-22

Table 7-A1-5. Stress Laminated Panel Design Stresses, LL Deflection and Minimum Transverse Stressing Required for Various Span Lengths & Panel Thicknesses

AREMA Manual for Railway Engineering

© 2011, American Railway Engineering and Maintenance-of-Way Association

Species: Southern Pine Grade: No. 1

Allowable Stresses (psi) Wet Condition (> 19% M.C.)

Fb 1075 x Cls

1.5

Fv 75

1

x Cv

Fc+ 340 E

1500000

Fb’ 1613 Dead Load (includes: track, ballast, curb, protective cover, stressing system) Fv’ 75 4128 lb/ft Variable Dead Load due to various panels’ thicknesses (per inch of panel thickness) 70 lb/ft

7-A1-23

Appendix 1 - Contemporary Designs and Design Aids

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

Table 7-A1-5. Stress Laminated Panel Design Stresses, LL Deflection and Minimum Transverse Stressing Required for Various Span Lengths & Panel Thicknesses (Continued)

Species: Red Oak Grade: No. 1

Allowable Stresses (psi) Wet Condition (> 19% M.C.)

Fb 1000 x Cls

1.5

Fv 75

1.33

x Cv

Fc+ 495 E

1350000

Fb’ 1500 Dead Load (includes: track, ballast, curb, Fv’ 99.8 protective cover, stressing system) 4128 lb/ft Variable Dead Load due to various panels’ thicknesses (per inch of panel thickness) 70 lb/ft

Timber Structures

7-A1-24

Table 7-A1-6. Stress Laminated Panel Design Stresses, LL Deflection and Minimum Transverse Stressing Required for Various Span Lengths & Panel Thicknesses

AREMA Manual for Railway Engineering

© 2011, American Railway Engineering and Maintenance-of-Way Association

Species: Red Oak Grade: No. 1

Allowable Stresses (psi) Wet Condition (> 19% M.C.)

Fb 1000 x Cls

1.5

Fv 75

1.33

x Cv

Fc+ 495 E

1350000

Fb’ 1500 Dead Load (includes: track, ballast, curb, Fv’ 99.8 protective cover, stressing system) 4128 lb/ft Variable Dead Load due to various panels’ thicknesses (per inch of panel thickness) 70 lb/ft

7-A1-25

Appendix 1 - Contemporary Designs and Design Aids

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

Table 7-A1-6. Stress Laminated Panel Design Stresses, LL Deflection and Minimum Transverse Stressing Required for Various Span Lengths & Panel Thicknesses (Continued)

Ensure that the allowable stresses for the material you have Dead Load (includes: track, ballast, curb, protective cover, stressing system): selected are not exceeded by any of the design stresses tabulated for the particular span and panel thickness chosen. 4128 lb/ft

AREMA Manual for Railway Engineering

© 2011, American Railway Engineering and Maintenance-of-Way Association

NOTE: i, ii, and iii are the governing case for max. longitudinal shear (AREMA); i = 1st driver @ qtr. point; ii = shear formula with 1st driver @ 3x height of beam; iii = revised shear formula with 1st driver @ 3x height of beam. See Table 7-A1- for details.

Variable Dead Load due to various panels’ thicknesses (per inch of panel thickness): 70 lb/ft

Timber Structures

7-A1-26

Table 7-A1-7. Stress Laminated Panel Design Stresses, LL Deflection and Minimum Transverse Stressing Required for Various Span Lengths & Panel Thicknesses

Ensure that the allowable stresses for the material you have Dead Load (includes: track, ballast, curb, protective cover, selected are not exceeded by any of the design stresses stressing system): tabulated for the particular span and panel thickness chosen. 4128 lb/ft NOTE: i, ii, and iii are the governing case for max. longitudinal shear (AREMA); i = 1st driver @ qtr. point; ii = shear formula with 1st driver @ 3x height of beam; iii = revised shear formula with 1st driver @ 3x height of beam. See Table 7-A1- for details.

Variable Dead Load due to various panels’ thicknesses (per inch of panel thickness): 70 lb/ft

7-A1-27

Appendix 1 - Contemporary Designs and Design Aids

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

Table 7-A1-7. Stress Laminated Panel Design Stresses, LL Deflection and Minimum Transverse Stressing Required for Various Span Lengths & Panel Thicknesses (Continued)

Timber Structures

A1.6.2 CALCULATION OF DECK LOADS FOR STRESS LAMINATED DECKS

Table 7-A1-8. Tabulation of Deck Loads for Stress Laminated Decks ASSUMPTIONS: width of timber portion of laminated deck = width of curb timber = maximum ballast depth below track ties = additional depth of ballast between track ties = weight per volume of treated timber = weight per volume of ballast = weight per volume of waterproofing = prestressing rods 2’ spacing, 1” dia. rod with nut & cap each end = bearing/anchorage = C15X40 each side with 20 lb anchor plates = walkway 0 lb/ft or 110 lb/ft = track tie length =

14 ft. 9 in. 24 in. 5 in. 60 lb/cu.ft. 120 lb/cu.ft. 0.2 lb/sq.ft. 20 lb/ft. 100 lb/ft. 0 lb/ft. 8.5 ft.

ITEMS (excluding laminate members): Track c/w rails, inside guard rails and fastenings

200 lb/ft

Ballast including track ties

3625 lb/ft

Curb timbers on both sides

180 lb/ft

Protective cover (Geotextile)

3 lb/ft

Walkway

0 lb/ft

Prestressing rods

20 lb/ft

Bearing/Anchorage

100 lb/ft

TOTAL

4128 lb/ft

DECK LAMINAE: Per inch thickness of deck

70 lb/ft

(i.e. 14” thick deck panel, 14 x 70 = 980 lb/ft)

A1.6.3 ALLOWABLE UNIT STRESSES FOR STRESS GRADED LUMBER - RAILROAD LOADING (VISUAL GRADING)

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A1-28

AREMA Manual for Railway Engineering

Cls - load sharing factor applied to Fb, 1.3 for select structural and 1.5 for No. 1 or No. 2 Cv - Shear stress factor applied to Fv, provided length for split on wide face is limited to 1 x wide face (not applicable for Southern Pine as per AREMA Manual)

A1.6.4 TYPICAL DESIGN EXAMPLE FOR A SIMPLE STRESS LAMINATED LUMBER DECK PANEL 7-A1-29

Appendix 1 - Contemporary Designs and Design Aids

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

Table 7-A1-9. Allowable Unit Stresses for Stress Graded Lumber - Railroad Loading (Visual Grading)

Timber Structures

Figure 7-A1-4. Typical Design Example for a Simple Stress Laminated Lumber Deck Panel

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A1-30

AREMA Manual for Railway Engineering

Appendix 1 - Contemporary Designs and Design Aids

1

3

4

Figure 7-A1-4. Typical Design Example for a Simple Stress Laminated Lumber Deck Panel (Continued)

A1.6.5 TABLES FOR SIMPLE STRESS LAMINATED LUMBER DECK PANEL DESIGN

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A1-31

Timber Structures

Table 7-A1-10. Tables for Simple Stress Laminated Lumber Deck Panel Design The following table has been developed for Cooper’s E 80 loading and is used as a base for all other E loadings. Multiply the table value by the design E-rating and divide by 80.

The following tables are based on an HS 20-44 vehicle with maximum wheel load of 16,000 lbs. vt & mt must be multiplied by the design axle load in kips (or E-rating) and divided by 32 kips (2 x 16,000 lbs wheel load) to obtain the appropriate Mt & Vt.

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A1-32

AREMA Manual for Railway Engineering

30

Appendix 2 - Temporary Structures — 2010 — TABLE OF CONTENTS Section/Article

Description

Page

A2.1 General Considerations (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-A2-1

A2.2 Criteria for Use of Increased Allowable Stresses (2003) . . . . . . . . . . . . . . . . . . . . . . .

7-A2-1

A2.3 Increases to Allowable Stresses to Temporary Structures (2003) . . . . . . . . . . .. . . . .

7-A2-2

A2.4 Load for the Design of Temporary Structures (2003) . . . . . . . . . . . . . . . . . . . . . . . . . .

7-A2-2

1

A2.1 GENERAL CONSIDERATIONS (2003) In general, temporary timber structures, temporary blocking, falsework and similar constructions supporting railroad loading should be designed in accordance with the requirements of Section 2.1 through Section 2.4. Under certain conditions it may be permissible to increase the allowable design stresses because of the limited duration of use and the controlled conditions. The use of allowable stresses greater than those indicated in Section 2.2 will only be allowed when the design engineer has carefully reviewed the specific application to verify its appropriateness and has received approval from the Chief Engineer of the operating railroad.

A2.2

CRITERIA FOR USE OF INCREASED ALLOWABLE STRESSES (2003)

Before using increased allowable stresses in the design of temporary structures, the designer shall ensure the following requirements are met. a.

The design engineer has reviewed the specific application verifying that the use of increased allowable design stresses is appropriate, has clearly defined the duration of the temporary structure’s service life, and has obtained authorization from the Chief Engineer of the operating railroad.

b. New material should be properly seasoned. c.

No increase in allowable stresses shall be permitted when reused or second-hand material is used unless authorized by the railroad’s Chief Engineer.

d. If green lumber is used in temporary construction, considerations should be made for this in the allowable stresses used and also provisions should be made to ensure that connections will be continuously checked and tightened as required.

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A2-1

3

Timber Structures

e.

If untreated material is used, the designer shall ensure that the conditions of use and the duration of use are such that decay will not become a factor.

f.

The structure shall be inspected at intervals as determined by the Chief Engineer of the operating railroad.

A2.3 INCREASES TO ALLOWABLE STRESSES TO TEMPORARY STRUCTURES (2003) If the conditions of Paragraph 2.4.1 are satisfied, the allowable stresses listed in Table 7-2-7 may be multiplied by a factor of 1.1. The modulus of elasticity, E, shall remain unchanged.

A2.4 LOAD FOR THE DESIGN OF TEMPORARY STRUCTURES (2003) The live load used for the design of temporary structures shall be Cooper E-80, unless otherwise directed by the Chief Engineer of the operating railroad. Refer to Chapter 8 Concrete Structures and Foundations or Chapter 15 Steel Structures for the axle load and axle spacing configuration for Cooper E-80 loading.

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A2-2

AREMA Manual for Railway Engineering

30

Appendix 3 - Legacy Designs — 2011 — TABLE OF CONTENTS Section/Article

Description

Page

A3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A3.1.1 Fire Tests (2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . . . .

7-A3-3 7-A3-4

A3.2 Pile Design Aids. . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-A3-8

A3.3 Legacy Timber Trestle Designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-A3-43

A3.4 Legacy Culvert Designs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-A3-92

1

LIST OF FIGURES Figure 7-A3-1 7-A3-2 7-A3-3 7-A3-4 7-A3-5 7-A3-6 7-A3-7 7-A3-8 7-A3-9 7-A3-10 7-A3-11 7-A3-12 7-A3-13 7-A3-14 7-A3-15 7-A3-16 7-A3-17 7-A3-18 7-A3-19 7-A3-20

Description Fire Test Cabinet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fire Test Cabinet Door. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fire Test Cabinet Burner. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fire Test Cabinet with Door and Burner in Place . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-Pile Bent 12” x 14” Timber Cap a=23” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-Pile Bent 12” x 14” Timber Cap a=29”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-Pile Bent 12” x 14” Timber Cap a=31”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-Pile Bent 14” x 14” Timber Cap a=23” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-Pile Bent 14” x 14” Timber Cap a=29”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-Pile Bent 14” x 14” Timber Cap a=31”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-Pile Bent 15” x 15” Concrete Cap a=23” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-Pile Bent 15” x 15” Concrete Cap a=29” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-Pile Bent 15” x 15” Concrete Cap a=31” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-Pile Bent 12” x 14” Timber Cap a=29”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-Pile Bent 12” x 14” Timber Cap a=31”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-Pile Bent 12” x 14” Timber Cap a=39”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-Pile Bent 12” x 14” Timber Cap a=60” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-Pile Bent 14” x 14” Timber Cap a=29” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-Pile Bent 14” x 14” Timber Cap a=31”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-Pile Bent 14” x 14” Timber Cap a=39”. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

© 2011, American Railway Engineering and Maintenance-of-Way Association

Page 7-A3-4 7-A3-5 7-A3-6 7-A3-7 7-A3-9 7-A3-9 7-A3-10 7-A3-10 7-A3-11 7-A3-11 7-A3-12 7-A3-12 7-A3-13 7-A3-15 7-A3-15 7-A3-16 7-A3-16 7-A3-17 7-A3-17 7-A3-18

7-A3-1

3

Timber Structures

LIST OF FIGURES (CONT) Figure 7-A3-21 7-A3-22 7-A3-23 7-A3-24 7-A3-25 7-A3-26 7-A3-27 7-A3-28 7-A3-29 7-A3-30 7-A3-31 7-A3-32 7-A3-33 7-A3-34 7-A3-35 7-A3-36 7-A3-37 7-A3-38 7-A3-39 7-A3-40 7-A3-41 7-A3-42 7-A3-43 7-A3-44 7-A3-45 7-A3-46 7-A3-47 7-A3-48 7-A3-49 7-A3-50 7-A3-51 7-A3-52 7-A3-53 7-A3-54 7-A3-55 7-A3-56 7-A3-57 7-A3-58 7-A3-59 7-A3-60 7-A3-61 7-A3-62 7-A3-63 7-A3-64 7-A3-65 7-A3-66 7-A3-67 7-A3-68 7-A3-69

Description

Page

5-Pile Bent 14” x 14” Timber Cap a=60” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-Pile Bent 16” x 16” Timber Cap a=29” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-Pile Bent 16” x 16” Timber Cap a=31” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-Pile Bent 16” x 16” Timber Cap a=39” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-Pile Bent 16” x 16” Timber Cap a=60” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-Pile Bent 15” x 15” Concrete Cap a=29” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-Pile Bent 15” x 15” Concrete Cap a=31” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-Pile Bent 15” x 15” Concrete Cap a=39” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-Pile Bent 15” x 15” Concrete Cap a=60” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-Pile Bent 12” x 14” Timber Cap a=29” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-Pile Bent 12” x 14” Timber Cap a=31” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-Pile Bent 12” x 14” Timber Cap a=39” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-Pile Bent 12” x 14” Timber Cap a=60” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-Pile Bent 14” x 14” Timber Cap a=29” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-Pile Bent 14” x 14” Timber Cap a=31” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-Pile Bent 14” x 14” Timber Cap a=39” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-Pile Bent 14” x 14” Timber Cap a=60” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-Pile Bent 16” x 16” Timber Cap a=29” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-Pile Bent 16” x 16” Timber Cap a=31” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-Pile Bent 16” x 16” Timber Cap a=39” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-Pile Bent 16” x 16” Timber Cap a=60” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-Pile Bent 15” x 15” Concrete Cap a=29” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-Pile Bent 15” x 15” Concrete Cap a=31” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-Pile Bent 15” x 15” Concrete Cap a=39” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-Pile Bent 15” x 15” Concrete Cap a=60” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-Pile Bent 15” x 18” Concrete Cap a=29” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-Pile Bent 15” x 18” Concrete Cap a=31” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-Pile Bent 15” x 18” Concrete Cap a=39” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-Pile Bent 15” x 18” Concrete Cap a=60” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-Pile Bent 14” x 14” Timber Cap a=39” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-Pile Bent 14” x 14” Timber Cap a=60” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-Pile Bent 16” x 16” Timber Cap a=39” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-Pile Bent 16” x 16” Timber Cap a=60” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-Pile Bent 15” x 15” Concrete Cap a=39” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-Pile Bent 15” x 15” Concrete Cap a=60” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-Pile Bent 15” x 18” Concrete Cap a=39” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-Pile Bent 15” x 18” Concrete Cap a=60” . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reinforced Concrete Piers and Bents as Fire Stops . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wood Bents Faced with Fire Resisting Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Application of Mastic Material in Open-Deck Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Floor Plan for Open-Deck Trestles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Floor Plan for Ballasted-Deck Trestles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bulkheads and Miscellaneous Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cap Stringer Fastening and Pile Top Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bent Details for Open-Deck Pile Trestles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bent Details for Ballasted-Deck Pile Trestles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Longitudinal Bracing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Details of Footings for Framed Bents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Multiple-Story Trestle Bents (6 Post Bent) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

7-A3-18 7-A3-19 7-A3-19 7-A3-20 7-A3-20 7-A3-21 7-A3-21 7-A3-22 7-A3-22 7-A3-24 7-A3-24 7-A3-25 7-A3-25 7-A3-26 7-A3-26 7-A3-27 7-A3-27 7-A3-28 7-A3-28 7-A3-29 7-A3-29 7-A3-30 7-A3-30 7-A3-31 7-A3-31 7-A3-32 7-A3-32 7-A3-33 7-A3-33 7-A3-35 7-A3-36 7-A3-37 7-A3-38 7-A3-39 7-A3-40 7-A3-41 7-A3-42 7-A3-43 7-A3-44 7-A3-45 7-A3-46 7-A3-47 7-A3-48 7-A3-49 7-A3-50 7-A3-51 7-A3-52 7-A3-53 7-A3-54

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-2

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

LIST OF FIGURES (CONT) Figure

Description

Page

7-A3-70 7-A3-71 7-A3-72 7-A3-73 7-A3-74 7-A3-75 7-A3-76 7-A3-77

Multiple-Story Trestle Bents (5 Post Bent) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-A3-55 Walk and Handrail - Open-Deck Trestles (to be used where required) . . . . . . . . . . . . . . . . . . 7-A3-56 Water Barrel and Refuge Platform - Open-Deck Trestles (to be used where required). . . . . . 7-A3-57 Track Car Platforms - Open-Deck Trestles (to be used where required) . . . . . . . . . . . . . . . . . 7-A3-58 Walk and Handrail - Ballasted-Deck Trestles (to be used where required) . . . . . . . . . . . . . . . 7-A3-59 Water Barrel and Refuge Platform - Ballasted-Deck Trestles (to be used where required) . . 7-A3-60 Track Car Platform - Ballasted-Deck Trestles (to be used where required). . . . . . . . . . . . . . . 7-A3-61 Recommended Practice for Creosoted Timber Pile Piers for Long Spans, E60 Loading-Pier for 150-foot and 80-foot Spans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-A3-62 7-A3-78 Recommended Practice for Creosoted Timber Pile Piers for Long Spans, E60 Loading-Pier for 150-foot Span and Trestle Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-A3-64 7-A3-79 Recommended Practice for Design of Wood Culverts, E 72 Loading, for Heights up to 15 Foot Base of Rail to Flow Line area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-A3-92

LIST OF TABLES Table

Description

7-A3-1 4-Pile Bents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-A3-2 5-Pile Bents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-A3-3 6-Pile Bents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-A3-4 7-Pile Bents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-A3-5 Comparison of Unit Stresses in Open Deck Trestles, Cooper E 60 Loading, No Impact. . . . . . 7-A3-6 Comparison of Unit Stresses in Open Deck Trestles, Cooper E 72 Loading, No Impact. . . . . . 7-A3-7 Comparison of Unit Stresses in Open Deck Trestles, Various Cooper Loadings, No Impact . . 7-A3-8 Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 60 Loading, No Impact . . 7-A3-9 Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 72 Loading, No Impact . . 7-A3-10Typical Size Boxes and Unit Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Page 7-A3-8 7-A3-14 7-A3-23 7-A3-34 7-A3-66 7-A3-72 7-A3-78 7-A3-80 7-A3-86 7-A3-93

A3.1 INTRODUCTION

3

4

This Appendix contains information useful for Rating purposes of existing structures of many existing legacy designs.

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

1

7-A3-3

Timber Structures

A3.1.1 FIRE TESTS (2011)

Figure 7-A3-1. Fire Test Cabinet

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-4

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

1

3

4

Figure 7-A3-2. Fire Test Cabinet Door

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-5

Timber Structures

Figure 7-A3-3. Fire Test Cabinet Burner

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-6

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

1

Figure 7-A3-4. Fire Test Cabinet with Door and Burner in Place

3

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-7

Timber Structures

A3.2 PILE DESIGN AIDS

Table 7-A3-1. 4-Pile Bents b=80, 90, 100, 110, 120, 130, 132, 140 & 144 inches Pile Cap

Eff. Pile Length

a

C1

Figure No.

12” x 14” Timber

10’

23

12, 18, 24

Figure 7-A3-5

29

12, 18, 24

Figure 7-A3-6

31

12, 18, 24

Figure 7-A3-7

23

12, 18, 24

Figure 7-A3-5

29

12, 18, 24

Figure 7-A3-6

31

12, 18, 24

Figure 7-A3-7

23

12, 18, 24

Figure 7-A3-8

29

12, 18, 24

Figure 7-A3-9

31

12, 18, 24

Figure 7-A3-10

23

12, 18, 24

Figure 7-A3-8

29

12, 18, 24

Figure 7-A3-9

31

12, 18, 24

Figure 7-A3-10

23

12, 18, 24

Figure 7-A3-11

29

12, 18, 24

Figure 7-A3-12

31

12, 18, 24

Figure 7-A3-13

23

12, 18, 24

Figure 7-A3-11

29

12, 18, 24

Figure 7-A3-12

31

12, 18, 24

Figure 7-A3-13

30’

14” x 14” Timber

10’

30’

15” x 15” Concrete

10’

30’

© 2011, American Railway Engineering and Maintenance-of-Way Association

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AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

1

3 Figure 7-A3-5. 4-Pile Bent 12” x 14” Timber Cap a=23” Figure 7-A3-6. 4-Pile Bent 12” x 14” Timber Cap a=29”

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-9

Timber Structures

Figure 7-A3-7. 4-Pile Bent 12” x 14” Timber Cap a=31”

Figure 7-A3-8. 4-Pile Bent 14” x 14” Timber Cap a=23”

© 2011, American Railway Engineering and Maintenance-of-Way Association

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AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

1

3 7Figure 7-A3-9. 4-Pile Bent 14” x 14” Timber Cap a=29” Figure 7-A3-10. 4-Pile Bent 14” x 14” Timber Cap a=31” Part 2

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-11

Timber Structures

Figure 7-A3-11. 4-Pile Bent 15” x 15” Concrete Cap a=23”

Figure 7-A3-12. 4-Pile Bent 15” x 15” Concrete Cap a=29”

© 2011, American Railway Engineering and Maintenance-of-Way Association

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AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

1

3 Figure 7-A3-13. 4-Pile Bent 15” x 15” Concrete Cap a=31”

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-13

Timber Structures

Table 7-A3-2. 5-Pile Bents b= 90, 100, 110, 120, 130, 132, 140, 144 & 150 inches Pile Cap

Eff. Pile Length

a

C2

Figure No.

12” x 14” Timber

10’

29

24, 30, 36, 42

Figure 7-A3-14

31

24, 30, 36, 42

Figure 7-A3-15

39

24, 30, 36, 42

Figure 7-A3-16

60

24, 30, 36, 42

Figure 7-A3-17

29

24, 30, 36, 42

Figure 7-A3-14

31

24, 30, 36, 42

Figure 7-A3-15

39

24, 30, 36, 42

Figure 7-A3-16

60

24, 30, 36, 42

Figure 7-A3-17

29

24, 30, 36, 42

Figure 7-A3-18

31

24, 30, 36, 42

Figure 7-A3-19

39

24, 30, 36, 42

Figure 7-A3-20

60

24, 30, 36, 42

Figure 7-A3-21

29

24, 30, 36, 42

Figure 7-A3-18

31

24, 30, 36, 42

Figure 7-A3-19

39

24, 30, 36, 42

Figure 7-A3-20

60

24, 30, 36, 42

Figure 7-A3-21

29

24, 30, 36, 42

Figure 7-A3-22

31

24, 30, 36, 42

Figure 7-A3-23

39

24, 30, 36, 42

Figure 7-A3-24

60

24, 30, 36, 42

Figure 7-A3-25

29

24, 30, 36, 42

Figure 7-A3-22

31

24, 30, 36, 42

Figure 7-A3-23

39

24, 30, 36, 42

Figure 7-A3-24

60

24, 30, 36, 42

Figure 7-A3-25

29

24, 30, 36, 42

Figure 7-A3-26

31

24, 30, 36, 42

Figure 7-A3-27

39

24, 30, 36, 42

Figure 7-A3-28

60

24, 30, 36, 42

Figure 7-A3-29

29

24, 30, 36, 42

Figure 7-A3-26

31

24, 30, 36, 42

Figure 7-A3-27

39

24, 30, 36, 42

Figure 7-A3-28

60

24, 30, 36, 42

Figure 7-A3-29

30’

14” x 14” Timber

10’

30’

16” x 16” Timber

10’

30’

15” x 15” Concrete

10’

30’

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-14

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

1

3 7 Figure 7-A3-14. 5-Pile Bent 12” x 14” Timber Cap a=29” Part 2

Figure 7-A3-15. 5-Pile Bent 12” x 14” Timber Cap a=31”

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-15

Timber Structures

Figure 7-A3-16. 5-Pile Bent 12” x 14” Timber Cap a=39” Figure 7-A3-17. 5-Pile Bent 12” x 14” Timber Cap a=60”

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-16

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

1

3 Figure 7-A3-18. 5-Pile Bent 14” x 14” Timber Cap a=29”

Example:

Given:

Note:

Figure 7-A3-19. 5-Pile Bent 14” x 14” Timber Cap a=31”

The 5 pile-bent of a trestle which carries a chord of bunched stringers under each rail, has a 14" x 14" timber cap. The spacing of the piles is 36" and the effective length of piles (i.e. the exposed length plus onehalf of the penetration) is 30 feet. Each chord possesses four 8" x 16" stringers. Using graphs or tables, find out the distribution of the wheel load (assumed as one or axle assumed as two) on the piles. a = 31", c2 = 36", b = 144" and L = 30 feet Intermediate pile (2)=0.562 Outside pile (3)=0.133 Centre pile (1)=2x (1-(0.562+0.133)) = 0.610 Answer:Pile #12345 Load0.1330.5620.6100.5620.133 The middle pile takes the maximum load, then the intermediate piles and the load carried by the outside piles is the smallest.

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-17

Timber Structures

Figure 7-A3-20. 5-Pile Bent 14” x 14” Timber Cap a=39”

Example:

Given:

Note:

Figure 7-A3-21. 5-Pile Bent 14” x 14” Timber Cap a=60”

Data same as in the previous Example in Figure 7-A3-19, except that the chords now consist of five 8" x 16" stringers. Find out the distribution of wheel load on piles of the bent. a = 39" and the rest of the data is same as in the Example in Figure 7-A3-19. Intermediate pile (2)=0.550 Outside pile (3)=0.143 Centre pile (1)=2x(1-0.550+0.143)) = 0.614 Answer:Pile #12345 Load0.1430.5500.6140.5500.143 Increase in the value of "a" has resulted in decrease of load on the intermediate piles and a corresponding increase of load on the outside and the centre pile.

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-18

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

1

3 Figure 7-A3-22. 5-Pile Bent 16” x 16” Timber Cap a=29”

Figure 7-A3-23. 5-Pile Bent 16” x 16” Timber Cap a=31”

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-19

Timber Structures

7 Figure 7-A3-24. 5-Pile Bent 16” x 16” Timber Cap a=39” Part 2

Figure 7-A3-25. 5-Pile Bent 16” x 16” Timber Cap a=60”

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-20

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

1

3 Figure 7-A3-26. 5-Pile Bent 15” x 15” Concrete Cap a=29”

Figure 7-A3-27. 5-Pile Bent 15” x 15” Concrete Cap a=31”

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-21

Timber Structures

7

Part 2 x 15” Concrete Cap a=39” Figure 7-A3-29. 5-Pile Bent 15” x 15” Concrete Cap a=60” Figure 7-A3-28. 5-Pile Bent 15”

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-22

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

Table 7-A3-3. 6-Pile Bents b= 100, 110, 120, 130, 132, 140, 144 & 150 inches Pile Cap

Eff. Pile Length

12” x 14” Timber

10’

30’

14” x 14” Timber

10’

30’

16” x 16” Timber

10’

30’

15” x 15” Concrete

10’

30’

15” x 18” Concrete

10’

30’

a

C1

C2

Figure No.

29 31 39 60 29 31 39 60 29 31 39 60 29 31 39 60 29 31 39 60 29 31 39 60 29 31 39 60 29 31 39 60 29 31 39 60 29 31 39 60

12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15 12, 15, 15

36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45 36, 39, 45

Figure 7-A3-30 Figure 7-A3-31 Figure 7-A3-32 Figure 7-A3-33 Figure 7-A3-30 Figure 7-A3-31 Figure 7-A3-32 Figure 7-A3-33 Figure 7-A3-34 Figure 7-A3-35 Figure 7-A3-38 Figure 7-A3-37 Figure 7-A3-34 Figure 7-A3-35 Figure 7-A3-36 Figure 7-A3-37 Figure 7-A3-38 Figure 7-A3-39 Figure 7-A3-40 Figure 7-A3-41 Figure 7-A3-38 Figure 7-A3-39 Figure 7-A3-40 Figure 7-A3-41 Figure 7-A3-42 Figure 7-A3-43 Figure 7-A3-44 Figure 7-A3-45 Figure 7-A3-42 Figure 7-A3-43 Figure 7-A3-44 Figure 7-A3-45 Figure 7-A3-46 Figure 7-A3-47 Figure 7-A3-48 Figure 7-A3-49 Figure 7-A3-46 Figure 7-A3-47 Figure 7-A3-48 Figure 7-A3-49

1

3

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-23

Timber Structures

Figure 7-A3-30. 6-Pile Bent 12” x 14” Timber Cap a=29”

Figure 7-A3-31. 6-Pile Bent 12” x 14” Timber Cap a=31”

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-24

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

1

3 7 Figure 7-A3-32. 6-Pile Bent 12” x 14” Timber Cap a=39” Part 2

Figure 7-A3-33. 6-Pile Bent 12” x 14” Timber Cap a=60”

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-25

Timber Structures

Figure 7-A3-34. 6-Pile Bent 14” x 14” Timber Cap a=29” Figure 7-A3-35. 6-Pile Bent 14” x 14” Timber Cap a=31”

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-26

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

1

3 7 Figure 7-A3-36. 6-Pile Bent 14” x 14” Timber Cap a=39” Part 2

Example:

Given:

Answer: Note:

Figure 7-A3-37. 6-Pile Bent 14” x 14” Timber Cap a=60”

The 6 pile-bent of a trestle which carries a ballast deck and has a 14" x 14" timber cap. The spacing of the piles is 30" and the effective length of piles (i.e. the exposed length plus one-half of the penetration) is 30 feet. The deck possesses ten 8" x 16" stringers. Using graphs or tables, find out the distribution of the wheel load (assumed as one) on piles of the bent. A = 60", c1 = 15", c2 = 45", b = 150" and L = 30 feet. Intermediate pile (2) =0.380 Outside pile(3)=0.114 Middle pile (1)= 1-(0.380+0.114) = 0.506 Pile #123456 Load0.1140.3800.5060.5060.3800.114 The outside piles are carrying a smaller amount of wheel load even when compared to a 5 - pile bent of the Example in Figure 7-A3-31 and Figure 7-A3-22 (See Appendix 3 - Legacy Designs).

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-27

Timber Structures

7 Figure 7-A3-38. 6-Pile Bent 16” x 16” Timber Cap a=29” Part 2

Figure 7-A3-39. 6-Pile Bent 16” x 16” Timber Cap a=31”

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-28

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

1

3 Figure 7-A3-40. 6-Pile Bent 16” x 16” Timber Cap a=39”

Figure 7-A3-41. 6-Pile Bent 16” x 16” Timber Cap a=60”

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-29

Timber Structures

Figure 7-A3-42. 6-Pile Bent 15” x 15” Concrete Cap a=29”

Figure 7-A3-43. 6-Pile Bent 15” x 15” Concrete Cap a=31”

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-30

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

1

3 Figure 7-A3-44. 6-Pile Bent 15” x 15” Concrete Cap a=39”

Figure 7-A3-45. 6-Pile Bent 15” x 15” Concrete Cap a=60”

Example:

Given:

Note:

Same as the Example in Figure 7-A3-37, except that the timber cap is now substituted with a 15" x 15" concrete cap. Other data remains the same as for the Example in Figure 7-A3-37. Intermediate pile (2) =0.363 Outside pile (3)=0.159 Middle pile (1)= 1-(0.363+0.159) = 0.478 The 15" x 15" concrete cap being stiffer than the 14" x 14" timber cap of the Example No. 6 provides a better distribution of wheel load on piles.

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-31

Timber Structures

Figure 7-A3-46. 6-Pile Bent 15” x 18” Concrete Cap a=29”

Figure 7-A3-47. 6-Pile Bent 15” x 18” Concrete Cap a=31”

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-32

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

1

3 Figure 7-A3-48. 6-Pile Bent 15” x 18” Concrete Cap a=39”

Figure 7-A3-49. 6-Pile Bent 15” x 18” Concrete Cap a=60”

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-33

Timber Structures

Table 7-A3-4. 7-Pile Bents b= 120, 130, 132, 140, 144, 150, 156, 160 & 168 inches Pile Cap

Eff. Pile Length

a

C2

C3

Figure No.

14” x 14” Timber

10’

39

24, 27, 27, 30, 30

48, 51, 57, 54, 60

Figure 7-A3-50

60

24, 27, 27, 30, 30

48, 51, 57, 54, 60

Figure 7-A3-51

39

24, 27, 27, 30, 30

48, 51, 57, 54, 60

Figure 7-A3-50

60

24, 27, 27, 30, 30

48, 51, 57, 54, 60

Figure 7-A3-51

39

24, 27, 27, 30, 30

48, 51, 57, 54, 60

Figure 7-A3-52

60

24, 27, 27, 30, 30

48, 51, 57, 54, 60

Figure 7-A3-53

39

24, 27, 27, 30, 30

48, 51, 57, 54, 60

Figure 7-A3-52

60

24, 27, 27, 30, 30

48, 51, 57, 54, 60

Figure 7-A3-53

39

24, 27, 27, 30, 30

48, 51, 57, 54, 60

Figure 7-A3-54

60

24, 27, 27, 30, 30

48, 51, 57, 54, 60

Figure 7-A3-55

39

24, 27, 27, 30, 30

48, 51, 57, 54, 60

Figure 7-A3-54

60

24, 27, 27, 30, 30

48, 51, 57, 54, 60

Figure 7-A3-55

39

24, 27, 27, 30, 30

48, 51, 57, 54, 60

Figure 7-A3-56

60

24, 27, 27, 30, 30

48, 51, 57, 54, 60

Figure 7-A3-57

39

24, 27, 27, 30, 30

48, 51, 57, 54, 60

Figure 7-A3-56

60

24, 27, 27, 30, 30

48, 51, 57, 54, 60

Figure 7-A3-57

30’

16” x 16” Timber

10’

30’

15” x 15” Concrete

10’

30’

15” x 18” Concrete

10’

30’

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-34

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

1

3 Figure 7-A3-50. 7-Pile Bent 14” x 14” Timber Cap a=39”

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-35

Timber Structures

Figure 7-A3-51. 7-Pile Bent 14” x 14” Timber Cap a=60”

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-36

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

1

3 Figure 7-A3-52. 7-Pile Bent 16” x 16” Timber Cap a=39”

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-37

Timber Structures

7

Part 2

Figure 7-A3-53. 7-Pile Bent 16” x 16” Timber Cap a=60”

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-38

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

1

3 Figure 7-A3-54. 7-Pile Bent 15” x 15” Concrete Cap a=39”

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-39

Timber Structures

Part 2

Figure 7-A3-55. 7-Pile Bent 15” x 15” Concrete Cap a=60”

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-40

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

1

3 Figure 7-A3-56. 7-Pile Bent 15” x 18” Concrete Cap a=39”

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-41

Timber Structures

Figure 7-A3-57. 7-Pile Bent 15” x 18” Concrete Cap a=60”

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-42

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

A3.3 LEGACY TIMBER TRESTLE DESIGNS

1

3

4

Figure 7-A3-58. Reinforced Concrete Piers and Bents as Fire Stops

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-43

Timber Structures

Figure 7-A3-59. Wood Bents Faced with Fire Resisting Material

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-44

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

1 Figure 7-A3-60. Application of Mastic Material in Open-Deck Structures

3

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-45

Timber Structures

10’-0 TIES

4x8 SPACER TIMBER

NOTE: 3’-0

FOR ALTERNATE CAP-

CLASS OF LOADING

FOR PILE TOP

STRINGER FASTENING,

AND SPECIES OF

PROTECTION SEE

SEE FIGURE 7-4-16

LUMBER USED

FIGURE 7-4-16

WILL GOVERN SIZE OF TIES.

END SPAN

INTERMEDIATE SPAN

ELEVATION 34 34

DIA. PACKING BOLTS

DIA. DRIFT BOLTS

34

DIA. x 10 WASHER

PENETRATION 8 IN.

HEAD DRIVE SPIKE,

INTO CAP

SINGLE GRIP

C L RAIL

C L RAIL

34

DIA. WASHER HEAD DRIVE

34

DIA.

SPIKE, SINGLE GRIP, 5 IN.

BOLTS

PENETRATION INTO

AT ENDS

STRINGERS

34

C L STRINGERS C L BENT

C L BENT

C L BENT

PLAN (4 PLY CHORD)

DIA. PACKING BOLTS

C L RAIL

SCHEMATIC DIAGRAM CONTINUOUS LAP-TYPE DECK - 4 PLY CHORD C L STRINGERS C L BENT

C L BENT

C L BENT

C L RAIL

PLAN (3 PLY CHORD) SCHEMATIC DIAGRAM CONTINUOUS LAP-TYPE DECK - 3 PLY CHORD

Figure 7-A3-61. Floor Plan for Open-Deck Trestles

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-46

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

1

3

4

Figure 7-A3-62. Floor Plan for Ballasted-Deck Trestles

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-47

Timber Structures

Figure 7-A3-63. Bulkheads and Miscellaneous Details

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-48

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

1

3

4

Figure 7-A3-64. Cap Stringer Fastening and Pile Top Protection

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-49

Timber Structures

Figure 7-A3-65. Bent Details for Open-Deck Pile Trestles

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-50

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

1

3

4

Figure 7-A3-66. Bent Details for Ballasted-Deck Pile Trestles

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-51

Timber Structures

Figure 7-A3-67. Longitudinal Bracing

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-52

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

1

3

4

Figure 7-A3-68. Details of Footings for Framed Bents

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-53

Timber Structures

Figure 7-A3-69. Multiple-Story Trestle Bents (6 Post Bent)

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-54

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

1

3

4

Figure 7-A3-70. Multiple-Story Trestle Bents (5 Post Bent)

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-55

Timber Structures

Figure 7-A3-71. Walk and Handrail - Open-Deck Trestles (to be used where required)

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-56

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

1

3

4

Figure 7-A3-72. Water Barrel and Refuge Platform - Open-Deck Trestles (to be used where required)

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-57

Timber Structures

Figure 7-A3-73. Track Car Platforms - Open-Deck Trestles (to be used where required)

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-58

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

1

3

4

Figure 7-A3-74. Walk and Handrail - Ballasted-Deck Trestles (to be used where required)

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-59

Timber Structures

Figure 7-A3-75. Water Barrel and Refuge Platform - Ballasted-Deck Trestles (to be used where required)

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-60

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

1

3

4

Figure 7-A3-76. Track Car Platform - Ballasted-Deck Trestles (to be used where required)

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-61

Timber Structures

Figure 7-A3-77. Recommended Practice for Creosoted Timber Pile Piers for Long Spans, E60 LoadingPier for 150-foot and 80-foot Spans Sheet 1 of 2 © 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-62

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

1

3

4

Figure 7-A3-77. Recommended Practice for Creosoted Timber Pile Piers for Long Spans, E60 LoadingPier for 150-foot and 80-foot Spans Sheet 2 of 2

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-63

Timber Structures

Figure 7-A3-78. Recommended Practice for Creosoted Timber Pile Piers for Long Spans, E60 LoadingPier for 150-foot Span and Trestle Approach Sheet 1 of 2

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-64

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

1

3

4

Figure 7-A3-78. Recommended Practice for Creosoted Timber Pile Piers for Long Spans, E60 LoadingPier for 150-foot Span and Trestle Approach Sheet 2 of 2

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-65

Timber Structures

Table 7-A3-5. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 60 Loading, No Impact 12 ¢ and 13 ¢ Spans All loads in pounds per track. All moments in foot-pounds per track Panel Length C to C of Bents

12¢

13¢

13¢

13¢

Number and Size of Stringers

8-7² ´ 16²

8-8² ´ 16²

8-9² ´ 16²

6-10² ´ 16²

490

Dead load per foot of track Above stringers

490

490

490

Stringers-nominal size

375

430

480

400

865

920

970

890

Total dead load Reaction on bent in pounds Dead load

10380

11960

12610

11570

Live load

139980

147660

147660

147660

Total

150360

159620

160270

159230

Kind of bent

Pile

Frame

5

5

5

5

5

5

5

5

14² D

12´ 14

14² D

12´ 14

14² D

12´ 14

14² D

12´ 14

Total area of piles or posts-sq. in.

770

840

770

840

770

840

770

840

Unit bearing stress on piles or posts-lb per sq. in.

195

179

207

190

208

191

207

190

Average load in tons per pile or post

15.0

150

16.0

16.0

16.0

16.0

15.9

15.9

Number of piles or posts Size of piles or posts

Pile

Frame

Pile

Frame

Pile

Frame

Bearing-Stringers on caps for continuous butt type deck Area sq. in.-14² cap

784

896

1008

Bearing stress-lb per sq. in.-14² cap

192

178

159

840 190

Area sq. in.-16² cap

896

1024

1152

960

Bearing stress-lb per sq. in.-16² cap

168

156

189

166

Dead load moment-foot pounds per track

13888

17493

18443

16917

Live load moment-foot pounds per track

210000

255000

255000

255000

Total load moment-foot pounds per track

223888

272493

273443

271917

Section modulus-nominal size

2389

2730

3072

2560

Bending stress-lb per sq. in.-nominal size

1124

1198

1068

1275

Section modulus-dressed size

2242

2563

2883

2402

Bending stress-lb per sq. in.-dressed size

1196

1276

1138

1358

Bending in stringers

Assumptions: L = Distance C to C bents for bearing on caps in feet = Distance face to face of caps plus 0.5 ft for stringer bending and shear. (Assume 14² cap) W = Total Dead Load per linear foot of track: Rail and fastenings = 200 pounds per linear foot Ties 8² ´ 8² ´ 10¢ @ 12² ctrs = 267 pounds per linear foot R = Total Reaction

h = Height of stringer in feet b = Breadth of stringers in feet P = Weight on one driving axle = 60000 pounds a = Distance from load P to support, in feet Dressed size = Nominal size less 1/2² in depth

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-66

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

Table 7-A3-5. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 60 Loading, No Impact 12 ¢ and 13 ¢ Spans (Continued) All loads in pounds per track. All moments in foot-pounds per track Panel Length C to C of Bents

12¢

13¢

13¢

13¢

Number and Size of Stringers

8-7² ´ 16²

8-8² ´ 16²

8-9² ´ 16²

6-10² ´ 16²

Longitudinal shear-Standard formula-First driver at height of the beam from the support. Depth nominal

16

16

16

16

c to c

12

13

13

13

L = (c to c) + 0.5 - 14/12

11.33

12.33

12.33

12.33

L’ ignore with d of face

8.17

9.17

9.17

9.17

a

10

11

11

11

b

5

6

6

6

W

865

920

970

890

WL Dead load = --------2

3532

4217

4446

4079

c, if > d

Live load

76765

80270

80270

80270

Total load

80297

84487

84716

84349

Cross section-sq. in.-nominal size

896

1024

1152

960

3 R Unit shear-lb per sq. in. = --- -----2 bh

134

124

110

132

Cross section-sq. in.-dressed size

868

992

1116

930

3 R Unit shear-lb per sq. in. = --- -----2 bh

139

128

114

136

1

3

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-67

Timber Structures

Table 7-A3-5. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 60 Loading, No Impact 14 ¢ Spans All loads in pounds per track. All moments in foot-pounds per track Panel Length C to C of Bents

14¢

14¢

14¢

14¢

14¢

Number and Size of Stringers

8-8² ´ 16²

8-9² ´ 16²

8-10² ´ 16²

6-9² ´ 18²

6-10² ´ 18²

Above stringers

490

490

490

490

490

Stringers-nominal size

430

480

535

405

450

920

970

1025

895

940

Dead load per foot of track

Total dead load Reaction on bent in pounds Dead load

12880

13580

14350

12540

13160

Live load

156360

156360

156360

156360

156360

Total

169240

169940

170710

168900

169520

Kind of bent Number of piles or posts

Pile

Frame

Pile

Frame

Pile

Frame

Pile

Frame

Pile

Frame

5

5

5

5

5

5

5

5

5

5

14² D

12´ 14

14² D

12´ 14

14² D

12´ 14

14² D

12´ 14

14² D

12´ 14

Total area of piles or posts-sq. in.

770

840

770

840

770

840

770

840

770

840

Unit bearing stress on piles or posts-lb per sq. in.

220

201

221

202

222

203

220

201

220

202

Average load in tons per pile or post

16.9

16.9

17.0

17.0

17.1

17.1

16.9

16.9

17.0

17.0

Size of piles or posts

Bearing-Stringers on caps for continuous butt type deck Area sq. in.-14² cap

896

1008

1120

756

840

Bearing stress-lb per sq. in.-14² cap

189

169

152

224

202

Area sq. in.-16² cap

1024

1152

1280

864

960

Bearing stress-lb per sq. in.-16² cap

165

148

133

196

176

Dead load moment-foot pounds per track

20440

21555

22778

19870

20888

Live load moment-foot pounds per track

300000

300000

300000

300000

300000

Total load moment-foot pounds per track

320440

321555

322778

319870

320888

Section modulus-nominal size

2730

3072

3413

2916

3240

Bending stress-lb per sq. in.-nominal size

1409

1256

1135

1317

1190

Section modulus-dressed size

2563

2883

3203

2756

3062

Bending stress-lb per sq. in.-dressed size

1500

1340

1209

1392

1257

Bending in stringers

Assumptions: L = Distance C to C bents for bearing on caps in feet = Distance face to face of caps plus 0.5 foot for stringer bending and shear. (Assume 14² cap) W = Total Dead Load per linear foot of track: Rail and fastenings = 200 pounds per linear foot Ties 8² ´ 8² ´ 10¢ @ 12² ctrs = 267 pounds per linear foot R = Total Reaction

h = Height of stringer in feet b = Breadth of stringers in feet P = Weight on one driving axle = 60000 pounds a = Distance from load P to support, in feet Dressed size = Nominal size less 1/2² in depth

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-68

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

Table 7-A3-5. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 60 Loading, No Impact 14 ¢ Spans (Continued) All loads in pounds per track. All moments in foot-pounds per track Panel Length C to C of Bents

14¢

14¢

14¢

14¢

14¢

Number and Size of Stringers

8-8² ´ 16²

8-9² ´ 16²

8-10² ´ 16²

6-9² ´ 18²

6-10² ´ 18²

18

Longitudinal shear-Standard formula-First driver at height of the beam from the support. Depth nominal

16

16

16

18

c to c

14

14

14

14

14

L = (c to c) + 0.5 - 14/12

13.33

13.33

13.33

13.33

13.33

L’ ignore within d of face

10.17

10.17

10.17

9.83

9.83

a

12

12

12

11.83

11.83

b

7

7

7

6.83

6.83

c, if > d

2

2

2

1.83

1.83

W

920

970

1025

895

940

WL Dead load = --------2

4677

4931

5210

4400

4622

Live load

91125

91125

91125

88875

88875

Total load

95802

96056

96335

93275

93497

Cross section-sq. in.-nominal size

1024

1152

1280

972

1080

3 R Unit shear-lb per sq. in. = --- -----2 bh

140

125

113

144

130

Cross section-sq. in.-dressed size

992

1116

1240

945

1050

R--- ----Unit shear-lb per sq. in. = 3 2 bh

145

129

117

149

134

1

3

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-69

Timber Structures

Table 7-A3-5. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 60 Loading, No Impact 15 ¢ and 16 ¢ Spans All loads in pounds per track. All moments in foot-pounds per track Panel Length C to C of Bents

15¢

15¢

16¢

16¢

16¢

Number and Size of Stringers

8-10² ´ 16²

8-9² ´ 18²

8-9² ´ 18²

8-10² ´ 18²

6-10² ´ 20²

Above stringers

490

490

490

490

490

Stringers-nominal size

535

540

540

600

500

1025

1030

1030

1090

990

Dead load per foot of track

Total dead load Reaction on bent in pounds Dead load

15375

15450

16480

17440

15840

Live load

163920

163920

170580

170580

170580

Total

179295

179370

187060

188020

186420

Kind of bent Number of piles or posts

Pile

Frame

Pile

Frame

Pile

Frame

Pile

Frame

Pile

Frame

5

5

5

5

6

6

6

6

6

6

14² D

12´ 14

14² D

12´ 14

14² D

12´ 14

14² D

12´ 14

14² D

12´ 14

Total area of piles or posts-sq. in.

770

840

770

840

924

1008

924

1008

924

1008

Unit bearing stress on piles or posts-lb per sq. in.

233

214

233

214

202

185

204

187

202

185

Average load in tons per pile or post

17.9

17.9

17.9

17.9

15.6

15.6

15.7

15.7

15.6

15.6

Size of piles or posts

Bearing-Stringers on caps for continuous butt type deck Area sq. in.-14² cap

1120

1008

1008

1120

Bearing stress-lb per sq. in.-14² cap

176

180

185

168

840 222

Area sq. in.-16² cap

1280

1152

1152

1280

960

Bearing stress-lb per sq. in.-16² cap

155

140

162

147

194

Dead load moment-foot pounds per track

26323

26450

30270

32003

29100

Live load moment-foot pounds per track

345000

345000

390000

390000

390000

Total load moment-foot pounds per track

371323

371450

420270

422003

419100

Section modulus-nominal size

3413

3888

3888

4320

4000

Bending stress-lb per sq. in.-nominal size

1304

1145

1297

1172

1259

Section modulus-dressed size

3203

3675

3675

4083

3802

Bending stress-lb per sq. in.-dressed size

1390

1212

1372

1240

1323

Bending in stringers

Assumptions: L = Distance C to C bents for bearing on caps in feet = Distance face to face of caps plus 0.5 foot for stringer bending and shear. (Assume 14² cap) W = Total Dead Load per linear foot of track: Rail and fastenings = 200 pounds per linear foot Ties 8² ´ 8² ´ 10¢ @ 12² ctrs = 267 pounds per linear foot R = Total Reaction

h = Height of stringer in feet b = Breadth of stringers in feet P = Weight on one driving axle = 60000 pounds a = Distance from load P to support, in feet Dressed size = Nominal size less 1/2² in depth

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-70

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

Table 7-A3-5. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 60 Loading, No Impact 15 ¢ and 16 ¢ Spans (Continued) All loads in pounds per track. All moments in foot-pounds per track Panel Length C to C of Bents

15¢

15¢

16¢

16¢

16¢

Number and Size of Stringers

8-10² ´ 16²

8-9² ´ 18²

8-9² ´ 18²

8-10² ´ 18²

6-10² ´ 20²

20

Longitudinal shear-Standard formula-First driver at height of the beam from the support. Depth nominal

16

18

18

18

c to c

15

15

16

16

16

L = (c to c) + 0.5 - 14/12

14.33

14.33

15.33

15.33

15.33

L’ ignore within d of face

11.17

10.83

11.83

11.83

11.50

a

13

12.83

13.83

13.83

13.67

b

8

7.83

8.83

8.83

8.67

c, if > d

3

2.83

3.83

3.83

3.67

W

1025

1030

1030

1090

990

WL Dead load = --------2

5723

5579

6094

6449

5693

Live load

97326

95233

100761

100761

98804

Total load

403048

100812

106855

107210

104497

Cross section-sq. in.-nominal size

1280

1296

1296

1440

1200

3 R Unit shear-lb per sq. in. = --- -----2 bh

121

117

12498

11288

131

Cross section-sq. in.-dressed size

1240

1260

1260

1400

1170

R--- ----Unit shear-lb per sq. in. = 3 2 bh

125

120

127

115

134

1

3

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-71

Timber Structures

Table 7-A3-6. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 72 Loading, No Impact 12 ¢ and 12 ¢ 6 ² Spans All loads in pounds per track. All moments in foot-pounds per track Panel Length C to C of Bents

12¢

12¢

12¢ 6²

Number and Size of Stringers

8-8² ´ 16²

6-9² ´ 18²

8-8² ´ 16²

Dead load per foot of track Above stringers

500

500

500

Stringers-nominal size

427

405

427

927

905

927

Total dead load Reaction on bent in pounds Dead load

11100

10900

11600

Live load

168000

168000

173000

Total

179100

Kind of bent Number of piles or posts Size of piles or posts

178900 Pile

Frame

184600

Pile

Frame

Pile

5

5

5

5

6

Frame 6

14² D

12´ 14

14² D

12´ 14

14² D

12´ 14

Total area of piles or posts-sq. in.

770

840

770

840

924

1008

Unit bearing stress on piles or posts-lb per sq. in.

233

213

232

213

200

183

Average load in tons per pile or post

17.9

17.9

17.9

17.9

15.4

15.4

Bearing-Stringers on caps for continuous butt type deck Area sq. in.-14² cap

896

756

Bearing stress-lb per sq. in.-14² cap

200

237

896 206

Area sq. in.-16² cap

1024

864

1024

Bearing stress-lb per sq. in.-16² cap

176

207

180

Bending in stringers Dead load moment-foot pounds per track

14900

14500

16200

Live load moment-foot pounds per track

255000

255000

279000

Total load moment-foot pounds per track

269900

269500

295200

Section modulus-nominal size

2730

2916

2730

Bending stress-lb per sq. in.-nominal size

1190

1110

1300

Section modulus-dressed size

2560

2756

2560

Bending stress-lb per sq. in.-dressed size

1270

1170

1380

Longitudinal shear-Standard formula-First driver at height of the beam from the support. Depth nominal

16

18

16

c to c

12

12

12.5

L = (c to c) + 0.5 - 14/12

11.33

11.33

11.83

L’ ignore within d of face

8.17

7.83

8.67

a

10

9.83

10.5

b

5

4.83

5.5

W

927

905

927

WL Dead load = --------2

3785

3545

4017

Live load

92118

90000

94310

Total load

95903

93545

98327

c, if > d

Assumptions: L= Distance C to C bents for bearing on caps in feet = Distance face to face of caps plus 0.5 foot for stringer bending and shear. (Assume 14² Cap) W = Total Dead Load per linear foot of track: Rail and fastenings = 200 pounds per linear foot Ties 8² ´ 8² ´ 10¢ @ 12² ctrs = 267 pounds per linear foot R= Total Reaction

h= Height of stringer in feet b= Breadth of stringers in feet P= Weight on one driving axle = 72000 pounds a= Distance from load P to support, in feet Dressed size = Nominal size less 1/2² in depth

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-72

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

Table 7-A3-6. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 72 Loading, No Impact 12 ¢ and 12 ¢ 6 ² Spans (Continued) All loads in pounds per track. All moments in foot-pounds per track Panel Length C to C of Bents

12¢

12¢

12¢ 6²

Number and Size of Stringers

8-8² ´ 16²

6-9² ´ 18²

8-8² ´ 16²

Cross section-sq. in.-nominal size

1024

1024

1152

RUnit shear-lb per sq. in. = 3 --- ----2 bh

140

137

128

Cross section-sq. in.-dressed size

992

992

1116

3 R Unit shear-lb per sq. in. = --- -----2 bh

145

141

132

1

3

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-73

Timber Structures

Table 7-A3-6. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 72 Loading, No Impact 13 ¢ Spans All loads in pounds per track. All moments in foot-pounds per track Panel Length C to C of Bents

13¢

13¢

Number and Size of Stringers

8-10² ´ 16²

6-10² ´ 18²

Dead load per foot of track Above stringers

500

500

Stringers-nominal size

533

450

1033

950

Total dead load Reaction on bent in pounds Dead load

13400

12400

Live load

177000

177000

Total

194400

Kind of bent Number of piles or posts Size of piles or posts

189400

Pile

Frame

Pile

6

6

6

Frame 6

14² D

12´ 14

14² D

12´ 14

Total area of piles or posts-sq. in.

924

1008

924

1008

Unit bearing stress on piles or posts-lb per sq. in.

206

189

205

188

Average load in tons per pile or post

15.9

15.9

15.8

15.8

Bearing-Stringers on caps for continuous butt type deck Area sq. in.-14² cap

1120

840

Bearing stress-lb per sq. in.-14² cap

170

225

Area sq. in.-16² cap

1280

960

Bearing stress-lb per sq. in.-16² cap

149

197

Bending in stringers Dead load moment-foot pounds per track

19600

18100

Live load moment-foot pounds per track

30600

306000

Total load moment-foot pounds per track

325600

324100

Section modulus-nominal size

3413

3240

Bending stress-lb per sq. in.-nominal size

1150

1200

Section modulus-dressed size

3200

3060

Bending stress-lb per sq. in.-dressed size

1220

1270

Longitudinal shear-Standard formula-First driver at height of the beam from the support Depth nominal

16

c to c

13

18 13

L = (c to c) + 0.5 - 14/12

12.33

12.33

L’ ignore within d of face

9.17

8.83

a

11

10.83

b

6

5.83

W

1033

950

WL Dead load = --------2

4735

4196

Live load

96324

94378

Total load

101059

98574

c, if > d

Assumptions: L= Distance C to C bents for bearing on caps in feet = Distance face to face of caps plus 0.5 foot for stringer bending and shear. (Assume 14² Cap) W = Total Dead Load per linear foot of track: Rail and fastenings = 200 pounds per linear foot Ties 8² ´ 8² ´ 10¢ @ 12² ctrs = 267 pounds per linear foot R= Total Reaction

h =Height of stringer in feet b =Breadth of stringers in feet P =Weight on one driving axle = 72000 pounds a =Distance from load P to support, in feet Dressed size = Nominal size less 1/2² in depth

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-74

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

Table 7-A3-6. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 72 Loading, No Impact 13 ¢ Spans (Continued) All loads in pounds per track. All moments in foot-pounds per track Panel Length C to C of Bents

13¢

13¢

Number and Size of Stringers

8-10² ´ 16²

6-10² ´ 18²

Cross section-sq. in.-nominal size

1280

1080

RUnit shear-lb per sq. in. = 3--- ----2 bh

118

137

Cross section-sq. in.-dressed size

1240

1050

3 R Unit shear-lb per sq. in. = --- -----2 bh

122

141

1

3

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-75

Timber Structures

Table 7-A3-6. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 72 Loading, No Impact 14 ¢ Spans All loads in pounds per track. All moments in foot-pounds per track Panel Length C to C of Bents

14¢

14¢

14¢

14¢

Number and Size of Stringers

8-10² ´ 16²

8-9² ´ 18²

6-10² ´ 18²

6-10² ´ 20²

Dead load per foot of track Above stringers

500

500

500

500

Stringers-nominal size

533

540

450

500

1033

1040

950

1000

Total dead load Reaction on bent in pounds Dead load

14500

14600

13300

14000

Live load

188000

188000

188000

188000

Total

202500

Kind of bent

Pile

Number of piles or posts Size of piles or posts Total area of piles or posts-sq. in.

Frame

202600 Pile

Frame

201300 Pile

Frame

202000 Pile

Frame

6

6

6

6

6

6

6

6

14² D

12´ 14

14² D

12´ 14

14² D

12´ 14

14² D

12´ 14

1008

924

1008

924

1008

924

1008

Unit bearing stress on piles or posts-lb 219 per sq. in.

924

200

219

201

216

199

219

200

Average load in tons per pile or post

16.9

16.9

16.9

16.8

16.8

16.8

16.8

16.9

Bearing-Stringers on caps for continuous butt type deck Area sq. in.-14² cap

1120

1008

840

840

Bearing stress-lb per sq. in.-14² cap

181

201

240

240

Area sq. in.-16² cap

1280

1152

960

960

Bearing stress-lb per sq. in.-16² cap

158

176

210

210

Bending in stringers Dead load moment-foot pounds per track

23000

23100

21100

22200

Live load moment-foot pounds per track

360000

360000

360000

360000

Total load moment-foot pounds per track

383000

383100

381100

382200

Section modulus-nominal size

3413

3888

3240

4000

Bending stress-lb per sq. in.-nominal size

1350

1180

1410

1150

Section modulus-dressed size

3200

3680

3060

3802

Bending stress-lb per sq. in.-dressed size

1140

1250

1490

1210

Longitudinal shear-Standard formula-First driver at height of the beam from the support. Depth nominal

16

18

18

c to c

14

14

14

14

L = (c to c) + 0.5 - 14/12

13.33

13.33

13.33

13.33

L’ ignore within d of face

10.17

9.83

9.83

9.50

12

11.83

11.83

11.67

b

7

6.83

6.83

6.67

c, if > d

2

a

20

W

1033

1040

950

1000

WL Dead load = --------2

5251

5113

4671

4750

Live load

109350

98100

98100

96300

Total load

114601

103213

102771

101050

Assumptions: L= Distance C to C bents for bearing on caps in feet = Distance face to face of caps plus 0.5 foot for stringer bending and shear. (Assume 14² Cap) W = Total Dead Load per linear foot of track: Rail and fastenings = 200 pounds per linear foot Ties 8² ´ 8² ´ 10¢ @ 12² ctrs = 267 pounds per linear foot R= Total Reaction

h= Height of stringer in feet b= Breadth of stringers in feet P= Weight on one driving axle = 72000 pounds a= Distance from load P to support, in feet Dressed size = Nominal size less 1/2² in depth

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-76

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

Table 7-A3-6. Comparison of Unit Stresses in Open Deck Trestles, Cooper E 72 Loading, No Impact 14 ¢ Spans (Continued) All loads in pounds per track. All moments in foot-pounds per track Panel Length C to C of Bents

14¢

14¢

14¢

14¢

Number and Size of Stringers

8-10² ´ 16²

8-9² ´ 18²

6-10² ´ 18²

6-10² ´ 20²

Cross section-sq. in.-nominal size

1280

1296

1080

1200

RUnit shear-lb per sq. in. = 3 --- ----2 bh

134

119

143

126

Cross section-sq. in.-dressed size

1240

1260

1050

1170

3 R Unit shear-lb per sq. in. = --- -----2 bh

139

123

147

130

1

3

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-77

p

AREMA Manual for Railway Engineering

© 2011, American Railway Engineering and Maintenance-of-Way Association

Cooper Design Load 55.6 69.8 Panel Length C to C of Bents 12 12 Number and size of Stringers 6- 8 × 16 6- 10 × 16 Dead Load per foot of track Above Stringers 490 500 Stringers -nominal size 320 400 Total Dead Load 810 900 Reaction on bent, pounds Dead Load 10800 9720 Live Load 129733 162864 Total 139453 173664 Kind of Bent Pile Frame Pile Frame Number of piles or posts 5 5 5 5 Size of piles or posts 14" D 12 x 14 14" D 12 x 14 Total Area of piles of posts, sq.-in. 770 840 770 840 Unit bearing stress on piles or posts, lb. per sq. 181 166 226 207 in. Average load in Tons per pile or post 14 14 17 17 Bearing-Stringers on caps for continuous Butt type Deck Area sq. in. - 14" cap 672 840 Bearing Stress - lb. Per sq. in. - 14" cap 208 207 Average sq. in. 16" cap 960 768 Bearing stress - lb. Per sq. in. - 16" cap 181 182 Bending in Stringers Dead Load Moment - ft. pounds per track 13005 14450 Live Load Moments - ft. pounds per track 194600 244300 Total Load Moment - ft. pounds per track 207605 258750 Section Modulus-nominal size 2048 2560 Bending stress-lb per sq. in. -nominal size 1216 1213 Section modulus- dressed size 1922 2403 Bending stress-lb per sq. in. - dressed size 1296 1292 Longitudinal shear-Standard formula-First driver at height of the beam from the support. depth nominal 16 16 c to c 12 12 L = (c to c) +0.5-14/12 11.33 11.33 L' ignore within d of face 8.17 8.17 a 9.75 9.75 b 4.75 4.75

p

p

p

69.0 13' 6- 9 × 18

76.8 11'-6" 8- 8 × 16

72.8 12' 6- 9 × 18

78.8 12' 6" 6- 10 × 18

76.9 13' 6- 10 × 18

72.0 15' 6- 10 × 20

500 405 905

500 427 927

500 405 905

500 450 950

500 450 950

500 500 1000

11765 169846 181611 Pile Frame 6 6 14" D 12 x 14 924 1008

10657 173635 184291 Pile Frame 6 6 14" D 12 x 14 924 1008

10860 169866 180726 Pile Frame 6 6 14" D 12 x 14 924 1008

11875 189120 200995 Pile Frame 6 6 14" D 12 x 14 924 1008

12350 191599 203949 Pile Frame 6 6 14" D 12 x 14 924 1008

15000 196800 211800 Pile Frame 6 6 14" D 12 x 14 924 1008

197

180

199

183

196

179

218

199

221

202

229

210

15

15

15

15

15.1

15.1

16.7

16.7

17.0

17.0

17.6

17.6

756 240 864 210

896 206 1024 180

756 239 864 209

840 239 960 209

840 243 960 212

840 252 960 221

17207 293250 310457 2916 1278 2756 1352

13594 246154 259748 2731 1141 2563 1216

14530 254800 269330 2916 1108 2756 1173

16628 305350 321978 3240 1193 3063 1262

18063 326825 344888 3240 1277 3063 1351

25680 414000 439680 4000 1319 3803 1388

18 13 12.33 8.83 10.58 5.58

16 11.5 10.83 7.67 9.25 4.25

18 12 11.33 7.83 9.58 4.58

18 12.5 11.83 8.33 10.08 5.08

18 13 12.33 8.83 10.58 5.58

20 15 14.33 10.50 12.42 7.42

Timber Structures

7-A3-78

Table 7-A3-7. Comparison of Unit Stresses in Open Deck Trestles, Various Cooper Loadings, No Impact All loads in pounds per track. All moments in foot-pounds per track.

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

Table 7-A3-7. Comparison of Unit Stresses in Open Deck Trestles, Various Cooper Loadings, No Impact All loads in pounds per track. All moments in foot-pounds per track. (Continued) c, if > d W 810 Dead load = WL'/2 3308 Live load 71135 Total load 74443 Cross section - sq. in.-nominal size 768 Unit shear-lb per sq. in. = 3R/2bh 145 Cross section - sq. in.-dressed size 744 Unit shear-lb per sq. in. = 3R/2bh 150 Assumptions: L = Distance C to C bents for bearing on caps in feet = Distance face to face of caps plus 0.5 foot for stringer bending and shear. (Assume 14 cap) W = Total Dead Load per linear foot of track: Rail and fastenings = 200 pounds per linear foot Ballast = 120 pounds per cubic foot R = Total Reaction

900 3675 89303 92978 960 145 930 150

905 3997 90446 94443 972 146 945 150

927 3552 95705 99257 1024 145 992 150

905 3545 91000 94545 972 146 945 150

950 3958 100997 104956 1080 146 1050 150

950 4196 100801 104997 1080 146 1050 150

2.42 1000 5250 111767 117017 1200 146 1170 150

h = Height of stringer in feet b = Breadth of stringers in feet P = Weight on one driving axle = 72000 pounds a = Distance from load P to support, in feet Dressed size = Nominal size less 1/2 in depth In calculating bearing, bending, and shear stresses, outer stringers are considered as carrying no load.

Outer stringers are considered as carrying no load. Based on appropriate grades of Douglas Fir and Southern Yellow Pine from Table Table 30-A-2-13

Appendix 3 - Legacy Designs

7-A3-79

Timber Structures

Table 7-A3-8. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 60 Loading, No Impact 12 ¢ and 12 ¢ 6 ² Spans All loads in pounds per track. All moments in foot-pounds per track Panel Length C to C of Bents

12¢

12¢

12¢ 6²

Number and Size of Stringers

12-7² ´ 14²

10-7² ´ 16²

10-8² ´ 16²

Above stringers

2310

2310

2310

Stringers-nominal size

490

470

535

2800

2780

2845

Dead load per foot of track

Total dead load Reaction on bent in pounds Dead load

33600

33400

35600

Live load

140000

140000

144000

Total

173600

Kind of bent

Pile

Number of piles or posts Size of piles or posts

Frame

173400 Pile

Frame

179600 Pile

Frame

6

6

6

6

6

6

14² D

12´ 14

14² D

12´ 14

14² D

12´ 14

Total area of piles or posts-sq. in.

924

1008

924

1008

924

1008

Unit bearing stress on piles or posts-lb per sq. in.

188

172

188

172

194

178

Average load in tons per pile or post

14.5

14.5

14.5

14.5

15.0

15.0

Bearing-Stringers on caps for continuous butt type deck Area sq. in.-14² cap

980

784

Bearing stress-lb per sq. in.-14² cap

177

221

896 200

Area sq. in.-16² cap

1120

896

1024

Bearing stress-lb per sq. in.-16² cap

155

194

175

Dead load moment-foot pounds per track

45000

44500

49800

Live load moment-foot pounds per track

210000

210000

252500

Total load moment-foot pounds per track

255000

254500

282300

Section modulus-nominal size

2285

2380

2728

Bending stress-lb per sq. in.-nominal size

1340

1280

1240

Section modulus-dressed size

2125

2240

2560

Bending stress-lb per sq. in.-dressed size

1440

1360

1320

Bending in stringers

Longitudinal shear-Standard formula-First driver at height of the beam from the support. Depth nominal

14

16

16

c to c

12

12

12.5

L = (c to c) + 0.5 - 14/12

11.33

11.33

11.83

L’ ignore within d of face

8.50

8.17

8.67

a

10.17

10.00

10.50

b

5.17

5.00

5.50

2800

2780

2845

11900

11352

12328

c, if > d W

WL Dead load = --------2 Live load

78529

76765

78592

Total load

90429

88116

90920

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-80

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

Table 7-A3-8. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 60 Loading, No Impact 12 ¢ and 12 ¢ 6 ² Spans (Continued) All loads in pounds per track. All moments in foot-pounds per track Panel Length C to C of Bents

12¢

12¢

12¢ 6²

Number and Size of Stringers

12-7² ´ 14²

10-7² ´ 16²

10-8² ´ 16²

Cross section-sq. in.-nominal size

1176

1120

1280

3 R Unit shear-lb per sq. in. = --- -----2 bh

115

118

107

Cross section-sq. in.-dressed size

1134

1085

1240

3 R Unit shear-lb per sq. in. = --- -----2 bh

120

122

110

Assumptions: L = Distance C to C bents for bearing on caps in feet = Distance face to face of caps plus 0.5 foot for stringer bending and shear. (Assume 14² cap) W = Total Dead Load per linear foot of track: Rail and fastenings = 200 pounds per linear foot Ballast = 120 pounds per cubic foot R = Total Reaction

h = Height of stringer in feet b = Breadth of stringers in feet P = Weight on one driving axle = 60000 pounds a = Distance from load P to support, in feet Dressed size = Nominal size less 1/2² in depth In calculating bearing, bending, and shear stresses outer stringers are considered as carrying no load.

1

3

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-81

Timber Structures

Table 7-A3-8. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 60 Loading, No Impact 13 ¢ Spans All loads in pounds per track. All moments in foot-pounds per track Panel Length C to C of Bents

13¢

13¢

13¢

13¢

Number and Size of Stringers

12-7² ´ 16²

10-8² ´ 16²

9-10² ´ 16²

8-9² ´ 18²

Above stringers

2310

2310

2310

2310

Stringers-nominal size

560

535

600

540

2870

2845

2910

2850

Dead load per foot of track

Total dead load Reaction on bent in pounds Dead load

37400

37000

37800

37100

Live load

147800

147800

147800

147800

Total

185200

Kind of bent

Pile

Number of piles or posts Size of piles or posts Total area of piles or posts-sq. in.

Frame

184800 Pile

Frame

185600 Pile

Frame

184900 Pile

Frame

6

6

6

6

6

6

6

6

14² D

12´ 14

14² D

12´ 14

14² D

12´ 14

14² D

12´ 14

1008

924

1008

924

1008

924

1008

Unit bearing stress on piles or posts-lb 200 per sq. in.

924

184

200

184

202

184

200

183

Average load in tons per pile or post

15.4

15.4

15.4

15.4

15.4

15.4

15.4

15.4

Bearing-Stringers on caps for continuous butt type deck Area sq. in.-14² cap

980

896

980

756

Bearing stress-lb per sq. in.-14² cap

189

206

189

244

Area sq. in.-16² cap

1120

1024

1120

865

Bearing stress-lb per sq. in.-16² cap

165

180

166

214

Dead load moment-foot pounds per track

54600

54100

55500

54200

Live load moment-foot pounds per track

255000

255000

255000

255000

Total load moment-foot pounds per track

309600

309100

310500

309200

Section modulus-nominal size

2980

2728

2990

2920

Bending stress-lb per sq. in.-nominal size

1250

1360

1245

1270

Section modulus-dressed size

2800

2560

2800

2750

Bending stress-lb per sq. in.-dressed size

1320

1450

1330

1350

Bending in stringers

Assumptions: L = Distance C to C bents for bearing on caps in feet = Distance face to face of caps plus 0.5 foot for stringer bending and shear. (Assume 14² cap) W = Total Dead Load per linear foot of track: Rail and fastenings = 200 pounds per linear foot Ballast = 120 pounds per cubic foot R = Total Reaction

h = Height of stringer in feet b = Breadth of stringers in feet P = Weight on one driving axle = 60000 pounds a = Distance from load P to support, in feet Dressed size = Nominal size less 1/2² in depth In calculating bearing, bending, and shear stresses outer stringers are considered as carrying no load.

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-82

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

Table 7-A3-8. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 60 Loading, No Impact 13 ¢ Spans (Continued) All loads in pounds per track. All moments in foot-pounds per track Panel Length C to C of Bents

13¢

13¢

13¢

13¢

Number and Size of Stringers

12-7² ´ 16²

10-8² ´ 16²

9-10² ´ 16²

8-9² ´ 18²

Longitudinal shear-Standard formula-First driver at height of the beam from the support. Depth nominal

16

16

16

c to c

13

13

13

18 13

L = (c to c) + 0.5 - 14/12

12.33

12.33

12.33

12.33

L’ ignore within d of face

9.17

9.17

9.17

8.83

a

11.00

11.00

11.00

10.83

b

6.00

6.00

6.00

5.83

W

2870

2845

2910

2850

WL Dead load = --------2

13154

13040

13338

12588

Live load

80270

80270

80270

78649

Total load

93424

93310

93608

91236

Cross section-sq. in.-nominal size

1344

1280

1440

1296

3 R Unit shear-lb per sq. in. = --- -----2 bh

104

109

98

106

Cross section-sq. in.-dressed size

1302

1240

1395

1260

3 R Unit shear-lb per sq. in. = --- -----2 bh

108

113

101

109

c, if > d

1

3

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-83

Timber Structures

Table 7-A3-8. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 60 Loading, No Impact 15 ¢ Spans All loads in pounds per track. All moments in foot-pounds per track Panel Length C to C of Bents

15¢

15¢

15¢

15¢

Number and Size of Stringers

13-8² ´ 16²

11-10² ´ 16²

10-9² ´ 18²

9-10² ´ 18²

Above stringers

2310

2310

2310

2310

Stringers-nominal size

690

740

680

680

3000

3050

2990

2990

Dead load per foot of track

Total dead load Reaction on bent in pounds Dead load

45000

48700

44900

44900

Live load

164200

164200

164200

164200

Total

209200

Kind of bent

Pile

Number of piles or posts Size of piles or posts Total area of piles or posts-sq. in.

Frame

209900 Pile

Frame

209100 Pile

Frame

209100 Pile

Frame

6

6

6

6

6

6

6

6

14² D

12´ 14

14² D

12´ 14

14² D

12´ 14

14² D

12´ 14

1008

924

1008

924

1008

924

1008

Unit bearing stress on piles or posts-lb 226 per sq. in.

924

206

227

208

226

207

226

207

Average load in tons per pile or post

17.4

17.5

17.5

17.4

17.4

17.4

17.4

17.4

Bearing-Stringers on caps for continuous butt type deck Area sq. in.-14² cap

1252

1260

1008

980

Bearing stress-lb per sq. in.-14² cap

170

167

208

214

Area sq. in.-16² cap

1408

1440

1152

1120

Bearing stress-lb per sq. in.-16² cap

148

146

182

187

Dead load moment-foot pounds per track

77000

78500

76700

76700

Live load moment-foot pounds per track

346000

346000

346000

346000

Total load moment-foot pounds per track

423000

424500

422700

422700

Section modulus-nominal size

3750

3840

3890

3780

Bending stress-lb per sq. in.-nominal size

1260

1320

1300

1340

Section modulus-dressed size

3520

3600

3660

3570

Bending stress-lb per sq. in.-dressed size

1440

1410

1380

1420

Bending in stringers

Assumptions: L = Distance C to C bents for bearing on caps in feet = Distance face to face of caps plus 0.5 fooot for stringer bending and shear. (Assume 14² cap) W = Total Dead Load per linear foot of track: Rail and fastenings = 200 pounds per linear foot Ballast = 120 pounds per cubic foot R = Total Reaction

h = Height of stringer in feet b = Breadth of stringers in feet P = Weight on one driving axle = 60000 pounds a = Distance from load P to support, in feet Dressed size = Nominal size less 1/2² in depth In calculating bearing, bending, and shear stresses outer stringers are considered as carrying no load.

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-84

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

Table 7-A3-8. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 60 Loading, No Impact 15 ¢ Spans (Continued) All loads in pounds per track. All moments in foot-pounds per track Panel Length C to C of Bents

15¢

15¢

15¢

15¢

Number and Size of Stringers

13-8² ´ 16²

11-10² ´ 16²

10-9² ´ 18²

9-10² ´ 18²

Longitudinal shear-Standard formula-First driver at height of the beam from the support. Depth nominal

16

16

18

c to c

15

15

15

18 15

L = (c to c) + 0.5 - 14/12

14.33

14.33

14.33

14.33

L’ ignore within d of face

11.17

11.17

10.83

10.83

a

13.08

13.08

13.08

13.08

b

8.08

8.08

8.08

8.08

c, if > d

3.08

3.08

3.08

3.08

W

3000

3050

2990

2990

WL Dead load = --------2

16750

17029

16196

16196

Live load

97326

97326

95233

95233

Total load

114076

114355

111428

111428

Cross section-sq. in.-nominal size

1664

1760

1620

1620

3 R Unit shear-lb per sq. in. = --- -----2 bh

103

97

103

103

Cross section-sq. in.-dressed size

1612

1705

1575

1575

3 R Unit shear-lb per sq. in. = --- -----2 bh

106

101

106

106

1

3

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-85

Timber Structures

Table 7-A3-9. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 72 Loading, No Impact 12 ¢ and 12 ¢ 6 ² Spans All loads in pounds per track. All moments in foot-pounds per track Panel Length C to C of Bents

12¢

12¢

12¢ 6²

Number and Size of Stringers

14-7² ´ 14²

12-7² ´ 16²

12-8² ´ 16²

Above stringers

2310

2310

2310

Stringers-nominal size

570

560

640

2880

2870

2950

Dead load per foot of track

Total dead load Reaction on bent in pounds Dead load

34600

34500

36900

Live load

168000

168000

173000

Total

202000

Kind of bent

Pile

Number of piles or posts Size of piles or posts Total area of piles or posts-sq. in.

Frame

202500 Pile

Frame

209900 Pile

Frame

6

6

6

6

6

6

14² D

12´ 14

14² D

12´ 14

14² D

12´ 14

1008

924

1008

924

1008

Unit bearing stress on piles or posts-lb 219 per sq. in.

924

201

219

201

227

208

Average load in tons per pile or post

16.9

16.9

16.9

17.5

17.5

16.9

Bearing-Stringers on caps for continuous butt type deck Area sq. in.-14² cap

1176

980

Bearing stress-lb per sq. in.-14² cap

173

207

1120 187

Area sq. in.-16² cap

1344

1120

1280

Bearing stress-lb per sq. in.-16² cap

151

181

164

Dead load moment-foot pounds per track

46200

46100

51600

Live load moment-foot pounds per track

252000

252000

279000

Total load moment-foot pounds per track

298200

298100

330600

Section modulus-nominal size

2740

2990

3410

Bending stress-lb per sq. in.-nominal size

1310

1200

1170

Section modulus-dressed size

2550

2800

3200

Bending stress-lb per sq. in.-dressed size

1400

1280

1240

Bending in stringers

Assumptions: L = Distance C to C bents for bearing on caps in feet = Distance face to face of caps plus 0.5 foot for stringer bending and shear. (Assume 14² cap) W = Total Dead Load per linear foot of track: Rail and fastenings = 200 pounds per linear foot Ballast = 120 pounds per cubic foot R = Total Reaction

h= b= P=

Height of stringer in feet Breadth of stringers in feet Weight on one driving axle = 60000 pounds a = Distance from load P to support, in feet Dressed size = Nominal size less 1/2 in depth In calculating bearing, bending, and shear stresses outer stringers are considered as carrying no load.

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-86

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

Table 7-A3-9. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 72 Loading, No Impact 12 ¢ and 12 ¢ 6 ² Spans (Continued) All loads in pounds per track. All moments in foot-pounds per track Panel Length C to C of Bents

12¢

12¢

12¢ 6²

Number and Size of Stringers

14-7² ´ 14²

12-7² ´ 16²

12-8² ´ 16²

Longitudinal shear-Standard formula-First driver at height of the beam from the support. Depth nominal

14

16

16

c to c

12

12

12.5

L = (c to c) + 0.5 - 14/12

11.33

11.33

11.83

L’ ignore within d of face

8.50

8.17

8.67

a

10.17

10.00

10.5

b

5.17

5.00

5.5

W

2880

2870

2950

--------Dead load = WL 2

12240

11719

12783

c, if > d

Live load

94235

92118

94310

Total load

106475

103837

107093

Cross section-sq. in.-nominal size

1372

1344

1536

3 R Unit shear-lb per sq. in. = --- -----2 bh

116

116

105

Cross section-sq. in.-dressed size

1323

1302

1488

3 R Unit shear-lb per sq. in. = --- -----2 bh

121

120

108

1

3

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-87

Timber Structures

Table 7-A3-9. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 72 Loading, No Impact 13 ¢ Spans All loads in pounds per track. All moments in foot-pounds per track Panel Length C to C of Bents

13¢

13¢

13¢

13¢

Number and Size of Stringers

14-7² ´ 16²

12-8² ´ 16²

10-10² ´ 16²

10-9² ´ 18²

Above stringers

2310

2310

2310

2310

Stringers-nominal size

650

640

670

675

2960

2950

2980

2985

Dead load per foot of track

Total dead load Reaction on bent in pounds Dead load

38500

38400

38800

38800

Live load

177200

177200

177200

177200

Total

215700

Kind of bent

Pile

Number of piles or posts Size of piles or posts

Frame

215600 Pile

Frame

216000 Pile

Frame

216000 Pile

Frame

7

6

7

6

7

6

7

6

14² D

12´ 14

14² D

12´ 14

14² D

12´ 14

14² D

12´ 14

Total area of piles or posts-sq. in.

1077

1008

1077

1008

1077

1008

1077

1008

Unit bearing stress on piles or posts-lb per sq. in.

200

214

200

214

201

214

201

214

Average load in tons per pile or post

15.4

18.0

15.4

18.0

15.4

18.0

15.4

18.0

Bearing-Stringers on caps for continuous butt type deck Area sq. in.-14² cap

1176

1120

1120

Bearing stress-lb per sq. in.-14² cap

183

192

193

1008 214

Area sq. in.-16² cap

1344

1280

1280

1152

Bearing stress-lb per sq. in.-16² cap

160

168

169

187 56700

Bending in stringers Dead load moment-foot pounds per track

56200

56000

56600

Live load moment-foot pounds per track

306000

306000

306000

Total load moment-foot pounds per track

362200

362000

362600

306000

Section modulus-nominal size

3580

3410

3410

3890

Bending stress-lb per sq. in.-nominal size

1220

1280

1280

1120

Section modulus-dressed size

3360

3200

3200

3670

Bending stress-lb. per sq. in.-dressed size

1300

1360

1360

1190

Longitudinal shear-Standard formula-First driver at height of the beam from the support. Depth nominal

16

16

16

c to c

13

13

13

13

12.33

12.33

12.33

12.33

L = (c to c) + 0.5 - 14/12

18

L’ ignore within d of face

9.17

9.17

9.17

8.83

a

11.00

11.00

11.00

10.83

b

6.00

6.00

6.00

5.83

W

2960

2950

2980

2985

WL Dead load = --------2

13567

13521

13658

13184

c, if > d

Live load

96324

96324

96324

94378

Total load

109891

109845

109983

107562

Assumptions: L= Distance C to C bents for bearing on caps in feet = Distance face to face of caps plus 0.5 foot for stringer bending and shear. (Assume 14² cap) W = Total Dead Load per linear foot of track: Rail and fastenings = 200 pounds per linear foot Ballast = 120 pounds per cubic foot R= Total Reaction

h= Height of stringer in feet b= Breadth of stringers in feet P= Weight on one driving axle = 72000 pounds a= Distance from load P to support, in feet Dressed size = Nominal size less 1/2² in depth In calculating bearing, bending, and shear stresses outer stringers are considered as carrying no load.

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-88

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

Table 7-A3-9. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 72 Loading, No Impact 13 ¢ Spans (Continued) All loads in pounds per track. All moments in foot-pounds per track Panel Length C to C of Bents

13¢

13¢

13¢

13¢

Number and Size of Stringers

14-7² ´ 16²

12-8² ´ 16²

10-10² ´ 16²

10-9² ´ 18²

Cross section-sq. in.-nominal size

1568

1536

1600

1620

RUnit shear-lb per sq. in. = 3 --- ----2 bh

105

107

103

100

Cross section-sq. in.-dressed size

1519

1488

1550

1575

3 R Unit shear-lb per sq. in. = --- -----2 bh

109

111

106

102

1

3

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-89

Timber Structures

Table 7-A3-9. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 72 Loading, No Impact 15 ¢ Spans All loads in pounds per track. All moments in foot-pounds per track Panel Length C to C of Bents

15¢

15¢

15¢

15¢

Number and Size of Stringers

14-8² ´ 16²

12-10² ´ 16²

12-9² ´ 18²

10-10² ´ 18²

Above stringers

2310

2310

2310

2310

Stringers-nominal size

750

800

810

750

3050

3110

3120

3060

Dead load per foot of track

Total dead load Reaction on bent in pounds Dead load

46000

46600

46800

46000

Live load

197000

197000

197000

197000

Total

243000

Kind of bent

Pile

Number of piles or posts Size of piles or posts

Frame

243600 Pile

Frame

243800 Pile

Frame

243000 Pile

Frame

7

6

7

6

7

6

7

6

14² D

12´ 14

14² D

12´ 14

14² D

12´ 14

14² D

12´ 14

Total area of piles or posts-sq. in.

1077

1008

1077

1008

1077

1008

1077

1008

Unit bearing stress on piles or posts-lb per sq. in.

226

241

226

242

226

242

226

241

Average load in tons per pile or post

17.4

17.4

20.3

17.4

20.3

17.4

20.2

20.2

Bearing-Stringers on caps for continuous butt type deck Area sq. in.-14² cap

1344

1400

1260

Bearing stress-lb per sq. in.-14² cap

181

174

193

1120 217

Area sq. in.-16² cap

1536

1600

1440

1280

Bearing stress-lb per sq. in.-16² cap

158

152

169

190

Bending in stringers Dead load moment-foot pounds per track

78500

79800

80100

78500

Live load moment-foot pounds per track

415000

415000

415000

415000

Total load moment-foot pounds per track

493500

494800

495100

493500

Section modulus-nominal size

4100

4270

4860

4320

Bending stress-lb per sq. in.-nominal size

1450

1390

1220

1370

Section modulus-dressed size

3840

4000

4600

4080

Bending stress-lb per sq. in.-dressed size

1540

1490

1290

1450

Longitudinal shear-Standard formula-First driver at height of the beam from the support. Depth nominal

16

16

18

c to c

15

15

15

15

14.33

14.33

14.33

14.33

L = (c to c) + 0.5 - 14/12

18

L’ ignore within d of face

11.17

11.17

10.83

10.83

a

13.00

13.00

12.83

12.83

b

8.00

8.00

7.83

7.83

c, if > d

3.00

3.00

2.83

2.83

W

3050

3110

3120

3060

WL Dead load = --------2

17029

17364

16900

16575

Live load

116791

116791

114279

114279

Total load

133820

134155

131179

130854

Assumptions: L= Distance C to C bents for bearing on caps in feet = Distance face to face of caps plus 0.5 foot for stringer bending and shear. (Assume 14² cap) W = Total Dead Load per linear foot of track: Rail and fastenings = 200 pounds per linear foot Ballast = 120 pounds per cubic foot R= Total Reaction

h= Height of stringer in feet b= Breadth of stringers in feet P= Weight on one driving axle = 72000 pounds a= Distance from load P to support, in feet Dressed size = Nominal size less 1/2² in depth In calculating bearing, bending, and shear stresses outer stringers are considered as carrying no load.

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-90

AREMA Manual for Railway Engineering

Appendix 3 - Legacy Designs

Table 7-A3-9. Comparison of Unit Stresses in Ballasted Deck Trestles, Cooper E 72 Loading, No Impact 15 ¢ Spans (Continued) All loads in pounds per track. All moments in foot-pounds per track Panel Length C to C of Bents

15¢

15¢

15¢

15¢

Number and Size of Stringers

14-8² ´ 16²

12-10² ´ 16²

12-9² ´ 18²

10-10² ´ 18²

Cross section-sq. in.-nominal size

1792

1920

1944

1800

RUnit shear-lb per sq. in. = 3 --- ----2 bh

112

105

101

109

Cross section-sq. in.-dressed size

1736

1860

1890

1750

3 R Unit shear-lb per sq. in. = --- -----2 bh

116

108

104

112

1

3

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

7-A3-91

Timber Structures

A3.4 LEGACY CULVERT DESIGNS

Figure 7-A3-79. Recommended Practice for Design of Wood Culverts, E 72 Loading, for Heights up to 15 Foot Base of Rail to Flow Line area

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-92

AREMA Manual for Railway Engineering

Size of Boxes and Requirements

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

Table 7-A3-10. Typical Size Boxes and Unit Stresses Maximum Stress in Timber in lb per square inch Top and Bottom Bending

Holdbacks

Width W in Ft-In.

Height Top and Sides H Bottom B in in in Ft-In. Inches Inches

2¢ -0²

1¢ -0²

3

3

NONE

2¢ -0²

1¢ -6²

3

4

4´ 4

5

2¢ -0²

2¢ -0²

3

4

4´ 6

2¢ -6²

2¢ -6²

3

4

3¢ -0²

2¢ -0²

4

3¢ -0²

3¢ -0²

3¢ -6²

Size in Inches

Max Spacing Feet

Side Walls Bearing

Center Wall Bearing

Holdbacks Bending

Max Tension in Bolts lb per Bolt

Number Min Max Min Max Min Max Min Max Min of Bolts Depth Depth Depth Depth Depth Depth Depth Depth Depth

Max Depth

730

990

60

83

135

183

2

785

1040

48

64

105

139

1033

1450

1800

2540

6

2

785

1020

48

63

105

136

905

1270

2860

4000

4´ 6

5

2

1156

1480

57

73

127

163

1128

1565

2930

4130

4

4´ 6

6

2

901

1170

66

86

151

195

975

1370

2860

4020

4

6

6´ 6

5

3

1000

1240

48

61

105

132

1153

1520

2390

3270

3¢ -6²

6

6

6´ 8

6

3

582

702

55

66

121

145

1078

1440

3360

4550

4¢ -0²

3¢ -0²

6

6

6´ 6

5

3

736

910

61

75

136

169

1217

1650

2390

3240

4¢ -0²

4¢ -0²

6

6

6´ 8

5

3

736

880

61

72

136

163

1140

1525

3200

4300

4¢ -0²

6¢ -0²

6

6

8 ´ 10

5

4

736

816

61

67

136

154

1165

1470

3670

4650

4¢ -6²

4¢ -6²

6

8

8´ 8

6

4

970

1135

53

62

118

138

1273

1680

3260

4320

5¢ -0²

5¢ -0²

6

8

8´ 8

5

4

1170

1345

58

66

129

148

1291

1675

3040

3950

6¢ -0²

6¢ -0²

8

8

8 ´ 10

5

4

912

1010

67

74

152

168

1230

1545

3700

4650

Appendix 3 - Legacy Designs

7-A3-93

Timber Structures

THIS PAGE INTENTIONALLY LEFT BLANK.

© 2011, American Railway Engineering and Maintenance-of-Way Association

7-A3-94

AREMA Manual for Railway Engineering

8

CHAPTER 8 CONCRETE STRUCTURES AND FOUNDATIONS1 FOREWORD

The material in this chapter is written with regard to typical North American Railroad Concrete Structures and Foundations and other structures mentioned herein with • Standard Gage Track,

1

• Normal North American passenger and freight equipment, and • Speeds of freight trains up to 80 mph and passenger trains up to 90 mph. Additional special provisions for speeds higher than those listed above may be added by the Engineer as necessary. This chapter is presented as a consensus document by a committee composed of railroad industry professionals having substantial and broad-based experience designing, evaluating, and investigating Concrete Structures and Foundations used by railroads. The recommendations contained herein are based upon past successful usage, advances in the state of knowledge, and current design and maintenance practices. These recommendations are intended for routine use and might not provide sufficient criteria for infrequently encountered conditions. Professional judgement must be exercised when applying the recommendations of this chapter as part of an overall solution to any particular issue. This chapter is published annually, incorporating revisions made in the previous year. The latest published edition of the chapter should be used, regardless of the age of an existing structure. For purposes of determining historical recommendations under which an existing structure may have been built and maintained, it can prove useful to examine previous editions of the chapter. However, when historical recommendations differ from the recommendations contained in the latest published edition of the chapter, the recommendations of the latest published edition of the chapter should be used. Part 8, Rigid Frame Concrete Bridges was deleted from the manual in 1975. Part 9, Reinforced Concrete Trestles was deleted from the manual in 1971. Part 15 is reserved for future use. Part 18, Elastomeric Bridge Bearings was moved to Chapter 15 in 2001. 1

The material in this and other chapters in the AREMA Manual for Railway Engineering is published as recommended practice to railroads and others concerned with the engineering, design and construction of railroad fixed properties (except signals and communications), and allied services and facilities. For the purpose of this Manual, RECOMMENDED PRACTICE is defined as a material, device, design, plan, specification, principle or practice recommended to the railways for use as required, either exactly as presented or with such modifications as may be necessary or desirable to meet the needs of individual railways, but in either event, with a view to promoting efficiency and economy in the location, construction, operation or maintenance of railways. It is not intended to imply that other practices may not be equally acceptable.

© 2011, American Railway Engineering and Maintenance-of-Way Association

8-i

3

TABLE OF CONTENTS Part/Section

Description

Page

1

Materials, Tests and Construction Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Cement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 Other Cementitious Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 Aggregates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5 Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6 Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7 Concrete Admixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.8 Storage of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.9 Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.10 Details of Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.11 Concrete Jointing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.12 Proportioning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.13 Mixing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.14 Depositing Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.15 Depositing Concrete Under Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.16 Concrete in Sea Water. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.17 Concrete in Alkali Soils or Alkali Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.18 Curing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.19 Formed Surface Finish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.20 Unformed Surface Finish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.21 Decorative Finishes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.22 Penetrating Water Repellent T reatment of Concrete Surfaces . . . . . . . . . . . . . . . . . . . . . . . 1.23 Repairs and Anchorage Using Reactive Resins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.24 High Strength Concrete (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.25 Specialty Concretes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-1-1 8-1-6 8-1-8 8-1-9 8-1-11 8-1-16 8-1-16 8-1-19 8-1-19 8-1-21 8-1-24 8-1-27 8-1-31 8-1-38 8-1-39 8-1-44 8-1-47 8-1-48 8-1-49 8-1-52 8-1-53 8-1-54 8-1-54 8-1-56 8-1-57 8-1-58 8-1-60

2

Reinforced Concrete Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2 Notations, Definitions and Design Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4 Hooks and Bends. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.5 Spacing of Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6 Concrete Protection for Reinforcement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.7 Minimum Reinforcement of Flexural Members (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.8 Distribution of Reinforcement in Flexural Members (2005) . . . . . . . . . . . . . . . . . . . . . . . . . 2.9 Lateral Reinforcement of Flexural Members (2005). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.10 Shear Reinforcement – General Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.11 Limits for Reinforcement of Compression Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.12 Shrinkage and Temperature Reinforcement (2005). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-2-1 8-2-5 8-2-8 8-2-20 8-2-21 8-2-22 8-2-22 8-2-23 8-2-23 8-2-24 8-2-25 8-2-26 8-2-27

© 2011, American Railway Engineering and Maintenance-of-Way Association

8-ii

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TABLE OF CONTENTS (CONT) Part/Section

3

4

Description

Page

2.13 Development Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.14 Development Length of Deformed Bars and Deformed Wire in Tension (2005) . . . . . . . . . . 2.15 Development Length of Deformed Bars in Compression (2005). . . . . . . . . . . . . . . . . . . . . . . 2.16 Development Length of Bundled Bars (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.17 Development of Standard Hooks in Tension (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.18 Combination Development Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.19 Development of Welded Wire Fabric in Tension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.20 Mechanical Anchorage (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.21 Anchorage of Shear Reinforcement (2005). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.22 Splices of Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.23 Analysis Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.24 Design Methods (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.25 General Requirements (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.26 Allowable Service Load Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.27 Flexure (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.28 Compression Members with or without Flexure (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.29 Shear. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.30 Strength Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.31 Design Assumptions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.32 Flexure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.33 Compression Members with or without Flexure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.34 Slenderness Effects in Compression Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.35 Shear. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.36 Permissible Bearing Stress (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.37 Serviceability Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.38 Fatigue Stress Limit for Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.39 Distribution of Flexural Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.40 Control of Deflections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-2-28 8-2-29 8-2-31 8-2-31 8-2-31 8-2-33 8-2-33 8-2-34 8-2-34 8-2-35 8-2-38 8-2-43 8-2-43 8-2-43 8-2-45 8-2-45 8-2-45 8-2-53 8-2-54 8-2-55 8-2-57 8-2-60 8-2-62 8-2-70 8-2-70 8-2-70 8-2-71 8-2-71 8-2-72

Spread Footing Foundations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Information Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 Depth of Base of Footings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4 Sizing of Footings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5 Footings with Eccentric Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6 Footing Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7 Field Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.8 Combined Footings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-3-1 8-3-2 8-3-4 8-3-7 8-3-7 8-3-12 8-3-14 8-3-14 8-3-15

Pile Foundations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 Allowable Load on Piles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 Pile T ypes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5 Installation of Piles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6 Inspection of Pile Driving (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-4-1 8-4-2 8-4-2 8-4-5 8-4-9 8-4-14 8-4-16 8-4-16

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Retaining Walls, Abutments and Piers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2 Information Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3 Computation of Applied Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4 Stability Computation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5 Design of Backfill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6 Designing Bridges to Resist Scour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.7 Details of Design and Construction for Abutments and Retaining Walls . . . . . . . . . . . . . . . 5.8 Details of Design and Construction for Bridge Piers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-5-1 8-5-2 8-5-4 8-5-5 8-5-7 8-5-8 8-5-9 8-5-11 8-5-12

6

Crib Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 Design of Crib Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 Requirements for Reinforced Concrete Crib Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4 Requirements for Metal Crib Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5 Requirements for Timber Crib Walls. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-6-1 8-6-2 8-6-2 8-6-3 8-6-5 8-6-6

7

Mechanically Stabilized Embankment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2 Design of Mechanically Stabilized Embankments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3 Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-7-1 8-7-2 8-7-2 8-7-3

10 Reinforced Concrete Culvert Pipe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-10-1 8-10-2 8-10-3 8-10-4 8-10-12

11 Lining Railway Tunnels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.3 Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4 Concrete. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-11-1 8-11-2 8-11-2 8-11-7 8-11-8

12 Cantilever Poles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.2 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.3 Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.4 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-12-1 8-12-2 8-12-2 8-12-2 8-12-3

14 Repair and Rehabilitation of Concrete Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.1 Scope (2006). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.2 Determination of the Causes of Concrete Deterioration (2006). . . . . . . . . . . . . . . . . . . . . . . 14.3 Evaluation of the Effects of Deterioration and Damage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.4 Principal Materials Used in the Repair of Concrete Structures . . . . . . . . . . . . . . . . . . . . . . 14.5 Repair Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.6 Repair Methods for Prestressed Members. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-14-1 8-14-3 8-14-3 8-14-4 8-14-5 8-14-7 8-14-22 8-14-25

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16 Design and Construction of Reinforced Concrete Box Culverts . . . . . . . . . . . . . . . . . . . 16.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.2 Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.3 Design Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.4 Design Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.5 Details of Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.6 Manufacture of Precast Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.7 Construction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-16-1 8-16-2 8-16-4 8-16-6 8-16-7 8-16-13 8-16-16 8-16-17

17 Prestressed Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.1 General Requirements and Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.2 Notations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.3 Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.4 Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.5 Details of Prestressing Tendons and Ducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.6 General Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.7 Expansion and Contraction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.8 Span Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.9 Frames and Continuous Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.10 Effective Flange Width . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.11 Flange and Web Thickness-Box Girders. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.12 Diaphragms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.13 Deflections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.14 General Design. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.15 Load Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.16 Allowable Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.17 Loss of Prestress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.18 Flexural Strength. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.19 Ductility Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.20 Non-Prestressed Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.21 Shear. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.22 Post-Tensioned Anchorage Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.23 Pretensioned Anchorage Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.24 Concrete Strength at Stress Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.25 General Detailing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.26 General Fabrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.27 Mortar and Grout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.28 Application of Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.29 Materials - Reinforcing Steel. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.30 Prestressed Concrete Cap and/or Sill for Timber Pile Trestle (2003) . . . . . . . . . . . . . . . . . . Commentary (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-17-1 8-17-4 8-17-5 8-17-7 8-17-10 8-17-11 8-17-13 8-17-13 8-17-13 8-17-14 8-17-15 8-17-16 8-17-16 8-17-16 8-17-17 8-17-18 8-17-18 8-17-21 8-17-26 8-17-28 8-17-29 8-17-30 8-17-35 8-17-45 8-17-46 8-17-46 8-17-50 8-17-53 8-17-54 8-17-54 8-17-56 8-17-58

19 Rating of Existing Concrete Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.2 Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.3 Loads and Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.4 Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.5 Load Combinations and Rating Formulas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.6 Excessive Loading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-19-11

20 Flexible Sheet Pile Bulkheads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.2 Information Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.3 Computation of Lateral Forces Acting on Bulkheads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.4 Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.5 Design of Anchored Bulkheads. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.6 Cantilever Bulkheads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.7 Notations (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-20-1 8-20-2 8-20-3 8-20-5 8-20-9 8-20-10 8-20-13 8-20-15 8-20-16

21 Inspection of Concrete and Masonry Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.1 General (2006). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.2 Reporting of Defects (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.3 Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-21-1 8-21-1 8-21-2 8-21-2 8-21-20

22 Geotechnical Subsurface Investigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.1 General (1992). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.2 Scope (1992). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.3 Classification of Investigations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.4 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.5 Exploration Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.6 Determination of Groundwater Level (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.7 Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.8 Records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.9 Inspection (1992). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.10 Geophysical Explorations (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.11 In-Situ Testing of Soil (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.12 Backfilling Bore Holes (1992). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.13 Cleaning Site (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-22-1 8-22-2 8-22-2 8-22-2 8-22-3 8-22-5 8-22-6 8-22-6 8-22-7 8-22-9 8-22-9 8-22-10 8-22-10 8-22-10

23 Pier Protection Systems at Spans Over Navigable Streams. . . . . . . . . . . . . . . . . . . . . . . 23.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.2 Special Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.3 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.4 Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Commentary (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-23-1 8-23-2 8-23-3 8-23-4 8-23-20 8-23-24

24 Drilled Shaft Foundations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.2 Information Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.3 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.4 Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.5 Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.6 Testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C - Commentary (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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25 Slurry Wall Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.2 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.3 Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.4 Construction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-25-1 8-25-2 8-25-3 8-25-7 8-25-10

26 Recommendations for the Design of Segmental Bridges . . . . . . . . . . . . . . . . . . . . . . . . . 26.1 General Requirements and Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.2 Methods of Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.3 Design Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.4 Load Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.5 Allowable Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.6 Prestress Losses (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.7 Flexural Strength. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.8 Shear and Torsion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.9 Fatigue Stress Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.10 Design of Local and General Anchorage Zones, Anchorage Blisters and Deviation Saddles 26.11 Provisional Post-Tensioning Ducts and Anchorages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.12 Duct Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.13 Couplers (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.14 Connection of Secondary Beams (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.15 Concrete Cover and Reinforcement Spacing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.16 Inspection Access (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.17 Box Girder Cross Section Dimensions and Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-26-1 8-26-4 8-26-8 8-26-12 8-26-16 8-26-21 8-26-22 8-26-23 8-26-23 8-26-32 8-26-33 8-26-36 8-26-37 8-26-39 8-26-39 8-26-41 8-26-41 8-26-41 8-26-42

27 Concrete Slab Track . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.1 Scope and Notations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.2 Application and Definitions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.3 General Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.4 Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.5 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.6 Construction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.7 Direct Fixation Fastening System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.8 Special Considerations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-27-1 8-27-3 8-27-3 8-27-6 8-27-7 8-27-8 8-27-10 8-27-15 8-27-18 8-27-26

28 Temporary Structures for Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.2 Information Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.3 Computation of Lateral Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.4 Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.5 Design of Shoring Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.6 Design of Falsework Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-28-1 8-28-2 8-28-4 8-28-5 8-28-5 8-28-5 8-28-14 8-28-20

29 Waterproofing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.1 General Principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.2 Waterproofing (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-29-1 8-29-4 8-29-4

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29.3 Dampproofing (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.4 Specific Application. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.5 Terms (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.6 Applicable ASTM Designations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.7 General Practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.8 Primers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.9 Membranes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.10 Membrane Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.11 Sealing Compounds for Joints and Edges of Membrane Protection (2001) . . . . . . . . . . . . . 29.12 Anti-Bonding Paper (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.13 Inspection and Tests (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.14 Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.15 Introduction to Damproofing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.16 Materials for Damproofing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.17 Application of Damproofing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C - Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-29-5 8-29-5 8-29-8 8-29-8 8-29-12 8-29-13 8-29-14 8-29-17 8-29-20 8-29-20 8-29-20 8-29-20 8-29-28 8-29-28 8-29-29 8-29-30

Chapter 8 Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-G-1

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-R-1

INTRODUCTION The Chapters of the AREMA Manual are divided into numbered Parts, each comprised of related documents (specifications, recommended practices, plans, etc.). Individual Parts are divided into Sections by centered headings set in capital letters and identified by a Section number. These Sections are subdivided into Articles designated by numbered side headings.

Page Numbers – In the page numbering of the Manual (8-2-1, for example) the first numeral designates the Chapter number, the second denotes the Part number in the Chapter, and the third numeral designates the page number in the Part. Thus, 8-2-1 means Chapter 8, Part 2, page 1. In the Glossary and References, the Part number is replaced by either a “G” for Glossary or “R” for References.

Document Dates – The bold type date (Document Date) at the beginning of each document (Part) applies to the document as a whole and designates the year in which revisions were last made somewhere in the document, unless an attached footnote indicates that the document was adopted, reapproved, or rewritten in that year. Article Dates – Each Article shows the date (in parenthesis) of the last time that Article was modified. Revision Marks – All current year revisions (changes and additions) which have been incorporated into the document are identified by a vertical line along the outside margin of the page, directly beside the modified information. Proceedings Footnote – The Proceedings footnote on the first page of each document gives references to all Association action with respect to the document. Annual Updates – New manuals, as well as revision sets, will be printed and issued yearly. © 2011, American Railway Engineering and Maintenance-of-Way Association

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Part 1 Materials, Tests and Construction Requirements1 — 2011 — TABLE OF CONTENTS

Section/Article

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1.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.1 Purpose (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.2 Scope (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.3 Terms (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.4 Acceptability (2004). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.5 ASTM - International (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.6 Selection of Materials (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.7 Test of Materials (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.8 Defective Materials (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.9 Equipment (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-1-6 8-1-6 8-1-6 8-1-6 8-1-7 8-1-7 8-1-7 8-1-7 8-1-7 8-1-7

1.2 Cement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2.1 General (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2.2 Specifications (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2.3 Quality, Sampling and Testing (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-1-8 8-1-8 8-1-8 8-1-9

1.3 Other Cementitious Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.1 General (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.2 Acceptability (2004). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.3 Specifications (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.4 Materials Not Included in This Recommended Practice (2004) . . . . . . . . . . . . . . . . . . . . . 1.3.5 Documentation (2004). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-1-9 8-1-9 8-1-9 8-1-10 8-1-10 8-1-10

1.4 Aggregates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4.1 General (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4.2 Fine Aggregates (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4.3 Normal Weight Coarse Aggregate (2004). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-1-11 8-1-11 8-1-12 8-1-14

1

References, Vol. 3, 1902, p. 311; Vol. 4, 1903, pp. 336,397; Vol. 5, 1904, pp. 605,610; Vol. 6, 1905, pp. 704,726; Vol. 11, 1910, p. 956; Vol. 13, 1912, pp. 333, 1564; Vol. 24, 1923, pp. 478, 1324; Vol. 28, 1927, pp. 1056, 1436; Vol. 29, 1928, pp. 607, 1399; Vol. 30, 1929, pp. 783, 1461; Vol. 31, 1930, pp. 1148, 1737; Vol. 32, 1931, pp. 330, 796; Vol. 33, 1932, pp. 622, 732; Vol. 34, 1933, pp. 578, 868; Vol. 35, 1934, pp. 953, 1130; Vol. 36, 1935, pp. 843, 1018; Vol. 37, 1936, pp. 632, 1040; Vol. 39, 1938, pp. 136, 332; Vol. 45, pp. 227, 642; Vol. 54, 1953, pp. 793, 1341; Vol. 56, 1955, pp. 436, 1084; Vol. 58, 1957, pp. 650, 1182; Vol. 59, 1958, pp. 637, 1970, p. 230; Vol. 72, 1971, p. 136; Vol. 74, 1973, p. 138; Vol. 75, 1974, p. 465; Vol. 78, 1977, p. 108; Vol. 83, 1982, p. 285; Vol. 92, 1991, p. 62; Vol. 93, 1992, p. 78; Vol. 96, p. 55; Vol. 97, p. 57.

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Concrete Structures and Foundations

TABLE OF CONTENTS (CONT) Section/Article 1.4.4

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Lightweight Coarse Aggregate for Structural Concrete (2004) . . . . . . . . . . . . . . . . . . . . .

8-1-15

1.5 Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.1 General (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-1-16 8-1-16

1.6 Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6.1 General (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6.2 Welding (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6.3 Specifications (2003). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6.4 Bending and Straightening (2003). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-1-16 8-1-16 8-1-16 8-1-16 8-1-18

1.7 Concrete Admixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7.1 General (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7.2 Types of Admixtures and Standard Specifications (2004) . . . . . . . . . . . . . . . . . . . . . . . . .

8-1-19 8-1-19 8-1-19

1.8 Storage of Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.8.1 Cementitious Materials and Concrete Admixtures (2009). . . . . . . . . . . . . . . . . . . . . . . . . 1.8.2 Aggregates (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.8.3 Reinforcement (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-1-19 8-1-19 8-1-20 8-1-20

1.9 Forms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.9.1 General (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.9.2 Safety (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.9.3 Design (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.9.4 Construction (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.9.5 Moldings (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.9.6 Form Coating and Release (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.9.7 Temporary Openings (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.9.8 Removal (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-1-21 8-1-21 8-1-21 8-1-21 8-1-22 8-1-22 8-1-22 8-1-23 8-1-23

1.10 Details of Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.10.1 Surface Conditions of Reinforcement (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.10.2 Fabrication (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.10.3 Provisions for Seismic Loading (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.10.4 Placing of Reinforcement (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.10.5 Spacing of Reinforcement (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.10.6 Concrete Protection for Reinforcement (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.10.7 Future Bonding (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-1-24 8-1-24 8-1-24 8-1-24 8-1-24 8-1-26 8-1-26 8-1-27

1.11 Concrete Jointing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.11.1 Scope (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.11.2 Types of Jointing (2009). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.11.3 Expansion Joints (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.11.4 Expansion Joints in Walls (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.11.5 Contraction Joints (2009). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.11.6 Construction Joints (2009). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.11.7 Watertight Construction Joints (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-1-27 8-1-27 8-1-27 8-1-27 8-1-28 8-1-28 8-1-29 8-1-29

1.12 Proportioning. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.12.1 General (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Measurement of Materials (2009). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1-31 Water-Cementitious Materials Ratio (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1-31 Air Content of Air-Entrained Concrete (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1-32 Strength of Concrete Mixtures (2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1-33 Workability (2009). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1-35 Slump (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1-35 Compression Tests (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1-35 Field Tests (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1-35 Special Provisions When Using Cementitious Materials Other Than Portland Cement (2009 ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1- 36

1.13 Mixing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.13.1 General (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.13.2 Site-Mixed Concrete (2009). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.13.3 Ready-Mixed Concrete (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.13.4 Delivery (2009). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.13.5 Requirements When Using Silica Fume in Concrete (2009). . . . . . . . . . . . . . . . . . . . . . . .

8-1-38 8-1-38 8-1-38 8-1-39 8-1-39 8-1-39

1.14 Depositing Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.14.1 General (2000) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.14.2 Handling and Placing (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.14.3 Chuting (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.14.4 Pneumatic Placing (Shotcreting) (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.14.5 Pumping Concrete (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.14.6 Compacting (1993). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.14.7 Temperature (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.14.8 Continuous Depositing (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.14.9 Bonding (1993). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.14.10 Placing Cyclopean Concrete (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.14.11 Placing Rubble Concrete (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.14.12 Placing Concrete Containing Silica Fume (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.14.13 Placing Concrete Containing Fly Ash (2004). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.14.14 Water Gain (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-1-39 8-1-39 8-1-40 8-1-40 8-1-40 8-1-41 8-1-41 8-1-42 8-1-42 8-1-42 8-1-43 8-1-43 8-1-43 8-1-43 8-1-43

1.15 Depositing Concrete Under Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.15.1 General (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.15.2 Capacity of Plant (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.15.3 Standard Specifications (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.15.4 Cement (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.15.5 Coarse Aggregates (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.15.6 Mixing (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.15.7 Caissons, Cofferdams or Forms (1993). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.15.8 Leveling and Cleaning the Bottom to Receive Concrete (1993) . . . . . . . . . . . . . . . . . . . . . 1.15.9 Continuous Work (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.15.10 Methods of Depositing (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.15.11 Soundings (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.15.12 Removing Laitance (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.15.13 Concrete Seals (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-1-44 8-1-44 8-1-44 8-1-44 8-1-44 8-1-44 8-1-44 8-1-44 8-1-45 8-1-45 8-1-45 8-1-46 8-1-46 8-1-46

1.16 Concrete in Sea Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Concrete (2004). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Depositing in Sea Water (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Construction Joints (1993). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Minimum Cover (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Protecting Concrete in Sea Water (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-1-47 8-1-47 8-1-47 8-1-47 8-1-47

1.17 Concrete in Alkali Soils or Alkali Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.17.1 Condition of Exposure (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.17.2 Concrete for Moderate Exposure (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.17.3 Concrete for Severe Exposure (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.17.4 Concrete for Very Severe Exposure (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.17.6 Construction Joints (1993). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.17.7 Minimum Cover (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.17.8 Placement of Concrete (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-1-48 8-1-48 8-1-48 8-1-48 8-1-48 8-1-49 8-1-49 8-1-49

1.18 Curing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.18.1 General (2000) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.18.2 Hot Weather Curing (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.18.3 Wet Curing (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.18.4 Membrane Curing (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.18.5 Steam Curing (1993). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.18.6 Curing Concrete Containing Silica Fume (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.18.7 Curing Concrete Containing Ground Granulated Blast-Furnace Slag (2004) . . . . . . . . . 1.18.8 Curing Concrete Containing Fly Ash (2004). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-1-49 8-1-49 8-1-50 8-1-50 8-1-51 8-1-51 8-1-51 8-1-52 8-1-52

1.19 Formed Surface Finish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.19.1 General (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.19.2 Rubbed Finish (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-1-52 8-1-52 8-1-53

1.20 Unformed Surface Finish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.20.1 General (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.20.2 Sidewalk Finish (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.20.3 Finishing Concrete Containing Silica Fume (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.20.4 Finishing Concrete Containing Ground Granulated Blast-Furnace Slag (2004) . . . . . . . 1.20.5 Finishing Concrete Containing Fly Ash (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-1-53 8-1-53 8-1-53 8-1-53 8-1-53 8-1-53

1.21 Decorative Finishes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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1.22 Penetrating Water Repellent Treatment of Concrete Surfaces. . . . . . . . . . . . . . . . . . . 1.22.1 General (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.22.2 Surface Preparation (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.22.3 Environmental Requirements (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.22.4 Application (2003). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.22.5 Materials (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.22.6 Quality Assurance (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.22.7 Delivery, Storage and Handling (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-1-54 8-1-54 8-1-54 8-1-54 8-1-55 8-1-55 8-1-56 8-1-56

1.23 Repairs and Anchorage Using Reactive Resins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.23.1 General (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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1.23.2 Surface Preparation (2003). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.23.3 Application (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-1-57 8-1-57

1.24 High Strength Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.24.1 General (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.24.2 Materials (1995). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.24.3 Concrete Mixture Proportions (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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1.25 Specialty Concretes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.25.1 General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.25.2 Sulfur Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.25.3 Heavyweight Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-1-60

LIST OF FIGURES Figure 8-1-1 8-1-2 8-1-3

Description Full-Depth Expansion Joint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Two Methods for Making Contraction Joints for Slabs-on-Grade . . . . . . . . . . . . . . . . . . . . . . . Keyed Construction Joint with Waterstop Inserted Perpendicular to the Plane of the Joint .

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1

LIST OF TABLES Table 8-1-1 8-1-2 8-1-3 8-1-4 8-1-5 8-1-6 8-1-7 8-1-8 8-1-9 8-1-10 8-1-11 8-1-12 8-1-13 8-1-14

Description Portland Cement ASTM C150 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Blended Hydraulic Cements ASTM C595. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sampling and Testing Methods in Addition to those of ASTM C33 . . . . . . . . . . . . . . . . . . . . . . Aggregate Soundness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fine Aggregate Grading. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Deleterious Substances in Fine Aggregate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ASTM Specifications for Reinforcement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ASTM Specifications for Coated Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Maximum Permissible Water-Cementitious Materials Ratio (by Weight) for Different Types of Structures and Degrees of Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . Air-Entrained Concrete Volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Water-Cementitious Materials Ratio for Air Entrained Concrete . . . . . . . . . . . . . . . . . . . . . . . Concrete Exposed to Deicing Chemicals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Concrete Temperature Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Recommendations For Concrete In Sulfate Exposures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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SECTION 1.1 GENERAL 1.1.1 PURPOSE (2004) This recommended practice is for work carried out by the Company or by Contractors for the Company when so requested by the Engineer.

1.1.2 SCOPE (2004) This recommended practice describes the selection, sampling and testing of materials to be used, the composition of concrete, and the mixing, transporting, placing, finishing and curing of concrete. This recommended practice shall govern whenever it is in conflict with other cited references.

1.1.3 TERMS (2006) Following is a list of terms associated with this Part. These terms are defined in the Glossary located at the end of this Chapter. AASHTO Absorption ACI International Admixture Admixture, Accelerating Admixture, Air-Entraining Admixture, Retarding Admixture, Water Reducing Admixture, Water Reducing (High Range) Admixture, Water Reducing and Accelerating Admixture, Water Reducing and Retarding Agent, Bonding Aggregate Air, Entrained Approved or Approval ASTM - International Blast-Furnace Slag Blast-Furnace Slag, Ground Granulated Bleeding Cement, Blended Cement, Hydraulic Cement, Slag Cementitious Centering Company Compound, Curing Concrete Concrete, Cyclopean

Concrete, Polymer Concrete, Polymer Cement Concrete, Structural Lightweight Contractor Engineer Falsework FHWA Fly Ash Form / Formwork Honeycomb Joint, Expansion Laitance Modulus, Fineness PCI Plans Plasticizer Pozzolan Reinforcement Reinforcement, Deformed Reinforcement, Plain Resistance, Chemical Shore / Shoring Sieve Sieve Analysis Sieve Number Silica Fume Slump Soundness

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Strength, Compressive Superplasticizer USDOT

Water Absorption Water-Cementitious Material Ratio

1.1.4 ACCEPTABILITY (2004) a.

Concrete shall be proportioned, mixed, transported, placed and cured by the methods herein recommended.

b. All materials used in the work shall be subject to the approval of the Engineer who shall be the sole judge of their quality, suitability, and acceptability as to type. The Engineer shall be notified in advance whenever any phase of the work is to begin.

1.1.5 ASTM - INTERNATIONAL (2004) Whenever reference is made to the ASTM - International (ASTM), the letter ‘M’ indicating a metric edition and the number indicating the year of issue are omitted from the designation. The latest issue of the referenced designation is to be used in each case.

1.1.6 SELECTION OF MATERIALS (2004) The concrete materials shall be selected for strength, durability and chemical resistance, and ability to attain specified properties as required, in accordance with this recommended practice and as approved by the Engineer. They shall be combined in such a manner as to produce uniformity of color and texture in the surface of any structure or group of structures in which they are to be used. No change shall be made in the brand, type, source or characteristics of cementitious materials, the character and source of aggregate or water, or the class of concrete and method of transporting, placing, finishing or curing without approval of the Engineer.

1

1.1.7 TEST OF MATERIALS (2004)

3 a.

The Engineer shall have the right to order testing of any materials used in concrete construction to determine if they are of the quality specified.

b. Tests of materials and concrete shall be made in accordance with appropriate standards of the ASTM International as specified. c.

Pre-construction tests shall be carried out on cementitious materials, other than portland cement, as indicated in this recommended practice.

1.1.8 DEFECTIVE MATERIALS (2004) All materials of any kind rejected by the Engineer shall be immediately removed from the site and any work affected by the defective material shall be remedied by the Contractor at his own expense and to the satisfaction of the Engineer.

1.1.9 EQUIPMENT (2004) The Contractor shall provide all equipment required for the work, including all staging, scaffolding, apparatus, tools, etc., as necessary. All equipment must be approved by the Engineer who may require the removal of any piece of equipment. The Contractor shall substitute satisfactory equipment to replace rejected equipment without delay. Upon request, the Contractor shall furnish for approval a statement of methods and equipment proposed for use in all aspects of the work. Exercise of this approval by the Engineer shall not relieve the

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Contractor of his sole responsibility for the safe, adequate and lawful construction, maintenance and use of such methods and equipment.

SECTION 1.2 CEMENT 1.2.1 GENERAL (2004) Cement shall be furnished by the Contractor or the Company as provided for in the contract. Cement used in the work shall be the same as that required by the mix design.

1.2.2 SPECIFICATIONS (2004)1 a.

Cement shall conform to one of the following Standard Specifications except as modified in this Chapter. (1) ASTM C150 Standard Specification for Portland Cement as shown in Table 8-1-1 (2) ASTM C595 Standard Specification for Blended Hydraulic Cements as shown in Table 8-1-2

b. The use of slag cement Types ‘S’ and ‘S(A)’ as defined in ASTM C595 are not included in this recommended practice. c.

Refer also to Section 1.3 Other Cementitious Materials.

Table 8-1-1. Portland Cement ASTM C150 Type

1

Description

Type I

For use when the special properties specified for any other type are not required.

Type IA

Air-entraining cement for the same uses as Type I, where air-entrainment is desired.

Type II

For general use, especially when moderate sulfate resistance, or moderate heat of hydration is desired.

Type IIA

Air-entraining cement for the same uses as Type II, where air-entrainment is desired.

Type III

For use when high early strength is desired.

Type IIIA

Air-entraining cement for the same use as Type III, where air-entrainment is desired.

Type IV

For use when a low heat of hydration is desired.

Type V

For use when high sulfate resistance is desired.

See C - Commentary

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Materials, Tests and Construction Requirements Table 8-1-2. Blended Hydraulic Cements ASTM C595 Type

Description Portland Blast-Furnace Slag Cement

Type IS

Portland blast-furnace slag cement for use in general concrete construction.

Type IS( )

Modified sulfate resistant (MS), air-entrainment (A), or moderate heat of hydration (MH), or any combination may be specified by adding the appropriate suffixes. Portland-Pozzolan Cement

Type IP

Portland-pozzolan cement for use in general concrete construction.

Type IP( )

Moderate sulfate resistance (MS), air-entrainment (A), or moderate heat of hydration (MH), or any combination may be specified by adding the appropriate suffixes.

Type P

Portland-pozzolan cement for use in concrete construction where high early strengths are not required.

Type P( )

Modified sulfate resistance (MS), air-entrainment (A), or low heat of hydration (LH), or any combination may be specified by adding the appropriate suffixes. Pozzolan-Modified Portland Cement

Type I(PM)

Pozzolan-modified portland cement for use in general concrete construction.

Type I(PM)( ) Modified sulfate resistance (MS), air-entrainment (A), or moderate heat of hydration (MH), or any combination may be specified by adding the appropriate suffixes.

1

Slag-Modified Portland Cement Type I(SM)

Cement for use in general concrete construction.

Type I(SM)( ) Modified sulfate resistance (MS), air-entrainment (A), or moderate heat of hydration (MH), or any combination may be specified by adding the appropriate suffixes.

3

1.2.3 QUALITY, SAMPLING AND TESTING (2004) The quality of the cement and the methods of sampling and testing shall meet the requirements of the appropriate ASTM Standard Specification or Method of Test.

4 SECTION 1.3 OTHER CEMENTITIOUS MATERIALS 1.3.1 GENERAL (2004) When using cementitious materials other than portland cement, reference should also be made to the provisions of Section 1.12 Proportioning; Section 1.13 Mixing; Section 1.14 Depositing Concrete; Section 1.16 Concrete in Sea Water; Section 1.17 Concrete in Alkali Soils or Alkali Water; Section 1.18 Curing; and Section 1.20 Unformed Surface Finish.

1.3.2 ACCEPTABILITY (2004) Cementitious materials other than portland cement will be permitted only if approved in writing by the Engineer of the Railroad Company.

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1.3.3 SPECIFICATIONS (2004)1 The specifications listed in Articles 1.3.3.1 and 1.3.3.2 apply to the use of other cementitious materials, either supplied in blended form with portland cement or added separately at the time of mixing. 1.3.3.1 ASTM C595 Standard Specification for Blended Hydraulic Cements; and ASTM C618 Standard Specification for Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture in Portland Cement Concrete, and the following: a.

Silica Fume - ASTM C1240 Standard Specification for Silica Fume for Use in Hydraulic-Cement Concrete, Mortar, and Grout, of the following types: (1) As-produced silica fume -- in its original form of an extremely fine powder (2) Slurried silica fume -- in a water base, containing 40 to 60% silica fume by mass (3) Densified silica fume -- a compacted form of as-produced silica fume

b. Fly Ash - ASTM C618 Standard Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture in Concrete, of the following Classes: (1) Class F -- Normally produced from high energy coals such as bituminous and anthracite coals, but sometimes produced with sub-bituminous and lignite coals (2) Class C -- Normally produced from sub-bituminous and lignite coals (3) Class N – Natural materials such as highly reactive volcanic ash, metakaolin (and other calcined clays), diatomaceous earths, calcined shales, and other reactive materials 1.3.3.2 Ground Granulated Blast-Furnace Slag - ASTM C989 Standard Specification for Ground Granulated Iron Blast-Furnace Slag for Use in Concrete and Mortars.

1.3.4 MATERIALS NOT INCLUDED IN THIS RECOMMENDED PRACTICE (2004) The following materials are not included in this recommended practice: a.

Pelletized silica fume -- consisting of hard pellets, not presently being used as an additive for concrete.

b. Types of slag not produced in the iron making process. c.

Types ‘S’ and ‘S(A)’ blended hydraulic cements containing ground granulated blast-furnace slag, as defined in ASTM C595.

d. Blended cements containing ground granulated blast-furnace slag blended with hydrated lime.

1.3.5 DOCUMENTATION (2004) a.

Each shipment of fly ash or silica fume or ground granulated blast-furnace slag used on a project shall have a certificate of compliance which includes the following: (1) Name of supplier

1

See C - Commentary

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(2) Consignee and destination of the shipment (3) Vehicle identification number (4) A unique unrepeated order number or other identification number for each shipment (5) Source b. Each shipment of fly ash shall also include a certificate of compliance indicating the Class (either Class C or Class F), with certified test numbers demonstrating that the material meets ASTM C618. c.

Each shipment of silica fume shall also include a certificate of compliance demonstrating that it meets the requirements of ASTM C1240.

d. Each shipment of ground granulated blast-furnace slag shall also include a certificate of compliance indicating its grade (either Grade 80, 100 or 120), with certified test numbers demonstrating that it meets the requirements of ASTM C989.

SECTION 1.4 AGGREGATES 1.4.1 GENERAL (2004)

1

1.4.1.1 Specifications Except as specified otherwise herein, all aggregates shall conform to the requirements of ASTM C33, Standard Specification for Concrete Aggregates.

3

1.4.1.2 Sampling and Testing a.

Representative samples shall be selected and sent to the testing laboratory at frequent intervals as directed by the Engineer. Aggregates may not be used until the samples have been tested by the laboratory and approved by the Engineer.

b. Sampling and testing shall be in accordance with ASTM C33 and the Standard Specifications and Methods of Test of ASTM - International found in Table 8-1-3.

4

Table 8-1-3. Sampling and Testing Methods in Addition to those of ASTM C33 Type

c.

ASTM Designation

Surface Moisture in Fine Aggregate

C70

Specific Gravity and Absorption of Coarse Aggregate

C127

Specific Gravity and Absorption of Fine Aggregate

C128

Standard Sand

C778

The required tests shall be made on test samples that comply with requirements of the designated test methods and are representative of the grading that will be used in the concrete. The same test sample may be used for sieve analysis and for determination of material finer than the No. 200 (75 mm) sieve.

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Separated sizes from the sieve analysis may be used in preparation of samples for soundness or abrasion tests. For determination of all other tests and for evaluation of potential alkali reactivity where required, independent test samples shall be used. d. The fineness modulus of an aggregate is the sum of the percentages of a sample retained on each of a specified series of sieves divided by 100, using the following standard sieve sizes: No. 100, No. 50, No. 30, No. 16, No. 8, No. 4, 3/8 inch, 3/4 inch, 1-1/2 inches (150 mm, 300 mm, 600 mm, 1.18 mm, 2.36 mm, 4.75 mm, 9.5 mm, 19.0 mm, 37.5 mm) and larger, increasing in the ratio of 2 to 1. Sieving shall be done in accordance with ASTM Method C136. 1.4.1.3 Soundness a.

Except as provided in Paragraph 1.4.1.3(b), aggregate subjected to five cycles of ASTM C88 Soundness of Aggregates by Use of Sodium Sulfate or Magnesium Sulfate shall show a loss weighed in accordance with the grading procedures, not greater than the percentages found in Table 8-1-4. Table 8-1-4. Aggregate Soundness Aggregate

Sodium Sulfate

Magnesium Sulfate

Fine

10

15

Coarse

12

18

b. Aggregate failing to meet the requirements of Paragraph 1.4.1.3(a) may be accepted provided that concrete of comparable properties, made with similar aggregate from the same source, has given satisfactory service when exposed to weathering similar to that to be encountered.

1.4.2 FINE AGGREGATES (2004) 1.4.2.1 General1 Fine aggregate shall consist of natural sand or, subject to the approval of the Engineer, manufactured sand with similar characteristics. Lightweight fine aggregate shall not be used. 1.4.2.2 Grading a.

1

Sieve Analysis–Fine aggregate, except as provided in ASTM C33, shall be graded within the limits found in Table 8-1-5.

See C - Commentary

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Materials, Tests and Construction Requirements Table 8-1-5. Fine Aggregate Grading

Sieve Size 3/8 inch (9.5 mm)

Total Passing Percentage by Weight 100

No. 4 (4.75 mm)

95-100

No. 8 (2.36 mm)

80-100

No. 16 (1.18 mm)

50-85

No. 30 (600 mm)

25-60

No. 50 (300 mm)

10-30

No. 100 (150 mm)

2-10

No. 200 (75 mm)

zero

b. The minimum percentages shown above for material passing the No. 50 (300 mm) and No. 100 (150 mm) sieves may be reduced to 5 and 0, respectively, if the aggregate is to be used in air-entrained concrete containing more than 420 lb of cement per cubic yard (250 kg per cubic meter), or in non-air-entrained concrete containing more than 520 lb of cement per cubic yard (310 kg per cubic meter). Air-entrained concrete is here considered to be concrete containing air-entraining cement or an air-entraining admixture and having an air content of more than 3%. c.

The fine aggregate shall have not more than 45% retained between any two consecutive sieves of those shown in Table 8-1-5 and its fineness modulus shall be not less than 2.3 nor more than 3.1.

d. For walls and other locations where smooth surfaces are desired, the fine aggregate shall be graded within the limits shown in Table 8-1-5, except that not less than 15% shall pass the No. 50 (300 mm) sieve and not less than 3% shall pass the No. 100 (150 mm) sieve. e.

To provide the uniform grading of fine aggregate, a preliminary sample representative of the material to be furnished shall be submitted at least 10 days prior to actual deliveries. Any shipment made during progress of the work which varies by more than 0.2 from the fineness modulus of the preliminary sample shall be rejected or, at the option of the Engineer, may be accepted provided that suitable adjustments are made in concrete proportions to compensate for the difference in grading.

f.

The percentages listed above do not apply when using pozzolans or ground granulated blast-furnace slag. Such percentages shall be determined by tests as outlined in this recommended practice.

1.4.2.3 Mortar Strength Fine aggregate shall be of such quality that when made into a mortar and subjected to the mortar strength test prescribed in ASTM C87, the mortar shall develop a compressive strength not less than that developed by a mortar prepared in the same manner with the same cementitious materials and graded standard sand having a fineness modulus of 2.40±0.10. The graded sand shall conform to the requirements of ASTM C778. 1.4.2.4 Deleterious Substances a.

The amount of deleterious substances in fine aggregate shall not exceed the limits found in Table 8-16.

b. A fine aggregate failing the test for organic impurities may be used provided that, when tested for mortar-making properties, the mortar develops a compressive strength at 7 and 28 days of not less than © 2011, American Railway Engineering and Maintenance-of-Way Association

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3

4

Concrete Structures and Foundations Table 8-1-6. Deleterious Substances in Fine Aggregate Item

Maximum Limit Percentage by Weight

Clay Lumps

1.0

Coal and Lignite

0.5 (Note 1)

Material finer than No. 200 sieve (75 mm): Concrete subject to abrasion All other classes of concrete

3.0 (Note 2) 5.0 (Note 2)

Note 1: Does not apply to manufactured sand produced from blast-furnace slag. Note 2: For manufactured sand, if the material finer than the No. 200 (75 mm) sieve consists of the dust of fracture, essentially free from clay or shale, these limits do not apply. 95% of that developed in a similar mortar made from another portion of the same sample which has been washed in a 3% solution of sodium hydroxide followed by thorough rinsing in water. The treatment shall be sufficient so that the test of the washed material made in accordance with ASTM C40 will have a color lighter than the standard color solution. c.

Fine aggregate for use in concrete that will be subject to wetting, extended exposure to humid atmosphere, or contact with moist ground shall not contain any materials that are deleteriously reactive with the alkalies in the cement in an amount sufficient to cause excessive expansion of mortar or concrete, except that if such materials are present in injurious amounts, the fine aggregate may be used with a cement containing less than 0.6% alkalies as measured by percentage of sodium oxide plus 0.658 times percentage of potassium oxide, or with the addition of a material that has been shown to prevent harmful expansion due to the alkali-aggregate reaction.

1.4.3 NORMAL WEIGHT COARSE AGGREGATE (2004) 1.4.3.1 General a.

Coarse aggregate shall consist of crushed stone, gravel, crushed slag, or a combination thereof or, subject to the approval of the Engineer, other inert materials with similar characteristics, having hard, strong durable pieces, free from adherent coatings, and shall conform to the requirements of ASTM C33 except as required by this Part.

b. Crushed slag shall be rough cubical fragments of air-cooled blast-furnace slag, which when graded as it is to be used in the concrete, shall have a compact weight of not less than 70 lb per cubic foot (1100 kg per cubic meter). It shall be obtained only from sources approved by the Engineer. 1.4.3.2 Grading a.

Coarse aggregate shall be graded between the limits specified by ASTM C33.

b. The maximum size of aggregate shall be not larger than one-fifth of the narrowest dimension between forms of the member for which concrete is used, nor larger than one-half of the minimum clear space between reinforcing bars, except as provided for precast concrete in Section 2.5.

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Materials, Tests and Construction Requirements 1.4.3.3 Deleterious Substances a.

The amount of deleterious substances in coarse aggregate shall not exceed the limits found in ASTM C33.

1.4.3.4 Abrasion Loss Coarse aggregate to be used in concrete when subjected to test for resistance to abrasion (ASTM C535 or ASTM C131) shall show a loss of weight not more than the following: a.

For concrete subject to severe abrasion such as concrete in water, precast concrete piles, paving for sidewalks, platforms or roadways, floor wearing surfaces, and concrete cross or bridge ties, the loss of weight shall not exceed 40%.

b. For concrete subject to medium abrasion such as concrete exposed to the weather, the loss of weight shall not exceed 50%. c.

For concrete not subject to abrasion, the loss in weight shall not exceed 60%.

1.4.3.5 Rubble Aggregate Rubble aggregate shall consist of clean, hard, durable stone retained on a 6-inch (150 mm) square opening and with individual pieces weighing not more than 100 lb (45 kg).

1

1.4.3.6 Cyclopean Aggregate Cyclopean aggregate shall consist of clean, hard, durable stone with individual pieces weighing more than 100 lb (45 kg).

1.4.4 LIGHTWEIGHT COARSE AGGREGATE FOR STRUCTURAL CONCRETE (2004)

3

1.4.4.1 Scope a.

This recommended practice covers lightweight coarse aggregates intended for use in lightweight concrete in which prime considerations are durability, compressive strength, and light weight. Structural lightweight concrete shall only be used where shown on the plans or specified.

b. Aggregates for use in non-structural concrete such as fireproofing and fill, and for concrete construction where capacity is based on load tests rather than conventional design procedures, are not included in this recommended practice. 1.4.4.2 General Characteristics The aggregates shall conform to the requirements of ASTM C330 Standard Specifications for Lightweight Aggregates for Structural Concrete, except as otherwise specified herein. 1.4.4.3 Unit Weight (Mass Density) a.

The dry weight (mass density) of lightweight aggregates shall not exceed 55 lb per cubic foot (880 kg per cubic meter), measured loose by accepted ASTM practice.

b. Uniformity of weight (density). The unit weight (mass density) of successive shipments of lightweight aggregate shall not differ by more than 6% from that of the sample submitted for acceptance tests.

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Concrete Structures and Foundations 1.4.4.4 Concrete Making Properties Concrete specimens containing lightweight coarse aggregate under test shall conform to ASTM C330 and shall meet the following requirements. A magnesium sulfate soundness test shall be conducted for 10 cycles in accordance with ASTM C88. Loss thus determined shall not exceed 15%. Loss of individual gradation size shall not exceed 20% of that size.

SECTION 1.5 WATER 1.5.1 GENERAL (2010) 1.5.1.1 Specifications Mixing water shall conform to the requirements of ASTM C 1602, Standard Specification for Mixing Water Used in the Production of Hydraulic Cement Concrete.

SECTION 1.6 REINFORCEMENT 1.6.1 GENERAL (2003) Reinforcement shall be deformed reinforcement, except that plain bars and plain wire shall be permitted for spirals or tendons, or for dowels at expansion or contraction joints. Reinforcement consisting of structural steel, steel pipe, or steel tubing shall be permitted for composite compression members.

1.6.2 WELDING (2003) a.

Welding of reinforcing bars shall conform to “Structural Welding Code–Reinforcing Steel” (ANSI/AWS D1.4) of the American Welding Society. Type and location of welded splices and other required welding of reinforcing bars shall be indicated on the plans or in the project specifications. The ASTM specifications for reinforcing bars, except for ASTM A706, shall be supplemented to require a report of material properties necessary to conform to welding procedures specified in ANSI/AWS D1.4.

b. If welding of wire to wire, and of wire or welded wire fabric to reinforcing bars or structural steel is to be required on a project, the Engineer shall specify procedures or performance criteria for the welding. c.

Welders of reinforcing bars shall maintain certification by the American Welding Society.

1.6.3 SPECIFICATIONS (2003) 1.6.3.1 Reinforcement Bars, wire, welded wire fabric, prestressing tendons, structural steel, steel pipe and tubing shall conform to one of the ASTM specifications found in Table 8-1-7.

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Materials, Tests and Construction Requirements

Table 8-1-7. ASTM Specifications for Reinforcement Type

Designation Bars, Wire and Fabric

Deformed and Plain Billet-Steel Bars Deformed and Plain Low-Alloy Steel Bars Deformed Rail-Steel and Axle-Steel Bars Deformed and Plain Stainless Steel Bars Welded or Forged Headed Bars Steel Wire, Plain (wire shall not be smaller than size W4 (0.226 inch (5.74 mm) dia.)) Steel Welded Wire Fabric, Plain Steel Wire, Deformed (wire shall not be smaller than size D4 (0.225 inch (5.72 mm) dia.)) Steel Welded Wire Fabric, Deformed (welded intersections shall not be spaced farther apart than 16 inches (400 mm) in direction of primary flexural reinforcement)

A615 A706 A996 A955 A970 A82 A185 A496 A497

1

Prestressing Tendons Uncoated Seven-Wire Steel Strand Uncoated Stress-Relieved Steel Wire Uncoated High-Strength Steel Bar

A416 A421 A722

Structural Steel, Steel Pipe and Tubing Structural-Steel

A36, A242, A529, A572, A588 or A709 (Grade 36, 50 or 50W) A53 (Grade B) A500, A501 or A618

Steel Pipe Steel Tubing

1.6.3.2 Coated Reinforcement a.

3

4

Coated reinforcement, when specified or shown on the plans as a corrosion-protection system, shall conform to one of the ASTM specifications found in Table 8-1-8.

Table 8-1-8. ASTM Specifications for Coated Reinforcement Type

Specification

Epoxy-Coated Steel Reinforcing Bars

A775

Epoxy-Coated Prefabricated Steel Reinforcing Bars

A934

Epoxy-Coated Steel Wire and Welded Wire Fabric

A884

Epoxy-Coated Seven-Wire Prestressing Steel Strand

A882

Zinc-Coated (Galvanized) Steel Reinforcing Bars

A767

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b. Repair all damaged epoxy coating on reinforcing bars due to shipping, handling and placing with patching material conforming to ASTM A775 or A934. Repair shall be done in accordance with the material manufacturer’s recommendations. c.

Repair all damaged epoxy coating on wire or welded wire fabric due to shipping, handling and placing with patching material conforming to ASTM A884. Repair shall be done in accordance with the material manufacturer’s recommendations.

d. Repair all damaged zinc coating on reinforcing bars due to shipping, handling, and placing in accordance with ASTM A780. The maximum amount of damaged areas shall not exceed 2% of the total surface area in each linear foot (300 mm) of the bar. e.

Equipment for handling epoxy-coated reinforcing bars shall have protected contact areas. Bundles of coated bars shall be lifted at multiple pickup points to prevent bar-to-bar abrasion from sags in the bundles. Coated bars or bundles of coated bars shall not be dropped or dragged. Coated bars shall be stored on protective cribbing. All damaged coating due to handling, shipping, and placing shall be repaired. The maximum amount of damaged areas shall not exceed 2% of the surface area of each linear foot (300 mm) of the bar. If the damaged areas exceed 2% of the total surface area in each linear foot (300 mm) of the bar, the bar shall be replaced.

f.

After installation of mechanical splices on epoxy-coated or zinc-coated (galvanized) reinforcing bars, any damaged coating shall be repaired. All parts of mechanical splices used on coated bars, including steel splice sleeves, bolts, and nuts shall be coated with the same material used for repair of damaged coating on the spliced material. Remove coating for two inches (50 mm) back from the mechanical splice to bright metal before repair.

g.

After completion of welding for welded splices on epoxy-coated or zinc-coated (galvanized) reinforcing bars, coating damage shall be repaired. All welds, and steel splice members when used to splice bars, shall be coated with the same material used for repair of damaged coating. Remove coating for six inches (150 mm) back from the welded splice to bright metal before repair.

h. Plants applying fusion-bonded epoxy coatings to reinforcing bars shall maintain certification by the Concrete Reinforcing Steel Institute.

1.6.4 BENDING AND STRAIGHTENING1 (2003) a.

Reinforceing bars shall be fabricated in accordance with Article 1.10.2 and Part 2, Reinforced Concrete Design, Article 2.4.2. Field bending and/or straightening of bars that are partially embedded in concrete shall be done in accordance with the Plans or as permitted by the Engineer.

b. When epoxy-coated reinforcing bars or zinc-coated (galvanized) reinforcing bars are field bent and/or straightened, damaged coating shall be repaired in accordance with Articles 1.6.3.2b and 1.6.3.2d, respectively. Field bending and/or straightening of epoxy-coated reinforcing bars conforming to ASTM A934 shall be prohibited.

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See C - Commentary

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SECTION 1.7 CONCRETE ADMIXTURES 1.7.1 GENERAL (2004) a.

The selection of admixtures to be used in concrete, if any, shall be subject to the prior written approval of the Engineer of the Railroad Company.

b. An admixture shall be shown capable of maintaining essentially the same composition and performance throughout the work as the product used in establishing concrete proportions in accordance with Section 1.12 Proportioning. c.

Admixtures containing chloride ions shall not be used unless approved by the Engineer.

d. Special purpose admixtures may be used if approved in writing by the Engineer of the Railroad Company. However, before an admixture can be approved for use, it must be shown that its use will not adversely affect the placement, strength and/or durability of the concrete. Admixtures used in combination may be incompatible and their performance should be verified by prior testing.

1.7.2 TYPES OF ADMIXTURES AND STANDARD SPECIFICATIONS (2004) The specifications listed in Paragraphs 1.7.2(a) and 1.7.2(b) apply in the use of admixtures. a.

Air Entraining Agent - ASTM C260 Air-Entraining Admixtures for Concrete.

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b. ASTM C494 Standard Specification for Chemical Admixtures for Concrete: (1) Accelerating Admixture (2) Retarding Admixture

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(3) Water-Reducing Admixture (4) Water-Reducing Admixture, High-Range (5) Water-Reducing and Accelerating Admixture (6) Water-Reducing and Retarding Admixture

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SECTION 1.8 STORAGE OF MATERIALS 1.8.1 CEMENTITIOUS MATERIALS AND CONCRETE ADMIXTURES (2009) a.

Immediately upon delivery, all cement shall be stored in watertight ventilated structures to prevent absorption of water.

b. Sacked cement shall be stacked on pallets or similar platforms to permit circulation of air and access for inspection. The cement sacks shall not be stacked against outside walls.

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c.

Cement sacks shall not be stacked more than 14 layers high for periods of up to 60 days, nor more than 7 layers high for periods over 60 days. Older cement shall be used first.

d. Storage facilities for bulk cement shall include separate compartments for each type of cement used. The bins shall be so constructed as to prevent dead storage in corners. e.

All cement shall be subject at any time to retest. If under retest it fails to meet any of the requirements of the specifications, it will be rejected and shall be promptly removed from the site of the work by the Contractor.

f.

Where the Company furnishes the cement and the failure of the cement to pass the retest is due to negligence on the part of the Contractor to store it properly, the cost of such cement shall be charged to the Contractor.

g.

The above provisions also apply to other cementitious materials and blended cementitious materials, except that fly ash shall be stored in a separate structure or bin without common walls to avoid leakage of the fly ash into the other cementitious materials.

h. Liquid admixtures shall be protected from freezing. If freezing occurs then the material shall not be used in concrete unless the manufacturer approves a method of ensuring the effectiveness of the thawed material, such as agitation.

1.8.2 AGGREGATES (2009) a.

The storage of coarse aggregates shall be minimized, as to avoid the natural tendency of such stockpiles to segregate.

b. Fine and coarse aggregates shall be stored separately and in such a manner as to avoid the inclusion of foreign materials in the concrete. Aggregates shall be unloaded and piled in such a manner as to maintain the uniform grading of the sizes. Stockpiles of coarse aggregates shall be built in horizontal layers, not by end dumping, to avoid segregation. Equipment such as dozers and loaders shall not be operated on the stockpile, so as to avoid contamination, segregation and breakage. c.

A hard base shall be provided to prevent contamination from underlying material. Overlap of the different sizes shall be prevented by suitable walls or ample spacing between stockpiles. Stockpiles shall not be contaminated by swinging aggregate-filled buckets or clams over the various stockpiled aggregate sizes. Crushed slag shall be wetted down when necessary to ensure a minimum 3% moisture content.

d. Special measures shall be taken to maintain a uniform moisture content in the aggregates as batched. Control and testing procedures shall be subject to the approval of the Engineer.

1.8.3 REINFORCEMENT (2009) a.

Reinforcement shall be stored in such a manner as to avoid contact with the ground. If reinforcement remains in storage at the site for more than 1 month, it shall be covered to protect it from the weather. If reinforcement accumulates heavy rust, dirt, mud, loose scale, paint, oil, or any foreign substance during storage, it shall be cleaned before being used. Deterioration may be a basis for rejection. Reinforcement shall be handled in accordance with Section 1.6.

b. Epoxy-coated reinforcement shall be covered by an opaque polyethylene sheeting or other suitable opaque protective material as approved by the Engineer. For stacked bundles, the protective covering shall be draped around the perimeter of the stack. The covering shall be secured in a manner that allows

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for air circulation around the bars to minimize condensation under the covering. Epoxy-coated reinforcement shall be handled and repaired in accordance with Section 1.6.

SECTION 1.9 FORMS 1.9.1 GENERAL (2009) Forms shall be constructed of wood, steel, or other suitable material, and be of a type, size, shape, quality and strength, which will produce true, smooth lines and surfaces conforming to the lines and dimensions shown on the plans. Forms shall be substantial and designed to resist the pressures to which they are subjected. Lumber in forms for exposed surfaces should be dressed to a uniform thickness. Undressed lumber may be used in forms for unexposed surfaces. Forms shall be kept free of rust, grease and other foreign matter which will discolor the concrete. Forms may be omitted for foundation concrete if, in the opinion of the Engineer, the sides of the excavation are sufficiently firm so that the concrete may be thoroughly vibrated without causing the adjacent earth to slough. The actual dimensions of the excavation shall then be slightly greater than the plan dimensions of the foundation so as to ensure design requirements.

1.9.2 SAFETY (2009) The Contractor shall follow all local, state and federal codes, ordinances and regulations pertaining to forming of concrete at all stages of construction, in addition to the requirements of this Section and the railroad Company.

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1.9.3 DESIGN (2009) a.

The Contractor shall be responsible for the design of all forms required to complete the work.

b. Structural design of forms shall be performed in conformance with ACI 347R, Guide to Formwork for Concrete, or other generally accepted standards, subject to the approval of the Engineer. c.

Forms shall be designed by a licensed engineer.

d. Drawings and structural design calculations shall be provided to the Engineer for review and acceptance prior to undertaking the work, unless excluded by the project Plans. e.

Documentation demonstrating the adequacy of forms supports to safely resist the design loads shall be provided for review and acceptance prior to undertaking the work, unless excluded by the project Plans.

f.

Shoring and falsework shall be in accordance with Part 28 except as provided herein.

g.

Special provision for load transfer and movements shall be taken into account in the design of forms for prestressed concrete.

h. Special provision for forms supporting concrete that is required to act compositely with other materials in the finished work shall be made. i.

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The review and acceptance of Contractor’s submittals shall not relieve the Contractor of responsibility for the safe and functional design of the forms and their supports.

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1.9.4 CONSTRUCTION (2009) a.

The supervisor responsible for construction of forms should be certified by the American Concrete Institute Inspector Certification Program as a Concrete Transportation Construction Inspector. The Contractor may appoint a similarly qualified and experienced individual with the approval of the Engineer.

b. Forms shall be constructed mortar-tight, and shall be made sufficiently rigid by the use of ties and bracing to prevent displacement or sagging and to withstand the pressure and vibration without deflection and/or objectionable distortion from the prescribed lines during and after placement of the concrete. c.

Joints in forms shall be horizontal or vertical, and suitable devices shall be used to hold adjacent edges together in accurate alignment.

d. All forms shall be constructed and maintained so as to prevent warping and the opening of joints. e.

All forms shall be constructed so that they may be readily removed without damaging the concrete.

f.

Bolts and/or rods shall be used for internal form ties. They shall be so arranged that, when the forms are removed, no corrodible metal shall be within 1-1/2 inches (38 mm) of any surface.

g.

When wire form ties are used, where permitted, spacer blocks shall be removed as the concrete is placed. Wire form ties shall be cut back 1-1/2 inches (38 mm) from the face of the concrete upon removal of the forms.

h. All fittings for ties shall be of such a design that upon their removal the remaining cavities will be the smallest practicable size. The cavities shall be filled with cement mortar and the surfaces left in a sound condition, even and uniform in color with respect to the original surface. i.

All temporary fasteners in contact with concrete shall be countersunk.

j.

Any material once used in forms shall be thoroughly cleaned and form release agent shall be applied before erection in a new location. All rough surfaces shall be smoothed and repairs made to the satisfaction of the Engineer. Forms which have been used repeatedly and are not acceptable to the Engineer for further use shall be removed from the site.

k. In the case of long spans where no intermediate supports are possible, deflection in the forms due to the weight of the fresh concrete shall be compensated for by using camber strips, wedges or other devices so that the finished members conform accurately to the desired line and grade. l.

Foundations for falsework shall be provided in accordance with Part 28.

1.9.5 MOLDINGS (2009) Unless otherwise specified or directed by the Engineer, suitable moldings or bevels shall be placed in the angles of forms to round or bevel the edges of the concrete, including abutting edges of expansion joints.

1.9.6 FORM COATING AND RELEASE (2009) Prior to placing reinforcement, the inside surfaces of forms shall be coated with a non-staining form release agent. A thin film shall be applied to all surfaces that will be in contact with the fresh concrete.

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1.9.7 TEMPORARY OPENINGS (2009) Temporary openings shall be provided at the base of the column and wall forms, and at other locations where necessary, to facilitate cleaning and inspection immediately before depositing concrete. Forms for walls or other thin sections of considerable height shall be provided with openings or other devices which will permit the concrete to be placed in a manner to avoid accumulation of hardened concrete on the forms or reinforcement.

1.9.8 REMOVAL (2009) a.

Forms shall be removed in such a manner as to ensure the complete safety of the structure. Care shall be taken to preserve formed surfaces and not to damage the corners or surfaces of the concrete. Hammering on or prying between forms and concrete shall not be permitted.

b. Form and falsework shall not be removed until the following are achieved: (1) The concrete has adequately cured and has acquired sufficient strength to support its weight and any anticipated loads. (2) The minimum time specified in the Plans has elapsed. (3) The Contractor has submitted and the Engineer has accepted a procedure and schedule for removal of form and falsework with calculations, if applicable, for loads transferred to the structure during the process.

1 c.

The time of removal of forms will depend on the type of the concrete, the location of the form, and the temperature and moisture conditions which affect the strength of the concrete.

d. The age-strength relationship of the concrete used in determining the time for form and falsework removal shall be determined from tests conducted on representative samples of the same concrete as used in the structure and cured under job conditions, in accordance with ASTM C 39. e.

If not otherwise specified on the Plans or by the Engineer, formwork and supports shall not be released until the concrete has attained sufficient strength to support its weight and any anticipated loads upon it, but not less than 70% of its specified compressive strength. In continuous structures, support shall not be released in any span until the first and second adjoining spans on each side have reached the specified strength.

f.

Bulkheads at construction joints shall not be removed for a period of 15 hours after casting adjacent concrete.

g.

Forms for ornamental work, railings, parapets, and vertical surfaces which require a surface finishing operation shall be removed not less than 12 hours, nor more than 48 hours after casting the concrete, depending upon weather conditions.

h. Support for pretensioned and post-tensioned concrete members shall not be removed until sufficient prestress has been applied to enable the member to support its weight and anticipated loads.

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SECTION 1.10 DETAILS OF REINFORCEMENT 1.10.1 SURFACE CONDITIONS OF REINFORCEMENT (2003) a.

Reinforcement at the time concrete is placed shall be free from mud, oil, or other non-metallic coatings that adversely affect bonding capacity. Epoxy coatings on bars, wire, and welded wire fabric conforming to standards referenced in Table 8-1-8 is permitted.

b. Reinforcement, except prestressing tendons with rust, mill scale, or a combination of both, shall be considered as satisfactory, provided the minimum dimensions, including height of deformations, and weight of a hand wire-brushed test specimen are not less than the applicable ASTM designation requirements. c.

Prestressing tendons shall be clean and free of oil, excessive soaps, dirt, scale, pitting and excessive rust. A light coating of rust without pitting shall be permitted.

1.10.2 FABRICATION (2003) a.

Reinforcement shall be prefabricated to the dimensions shown on the plans. Reinforcement shall be bent cold, and shall not be bent or straightened in a manner that will damage the material. Bars with kinks or bends not shown on the plans shall be rejected. Hot bending of reinforcement will be permitted only when approved by the Engineer.

b. Diameter of bends measured on the inside of the bar shall be as shown on the plans. When diameter of bend is not shown, minimum bend diameter shall be in accordance with Part 2, Reinforced Concrete Design. c.

Unless otherwise specified by the Engineer, the tolerance in fabricated lengths of bars from that shown on the placing drawings shall be ±1 inch (25 mm) for bar sizes #11 (36 mm) and under and 2 inches (51 mm) for bar sizes #14 and #18 (43 mm and 57 mm); the tolerance in out-to-out dimensions of hooks shall be ±1/2 inch (13 mm); the tolerance in out-to-out dimensions of stirrups and ties shall be ±1 inch (25 mm) and the maximum angular deviation on 90 degree hooks or bends shall be 0.5 inches per foot (1 in 24).

1.10.3 PROVISIONS FOR SEISMIC LOADING (2003) For structures located in seismic risk areas as determined from Chapter 9, consideration shall be given to reinforcement details that will provide adequate ductility and enable reinforcement to be strained beyond yield to allow the structure to absorb the energy of an earthquake.

1.10.4 PLACING OF REINFORCEMENT (2003) 1.10.4.1 General a.

Reinforcement, prestressing tendons and ducts shall be accurately placed and adequately supported before concrete is placed, and shall be secured against displacement within permitted tolerances. Tie wire shall be 16-1/2 gage (1.4 mm) or heavier, black-annealed. Welding of crossing bars shall not be permitted for the assembly of reinforcement unless authorized by the Engineer.

b. Reinforcing bars shall not be cut in the field except when authorized by the Engineer. Flame-cutting of epoxy-coated reinforcing bars shall not be permitted.

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c.

When epoxy-coated or zinc-coated (galvanized) reinforcing bars are cut in the field, the ends of the bars shall be coated with the same material that is used for the repair of damaged coating and shall be repaired in accordance with Articles 1.6.3.2b and 1.6.3.2d. The limit on the amount of repaired damaged coating does not apply to cut ends that are coated with patching material.

d. The supervisor responsible for placing reinforcing bars, tendons, and ducts shall maintain certification by the American Concrete Institute as a Concrete Transportation Construction Inspector. 1.10.4.2 Tolerances Unless otherwise specified by the Engineer, reinforcement, prestressing tendons, and prestressing ducts shall be placed in flexural members, walls and compression members within the following tolerances: a.

Clear distance to formed or unformed concrete surfaces: When member size is 12 inches (300 mm) or less . . . . . . . . . . . . . . . . . . . . . . .

±3/8 inch (10 mm)

When member size is over 12 inches (300 mm) but not over 2 feet (600 mm). . . ±1/2 inch (13 mm) When member size is over 2 feet (600 mm) . . . . . . . . . . . . . . . . . . . . . . . . . . . .

±1 inch (25 mm)

Reduction in concrete cover shall not exceed one-third specified concrete cover. Reduction in concrete cover to formed soffits shall not exceed 1/4 inch (6 mm). Tolerances shall not permit a reduction in concrete cover except as shown above, and shall not permit reduction in concrete cover below values specified as minimums as defined in Article 1.10.6.

1

b. Tolerance on minimum distance between bars shall be minus 1/4 inch (6 mm). c.

Tolerance in uniform spacing of reinforcement from theoretical location shall be ±2 inches (50 mm).

d. Tolerance in uniform spacing of stirrups and ties from theoretical location shall be ±1 inch (25 mm). e.

Tolerance for longitudinal location of bends and ends of bars shall be ±2 inches (50 mm), except at discontinuous ends of members where the tolerance shall be ±1-1/2 inches (40 mm).

f.

Tolerance in length of bar laps shall be minus 1-1/2 inches (40 mm).

g.

Tolerance in embedded length shall be minus 1 inch (25 mm) for #3 to #11 bars (#10 to #36) and minus 2 inches (50 mm) for #14 and #18 bars (#43 and #57).

h. When it is necessary to move bars to avoid interference with other reinforcement, conduits, or embedded items by an amount exceeding the specified placing tolerances, the resulting arrangement of bars shall be approved by the Engineer. i.

Tolerance in the vertical and horizontal location of prestressing strand shall be ±1/4 inches (6 mm) except in precast slabs. The tolerance for vertical location in precast slabs shall be ±1/4 inches (6 mm). The tolerance for horizontal location of prestressing strand in precast slabs shall be ±1 inch (25 mm) in any 15 feet (4.5 m) of strand length.

j.

Tolerance in the vertical and horizontal location of unbonded post-tensioning tendons and ducts in bonded post-tensioning shall be ±1/4 inches (6 mm) except in slabs. The tolerance for vertical location in slabs shall be ±1/4 inches (6 mm). The tolerance for horizontal location of post-tensioning tendons and ducts in bonded post-tensioning in slabs shall be ±1 inch (25 mm) in any 15 feet (4.5 m) of strand length.

k. In precast elements the bearing plates shall be concentric with the tendons and tolerance for the perpendicularity with tendons in concrete shall be ±1 degree. © 2011, American Railway Engineering and Maintenance-of-Way Association

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Concrete Structures and Foundations 1.10.4.3 Bar Supports and Side-Form Spacers a.

Unless otherwise specified by the Engineer, reinforcement supported from the ground shall rest on precast concrete blocks not less than 4 inches (100 mm) square, and having a compressive strength equal to or greater than the specified compressive strength of the concrete being placed. Reinforcement supported by formwork shall rest on bar supports and spacers made of concrete, metal, plastic, or other materials approved by the Engineer.

b. Where noted on the plans and at all formed surfaces that will be exposed to the weather in the finished structure, bar supports and side-form spacers spaced no further than four feet (1200 mm) on center shall be provided. Bar supports and spacers and all other accessories within 1/2 inch (13 mm) of the concrete surface shall be noncorrosive or protected against corrosion. c.

Epoxy-coated reinforcing bars supported from formwork shall rest on coated wire bar supports, or on bar supports made of dielectric material and other acceptable materials. Wire bar supports shall be coated with dielectric material for a minimum distance of 2 inches (50 mm) from the point of contact with the epoxy-coated reinforcing bars. Reinforcing bars used as support bars shall be epoxy-coated. In walls having epoxy-coated reinforcing bars, spreader bars where specified shall be epoxy-coated. Proprietary combination bar clips and spreaders used in walls with epoxy-coated reinforcing bars shall be made of corrosion-resistant material or coated with dielectric material.

d. Zinc-coated (galvanized) reinforcing bars supported from formwork shall rest on galvanized wire bar supports coated with dielectric material, or on bar supports made of dielectric material or other acceptable materials. All other reinforcement and embedded steel items in contact with galvanized reinforcing bars, or within a minimum clear distance of 2 inches (50 mm) from galvanized reinforcing bars unless otherwise required or permitted, shall be galvanized. e.

Epoxy-coated reinforcing bars shall be fastened (tied) with plastic-coated or epoxy-coated tie wire; or other materials authorized by the Engineer.

f.

Zinc-coated (galvanized) reinforcing bars shall be fastened (tied) with zinc-coated tie wire, or nonmetallic-coated tie wire, or other materials authorized by the Engineer.

1.10.4.4 Draped Welded Wire Fabric When welded wire fabric with wire size not greater than W5 or D5 is used for slab reinforcement in slabs not exceeding 10 feet (3000 mm) in span, the reinforcement may be curved from a point near the top of the slab over the support to a point near the bottom of the slab at mid-span, provided such reinforcement is either continuous over, or securely anchored, at the support.

1.10.5 SPACING OF REINFORCEMENT (2003) Spacing of reinforcement shall be as shown on the plans. When spacing of reinforcement is not shown, spacing shall be in accordance with Part 2, Reinforced Concrete Design for reinforcing bars, and Part 17, Prestressed Concrete, Section 17.5 Details of Prestressing Tendons and Ducts.

1.10.6 CONCRETE PROTECTION FOR REINFORCEMENT (2003) Concrete cover for reinforcement shall be as shown on the plans. When concrete cover is not shown, minimum concrete cover shall be provided in accordance with Part 2, Reinforced Concrete Design, Details of Reinforcement, Section 2.6 for bars and wire, and Part 17, Prestressed Concrete, Article 17.5.2 for prestressing tendons and ducts.

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1.10.7 FUTURE BONDING (2003) Exposed reinforcement intended for bonding with future extensions shall be protected from corrosion in an approved manner.

SECTION 1.11 CONCRETE JOINTING 1.11.1 SCOPE (2009) This recommended practice is applicable to the design of concrete slabs and walls in concrete structures such as bridges, buildings and flat work, finger joints and other mechanical joint systems are not included in these recommended practices.

1.11.2 TYPES OF JOINTING (2009) a.

Expansion joints are filled separations between adjoining parts of the concrete structure which are provided to allow for relative movement such as those caused by thermal changes.

b. Contraction joints are sawed, tooled, or constructed in a concrete surface to create a weakened plane to control the location of cracking resulting from dimensional changes caused by shrinkage. c.

1

Construction joints occur where two successive placements of concrete meet, across which it is desired to maintain bond between two concrete placements, and through which any reinforcement which may be present is not interrupted.

1.11.3 EXPANSION JOINTS (2009) a.

Expansion joints allow for differential movement of the concrete mass on either side of the joint. These may also be referred to as isolation joints.

3

b. The Engineer may require that the joint be designed to resist movements in other directions, such as those resulting from shear. c.

Expansion joints shall be installed as shown on the Plans or as specified by the Engineer. Waterstops may also be required.

d. Jointing materials shall be in accordance with ASTM D994 or ASTM D1751. There shall be no connection across the joint except as shown on the Plans or as required by the Engineer.

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Figure 8-1-1. Full-Depth Expansion Joint

1.11.4 EXPANSION JOINTS IN WALLS (2009) Expansion joints between the finished surface and the waterstop shall be filled with a material such as a 1/2 inch (13 mm) thick strip of Preformed Expansion Joint meeting ASTM D994, ASTM D1751 or ASTM D1752.

1.11.5 CONTRACTION JOINTS (2009) a.

These recommended practices do not include full contraction joints, where all reinforcement is terminated at the joint and where joint details may include waterstops, bond breakers, joint sealant or shear connectors.

b. Contraction joints allow for differential movement across the joint only in one direction, usually in the plane of the finished surface. They are provided to allow for dimensional changes such as those caused by drying shrinkage of the concrete. c.

Contraction joints in slabs-on-grade shall be located and detailed as shown on the plans. Unless otherwise shown or noted, joints shall be placed at 15 to 25 foot (5 – 8 m) intervals in each direction.

d. Contraction joints for slabs-on-grade shall be made by one of the methods shown in Figure 8-1-2 or as shown on the plans. e.

Sawing of contraction joints shall be done as soon as the concrete has hardened sufficiently to prevent aggregates being dislocated by the saw and shall be completed within twelve hours after placement unless otherwise approved by the Engineer. Sawing shall not be done when the concrete temperature is falling, unless approved by the Engineer.

f.

Contraction joints may also be constructed by means or methods specifically designed to create a plane of weakness in freshly placed concrete. This may include a reduction in the amount of reinforcement passing through the joint if approved by the Engineer.

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g.

Contraction joints may also be made by other methods if approved by the Engineer. Sawed or tooled contraction joints shall be cleaned and filled with polymeric sealant conforming to ASTM D1190 or ASTM D3405 or as specified by the Engineer.

h. Prior to the application of a polymeric sealing material, a heat resistant backer rod shall be inserted to a minimum depth of 1/2 inch (13 mm) below the slab surface. The remaining reservoir shall then be filled flush with the slab surface (see Figure 8-1-2).

1.11.6 CONSTRUCTION JOINTS (2009) a.

Construction joints allow for no differential movement across the plane of the joint. They are provided only at locations where casting is temporarily suspended or interrupted.

b. The procedures specified in Article 1.14.9 for bonding fresh concrete to hardened concrete shall be followed in the formation of all construction joints. c.

Reinforcement shall continue through the joint. Additional reinforcement such as dowels and other features such as keys and waterstops may also be included. Special measures such as attention to vibration shall be taken in the casting of concrete to either side of the joint in the vicinity of keys.

d. Structures or portions of the structures shall be continuously cast except as specified herein. When necessary to provide construction joints not indicated or specified by the Plans, such construction joints shall be located as approved by the Engineer and formed so as not to impair the strength, appearance, or durability of the structure.

1

1.11.7 WATERTIGHT CONSTRUCTION JOINTS (2009) a.

Contraction joints shall not be used in watertight construction unless shown on the plans approved by the Engineer. See Figure 8-1-1.

b. Where a construction joint is used in watertight construction, special care shall be taken in finishing the concrete to which the succeeding concrete is to be bonded. The consistency of the concrete shall be carefully controlled and the surface shall be protected from loss of moisture as described in Article 1.18.4. c.

Where construction joints are required to be watertight, a continuous keyway shall be constructed in the interface of the first section of the concrete placed with an approved waterstop embedded in this first placement. One half of the waterstop shall be embedded in the first placement and the remaining material shall be embedded in the adjacent placement. See Figure 8-1-3 for details. The concrete shall be thoroughly vibrated to ensure uniform contact over the entire surface of the waterstop and the key on either side of the construction joint. The waterstop shall be in accordance with Corps of Engineers Specification CRD C 572 (PVC) or CRD C 513 (Rubber).

d. Keyed joints shall not be used in slabs less than 6 inches (150 mm) thick.

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Figure 8-1-2. Two Methods for Making Contraction Joints for Slabs-on-Grade

t

Figure 8-1-3. Keyed Construction Joint with Waterstop Inserted Perpendicular to the Plane of the Joint

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Materials, Tests and Construction Requirements

SECTION 1.12 PROPORTIONING 1.12.1 GENERAL (2009) Mix proportions shall be proposed by the Contractor for the various parts of the work subject to the approval of the Engineer. Revised mix proportions may be submitted by the Contractor for approval by the Engineer during the work to reflect concrete test results. Proportions of materials for making concrete shall be selected to provide the strength, workability, durability and other qualities specified on the Plans and required by the Engineer.

1.12.2 MEASUREMENT OF MATERIALS (2009) a.

In the measurement of cement, 94 lb, 1 bag, 1/4 barrel or 1#cubic foot all are assumed equivalent (1.5 Kg of cement shall be assumed as one liter). Materials shall be measured by weighing, except as otherwise specified or where other methods are specifically authorized by the Engineer. The apparatus provided for weighing the aggregates and cement shall be suitably designed and constructed for this purpose. The aggregates and cement shall be weighed separately. The accuracy of all weighing devices shall be such that successive quantities can be measured to within 1% of the desired amount. Cement in standard packages (bags) need not be weighed, but bulk cement and fractional packages shall be weighed. The mixing water shall be measured by volume or by weight. The water-measuring device shall be accurate to within 1/2%. All measuring devices shall be subject to approval of the Engineer.

b. Where volumetric measurements are authorized by the Engineer, the weight proportions shall be converted to equivalent volumetric proportions. In making this conversion, suitable allowance shall be made for variations in the moisture condition of the aggregates, including the bulking effect in the fine aggregate.

1

1.12.3 WATER-CEMENTITIOUS MATERIALS RATIO (2009) a.

The proportioning of materials shall be based on the requirements for a plastic and workable mix suited to the conditions of placement containing not more than the specified amount of water, including the free water contained in the aggregates. The maximum specified amount of water shall not exceed the quantities shown in Table 8-1-9 for the type of structure and the condition of exposure to which it will be subjected. Moisture in the aggregates shall be measured by methods satisfactory to the Engineer.

b. Free water content of aggregates included in the quantities specified must be deducted from the amounts given in the Table to determine the amount to be added at the mixer. Allowance may be made for absorption when aggregates are not saturated.

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Concrete Structures and Foundations Table 8-1-9. Maximum Permissible Water-Cementitious Materials Ratio (by Weight) for Different Types of Structures and Degrees of Exposure Exposure Conditions (Note 1) Severe wider range in temperature or frequent alternations of freezing and thawing (air-entrained conc. only)

Mild temperature rarely below freezing, or rainy, or arid

At the water line or within the range of fluctuating water level or spray

Description

In Air

In Sea Water or In In Fresh Contact With Water Sulfates (Note 2)

At the water line or within the range of fluctuating water level or spray In Air

In Sea Water or In In Contact Fresh With Water Sulfates (Note 2)

Thin sections, such as railings, curbs, sills, ledges, ornamental or architectural concrete, reinforced piles, and pipe

0.49

0.44

0.40 (Note 3)

0.53

0.49

0.40 (Note 3)

Moderate sections, such as retaining walls, abutments, piers, girders, beams

0.53

0.49

0.44 (Note 3)

(Note 4)

0.53

0.44 (Note 3)

Exterior portions of heavy (mass) sections

0.58

0.49

0.44 (Note 3)

(Note 4)

0.53

0.44 (Note 3)

Concrete deposited by tremie underwater

–

0.44

0.44

–

0.44

0.44

0.53

–

–

(Note 4)

–

–

Concrete protected from weather, interiors of buildings, concrete below ground

(Note 4)

–

–

(Note 4)

–

–

Concrete which will later be protected by enclosure of backfill but which may be exposed to freezing and thawing for several years before such protection is offered

0.53

–

–

(Note 4)

–

–

Concrete slabs laid on the ground

Note 1: Air-entrained concrete shall be used under all conditions involving severe exposure and may be used under mild exposure conditions to improve workability of the mixture. Note 2: Soil or ground water containing sulfate concentrations of more than 0.2%. Note 3: When sulfate resisting cement is used, maximum water-cementitious material ratio may be increased by 0.05. Note 4: Water-cementitious material ratio should be selected on basis of strength requirements. Note 5: The water-cementitious materials ratio may require adjustment as outlined in Article 1.12.10.

1.12.4 AIR CONTENT OF AIR-ENTRAINED CONCRETE (2009) a.

The volume of entrained air in concrete shall be within the limits shown in Table 8-1-10.

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Materials, Tests and Construction Requirements

Table 8-1-10. Air-Entrained Concrete Volume Maximum Size Coarse Aggregate Inches (mm)

Air Content % by Volume

1-1/2, 2, or 2-1/2 (38, 50, 63)

5

±1

3/4, 1 (19, 25)

6

±1

7-1/2

±1

3 / 8 , 1 / 2 (10 ,13 )

b. The air content shall be determined by one of the following methods: (1) The gravimetric method, ASTM C138. (2) The volumetric method, ASTM C173. (3) The pressure method, ASTM C231.

1.12.5 STRENGTH OF CONCRETE MIXTURES (2011) a.

The provisions of this Section are not applicable when using cementitious materials other than Portland cement.

b. When preliminary tests of the materials to be used are not available, the required water-cementitious materials ratio shall be determined in accordance with Method 1 (Article 1.12.5.1). When strengths in excess of 4000 psi (28 MPa) are required, or where lightweight aggregates or admixtures (other than those exclusively for the purpose of entraining air) are to be used, the required water-cementitious materials ratio shall be determined in accordance with Method 2 (Article 1.12.5.2). Method 3 (Article 1.12.5.3) may be used if statistical data conforming to Article 1.12.5.3 are available.

1

3

1.12.5.1 Method 1 – Without Preliminary Tests a.

Concrete proportions may be determined in accordance with this method if approved by the Engineer. Concrete proportions shall then be based on the water-cementitious materials ratio limits found in Table 8-1-11. These limits are only for concrete that is made with cements meeting Types I, IA, II, IIA, III, IIIA, or V of ASTM C150, or Types IS, IS-(A), IS(MS), IS-(A)(MS), IP or IP-(A), of ASTM C595. Volume of entrained air shall be within limits of Article 1.12.4. Air Content of Air-Entrained Concrete (2009) ratio shall not be greater than that required by Article 1.12.3. Table 8-1-11. Water-Cementitious Materials Ratio for Air Entrained Concrete Specified 28 Day Compressive Strength of Concrete, f¢ c psi (MPa)

Absolute Water-Cementitious Materials Ratio by Weight (Mass)(Note)

2,500 (17)

0.66

3,000 (21)

0.58

3,500 (24)

0.51

4,000 (28)

0.46

5,000 (34)

0.40

Note:

Not applicable for concrete containing lightweight aggregates or admixtures other than for entraining air.

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b. The values in Table 8-1-11 are based on the use of cement and aggregates meeting the requirements of this Section and the concrete being sufficiently protected from loss of moisture and from low temperatures to ensure that proper curing will take place. When Type III Portland cement is used in lieu of Type I or Type II Portland cement, it may be assumed that the specified compressive strength will be obtained at the age of 7 days. c.

The strength of cylinders made with Types I, IA, II or IIA Portland cement and tested at the age of 7 days shall not fall below 65% of the assumed compressive strength at the age of 28 days. The strength of cylinders made with Types III or IIIA Portland cement and tested at the age of 3 days shall not fall below 65% of the assumed minimum compressive strength at the age of 28 days shown for Types I, IA, II and IIA Portland cement. The strength of cylinders tested at the age of 28 days shall be at least 1200 psi (8.3 MPa) greater than the strength specified on the plans when using this method.

1.12.5.2 Method 2 – With Preliminary Tests The strength of concrete shall be determined by tests made with representative samples of the materials to be used in the work. The results of the tests shall be submitted to the Engineer in advance of construction. These tests shall be made using the consistencies suitable for the work. These samples shall be proportioned to produce a slump of within 3/4 inch (19 mm) of the maximum permitted slump and with an entrained air content of within 0.5 percent of the maximum air content required. Tests shall be conducted in accordance with ASTM C192 Standard Practice for Making and Curing Concrete Test Specimens in the Laboratory and with ASTM C39 Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens. At least three tests shall be conducted for each of three water-cementitious material ratios that will encompass the required concrete strength. A curve representing the relation between the water content and the average 28 day compressive strength or earlier strength at which the concrete is to receive its full working load shall be established for this range of values. The maximum permissible water-cementitious material ratio for the concrete to be used shall be shown by the curve to produce a strength 15% greater than specified on the Plans or specifications. If any changes are to be made in the materials, new curves shall be established by tests as described above. 1.12.5.3 Method 3 – On Basis of Field Experience a.

Where a concrete production facility has a record based upon at least 30 consecutive strength tests that represent similar materials and conditions to those expected, required average compressive strength used as the basis for selecting concrete proportions shall exceed required f’c at designated test ages by at least: (1) 1.34 standard deviations, where the standard deviation is less than or equal to 500 psi (3.45 MPa). (2) 2.33 standard deviations less 500 psi (3.45 MPa), where the standard deviation is greater than 500 psi (3.45 MPa).

b. Strength test data for determining standard deviation shall be considered to comply with the above if data represents either a group of at least 30 consecutive tests or a statistical average for two groups totaling 30 or more tests. c.

Strength tests used to establish standard deviation shall represent concrete produced to meet a specified strength within ±1000 psi (±6.90 MPa) of that specified for the proposed work.

d. Changes in materials and proportions within the population of background tests used to establish standard deviation shall not have been more closely restricted than for the proposed work.

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Materials, Tests and Construction Requirements

1.12.6 WORKABILITY (2009) The concrete shall be of such consistency and composition that it can be worked readily into the corners and angles of the forms and around the reinforcement without segregation of materials or the collection of free water on the surface. Subject to the limiting requirements of Article 1.12.3, the contractor shall, if the Engineer requires, submit a new mix design to adjust the proportions of cement and aggregates so as to produce a mixture which will be easily placeable at all times, due consideration being given to the methods of placing and compacting used on the work and subject to the approval of the Engineer.

1.12.7 SLUMP (2009) The slump test may be used as a control measure to maintain the consistency suitable for the work. When mechanical vibrators are used to compact the concrete, the consistency suitable to that method shall be used. The slump test shall be made in accordance with the ASTM Method of Test C143 Standard Test Method for Slump of Hydraulic Cement Concrete.

1.12.8 COMPRESSION TESTS (2009) Specimens for compression tests shall be made and stored in accordance with ASTM C31 Standard Practice for Making and Curing Concrete Test Specimens in the Field. These specimens shall be tested in accordance with ASTM C39.

1.12.9 FIELD TESTS (2009) a.

1

During the progress of construction, the Engineer will have tests made to determine whether the concrete produced compares to the quality specified by the Plans. The Contractor shall cooperate in the making of such tests and allow free access to the work for selection of samples and storage of specimens and in affording protection to the specimens against injury or loss through construction operations.

b. Four cylinders will generally be made for each class of concrete used in any one day’s operation. In special cases, this normal number of control specimens may be exceeded when in the opinion of the Engineer such additional tests are required. The Contractor, however, shall not be required to furnish for such additional tests more than 2 cubic feet (75 liters) of concrete for each 100 cubic yard (76 cubic meter) of concrete being placed (75 liters for each 100 cu. m). c.

Samples of concrete for test specimens shall be taken at the mixer, or in the case of ready-mix concrete, from the transportation vehicle during discharge. When, in the opinion of the Engineer, it is desirable to take samples elsewhere, they shall be taken as directed. Specimens shall be made and stored in accordance with Article 1.12.8.

d. The air content of freshly mixed air-entrained concrete shall be checked at least twice daily for each class of concrete, or each time cylinders are cast. Changes in air content above or below the amount specified shall be corrected by adjustment in the mix design or quantities of air-entraining material being used. e.

If the strengths shown by the test specimens fall below the values given in Article 1.12.5 or as specified by the Plans, then the Engineer shall have the right to require changes in proportions to apply on the remainder of the work.

f.

Technicians performing field tests of concrete materials shall maintain Level I certification by the American Concrete Institute as a Concrete Field Testing Technician. The person in responsible charge of field test operations shall maintain Level 3 certification by the National Ready Mix Concrete Association as a Concrete Technologist.

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1.12.10 SPECIAL PROVISIONS WHEN USING CEMENTITIOUS MATERIALS OTHER THAN PORTLAND CEMENT (2009) 1.12.10.1 Maximum Cementitious Materials Concrete exposed to deicing chemicals shall contain total weights (masses) of cementitious materials no greater than those specified in Table 8-1-12. Table 8-1-12. Concrete Exposed to Deicing Chemicals Cementitious Material

Maximum Percentage of Total Cementitious Materials by Weight (mass)

Fly ash or other pozzolans conforming to ASTM C618

25

Ground granulated blast-furnace slag conforming to ASTM C989

50

Silica fume conforming to ASTM C1240

10

Total fly ash or other pozzolans, ground granulated blast-furnace slag and silica fume

50

Total fly ash or other pozzolans, and silica fume

35

Notes: Total cementitious material also includes ASTM C150, ASTM C595, ASTM C845 and ASTM C1157 cements (ASTM C845 is the Standard Specification for Expansive Hydraulic Cement and is not included in this recommended practice). The maximum percentages include: a. Fly ash and other pozzolans and ground granulated blast-furnace slag included in Types IP or I(PM) or IS or I(SM) blended cements, ASTM C595 b. Silica fume, ASTM C1240, present in blended cements 1.12.10.2 Requirements When Using Silica Fume in Concrete 1.12.10.2.1 General The ability of the concrete mixture to exhibit special properties should be determined by tests for each source of silica fume. 1.12.10.2.2 High-Range Water Reducing Admixtures High-range water reducing admixtures should be used in concrete containing silica fume in order to achieve the desired workability.

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Materials, Tests and Construction Requirements 1.12.10.2.3 Entrained Air The amount of admixture required to entrain the desired amount of air should be determined by tests as part of the design of the concrete mixture. 1.12.10.3 Requirements When Using Fly Ash in Concrete 1.12.10.3.1 General Mix proportions, including the proportions of fly ash, shall be determined by tests. 1.12.10.3.2 Water-Reducing Admixtures and High Range Water-Reducing Admixtures Water reducing admixtures and high-range water reducing admixtures may be used in concrete containing fly ash. 1.12.10.3.3 Testing to Verify Mix Design The mixture shall be designed and proportioned to provide the properties for which the fly ash was used, and to avoid other possible undesirable properties. Tests shall include slump/workability, requirements for airentraining admixtures, the rate of bleeding of fresh concrete, the time of setting, the rate of early strength gain and any need to use an accelerating admixture or a water-reducing admixture, the heat of hydration (if required), reactivity with sulphates or expansion due to alkali-silica reactions (if required), and the 28-day or later strength as required by the design parameters.

1

1.12.10.3.4 Water to Cementitious Materials Ratio The water to cementitious material ratio will normally be reduced in concrete containing fly ash. 1.12.10.3.5 Air Entrainment Concrete containing fly ash should be air entrained if it is to be subjected to freezing and thawing conditions. Concrete should also attain the desired design strength before being subjected to chlorides.

3

1.12.10.4 Requirements When Using Ground Granulated Blast-Furnace Slag in Concrete 1.12.10.4.1 General

4 Mix proportions, including the proportion of ground granulated blast-furnace slag, shall be determined by tests. 1.12.10.4.2 Water-Reducing Admixtures Water-reducing admixtures may be used in concrete containing ground granulated blast-furnace slag, in order to increase the rate of strength gain. 1.12.10.4.3 Accelerators An accelerating admixture may be used when using ground granulated blast-furnace slag in a concrete mix. 1.12.10.4.4 Proportioning of Aggregates Concrete containing ground granulated blast-furnace slag will normally be proportioned for a larger quantity of coarse aggregate than normal Portland cement concrete.

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Concrete Structures and Foundations 1.12.10.4.5 Entrained Air The amount of admixture required to entrain the desired amount of air should be determined by tests as part of the design of the concrete mixture.

SECTION 1.13 MIXING 1.13.1 GENERAL (2009) a.

The concrete shall be mixed only in the quantity required for immediate use. Concrete that has developed an initial set shall not be used.

b. The first batch of concrete materials placed in the mixer shall contain a sufficient excess of cement, sand, and water to coat the inside of the drum without reducing the required mortar content of the mix. The mixer shall be thoroughly cleaned if mixing is interrupted for a period that would permit initial set to take place. c.

Concrete may be mixed at the site of construction, at a central point, and/or in truck mixers.

d. The ingredients shall be thoroughly mixed to specification.

1.13.2 SITE-MIXED CONCRETE (2009) a.

Unless authorized by the Engineer, the concrete shall be mixed in a batch mixer of approved type and size which will ensure a uniform distribution of the material throughout the mass. The equipment at the mixing plant shall be so constructed that all materials (including the water) entering the drum can be accurately measured and weighed. The batch shall be fully discharged from the mixer before recharging. The volume of the mixed material per batch shall not exceed the manufacturer’s rated capacity of the mixer. Mixing of each batch shall continue for the periods noted below, during which time the drum shall rotate at a peripheral speed as recommended by the manufacturer. The mixing time shall be measured from the time when all of the solid materials are in the mixer drum, provided that all of the mixer water has been introduced before one-fourth of the mixing time has elapsed. The mixer shall have a timing device with a bell or other suitable warning device adjusted to give a clearly audible signal each time the lock is released. In case of failure of the timing device, the contractor shall be permitted to operate while it is being repaired, provided an approved timepiece equipped with minute and second readings is furnished. If the timing device is not placed in good working order within 24 hours, further use of the mixer will be prohibited until repairs are made.

b. Minimum mixing time shall be as follows: (1) For mixers of a capacity of 1 cubic yard (0.8 cubic meter) or less – 90 seconds unless a shorter time is shown to be satisfactory in accordance with concrete uniformity test requirements of ASTM C94. (2) For mixers of a capacity greater than 1 cu yd (0.8 cubic meter), the time of mixing shall be increased 25 seconds for each cubic yard (0.8 cubic meter) of capacity or fraction thereof or as determined by the concrete uniformity test requirements of ASTM C94. c.

The production of concrete shall meet the applicable requirements of ASTM C94.

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Materials, Tests and Construction Requirements

1.13.3 READY-MIXED CONCRETE (2009) Ready mixed concrete shall be mixed and delivered to the site by any of three methods of operation: central mixing, shrink mixing or truck mixing. The production of ready-mixed concrete shall conform to the requirements of ASTM C94. The batch plant providing ready-mixed concrete shall be certified by the National Ready Mix Concrete Association.

1.13.4 DELIVERY (2009) a.

The organization supplying concrete shall have sufficient plant capacity and transporting equipment to ensure continuous delivery at the rate required. The rate of delivery of concrete during concrete operations shall be such as to provide for the proper handling, placing, and finishing of the concrete. The methods of delivering and handling concrete shall facilitate placing with minimum rehandling and without damage to the structure or concrete.

b. The Contractor shall submit records to the Engineer showing the time and date of each batch produced and the mix proportions and the approximate location within the structure of each batch.

1.13.5 REQUIREMENTS WHEN USING SILICA FUME IN CONCRETE (2009) 1.13.5.1 Material Handling Procedures When Using Silica Fume It is recommended that persons handling silica fume use protective equipment and procedures to minimize the generation and accumulation of dust. Manufacturers’ material safety data sheets should be consulted for specific health and safety practices to be followed.

1

1.13.5.2 Workability of Delivered Concrete Tests for slump and entrained air content should be carried out at the site before placing concrete containing silica fume to ensure that specification limits are met.

3

SECTION 1.14 DEPOSITING CONCRETE

4

1.14.1 GENERAL (2000) Before beginning placement of concrete, hardened concrete and foreign materials shall be removed from the inner surfaces of the mixing and conveying equipment. Before depositing any concrete all debris shall be removed from the space to be occupied by the concrete, and mortar splashed upon the reinforcement and surfaces of forms shall be removed. Reinforcement shall be checked for position and fastening and approval of the Engineer obtained. Where concrete is to be placed on a rock foundation, all loose rock, clay, mud, etc., shall be removed from the surface of the rock. Any unusual conditions or excess fissures shall be treated as directed by the Engineer. Water shall be removed from the space to be occupied by the concrete before concrete is deposited, unless otherwise directed by the Engineer. Any flow of water into an excavation shall be diverted through proper side drains to a sump, or be removed by other approved methods which will avoid washing the freshly deposited concrete. If directed by the Engineer water ventpipes and drains shall be filled by grouting or otherwise after the concrete has thoroughly hardened. All temporary runways for delivery of concrete must be supported free from all reinforcing steel. The supervisor of the concrete placing crew shall maintain certification by the American Concrete Institute as a Concrete Flatwork Finisher, or Concrete Transportation Construction Inspector.

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Concrete Structures and Foundations

1.14.2 HANDLING AND PLACING (1993) a.

Concrete shall be handled from the mixer, or in case of ready-mixed concrete, from the transporting vehicle, to the place of final deposit as rapidly as practicable by methods which will prevent the separation or loss of the ingredients. Special care shall be taken to fill each part of the forms by depositing concrete as near final position as possible, to work the coarser aggregates back from the face and to force the concrete under and around the reinforcement without displacing it. Concrete shall not have a free fall of more than 4 feet unless permitted by the Engineer. Depositing a large quantity at any point and working it to final position, shall not be permitted.

b. Concrete shall be placed in horizontal layers and each layer shall be placed and compacted before the preceding layer has taken initial set so as to prevent formation of a joint. It shall be so deposited as to maintain, until the completion of the unit, a plastic surface approximately horizontal, except in arch rings. Temporary struts or braces within the form shall be removed when concrete has reached an elevation rendering their further service unnecessary. These temporary members shall be entirely removed from the forms and not buried in the concrete. After the concrete has taken its initial set, care shall be exercised to avoid jarring the forms or placing any strain on the ends of the projecting reinforcement. Under no circumstances shall concrete that has partially hardened be deposited in the work. c.

In placing concrete for an arch ring, the work shall be carried on symmetrically with respect to the center line, and the working faces of the completed courses shall be on approximately radial planes. This requirement applies whether or not the arch is placed in voussoir sections with allowance for key sections for final placement.

d. In order to allow for shrinkage or settlement, at least 2 hours shall elapse after placing concrete in walls, columns or stems of deep T-beams before depositing concrete in girders, beams or slabs supported thereon, unless otherwise specified or shown on the plans. If the columns are structural steel encased in concrete, the lapse of time to allow for shrinkage or settlement need not be observed. e.

Concrete in girders, slabs and shallow T-beam construction shall be placed in one continuous operation for each span, unless otherwise provided. Concrete shall be deposited uniformly for the full length of the span and brought up evenly in horizontal layers.

f.

No concrete shall be placed in the superstructure until the pier forms have been stripped sufficiently to determine the character of the concrete in the piers, and the load of the superstructure shall not be allowed to come upon abutments, piers and column bents until they have been in place at least 7 days, unless otherwise permitted by the Engineer.

1.14.3 CHUTING (1993) When concrete is conveyed by chuting, the plant shall be of such size and design as to insure a practically continuous flow in the chute. The chutes shall be of metal or metal lined. The angle of the chute with the horizontal and the shape of the chute shall be such as to allow the concrete to slide without separation of the ingredients. The delivery end of the chute shall be as close as possible to the point of deposit. When the operation is intermittent, the chute shall discharge into a hopper. The chute shall be thoroughly flushed with water before and after each run: the water used for this purpose shall be discharged outside the forms. Chutes must be properly baffled or hooded at the discharging end to prevent separation of the aggregates.

1.14.4 PNEUMATIC PLACING (SHOTCRETING) (1993) Shotcrete construction shall be in accordance with ACI Standard “Guide to Shotcrete” (ACI 506) and ACI Standard “Specification for Materials, Proportioning, and Application of Shotcrete” (ACI 506.2) of the ACI. © 2011, American Railway Engineering and Maintenance-of-Way Association

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Materials, Tests and Construction Requirements

1.14.5 PUMPING CONCRETE (1993) a.

The pump and all appurtenances shall be so designed and arranged that the specified concrete can be transported and placed in the forms without segregation. The pump shall be capable of developing a working pressure of at least 300 psi and the pipeline and fittings shall be designed to withstand twice the working pressure.

b. Where it is necessary to lay the pipe on a down grade, a reducer shall be placed at the discharge end of the pipe to provide a choke and thus produce a continuous flow of concrete. When the type of pump is such that it discharges the concrete in small batches, or “belching,” a baffle box shall be provided into which the concrete shall be discharged. This box should preferably be of metal, about 2 feet square, with open sides so as to permit the concrete to flow into the forms at right angles to line of discharge. The pipe shall be not less than 6 inches nor more than 8 inches outside diameter, and the line shall be laid with as few bends as possible. When changes in direction are necessary they shall be made with bends of 45 degrees or less, unless greater bends are specifically permitted. If greater bends are permitted in special cases, they shall be long-radius bends. The maximum distance of delivery of concrete by pumping shall be 1000 feet horizontally and 100 feet vertically, unless otherwise specifically permitted by the Engineer. (A 90-degree bend is figured as equivalent to 40 feet of horizontal piping. A 45-degree bend is equivalent to 20 feet. A 22.5-degree bend is equivalent to 10 feet.) When pumping is completed, the concrete remaining in the pipeline if it is to be used, shall be ejected in such a manner that there will be no contamination of the concrete or separation of the ingredients. The pipeline and equipment must then be thoroughly cleaned. The pipeline can be cleaned by either water or air. If water is used, a pump shall be provided with a capacity of at least 80 gpm and capable of developing a pressure of 400 psi. Cleaning of the pipe can also be accomplished by the use of a “go-devil” which is propelled through the line by water or air pressure. (The “go-devil” is a dumbbell shaped piece with a rubber cup on each end. The cups are turned toward the liquid, or air, and the seal is the same as in a simple plunger pump.) If water is used, it must be discharged outside of the forms. On important work duplicate pumping equipment and additional pipe shall be provided to prevent delay due to breakdown of equipment.

1.14.6 COMPACTING (1993) a.

3

Concrete shall be thoroughly compacted during and immediately after depositing by vibrating the concrete internally by means of mechanical vibrating equipment, unless otherwise directed by the Engineer.

b. Internal mechanical vibrators shall be of a type approved by the Engineer. They shall be of sturdy construction, adequately powered, capable of transmitting vibration to the concrete in frequencies of not less than 3500 impulses per minute and shall produce a vibration of sufficient intensity to consolidate the concrete into place without a separation of the ingredients. c.

1

The vibratory elements shall be inserted into the concrete at the point of deposit and in the areas of freshly placed concrete. The time of vibration shall be of sufficient duration to accomplish thorough consolidation, complete embedment of the reinforcement, the production of smooth surfaces free from honeycomb and air bubbles, and to work the concrete into all angles and corners of the forms. However, over-vibration shall be avoided, and vibration shall continue in a spot only until the concrete has become uniformly plastic and shall not continue to the extent that pools of grout are formed. The length of time of vibration depends upon the frequency of the vibration (impulses per minute), size of vibrators and the slump of the concrete. This length of time must be determined in the field.

d. The internal vibrators shall be applied at points uniformly spaced, not farther apart than the radius over which the vibration is visibly effective, and shall be applied close enough to the forms effectively to vibrate the surface concrete. The vibration shall not be dissipated in lateral motion but shall be concentrated in vertical settlement in consolidation of the concrete.

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e.

The vibrator shall not be used to push or distribute the concrete laterally. The vibrating element shall be inserted in the concrete mass a sufficient depth to vibrate the bottom of each layer effectively, in as nearly a vertical position as practicable. It shall be withdrawn completely from the concrete before being advanced to the next point of application.

f.

To secure even and dense surfaces, free from aggregate pockets or honeycomb, vibration shall be supplemented by working or spading by hand in the corners and angles of forms and along form surfaces while the concrete is plastic under the vibratory action.

g.

A sufficient number of vibrators shall be employed so that, at the required rate of placement, thorough consolidation is secured throughout the entire volume of each layer of concrete. Extra vibrators shall be on hand for emergency use and for use when other vibrators are being serviced.

h. The use of surface vibrators to supplement internal vibration will be permitted when satisfactory surfaces cannot be obtained by the internal vibrations alone and when the contractor has obtained the approval of the Engineer of the equipment to be used. Surface vibrators shall be applied only long enough to embed the coarse aggregate and to bring enough mortar to the surface for satisfactory finishing. i.

The use of approved form vibrators will be permitted by the Engineer only when it is impossible to use internal vibrators. They shall be attached to or held on the forms in such a manner as to effectively transmit the vibration to the concrete and so that the principal path of motion of the vibration is in a horizontal plane.

1.14.7 TEMPERATURE (1993) a.

Concrete when deposited shall have temperatures within the limits shown in Table 8-1-13. Table 8-1-13. Concrete Temperature Limits Temperature of Air Degrees - F

Temperature of Concrete When Placed–Degrees F Minimum

Maximum

Below 30

70

90

Between 30 and 45

60

90

Above 45

50

90

b. The method of controlling the temperature of the concrete shall be approved by the Engineer.

1.14.8 CONTINUOUS DEPOSITING (1993) Concrete shall be deposited continuously and as rapidly as practicable until the unit of operation approved by the Engineer is completed. Construction joints in addition to those provided on the plans will not be allowed unless authorized by the Engineer. If so authorized, they shall be made in accordance with Section 1.11, Concrete Jointing.

1.14.9 BONDING (1993) Before new concrete is placed against hardened concrete, the surface of the hardened concrete shall be cleaned and all laitance removed. Immediately before new concrete is placed, the existing surfaces shall be thoroughly wetted and all standing water removed. Prior to placing fresh concrete, apply a bonding layer of mortar, usually © 2011, American Railway Engineering and Maintenance-of-Way Association

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1/8 inch to 1/2 inch in thickness, which is spread on the moist and prepared hardened concrete surface. In lieu of mortar, a suitable commercial bonding agent may be used, when applied in accordance with manufacturer’s recommendations.

1.14.10 PLACING CYCLOPEAN CONCRETE (1993) Cyclopean aggregate shall be thoroughly embedded in the concrete. The individual stones shall not be closer than 12 inches to any surface or adjacent stones. Stratified stone shall be laid on its natural bed. Cyclopean aggregate shall be carefully placed to avoid injury to forms or adjoining masonry.

1.14.11 PLACING RUBBLE CONCRETE (1993) Rubble aggregate shall be thoroughly embedded in the concrete. The individual stones shall not be closer than 4 inches to any surface or adjacent stones. Rubble aggregate shall be carefully placed to avoid injury to forms or adjacent masonry.

1.14.12 PLACING CONCRETE CONTAINING SILICA FUME (2004)1 1.14.12.1 Protection from Moisture Loss Protection of concrete from early moisture loss is to begin at the first opportunity after placement and may require that such measures precede the curing phase of the work. Evaporation retarders, fogging and protection from the wind during the placement stage, or immediate curing, may be options included in the project specifications. Appropriate measures to protect against early moisture loss in concrete containing silica fume should be included and stressed in the project specifications. Subgrade moistening may be required to prevent excessive drying from the underside of the concrete.

1

1.14.12.2 Consolidation Careful attention to effective vibration is required for concrete containing silica fume.

3

1.14.13 PLACING CONCRETE CONTAINING FLY ASH (2004) 1.14.13.1 Air Entrainment Tests shall be performed at the site to verify that the required amount of entrained air is present at the time of depositing the concrete.

1.14.14 WATER GAIN (1993) Water gain is characterized by an accumulation of water at the surface. Whenever water gain appears in the concrete placed, the succeeding batches must be placed sufficiently dry to correct the over-wet condition by the reduction of the water cement ratio without changing the proportions of the other ingredients.

1

See C - Commentary

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SECTION 1.15 DEPOSITING CONCRETE UNDER WATER 1.15.1 GENERAL (1993) a.

The methods specified in Section 1.14, Depositing Concrete shall be used except when the space to be filled with concrete contains water which cannot be removed in some practical way. In such cases, and when authorized by the Engineer, concrete shall be deposited under water in accordance with the following.

b. The methods, equipment and materials proposed to be used, shall be submitted first to the Engineer for approval before the work is started. The methods used shall be such as will prevent the washing out of the cement from the concrete mixture, minimize the segregation of materials and the formation of laitance, and prevent the flow of water through or over the new concrete until it has fully hardened. Concrete shall not be placed in water having a temperature below 35 degrees F.

1.15.2 CAPACITY OF PLANT (1993) Sufficient mixing, transporting and placing equipment shall be provided to insure that the depositing of all underwater concrete for each predetermined section or unit of the work to be done, shall be continuous until completion.

1.15.3 STANDARD SPECIFICATIONS (1993) The materials, preparations and methods to be used in making concrete to be deposited under water shall all conform to the requirements of these specifications except as modified or supplemented by the following Articles.

1.15.4 CEMENT (1993) Not less than 610 lb of cement per cubic yard of concrete shall be used.

1.15.5 COARSE AGGREGATES (1993) Aggregate for this work shall be of exceptionally good quality, strong and durable. The maximum size of aggregate preferably shall be 2 inches and shall not exceed 3 inches. The coarse aggregate shall be well graded in such proportions that the weight of the coarse aggregate shall be not less than 1.25 nor more than 2.0 times that of the fine aggregate.

1.15.6 MIXING (1993) The cement and aggregates shall be mixed for a period of 2 minutes with sufficient water to produce a concrete having a slump of not less than 6 inches nor more than 8 inches for concrete placed by tremies, and not less than 3 inches nor more than 6 inches for concrete placed by bottom dump buckets or for concrete placed in sacks.

1.15.7 CAISSONS, COFFERDAMS OR FORMS (1993) Caissons, cofferdams or forms shall be sufficiently tight to prevent loss of mortar or flow of water through the space in which the concrete is to be deposited. Pumping will not be permitted while concrete is being deposited, nor until a minimum of 24 hours thereafter or longer period if required by the Engineer.

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1.15.8 LEVELING AND CLEANING THE BOTTOM TO RECEIVE CONCRETE (1993) a.

Before starting to deposit concrete under water, the condition of the bottom shall be examined and reported upon to the Engineer by a competent diver, and shall be approved by the Engineer.

b. The surface of the bottom, whether of clay, rock, or other material, shall be leveled as directed by the Engineer, before depositing concrete under water. c.

Where the bottom on which concrete is to be deposited under water is, or is likely to be, covered with silt, such material shall be removed down to solid material before any concrete is placed. The method to be used to clean the bottom of silt or similar material, shall be subject to the approval of the Engineer.

1.15.9 CONTINUOUS WORK (1993) Concrete shall be deposited continuously until it is brought up to the required elevation. While depositing, the top surface shall be kept as nearly level as possible, and the formation of laitance planes avoided.

1.15.10 METHODS OF DEPOSITING (1993) a.

Tremie. When concrete is to be deposited under water by means of a tremie, the top section of the tremie shall be a hopper large enough to hold one entire batch of the mix or the entire contents of the transporting bucket, when one is used. The tremie pipe shall be not less than 8 inches in diameter and shall be large enough to allow a free flow of concrete and strong enough to withstand the external pressure of the water in which it is suspended, even if a partial vacuum develops inside the pipe. Preferably, flanged steel pipe should be used, of adequate strength to sustain the greatest length and weight required for the job. A separate lifting device shall be provided for each tremie pipe with its hopper at the upper end. Unless the lower end of the pipe is equipped with an approved automatic check valve, the upper end of the pipe shall be plugged with an approved material, before delivering the concrete to the tremie pipe through the hopper, which plug will be forced to and out of the bottom end of the pipe by filling the pipe with concrete. It will be necessary to slowly raise the tremie in order to cause a uniform flow of the concrete, but the tremie shall not be emptied so that water enters above the concrete in the pipe. At all times after the start of placing the concrete and until all concrete is placed, the lower end of the tremie pipe shall be below the top surface of the plastic concrete. This will cause the concrete to build up from below instead of flowing out over the surface thus avoiding formation of laitance layers. If the charge in the tremie is lost while depositing, the tremie shall be raised above the concrete surface, and unless sealed by a check valve it shall be replugged at the top end, as at the beginning, before refilling for depositing concrete. NOTE:

Experience has shown that tremie concrete can be placed as above specified, so that it will flow as much as 50 feet horizontally from the discharge end of the tremie with a slope of less than 3 feet in 50 feet.

b. Bottom Dump Bucket. Where concrete is to be deposited under water by means of a bottom dump bucket, the bucket shall be of the type that cannot be dumped until after it has rested, with its load, on the surface upon which the concrete is to be deposited. The bottom doors shall be so equipped as to be automatically unlatched by the release of tension on the supporting line or cable of the bucket, and the bottom doors shall then open downward and outward as the bucket is raised. The top of the bucket shall be fitted with double, overlapping canvas flaps, or other approved covers, to cover the contained concrete and to protect it from wash when it enters the water and as the bucket descends to the bottom. The bucket, preferably, should be so designed that the hinged bottom doors will operate inside of a steel skirt, which skirt will surround the bucket while the bottom doors are shut and will extend below the bucket as the bottom doors open and hence minimize turbulence and motion while the concrete is being deposited. The bucket shall be submerged slowly until it is completely under water. The normal line

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speed after that shall not exceed 200 feet per minute. After the bucket has reached the surface on which the concrete is to be deposited, it shall be raised slowly for the first 6 or 8 feet while the concrete is being deposited. c.

Placing Sacks of Concrete. Where a relatively small amount of concrete is to be placed that does not warrant the equipment required for other tremie or open-bottom bucket methods, concrete may be placed under water in sacks or bags. In such case the space shall be filled with sacks of concrete carefully placed by hand in header and stretcher formation, so that the whole mass becomes interlocked. Sacks used for this purpose shall be made of jute or other coarse material free from deleterious materials, and shall be filled about two-thirds full of concrete and the sack openings securely tied.

d. Grouted Aggregate. Installed by placing course aggregate in the forms, then injecting cement grout through pipes which extend to the bottom of the forms. The pipes are withdrawn as grouting proceeds. The grout forces the water from the forms and fills interstices in the aggregate. (1) Grout insert pipe system shall be designed and installed to deliver grout to the entire mass. Vent pipes shall be required to relieve entrapped water or air. Sounding wells should be provided to determine the location of grout surface during the grout injection. (2) The coarse aggregate shall be placed in horizontal layers of such maximum thickness as will provide a dense fill without segregation and shall be well compacted. (3) The grout mixture shall be applied under such pressure and at such consistency as will insure complete filling of voids, and group pipes shall be properly spaced to be consistent with this requirement. (4) Mineral fillers and admixtures may be added to the grout mixture if approved by the Engineer. (5) The grout mixture required for this class of work necessitates the use of special mixers and agitators to deliver suitable grout in place. This equipment and all grout lines shall be maintained in good operating condition. After every shift or work stoppage, they shall be cleaned of all grout.

1.15.11 SOUNDINGS (1993) During the time that concrete is being deposited under water, soundings shall be continuously taken to the surface of the deposited concrete and recorded. The surface of the deposited concrete shall be maintained relatively level over the area being covered.

1.15.12 REMOVING LAITANCE (1993) Upon completing a unit or section of underwater concrete, any laitance or silt collecting on the upper surface of the same shall be removed and the concrete surface thoroughly cleaned, if additional concrete is to be deposited on that surface.

1.15.13 CONCRETE SEALS (1993) Under favorable conditions it is possible to place underwater concrete of a limited thickness in the bottoms of caissons or cofferdams and so completely seal the structures that after the concrete has set, all water can be pumped out. In such cases, if it is economical to do so, the water shall be pumped out, the exposed surfaces cleaned and the balance of the concrete deposited in air.

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SECTION 1.16 CONCRETE IN SEA WATER 1.16.1 CONCRETE (2004) a.

Unless otherwise specifically provided, concrete for structures in, or exposed to, sea water shall be airentrained in accordance with Article 1.12.4, and shall be made with Type II or IIA portland cement having a maximum tricalcium aluminate content of 8%. Concrete in sea water or exposed directly along the sea coast shall contain a minimum of 560 lb of portland cement per cubic yard. The concrete shall be mixed for a period of not less than 2 minutes and the water content of the mixture shall be carefully controlled and regulated so as to produce concrete of maximum impermeability. Porous or weak aggregates shall not be used.

b. When concrete mix designs include cementitious materials other than portland cement, the resistance to the harmful effects of exposure to sea water shall be determined by tests, or by experience from using materials from the same sources.

1.16.2 DEPOSITING IN SEA WATER (1993) Between levels of extreme low water and extreme high water as determined by the Engineer, sea water shall not come in direct contact with the concrete for a period of not less than 30 days. Sea water shall not be allowed to come in contact with other concrete that will be in or exposed to sea water until it is hardened for at least 4 days. Concrete may be deposited in sea water only when so approved by the Engineer. The original surface, as the forms are removed from the concrete, shall be left undisturbed.

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1.16.3 CONSTRUCTION JOINTS (1993) Concrete shall be placed in such a manner that no construction joints shall be formed between levels of extreme low water and extreme high water as determined by the Engineer. Construction joints outside the level between extreme low water and extreme high water shall be held to the minimum necessary, and all construction joints shall be made as described in Section 1.11, Concrete Jointing and Section 1.14, Depositing Concrete, Article 1.14.9.

3

1.16.4 MINIMUM COVER (1993) Reinforcing steel or other corrodible metal shall have a cover of not less than 4 inches of concrete.

4

1.16.5 PROTECTING CONCRETE IN SEA WATER (1993) Where severe climatic conditions or severe abrasions are anticipated, the face of the concrete from 2 feet below low water to 2 feet above high water, or from a plane below to a plane above wave action, shall be protected by stone of suitable quality, dense vitrified shale brick as designated or as required by the Engineer, or in special cases the protection may be creosoted timber.

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SECTION 1.17 CONCRETE IN ALKALI SOILS OR ALKALI WATER 1.17.1 CONDITION OF EXPOSURE (1993) In areas where concrete may be exposed to injurious concentrations of sulfates from soils and waters, concrete shall be made with sulfate resisting cement. Table 8-1-14 gives limitations on tricalcium aluminate content in cement for various exposure conditions, severity of conditions may be judged by the extent of deterioration which has occurred to concrete previously used in the immediate vicinity or from the sulfate concentrations found in either the soil or the water. Table 8-1-14. Recommendations For Concrete In Sulfate Exposures Normal Weight Aggregate Concrete

Sulfate Concentration as SO4

Sulfate Exposure

Maximum Tricalcium Aluminate in Maximum WaterCement, Percent Cementitious In Soil, Percent In Solution, PPM (Note 1) by Weight Material Ratio, by Weight

Lightweight Aggregate Concrete Minimum Compression Strength, f¢ c, psi

Moderate

0.10–0.20

150–1500

8

0.50

3750

Severe

0.20–2.00

1500–10,000

5

0.45

4000

Very Severe

over 2.00

over 10,000

5 plus pozzolan (Note 2)

0.45

4000

Note 1: Maximum tricalcium aluminate content of cement for concrete in seawater shall be 8%. Note 2: Use a pozzolan which has been determined by tests to improve sulfate resistance when used in concrete containing a cement with a maximum tricalcium aluminate content of 5% or less.

1.17.2 CONCRETE FOR MODERATE EXPOSURE (1993) Concrete for moderate sulfate exposure shall be made from Type II or specified portland blast furnace slag cement Type IS (MS), and portland pozzolan cement Type IP (MS) may be used to meet the 8% tricalcium aluminate limitation. Concrete shall contain not less than 610 lb of cement per cu yd. The concrete shall be airentrained in accordance with Section 1.12, Proportioning, Article 1.12.4.

1.17.3 CONCRETE FOR SEVERE EXPOSURE (1993) Concrete for severe sulfate exposure shall be made using Type V portland cement with a 5% maximum tricalcium aluminate content. Concrete shall contain not less than 660 lb of cement per cu yd. The concrete shall be air-entrained in accordance with Section 1.12, Proportioning, Article 1.12.4.

1.17.4 CONCRETE FOR VERY SEVERE EXPOSURE (1993) Concrete for very severe exposure shall be made using Type V portland cement with a 5% maximum tricalcium aluminate content plus pozzolan. The pozzolan used should have been determined by tests to improve the sulfate resistance of concrete containing a cement with a maximum tricalcium aluminate content of 5% or less. The concrete shall contain not less than 660 lb of cement per cu yd. The concrete shall be air-entrained in accordance with Section 1.12, Proportioning, Article 1.12.4.

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Type III may also be specified to meet either the 5% or 8% tricalcium aluminate limitation. In certain areas the tricalcium aluminate content of other types of cement may be less than 5% or 8%. Sulfate resisting cement will not increase resistance to some chemically aggressive solutions, for example ammonium nitrate. The special provisions of the project specifications shall cover all special cases.

1.17.5 CONCRETE FOR ALKALI SOILS OR ALKALI WATER (2004) When concrete mix designs include cementitious materials other than portland cement, resistance to the harmful effects of exposure to alkali soils or alkali water shall be determined by tests, or by experience from using materials from the same sources.

1.17.6 CONSTRUCTION JOINTS (1993) Wherever possible, placing of concrete shall be continuous until completion of the section or until the concrete is at least 18 inches above ground or water level. If construction joints are required they shall be minimized, and all construction joints shall be made as described in Section 1.11, Concrete Jointing and Section 1.14, Depositing Concrete, Article 1.14.9.

1.17.7 MINIMUM COVER (1993) Reinforcing steel or other corrodible metal shall have a cover of not less than 4 inches of concrete.

1

1.17.8 PLACEMENT OF CONCRETE (1993) Alkaline water or soils shall not be in contact with the concrete during placement and for a period of at least 72 hours thereafter.

3 SECTION 1.18 CURING 1.18.1 GENERAL (2000) a.

In freezing weather, or when there is likelihood of freezing temperatures within the specified curing period, suitable and sufficient means must be provided before concreting, for maintaining all concrete surfaces at a temperature of not less than 50 degrees F (10 degrees C) for a period of not less than 7 days after the concrete is placed when Type I, IA, II or IIA portland cement is used, and not less than 3 days when Type III or IIIA portland cement is used.

b. The temperature of concrete surfaces shall be determined by thermometers placed against the surface of the concrete. Provision shall be made in form construction to permit the removal of small sections of forms to accommodate the placing of thermometers against concrete surfaces at locations designated by the Engineer. After thermometers are placed, the apertures in forms shall be covered in a way to simulate closely the protection afforded by the forms. c.

In determining the temperatures at angles and corners of a structure, thermometers shall be placed not more than 8 inches (200 mm) from the angles and corners. In determining temperatures of horizontal surfaces, thermometers shall rest upon the surface under the protection covering normal to section involved.

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d. Temperature readings shall be taken and recorded at intervals to be designated by the Engineer, over the entire curing period specified, and the temperatures so recorded shall be interpreted as the temperature of the concrete surfaces when the thermometers were placed. e.

When protection from cold is needed to insure meeting these specification requirements, all necessary materials for covering or housing must be delivered at the site of the work before concreting is started and must be effectively applied or installed, and such added heat must be furnished as may be necessary without depending in any way upon the heat of hydration during the first 24 hours after concrete is placed when Type I, IA, II or IIA portland cement is used, or the first 18 hours when Type III or IIIA portland cement is used. The methods of heating and protecting the concrete shall be approved by the Engineer. Chemicals or other foreign materials shall not be mixed with the concrete for the purpose of preventing freezing, unless approved by the Engineer.

f.

When heat is supplied by steam or salamanders, covering or housing of the structure shall be so placed as to permit free circulation of air above and around the concrete within the enclosure, but to the exclusion of air currents from without, except that where salamanders are used, sufficient ventilation shall be provided to carry off gases. Special care shall be exercised to maintain the specified temperature continuously and uniformly in all parts of the structure enclosures, and to exclude cold drafts from angles and corners and from all projecting reinforcing steel. All exposed surfaces in the heated enclosure shall be kept continuously wet during the heating period unless heat is supplied in the form of live steam.

g.

The supervisor responsible for curing procedures shall maintain certification by the American Concrete Institute as a Concrete Flatwork Finisher or Concrete Transportation Construction Inspector.

1.18.2 HOT WEATHER CURING (1993) a.

The temperature of concrete at times of placement shall not exceed 90 degrees F (32 degrees C). When the temperature of the concrete approaches 90 degrees F (32 degrees C), special efforts to prevent too rapid drying out must be made.

b. Continuous wet curing is preferred and shall commence as soon as the concrete has hardened sufficiently to resist surface damage. Wet curing shall be carried out in accordance with the practice recommended under Article 1.18.3. Curing water shall not be much cooler than the concrete to avoid temperaturechange stresses resulting in cracking. Exposed, unformed concrete surfaces shall be protected from wind and direct sun.

1.18.3 WET CURING (1993) a.

All concrete surfaces when not protected by forms, or membrane curing compounds, must be kept constantly wet for a period of not less than 7 days after concrete is placed when Type I, IA, II or IIA portland cement is used, or not less than 3 days when Type III or IIIA portland cement is used.

b. The wet curing period for all concrete which will be in contact with brine drip, sea water, salt spray, alkali or sulfate-bearing soils or waters, or similar destructive agents, shall be increased to 50% more than the periods specified for normal exposures. Salt water and corrosive waters and soils shall be kept from contact with the concrete during placement and for the curing period. c.

When wood forms are left in place during the curing period they shall be kept sufficiently damp at all times to prevent openings at the joints and drying of the concrete.

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1.18.4 MEMBRANE CURING1 (1993) a.

In lieu of wet curing, a concrete curing compound in full conformance to ASTM C309 may be used, with the approval of the Engineer.

b. Liquid Membrane-Forming Curing Compounds shall meet the requirements of ASTM C309: (1) Type 1 (Clear). (2) Type 1D (Clear with Fugitive Dye). (3) Type 2 (White Pigmented). (4) Class B (Solids Restricted to Resin Only). c.

The compounds shall be applied to all exposed concrete surfaces except those areas where concrete or other materials are to be bonded, such as construction joints or areas to be dampproofed or waterproofed.

d. The compound shall be sprayed on finished surfaces as soon as the surface water has disappeared. Spraying equipment shall be of the pressure-tank type with mist producing spray orifice. If forms are removed during the curing period, concrete shall be sprayed lightly with water and the moistening continued until the surface will not readily absorb more water. The curing compound shall then be sprayed on the concrete surface as soon as the moisture film has disappeared.

1

1.18.5 STEAM CURING (1993) Steam curing shall be done in an enclosure capable of containing the live steam in order to minimize moisture and heat losses. The application of the steam shall be delayed from 2 to 4 hours after final placement of concrete to allow the initial set of the concrete to take place. If retarders are used, the waiting period before application of the steam may be increased to 4 to 6 hours. The steam shall be at 100% relative humidity to prevent loss of moisture and to provide excess moisture for proper hydration of the cement. Application of the steam shall not be directly on the concrete. During application of the steam, the ambient air temperature shall increase at a rate not to exceed 40 degrees F (4.5 degrees C) per hour until a maximum temperature of 140 degrees F to 160 degrees F (60 degrees C to 70 degrees C) is reached. This temperature shall be held for 12 to 18 hours or until the concrete has reached the required strength. In discontinuing the steam, the ambient air temperature shall decrease at a rate not to exceed 40 degrees F (4.5 degrees C) per hour until a temperature has been reached about 20 degrees F (-7 degrees C) above the temperature of the air to which the concrete will be exposed. The concrete shall not be exposed to temperatures below freezing for 6 days after casting.

1.18.6 CURING CONCRETE CONTAINING SILICA FUME (2003)2 1.18.6.1 Delays in Implementing Curing Curing of freshly placed concrete as outlined in this Article should be implemented immediately upon having placed the concrete or other measures should be taken to minimize the opportunity for shrinkage cracking to occur.

1 2

See C - Commentary See C - Commentary

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1.18.7 CURING CONCRETE CONTAINING GROUND GRANULATED BLAST-FURNACE SLAG (2004)1 1.18.7.1 General Curing time may have to be extended due to slower strength gain during the initial curing period. 1.18.7.2 Delays in Implementing Curing Curing of freshly placed concrete as outlined in this Article may require implementation sooner than normal if the mix exhibits less bleed water than normal.

1.18.8 CURING CONCRETE CONTAINING FLY ASH (2004)2 Curing procedures and times should be determined from the concrete mix design requirements.

SECTION 1.19 FORMED SURFACE FINISH 1.19.1 GENERAL (2005) The following requirements, except as modified by the Plans or as approved by the Engineer, shall apply to the construction of concrete surfaces exposed upon the completion of the structure: a.

Construct all face forms smooth and watertight. If constructed of wood, size the face boards to a uniform thickness and dress all offsets or inequalities to a smooth surface. Fill and point flush all openings and cracks, as approved by the Engineer, to prevent leakage and the formation of fins.

b. Cast concrete in one continuous operation between prescribed construction limits, true to line with sharp, unbroken edges beveled or rounded as specified. Make joints not shown on the plans only if approved by the Engineer. c.

Mix, place and consolidate concrete so that the aggregate is uniformly distributed and a full surface of mortar, free from air pockets and void spaces, is brought against the form.

d. Remove the forms carefully. Remove any fins or projections neatly as approved by the Engineer. If any small pits or openings appear in the exposed surface of the concrete, or if the removal of bolts used for securing the forms leave small holes, thoroughly saturate the surface with water and neatly fill all such holes, pits, etc., with an approved mortar. Smooth with a wooden float to achieve an even finish. Mix the pointing mortar in small quantities, and use while still plastic.

1 2

e.

Perform all work in connection with the correction of damaged sections, voids or honeycomb as approved by the Engineer.

f.

Do not apply mortar or cement to the surface except to fill pits or voids, tie bolt holes, etc., as provided above, and not by plastering.

See C - Commentary See C - Commentary

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1.19.2 RUBBED FINISH (2005) a.

Do not rub the surface unless called for on the plans or directed by the Engineer.

b. Fill all voids. Then thoroughly wet the surface and rub with a carborundum brick, or similar abrasive, to a smooth, even finish of uniform appearance without applying any cement or other coating.

SECTION 1.20 UNFORMED SURFACE FINISH 1.20.1 GENERAL (2005) a.

After placing and consolidating concrete, strike off and finish with floats and trowels or finishing machines in a manner approved by the Engineer. Finish edges with an edging tool satisfactory to the Engineer. Take care to avoid an excess of water in the concrete and drain or otherwise promptly remove any water that accumulates on the surface. Do not sprinkle dry cement, or a mixture of cement and sand, directly onto the surface.

b. Slope all horizontal surfaces of bridge seats to drain, except those directly under bearing plates. c.

Require the supervisor responsible for finishing unformed surfaces to have and maintain certification by the American Concrete Institute as a Concrete Flatwork Finisher.

1

1.20.2 SIDEWALK FINISH (2005) Float and trowel the top surface of all walks to a smooth finish with a steel trowel. After the water sheen has disappeared, final finish the surface by brushing with a bristle brush. Draw the brush across the walk, at right angles to the edge of the walk. Adjacent strokes should slightly overlap, to produce a uniform surface, moderately roughened by parallel brush marks. The stiffness of the bristles and the time at which the surface is finished shall leave well defined brush marks. Keep the brush clean at all times to avoid depositing mortar picked up during previous strokes.

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1.20.3 FINISHING CONCRETE CONTAINING SILICA FUME (2004)1 For concrete containing silica fume, trial placements and finishing may be required prior to the start of the project.

1.20.4 FINISHING CONCRETE CONTAINING GROUND GRANULATED BLAST-FURNACE SLAG (2004)2 Finishing techniques may have to be adjusted to account for reduced amounts of bleed water.

1.20.5 FINISHING CONCRETE CONTAINING FLY ASH (2004) Finishing may have to be delayed unless the concrete mix was proportioned to avoid delayed setting.

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See C - Commentary See C - Commentary

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SECTION 1.21 DECORATIVE FINISHES Construct special or decorative finishes as called for on the Plans and as set forth in a special specification or special provision.

SECTION 1.22 PENETRATING WATER REPELLENT TREATMENT OF CONCRETE SURFACES1 1.22.1 GENERAL (1993) When called for on the plans, in the specifications or ordered by the Engineer the following requirements shall be applicable to the treatment of exposed concrete surfaces upon completion of the structure or precast member. Water repellent treatment is not intended to be used on surfaces subject to hydrostatic pressure.

1.22.2 SURFACE PREPARATION (2003) a.

Concrete surfaces shall be cleaned by light sand or shot blasting, followed by vacuum cleaning to remove all traces of curing compounds, laitance, dirt, salt, oil, grease, fluids or other foreign material that would prevent penetration or adhesion of the sealer.

b. Concrete surface shall be clean and dry or as recommended by manufacturer. If concrete is subjected to rain or moisture the surface should be allowed to air dry for a minimum of forty-eight (48) hours before treatment. c.

The cleaning process shall not alter the existing surface finish unless specified by the Engineer as an intentional part of the design.

1.22.3 ENVIRONMENTAL REQUIREMENTS (2003) a.

Volatile Organic Compound regulations may vary by individual state. Therefore, it is mandatory that materials selected for use be in total conformance to the applicable legislation of the state within which the work will be performed.

b. Ambient and surface temperatures at time of application shall be as specified by the manufacturer but not less than 40 degrees F (5 degrees C) or greater than 100 degrees F (38 degrees C). c.

No rain shall be predicted for a minimum of 12 hours after completion of water repellent treatment.

d. No precipitation shall occur within 24 hours preceding application.

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e.

No wind shall be predicted of velocity, per the manufacturer, greater than that which will cause an improper application rate to drift, etc.

f.

Adjoining surfaces of other materials shall be protected unless solvent carrier is certified as harmless to these materials by water repellent manufacturer.

See C - Commentary

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1.22.4 APPLICATION (2003) a.

The penetrating water repellent treatment solution shall be applied in strict accordance with manufacturer’s instructions and not diluted or altered unless specified by the manufacturer. Equipment for the application of the water-repellent treatment shall be clean of foreign materials and approved by the Engineer before use. The sealer shall be applied by brushing, spraying or rolling, as recommended by the manufacturer.

b. Surface treatment of new concrete prior to 28 days curing is not permitted, unless approved by the manufacturer and the Engineer. c.

The sealer manufacturer should be consulted on the recommended treatment of cracks.

d. Follow all safety precautions required by occupational jurisdiction. e.

A minimum of two (2) coats of water-repellent treatment is recommended to achieve uniform coverage. The second and each additional coat shall be applied perpendicular to the previous coat. Care shall be taken when applying each coat, such that running or puddling does not occur. Each coat shall be allowed to dry for a minimum of two (2) hours before the next coat is applied. The final coat shall be allowed to dry according to the manufacturer’s instructions before applying ballast and track.

1.22.5 MATERIALS (2003) a.

The penetrating water repellent material shall consist of an isobutyltrialkoxy silane, n-octyltrialkoxy silane or iso-octytrialkoxy silane dissolved in a suitable solvent that will produce a hydrophobic surface covalently bonded to the concrete. Only one (1) brand and specific type of penetrating sealer shall be used on each individual concrete element (i.e., each pier, deck, abutment, etc.). The penetrating sealer must be a one part liquid, with no field blending required.

b. Qualities of the material to be furnished for the project shall be tested and results certified by an independent testing laboratory with report provided to the owner. The following tests shall be performed on standardized laboratory specimens:

1

3

(1) Water Penetration. ASTM C642–50 Day Soak less 1% Absorption (untreated specimen 4%, 0.2% absorption). (2) Water Penetration. National Cooperative Highway Research Program Report 244–21 Day Soak– Effective Average Minimum 80% (Series II). (3) Vapor Transmission. National Cooperative Highway Research Program Report 244–Minimum 100%. (4) Surface Appearance. No change in surface appearance or texture. (5) Penetration. Oklahoma DOT OHD L-34 Visible Average 0.15 inches. (6) Drying Time. Dry and ready for use 1 hour after application. (7) Accelerated Weathering. ASTM G23–2000 hours are weatherometer–Maximum 3% loss of effectiveness. (8) Water Penetration. Alberta DOT Type 1 Class B minimum.

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Concrete Structures and Foundations (9) Salt Water Ponding. AASHTO T-259–Maximum 1.50 lb per cubic yard at 1/16 inch to 1/2 inch; 0.75 lb per cubic yard at 1/2 inch to 1 inch. (10) Traction – ASTM E303. No change when treated surface is compared to control surface. Measured in British Pendulum Numbers.

1.22.6 QUALITY ASSURANCE (1993) a.

The manufacturer shall provide written certification of the quality of the product being offered and issue a warranty as to its effectiveness when it is applied in accordance with the manufacturer’s specifications.

b. Manufacturer shall have an established Quality Assurance Program with the Program available to the owner or buyer. c.

Pre-Test. An eight square feet (0.75 square meter) test panel on the job shall be treated and evaluated in accordance with the primary water repellent manufacturer’s recommendations and written test procedures which would allow the water repellent to cure for a minimum of 5 days. Two test cores (minimum 3 inches (75 mm) diameter and 3 inches (75 mm) deep) should be taken at locations determined by the Engineer. In the presence of the manufacturer, or one of its representatives, the cores should be split by chisel. One core should be retained by the Engineer. The water repellent material shall have penetrated the core at least 1/8 inch (3 mm) (avg) and shall appear as a band of non-wettable concrete.

d. Test Data. All test data submitted by the water repellent manufacturer must be data generated by an independent testing laboratory. Product tests must be totally controlled by the testing laboratory. Specimens cannot be pre-treated by the manufacturer.

1.22.7 DELIVERY, STORAGE AND HANDLING (1995) a.

Materials shall be delivered to job site in manufacturer’s original undamaged containers with labels and seals intact.

b. Materials shall be stored in accordance with manufacturer’s requirements and in a dry area with a temperature range of not less than 32 degrees F (0 degrees C) and not more than 120 degrees F (49 degrees C). Adequate ventilation shall be provided, away from sources of ignition. c.

Manufacturer’s application instructions and Material Safety Data Sheet shall be consulted for additional safety instructions.

SECTION 1.23 REPAIRS AND ANCHORAGE USING REACTIVE RESINS1 1.23.1 GENERAL (2003) a.

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This recommended practice covers reactive resin polymer materials (i.e. epoxy) used for concrete repairs and installation of anchor bolts and other miscellaneous items in concrete.

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b. The material shall be a non-metallic, non-shrinking polymer resin supplied in prepackaged and/or premeasured containers. It shall contain no rust or corrosion promoting agents and shall be moisture insensitive. c.

Packaged stability of each component in original unopened containers stored in temperatures between 40 degrees F (5 degrees C) and 90 degrees F (32 degrees C) shall be a minimum of six months. The mixing instructions, setting time and expiration date of the material shall appear on each container.

1.23.2 SURFACE PREPARATION (2003) a.

The surface of the concrete should be prepared per the manufacturer’s recommendations for the type of application being conducted.

b. The concrete surface shall be clean and dry, with no traces of curing compounds, laitance, dirt, salt, oil, or grease.

1.23.3 APPLICATION (2003) a.

The reactive resins should be chosen to provide the requirements (i.e. viscosity, strength, flexibility, adhesion etc.) of the specific repair to be performed. The specific type, grade and class of material is to be selected by the Engineer in accordance with the recommendations of the manufacturer.

1 SECTION 1.24 HIGH STRENGTH CONCRETE1 1.24.1 GENERAL (1995) a.

The following specifications shall apply to structures with a minimum specified concrete compressive strength of 6,000 psi (41 MPa) and made with portland cement concrete. These provisions do not apply to “exotic” materials and techniques such as polymer-impregnated concrete, polymer concrete, or concrete with artificial aggregates.

b. The compressive strength of production concrete shall be tested at 7 and 28 days and at other times as required by the Engineer in accordance with ASTM C39.

1.24.2 MATERIALS (1995) Trial batches containing the materials to be used on the job shall be prepared at the proposed slump and tested to determine compressive strength. Unless tests on additional trial batches are performed, materials shall be of the same type, brand and source of supply throughout the duration of the project. 1.24.2.1 Cement a.

Cement mill test reports shall be submitted by cement suppliers for each shipment of cement. Silo test certificates shall be submitted for the previous 6 to 12 months. Cement uniformity in accordance with ASTM C917 shall be reported. Variations shall be limited to the following: Tricalcium silicate (C3S). . . . . . . . . . . . . . . . . . . . . .

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4%

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Ignition Loss. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.5% Fineness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375 cm2/g (Blaine) Sulfate (SO3). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.20% of optimum b. Mortar cube tests shall be performed in accordance with ASTM C109. 1.24.2.2 Chemical Admixtures Chemical admixtures shall conform to the following ASTM specifications: Air-entraining admixtures . . . . . . . . . . . . . . . . . . . . ASTM C260 Retarders. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ASTM C494, Types B and D Normal-setting water reducers . . . . . . . . . . . . . . . . ASTM C494, Type A High-range water reducers . . . . . . . . . . . . . . . . . . . ASTM C494, Types F and G Accelerators. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ASTM C494, Types C and E 1.24.2.3 Mineral Admixtures Mineral admixtures consist of fly ash (Class C and F), silica fume and ground granulated blast-furnace slag. Fly ash shall conform to ASTM C618 specifications. Methods for sampling and testing of fly ash shall conform to ASTM C311. Silica fume shall conform to ASTM C1240. Slag shall conform to ASTM C989. 1.24.2.4 Aggregates Fine and coarse aggregate shall meet the requirements of ASTM C33. 1.24.2.5 Water Water for use in high-strength concrete shall conform to Section 1.5, Water. Acceptance requirements specified in Table 1 of ASTM C94 shall be met.

1.24.3 CONCRETE MIXTURE PROPORTIONS (1995) Trial batches shall be performed to generate sufficient data to obtain optimum mixture proportions.

SECTION 1.25 SPECIALTY CONCRETES 1.25.1 GENERAL This manual article describes and provides requirements for specialty concretes that may be used in railroad construction. Before any specialty concrete is used, additional investigation of specific and detailed specifications shall be made.

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1.25.2 SULFUR CONCRETE1 1.25.2.1 General Sulfur concrete is a thermoplastic material produced by mixing heated aggregate 350F to 400F (177C to 204C) with modified sulfur cement and fine mineral filler (ambient temperature) to prepare a well-mixed concrete that is maintained within a temperature range of 270F to 285F (132C to 141C) until placed. The ACI Manual of Concrete Practice contains detailed information. 1.25.2.2 Design a.

Mixture design for sulfur concrete is different from portland cement concrete.

b. Aggregate for sulfur concrete shall conform with ASTM C33. c.

Reinforcement may be with reinforcing steel, epoxy-coated reinforcing steel or with fibers.

1.25.2.3 Handling The requirements for mixing/transporting equipment are defined by the unique thermoplastic characteristic of sulfur concrete. Sulfur concrete must be maintained in a molten state and continuously monitored to maintain the temperature range of 270F (133C) to 285F (147C). The concrete mixture must be thoroughly mixed so the molten sulfur cement adequately coats the fine and coarse aggregate and mineral filler.

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1.25.2.4 Placing Sulfur concrete can be placed in either wooden or metal forms.

1.25.3 HEAVYWEIGHT CONCRETE

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1.25.3.1 Design Heavyweight concrete, unless otherwise stipulated, shall conform to the other requirements of Chapter 8, Part 1, shall be made with Type II cement, and shall be proportioned as directed by the Engineer, with not more than 6 gal. (22.7 L) of water per 94 lb (42.8 kg) of cement. Where heavyweight concrete is required for counterweights, the coarse aggregate shall be trap rock, iron ore, or other heavy material or the concrete may incorporate steel punchings or scrap metal. The mortar shall be composed of 1 part of cement and 2 parts of fine aggregate. Fine metallic aggregate shall consist of commercial chilled-iron or steel shot or ground iron, meeting SAE J 444a. All metallic aggregate shall have a specific gravity of 6.50 or greater and be clean and free from foreign coatings of grease, oil, machine shop compounds, zinc chromate, loose scale, and dirt. The maximum weight of heavy concrete shall be 315 lb per cu feet (5,050 kg per cu m). 1.25.3.2 Placing a.

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Heavyweight concrete shall be placed in layers and consolidated with vibrators or tampers. Heavyweight concrete usually will not “flow” in a form and must be placed uniformly throughout the area and compacted in place with a minimum of vibration. Under no circumstances shall an attempt be made to move heavyweight concrete during consolidation with vibration equipment. Layers shall be limited to a maximum 12 inch (300 mm) thickness. Consolidation shall be by internal vibrators to achieve uniform and optimum density. In heavyweight concrete vibrators have a smaller effective area, or radius of action; therefore greater care shall be exercised to insure that the concrete is properly consolidated.

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Vibrators shall be inserted at closely spaced intervals and only to a depth sufficient to cause complete intermixing of adjacent layers. Counterweights containing punchings or scrap metal or iron ore aggregates shall be enclosed in steel boxes. b. Heavyweight concrete not enclosed in steel boxes shall be adequately reinforced. 1.25.3.3 Determining Weight For ascertaining the weight of the concrete, test blocks having a volume of not less than 0.1 cu m (4 cu feet) for ordinary concrete, and 1 cu feet (0.03 cu m) for heavy concrete, and 1 cu feet (0.03 cu m) for the mortar for heavy concrete, shall be cast at least 30 days before concreting is begun. Two test blocks of each kind shall be provided, and one weighed immediately after casting and the other after it has cured for 28 days.

C - COMMENTARY The purpose of this part is to furnish the technical explanation of various Articles in Part 1, Materials, Tests and Construction Requirements. In the numbering of Articles of this section, the numbers after the “C-” correspond to the Section/Article being explained.

C - SECTION 1.2 CEMENT C - 1.2.2 SPECIFICATIONS (2004) The use of slag cement Types ‘S’ and ‘S(A)’ as defined in Standard Specification C 595 is not included in this recommended practice as these cements are not intended to be used alone in producing structural concrete.

C - SECTION 1.3 OTHER CEMENTITIOUS MATERIALS C - 1.3.3.1(a) Silica Fume One of the primary benefits of including silica fume in a concrete mix design is to reduce the permeability of the hardened concrete. Porosity will be significantly reduced if proper proportioning, pre-construction testing, and curing methods are used. Long term durability, resistance to chemical attack including sulphate attack, and penetration of chloride ions can all be favorably affected. Other possible benefits include improved resistance to abrasion. Silica fume has been used to obtain both of these properties. However, the replacement method may inhibit other special properties. C - 1.3.3.1(b) Fly Ash All fly ashes contain pozzolanic materials, but some fly ashes also exhibit cementitious properties of their own. Factors affecting this are the glass content, its fineness and gradation, and silica or silica-plus-alumina content. There is therefore a wide variation in pozzolanic and cementitious efficiency of different fly ashes, which cannot be predicted by selecting Class C, Class F or Class N. Direct tests of strength development, and tests to determine the efficiency of fly ash to produce special properties such as sulphate resistance, or resistance to alkali-silica reactions, are necessary. Possible benefits of using fly ash in a concrete mix which is properly designed, deposited and cured include increased long-term strength potential, improved workability and pumpability, reductions in the heat of hydration when using fly ash as a replacement for some of the cement that would otherwise be used, a finer pore structure which reduces the ingress of chloride ions, and improved resistance to sulphate attack and to alkali silica reactions. Possible difficulties in using fly ash include a need to adjust the dosage of air entraining

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admixture, reduced bleeding of fresh concrete, reduced rate of strength gain which could effect form and/or falsework removal parameters, and a need to delay finishing of unformed surfaces under some circumstances. C - 1.3.3.2 Ground Granulated Blast-Furnace Slag When used as provided in this recommended practice, replacement of part of the portland cement that would otherwise be required in a concrete mix design with ground granulated blast-furnace slag may impart several benefits. These include a much reduced permeability, with a consequent reduction of penetration of chloride ions and reductions in corrosion of reinforcement; reduced heat of hydration at early ages; improved sulphate resistance; and reduced levels of alkali silica reactivity. Reductions in alkali silica reactivity are due to reduced permeability, reductions in available alkali, chemical effects, and other effects.

C - SECTION 1.4 AGGREGATES C - 1.4.2.1 General Use of lightweight fine aggregates is not allowed because of their poor performance in all lightweight concrete, and the many difficulties and restrictions to their use.

C - SECTION 1.5 WATER Non-potable water (not fit for human consumption) is being used as mixing water in hydraulic cement concrete to a much larger extent than when the AREMA recommendation effective in 2009 was written. Use of a nonpotable water source requires limiting the solids content of the water. ASTM C1603, which is referenced by ASTM C1602, provides a test method for measurement of the solids content of water by means of measuring the water’s density.

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In addition to limiting the amount of solids in mixing water, maximum concentrations of other materials that impact the quality of concrete must be limited. These include levels of chloride ions, sulfates, and alkalies. ACI 318-08, R 3.4.1 is the requirement that water used to mix concrete must comply with ASTM C1602. As indicated in ACI 318-08, R 3.4.1, ASTM C1602 permits the use of potable water without testing.

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The chief concern over high chloride content is the possible effect of chloride ions on the corrosion of embedded reinforcing steel, prestressing tendons, aluminum embedments or stay-in-place galvanized metal forms. Limitations placed on the maximum concentration of chloride ions that are contributed by the ingredients including water, aggregates, cement, and admixtures are given in ACI 318-08, Chapter 4, Table 4.3.1. ASTM C1602 limits the chloride ions in ppm (parts per million) and only applies to that contributed by the mixing water.

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Test results for non-potable water shall be furnished to the Engineer and approved prior to use.

C - SECTION 1.6 REINFORCEMENT C - 1.6.4 BENDING AND STRAIGHTENING (2003) a.

Field bending and straightening of partially embedded reinforcement bars is discouraged but when this operation is required it should be closely controlled. Construction conditions that make field bending or straightening necessary also make it difficult to control the conditions under which it is done thus making field inspection even more critical. © 2011, American Railway Engineering and Maintenance-of-Way Association

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b. There are numerous papers written on this subject with varying opinions on the best procedures to use. There is ongoing research that should supply additional test results to clarify current assumptions. A few of the current known factors that affected these standards are that: (1) Application of heat appears to be necessary to bend or straighten larger sized rebar but either over heating (above 1800 F (980 C)) or under heating between 450 F (230 C) and 650 F (340 C) can create much reduced rebar strength or even cause failure. (2) Repeated bending and straightening weakens the metal and will result in failure even under the best controlled conditions. (3) Tight bending diameters decreases the metal’s strength. c.

The reworking of reinforcing bars that are partially embedded in concrete involves some level of risk and is not encouraged. Risks may be minimized by using reinforcing bars of a more ductile steel such as A 706 rather than A 615 in locations where field bending and/or straightening will be required. This is awkward from a constructability standpoint.

d. When field bending and straightening of partially embedded bars, for A 615 grade 40 or grade 60 steel, is permitted by the Engineer, an example procedural guideline is the following: (1) Bars of size #3 (#10) through #7 (#22). (a) Bend or straighten bars cold (bars should be above freezing temperature). (b) Do not allow more than one cycle of bending and straightening. (c) Diameter of bends should conform to Part 2, Reinforced Concrete Design, Table 8-2-6. Bends should not exceed 90 degrees. (d) Bending should be done with as smooth an application of force as possible. (e) Straightening should be accomplished by using a steel pipe pushed tight against the bend and with application of force and reset periodically as follows: 1 Steel pipe should have inside diameter 1/8 inch to 3/8 inch (3 mm to 9 mm) larger than outside diameter of bar to be straightened. 2 Steel pipe should be a minimum length of 8 inches (200 mm) times the bar number size of the bar to be straightened to provide sufficient leverage. 3 Straightening pipe should be reset against the bar at 45 degrees for #4 (#13) and smaller bars and at 30 degrees and 60 degrees for #5 to #7 (#16 to #22) bars. 4 Workers must have a firm base from which to apply straightening pressure to reduce the risk of injury if the bar suddenly fails. (2) Bars of size #8 through #11 (#25 through #36). (a) Bend or straighten bars after preheating to 1100 degrees F to 1500 degrees F (590 degrees to 810 degrees C) as measured with temperature sticks. (b) Concrete must be protected from exposure to excessive heat. If necessary protective insulation should be used.

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(c) Atmospherically cool bars. Do not expose to water or other cooling mediums. (d) Do not allow more than one cycle of bending and straightening. (e) Diameter of bends should conform to Part 2, Reinforced Concrete Design, Table 8-2-6. (f) Bending should be done with as smooth an application of force as possible. (g) Straightening should be accomplished by using a steel pipe pushed tight against the bend and with application of force and reset periodically. (h) Steel pipe should have inside diameter 1/8 inch to 3/8 inch (3 mm to 9 mm) larger than outside diameter of bar to be straightened. 1 Steel pipe should be long enough to provide sufficient leverage. 2 Straightening pipe should be reset progressively against the bar around the bend. 3 Workers must have a firm base from which to apply straightening pressure to reduce the risk of injury if the bar suddenly fails.

C - SECTION 1.12 PROPORTIONING C - 1.12.10 SPECIAL PROVISIONS WHEN USING CEMENTITIOUS MATERIALS OTHER THAN PORTLAND CEMENT (2009)

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C - 1.12.10.2 Requirements When Using Silica Fume in Concrete ACI 211.1 provides guidance for proportioning concrete containing silica fume. C - 1.12.10.2.2 High-Range Water Reducing Admixtures

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Concrete containing silica fume will have a greater water demand to maintain workability than concrete not containing silica fume. However, this additional water is rarely provided since it would negate the potential benefits of using silica fume. High range water reducers (superplasticizers) are commonly used instead. If a superplasticizer is not used, then the fresh concrete would appear sticky and not consolidate properly. Concrete containing silica fume is more cohesive and less prone to segregation than other fresh concretes. It is common to increase the slump by 2 inches (50mm) from what would otherwise be provided. The use of a high range water reducing admixture will also benefit the rate of strength gain. Initial strength gain will be slower when using silica fume. Twenty-eight (28) to ninety (90) day strengths can be enhanced using silica fume, however, as long as the water to cementitious material ratio is kept low by using a high range water reducing admixture. C - 1.12.10.2.3 Entrained Air Concrete containing silica fume will require more air entraining admixture than normal concrete to obtain the desired result. The amount will depend upon the amount of silica fume and the type of air entraining admixture used. C - 1.12.10.3 Requirements When Using Fly Ash in Concrete ACI 211.1 provides guidance for proportioning concrete containing fly ash.

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Concrete Structures and Foundations C - 1.12.10.3.3 Testing to Verify Mix Design Reduced bleeding rates in fresh concrete may result in raising the possibility of plastic shrinkage cracking. Initial setting time and the rate of early strength gain may be retarded by the use of fly ash. Setting time requirements can also delay finishing. The rate of early strength gain can be satisfactory with a properly designed and tested mix, which usually includes increases in the total cementitious material (fly ash plus portland cement) content. The proportion of fly ash to cement may be varied from winter to summer. Air entraining admixture requirements will be different for concrete containing fly ash to achieve the same amount of air that would have resulted in concrete not containing fly ash. The heat of hydration can be reduced if the fly ash is used to replace some of the portland cement instead of being added as additional cementitious material. The long term strength of the hardened concrete may be enhanced using fly ash. Improved performance against sulphate attack and resistance to alkali aggregate reactivity will require the addition of sufficient quantities of cementitious materials other than portland cement that may exceed the proportions of what would be used otherwise. C - 1.12.10.3.4 Water to Cementitious Materials Ratio The improved workability and pumpability of concrete containing fly ash will permit reductions in the amount of water. This is due to the spherical shape of the fly ash particles imparting improved workability; and to the reduced unit weight of fly ash as compared with cement which can result in increased paste content when cement replacement with fly ash is by weight. Reductions in the amount of water can also reduce the possibility of plastic shrinkage. The measurement of water as a proportion of total cementitious material by weight provides a consistent approach which is also applicable when using blended cements. C - 1.12.10.4 Requirements When Using Ground Granulated Blast-Furnace Slag in Concrete ACI 211.1 provides guidance for proportioning concrete containing ground granulated blast-furnace slag. C - 1.12.10.4.1 General The amount of ground granulated blast-furnace slag as a proportion of the total cementitious material normally varies between 25% and 70%, with approximately 40% to 50% being a common proportional amount. A maximum amount of 50% can also be applicable, per Table 8-1-12. Final concrete properties will also be determined by the portland cement used, the grade or reactivity of the ground granulated blast-furnace slag, curing conditions, and the special properties for which the material was used, such as reduced early heat of hydration. C - 1.12.10.4.2 Water-Reducing Admixtures Concrete containing ground granulated blast-furnace slag will have a slower rate of strength gain than normal portland cement concretes, especially at early ages, unless the water content is reduced. C - 1.12.10.4.3 Accelerators Significant retardation has been observed at low temperatures when using ground granulated blast-furnace slag. Accelerating admixtures can be used to counter this effect. However, the source and reactivity of the ground granulated blast-furnace slag, the ratio of ground granulated blast-furnace slag to normal portland

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cement, the characteristics of the cement, and the water to cementitious material ratio will also influence set time. Therefore the need for pre-construction tests, as noted previously, is also confirmed here. C - 1.12.10.4.4 Proportioning of Aggregates Portland cement concrete containing ground granulated blast-furnace slag will have a higher volume of paste than normal portland cement concrete when both mixes are proportioned by weight (mass). The proportional difference is due to ground granulated blast-furnace slag being lighter than portland cement. The coarse to fine aggregate ratio can therefore be increased or the water to cementitious material ratio can be reduced. Increases in the amount of coarse aggregate may be beneficial to finishing, which may aid in reducing shrinkage and potential for scaling. The natural tendency of concrete containing ground granulated blastfurnace slag is to be more workable and easier to place and consolidate. This will compensate for some increases in the proportion of coarse aggregate.

C - SECTION 1.13 MIXING C - 1.13.5 REQUIREMENTS WHEN USING SILICA FUME IN CONCRETE (2009) C - 1.13.5.2 Workability of Delivered Concrete Refer to Commentary for Article 1.12.10.2.2.

C - SECTION 1.14 DEPOSITING CONCRETE

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C - 1.14.12 PLACING CONCRETE CONTAINING SILICA FUME (2004) C - 1.14.12.1 Protection from Moisture Loss Fresh concrete containing silica fume displays significantly less bleeding than normal concrete. There is therefore the potential that shrinkage cracking will occur if the evaporation rate exceeds the bleeding rate. Increased amounts of silica fume will increase the potential for such shrinkage cracking. Other conditions including adverse temperatures, wind, or low humidity could also increase the potential for shrinkage cracking. Evaporation retarders, fogging, and protection from the wind during the placement stage are options which may be included in the project specifications to counter this. Measures to protect against early moisture loss in concrete containing silica fume should included in the project specifications. Shrinkage cracking can be eliminated through the use of proper procedures. C - 1.14.12.2 Consolidation The cohesive nature of concrete containing silica fume makes it susceptable to excessive entrapment of air, even with higher slumps. Proper placing techniques are essential to achieving any special properties for which silica fume is specified.

C - SECTION 1.18 CURING C - 1.18.4 MEMBRANE CURING (1993) a.

With the emergence of legislation designed to limit the amounts of Volatile Organic Compound (V.O.C.) emission, it is incumbent upon specifying Engineers to be cognizant of these new laws.

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b. Volatile Organic Compound regulations may vary by individual state. Therefore, it is mandatory that materials selected for use be in total conformance to the applicable legislation of the state within which the work will be performed.

C - 1.18.6 CURING CONCRETE CONTAINING SILICA FUME (2003) C - 1.18.6.1 Delays in Implementing Curing Refer to the commentary concerning Article 1.14.12.1.

C - 1.18.7 CURING CONCRETE CONTAINING GROUND GRANULATED BLASTFURNACE SLAG (2004) C - 1.18.7.1 General Strength gain may be slower at low temperatures during the initial curing period when the ground granulated blast-furnace slag is used to replace part of the portland cement in a mix. The amount of retardation will depend upon the temperature, the proportions and characteristics of each of the cementitious materials, the total content of cementitious material and other factors. Little, if any, retardation occurs at temperatures above about 70° F (21° C), and the behavior of concretes containing ground granulated blast-furnace slag under elevated curing temperatures has been reported to be good. Refer also to the commentary concerning accelerators, in Article 1.12.10.4.3. C - 1.18.7.2 Delays in Implementing Curing Ground granulated blast-furnace slags that are finer than portland cements are likely to produce mixes with reduced bleed water when the combined amount of cementitious material is not also reduced.

C - 1.18.8 CURING CONCRETE CONTAINING FLY ASH (2004) Time of setting and the rate of early strength gain will have been prescribed in arriving at the mix design and proportioning. This will have determined the water to cementitious material ratio that, if high, may require special curing measures to avoid plastic shrinkage cracking. Special curing requirements may also result if a minimum specified strength is to be attained before subjecting the hardened concrete to freeze-thaw cycles or to chlorides.

C - SECTION 1.20 UNFORMED SURFACE FINISH C - 1.20.3 FINISHING CONCRETE CONTAINING SILICA FUME (2004) The tackiness and lack of bleed water of concrete containing 10% to 20% silica fume will make finishing of unformed surfaces more difficult and may require trial placements in order to determine finishing methods. The use of evaporation retarders and other methods to reduce evaporation will aid the finishing process.

C - 1.20.4 FINISHING CONCRETE CONTAINING GROUND GRANULATED BLASTFURNACE SLAG (2004) See the commentary for Article 1.18.7.2 regarding delays in implementing curing procedures.

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C - SECTION 1.22 PENETRATING WATER REPELLENT TREATMENT OF CONCRETE SURFACES C - 1.22.1 GENERAL (1993) a.

Penetrating sealers are primarily intended for use in sealing the surface of concrete structures against intrusion of water and chlorides, while having a minimum effect on the concrete’s ability to breathe (transfer water vapor). Of the 21 materials tested and addressed in National Cooperative Highway Research Program Report 244, only the silane exhibited a measurable penetration effect. NCHRP Report 244: “This silane material produces a non-wettable concrete surface to a depth of 0.10 inch (2.5 mm). The other materials tested in this project, including boiled linseed oil, generally do not produce a measurable penetration or a measurable thickness of non-wettable concrete. Most of these other materials are coatings and should not be referred to in specifications as ‘penetrating sealers’.”

b. With the emergence of new legislation designed to limit the amounts of Volatile Organic Compound (V.O.C.) emission, it is incumbent upon specifying Engineers to be cognizant of these new laws.

C - 1.22.2 SURFACE PREPARATION (2003) a.

Good surface preparation, prior to applying the sealer, is essential to achieve the desired maximum penetration into the concrete. When the sealers penetrate below the surface of the concrete, they chemically bond to the concrete and prevent water and chlorides from entering the concrete. Contaminants must be totally removed and the surface allowed to dry. Properly applied sealers shall provide protection from the ingress of water and chlorides for a period of five (5) years.

1

b. Surface preparation may be accomplished by: (1) High pressure water (hot or cold).

3

(2) Chemical cleaners. (3) Sandblasting. (4) Shotblasting. c.

When high pressure water is employed, all surfaces shall be free of standing water or moisture at the time of the treatment which could restrict surface penetration. Care must be taken when using highpressure water steam to avoid excessive exposure of coarse aggregate.

C - 1.22.3 ENVIRONMENTAL REQUIREMENTS (2003) There is some question of the effects of high temperature on water repellent treatments as one author states that high temperatures actually speed up the condensation reaction of monomeric silanes into oligomeric siloxanes. Because of this, application of treatment at temperatures over 100 degrees F should be carefully considered.

C - 1.22.4 APPLICATION (2003) Consult the manufacturer’s material safety data sheet and application instructions for further safety information.

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C - 1.22.6 QUALITY ASSURANCE (1993) a.

The owner of a concrete structure or buyer of a concrete sealer shall be satisfied that the manufacturer can furnish the quality assurance claimed. This can be done by comparing test results of the product against test results obtained by independent test studies, several of which are listed in the References found at the end of this Chapter. The buyer or owner should also be satisfied that an agent or distributor who makes such claims or offers such a warranty has the full authority to do so by the manufacturer.

b. The owner of a concrete structure or buyer of a concrete sealer should seek out an applicator (either owner’s own employee or outside contractor) approved by the manufacturer in order to validate its warranty.

C - SECTION 1.23 REPAIRS AND ANCHORAGE USING REACTIVE RESINS a.

Reactive resins may be selected for inclusion with fine and/or coarse aggregate in polymer concrete or included with a clean, dry, fine aggregate in a polymer mortar. Reactive resins can be used in chemical bonding systems as an adhesive for concrete or as a binder for mortars or concrete.

b. Reactive resins may also be used neat (without the addition of aggregate) as a bonding agent, as a bonding coat for adhesion, as well as anchoring between metallic inserts and concrete when the spacing between the metallic insert and the interior wall of the bored hole in the concrete is 1/8 inch (3.2 mm) minimum. While the general rule for anchor bolt embedment is ten (10) to fifteen (15) times the bolt diameter, the embedment shall be designed based upon loads to be carried.

C - SECTION 1.24 HIGH STRENGTH CONCRETE C - 1.24.1 GENERAL (1995) a.

With the advances in concrete technology during the last few decades, the commonly achievable limits of concrete strength have steadily increased. The use of high-strength concrete in construction has also increased. Concrete compressive strengths approaching 20,000 psi (138 MPa) have been used in cast-inplace concrete buildings. High-strength concrete has also been used in bridge structures. Research has been conducted on the performance of high-strength prestressed concrete in bridges.

b. Because of the continuing advances in technology, the definition of the minimum concrete compressive strength for high-strength concrete is changing with time. Different geographic locations may also have varying limits for what they consider as high-strength concrete. The ACI Committee 363 report on highstrength concrete (ACI 363R-92) defines high-strength as having compressive strengths of 6,000 psi (41 MPa) or greater. c.

The ACI Committee 363 report on high-strength concrete provides detailed information on material and structural aspects of high-strength concrete.

C - 1.24.2 MATERIALS (1995) a.

To achieve adequate consistency and quality of high-strength concrete, stringent control of constituent materials is necessary. Variations in type, brand and source of supply of the components can have major influences on the properties of high-strength concrete. Therefore, emphasis is placed on the preparation of trial batches and maintenance of the same component materials throughout the project.

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b. Testing and comparison of laboratory and production-sized trial batches are needed to establish the required strength of laboratory trial batches. This is because the laboratory trial batches have often exhibited significantly higher strength than production batches. C - 1.24.2.1 Cement The quality and consistency of cement used in high-strength concrete need verification through mill test reports, and mortar cube tests. The most suitable types of cement for high-strength concrete are Type I or Type III with minimum 7-day cube compressive strength of 4500 psi (31 MPa). In addition, cement should not show signs of false set. C - 1.24.2.2 Chemical Admixtures a.

Chemical admixtures are commonly used in high-strength concrete to increase compressive strength through reduction of water, control rate of hardening, accelerate strength gain, and improve workability and durability. Performance of all materials in high-strength concrete as a whole should be considered when selecting the type, brand and dosage of any admixtures.

b. Air-entraining admixtures (ASTM C260) are used to improve durability and freeze-thaw resistance. However, air voids have the effect of reducing compressive strength and their use is therefore recommended only when durability is a concern. Incorporation of entrained air may reduce strength at a rate of 5% to 7% for each percent of air in the mix. c.

Retarders (ASTM C494, Types B and D) are used to control early hydration and hardening of concrete. Factors such as an increase in strength and temperature effects should be considered.

1

d. Normal-setting water reducers (ASTM C494, Type A) are used to increase strength without affecting the rate of hardening. High-range water reducers (ASTM C494, Types F and G) are used to increase strength (decrease water demand) especially high early strength (24 hours) or increase slump. Matching the admixture to the cement used (both in type and dosage rate) is an important consideration. e.

High-range water reducers (ASTM C494, Types F and G) are often used in high-strength concrete mixtures and are essential with the very high-strength concretes to ensure adequate workability with low water-cementitious ratios. Further information is available in ACI SP-68.

f.

Accelerators (ASTM C494, Types C and E) are not normally used in high strength concrete except when early form removal is critical. Accelerators will normally be counterproductive in long-term strength development.

C - 1.24.2.3 Mineral Admixtures a.

Mineral admixtures such as fly ash, silica fume, and ground granulated blast-furnace slag have been widely used in high-strength concrete. Variations in physical and chemical properties of mineral admixtures (even when within tolerance of specifications) can have a major influence on properties of high-strength concrete.

b. Fly ash generally reduces early strength gain and improves late age strength of concrete. There are two (2) classes of fly ash available (ASTM C618). Class F fly ash is generally available in eastern U.S. and Canada and has pozzolanic properties, but little or no cementitious properties. Class C fly ash is generally available in western U.S. and Canada and has pozzolanic and some autogenous cementitious properties. An ignition loss of 3% or less is desirable, although ASTM C618 permits a higher value. ASTM C311 provides standard test methods for sampling and testing of fly ash or natural pozzolans.

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c.

Silica fume consists of very fine spherical particles, approximately 100 times smaller than the average cement particle, and is a highly effective pozzolanic material. It is used in concrete in applications where abrasion resistance and low permeability are desired. Normally, silica fume content ranges from 5% to 15% of portland cement content. The availability of high-range water reducers has facilitated the use of silica fume in high-strength concrete. However, concrete with silica fume has an increased tendency to develop plastic shrinkage cracks. Therefore steps should be taken to prevent rapid water evaporation.

d. Ground granulated blast furnace slag (ASTM C989) is used as a partial replacement for portland cement in various proportions to enhance different properties of concrete. Research has shown promise for its use in high-strength concrete. C - 1.24.2.4 Aggregates a.

The optimum gradation of fine aggregates for high-strength concrete is mainly determined by its effect on water requirement rather than physical packing. High-strength concrete has high contents of fine cementitious materials and therefore the grading of fine aggregates is relatively unimportant compared to conventional concrete. Fine aggregates with rounded particle shapes and smooth texture require less mixing water and are therefore preferred in high-strength concrete.

b. The desirable maximum size of coarse aggregate should be 1/2 inch (13 mm) or 3/8 inch (10 mm). Mix designs with maximum size aggregate of 3/4 inch (19 mm) and 1 inch (25 mm) have also been successfully used. Many studies have shown that crushed stone produces higher strengths than rounded gravel because of improved mechanical bond in angular particles. However, accentuated angularity can result in higher water requirement and reduced workability and therefore should be avoided. The ideal aggregate should be clean, cubical, angular, 100% crushed aggregate with a minimum of flat and elongated particles. It would also be beneficial if the aggregate has moderate absorption capability to provide added curing water for high-strength concrete. c.

High-strength concrete requires high-strength aggregates. However, this trend holds only true until the limit of the bonding potential of the cement-aggregate combination is reached.

C - 1.24.3 CONCRETE MIXTURE PROPORTIONS (1995) a.

High-strength concrete mix proportioning is a more critical process than the design of normal-strength concrete mixtures. Generally, chemical admixtures and pozzolanic materials are added and the attainment of low water-cementitious ratio is essential. Trial batches are often required to optimize constituent materials and mixture proportions. Additional information can be found in ACI 211.1, ACI 211.4, and ACI Publication SP-46.

b. The relationship between water-cementitious ratio and compressive strength in high-strength concrete is similar to that identified for normal-strength concrete. The use of high-range water reducers has provided lower water-cementitious ratios and higher slumps. Water-cementitious ratios by weight for high-strength concrete typically have ranged from approximately 0.27 to 0.50. The compressive strength of concrete at a given water-cementitious ratio varies widely depending on the cement, aggregates and admixtures used. The quantity of liquid admixtures, particularly high-range water reducers, has sometimes been included in the calculation of water-cementitious ratio. When silica fume as a slurry is used, its water content must be included in the water-cementitious ratio. c.

Typical cement contents in high-strength concrete range from 660 lb/cy (390 kg/m3) to 940 lb/cy (560 kg/m3). For any given set of materials in a concrete mixture, there may be an optimum cement content that produces maximum concrete strength. The strength of concrete may decrease if cement is added in excess of the optimum level. The strength for any given cement content will vary with the water demand

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of the mixture and the strength-producing characteristics of that particular cement. Loss of workability (stickiness) will be increased as higher cement amounts are used. d. The maximum temperature desired in the concrete element may limit the quantity or type of cement. Addition of ice, set retarders or pozzolans may be considered. C - 1.24.3.1 Aggregate Proportions Table 3.1 in the ACI 363R-92 suggests the amounts of coarse aggregate based on the fineness modulus of sand for the purpose of initial proportioning. In general, the least sand consistent with necessary workability has given the best strengths for a given paste. The use of smaller coarse aggregates (maximum 3/8 inch (10 mm) to 1/2 inch (13 mm)) are generally beneficial, and crushed aggregates seem to bond best to the cementitious paste. C - 1.24.3.2 Proportioning of Admixtures a.

In high-strength concrete, pozzolanic admixtures have been used to supplement the portland cement from 10% to 40% by weight of the cement content. The use of fly ash has often reduced the water demand of the mixture. Silica fume, on the other hand, dramatically increases the water demand of the mixture which has made the use of retarding and high-range water-reducing admixture (superplasticizing) admixtures a requirement.

b. The amount of conventional water reducers and retarders in high-strength concrete varies depending on the particular admixture and application. In general, the tendency has been to use maximum quantities of these admixtures. Typically, water reductions of 5% to 8% may be increased to 10%. Corresponding increases in fine aggregate content have been made to compensate for the loss of volume due to the reduction of water. c.

Most high-strength concretes contain both mineral admixtures and chemical admixtures. It is common for these mixtures to contain combinations of chemical admixtures. High-range water reducers have performed better in high-strength concretes when used in combination with conventional water reducers or retarders.

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C - 1.24.3.3 Workability a.

High-strength concrete mixtures tend to lose slump more rapidly than lower-strength concrete. If slump is to be used as a field control, testing should be done at a prescribed time after mixing. Concrete should be discharged before the mixture becomes unworkable.

4 b. High-strength concrete, often placed with 1/2 inch (13 mm) maximum size aggregate and with a high cementitious content, is inherently placeable provided attention is given to optimizing the ratio of fine to coarse aggregate. Local material characteristics have a marked effect on proportions. Cement fineness and particle size distribution influence the character of the mixture. Appropriate admixtures improve the placeability of the mixture. c.

Mixtures that were proportioned properly but appear to change in character and become more sticky should be considered suspect and checked for proportions, possible false setting of cement, undesirable air-entrainment, or other changes. A change in the character of a high-strength mixture could be a warning sign for quality control.

C - 1.24.3.4 Trial Batches Frequently, the development of a high-strength concrete program has required a large number of trial batches. In addition to laboratory trial batches, field-sized trial batches have been used to simulate typical production

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conditions. Once a desirable mixture has been formulated in the laboratory, field testing with production-sized batches should be preformed.

C - 1.25.2 SULFUR CONCRETE C - 1.25.2.1 General c.

Sulfur concrete is generally not resistant to alkalis or oxidizers. However sulfur concrete exhibits excellent characteristics of: (1) High strength [in excess of 62 MPa (9,000 psi)] and fatigue resistance; (2) Excellent corrosion resistance against salts and most acids; (3) Extremely rapid set and strength gains and achieves a minimum of 70% to 80% of ultimate compressive strength within 24 hours; (4) Placement year round, above and below freezing temperatures; (5) Very low water permeability.

C - 1.25.2.2 Handling Extreme care should be used when handling sulfur concrete to avoid burns. C - 1.25.2.3 Placing Wall construction should be given special consideration to preclude poor consolidation. Preheating the reinforcing steel and forms using infrared or suitable heaters, plus using insulation on the outside of wall forms should be utilized to retain heat during placement.

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8

Part 2 Reinforced Concrete Design1 — 2010 — TABLE OF CONTENTS

Section/Article

Description

Page

2.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.1 Scope (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.2 Design Methods (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.3 Highway Bridges (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.4 Buildings (2005). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.5 Pier Protection (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.6 SuperStructure Protection (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1.7 Skewed Concrete Bridges (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-2-5 8-2-5 8-2-5 8-2-5 8-2-6 8-2-6 8-2-6 8-2-7

2.2 Notations, Definitions and Design Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.1 Notations (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.2 D e f i ni ti on s (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.3 Design Loads (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.4 Loading Combinations (2005). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-2-8 8-2-8 8-2-11 8-2-12 8-2-19

2.3 Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.1 Concrete (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.2 Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Details of Reinforcement 2.4 Hooks and Bends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4.1 Standard Hooks (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4.2 Minimum Bend Diameter (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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2.5 Spacing of Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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2.6 Concrete Protection for Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6.1 Minimum Concrete Cover (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6.2 Concrete Cover for Bar Bundles (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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References, Vol. 31, 1930, pp. 1148, 1787; Vol. 48, 1947, p. 418; Vol. 50, 1949, pp. 291, 757; Vol. 54, 1953, pp. 794, 1341; Vol. 57, 1956, p. 996; Vol. 63, 1962, pp. 278, 688; Vol. 68, 1967, p. 313; Vol. 71, 1970, pp. 230, 242; Vol. 72, 1971, p. 136; Vol. 76, 1975, p. 205; Vol. 80, 1979, p. 91; Vol. 90, 1989, p. 53; Vol. 91, 1990, p 63; Vol. 93, 1992, pp. 78, 92; Vol. 94, 1994, p. 98.

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TABLE OF CONTENTS (CONT) Section/Article 2.6.3 2.6.4

Description

Page

Concrete Cover for Corrosive and Marine Environments (1992) . . . . . . . . . . . . . . . . . . . Corrosion Protection (1992). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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2.7 Minimum Reinforcement of Flexural Members (1992) . . . . . . . . . . . . . . . . . . . . . . . . . .

8-2-23

2.8 Distribution of Reinforcement in Flexural Members (2005) . . . . . . . . . . . . . . . . . . . . .

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2.9 Lateral Reinforcement of Flexural Members (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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2.10 Shear Reinforcement – General Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.10.1 Minimum Shear Reinforcement (2005). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.10.2 Types of Shear Reinforcement (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.10.3 Spacing of Shear Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-2-25 8-2-25 8-2-25 8-2-25

2.11 Limits for Reinforcement of Compression Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.11.1 Longitudinal Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.11.2 Lateral Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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2.12 Shrinkage and Temperature Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-2-27

Development and Splices of Reinforcement 2.13 Development Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.13.1 General (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.13.2 Positive Moment Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.13.3 Negative Moment Reinforcement (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.13.4 Special Members (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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2.14 Development Length of Deformed Bars and Deformed Wire in Tension (2005) . . . . .

8-2-29

2.15 Development Length of Deformed Bars in Compression (2005) . . . . . . . . . . . . . . . . . .

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2.16 Development Length of Bundled Bars (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-2-31

2.17 Development of Standard Hooks in Tension (2005). . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-2-31

2.18 Combination Development Length. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-2-33

2.19 Development of Welded Wire Fabric in Tension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.19.1 Deformed Wire Fabric (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.19.2 Smooth Wire Fabric (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-2-33 8-2-33 8-2-33

2.20 Mechanical Anchorage (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-2-34

2.21 Anchorage of Shear Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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AREMA Manual for Railway Engineering

Reinforced Concrete Design

TABLE OF CONTENTS (CONT) Section/Article

Description

2.22 Splices of Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.22.1 Lap Splices (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.22.2 Welded Splices and Mechanical Connections (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.22.3 Splices of Deformed Bars and Deformed Wire in Tension (2005). . . . . . . . . . . . . . . . . . . . 2.22.4 Splices of Deformed Bars in Compression (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.22.5 End Bearing Splices (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.22.6 Splices of Welded Deformed Wire Fabric in Tension (2005) . . . . . . . . . . . . . . . . . . . . . . . . 2.22.7 Splices of Welded Smooth Wire Fabric in Tension (2005) . . . . . . . . . . . . . . . . . . . . . . . . . .

Page 8-2-35 8-2-35 8-2-35 8-2-36 8-2-37 8-2-37 8-2-37 8-2-37

Analysis and Design – General Considerations 2.23 Analysis Methods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.23.1 General (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.23.2 Expansion and Contraction (2005). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.23.3 Stiffness (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.23.4 Modulus of Elasticity (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.23.5 Thermal and Shrinkage Coefficients (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.23.6 Span Length (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.23.7 Computation of Deflections (2005). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.23.8 Bearings (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.23.9 Composite Concrete Flexural Members (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.23.10 T-Girder Construction (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.23.11 Box Girder Construction (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-2-38 8-2-38 8-2-38 8-2-38 8-2-38 8-2-38 8-2-39 8-2-39 8-2-40 8-2-40 8-2-41 8-2-41

2.24 Design Methods (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-2-43

3

Service Load Design 2.25 General Requirements (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-2-43

2.26 Allowable Service Load Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.26.1 Concrete (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.26.2 Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-2-43 8-2-43 8-2-44

2.27 Flexure (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-2-45

2.28 Compression Members with or without Flexure (1992) . . . . . . . . . . . . . . . . . . . . . . . . .

8-2-45

2.29 Shear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.29.1 Shear Stress (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.29.2 Permissible Shear Stress (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.29.3 Design of Shear Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.29.4 Shear-Friction (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.29.5 Horizontal Shear Design for Composite Concrete Flexural Members (2005) . . . . . . . . . . 2.29.6 Special Provisions for Slabs and Footings (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.29.7 Special Provisions for Brackets and Corbels (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-2-45 8-2-45 8-2-46 8-2-48 8-2-48 8-2-50 8-2-51 8-2-52

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Concrete Structures and Foundations

TABLE OF CONTENTS (CONT) Section/Article

Description

Page

Load Factor Design 2.30 Strength Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.30.1 Required Strength (2005). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.30.2 Design Strength (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-2-53 8-2-53 8-2-53

2.31 Design Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.31.1 Strength Design (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-2-54 8-2-54

2.32 Flexure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.32.1 Maximum Reinforcement of Flexural Members (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.32.2 Rectangular Sections With Tension Reinforcement Only (2005) . . . . . . . . . . . . . . . . . . . 2.32.3 I- and T-Sections With Tension Reinforcement Only (2005) . . . . . . . . . . . . . . . . . . . . . . . 2.32.4 Rectangular Sections With Compression Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . 2.32.5 Other Cross Sections (1992). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-2-55 8-2-55 8-2-55 8-2-55 8-2-56 8-2-57

2.33 Compression Members with or without Flexure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.33.1 General Requirements (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.33.2 Compression Member Strengths (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.33.3 Biaxial Loading (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-2-57 8-2-57 8-2-58 8-2-59

2.34 Slenderness Effects in Compression Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.34.1 General Requirements (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.34.2 Approximate Evaluation of Slenderness Effects (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-2-60 8-2-60 8-2-60

2.35 Shear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.35.1 Shear Strength (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.35.2 Permissible Shear Stress (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.35.3 Design of Shear Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.35.4 Shear-Friction (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.35.5 Horizontal Shear Design for Composite Concrete Flexural Members (2005). . . . . . . . . . 2.35.6 Special Provisions for Slabs and Footings (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.35.7 Special Provisions for Brackets and Corbels (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-2-62 8-2-62 8-2-62 8-2-64 8-2-65 8-2-66 8-2-67 8-2-69

2.36 Permissible Bearing Stress (2005). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-2-70

2.37 Serviceability Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.37.1 Application (1992). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.37.2 Service Load Stresses (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-2-70 8-2-70 8-2-70

2.38 Fatigue Stress Limit for Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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2.39 Distribution of Flexural Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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2.40 Control of Deflections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.40.1 General (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.40.2 Superstructure Depth Limitations (1992). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-2-71 8-2-71 8-2-71

Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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LIST OF FIGURES Figure

Description

8-2-1 Cooper E 80 (EM 360) Axle Load Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-2-2 Reinforcement Spacing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-2-3 Standard Hook Bars. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-2-4 #6, 7, or 8 Stirrups (fy > 40,000 psi) (#19, 22, or 25) (fy > 280 MPa) . . . . . . . . . . . . . . . . . . . . C-8-2-1 Pier Protection: Minimum Crash Wall Requirements (Not To Scale) . . . . . . . . . . . . . . . . . . . . C-8-2-2 Comparison of Impact Formulas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Page 8-2-13 8-2-31 8-2-32 8-2-35 8-2-74 8-2-75

LIST OF TABLES Table 8-2-1 8-2-2 8-2-3 8-2-4 8-2-5 8-2-6 8-2-7 8-2-8 8-2-9 8-2-10

Description Coefficient for Nose Inclination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Coefficient for Design Ice Thickness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Temperature Ranges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Group Loading Combinations – Service Load Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Group Loading Combinations – Load Factor Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Minimum Diameter of Bend . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Minimum Concrete Cover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Development Length for Deformed Bars and Wire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tension Lap Splices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Recommended Minimum Thickness For Constant Depth Members . . . . . . . . . . . . . . . . . . . . .

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SECTION 2.1 GENERAL

1

3

2.1.1 SCOPE (2005) These recommended practices shall govern the design of reinforced concrete members of railway structures supporting or protecting tracks and shall govern both SERVICE LOAD DESIGN and LOAD FACTOR DESIGN.

4

2.1.2 DESIGN METHODS (2005) a.

The design of reinforced concrete members shall be made either with reference to service loads and allowable service load stresses as provided in the Service Load Design Section or, alternately, with reference to load factors and strength as provided in the Load Factor Design section. The design method to be used, SERVICE LOAD DESIGN or LOAD FACTOR DESIGN, shall be as directed by the Engineer.

2.1.3 HIGHWAY BRIDGES (2005) Unless otherwise specified by highway authority, all highway bridges shall be designed in accordance with the latest Specifications for Highway Bridges adopted by the American Association of State Highway and Transportation Officials.

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2.1.4 BUILDINGS (2005) Unless otherwise specified by local governing ordinances or state codes, all concrete railway buildings shall be designed in accordance with the latest “Building Code Requirements for Reinforced Concrete (ACI 318)” of the American Concrete Institute, subject to design loads conforming to railway requirements.

2.1.5 PIER PROTECTION (2005) 2.1.5.1 Adjacent to Railroad Tracks1 a.

To limit damage by the redirection and deflection of railroad equipment, piers supporting bridges over railways and with a clear distance of 25 feet (7600 mm) or less from the centerline of a railroad track shall be of heavy construction (defined below) or shall be protected by a reinforced concrete crash wall. Crash walls for piers from 12 to 25 feet (3600 to 7600 mm) clear from the centerline of track shall have a minimum height of 6 feet (1800 mm) above the top of rail. Piers less than 12 feet (3600 mm) clear from the centerline of track shall have a minimum crash wall height of 12 feet (3600 mm) above the top of rail.

b. The crash wall shall be at least 2¢ -6² (760 mm) thick and at least 12 feet (3600 mm) long. When two or more columns compose a pier, the crash wall shall connect the columns and extend at least 1 foot (300 mm) beyond the outermost columns parallel to the track. The crash wall shall be anchored to the footings and columns, if applicable, with adequate reinforcing steel and shall extend to at least 4 feet (1200 mm) below the lowest surrounding grade. c.

Piers shall be considered of heavy construction if they have a cross-sectional area equal to or greater than that required for the crash wall and the larger of its dimensions is parallel to the track.

d. Consideration may be given to providing protection for bridge piers over 25 feet (7600 mm) from the centerline of track as conditions warrant. In making this determination, account shall be taken of such factors as horizontal and vertical alignment of the track, embankment height, and an assessment of the consequences of serious damage in the case of a collision. 2.1.5.2 Over Navigable Streams Piers located adjacent to channels of navigable waterways shall have a protection system in accordance with Part 23 Pier Protection Systems at Spans Over Navigable Streams.

2.1.6 SUPERSTRUCTURE PROTECTION (2010)2 2.1.6.1 General Requirements a.

An evaluation of a railroad bridge over a roadway should be performed when the risk potential and consequence from a vehicular collision with a railroad superstructure is deemed necessary by the Engineer. Factors to be considered in the evaluation should include but not limited to railroad safety and operational requirements, vertical clearance over roadway surface, roadway functional classification, roadway design speed, roadway sight distance, traffic data, and other reasonable data for the specific location. Reasonable protection of the superstructure should be determined based upon results from the evaluation and approval by the Engineer.

b. A re-evaluation of the grade separation requirements should be performed when changes in conditions at the location or other factors warrant. 1 2

See Commentary See Commentary

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2.1.7 SKEWED CONCRETE BRIDGES (2005)1 a.

The skew angle, on most concrete bridges, is the smallest angle measured between a line perpendicular to the centerline of bridge and the centerline of the abutments or piers. Skewed concrete bridges should be avoided when possible. When skewed bridges are unavoidable, cast-in-place concrete bridges are preferable. The following table illustrates the maximum recommended skew for different types of concrete bridges. TYPE OF STRUCTURE

SKEW IN DEGREES

Precast concrete slabs and box girders

15

Precast concrete I-girders and T-girders

30

Cast-in-place concrete slabs and girders

60

b. When interior diaphragms are used on concrete girder bridges, they should be placed perpendicular to the web of the girder. c.

Abutments may be skewed, provided there is either a haunch in the backwall of the abutment, or an approach slab is provided for each track. The end of the haunch in the backwall of the abutment and the end of the approach slab shall be set perpendicular to the center of the track.

d. Concrete bridges with a curved superstructure should not be skewed. Piers and abutments for these bridges should be placed radial to the centerline of the bridge. e.

The ends of concrete slabs and concrete box girders with flange widths 5’-0” (1525 mm) and wider may be skewed. Skews on the ends of concrete I-girders, concrete T-girders and concrete box girders with flange widths less than 5’-0” (1525 mm) should be avoided.

f.

All concrete bridges that differ from these guidelines should be evaluated on a case by case basis.

1

3

4

1

See Commentary

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SECTION 2.2 NOTATIONS, DEFINITIONS AND DESIGN LOADS 2.2.1 NOTATIONS (2005) a

= depth of equivalent rectangular stress block, inches (mm). See Article 2.31.1f

ab

= depth of equivalent rectangular stress block for balanced strain conditions, inches (mm). See Article 2.33.2

av

= shear span, distance between concentrated load and face of support, inches (mm). See Article 2.29.7 and Article 2.35.7

A

= effective tension area of concrete surrounding the main tension reinforcing bars and having the same centroid as that reinforcement, divided by the number of bars, square inches (mm2). When the main reinforcement consists of several bar sizes the number of bars shall be computed as the total steel area divided by the area of the largest bar used. See Section 2.39

Ab = area of an individual bar, square inches (mm2). See Section 2.14 Ac

= area of the core of a spirally reinforced compression member measured to the outside diameter of the spiral, square inches (mm2). See Article 2.11.2

Af

= area of reinforcement in bracket or corbel resisting moment, square inches (mm2). See Article 2.29.7 and Article 2.35.7

Ag = gross area of section, square inches (mm2). Ah = area of shear reinforcement parallel to flexural tension reinforcement, square inches (mm2). See Article 2.29.7 and Article 2.35.7 An = area of reinforcement in bracket or corbel resisting tensile force, Nc(Nuc), square inches (mm2). See Article 2.29.7 and Article 2.35.7 As

= area of tension reinforcement, square inches (mm2)

A¢ s = area of compression reinforcement, square inches (mm2) Asf = area of reinforcement to develop compression strength of overhanging flanges of I- and T-sections, square inches (mm2). See Article 2.32.3 Ask = area of skin reinforcement per unit height in one side face, square inches/foot (mm2/m). See Section 2.8 Ast = total area of longitudinal reinforcement, square inches (mm2). See Article 2.33.1 and 2.33.2 Av

= area of shear reinforcement within a distance s, square inches (mm2)

Avf = area of shear-friction reinforcement, square inches (mm2). See Article 2.29.4 and Article 2.35.4 Aw = area of individual wire to be developed or spliced, square inches (mm2) b

= width of compression face of member, inches (mm)

bo

= perimeter of critical section for slabs and footings, inches (mm). See Article 2.29.6 and Article 2.35.6

bv

= width of cross section being investigated for horizontal shear, inches (mm). See Article 2.29.6 and Article 2.35.5

bw = web width, or diameter of circular section. For tapered webs, the average width or 1.2 times the minimum width, whichever is smaller, inches (mm). See Article 2.29.1 and Article 2.35.1 c

= distance from extreme compression fiber to neutral axis, inches (mm). See Article 2.31.1

Cm = a factor relating the actual moment diagram to an equivalent uniform moment diagram. See Article 2.34.2 d

= distance from extreme compression fiber to centroid of tension reinforcement, inches (mm)

d¢

= distance from extreme compression fiber to centroid of compression reinforcement, inches (mm)

d²

= distance from centroid of gross section neglecting the reinforcement, to centroid of tension reinforcement, inches (mm)

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db

= diameter of bar or wire, inches (mm)

dc

= thickness of concrete cover measured from extreme tension fiber to center of bar located closest thereto, inches (mm). See Section 2.39

dp

= diameter of round pile or cross sectional depth of H-pile at footing base, inches (mm). See Article 2.29.6 and Article 2.35.6

Ec

= modulus of elasticity of concrete, psi (MPa). See Article 2.23.4

EI = flexural stiffness of compression member. See Article 2.34.2 Es

= modulus of elasticity of steel, psi (MPa). See Article 2.23.4

fb

= average bearing stress in concrete on loaded area, psi (MPa). See Article 2.26.1 and Section 2.36

fc

= extreme fiber compressive stress in concrete at service loads, psi (MPa). See Article 2.26.1

f ¢ c = specified compressive strength of concrete, psi (MPa) f¢ c= square root of specified compressive strength of concrete, psi (MPa) fct = average splitting tensile strength of lightweight aggregate concrete, psi (MPa) fmin = algebraic minimum stress level, tension positive, compression negative, psi (MPa). See Section 2.38 fr

= modulus of rupture of concrete, psi (MPa). See Article 2.26.1

ff

= stress range in steel reinforcement, ksi (MPa). See Section 2.38 and Article 2.26.2

fs

= tensile stress in reinforcement at service loads, psi (MPa). See Article 2.26.2

f ¢ sb = stress in compression reinforcement at balanced strain conditions, psi (MPa). See Article 2.32.4 and Article 2.33.2 ft

= extreme fiber tensile stress in concrete at service loads, psi (MPa). See Article 2.26.1

fy

= specified yield strength of reinforcement, psi (MPa)

h

= overall thickness of member, inches (mm)

hf

= compression flange thickness of I- and T-sections, inches (mm)

1

Icr = moment of inertia of cracked section transformed to concrete. See Article 2.23.7 Ie

= effective moment of inertia for computation of deflection. See Article 2.23.7

Ig

= moment of inertia of gross concrete section about centroidal axis, neglecting reinforcement

Io

= moment of inertia of reinforcement about centroidal axis of member cross section

k

= effective length factor for compression member. See Article 2.34.2

la

= additional embedment length at support or at point of inflection, inches (mm). See Article 2.13.2

ld

= development length, inches (mm). See Section 2.13 through Section 2.22

3

ldh = development length of standard hook in tension, measured from critical section to outside end of hook (straight embedment length between critical section and start of hook [point of tangency] plus radius of bend and one bar diameter), inches (mm). lhb x applicable modification factors lhb = basic development length of standard hook in tension, inches (mm). lu

= unsupported length of compression member. See Section 2.34

M

= computed moment capacity as defined in Article 2.13.2

Ma = maximum moment in member at section for which deflection is being computed. See Article 2.23.7 Mb = nominal moment strength of a section at balanced strain conditions. See Article 2.33.2 Mc = moment to be used for design of compression member. See Article 2.34.2 Mcr = cracking moment. See Article 2.23.7 Mn = nominal moment strength of a section Mnx = nominal moment strength of a section considered about the x axis. See Article 2.33.3 Mny = nominal moment strength of a section considered about the y axis. See Article 2.33.3

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Concrete Structures and Foundations

Mu = factored moment at section £ FMn Mux = factored moment component in direction of x axis. See Article 2.33.3 Muy = factored moment component in direction of y axis. See Article 2.33.3 M1b = value of small end moment on compression member due to loads that result in no appreciable side sway, calculated by conventional elastic frame analysis, positive if member is bent in single curvature, negative if bent in double curvature. See Article 2.34.2 M2b = value of larger end moment on compression member due to loads that result in no appreciable side sway, calculated by conventional elastic frame analysis, always positive. See Article 2.34.2 M2s = value of larger end moment on compression member due to loads that result in appreciable side sway, calculated by conventional elastic frame analysis, always positive. See Article 2.34.2 n

= modular ratio = Es/Ec. See Article 2.27

N

= design axial load normal to cross section occurring simultaneously with V to be taken as positive for compression, negative for tension, and to include the effects of tension due to shrinkage and creep. See Article 2.29.2

Nc = design tensile force applied at top of bracket or corbel acting simultaneously with V, to be taken as positive for tension. See Article 2.29.7 Nu = factored axial load normal to the cross section occurring simultaneously with Vu to be taken as positive for compression, negative for tension, and to include the effects of tension due to shrinkage and creep. See Article 2.35.2 Nuc = factored tensile force applied at top of bracket or corbel acting simultaneously with Vu, to be taken as positive for tension. See Article 2.35.7 Pb = nominal axial load strength of a section at balanced strain conditions. See Article 2.33.2 Pc

= critical load. See Article 2.34.2

Pn = nominal axial load strength at given eccentricity. Pnx = nominal axial load strength corresponding to Mnx with bending considered about the x axis only. See Article 2.33.3 Pny = nominal axial load strength corresponding to Mny with bending considered about the y axis only. See Article 2.33.3 Pnxy = nominal axial load strength with biaxial loading. See Article 2.33.3 Po

= nominal axial load strength of a section at zero eccentricity. See Article 2.33.2 and Article 2.33.3

Pu = factored axial load at given eccentricity £ F Pn r = radius of gyration of cross section of compression member. See Article 2.34.2 s

= tie spacing, inches (mm). See Article 2.22.4

s

= shear reinforcement spacing in a direction parallel to the longitudinal reinforcement, inches (mm)

sw

= spacing of wire to be developed or spliced, inches (mm)

S

= span length as defined in Article 2.23.6, feet (meters)

v

= design shear stress at section. See Section 2.29

vc

= permissible shear stress carried by concrete. See Section 2.29 and Section 2.35

vdh = design horizontal shear stress at any cross section. See Article 2.29.5 vh

= permissible horizontal shear stress. See Article 2.29.5 and Article 2.35.5

vu

= factored shear stress at section. See Section 2.35

vuh = factored horizontal shear stress at any cross section. See Article 2.35.5 V

= design shear force at section. See Section 2.29

Vu = factored shear force at section. See Section 2.35 wc = weight of concrete, pounds per cubic foot (kg/m3)

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Reinforced Concrete Design

yt

= distance from centroidal axis of gross section, neglecting reinforcement, to extreme fiber in tension, inches (mm). See Article 2.23.7

Z

= a quantity limiting distribution of flexural reinforcement. See Section 2.39

a

= angle between inclined shear reinforcement and longitudinal axis of member

af

= angle between shear-friction reinforcement shear plane. See Article 2.29.4 and Article 2.35.4

bb

= ratio of area of bars cut off to total area of bars at the section. See Article 2.13.1

bc

= ratio of long side to short side of concentrated load or reaction area. See Article 2.29.6 and Article 2.35.6

bd

= ratio of maximum factored axial dead load to maximum total factored axial load, where the load is due to gravity effects only in the calculation of Pc in EQ 2-43, or ratio of the maximum factored sustained lateral load to the maximum total factored lateral load in that level in the calculation of Pc in EQ 2-43. See Article 2.34.2

b1

= a factor defined in Article 2.31.1

db

= Moment magnification factor for members braced against sidesway to reflect effects of member curvature between ends of compression member.

ds

= Moment magnification factor for members not braced against sidesway to reflect lateral drift resulting from lateral and gravity loads.

l

= correction factor related to unit weight of concrete. See Article 2.29.4 and Article 2.35.4

m

= coefficient of friction. See Article 2.29.4 and Article 2.35.4

r

= tension reinforcement ratio = As/bd

1

r¢

= compression reinforcement ratio = A¢ s/bd

rb

= reinforcement ratio producing balanced strain conditions. See Article 2.32.1

rs

= ratio of volume of spiral reinforcement to total volume of core (out-to-out of spirals) of a spirally reinforced compression member. See Article 2.11.2

rv

= ratio of tie reinforcement area to area of contact surface

r w = reinforcement ratio (As/bwd) used in EQ 2-15 and EQ 2-46. See Article 2.29.2 and Article 2.35.2 F

3

= strength reduction factor. See Article 2.30.2

2.2.2 DEFINITIONS (2005) The following terms are for general use in Part 2 Reinforced Concrete Design. Specialized terms appear in individual paragraphs. Refer to the Chapter 8 Glossary located at the end of the chapter for definitions.

Compressive Strength of Concrete (f ¢ c)

Nominal Strength

Deformed Reinforcement

Plain Reinforcement

Design Load

Required Strength

Design Strength

Service Load

Development Length

Spiral

Embedment Length

Stirrups or Ties

Embedment Length, Equivalent (le)

Yield Strength or Yield Point (fy)

End Anchorage

Concrete, Structural Lightweight

Factored Load

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Concrete Structures and Foundations

2.2.3 DESIGN LOADS (2009) a.

General. (1) The following loads and forces shall be considered in the design of railway concrete structures supporting tracks: D

= Dead Load

F

= Longitudinal Force due to Friction or Shear Resistance at Expansion Bearings

L

= Live Load

I

= Impact

CF

= Centrifugal Force

EQ

= Earthquake (Seismic)

E

= Earth Pressure

SF

= Stream Flow Pressure

B

= Buoyancy

ICE = Ice Pressure

W

= Wind Load on Structure

OF

WL

= Wind Load on Live Load

LF

= Longitudinal Force from Live Load

= Other Forces (Rib Shortening, Shrinkage, Temperature and/or Settlement of Supports)

(2) Each member of the structure shall be designed for that combination of such loads and forces that can occur simultaneously to produce the most critical design condition as specified in Article 2.2.4. b. Dead Load. (1) The dead load shall consist of the estimated weight of the structural member, plus that of the track, ballast, fill, and other portions of the structure supported thereby. (2) The unit weight of materials comprising the dead load, except in special cases involving unusual conditions or materials, shall be assumed as follows: • Track rails, inside guardrails and fastenings – 200 lb per linear foot of track. (3kN/m) • Ballast, including track ties – 120 lb per cubic foot. (1900 kg/m3) • Reinforced concrete – 150 lb per cubic foot. (2400 kg/m3) • Earthfilling materials – 120 lb per cubic foot. (1900 kg/m3) • Waterproofing and protective covering – estimated weight. c.

Live Load. (1) The recommended live load for each track of main line structure is Cooper E 80 (EM 360) loading with axle loads and axle spacing as shown in Figure 8-2-1. On branch lines and in other locations where the loading is limited to the use of light equipment, or cars only, the live load may be reduced, as directed by the engineer. For structures wherein the material in the primary load-carrying members is not concrete, the E loading used for the concrete design shall be that used for the primary members. (2) The axle loads on structures may be assumed as uniformly distributed longitudinally over a length of 3 feet (900 mm), plus the depth of ballast under the tie, plus twice the effective depth of slab, limited, however, by the axle spacing.

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Figure 8-2-1. Cooper E 80 (EM 360) Axle Load Diagram (3) Live load from a single track acting on the top surface of a structure with ballasted deck or under fills shall be assumed to have uniform lateral distribution over a width equal to the length of track tie plus the depth of ballast and fill below the bottom of tie, unless limited by the extent of the structure. (4) The lateral distribution of live load from multiple tracks shall be as specified for single tracks and further limited so as not to exceed the distance between centers of adjacent tracks. (5) The lateral distribution of the live load for structures under deep fills carrying multiple tracks, shall be assumed as uniform between centers of outside tracks, and the loads beyond these points shall be distributed as specified for single track. Widely separated tracks shall not be included in the multiple track group.

1

(6) In calculating the maximum live loads on a structural member due to simultaneous loading on two or more tracks, the following proportions of the specified live load shall be used: • For two tracks – full live load,

3

• For three tracks – full live load on two tracks and one-half on the other track, • For four tracks – full live load on two tracks, one-half on one track, and one-fourth on the remaining track. (7) The tracks selected for full live load in accordance with the listed limitations shall be those tracks which will produce the most critical design condition on the member under consideration. d. Impact Load.1 (1) Impact forces, applied at the top of rail, shall be added to the axle loads specified. For rolling equipment without hammer blow (diesels, electric locomotives, tenders alone, etc.), the impact shall be equal to the following percentages of the live load:

1

See Commentary

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Concrete Structures and Foundations

(U.S. Customary) For L £14 feet

I = 60

For 14 feet < L £127 feet

I =225 ¤ ( L )

For L > 127 feet

I = 20

(Metric) For L £4 meters

I = 60

For 4 meters < L £39 meters

I =125 ¤ ( L )

For L > 39 meters

I = 20

Where L is the span length in feet (meters). This formula is intended for ballasted-deck spans and substructure elements as required. (2) For continuous structures, the impact value calculated for the shortest span shall be used throughout. (3) Impact may be omitted in the design for massive substructure elements which are not rigidly connected to the superstructure. (4) For steam locomotives with hammer blow, the impact calculated according to Article 2.2.3d(1) shall be increased by 20%. e.

Centrifugal Force. (1) On curves, a centrifugal force corresponding to each axle load shall be applied horizontally through a point 8 feet (2450 mm) above the top of rail measured along a line perpendicular to the line joining the tops of the rails and equidistant from them. This force shall be the percentage of the live load computed from the formulas below. (2) On curves, each axle load on each track shall be applied vertically through the point defined in the first paragraph of this article. (3) The greater of loads on high and low sides of a superelevated track shall be used for the design of supports under both sides. (4) The relationships between speed, degree of curve, centrifugal force and a superelevation which is 3 inches (75 mm) less than that required for zero resultant flange pressure between wheel and rail are expressed by the formulas: C = 0.00117 S2D C = 0.000452 S2D

EQ 2-1 EQ 2-1M

E = 0.0007 S2D – 3 E = 0.0068 S2D – 75

EQ 2-2 EQ 2-2M

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S =

S =

E+3 ----------------------0.0007D

EQ 2-3 EQ 2-3M

E + 75 ----------------------0.0068D

where: C = Centrifugal force in percentage of the live load D = Degree of curve (Degrees based on 100 foot (30 m) chord) E = Actual superelevation in inches (mm) S = Permissible speed in miles per hour (km/hr) f.

Earth Pressure. Earth pressure forces to be applied to the structure shall be determined in accordance with the provisions of Part 5 Retaining Walls, Abutments and Piers.

g.

Buoyancy. Buoyancy shall be considered as it affects the design of either substructure, including piling, or the superstructure.

h. Wind Load on Structure. The base wind load acting on the structure is assumed to be 45 lb per square foot (2160 Pa) on the vertical projection of the structure applied at the center of gravity of the vertical projection in any horizontal direction. A base wind velocity of 100 miles per hour (160 km/h) was used to determine the base wind load. If an increase in the design wind velocity is made, the design wind velocity and design wind load shall be shown on the plans.

1

For Group II and Group V loadings, when a design wind velocity greater than 100 miles per hour (160 km/h) is advisable the base wind load may be increased by the ratio of the square of the design wind velocity to the square of the base wind velocity. This increase shall not apply to Group III and Group VI Loadings.

3 i.

Wind Load on Live Load. A wind load of 300 lb per linear foot (4.4 kN/m) on the train shall be applied 8 feet (2450 mm) above the top of rail in a horizontal direction perpendicular to the centerline of the track.

j.

Longitudinal Force.1 (1) The longitudinal force for E-80 (EM 360) loading shall be taken as the larger of:

4

– Force due to braking, as prescribed by the following equation, acting 8 feet (2450 mm) above top of rail. Longitudinal braking force (kips) = 45+1.2L (Longitudinal braking force (kN) = 200+17.5L) where L is the length in feet (meters) of the portion of the bridge under consideration – Force due to traction, as prescribed by the following equation, acting 3 feet (900 mm) above top of rail. Longitudinal traction force (kips) = 25 L

1

See Commentary

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(Longitudinal traction force (kN) = 200 L ) where L is the length in feet (meters) of the portion of the bridge under consideration For design loads other than E-80 (EM 360), these forces shall be scaled proportionally. The points of force application shall not be changed. (2) The effective longitudinal force shall be distributed to the various components of the supporting structure, taking into account their relative stiffness. The resistance of the backfill behind the abutments shall be utilized where applicable. The mechanisms (rail, bearings, load transfer devices, etc.) available to transfer the force to the various components shall also be considered. (3) The longitudinal deflection of the superstructure due to longitudinal force computed in (1) above shall not exceed 1 inch (25 mm) for E-80 (EM 360) loading. For design loads other than E-80 (EM 360), the maximum allowable longitudinal deflection shall be scaled proportionally. In no case, however, shall the longitudinal deflection exceed 1-1/2 inches (38 mm). k. Longitudinal Force Due to Friction or Shear Resistance at Expansion Bearings. Provisions shall be made to accommodate forces due to friction or shear resistance due to expansion bearings. l.

Earthquake. In regions where earthquakes may be anticipated, structures may be designed to resist earthquake motions by considering the relationship of the site to active faults, the seismic response of the soils at the site, and the dynamic response characteristics of the total structure. Refer to Chapter 9 Seismic Design for Railway Structures for additional guidance.

m. Stream Flow Pressure. All piers and other portions of structures which are subject to the force of flowing water or drift shall be designed to resist the maximum stresses induced thereby. (1) Stream Pressure The effect of flowing water on piers and drift build up, assuming a second-degree parabolic velocity distribution and thus a triangular pressure distribution, shall be calculated by the formula: Pavg = K(Vavg)2

EQ 2-4

where: Pavg = average stream pressure, in pounds per square foot, (Pa) Vavg = average velocity of water in feet per second, (m/s) computed by dividing the flow rate by the flow area, K = a constant, being 1.4 (or 725 for metric) for all piers subjected to drift build up and square-ended piers, 0.7 (or 360 for metric) for circular piers, and 0.5 (or 260 for metric) for angle-ended piers where the angle is 30 degrees or less. The maximum stream flow pressure, Pmax, shall be equal to twice the average stream flow pressure, Pavg, computed by EQ 2-4. Stream flow pressure shall be a triangular distribution with Pmax located at the top of water elevation and a zero pressure located at the flow line. (2) The stream flow forces shall be computed by the product of the stream flow pressure, taking into account the pressure distribution, and the exposed pier area. In cases where the corresponding top of water elevation is above the low beam elevation, stream flow loading on the superstructure shall

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be investigated. The stream flow pressure acting on the superstructure may be taken as Pmax with a uniform distribution. (3) Pressure Components When the direction of stream flow is other than normal to the exposed surface area, or when bank migration or a change of stream bed meander is anticipated, the effects of the directional components of stream flow pressure shall be investigated. (4) Drift Lodge Against Pier Where a significant amount of drift lodge against a pier is anticipated, the effects of this drift build up shall be considered in the design of the bridge opening and the bridge components. The overall dimensions of the drift build up shall reflect the selected pier locations, site conditions, and known drift supply upstream. When it is anticipated that the flow area will be significantly blocked by drift build up, increases in high water elevations, stream velocities, stream flow pressures, and the potential increases in scour depths shall be investigated. n. Ice Pressure. The effects of ice pressure, both static and dynamic, shall be accounted for in the design of piers and other portions of the structure where, in the judgment of the Engineer, conditions so warrant. (1) General. Ice forces on piers shall be selected having regard to site conditions and the mode of ice action to be expected. Consideration shall be given to the following modes: (a) dynamic ice pressure due to moving ice sheets and floes carried by streamflow, wind or currents;

1

(b) static ice pressure due to thermal movements of continuous stationary ice sheets onlarge bodies of water; (c) static pressure resulting from ice jams;

3

(d) static uplift or vertical loads resulting from adhering ice in waters of fluctuating level. The expected thickness of ice, the direction of its movement, and the height at which it acts shall be determined by field investigations, published records, aerial photography and other means. Consideration shall be given to the worst expected combination of height, thickness and pressure, to the possibility of unusual thicknesses resulting from special circumstances or operations, and to the natural variability of ice conditions from year to year. (2) Dynamic Ice Pressure. Horizontal forces resulting from the pressure of moving ice are to be calculated by the formula: EQ 2-5

F = Cnptw where: F = horizontal ice force on pier; pounds (N) Cn = coefficient for nose inclination from Table 8-2-1; p = ice pressure as indicated below; psi (MPa) t = thickness of ice in contact withpier; inches (mm)

w = width of pier or diameter of circular-shaft pier at the level of ice action; inches (mm)

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Table 8-2-1. Coefficient for Nose Inclination Inclination of Nose to Vertical

Cn

0 degrees to 15 degrees

1.00

15 degrees to 30 degrees

0.75

30 degrees to 45 degrees

0.50

(3) The ice pressure “p” shall normally be taken in the range of 100 psi (0.7 MPa) to 400 psi (2.8 MPa) on the assumption that crushing or splitting of the ice takes place on contact with the pier. The value used shall be based on an assessment of the probable condition of the ice at time of movement, on previous local experience, and on assessment of existing structure performance. Relevant ice conditions include the expected temperature of the ice at time of movement, the size of moving sheets and floes and the velocity at contact. Due consideration shall be given to probability of extreme rather than average conditions at the site in question. NOTE:

The following values of ice pressure appropriate to various situations may be used as a guide:

(a) In the order of 100 psi (0.7 MPa) where break-up occurs at melting temperatures and where the ice runs as small “cakes” and is substantially disintegrated in its structure; (b) In the order of 200 psi (1.4 MPa) where break-up occurs at melting temperatures, but the ice moves in large pieces and is internally sound; (c) In the order of 300 psi (2.1 MPa) where at break-up there is an initial movement of the ice sheet as a whole or where large sheets of sound ice may strike the piers; (d) In the order of 400 psi (2.8 MPa) where break-up or major ice movement may occur with ice temperature significantly below the melting point. (4) The ice pressure values listed above apply to piers of substantal mass and dimensions. The values shall be modified as necessary for variations inpier width or pile diameter, and design ice thickness by multiplying by the appropriate coefficient obtained from Table 8-2-2. Table 8-2-2. Coefficient for Design Ice Thickness b/t

Coefficient

0.5

1.8

1.0

1.3

1.5

1.1

2.0

1.0

3.0

0.9

4.0 or greater

0.8

where: b = width of pier or diameter of pile; t = design ice thickness.

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(5) Piers should be placed with their longitudinal axes parallel to the principal direction of ice action. The force calculated by the formula shall then be taken to act along the direction of the long axis. A force transverse to the longitudinal axis and amounting to not less than 15% of the longitudinal force shall be considered to act simultaneously. (6) Where the longitudinal axis of a pier cannot be placed parallel to the principal direction of ice action, or where the direction of ice action may shift, the total force on the pier shall be figured by the formula and resolved into vector components. In such conditions, forces transverse to the longitudinal axis of the pier shall in no case be taken as less than 20% of the total force. (7) In the case of slender and flexible piers, consideration should be given to the vibrating nature of dynamic ice forces and to the possibility of high momentary pressures and structural resonance. (8) Ice pressure on piers frozen into ice sheets on large bodies of water shall receive special consideration where there is reason to believe that the ice sheets are subject to significant thermal movements relative to the piers. o.

Other Forces (Rib Shortening, Shrinkage, Temperature and/or Settlement of Supports). (1) The structure shall be designed to resist the forces caused by rib shortening, shrinkage, temperature rise and/or drop and the anticipated settlement of supports. (2) The range of temperature shall generally be as shown in Table 8-2-3.

1

Table 8-2-3. Temperature Ranges Climate

Temperature Rise

Temperature Fall

Moderate

30 degrees F (17 degrees C) 40 degrees F (22 degrees C)

Cold

35 degrees F (20 degrees C) 45 degrees F (25 degrees C)

4 2.2.4 LOADING COMBINATIONS (2005) a.

General. The following groups represent various combinations of loads and forces to which a structure may be subjected. Each component of the structure, or the foundation on which it rests, shall be proportioned for the group of loads that produce the most critical design condition.

b. Service Load Design. (1) The group loading combinations for SERVICE LOAD DESIGN are as shown in Table 8-2-4. (2) No increase in allowable unit stresses shall be permitted for members or connections carrying wind load only. If predictability of service load conditions is different from the specifications, this difference should be accounted for in the appropriate service load analyses or in the unit stress increase percentages.

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Table 8-2-4. Group Loading Combinations – Service Load Design Group

c.

Allowable Percentage of Basic Unit Stress

Item

I

D + L + I + CF + E + B + SF

100

II

D + E + B + SF + W

125

III

Group I + 0.5W + WL + LF + F

125

IV

Group I + OF

125

V

Group II + OF

140

VI

Group III + OF

140

VII

Group I + ICE

140

VIII

Group II + ICE

150

Load Factor Design. (1) The group loading combinations for LOAD FACTOR DESIGN are as shown in Table 8-2-5. Table 8-2-5. Group Loading Combinations – Load Factor Design Group I

Item 1.4 (D + 5/3 (L + I) + CF + E + B + SF)

IA

1.8 (D + L + I + CF + E + B + SF)

II

1.4 (D + E + B + SF + W)

III

1.4 (D + L + I + CF + E + B + SF + 0.5W + WL + LF + F)

IV

1.4 (D + L + I + CF + E + B + SF + OF)

V

Group II + 1.4 (OF)

VI

Group III + 1.4 (OF)

VII

1.0 (D + E + B + EQ)

VIII

1.4 (D + L + I + E + B + SF + ICE)

IX

1.2 (D + E + B + SF + W + ICE)

(2) The load factors given are only intended for designing structural members by the load factor concept. The actual loads should not be increased by these factors when designing for foundations (soil pressure, pile loads, etc.). The load factors are not intended to be used when checking for foundation stability (safety factors against overturning, sliding, etc.) of a structure. The load factors given above represent usual conditions and should be increased if, in the Engineer’s judgment, the predictability of loads is different than anticipated by the specifications.

SECTION 2.3 MATERIALS 2.3.1 CONCRETE (1992) a.

Compressive strength of concrete f ¢ c for which each part of the structure is designed, shall be shown on the plans. © 2011, American Railway Engineering and Maintenance-of-Way Association

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Reinforced Concrete Design b. Specified compressive strength of concrete f ¢ c shall be the basis for acceptance. Requirements for f ¢ c shall be based on tests of cylinders made and tested in accordance with the methods as prescribed in Part 1 Materials, Tests and Construction Requirements.

2.3.2 REINFORCEMENT (2005) a.

Yield strength or grade of reinforcement used in design shall be shown on the plans.

b. Reinforcement to be welded shall be indicated on the plans and the welding procedure to be used shall be specified. ASTM steel specifications, except for ASTM A706, shall be supplemented to require a report of material properties (chemical analysis) necessary to conform to welding procedures specified in “Structural Welding Code–Reinforcing Steel” (AWS D 1.4) of the American Welding Society. If coated bars are to be welded, the Engineer should specify any additional requirements to those contained in AWS D 1.4, such as removal of zinc or epoxy coating for welding and field application of new coatings in the weld region if protection is required. c.

Designs shall not be based on a yield strength fy in excess of 60,000 psi (420 MPa).

d. Only deformed reinforcement shall be used except that plain bars or smooth wire may be used as spirals. e.

Reinforcement shall conform to the specifications listed in Part 1 Materials, Tests and Construction Requirements, except that, for reinforcing bars, the yield strength shall correspond to that determined by tests on full-size bars.

1 DETAILS OF REINFORCEMENT

3

SECTION 2.4 HOOKS AND BENDS 2.4.1 STANDARD HOOKS (2005) The term “standard hook” as used herein, shall mean one of the following: a.

4

180-degree bend plus 4db extension, but not less than 2-1/2 inches (60 mm) at free end of bar.

b. 90-degree bend plus 12db extension at free end of bar. c.

For stirrup and tie hooks: (1) #5 (#16) bar and smaller, 90-degree bend plus 6db extension at free end of bar, or (2) #6, #7, and #8 (#19, #22, #25) bar, 90-degree bend plus 12db extension at free end of bar, or (3) #8 (#25) bar and smaller, 135-degree bend plus 6db extension at free end of bar.

2.4.2 MINIMUM BEND DIAMETER (2005) a.

Diameter of bend measured on the inside of the bar, other than for stirrups and ties in sizes #3 (#10) through #5 (#16), shall not be less than the values in Table 8-2-6. © 2011, American Railway Engineering and Maintenance-of-Way Association

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Table 8-2-6. Minimum Diameter of Bend Bar Size #3 through #8 (#10 through #25)

Minimum Diameter 6 bar diameters

#9, #10 and #11 (#29, #32 and #36) 8 bar diameters #14 and #18 (#43 and #57)

10 bar diameters

b. Inside diameter of bends for stirrups and ties shall not be less than 4db for #5 (#16) bar and smaller. For bars larger than #5 (#16), diameter of bend shall be in accordance with Table 8-2-6. c.

Inside diameter of bend in welded wire fabric, smooth or deformed, for stirrups and ties shall not be less than four wire diameters for deformed wire larger than D6 and two wire diameters for all other wires. Bends with inside diameter of less than eight wire diameters shall not be less than four wire diameters from the nearest welded intersection.

SECTION 2.5 SPACING OF REINFORCEMENT (2005) a.

For cast-in-place concrete the clear distance between parallel bars in a layer shall not be less than one and one-half times the diameter of the bars, two times the maximum size of the coarse aggregate, nor 11/2 inches (40 mm).

b. For precast concrete (manufactured under plant control conditions) the clear distance between parallel bars in a layer shall be not less than the diameter of the bars, one and one-third times the maximum size of the coarse aggregate, nor 1 inch (25 mm). c.

Where positive or negative reinforcement is placed in two or more layers, bars in the upper layers shall be placed directly above those in the bottom layer with the clear distance between layers not less than 1 inch (25 mm).

d. Clear distance limitation between bars shall also apply to the clear distance between a contact lap splice and adjacent splices or bars. e.

Groups of parallel reinforcing bars bundled in contact to act as a unit shall be limited to four in any one bundle. Bars larger than #11 (#36) shall not be bundled in beams. Bundled bars shall be located within stirrups or ties. Individual bars in a bundle cut off within the span of a member shall terminate at different points with at least 40 bar diameters stagger. Where spacing limitations are based on bar size, a unit of bundled bars shall be treated as a single bar of a diameter derived from the equivalent total area.

f.

In walls and slabs the principal reinforcement shall be spaced not farther apart than one and one-half times the wall or slab thickness, nor more than 18 inches (450 mm).

SECTION 2.6 CONCRETE PROTECTION FOR REINFORCEMENT 2.6.1 MINIMUM CONCRETE COVER (2005) Table 8-2-7 defines the minimum concrete cover that shall be provided for reinforcement.

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Table 8-2-7. Minimum Concrete Cover Minimum Cover (Inches)

Minimum Cover (mm)

3

75

Concrete exposed to earth or weather Principal reinforcement Stirrups, ties and spirals

2 1-1/2

50 40

Concrete bridge slabs Top reinforcement Bottom reinforcement

2 1-1/2

50 40

Concrete not exposed to weather or in contact with ground Principal reinforcement Stirrups, ties and spirals

1-1/2 1

40 25

Condition of Concrete Concrete cast against and permanently exposed to earth

2.6.2 CONCRETE COVER FOR BAR BUNDLES (2005) For bar bundles, minimum concrete cover shall be equal to the lesser of the equivalent diameter of the bundle or 2 inches (50 mm), but not less than that given in Article 2.6.1.

2.6.3 CONCRETE COVER FOR CORROSIVE AND MARINE ENVIRONMENTS (1992) In corrosive or marine environments or other severe exposure conditions, the amount of concrete protection shall be suitably increased, and the denseness and nonporosity of the protecting concrete shall be considered, or other protection shall be provided.

1

2.6.4 CORROSION PROTECTION (1992) Exposed reinforcing bars, inserts, and plates intended for bonding with future extensions shall be protected from corrosion.

SECTION 2.7 MINIMUM REINFORCEMENT OF FLEXURAL MEMBERS (1992) a.

4

At any section of a flexural member where tension reinforcement is required by analysis, the reinforcement provided shall be adequate to develop a design moment strength FMn at least 1.2 times the cracking moment calculated on the basis of the modulus of rupture for normal weight concrete specified in Article 2.26.1a.

b. The requirements of Section 2.7a may be waived if the area of reinforcement provided at the section under consideration is at least one-third greater than that required by analysis based on the load factors specified in Article 2.2.4c.

SECTION 2.8 DISTRIBUTION OF REINFORCEMENT IN FLEXURAL MEMBERS (2005) a.

Flexural tension reinforcement shall be well distributed in the zones of maximum tension. © 2011, American Railway Engineering and Maintenance-of-Way Association

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(1) For T-girder and box-girder flanges, tension reinforcement shall be distributed over an effective tension flange width equal to 1/10 the girder span length, or a width as defined in Article 2.23.10b, whichever is smaller. If the actual slab width, center-to-center of girder webs, exceeds the effective tension flange width, and for excess portions of deck slab overhang, additional longitudinal reinforcement having a total area at least equal to 0.4% of excess slab area shall be provided in the outer portions of the slab. (2) For integral bent caps of T-girder and box girder construction, tension reinforcement shall not be placed outside the bent cap web farther than an overhanging slab width on each side of the bent cap equal to 1/4 the average spacing of intersecting girder webs or a width as defined in Article 2.23.10b for integral bent caps, whichever is smaller. b. If the depth of web exceeds 3 feet (900 mm), longitudinal skin reinforcement shall be uniformly distributed along both side faces of the member for a distance d/2 nearest the flexural tension reinforcement. The area of skin reinforcement Ask per foot (m) of height on each side face shall be ³0.012(d-30) (or Ask ³ 0.3 (d-750) in metric). The maximum spacing of the skin reinforcement shall be the smaller of d/6 or 12 inches (300 mm). Such reinforcement may be included in strength computations if a strain compatibility analysis is made to determine stresses in the individual bars or wires. The total area of longitudinal skin reinforcement in both faces need not exceed one-half of the required flexural tensile reinforcement. c.

For LOAD FACTOR DESIGN, the distribution of flexural reinforcement requirements of Article 2.39 shall also apply.

SECTION 2.9 LATERAL REINFORCEMENT OF FLEXURAL MEMBERS (2005) a.

Compression reinforcement used to increase the strength of flexural members shall be enclosed by ties or stirrups, at least #3 (#10) in size for longitudinal bars #10 (#32) or smaller, and at least #4 (#13) in size for #11, #14, #18 (#36, #43, #57) and bundled longitudinal bars, or by welded wire fabric of equivalent area. Spacing of the ties shall not exceed 16 longitudinal bar diameters. Such stirrups or ties shall be provided throughout the distance where the compression reinforcement is required.

b. Torsion reinforcement, where required, shall consist of closed stirrups, closed ties, or spirals, combined with longitudinal bars. c.

Closed stirrups or ties may be formed in one piece by overlapping standard stirrup or tie end hooks around a longitudinal bar, or formed in one or two pieces lap spliced with a Class C splice (lap of 1.7ld).

d. In seismic areas, where an earthquake of such magnitude as to cause major damage to construction has a high probability of occurrence, lateral reinforcement shall be designed and detailed to provide adequate strength and ductility to resist anticipated seismic movements.

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SECTION 2.10 SHEAR REINFORCEMENT – GENERAL REQUIREMENTS 2.10.1 MINIMUM SHEAR REINFORCEMENT (2005) a.

A minimum area of shear reinforcement shall be provided in all flexural members, except slabs, footings, and shallow beams, where the design shear stress is greater than one-half the permissible shear stress vc carried by concrete. Beams where total depth does not exceed either 10 inches (250 mm), 2-1/2 times the thickness of the flange, or one-half the width of the web shall be considered shallow beams.

b. Where shear reinforcement is required by Article 2.10.1a, or by analysis, the area provided shall not be less than EQ 2-6 EQ 2-6M

Av = 60 bws/fy Av = 0.42 bws/fy where: bw = inches (mm) s = inches (mm) c.

Minimum shear reinforcement requirements may be waived if it is shown by test that the required ultimate flexural and shear strength can be developed when shear reinforcement is omitted.

1

2.10.2 TYPES OF SHEAR REINFORCEMENT (1992) a.

Shear reinforcement may consist of: (1) Stirrups perpendicular to axis of member or making an angle of 45 degrees or more with the longitudinal tension reinforcement.

3

(2) Welded wire fabric with wires located perpendicular to axis of member. (3) Longitudinal bars with a bent portion making an angle of 30 degrees or more with the longitudinal tension bars.

4

(4) Combinations of stirrups and bent bars. (5) Spirals. b. Shear reinforcement shall be anchored at both ends in accordance with requirements of Section 2.21.

2.10.3 SPACING OF SHEAR REINFORCEMENT (2005) Where shear reinforcement is required and is placed perpendicular to axis of member, it shall be spaced not further apart than 0.50d, but not more than 24 inches (600 mm). Inclined stirrups and bent bars shall be so spaced that every 45 degree line, extending toward the reaction from the mid-depth of the member, 0.50d, to the longitudinal tension bars, shall be crossed by at least one line of shear reinforcement.

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SECTION 2.11 LIMITS FOR REINFORCEMENT OF COMPRESSION MEMBERS 2.11.1 LONGITUDINAL REINFORCEMENT (2005) a.

Longitudinal reinforcement for compression members shall not be less than 0.01 nor more than 0.08 times the gross area of Ag of the section. The minimum number of longitudinal reinforcing bars shall be six for bars in a circular arrangement and four for bars in a rectangular arrangement. The minimum size of bar shall be #5 (#16).

b. When the cross section is larger than that required by consideration of loading, a reduced effective area may be used. The reduced effective concrete area shall not be less than that which would require 1% of longitudinal reinforcement to carry the loading.

2.11.2 LATERAL REINFORCEMENT (2005) a.

Spirals. Spiral reinforcement for compression members shall conform to the following: (1) Spirals shall consist of evenly spaced continuous bar or wire, with a minimum diameter of 3/8 inch (10 mm). (2) Ratio of spiral reinforcement r s shall not be less than the value given by: f¢ c Ag r s = 0.45 æ ------- – 1ö -------èA ø f y c

EQ 2-7

where: fy = the specified yield strength of spiral reinforcement but not more than 60,000 psi (420 MPa) (3) Clear spacing between spirals shall not exceed 3 inches (75 mm) nor be less than 1-1/2 inches (40 mm) or 2 times the maximum size of coarse aggregate used. (4) Anchorage of spiral reinforcement shall be provided by 1-1/2 extra turns of spiral bar or wire at each end of a spiral unit. (5) Spirals shall extend from top of footing or other support to level of lowest horizontal reinforcement in members supported above. (6) Splices in spiral reinforcement shall be welded splices, or they shall be lap splices not less than the larger of 12 inches (300 mm) and the length indicated in one of (a) through (e) below: (a) deformed uncoated bar or wire......................................................................................................48db (b) plain uncoated bar or wire.............................................................................................................72db (c) epoxy-coated deformed bar or wire...............................................................................................72db (d) plain uncoated bar or wire with a standard stirrup or tie hook in accordance with Article 2.4.1c at ends of lapped spiral reinforcement. The hooks shall be embedded within the core confined by the spiral reinforcement................................................................................................................48db

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(e) epoxy-coated deformed bar or wire with a standard stirrup or tie hook in accordance with Article 2.4.1c at ends of lapped spiral reinforcement. The hooks shall be embedded within the core confined by the spiral reinforcement....................................................................................48db (7) Spirals shall be of such size and so assembled to permit handling and placing without distortion from designed dimensions. (8) Spirals shall be held firmly in place and true to line by vertical spacers. For spiral bar or wire smaller than 5/8 inch (16 mm) diameter, a minimum of two spacers shall be used for spirals less than 20 inches (500 mm) in diameter, three spacers for spirals 20 to 30 inches (500 to 750 mm) in diameter, and four spacers for spirals greater than 30 inches (750 mm) in diameter. For spiral bar or wire 5/8 inch (16 mm) diameter or larger, a minimum of three spacers shall be used for spirals 24 inches (600 mm) or less in diameter, and four spacers for spirals greater than 24 inches (600 mm) in diameter. b. Ties. Tie reinforcement for compression members shall conform to the following: (1) All bars shall be enclosed by lateral ties, at least #3 (#10) in size for longitudinal bars #10 (#32) or smaller, and at least #4 (#13) in size for #11, #14, #18 (#36, #43, #57), and bundled longitudinal bars. Deformed wire or welded wire fabric of equivalent area may be used. (2) Vertical spacing of ties shall not exceed the least dimension of the compression member or 12 inches (300 mm). When bars larger than #10 (#32) are bundled more than two in any one bundle, tie spacing shall be one-half that specified above. (3) Ties shall be located vertically not more than half a tie spacing above the footing or other support and shall be spaced as provided herein to not more than half a tie spacing below the lowest horizontal reinforcement in members supported above. (4) At each tie location, the lateral ties shall be so arranged that no longitudinal bar is farther than 2 feet (600mm) on either side along the tie from a bar with lateral support provided by the corner of a tie having an included angle of not more than 135 degrees. Where longitudinal bars are located around the perimeter of a circle, a complete circular tie may be used. c.

1

3

In a compression member which has a larger cross section than required by conditions of loading, the lateral reinforcement requirements may be waived where structural analysis or tests show adequate strength feasibility of construction.

d. In seismic areas, where an earthquake of such magnitude as to cause major damage to construction has a high probability of occurrence, lateral reinforcement for column piers shall be designed and detailed to provide adequate strength and ductility to resist anticipated seismic movements.

SECTION 2.12 SHRINKAGE AND TEMPERATURE REINFORCEMENT (2005) Reinforcement for shrinkage and temperature stresses shall be provided near exposed surfaces of walls and slabs not otherwise reinforced. The total area of reinforcement provided shall be at least 0.25 in2/ft (530 mm2/m) measured in the direction perpendicular to the direction of the reinforcement and be spaced not farther apart than three times the wall or slab thickness, nor 18 inches (450 mm).

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Concrete Structures and Foundations

DEVELOPMENT AND SPLICES OF REINFORCEMENT

SECTION 2.13 DEVELOPMENT REQUIREMENTS 2.13.1 GENERAL (2005) a.

The calculated tension or compression in the reinforcement at each section shall be developed on each side of that section by embedment length or end anchorage or a combination thereof. For bars in tension, hooks may be used in developing the bars.

b. Tension reinforcement may be anchored by bending it across the web and making it continuous with the reinforcement on the opposite face of the member, or anchoring it there. c.

Critical sections for development of reinforcement in flexural members are at points of maximum stress and at points within the span where adjacent reinforcement terminates, or is bent. The provisions of Article 2.13.2c must also be satisfied.

d. Reinforcement shall extend beyond the point at which it is no longer required to resist flexure for a distance equal to the effective depth of the member, 15 bar diameters, or 1/20 of the clear span, whichever is greater, except at supports of simple spans and at the free end of cantilevers. e.

Continuing reinforcement shall have an embedment length not less than the development length ld beyond the point where bent or terminated tension reinforcement is no longer required to resist flexure.

f.

Flexural reinforcement located within the width of a member used to compute the shear strength shall not be terminated in a tension zone unless one of the following conditions is satisfied. (1) Shear at the cutoff point does not exceed one-half of the design shear strength, FVn, including the shear strength of furnished shear reinforcement. (2) Stirrup area in excess of that required for shear is provided along each terminated bar over a distance from the termination point equal to three-fourths the effective depth of the member. The excess stirrups shall be proportioned such that their (Av/bws)fy is not less than 60 psi (0.42 MPa). The resulting spacings shall not exceed d/(8bb) where bb is the ratio of the area of bars cut off to the total area of bars at the section. (3) For #11 (#36) and smaller bars, the continuing bars provide double the area required for flexure at the cutoff point and shear does not exceed three-fourths of the design shear strength, FVn.

2.13.2 POSITIVE MOMENT REINFORCEMENT (2005) a.

At least one-half the positive moment reinforcement in simple members and one-fourth the positive moment reinforcement in continuous members shall extend along the same face of the member into the support. In beams, such reinforcement shall extend into the support a distance of 12 or more bar diameters, or shall be extended as far as possible into the support and terminated in standard hooks or other adequate anchorage.

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b. When a flexural member is part of the lateral load resisting system, the positive reinforcement required to be extended into the support by Article 2.13.2a shall be anchored to develop the full fy in tension at the face of the support. c.

At simple supports and at points of inflection, positive moment tension reinforcement shall be limited to a diameter such that ld computed for fy by Section 2.14 satisfies EQ 2-8; except EQ 2-8 need not be satisfied for reinforcement terminating beyond centerline of simple supports by a standard hook, or a mechanical anchorage at least equivalent to a standard hook. M ld £----V

EQ 2-8

+ la

where: M = the computed moment capacity assuming all positive moment tension reinforcement at the section to be fully stressed V = the maximum applied design shear at the section la = the embedment length beyond center of support or point of inflection la at a point of inflection shall be limited to the effective depth of the member 12d b , whichever is greater. The value of M/V in the development length limitation may be increased 30% when the ends of the reinforcement are confined by a compressive reaction.

1

2.13.3 NEGATIVE MOMENT REINFORCEMENT (1994) a.

Tension reinforcement in a continuous, restrained, or cantilever member, or in any member of a rigid frame, shall be anchored in or through the supporting member by embedment length, hooks, or mechanical anchorage.

3

b. Negative moment reinforcement shall have an embedment length into the span as required by Article 2.13.1a and Article 2.13.1d. c.

At least one-third the total reinforcement provided for negative moment at the support shall have an embedment length beyond the point of inflection not less than the effective depth of the member, 12 bar diameters, or one-sixteenth of the clear span, whichever is greater.

4

2.13.4 SPECIAL MEMBERS (1994) Adequate end anchorage shall be provided for tension reinforcement in flexural members where reinforcement stress is not directly proportional to moment, such as: sloped, stepped, or tapered footings; brackets; deep beams; or members in which the tension reinforcement is not parallel to the compression face.

SECTION 2.14 DEVELOPMENT LENGTH OF DEFORMED BARS AND DEFORMED WIRE IN TENSION (2005) Development length ld, in inches (mm), of deformed bars and deformed wire in tension shall be computed as the product of the basic development length of Section 2.14a and the applicable modification factor or factors of Section 2.14b through Section 2.14e, but ld shall be not less than that specified in Section 2.14f.

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a.

The basic development length is shown in Table 8-2-8. Table 8-2-8. Development Length for Deformed Bars and Wire Type For #11 or smaller bars

Development Length 0.04A b f y -----------------------f¢ c

(Note 1)

but not less than: 0.0004dbfy (Note 2) For #14 bars

For #18 bars

For deformed wire

0.085f y -------------------f¢ c 0.11f y ---------------f¢ c

(Note 3)

(Note 3)

0.03d b f y ----------------------f¢ c

Note 1: The constant carries the unit of 1/inch. Note 2: The constant carries the unit of inch2/lb. Note 3: The constant carries the unit of inch.

b. The basic development length shall be multiplied by a factor of 1.4 for top reinforcement. NOTE:

c.

Top reinforcement is horizontal reinforcement so placed that more than 12 inches (300 mm) of concrete is cast in the member below the bar.

When lightweight aggregate concrete is used, the basic development lengths in Section 2.14a shall be multiplied by 1.18, or the basic development length may be multiplied by

6.7 f¢ c ¤ f ct

(or

0.56 f¢ c ¤ f ct in metric), but not less than 1.0, when fct is specified. The factors of Section 2.14b and Section 2.14d shall also be applied. d. The basic development length may be multiplied by the applicable factor or factors for: Reinforcement being developed in length under consideration and spaced laterally at least 6 inches (150 mm) on center with at least 3 inches (75 mm) clear from face of member to edge bar, measured in the direction of the spacing (Figure 8-2-2). . . . . . . . . . . 0.8 Bars enclosed within a spiral which is not less than 1/4 inch (6 mm) diameter and not more than 4 inch (100 mm) pitch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.75

e.

The basic development length for bars coated with epoxy with cover less than 3 bar diameters or clear spacing between bars less than 6 bar diameters shall be multiplied by a factor of 1.5. The basic development length for all other epoxy coated bars shall be multiplied by a factor of 1.15. The product obtained when combining the factor for top reinforcement with the applicable factor for epoxy coated reinforcement need not be taken greater than 1.7.

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f.

The development length ld shall be taken as not less than 12 inches (300 mm) except in the computation of lap splices by Article 2.22.3 and anchorage of shear reinforcement by Section 2.21.

Figure 8-2-2. Reinforcement Spacing

SECTION 2.15 DEVELOPMENT LENGTH OF DEFORMED BARS IN COMPRESSION (2005) The development length ld for bars in compression shall be computed as 0.02f y d b ¤ ( f ¢ c) (or f y d b ¤ 4 ( f ¢ c) in metric), but shall not be less than 0.0003 fydb or 8 inches [or (0.04 dbfy) or 200 mm in metric]. Where excess bar area is provided the ld length may be reduced by the ratio of required area to area provided. The development length may be reduced 25% when the reinforcement is enclosed by spirals not less than 1/4 inch (6 mm) in diameter and not more than 4 inch (100 mm) pitch.

1

3 SECTION 2.16 DEVELOPMENT LENGTH OF BUNDLED BARS (1990) The development length of each bar of bundled bars shall be that for the individual bar, increased by 20% for a three-bar bundle, and 33% for a four-bar bundle.

4 SECTION 2.17 DEVELOPMENT OF STANDARD HOOKS IN TENSION (2005) a.

Development length ldh, in inches (mm), for deformed bars in tension terminating in a standard hook (Article 2.4.1) shall be computed as the product of the basic development length lhb of Section 2.17b and the applicable modification factor or factors of Section 2.17c but ldh shall not be less than 8db or 6 inches (150 mm), whichever is greater.

b. Basic development length lhb for a hooked bar with fy equal to 60,000 psi (420 MPa) shall be 1200d b ¤ ( f ¢ c) (or 100d b ¤ ( f ¢ c) in metric). c.

Basic development length lhb shall be multiplied by applicable modification factor or factors for:

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(1) Bar yield strength Bars with fy other than 60,000 psi (420 MPa) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . fy/60,000 (fy/420) (2) Concrete cover For #11 (#36) bar and smaller, side cover (normal to plane of hook) not less than 2-1/2 inches (60 mm), and for 90 degree hook, cover on bar extension beyond hook not less than 2 inches (50 mm).. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.7 (3) Ties or stirrups For #11 (#36) bar and smaller, hook enclosed vertically or horizontally within ties or stirrup-ties spaced along full development length ldh not greater than 3db, where db is diameter of hooked bar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.8 (4) Excess reinforcement Where anchorage or development for fy is not specifically required, ( A s required ) reinforcement in excess of that required by analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . ------------------------------------( A s provided ) (5) Lightweight aggregate concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 d. For bars being developed by a standard hook at discontinuous ends of members with both side cover and top (or bottom) cover over hook less than 2-1/2 inches (60 mm), hooked bar shall be enclosed within ties or stirrups spaced along full development length ldh not greater than 3db, where db is diameter of hooked bar (Figure 8-2-3). For this case, factor of Section 2.17c(3) shall not apply. e.

Hooks shall not be considered effective in developing bars in compression.

Figure 8-2-3. Standard Hook Bars © 2011, American Railway Engineering and Maintenance-of-Way Association

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SECTION 2.18 COMBINATION DEVELOPMENT LENGTH Information deleted in 1990 revision.

SECTION 2.19 DEVELOPMENT OF WELDED WIRE FABRIC IN TENSION 2.19.1 DEFORMED WIRE FABRIC (2005) a.

Development length ld, in inches (mm), of welded deformed wire fabric measured from point of critical section to end of wire shall be computed as the product of the basic development length of Article 2.19.1b or Article 2.19.1c and applicable modification factor or factors of Section 2.14b, Section 2.14c and Section 2.14d; but ld shall not be less than 8 inches (200 mm) except in computation of lap splices by Article 2.22.6 and development of shear reinforcement by Section 2.21.

b. Basic development length of welded deformed wire fabric, with at least one cross wire within the development length not less than 2 inches (50 mm) from point of critical section, shall be 0.03d b ( f y – 20, 000 ) ¤ 0.36d b ( f y – 140 ) ¤

f¢

f¢ c

NOTE: The 20,000 has units of psi. NOTE: The 140 has units of MPa.

EQ 2-9 EQ 2-9M

1

but not less than 0.20A w æ f y ö -------------------- ç ------------÷ s w è f¢ ø c c.

EQ 2-10

3

Basic development length of welded deformed wire fabric, with no cross wires within the development length, shall be determined as for deformed wire.

2.19.2 SMOOTH WIRE FABRIC (2005) Yield strength of welded smooth wire fabric shall be considered developed by embedment of two cross wires with the closer cross wire not less than 2 inches (50 mm) from point of critical section. However, development length ld measured from point of critical section to outermost cross wire shall not be less than 0.27A w æ f y ö -------------------- ç ------------÷ s w è f¢ ø c

EQ 2-11

3.3A w æ f y ö ---------------- ç ------------÷ s w è f¢ ø c

EQ 2-11M

modified by a factor of Section 2.14c for lightweight aggregate concrete, but ld shall not be less than 6 inches (150 mm) except in computation of lap splices by Article 2.22.7.

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SECTION 2.20 MECHANICAL ANCHORAGE (1992) a.

Any mechanical device shown by tests to be capable of developing the strength of reinforcement without damage to concrete may be used as anchorage.

b. Development of reinforcement may consist of a combination of mechanical anchorage plus additional embedment length of reinforcement between point of maximum bar stress and the mechanical anchorage.

SECTION 2.21 ANCHORAGE OF SHEAR REINFORCEMENT (2005) a.

Shear reinforcement shall extend to a distance d from the extreme compression fiber and shall be carried as close to the compression and tension surfaces of the member as cover requirements and the proximity of other reinforcement permit. Shear reinforcement shall be anchored at both ends for its design yield strength.

b. The ends of single leg, single U-, or multiple U-stirrups shall be anchored by one of the following means: (1) For #5 (#16) bar and D31 wire, and smaller, and for #6, #7, and #8 (#19, #22, and #25) bars with fy of 40,000 psi (280 MPa) or less, a standard hook around longitudinal reinforcement. (2) See Figure 8-2-4. For #6, #7, and #8 (#19, #22, and #25) stirrups with fy greater than 40,000 psi (280 MPa), a standard hook around a longitudinal bar plus an embedment between mid-height of the member and the outside end of the hook equal to or greater than 0.014d b f y ¤ f ¢ c ( 0.17d b f y ¤ f ¢ c in metric). (3) For each leg of welded plain wire fabric forming single U-stirrups, either: (a) Two longitudinal wires spaced at 2 inch (50 mm) spacing along the beam at the top of the U. (b) One longitudinal wire located not more than d/4 from the compression face and a second wire closer to the compression face and spaced at least 2 inches (50 mm) from the first wire. The second wire may be located beyond a bend or on a bend which has an inside diameter of at least 8 wire diameters. c.

Pairs of U-stirrups or ties so placed as to form a closed unit shall be considered properly spliced when the laps are 1.7 ld.

d. Between the anchored ends, each bend in the continuous portion of a transverse single U- or multiple Ustirrup shall enclose a longitudinal bar. e.

Longitudinal bars bent to act as shear reinforcement shall, in a region of tension, be continuous with the longitudinal reinforcement and in a compression zone shall be anchored, above or below the mid-depth d/2 as specified for development length in Section 2.14 for that part of the stress in the reinforcement needed to satisfy EQ 2-21 or EQ 2-52.

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Figure 8-2-4. #6, 7, or 8 Stirrups (fy > 40,000 psi) (#19, 22, or 25) (fy > 280 MPa)

1 SECTION 2.22 SPLICES OF REINFORCEMENT Splices of reinforcement shall be made only as shown on design drawings, or as specified, or as authorized by the Engineer.

3

2.22.1 LAP SPLICES (2005) a.

Lap splices shall not be used for bars larger than #11 (#36).

b. Lap splices of bundled bars shall be based on the lap splice length required for individual bars within a bundle, increased 20% for a 3-bar bundle and 33% for a 4-bar bundle. Individual bar splices within a bundle shall not overlap. c.

Bars spliced by noncontact lap splices in flexural members shall not be spaced transversely farther apart than 1/5 the required lap splice length, nor 6 inches (150 mm).

2.22.2 WELDED SPLICES AND MECHANICAL CONNECTIONS (2005) a.

Welded splices and other mechanical connections may be used. Except as provided herein, all welding shall conform to “Structural Welding Code–Reinforcing Steel” (AWS D1.4).

b. A full welded splice shall have bars butted and welded to develop in tension at least 125% of specified yield strength fy of the bar. c.

A full mechanical connection shall develop in tension or compression, as required, at least 125% of specified yield strength fy of the bar.

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d. Welded splices and mechanical connections not meeting requirements of Article 2.22.2b or Article 2.22.2c may be used in accordance with Article 2.22.3d.

2.22.3 SPLICES OF DEFORMED BARS AND DEFORMED WIRE IN TENSION (2005) a.

Minimum length of lap for tension lap splices shall be as required for Class A, B, or C splice, but not less than 12 inches (300 mm), where: Class A splice = 1.0ld Class B splice = 1.3ld Class C splice = 1.7ld where: ld = the tensile development length for the specified yield strength fy in accordance with Section 2.14.

b. Lap splices of deformed bars and deformed wire in tension shall conform to Table 8-2-9. Table 8-2-9. Tension Lap Splices (As Provided/As Required) (Note 1)

Maximum Percent of As Spliced within Required Lap Length 50

75

100

Equal to or greater than 2

Class A

Class A

Class B

Less than 2

Class B

Class C

Class C

Note 1: Ratio of area of reinforcement provided to area of reinforcement required by analysis at splice location. c.

Welded splices or mechanical connections used where area of reinforcement provided is less than twice that required by analysis shall meet requirements of Article 2.22.2b or Article 2.22.2c.

d. Welded splices or mechanical connections used where area of reinforcement provided is at least twice that required by analysis shall meet the following: (1) Splices shall be staggered at least 24 inches (600 mm) and in such manner as to develop at every section at least twice the calculated tensile force at that section but not less than 20,000 psi (140 MPa) for total area of reinforcement provided. (2) In computing tensile force developed at each section, spliced reinforcement may be rated at the specified splice strength. Unspliced reinforcement shall be rated at that fraction of fy defined by the ratio of the shorter actual development length to ld required to develop the specified yield strength fy. e.

Splices in “tension tie members” shall be made with a full welded splice or full mechanical connection and splices in adjacent bars shall be staggered at least 30 inches (750 mm).

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2.22.4 SPLICES OF DEFORMED BARS IN COMPRESSION (2005) a.

Minimum length of lap for compression lap splices shall be 0.0005fydb, in inches (or 0.07fydb in millimeters), but not less than 12 inches (300 mm). For f ¢ c less than 3000 psi (20 MPa), length of lap shall be increased by/1/3.

b. In tied reinforced compression members, where ties throughout the lap splice length have an effective area not less than 0.0015hs, lap splice length may be multiplied by 0.83, but lap length shall not be less than 12 inches (300 mm). Tie legs perpendicular to dimension h shall be used in determining effective area. c.

In spirally reinforced compression members, lap splice length of bars within a spiral may be multiplied by 0.75, but lap length shall not be less than 12 inches (300 mm).

d. Welded splices or mechanical connections used in compression shall meet requirements of Article 2.22.2b or Article 2.22.2c.

2.22.5 END BEARING SPLICES (1992) In bars required for compression only, compressive stress may be transmitted by bearing of square cut ends held in concentric contact by a suitable device. Bar ends shall terminate in flat surfaces within 1-1/2 degrees of a right angle to the axis of the bars and shall be fitted within 3 degrees of full bearing after assembly. End bearing splices shall be used only in members containing closed ties, closed stirrups, or spirals.

1 2.22.6 SPLICES OF WELDED DEFORMED WIRE FABRIC IN TENSION (2005) a.

Minimum length of lap for lap splices of welded deformed wire fabric measured between the end of each fabric sheet shall not be less than 1.7ld nor 8 inches (200 mm), and the overlap measured between outermost cross wires of each fabric sheet shall not be less than 2 inches (50 mm). ld shall be the development length for the specified yield strength fy, in accordance with Article 2.19.1.

3

b. Lap splices of welded deformed wire fabric, with no cross wires within the lap splice length, shall be determined as for deformed wire.

2.22.7 SPLICES OF WELDED SMOOTH WIRE FABRIC IN TENSION (2005) Minimum length of lap for lap splices of welded smooth wire fabric shall be in accordance with the following: a.

When area of reinforcement provided is less than twice that required by analysis at splice location, length of overlap measured between outermost cross wires of each fabric sheet shall not be less than one spacing of cross wire plus 2 inches (50 mm), nor less than 1.5ld nor 6 inches (150 mm). ld shall be the development length for the specified yield strength fy in accordance with Article 2.19.2.

b. When area of reinforcement provided is at least twice that required by analysis at splice location, length of overlap measured between outermost cross wires of each fabric sheet shall not be less than 1.5ld nor 2 inches (50 mm). ld shall be the development length for the specified yield strength fy in accordance with Article 2.19.2.

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ANALYSIS AND DESIGN – GENERAL CONSIDERATIONS

SECTION 2.23 ANALYSIS METHODS 2.23.1 GENERAL (1992) a.

All members of continuous and rigid frame structures shall be designed for the maximum effects of the loads specified in Article 2.2.3 as determined by the theory of elastic analysis.

b. Consideration shall be given to the effects of forces due to shrinkage, temperature changes, creep, and unequal settlement of supports.

2.23.2 EXPANSION AND CONTRACTION (2005) a.

In general, provision for temperature changes shall be made in simple spans when the span length exceeds 40 feet (12 m).

b. In continuous bridges, provision shall be made in the design to resist thermal stresses induced or means shall be provided for movement caused by temperature changes. c.

Movements not otherwise provided for shall be provided by rockers, sliding plates, elastomeric pads or other means.

2.23.3 STIFFNESS (1992) a.

Any reasonable assumptions may be adopted for computing the relative flexural and torsional stiffnesses of continuous and rigid frame members. The assumptions made shall be consistent throughout the analysis.

b. Effect of haunches shall be considered both in determining moments and in design of members.

2.23.4 MODULUS OF ELASTICITY (2005) a.

Modulus of elasticity Ec for concrete may be taken as w c

1.5

33 f ¢ c , in psi (or w c

1.5

0.043 f ¢ c in MPa), for

values of wc between 90 and 155 pcf (1500 and 2500 kg/m3). For normal weight concrete (wc = 145 pcf, wc = 2300 kg/m3), Ec may be considered as 57, 000 f ¢ c (or 4700 f ¢ c in metric) . b. Modulus of elasticity of nonprestressed steel reinforcement may be taken as 29,000,000 psi (200 GPa).

2.23.5 THERMAL AND SHRINKAGE COEFFICIENTS (2005) a.

Thermal coefficient for normal weight concrete may be taken as 0.000006 per degree F (or 0.0000105 per degree C).

b. Shrinkage coefficient for normal weight concrete may be taken as 0.0002.

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c.

Thermal and shrinkage coefficients for lightweight concrete shall be determined for the type of lightweight aggregate used.

2.23.6 SPAN LENGTH (1992) a.

Span length of members not built integrally with supports shall be considered the clear span plus depth of member, but need not exceed distance between centers of supports.

b. In analysis of continuous and rigid frame members, center-to-center distances shall be used in the determination of moments. Moments at faces of support may be used for member design. When fillets making an angle of 45 degrees or more with the axis of a continuous or restrained member are built monolithic with the member and support, face of support shall be considered at a section where the combined depth of the member and fillet is at least one and one-half times the thickness of the member. No portion of a fillet shall be considered as adding to the effective depth. c.

Effective span length of slabs shall be as follows: (1) Slabs monolithic with beams or walls (without haunches), S = clear span. (2) Slabs supported on steel stringers, S = distance between edges of flanges plus 1/2 the stringer flange width.

2.23.7 COMPUTATION OF DEFLECTIONS (2005) a.

Where deflections are to be computed, they shall be based on the cross-sectional properties of the entire superstructure section except railings, curbs, sidewalks or any element not placed monolithically with the superstructure section before falsework removal. Deflections of composite members shall take into account shoring during erection, differential shrinkage of the elements and the magnitude and duration of load prior to the beginning of effective composite action.

b. Computation of live load deflection may be based on the assumption that the superstructure flexural members act together and have equal deflection. The live loading shall consist of all tracks loaded as specified in Article 2.2.3c. The live loading shall be considered uniformly distributed to all longitudinal flexural members. c.

1

3

Computation of Immediate Deflection. (1) Deflections that occur immediately on application of load shall be computed by the usual methods of formulas for elastic deflections. Unless values are obtained by a more comprehensive analysis, deflections shall be computed taking the modulus of elasticity for concrete as specified in Article 2.23.4a for normal weight or lightweight concrete and taking the effective moment of inertia as follows, but not greater than Ig. M cr 3 M cr 3 I c = æ ----------ö I g + 1 – æ ----------ö I cr èM ø èM ø a a

EQ 2-12

where: fr Ig Mcr= ---------yt

EQ 2-13

fr = modulus of rupture of concrete specified in Article 2.26.1a

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(2) For continuous spans, the effective moment of inertia may be taken as the average of the values obtained from EQ 2-12 for the critical positive and negative moment sections. 2.23.7.1 Computation of Long-time Deflection Unless values are obtained by more comprehensive analysis, the additional long-term deflection for both normal weight and lightweight concrete flexural members shall be obtained by multiplying the immediate deflection caused by the sustained load considered, computed in accordance with Article 2.23.7c, by the factor æ 2 – 1.2 A¢ ---------s-ö ³ 0.6 è A ø s

2.23.8 BEARINGS (2005) Bearing devices shall be designed in accordance with Part 18 Elastomeric Bridge Bearings and Chapter 15, Part 10 and Part 11. Bearing stresses in concrete shall not exceed the values given in Section 2.26 or Section 2.36.

2.23.9 COMPOSITE CONCRETE FLEXURAL MEMBERS (1992) a.

Application. Composite flexural members consist of concrete elements constructed in separate placements but so interconnected that the elements respond to loads as a unit.

b. General Considerations. (1) The total depth of the composite member or portions thereof may be used in resisting the shear and the bending moment. The individual elements shall be investigated for all critical stages of loading. (2) If the specified strength, unit weight, or other properties of the various components are different, the properties of the individual components, or the most critical values, shall be used in design. (3) In calculating the flexural strength of a composite member by load factor design, no distinction shall be made between shored and unshored members. (4) All elements shall be designed to support all loads introduced prior to the full development of the design strength of the composite member. (5) Reinforcement shall be provided as necessary to control cracking and to prevent separation of the components. c.

Shoring. When used, shoring shall not be removed until the supported elements have developed the design properties required to support all loads and limit deflections and cracking at the time of shoring removal.

d. Vertical Shear. (1) When the total depth of the composite member is assumed to resist the vertical shear, the design shall be in accordance with the requirements of Section 2.29 or Section 2.35 as for a monolithically cast member of the same cross-sectional shape. (2) Shear reinforcement shall be fully anchored in accordance with Section 2.21. Extended and anchored shear reinforcement may be included as ties for horizontal shear.

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e.

Horizontal Shear. In a composite member, full transfer of the shear forces shall be assured at the interfaces of the separate components. Design for horizontal shear shall be in accordance with the requirements of Article 2.29.5 or Article 2.35.5.

2.23.10 T-GIRDER CONSTRUCTION (1992) a.

In T-girder construction, the girder web and slab shall be built integrally or otherwise effectively bonded together. Full transfer of shear forces shall be assured at the interface of web and slab. Where applicable, the design requirements of Article 2.23.9 for composite concrete members shall apply.

b. Compression Flange Width. (1) The effective slab width acting as a T-girder flange shall not exceed one-fourth of the span length of the girder, and its overhanging width on either side of the girder shall not exceed six times the thickness of the slab or one-half the clear distance to the next girder. (2) For girders having a slab on one side only, the effective overhanging flange width shall not exceed 1/12 of the span length of the girder, nor 6 times the thickness of the slab, nor one-half the clear distance to the next girder. (3) Isolated T-girders in which the flange is used to provide additional compression area shall have a flange thickness not less than one-half the width of the girder web and a total flange width not more than four times the width of the girder web. (4) For integral bent caps, the effective overhanging slab width on each side of a bent cap web shall not exceed six times the least slab thickness, nor 1/10 the span length of the bent cap. For cantilevered bent caps, the span length shall be taken as two times the length of cantilever span. c.

Diaphragms. Diaphragms shall be used at span ends. Intermediate diaphragms shall be used where required in the judgment of the Engineer.

1

3

2.23.11 BOX GIRDER CONSTRUCTION (2005) a.

In box girder construction, the girder web and top and bottom slab shall be built integrally or otherwise effectively bonded together. Full transfer of shear forces shall be assured at the interfaces of the girder web with the top and bottom slab. Design shall be in accordance with the requirements of Article 2.23.9. When required by design, changes in girder web thickness shall be tapered for a minimum distance of 12 times the difference in web thickness.

b. Compression Flange Width. (1) For box girder flanges, the entire slab width shall be assumed effective for compression. (2) For integral bent caps, the effective overhanging slab width on each side of a bent cap web shall not exceed six times the least slab thickness, nor 1/10 the span length of the bent cap. For cantilevered bent caps, the span length shall be taken as two times the length of cantilever span. c.

Top and Bottom Slab Thickness. (1) The thickness of the top slab shall be designed for loads specified in Article 2.2.3c, but shall be not less than the minimum specified in Table 8-2-10.

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Table 8-2-10. Recommended Minimum Thickness For Constant Depth Members (Note 1) Minimum Thickness In Feet (Note 2)

Minimum Thickness In Meters (Note 2)

S + 10 ---------------20 but not less than 0.75

S+3 ------------20 but not less than 0.23

T-Girders

S+9 ------------15

S + 2.75 --------------------15

Box Girders

S + 10 ---------------17

S+3 ------------17

Superstructure Type Bridge slabs with main reinforcement parallel or perpendicular to traffic

Note 1: When variable depth members are used, table values may be adjusted to account for change in relative stiffness of positive and negative moment sections. Note 2: Recommended values for simple spans; continuous spans may be about 90% of thickness given. S = span length as defined in Article 2.23.6, in feet (meters). (2) The thickness of the bottom slab shall be not less than 1/16 of the clear span between girder webs or 6 inches (150 mm), whichever is greater, except that the thickness need not be greater than the top slab unless required by design. d. Top and Bottom Slab Reinforcement. (1) Minimum distributed reinforcement of 0.4% of the flange area shall be placed in the bottom slab parallel to the girder span. A single layer of reinforcement may be provided. The spacing of such reinforcement shall not exceed 18 inches (450 mm). (2) Minimum distributed reinforcement of 0.5% of the cross-sectional area of the slab, based on the least slab thickness, shall be placed in the bottom slab transverse to the girder span. Such reinforcement shall be distributed over both surfaces with a maximum spacing of 18 inches (450 mm). All transverse reinforcement in the bottom slab shall extend to the exterior face of the outside girder web in each group and be anchored by a standard 90 degree hook. (3) At least 1/3 of the bottom layer of the transverse reinforcement in the top slab shall extend to the exterior face of the outside girder web in each group and be anchored by a standard 90 degree hook. If the slab extends beyond the last girder web, such reinforcement shall extend into the slab overhang and shall have an anchorage beyond the exterior face of the girder web not less than that provided by a standard hook. e.

Diaphragms. Diaphragms shall be used at span ends. Intermediate diaphragms shall be used where required in the judgment of the Engineer. Diaphragm spacing for curved girders shall be given special consideration.

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SECTION 2.24 DESIGN METHODS (1992) The design methods to be used, SERVICE LOAD DESIGN or LOAD FACTOR DESIGN, shall be as directed by the Engineer.

SERVICE LOAD DESIGN (APPLICABLE TO Section 2.25 THROUGH Section 2.29)

SECTION 2.25 GENERAL REQUIREMENTS (1992) a.

For reinforced concrete members designed with reference to service loads and allowable stresses, the service load stresses shall not exceed the values given in Section 2.26.

b. Development and splices of reinforcement shall be as required under Development and Splices of Reinforcement.

1 SECTION 2.26 ALLOWABLE SERVICE LOAD STRESSES 2.26.1 CONCRETE (2005)

3

For service load design, stresses in concrete shall not exceed the following: a.

Flexure: Extreme fiber stress in compression fc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.40 f ¢ c Extreme fiber stress in tension for plain concrete, ft . . . . . . . . . . . . . . . . . . . . . 0.21 fr

4

Modulus of rupture f r, from tests, or if data are not available: Normal weight concrete. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5 f ¢ c 0.62 f ¢ c (metric) Lightweight concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 f ¢ c 0.52 f ¢ c (metric)

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b. Shear: NOTE:

For more detailed analysis of permissible shear stress vc carried by concrete, and shear values for lightweight aggregate concrete – see Article 2.29.2.

Beams and one-way slabs and footings: Shear carried by concrete vc, but not to exceed 95 psi (0.66 MPa) 0.95 f ¢ c 0.079 f ¢ c (metric) Maximum shear carried by concrete plus shear reinforcement

vc + 4 f ¢ c v c + 0.33 f ¢ c (metric)

Two-way slabs and footings: (If shear reinforcement is provided see Article 2.29.6d) 2ö æ 0.8 + ---- f¢ c è bø

Shear carried by concrete vc

c

æ 0.066 + 0.17 -----------ö f ¢ c (metric) è b ø c

but not greater than

1.8 f ¢ c 0.15 f ¢ c (metric)

c.

Bearing on loaded area fb, but not to exceed 1050 psi (7.2 MPa) . . . . . . . . . . . . . 0.30 f ¢ c Minimum distance from edge of bearing to edge of supporting concrete shall be 6 inches (150 mm).

2.26.2 REINFORCEMENT (2005) a.

For service load design, tensile stress in reinforcement fs shall not exceed the following: Grade 40 (Grade 280) reinforcement

20,000 psi (140 MPa)

Grade 60 (Grade 420) reinforcement

24,000 psi (170 MPa)

b. Fatigue Stress Limit. (1) The range between a maximum tensile stress and minimum stress in straight reinforcement caused by live load plus impact shall not exceed the value obtained from: ff = 21 – 0.33fmin + 8 (r / h) ff = 145 – 0.33fmin + 55 (r / h)

(metric)

where: ff = stress range in steel reinforcement, ksi (MPa).

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fmin = algebraic minimum stress level, tension positive, compression negative, ksi (MPa). r/h = ratio of base radius to height of rolled-on transverse deformations; when the actual value is not known, use 0.3. (2) Bends in primary reinforcement shall be avoided in regions of high stress range.

SECTION 2.27 FLEXURE (2005) For investigation of service load stresses, the straight-line theory of stress and strain in flexure shall be used and the following assumptions shall be made: a.

A section plane before bending remains plane after bending; strains vary as the distance from the neutral axis.

b. Stress-strain relation of concrete is a straight line under service loads within the allowable service load stresses. Stresses vary as the distance from the neutral axis except, for deep flexural members with overall depth-clear-span ratios greater than 2/5 for continuous spans and 4/5 for simple spans, a nonlinear distribution of stress should be considered. c.

Steel takes all the tension due to flexure.

1

d. Modular ratio n = Es/Ec may be taken as the nearest whole number (but not less than 6). Except in calculations for deflections, the value of n for lightweight concrete shall be assumed to be the same as for normal weight concrete of the same strength. e.

In doubly reinforced flexural members, an effective modular ratio of 2Es/Ec shall be used to transform the compression reinforcement for stress computations. The compressive stress in such reinforcement shall not be greater than the allowable tensile stress.

SECTION 2.28 COMPRESSION MEMBERS WITH OR WITHOUT FLEXURE (1992) The combined axial load and moment capacity of compression members shall be taken as 35% of that computed in accordance with the provisions of Section 2.33. Slenderness effects shall be included according to the requirements of Section 2.34. The term Pu in Article 2.33.1b shall be replaced by 2.85 times the design axial load. In using the provisions of Section 2.33 and Section 2.34, F shall be taken as 1.0.

SECTION 2.29 SHEAR 2.29.1 SHEAR STRESS (2005) a.

Design shear stress v shall be computed by:

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V v = ----------bw d

EQ 2-14

where: bw = the width of web d = the distance from the extreme compression fiber to the centroid of the longitudinal tension reinforcement. For a circular section, bw shall be taken as the diameter and d shall be taken as 0.8 times the diameter of the section. b. When the reaction in the direction of the applied shear introduces compression into the end region of the member, sections located less than a distance d from the face of the support may be designed for the same shear v as that computed at a distance d. An exception occurs when major concentrated loads are imposed between that point and the face of support. In that case sections closer than d to the support shall be designed for V at distance d plus the major concentrated loads. c.

Shear stress carried by concrete vc shall be calculated according to Article 2.29.2. When v exceeds vc, shear reinforcement shall be provided according to Article 2.29.3. Whenever applicable, the effects of torsion shall be added.

d. For tapered webs, bw shall be the average width or 1.2 times the minimum width, whichever is smaller.

2.29.2 PERMISSIBLE SHEAR STRESS (2005) NOTE:

The value of

f ¢ c used in computing vc in this paragraph shall not be taken greater than

100 psi (0.69 MPa). a.

Shear stress carried by concrete vc shall not exceed 0.95 f ¢ c (or 0.079 f ¢ c in metric) unless a more detailed analysis is made in accordance with Article 2.29.2b or Article 2.29.2c. For members subject to axial tension, vc shall not exceed the value given in Article 2.29.2d. For lightweight concrete, the provisions of Article 2.29.2f shall apply.

b. Shear stress carried by concrete vc, for members subject to shear and flexure only, may be computed by: Vd v c = 0.9 f ¢ c + 1100r w -------M

EQ 2-15

Vd v c = 0.075 f ¢ c + 7.58r w -------M

EQ 2-15M

Vd but vc shall not exceed 1.6 f ¢c (or 0.13 f ¢c in metric). The quantity -------- shall not be taken greater than M 1.0, where M is the design moment occurring simultaneously with V at the section considered. c.

For members subject to axial compression, vc may be computed by:

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0.0006N v c = 0.9 æ 1 + -----------------------ö f ¢ c è Ag ø

EQ 2-16

0.0006N v c = 10.8 æ 0.0069 + -----------------------ö f ¢ c è Ag ø

EQ 2-16M

N The quantity ------- shall be expressed in psi (MPa). Ag d. For members subject to significant axial tension, shear reinforcement shall be designed to carry the total shear, unless a more detailed analysis is made using: 0.004N v c = 0.9 æ 1 + --------------------ö f¢ c è Ag ø

EQ 2-17

0.004N v c = 10.8 æ 0.0069 + --------------------ö f¢ c è Ag ø

EQ 2-17M

where: N = negative for tension

e.

N The quantity ------- shall be expressed in psi (MPa). Ag Special provisions for slabs of box culverts. For slabs of box culverts under 2 feet (600 mm) or more fill, shear stress vc may be computed by: vc =

Vd f¢ c + 2200r -------M

EQ 2-18

Vd v c = 0.083 f¢ c + 15.2r -------M

taken less than 1.4 f¢ c (or 0.12 f¢ c in metric) for slabs monolithic with walls or 1.2 f¢ c (or 0.10 f¢ c Vd in metric) for slabs simply supported. The quantity of -------- shall not be taken greater than 1.0, where M is M moment occurring simultaneously with V at section considered. The provisions for shear stress vc carried by concrete apply to normal weight concrete. When lightweight aggregate concretes are used, one of the following modifications shall apply: (1) When fct is specified, shear stress vc shall be modified by substituting fct/6.7 (or 1.8 fct in metric) for f¢ c but the value of fct/6.7 (or 1.8 fct in metric) used shall not exceed

f¢ c.

(2) When fct is not specified, shear stress vc shall be multiplied by 0.85.

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EQ 2-18M

but vc shall not exceed 1.8 f¢ c (or 0.15 f¢ c in metric). For single cell box culverts only, vc need not be

f.

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Concrete Structures and Foundations

2.29.3 DESIGN OF SHEAR REINFORCEMENT (2005) a.

Shear reinforcement shall conform to the general requirements of Section 2.10. When shear reinforcement perpendicular to the axis of the member is used, required area shall be computed by: ( v – v c )b w s A v = -----------------------------fs

EQ 2-19

b. When inclined stirrups or bent bars are used as shear reinforcement the following provisions apply: (1) When inclined stirrups are used, required area shall be computed by: ( v – v c )b w s A v = ----------------------------------------f s ( sin a + cos a)

EQ 2-20

(2) When shear reinforcement consists of a single bar or a single group of parallel bars, all bent up at the same distance from the support, required area shall be computed by: ( v – v c )b w d A v = ------------------------------f s sin a

EQ 2-21

in which (v – vc) shall not exceed 1.5 f¢ c (or 0.12 f¢ c in metric). (3) When shear reinforcement consists of a series of parallel bent-up bars or groups of parallel bent-up bars at different distances from the support, required area shall be computed by Article 2.29.3b(1). (4) Only the center three-fourths of the inclined portion of any longitudinal bar that is bent shall be considered effective for shear reinforcement. c.

Where more than one type of shear reinforcement is used to reinforce the same portion of the member, required area shall be computed as the sum for the various types separately. No one type shall resist more than 2/3 of the total shear resisted by reinforcement. In such computations, vc shall be included only once.

d. When (v – vc) exceed 2 f¢ c (or 0.17 f¢ c in metric), maximum spacings given in Article 2.10.3 shall be reduced by one-half. e.

The value of (v – vc) shall not exceed 4 f¢ c (or 0.33 f¢ c in metric).

f.

When flexural reinforcement located within the width of a member used to compute the shear strength is terminated in a tension zone, shear reinforcement shall be provided in accordance with Article 2.13.1f.

2.29.4 SHEAR-FRICTION (2005) a.

Provisions for shear-friction are to be applied where it is appropriate to consider shear transfer across a given plane, such as: an existing or potential crack, an interface between dissimilar materials, or an interface between two concretes cast at different times.

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b. A crack shall be assumed to occur along the shear plane considered. Required area of shear-friction reinforcement Avf across the shear plane may be designed using either Article 2.29.4c or any other shear transfer design methods that result in prediction of strength in substantial agreement with results of comprehensive tests. Provisions of Article 2.29.4d through Article 2.29.4h shall apply for all calculations of shear transfer strength. c.

Shear-friction design method. (1) Shear-friction reinforcement is perpendicular to shear plane, area of shear-friction reinforcement Avf shall be computed by: V A vf = ------fs m

EQ 2-22

where: m = the coefficient of friction in accordance with Article 2.29.4c(3). (2) When shear-friction reinforcement is inclined to shear plane such that the shear force produces tension in shear-friction reinforcement, area of shear-friction reinforcement Avf shall be computed by: V A vf = -----------------------------------------------f s ( m sin af + cos af )

EQ 2-23

1

where: af = angle between shear-friction reinforcement and shear plane.

3

(3) Coefficient of friction m in EQ 2-22 and EQ 2-23 shall be concrete placed monolithically. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4l concrete placed against hardened concrete with surface intentionally roughened as specified in Article 2.29.4g . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.0l

4

concrete placed against hardened concrete not intentionally roughened . . . . 0.6l concrete anchored to as-rolled structural steel by headed studs or by reinforcing bars (see Article 2.29.4h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.7l where: l = 1.0 for normal weight concrete and 0.85 for lightweight concrete.

d. Shear stress v on area of concrete section resisting shear transfer shall not exceed 0.09 f ¢ c nor 360 psi (2.5 MPa). e.

Net tension across shear plane shall be resisted by additional reinforcement. Permanent net compression across shear plane may be taken as additive to the force in the shear-friction reinforcement A v f f s , when calculating required A v f .

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Concrete Structures and Foundations

f.

Shear-friction reinforcement shall be appropriately placed along the shear plane and shall be anchored to develop the specified yield strength on both sides by embedment, hooks, or welding to special devices.

g.

For the purpose of Article 2.29.4, when concrete is placed against previously hardened concrete, the interface for shear transfer shall be clean and free of laitance. If m is assumed equal to 1.0l, interface shall be roughened to a full amplitude of approximately 0.25 inches (6 mm).

h. When shear is transferred between as-rolled steel and concrete using headed studs or welded reinforcing bars, steel shall be clean and free of paint.

2.29.5 HORIZONTAL SHEAR DESIGN FOR COMPOSITE CONCRETE FLEXURAL MEMBERS (2005) a.

In a composite member, full transfer of horizontal shear forces shall be assured at contact surfaces of interconnected elements.

b. Design of cross sections subject to horizontal shear may be in accordance with provisions of Article 2.29.5c or Article 2.29.5d, or any other shear transfer design method that results in prediction of strength in substantial agreement with results of comprehensive tests. c.

Design horizontal shear stress vdh at any cross section may be computed by: V v dh = ----------bw d

EQ 2-24

where: V = design shear force at section considered d = depth of entire composite section Horizontal shear vdh shall not exceed permissible horizontal shear vh in accordance with the following: (1) When contact surface is clean, free of laitance, and intentionally roughened, shear stress vh shall not exceed 36 psi (0.25 MPa). (2) When minimum ties are provided in accordance with Article 2.29.5e, and contact surface is clean and free of laitance, but not intentionally roughened, shear stress vh shall not exceed 36 psi (0.25 MPa). (3) When minimum ties are provided in accordance with Article 2.29.5e, and contact surface is clean, free of laitance, and intentionally roughened to a full amplitude of approximately 1/4 inch (6 mm), shear stress vh shall not exceed 160 psi (1.1 MPa). (4) For each percent of tie reinforcement crossing the contact surface in excess of the minimum required by Article 2.29.5e, permissible vh may be increased by 72fy /40,000 psi (or 72fy /280 MPa in metric). d. Horizontal shear may be investigated by computing, in any segment not exceeding one-tenth of the span, the actual change in compressive or tensile force, and provisions made to transfer that force as horizontal shear between interconnected elements. Horizontal shear shall not exceed the permissible horizontal shear stress vh in accordance with Article 2.29.5c. e.

Ties for horizontal shear.

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Reinforced Concrete Design

(1) A minimum area of tie reinforcement shall be provided between interconnected elements. Tie area shall not be less than 50bws/fy (or 0.35bws/fy in metric), and tie spacing ‘s’ shall not exceed 4 times the least web width of support element, nor 24 inches (600 mm). (2) Ties for horizontal shear may consist of single bars or wire, multiple leg stirrups, or vertical legs of welded wire fabric (smooth or deformed). All ties shall be adequately anchored into interconnected elements by embedment or hooks. (3) All beam shear reinforcement shall extend into cast-in-place deck slabs. Extended shear reinforcement may be used in satisfying the minimum tie reinforcement.

2.29.6 SPECIAL PROVISIONS FOR SLABS AND FOOTINGS (2005) a.

Shear capacity of slabs and footings in the vicinity of concentrated loads or reactions shall be governed by the more severe of two conditions: (1) The slab or footing acting as a wide beam, with a critical section extending in a plane across the entire width and located at a distance d from the face of the concentrated load or reaction area. For this condition, the slab or footing shall be designed in accordance with Article 2.29.1 through Article 2.29.3. (2) Two-way action for the slab or footing, with a critical section perpendicular to the plane of the slab and located so that its perimeter is a minimum and approaches no closer than d/2 to the perimeter of the concentrated load or reaction area. For this condition, the slab or footing shall be designed in accordance with Article 2.29.6b and Article 2.29.6c.

1

(3) At footings supported on piles the shear on the critical section shall be determined in accordance with: (a) Entire reaction from any pile whose center is located dp/2 or more outside the critical section shall be considered as producing shear on that section.

3

(b) Reaction from any pile whose center is located dp/2 or more inside the critical section shall be considered as producing no shear on that section. (c) For intermediate positions of pile center, the portion of the pile reaction to be considered as producing shear on the critical section shall be based on linear interpolation between full value at dp/2 outside the section and zero value at dp/2 inside the section. b. Design shear stress for two-way action shall be computed by: V v = --------bo d

EQ 2-25

where: V and bo = are taken at the critical section defined in Article 2.29.6a(2). c.

Design shear v shall not exceed the smallest vc given by EQ 2-26 or EQ 2-27 unless shear reinforcement is provided in accordance with Article 2.29.6d.

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2 v c = æ 0.8 + -----ö f¢ c ; f’c in psi è bø

EQ 2-26

c

0.17 v c = æ 0.066 + -----------ö è b ø

EQ 2-26M

f¢ c ; f’c in MPa

c

or as d v c = æ 0.8 + ---------ö f¢ c ; f’c in psi è b ø

EQ 2-27

o

as d f¢ c v c = æ 0.8 + ---------ö ------------ ; f’c in MPa è b ø 12

EQ 2-27M

o

but not greater than 1.8 f¢ (or 0.15 f¢ in metric). bc is the ratio of long side to short side of c c concentrated load or reaction area. as is 20 for interior concentrated loads or reaction areas, 15 for edge concentrated loads or reaction areas and 10 for corner concentrated loads or reaction areas. d. If shear reinforcement consisting of bars or wires is provided in accordance with Article 2.29.3, vc at any section shall not exceed 0.9 f¢ c (or 0.075 f¢ c in metric) and v shall not exceed 3 f¢ c (or 0.25 f¢ c in metric). Shear stresses shall be investigated at the critical section defined in Article 2.29.6a(2) and at successive sections more distant from the support.

2.29.7 SPECIAL PROVISIONS FOR BRACKETS AND CORBELS (2005) a.

The following provisions shall apply to brackets and corbels with a shear span-to-depth ratio av/d not greater than unity, and subject to a horizontal tensile force Nc not larger than V. Distance d shall be measured at face of support.

b. Depth at outside edge of bearing area shall not be less than 0.5d. c.

Section at face of support shall be designed to resist simultaneously a shear V, a moment [Vav + Nc(h-d)], and a horizontal tensile force Nc. (1) Design of shear-friction reinforcement Avf to resist shear V shall be in accordance with Article 2.29.4. For normal weight concrete, shear stress v shall not exceed 0.09f ¢ c nor 360 psi (2.5 MPa). For “sandlightweight” concrete, shear stress v shall not exceed (0.09 – 0.03av/d)f ¢ c nor (360 – 126av/d) psi (or 2.5 – 0.09av/d) MPa in metric). (2) Reinforcement Af to resist moment [Vav + Nc(h-d)] shall be computed in accordance with Section 2.26 and Section 2.27. (3) Reinforcement An to resist tensile force Nc shall be computed by An = Nc /fs. Tensile force Nc shall not be taken less than 0.2V unless special provisions are made to avoid tensile forces. (4) Area of primary tension reinforcement As shall be made equal to the greater of (Af + An), or (2Av f / 3 + An).

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d. Closed stirrups or ties parallel to As, with a total area Ah not less than 0.5 (As – An), shall be uniformly distributed within two-thirds of the effective depth adjacent to As. e.

Ratio r = As/bd shall not be taken less than 0.04 (f ¢ c /fy).

f.

At front face of bracket or corbel, primary tension reinforcement As shall be anchored by one of the following: (1) a structural weld to a transverse bar of at least equal size; weld to be designed to develop specified yield strength fy of As bars; (2) bending primary tension bars As back to form a horizontal loop, or (3) some other means of positive anchorage.

g.

Bearing area of load on bracket or corbel shall not project beyond straight portion of primary tension bars As, nor project beyond interior face of transverse anchor bar (if one is provided).

LOAD FACTOR DESIGN

1

(APPLICABLE TO Section 2.30 THROUGH Section 2.39) SECTION 2.30 STRENGTH REQUIREMENTS 2.30.1 REQUIRED STRENGTH (2005)

3

Structures and structural members shall be designed to have design strengths at all sections at least equal to the required strengths calculated for the factored loads and forces in such combinations as stipulated in Article 2.2.4c, which represent various combinations of loads and forces to which a structure may be subjected. Each part of such structure shall be proportioned for the group loads that are applicable, and the maximum design required shall be used. Members shall also follow all other requirements of this Chapter to ensure adequate performance at service load levels.

2.30.2 DESIGN STRENGTH (1992) a.

For reinforced concrete members designed with reference to load factors and strengths, the design strength provided by a member, its connections to other members, and its cross sections, in terms of flexure, axial load, and shear, shall be taken as the nominal strength calculated in accordance with the requirements and assumptions of LOAD FACTOR DESIGN, multiplied by a strength reduction factor f.

b. Strength reduction factor f shall be taken as follows: For flexure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . f = 0.90 For shear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . f = 0.85 For spirally reinforced compression members, with or without flexure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . f = 0.75

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For tied reinforced compression members with or without flexure . . . f = 0.70 NOTE:

The value of f may be increased linearly from the value for compression members to the value for flexure as the axial load strength Pn decreases from Pb to zero.

For bearing on concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . f = 0.70 NOTE:

Development and splices of reinforcement specified in Section 2.13 through Section 2.22 do not require a f factor.

SECTION 2.31 DESIGN ASSUMPTIONS 2.31.1 STRENGTH DESIGN (2005) Strength design of members for flexure and axial loads shall be based on the assumptions given in this article, and on satisfaction of the applicable conditions of equilibrium and compatibility of strains. a.

Strain in the reinforcing steel and concrete shall be assumed directly proportional to the distance from the neutral axis.

b. Maximum usable strain at the extreme concrete compression fiber shall be assumed equal to 0.003. c.

Stress in reinforcement below the specified yield strength fy for the grade of steel used shall be taken as Es times the steel strain. For strains greater than that corresponding to fy the stress in the reinforcement shall be considered independent of strain and equal to fy.

d. Tensile strength of concrete shall be neglected in flexural calculations of reinforced concrete. e.

The relationship between concrete compressive stress distribution and concrete strain may be assumed to be a rectangle, trapezoid, parabola, or any other shape which results in prediction of strength in substantial agreement with the results of comprehensive tests.

f.

The requirements of Article 2.31.1e may be considered satisfied by an equivalent rectangular concrete stress distribution defined as follows: A concrete stress of 0.85 f ¢ c shall be assumed uniformly distributed over an equivalent compression zone bounded by the edges of the cross section and a straight line located parallel to the neutral axis at a distance (a = b1c) from the fiber of maximum compressive strain. The distance c from the fiber of maximum strain to the neutral axis is measured in a direction perpendicular to that axis. The factor b1 shall be taken as 0.85 for concrete strength f¢ c up to and including 4000 psi (28 MPa). For strengths above 4000 psi (28 MPa) b1 shall be reduced continuously at a rate of 0.05 for each 1000 psi (7 MPa) of strength in excess of 4000 psi (28 MPa), but b1 shall not be taken less than 0.65.

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SECTION 2.32 FLEXURE 2.32.1 MAXIMUM REINFORCEMENT OF FLEXURAL MEMBERS (1992) a.

For flexural members, the reinforcement r provided shall not exceed 0.75 of that ratio r b which would produce balanced strain conditions for the section under flexure. For flexural members with compression reinforcement, the portion of r b balanced by compression reinforcement need not be reduced by the 0.75 factor.

b. Balanced strain conditions exist at a cross section when the tension reinforcement reaches its specified yield strength fy just as the concrete in compression reaches its assumed ultimate strain of 0.003.

2.32.2 RECTANGULAR SECTIONS WITH TENSION REINFORCEMENT ONLY (2005) a.

For rectangular sections, when r £0.75 r b the design moment strength FMn may be computed by: 0.6r f y FM n = F A s f y d æ 1 – -----------------ö è f¢ c ø

EQ 2-28

a = F A s f y æ d – ---ö è 2ø

EQ 2-29

1

where: As fy a = ----------------------0.85f¢ c b

3

b. The balanced reinforcement ratio r b for rectangular sections with tension reinforcement only is given by: 0.85b 1 f¢ c 87, 000 r b = -------------------------- æ --------------------------------ö è 87, 000 + f ø fy y 0.85b 1 f¢ c 600 r b = -------------------------- æ ---------------------ö è 600 + f ø fy y

EQ 2-30

EQ 2-30M

2.32.3 I- AND T-SECTIONS WITH TENSION REINFORCEMENT ONLY (2005) a.

When the compression flange thickness is equal to or greater than the depth of the equivalent rectangular stress block a and r £0.75 r b, the design moment strength FMn may be computed by the equations given in Article 2.32.2.

b. When the compression flange thickness is less than a, the design moment strength FMn may be computed by:

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Concrete Structures and Foundations

FM n = F ( A s – A sf )f y æ d – --a-ö + A sf f y ( d – 0.5h f ) è 2ø

EQ 2-31

where: h Asf = 0.85f¢ c ( b – b w ) -----f fy ( A s – A sf )f y a = ------------------------------0.85f¢ c b w c.

The balanced reinforcement ratio r b for I- and T-sections with tension reinforcement only is given by: b w 0.85b 1 f¢ c 87, 000 r b = ------- -------------------------- æ --------------------------------ö + r f è 87, 000 + f ø b fy y

EQ 2-32

b w 0.85b 1 f¢ c 600 r b = ------- -------------------------- æ ---------------------ö + r f è 600 + f ø b fy y

EQ 2-32M

where: A sf r f = ----------bw d d. When the compression flange thickness is greater than a, the design moment strength, FMn, may be computed by using the equations in Article 2.32.2. e.

For T-girder and box-girder construction defined by Article 2.23.10 and Article 2.23.11, the width of the compression face b shall be equal to the effective slab width.

2.32.4 RECTANGULAR SECTIONS WITH COMPRESSION REINFORCEMENT (2005) a.

For rectangular sections when r £0.75 r b, the design moment strength FMn may be computed by: FM n = F ( A s – A¢ s )f y æ d – --a-ö + A¢ s f y ( d – d¢ ) è 2ø

EQ 2-33

where: ( A s – A¢ s )f y a = -------------------------------0.85f¢ c b and the following condition shall be satisfied:

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A s – A¢ s 0.85b 1 f¢ c d ¢ æ 87, 000 ö ---------------------- ³ --------------------------------- -------------------------------è 87, 000 – f ø fy d bd y

EQ 2-34

A s – A¢ s 0.85b 1 f¢ c d ¢ æ 600 ö ----------------------- ³ --------------------------------- -------------------è 600 – f yø fy d bd

EQ 2-34M

b. When the value of (As – A¢ s)/bd is less than the value given by EQ 2-34, so that the stress in the compression reinforcement is less than the yield strength fy or when effects of compression reinforcement are neglected, the moment strength may be computed by the equations in Article 2.32.2, except when a general analysis is made based on stress and strain compatibility using the assumptions given in Section 2.31. c.

The balanced reinforcement ratio r b for rectangular section with compression reinforcement is given by: 0.85b 1 f¢ c æ 87, 000 ö r ¢ f¢ sb - -------------------------------- + -----------------r b = ------------------------è 87, 000 – f yø fy fy

EQ 2-35

0.85b 1 f¢ c æ 600 ö r ¢ f¢ sb - -------------------- + -----------------r b = ------------------------è 600 – f yø fy fy

EQ 2-35M

1

where: f ¢ sb is stress in compression reinforcement at balanced strain conditions f ¢ sb =

f ¢ sb =

d¢ 87, 000 – ------- ( 87, 000 – f y ) £f y d d¢ 600 – ------- ( 600 – f y ) £f y d

3

(metric)

2.32.5 OTHER CROSS SECTIONS (1992) For other cross sections the design moment strength FMn shall be computed by a general analysis based on stress and strain compatibility using the assumptions given in Section 2.31. The requirements of Article 2.32.1 shall also be satisfied.

SECTION 2.33 COMPRESSION MEMBERS WITH OR WITHOUT FLEXURE 2.33.1 GENERAL REQUIREMENTS (2005) a.

Design of cross sections subject to axial load or to combined flexure and axial load shall be based on stress and strain compatibility using the assumptions given in Section 2.31. Slenderness effects shall be included in accordance with Section 2.34.

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b. Members subject to compressive axial load shall be designed for the maximum moment that can accompany the axial load. The factored axial load Pu at given eccentricity shall not exceed that given in Article 2.33.1c. The maximum factored moment Mu shall be magnified for slenderness effects in accordance with Section 2.34. c.

Design axial load strength FPa of compression members shall not be taken greater than the following: (1) For members with spiral reinforcement conforming to Article 2.11.2a: EQ 2-36

FP a (max) = 0.85F[ 0.85f¢ c ( A g – A st ) + f y A st ] (2) For members with tie reinforcement conforming to Article 2.11.2b:

EQ 2-37

FP a (max) = 0.80F[ 0.85f¢ c ( A g – A st ) + f y A st ]

2.33.2 COMPRESSION MEMBER STRENGTHS (2005) The following provisions may be used as a guide to define the range of the load-moment interaction relationship for members subjected to combined flexure and axial load. a.

Pure Compression. (1) The design axial load strength at zero eccentricity FPo may be computed by: EQ 2-38

FP o = F[ 0.85f¢ c ( A g – A st ) + A st f y ]

(2) For design, pure compression strength is a hypothetical loading condition since Article 2.33.1c limits the axial load strength of compression members to 85% and 80% of the design axial load strength at zero eccentricity. b. Pure Flexure. The assumptions given in Section 2.31, or the applicable equations for flexure given in Section 2.32 may be used to compute the design moment strength FMn in pure flexure. c.

Balanced Strain Conditions. Balanced strain conditions for a cross section are defined in Article 2.32.1b. For a rectangular section with reinforcement in one or two faces and located at approximately the same distance from the axis of bending, the balanced load strength FPb and balanced moment strength FMb may be computed by: EQ 2-39

FP b = F[ 0.85f¢ c ba b + A¢ s f¢ sb – A s f y ] and a FM b = F 0.85f¢ c ba b æ d – d² – -----b-ö + A¢ s f¢ sb ( d – d¢ – d² ) + A s f y d² è 2ø

EQ 2-40

where: 87, 000 ab = æè --------------------------------öø b 1 d 87, 000 + f y

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600 ab = æè ---------------------öø b 1 d 600 + f y

(metric)

f ¢ sb = 87, 000 – d¢ ------- ( 87, 000 + f y ) £ f y d f ¢ sb = 600 – d¢ ------- ( 600 + f y ) £ f y d

(metric)

d. Combined Flexure and Axial Load. (1) The design strength under combined flexure and axial load shall be based on stress and strain compatibility using the assumptions given in Section 2.31. The strength of a cross section is controlled by tension when the nominal axial load strength Pn is less than Pb. The strength of a cross section is controlled by compression when the nominal axial load strength Pn is greater than Pb. (2) The nominal values of axial load strength Pn and moment strength Mn must both be multiplied by the appropriate strength reduction factor F for spirally reinforced or tied compression members as given in Article 2.30.2. The value of F may be increased linearly from the value for compression members to the value for flexure as the design axial load strength FPn decreases from 0.10f ¢ c A g or FPb whichever is smaller, to zero.

2.33.3 BIAXIAL LOADING (1992)

1

In lieu of a general section analysis based on stress and strain compatibility for a loading condition of biaxial bending, the strength of non-circular members subject to biaxial bending may be computed by the following approximate expressions: 1 P nxy = --------------------------------------------------------1 -ö – æ -----1ö 1 -ö + æ --------æ --------èP ø èP ø èP ø nx ny o

EQ 2-41

3

where the factored axial load, P u ³ 0.1f¢ c A g

4

or M uy M ux --------------- £1 + -------------FM nx FM ny

EQ 2-42

when the factored axial load, P u < 0.1f¢ c A g

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SECTION 2.34 SLENDERNESS EFFECTS IN COMPRESSION MEMBERS 2.34.1 GENERAL REQUIREMENTS (2005) a.

Design of compression members shall be based on forces and moments determined from an analysis of the structure. Such an analysis shall take into account the influence of axial loads and variable moment of inertia on member stiffness and fixed-end moments, the effect of deflections on the moments and forces, and the effects of the duration of the loads.

b. In lieu of the procedure described in Article 2.34.1a, the design of compression members may be based on the approximate procedure given in Article 2.34.2.

2.34.2 APPROXIMATE EVALUATION OF SLENDERNESS EFFECTS (2005) a.

Unsupported length lu of a compression member shall be taken as the clear distance between slabs, girders, or other members capable of providing lateral support for the compression member. When haunches are present, the unsupported length shall be measured to the lower extremity of the haunch in the plane considered.

b. Radius of gyration r may be taken equal to 0.30 times the overall dimension in the direction in which stability is being considered for rectangular compression members, and 0.25 times the diameter for circular compression members. For other shapes, r may be computed from the gross concrete section. c.

For compression members braced against sidesway, the effective length factor k shall be taken as 1.0, unless an analysis shows that a lower value may be used. For compression members not braced against sidesway, the effective length factor k shall be determined with due consideration of cracking and reinforcement on relative stiffness, and shall be greater than 1.0.

d. For compression members braced against sidesway, the effects of slenderness may be neglected when klu/r is less than 34 – 12M1b/M2b. For compression members not braced against sidesway, the effects of slenderness may be neglected when klu/r is less than 22. For all compression members with klu/r greater than 100, an analysis as defined in Article 2.34.1a shall be made. M1b = value of smaller end moment on compression member calculated from a conventional elastic analysis, positive if member is bent in single curvature, negative if bent in double curvature, M2b = value of larger end moment on compression member calculated from a conventional elastic analysis, always positive. e.

Compression members shall be designed using the factored axial load Pu from a conventional frame analysis and a magnified factored moment Mc defined by EQ 2-43. For members braced against sidesway, ds shall be taken as 1.0. For members not braced against sidesway, db shall be evaluated as for a braced member and ds as for an unbraced member. EQ 2-43

M c = db M 2b + ds M 2s where:

db =

Cm ------------------ ³ 1.0 Pu 1 – --------fP c

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ds =

1 - ³ 1.0 ---------------------SP u 1 – -----------fSP c

Pc =

p EI ---------------2 ( kl u )

and 2

In lieu of a more precise calculation, EI may be taken either as Ec Ig ----------- + Es Is 5 EI = -----------------------------1 + bd or conservatively Ec Ig -----------2.5 EI = --------------1 + bd

1

For members braced against sidesway and without transverse loads between supports, Cm may be taken as: M 1b - but not less than 0.4. C m = 0.6 + 0.4 ---------M 2b

EQ 2-44

3

For all other cases Cm shall be taken as 1.0. f.

g.

When a group of compression members on one level composes a bent, or when they are connected integrally to the same superstructure, and all collectively resist the sidesway of the structure, the value of ds shall be computed for the member group with SPu and SPc equal to the summations for all compression members in the group. If computations show that there is no moment at both ends of a compression member or that computed end eccentricities are less than (0.6 + 0.03h) inches ((15 + 0.03h)mm); M2b in EQ 2-43 shall be based on a minimum eccentricity of (0.6 + 0.03h) inches ((15 + 0.03h)mm) about each principal axis separately. Ratio M1b /M2b in EQ 2-44 shall be determined by either of the following: (1) When computed end eccentricities are less than (0.6 + 0.03h) inches ((15 + 0.03h)mm), computed end moments may be used to evaluate M1b /M2b in EQ 2-44. (2) If computations show that there is essentially no moment at both ends of a compression member, the ratio M1b/M2b shall be taken equal to one.

h. When compression members are subject to bending about both principal axes, the moment about each axis shall be amplified by d computed from the corresponding conditions of restraint about that axis. i.

In structures which are not braced against sidesway, the flexural members shall be designed for the total magnified end moments of the compression members at the joint.

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SECTION 2.35 SHEAR 2.35.1 SHEAR STRENGTH (2005) a.

Factored shear stress vu shall be computed by: Vu v u = -------------Fb w d

EQ 2-45

where: bw = the width of web d = the distance from the extreme compression fiber to the centroid of the longitudinal tension reinforcement For a circular section, bw shall be taken as the diameter, and d need not be taken less than the distance from the extreme compression fiber to the centroid of the longitudinal reinforcement in the opposite half of the member. b. When the reaction in the direction of the applied shear introduces compression into the end region of the member and loads are applied at or near the top of the member, sections located less than a distance d from the face of the support may be designed for the same shear vu as that computed at a distance d. An exception occurs when major concentrated loads are imposed between that point and the face of support. In that case sections closer than d to the support shall be designed for Vu at distance d plus the major concentrated loads. c.

Shear stress carried by concrete vc shall be calculated according to Article 2.35.2. When vu exceeds vc, shear reinforcement shall be provided according to Article 2.35.3. Whenever applicable, the effects of torsion shall be added. NOTE:

The design criteria for combined shear and torsion given in “Building Code Requirements for Reinforced Concrete – ACI318-02” may be used.

d. For tapered webs, bw shall be the average width or 1.2 times the minimum width, whichever is smaller.

2.35.2 PERMISSIBLE SHEAR STRESS (2010) NOTE: a.

The value f’c used in computing vc shall not be taken greater than 10,000 psi (69 MPa).

Shear stress carried by concrete vc shall not exceed 2 f¢ c (or 0.17 f¢ c in metric) unless a more detailed analysis is made in accordance with Article 2.35.2b or Article 2.35.2c. For members subject to axial tension, vc shall not exceed the value given in Article 2.35.2d. For lightweight concrete, the provisions of Article 2.35.2f shall apply.

b. Shear stress carried by concrete vc, for members subject to shear and flexure only, may be computed by: Vu d v c = 1.9 f¢ c + 2500r w ---------M

EQ 2-46

u

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Vu d v c = 0.16 f¢ c + 17r w ---------M

EQ 2-46M

u

Vu d - shall not be taken greater but vc shall not exceed 3.5 f¢ c (or 0.29 f¢ c in metric). The quantity ---------Mu than 1.0, where Mu is the factored moment occurring simultaneously with Vu at the section considered. c.

For members subject to axial compression, vc may be computed by: N v c = 2 æ 1 + 0.0005 -------u-ö f¢ c è Ag ø N v c = 0.17 æ 1 + 0.072 -------u-ö è A ø

f¢ c

EQ 2-47

EQ 2-47M

g

N The quantity -------u- shall be expressed in psi (MPa). Ag d. For members subject to significant axial tension, shear reinforcement shall be designed to carry the total shear, unless a more detailed analysis is made using N v c = 2 æ 1 + 0.002 -------u-ö è Ag ø

f¢ c

N v c = 0.17 æ 1 + 0.29 -------u-ö è A ø

1

EQ 2-48

3 f¢ c

EQ 2-48M

g

where: Nu is negative for tension

4

N the quantity -------u- shall be expressed in psi (MPa). Ag e.

Special provisions for slabs of box culverts. For slabs of box culverts under 2 feet (600 mm) or more fill, shear stress vc may be computed by: Vu d v c = 2.14 f¢ c + 4600r ---------M

EQ 2-49

u

Vu d v c = 0.18 f¢ c + 32r ---------M

EQ 2-49M

u

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1 but vc shall not exceed 4 f¢ c (or --- f¢ c in metric). For single cell box culverts only, vc need not be taken 3 f¢ c 5 less than 3 f¢ c (or ------------ in metric) for slabs monolithic with walls or 2.5 f¢ c (or ------ f¢ c in metric) for 24 4 Vu d - shall not be taken greater than 1.0, where Mu is factored slabs simply supported. The quantity ---------Mu moment occurring simultaneously with Vu at section considered. f.

The provisions for shear stress vc carried by concrete apply to normal weight concrete. When lightweight aggregate concretes are used, one of the following modifications shall apply: (1) When fct is specified, shear stress vc shall be modified by substituting fct/6.7 (or 1.8fct in metric) for f¢ c , but the value of fct/6.7 (or 1.8fct in metric) used shall not exceed

f¢ c.

(2) When fct is not specified, shear stress vc shall be multiplied by 0.85 for sand-lightweight concrete.

2.35.3 DESIGN OF SHEAR REINFORCEMENT (2005) a.

Shear reinforcement shall conform to the general requirements of Section 2.10. When shear reinforcement perpendicular to the axis of the member is used, required area shall be computed by: ( v u – v c )b w s A v = --------------------------------fy

EQ 2-50

b. When inclined stirrups or bent bars are used as shear reinforcement the following provisions apply: (1) When inclined stirrups are used, required area shall be computed by: ( v u – v c )b w s A v = ----------------------------------------f y ( sin a + cos a)

EQ 2-51

(2) When shear reinforcement consists of a single bar or a single group of parallel bars, all bent up at the same distance from the support, required area shall be computed by: ( v u – v c )b w d A v = ---------------------------------f y sin a

EQ 2-52

f¢ c in which (vu – vc) shall not exceed 3 f¢ c (or ------------ in metric). 4 (3) When shear reinforcement consists of a series of parallel bent-up bars or groups of parallel bent-up bars at different distances from the support, required area shall be computed using Article 2.35.3b(1). (4) Only the center three-fourths of the inclined portion of any one longitudinal bar that is bent shall be considered effective for shear reinforcement. c.

When more than one type of shear reinforcement is used to reinforce the same portion of the member, required area shall be computed as the sum for the various types separately. No one type shall resist © 2011, American Railway Engineering and Maintenance-of-Way Association

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more than 2/3 of the total shear resisted by reinforcement. In such computations, vc shall be included only once. f¢ c d. When (vu – vc) exceeds 4 f¢ c (or ------------ in metric), maximum spacings given in Article 2.10.3 shall be 3 reduced by one-half.

e. f.

2 f¢ c The value of (vu – vc) shall not exceed 8 f¢ c (or ---------------- in metric). 3 When flexural reinforcement located within the width of a member used to compute the shear strength is terminated in a tension zone, shear reinforcement shall be provided in accordance with Article 2.13.1f.

2.35.4 SHEAR-FRICTION (2005) a.

Provisions for shear-friction are to be applied where it is appropriate to consider shear transfer across a given plane, such as: an existing or potential crack, an interface between dissimilar materials, or an interface between two concretes cast at different times.

b. A crack shall be assumed to occur along the shear plane considered. Required area of shear-friction reinforcement Avf across the shear plane may be designed using either Article 2.35.4c or any other shear transfer design method that results in prediction of strength in substantial agreement with results of comprehensive tests. Provisions of Article 2.35.4d through Article 2.35.4h shall apply for all calculations of shear transfer strength. c.

1

Shear-friction design method. (1) When shear-friction reinforcement is perpendicular to shear plane, area of shear-friction reinforcement Avf shall be computed by: Vu A vf = ----------ff y m

3 EQ 2-53

where:

4

m = the coefficient of friction in accordance with Article 2.35.4c(3). (2) When shear-friction reinforcement is inclined to shear plane such that the shear force produces tension in shear-friction reinforcement, area of shear friction reinforcement Avf shall be computed by: Vu A vf = --------------------------------------------------ff y ( m sin af + cos af )

EQ 2-54

where: af = angle between shear-friction reinforcement and shear plane

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(3) Coefficient of friction m in EQ 2-53 and EQ 2-54 shall be: concrete placed monolithically . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4l concrete placed against hardened concrete with surface intentionally roughened as specified in Article 2.35.4g . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.0l concrete placed against hardened concrete not intentionally roughened . . . . . . . . . . . . . 0.6l concrete anchored to as-rolled structural steel by headed studs or by reinforcing bars (see Article 2.35.4h). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.7l where l = 1.0 for normal weight concrete and 0.85 for sand-lightweight concrete. d. Shear stress vu on area of concrete section resisting shear transfer shall not exceed 0.2f ¢ c nor 800 psi (5.5 MPa). e.

Net tension across shear plane shall be resisted by additional reinforcement. Permanent net compression across shear plane may be taken as additive to the force in the shear-friction reinforcement A v f f y, when calculating required A v f .

f.

Shear-friction reinforcement shall be appropriately placed along the shear plane and shall be anchored to develop the specified yield strength on both sides by embedment, hooks, or welding to special devices.

g.

For the purpose of this paragraph, when concrete is placed against previously hardened concrete, the interface for shear transfer shall be clean and free of laitance. If m is assumed equal to 1.0l, interface shall be roughened to a full amplitude of approximately 1/4 inch (6 mm).

h. When shear is transferred between as-rolled steel and concrete using headed studs or welded reinforcing bars, steel shall be clean and free of paint.

2.35.5 HORIZONTAL SHEAR DESIGN FOR COMPOSITE CONCRETE FLEXURAL MEMBERS (2005) a.

In a composite member, full transfer of horizontal shear forces shall be assured at contact surfaces of interconnected elements.

b. Design of cross sections subject to horizontal shear may be in accordance with provisions of Article 2.35.5c or Article 2.35.5d, or any other shear transfer design method that results in prediction of strength in substantial agreement with results of comprehensive tests. c.

Design horizontal shear stress vuh at any cross section may be computed by Vu v uh = ----------fb v d

EQ 2-55

where: Vu = factored shear force at section considered d = depth of entire composite section Horizontal shear vuh shall not exceed permissible horizontal shear vh in accordance with the following:

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(1) When contact surface is clean, free of laitance, and intentionally roughened, shear stress vh shall not exceed 80 psi (0.55 MPa). (2) When minimum ties are provided in accordance with Article 2.35.5e, and contact surface is clean and free of laitance, but not intentionally roughened, shear stress vh shall not exceed 80 psi (0.55 MPa). (3) When ties are provided in accordance with Article 2.35.5e and contact surfaces are clean, free of laitance and intentionally roughened to a full amplitude of 1/4 inch (6 mm), shear stress, vh, shall be taken equal to (260 + 0.6r vfy) l in psi [(1.8 + 0.6r vfy) l in MPa]; but not greater than 500 psi (3.5 MPa). (4) When factored shear stress, vu, at section considered exceeds f 500 psi (f 3.5 in MPa), design for horizontal shear shall be in accordance with Article 2.35.4. d. Horizontal shear may be investigated by computing, in any segment not exceeding one-tenth of the span, the actual change in compressive or tensile force to be transferred, and provisions made to transfer that force as horizontal shear between interconnected elements. The factored horizontal shear stress shall not exceed the horizontal shear strength vuh in accordance with Article 2.35.5c, except that length of segment considered shall be substituted for d. e.

Ties for horizontal shear. (1) A minimum area of tie reinforcement shall be provided between interconnected elements. Tie area shall not be less than 50bws/fy (or 0.35bws/fy in metric), and tie spacing s shall not exceed 4 times the least web width of support element, nor 24 inches (600 mm).

1

(2) Ties for horizontal shear may consist of single bars or wire, multiple leg stirrups, or vertical legs of welded wire fabric (smooth or deformed). All ties shall be adequately anchored into interconnected elements by embedment or hooks. (3) All beam shear reinforcement shall extend into cast-in-place deck slabs. Extended shear reinforcement may be used in satisfying the minimum tie reinforcement.

3

2.35.6 SPECIAL PROVISIONS FOR SLABS AND FOOTINGS (2005) a.

Shear strength of slabs and footings in the vicinity of concentrated loads or reactions shall be governed by the more severe of the following conditions: (1) The slab or footing acting as a wide beam, with a critical section extending in a plane across the entire width and located at a distance d from the face of the concentrated load or reaction area. For this condition, the slab or footing shall be designed in accordance with Article 2.35.1 through Article 2.35.3. (2) Two-way action for the slab or footing, with a critical section perpendicular to the plane of the slab and located so that its perimeter is a minimum and approaches no closer than d/2 to the perimeter of the concentrated load or reaction area. For this condition, the slab or footing shall be designed in accordance with Article 2.35.6b and Article 2.35.6c. (3) For footings supported on piles the shear on the critical section shall be determined in accordance with: (a) Entire reaction from any pile whose center is located dp/2 or more outside the critical section shall be considered as producing shear on that section.

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(b) Reaction from any pile whose center is located dp/2 or more inside the critical section shall be considered as producing no shear on that section. (c) For intermediate positions of pile center, the portion of the pile reaction to be considered as producing shear on the critical section shall be based on linear interpolation between full value at dp/2 outside the section and zero value at dp/2 inside the section. b. Factored shear stress for two-way action shall be computed by: Vu v u = ------------Fb o d

EQ 2-56

where: Vu and bo = are taken at the critical section defined in Article 2.35.6a(2). c.

Factored shear stress vu shall not exceed vu given by EQ 2-57, EQ 2-58, or EQ 2-59 unless shear reinforcement is provided in accordance with Article 2.35.6d. as d - + 2ö v c = æ -------èb ø

f¢ c

EQ 2-57

f¢ as d - + 2ö ------------c v c = æ -------èb ø 12

EQ 2-57M

o

o

4-ö f¢ v c = æ 2 + ---c è bø

EQ 2-58

f¢ c 2 v c = æ 1 + -----ö -----------è bø 6

EQ 2-58M

c

c

v c = 4 f¢ c

EQ 2-59

1 v c = --- f¢ c 3

EQ 2-59M

bc is the ratio of long side to short side of concentrated load or reaction area. as is 40 for interior concentrated loads or reaction areas, 30 for edge concentrated loads or reaction areas, and 20 for corner concentrated loads or reaction areas. d. If shear reinforcement consisting of bars or wires is provided in accordance with Article 2.35.3, vc at any 1 1 section shall not exceed 2 f¢ c (or --- f¢ c in metric) and vu shall not exceed 6 f¢ c (or --- f¢ c in metric). 6 2 Shear stresses shall be investigated at the critical section defined in Article 2.35.6a(2) and at successive sections more distant from the support.

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2.35.7 SPECIAL PROVISIONS FOR BRACKETS AND CORBELS (2005) a.

The following provisions shall apply to brackets and corbels with a shear span-to-depth ratio and av/d not greater than unity, and subject to a horizontal tensile force Nuc not larger than Vu. Distance d shall be measured at face of support.

b. Depth at outside edge of bearing area shall not be less than 0.5d. c.

Section at face of support shall be designed to resist simultaneously a shear Vu, a moment [Vuav + Nuc(h – d)], and a horizontal tensile force Nuc . (1) In all design calculations in accordance with this paragraph, strength reduction factor f shall be taken equal to 0.85. (2) Design of shear-friction reinforcement Avf to resist shear Vu shall be in accordance with Article 2.35.4. For normal weight concrete, shear stress vu shall not exceed 0.2 f ¢ c nor 800 psi (5.5 MPa). For “sand-lightweight” concrete, shear stress vu shall not exceed (0.2 – 0.07a v /d) f ¢ c nor (800 – 280a v /d) psi (5.5 – 1.9a v /d MPa). (3) Reinforcement Af to resist moment [Vuav + Nuc(h – d)] shall be computed in accordance with Section 2.31 and Section 2.32. (4) Reinforcement An to resist tensile force Nuc shall be computed by An = Nuc/ffy. Tensile force Nuc shall not be taken less than 0.2Vu unless special provisions are made to avoid tensile forces.

1

(5) Area of primary tension reinforcement As shall be made equal to the greater of (Af + An), or (2 A v f /3 + An). d. Closed stirrups or ties parallel to As, with a total area of Ah not less than 0.5(As – An), shall be uniformly distributed within two-thirds of the effective depth adjacent to As. e.

Ratio r = As/bd shall not be taken less than 0.04 (f ¢ c /fy).

f.

At front face of bracket or corbel, primary tension reinforcement As shall be anchored by one of the following: (1) a structural weld to a transverse bar of at least equal size; weld to be designed to develop specified yield strength fy of As bars; (2) bending primary tension bars As back to form a horizontal loop, or (3) some other means of positive anchorage.

g.

Bearing area of load on bracket or corbel shall not project beyond straight portion of primary tension bars As, nor project beyond interior face of transverse anchor bar (if one is provided).

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SECTION 2.36 PERMISSIBLE BEARING STRESS (2005) Design bearing stress shall not exceed f (0.85f ¢ c), except when the supporting surface is wider on all sides than the loaded area, then the design bearing stress on the loaded area shall be permitted to be multiplied by A 2 ¤ A 1, but not more than 2, where: A1 = load area A2 = the area of the lower base of the largest frustrum of a pyramid, cone, or tapered wedge contained wholly within the support and having for its upper base the loaded area, and having side slopes of 1 vertical to 2 horizontal. Minimum distance from edge of bearing to edge of supporting concrete shall be 6 inches (150 mm).

SECTION 2.37 SERVICEABILITY REQUIREMENTS 2.37.1 APPLICATION (1992) For flexural members designed with reference to load factors and strengths by LOAD FACTOR DESIGN, stresses at service load shall be limited to satisfy the requirements for fatigue in Section 2.38, and the requirements for distribution of reinforcement in Section 2.39. The requirements for deflection control in Section 2.40 shall also apply.

2.37.2 SERVICE LOAD STRESSES (1992) For investigation of service load stresses to satisfy the requirements of Section 2.38 and Section 2.39, the straight-line theory of stress and strain in flexure shall be used, and the assumptions given in Section 2.27 shall apply.

SECTION 2.38 FATIGUE STRESS LIMIT FOR REINFORCEMENT (2005) a.

The range between a maximum tension stress and minimum stress in straight reinforcement caused by live load plus impact at service load shall not exceed: ff = 21 – 0.33fmin + 8(r/h) ff = 145 – 0.33fmin + 55(r/h)

(metric)

where: ff = stress range in steel reinforcement, ksi (MPa) fmin = algebraic minimum stress level, tension positive, compression negative, ksi (MPa)

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r/h = ratio of base radius to height of rolled-on transverse deformations; when the actual value is not known, use 0.3 b. Bends in primary reinforcement shall be avoided in regions of high stress range.

SECTION 2.39 DISTRIBUTION OF FLEXURAL REINFORCEMENT (2005) a.

Tension reinforcement shall be well distributed in the zones of maximum tension. When the design yield strength fy for tension reinforcement exceeds 40,000 psi (280 MPa), cross sections of maximum positive and negative moment shall be so proportioned that the calculated stress in the reinforcement at service load fs in ksi (MPa), does not exceed the value computed by: Z - but f shall not be greater than 0.5 f f s = -------------s y 3 d A c

EQ 2-60

where: A = effective tension area of concrete surrounding the main tension reinforcing bars and having the same centroid as that reinforcement, divided by the number of bars, square inches (mm2). When the main reinforcement consists of several bar sizes the number of bars shall be computed as the total steel area divided by the area of the largest bar used

1

dc = thickness of concrete cover measured from extreme tension fiber to center of bar located closest thereto, inches (mm), but dc shall not exceed (2 inches + 1/2 db) (or (50 mm + 1/2 db) in metric). b. The quantity Z in EQ 2-60 shall not exceed 170 kips per inch (30 kN/mm) for members in moderate exposure conditions and 130 kips per inch (23 kN/mm) for members in severe exposure conditions. Where members are exposed to very aggressive exposure or corrosive environments, such as deicer chemicals, the denseness and nonporosity of the protecting concrete should be considered, or other protection, such as a waterproof protecting system, should be provided in addition to satisfying EQ 2-60.

3

4 SECTION 2.40 CONTROL OF DEFLECTIONS 2.40.1 GENERAL (1992) Flexural members of bridge structures shall be designed to have adequate stiffness to limit deflections or any deformations which may adversely affect the strength or serviceability of the structure at service load.

2.40.2 SUPERSTRUCTURE DEPTH LIMITATIONS (1992) The minimum thicknesses stipulated in Table 8-2-10 are recommended unless computation of deflection indicates that lesser thickness may be used without adverse effects.

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C - COMMENTARY The purpose of this part is to furnish the technical explanation of various paragraphs in Part 2 Reinforced Concrete Design. In the numbering of paragraphs of this section, the numbers after the “C-” correspond to the section/paragraph being explained.

C - SECTION 2.1 GENERAL C - 2.1.5 PIER PROTECTION (2005) C - 2.1.5.1 Adjacent to Railroad Tracks a.

The provisions of this section are not intended to create a structure that will resist the full impact of a direct collision by a loaded train at high speed. Rather, the intent is to reduce the damage caused by shifted loads or derailed equipment. This is accomplished by: deflecting or redirecting the force from the pier; providing a smooth face; providing resisting mass; and distributing the collisions forces over several columns.

b. Research by the National Transportation Safety Board found no clear break point in the distribution of the distance traveled from the centerline of the track by derailed equipment. It was therefore decided to retain the existing 25 feet (7600 mm) distance within which collision protection is required. In addition, it is recognized that the distance traveled by equipment in a derailment is related to the speed of the train, the weight of the equipment, whether the side slopes tend to restrain or distribute the equipment and the alignment of the track. In cases where these factors would cause the equipment to travel farther than normal in a derailment, the required distance should be increased. Structures not otherwise requiring protection under this section along the railroad right-of-way may also warrant protection by using crash walls or earthen berms. c.

Where the risk of serious damage to the overhead structure is estimated to be higher than normal in case of an impact, this distance should also be increased. Among the factors to be considered in this evaluation are: the height of the pier, bearing type, redundancy of the structure, length of the span and consequences of loss of use of the structure.

d. Examples of crash walls and pier protection for tracks on one side of piers are shown in Figure C-8-2-1. Where tracks are on both sides of the pier the wall shall protect both sides.

C - 2.1.6 SUPERSTRUCTURE PROTECTION (2010) C - 2.1.6.1 General Requirements a.

The purpose for this guideline stems from the fact that many existing railroad bridge superstructures have been struck by trucks and other over-height loads and vehicles. Many of these bridges play a pivotal role in the day-to-day operations of the railroads and the transportation of goods. Railway networks are less extensive than those of other modes of transportation to the extend that unplanned shutdowns can have an adverse impact on railroad operations, particularly along core routes of a railway network. Protection of railroad bridge superstructures to abate impacts to daily railroad operations is critical and should be evaluated. Parameters that affect railroad operational requirements include: (1) The availability of other routes between linked markets (2) The freight tonnage hauled over the route relative to the rest of the rail network

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(3) The types of commodity handled on the line (4) Future growth of freight or passenger traffic between the served markets or terminals (5) The density of passenger traffic on the line Roadway functional classification, which is influenced by traffic volume and type of service it provides for the community, determines: (1) Vehicular design speed (2) Vertical and horizontal alignment of the roadway (3) Cross section of the roadway

C - 2.1.7 SKEWED CONCRETE BRIDGES (2005) b. There is no supporting documentation for the maximum recommended skew angles given. The information was compiled from a questionnaire that was sent to several Chief Bridge Engineers of Class I railroad companies. The skew angle recommendations resulted from the Chief Engineers’ past experience. The preference to use cast-in-place concrete for skewed bridges is due to the high torsional stiffness of concrete bridges and the flexibility of forming the concrete to fit the bearing area. The maximum recommended skew angle is reduced for precast slabs and box beams since the bearing area of precast box beams and slabs is longer. This longer bearing area can result in warping of the section during precasting due to the varying cambers. c.

3

The placement of interior diaphragms perpendicular to the webs is recommended since they allow for easier construction or installation of transverse post-tensioning.

d. On skewed abutments, the end of the haunch in the backwall of the abutment or the end of the approach slab is set perpendicular to the centerline of track to ensure adequate stiffness for the last tie off the bridge. e.

1

The ends of concrete slabs and concrete box girders with flanges 5’-0” wide and wider may be skewed to reduce the width of pier cap or abutment seat.

C - 2.2.3 DESIGN LOADS (2008) C - 2.2.3 (d.) IMPACT LOAD Previously, different impact formulas were included in the Manual for reinforced concrete in Part 2 and prestressed concrete in Part 17. It was known however that impact values should be similar for both types of structures (ref. 1). In order to resolve this discrepancy, a new impact formula was developed based on work in Europe (ref. 1) and Canada (ref. 6, 7). The resulting impact is generally lower than that recommended previously for reinforced concrete, particularly for longer spans. It is generally higher than that recommended previously for prestressed concrete, particularly for shorter spans. This is illustrated in Figure C-8-2-2.

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Figure C-8-2-1. Pier Protection: Minimum Crash Wall Requirements (Not To Scale)

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Figure C-8-2-2. Comparison of Impact Formulas

Concrete Structures and Foundations

According to the ORE report (ref. 1) the impact can be expressed as: I = 0.65 x K / (1 - K + K2)

where K = V/(2/Lf)

V = speed of train in feet/second (meters/second) L = span length in feet (meters) f = natural frequency of the loaded bridge in hertz In order to get the impact value as a percentage, this formula is multiplied by 100 I = 65 x K / (1 - K + K2) For simply supported undamped beams, the natural frequency of the bridge can be estimated (see ref. 5) as: f = 3.5 ¤ ( d) where d is the deflection due to dead and live load in inches or; f = 5.6 ¤ ( d) where d is in centimeters. NOTE:

Limited data exist for impact on continuous structures. The ORE has done one test on such structures which suggests that impact values do not normally exceed those for simple spans. Article 2.2.3d(2) recommends using for the entire continuous structure the impact value calculated for the shortest of the continuous spans.

Assuming the deflection under dead and live load is equal to L/750 (where L is the span length) and the speed is 100 miles per hour (160 kilometers per hour) and transforming to consistent units we get: K = V/(2Lf) = 2.64/ L

where L is the span length in feet or;

K = V/(2Lf) = 1.47/ L

where L is in meters

Replacing this value for K in the ORE impact formula and considering the fact that the denominator is practically a constant for the range of span lengths where the formula is applicable, the impact formula is simplified to: I = 225/ L

where L is the span length in feet or;

I = 125/ L

where L is in meters

This formula was validated by the ORE with tests on 37 reinforced concrete, prestressed concrete and steel bridges, small scale models and theoretical calculations. It was found that the formula gave a good representation of the mean impact values for European railway bridges. For North American bridges, the formula had to be adjusted for higher impacts due to different track and equipment maintenance standards. It was decided to address this issue by using in the ORE formula a design speed of 100 mph (160 km/h) which is higher than the actual speed for North American freight operations. Therefore, for bridge rating purposes, one should not attempt to input actual train speeds in the ORE formula. Impact reduction for bridge rating purposes is given in Part 19. The different safety factors given in the Manual for impact loading will cover the cases where the impact would be higher than the mean value. For piers and abutments, where the weight of the substructure is much greater than the live load, the effects of impact will generally be minimal and therefore can be neglected in the design.

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When the substructure and superstructure are rigidly connected together, the superstructure will undergo additonal rotation due to the impact loading at the point where it is connected to the substructure. In order to maintain compatibility of deformations, the substructure will experience the same additional rotations. Therefore, impact must be used in this case for the design of the substructure. Particular attention should be given to short structural members spanning in the direction perpendicular to the track and located next to the bridge approach. These members will be subjected to higher impacts due to the transition in stiffness of the riding surface between the bridge and the approach. Members such as concrete deck slabs and flanges of precast concrete beams are known to experience higher impacts. However, very limited test data is available to evaluate accurately the level of impact experienced by these members. Some Railways design these members for impacts as high as 100 percent. It should be noted that direct fixation can result in much higher impacts than reflected by the formula. This formula is intended for ballasted deck spans and substructure elements as required. For bridges with direct fixation, refer to Part 27 Concrete Slab Track. The Association of American Railroads (AAR) conducted a series of tests on nine prestressed concrete bridges in the late 1950s and early- to mid-1960s from which impact data was gathered. Spans varied from 18 feet to 70 feet in length. This data is summarized in the Committee 30 report found in AREA Bulletin 597, January 1966. The highest impacts measured were 45 percent in a 30 foot span. Other spans tested al had impacts less than 30 percent. The AAR performed further testing on three prestressed concrete bridges in the early 1990s [ref. 5]. Tests included cars equipped with flat wheels or out-of-round wheels near the condemning limit. Impacts up to 51 percent were measured on an 18-foot span.

1

References (1) Office de Recherche et d’Essais (ORE), ORE Committee D23 - Report No. 17 Final Report, Utrecht, April 1970.

3

(2) Skaberna, S., “A Review of Studies of Impact in Concrete Railway Bridges”, Railway Track & Structures, November 1988, pp. 23-25. (3) Sharma, V., Gamble, W.G., and Choros, J., Impact Factor Measurements for Three Precast Pretensioned Concrete Railway Bridges, Association of American Railroads, Report No. R-824, January 1993.

4 (4) Sharma, Vinaya, Flat Wheel Impacts and TLV Tests on a Prestressed Concrete Bridge, Technology Digest TD 94-016, Association of American Railroads, September 1994. (5) Fryba, Ladislav, “Dynamics of Railway Bridges”, Thomas Telford Services, London, P. 92, 1996. (6) Skaberna, S. AREA correspondence, April 24 1986. (7) Skaberna, S. AREA correspondence, January 18 1988.

C - 2.2.3 (j.) LONGITUDINAL LOAD. (2008) (References 33, 34, 35, 45, 51, 54, 65, 66, 67, 68, and 102) a.

Longitudinal loads due to train traffic can vary tremendously from train to train. These loads are dependent on train handling and operating practices. The greatest longitudinal loads result from

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starting or stopping a train, or moving a train up or down a grade. The longitudinal loads applied to a bridge from normal train operations could be small in comparison to the design loads. b. Maximum adhesion between wheel and rail for train braking is about 15 percent. This level of adhesion would typically be reached with an emergency application of the train air brakes. The equation for train braking is derived using 15 percent of the Cooper E-80 (EM 360) live loading. c.

Longitudinal load due to braking acts at the center of gravity of the live load. Center of gravity height is taken as 8 feet (2450 mm) above top of rail. This load is transferred from vehicle to rail as a horizontal force at the top of rail and a vertical force couple transmitted through the wheels.

d. Locomotive traction can be applied at levels of adhesion approaching 50 percent, particularly with locomotives using AC traction motors. Locomotive tractive effort is generally limited by drawbar and coupler capacity to less than about 500 kips (2200 kN), depending on equipment. Large applications of dynamic braking effort (which generate tractive forces) are also possible. The greatest locomotive tractive efforts are generally reached at speeds below 25 mph (40 km/h). Above this speed, locomotive horsepower generally governs, and available tractive effort drops. e.

Longitudinal load due to locomotive traction acts at the drawbar. Drawbar height is taken as 3 feet (900 mm) above top of rail. As with braking, this force is transferred from vehicle to rail as a horizontal force at the top of rail and a vertical force couple transmitted through the wheels.

f.

The equation for longitudinal load due to locomotive traction is based on maximum values from AAR measurements on bridges tested with AC locomotives. The equipment used in the tests was approximately equivalent to a Cooper E-60 (EM 270) loading on the spans tested. The formula has been scaled to be consistent with the E-80 (EM 360) design loading.

g.

Longitudinal deflection limits are required to increase serviceability of the structure. They can also potentially reduce track problems (buckling, ballast degradation, etc.) on or just beyond the ends of the bridge.

h. The longitudinal deflection is computed assuming the entire bridge acts as a unit. The stiffness of individual substructure components must be considered. Stiffer components deflect the same amount as more flexible components; the stiffer components resist more load. i.

For the case where longitudinal deflection controls the design of fairly tall flexible pile bents, the designer should consider adding longitudinal bracing to some of the double bents to stiffen them above the ground line, and thus reduce longitudinal deflection. Battering or increasing the batter of piles, and/or adding more piles can also reduce deflection.

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Part 3 Spread Footing Foundations1 — 1995 — TABLE OF CONTENTS

Section/Article

Description

Page

3.1 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.1 General (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.2 Classification (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-3-2 8-3-2 8-3-2

3.2 Information Required. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.1 Field Survey (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.2 Controlling Dimensions (1995). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.3 Loads (1995). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.4 Character of Subsurface Materials (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-3-4 8-3-4 8-3-4 8-3-4 8-3-5

3.3 Depth of Base of Footings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.1 Selection of Tentative Depths (1995). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.2 Revision of Depths of Footings (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-3-7 8-3-7 8-3-7

3.4 Sizing of Footings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.1 Definitions (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.2 Safety Factors (1995). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.3 Shallow Footings on Granular Material (Cohesion = 0) (1995) . . . . . . . . . . . . . . . . . . . . . 3.4.4 Shallow Footings on Saturated Clay (f = 0) (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.5 Footings on Unsaturated Silts and Clays (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.6 Footings on Non-Homogeneous Deposits (1989). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.7 Footings on Soils with Cohesion and Friction (Preconsolidated Clays) (1989) . . . . . . . . .

8-3-7 8-3-7 8-3-8 8-3-8 8-3-10 8-3-11 8-3-11 8-3-12

3.5 Footings with Eccentric Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.1 Loads Eccentric in One Direction (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.2 Loads Eccentric in Two Directions (1989). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.3 Sizing Footings with Eccentric Loads (1989). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-3-12 8-3-12 8-3-13 8-3-13

3.6 Footing Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6.1 Loads Eccentric in Two Directions (1989). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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1

References, Vol. 58, 1957, pp. 633, 1182; Vol. 59, 1958, pp. 676, 1188; Vol. 62, 1961, pp. 438, 860; Vol. 74, 1973, p. 138; Vol. 76, 1975, p. 206; Vol. 78, 1977, p. 108; Vol. 90, 1989, pp. 53, 56; Vol. 96, p. 59. Revised 1995.

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TABLE OF CONTENTS (CONT) Section/Article

Description

Page

3.7 Field Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7.1 Modification of Design (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7.2 Reinforcement (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7.3 Footings at Varying Levels (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7.4 Drainage (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7.5 Treatment of Bottom of Excavation (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7.6 Stresses (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7.7 Information on Drawings (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-3-14 8-3-14 8-3-14 8-3-14 8-3-14 8-3-15 8-3-15 8-3-15

3.8 Combined Footings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.8.1 Uses and Types (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.8.2 Allowable Soil Pressures (1995). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.8.3 Column Loads (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.8.4 Sizing Combined Footings (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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LIST OF FIGURES Figure 8-3-1 8-3-2 8-3-3 8-3-4

Description

Page

Factors Affected by Depth. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Extreme Frost Penetration, in Inches, Based upon State Averages. Source: U.S. National Weather Records Center . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Relationship Among f, N, and Bearing Capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Types of Combined Footings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-3-3 8-3-6 8-3-9 8-3-16

SECTION 3.1 DEFINITIONS 3.1.1 GENERAL (1995) a.

A spread footing is a structural unit which transfers and distributes a load to the underlying soil or rock at a pressure consistent with the requirements of the structure and the supporting capacity of the soil or rock. The general approach to sizing footings on soil is to assure that the contact pressure defined in Article 3.4.1 is equal to or less than the allowable soil pressure defined in Article 3.4.1.

b. Sizing of footings on rock is not discussed. The designer should be aware that the approaches presented here are for the least complicated situations; and where unusual geology or loadings are encountered, geotechnical engineering specialists should be consulted.

3.1.2 CLASSIFICATION (1995) a.

Spread footings may be classified according to their structural arrangement: (1) An individual column footing which supports a single column or isolated load.

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(2) A wall footing or continuous footing which supports a wall. (3) A combined footing which supports more than one column. (4) A raft or mat footing, which supports all the columns in a structure or a large portion thereof. b. Spread footings may be classified according to their depth and dimensions: (1) Shallow footings for which the depth of foundation, Df, defined as the minimum vertical distance from the base of the footing to the surface of the surrounding ground or floor, does not exceed the least width, B, of the footing. See Figure 8-3-1. (2) Deep footings, for which the depth, Df, is greater than the width, B, are described in Part 4, Pile Foundations and Part 24, Drilled Shaft Foundations. c.

Spread footings may be classified with respect to the subsurface material from which they derive their support: (1) Footings on granular, non-cohesive soils. (2) Footings on saturated clay or plastic silt. (3) Footings on unsaturated clay or silt.

1

(4) Footings on nonhomogeneous deposits. (5) Footings on preconsolidated clay.

3

4

NO REDUCTION IN ALLOWABLE SETTLEMENT PRESSURE IS REQUIRED WHEN WATER TABLE IS BELOW THIS ELEVATION - SEE ARTICLE 3.4.3.3A(3).

Reduction in allowable pressure on footing on granular material. Figure 8-3-1. Factors Affected by Depth

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SECTION 3.2 INFORMATION REQUIRED 3.2.1 FIELD SURVEY (1995) a.

All available information shall be furnished in the form of a topographic map, in order to adapt the structural requirements to the field conditions. The locations and dimensions of underground utilities, existing foundations, roads, tracks, or other structures shall be indicated. In connection with footings for river crossings, the records of normal high water, low water, floodwater level, depth of scour, stream velocities, and alignment of the stream shall be provided.

b. All available information concerning the nature of the foundations of neighboring structures, the nature of the underlying materials, and of the settlement and behavior of these foundations shall be assembled and condensed as a guide to the judgment of the engineer in the design of the new structure.

3.2.2 CONTROLLING DIMENSIONS (1995) Information shall be assembled concerning the proposed arrangement of the column, piers, abutments or equipment to be supported; the depths of basements, tunnels, and other excavations; the surface elevation of fill areas; and all other factors that may affect or be affected by the construction.

3.2.3 LOADS (1995) a.

The loads to be supported by the foundations shall be indicated. These shall be subdivided into the following categories: (1) Dead load. (2) Normal live load, defined as the live load that is likely to be transmitted to the foundation throughout the greater portion of the useful lifetime of the structure, is commonly used when the foundation soil is a saturated clay. (3) Maximum live load, defined as the greatest live load that may be anticipated at any time during the lifetime of the structure, is commonly used when the foundation soil is a freely draining sand. (4) Longitudinal and lateral forces. (5) Snow load. (6) Ice load. (7) Earthquake load. (8) Wind load. (9) Loads from pore water pressures including buoyancy and seepage forces. (10) Area load, defined as any load transmitted to the supporting soil by the addition of fill or adjacent structures. (11) Impact normally is not considered in the design of a footing except for special circumstances. (12) Vibratory loads to footings on granular material shall be considered.

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b. An estimate shall be made of the duration of each loading, because the settlement of some types of subsurface materials depends upon the proportion of the total time the loads are active. c.

The character, frequency, and amplitude of any vibratory loads including earthquakes shall be noted for further analysis. If such loads are an important consideration, the foundation design shall be referred to a geotechnical engineer with expertise in dynamics.

d. Footings shall be designed by using the following combinations of loads: (1) Primary: Dead + Live + Centrifugal Force + Earth Pressure + Pore Water Pressures + Area Load + Special Vibratory Loads. (2) Secondary: Longitudinal Force + Wind + Ice and Stream Flow Pressures + Seismic Forces.

3.2.4 CHARACTER OF SUBSURFACE MATERIALS (1989) 3.2.4.1 General a.

Pertinent supplementary data with respect to local geological or foundation conditions, including aerial photographs and agricultural soil maps, should be assembled if available. Data concerning changes in groundwater level should also be investigated.

b. The data concerning subsurface materials shall be assembled in suitable graphical form, such as cross sections through the various deposits, showing the probable arrangement and sequence of lenses or strata, the pertinent physical properties of each element of the deposit, and the location of the groundwater table.

1

3.2.4.2 Field Investigation a.

The nature and extent of the various formations of soil and rock beneath the site and the depth to groundwater shall be determined by means of test borings or probes and physical tests of a type and to an extent appropriate to the character and importance of the structure and the nature of the subsurface materials. The borings shall be made in accordance with the AREMA recommendations in Part 22, Geotechnical Subsurface Investigation.

b. For major structures, at least one boring should, if practicable, extend into bedrock. Borings should at least extend to a depth equal to three times the least footing width plus the depth of the footing from the ground surface. For major structures on cohesive soils undisturbed samples should generally be recovered for laboratory testing. The recovery of undisturbed samples in granular soil has not proven satisfactory. In site tests may provide useful data for foundation design. These tests include standard penetration test, vane shear test, Dutch cone penetration test (static penetration test), pressuremeter test, and other tests as described in Part 22, Geotechnical Subsurface Investigation.

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Concrete Structures and Foundations 3.2.4.3 Depth of Frost and Volume Change a.

The maximum depth of frost penetration shall be determined, usually on the basis of local experience and records. Figure 8-3-2 is a map showing the depths of frost penetration in the contiguous 48 states. Similarly, in regions of excessively swelling or shrinking soils, the depth to which significant volume changes occur as a result of seasonal variations in moisture content shall be determined.

b. Permafrost, or permanently frozen ground, exists in the northern hemisphere in arctic and subarctic regions. Although the southern boundary of permafrost is irregular, it may extend as far south as the 50th parallel. Foundations for structures, in areas of permafrost, should be designed in such a way as to not disturb the permanently frozen ground; or if this is impossible, the influence of the foundation on the permafrost should be predicted so the effect of the changes can be accommodated in the design. A geotechnical engineer with experience in these ground conditions should be consulted for design of foundations to be placed on permafrost.

Figure 8-3-2. Extreme Frost Penetration, in Inches, Based upon State Averages. Source: U.S. National Weather Records Center

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SECTION 3.3 DEPTH OF BASE OF FOOTINGS 3.3.1 SELECTION OF TENTATIVE DEPTHS (1995) On the basis of the data concerning the subsurface materials, tentative elevations for the bases of the footing should be selected. Unless special provisions are made, the depth shall not be less than the depth of frost penetration, scour, or, in expansive clay subsoils, less than the thickness of the zone of significant volume change of the subsoil due to seasonal moisture variations. Footings should be placed below disturbed shallow soils, uncontrolled fills, collapse susceptible soils, and organic soils.

3.3.2 REVISION OF DEPTHS OF FOOTINGS (1995) After the preliminary depths have been selected, the allowable soil pressure shall be determined and the sizes of the footings proportioned to the pressures. If the resulting design is not feasible or economical, similar studies shall be made for footings established at other depths until the most suitable and economical arrangement is determined. In considering the relative economy of footings at various levels, the cost and difficulty of excavation below groundwater level in pervious soils shall be taken into account. The economy and suitability of other types of foundations, such as piles or drilled shafts, shall also be considered. For deep foundations, the designer should refer to Part 4, Pile Foundations and Part 24, Drilled Shaft Foundations.

SECTION 3.4 SIZING OF FOOTINGS

1

3.4.1 D E F I N I T I O N S (1995) The following definitions will be used in the design procedures described below. • Net Bearing Capacity. The ultimate pressure at which the supporting material will fail in shear beneath the footing, less the pressure due to the weight of the soil at that depth.

3

• Allowable Bearing Capacity. The net bearing capacity divided by an appropriate factor of safety. • Allowable Settlement Pressure. The maximum pressure to which the footings of the structure may be subjected without producing excessive settlement or excessive differential settlement of the structure. This settlement consists of two stages: – Initial Settlement or Elastic Settlement. Occurs shortly after loading. – Consolidation. Occurs over an extended time period. The pressures for settlement are net pressures; that is, they represent pressures at the base level of the footing in excess of pressures at the same level due to the weight of the surrounding soil immediately adjacent to the footing. • Allowable Soil Pressure. Shall be taken as the smaller of the allowable bearing capacity or the allowable pressure for settlement. • Contact Pressure. The total load divided by the area for vertically loaded footings and the maximum pressure applied by the combined effects of vertical and horizontal loads for eccentrically loaded footings as described in Part 3, Spread Footing Foundations, Section 3.5, Footings with Eccentric Loads.

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3.4.2 SAFETY FACTORS (1995) The safety factor for Primary Loads shall not be less than 3; for Primary + Secondary Loads the safety factor shall not be less than 2. Additional consideration shall be taken of load duration in relation to foundation soil type and groundwater conditions when selecting a safety factor.

3.4.3 SHALLOW FOOTINGS ON GRANULAR MATERIAL (COHESION = 0) (1995) 3.4.3.1 General a.

The allowable soil pressure for a shallow footing on granular material depends on the width B of the footing, the shape of the footing, the depth of foundation Df, the unit weight of the foundation material, and the position of the groundwater table.

b. The location of the present and/or future groundwater level will noticeably affect the bearing capacity and allowable settlement pressure of the footing. Due consideration should be given to the future groundwater level. c.

Vibrational loads can cause severe settlement of a footing founded on loose to medium granular soils. If future construction in the immediate area will require pile driving, vibratory compaction of subsoil, or other vibrations, then consideration should be given to a more extensive vibratory analysis and a geotechnical engineer knowledgeable in soil dynamics should be consulted.

3.4.3.2 Net Bearing Capacity of a Footing on Granular Material (Cohesion = 0) a.

The net bearing capacity of a footing on sand can be calculated from the following formulae: For a continuous footing: Q u = 0.5gBN g + D f g ( N q – 1 ) For a square footing: Q u = 0.4gBN g + D f g ( N q – 1 ) For a circular footing: Q u = 0.3gBN g + D f g ( N q – 1 ) where: Qu = the net bearing capacity in lb/square foot B = the footing width in feet Df = the footing depth in feet g = the unit weight of the sand in lb/cubic foot Ng and Nq = dimensionless bearing capacity factors which are a function of f, the internal angle of friction, or of N, the standard penetration blow count.

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The standard penetration blow count is described in Part 22, Geotechnical Subsurface Investigation. The relationships between f, N, and the bearing capacity factors are shown in Figure 8-3-3 as proposed by Peck, Hanson and Thornburn. b. For saturated sands the buoyant unit weight should be used in the equations above.

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3

4

Figure 8-3-3. Relationship Among f, N, and Bearing Capacity

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Concrete Structures and Foundations 3.4.3.3 Allowable Settlement Pressure for Sand a.

An empirical equation by Meyerhof may be used to estimate the allowable settlement pressure, Qs, of a footing on sand. (1) For B £ 4 feet: Q s = Ns ------8 (2) For B > 4 feet: B + 1) ö (-----------------Q s = æ Ns è ------ø 12 B where: Qs = is in tons/square foot N = the standard penetration blow count B = the footing width in feet s = the allowable settlement in inches (3) The presence of a water table will have the effect of reducing the allowable settlement pressure as the effective stress is lowered. Therefore the allowable settlement pressure shall be reduced 50% if the water table is at the base of the footing and 0% if the water table is at a depth greater than B. The reduction for intermediate depths can be interpolated.

3.4.3.4 Sizing Footings on Granular Material A trial footing size is used to determine the net bearing capacity from Article 3.4.3.2 and the allowable bearing capacity described in Article 3.4.1 is calculated by dividing the net bearing capacity by the appropriate safety factor from Article 3.4.2. The trial footing size is used to determine the allowable settlement pressure defined in Article 3.4.3.3. The loads defined in Article 3.2.3 are divided by the trial footing area to give the contact pressure defined in Article 3.4.1. If the contact pressure is greater than either the allowable bearing capacity or the allowable settlement pressure, the footing size must be increased until the contact pressure is less than the allowable soil pressure defined in Article 3.4.1.

3.4.4 SHALLOW FOOTINGS ON SATURATED CLAY (f = 0) (1989) 3.4.4.1 Net Bearing Capacity (Qu) a.

The net bearing capacity of shallow footings on saturated clays or clayey soils depends on the footing width, B; the footing length, L; the depth, Df, of the footing below the surface and on the unconfined compressive strength, qu, of the clay. The net bearing capacity for a footing may be determined by means of the following equations. (1) For a continuous footing: Qu = 2.7qu

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(2) For a square or rectangular footing: Qu = 2.7qu (1 + 0.3 B/L) (3) For a circular footing: Qu = 3.5qu b. In these equations, Qu and qu are expressed in tons/square foot. The value of qu shall be taken as the average unconfined compressive strength of the clay within a depth B below the base of the footing; provided, however, that the strength of the clay does not decrease significantly with increasing depth below the footing. In the event that soft material underlies stiffer material, a special investigation of the bearing capacity of this level shall be undertaken. 3.4.4.2 Sizing Footings on Clay The correct factor of safety as indicated in Article 3.4.1 and Article 3.4.2 shall be used in order to obtain an allowable bearing capacity. The required footing area is determined by dividing the column or wall load by the allowable bearing capacity. 3.4.4.3 Settlement Characteristics a.

For footings located on or above medium clays, (qu below 2.0 tons per square foot) settlement analysis should generally be undertaken using the footing size and contact pressure determined in Article 3.4.1. In certain cases, large settlements will occur by consolidation of an underlying layer under very small additional loads. If any doubt exists concerning the consolidation characteristics of the soil, one or more consolidation tests should be undertaken. Settlement by “consolidation” of underlying clay layers can be many times the initial “elastic settlement.” Both the consolidation and elastic settlements can be estimated by laboratory analysis. If the estimated settlement is greater than the allowable settlement, the footing size shall be increased to bring the estimated settlement below the allowable limit or a deep foundation shall be used.

1

3

b. The effect of subsidance due to drainage of the soil shall be considered in the design of the structure.

3.4.5 FOOTINGS ON UNSATURATED SILTS AND CLAYS (1989) a.

Accurate determination of the bearing capacity of such soils is very difficult; and complicated laboratory testing is required. Due to the existence of hairline cracks in the soil structure, and unknown pore-air pressures, an extensive field investigation may be required. Each structure will have a different solution. Careful evaluation is necessary in order to arrive at a satisfactory footing design. A rise in the groundwater table will reduce the allowable capacity and complicate the analysis.

b. Where loadings on footings are light, or in the case of a floor slab, roadway, walks or other similar lightly loaded areas, due consideration to swelling of a clay soil shall be given. This may be especially important if the percent of soil with particle diameters less than 0.001 mm is greater than 15%.

3.4.6 FOOTINGS ON NON-HOMOGENEOUS DEPOSITS (1989) a.

Footings established above stratified or other non-homogeneous formations shall be proportioned on the assumption that the most unfavorable condition disclosed by the subsurface exploration may be present under the most heavily loaded footings, unless detailed information is obtained concerning the actual conditions beneath each footing.

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b. Subsoil of this type requires extensive knowledge and investigation in order to obtain an accurate solution. However, in many cases using the above assumption in order to simplify the solution is satisfactory.

3.4.7 FOOTINGS ON SOILS WITH COHESION AND FRICTION (PRECONSOLIDATED CLAYS) (1989) a.

Many soils fit this category and an accurate analysis can be carried out. The investigation must be undertaken without the use of the simplifying assumptions made for granular or cohesive soils, and more extensive laboratory information is required. Triaxial shear tests are required for this analysis.

b. At times, it will be satisfactory to assume the soil alternately only granular or cohesive and use the lower value for allowable pressure.

SECTION 3.5 FOOTINGS WITH ECCENTRIC LOADS 3.5.1 LOADS ECCENTRIC IN ONE DIRECTION (1989) a.

In cases where a footing is subjected to moments in addition to vertical loads, the line of action of the resultant force is located some distance from the centerline of the footing. This distance, called eccentricity, e, is calculated by the equation M e = ----P where: M = the moment P = the total vertical load The total vertical load is equal to live load plus dead load. The eccentricity shall have a maximum value of B/6.

b. The pressure distribution beneath a footing subjected to moment will be non-uniform and the maximum pressure, Pmax and minimum pressure, Pmin, can be calculated from: P 6M P max = ------- + ----------BL B 2 L P – 6M P min = ------- ----------BL B 2 L where: B = the footing width L = the footing length M = the moment P = the total vertical load

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3.5.2 LOADS ECCENTRIC IN TWO DIRECTIONS (1989) a.

In cases where a footing is subjected to moments in two directions, the vertical load, P, is calculated by adding dead loads to live loads. Horizontal loads and their lines of action in each direction are determined, and the moments in the two directions are computed by multiplying the force times the moment arm for each load. The eccentricity in each direction is computed by dividing the moment in each direction by the vertical load as follows: M M e x = -------x- and e y = -------yP P where: ex and ey = the eccentricities in the two directions Mx and My = the moments in the respective directions

b. Next, select trial footing dimensions B and L, where B is the footing dimension parallel to the x direction and L is parallel to the y direction. Using these dimensions, the previously determined eccentricities, and the vertical load, calculate the maximum and minimum contact pressures beneath the footing according to: 6e 6e P P max = -------- æ 1 + --------x- + --------y-ö è B L ø BL

1

6e 6e P P min = -------- æ 1 – --------x- – --------y-ö è BL B L ø

3

where all terms are as previously defined. c.

If Pmin is negative, that corner of the footing is in tension and so larger footing dimensions should be tried. The computations of maximum and minimum pressures are repeated with new trial dimensions until Pmin is positive. This indicates that the entire footing is in compression and the entire surface area will contribute to the footing’s load carrying capacity.

4

3.5.3 SIZING FOOTINGS WITH ECCENTRIC LOADS (1989) a.

Footings shall be designed using Primary Loads with the required factor of safety and checked by using Primary + Secondary Loads with their required factor of safety. Both design criteria must be met.

b. If the footing is subjected to eccentric loads, the maximum footing contact pressure as determined in either Article 3.5.1 or Article 3.5.2 is compared with the allowable soil pressure determined from either Article 3.4.3.3 or Article 3.4.3.4 for sands, or Article 3.4.4.2 for clays. In the case of clays, the settlement should be estimated according to Article 3.4.4.3. If the contact pressures are less than allowable pressures and the amount of settlement is acceptable, the footing size is adequate; however, if the maximum contact pressure exceeds the allowable soil pressures or if the settlement is excessive, the footing size shall be increased in order to decrease maximum contact pressure and settlement. If the resulting footing size is too large to be practical, deep foundations, such as piles as described in Part 4, Pile Foundations or drilled shafts as described in Part 24, Drilled Shaft Foundations, shall be considered.

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SECTION 3.6 FOOTING STRESSES 3.6.1 LOADS ECCENTRIC IN TWO DIRECTIONS (1989) a.

For computation of the stress within the footing itself, the pressures on the foundation may be calculated by the procedure given in Article 3.5.2: 6e 6e P P = -------- æ 1 ± --------x- ± --------y-ö x y ø BL è

b. However it is desirable, if possible, to proportion the footing for an equal pressure distribution. c.

A more detailed study may be required for a flexible, combined, or mat footing. In actual practice the pressure distribution may vary materially from this ideal distribution. The correct distribution of the reaction is dependent upon the rigidity of the footing, distribution of the loading, characteristics of the soil, and the factor of safety.

SECTION 3.7 FIELD CONDITIONS 3.7.1 MODIFICATION OF DESIGN (1989) If excavation discloses soils or soil conditions different from those upon which the design of the footings has been based, the design shall be altered as necessary. The plans for the footing should indicate the type of soil and soil pressure upon which the design is based.

3.7.2 REINFORCEMENT (1989) Wherever the concrete of a reinforced footing is in contact with the soil, steel reinforcement shall be provided with a cover of not less than 3 inches. If the concrete is placed against a seal coat or against steel sheeting that is to remain in place, the cover shall be not less than 2 inches.

3.7.3 FOOTINGS AT VARYING LEVELS (1989) If the footings for two adjacent parts of a structure are established at different levels, the difference in elevation of the bases of adjacent footings, divided by the least horizontal clear distance between the footings, shall not exceed a value appropriate to the characteristics of the subsoil, and in general should not exceed 1.0. An increased load on the lower footing will result from this configuration.

3.7.4 DRAINAGE (1989) Unless underwater construction is specified, surface water or groundwater shall not be permitted to accumulate in excavations for footings. Such water shall be conducted to sumps located outside the boundaries of the footing and removed. If the water cannot be handled by this procedure, groundwater lowering should be accomplished by well points, a tremie seal coarse, or other appropriate means.

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3.7.5 TREATMENT OF BOTTOM OF EXCAVATION (1995) a.

Care shall be exercised to prevent disturbance of the materials at the bottom of the excavation by equipment or by the feet of the workmen. The bottom 2 inches of concrete in the footing shall be neglected for strength calculations.

b. On soft clayey or silty soils a working platform or mud coat of lean concrete, from 2 inches to 3 inches in thickness, is recommended if disturbance is probable. Otherwise, final excavation of the last 3 inches to 6 inches above grade should be deferred until immediately before placement of the reinforcement. The concrete in a working platform or mud coat shall not be considered as contributing to the strength of the footing. c.

If a tremie seal is to be placed to permit dewatering of the cofferdam for pier, the thickness of the seal shall be adequate to withstand the upward pressure of the water beneath the seal at the time of dewatering. This uplift force shall be determined by a rational analysis.

3.7.6 STRESSES (1995) Concrete and steel allowable stresses shall be in accordance with Part 2, Reinforced Concrete Design.

3.7.7 INFORMATION ON DRAWINGS (1995) Design drawings shall indicate the allowable soil pressure, type of soil, grade of the reinforcing steel, strength of concrete, minimum cement factor, and other pertinent data.

1 SECTION 3.8 COMBINED FOOTINGS 3.8.1 USES AND TYPES (1995) a.

3

Combined footings are those which carry more than one column and are used for reasons such as: (1) Wall column is so close to property line or obstruction(s) that it is impossible to center column on footing. (2) Allowable soil pressures are so low or column loads so large that individual footings would overlap.

b. Combined footing types are illustrated in Figure 8-3-4 and include: rectangular, trapezoidal, and strap footings.

3.8.2 ALLOWABLE SOIL PRESSURES (1995) a.

Allowable soil pressures defined in Article 3.4.1 are determined from Article 3.4.3.3 or Article 3.4.3.4 for sands and Article 3.4.4.2 for clays. For clays, settlements should be estimated according to Article 3.4.4.3. For combined footings a minimum safety factor is 3.

b. A combined footing is ideally proportioned such that the centroid of the contact area lies on the line of action of the resultant of column loads, thereby producing a uniform pressure distribution. In situations where it is impossible to produce a uniform pressure distribution, the pressure distribution is computed and the footing sized according to the principles outlined in Section 3.5, Footings with Eccentric Loads. The dimensions of the footing are selected so that the allowable soil pressure is not exceeded.

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Figure 8-3-4. Types of Combined Footings

3.8.3 COLUMN LOADS (1995) Combined footings should be proportioned for uniform soil pressure under dead load plus the amount of live load that is likely to govern settlement as recommended in Article 3.2.3. The centroid of the footing must lie on the line of action of the resultant column loads consisting of dead load plus a fraction of live load specified by the specifications or building code if applicable.

3.8.4 SIZING COMBINED FOOTINGS (1995) 3.8.4.1 Rectangular Footings A rectangular footing is used if the rectangle can extend beyond each column the distance necessary to make the centroid of the rectangle coincide with the point where the resultant of the column loads intersects the base. 3.8.4.2 Trapezoidal Footings A trapezoidal footing is used if a rectangular footing cannot project the required distance beyond one or both columns. 3.8.4.3 Strap Footings The strap footing is considered as two individual footings connected by a beam.

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Part 4 Pile Foundations1 — 1994 — TABLE OF CONTENTS

Section/Article

Description

Page

4.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1.1 Scope (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-4-2 8-4-2

4.2 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.1 Loads (1994). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.2 Loads on Piles (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.3 Eccentricity of Loads (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.4 Uplift on Piles (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.5 Spacing of Piles (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.6 Batter Piles (1990). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.7 Scour (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-4-2 8-4-2 8-4-3 8-4-3 8-4-3 8-4-4 8-4-4 8-4-5

4.3 Allowable Load on Piles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.1 Subsurface Investigation (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.2 End Bearing Piles (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.3 Friction Piles (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.4 Lateral Support (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.5 Pile Length Determination (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.6 Pile Driving and Loading Tests (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-4-5 8-4-5 8-4-5 8-4-5 8-4-6 8-4-6 8-4-8

4.4 Pile Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.1 General (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.2 Timber Piles (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.3 Steel Piles (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.4 Precast Concrete Piles (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.5 Cast-in-Place Concrete Piles (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4.6 Augered Cast-in-Place Piles (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-4-9 8-4-9 8-4-9 8-4-10 8-4-11 8-4-11 8-4-13

4.5 Installation of Piles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5.1 Driven Piles (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5.2 Augered Cast-in-Place Piles (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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1

References, Vol. 40, 1939, pp. 418, 764; Vol. 41, 1940, pp. 369, 843; Vol. 49, 1948, p. 254; Vol. 50, 1949, pp. 311, 758; Vol. 52, 1951, pp. 382, 861; Vol. 63, 1962, pp. 276, 687; Vol. 64, 1963, pp. 226, 624; Vol. 80, 1979, p. 136; Vol. 91, 1990, pp. 63, 74; Vol. 94, 1994, p. 99.

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TABLE OF CONTENTS (CONT) Section/Article

Description

Page

4.6 Inspection of Pile Driving (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-4-16

Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-4-16

LIST OF TABLES Table 8-4-1

Description

Page

Recommended Pile Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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SECTION 4.1 GENERAL 4.1.1 SCOPE (1994) a.

This part of the Manual covers the investigation, design and construction of pile foundations.

b. For the purpose of this part, a pile shall be considered as a relatively slender structural member continuously driven or augered into the earth. Drilled shafts placed in predrilled holes are addressed in Part 24, Drilled Shaft Foundations. c.

In this part, factors of safety are suggested; however, where information on loads or soil conditions is limited, larger factors of safety should be used.

SECTION 4.2 DESIGN 4.2.1 LOADS (1994) a.

Pile foundations shall be designed to carry the entire superimposed load, including the weight of the footing and overlying loads supported by the footing.

b. Pile foundations shall be designed for that reasonable combination of the following loads and forces which produce maximum load and in accordance with Section 4.3, Allowable Load on Piles: 4.2.1.1 Primary Loads and Forces a.

Dead.

b. Live – Vertical. c.

Live – Horizontal due to surcharge.

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d. Centrifugal force. e.

Earth pressure.

f.

Buoyancy.

g.

Negative skin friction.

NOTE:

Live Load Impact shall be considered only in Case A of Article 4.2.2 for steel or concrete piles above the ground line where they are rigidly connected to the member supporting the superstructure.

4.2.1.2 Secondary Loads and Forces (Occasional) a.

Wind and other lateral forces.

b. Ice and Stream flow. c.

Longitudinal forces.

d. Seismic forces.

4.2.2 LOADS ON PILES (1994) a.

1

Pile foundations shall be designed using the most restrictive of the following load capacity cases: • Case A: The capacity of an individual pile as a structural member. • Case B: The capacity of the pile to transfer its load to the ground. • Case C: The capacity of the ground to support the load from the pile or piles.

3

b. When pile foundations are designed for primary and secondary loads in combination, as defined in Article 4.2.1, the allowable loads may be increased 25% for Load Cases A, B, and C, but the number of piles shall not be less than is required for primary forces alone with no increases in allowable stress for Case A and the minimum factor of safety shall be 2.0 for Cases B and C. For group friction piles, the factor of safety for Case C shall not fall below 2.0 for primary and secondary load combinations.

4

4.2.3 ECCENTRICITY OF LOADS (1990) The maximum design pile load under eccentric loading shall not exceed the allowable load as determined under Section 4.3, Allowable Load on Piles with the appropriate factors of safety stipulated in Article 4.2.2. The piles shall be so spaced that the eccentric load on the piles, due to primary forces, will be distributed as equally as practicable to the piles in the group. Pile loads due to combinations of primary and secondary forces shall not exceed that permitted by Article 4.2.2.

4.2.4 UPLIFT ON PILES (1990) a.

In special cases when piles or pile groups are subjected to uplift, and sufficient bond and anchorage are provided between the pile and the supported structure, the uplift shall be considered in the design of the pile foundation. The pile foundation shall be designed for uplift considering load capacity Cases A, B, and C of Article 4.2.2. The factor of safety for Cases B and C shall be a minimum of 2.0 for combinations of primary and secondary forces, and a minimum of 3.0 for combinations of secondary forces with dead load

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alone. The capacity of the pile as a structural member (Case A) shall be based on allowable stresses established in the applicable AREMA Specifications for Timber Structures, Chapter 7, Timber Structures; in Part 2, Reinforced Concrete Design; or in the AREMA Specifications for Steel Structures, Chapter 15, Steel Structures. The allowable stresses may be increased 25% for combinations of primary and secondary forces. b. The ultimate uplift value of an individual pile shall be determined by jacking test piles of identical type and dimension to that used in the design, and measuring the pull required per square foot of embedded surface area to raise the pile. When a tension pile group is involved, a group analysis shall also be undertaken. The maximum capacity of a tension pile group shall be considered to be the smaller of (1) the capacity of a single pile multiplied by the number of piles in the group, or (2) the weight of the block of soil contained within the perimeter of the groups, each with a minimum safety factor of 2.0, except as noted in paragraph a.

4.2.5 SPACING OF PILES (1990) a.

Piles shall be spaced to nearly equalize their load consistent with economical design of the footings. The spacing of piles shall depend upon: the type of pile, that is whether friction or end bearing; the pile’s structural and crushing strength; and the type of material sustaining the pile. Generally, piles should be spaced, center-to-center, at least three times the minimum butt width of the pile. Piles should be spaced far enough apart, or other suitable means used, to prevent heaving or uplifting of adjacent piles during driving.

b. In small groups, the piles may be battered to enlarge the area sustaining the group, thereby increasing the load-carrying capacity of the group without unreasonably increasing the size of the foundation. Endbearing piles may be spaced in accordance with the capacity of the pile and the end-bearing stratum that will carry the design load. When closely spaced friction piles are contemplated, their total group capacity shall be verified by an acceptable geotechnical method which considers the capacity of the engaged soil mass to support the applied pile loads. c.

When determining spacing of piles in granular soils, consideration should be given to the increased difficulty of driving due to the increased soil density that will occur because of soil packing or consolidation within the pile group.

4.2.6 BATTER PILES (1990) a.

Piles may be battered to help resist horizontal forces. Primary horizontal forces on pile foundations shall be resisted by batter piles where practicable. Such piles shall be designed to carry horizontal forces combined with their share of the vertical loads. In general, batter should not exceed 3 (horizontal) to 12 (vertical), due to increased difficulty in driving piles with a greater batter.

b. Secondary horizontal forces on pile foundations may be accommodated by the shear resistance of the vertical piles, passive soil pressure, or friction between the soil/foundation interface where these resisting forces can be determined to exist for a particular foundation system. Where these resisting forces cannot be shown to be reliable over the expected life of the structure, batter piles or other dependable means of resisting these forces shall be used. c.

Where large pile groups are involved, where clearance problems limit the pile foundation area, where secondary horizontal loads are small or in areas of the country where earthquake loading makes use of batter piles undesirable, the foundation shall be specially designed to include the horizontal forces as acting on the vertical piles. In such a case, the piles shall be designed to resist all loads, and the structure designed for the horizontal movement to be encountered.

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4.2.7 SCOUR (1990) a.

The possible effects of scour to pile foundations located in or adjacent to water should be reviewed as part of the total foundation design.

b. When there is a possibility that the upper portion of the soil formations may be removed by scour, the piles or pile group shall be designed to have adequate bearing capacity and lateral support below the projected depth of scour. The free standing portions of the exposed piles shall be designed as columns. c.

Determination of the probable depth of scour at a given location may have to be based largely on past records of stream bed erosion or wave action in the area, and how it has affected existing structures.

SECTION 4.3 ALLOWABLE LOAD ON PILES 4.3.1 SUBSURFACE INVESTIGATION (1990) a.

Test borings shall be made at enough locations and to a sufficient depth below the anticipated tip elevation of the piles to determine adequately the character of the material through which the piles are to be driven and of the materials underlying the pile tips. The results of the borings and soil tests, taken into consideration with the function of the piles in service, will assist in determining the type, spacing, and length of piles that should be used and whether the piles will be end bearing, friction or a combination of both types.

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b. The subsurface investigation should be made in accordance with provisions outlined in Part 22, Geotechnical Subsurface Investigation.

4.3.2 END BEARING PILES (1990) a.

A pile may be considered end bearing when it passes through soil having low frictional resistance, and has its tip resting on relatively impenetrable material such as rock, or enters other material that offers rapidly increasing resistance to further penetration. The capacity of end-bearing piles depends on the bearing capacity of soil or rock material underlying the piles, and upon the structural capacity of the pile. The dynamic characteristics of the soil-hammer cushion-pile system coupled with the installation technique will determine the ability of the pile to penetrate overlaying strata to reach the bearing stratum.

b. Allowable stresses for pile materials are given elsewhere in this part. When end-bearing piles pass through unconsolidated material, consideration should be given in design to the additional load (negative skin friction) that may be imposed on the pile as the material consolidates above the bearing stratum. The bearing stratum must be of sufficient thickness and strength to support the entire pile group loading. The design load shall preferably be determined by loading test piles. In addition, an analysis of the group of piles must show that the allowable load on the soil or rock supporting material is not exceeded.

4.3.3 FRICTION PILES (1990) a.

A friction pile derives its support principally from the surrounding soil through the development of shearing or frictional resistance. The capacity of friction piles depends upon the ability of the soil to carry the load distributed by the piles within the limits of settlement that can be tolerated by the structure.

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Concrete Structures and Foundations

b. The design load shall preferably be determined by loading test piles in accordance with the provisions of Article 4.3.6. Where groups of piles are driven into plastic materials, consideration should be given not only to the allowable load per pile, but also to the total load that can be safely assigned to the group. The design load shall be determined by loading a group of piles or by making an allowance for the difference between the capacity of a single pile and a group of piles by means of a block analysis. A single row of piles need not be considered as a group, provided the piles are spaced at least three times their butt width. c.

In many cases, a study of the borings and the estimation of approximate soil constants will determine the ability of the soil to carry the applied loads. In foundations involving cohesive soils, the load-settlement relationship should be investigated by recognized geotechnical methods and procedures.

4.3.4 LATERAL SUPPORT (1990) A fully embedded pile can generally be considered laterally supported. A pile that is not fully embedded, or may be as a result of scour, in air or water, or which may be in muck, peat, thin mud, or fluid material, shall be investigated for the allowable capacity by the methods given in the Report of ACI Committee 543 “Recommendations for Design, Manufacture, and Installation of Concrete Piles” or other acceptable method approved by the engineer.

4.3.5 PILE LENGTH DETERMINATION (1990) The determination of the most satisfactory and economical length of piles is one of the key factors in securing an adequate foundation. In addition to information that can be developed through soil borings, pile driving tests, pile load tests, and pile driving formulas, the use of the one-dimensional wave equation can be a valuable tool on large or difficult foundations, and is recommended for design and field control purposes (Reference 71). Pile driving records of nearby adjacent piles may also be used in determining pile length if definite correlation between the existing and proposed piles as to type, loading, and use can be determined as well as the veracity of the previous pile driving record. The use of pile driving records to establish pile lengths without the benefit of a subsurface investigation and geotechnical analysis on projects which are not relatively small and where the conditions above cannot be met is not recommended. 4.3.5.1 Estimated Tip Elevation and Estimated Length a.

At each boring location, using recognized geotechnical methods, the theoretical length of piles shall be computed considering contributions from both bearing and frictional resistance. Piles in very deep deposits are likely to receive support primarily through friction, whereas relatively shallow hardpan or rock conditions are likely to provide support primarily through end bearing. Many foundation conditions will provide both bearing and frictional support.

b. At each individual boring, an estimated tip elevation and an estimated pile length shall be selected and tabulated based on the design cutoff elevation. 4.3.5.2 Minimum Tip Elevation a.

At each boring location, a minimum tip elevation shall be computed above which no structure piles will be permitted to stop. The minimum tip elevation reflects the design intent of the pile foundation design and is determined by an experienced foundation engineer’s review of the estimated tip elevations, recognizing practical aspects of foundation construction practice. As an example, if geotechnical calculations demonstrate that piles should penetrate into a hardpan layer at varying depths, the minimum tip elevation will be shown at the top of this layer. In certain cases, field conditions during driving may modify this elevation.

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Pile Foundations

b. The minimum tip elevation will usually be above the estimated tip elevation. 4.3.5.3 Wave Equation a.

The use of the one dimensional wave equation will greatly assist the engineer and contractor in determining the foundation adequacy and the construction of the project as planned.

b. By the use of this tool, several values will be obtained: (1) the ability of the soil-hammer cushion-pile system to obtain the required design capacity, (2) the estimated blows per foot needed to obtain the required ultimate load at the estimated depth, (3) the means whereby the required blows per foot at other depths can be evaluated, (4) a means of evaluating the required blows per foot when the hammer fails to produce the manufacturer’s rated energy. c.

When this procedure is followed, the engineer can have the opportunity to modify his design before construction is started, and the contractor can be appraised of his hammer requirement.

d. This procedure is recommended for all large and/or important projects. 4.3.5.4 Pile Driving Formulas

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Many dynamic pile driving formulas have been developed as an aid in determining pile capacities. While such formulas serve a useful purpose, particularly on smaller projects, greater accuracy, and economy can usually be obtained by use of the wave equation method as described in Article 4.3.5.3. If pile driving formulas are proposed for use, formulas that take into account the relationship between the weight of pile and weight of the pile hammer striking parts should be used.

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4.3.5.5 Plan Tip Elevations 4.3.5.5.1 Friction Piles For those piles which can be considered to act as true friction piles, i.e. no end bearing stratum is in evidence within reasonable depths, only a design tip elevation is required. In uniform soils, where a complete soil investigation has determined the tip elevation, no further driving criteria is required, except the statement that the piles must be driven to the design tip elevation. A variation in the expected rate of penetration at the required tip elevation would indicate a variable soil layer, and a reappraisal of the tip elevation will be required. 4.3.5.5.2 Combined Bearing and Friction Piles, or Bearing Piles Plans and specifications should require that all piles be driven to the minimum tip elevation shown on the plans. At the minimum tip elevation, driving shall be continued until the required resistance is achieved, as determined by the load tests, a wave equation analysis, or some pile driving formula specified by the engineer. The latter provision will insure against variations in the consistency and depth of the bearing layer. An important judgement factor is selection of required hammer energy-type, and cushion. This decision can best be achieved by a wave equation analysis. 4.3.5.5.3 Estimated Lengths The plans should show estimated lengths which have been used for calculation of the engineer’s estimate, and will provide the bidders with a reasonable basis for pricing the pile foundations. © 2011, American Railway Engineering and Maintenance-of-Way Association

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4.3.6 PILE DRIVING AND LOADING TESTS (1990) 4.3.6.1 Driving Tests a.

Where variable soil conditions are known to exist, the following procedure is suggested. A few of the structure piles should be selected, including at least one from each substructure unit of the bridge or structure, and they should be driven first before other service piles are ordered. Their installations should be designated as Pile Driving Tests. A separate pay item should be provided, to cover piles installed by Pile Driving Tests.

b. Where practical, piles installed by driving tests should have their tips carried five to ten feet below the estimated tip elevation for the service piles at each particular location. Driving records for each foot of driving of each pile shall be kept and plotted in the field to provide exploratory information. The plot should be on a log containing the generalized information from the nearest structure boring. This record will provide an immediate correlation of driving resistance and subsoil conditions for the pile, hammer and cushion arrangement being used. The record will also provide information on where to select suitable locations for future load tests if required. (Load tests should be applied only to standard service piles, not to piles installed by pile driving tests. This is because piles installed by pile driving tests are deliberately overdriven and, therefore, are not typical of the service piles.) c.

Piles installed by driving tests are recommended both for the situation where later load tests are to be performed and where load tests are not expected to be performed. The driving tests are of particular importance where load tests are not contemplated, because in that case, they provide the only correlation between soil boring data and driving data.

d. If possible, piles installed by driving tests should be placed in a position where they can serve as service piles in the completed structure. It is permissible on small projects to overdrive all service piles (similar to the installation of driving tests described above) in lieu of load testing which, from a cost standpoint, may not be practical. 4.3.6.2 Pile Load Tests a.

Pile load tests are considered essential for large or important jobs, or in subsurface conditions where there is little precedent for major construction. To date, they give the best knowledge of the probable capacity of an individual pile.

b. It is preferred that load tests be carried to failure to determine the true factor of safety for the proposed design. If the margin of safety is higher or lower than desired, driving and elevation criteria can be modified. If, due to very high loads, tests to failure are not practicable, testing should be carried to not less than twice the design load. Test loads should not exceed the ultimate capacity of the pile as a structural member, or the capacity of the jack frame. c.

The test apparatus and procedure shall be in accordance with the current ASTM Designation: D1143 “Standard Method of Testing Piles under Axial Compressive Load.”

d. By analyzing and interpreting the load tests with the driving test data and subsoil information, it will be possible to affirm the adequacy of the design and the installation criteria and introduce field modifications as may be necessary.

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SECTION 4.4 PILE TYPES 4.4.1 GENERAL (1990) a.

Selection of the type of foundation pile for a particular structure should be based on the following criteria: (1) Design load per pile or pile group. (2) Type of foundation material to be penetrated. (3) Relative costs of the piles and pile driving. (4) Equipment available for driving piles. (5) Availability of desired pile type. (6) Special considerations based on specific job conditions, including, but not limited to: (a) Restricted space for pile driving. (b) Possible damage to existing structures.

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(c) Exposure to sea water. (d) Possible damage from marine organisms. (e) Chemical attack. (f) Possible damage to adjacent structures caused by vibration or soil movement during driving.

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(g) Noise level during driving. b. Full-length piles shall be used wherever practicable, but if splices cannot be avoided, an approved method of splicing shall be used which will develop the full strength of the pile. Piles shall not be spliced except by permission of the engineer, who must also approve all splice locations.

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4.4.2 TIMBER PILES (1990) a.

Timber piles shall conform to the AREMA specifications for wood piles, Chapter 7, Timber Structures, Part 1, Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Timber Bridge Ties and Recommendations for Fire-Retardant Coating for Creosoted Wood and Part 3, Rating Existing Wood Bridges and Trestles. If treatment is required, it shall conform to AREMA specifications for wood preservation – Chapter 30, Ties, Section 3.6, Wood Preserving.

b. For a timber pile which is primarily a friction pile, the maximum allowable load in pounds shall be computed by multiplying the tip area in square inches (small end) by the figure 1,200; the maximum load thus being equivalent to 1,200 psi acting at the tip. c.

For a timber pile that is primarily a point bearing pile, the maximum allowable load shall be computed as above, but using the figure 800 instead of 1,200.

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Concrete Structures and Foundations

4.4.3 STEEL PILES (1990) 4.4.3.1 Types This type of piling shall include all steel H-section piles and open-end steel pipe piles. 4.4.3.2 Material All steel used for the piles shall conform to the current ASTM Designations: A36 for H-pile sections, and A252 for pipe sections. Special steels may be used for corrosion protection or other purposes, but where welding is required weldability must be assured. 4.4.3.3 Size a.

The minimum depth of a steel H-section shall be 8 inches. The minimum thickness of metal in the flange or web shall be 3/8 inch. The flange width shall be not less than 85% of the depth of the section.

b. The minimum outside diameter of open-end pipe piles shall be 8-5/8 inches. The minimum wall thickness shall be 3/8 inch. 4.4.3.4 Pile Caps In general, steel bearing caps are not required on steel H-piles embedded at least 1 foot in concrete, providing the footing reinforcement is adequately designed to transmit the imposed loads. 4.4.3.5 Protection Against Corrosion a.

Steel piles that will be exposed to corrosive environments shall be protected by concrete encasement or other suitable means; such as specially formulated epoxy or bituminous coatings, or additional steel thickness. Protection at ground surfaces or normal water lines shall be provided and shall extend at least 1 foot above and 3 feet below the ground surface or low-water line. Concrete protection, where provided shall have a minimum thickness of 4 inches and shall contain nominal steel reinforcement.

b. Structural steel piles shall not be used through active corrosion-inducing material or where electrolysis may occur, without adequate provision for the protection of such piles. 4.4.3.6 Allowable Stresses The allowable load per pile shall be determined as specified in Section 4.3, Allowable Load on Piles, but the unit stresses due to axial load shall not exceed 12,600 psi. Due allowance shall be made for any bending stresses caused by horizontal or eccentric loads and consideration shall be given to any column action of an unsupported pile. 4.4.3.7 Pile Tip Reinforcement Pile tip reinforcement may be required to prevent damage to H-piles when driving through heavy gravel, boulders, or formations known to contain obstructions, or when driving end bearing piles. Heavy cast steel tips are recommended for this purpose where the conditions so justify their use.

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4.4.4 PRECAST CONCRETE PILES (1990) 4.4.4.1 General a.

This type of piling includes both conventionally reinforced concrete piles and prestressed concrete piles. Both types can be formed by either casting, centrifugal casting, or extrusion methods. They are made in various cross section shapes such as square, octagonal, and round. Often such piles are cast with a hollow core. The piles are usually of constant cross section but may have a tapered tip.

b. Precast concrete piles must be designed and manufactured to withstand handling and driving stresses in addition to service loads. The workmanship, material, and proportioning shall conform to the requirements specified in Part 1, Materials, Tests and Construction Requirements. 4.4.4.2 Design The minimum acceptable diameter or side dimension for driven piles is usually 8 inches. This may be satisfactory for short piles which are lightly loaded, however, as a general rule, it is recommended that the minimum average dimension be 10 inches, except that the pile tip may be 8 inches. Piles may be pointed or not as directed by the engineer. 4.4.4.3 Manufacture The manufacture of the various types of precast concrete piles shall be in accordance with the current Chapter 4 of American Concrete Institute (ACI) Committee 543 report titled “Recommendations for Design, Manufacture, and Installation of Concrete Piles.”

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4.4.4.4 Cut-Off Precast piles shall be driven to or cut off within 2 inches of the elevation shown on the plans, but in all cases, the cutoff shall be below any indication of fracture. If piles are cut off or driven below the required elevation, they shall be built-up to the cutoff line as determined by the engineer. Standard details are to be shown on the project plans.

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4.4.4.5 Allowable Stresses The allowable load per pile shall be determined as specified in Section 4.3, Allowable Load on Piles, but the concrete unit stresses shall not exceed 0.3 f ¢c with a maximum of 1,600 psi. Other stresses shall conform to the requirements of Part 2, Reinforced Concrete Design and Part 17, Prestressed Concrete.

4.4.5 CAST-IN-PLACE CONCRETE PILES (1990) 4.4.5.1 Types Cast-in-place piles shall be cast in previously driven metal casings or shells which shall remain permanently in place. They may be tapered or cylindrical, or a combination of tapered and cylindrical shapes. 4.4.5.2 Tapered Piles Tapered piles shall not be less than 8 inches in diameter at the tip and shall be uniformly tapered at the rate of not more than 1 inch in 8 feet, or step tapered, at the same average rate. 4.4.5.3 Cylindrical Piles Cylindrical piles shall have a minimum diameter of 8 inches.

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Concrete Structures and Foundations 4.4.5.4 Pipe Casings and Shells a.

Pipe casings driven without a mandrel shall be formed of steel conforming to the current ASTM Designation: A252, Grade 2. Metal shells driven with a mandrel shall have a thickness of not less than No. 16 USMSG and a minimum yield strength of 30,000 psi. Casings shall be in one integral piece or adequately spliced, and shall be of sufficient thickness to withstand installation pressures without leakage or harmful distortion.

b. All piles shall be equipped with approved watertight flat plates or conical points welded to the tip end of the casing. The end closures approved for cylindrical piles shall not project beyond the diameter of the pile casing when used on friction piles. 4.4.5.5 Placing Concrete a.

Casings or shells shall be inspected and approved by the engineer immediately before any concrete is placed. A suitable light shall be used to inspect the entire length. Any accumulated foreign matter, or water shall be removed before the concrete is placed. Any broken or otherwise defective shells shall be corrected by removal and replacement, or by driving an additional pile, as directed by the engineer. Concrete having a minimum compressive strength of at least 2,500 psi at 28 days shall be used to fill the shell. The placing of the concrete shall be carried out as a continuous operation from the tip to the cutoff elevation, and shall be performed in such a manner as to minimize segregation and insure complete filling of the casing or shell.

b. No pile shall be driven within 15 feet of a pile that has been filled with concrete for more than 2 hours but less than 24 hours. The driving procedure for any particular project shall be approved by the engineer in charge, before commencing work. 4.4.5.6 Allowable Stresses The allowable load per pile shall be determined as specified in Section 4.3, Allowable Load on Piles, but the unit stresses, shall not exceed the following: a.

Concrete. 0.3 of the ultimate compressive unit strength of the concrete used (f ¢c), but not to exceed 1,600 psi.

b. Steel. The unit stresses shall not exceed 12,600 psi. 4.4.5.7 Protection Against Corrosion a.

When the steel casing is used in computing the strength of the pile and the piles will be exposed, they shall be protected from corrosion as specified in Article 4.4.3.5.

b. If the strength of the steel is considered in computing the strength of the pile, the pile shall not be used through active rust-inducing material or where electrolysis may occur without adequate provision for the protection of such pile. 4.4.5.8 Reinforcement Cast-in-place piles may be reinforced to provide needed bending strength, or for uplift anchorage. When used, the reinforcing steel should be preassembled into cages and accurately placed in accordance with design drawings. The reinforcement shall be clean of foreign material that could affect bond, and securely positioned before concrete fill is placed.

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4.4.6 AUGERED CAST-IN-PLACE PILES (1990) 4.4.6.1 General Augered Cast-In-Place piles are primarily used as friction piles. They are installed by rotating a continuous flight hollow-shaft auger into the ground to a predetermined pile depth. High-strength mortar is pumped with sufficient pressure as the auger is withdrawn, to fill the hole preventing hole collapse and causing the lateral penetration of the mortar into soft or porous zones of the surrounding soil. A head of at least several feet of mortar above the injection point is carried around the perimeter of the auger at all times during the raising of the auger so that the high strength mortar has a displacing action removing any loose material from the hole. 4.4.6.2 Design The length of pile will be determined from the examination of soil borings using the shear strength of the soil, and preferably, verified by pile load tests as described in Article 4.3.6.2. Recommended pile loads for varying pile diameters, depending on soil strengths, are given in Table 8-4-1. Table 8-4-1. Recommended Pile Loads Nominal Size of Pile (Inches)

Normal Loadings Range (Tons)

Normal Required Compression Strength of Mortar (PSI)

12

10-40

2,000-2,500

14

40-75

2,500-3,000

16

75-100

3,000-4,000

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4.4.6.3 Materials a.

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The material used to fill the holes shall consist of a mixture of Portland Cement, concrete sand, fluidizer and water proportioned and mixed as to provide a mortar capable of maintaining the solids in suspension without appreciable water gain and which will laterally penetrate and fill any voids in the foundation material. Portland Cement shall conform to Part 1, Materials, Tests and Construction Requirements, Section 1.2, Cement. The fine aggregate shall conform to Section 1.3, Other Cementitious Materials, with a fineness modulus between 1.40 and 3.40. Fluidizer shall meet the requirements of the current Corps of Engineers, USA, Spec. No. CRDC 566.

b. The mortar shall be so proportioned as to have a minimum ultimate compressive strength of 2,000 psi at 28 days. A set of 6 mortar cubes shall be made each day and tested in accordance with the current ASTM Designation: C109, with the exception that the mortar should be restrained from expansion by a top plate. 4.4.6.4 Tension Piles Where tension is required, a special continuous flight hollow-shaft auger shall be rotated into the ground to the required depth. A steel bar shall be inserted into the hollow center shaft of the auger. The auger head closure shall be detached allowing the steel bar to remain in place and be centered in the tension pile as the continuous flight auger is slowly withdrawn from the hole. During this withdrawal process, high strength mortar shall be placed under pressure through the space between the steel rod left in place and the wall of the hollow shaft auger.

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SECTION 4.5 INSTALLATION OF PILES 4.5.1 DRIVEN PILES (1990) Piles shall be driven with steam, air, or diesel powered hammers. Size of the type of hammer used should be determined by guidelines noted in Article 4.5.1.1. The hammer shall be operated at all times at pressures and speeds recommended by the manufacturer. Use of vibratory type hammers may be allowed if pile capacities have been determined by load tests. Use of a gravity drop hammer for driving piles should be limited to relatively unimportant foundations where uniform pile capacity is not critical. 4.5.1.1 Selection of Hammer-Cushion Combination a.

Preliminary selection of the hammer-cushion combination for driving piles can be made with the following guide: (1) Steel Piles – Air or Steam Operated Hammers. • Minimum size: 170 ft-lb of rated energy per ton of pile service load. Stiff or hard internal cushion. • Desired size: 250-340 ft-lb of rated energy per ton of pile service load. • Pile Cushion: Moderately stiff to soft (wood) internal cushion. • Diesel Hammers: – Use 100 to 135% of size determined for air or steam hammers. – Use standard (stiff) internal cushion. (2) Mandrel-Driven Piles – Same as Steel. (3) Precast or Prestressed Concrete Piles – Air or Steam Operated Hammers. • Desired size: 250 ft-lb of rated energy per ton of pile service load. The weight of the ram shall generally not be less than one-fourth of the weight of the pile being driven. Use wood, or equivalent, internal cushion. • Pile Cushion: Design by one-dimensional wave theory, or by experience. • Diesel Hammers: – Use 100 to 135% of size determined for air or steam hammers. – Use standard (stiff) internal cushion. (4) Wood Piles – Air or Steam Operated Hammers. • For normal capacity piles (up to 30 tons service load) excluding abnormally large timbers or fabricated sections, use 15,000 ft-lb maximum rated energy with a wood internal cushion. Diesel hammers may be rated up to 20,000 ft-lb with standard (stiff) internal cushions.

b. The foregoing preliminary selection of hammer and cushion combinations should preferably be confirmed by a wave equation analysis of pile driving indicating the pile yield stresses are not exceeded and that the desired ultimate load capacity can be achieved (see Article 4.3.5.3).

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Pile Foundations 4.5.1.2 Pile Leads Pile drivers shall have firmly supported leads extending from the highest point to the lowest point that the hammer must travel. The leads should be supported independently of the pile and constructed to guide and stay the pile during driving. 4.5.1.3 Splicing Driving shall be continued until the plan tip elevation is reached or until the rate of penetration specified is obtained. If the proper resistance to driving is not attained at the plan cutoff, the driving shall be continued and the additional length of pile required shall be supplied by splicing in such a way as to develop the full strength of the section of the pile. The splice shall be made a sufficient distance, but not less than 1 foot above the ground or water surface so that the splice can be observed during subsequent driving. 4.5.1.4 Jetting Piles may be jetted, when permitted by the engineer, either by use of water jets alone or in combination with the hammer. The volume and pressure of the water at the jet nozzles shall be sufficient to freely erode the material adjacent to the pile. Before the desired penetration is reached, jetting shall be discontinued at the elevation specified by the engineer and the piles driven to required penetration or resistance. 4.5.1.5 Preboring Where piles must be installed through strata offering high resistance to driving, where jetting would cause damage, to prevent excessive heaving of cohesive soils, for driving through relatively impenetrable material or for other valid reasons, the engineer may require or permit holes to be bored with a power auger or other equipment especially designed for the purpose. Depending upon the reasons for preboring, the diameter of the hole shall be as directed by the engineer to obtain the proper pile penetration and carrying capacity. The pile shall be inserted into the hole immediately after boring and be driven to required penetration or resistance.

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4.5.1.6 Improperly Driven and Damaged Piles Piles shall be driven within 3 inches of the plan location. Variations of more than 1/4 inch per foot from the vertical, or from the batter line when batter piles are required, may be subject to rejection by the engineer. Any pile so out of line or plumb as to impair its usefulness shall be pulled and/or an additional pile driven, as required by the engineer. Any pile so injured in driving or handling as to impair its structural capacity as a pile under conditions of use shall be replaced by a new pile, or the injured part shall be replaced by splicing or other remedial measures–all as directed by the engineer.

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4.5.1.7 Redriving of Heaved Piles Previously driven piles shall be carefully checked during the driving of adjacent piles, and if any uplift occurs, they shall be redriven to the required penetration or resistance as directed by the engineer. 4.5.1.8 Underwater Driving While it is possible to drive piles underwater by use of a follower between the pile and hammer, or by use of a submersible pile hammer, such driving methods should be avoided when it is necessary to drive piles to obtain a predetermined bearing capacity, unless such capacity is determined by a pile load test under similar conditions. 4.5.1.9 Interrupted Driving When driving is interrupted or the rate of blows retarded for any reason, a careful record shall be kept of the extent of the delay or retardation. Any decrease in the penetration per blow immediately following such stoppage, shall be cause to suspect the interpretation of the preceding blows per foot.

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Concrete Structures and Foundations

4.5.2 AUGERED CAST-IN-PLACE PILES (1990) 4.5.2.1 Augering Equipment a.

The hole through which the high-strength mortar is pumped during the placement of the pile shall be located at the bottom of the auger head below the bar containing the cutting teeth.

b. The auger flighting shall be continuous from the auger head to the top of auger with no gaps or other breaks. The pitch of the auger flighting shall not exceed 9 inches. c.

Augers over 40 feet in length shall contain a middle guide. The piling leads should be prevented from rotating by a stabilizing arm.

4.5.2.2 Mixing and Pumping of High-Strength Cement Mortar a.

Only approved pumping, continuous mixing, and agitating equipment shall be used in the preparation and handling of the mortar. All oil or other rust inhibitors shall be removed from mixing drums and mortar pumps. If ready-mix mortar is used, an agitating storage tank of sufficient size shall be used between the ready-mix truck and the mortar pump to insure a homogeneous mix and continuity in the pumping operations. All materials shall be such as to produce a homogeneous mortar of the desired consistency. If there is a lapse in the operation, the mortar shall be recirculated through the pump.

b. The mortar pump shall be a positive displacement piston type pump capable of developing displacing pressures at the pump of up to 350 psi. 4.5.2.3 Pile Top Encasement Metal sleeves or casing of the proper diameter and at least 18 inches in length shall be placed around the pile tops. (Special conditions may require metal sleeves of additional length.)

SECTION 4.6 INSPECTION OF PILE DRIVING (1994) Pile driving and augering operations shall be inspected and documented completely as directed by the engineer. Recommended techniques of inspection and records to be compiled can be found in the publication titled “Inspection of Pile Driving Operations” Technical Report M-22, Department of the Army, Construction Engineering Research Laboratory, Champaign, Illinois, July 1972.

C - COMMENTARY The purpose of this part is to furnish the technical explanation of various Articles in Part 4, Pile Foundations. In the numbering of Articles of this Section, the numbers after the “C-” correspond to the Section/Article being explained.

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C - SECTION 4.1 GENERAL C - 4.1.1 SCOPE (1994) a.

Many texts and foundation reference sources consider drilled shafts as cast-in-place concrete piles. In view of the special techniques required for the installation of drilled shafts as opposed to driven or augered piles, they have been treated separately in Part 24, Drilled Shaft Foundations.

b. Since it is not often practical to obtain definitive geotechnical information for every part of a pile foundation system, good engineering judgement and experience should be used to increase stated factors of safety where warranted by local conditions.

C - SECTION 4.2 DESIGN C - 4.2.1 LOADS (1994) It is not possible to accurately predict the behavior of a combined pile and soil bearing footing. In most cases, because of the pile supporting system, little load, including that of the footing, will be transferred to the material directly under the footing after it has been cast. Therefore, in analysis, the pile system will be considered as carrying all loads, with no load being transferred to the underlying soil. C - 4.2.1.1 Primary Loads and Forces Live loads are separated into two cases, vertical and horizontal due to surcharge, to ensure that these loads are considered separately and in combination.

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C - 4.2.1.2 Secondary Loads and Forces (Occasional) (Reference 89) The effect of seismic events on pile foundation may not be limited in all cases to the additional loads imposed on the piles. In certain types of water-bearing sands, a phenomenon referred to as soil liquefaction may be precipitated by the vibrations induced by a seismic event or other source. When this occurs, soil shear strength is eliminated and support for piles, both vertically and laterally, is diminished. In geographical areas susceptible to seismic events, the potential for liquefaction should be evaluated through a competent geotechnical investigation and measures to ensure the stability of foundations should be employed. Further discussion on methods to predict the occurrence and extent of liquefaction may be found in the References.

4

C - 4.2.2 LOADS ON PILES (1994) Cases A, B and C are listed to ensure that complete consideration is given to the possible failure modes of a pile foundation. A safety factor of 2.0 is prescribed for Cases B and C for all primary loads or possible primary load combinations. An increase of 25% in stresses or load capacity is allowed for individual piles in a foundation system for combinations of secondary loads and primary loads except for Case C for group friction pile effect. No increase is specified for this case due to greater relative uncertainty that is associated with its analysis when compared to individual bearing pile analysis.

C - 4.2.6 BATTER PILES (1990) (Reference 79 and 94) a.

It is intended that battered piles be used to resist lateral foundation loads due to primary forces. Where this is not practical, the lateral resistance of vertical piles can be utilized to resist horizontal forces. The engineer should make a careful evaluation of the pile foundation system to ascertain its lateral resistance capacity. Much research has been done concerning the lateral resistance of vertical piles. The

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Concrete Structures and Foundations FHWA Manual on Design of Piles and Drilled Shafts Under Lateral Load should be consulted for the design of such pile foundations. b. Cases A, B and C of Article 4.2.2 should be evaluated for lateral loads on vertical piles. Recent research has indicated that under certain conditions that may be encountered during a seismic event, battered piles should not be used. The designer should consult the AASHTO “Standard Specifications for Seismic Design” for guidance.

C - 4.2.7 SCOUR (1990) (Reference 30, 31 and 37) Research is continuing into the prediction of the occurrence and extent of scour. The FHWA Technical Advisory, Scour at Bridges and publication RD78-162, Countermeasures for Hydraulic Problems at Bridges, provide references for scour analysis.

C - SECTION 4.3 ALLOWABLE LOAD ON PILES C - 4.3.5.3 Wave Equation (Reference 91) The Wave Equation method of analyzing pile capacity and pile length was developed by Smith (1960). For a detailed explanation of the Wave Equation methodology, the designer may consult FHWA documentation of the WEAP program. C - 4.3.5.4 Pile Driving Formulas Historically, pile driving formulas which make use of the relationship between the hammer energy and the pile movement when driven have been used to approximate safe pile loads. Most notably, the Engineering News Record formula has been used extensively for this purpose. Tests have shown that these formulas do not give consistent results whereby excessive pile lengths may be dictated in some instances while in others insufficient factors of safety may result from their use. For these reasons, the use of these formulas should be limited to projects whose size and importance may justify their use in lieu of the more elaborate Wave Equation method. When these formulas are to be used, their application should be guided by good engineering judgement and experience. Careful evaluation of the actual hammer energy applied to the pile through the hammer-pile cushion-pile system is also required.

C - SECTION 4.4 PILE TYPES C - 4.4.2 Timber Piles (1990) Timber piles shall be of a length which will allow driving to the minimum specified tip elevation and which also will allow the complete removal of timber damaged by driving. C - 4.4.3.6 Allowable Stresses The compressive stress at the tip of steel H-piles has been limited to 12,600 psi for design loads. It should be recognized that stresses during driving may considerably exceed this stress. The Wave Equation formula can predict these driving stresses. In general, driving stresses should be limited to 0.8 of the yield strength of the pile steel. C - 4.4.5.4 Pipe Casings and Shells Where the pipe casing or shell is to serve only as a form for the cast-in-place concrete piles, the steel thickness need only be sufficient to withstand soil pressures and driving forces subject to the stated minimum thickness and strength for mandrel driven piles. If the casing or shell is to be used to compute the structural capacity of © 2011, American Railway Engineering and Maintenance-of-Way Association

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the pile, the plans must show the steel thickness to be used and also splicing details and the grade of steel to be used.

C - SECTION 4.5 INSTALLATION OF PILES C - 4.5.1.3 Splicing a.

Piles may be spliced in a variety of methods to fully develop the strength of the pile section. The following methods may be employed:

b. Steel Piles. The method of splicing shall be shown on the plans or as approved by the engineer. Piles may be spliced by full penetration butt welds, by the addition of welded splice plates, by a combination of these methods or by other means approved by the engineer which fully maintains the strength of the pile section. c.

Concrete Piles. Concrete piles shall preferably not be spliced, unless specifically provided for by the plans, special provisions or by the engineer in writing. Short extensions may be added to tops of reinforced concrete piles after completion of driving when the required capacity is not attained at the planned top of pile elevation. These extensions shall be made by exposing the pile reinforcing steel a sufficient distance to provide a full strength lap splice with the extension segment steel. Concrete for the extension shall be of the same quality and strength of the pile concrete and shall be placed in forms of the same shape and dimensions as the driven pile. Prior to placement of the new concrete, the top of the driven pile shall be cleaned and coated with neat cement or an approved bonding agent.

1

C - SECTION 4.6 INSPECTION OF PILE DRIVING (1994) (Reference 106) Other useful documents to aid in inspection of the pile driving may be found in: • The Performance of Pile Driving Systems: Inspection Manual, FHWA RD-86-160.

3

• Inspectors Manual for Pile Foundations and A Pile Inspector’s Guide to Hammers, from the: Deep Foundation Institute P.O. Box 359 Springfield, NJ 07081

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Part 5 Retaining Walls, Abutments and Piers — 2002 — TABLE OF CONTENTS

Section/Article

Description

Page

5.1 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.1 Types of Retaining Walls, Abutments and Piers (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.1.2 Scour (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-5-2 8-5-2 8-5-3

5.2 Information Required. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.1 Field Survey (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.2 Subsurface Exploration (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.3 Controlling Dimensions (1989). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.4 Loads (2002). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.5 Type of Backfill (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.2.6 Character of Foundation (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-5-4 8-5-4 8-5-4 8-5-4 8-5-4 8-5-4 8-5-5

5.3 Computation of Applied Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.1 Loads Exclusive of Earth Pressure (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3.2 Computation of Backfill Pressure (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-5-5 8-5-5 8-5-6

5.4 Stability Computation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4.1 Point of Intersection of Resultant Force and Base (2002) . . . . . . . . . . . . . . . . . . . . . . . . . 5.4.2 Resistance Against Sliding (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4.3 Soil Pressure (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.4.4 Settlement and Tilting (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-5-7 8-5-7 8-5-7 8-5-8 8-5-8

5.5 Design of Backfill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5.1 Drainage (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5.2 Compaction (2002). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-5-8 8-5-8 8-5-8

5.6 Designing Bridges to Resist Scour . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6.1 Design Philosophy and Concepts (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6.2 Design Considerations (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.6.3 Design Procedure (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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5.7 Details of Design and Construction for Abutments and Retaining Walls . . . . . . . . . . 5.7.1 General (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.7.2 Cantilever Walls (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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TABLE OF CONTENTS (CONT) Section/Article 5.7.3

Description

Page

Counterfort and Buttress Walls (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-5-11

5.8 Details of Design and Construction for Bridge Piers . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.8.1 Pier Spacing, Orientation and Type (2002). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.8.2 Pier Shafts (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.8.3 Caissons (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.8.4 Bearings and Anchorage (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.8.5 Piers in Navigable Streams (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-5-12 8-5-12 8-5-12 8-5-13 8-5-13 8-5-13

Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-5-13

LIST OF FIGURES Figure

Description

Page

C-8-5-1 Cases 1, 2 and 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-8-5-2 Cases 4, 5 and 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-8-5-3 Cases 7, 8 and 9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-8-5-4 Earth Pressure Computation – Walls with Heels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-8-5-5 Earth Pressure Computation – Walls without Heels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-8-5-6 Earth Pressure Charts for Walls Less than 20 Feet High . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-5-16 8-5-17 8-5-18 8-5-21 8-5-22 8-5-26

LIST OF TABLES Table 8-5-1 8-5-2

Description

Page

Types of Backfill for Retaining Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Properties of Backfill Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-5-5 8-5-6

SECTION 5.1 DEFINITIONS 5.1.1 TYPES OF RETAINING WALLS, ABUTMENTS AND PIERS (2002) a.

A retaining wall is a structure used to provide lateral support for a mass of soil which, in turn, may provide vertical support for loads acting on or within the soil mass.

b. The principal types of retaining walls are as follows: (1) The gravity wall, which is so proportioned that no reinforcement other than temperature steel is required. (2) The semi-gravity wall, which is so proportioned that some steel reinforcement is required along the back and along the lower side of the toe.

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(3) The cantilever wall, which has a cross section resembling an L or an inverted T, and which requires extensive steel reinforcement. (4) The counterfort wall, which consists of a reinforced vertical face slab supported laterally at intervals by vertical reinforced counterforts extending into the backfill and supported by a reinforced base slab which usually projects in front of the face slab to form a toe. (5) The buttress wall, which is similar to the counterfort wall except that the vertical members, called buttresses, are exposed on the face of the wall rather than buried in the backfill. (6) The crib wall, which consists of an earth-filled assembly of individual structural units, and which relies for its stability on the weight and strength of the earth fill. The design of such walls is treated in Part 6, Crib Walls. (7) Mechanically Stabilized Embankments (MSE) are covered by Part 7, Mechanically Stabilized Embankment of this Chapter. c.

An abutment commonly consists of a retaining wall that incorporates a bridge seat in its face. It may also be of the spill-through type in which the bridge seat rests on horizontal beams supported by piles or columns between which the fill is permitted to extend. Preferably, abutments shall be of the gravity or semi-gravity type.

d. A pier is an intermediate support for the superstructure. The principal pier types are:

1

(1) Solid wall, reinforced for strength and temperature. (2) Rigid frame, consisting of multiple columns with a cap reinforced to act as a frame. (3) Bents, consisting of multiple piles extended to a cap. (4) Hammerhead, consisting of a column supporting a cap which cantilevers beyond the column.

3

(5) Drilled shafts, consisting of poured concrete columns extending to a cap.

5.1.2 SCOUR (2002)1 Scour is the result of the erosive action of flowing water excavating and carrying away material from the bed and banks of waterways. There are three types of scour all of which are likely to be present at a structure. a.

Aggradation and Degradation. These are long term streambed elevation changes due to natural or man induced causes within the reach of the river over which the bridge is located. Aggradation involves the deposition of material eroded from other sections of a stream reach, whereas degradation involves the lowering or scouring of the bed of a stream.

b. Contraction Scour.2 Contraction scour in a natural channel involves the removal of material from the bed and banks across all or most of the channel width. This component of scour results from a contraction of the flow, such as a change in downstream control of the water surface elevation. Increased velocities and a resulting increase in bed shear stresses cause scour. Contraction of the flow by bridge approach embankments encroaching onto the floodplain and/or into the main channel is the most common cause of contraction scour. 1 2

See Commentary See Commentary

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c.

Local scour.1 Local scour involves removal of material from around piers, abutments, spurs, and embankments. It is caused by an acceleration of flow and resulting vortices induced by flow obstructions.

SECTION 5.2 INFORMATION REQUIRED 5.2.1 FIELD SURVEY (2002) a.

Sufficient information shall be furnished, in the form of a profile and cross-sections or a topographic map, to determine the structural requirements. Present grades and alignments of tracks and roads shall be indicated, together with the records of high water, low water, and depth of scour, the location of underground utilities, change in channel location characteristics, site history from local sources, and information concerning the structures that may affect or be affected by this construction.

b. For bridge construction at a new location, a complete survey is required as detailed in Part 3, Spread Footing Foundations, Article 3.2.1.

5.2.2 SUBSURFACE EXPLORATION (2002) a.

Sufficient borings shall be made along the length of the structure to determine, with a reasonable degree of certainty, the subsurface conditions. Irregularities found during the initial soil boring program may dictate that additional borings be taken.

b. The subsurface investigation shall be made in accordance with the provisions of Part 22, Geotechnical Subsurface Investigation.

5.2.3 CONTROLLING DIMENSIONS (1989) Information shall be assembled concerning clearances, proposed grades of tracks and roads, and all other factors that may influence the limiting dimensions of the proposed structure.

5.2.4 LOADS (2002) Loads to be superimposed on piers, retaining walls, abutments, or on backfill, shall be determined and indicated on the plans. See Part 2, Reinforced Concrete Design and Chapter 9 for seismic loading.

5.2.5 TYPE OF BACKFILL (2002)2 a.

Backfill is defined as all material behind the wall, whether undisturbed ground or fill, that contributes to the pressure against the wall.

b. The backfill shall be investigated and classified with reference to the soil types described in Table 8-5-1.

1 2

See Commentary See Commentary

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Table 8-5-1. Types of Backfill for Retaining Walls Backfill Type 1 2 3 4 5

c.

Backfill Description Coarse-grained soil without admixture of fine soil particles, very freedraining (sand, gravel or broken stone). Coarse-grained soil of low permeability due to admixture of particles of silt size. Fine silty sand; granular materials with conspicuous clay content; or residual soil with stones. Soft or very soft clay, organic silt; or soft silty clay. Medium or stiff clay that may be placed in such a way that a negligible amount of water will enter the spaces between the chunks during floods or heavy rains.

Types 4 and 5 backfill shall be used only with the permission of the Engineer. In all cases the wall design shall be based on the type of backfill used.

5.2.6 CHARACTER OF FOUNDATION (2002) The character of the foundation material shall be investigated as specified under Part 3, Spread Footing Foundations of Article 3.2.4. Where pile supported foundations are required, the provisions of Article 4.3.1 of Part 4, Pile Foundations, shall be followed for the necessary subsurface investigation.

1

3

SECTION 5.3 COMPUTATION OF APPLIED FORCES 5.3.1 LOADS EXCLUSIVE OF EARTH PRESSURE (2002) a.

In the analysis of piers, retaining walls and abutments, due account shall be taken of all superimposed loads carried directly on them, such as building walls, columns, or bridge structures; and of all loads from surcharges caused by railroad tracks, highways, building foundations, or other loads supported on the backfill. Piers must also be designed for stream flow pressures as well as ice flow pressures and collision forces where applicable.

b. In calculating the surcharge due to track loading on an abutment and on wingwalls that are in line with the abutment backwalls, the entire load shall be taken as distributed uniformly on the surface of the ballast immediately below the tie, over a width equal to the length of the tie. With increased depth, the width for distribution can be increased on slopes of 1 horizontal to 2 vertical, with surcharge loads from the adjacent tracks not being permitted to overlap. c.

To account for variability in backfilling and the dynamic effects of axle loads, abutment backwalls above bridge seats shall be designed for earth pressures and live load surcharge increased by 100%. This does not apply to the portion of the abutment below the bridge seat nor the stability of the abutment.

d. In calculating the surcharge due to track loading above a wall and parallel, or roughly parallel, to the wall, the entire load shall be taken as distributed uniformly over a width equal to the length of the tie.

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e.

The stability of the abutment or wall as a whole unit, regardless of the distribution of the loads and surcharges, shall always be checked and shall conform to the requirement of Section 5.4, Stability Computation.

f.

Live load impact shall not be considered in the design of an abutment or pier unless the bridge bearings are supported by a structural beam, such as the seat of a spill-through abutment or a pier cap supported by individual columns, piles, or shafts. In such a case, the impact shall be applied to the beam only, and not to footings, or piles.

g.

For the design of abutments and piers, consideration must be given to all forces transmitted from the superstructure to the substructure, depending on the bearing fixity conditions.

5.3.2 COMPUTATION OF BACKFILL PRESSURE (2002)1 a.

Values of the unit weight, cohesion, and angle of internal friction of the backfill material shall be determined directly by means of soil tests or, if the expense of such tests is not justifiable, by means of Table 8-5-2 referring to the soil types defined in Table 8-5-1. Unless the minimum cohesive strength of the backfill material can be evaluated reliably, the cohesion shall be neglected and only the internal friction considered. See Part 20, Flexible Sheet Pile Bulkheads, Table 8-20-3. Table 8-5-2. Properties of Backfill Materials Type of Unit Weight Cohesion Backfill Lb. Per Cu. Ft. “c”

Angle of Internal Friction

1

105

0

33° 42¢ (38° for broken stone)

2

110

0

30°

3

125

0

28°

4

100

0

0°

5

120

240

0°

b. The magnitude, direction and point of application of the backfill pressure shall be computed on the basis of appropriate values of the unit weight, cohesion and internal friction. c.

When the backfill is assumed to be cohesionless and when 1) the surcharge load, if any, on the backfill can be converted into an equivalent uniform load or when 2) the surcharge can be converted into an equivalent uniform earth surcharge, Rankine’s or Coulomb’s formulas may be used under the conditions to which each applies. Formulas and charts given in the Commentary and the trial wedge methods given in the Commentary are both applicable.

d. When the backfill cannot be considered cohesionless, when the surcharge on the backfill is irregular, or when the surcharge cannot be converted to an equivalent uniform earth surcharge, the trial wedge methods illustrated in the Commentary are preferable.

1

e.

If the wall or abutment is not more than 20 ft. high and if the backfill has been classified according to Table 8-5-1, the charts given in the Commentary may be used.

f.

If the surcharge is of a lesser width than the height of the wall, a more satisfactory design can be obtained by the use of trial wedge methods given in the Commentary.

See Commentary

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g.

If the wall or abutment is prevented from deflecting freely at its crest, as in a rigid frame bridge, some types of U-shaped abutments, or in laterally braced or anchored walls, the computed backfill pressure shall be increased 25%.

h. In spill-through abutments, the increase of pressure against the columns due to the shearing strength of the backfill shall not be overlooked. If the space between columns is not greater than twice the width across the back of the columns, no reduction in backfill pressure shall be made on account of the openings. No more than the active earth pressure shall be considered as the resistance offered by the fill in front of the abutment. In computing the active earth pressure of this fill, the negative or descending slope of the surface shall be taken into consideration. i.

The backfilled areas behind a wall or abutment shall be designed to dissipate water pressures by the use of free-draining backfill material in conjunction with drains. It is preferable that the free-draining backfill material be used within a wedge behind the wall, bounded by a plane rising at 60 degrees to the horizontal.

j.

If local conditions do not permit the construction of drains and, consequently, water may accumulate behind the wall, the resulting additional pressure shall be taken into account. Consideration should also be given to the eventual plugging of the drains due to infiltration of soil.

SECTION 5.4 STABILITY COMPUTATION

1

5.4.1 POINT OF INTERSECTION OF RESULTANT FORCE AND BASE (2002) The resultant force on the base of a wall or abutment shall fall within the middle third of the structure if founded on soil, and within the middle half if founded on rock or piles. The resultant force on any horizontal section above the base of a solid gravity wall should intersect this section within its middle half. If these requirements are satisfied, safety against overturning need not be investigated.

3

5.4.2 RESISTANCE AGAINST SLIDING (2002) a.

The factor of safety against sliding at the base of the structure is defined as the sum of the forces at or above base level available to resist horizontal movement of the structure divided by the sum of the forces at or above the same level tending to produce horizontal movement. The numerical value of this factor of safety shall be at least 1.5. If the factor of safety is inadequate, it shall be increased by increasing the width of the base, by the use of a key, or by the use of batter piles.

b. In computing the resistance against sliding, the passive earth pressure of the soil in contact with the face of the wall shall be neglected. The frictional resistance between the wall and a non-cohesive subsoil may be taken as the normal force on the base times the coefficient of friction f of mass concrete on soil. For coarse-grained soil without silt, f may be taken as 0.55; for coarse-grained soil with silt, 0.45; for silt, 0.35. c.

If the wall rests upon clay, the resistance against sliding shall be based upon the cohesion of the clay, which may be taken as one-half the unconfined compressive strength. If the clay is very stiff or hard the surface of the ground shall be roughened before the concrete is placed.

d. If the wall rests upon rock, consideration shall be given to such features of the rock structure as may constitute surfaces of weakness. For concrete on clean sound rock the coefficient of friction may be taken as 0.60.

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e.

The factor of safety against sliding on other horizontal surfaces below the base shall be investigated and shall not be less than 1.5.

5.4.3 SOIL PRESSURE (1989) The allowable soil pressure beneath the footing shall be determined in accordance with Part 3, Spread Footing Foundations.

5.4.4 SETTLEMENT AND TILTING (2002)1 a.

The soil pressure determined in accordance with Article 5.4.3 provide for adequate safety against failure of the soil beneath the structure. If the subsoil consists of soft clay or silt, or if a layer of such material lies beneath the subsoil and is within the pressure zone of influence generated by the base pressure, it is necessary to determine the compressibility of the soil and to estimate the amount of settlement.

b. If the compressibility of the subsoil would lead to excessive settlement or tilting, the movement can be reduced by designing the wall so that the resultant of the forces acting at the base of the wall intersects the base near its midpoint. Otherwise, pile foundations shall be considered.

SECTION 5.5 DESIGN OF BACKFILL 5.5.1 DRAINAGE (2002) a.

The material immediately adjacent to the wall should be noncohesive and free draining. Cinders shall not be used. If a special back drain is installed, the pore size within the drain shall be coarse enough to permit free flow of water, but not so coarse that the fill material may ultimately move into it and clog it. Water from the free-draining materials shall be removed, preferably by horizontal drain pipes or by weep holes. Horizontal drain pipes, if used, shall be installed in such a position that they will function properly. Such drains shall be accessible for cleaning. Weep holes are considered less satisfactory than horizontal drains. If used, they shall have diameters not less than 6 inches and shall be spaced not over 10 feet.

b. Geocomposite and/or geotextile materials in conjunction with free draining backfill may be used as approved by the Engineer.

5.5.2 COMPACTION (2002) a.

The backfill shall preferably be placed in loose layers not to exceed 12 inches in thickness. Each layer shall be compacted before placing the next, but overcompaction shall be avoided.2

b. It is recommended that backfill be compacted to no less than 95% of maximum dry density per ASTM D698 and at a moisture content within 2% of optimum. c.

1 2

No dumping of backfill material shall be permitted in such a way that the successive layers slope downward toward the wall. The layers shall be horizontal or shall slope downward away from the wall.

See Commentary See Commentary

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SECTION 5.6 DESIGNING BRIDGES TO RESIST SCOUR 5.6.1 DESIGN PHILOSOPHY AND CONCEPTS (2002)1 Bridges shall be designed through careful evaluation of the hydraulic, structural, and geotechnical aspects of the bridge foundation to withstand the effects of scour from the design flood.

5.6.2 DESIGN CONSIDERATIONS (2002) 5.6.2.1 General a.

Scour types are additive. The design shall provide for the total of all scour types at a location. Local scour holes at piers and abutments may overlap one another. If scour holes do overlap, the local scour shall be the total depth from both.2

b. For pile and drilled shaft designs subject to scour, consideration shall be given to using a lesser number of longer piles or shafts as compared with a greater number of shorter piles or shafts to develop bearing loads. This approach will provide a greater factor of safety against pile failure due to scour. 5.6.2.2 Piers a.

Pier foundations not in the exisiting channel shall be designed in the same manner as the pier foundations in the stream channel if there is likelihood that the channel will shift its location to include such piers.

1

b. Consideration shall be given to changes in the flow direction during floods when determining shape and orientation of piers.3 c.

The effects of ice and debris build-up shall be evaluated when considering use of piers in stream channels. Use ice and debris deflectors where appropriate.4

3

5.6.2.3 Abutments a.

Relief openings, spur dikes, and river channelization should be used where needed to minimize the effects of adverse flow conditions at abutments.

b. Utilize riprap or other protection devices where needed to protect abutments. c.

4

Where ice build-up is likely to be a problem, set the toe of spill-through slopes or vertical abutment walls some distance from the edge of the channel bank to facilitate passage of the ice.

5.6.3 DESIGN PROCEDURE (2002)5 The design procedure for scour outlined in the following steps is recommended for bridge substructure units:

1

See See 3 See 4 See 5 See 2

Commentary Commentary Commentary Commentary Commentary

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(1) Select the design flood event(s). Also check the overtopping flood (if less than the design flood) and other flood events if there is evidence that such events would create deeper scour than the design flood or overtopping floods.1 (2) Develop water surface profiles for the flood flows in Step 1, taking care to evaluate the range of potential tailwater conditions below the bridge which could occur during these floods. (3) Estimate total scour for the worst condition from Steps 1 and 2 above. (4) Plot the total scour depths obtained in Step 3 on a cross section of the stream channel and flood plain at the bridge site. (5) Evaluate the scour depths obtained in Steps 3 and 4 for reasonableness.2 (6) Evaluate the bridge on the basis of the scour analysis performed in Steps 3-5. Modify the design as necessary.3 (7) Analyze the bridge foundation on the basis that all stream bed material in the scour prism above the total scour line (Step 4) has been removed and is not available for bearing or lateral support. In the case of a pile foundation, the piling shall be designed for reduced lateral restraint and column action because of the increase in unsupported pile length after scour. In areas where the local scour is confined to the proximity of the footing, the lateral ground stresses on the pile length that remains embedded may not be significantly reduced from the pre-local scour conditions. The depth of local scour and volume of soil removed from above the pile group shall be considered when computing pile embedment to sustain vertical load. (a) Spread Footings on Soil. Place the top of the footing below the design scour line. The bottom of the footing shall be at least 6.0 feet below the streambed. (b) Spread Footings on Rock Highly Resistant to Scour.4 The bottom of the footing shall be placed directly on the cleaned rock surface for massive rock formations (such as granite) that are highly resistant to scour. (c) Spread Footings on Erodible Rock. Carefully assess weathered or other potentially erodible rock formations for scour prior to determining footing elevation. (d) Spread Footings Placed on Tremie Seals and Supported on Soil. The tremie base shall be placed at least three feet below the scour line if the tremie is structurally capable of sustaining the imposed structural load without lateral soil support. (e) Deep Foundations (Piling or Drilled Shafts) with Footings.5 1

See See 3 See 4 See 5 See 2

Commentary Commentary Commentary Commentary Commentary

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Preferably place the top of the footing or pile cap below the streambed a depth equal to the estimated contraction scour depth to minimize obstruction to flood flows and resulting local scour. (8) For certain locations and conditions it may be necessary to calculate the scour for a superflood. See the Commentary for further discussion of superfloods.

SECTION 5.7 DETAILS OF DESIGN AND CONSTRUCTION FOR ABUTMENTS AND RETAINING WALLS 5.7.1 GENERAL (2002) a.

The principles of design and permissible unit stresses for walls and abutments shall conform to Part 2, Reinforced Concrete Design, with the modifications or additions in the following Articles:

b. The width of the stem of a semi-gravity wall, at the level of the top of the footing shall be at least onefourth of its height. c.

The base of a retaining wall, or abutment supported on soil shall be located below frost line, and in no case at a depth less than 3 ft. below the surface of the ground in front of the toe. The base shall be located below the anticipated maximum depth of scour. Where this is not practicable the base shall be supported by piles or other suitable means.

1

d. To reduce temperature and shrinkage cracks in exposed surfaces, reinforcement shall be provided as specified in Part 2 of this Chapter, irrespective of the type of structure. e.

The backs of retaining walls and abutments shall be damp-proofed by an approved material. Particular attention shall be given to protection of the joint where the bottom of stem meets the top of heel.

f.

At horizontal joints between the bases and stems of piers and retaining walls, raised keys should be used. In lieu of raised shear keys, shear friction may be used.

g.

Vertical keyed expansion joints shall be placed not over 60 ft. apart to take care of temperature changes. They shall be protected by membrane waterproofing or noncorrosive water stops.

h. The walls above the footings shall be cast as units between expansion joints, unless construction joints are formed in accordance with the provisions of these specifications.

5.7.2 CANTILEVER WALLS (2002) a.

The unsupported toe and heel of the base slab shall each be considered as a cantilever beam fixed at the edge of the support.

b. The vertical section shall be considered as a cantilever beam fixed at the top of the base.

5.7.3 COUNTERFORT AND BUTTRESS WALLS (2002) a.

The face walls of counterfort and buttress walls and parts of base slabs supported by the counterforts or buttresses shall be designed in accordance with the requirements of a continuous slab, Part 2 of this

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Chapter. Due allowance shall be made for the effect of the toe moment on shears and bending moments in the heel slabs of counterfort walls. b. Counterforts may be designed in accordance with the requirements of T-beams. As T-beams, reinforcement or stirrups shall be provided to anchor the face slabs and the heel slabs to the counterforts. Reinforcement shall be proportioned to carry the end shears of the slabs. Stirrups shall be anchored as near to the outside face of the face walls and as near to the bottom of the base slab as the requirements for the protective covering permit. It is desirable to run reinforcing bars through the loops of U-shaped stirrups. c.

Buttresses shall be designed in accordance with the requirements for rectangular beams.

SECTION 5.8 DETAILS OF DESIGN AND CONSTRUCTION FOR BRIDGE PIERS 5.8.1 PIER SPACING, ORIENTATION AND TYPE (2002) 5.8.1.1 Grade Separation Structures a.

Piers shall be located to provide the required horizontal and vertical clearances for traffic (highway, railway or other), to accommodate underground utilities and structures, and to permit the maintenance of surface drainage and other surface facilities.1

b. Piers supporting bridges over railways and located less than 25 feet clear from centerline of the near railroad track shall be provided with pier protection conforming with the requirements of Part 2, this Chapter. 5.8.1.2 Structures over Waterways a.

Where possible, the bridge pier axis should be parallel to the direction of the flow. When this is not feasible, special consideration must be given to additional loads placed on the substructure by the nonparallel flow. Consideration shall also be given to scour effects.

b. Where piers are exposed to heavy flows, or ice and debris collisions, consideration should be given to longer span lengths, the use of nose guards, starlings, or other systems to protect against damage to the structures.

5.8.2 PIER SHAFTS (2002) a.

Design of concrete piers shall be in accordanc with Part 2, Reinforced Concrete Design. Piers consisting of piles or drilled shafts shall be in accordance with Part 4, Pile Foundations and Part 24, Drilled Shaft Foundations of this Chapter.

b. The bridge seat/pier cap shall be of sufficient size to keep bearing stresses within allowances and provide adequate edge distances.2

1 2

See Commentary See Commentary

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c.

The depths of a pier footing shall not be less than the depth of frost penetration in that part of the country (see Part 3, Spread Footing Foundations of this Chapter) and not less than 3 feet below grade unless founded on solid, nonerodible rock.

5.8.3 CAISSONS (2002) Caisson design shall meet all of the design requirements for transferring the loads from the substructure element being supported to the soil without exceeding allowable stresses and soil pressures. In addition, caissons shall be designed for (1) stresses during sinking, including, but not limited to, lateral soil pressures and unequal hydrostatic pressure; (2) adequate weight or other means of overcoming skin friction of the soil; and (3) means of support during the tremie sealing operation.

5.8.4 BEARINGS AND ANCHORAGE (2002) The design of bearings and anchorage for steel spans shall be in accordance with Chapter 15 and Part 2, Reinforced Concrete Design. Any uplift forces caused by buoyancy or the use of continuous spans shall be considered in the design of a pier and its components with particular emphasis on anchorage of the superstructure. Anchorage that is subject to uplift forces shall be designed to develop a minimum of one and one-half times the calculated force.

5.8.5 PIERS IN NAVIGABLE STREAMS (2002)1 a.

Consideration shall be given to collision damage. Piers shall be of sufficient size and mass to withstand a reasonable anticipated collision or be protected in accordance with Part 23, Pier Protection Systems at Spans Over Navigable Streams.

1

b. Unprotected piers shall be solid structures capable of resisting collision impacts in all directions including torsion.

3

COMMENTARY The purpose of this part is to furnish the technical explanation of various articles in Part 5, Retaining Walls, Abutments and Piers. In the numbering of articles in this section, the numbers after the “C-” correspond to the section/article being explained.

4

C - SECTION 5.1 DEFINITIONS C - 5.1.2 SCOUR (2002) Different materials scour at different rates. Loose granular soils are rapidly eroded by flowing water, while cohesive or cemented soils are more scour resistant. However, ultimate scour in cohesive or cemented soils can be as deep as scour in sandbed streams. Scour will reach its maximum depth in sand and gravel bed material in hours; cohesive bed material in days; glacial tills, sandstones and shales in months; limestones in years and dense granites in centuries. Massive rock formations with few discontinuities are highly resistant to scour during the lifetime of a typical bridge. Scour holes may not be visible during low water stages. b.

1

Contraction scour occurs when the flow area of a stream at flood stage is decreased from the normal, either by a natural constriction or by a bridge. With the decrease in flow area there is an increase in average velocity and bed shear stress. Hence, there is an increase in stream power at the contraction

See Commentary

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and more bed material is transported from the contracted reach than is transported into the reach. This increase in the transport of bed material lowers the bed elevation. Contraction scour is typically cyclic. That is, the bed scours during the rising stage of a runoff event, and fills on the falling stage. Other factors that can cause contraction scour are: (1) a natural stream constriction, (2) long embankment approaches over the flood plain to the bridge, (3) ice formation or jams, (4) a natural berm forming along the banks due to sediment deposits, (5) island or bar formations upstream or downstream of the bridge opening, (6) debris, and (7) the growth of vegetation in the channel or flood plain. In a natural channel, the depth of flow is always greater on the outside of a bend. In fact, there may well be deposition on the inner portion of the bend. If a bridge is located on or close to a bend, the contraction scour will be concentrated on the outer part of the bend. C - 5.1.2 (c) Local Scour Local scour is caused by the formation of vortices at the base of an abutment or pier. The formation of these vortices results from the pileup of water on the upstream face and the acceleration of the flow around the pier or abutment. The action of the vortex removes bed material from the area around the base of the pier. As the depth of the resulting scour hole increases, the strength of the vortex decreases and equilibrium is eventually reached. Factors affecting local scour are: a.

Pier width has a direct influence on depth of local scour. As width of the pier perpendicular to the flow increases, there is an increase in scour depth.

b. Projected length of an abutment into the stream affects the depth of local scour. An increase in the projected length of an abutment into the flow increases scour. However, there is a limit on the increase in scour depth with an increase in length. This limit is reached when the ratio of projected length into the flow to the depth of the approach flow is 25. c.

Pier length has no appreciable effect on local scour depth as long as the pier is aligned with the flow. When the pier is skewed to the flow, the length has a significant effect; i.e., with the same angle of attack, doubling the length of the pier increases scour depth 33 percent.

d. Flow depth has an effect on the depth of local scour. An increase in flow depth can increase scour depth by a factor of 2 or greater for piers. With abutments the increase is from 1.1 to 2.15 depending on the shape of the abutment. e.

The approach flow velocity affects scour depth-the greater the velocity, the deeper the scour.

f.

Bed material characteristics such as grain size, gradation, and cohesion can affect local scour. Variation in bed material within the sand size range has no effect on local scour depth. Larger size bed material that can be moved by the flow or by the vortices and turbulence created by the pier or abutment will not affect the maximum scour depth but only the time it takes to attain it. Very large particles in the bed material, such as cobbles or boulders, may armor the scour hole. Fine bed material (silts and clays) will have scour depths as deep as sand bed streams. This is true even if bonded together by cohesion. The effect of cohesion is to influence the time it takes to reach the maximum scour. With sand bed material, the maximum depth of scour is reached in hours and can result from a single flood event. With cohesive bed materials it may take days, months, or even years to reach the maximum scour depth, the result of many flood events.

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g.

The angle of attack of the flow to the pier or abutment has a significant effect on local scour, as was pointed out in the discussion of pier length. Abutment scour is reduced when embankments are angled downstream and increased when embankments are angled upstream.

h. Shape of the nose of a pier or an abutment has a significant effect on scour. Streamlining the front end of a pier reduces the strength of the horseshoe vortex, thereby reducing scour depth. Streamlining the downstream end of piers reduces the strength of the wake vortices. A square-nose pier will have maximum scour depths about 20 percent greater than a sharp-nose pier and 10 percent greater than either a cylindrical or round nose pier. i.

Full retaining abutments with vertical walls on the streamside (parallel to the flow) will produce scour depths about double that of spill-through abutments.

j.

Ice and debris accumulations potentially increase the effective width of the piers, change the shape of piers and abutments, increase the projected length of an abutment, and cause the flow to plunge downward against the bed. This can increase both the local and contraction scour. The magnitude of the increase is still largely undetermined. Debris can be taken into account in the scour equations by estimating how much debris will increase the width of the pier or length of an abutment. Debris and ice effects on contraction scour can also be accounted for by estimating the amount of flow blockage (decrease in width of the bridge opening) in the equations for contraction scour.

C - SECTION 5.2 INFORMATION REQUIRED

1

C - 5.2.5 TYPE OF BACKFILL (2002) Type 1 backfill shall be used where feasible. Types 2 and 3, in declining order of preference, may be used due to economic or other considerations.

C - SECTION 5.3 COMPUTATION OF APPLIED FORCES

3

C - 5.3.2 COMPUTATION OF BACKFILL PRESSURE (2002) I. EARTH PRESSURE FORMULAS FROM RANKINE-COULOMB THEORIES a.

The following formulas are applicable only to materials that may be considered cohesionless. (1) Cases 1 to 3 are for vertical walls without heels. The pressure P is the same as the pressure on a vertical plane in the backfill (Figure C-8-5-1). Vertical walls with heels come under Cases 4 to 6. (2) Cases 4 to 6 are for walls with heels (Figure C-8-5-2). The wall may be vertical or may lean forward, or may lean backward as long as the upper edge of the back of the wall is in front of the vertical plane through the edge of the heel. (3) Cases 7 to 9 are for walls without heels, leaning backward (Figure C-8-5-3). Walls with heels come under Cases 4 to 6 as long as the upper edge of the back of the wall is in front of the vertical plane through the edge of the heel; if the upper edge of the back of the wall extends back to the vertical plane through the edge of the heel, the problem can be solved by combining the solutions of Cases 4 to 6 and 7 to 9.

b. For walls leaning forward or walls with the heel extending into the backfill, the pressure of the backfill on a vertical plane through the back of the heel of the wall is to be combined with the weight of backfill contained between this vertical plane and the back of the wall.

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Figure C-8-5-1. Cases 1, 2 and 3 c.

For walls leaning toward the backfill the resultant pressure P will be horizontal for a wall without surcharge, or for a wall with uniform surcharge, if the surface of the backfill is horizontal; and will make an angle l with the horizontal for a wall with a sloping surcharge. The values of l will vary from d, where the wall is vertical, to zero, where Rankine’s theory shows that the resultant pressure is horizontal. Values of l and values of K, where P = 1/2 wh2K, are given in Figure C-8-5-3.

II. TRIAL WEDGE METHOD OF EARTH PRESSURE COMPUTATION A. Scope

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3

4

Figure C-8-5-2. Cases 4, 5 and 6

The trial wedge method is applicable for backfills of soils possessing cohesion, internal friction, or both; for backfills having any configuration of ground surface; and for surcharges located at any position on the backfill. The procedure, illustrated in Figure C-8-5-4 and Figure C-8-5-5, is outlined in the following Articles.

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Figure C-8-5-3. Cases 7, 8 and 9

B. Computation of Total Pressure (1) Make scale drawing of the wall with backfill and any surcharge loads.

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(2) Locate surface AB against which earth pressure is to be computed. For walls with heels use vertical section as shown in Figure C-8-5-4. For walls without heels use back of wall as shown in Figure C-85-5. (3) Establish direction of earth pressure with respect to line AB, by the procedure described below under “Direction of Pressure P”. (4) Compute depth ho of tension cracks if soil has cohesion. (5) Draw boundaries of trial wedges BC1, BD2, etc., wherein BC, BD, etc., are assumed plane surfaces of sliding. (6) Compute weights of successive wedges ABC 1, ABD 2, etc., including any surcharge acting on the ground surface within the limits of each wedge. (7) Lay off weight vectors for successive wedges. (8) Compute total cohesion on each surface of sliding BC, BD, etc. (9) Lay off cohesion vectors from lower ends of weight vectors, each parallel to the surface of sliding on which it acts. (10)From end of each cohesion vector draw line parallel to earth pressure P. (11)From point B in force diagram lay off of radial lines BC, BD, etc., each making an angle f with the normal to its respective surface of sliding (as force R on surface BF).

1

(12)Locate intersections of vectors R with corresponding lines drawn in paragraph 10 and connect intersections with smooth curve. This is the earth pressure locus. (13)Determine maximum distance between the TT¢ and the earth pressure locus, measured parallel to line of action of P. This distance represents the active earth pressure P.

3

C. Direction of Pressure P

4

(1) For walls with heels, the following procedure is applicable: – Determine height h of wall, measured from point a. – Locate point b on the surface of the backfill at the distance 2h measured horizontally from a. – Draw line ab. – Take direction of resultant earth pressure P as parallel to line ab. (2) For walls without heels, where AB is the back of wall, take angle f equal to 2/3 f. D. Point of Application Process (1) The point of application of the resultant pressure P can be obtained by determining the approximate pressure-distribution diagram (Figure C-8-5-4). The procedure is as follows:

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– Subdivide the line BB¢ into about 4 equal parts h1 below the depth h0 of tension cracking. – Compute the active earth pressures, P1, P2, P3, etc., as if each of the points C¢, D¢, E¢, etc., were at the base of the wall. The trial wedge method is used for each computation. – Determine the average pressures P1, P2, etc., over each distance B¢C¢, C¢D¢, etc., as indicated in Figure C-8-5-4. – Determine the elevation of the centroid of this approximate pressure diagram. This is the approximate elevation of the point of application of the resultant earth pressure P. (2) If the backfill may be considered cohesionless, the point of application of pressure may be obtained as follows: – Determine the center of gravity of the earth and ballast in the wedge between the plane of rupture and the vertical plane passing through the heel of the wall (Figure C-8-5-4) or the back of the wall (Figure C-8-5-5). – Assume the center of gravity of the surcharge loads to be located at the surface of the backfill. – Determine the center of gravity of the combined loads and draw a line from this point parallel to the plane of rupture to a point of intersection with the vertical plane through the heel of the wall (Figure C-8-5-4) or the back of the wall (Figure C-8-5-5).

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1

3

4

Figure C-8-5-4. Earth Pressure Computation – Walls with Heels

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Figure C-8-5-5. Earth Pressure Computation – Walls without Heels

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C - SECTION 5.4 STABILITY COMPUTATION C - 5.4.4 SETTLEMENT AND TILTING (2002) If the pressure on a subsoil containing fairly thick layers of soft clay or peat is increased by the weight of the backfill, the wall may tilt backward because of the compression of the clay or peat. The tilt may be estimated on the basis of a knowledge of the compressibility of the subsoil. If the tilt is likely to be excessive, it is advisable to use backfill of lightweight material, to replace the backfill by a structure, or otherwise to change the type of construction so as to avoid overloading the subsoil. Progressive Creep or Movement If the weight of the backfill is greater than one-half the ultimate bearing capacity of a clay subsoil, progressive movement of the wall or abutment is likely to occur, irrespective of the use of a key or batter piles. In such case, it is advisable to use backfill of lightweight material, to replace the backfill by a structure, or otherwise to change the construction so as to avoid overloading the subsoil.

C - SECTION 5.5 DESIGN OF BACKFILL C - 5.5.2 COMPACTION (2002) a.

For backfill type 4 and 5 a minimum number of passes is required if the moisture content is near optimum (OCM).

1

When the water content of clayey soil is too high, lamination sometimes occurs as the number of passes increases. This phenomenon is harmful, so it is advisable to break up layers where this has happened.

C - SECTION 5.6 DESIGNING BRIDGES TO RESIST SCOUR

3

C - 5.6.1 DESIGN PHILOSOPHY AND CONCEPTS (2002) The principles of economic analysis and experience with actual flood damage indicate that it is almost always cost-effective to provide a foundation that will not fail, even from a very large flood event.

C - 5.6.2 DESIGN CONSIDERATIONS (2002)

4

C - 5.6.2.1 General a.

The top width of a local scour hole is about 2.75 times the depth of scour.

C - 5.6.2.2 Piers b. Assess the hydraulic advantages of various pier shapes where there are complex flow patterns during flood events. c. Streamline pier shapes to decrease scour and minimize potential for build-up of ice and debris. Where ice and debris build-up is an obvious problem, design mulitiple pile bents as though they were a solid pier for purposes of estimating scour. Consider various pier types and span arrangements to minimize scour effects.

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C - 5.6.3 DESIGN PROCEDURE (2002) Design measures incorporated in the original construction are almost always less costly than retrofitting scour countermeasures. The method used to calculate the support for a spread footing foundation on weathered or potentially erodable rock should be based on an analysis of intact rock cores including rock quality designations and local geology, as well as hydraulic data and anticipated structure life. An important consideration may be the existence of a high quality rock formation below a thin weathered zone. For deep deposits of weathered rock, the potential scour depth should be estimated and the footing base placed below that depth. Excavation into weathered rock should be made with care. If blasting is required, light, closely spaced charges should be used to minimize overbreak beneath the footing level. Loose rock pieces should be removed and the zone filled with lean concrete. In any event, the final footing should be poured in contact with the sides of the excavation for the full design footing thickness to minimize water intrusion below footing level. The excavation above the top of the spread footing should be filled with riprap sized to withstand flood flow velocities. (1) The FHWA microcomputer software WSPRO, “Bridge Waterways Analysis Model” (21), the Corps of Engineers HEC 2, and other current software programs are available for this task. (5) Consider the limitations in the accuracy of the model and of the scour estimating procedures. (6) Visualize the overall flood flow pattern at the bridge site for the design conditions. Use this mental picture to identify those bridge elements most vulnerable to flood flows and resulting scour. Consider any other factors that may affect scour such as prop wash, etc. The extent of protection to be provided should be determined by: – The degree of uncertainty in the scour prediction method. – The potential for and consequences of failure. – The added cost of making the bridge less vulnerable to scour. (7b)Spread Footings on Rock Highly Resistant to Scour. Small embedments (keying) should be avoided since blasting to achieve keying frequently damages the sub-footing rock structure and makes it more susceptible to scour. If footings on smooth massive rock surfaces require lateral constraint, steel dowels should be drilled and grouted into the rock below the footing level. (7e)Deep Foundations (Piling or Drilled Shafts) with Footings. Even lower footing elevations may be desirable for pile supported footings when the piles could be damaged by erosion from exposure to river currents and corrosion from the elements.

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C - SECTION 5.8 DETAILS OF DESIGN AND CONSTRUCTION FOR BRIDGE PIERS C - 5.8.1 PIER SPACING, ORIENTATION AND TYPE (2002) C - 5.8.1.1 Grade Separation Structures a.

“Highway Clearances for Bridges” and “Highway Clearances for Underpasses” of the Specifications of the American Association of State Highway and Transportation Officials, and local and state clearance requirements are referred to for appropriate highway clearance requirements.

C - 5.8.2 PIER SHAFTS (2002) b.

Consideration shall be given to providing a large enough seat to allow for jacking and blocking of the proposed superstructure.

C - 5.8.5 PIERS IN NAVIGABLE STREAMS (2002) The more massive the bridge pier, the less damage it will suffer in a collision. The compressive and ultimate bending capacity of concrete piles can be significantly increased by increasing the confining reinforcement. Battered exterior piles will improve the stability of the substructure as long as there is no seismic activity. Vertical bar splices in pier shafts are subject to bond failure during impact. For this reason, increased development lengths or mechnical splices are recommended. Splices should be staggered as far above the pier base as practical.

1

Laps should be tied at both ends to prevent initiating compression failure due to high bearing under the ends of bars. Increasing the vertical steel reinforcement in pier shafts at the junction with the base and the cap can significantly increase ductility as well as ultimate moment capacity, especially if combined with increased lateral reinforcement.

3

The use of redudant structural systems may allow for local failures without structure collapse. Tension ties should be considered between the pile and the pier footing. Consideration should be given to designing the pier footing block to develop the ultimate capacity of the piles without punching shear failure. The following methods should be considered to increase the capacity of pier shafts to withstand collisions: (1) Splice vertical bars at different elevations and double the development length for overlap or use mechanical splices, certified to develop full strength of the bars under impact load. (2) Tie bar laps at both ends. (3) Provide confining spirals or ties, in an amount similar to that required for seismic design for columns. Hooks of ties should be turned in and anchored in compressive zones. (4) Increase the vertical steel reinforcement near the junction with the base and the cap. (5) Design multiple shaft piers so that with the rupture of one shaft, the cap is so connected to the remaining shafts that it can carry the dead load of the span as a cantilever without collapse.

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Concrete Structures and Foundations

(6) Provide shear walls between two or more shafts. (7) Utilize keys and dowels for piers founded on firm foundation soil or rock.

The charts may be used for estimating the backfill pressure if the backfill material has been classified in accordance with Table 8-5-1.

NOTE:

Numerals on Curves indicate soil types as described inTable 8-5-1. For materials of Type 5 computations should be based on value of H four feet less than actual value.

Figure C-8-5-6. Earth Pressure Charts for Walls Less than 20 Feet High (Sheet 1 of 2)

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3

4

Figure C-8-5-6. Earth Pressure Charts for Walls Less than 20 Feet High (Sheet 2 of 2)

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Part 6 Crib Walls1 — 1997 — TABLE OF CONTENTS

Section/Article

Description

Page

6.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.1 Scope (1997) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.2 Definitions (1997) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-6-2 8-6-2 8-6-2

6.2 Design of Crib Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.1 General (1997) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-6-2 8-6-2

6.3 Requirements for Reinforced Concrete Crib Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.1 General (1997) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.2 Manufacture (1997) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.3 Installation (1997) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-6-3 8-6-3 8-6-4 8-6-4

6.4 Requirements for Metal Crib Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.1 General (1997) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.2 Manufacture (1997) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.3 Installation (1997) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-6-5 8-6-5 8-6-5 8-6-5

6.5 Requirements for Timber Crib Walls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5.1 General (1997) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5.2 Materials (1997). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5.3 Installation (1997) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-6-6 8-6-6 8-6-6 8-6-6

LIST OF FIGURES Figure 8-6-1 8-6-2 8-6-3

1

Description Typical Sections through Walls of Timber Cribbing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Walls of Open-Face Timber Cribbing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Walls of Closed-Face Timber Cribbing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Page 8-6-7 8-6-7 8-6-8

References, Vol. 49, 1948, p. 244; Vol. 50, 1949, pp. 290, 757; Vol. 62, 1961, p. 438, 861; Vol. 70, 1969, p. 223; Vol. 71, 1970, p. 231; Vol. 88, 1987, p 62.

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SECTION 6.1 GENERAL 6.1.1 SCOPE (1997) This part of the Manual covers the design, manufacture and installation of crib walls as defined hereinafter.

6.1.2 DEFINITIONS (1997) 6.1.2.1 Crib Wall a.

A “Crib Wall” is an earth-retaining structure, made up of rigid members that are fabricated in the shape of open squares, open rectangles or other open shapes, or are assembled in the shape of square or rectangular cells, or cells of other shapes. The cells are filled with granular material. The structure of cells and granular infill all act together as a gravity structure, obtaining its safety and stability from the proper proportioning of its shape and weight.

b. Crib wall members can be of concrete, metal, or timber. They can form cells with solid-surfaced walls (known as “closed face” walls) or with slotted openings (known as “open face” walls). The members should interlock with each other, or otherwise be connected in such a way as to resist the pressures of the granular fill and the retained earth material. Crib walls can be a traditional cribbing as described in Article 6.1.2.2, or of other units that behave in accordance with this definition. 6.1.2.2 Cribbing “Cribbing” defines a traditional assembly of headers and stretchers, used to form the most common kind of crib wall.

SECTION 6.2 DESIGN OF CRIB WALLS 6.2.1 GENERAL (1997) a.

Crib walls shall be assumed to act as a unit and shall be designed to resist the overturning and sliding forces specified in Part 5, Retaining Walls, Abutments and Piers.

b. The wall section resisting overturning shall be taken as a rectangle having a height equal to the total height of the crib structure and a depth, normal to the front surface, equal to the distance between the front and rear outside faces of the crib structure. c.

The unit weight of the crib wall section within the above limits, including the weight of the crib members, may be assumed to be equal to that of the compacted filling material.

d. In general, crib walls shall have a batter of 2:12 on the face, except that low walls, 1.8 meters (6 ft) high and under, may be made with a plumb face. For walls over 3.6 meters (12 ft) high, supplemental crib units may be added to provide stability in order to meet design requirements. Crib walls shall generally not exceed 7.2 meters (24 ft) in height. Higher walls shall receive special engineering considerations. e.

The wall shall be so located that no track tie will bear directly on any crib member.

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f.

Crib wall foundations shall be designed not to exceed safe soil pressures specified in Part 3, Spread Footing Foundations, Section 3.4, Sizing of Footings. The possibility of a deep shear failure of the embankment shall be considered similar to the failure illustrated in Part 20, Flexible Sheet Pile Bulkheads.

g.

All structural crib units, including stretchers, headers, or other units, shall be so designed that they will resist the tensile, bending and shearing stresses imposed on them and shall provide adequate bearing at all contact surfaces. For walls of cribbing, stretchers at the rear of the cells shall have the same bearing area as those at the front in the same courses.

h. The headers and stretchers or other units shall be so designed that when assembled in a wall, they form a cellular structure that will be flexible enough to withstand a reasonable amount of differential settlement. These flexibility requirements will generally depend on the use of the wall and on the designer’s judgement. However, any crib wall cell will be expected to withstand a differential deflection of at least 0.015L without damage, where L is the length of the cell as measured along the face of the wall. i.

The vertical openings within the front face of the assembly shall be small enough to retain the fill material, placed as described in Article 6.3.3.3, Article 6.4.3.3, or Article 6.5.3.5.

j.

Crib walls shall be designed in sections usually not to exceed 30 meters (100 ft) in length. If the soil conditions vary considerably along this length, it may be necessary to build the crib wall in sections that are shorter than 30 meters (100 ft).

k. Provision shall be made for drainage, if necessary, behind or within cells by means of French drains or other approved methods, and potential hydrostatic pressure shall be taken into consideration in the wall design.

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3

SECTION 6.3 REQUIREMENTS FOR REINFORCED CONCRETE CRIB WALLS 6.3.1 GENERAL (1997) a.

Crib wall units defined as cribbing shall be rectangular in cross section with all exposed edges beveled. Each cribbing unit shall be reinforced with deformed bars or with welded wire fabric, proportioned in accordance with Part 2, Reinforced Concrete Design. However, the area of reinforcement for each unit shall be not less than 0.9 percent of its gross cross-sectional area.

b. Members shall be provided with effective locking devices. They shall be of a type which will permit a slight movement in the wall without damage to the crib units. c.

The headers and stretchers shall be so designed that when assembled in a wall they will bear at two points only, with bearing points for other kinds of units subject to the engineer’s approval. The arrangement must form a cellular structure flexible enough to withstand a reasonable amount of settlement.

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6.3.2 MANUFACTURE (1997) 6.3.2.1 General The materials, proportioning and workmanship shall conform to Part 1, Materials, Tests and Construction Requirements, with the following modifications: a.

Aggregates. The maximum size of the coarse aggregate shall not be more than 25 mm (1 in).

b. Class of Concrete. Air-entrained concrete as specified in Part 1, Materials, Tests and Construction Requirements, shall be used, having a minimum compressive strength of 28 MPa (4,250 psi) at 28 days. c.

Workability and Placement. The concrete mixture shall be of a workable consistency and placed to prevent honeycombing. Vibrating equipment shall be used in the manufacturing process.

d. Curing. Curing shall be started as soon as possible after completion of placement of the concrete and shall comply with the Articles on curing in Part 1, Materials, Tests and Construction Requirements. 6.3.2.2 Defects All members shall be true to size, and free of depressions and of spalled, patched or plastered surfaces or other defects that may impair strength or durability. 6.3.2.3 Handling Members shall be handled carefully. Dropping or severe jarring shall be avoided. Any cracked or otherwise defective members will be rejected.

6.3.3 INSTALLATION (1997) 6.3.3.1 Preparing Base a.

The foundation or bed for the crib wall shall be firm and as uniform as possible, and shall be approved by the Engineer before any members are placed. If any members are located directly above rock, a cushion of sand or gravel not less than 200 mm (8 in) thick shall be provided.

b. The foundation shall be sloped at a right angle to the batter on the face of the finished crib wall. 6.3.3.2 Placing a.

Stretchers or equivalent members shall be used to provide adequate support of the lowest course, front and back.

b. Crib members shall be carefully handled and installed in such a manner as to avoid any damage due to shock or impact. Any member which becomes cracked or otherwise damaged during erection shall be removed and replaced. 6.3.3.3 Filling a.

The filling of the interior of the crib wall shall follow closely the erection of the successive tiers of units, and at no time shall the wall be laid up higher than 1 meter (3 ft) above the backfilled portion.

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b. Approved fill material shall be pervious, free draining, preferably crushed stone, gravel, or other coarse granular material, well graded from a maximum size of 100 mm (4 in) down, and shall be placed compacted in the cells and for 600 mm (2 ft) immediately behind the cell in such a manner as to provide a minimum of voids. All organic matter shall be excluded from the fill materials. The fill and backfill material shall not contain any element detrimental to concrete. 6.3.3.4 Drainage See Article 6.2.1k, for any special conditions.

SECTION 6.4 REQUIREMENTS FOR METAL CRIB WALLS 6.4.1 GENERAL (1997) a.

The sheets from which all members are manufactured shall be made of a base metal meeting the requirements for chemical composition and zinc coating as specified by the Engineer in conformity with Chapter 1, Roadway and Ballast, Part 4, Culverts.

b. Aluminum materials may only be used with the engineer’s specific approval.

6.4.2 MANUFACTURE (1997) a.

1

All members shall be prefabricated in the manufacturer’s plant prior to shipment to the site. If specified by the Engineer, the crib members shall be specially coated.

b. Headers and stretchers and other members shall interlock or be joined together by means of flexible bolted connections. Bolts shall be of proper length, made of steel, and galvanized. c.

The various members shall be constructed of a base metal of the gage shown on the plans and not less than 1.5 mm (16 ga) for walls up to 10 feet in height and of heavier gage for higher walls.

3

d. The members shall be so fabricated that units of the same nominal depth and length shall be fully interchangeable. All members shall be straight and true before assembly, and the galvanizing or other coating shall not be damaged. Any bent or otherwise defective members will be rejected.

4

6.4.3 INSTALLATION (1997) 6.4.3.1 Preparing Base a.

The foundation or bed for the crib wall shall be firm and as uniform as possible, and shall be approved by the Engineer before any members are placed. If any members are located directly above rock, a cushion of sand or gravel not less than 200 mm (8 in) thick shall be provided.

b. The foundation shall be sloped at a right angle to the batter on the face of the finished crib wall. 6.4.3.2 Placing Crib members shall be carefully handled and installed in such a manner as to avoid damage. Any member which becomes bent or otherwise damaged during erection shall be removed and replaced.

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Concrete Structures and Foundations 6.4.3.3 Filling a.

The filling of the interior of the crib wall shall follow closely the erection of the successive tiers of units, and at no time shall the wall be laid up higher than 1 meter (3 ft) above the backfilled portion.

b. Approved fill material shall be pervious, free draining, preferably crushed stone, gravel, or other coarse granular material, well graded from a maximum size of 100 mm (4 in) down, and shall be placed and compacted in the cells and for 600 mm (2 ft) immediately behind the cell in such a manner as to provide a minimum of voids. All organic matter shall be excluded from the filling materials. The fill and backfill material shall not contain any element detrimental to metal. 6.4.3.4 Drainage See Article 6.2.1k, for any drainage requirements.

SECTION 6.5 REQUIREMENTS FOR TIMBER CRIB WALLS 6.5.1 GENERAL (1997) Timber crib walls are made of timber cribbing, as defined in Article 6.1.2.2 and no other kinds of timber units are considered or included herein. Each crib unit shall be rectangular in cross section.

6.5.2 MATERIALS (1997) a.

Timber used for cribbing shall be sawn, and new timber shall conform to the requirements of Chapter 7, Timber Structures, Part 1, Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Timber Bridge Ties and Recommendations for Fire-Retardant Coating for Creosoted Wood for the grade and species specified. Timber shall be treated in accordance with the requirements of Chapter 30, Ties.

b. All cutting and framing indicated on the plans shall be completed before treatment. All framing shall be done in a workmanlike manner, true to line and angle. When any field framing, boring, and cutting of treated material is required, all such framing and cuts shall receive a thorough coating of approved preservative before assembly.

6.5.3 INSTALLATION (1997) 6.5.3.1 Preparing Base a.

The foundation or bed for the crib wall shall be firm and as uniform as possible, and shall be approved by the Engineer before any cribbing is placed.

b. The foundation shall be sloped at a right angle to the batter on the face of the finished crib wall. 6.5.3.2 Mud Sills When mud sills are used, they shall be set at right angles to the face of the crib wall and bear firmly and evenly on the foundation material (see Figure 8-6-1). Mud sills shall be leveled to fit the base tier of face timbers resting directly on them.

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Crib Walls 6.5.3.3 Timbers a.

The timber in the base tier and in alternate tiers above the base shall be as long as practicable. Preferably they shall have a minimum length of 2.5 meters (8 ft). Joints in each tier shall stagger with joints in adjacent tiers. Crib wall faces shall be laid closed or open as indicated on the plans.

b. Care shall be exercised in the installation of crib walls to produce a true and even face built to the line and grade shown on the plans. All face timber shall be set horizontally (See Figure 8-6-2 and Figure 8-63). c.

Headers shall be spaced not more than 2.5 meters (8 ft) center to center in any horizontal tier if staggered with the headers in tiers above and below. If headers are not staggered, they shall be spaced not more than 1.8 meters (6 ft) center to center. The vertical spacing between headers in the same vertical plane shall not exceed 900 mm (3 ft).

1

3

Figure 8-6-1. Typical Sections through Walls of Timber Cribbing

4

TIES STAGGERED

TIES IN LINE

Figure 8-6-2. Walls of Open-Face Timber Cribbing

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Figure 8-6-3. Walls of Closed-Face Timber Cribbing 6.5.3.4 Fastenings a.

Each successive tier of closed-face cribbing shall be drift bolted to the one upon which it rests by drift bolts not less than 19 mm (3/4 in) in diameter and of sufficient length to extend through two tiers and not less than 100 mm (4 in) into the third tier. Drift bolts shall be staggered and not more than 2.5 meters (8 ft) center to center in each tier.

b. All end joints and splices shall be lapped and drift bolted at the center; headers shall be drift bolted to face timbers in like manner (see Figure 8-6-3). c.

Each tier of open-face cribbing shall be drift bolted to the tiers beneath at each header using 19 mm (3/4 in) drift bolts at each intersection where no splice occurs or at lap joints, and two 19 mm (3/4 in) inch drift bolts at butt joints. Drift bolts shall be long enough to extend through one tier and at least threequarters of the distance into the next tier. Drift bolts shall be staggered from tier to tier (see Figure 8-62).

d. In treated timber cribbing, the hardware shall be galvanized. 6.5.3.5 Filling a.

The filling of the interior of the crib wall shall follow closely the erection of the successive tiers of units, and at no time shall the wall be laid up higher than 1 meter (3 ft) above the backfilled portion.

b. Approved fill material of pervious, free draining, preferably crushed stone, gravel or other coarse granular material, well graded from a maximum size of 100 mm (4 in) down, shall be placed in the cells in such a manner as to provide a minimum of voids. Larger stones may be included if carefully embedded. All organic matter shall be excluded from the filling material. Clay or material having a large percentage of clay shall not be used as fill. 6.5.3.6 Drainage See Article 6.2.1k, for drainage requirements.

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Part 7 Mechanically Stabilized Embankment — 1997 — TABLE OF CONTENTS

Section/Article

Description

Page

7.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.1 Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-7-2 8-7-2

7.2 Design of Mechanically Stabilized Embankments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.1 General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.2 Special Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-7-2 8-7-2 8-7-2

7.3 Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.1 General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-7-3 8-7-3

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SECTION 7.1 GENERAL 7.1.1 DEFINITIONS a.

A “Mechanically Stabilized Embankment (MSE)” is an embankment that has its strength increased by the inclusion of horizontal tensile members within the soil mass. The composite embankment material exhibits improved shear strength and compressive strength relative to unreinforced material. The MSE will always consist of at least two elements: 1) earth, and 2) tensile reinforcement; and may have facing elements to provide a vertical or nearly vertical face.

b. “Reinforcing Elements” are horizontal elements placed within the soil mass between successive layers of compacted soil which are designed to provide tensile reinforcement to restrain soil deformation in the direction of the reinforcement; and which are placed between successive layers of compacted earth. c.

“Inextensible Reinforcing Elements” are those elements within the soil mass that do not elongate sufficiently under the design load to allow soil deformations to develop the “active state” on the potential failure surface within the soil mass. Inextensible reinforcing elements are generally metallic.

d. “Extensible Reinforcing Elements” are those elements within the soil mass that do elongate sufficiently under the design load to allow soil deformations to develop the “active state” along the potential failure surface within the soil mass. Extensible reinforcing elements are generally high strength polymer geogrids and other geosynthetic materials. e.

“Facing Elements” are those elements of an MSE that are placed to prevent localized sloughing and erosion of the embankment face. Facing elements can consist of precast concrete panels, metal panels, polymer panels, wire mesh, timber, or the polymer reinforcing materials themselves.

SECTION 7.2 DESIGN OF MECHANICALLY STABILIZED EMBANKMENTS 7.2.1 GENERAL a.

Use of any MSE must be approved by the controlling railroad.

b. Design of MSE shall be in accordance with the current AASHTO STANDARD SPECIFICATIONS FOR HIGHWAY BRIDGES, except as modified by other provisions of this part of this chapter. c.

The factor of safety against pullout of reinforcing elements shall be 1.75 to account for rail traffic induced vibrations.

d. Surcharge live loads applied in the design of MSE shall be those in Part 20.3.2.3 of this chapter. e.

Design live loadings shall be, as given in Part 2.2.3(c) of this chapter, subject to change at the discretion of the railroad.

7.2.2 SPECIAL CONSIDERATIONS a.

Where the use of MSE is proposed on electric traction railroads utilizing direct current, an engineer specializing in corrosion protection/prevention shall investigate and make site-specific recommendations for special design considerations.

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Mechanically Stabilized Embankment

b. Consideration shall be given to the potential for accelerated corrosion or deterioration of structural elements of MSE due to the relatively high permeability of railroad roadbeds and the potential for precipitation and other potentially corrosive substances infiltrating the roadbed. The use of an impermeable geomembrane connected to lateral drains below the sub-ballast, but above the top level of reinforcements should be considered. c.

Consideration should be given to placing the first level of reinforcing elements below the depth of excavation that would be reached in the placement of utilities within the R.O.W. Alternately, conduits for utilities can be placed during the MSE construction.

d. Excavation to, or below, the top level of reinforcing elements shall not be allowed following the construction of the MSE.

SECTION 7.3 CONSTRUCTION 7.3.1 GENERAL a.

Construction of MSE shall be in conformance with the provisions of the current edition of the AASHTO STANDARD SPECIFICATIONS FOR HIGHWAY BRIDGES, DIVISION II - CONSTRUCTION, unless modified for application to the specific MSE.

1 b. Special contract provisions shall be provided as necessary for proper construction of the specific MSE.

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4

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Concrete Structures and Foundations

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Part 10 Reinforced Concrete Culvert Pipe1 — 2003 — Reaffirmed without changes.

TABLE OF CONTENTS Section/Article

Description

Page

10.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.1.1 Scope (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.1.2 Definitions (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-10-2 8-10-2 8-10-2

10.2 Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.1 Pipe (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.2 Manholes (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.3 Rubber Gaskets (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.4 Acid Resistant Coatings (1989). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-10-3 8-10-3 8-10-3 8-10-4 8-10-4

10.3 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3.1 General (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3.2 References (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3.3 Loads (1989). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3.4 Bedding Factors (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3.5 Minimum Pipe Strength (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3.6 Factor of Safety (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3.7 Alternate Design Procedure (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3.8 Pipe Strength (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-10-4 8-10-4 8-10-4 8-10-4 8-10-6 8-10-12 8-10-12 8-10-12 8-10-12

10.4 Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4.1 Preparation of Subgrade (1989) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4.2 Pipe Installation (1989). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4.3 Backfill and Embankment (1989). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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1

References, Vol. 81, 1980, p. 235; Vol 90, 1989, pp. 53, 67. Revised 1989.

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3

Concrete Structures and Foundations

LIST OF FIGURES Figure 8-10-1 8-10-2 8-10-3 8-10-4 8-10-5 8-10-6

Description

Page

Track Loading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Embankment Beddings – Circular Pipe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Embankment Beddings – Horizontal Elliptical, Arch, and Vertical Elliptical Pipe . . . . . . . . . Trench Beddings – Circular Pipe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Trench Beddings – Horizontal Elliptical, Arch, and Vertical Elliptical Pipe. . . . . . . . . . . . . . . Induced and Alternate Induced Trench . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-10-5 8-10-7 8-10-8 8-10-9 8-10-10 8-10-11

LIST OF TABLES Table

Description

Page

8-10-1 Bedding Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-10-6

SECTION 10.1 GENERAL 10.1.1 SCOPE (1989) This part of the Manual covers the design and installation of reinforced concrete pipe for railway culverts.

10.1.2 DEFINITIONS (1989) 10.1.2.1 Pipe Installation Conditions a.

Trench Installation. The pipe is installed in a relatively narrow trench excavated in undisturbed soil and then covered with backfill extending to the ground surface.

b. Positive Projecting Embankment Installation. The pipe is installed on original ground or compacted fill with the top of the pipe above the ground, or compacted fill and then covered by embankment. c.

Negative Projecting Embankment Installation. The pipe is installed within a relatively narrow trench with the top of the pipe below the natural ground, or compacted fill and then covered with embankment.

d. Induced Trench Installation. The pipe is installed in a trench, backfilled with compressible material over the pipe, and then covered by a high embankment. e.

Jacked or Tunneled Installation. The pipe is installed without removal of the ground above the pipe. Grouting of the exterior annular space around the pipe may be required to ensure full contact with the soil around the pipe. If existing soil conditions require an oversized tunnel, or if anticipated service conditions require access to the pipeline, a carrier pipe may be installed within the tunnel or casing pipe.

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AREMA Manual for Railway Engineering

Reinforced Concrete Culvert Pipe 10.1.2.2 Symbols Bc = Outside width of the pipe in the in-place condition (ft) Bd = Width of the pipe trench (ft) Bf = Bedding factor is defined as the ratio between the supporting strength of buried pipe to the strength of the pipe determined in the three-edge bearing test obtained according to the requirements of ASTM Designation C497. D = Inside span (or horizontal width) of the pipe (ft) D-Load = The supporting strength of a pipe loaded under the three-edge bearing test conditions expressed in pounds per linear foot per foot of inside diameter or horizontal span. FS = Factor of Safety (normally taken as 1.0) H = Height of cover over the top of the pipe (ft) p = Projection Ratio is defined as the vertical distance between the top of the pipe and the top of the trench divided by the trench width (negative projecting), or the height of the induced trench divided by the outside horizontal span of the pipe (induced trench). w = Unit weight of the backfill material (lb per cubic foot) WL = Live Load including Impact transmitted to the pipe (lb per square foot) WE = Earth loads transmitted to the pipe (lb per linear foot) Ws = Other loads transmitted to the pipe (lb per square foot)

1

SECTION 10.2 MATERIALS 10.2.1 PIPE (1989)

3

Pipe shall conform to the following ASTM Standards for type, size, shape, manufacturing, testing, and strength requirements as specified by the Engineer: a.

ASTM Designation C76, Specification for Reinforced Concrete Culvert, Storm Drain and Sewer Pipe.

b. ASTM Designation C506, Specification for Reinforced Concrete Arch Culvert, Storm Drain, and Sewer Pipe. c.

ASTM Designation C507, Specification for Reinforced Concrete Elliptical Culvert, Storm Drain, and Sewer Pipe.

d. ASTM Designation C655, Specification for Reinforced Concrete D-Load Culvert, Storm Drain, and Sewer Pipe.

10.2.2 MANHOLES (1989) Precast concrete manholes, if required, shall conform to ASTM Designation C478, Specification for Precast Concrete Manhole Sections.

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Concrete Structures and Foundations

10.2.3 RUBBER GASKETS (1989) Rubber gaskets, if required, shall conform to ASTM Designation C443, Specification for Joints for Circular Concrete Sewer and Culvert Pipe.

10.2.4 ACID RESISTANT COATINGS (1989) These coatings shall be specified by the Engineer for the particular condition required.

SECTION 10.3 DESIGN 10.3.1 GENERAL (1989) The design of reinforced concrete pipe culverts must take into account the type of installation and bedding, the soil constants of the natural ground and backfill, the relative settlements of the pipe, pipe foundation, bedding, backfill and natural ground, acidity of the flow, the physical measurements such as depth of cover and width of cut, determination of earth load, live load, impact, and any additional loading.

10.3.2 REFERENCES (1989) Satisfactory design methods, utilizing more exact design procedures, are referenced for the use of the Engineer: a.

United States Department of Agriculture Soil Conservation Service Engineering Division Technical Release No. 5.

b. American Concrete Pipe Association Concrete Pipe Design Manual. c.

American Concrete Pipe Association Concrete Pipe Handbook.

10.3.3 LOADS (1989) a.

Design loading on the pipe shall include Earth Load, Cooper E 80 Live Load, Impact, and any other surcharge loads.

b. Earth load tables from the references given in Article 10.3.2 may be used to calculate the weight of earth on the pipe. The earth load carried by the pipe is generally more than Bc ´ H ´ w. c.

The Engineer may use the equations below in order to determine the earth load transmitted to the pipe. Other acceptable methods of analysis are given in Article 10.3.2. (1) Trench Installation: WE = 0.85 ´ Bd ´ H ´ w (2) Positive Projecting Embankment Condition: WE = 2.00 ´ Bc ´ H ´ w

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Reinforced Concrete Culvert Pipe

(3) Negative Projecting Embankment Condition: WE = 1.00 ´ Bd ´ H ´ w d. Track Loading to be supported by the pipe is shown in Figure 8-10-1 of these specifications. The indicated loading includes a variable Impact Load of 40% at 0 feet, and 0% at 10 feet. e.

Any surface surcharges, other than track load, shall be converted to additional height of fill to determine their loading on the pipe.

f.

Loading on a carrier pipe, that is within a casing pipe, shall be taken as the full Dead + Live + Impact Load without consideration of the presence of the casing, unless the casing pipe is permanently protected from corrosion using such means as providing extra pipe thickness or a resistant coating.

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3

4

Figure 8-10-1. Track Loading

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Concrete Structures and Foundations

g.

The design trench width shall be indicated on the construction drawings as a maximum width of trench, or the Engineer shall design the pipe for the maximum effective trench width (transition width) as indicated in the Concrete Pipe Association Design Manual. The minimum width of the trench shall be Bc+2 feet or 1.5 Bc whichever is greater.

10.3.4 BEDDING FACTORS (1989) Bedding factors to be used in the equation for determination of the D-Load shall be obtained from Table 8-10-1 or as permitted within that table by more elaborate analysis. Table 8-10-1. Bedding Factors

Pipe Installation Methods

Bedding Class (Note 1) A

B

C

D

Tunnel

Trench

2.8 (Note 2)

1.9

1.5

1.0

–

Positive Projecting Embankment

2.8 (Note 2)

2.0 (Note 2)

1.7 (Note 2)

1.0

–

Negative Projecting Embankment

2.8 (Note 2)

1.9 (Note 2)

1.5 (Note 2)

1.0

–

Induced Trench

2.8 (Note 2)

2.0 (Note 2)

1.7 (Note 2)

1.0

–

Carrier Pipe

2.8

1.9

1.5

–

–

Casing Pipe

–

–

–

–

3.0

1.5

1.5

1.5

–

–

Jacked or Tunneled

Any Pipe with less than 3¢-0² of cover between bottom of tie and the top of the pipe

Note 1: See Figure 8-10-2, Figure 8-10-3, Figure 8-10-4, Figure 8-10-5, and Figure 8-10-6. Note 2: More elaborate analysis, using the procedures referenced in Article 10.3.2, can result in a more economical design with greater load factors.

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Figure 8-10-2. Embankment Beddings – Circular Pipe © 2011, American Railway Engineering and Maintenance-of-Way Association

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Concrete Structures and Foundations

FOR CLASS D BEDDING SEE FIGURE 8-10-2

Figure 8-10-3. Embankment Beddings – Horizontal Elliptical, Arch, and Vertical Elliptical Pipe © 2011, American Railway Engineering and Maintenance-of-Way Association

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4

Figure 8-10-4. Trench Beddings – Circular Pipe

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Concrete Structures and Foundations

For Class D bedding see Figure 8-10-4.

Figure 8-10-5. Trench Beddings – Horizontal Elliptical, Arch, and Vertical Elliptical Pipe © 2011, American Railway Engineering and Maintenance-of-Way Association

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Reinforced Concrete Culvert Pipe

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4

Figure 8-10-6. Induced and Alternate Induced Trench

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Concrete Structures and Foundations

10.3.5 MINIMUM PIPE STRENGTH (1989) Pipe subjected to track loads shall have a minimum strength of D = 1350 (Class III) even if analysis indicates that a lower D-Load is satisfactory.

10.3.6 FACTOR OF SAFETY (1989) The standard Factor of Safety of 1.0 against a 0.01 inch crack should be used for design unless the Engineer indicates that a higher Factor of Safety is required.

10.3.7 ALTERNATE DESIGN PROCEDURE (1989) a.

In lieu of carrying out the complete design analysis required by these specifications, the Designer may use Class V RCP for all sizes up to a height of cover of 14 feet; for greater heights of cover, the designer must make an analysis. For Elliptical or Arch Pipe where D = 3000 RCP is not available, a design analysis shall be made.

b. The Engineer may specify the use of Class V RCP if he feels that the conditions of the site, or construction procedures, require this strength of pipe.

10.3.8 PIPE STRENGTH (1989) The required D-Load of the pipe shall be determined by the following equation: ( W L ´ B c + W E + W s ´ B c ) ´ FS D-Load = -----------------------------------------------------------------------------------Bf ´ D

SECTION 10.4 INSTALLATION 10.4.1 PREPARATION OF SUBGRADE (1989) 10.4.1.1 Excavation a.

Trenches shall be excavated in accordance with the bank stability requirements to a width sufficient to allow for proper jointing of the pipe and thorough compaction of the bedding and backfill material under and around the pipe. Where feasible, trench walls shall be vertical. A maximum trench width in conformance with the design assumptions, should be specified on the construction plans. Wide trenches generally require the use of stronger pipe, and require a more complete design analysis. The completed trench bottom shall be firm and cleaned for its full length and width.

b. Where specifically requested the pipe trench bottom may be cambered longitudinally to provide for expected settlement. If camber of the pipe trench is required, the indicated camber must be shown on the plans. c.

Where specified on the plans, the excavation for a pipe to be placed within embankment fill shall be made after the embankment has been completed to a specified height above the top of the pipe.

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Reinforced Concrete Culvert Pipe 10.4.1.2 Foundation a.

If the foundation is incapable of supporting the pipe loads, an adequate support shall be supplied by excavating the unstable soil and backfilling with compacted material, or by such other means as may be specified or approved by the Engineer.

b. If the foundation is muck, or similar yielding material, the pipe shall be supported by piling, or by other such means as may be specified or approved by the Engineer. c.

For Class B or Class C Beddings, the subgrade should be undercut and replaced with compacted granular material, if necessary, so that a firm foundation free of protruding rocks is provided. Special care may be necessary with Class A or other unyielding foundation to cushion the pipe from shock when blasting can be anticipated in the area.

10.4.2 PIPE INSTALLATION (1989) 10.4.2.1 Laying Pipe a.

Pipe laying shall begin at the downstream end of the culvert. The bell or groove end of the pipe shall be placed upstream. No culvert shall be put into service until a suitable outlet is provided for the water.

b. Elliptical pipe shall be placed with the vertical axis within 5 degrees of a vertical plane through the longitudinal axis of the culvert.

1

10.4.2.2 Bedding a.

Pipe bedding and placement shall be specified to conform to one of the Bedding Classes illustrated in Figure 8-10-2, Figure 8-10-3, Figure 8-10-4, Figure 8-10-5, and Figure 8-10-6.

b. When pipe cannot be placed on a prepared surface but must instead be placed on an unprepared surface, the bedding shall be considered to be Class D Bedding. Class D Bedding should only be used for emergency work, and is not permitted for permanent installations unless authorized by the Engineer. For typical Class D Bedding see Figure 8-10-2 and Figure 8-10-4.

3

10.4.2.3 Joining Pipe a.

Pipe may be either bell and spigot, or tongue and groove design unless otherwise specified. When bell pipe is used, a shallow excavation shall be made underneath the bell of sufficient depth so that the bell does not rest on the bedding material.

b. Pipe sections shall be joined so that the ends are fully entered and the inner surfaces are reasonably flush and even. c.

Joints shall be made with either mortar, grout, rubber gaskets, plastic mastic compounds, or other combination of these types as approved and specified by the Engineer. Mortar joints in pipe that is jacked into place shall not be sealed with mortar until the culvert jacking is complete.

d. In areas where a tendency exists for pipe sections to separate, suitable ties shall be fabricated and installed to prevent this separation. e.

Endwalls or headwalls should be used for culverts under tracks and designed to resist pipe separation as well as to retain the embankment.

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4

Concrete Structures and Foundations 10.4.2.4 Water Tightness If water tightness is a problem, rubber gasketed pipe is recommended. When such joints are specified the pipe should be tested for infiltration or exfiltration as stipulated by the Engineer. The maximum rate of leakage shall conform to the following accepted requirements, or to other standards set forth by the Engineer: • Infiltration – 0.6 gallons per inch of diameter per 100 feet of pipe per hour. • Exfiltration – 0.6 gallons per inch of diameter per 100 feet of pipe per hour when subjected to an internal head of 2 feet, and increased by 10% for each additional 2 feet of head. 10.4.2.5 Culverts Carrying High Acid Fluids Where the PH of the conducted fluid is less than 4.5, the internal surfaces of the culvert should be protected from acid attack by a special permanent coating. The Engineer shall specify the type of coating and the means of application.

10.4.3 BACKFILL AND EMBANKMENT (1989) 10.4.3.1 General a.

The backfill around the culvert shall be placed in accordance with the bedding requirements illustrated in Figure 8-10-2, Figure 8-10-3, Figure 8-10-4, Figure 8-10-5, and Figure 8-10-6, and other requirements of these specifications.

b. All culverts that are to carry track load shall have the backfill thoroughly compacted to a minimum density of 95% as determined by ASTM D698, and as specified elsewhere in the project specifications for adjacent embankment. c.

Where the pipe is placed on a shaped subgrade, see Figure 8-10-2 and Figure 8-10-4, extreme care shall be taken not to overexcavate the shaped surface so that point loading shall not occur on the pipe bottom.

10.4.3.2 Embankment Bedding (See Figure 8-10-2 and Figure 8-10-3). a.

Where rock or noncompressible foundation material is encountered, the hard unyielding material should be excavated below the elevation of the concrete cradle (Class A) or the bottom of the pipe or pipe bell (Class B and C Beddings) for a depth of at least 6 inches or 1/2 inch for each foot of fill over the top of the pipe whichever is greater, but not more than 3/4 inch of the diameter (or horizontal span) of the pipe.

b. For the Negative Projecting Embankment Condition, the width of the excavation, Bd, should be at least 1.5 ´ Bc and with a minimum of 2 feet greater than the outside diameter of the pipe for thorough filling and compaction of the void space under the pipe haunch. 10.4.3.3 Trench Bedding (See Figure 8-10-4 and Figure 8-10-5) a.

Materials for backfill on each side of the pipe for the full width of the trench and to an elevation of 1 foot above the top of the pipe shall be fine, readily compacted soil or granular material, and shall not contain frozen lumps, stones that would be retained on a 2 inches sieve, chunks, highly plastic clay, or other objectionable material. Granular backfill material shall have 100% passing a 3/4 inch sieve, not less than 95% passing a 1/2 inch sieve, and not less than 95% retained on a No. 16 sieve. Oversized material shall be removed at the source of the material, except as directed by the Engineer.

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Reinforced Concrete Culvert Pipe

b. When the top of the pipe is even with or below the top of the trench, backfill material shall be placed at or near the optimum moisture content and compacted in layers not exceeding 6 inches (compacted) on both sides of the pipe for the full required length. c.

Backfill material shall be placed and compacted for the full depth of the trench, unless induced trench installation is used.

d. When the top of the pipe is above the top of the trench, backfill shall be placed at or near optimum moisture content and compacted in layers not exceeding 6 inches (compacted) and shall be brought up evenly on both sides of the pipe for its full length to an elevation 1 foot above the top of the pipe. The width of backfill on each side of the pipe for the portion above the top of the trench shall be equal to twice the diameter of the pipe or 12 feet whichever is less. The backfill material used in the trench section and the portion above the top of the trench for a distance on each side of the pipe equal to the horizontal diameter and to 1 foot above the top of the pipe shall conform to the requirements for backfill in paragraph a. The remainder of the backfill shall meet the requirements for embankment construction. e.

The width of the trench, Bd, shall be 1.5 ´ Bc but not less than 2 feet greater than the outside diameter of the pipe in order to completely fill the void.

10.4.3.4 Induced Trench Bedding (See Figure 8-10-6) a.

The Induced Trench method shall not be used when the pipe is subjected to track loading without making a complete investigation of the settlements involved.

b. When the Induced Trench method is used, the embankment shall be completed as required in Article 10.4.3.3 and as illustrated in Figure 8-10-6, to a height above the pipe equal to the vertical outside diameter of the pipe plus 1 foot. A trench equal in width to the outside horizontal diameter of the pipe, in depth equal to the vertical outside diameter of the pipe, and to the length shown on the plans shall then be excavated to within 1 foot of the top of the pipe, trench walls being as nearly vertical as possible. This trench shall be loosely filled with highly compressible material. Construction of the embankment above the pipe shall then proceed in a normal manner using regular fill material. c.

1

3

The length of the Induced Trench method shall be determined by the designer in keeping with the design assumptions and the pipe strength being used.

d. When the Alternate Induced Trench method is used, the embankment shall be constructed in a normal manner to a height above the culvert bedding elevation equal to twice the outside diameter of the pipe. A trench as required shall then be excavated with the walls as nearly vertical as possible, and the pipe bedded and backfilled to 1 foot above the pipe as called for in Article 10.4.3.3. The remaining portion of the trench shall then be loosely filled with highly compressible material. Construction of embankment shall then proceed in a normal manner. e.

In no case shall the length of compressible material extend to the ends of the culvert.

f.

Rock fill shall not be dumped over the culvert without a sufficient cushion of earth to prevent breakage of the pipe.

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Concrete Structures and Foundations 10.4.3.5 Jacking Pipe a.

Pipe used for jacking through fills shall be tongue and groove design. The tongue shall preferably be at the downstream end. Jacking frames shall be so constructed as to avoid breaking the pipe or forcing it out of alignment. The pipe shall preferably be jacked upgrade in order to provide drainage at the heading during excavation. Satisfactory means shall be provided for maintaining the lead pipe at the correct line and grade.

b. The pipe shall be installed according to specially prepared plans and specifications. The contractor shall set forth the construction procedure, extra pipe reinforcement and jack shield (if required), jacking pit location and shoring, and other special features for the safe and satisfactory completion of the work. Plans prepared by the contractor giving the construction details shall be submitted for review by the Engineer. c.

Straw filler shall be inserted into voids created by excavation during jacking operations. Locations shall be recorded and after mining is completed, grout holes are to be drilled through the pipe and the voids filled with grout.

d. A survey crew must continually monitor elevation and alignment of the railroad track above during the jacking procedures. Jacking must be stopped and any problems corrected if track movement is detected. 10.4.3.6 Constructing Pipe in Tunnels When it is necessary to place culvert pipe by tunneling, plans and specifications for the completed structure shall be prepared by the Engineer. The contractor shall set forth the construction procedures and other necessary details and submit them for review by the Engineer.

© 2011, American Railway Engineering and Maintenance-of-Way Association

8-10-16

AREMA Manual for Railway Engineering

8

Part 11 Lining Railway Tunnels1 — 2004 – TABLE OF CONTENTS

Section/Article

Description

Page

11.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1.1 Scope (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-11-2 8-11-2

11.2 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2.1 Interior Dimensions (2004). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2.2 Preliminary Data (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2.3 Floors (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2.4 Sidewalls and Arch (2004). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2.5 Construction and Expansion Joints (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2.6 Drains (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2.7 Refuge Niches (Bays) (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2.8 Conduit and Inserts (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-11-2 8-11-2 8-11-2 8-11-2 8-11-3 8-11-3 8-11-7 8-11-7 8-11-7

11.3 Forms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.3.1 General (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.3.2 Filling of Forms (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.3.3 Removal of Forms (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.3.4 Inspection Doors (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-11-7 8-11-7 8-11-7 8-11-7 8-11-8

11.4 Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4.1 Specification (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4.2 Order of Placing (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4.3 Consolidation (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4.4 Laitance and Bonding (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4.5 Drainage During Placing (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4.6 Shotcrete (2004). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-11-8 8-11-8 8-11-8 8-11-8 8-11-8 8-11-8 8-11-8

1

References Vol. 37, 1936, pp. 645, 1042; Vol. 42, 1941, pp. 309, 878; Vol. 54, 1953, pp. 814, 1343; Vol. 62, 1961, pp. 445, 861; Vol. 63, 1962, pp. 277, 687; Vol. 74, 1973, p. 140; Vol. 89, 1988, p. 108. Rewritten 1988.

© 2011, American Railway Engineering and Maintenance-of-Way Association

8-11-1

1

3

Concrete Structures and Foundations

LIST OF FIGURES Figure

Description

Page

8-11-1 Plain Concrete Tunnel Lining – Rock Section Single Track . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-11-2 Plain Concrete Tunnel Lining – Single Track Temporary Supports . . . . . . . . . . . . . . . . . . . . . 8-11-3 Plain Concrete Tunnel Lining – Double Track . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-11-4 8-11-5 8-11-6

SECTION 11.1 GENERAL 11.1.1 SCOPE (2004) This recommended practice covers the lining of new tunnels in rock and those portions of old tunnels in rock which involve no extraordinary side pressure or special features. The recommended practice covers linings of cast-in-place concrete and shotcrete with steel sets.

SECTION 11.2 DESIGN 11.2.1 INTERIOR DIMENSIONS (2004) a.

The interior dimensions of the clear space provided for single and double-track tunnels should not at any point be less than tunnel clearances recommended by the AREMA Manual. Where legal requirements provide clearances greater than AREMA, such legal requirements shall govern.

b. On curved track, the lateral clearance should be increased in conformance with Chapter 28, Clearances, Part 1, Clearance Diagrams – Fixed Obstructions. The superelevation of the outer rail should be in accordance with the recommended practice of Chapter 5, T rack. c.

To provide for drainage, minimum side clearance of 10 feet (3 m) from centerline of track should be used in tunnels likely to be wet. Where ventilation is required, the height of single-track tunnel should be increased 1 foot (300 mm) minimum.

11.2.2 PRELIMINARY DATA (2004) Information shall be obtained for design of new tunnels, consisting of field surveys showing geological formations, groundwater conditions, environmental conditions, adjacent structures, locations of faults, core borings, hardness and condition of rock to be encountered, together with any special features and data on existing tunnels through similar formations. Where a new tunnel is driven adjacent to an existing tunnel, records shall be searched for data as to groundwater conditions, fault zones, and other special features. Consideration should be given to taking core borings from existing adjacent tunnels.

11.2.3 FLOORS (2004) Floors should, if practical, be paved and may have a ballasted track section, direct fixation to the concrete floor, or other suitable track design. Paved floors shall be designed for the track section to be used.

© 2011, American Railway Engineering and Maintenance-of-Way Association

8-11-2

AREMA Manual for Railway Engineering

Lining Railway Tunnels

11.2.4 SIDEWALLS AND ARCH (2004) a.

The depth of sidewalls in sound rock shall be at least 6 inches (150 mm) below the bottom of the gutter and at least 6 inches (150 mm) below the intersection of the floor surface with the sidewalls. In unsound rock, the sidewalls shall be carried down to provide a stable foundation. At portals and vicinity, sidewalls shall extend at least 6 inches (150 mm) below the frost line.

b. The minimum thickness of the cast-in-place sidewalls and arch shall be: (1) Where temporary supports for excavation are not required: • Single track – See Figure 8-11-1. • Double track – See Figure 8-11-3. (2) Where temporary supports are required for face of excavation see Figure 8-11-2 or Figure 8-113. c.

Encased timber sets are subject to decay and are not recommended. Exposed timber sets create a fire hazard and also are not recommended.

d. Steel sets are spaced at least 8 inches (200 mm) apart, and in general not greater than 4 feet (1.2 m) apart. Solid liners may also be considered. e.

f.

Lagging may be wood, steel lags, steel liner plates, or steel water-diverting lagging. Where the nature of the rock and water conditions permit, lagging shall be spaced to allow a clearance of 4 inches (100 mm) or more between lags to permit free access of concrete to the face of the tunnel excavation. Prior to concreting, remove as many lags as is possible. Where it is necessary to solid-lag for protection during excavation and where it is impractical to open up the lagging just prior to concreting, the space between the lagging and face of excavation shall be packed with lean concrete, crushed stone, coarse gravel, or pea gravel placed pneumatically. Consolidation grouting shall be used to fill any voids behind lining. Where timber lagging is used, or where existing packing consists of timber, special care must be exercised in torch cutting or welding of steel ribs or other components to eliminate the risk of fire.

1

3

Rock bolts may be considered as part of a support system.

11.2.5 CONSTRUCTION AND EXPANSION JOINTS (2004) a.

Properly placed and consolidated construction joints do not require keyways. Waterstops shall be provided as necessary. Monoliths shall be as long as practical to minimize the number of construction joints.

b. Construction joints shall not be formed at such locations where they might reduce the effectiveness of the lining to resist pressure from surrounding earth or rock. c.

Where construction joints are provided, expansion joints are not required.

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

8-11-3

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Concrete Structures and Foundations

Figure 8-11-1. Plain Concrete Tunnel Lining – Rock Section Single Track

© 2011, American Railway Engineering and Maintenance-of-Way Association

8-11-4

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Lining Railway Tunnels

1

3

4 Figure 8-11-2. Plain Concrete Tunnel Lining – Single Track Temporary Supports

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

8-11-5

Concrete Structures and Foundations

Figure 8-11-3. Plain Concrete Tunnel Lining – Double Track

© 2011, American Railway Engineering and Maintenance-of-Way Association

8-11-6

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Lining Railway Tunnels

11.2.6 DRAINS (2004) a.

Wherever groundwater is encountered or anticipated, vertical and diagonal openings, trench drains, PVC or iron pipe drains shall be installed between the concrete lining and rock. Adequate outlets shall be provided through sidewalls with the outer end of the outlets not less than 12 inches (300 mm) above the bottom of the gutter. Subdrains shall be provided under the concrete floor wherever groundwater is found. Drains shall be provided through curb to drain ballast section.

b. Where hydrostatic pressure below the floor may be present, consideration should be given to designing the floor to withstand the pressure. c.

Wherever groundwater drains are installed, they shall be attached to the rock so as to prevent being clogged when concrete is poured.

d. Drain type selection should take into consideration an analysis of groundwater constituents and effects of water aeration to discourage formation of precipitates or adverse chemical reaction which may plug or damage the drainage system.

11.2.7 REFUGE NICHES (BAYS) (2004) Refuge niches shall be provided as shown on the example figures at approximate intervals of 200 feet (60 m) and staggered with opposite sides so that spacing of niches shall be approximately 100 feet (30 m). Width of niches should accommodate the number of people and the equipment to be protected. Bottom of niches shall be at elevation of bottom of track ties for ballasted track sections and at elevation of intersection of invert and walls for solid track sections. For long tunnels, larger refuge niches should be considered at appropriate intervals to accommodate equipment.

1

11.2.8 CONDUIT AND INSERTS (2004) Where required, provisions shall be made in the lining for conduit or hangers for cables, wires, and lights.

3 SECTION 11.3 FORMS 11.3.1 GENERAL (2004) a.

4

Forms shall conform to requirements as outlined in Part 1, Materials, Tests and Construction Requirements, together with additional provisions given herewith.

b. The length of forms between construction joints shall be as long as possible to limit number of joints. Waterproofing at joints should be considered where appropriate.

11.3.2 FILLING OF FORMS (2004) The space between the face of the form and face of excavation or tight lagging shall be entirely filled with concrete, except for drainage openings, and except that large cavities back of the normal face of excavation may be packed as outlined in Paragraph 11.2.4(e).

11.3.3 REMOVAL OF FORMS (2004) Forms shall not be removed until concrete has reached strength sufficient to prevent distortion and sustain the applied load.

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AREMA Manual for Railway Engineering

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Concrete Structures and Foundations

11.3.4 INSPECTION DOORS (2004) Forms shall be provided with inspection doors in the arch and walls so that the concrete can be thoroughly vibrated and inspected during the placing.

SECTION 11.4 CONCRETE 11.4.1 SPECIFICATION (2004) Concrete for lining shall be proportioned and placed in accordance with Part 1, Materials, Tests and Construction Requirements, together with the additional provisions given herewith. Placement of reinforcement shall be in accordance with Part 2, Reinforced Concrete Design.

11.4.2 ORDER OF PLACING (2004) A section of the wall and footing may be placed separately from the rest of the wall, but a construction joint shall not be more than 2 feet (600 mm) above the top of ballast curb elevation. The remainder of the wall and arch shall be placed monolithically. The floor ballast retainers shall preferably be placed in one operation.

11.4.3 CONSOLIDATION (2004) All concrete shall be consolidated during and immediately after placing by means of internal vibration applied in the mass of concrete and external vibration applied to the forms.

11.4.4 LAITANCE AND BONDING (2004) a.

Concrete surfaces receiving new concrete shall be roughened and cleaned of all laitance, dirt, and water before fresh concrete is placed. The consistency of the concrete and method of placement shall be such that laitance seams are not formed. If such seams are formed, they shall be completely removed before additional concrete is placed.

b. All loose or unsound rock shall be removed behind walls and below floors before concrete is placed. Where the type of rock makes this impractical, the floor and foundations for the walls shall be reinforced.

11.4.5 DRAINAGE DURING PLACING (2004) Concrete shall not be placed in moving water. Separate and distinct provisions shall be provided to drain any area receiving fresh concrete. Effective weeps and drains shall be provided to prevent any hydrostatic pressure against the lining. Temporary drains shall be grouted after concrete liner has attained design strength.

11.4.6 SHOTCRETE (2004) Shotcrete and reinforcement for shotcrete for lining shall be proportioned in accordance with Part 14, Repair and Rehabilitation of Concrete Structures.

© 2011, American Railway Engineering and Maintenance-of-Way Association

8-11-8

AREMA Manual for Railway Engineering

8

Part 12 Cantilever Poles1 — 2003 — Reaffirmed without changes.

TABLE OF CONTENTS Section/Article

Description

Page

12.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.1.1 Scope (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.1.2 Introduction (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-12-2 8-12-2 8-12-2

12.2 Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.2.1 Pole (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-12-2 8-12-2

12.3 Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.3.1 Installation (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-12-2 8-12-2

12.4 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12.4.1 General (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-12-3 8-12-3

LIST OF FIGURES Figure

Description

8-12-1 Pole Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-12-2 Bearing Capacity Factors vs. Depth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-12-3 Granular Soils. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Page 8-12-4 8-12-7 8-12-8

LIST OF TABLES Table

Description

8-12-1 Recommended Value of “nh” for Sands lb/in3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-12-2 Recommended Value of “K” for Clays for qu>1 tsf . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-12-3 Constants Used in Calculations and their Variances. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

Page 8-12-5 8-12-6 8-12-8

References, Vol. 71, 1970, p. 232; Vol. 93, 1992, p. 78, 98.

© 2011, American Railway Engineering and Maintenance-of-Way Association

8-12-1

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3

Concrete Structures and Foundations

SECTION 12.1 GENERAL 12.1.1 SCOPE (1992) a.

This part of the Manual covers the design of the required embedment for poles in cohesive and granular soils that are subjected to vertical and horizontal forces.

b. Loading on the poles is not considered in this Manual and the loads shall be determined by the applicable sections of this Manual.

12.1.2 INTRODUCTION (1992) a.

In certain types of construction, poles are subjected to overturning forces. The most common usage of these types of construction are transmission lines and sign poles. Under certain conditions, piles such as soldier piles for the protection of excavations, capped pile abutments where the piling acts as a backwall, and stabilization piles for embankment slopes can be analyzed as poles. This Manual is intended to offer a design procedure which will determine the required pole embedment.

b. Several factors which will affect the design of cantilever embedded poles and that should be taken into account during analysis and final design are: cyclical nature of the loads which may leave a void around the pole and allow infiltration of water, plumbness of the pole, variations in the soil strata, variation of the soil at different locations, and the indeterminate nature of the loading conditions.

SECTION 12.2 MATERIALS 12.2.1 POLE (1992) The type, size, shape, manufacture, and construction shall be as specified by the Engineer, and shall conform to the following sections of the Manual: a.

Concrete – Chapter 8, Concrete Structures and Foundations, Part 2, Reinforced Concrete Design.

b. Steel – Chapter 15, Steel Structures, Part 1, Design and Part 3, Fabrication. c.

Timber – Chapter 7, Timber Structures, Part 1, Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Timber Bridge Ties and Recommendations for Fire-Retardant Coating for Creosoted Wood.

SECTION 12.3 CONSTRUCTION 12.3.1 INSTALLATION (1992) 12.3.1.1 Driven Poles Poles can be installed by pile driving methods, in which case the installation requirements shall be governed by Chapter 8, Concrete Structures and Foundations, Part 4, Pile Foundations. 12.3.1.2 Set Poles a.

After the location of the poles has been selected, an oversized hole shall be augered to the design depth, the pole inserted to the bottom of the hole, and the annular space filled with either compacted soil or concrete.

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8-12-2

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Cantilever Poles

b. The size of the hole and the method of backfill shall be determined by the use of the pole, and the assumptions made for design. If the full diameter of the hole is to be used in the structural analysis, concrete backfill shall be used to fill the annular space between the pole and the surrounding earth. The need for reinforcement of the concrete shall be determined by analysis. c.

Soil backfill of the annular space shall completely fill the voids, and be compacted to the density of the surrounding soil.

d. The pole shall be held plumb in such a manner that transverse and vertical loads are not restrained by the ground around the pole until the backfilling is complete and able to withstand the imposed loads. e.

If concrete backfill is intended to enlarge the diameter of the pole embedment, then suitable bracing shall remain in place until the concrete has attained the strength set forth on the drawings.

SECTION 12.4 DESIGN 12.4.1 GENERAL (1992) a.

The design of the particular installation will be determined by many different factors. In all cases, the requirements can be reduced to: (1) External Loads. The vertical loads and their eccentricity; the magnitude, direction, and location of the horizontal loads, and the frequency and cyclical nature of the loads shall be included in the design loads.

1

(2) Soil Characteristics. The soil type, unit weight, angle of internal friction for granular soils, cohesion of the soil, location of the water table, and any variation in the soil. Soil strength values given here are not for soil below the water table. Soil investigation shall be made in accordance with the requirements of Chapter 8, Concrete Structures and Foundations, Part 22, Geotechnical Subsurface Investigation, taking into account the value and use of the pole.

3

b. When a pole set directly into the earth is dependent upon the horizontal resistance (horizontal subgrade reaction) of the supporting soil for its stability, and has not been permanently stayed by external supports, the following procedure is recommended to determine the required embedment of the pole. (1) The design of the proper pole diameter and depth of embedment is obtained by a trial and error solution. The design is considered to be complete when the size of the pole (and/or its encasement), depth of embedment, bending moments, shears, and deflection of the pole have been determined. (2) Upon completion of the given design, the Engineer shall verify that the pole (and its structural encasement if used) is capable of withstanding the previously determined moments and shears. The structural design for steel poles shall conform to the requirements of Chapter 15, Steel Structures, concrete poles according to Chapter 8, Concrete Structures and Foundations, and timber poles should conform to Chapter 7, Timber Structures. c.

The equations found in Article 12.4.1.1, Article 12.4.1.2 and Figure 8-12-1 may be used to determine the required depth of embedment and width of the pole.

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Concrete Structures and Foundations

pa

pb Figure 8-12-1. Pole Design

Nomenclature P= Q= D= Do =

Vertical load on the pole acting at an eccentricity e and a distance h above grade. Resultant of all horizontal loads acting on the pole at a height H above grade. Depth of embedment. Distance below the ground surface to a point where the horizontal deflection is zero.

B= M= EI = pa =

Width of the pole and/or encasement resisting the horizontal load at the point under consideration. Net overturning moment at the ground surface. Average flexural stiffness of the pole and/or encasement below grade. Maximum positive subgrade reaction.

pb = Maximum negative subgrade reaction. nh = Soil modulus for granular soils. K = Soil modulus for cohesive soils. Pcr = Critical vertical load on the pole. y= x= w= c=

The lateral deflection of the pole at the groundline. Distance from the ground surface, positive downward. Unit weight of the soil. Cohesion of the soil.

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Cantilever Poles 12.4.1.1 Granular Soils M 3 a --------- + --- – -----Do QD 4 12 ------- = -------------------------------D 3 M --- --------- + 1 2 QD

where

hö 36P æ 1 + --è Dø a = ------------------------------3 nh D

(See Table 8-12-1)

EQ 12-1

Table 8-12-1. Recommended Value of “nh” for Sands lb/in3

D 3Q p a = ------------------------------- -------o2D 3D D ----------o- – 1 2D

Density

Dry

Submerged

Loose

10

5

Medium

30

20

Dense

75

45

2

EQ 12-2

D D 1 p a £ -----------B æè ------o-öø w N q determine N q at x = ------oF.S. 2 2

(See Figure 8-12-2)

D 3Q p b = ------------------------------- ------o- – 1 D 3D D ----------o- – 1 2D

where

T = EI ------nh

1

EQ 12-4

1 p b £ – ------------BDwN q determine N q at x = D F.S. D£3 ---T

EQ 12-3

1¤5

(See Figure 8-12-2)

(See Table 8-12-1)

D B.M. max = M + 0.89QD ------o- – 0.667 D

0.508

EQ 12-5

EQ 12-6

4 EQ 12-7

P P cr = ---a D 3Q æ ------o-ö è Dø y = ----------------------------------------2 3D n h D ----------o- – 1 2D

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AREMA Manual for Railway Engineering

3

8-12-5

Concrete Structures and Foundations 12.4.1.2 Cohesive Soils M b --------- + 0.683 – ----------Do QD 6.78 ------- = ------------------------------------------------D 1.87M ----------------- + 1 QD

EQ 12-8

hö 14.6P æ 1 + ---ø è D where b = -----------------------------------2 KD

(See Table 8-12-2)

Table 8-12-2. Recommended Value of “K” for Clays for qu>1 tsf qu tsf

“K” psi

1–2

700

2–4

1400

over 4

2800

qu is the unconfined compressive strength of the clay. D 1.377Q p a = --------------------------------------- ------oD D D 1.87 ------o- – 1 D 1 p a £ ----------BcN c F.S.

1.15

EQ 12-9

determine Nc at x = 0.13 Do (See Figure 8-12-2)

D 2.15Q p b = --------------------------------------- ------o- – 1 D D D 1.87 ------o- – 1 D 1 p b £ ----------BcN c F.S.

EQ 12-11

determine Nc at x = D (See Figure 8-12-2)

D £ 3 where R = EI ---------R K

1¤4

EQ 12-12

EQ 12-13

(See Table 8-12-2)

D B.M. max = M + 0.80QD ------o- – 0.535 D

EQ 12-10

0.823

EQ 12-14

P P cr = ---b D 2.15Q æ ------o-ö è Dø y = ------------------------------------------Do KD 1.87 ------- – 1 D

© 2011, American Railway Engineering and Maintenance-of-Way Association

8-12-6

AREMA Manual for Railway Engineering

Cantilever Poles

1 Figure 8-12-2. Bearing Capacity Factors vs. Depth 12.4.1.3 Procedure a.

Determine all loads acting on the pole and assume a desired pole and/or encasement diameter B. Estimate the depth D as the maximum allowable for the assumed pole cross section, as determined by EQ 12-6 or EQ 12-13.

3

b. Figure 8-12-3 can be used to assist in the design for poles embedded in granular soils. c.

Use a factor of safety of three for permanent loads and two for temporary loads.

d. Carry through several trial designs until the depth chosen corresponds to the allowable soil stresses, as shown in Article 12.4.1.4 and Article 12.4.1.5. (In EQ 12-2, EQ 12-4, EQ 12-9, and EQ 12-11 the fourth significant figure is important in the denominator.) e.

Where the vertical load is large, the pole shall be investigated as a friction pile. In this investigation the top 2 feet of the embedded portion of the pole shall be neglected unless the horizontal load is quite small and the eccentricity of the vertical load is nominal.

f.

Table 8-12-3 shows the constants used in the calculations and how to vary them.

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

8-12-7

4

Concrete Structures and Foundations

NOTE:Graph will determine approximate values only. Check EQ 12-6 for limitation on pole embedment depth. Figure 8-12-3. Granular Soils

Table 8-12-3. Constants Used in Calculations and their Variances Existing Constant B = 18 inches w = 100 pcf

nh = 20 F.S. = 2

lb/in3

Variations New Constant

Change

B = 24 inches

Reduce obtained value of “D” by 1 foot

w = 70 pcf

Increase obtained value of “D” by 1 foot

w = 120 pcf

No change in value

nh = 10 lb/in3

Increase obtained value of “D” by 1 foot

nh = 30 lb/in3

Reduce obtained value of “D” by 1 foot

F.S. = 3

Increase obtained value of “D” by 1 foot

© 2011, American Railway Engineering and Maintenance-of-Way Association

8-12-8

AREMA Manual for Railway Engineering

Cantilever Poles 12.4.1.4 Example A – Granular Soils a.

Soil: • Granular and dry with f = 35 degrees • Unit weight = w = 110 lb/cubic feet + 30 • Medium dense: n h = 75 ------------------- = 52.5 lb/in2 2

b. Loading: • P = 5 kips, h = 20 feet, e = 12 inches • Q = 2 kips, H = 25 feet • Factor of Safety = F.S. = 3 c.

Trial Design: • It is desired to have a timber pole with a diameter of B = 18 inches with a modulus of elasticity = E = 1.6 (10)6 psi

1

• M = 25 (2) + 1(5) = 55 kip-ft. • EI = 1.6 ( 10 )

6

4

9 p ( 18 ) ------------------ = 8.245 ( 10 ) 64

d. Using EQ 12-6:

3 9 1¤5

8.245 ( 10 ) T = ----------------------------52.5

= 44.0 and Dmax £ 3(44.0) = 132 inches = 11 feet

Try D = 11 feet e.

4

Using EQ 12-1: 55 3 a --------------- + --- – -----Do 2 ( 11 ) 4 12 ------- = -------------------------------------- = 0.685 neglect “a” for all trial solutions, and check only final design. D 3 55 --- --------------- + 1 2 2 ( 11 )

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AREMA Manual for Railway Engineering

8-12-9

Concrete Structures and Foundations

f.

Using EQ 12-2: 2 3(2) p a = ----------------------------- ( 0.3425 ) = 2.327 kips/ft 11 ( 0.0275 )

g.

Using EQ 12-3: Nq = 11.5 for x = 0.3425(11) = 3.77 feet x 3.77 ---- = ----------- = 2.5 B 1.50 1 p a £ --- ( 1.5 ) ( 3.77 ) ( 110 ) ( 11.5 ) ¤ 1000 3 = 2.38 kips/ft

h. Using EQ 12-4: 3(2) p b = ----------------------------- ( 0.685 – 1.000 ) = – 6.25 kips/ft 11 ( 0.0275 ) i.

Using EQ 12-5: x Nq = 16.5 for ---- = 7.33 B pb £ – 1 --- ( 1.5 ) ( 11 ) ( 110 ) ( 16.5 ) ¤ 1000 3 = –9.88 kips/ft NOTE:

j.

A check using the value of “a” in EQ 12-1 will give no change.

Using EQ 12-7: B.M. max = 55.00 + 0.89 (0.685 - 0.677)0.508 (2)(11) = 56.69 kip-ft y = 3 (2000) (0.685)/52.5 (132) (132) (0.0275) = 0.17 inches Pcr = 5000/0.0044 = 1130 kips 20 36 ( 5000 ) æ 1 + ------ö è 11ø - = 0.0044 for a = ------------------------------------------------------------( 52.5 ) ( 132 ) ( 132 ) ( 132 )

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8-12-10

AREMA Manual for Railway Engineering

Cantilever Poles 12.4.1.5 Example B – Cohesive Soils a.

Soil: • Cohesive and dry with f = 0 degrees, • qu = 2 tons/square foot • Unit weight = 110 lb/cubic foot • c = 1 ton/square foot and use K = 1400 psi (See Table 8-12-2)

b. Loading: • Same as previous example c.

Trial Design. It is desired to use an 18-inch pole with • E = 1.6(10)6 psi • M = 55 kip-ft, and EI = 8.245(10)9

d. Using EQ 12-13: 9 1¤4

8.245 ( 10 ) R = ----------------------------1400

1 = 49.3

Dmax = 3 (49.3) = 147.9 = 12.3 feet. After several trials it was decided to try D = 7.5 feet. e.

3

Using EQ 12-8: 55 ---------------- + 0.683 Do 2 ( 7.5 ) ------- = -------------------------------------- = 0.554 D 1.87 ( 3.05 ) + 1

f.

4

Using EQ 12-11: 2.15 ( 2 ) p b = ------------------------------------------------------ ( – 0.446 ) = – 6.73 kips/ft 7.5 [ 1.87 ( 0.554 ) – 1 ]

g.

Using EQ 12-12: 1 p b = --- ( 1.5 ) ( 2 ) ( 6.9 ) = – 6.90 kips/ft 3

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AREMA Manual for Railway Engineering

8-12-11

Concrete Structures and Foundations

h. Using EQ 12-9: 1.377 ( 2 ) ( 0.554 ) 1.15 = 4.89 kips/ft p a = --------------------------7.5 ( 0.038 ) i.

Using EQ 12-10: pa £ 1 --- ( 1.5 ) ( 2 ) ( 3.8 ) = 3.80 kips/ft 3 Not satisfied for x = 0.13 (0.554) (7.5) = 0.53 feet. Nc = 3.8 (See Figure 8-12-2) Try D = 9 feet

j.

Using EQ 12-8: 55 ----------- + 0.683 Do 2(9) ------- = -------------------------------------- = 0.556 D 1.87 ( 3.05 ) + 1

k. Using EQ 12-9: 1.377 ( 2 ) ( 0.556 ) 1.15 = 3.80 kips/ft p a = --------------------------9.0 ( 0.041 ) l.

Using EQ 12-10: pa £ 1 --- ( 1.5 ) ( 2 ) ( 3.9 ) = 3.90 kips/ft 3 pb will obviously be satisfactory for this increased depth.

m. Using EQ 12-14: B.M. max = 55.00 + 0.80 (9) (2) (0.021)0.823 = 55.60 kip-ft y = 2.15 (2000) (0.556)/(1400) (108) (0.041) = 0.39 inches

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8-12-12

AREMA Manual for Railway Engineering

8

Part 14 Repair and Rehabilitation of Concrete Structures1 — 2006 — TABLE OF CONTENTS

Section/Article

Description

Page

14.1 Scope (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-14-3

14.2 Determination of the Causes of Concrete Deterioration (2006) . . . . . . . . . . . . . . . . . .

8-14-3

14.3 Evaluation of the Effects of Deterioration and Damage. . . . . . . . . . . . . . . . . . . . . . . . . 14.3.1 Methods of Evaluation (2006). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.3.2 Results of Evaluation (2006). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.3.3 Special Cases (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.3.4 Reevaluation (2006). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-14-4 8-14-4 8-14-4 8-14-5 8-14-5

14.4 Principal Materials Used in the Repair of Concrete Structures . . . . . . . . . . . . . . . . . . 14.4.1 Cement (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.4.2 Admixtures (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.4.3 Aggregate (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.4.4 Reinforcement (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.4.5 Polymers in Concrete (2006). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.4.6 Bonding Compounds (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.4.7 Epoxy Materials (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.4.8 Non-shrink Grouts (2006). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.4.9 Fiber Reinforced Polymers (FRP Composites) (2006). . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-14-5 8-14-5 8-14-5 8-14-5 8-14-5 8-14-6 8-14-6 8-14-6 8-14-6 8-14-6

14.5 Repair Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.5.1 Surface Repairs Using Portland Cement Materials (2006). . . . . . . . . . . . . . . . . . . . . . . . . 14.5.2 Surface Repairs Using Polymer Concretes and Polymer Portland Cement Concretes (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.5.3 Tuckpointing (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.5.4 Arch Lining (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.5.5 Internal Structural Repairs (2006). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.5.6 Non-Structural Crack Repair (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.5.7 Reinforcement Splices (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-14-7 8-14-7

1

8-14-12 8-14-12 8-14-13 8-14-13 8-14-19 8-14-21

References, Vol. 36, 1935, pp. 870, 1028; Vol. 42, 1941, pp. 297, 878; Vol. 43, 1942, pp. 336, 716; Vol. 51, 1950, pp. 365, 895; Vol. 53, 1952, p. 617; Vol. 54, 1953, pp. 819, 1343; Vol. 62, 1961, pp. 443, 444, 861; Vol. 63, 1962, pp. 277, 688; Vol. 65, 1964, pp. 362, 758; Vol. 67, 1966, pp. 357, 360, 657; Vol. 84, 1983, p. 93; Vol. 93, 1992, pp. 78, 98.

© 2011, American Railway Engineering and Maintenance-of-Way Association

8-14-1

1

3

Concrete Structures and Foundations

TABLE OF CONTENTS (CONT) Section/Article

Description

Page

14.6 Repair Methods for Prestressed Members. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.6.1 Cracks Exist with No Significant Section Loss and No Tendon Damage (2006) . . . . . . . 14.6.2 There is Minor Section Loss, but No Tendon Damage (2006). . . . . . . . . . . . . . . . . . . . . . 14.6.3 Shattered Concrete and/or Significant Section Loss, but No Tendon Damage (2006) . . 14.6.4 There is Section Loss and Tendon Damage (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.6.5 Member Is Damaged Beyond Reasonable Repair (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . 14.6.6 Member Has Inadequate Strength (2006). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.6.7 Summary (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-14-22 8-14-22 8-14-22 8-14-23 8-14-23 8-14-24 8-14-24 8-14-24

Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-14-25

LIST OF FIGURES Figure

Description

Page

8-14-1 Repair of Cracks by Stitching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-14-2 Repair of Cracks by Pinning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-14-3 External Stressing to Correct Cracking of Slab. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-14-4 External Stressing to Correct Cracking of Beam . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-14-5 Detail Copper Plate Joint Sealing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-14-6 Detail PVC Pipe Joint Sealing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-14-7 External Splice Sleeve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-8-14-1Preloading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-8-14-2External Post-Tensioning Section Between Corbels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-8-14-3Metal Splice Sleeve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-14-18 8-14-18 8-14-19 8-14-19 8-14-20 8-14-20 8-14-22 8-14-32 8-14-33 8-14-34

LIST OF TABLES Table

Description

Page

8-14-1 Supporting Loads for Expansion Bolts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-14-2 Expansion Bolt Placement – Concrete 4 Inches or More in Thickness . . . . . . . . . . . . . . . . . . .

8-14-8 8-14-8

© 2011, American Railway Engineering and Maintenance-of-Way Association

8-14-2

AREMA Manual for Railway Engineering

Repair and Rehabilitation of Concrete Structures

SECTION 14.1 SCOPE (2006)1 a.

This part applies to the repair and rehabilitation of concrete2 structures by the following methods: patching, encasement with concrete, shotcrete, pressure grouting, injection grouting of preplaced aggregates, tremie placement, bagged concrete, epoxy injection, external post-tensioning, splicing of damaged reinforcement and component replacement. They are intended to provide means of accomplishing repairs both above and below water using a variety of materials.

b. This part also identifies some of the major causes for the deterioration of concrete and the methods of protecting against deterioration. c.

Repair of a structure usually consists of five basic steps: (1) Identifying the deterioration. (2) Determining the cause. (3) Evaluating the strength of the existing structure. (4) Evaluating the need for repair. (5) Selecting and implementing a repair procedure.

1 SECTION 14.2 DETERMINATION OF THE CAUSES OF CONCRETE DETERIORATION (2006)3 a.

In order to select the proper repair procedure for concrete, the cause of the deterioration must first be established. One or more of the following factors may contribute to the deterioration of the concrete:

3

(1) Lack of quality in the original concrete and/or its placement. (2) Deficiency of reinforcement. (3) Properties of surrounding environment.

4

(4) Inadequate structural capacity. (5) Physical damage. b. The investigation should try to determine the possible cause(s) and then select a repair procedure which will correct the existing condition and prevent further deterioration by any and all of the suspect cause(s).

1

See Commentary May be applicable to either concrete or masonry. 3 See Commentary 2

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AREMA Manual for Railway Engineering

8-14-3

Concrete Structures and Foundations

SECTION 14.3 EVALUATION OF THE EFFECTS OF DETERIORATION AND DAMAGE 14.3.1 METHODS OF EVALUATION (2006) 14.3.1.1 Visual Inspection Periodic inspections (see Part 21 Inspection of Concrete and Masonry Structures) should be made to detect deterioration and damage before the structure becomes irreparable. The engineer in charge of maintenance and inspection should be experienced in determining the parts of structures in need of repair and the extent of deterioration or damage. 14.3.1.2 Analysis of Actual Stress Condition This method involves a stress analysis of the structure in its existing condition. 14.3.1.3 Non-Destructive Tests1 There are several common test procedures available to determine the in-place condition of the structure. The most appropriate test should be determined by the Engineer. 14.3.1.4 Sampling This procedure consists of removing samples of material, usually by coring, in order to analyze physical and chemical characteristics of concrete and reinforcing. 14.3.1.5 Load Test a.

This method involves the instrumenting of a structure to measure strains or deflections as a means of determining the capability of the structure to sustain service loads. A prescribed test load is permitted to cross the structure at a given speed. Often it is desirable to stop the test load on the structure at a predetermined position and take measurements under static conditions.

b. The test should be monitored as the loading progresses to verify that the observed data compares favorably with the theoretical calculations. If a significant difference is observed the test should be stopped and further evaluated before proceeding. c.

This method should be used only if calculations indicate a reasonable margin of safety against collapse under the test load. Loads considerably below the desired service load level may be used initially to make a preliminary evaluation and to predict the reaction of the structure under a full test load.

14.3.2 RESULTS OF EVALUATION (2006)2 Based on the evaluation, one or more of the following determinations can be made regarding the present condition: a.

Requires no action.

b. Requires action to arrest or minimize deterioration. c. 1 2

Requires action to repair or strengthen the structure.

See Commentary See Commentary

© 2011, American Railway Engineering and Maintenance-of-Way Association

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Repair and Rehabilitation of Concrete Structures

d. Requires reconstruction or replacement of the structure. e.

Requires restricting traffic speed and/or weight or closing the structure to traffic.

14.3.3 SPECIAL CASES (2006) In special cases (i.e. windstorm, flooding, scour, seismic activity, fire damage, etc.), the resulting damage to the structure may not be apparent to the inspector in a visual examination of the surface. Care should be exercised in these cases to properly evaluate all defects using, where necessary, special inspection and nondestructive testing techniques.

14.3.4 REEVALUATION (2006) During repair or rehabilitation of a structure it may be found that the extent of the damage or deterioration is greater than originally determined. This further damage should be reviewed for the effectiveness of the proposed repair under these conditions.

SECTION 14.4 PRINCIPAL MATERIALS USED IN THE REPAIR OF CONCRETE STRUCTURES NOTE:

1

The materials used should conform in physical properties to Part 1 Materials, Tests and Construction Requirements, or as hereinafter specified.

14.4.1 CEMENT (2006) See Part 1 Materials, Tests and Construction Requirements, Section 1.2 Cement and Section 1.3 Other Cementitious Materials.

3

14.4.2 ADMIXTURES (2006) See Part 1 Materials, Tests and Construction Requirements, Section 1.7 Concrete Admixtures.

14.4.3 AGGREGATE (2006)

4

See Part 1 Materials, Tests and Construction Requirements, Section 1.4 Aggregates.

14.4.4 REINFORCEMENT (2006) a.

See Part 1 Materials, Tests and Construction Requirements, Section 1.6 Reinforcement.

b. Reinforcement may consist of one or more of the following materials: Deformed steel bars, prestressing tendons, wire mesh or reinforcing fibers consisting of steel, glass, or plastic. c.

When increased protection from corrosion is required, coatings or cathodic protection of steel reinforcement may be considered.

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AREMA Manual for Railway Engineering

8-14-5

Concrete Structures and Foundations

14.4.5 POLYMERS IN CONCRETE (2006) a.

See Part 1 Materials, Tests and Construction Requirements, Article 1.14.9 Bonding (1993).

b. Polymer Concrete may be used as a patching material and where high strengths are needed in a short time. c.

Polymer Cement Concrete may be used as an overlay (an example of PCC is latex-modified concrete).

14.4.6 BONDING COMPOUNDS (2006) See Part 1 Materials, Tests and Construction Requirements, Section 1.7 Concrete Admixtures.

14.4.7 EPOXY MATERIALS (2006) Epoxy materials are manufactured with a wide range of properties for various applications and should be chosen to provide for the requirements (i.e. viscosity, strengths, flexibility, adhesion, etc.) of the specific repair. In addition, they should meet the requirements of ASTM Specification C881, Type 1, Epoxy Resin Base Compounds for Concrete. Epoxy materials are used for a variety of purposes including bonding new concrete to old, repair of cracks, sealing and patching. Selection is subject to approval of the Engineer.

14.4.8 NON-SHRINK GROUTS (2006)1 a.

Non-shrink grouts consist of either portland cement based grouts with an expanding agent added to counter the shrinkage from the hydration of the portland cement grout or non-cementitious based grouts such as epoxy grouts.

b. Non-shrink grouts are generally used for setting and leveling bearings. Selection of the grout is subject to approval by the Engineer. c.

Non-shrink grouts should conform to ASTM C1107. Design and use of portland cement non-shrink grouts should be in conformance with ACI-223 – Standard Practice for the Use of Shrinkage Compensating Concrete.

14.4.9 FIBER REINFORCED POLYMERS (FRP COMPOSITES) (2006) a.

Fiber reinforced polymers may be considered for strengthening or repairing existing reinforced or prestressed concrete.

b. Polymer resins are manufactured with a wide range of properties for various applications and should be chosen to provide for the requirements of the specific repair. Selection is subject to the approval of the Engineer. c.

Reinforcement typically consists of carbon, glass or aramid fiber. Reinforcement is manufactured with a wide range of properties for various applications and should be chosen to provide for the requirements of the specific repair. Selection is subject to approval of the Engineer.

d. Fiber-reinforced polymers are typically applied in alternating layers of polymer resin and woven-fabric fiber reinforcing. Concrete underlying repairs should be cleaned and checked for soundness prior to surface application. 1

See Commentary

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8-14-6

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Repair and Rehabilitation of Concrete Structures

e.

Design and application for FRP repairs should conform to manufacturer’s recommendations and sound engineering principles.

SECTION 14.5 REPAIR METHODS 14.5.1 SURFACE REPAIRS USING PORTLAND CEMENT MATERIALS (2006) 14.5.1.1 Scope a.

Repairs should consist of removal of soft, disintegrated, broken, or honeycombed concrete or stone; cleaning and preparing the bonding surface and exposed reinforcement; placing of anchors and reinforcement; placing of concrete by shotcreting, handpatching, forming and placing, tremieing, grouting of preplaced aggregate, or as specified. Such concrete is to be finished to true line and surface as shown on the plans and properly cured.

b. Concrete in the repaired area below the neutral axis in prestressed members should be repaired under an externally applied preload. Preload may be applied by means of jacks or a known load.1 14.5.1.2 Preparation2 a.

All loose, soft, honeycombed and disintegrated concrete or stone should be removed from the areas to be repaired by proper tools, to expose a bonding surface of sound material. Appropriately sized equipment should be used so as not to damage sound underlying material.

b. Following the removal of all loose, disintegrated or otherwise defective concrete, the entire exposed surfaces of the structure should be carefully inspected for locations of seepage, internal honeycombed areas, cracks or voids. c.

e.

The bonding surface should be rough, clean, sound concrete or stone. Oil or film of any sort that may reduce the bond should not be permitted. Loose particles, dust and dirt, should be removed.

f.

Sand and water blasting may require containment of dust and/or runoff water. Cracks are to be prepared as specified in Article 14.5.5.

14.5.1.3 Anchorage

1 2

3

In prestressed concrete, extreme care should be taken to avoid any damage to prestressing strands. Exposed strands should be chemically cleaned by an approved method.

d. Thin or feathered edges should be avoided and the boundaries of the areas to be repaired should be square cut or slightly undercut to a depth of 1 inch. For shotcreting, the boundary edges should be 45degree bevel cuts to a depth of at least 1 inch. The maximum depth of removal shall be determined based on an analysis of the existing structure and its condition.

a.

1

Concrete repairs applied less than 1-1/2 inches thick will not require anchorage, unless specified by the Engineer. A bonding compound may be specified.

See Commentary See Commentary

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Concrete Structures and Foundations b. Where new concrete greater than 1-1/2 inches thick and less than 4 inches thick is to be placed, 1/4 inch diameter galvanized expansion hook bolts should be spaced not more than 18 inches center to center on vertical surfaces and not more than 12 inches center to center on overhead surfaces. Each bolt should have sufficient engagement in the sound concrete to resist a pull of 150 pounds. When pried from the wall with a bar inserted under the bend of the bolt, the bend should straighten out without pulling the bolt. c.

The specified spacing of expansion bolts should be based on supporting three times the total weight of suspended concrete and two times the weight of concrete on vertical surfaces. Facilities should be provided for testing the supporting value of the bolts. Each bolt should be set in sound concrete and should be capable of supporting, without loosening, the suspended load indicated in Table 8-14-1. Table 8-14-1. Supporting Loads for Expansion Bolts Diameter of Expansion Bolt in Inches

Load in lb

1/4 3/8 1/2 5/8 3/4

150 400 750 1,200 1,750

d. Any expansion bolt failing to support such load should be reset and tested. e.

Where concrete 4 inches or more in thickness is to be placed, approved expansion bolts should be set where shown on the plans, or in accordance with Table 8-14-2. Table 8-14-2. Expansion Bolt Placement – Concrete 4 Inches or More in Thickness

Thickness of Concrete (Inch)

Spacing in Each Direction Suspended Concrete Inches Diameter at Feet-Inch

Vertical Surfaces Inches Diameter at Feet-Inch

Top Surfaces Inches Diameter at Feet-Inch

4 5 6 7 8

3/8 @ 1-8 3/8 @ 1-5 3/8 @ 1-4 3/8 @ 1-2 1/2 @ 1-7

3/8 @ 2-0 3/8 @ 1-9 3/8 @ 1-8 3/8 @ 1-6 1/2 @ 1-11

3/8 @ 3-0 3/8 @ 3-0 3/8 @ 3-0 3/8 @ 3-0 1/2 @ 3-0

9

1/2 @ 1-6

1/2 @ 1-10

1/2 @ 3-0

10

1/2 @ 1-5

1/2 @ 1-9

1/2 @ 2-0

11

1/2 @ 1-4

1/2 @ 1-8

1/2 @ 2-0

12

1/2 @ 1-3

1/2 @ 1-6

1/2 @ 2-0

f.

Where the thickness of concrete is more than 12 inches, the size, length, spacing and embedment of expansion bolts should be determined or approved by the Engineer.

g.

The exposed end of each expansion hook bolt should have a right angle, or greater, bend for engaging reinforcement.

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h. No isolated area greater than 2 square feet should have fewer than 3 bolts. i.

Where only a single line of bolts is required, the maximum spacing should be 24 inches and the size should be determined by the supported load shown in Table 8-14-1.

j.

Dowels made of deformed steel bars, grouted in, may be used instead of expansion bolts. When dowels are used, the size, spacing and bond capacity shall be the same as that required for expansion bolts. Horizontal dowel holes should be drilled downward on a slope of approximately 1 inch per foot.

14.5.1.4 Placement of Reinforcement 14.5.1.4.1 General Reinforcement should be securely wired to the anchors. The clear distance from the existing concrete to the first layer of reinforcing should be 1-1/2 times the maximum aggregate size, but not less than 1/2 inch. Cover of reinforcement should meet the requirements of Part 2 Reinforced Concrete Design, Section 2.6. 14.5.1.4.2 Shotcrete a.

No reinforcement is required for shotcrete encasement less than 1-1/2 inches thick unless specified by the Engineer.

b. A layer of reinforcement for each 4 inches (3 inches for suspended encasement) thickness of encasement or fraction thereof. Each layer should be 3²´ 3² – W 1.4 ´ W 1.4 welded wire reinforcing. c.

For encasement thicknesses in excess of 4 inches (3 inches suspended), an additional two-way system of No. 3 reinforcing bars spaced the same as the anchors in both directions should be provided. The last layer of wire mesh should be secured by wiring to the bars.

d. Each layer of mesh must be completely encased in the shotcrete or concrete which has taken initial set before the succeeding layer of mesh is applied. e.

Mesh extending around corners or reentrant angles should be bent to a template before securing to anchorage and not sprung or forced into position. At corners, double reinforcing mesh should be provided and extended a minimum distance of 6 inches beyond the intersection of the 2 planes.

f.

When splicing wire mesh is necessary, a lap of 1-1/2 mesh spacings should be required, wired together at intervals of not more than 18 inches.

g.

Where special reinforcement is required for structural strength, engineering plans should be furnished.

14.5.1.4.3 Concrete Reinforcement should meet the requirements of Part 2 Reinforced Concrete Design, Section 2.12 Shrinkage and Temperature Reinforcement (2005). 14.5.1.5 Bonding1 14.5.1.5.1 Slurry Bonding After the bonding surfaces of the old concrete have been prepared as outlined in Article 14.5.1.2, the bonding surface should be kept constantly wet for a minimum of 1 hour immediately prior to application of the bonding 1

1

See Commentary

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coat. In no case should fresh material be applied to a dry surface. The bonding coat should be applied to the damp bonding surface and should be vigorously brushed on to completely fill all surface pores immediately prior to placing the body of the new concrete. The bonding coat should be composed of cement or one part cement to one part fine sand and sufficient water to make a creamy mixture. If required by the Engineer, an approved shrinkage reducing material should be added. The bonding coat should not be troweled, screeded, disturbed or allowed to dry before the next layer of new concrete is applied. 14.5.1.5.2 Other Bonding Agent At locations where positive bond is mandatory, an approved bonding compound should be specified. Since a large variety of bonding products are available, surface preparation and compound application should be in accordance with the manufacturer’s recommendations. 14.5.1.6 Hand Patching Immediately after the bonding coat has been applied, the entire cavity should be filled and finished to true line and surfaced with an approved patching material suitable for hand patching vertically, horizontally or overhead. Application should be in conformance with manufacturer’s recommendations. 14.5.1.7 Cast-in-Place a.

When restoration or encasement is accomplished by placing concrete in between forms and the old surface by gravity or pressure placement, the forms should have sufficient strength to withstand the pressure of the new concrete without yielding appreciably.

b. The concrete should be proportioned per Part 1 Materials, Tests and Construction Requirements. c.

The new concrete should completely fill the space provided and present a surface comparable to the original.

d. Concrete is to be compacted per Part 1 Materials, Tests and Construction Requirements, Article 1.14.6. 14.5.1.8 Shotcrete1 14.5.1.8.1 General Shotcrete is a mixture of Portland cement, fine aggregate and water, shot into place by compressed air. There are two different processes in use, namely the “dry mix” process and “wet mix” process. 14.5.1.8.2 Dry Mix Method a.

Shotcrete should be made of a mixture of portland cement and sand in the proportion of one bag of cement for every 4 cubic feet of sand by volume. The amount of sand should be based on dry, loose measurement with proper correction in quantity for effect of bulking due to moisture content. The sand and cement should be thoroughly mixed dry, passed through a 3/8 inch screen before being placed in the pneumatic apparatus, and placed by pneumatic pressure through shotcrete equipment with proper amount of water applied in the mixing nozzle for the necessary placement consistency. The screened sand and cement should be applied on the surface within one hour after combining them. To avoid voids and reduce shrinkage cracks, shotcrete should be applied as dry as practicable. Suitable prepackaged materials may be used as approved by the engineer.

b. Shrinkage reducing and/or bonding compounds are to be applied as specified by the manufacturer.

1

See Commentary

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c.

The air pressure in the pneumatic apparatus should be maintained uniform and not less than 35 psi while placing the mixed material, with necessary increase in pressure for horizontal delivery distances of more than 100 feet or vertical distances of more than 25 feet. The water pressure applied through the nozzle should be not less than 10 psi greater than the air pressure in the shotcrete machine.

14.5.1.8.3 Wet Mix Method The wet mix method varies from the dry mix method only in that the materials are mixed in a vessel prior to pumping the mix to the nozzle, whereas the mixing with water occurs at the nozzle in the Dry Mix Method. This method may therefore require variations in pressure from those required for dry mixing. 14.5.1.8.4 Application a.

Shooting strips should be employed to ensure square corners, straight lines and a plane surface of shotcrete, except as otherwise permitted by plans or approved by the Engineer. They should be so placed as to keep the trapping of rebound at a minimum.

b. Where no separate bonding agent is used, the surface, particularly porous brick, to which shotcrete is to be applied should be thoroughly wet, without free water, to facilitate bond. c.

At the end of each day’s work, or similar stopping periods requiring construction joints, the shotcrete should be sloped off to a thin edge. No square joints will be allowed. In shooting vertical surfaces, care must be taken in general to begin the shotcrete area at the bottom and complete at the top. A sufficient number of coats should be applied to obtain the required thickness. The thickness of each coat should not be greater than 1 inch, except as approved by the Engineer, and should be so placed that it will neither slough nor decrease the bond of the preceding coat. Where a successive coat is applied on shotcrete, which has set more than two hours, the surface should be cleaned and water blasted.

d. When placing shotcrete, the stream of flowing material from the nozzle should impinge as nearly as possible at right angles to the surface being covered, and the nozzle should be held from 2 to 4 feet from the working surface. e.

Deposits of rebound from previous shooting, whether loose or cemented, should be removed and not covered up. Should any such deposits be covered, they should be cut out and the area reshot.

f.

The final surface of shotcrete should be given either: (1) a thin finishing or flash coat;

3

4

(2) a screeded finish; (3) a rubbed finish; or (4) a brush finish, as specified. 14.5.1.9 Preplaced Aggregate Grouting See Part 1 Materials, Tests and Construction Requirements, Article 1.15.10d. 14.5.1.10 Tremie Placement See Part 1 Materials, Tests and Construction Requirements, Article 1.15.10a.

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Concrete Structures and Foundations 14.5.1.11 Pumping Concrete See Part 1 Materials, Tests and Construction Requirements, Article 1.14.5. 14.5.1.12 Curing and Protection1 See Part 1 Materials, Tests and Construction Requirements, Section 1.18 Curing.

14.5.2 SURFACE REPAIRS USING POLYMER CONCRETES AND POLYMER PORTLAND CEMENT CONCRETES (2006)2 14.5.2.1 Scope a.

Repair should consist of removal of soft, disintegrated or honeycombed concrete; cleaning and preparing the bonding surface; placing the Polymer Concrete or Polymer Cement Concrete; and finishing to true lines and surface.

b. Preloading. Concrete in the repaired area below the neutral axis in prestressed members should be repaired under an externally applied preload. Preload may be applied by means of jacks or a known load. 14.5.2.2 Surface Preparation, Materials and Application Surface preparation materials and application should be in accordance with the manufacturer’s recommendations.

14.5.3 TUCKPOINTING (2006) 14.5.3.1 Scope Repair should consist of the removal of soft, disintegrated or loose grout between masonry units, cleaning the joints and filling the joints with mortar. 14.5.3.2 Preparation All deteriorated mortar, dirt and loose particles should be removed from the masonry joints with hand tools followed by blast cleaning with water or oil free air. 14.5.3.3 Materials a.

Mortar should consist of one part cement to three parts sand with sufficient water to produce a workable mixture.

b. Cement should be Portland cement C150, Type I or as specified by the Engineer. c.

Sand should be fine mason sand with a fineness modulus of not more than 2.0.

14.5.3.4 Procedure a.

1 2

Areas to be tuckpointed should be wet thoroughly to prevent absorption of water from the mortar.

See Commentary See Commentary

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b. All excess material should be removed and the joint tooled to a neat workmanlike appearance.

14.5.4 ARCH LINING (2006) The lining of stone and brick masonry arches with steel liner plates is covered in Chapter 1 Roadway and Ballast, Part 8 Tunnels. Lining with cast-in-place concrete or shotcrete is covered in Chapter 8, Part 11 Lining Railway Tunnels.

14.5.5 INTERNAL STRUCTURAL REPAIRS (2006) 14.5.5.1 Scope1 Internal structural repair of concrete consists of the filling of internal voids and/or restoring the cracked sections to meet original strength with Portland cement grouts or epoxies and reinforcement where required. 14.5.5.2 Cement Grouts 14.5.5.2.1 Preparation Before the grouting operation is started, all defective materials should be removed and the entire surface should be thoroughly inspected for points of leakage and indications of voids. Inserts for grouting should be so located and set that the pressure grout will reach all voids and paths of leakage. All defective exposed joints and cracks in the structure should be chipped out, then thoroughly cleaned of all foreign materials by means of high pressure air or water. The joints, cracks and disintegrated areas should be restored to the original surface with hand pointing or shotcrete.

1

14.5.5.2.2 Grout Holes in Stone a.

Before drilling of the grout holes is started, the test drillings should be made completely through the masonry to determine the thickness of the masonry. From the test drillings, the proper depth of grout holes should be determined in order that grout holes are not drilled completely through the masonry.

b. Grout holes should be drilled at regular intervals, staggered to include approximately 25 square feet of surface area per hole or at such other locations as may be specified. In cases of arch rings, the holes should be drilled diagonally to intercept the longitudinal joints (parallel to the barrel) and staggered at such intervals as to include approximately 12 square feet of surface area per hole. Holes should be 1-1/2 inches minimum diameter for Portland cement grout and should be drilled to such a depth, and in such manner, as necessary to intercept joints and internal voids, to completely consolidate the structure. Holes which have been drilled completely through the structure should not be used for pressure grouting and these holes must be completely plugged before grouting begins. c.

1

On structures, or parts of structures, of one stone thickness, the grout holes should be drilled in such a manner as to intercept the horizontal joints where possible; however, if, due to insufficient clearance, the holes cannot be drilled through the horizontal joints, they should then be drilled so as to intercept the vertical joints. The holes in the courses of masonry below ground line should be drilled diagonally downward at various angles to the natural foundation below the masonry, so that the bottom courses and any underlying cavities, including cavities in or under timber grillages, should be completely filled.

See Commentary

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Concrete Structures and Foundations 14.5.5.2.3 Grout Holes in Concrete For Portland cement grout 1-1/2 inches diameter grout holes should be drilled to a depth and spacing as necessary to provide maximum dissemination of the pressure grout throughout the repair areas. Prior to pressure grouting, the chipped areas should be restored as previously specified, provisions being made to extend the grout holes through the replacement material for grouting after the exposed surfaces are sealed. 14.5.5.2.4 Portland Cement Grout Mixture a.

For stone masonry the pressure grout mixture should consist of one part of cement, one-half part of sand and, if required, an approved type of shrinkage reducing material. The amount of sand to be used in the grouting mixture should be determined by starting the grouting operation with neat cement grout and adding sand in gradually increasing proportions until the optimum ratio of sand to cement has been reached which will give a free flowing grout.

b. If it is found through application of the above that the addition of sand retards the free flow of the grouting material, the sand should be omitted. c.

For concrete, the pressure grout should consist of neat cement grout only, and, if required by the Engineer, an approved type of shrinkage reducing materials.

d. Polymer grouts may be used for concrete or stone masonry, as specified by the Engineer. e.

Other suitable prepackaged materials may be used if approved by the Engineer.

14.5.5.2.5 Grouting Procedures for Portland Cement Grouts a.

Grout inserts should be set in drilled holes and the interior voids cleaned with water, prior to the application of the pressure grout.

b. The grout should be pressure induced into the internal voids and joints of the structure to fill them completely. c.

Grout should be applied by pumping or gravity pressure.

d. Excessive pressure should be avoided to prevent damage to the structure. e.

Grouting should be started at the lowest row of holes and at the hole nearest the center line of structure.

f.

If grout appears in adjacent holes at the same elevation, these holes should be temporarily plugged and grouting continued in the original hole until grout appears at the next adjacent hole at the same elevation or at the next line of holes above the one being grouted. When this condition occurs, grouting of the original hole should be discontinued and the grout line moved to the last hole at the current elevation at which grout appeared, and the same procedure followed until all holes in the current line have been grouted, at which time grouting should proceed in a like manner along the next line of holes above, etc., until the entire structure has been completely filled.

g.

During the course of all grouting operations, extreme care should be given to observing the surrounding ground, track subgrade, ballast and the stream bed for the breaking out of grout, and when such breaking out occurs, the grout line should be moved to some other part of structure. Grouting may be resumed in the original location after the elapse of 24 hours. In grouting foundations, pressure grout should be applied to the various holes in rotation. The above program should be followed until the grout is brought up into the masonry.

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h. When grouting foundations founded on rock, care should be taken to watch for movement of the track structure caused by the lifting of all or a portion of the structure. 14.5.5.3 Epoxy Injection 14.5.5.3.1 General a.

Epoxy injection is generally applicable to cracks ranging in width from 0.003 inch to 0.25 inch. Injection of epoxy into cracks wider than 0.25 inch should be approved by the Engineer.

b. Certain members, especially prestressed members, may require preloading during injection. c.

Cold weather epoxy injection may require special procedures and materials.

14.5.5.3.2 Preparation a.

The area surrounding the crack should be cleaned of efflorescence, deteriorated concrete and other contaminants that may be detrimental to adhesion of the epoxy gel. If unsound or deteriorated concrete is located adjacent to the crack, which could prevent the complete injection of the crack, the unsound or deteriorated concrete should be removed prior to the injection.

b. Cracks should be flushed with water under pressure to remove debris and other contaminants. 14.5.5.3.3 Injection Ports a.

1

Install the injection ports at appropriate intervals to accomplish full penetration of the injection resin. The spacing of the injection ports should be determined by the size of the crack and the depth of the concrete substrate.

b. Injection ports should be designed for the intended use and should be acceptable to the epoxy manufacturer. c.

3

Injection ports should have the capability of being positively capped and sealed following the injection work.

d. The injection ports should be installed using one or more of the following methods:

4

(1) Surface Mounted Injection Ports: (a) Center the injection port over the crack and secure in place using the epoxy gel. (b) Completely seal the exposed crack located between the injection ports and other area, as required to prevent leaking of the resins, using epoxy gel. (c) If the crack extends through the member, and is accessible, install telltale injection ports on the opposite side and seal all exposed areas of the crack. Generally, the spacing of the telltale injection ports should be between 12 inches and 24 inches. (2) Drilled-In Injection Ports:1 (a) The holes should be drilled a minimum of 5/8 inch deep. Exercise care so as not to drill beyond a crack which may be running at an angle to the surface. 1

See Commentary

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(b) The injection ports should be inserted into the drilled holes about 1/2 inch, allowing for a small reservoir below the injection port. Secure the injection ports into position using epoxy gel. Seal the exposed crack using the same procedures as described above. (3) Injection Ports Mounted Against a Head of Water: (a) For cracks that have water running from them, use an hydraulic cement (fast setting) to set the injection ports, and seal the crack. (b) After the hydraulic cement has cured, seal the cracks and injection ports by overlapping the hydraulic cement about 1 inch on either side using epoxy gel. 14.5.5.3.4 Curing of Epoxy Crack Surface Sealer Allow all bonded ports and sealed cracks to cure overnight at temperatures of 50 degrees F or above. Should temperatures below 50 degrees F exist, additional cure time may be required. Under these circumstances, it will be necessary to consult the manufacturer for proper cure times. In any event, pressure injection operations should not commence until the epoxy gel has adequately cured and has been deemed capable of sustaining pressures of the injection process. 14.5.5.3.5 Materials and Equipment a.

The following minimum properties should be required of all epoxy used in the repair of the damaged concrete: (1) Epoxy injection material should meet requirements of ASTM C881, Type IV, Grade 1, Class A, B or C. (2) Epoxy crack surface sealant gel (paste type) should meet the requirements of ASTM C881, Type 1, Grade 3, Class A, B or C. (3) It is recommended that the ratio of the components should be between 1:1 and 2:1 by volume, with similar viscosities of components.1 (4) The colors of the components should be distinctly different, and when mixed in proper ratio yield a distinctly different third color. (5) All injected epoxies should be wet bonding agents.

b. Epoxy injection equipment should be the automatic mixing and dispensing type. The equipment should include positive displacement pumps inline pressure gauges, pressure gauges on the mixed materials at the point of injection, and positive connection to the injection ports. The unit should be capable of delivering 125 psi dynamic fluid pressure at the point of injection at a minimum flow rate of 2 gpm. The equipment should indicate when the supply of one component has been exhausted to prevent injection of only a single component. 14.5.5.3.6 Injection of Epoxy a.

After proper curing of epoxy bonded ports and crack surfaces, commence pressure injection operations.

b. Take ratio checks as follows: The mixing head of the injection equipment should be disconnected and the two adhesive components should be pumped simultaneously into separate calibrated containers. The 1

See Commentary

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amounts discharged into the calibrated containers simultaneously during the same time period should be compared to determine the mix ratio. c.

After the test has been completed at a 200 psi discharge pressure the procedure should be repeated for 0 psi discharge pressure.

d. The ratio test should be run for each injection unit at the beginning of each day that unit is used. e.

Samples of the mixed epoxy should be taken before commencing work each day, at least once every hour during injection work, and each time the mixing head is flushed with solvent. Time, dates and curing of the samples are to be noted. The samples before work and after flushing should be from the injection nozzles. Samples during work should be from injected ports.

f.

Commence pumping at the lowest point possible, or first injection port in a line, whichever is applicable. Continue pumping until the epoxy appears at one or more of the next ports in line. When this occurs, stop pumping, cap the port through which liquids were being injected and move up to the next port in line from which liquids were observed to flow. Repeat this operation until all cracks have been filled to refusal.

g.

During installation pressures should normally be limited to a maximum of 100 psi.1

14.5.5.3.7 Cure Allow injected epoxies to cure overnight, or in accordance with the manufacturer’s directions for those temperatures prevailing during application. Generally, at temperatures above 50 degrees F, overnight cure is adequate.

1

14.5.5.3.8 Port Removal and Clean Up After adequate curing of injection epoxy, all ports and the epoxy gel should be ground smooth to eliminate any sharp edges or protrusions. No epoxy materials or injection ports should extend beyond the surface of the existing concrete.

3

14.5.5.3.9 Record Cores Obtain record cores of sufficient diameter (2 inches to 4 inches), and length (10 inches to 30 inches) from each member to determine the completeness of the injection and the bond. Each core should be identified. All core holes should be filled prior to completion of the work at the structure. Location of the core should be at the discretion of the Engineer. 14.5.5.4 Reinforcement of Cracks2 14.5.5.4.1 Stitching The integrity of a cracked concrete section can at times be restored by stitching. The process involves the application of steel reinforcing bars (stitching dogs or staples) across a cracked section (see Figure 8-14-1) on the surface of the members. Where surface appearance is a consideration, the stitches may be installed below the finished surface. The stitching dogs should be of various lengths, spacing and orientation so that a single plane is not overstressed. Their spacing should decrease near the ends of the crack to avoid stress concentration. The ends of the stitching dogs should be grouted with a non-shrink or expanding mortar so that

1 2

See Commentary See Commentary

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a proper anchorage is achieved. It should be realized that repairs of this type may cause the cracking to migrate to another portion of the structure.

STAPLES

Figure 8-14-1. Repair of Cracks by Stitching 14.5.5.4.2 Pinning Cracks may be immobilized by drilling holes through the concrete so as to intercept the crack and grouting reinforcing into them as specified by the Engineer. (See Figure 8-14-2.)

Figure 8-14-2. Repair of Cracks by Pinning 14.5.5.4.3 External Reinforcing a.

Placing external reinforcing across the crack and extending for a substantial length can distribute the stresses causing the crack. The stresses at the ends of such reinforcing should be considered to eliminate simply relocating the cracked condition.

b. Tensile stress cracks can be arrested by removing the stresses by tensioning the external reinforcement, thereby compressing the member. Cleaned cracks can be closed by inducing a compressive force sufficient to overcome the tension and to provide a residual compression.

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c.

The principle is similar to stitching and the problem of crack migration must be considered in this process also.

d. Anchorage is required for the external post-tensioning. Some form of abutment is needed such as a strongback bolted to the face of the concrete (see Figure 8-14-3 and Figure 8-14-4).

Figure 8-14-3. External Stressing to Correct Cracking of Slab

1

Figure 8-14-4. External Stressing to Correct Cracking of Beam

3

14.5.5.4.4 Banding Members which are exposed around their perimeter may have steel members placed around them to arrest movement in the crack. These bands should be anchored at regular intervals to the member.

4

14.5.6 NON-STRUCTURAL CRACK REPAIR (2006) 14.5.6.1 Sealing Cracks or Joints a.

Where there may be movement in the structure, by reason of expansion, contraction or vibration, structural joints subject to leakage may be sealed by using a water stop such as a 10 inch, 16 ounce, coldrolled copper expansion plate, preformed along the longitudinal centerline of the copper to produce a modified “V”-shape as shown in Figure 8-14-5, or a half round 2 inches diameter PVC pipe, secured in place with straps and anchors as shown in Figure 8-14-6, or similar noncorrosive materials with the necessary flexibility as approved by the Engineer.

b. The concrete or stone should be chipped out sufficiently to provide space for installation of a watertight joint between the water stop and concrete and also for a channel for water seepage, properly drained at the base of crack or joint, or as otherwise specified by the Engineer.

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Figure 8-14-5. Detail Copper Plate Joint Sealing

Figure 8-14-6. Detail PVC Pipe Joint Sealing c.

The expansion joint between the finished surface and the water stop should be filled with a flexible joint sealing material. The patch should be reinforced and placed as previously specified.

d. Non-leaking cracks or joints where movement in the structure by reason of expansion, contraction or vibration is apparent, may be sealed with a flexible joint sealing material. Where it has been determined that no movement exists, a rigid compound can be used. 14.5.6.2 Surface Crack Repairs Routing and sealing may be used to make surface crack repairs where surface appearance is not a consideration. This method consists of enlarging the crack along its exposed face with a concrete saw or hand pneumatic tools to open the crack sufficiently to receive the sealant. Minimum surface width should be 1/4 inch.

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The surface of the routed joint should be clean and dry before placing the sealant. Sealant and installation should be according to the sealant manufacturer’s recommendation.

14.5.7 REINFORCEMENT SPLICES (2006) 14.5.7.1 Scope Severely damaged reinforcing in members may be repaired by splicing. Where damaged reinforcement is spliced, the repairs should be designed so that there is no change in stress due to the damage. Preloading of the member may be required to achieve this, depending on the repair method used. The strength of the splice should meet the required ultimate strength of the member. 14.5.7.2 Internal Splicing of Prestressing Tendons or Conventional Reinforcement a.

Strands or bars should be spliced by attaching a coupling device to the severed ends. The ends should be trimmed to sound, undamaged material prior to splicing. The strand or bar should be stressed by tightening the coupling device until the desired stress is reached.

b. Consideration should be given to fatigue and space limitations in selecting this method of repair for multiple strands or bars. c.

Splices in conventional reinforcing may be accomplished by lap splices. Sufficient bar length must be exposed for development of the splice and preloading may be required.

1

14.5.7.3 External Post Tensioning a.

External post tensioning should consist of threaded bars or prestress strands applied to the member. The applied post tensioning force should be calculated based on the internal stresses required under live and dead loads. Location of the anchorage for the post tensioning system should be based upon the stresses at the transfer of load into the original member.

3

b. Anchorages typically consist of corbels attached to the concrete with expansion bolts and bonding agents. Care should be taken to ensure that existing tendons or bars are not damaged in the placement of anchor bolts. 14.5.7.4 External Metal Splice Sleeves a.

Metal sleeve splices consist of bonding steel plates across the damaged area with sufficient bond length to develop both the damaged reinforcing and the metal plates.

b. Concrete surfaces in the bond area must be clean. Metal plates are galvanized steel with the contact surface scored vertically by wire brushing. c.

The plates are bonded to the concrete by pressure injection by epoxy resin. A 1/16 inch gap should be left between the concrete and the steel. The gap should be maintained by use of metal spacers. The edges of the splice sleeve should be bolted to the concrete taking care not to damage existing reinforcing. Sufficient mechanical fasteners should be used to transfer the stresses from the concrete to the sleeve.

d. Damaged concrete areas within the splice area should be filled with concrete. See Figure 8-14-7.

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Concrete Structures and Foundations

Figure 8-14-7. External Splice Sleeve

SECTION 14.6 REPAIR METHODS FOR PRESTRESSED MEMBERS 14.6.1 CRACKS EXIST WITH NO SIGNIFICANT SECTION LOSS AND NO TENDON DAMAGE (2006)1 Cracks should be repaired by epoxy injection. Cracks in the precompression zone should be repaired under preload if live load alone applied to the section produces a tensile stress exceeding the bond strength or the base concrete allowable tension.

14.6.2 THERE IS MINOR SECTION LOSS, BUT NO TENDON DAMAGE (2006) 14.6.2.1 Minor Concrete Nicks, Spalls, or Scrapes (Adequate cover remains and there was not significant section loss)2 Clean and seal minor defects with penetrating sealer to prevent moisture intrusion.

1 2

See Commentary See Commentary

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Repair and Rehabilitation of Concrete Structures 14.6.2.2 Gouges Across Bottom Flange with Loss of Cover (No Significant Section Loss)1 a.

Girder designed for zero tension in bottom flange concrete under live load. Clean and seal minor defects with penetrating sealer to prevent moisture intrusion. Additional protection may be provided by patching with an acceptable concrete patching material.

b. Girder designed for tension in bottom flange concrete under live load. Clean and seal minor defects with penetrating sealer to prevent moisture intrusion. If patching is used to provide additional protection, the patch should be applied under preload. If under preload it is found that a crack has propagated from the gouge either the cracked concrete should be removed or the crack repaired by epoxy injection. The gouge should be patched with an approved concrete patching mortar and the preload removed after the patch has reached adequate strength. (This applies to existing girders that may have tension in the bottom flanges. Current standards do not allow this design).

14.6.3 SHATTERED CONCRETE AND/OR SIGNIFICANT SECTION LOSS, BUT NO TENDON DAMAGE (2006) a.

Replacement of lost concrete should be executed under preload if the repaired section would be subject to tensile stresses when live load is applied.

b. In preparation of the surface for placement of repair material and in removal of damaged concrete extreme care must be taken to avoid any damage to prestressing tendons. Tendons should be chemically cleaned.

1 14.6.4 THERE IS SECTION LOSS AND TENDON DAMAGE (2006) 14.6.4.1 General2 Repairs should be designed so there is no change in stress due to the damage. Preloading the member may be required to achieve this end. The ultimate strength of the splice should always meet or exceed the required ultimate strength. Splicing of reinforcing is covered in Article 14.5.7 Reinforcement Splices (2006).

3

14.6.4.2 Few Tendons Are Damaged3 a.

Tendons should be repaired by internal splicing. After tendons are repaired the concrete is repaired, usually under preload.

4

b. Repair of more than 2-4 tendons by this method is usually difficult. 14.6.4.3 Several Tendons Are Damaged (6-8 Tendons)4 The span may be repaired with external post-tensioning. Due to the externally applied tensioning, preload may not be required. The damaged concrete may be repaired utilizing appropriate patching methods. Protection of the post-tensioning system must be considered.

1

See Commentary See Commentary 3 See Commentary 4 See Commentary 2

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Concrete Structures and Foundations 14.6.4.4 Multiple Tendon Damage with Large Section Losses1 Repairs can be accomplished with metal splice sleeves. The damaged concrete areas within the splice area are filled with concrete. Preloading is not required if the stresses at the top and the end of the sleeve are within the allowable.

14.6.5 MEMBER IS DAMAGED BEYOND REASONABLE REPAIR (2006) Replacement of some severely damaged members may be the only solution.

14.6.6 MEMBER HAS INADEQUATE STRENGTH (2006) External post-tensioning and metal sleeve splices may be used to increase the strength of members.

14.6.7 SUMMARY (2006)2 The type of repair must be determined by the extent and type of damage, the time the structure will be out of service, the repair cost, durability, and the ultimate load capacity of the repair. Combinations of repairs such as internal splicing with external post-tensioning should also be considered.

1 2

See Commentary See Commentary

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C - COMMENTARY -2006The purpose of this part is to furnish the technical explanation of various paragraphs in Part 14 Repair and Rehabilitation of Concrete Structures. In the numbering of paragraphs of this section, the numbers after the “C-” correspond to the section/paragraph being explained.

C - SECTION 14.1 SCOPE (2006) (REFERENCES 5 AND 29) a.

The techniques and materials described in this chapter are applicable to cast-in-place and precast concrete, stone, and concrete and brick masonry. (1) UNDERWATER REPAIRS General - Repairs to submerged concrete elements can generally be performed by divers working underwater or by dewatering the work area and using conventional above water repair techniques. Most repairs can be satisfactorily completed below water, if appropriate preparation and installation procedures are followed. Underwater repairs, however, will generally take longer and be more expensive than comparable work done in the dry. Regardless, underwater repairs are often more cost-effective in consideration of the costs to dewater the repair site. The primary techniques available to permit work to be carried out under dry conditions are sheet pile cofferdams, earthen dikes, and portable dams. Because underwater repairs are specialized and more difficult to inspect, prequalification of the underwater contractor is recommended. Whether repairs are performed submerged or in the dry, all environmental regulations should be complied with. Final acceptance of below water repairs should be made in conjunction with an independent underwater inspection.

1

(2) UNDERWATER REPAIR OF CONCRETE

3

Materials - For underwater placement of concrete, durability and workability are usually as important as strength and those properties can be enhanced with the proper admixtures. For below water applications, the most important factor in achieving concrete durability is low permeability. This is accomplished with low water/cement ratio, the use of pozzolans, and good consolidation. Improper concrete workability will also adversely affect durability.

4 Specialized concrete mix designs, which differ for marine or freshwater applications, should be used to provide a durable, long lasting repair. Aggregates should themselves be durable, non-reactive and of the appropriate size for the means of concrete placement. Admixtures, including water reducers, air entrainers, pozzolans, retarders, and anti-washout additives, are available to assist concrete mixes in satisfying particular requirements. However, their use should be checked for the compatibility of those to be used together, as well as suitability for the means of concrete placement and the specific repair parameters. The implementation of trial mixes and placement is recommended prior to the performance of the repairs. Water reducers are usually used to obtain low water / cement ratios. Air entraining should be used for freeze-thaw exposures; however, it may not be suitable for other applications since it can increase permeability. The use of pozzolans (such as fly ash and silica fume) will aid in reducing permeability and susceptibility to sulfate attack; however, rate of strength gain will vary and moist curing will be needed for a dewatered application. Anti-washout admixtures (AWA) assist in retaining concrete mix fines during underwater placement, and can be used in conjunction with water reducers, rich mixes, and pozzolans to obtain maximum benefits. AWA's can have disadvantages, including high cost, sensitivity to mix changes, and incompatibility with other admixtures, so their use should be thoroughly investigated. © 2011, American Railway Engineering and Maintenance-of-Way Association

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When steel reinforcement is used for concrete repairs in water related applications, a dense concrete and adequate cover are imperative. Potential problems related to the concrete reinforcement can also be lessened with the use of epoxy coated, galvanized, stainless steel, fiberglass or composite reinforcement. Corrosion inhibitors, such as calcium nitrite, can also be added to the concrete to lower the corrosion potential of the reinforcement. Methods - Concrete substructure repairs made underwater can address material deterioration and/or undermining. For relatively small and shallow areas of concrete deterioration, hand-patching techniques can be used for placement of repair mortar above and below water. Materials commonly used for hand patching applications include mortars made with portland cement, hydraulic cement, epoxies or polymers, with the hydraulic mortars often having the smallest reduction from their dry bond strength when used underwater. For larger areas to be repaired, rigid or flexible forms, constructed from a variety of materials and designed to either stay-in-place or be removed, can be used for the placement of the mortar. Materials used for rigid forms include wood, steel, fiberglass and concrete, whereas flexible forms include fabric pile jackets, fabric bags and plastic membranes typically intended to be left in place. Grout filled fabric bags can be used to fill large irregularly shaped voids, including those created by undermining, when outward appearance is not a concern. Prior to any placement of repair materials, the affected area should be properly prepared by removing all unsound concrete and cleaning corrosion from any exposed reinforcement. Preparation techniques are similar to those used above water, including pneumatic and hand hammers, wire brushes, and water or abrasive blasting which can be used below water. Proper preparation may also include the installation of replacement or supplemental reinforcement and expansion or grouted anchorage mechanisms for the repair mortar/concrete. Underwater placement of concrete can be accomplished by tremie or pumping methods, with the incorporation of anti-washout admixtures in the concrete. Preplaced aggregate within the forms may also be used with a pumping application to enhance durability and reduce shrinkage of the repair. Cracks below water can be structurally repaired with the injection of specially formulated, water insensitive resins that contain particular polymers not found in true epoxies. The same injection techniques used above water are applicable underwater; however, cracks must be adequately flushed with clean water or cleaning agents for proper resin bond and penetration. Special resin compositions are required for water temperatures below 55°F (13°C). Hand applied or formed mortar repairs and crack injection can also be used for concrete piles below water. Synthetic membrane pile wraps can be used to inhibit further deterioration of concrete piles by creating a barrier against chloride penetration and chemically aggressive waters. The structural repair of a concrete pile can be accomplished with any of a number of pile jackets or encasements. Jacket repairs should typically incorporate reinforcement around the pile within the forming system, which can consist of either rigid or flexible forms usually intended to stay-in-place. Ideally, the forms should be filled by pumping of the grout from the bottom up, with underwater monitoring to ensure uniform consolidation during placement. Undermining of substructure footings caused by channel bottom scour can be repaired with grout bags, grouted stone, or formed concrete used to fill the void under the footing. Grout bags can be used to occupy the void entirely, or assembled as a form to contain the concrete that is placed behind to fill the void. Stone of the appropriate size can also be used to fill around and within the void, with grout again being placed behind and among the stone. Placement of the cement grout within the forms, bags or stones at the undermining can be accomplished by either a tremie or pumping process, with antiwashout admixtures and underwater monitoring for leakage being incorporated. Repairs to undermined substructures should be analyzed for effects on scour potential and the structural stability. The installation of scour countermeasures in conjunction with the repairs should be considered. © 2011, American Railway Engineering and Maintenance-of-Way Association

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(3) UNDERWATER REPAIR OF MASONRY Materials - For underwater repair of masonry, stone of good, durable quality should be specified. Specifications for stone should include minimum allowable compressive strengths, and limits on maximum porosity and bedding planes or cracks. Cut stone replacement blocks should be aged to allow stress relaxation and moisture equilibrium, as well as to allow time for the development of any cracks, which can occur in stone quarried by blasting. Mortars for masonry joints are typically made of sand, cement and lime with newer compositions incorporating polymers and/or fine aggregates. Older mortars were generally softer than those used in current practice, and new mortars should attempt to match existing properties to maintain structure flexibility. Hard mortars should be avoided since they are more inclined to crack or cause edge spalls. Methods - Underwater masonry repairs can address both stone and mortar joint deterioration. Common repair techniques include stone replacement with concrete to fill voids created by missing stones; mortar joint repointing; and encasement of a masonry substructure unit with concrete. Stone replacement is typically incorporated when appearance is a concern. Stones can also be replaced with concrete which is less expensive, but also less attractive. The stone void can be filled by pumping concrete behind formwork that should include a venting mechanism to completely fill the void. The repair of deteriorated masonry joints can be accomplished by hand-applied mortar. The joints should first be cleaned of all loose and unsound material, dirt and marine growth. Hand-applied mortar repairs below water are conducted in the same manner as above water, with repointing accomplished with a trowel or squeeze bag, although hydraulic cement mortars are often used underwater. Where joint strength is not a concern, caulk may be used in the joint to arrest further deterioration of the mortar. For deeper joint problems, joints can also be pressure-grouted with cement grout or epoxy after an exterior seal is installed along the joints. To restore deteriorated areas, as well as to afford future protection, masonry substructure units can be encased with concrete, either partially or completely. Dowels should be used to hold and aid in supporting the encasement. The methods for the placement of concrete for encasements, as well as for stone replacements, should be consistent with the recommendations for underwater concrete repairs.

1

3 C - SECTION 14.2 DETERMINATION OF THE CAUSES OF CONCRETE DETERIORATION (2006) a.

Several factors contribute to the deterioration of concrete. These include:

4

(1) Lack of quality in the original concrete and/or its placement can be caused by deficiencies in: (a) Quality of materials such as: improperly stored or handled cement; reactive, porous or soft aggregates; contaminated water; or inappropriate admixtures or combinations of admixtures (b) Mix design and proportioning (c) Workmanship, placing, finishing or curing (2) Deficiency of reinforcement such as: (a) Design deficiencies (b) Inadequate or improper details

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(c) Damaged coating on epoxy coated reinforcement (d) Insufficient concrete cover (3) Properties of surrounding environment including: (a) Use of deicing agents (b) Alkali soil or water (c) Industrial chemicals (d) Marine environment (4) Inadequate structural capacity due to: (a) Excessive loads (b) Design deficiencies (c) Inadequate or improper details (d) Inadequate consolidation (5) Physical damage due to: (a) Impact (b) Abrasion from ice, stream flow, traffic (c) Settlement of the foundation (d) Freeze-thaw cycles (e) Fire (f) Seismic activity (g) Wind (h) Storm

C - SECTION 14.3 EVALUATION OF THE EFFECTS OF DETERIORATION AND DAMAGE C - 14.3.1.3 Non-Destructive Tests a.

For determining the extent of concrete or masonry deterioration, the following are some of the nondestructive techniques available.

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(1) For surface conditions, visual inspection can be used to identify the location and size of cracks, voids, scaling, spalls, delaminations, and exposed (corroded) reinforcement. (2) For internal conditions and subsurface deterioration, conventional testing methods include: (a) Audio methods for detection of cracks, voids and delaminations require the use of hand tools, including hammers, steel rods and chains, which are used for striking the structure to detect sound differentials between good and defective ("hollow" sounding) material. (b) Electrical methods for evaluation of reinforcement corrosion activity include the use of half-cells or multiple electrode systems, which measure resistance and potential differences. The method requires connection be made to an exposed section of steel reinforcement. (c) Impulse radar uses electromagnetic wave (radar) reflection to detect voids, measure material thickness, and evaluate presence and location of embedments (reinforcement) in structures. This method is affected by moisture in the concrete or masonry, and relative measurements should be correlated to known dimensions. (d) Infrared thermography uses heat flow through structures to determine anomalies such as voids and delaminations. (e) Magnetic methods for determining location, size and depth of reinforcement include the use of pachometers or R-meters that make measurements based on the principles of induction. (f) Stress wave reflection/refraction methods, including pulse-echo, impact-echo and stress wave refraction, introduce a stress pulse into the structure, and reflections of the stress waves denote material flaws or interfaces such as voids, cracks, and delaminations. (g) Rebound (impact) hammers use a spring-loaded weight impacted against the structure, with the amount of rebound being a measurement of material hardness and strength. This commonly used method is inexpensive, but results can be affected by surface conditions, material moisture content and aggregate type. (h) Ultrasonic pulse velocity methods use measurements of the time for a sound wave to travel to and from a reflection surface (backside of a structure or internal discontinuity) to determine material thickness and to identify the presence and location of voids, cracks or delaminations. This method is affected by material density and component make-up, and relative measurements should be correlated to known dimensions.

C - 14.3.2 RESULTS OF EVALUATION (2006) Both cost-effectiveness of the repair and the business costs of the time impacts on rail operations should be considered in evaluating a course of action.

C - SECTION 14.4 PRINCIPAL MATERIALS USED IN THE REPAIR OF CONCRETE STRUCTURES C - 14.4.8 NON-SHRINK GROUTS (2006) Non-shrink grouts are available in a wide variety of compositions for special purposes. This results in highly variable properties of the products. The variables include flowability, resistance to chemical attack, set time, rate of strength gain, ultimate strength and impact resistance. No single product is applicable for all cases. Product should be checked for suitability of application. © 2011, American Railway Engineering and Maintenance-of-Way Association

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C - SECTION 14.5 REPAIR METHODS C - 14.5.1 SURFACE REPAIRS USING PORTLAND CEMENT MATERIALS (2006) C - 14.5.1.1 Scope b. Preload consists of the application of external loads during the repair process to restore the prestressing forces in members where the prestress has been lost due to damage. If the prestress is restored to a level less than the original design level, the capacity of the member should be evaluated at the reduced level of prestressing. C - 14.5.1.2 Preparation Proper preparation of the surfaces to be repaired is critical to the success of the repair. Failure to provide a sound, clean surface prior to application of repair material is a common cause of failure of repairs. C - 14.5.1.5 Bonding When using bonding agents, timing can be critical. Extended exposure of the bonding agent prior to application of the new material may cause failure of the bond. C - 14.5.1.8 Shotcrete The successful application of shotcrete requires experience and knowledge. The use of an experienced, qualified crew is recommended, especially in the nozzleman position. C - 14.5.1.12 Curing and Protection Curing of cast-in-place concrete and shotcrete repairs may be more critical than for concrete in new construction. Where there is an existing concrete or masonry substrate, shrinkage is limited to the repair material only and cracking may result. In addition, the substrate may pull water from the repair material, reducing the available water in the mix. In the case of shotcrete, which has a low water cement ratio, there is no form to reduce moisture loss further increasing the need for protection from drying during the curing process.

C - 14.5.2 SURFACE REPAIRS USING POLYMER CONCRETES AND POLYMER PORTLAND CEMENT CONCRETES (2006) Polymer concrete mixes may contain unpolymerized chemicals that can be hazardous. Particular attention should be given to the ingredients and handling instructions. Many of these materials have a very rapid strength gain, high strengths and high impact capacity. These features make these materials useful where load bearing concrete must be replaced in short time frames. The particular characteristics of the materials vary from product to product. The characteristics of the product should be evaluated before use.

C - 14.5.5 INTERNAL STRUCTURAL REPAIRS (2006) C - 14.5.5.1 Scope Care should be taken in the choice of whether to use portland cement grouts or epoxy for injection. The two materials have different characteristics and costs. Cement grouts are generally thicker and considerably less

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expensive, making them appropriate for applications where large internal voids, large cracks and a pathway to the earth fill behind the member are present. Where high strength is important, cracks are thin and the material can be well contained in the crack, epoxy materials are appropriate. C - 14.5.5.3 Epoxy Injection C - 14.5.5.3.3 Injection Ports d. (2) Care should be taken to prevent concrete dust generated during drilling from plugging the crack. A vacuum attached to the drill and hollow drill bits should be used to remove the dust as drilling occurs and prevent it from blocking the flow of the epoxy. C - 14.5.5.3.5 Materials and Equipment a. (3) Where one component is used in a high ratio to the other component it is difficult to assure even mixing and pockets of unmixed materials may result. When this occurs the epoxy may never jell or reach the desired strength. C - 14.5.5.3.6 Injection of Epoxy g.

Injection pressures above 100 psi (0.7 MPa) are not recommended as the pressure could cause further damage to the member. If the normal pressures are not sufficient to cause penetration of the materials into the cracks, a lower viscosity epoxy should be considered.

C - 14.5.5.4 Reinforcement of Cracks

1

Injection of materials into a crack should not be considered to restore the tensile capacity of the concrete. Where tension is to be transferred across the crack, reinforcement should be installed to carry the tension. The selection of the type of reinforcement should consider where the tension forces are to be transferred. The reinforcement should continue to a point where the existing capacity of the structure can resist the forces, with proper consideration to development of reinforcement.

3

C - SECTION 14.6 REPAIR METHODS FOR PRESTRESSED MEMBERS (REFERENCES 60 AND 61) C - 14.6.1 CRACKS EXIST WITH NO SIGNIFICANT SECTION LOSS AND NO TENDON DAMAGE (2006) The application of preload should be investigated in conjunction with concrete repairs. Applying preload prior to epoxy injection can result in live load stresses no greater than original.

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Figure C-8-14-1. Preloading

C - 14.6.2 THERE IS MINOR SECTION LOSS, BUT NO TENDON DAMAGE (2006) C - 14.6.2.1 Minor Concrete Nicks, Spalls, or Scrapes (Adequate cover remains and there was not significant section loss) The application of two coats of a penetrating sealer is recommended to prevent moisture intrusion or other corrosive elements to the prestressing steel. C - 14.6.2.2 Gouges Across Bottom Flange with Loss of Cover (No Significant Section Loss) Gouge patches should attain required strength prior to removal of preload.

C - 14.6.4 THERE IS SECTION LOSS AND TENDON DAMAGE (2006) C - 14.6.4.1 General Impact damage may cause sweep (lateral curvature in the bottom flange) or abrupt lateral curvature caused by the combination of torsional and transverse flexural stress induced by tendon eccentricities when strands are broken on one side of a girder. It may be possible to jack the tension flange into alignment and hold it using an additional diaphragm.

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Repair and Rehabilitation of Concrete Structures C - 14.6.4.2 Few Tendons Are Damaged One advantage of internal strand splices is that they restore strength internally. Combined with preloading, the girder should be restored to its original condition. C - 14.6.4.3 Several Tendons Are Damaged (6-8 Tendons) Jacking corbels may be used to secure the ends of post-tensioned rods. The strength of the corbels will generally control the number of severed strands that can be spliced by post-tensioning. Between corbels, the posttensioning rods should be grouted after post-tensioning inside of a conduit to protect the rods.

1

3 Figure C-8-14-2. External Post-Tensioning Section Between Corbels C - 14.6.4.4 Multiple Tendon Damage with Large Section Losses The use of metal splice sleeves does not restore prestress unless preloading is used. Intermediate cracks which are covered by the splice should not reduce structure integrity or durability.

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Figure C-8-14-3. Metal Splice Sleeve

C - 14.6.7 SUMMARY (2006) For independent precast members, replacement of the member may be the most effective solution.

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8

Part 16 Design and Construction of Reinforced Concrete Box Culverts — 2006 — TABLE OF CONTENTS

Section/Article

Description

Page

16.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.1.1 Scope (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.1.2 Units (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.1.3 Definition (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-16-2 8-16-2 8-16-3 8-16-3

16.2 Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.2.1 Existing Foundation Material (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.2.2 Existing Embankment Material (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.2.3 Backfill and Bedding Materials (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.2.4 Concrete (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.2.5 Reinforcement (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.2.6 Miscellaneous Metal (2006). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.2.7 Miscellaneous Materials (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-16-4 8-16-4 8-16-4 8-16-5 8-16-5 8-16-5 8-16-5 8-16-5

16.3 Design Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.3.1 Design Considerations (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.3.2 Design to Accommodate Flow (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.3.3 Structural Design (2006). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-16-6 8-16-6 8-16-6 8-16-6

16.4 Design Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.4.1 General (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.4.2 Dead Load (2006). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.4.3 Live Load (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.4.4 Impact Load (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.4.5 Other Forces (2006). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-16-7 8-16-7 8-16-7 8-16-9 8-16-13 8-16-13

16.5 Details of Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.5.1 General (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.5.2 Wingwalls (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.5.3 Barrel and Apron (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-16-13 8-16-13 8-16-13 8-16-13

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3

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TABLE OF CONTENTS (CONT) Section/Article

Description

Page

16.5.4 Longitudinal Reinforcement (2006). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.5.5 Drainage and Waterproofing (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.5.6 Backfill (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-16-15 8-16-15 8-16-15

16.6 Manufacture of Precast Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.6.1 General (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.6.2 Manufacturing Tolerances (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.6.3 Physical Requirements (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.6.4 Marking (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-16-16 8-16-16 8-16-16 8-16-16 8-16-17

16.7 Construction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.7.1 Construction Tolerances (2006). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.7.2 Joints (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.7.3 Waterproofing or Dampproofing (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.7.4 Handling Devices (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.7.5 Foundations (2006). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16.7.6 Backfilling (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-16-17 8-16-17 8-16-17 8-16-18 8-16-18 8-16-18 8-16-19

Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-16-19

LIST OF FIGURES Figure 8-16-1 8-16-2 8-16-3 8-16-4 8-16-5 8-16-6 8-16-7 8-16-8

Description

Page

Uniformly Distributed Load to Top of Box . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Distribution of Loads. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Design Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Design Equations U.S. Customary Units. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Design Equations Metric Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tongue and Groove Joint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Male and Female Joint . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Backfilling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-16-8 8-16-9 8-16-10 8-16-11 8-16-12 8-16-14 8-16-14 8-16-18

SECTION 16.1 GENERAL 16.1.1 SCOPE (2006)1 a.

This recommended practice governs the design and construction of precast or cast-in-place rigid frame reinforced concrete box culverts on soil foundations.

b. This recommended practice does not apply to installations where the vertical dimension (H) from the top of the structure to the base of rail is less than 18 inches (450 mm).

1

See Commentary

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Design and Construction of Reinforced Concrete Box Culverts

c.

This recommended practice does not provide for installation of precast units by jacking. Provisions for jacking must be considered separately and in addition to the recommendations of this Part.

d. This recommended practice applies to installations beneath conventional ballasted track.

16.1.2 UNITS (2006) This recommended practice uses U. S. customary units. The metric (SI) units in parentheses are approximate, and are provided for information only. ASTM Standard Specifications are cited, where available. Corresponding Metric ASTM International Specifications are shown in parenthesis where available.

16.1.3 DEFINITION (2006)1 A box culvert is a structure which forms one or more rectangular openings through an embankment. The size designation of a box culvert opening indicates first the width, followed by the height. 16.1.3.1 Notations

1

U.S. Customary

Metric Units

b

The width of a box culvert opening.

ft

m

b´

The horizontal distance between center lines of box culvert walls.

ft

m

h

The height of a box culvert opening.

ft

m

h´

The vertical distance between center lines of box culvert top and bottom slabs.

ft

m

H

The vertical distance between the top of a box culvert and the base of rail.

ft

m

H´

The vertical distance between the center of a box culvert opening and the base of rail.

ft

m

I

The impact load applied to the top of a box culvert, as a percentage of WLL.

%

%

IS

Moment of inertia of the box culvert top slab gross section, per foot (meter) of culvert length.

in4

mm4

IW

Moment of inertia of the box culvert wall gross section, per foot (meter) of culvert length.

in4

mm4

ke

The coefficient of active earth pressure of embankment fill excluding surcharge loading.

none

none

ks

The coefficient of active earth pressure of embankment fill including surcharge loading.

none

none

k

The ratio of S to R.

none

none

Ld

Lateral live load distribution length illustrated in Figure 8-16-2.

ft

m

1

3

4

See Commentary

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Concrete Structures and Foundations

U.S. Customary

Metric Units

MA

The maximum negative moment at the exterior corner of a box culvert per foot (meter) of culvert length.

kip.ft

kN.m

MB

The maximum positive moment in a box culvert top slab near the center of a culvert opening per foot (meter) of culvert length.

kip.ft

kN.m

MC

The maximum negative moment in the top slab of a box culvert at the top of a center wall per foot (meter) of culvert length.

kip.ft

kN.m

Pe

The uniformly distributed design load on the sides of a box culvert, excluding surcharge loading.

lbs/ft2

kN/m2

Ps

The uniformly distributed design load on the sides of a box culvert, including surcharge loading.

lbs/ft2

kN/m2

R

The ratio of b´ to h´.

none

none

S

The ratio of Is to Iw

none

none

VA

The maximum vertical shear in the top slab of a box culvert, at the face of support near an exterior corner per foot (meter) of culvert length.

lbs

kN

VC

The maximum vertical shear in the top slab of a box culvert, at the face of support near a center wall per foot (meter) of culvert length.

lbs

kN

W

The total uniformly distributed load on the top of a box culvert; a combination of WLL , WDL , and I.

lbs/ft2

kN/m2

WDL The uniformly distributed dead load on the top of a box culvert.

lbs/ft2

kN/m2

We

lbs/ft3

kg/m3

WLL The uniformly distributed live load on the top of a box culvert.

lbs/ft2

kN/m2

Ws

lbs/ft2

kg/m2

Weight density of embankment fill taken as 120 lbs/ft3 (Mass density of embankment fill taken as 1900 kg/m3).

Weight of concrete per square foot of top slab area (Mass of concrete per square meter of top slab area).

SECTION 16.2 MATERIALS 16.2.1 EXISTING FOUNDATION MATERIAL (2006) The Engineer shall investigate the characteristics of existing foundation materials as recommended in Part 22, Geotechnical Subsurface Investigation.

16.2.2 EXISTING EMBANKMENT MATERIAL (2006) The Engineer shall investigate the characteristics of existing embankment materials in conjunction with existing foundation conditions where existing embankment material will be excavated and reused.

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16.2.3 BACKFILL AND BEDDING MATERIALS (2006) a.

Backfill and bedding materials shall be subject to the approval of the Engineer. Wet or impervious materials shall not be used except as outlined in Article 16.2.3 g, and all backfill and bedding shall be free from brush and other organic materials.

b. Crushed stone for bedding shall consist of crushed rock graded such that 100% passes a 2 inch (50 mm) sieve, and 100% is retained on a 3/4 inch (19 mm) sieve. c.

Sand for foundation leveling shall consist of selected excavated sand, free from clay and organic materials, and free from rock fragments exceeding 3/4 inch (19 mm).

d. Crushed stone placed around drainage pipes shall meet the same requirements for bedding, except that the Engineer may specify a different grading. e.

Unless otherwise shown on the contract documents, structural granular backfill shall consist of wellgraded granular pit run gravel or crushed stone with 100% passing the 4-1/4 inch (106 mm) sieve and 100% retained on the Number 200 (75 µm) sieve.

f.

Native or imported backfill materials not meeting the requirements of structural granular backfill may be used subject to the approval of the Engineer.

g.

Clay for seepage barriers shall consist of clay or silty clay of a medium to high plasticity and of a low permeability, all subject to the approval of the Engineer.

1

16.2.4 CONCRETE (2006)1 a.

The minimum compressive strength of concrete shall be 4000 psi (28 MPa) at 28 days.

b. Concrete materials shall comply with the requirements of Part 1, Materials, Tests and Construction Requirements that affect the durability of the culvert, including alkali-aggregate reactions, sulfate and other chemical reactions, and freezing and thawing. Use air entraining and other admixtures only when approved by the Engineer. Admixtures containing chlorides shall not be used.

3

16.2.5 REINFORCEMENT (2006) Reinforcing steel shall meet the requirements of ASTM 615 (A615M) Grade 60 (Grade 420), or ASTM A706 (A706M), or welded steel wire fabric conforming to ASTM A497 (ASTM A497M), with an allowable tensile stress of 24,000 psi (165 MPa) for service load design.

16.2.6 MISCELLANEOUS METAL (2006) All hardware for sleeves, anchor bolts, inserts and other hardware shall be either hot-dip galvanized in accordance with ASTM A153, or epoxy coated in accordance with ASTM A775 (ASTM A775M), or stainless steel in accordance with ASTM A955 (A955M), as approved by the Engineer.

16.2.7 MISCELLANEOUS MATERIALS (2006) a.

1

Water stops shall meet the requirements of Part 1, Materials, Tests and Construction Requirements for watertight construction joints.

See Commentary

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b. Gasket material shall conform to ASTM C990-03 Preformed Flexible Joint Sealant, as approved by the Engineer.

SECTION 16.3 DESIGN METHODS 16.3.1 DESIGN CONSIDERATIONS (2006)1 a.

The design shall consider the following: (1) The purpose of the structure. (2) Depth of culvert from base of rail to invert level. (3) Requirements for soil cover above the top of the structure and below the base of rail, as specified by the Engineer, in addition to the requirements of these recommendations. (4) Waterway alignment and skew angle. (5) Subgrade width and embankment slopes. (6) Existing foundation conditions.

b. For precast culverts, the design shall consider the following: (1) Stresses induced by handling and transportation of units. (2) Methods of installation. (3) Methods of connecting sections of box culverts together to secure the units in their intended position.

16.3.2 DESIGN TO ACCOMMODATE FLOW (2006) Calculation of flow rates and the design of the culvert and approaches to accommodate flows in accordance with Chapter 1, Roadway and Ballast, Part 3, Natural Waterways.

16.3.3 STRUCTURAL DESIGN (2006)2 a.

The design shall comply with all provisions of Part 2, Reinforced Concrete Design, except as modified in this part.

b. The structure shall be analyzed assuming that all joints between slabs and walls are rigid, with positive and negative bending moments determined by the theory of elasticity.

1 2

See Commentary See Commentary

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Design and Construction of Reinforced Concrete Box Culverts

SECTION 16.4 DESIGN LOADS 16.4.1 GENERAL (2006) a.

The design of box culverts supporting track shall consider the following loads: (1) dead load, (2) live load, (3) impact load.

b. The loads, uniformly distributed per square foot (per square meter) to the top of the box, are shown in Figure 8-16-1 for various depths of fill.

16.4.2 DEAD LOAD (2006)1 a.

The vertical dead load consists of the estimated weight of the track, fill, and top slab of the structure. Dead load shall be determined from, and uniformly distributed to the culvert as shown on Figure 8-16-1 and Figure 8-16-2, respectively.

b. The minimum lateral pressure on the sides of the box shall be based on an assumed earth pressure coefficient of 0.33. c.

The maximum lateral pressure on the sides of the box shall be based on an assumed earth pressure coefficient of 1.0.

d. As an alternative to paragraph c, the Engineer may determine the maximum designed density of a fully saturated fill, and the corresponding earth pressure coefficient that would apply, and use these in the calculation of both vertical and lateral pressures from dead loads. e.

1

3

The lateral pressures on each side of the box may be assumed to be uniformly distributed over the entire height, equal and opposite in direction. This assumption has been made in the design equations shown in Figure 8-16-4 and Figure 8-16-5. If a more exact distribution is used, Figure 8-16-4 and Figure 8-16-5 do not apply.

4

1

See Commentary

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Concrete Structures and Foundations

DISTANCE H - BASE OF RAIL TO TOP OF BOX, METERS 0

1

2

3

4

5

6

7

8

9

4500

210

4250 4000 180

3750 3500

DEAD LOAD + LIVE LOAD + IMPACT 150

3000 2750 120

2500 2250 2000

90

DEAD LOAD

1750

UNIFORM LOAD W = kPa

UNIFORM LOAD W = LB. PER SQ FT.

3250

1500 60

1250 1000

LIVE LOAD E-80 (EM 360)

750

30 500

IMPACT

250 0

0 0

2

4

6

8

10

12

14

16

18

20

22

24

26

28

30

DISTANCE H - BASE OF RAIL TO TOP OF BOX, FEET

Figure 8-16-1. Uniformly Distributed Load to Top of Box

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Design and Construction of Reinforced Concrete Box Culverts

16.4.3 LIVE LOAD (2006)1 a.

Determine live load for each track in accordance with Part 2, Reinforced Concrete Design. Distribution of the live load to the culvert shall be in accordance with Figure 8-16-2.

Ld

1

Figure 8-16-2. Distribution of Loads

3

b. No increase in live load shall be used for multiple track loadings. c.

Calculate the minimum lateral pressure induced from live load on the sides of the box using the earth pressure coefficient determined by Article 16.4.2.

d. The maximum lateral pressures that may be generated on the sides of the box shall be considered in the design, except that the earth pressure coefficient of Article 16.4.2 c need not be applied to live loads. If the provisions of Article 16.4.2 d are used with respect to dead loads, then they shall be used for the calculation of maximum pressures from live loads also.

1

See Commentary © 2011, American Railway Engineering and Maintenance-of-Way Association

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Figure 8-16-3. Design Data

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Design and Construction of Reinforced Concrete Box Culverts

1

3

4

Figure 8-16-4. Design Equations U.S. Customary Units

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Concrete Structures and Foundations

Figure 8-16-5. Design Equations Metric Units

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Design and Construction of Reinforced Concrete Box Culverts

16.4.4 IMPACT LOAD (2006) a.

Add impact load to the live load as determined from Figure 8-16-1 or Figure 8-16-4 or Figure 8-16-5, respectively, and uniformly distributed to the culvert top slab in the same manner as the live load.

b. No impact shall be added to the lateral forces on the sides of the box.

16.4.5 OTHER FORCES (2006) a.

Centrifugal force, wind force, and longitudinal forces resulting from starting and stopping of trains need not be considered.

SECTION 16.5 DETAILS OF DESIGN 16.5.1 GENERAL (2006) a.

The contract documents shall show construction elements in detail including dimensions, spacing and size of reinforcement, permitted locations for the placement of handling devices and holes in the case of precast, construction and expansion joints, water stops, waterproofing, and drainage. The maximum design foundation pressure shall also be shown.

1

b. When it is anticipated that multiple culverts will be built, standardization of the design and construction details is recommended. c.

The culvert shall be designed with a camber along its longitudinal axis where required by the Engineer, to counteract the effects of settlement.

3

16.5.2 WINGWALLS (2006) a.

Wingwalls may be cast-in-place or precast.

b. Wingwalls shall have such slope and length as required to retain the embankment and maintain the culvert opening. c.

Wingwalls may be straight or flared, as local conditions and hydraulic design require.

16.5.3 BARREL AND APRON (2006) a.

The minimum concrete cover for reinforcement shall be 2 inches (50 mm) unless approved otherwise by the Engineer. This requirement does not apply at the joints of precast units.

b. The same barrel section shall be used throughout, except under deep fills where a reduced barrel section may be used toward the ends of the box. Consideration shall be given to the construction of future tracks. c.

Wall and top and bottom slab thicknesses shall be a minimum of 10 inches (250 mm), or as required by the Engineer. Greater wall and slab thicknesses should be considered for cast-in-place construction to facilitate concrete placement.

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d. A minimum haunch of 6 inches (150 mm) shall be provided. e.

In long culverts, or culverts under deep fills, consideration should be given to the placement of joints to provide for possible vertical and longitudinal movements of the barrel of cast-in-place culverts. If joints are used, the first joint shall be not less than 10 feet (3 meters) from the end of the cast-in-place barrel. For cast-in-place construction, joints should not be placed in regions of maximum stress.

f.

Precast units shall be designed with tongue and groove or male and female ends such as shown in Figure 8-16-6 and Figure 8-16-7 or as determined by the Engineer. The inside face reinforcement shall extend into the male portion of the joint, and the outside face reinforcement shall extend into the female portion of the joint.

g.

Where differential deflection from live load between units exceeds b/800, (where b is the width of the box opening) joints between precast units shall be capable of transferring shear loads through the top slab between adjacent units by a method or devices which may be mutually agreed upon by the box culvert manufacturer and the Engineer. If individual shear connectors are used to fasten the adjacent top slabs together, they shall be spaced no more than 30 inches (750 mm) on center, with a minimum of two shear connectors per joint.

Figure 8-16-6. Tongue and Groove Joint

Figure 8-16-7. Male and Female Joint

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Design and Construction of Reinforced Concrete Box Culverts

h. The floor of the barrel and apron may be sloped toward the center. Flow energy dissipation may be provided by texturing the floor of the culvert if this is taken into account in the flow capacity design. i.

The surface of the top slab in contact with the backfill may be sloped toward the sidewalls for drainage.

j.

The length of the apron, and rip-rap requirements, shall be determined by field conditions in accordance with Chapter 1, Roadway and Ballast.

k. Cutoff walls shall be used at inlet and outlet ends to a depth consistent with the field conditions and potential scour.

16.5.4 LONGITUDINAL REINFORCEMENT (2006) a.

The minimum longitudinal reinforcement in the top slab, bottom slab and walls shall be as follows: (1) 0.4% of concrete cross sectional area for fill depths over the top of the top slab equal to or less than 10 feet (3 meters). (2) For fill depths greater than 10 feet (3 meters), this percentage shall be increased proportionally to 1.0% for fills of 100 feet (30 meters).

b. The minimum reinforcement determined from paragraph a shall be provided half on each face of the slab or wall.

16.5.5 a.

1

DRAINAGE AND WATERPROOFING (2006)1

Pipe drains in the backfill adjacent to the side walls shall be shown on the contract drawings when necessary. Horizontal drain pipes shall be not less than 8 inches (200 mm) in diameter, perforated, and in such a position that they will function properly. Provisions shall be made for cleaning drainage pipes.

b. Special provision may be made for waterproofing by use of non-corrosive water stops in accordance with Part 1, Materials, Tests and Construction Requirements for watertight construction joints, and/or by use of a waterproofing membrane in accordance with Part 29, Waterproofing.

3

16.5.6 BACKFILL (2006) a.

4

The limits of structural granular backfill shall be shown on the contract drawings.

b. Where structural granular backfill is not required, the Engineer shall specify the materials to be used. c.

When a seepage barrier is required, the details of its location and thickness shall be shown on the contract drawings.

d. The Engineer shall specify any other backfill details required.

1

See Commentary

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AREMA Manual for Railway Engineering

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Concrete Structures and Foundations

SECTION 16.6 MANUFACTURE OF PRECAST UNITS 16.6.1 GENERAL (2006) a.

Manufacturer’s shop drawings shall be submitted to the Engineer for review and approval.

b. Precast reinforced concrete culvert units shall be manufactured using steel forms and cured in accordance with Part 1, Materials, Tests and Construction Requirements. c.

Concrete shall be placed by the wet cast method when air-entrainment is specified in the contract documents. When air-entrainment is not specified, the precast reinforced concrete culvert units may be manufactured by the dry cast method if approved by the Engineer.

d. Handling devices or holes shall be provided where shown on the contract drawings. Details of handling devices shall be shown on the shop drawings and shall be subject to the approval of the Engineer, and shall also satisfy the requirements of Article 16.7.4.

16.6.2 MANUFACTURING TOLERANCES (2006) a.

Opening Dimensions — The dimensions of the culvert opening shall vary by not more than +/– 1% from the dimensions shown on the contract documents. Such variations shall also satisfy the requirements of Article 16.6.3 a. The haunch dimensions shall vary by not more than 1/4 inch (7 mm) from the dimensions shown on the contract documents.

b. Slab and Wall Thickness — The slab and wall thickness shall not be less than 95% of that shown on the contract documents. A thickness more than that shown on the contract documents shall not be cause for rejection. c.

Length of Opposite Surfaces — Variations in laying lengths of two opposite surfaces of the box unit shall not be more than 1/8 inch per foot (10 mm per meter) of span, with a maximum of 3/4 inch (20 mm) in any box unit, except where beveled ends for laying on curves are specified on the contract documents.

d. Length of Precast Unit — The length of a precast unit shall vary by not more than 1/8 inch per foot (10 mm per meter) of length from that shown on the contract documents with a maximum variation of 1/2 inch (12 mm) in any box unit. e.

Position of reinforcement — The maximum variation in the position of reinforcement shall be 3/8 inch (10 mm) from that shown on the contract documents. In no case, however, shall the as-manufactured cover over the reinforcement be less than 1-1/2 inch (40 mm) as measured to the internal surface or the external surface of the completed box unit unless approved otherwise by the Engineer. This minimum cover limitation does not apply at the mating surfaces of joints.

f.

Area of Reinforcement — The areas of steel reinforcement shall be as required by the contract documents. Steel areas greater than those required shall not be cause for rejection.

16.6.3 PHYSICAL REQUIREMENTS (2006) a.

The ends of the units shall be produced with joints as shown on the contract documents, and so formed that when the units are laid together they will make a continuous line of box units with a smooth interior free of irregularities exceeding 3/8 inch (10 mm) at the joints.

b. The manufacturer may use alternate joint details to those shown on the contract documents subject to the approval of the Engineer. © 2011, American Railway Engineering and Maintenance-of-Way Association

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c.

When concrete is placed by the wet cast method concrete compressive strength shall be determined from cylindrical concrete specimens made in conformance with ASTM Standard C39/C39M, and prepared in conformance with ASTM Standard C31/C31M.

d. When units are manufactured by the dry cast method, cylinders shall be made in conformance with ASTM Standard C361, Article 10.3.2. e.

At least five test cylinders shall be prepared from each day’s production of concrete.

f.

Compression test requirements shall be in accordance with ASTM Standard C361, Article 10.3.3.

16.6.4 MARKING (2006) a.

The following information shall be clearly marked on each box unit by indentation, waterproof paint, or other approved means: (1) Project name. (2) Date of manufacture. (3) Name or trademark of the manufacturer. (4) Identification of the plant.

1

(5) Location number/match mark. (6) Identification of top slab. (7) Weight (mass) of unit.

3 SECTION 16.7 CONSTRUCTION 16.7.1 CONSTRUCTION TOLERANCES (2006)

4

The construction tolerances of Article 16.6.2 a, b, e, and f shall also apply for cast-in-place concrete.

16.7.2 JOINTS (2006) a.

Joints shall be located as shown on the contract drawings or as approved by the Engineer. Joints in castin-place box culverts shall be formed as prescribed in Part 1, Materials, Tests and Construction Requirements.

b. Premolded bituminous filler at least 1/2 inch (12 mm) thick may be used at joints in cast-in-place box culverts. c.

Precast units shall be placed against previously completed units in such a manner as to assure an adequate seal.

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16.7.3 WATERPROOFING OR DAMPPROOFING (2006) a.

Waterproofing, if any, shall be provided in accordance with Part 29, Waterproofing, or as specified by the Engineer.

b. Where no waterproofing is specified, the surface in contact with the backfill may be dampproofed. Dampproofing, if any, shall be in accordance with the provisions of Part 29, Waterproofing.

16.7.4 HANDLING DEVICES (2006) Following installation of precast units, and before waterproofing or backfilling, all protruding handling devices shall be removed, and all holes and pockets shall be filled with a non-shrink grout approved by the Engineer.

16.7.5 FOUNDATIONS (2006)1 a.

The foundation requirements apply where the reinforced concrete box culvert is to be constructed by open cut.

b. Foundation conditions shall be inspected and approved by the Engineer. c.

Existing unsuitable foundation materials shall be excavated and replaced with new material as required by the Engineer.

d. A compacted crushed stone bed shall be provided under precast reinforced concrete box culverts. The depth of the crushed stone bed shall be a minimum of 12 inches (300 mm), and shall extend 12 inches (300 mm) on each side of the precast reinforced concrete box culvert with a minimum one to one side slope as shown on Figure 8-16-8.

Figure 8-16-8. Backfilling

1

e.

In cast-in-place construction, the crushed stone bed may be omitted if foundation conditions are favorable, as determined by the Engineer.

f.

The foundation surface upon which the reinforced concrete box culvert is to be supported shall be carefully graded to the required line and grade. A well compacted sand layer not exceeding 4 inches (100 mm) in thickness may be provided directly under a precast culvert, and on top of the crushed stone bedding, to facilitate this.

See Commentary

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Design and Construction of Reinforced Concrete Box Culverts

16.7.6 BACKFILLING (2006) a.

The backfilling requirements apply where the reinforced concrete box culvert is to be constructed by open cut.

b. Structural granular backfill shall be used for the entire backfill area unless shown otherwise on the contract drawings, and except as required for: (1) foundations, as recommended in Article 16.7.5; and (2) drainage materials, as recommended in Article 16.2.3 d; and (3) parallel installations as recommended by Article 16.7.6 c. c.

When reinforced concrete culverts are used in parallel for multicell installations, positive means of ensuring lateral support shall be provided by grouting with non-shrink grout between the units or by filling the space between adjacent units with compacted granular or cementitious material as approved by the Engineer.

d. Backfill shall be placed alternately on each side of the box and deposited in layers not more than 12 inches (300 mm) thick. The layers shall be horizontal or sloping away from the structure, with each layer carefully tamped. e.

Care shall be taken in selecting and placing the backfill to prevent damage when the exterior of the culvert has a waterproofing coating or membrane. Protective cover material may be used to prevent damage to the waterproofing system.

1

COMMENTARY

3

C - 16.1 GENERAL C - 16.1.1 SCOPE (2006) The design and construction of reinforced concrete box culverts having more than two openings may be modeled upon these recommendations, but the design equations of Figure 8-16-4 and Figure 8-16-5 will not apply. For culverts of more than two openings the effects of unbalanced loading or pattern loading should be considered. The design of box culverts on pile or rock foundations is governed by support conditions, and box culverts on pile foundations will require a special analysis because of these different support conditions. However, the design of box culverts on rock foundations may be based on these recommendations if the Engineer ensures that there is sufficiently elastic backfill bedding between the culvert and the rock. The design and construction of reinforced concrete box structures having a vertical dimension from the top of the structure to the base of rail of less than 18 inches (450 mm) may be modeled upon these recommendations, but the effects of impact loading will require special determination. The design equations of Figure 8-16-4 and Figure 8-16-5 will not apply, particularly with regard to impact. Reinforced concrete box culvert installations will normally be by open cut, and the reference to jacking in Article 16.1.1 c will not apply.

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4

Concrete Structures and Foundations C - 16.1.3 DEFINITION (2006) Box culverts are used principally for waterways, but may also be used as pedestrian or livestock underpasses, or for other purposes.

C - 16.2 MATERIALS C - 16.2.4 CONCRETE (2006) Air entrainment should always be provided where concrete will be subjected to freeze-thaw cycles. To increase the imperviousness of the concrete, air entrainment should also be considered in chemically aggressive environments including dissolved sulfates, industrial effluent, and acid rain. Since the dry cast method is not compatible with air entrainment, the Engineer should consider this when preparing the contract specifications. The preparation of cylinders for determining concrete compressive strength differs for wet cast and dry cast concrete. The Engineer should determine the methods employed by potential manufacturers when preparing the contract specifications.

C - 16.3 DESIGN METHODS C - 16.3.1 DESIGN CONSIDERATIONS (2006) Shallow boxes or boxes without much fill may be subject to heaving depending on conditions of the soil below the box. C - 16.3.3 STRUCTURAL DESIGN (2006) A box culvert may be designed as a rigid “U” shape, with a top slab acting as a simple span without negative corner moments. A box culvert may also be designed as an inverted U-shape and placed upon a separate footing slab. Design of such culverts may be modeled upon these recommendations but the design equations of Figure 8-16-4 and Figure 8-16-5 will not apply.

C - 16.4 DESIGN LOADS C - 16.4.2 DEAD LOAD (2006) and C - 16.4.3 LIVE LOAD (2006) Pressures applied to a box culvert will vary with soil moisture content, and over time with increased compaction under traffic. To accurately account for these changes, it would be necessary to determine a range of soil density, earth pressure coefficients, and hydrostatic conditions. These would then be applied in combinations to determine both maximum positive and maximum negative moments. Article 16.4.2 and Article 16.4.3 permit such an approach, but also offer a simplified method. The intent of Article 16.4.2 c with regard to a maximum design earth pressure coefficient for the application of dead loads is to approximate the more rigorous analysis of maximum negative moments.

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Design and Construction of Reinforced Concrete Box Culverts

C - 16.5 DETAILS OF DESIGN C - 16.5.5 DRAINAGE AND WATERPROOFING (2006) Waterproofing will not normally be required for reinforced concrete box culverts. However, the Engineer may require waterproofing at special installations, such as where culverts are to serve as pedestrian underpasses.

C - 16.7 CONSTRUCTION C - 16.7.5 FOUNDATIONS (2006) The Engineer may determine that special foundation requirements should apply, for example, where precast culverts are to serve as pedestrian underpasses. In such cases, grillage supports may be considered in order to control differential displacements.

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Part 17 Prestressed Concrete1 — 2007 — TABLE OF CONTENTS

Section/Article

Description

Page

17.1 General Requirements and Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.1.1 Scope (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.1.2 Design Loads (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-17-4 8-17-4 8-17-4

17.2 Notations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-17-5

17.3 Terms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-17-7

17.4 Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.4.1 Concrete (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.4.2 Prestressing Tendons (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.4.3 Non-Prestressed Reinforcement (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.4.4 Grout for Post-Tensioning Tendons (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.4.5 Rigid Ducts (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-17-10 8-17-10 8-17-10 8-17-10 8-17-10 8-17-10

17.5 Details of Prestressing Tendons and Ducts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.5.1 Spacing of Tendons and Ducts (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.5.2 Minimum Concrete Cover (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.5.3 Protection for Prestressing Tendons (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.5.4 Protection for Debonded Prestressing Tendon (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.5.5 Post-Tensioning Ducts (2001). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.5.6 Post-Tensioning Anchorages and Couplers (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.5.7 Tendon Anchorage Zones (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.5.8 Development of Prestressing Strand (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-17-11 8-17-11 8-17-11 8-17-12 8-17-12 8-17-12 8-17-12 8-17-12 8-17-13

17.6 General Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-17-13

17.7 Expansion and Contraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-17-13

17.8 Span Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-17-13

17.9 Frames and Continuous Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-17-14

1

References, Vol. 84, 1983, p. 93; Vol. 90, 1989, p. 53; Vol. 94, 1994, p. 102.

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3

Concrete Structures and Foundations

TABLE OF CONTENTS (CONT) Section/Article

Description

Page

17.10 Effective Flange Width . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.10.1 Precast/Prestressed Concrete Beams with Wide Top Flanges (2001) . . . . . . . . . . . . . . . .

8-17-15 8-17-15

17.11 Flange and Web Thickness-Box Girders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-17-16

17.12 Diaphragms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-17-16

17.13 Deflections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-17-16

17.14 General Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.14.1 Design Theory and General Considerations (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.14.2 Basic Assumptions (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.14.3 Composite Flexural Members (2001). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-17-17 8-17-17 8-17-17 8-17-17

17.15 Load Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.15.1 Required Strength (2001). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-17-18 8-17-18

17.16 Allowable Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.16.1 Prestressing Tendons (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.16.2 Concrete (2001). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-17-18 8-17-18 8-17-19

17.17 Loss of Prestress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.17.1 Prestress Losses (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-17-21 8-17-21

17.18 Flexural Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.18.1 Introduction (2001). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.18.2 Rectangular Sections (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.18.3 Flanged Sections (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.18.4 Steel Stress (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-17-26 8-17-26 8-17-26 8-17-27 8-17-27

17.19 Ductility Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.19.1 Maximum Prestressing Steel (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.19.2 Minimum Reinforcement (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-17-28 8-17-28 8-17-29

17.20 Non-Prestressed Reinforcement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-17-29

17.21 Shear. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.21.1 General (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.21.2 Shear Strength Provided by Concrete (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.21.3 Shear Strength Provided by Web Reinforcement (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . 17.21.4 Horizontal Shear Design-Composite Flexural Members (2001) . . . . . . . . . . . . . . . . . . . .

8-17-30 8-17-30 8-17-30 8-17-32 8-17-34

17.22 Post-Tensioned Anchorage Zones. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.22.1 Geometry of Anchorage Zone (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.22.2 General Zone and Local Zone (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.22.3 Design of the General Zone (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.22.4 Application of Strut-and-Tie Models to the Design of Anchorage Zones (2001). . . . . . . . 17.22.5 Elastic Stress Analysis (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.22.6 Approximate Methods (2001). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-17-35 8-17-35 8-17-35 8-17-36 8-17-40 8-17-41 8-17-41

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TABLE OF CONTENTS (CONT) Section/Article

Description

17.22.7 Design of the Local Zone (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Page 8-17-43

17.23 Pretensioned Anchorage Zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-17-45

17.24 Concrete Strength at Stress Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-17-46

17.25 General Detailing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.25.1 Flange Reinforcement (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.25.2 Cover and Spacing of Reinforcement (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.25.3 Post-Tensioning Anchorages and Couplers (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.25.4 Embedment of Prestressed Tendon (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-17-46 8-17-46 8-17-46 8-17-46 8-17-49

17.26 General Fabrication. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.26.1 General (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.26.2 Contractor’s Drawings (2001). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.26.3 Materials and Fabrication (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.26.4 Curing (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.26.5 Storage and Handling (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.26.6 Erection (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.26.7 Placement of Ducts, Steel, and Anchorage Hardware (2001) . . . . . . . . . . . . . . . . . . . . . . . 17.26.8 Application and Measurement of Prestressing Force (2005) . . . . . . . . . . . . . . . . . . . . . . .

8-17-50 8-17-50 8-17-50 8-17-50 8-17-50 8-17-50 8-17-51 8-17-51 8-17-53

17.27 Mortar and Grout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.27.1 General (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.27.2 Materials and Mixing (2001). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.27.3 Placing and Curing (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-17-53 8-17-53 8-17-53 8-17-54

17.28 Application of Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-17-54

17.29 Materials - Reinforcing Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.29.1 General (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.29.2 Bar Lists and Bending Diagrams (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.29.3 Fabrication (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.29.4 Handling, Storing and Surface Condition of Reinforcement (2001) . . . . . . . . . . . . . . . . . 17.29.5 Placing and Fastening (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.29.6 Splicing of Bars (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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17.30 Prestressed Concrete Cap and/or Sill for Timber Pile Trestle (2003) . . . . . . . . . . . .

8-17-56

Commentary (2006). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-17-58

LIST OF FIGURES Figure

Description

8-17-1 Annual Average Ambient Relative Humidity, (R), %. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-17-2 Prestressed Concrete Cap and/or Sill for Timber Pile Trestle . . . . . . . . . . . . . . . .. . . . . . . . . .

Page 8-17-23 8-17-57

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AREMA Manual for Railway Engineering

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1

3

4

Concrete Structures and Foundations

LIST OF TABLES Table

Description

Page

8-17-1 Values for K and µ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-17-2 Estimated Loss of Prestress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-17-25 8-17-26

SECTION 17.1 GENERAL REQUIREMENTS AND MATERIALS 17.1.1 SCOPE1 (2001) a.

This recommended practice shall govern the design of prestressed concrete members of railway structures supporting or protecting tracks.

b. Provisions of Part 17 supplement Part 2 of Chapter 8. All provisions of Part 2 not in conflict with provisions of Part 17 shall apply to prestressed concrete. The following provisions of Part 2 shall not apply to prestressed concrete: Article 2.2.3d, Section 2.7, Section 2.8, Article 2.11.1, Article 2.23.9, Article 2.32.1, Section 2.38, Section 2.39 and Section 2.40. c.

Long span or unusual structures require detailed consideration of effects which have not been included under Part 17.

d. Bearing devices for prestressed concrete structures shall be designed in accordance with Chapter 15, Part 10. e.

Segmental concrete bridges shall be designed in accordance with the provisions of Part 26.

f.

Structures with direct fixation track shall be designed in accordance with Part 27.

17.1.2 DESIGN LOADS (2005) Design loads and loading combinations shall be in accordance with Part 2, Article 2.2.3 and Article 2.2.4, including that percentage of live-load for impact.

EQ 17-1

Equation 17-1 deleted.

1

See C - 17.1.1 Scope (2001)

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Prestressed Concrete

SECTION 17.2 NOTATIONS As = area of non-prestressed tension reinforcement (Articles 17.18, 17.20 and 17.22), in.2 (mm2) A¢s = area of compression reinforcement (Article 17.20), in.2 (mm2) As* = area of prestressing steel (Article 17.18), in.2 (mm2) Asf = steel area required to develop the compressive strength of the overhanging portions of the flange (Article 17.18), in.2 (mm2) Asr = steel area required to develop the compressive strength of the web of a flanged section (Articles 17.18-17.20), in.2 (mm2) Av = area of web reinforcement (Article 17.21), in.2 (mm2) b = width of flange of flanged member or width of rectangular member, in. (mm) bw = web width (Article 17.21), in. (mm) bv = width of cross section at the contact surface being investigated for horizontal shear (Article 17.21), in. (mm) b’ = width of a web of a flanged member, in. (mm) CRc = loss of prestress due to creep of concrete (Article 17.17), ksi (MPa) CRs = loss of prestress due to relaxation of prestressing steel (Article 17.17), ksi (MPa) D = nominal diameter of prestressing steel (Articles 17.18 and 17.24), in. (mm)

1

d = distance from extreme compression fiber to centroid of the prestressing force, or to centroid of negative moment reinforcing for pre-cast girder bridges made continuous, in. (mm) db = nominal diameter of prestressing wire, bar or strand, in. (mm) dburst = the distance from the loaded surface where the bursting force is computed, in. (mm)

3

dd = outside diameter of post-tensioning duct, in. (mm) dp = distance from extreme compression fiber to centroid of prestressing steel, in. (mm) dt = distance from the extreme compressive fiber to the centroid of the non-prestressed tension reinforcement (Articles 17.18-17.20), in. (mm) Ec = modulus of elasticity of concrete, ksi (MPa)

4

Eci = modulus of elasticity of concrete at transfer, ksi (MPa) Es = modulus of elasticity of steel reinforcement, ksi (MPa) ES = loss of prestress due to elastic shortening (Article 17.17), ksi (MPa) e = base of Naperian logarithms (Article 17.17) Fpu = ultimate load of the post-tensioned tendon (Article 17.25.3), lbs (N) fcds = average concrete compressive stress at the c.g. of the prestressing steel under full dead load (Article 17.17), psi (MPa) fcir = average concrete stress at the c.g. of the prestressing steel at time of release (Article 17.17), psi (MPa) f¢ c = compressive strength of concrete at 28 days, psi (MPa) f¢ ci = compressive strength of concrete at time of initial prestress (Article 17.16), psi (MPa) fct = average splitting tensile strength of light-weight aggregate concrete, psi (MPa)

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AREMA Manual for Railway Engineering

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Concrete Structures and Foundations

fd = stress due to unfactored dead load, at extreme fiber of section where tensile stress is caused by externally applied loads (Article 17.21), psi (MPa) fpc = compressive stress in concrete (after allowance for all prestress losses) at centroid of cross section resisting externally applied loads or at junction of web and flange when the centroid lies within the flange (In a composite member, fpc is resultant compressive stress at centroid of composite section, or at junction of web and flange when the centroid lies within the flange, due to both prestress and moments resisted by precast member acting alone) (Article 17.21), psi (MPa) fpe = compressive stress in concrete due to effective prestress forces only (after allowance for all prestress losses) at extreme fiber of section where tensile stress is caused by externally applied loads (Article 17.21), ksi (MPa) fps = guaranteed ultimate strength of the prestressing tendon, As*f’s, lbs (N) fr = modulus of rupture of concrete, as defined in Article 17.16.2.3 (Article 17.19), ksi (MPa) Df s = total prestress loss, excluding friction (Article 17.17), ksi (MPa) fse = effective stress prestress after losses (Article 17.17), ksi (MPa) f*su = average stress in prestressing steel at ultimate load (Article 17.18), ksi (MPa) f’s = ultimate strength of prestressing steel (Articles 17.16 and 17.18), ksi (MPa) fsy = yield strength of non-prestressed conventional reinforcement in tension (Articles 17.20 and 17.21), ksi (MPa) f’y = yield strength of non-prestressed conventional reinforcement in compression (Article 17.20), ksi (MPa) f*y = yield point stress of prestressing steel (Article 17.16), psi (MPa) h = overall depth of member (Article 17.21), in. (mm) I = moment of inertia about the centroid of the cross section (Article 17.21), in.4 (mm4) K = friction wobble coefficient per foot (meter) of prestressing steel (Article 17.17) l = length of prestressing steel element from jack end to point x (Article 17.17), in. (mm) Mcr = moment causing flexural cracking at section due to externally applied loads (Article 17.21), ft-lbs (N-m) M*cr = minimum steel cracking moment (Article 17.19), ft-lbs (N-m) Md/c = composite dead load moment at the section (Article 17.19), ft-lbs (N-m) Md/nc = non-composite dead load moment at the section (Article 17.19), ft-lbs (N-m) Mmax = maximum factored moment at section due to externally applied loads (Article 17.21), ftlbs (N-m) Mn = nominal moment strength of a section, ft-lbs (N-m) p = As/bdt ratio of non-prestressed tension reinforcements (Articles 17.18-17.20) p* = As*/bd, ratio of prestressing steel (Articles 17.18 and 17.20) p’ = A’s/bd, ratio of compression reinforcement (Article 17.20) Pu = factored tendon force, lbs (N) Q = statical moment of cross sectional area, above or below the level being investigated for shear, about the centroid (Article 17.21), in.3 (mm3)

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Prestressed Concrete

SH = loss of prestress due to concrete shrinkage (Article 17.17), ksi (MPa) s = longitudinal spacing of the web reinforcement (Article 17.21), in. (mm) Sb = noncomposite section modulus for the extreme fiber of section where the tensile stress is caused by externally applied loads (Article 17.19), in.3 (mm3) Sc = composite section modulus for the extreme fiber of section where the tensile stress is caused by externally applied loads (Article 17.19), in.3 (mm3) t = average thickness of the flange of a flanged member (Articles 17.18 and 17.19), in. (mm) Tburst = the bursting force computed from the post-tensioning tendon loads at a given point (Article 17.22), Kips (N) To = steel stress at jacking ends (Article 17.17), ksi (MPa) Tx = steel stress at any point x (Article 17.17), ksi (MPa) T1 = edge tension force (Article 17.22), Kips (N) T2 = bursting force (Article 17.22), Kips (N) v = permissible horizontal shear stress (Article 17.21), psi (MPa) Vc = nominal shear strength provided by concrete (Article 17.21), Kips (N) Vci = nominal shear strength provided by concrete when diagonal cracking results from combined shear and moment (Article 17.21), Kips (N) Vcw = nominal shear strength provided by concrete when diagonal cracking results from excessive principal tensile stress in web (Article 17.21), Kips (N)

1

Vd = shear force at section due to unfactored dead load (Article 17.21), Kips (N) Vi = factored shear force at section due to externally applied loads occurring simultaneously with Mmax (Article 17.21), Kips (N) Vnh = nominal horizontal shear strength (Article 17.21), Kips (N)

3

Vp = vertical component of effective prestress force at section (Article 17.21), Kips (N) Vs = nominal shear strength provided by shear reinforcement (Article 17.21), Kips (N) wc = unit density (weight) of concrete, Lbs/cu. ft. (kg/m3) yt = distance from centroidal axis of gross section, neglecting reinforcement, to extreme fiber in tension (Article 17.21), in. (mm)

4

m = friction curvature coefficient (Article 17.17) a = total angular change of prestressing steel profile in radians from jacking end to point x (Article 17.17) ß1 = factor for concrete strength, as defined in Part 2 of this Chapter (Articles 17.18-17.20) g* = factor for type of prestressing steel (Article 17.18) j = Strength Reduction Factor (Article 17.15)

SECTION 17.3 TERMS The following terms are defined for general use. Specialized definitions appear in individual articles.

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AREMA Manual for Railway Engineering

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Concrete Structures and Foundations Anchorage Device - Mechanical device to transmit post-tensioning force to concrete in a post-tensioned member. Also referred to as an End Anchorage. Anchorage Seating - Deformation of anchorage or seating of tendons in anchorage device when prestressing force is transferred from jack to anchorage device. Anchorage Spacing - Center-to-center spacing of anchorage devices. Anchorage Zone - The portion of the structure in which the concentrated prestressing force is transferred from the anchorage device into the concrete (Local Zone), and then distributed more widely into the structure (General Zone) (Article 17.22). Basic Anchorage Device - Anchorage device meeting the restricted bearing stress and minimum plate stiffness requirements of Articles 17.22.7.2b through 17.22.7.2d; no acceptance test is required for Basic Anchorage Devices. Bonded Tendon - Prestressing tendon that is bonded to concrete either directly or through grouting. Coating - Material used to protect prestressing tendons against corrosion, to reduce friction between tendon and duct, or to debond prestressing tendons. Coupler or Coupling - Means by which prestressing force is transmitted from one partial length prestressing tendon to another. Creep - Time-dependent deformation of concrete under sustained load. Curvature Friction - Friction resulting from bends or curves in the specified prestressing tendon profile. Debonding or Blanketing - Wrapping, sheathing or coating prestressing tendon to prevent bond between strand and surrounding concrete. Diaphragm - Transverse stiffener in girders to prevent buckling or rotation. Duct - Hole or void formed in prestressed member to accommodate tendon for post-tensioning. Edge Distance - Distance from the center of the anchorage device to the edge of the concrete member. Effective Prestress - Stress remaining in concrete due to prestressing after all calculated losses have been deducted, excluding effects of superimposed loads and weight of member; stress remaining in prestressing tendons after all losses have occurred excluding effects of dead load and superimposed load. Elastic Shortening of Concrete - Shortening of member caused by application of forces induced by prestressing. End Anchorage - Length of reinforcement, or mechanical anchor or a hook, or combination thereof, beyond point of zero stress in reinforcement. See Anchorage Device. End Block - Enlarged end section of member designed to reduce anchorage stresses. Friction - Surface resistance between tendon and duct in contact during stressing. General Zone - Region within which the concentrated prestressing force spreads out to a more linear stress distribution over the cross section of the member (Saint Venant Region). Grout Opening or Vent - Inlet, outlet, vent, or drain in post-tensioning duct for grout, water or air. © 2011, American Railway Engineering and Maintenance-of-Way Association

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AREMA Manual for Railway Engineering

Prestressed Concrete Intermediate Anchorage - Anchorage not located at the end surface of a member or segment; usually in the form of embedded anchors, blisters, ribs, or recess pockets. Jacking Force - Temporary force exerted by device that introduces tension into prestressing tendons. Loss of Prestress - Reduction in prestressing force resulting from combined effects of strains in concrete and steel, including effects of elastic shortening, creep and shrinkage of concrete, relaxation of steel stress, friction, and anchorage seating. Post-Tensioning - Method of prestressing in which tendons are tensioned after concrete has hardened. Precompressed Zone - Portion of flexural member cross-section compressed by prestressing force. Prestressed Concrete - Reinforced concrete in which internal stresses have been introduced to reduce potential tensile stresses in concrete resulting from loads. Pretensioning - Method of prestressing in which tendons are tensioned before concrete is placed. Relaxation of Tendon Stress - Time-dependent reduction of stress in prestressing tendon at constant strain. Shear Lag - Nonuniform distribution of transverse bending stress over the cross section. Shrinkage of Concrete - Time-dependent deformation of concrete caused by drying and chemical changes (hydration process).

1

Special Anchorage Device - Anchorage device whose adequacy must be proven empirically as specified by construction contract documents. Tendon - Wire, strand, or bar, or bundle of such elements, used to impart prestress to concrete. Transfer -

3

(1) Act of transferring stress in prestressing tendons from jacks or pretensioning bed to concrete member. (2) Transfer of stress in a pretensioned tendon to surrounding concrete. Transfer Length - Length over which prestressing force is transferred to concrete by bond in pretensioned members. Wobble Friction - Friction caused by unintended deviation of prestressing sheath or duct from its specified profile. Wrapping or Sheathing - Enclosure around a prestressing tendon to prevent bond between prestressing tendon and surrounding concrete.

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AREMA Manual for Railway Engineering

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Concrete Structures and Foundations

SECTION 17.4 MATERIALS 17.4.1 CONCRETE (2001) Concrete shall conform to the provisions of Part 1. The required compressive strength, fc', of the concrete for the various members shall be as shown on the plans. The minimum fc' for prestressed concrete should be 4500 psi (31 MPa).

17.4.2 PRESTRESSING TENDONS (2001) Provisions of Part 17 shall apply to members prestressed with wire, strands, or bars conforming to one of the following specifications: – "Standard Specification for Steel Strand Uncoated Seven-Wire for Prestressed Concrete" (ASTM A416). – "Standard Specification for Uncoated Stress-Relieved Steel Wire for Prestressed Concrete" (ASTM A421). – "Standard Specification for Uncoated High-Strength Steel Bar for Prestressing Concrete" (ASTM A722).

17.4.3 NON-PRESTRESSED REINFORCEMENT (2001) Non-prestressed reinforcement shall conform to the provisions of Part 1 and Article 17.28.

17.4.4 GROUT FOR POST-TENSIONING TENDONS (2006)1 All grout for post-tensioning tendons shall comply with the provisions of the current PTI GUIDE SPECIFICATION “SPECIFICATION FOR GROUTING OF POST-TENSIONED STRUCTURES” prepared by the Post-Tensioning Institute Committee on Grouting Specifications and published by the Post-Tensioning Institute. The applicable provisions of the PTI guide specification include the following: a.

Materials

b. Design c.

Testing, Quality Assurance and Quality Control

d. Requirements for Technician and Inspector Certification

17.4.5 RIGID DUCTS (2001) Rigid ducts shall have sufficient strength to maintain their correct alignment without visible wobble during placement of concrete. Rigid ducts may be fabricated with either welded or interlocked seams. Galvanizing of the welded seam will not be required.

1

See C - 17.4.4 Grout for Post-Tensioning Tendons (2006)

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Prestressed Concrete

SECTION 17.5 DETAILS OF PRESTRESSING TENDONS AND DUCTS 17.5.1 SPACING OF TENDONS AND DUCTS (2006)1 a.

The minimum clear distance between prestressing tendons at each end of a member shall not be less than 1-1/3 times the maximum size of the coarse aggregate. The minimum spacing center-to-center of tendon shall be as follows: Tendon Size

Spacing

1/2 inch special, 9/16 inch, 9/16 inch special, and 0.6 inch

2 inches (50 mm)

7/16 inch and 1/2 inch

1-3/4 inches (45 mm)

3/8 inch

1-1/2 inches (40 mm)

b. Clear distance between post-tensioning ducts or trumpets at each end of a member shall not be less than 1-1/2 in. (40 mm) nor 1-1/2 times the maximum size of the coarse aggregate. c.

Post-tensioning ducts may be bundled in groups of 3 maximum, provided the spacing limitations specified in Paragraph b are maintained in the end 3 feet (900 mm) of the member.

d. Where pretensioning tendons are bundled, all bundling shall be done in the middle third of the beam length and the deflection points shall be investigated for secondary stresses.

1

17.5.2 MINIMUM CONCRETE COVER (2001) a.

For Precast Concrete the following minimum concrete cover shall be provided for prestressing tendons and non-prestressed reinforcement, and ducts: Minimum Cover Pretensioning tendons .................................

1½ in. (40 mm)

3

Post-tensioning ducts ........................... 1½ in. (40 mm), but not less than dd/2 Non-prestressed reinforcement ....................... Stirrups, ties and spirals ..........................

1½ in. (40 mm) 1 in. (25 mm)

b. For Cast-in-Place Concrete, the following minimum concrete cover shall be provided for prestressing tendons and non-prestressed reinforcement, and ducts: Post-tensioning ducts ...........................

3 in. (75 mm), but not less than dd/2

Non-prestressed reinforcement ........................

1

2 in. (50 mm)

Stirrups, ties and spirals ......................

2 in. (50 mm)

Concrete cast against earth ......................

3 in. (75 mm)

See C - 17.5.1 Spacing of Tendons and Ducts (2006)

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Concrete Structures and Foundations

c.

In corrosive or marine environments or other severe exposure conditions, the amount of tendon and reinforcement protection shall be increased by use of more dense and impervious concrete, by increasing the minimum cover or other suitable means.

17.5.3 PROTECTION FOR PRESTRESSING TENDONS (2001) a.

Anchorages, end fittings, couplers, and exposed tendons shall be protected from corrosion.

b. Burning or welding operations in vicinity of prestressing tendons shall be carefully performed, so that tendons are not subjected to excessive temperatures, welding sparks, or ground currents and the shock to the concrete is minimized.

17.5.4 PROTECTION FOR DEBONDED PRESTRESSING TENDON (2001) Tendon wrapping, sheathing, or coating shall be continuous over entire debonded length, and shall prevent intrusion of cement paste during concrete placement.

17.5.5 POST-TENSIONING DUCTS (2001) a.

Ducts shall be mortar-tight and nonreactive with concrete, tendons, or grout.

b. Ducts for single wire, strand, or bar tendons shall have an inside diameter not less than ¼ in. (10 mm) larger than tendon diameter. c.

Ducts for multiple wire, strand, or bar tendons shall have an inside cross sectional area not less than 2 times the net area of tendons.

d. Ducts shall be maintained free of water. e.

Ducts shall be grouted within twenty-four hours of post-tensioning, unless otherwise directed by the Engineer.

17.5.6 POST-TENSIONING ANCHORAGES AND COUPLERS (2001) a.

Anchorages and couplers for post-tensioning tendons shall develop not less than 95 percent of the specified ultimate strength of the tendons, when tested in an unbonded condition, without exceeding anticipated set.

b. Couplers shall be located in areas approved by the Engineer and enclosed in housing long enough to permit necessary movements. Couplers shall not be located at points of sharp tendon curvature. Couplers located in areas of high stress range shall be investigated for fatigue.

17.5.7 TENDON ANCHORAGE ZONES (2001) a.

Reinforcement shall be provided where required in tendon anchorage zones to resist bursting, splitting, and spalling forces induced by tendon anchorages. Regions of abrupt change in section shall be adequately reinforced.

b. End blocks shall be provided where required for support bearing or for distribution of concentrated prestressing forces.

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c.

Post-tensioning anchorages and supporting concrete shall be designed to resist maximum jacking force for strength of concrete at time of prestressing.

d. For design criteria of post-tensioning anchorage zones refer to Article 17.22.

17.5.8 DEVELOPMENT OF PRESTRESSING STRAND1 (2001) a.

Seven-wire prestressing strand shall be bonded beyond the critical section for a development length, in inches (mm), not less than (f*su - 2/3 fse) D

EQ 17-2

(f*su - 2/3 fse) D/7

EQ 17-2 (Metric)

where D is strand diameter in inches (mm), and f*su and fse are expressed in ksi (MPa). b. Investigation may be limited to cross sections nearest each end of the member that are required to develop full design strength under specified factored loads.

1

SECTION 17.6 GENERAL ANALYSIS2 All members shall be designed for adequate strength and satisfactory behavior using these recommended practices as minimum guidelines. Behavior shall be determined by elastic analysis, taking into account the reactions, moments, shears, and axial forces produced by prestressing, the effects of temperature, creep, shrinkage, axial deformation, restraint of attached structural elements, and foundation settlement.

3

SECTION 17.7 EXPANSION AND CONTRACTION In all bridges, provisions shall be made in the design to resist thermal stresses induced, or means shall be provided for movement caused by temperature changes. Movements not otherwise provided for, including shortening during stressing, shall be provided for by means of hinged columns, rockers, sliding plates, elastomeric pads, or other devices.

SECTION 17.8 SPAN LENGTH The effective span lengths of simply supported beams shall be the distance center to center of bearings.

1 2

See C - 17.5.8 Development of Prestressing Strand (2001) See C - Section 17.6 General Analysis

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

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Concrete Structures and Foundations

The span length of continuous or restrained floor slabs and beams shall be the distance center to center of supports. Where fillets making an angle of 45 degrees or more with the axis of a continuous or restrained slab are built monolithic with the slab and support, the span shall be measured from the section where the combined depth of the slab and the fillet is at least one and one-half times the thickness of the slab. Maximum negative moments are to be considered as existing at the ends of the span, as above defined. No portion of the fillet shall be considered as adding to the effective depth.

SECTION 17.9 FRAMES AND CONTINUOUS CONSTRUCTION1 Frames and continuous construction of prestressed concrete, where permitted by the Engineer, shall be designed for adequate strength and for satisfactory performance at service load conditions. Moments to be used to compute required strength shall be the algebraic sum of the moments due to reactions induced by prestressing (with a load factor of 1.0) and the moments due to factored loads. Composite flexural members consisting of prestressed concrete elements shall be designed in accordance with Article 2.23.9. Design for horizontal shear shall be in accordance with Articles 2.29.5 or 2.35.5. Composite Semi-Continuous Construction a.

These provisions shall apply for design of superstructures of two or more spans composed of simple span precast-prestressed girders made continuous with deck slab for live load and superimposed dead load.

b. Positive Moment Connection at Piers (1) Provision shall be made for positive moments that may develop at piers due to combined effects of creep and shrinkage in girders and deck slab, and due to effects of live load in remote spans. (2) Non-prestressed positive moment connection reinforcement may be designed for a service load stress of 0.6 fy but not greater than 36 ksi (250 MPa). c.

Continuity Negative Moment Reinforcement (1) Non-prestressed negative moment reinforcement shall be proportioned by the strength design method of Part 2 of this Chapter. (2) Effect of initial precompression due to prestress in the precast girders may be neglected in calculation of negative moment strength if maximum precompression stress is limited to 0.45f 'c and continuity reinforcement ratio is less than 0.015. (3) Negative moment strength shall be calculated using compressive strength of girder concrete, regardless of strength of diaphragm concrete. (4) Extreme fiber stress in compression at ends of girders at piers due to prestress and negative continuity moment shall not exceed 0.60f 'c.

1

See C - Section 17.9 Frames and Continuous Construction

© 2011, American Railway Engineering and Maintenance-of-Way Association

8-17-14

AREMA Manual for Railway Engineering

Prestressed Concrete

Segmental Box Girders shall conform to the requirements of Part 26 of these recommended practices.

SECTION 17.10 EFFECTIVE FLANGE WIDTH For composite prestressed construction where slabs or flanges are assumed to act integrally with the beam, the effective flange width shall conform to the provisions for T-girder flanges in Article 2.23.10. For monolithic prestressed construction, with normal slab span and girder spacing, the effective flange width shall be the distance center-to-center of beams. For very short spans, or where girder spacing is excessive, analytical investigations shall be made to determine the effective width of flange acting with the beam. For monolithic prestressed design of isolated beams, the flange width shall not exceed 15 times the web width and shall be adequate for all design loads. For cast-in-place box girders with normal slab span and girder spacing, where the slabs are considered an integral part of the girder, the entire slab width shall be assumed to be effective in compression. For box girders of unusual proportions, methods of analysis which consider shear lag shall be used to determine stresses in the cross section due to longitudinal bending. Adequate fillets shall be provided at the intersections of all surfaces within the cell of a box girder, except at the junction of web and bottom flange where none are required.

1

17.10.1 PRECAST/PRESTRESSED CONCRETE BEAMS WITH WIDE TOP FLANGES (2001) a.

For composite prestressed concrete where slabs or flanges are assumed to act integrally with the precast beam, the effective web width of the precast beam shall be the lesser of:

3

(1) six (6) times the maximum thickness of the flange (excluding fillets) on either side of the web plus the web and fillets; and, (2) the total width of the top flange.

4

b. The effective flange width of the composite section shall be the lesser of: (1) one-fourth of the span length of the girder; (2) six (6) times the thickness of the slab on each side of the effective web width as determined by Article 17.10.1a plus the effective web width; and, (3) one-half the clear distance on each side of the effective web width plus the effective web width.

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

8-17-15

Concrete Structures and Foundations

SECTION 17.11 FLANGE AND WEB THICKNESS-BOX GIRDERS1 The minimum top flange thickness shall be 1/30th of the clear distance between fillets or webs but not less than 6 inches (150 mm), except the minimum thickness may be reduced for factory produced precast, pretensioned elements to 5 ½ inches (140 mm). The minimum bottom flange thickness shall be 1/30th of the clear distance between fillets or webs but not less than 5 ½ inches (140 mm), except the minimum thickness may be reduced for factory produced precast, pretensioned elements to 5 inches (130 mm). Changes in girder stem thickness shall be tapered for a minimum distance of 12 times the difference in web thickness.

SECTION 17.12 DIAPHRAGMS2 a.

Diaphragms shall be provided in accordance with Articles 17.12b through 17.12e, except that adequate bracing of the compression flange shall be provided by a cast-in-place deck.

b. Diaphragms or other means shall be used at span ends to strengthen the free edge of the slab and to transmit forces to the substructure. c.

For spread box beams, diaphragms shall be placed within the box and between boxes at span ends and at the points of maximum moment for spans over 80 feet (24 m).

d. For precast box multi-beam bridges, diaphragms are required only if necessary for slab end support or to contain or resist transverse tension ties. e.

For cast-in-place box girders, diaphragms or other means shall be used at span ends to resist lateral forces and maintain section geometry. Intermediate diaphragms are not required for bridges with inside radius of curvature of 800 feet (245 m) or greater.

f.

For all types of prestressed boxes in bridges with inside radius of curvature less than 800 feet (245 m), intermediate diaphragms may be required and the spacing and strength of diaphragms shall be given special consideration in the design of the structure.

SECTION 17.13 DEFLECTIONS Flexural members of bridge structures shall be designed to have adequate stiffness to limit deflections or any deformations that may adversely affect strength and serviceability of the structure at service load. Members having simple or continuous spans shall be designed so that the deflection due to service live load plus impact does not exceed l/640 of the span. Deflections that occur immediately on application of load shall be computed by usual methods or formulas for elastic deflections, and moment of inertia of gross concrete section may be used for uncracked sections. 1 2

See C - Section 17.11 Flange and Web Thickness-Box Girders See C - Section 17.12 Diaphragms

© 2011, American Railway Engineering and Maintenance-of-Way Association

8-17-16

AREMA Manual for Railway Engineering

Prestressed Concrete

Additional long-time deflection shall be computed taking into account stresses in concrete and steel under sustained load and including effects of creep and shrinkage of concrete and relaxation of prestressing steel. Modulus of elasticity Ec for concrete and Es for nonprestressed steel reinforcement shall be as specified in Article 2.23.4. Modulus of elasticity Es for prestressing tendons shall be determined by tests or supplied by manufacturer.

SECTION 17.14 GENERAL DESIGN 17.14.1 DESIGN THEORY AND GENERAL CONSIDERATIONS (2001) 17.14.1.1 Design of prestressed members shall be based on strength (Load Factor Design) and on behavior at service load conditions (Article 17.6) at all load stages that may be critical during the life of the structure from the time prestressing is first applied. 17.14.1.2 Stress concentrations due to prestressing shall be considered in design. 17.14.1.3 Effects of temperature, creep and shrinkage shall be considered in design.

17.14.2 BASIC ASSUMPTIONS (2001)

1

17.14.2.1 Strength design of prestressed members for flexure and axial loads shall be based on the following assumptions for design of monolithic members: a.

Strains vary linearly over the depth of the member throughout the entire load range.

b. Before cracking, stress is linearly proportional to strain. c.

3

After cracking, tension in the concrete is neglected.

17.14.3 COMPOSITE FLEXURAL MEMBERS (2001)1 Composite flexural members consisting of precast and/or cast-in-place concrete elements constructed in separate placements but so interconnected that all elements respond to superimposed loads as a unit shall conform to the provisions of Articles 17.21.4 and the following:

1

See C - 17.14.3 Composite Flexural Members (2001)

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AREMA Manual for Railway Engineering

8-17-17

4

Concrete Structures and Foundations 17.14.3.1 When an entire member is assumed to resist the vertical shear, the design shall be in accordance with the requirements of Articles 17.21.1 through 17.21.3. 17.14.3.2 The design shall provide for full transfer of horizontal shear forces at contact surfaces of interconnected elements. Design for horizontal shear shall be in accordance with the requirements of 17.21.4.

SECTION 17.15 LOAD FACTORS 17.15.1 REQUIRED STRENGTH (2001) a.

Prestressed members shall have design strengths at all sections at least equal to the required strengths calculated for the factored loads and forces in such combinations as stipulated in Article 2.2.4c for the load groups that are applicable. For the design of post-tensioned anchorage zones, a load factor of 1.2 shall be applied to the maximum tendon jacking force.

b. The following strength capacity reduction factors shall be used: (1) For flexure: j = 0.95 (2) For shear j = 0.90 (3) For anchorage zones j = 0.85 for normal weight concrete and j = 0.70 for lightweight concrete

SECTION 17.16 ALLOWABLE STRESSES The design of precast prestressed members and cast-in-place post-tensioned concrete spans ordinarily shall be based on f 'c = 5000 psi (35 MPa). An increase to 6000 psi (40 MPa) is permissible where, in the Engineer’s judgement, it is reasonable to expect that this strength will be obtained consistently. Higher concrete strengths may be considered on an individual basis. In such cases, the Engineer shall satisfy himself completely that the controls over materials and fabrication procedures will provide the required strengths. The provisions of this Article are equally applicable to prestressed concrete structures and components designed with lower concrete strengths.

17.16.1 PRESTRESSING TENDONS (2001) 17.16.1.1 Tensile stress in prestressing tendons shall not exceed the following: a.

Due to tendon jacking force .................................................................................................. 0.75f 's or 0.90f*y whichever is smaller, but not greater than the maximum value recommended by the manufacturer of the prestressing tendons or anchorages.

b. Slight over stressing of pretensioning tendons up to 0.85f 's for short periods of time may be permitted to offset seating losses, provided the stress after seating does not exceed the value in Paragraph a. c.

Stress-relieved pretensioning tendons immediately after prestress transfer .................... 0.82f*y or 0.70f 's © 2011, American Railway Engineering and Maintenance-of-Way Association

8-17-18

AREMA Manual for Railway Engineering

Prestressed Concrete

whichever is larger. d. Stabilized (low-relaxation) pretensioning tendons immediately after prestress transfer..0.82f*y or 0.75f 's whichever is larger. 17.16.1.2 Tensile stress in post-tensioning shall not exceed the following: a.

Immediately after tendon anchorage ....................................................................................0.82f*y or 0.70f 's whichever is larger, but not greater than 0.70f 's at end anchorage.

b. Over stressing of post-tensioning tendons up to 0.90f 's for short periods of time may be permitted to offset seating and friction losses provided the stress at the anchorage does not exceed the value in Paragraph a. above. The stress at the end of the seating loss zone must not exceed 0.82f*y immediately after seating.

17.16.2 CONCRETE (2001)1 17.16.2.1 Stresses in concrete immediately after prestress transfer (before time-dependent prestress losses-Creep and Shrinkage) shall not exceed the following: a.

Extreme fiber stress in compression

1

Pretensioned members..................................................................0.60f 'ci Post-tensioned members...............................................................0.55f 'ci b. Extreme fiber stress in tension

3

(1) Members without bonded auxiliary reinforcement .............................. 200 psi (1.38 MPa) or 3 f ¢ ci

0.25 f ¢ ci (metric)

Where the calculated tensile stress exceeds this value, bonded reinforcement shall be provided to resist the total tension force in the concrete computed on the assumption of an uncracked section.

1

See C - 17.16.2 Concrete (2001)

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

8-17-19

4

Concrete Structures and Foundations (2) Members with bonded auxiliary reinforcement provided in the tensile zone to resist the total tensile force in concrete computed with the assumption of an uncracked section .......................... 7.5 f ¢ ci

0.623 f ¢ ci (metric) 17.16.2.2 Stresses in concrete at service loads (after allowance for all prestress losses) shall not exceed the following: Compression...........................................................................................................................0.40f 'c Tension in the precompressed tensile zone...................................................................................0 Tension in other areas is limited by allowable temporary stresses specified in Article 17.16.2.1. 17.16.2.3 Cracking Stress1 Modulus of rupture from tests or if not available: For normal weight concrete................................................................................ 7.5 f ¢ c

0.623 f ¢ c (metric)

For sand lightweight concrete............................................................................... 6.3 f ¢ c

0.523 f ¢ c (metric) 17.16.2.4 Anchorage Bearing Stress Post-tensioned anchorage at service load.......................................................................................3000 psi (21 MPa) (but not to exceed 0.9f 'ci)

1

Refer to Article 17.19 © 2011, American Railway Engineering and Maintenance-of-Way Association

8-17-20

AREMA Manual for Railway Engineering

Prestressed Concrete

SECTION 17.17 LOSS OF PRESTRESS 17.17.1 PRESTRESS LOSSES (2004) a.

To determine effective prestress fse, allowance for the following sources of loss of prestress shall be considered: Df s = ES + CR c + SH + CR s where: ES =Elastic shortening of concrete CRc =Creep of concrete SH =Shrinkage of concrete CRs =Relaxation of tendon stress Anchorage seating and friction due to intended or unintended curvature in post-tensioning tendons shall be considered.

1 b. Total loss of prestress shall be determined in accordance with a method of calculating prestress losses supported by appropriate research data, representing properties of the materials to be used, methods of curing, ambient service conditions, and any pertinent structural details.1 c.

In lieu of the more exact procedure prescribed in Paragraph b, loss of prestress may be determined in accordance with either Paragraph d or Paragraph e for the conditions stated.

3

d. Loss of prestress may be determined by the following procedure for normal weight concrete and the following types of prestressing tendons: 270 ksi (1860 MPa) uncoated seven-wire stress-relieved or low-relaxation strand; 145 to 160 ksi (1000 to 1100 MPa) uncoated high-strength steel bar (plain or deformed). Data representing properties and effects of lightweight concrete shall be determined from documented tests. (1) Elastic shortening of concrete (a) For Pretensioned members: E ES = æ -------s-ö f cir èE ø ci

1

EQ 17-3

“Estimating Prestress Losses” by Paul Zia, H. Kent Preston, Norman L. Scott, and Edwin B. Workman, ACI Concrete International, June 1979, pp. 32-38.

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AREMA Manual for Railway Engineering

8-17-21

4

Concrete Structures and Foundations (b) For Post-tensioned1 members:

E ES = 0.5 æ -------s-ö f cir èE ø ci

EQ 17-4

Es = modulus of elasticity for prestressing tendons to be determined from documented test data. Eci = modulus of elasticity for concrete at time of transfer; may be taken as wc

wc

1.5

1.5

( 33 ) f

¢

ci

( 0.0428 ) f

¢

in pounds per square inch

ci

in MPa

fcir = stress in concrete at centroid of prestressing reinforcement immediately after transfer, due to total prestress force and dead load acting at transfer. fcir shall be computed at the section or sections of maximum moment. For pretensioned members, fcir shall be calculated using a prestress force reduced below stress at transfer by elastic shortening of concrete and tendon relaxation during placing and curing of concrete. For post-tensioned members, fcir shall be calculated using a prestress force reduced below stress at transfer by elastic shortening of concrete and tendon friction. Amount of reduction below prestress stress at transfer can be estimated, or for pretensioned members the reduced tendon stress may be taken as 0.63fs', for stress relieved strand or 0.69fs' for low relaxation strand. (2) Creep of concrete (a) For pretensioned and post-tensioned members: EQ 17-5

CRc = 12fcir - 7fcds where:

fcds = stress in concrete at centroid of prestressing reinforcement, due to all dead load not included in calculation of fcir. (3) Shrinkage of Concrete

1

Certain post-tensioning procedures may alter the elastic shortening loss.

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8-17-22

AREMA Manual for Railway Engineering

Prestressed Concrete (a) For pretensioned members: SH = 17 - 0.150 R

EQ 17-6

SH = 117 - 1.03 R

EQ 17-6 (Metric)

(b) For post-tensioned members: SH = 0.8 (17 - 0.150 R)

EQ 17-7

SH = 0.8 (117 - 1.03 R)

EQ 17-7 (Metric)

where: R = annual average ambient relative humidity in percent. The following map may be used to determine R.

1

3

Figure 8-17-1. Annual Average Ambient Relative Humidity, (R), %

4

(4) Relaxation of tendon stress

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

8-17-23

Concrete Structures and Foundations

(a) For Pretensioning tendons: 1

270 ksi stress-relieved strand tensioned to 0.70f's EQ 17-8a

CRs = 20 - 0.4 ES - 0.2 (SH + CRc) 2

1860 MPa stress-relieved strand tensioned to 0.70f's EQ 17-8a (Metric)

CRs = 138 - 0.4 ES - 0.2 (SH + CRc) 3

270 ksi low-relaxation strand tensioned to 0.75f's EQ 17-8b

CRs = 5 - 0.10 ES - 0.05 (SH + CRc) 4

1860 MPa low-relaxation strand tensioned to 0.75f's EQ 17-8b (Metric)

25% of CRs in previous above (b) For Post-tensioning tendons: 1

270 ksi stress-relieved strand anchored at 0.70f's EQ 17-9a

CRs = 20 - 0.3 FR - 0.4 ES - 0.2 (SH + CRc) 2

1860 MPa stress-relieved strand anchored at 0.70f's EQ 17-9a (Metric)

CRs = 138 - 0.3 FR - 0.4 ES - 0.2 (SH + CRc) 3

270 ksi low-relaxation strand anchored at 0.75 f's EQ 17-9b

CRs = 5 - 0.07 FR - 0.1 ES - 0.05 (SH + CRc) 4

1860 MPa low-relaxation strand anchored at 0.75f's EQ 17-9b (Metric)

CRs = 25% of CRs in EQ 17-9a above 5

145 to 160 ksi high-strength steel bar EQ 17-9c

CRs = 3.0 6

1000 to 1100 MPa high-strength steel bar CRs = Loss due to relaxation should be based on approved test data. If test data are not available the loss may be assumed to be 21 MPa

EQ 17-9c (Metric)

where: FR = friction loss below 0.70f's at point being considered, computed according to Paragraph d(6) below. ES, SH, CRc = appropriate values as determined for either pretensioned or post-tensioned member.

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8-17-24

AREMA Manual for Railway Engineering

Prestressed Concrete

(5) Anchorage Seating Allowance shall be made for loss of prestress in post-tensioning tendons due to anchorage seating. Calculations shall be made in accordance with a method consistent with the friction coefficients for the materials used. (6) Friction Effect of friction loss due to intended or unintended curvature in post-tensioning tendons shall be computed by: f lfx = f po [ l – e – ( Kl x + ma ) ]

EQ 17-10

T o = T x e ( KL + ma ) When (Klx + µa) is not greater than 0.3, effect of friction loss may be computed by: f lfx = f po ( Kl x + ma )

1

T o = T x ( 1 + KL + ma )

EQ 17-11

Friction coefficients K and µ shall be determined experimentally, and shall be verified during tendon stressing operations. When experimental data for the materials used are not available, the following values for K and µ may be used.

3

Table 8-17-1. Values for K and µ

4 K

m

Bright Metal Sheathing

0.0020 (0.0027)

0.30

Galvanized Metal Sheathing

0.0015 (0.0020)

0.25

Galvanized Rigid

0.0002 (0.00027)

0.25

Polyethylene

0.0020 (0.0027)

0.25

0.0003 (0.0004)

0.20

0.0002 (0.00027)

0.15

Type of Steel

Type of Duct

Uncoated wire or strand

Uncoated high strength bar Bright Metal Sheathing Galvanized Metal Sheathing

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

8-17-25

Concrete Structures and Foundations

Friction losses should be estimated for design and verified during stressing operations. Rigid ducts shall have sufficient strength to maintain proper alignment without visible wobble during placement of concrete. Rigid ducts may be fabricated with either welded or interlocked seams. Galvanizing of the welded seam will not be required. e.

Loss of prestress, excluding friction loss, may be estimated for preliminary design in accordance with the following values for prestressed members or structures of usual design. Tabulated estimates are based on normal weight concrete, normal prestressing levels, and average exposure conditions. Friction loss in post-tensioning tendons shall be determined in accordance with Paragraph d(6), above. Table 8-17-2. Estimated Loss of Prestress

Total Loss of Prestress (Note 1) Type of Prestressing Tendon

f¢c = 5,000 psi (35 MPa)

f¢c = 4,000 psi (28 MPa)

Pretensioning tendon: Stress relieved

45,000 psi (310 MPa)

Low relaxation

35,000 psi (240 MPa)

Post-tensioning wire or strand: Stress relieved

32,000 psi (220 MPa)

33,000 psi (228 MPa)

Low relaxation

24,000 psi (165 MPa)

25,000 psi (172 MPa)

Post-tensioning bar

22,000 psi (152 MPa)

23,000 psi (158 MPa)

Note 1: Excluding friction losses in post-tensioning tendons.

SECTION 17.18 FLEXURAL STRENGTH1 17.18.1 INTRODUCTION (2001) Prestressed concrete members may be assumed to act as uncracked members subjected to combined axial and bending stresses within specified service loads. In calculations of section properties, the transformed area of bonded reinforcement may be included in pretensioned members and in post-tensioned members after grouting; prior to bonding of tendons, areas of the open ducts shall be deducted.

17.18.2 RECTANGULAR SECTIONS (2001) For rectangular or flanged sections having prestressing steel only, in which the depth of the equivalent rectangular stress block, defined as (A*s f*su)/(0.85 f 'cb), is not greater than the compression flange thickness “t”, and which satisfy EQ 17-23, the design flexural strength shall be assumed as: jMn = j[A*s f*su d{1-0.6(p*f*su/f'c)}]

1

EQ 17-12

See C - Section 17.18 Flexural Strength

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8-17-26

AREMA Manual for Railway Engineering

Prestressed Concrete

For rectangular or flanged sections with non-prestressed tension reinforcement included, in which the depth of the equivalent rectangular stress block, defined as (A*s f*su + As fsy)/(0.85 f'c b), is not greater than the compression flange thickness “t” and which satisfy EQ 17-24, the design flexural strength shall be assumed as: jMn=j{A*sf*sud[1-0.6((p*f*su/f'c)+(dt/d)(pfsy/f'c))]+Asfsydt[1-0.6((d/dt)(p*f*su/f'c)+(pfsy/f'c))]}EQ 17-13

17.18.3 FLANGED SECTIONS (2001) For sections having prestressing steel only, in which the depth of the equivalent rectangular stress block, defined as (Asr f*su)/(0.85 f'cb') is greater than the compression flange thickness “t”, and which satisfy EQ 17-24 the design flexural strength shall be assumed as: jMn = j{Asrf*sud[1-0.6(Asrf*su/b'df 'c)] + 0.85 f'c(b-b')(t)(d-0.5t)}

EQ 17-14

For sections with non-prestressed tension reinforcement included, in which the depth of the equivalent rectangular stress block, defined as (Asr f*su)/(0.85 f'cb') is greater than the compression flange thickness “t”, and which satisfy EQ 17-24, the design flexural strength shall be assumed as: jMn = j{Asrf*sud[1-0.6(Asrf*su/b' df'c)] + Asfsy(dt-d) + 0.85 f'c(b-b')(t)(d-0.5t)}

EQ 17-15

Asr = A*s - Asf, in EQ 17-14

EQ 17-16

Asr = A*s + (Asfsy/f*su) - Asf, in EQ 17-15

EQ 17-17

Asf = 0.85f'c(b-b')t/f*su

EQ 17-18

where:

Asf = The steel area required to develop the ultimate compressive strength of the overhanging portions of the flange.

1

3

17.18.4 STEEL STRESS (2001) 17.18.4.1 As an alternative to a more accurate determination of f*su based on strain compatibility, the following approximate values of f*su shall be permitted to be used: Bonded Members: with prestressing only (as defined): f*su = f's[1-(g*/ß1)(p*f's/f'c)]

EQ 17-19

with non-prestressed tension reinforcement included: f*su = f's{1-(g*/ß1)[(p*f's/f'c)+dt/d(pfsy/f'c)]}

EQ 17-20

where g* : = 0.28 for low-relaxation steel

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AREMA Manual for Railway Engineering

8-17-27

4

Concrete Structures and Foundations = 0.40 for stress-relieved steel = 0.55 for bars Unbonded members: f*su = fse + 15,000 f*

su

EQ 17-21 EQ 17-21 (Metric)

= fse + 100

provided that: a.

The stress strain properties of the prestressing steel conform to the requirements of ASTM A416 (LowRelaxation).

b. The effective prestress after losses is not less than 0.5 f 's. 17.18.4.2 At ultimate load, the stress in the prestressing steel of precast deck panels shall be limited to: f*su = lx/D + 2/3 fse

EQ 17-22

f*su = 7 lx/D + 2/3 fse

EQ 17-22 (Metric)

but shall not be greater the f*su as given by the equations in Article 17.18.4.1. In the above equation: D = nominal diameter of strand in inches (mm); fse = effective stress in prestressing strand after losses in psi (MPa); lx = distance from end of prestressing strand to center of panel in inches (mm).

SECTION 17.19 DUCTILITY LIMITS 17.19.1 MAXIMUM PRESTRESSING STEEL (2001) Prestressed concrete members shall be designed so that the steel is yielding as ultimate capacity is approached. In general, the reinforcement index shall be such that: EQ 17-23

p*f*su/f 'c, for rectangular sections and

EQ 17-24

Asrf*su/b'df 'c, for flanged sections does not exceed 0.36ß1. (See Article 17.20 for reinforcement indices of sections with non-prestressed reinforcement).

For members with reinforcement indices greater than 0.36ß1, the design flexural strength shall be assumed not greater than:

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8-17-28

AREMA Manual for Railway Engineering

Prestressed Concrete

jMn = j[(0.36ß1 - 0.08ß12)f'cbd2]

For rectangular sections:

jMn = j[(0.36ß1 - 0.08ß12)f'cbd2 +0.85f'c(b-b')t(d-0.5t)]

For flanged sections:

EQ 17-25 EQ 17-26

17.19.2 MINIMUM REINFORCEMENT (2001) 17.19.2.1 The total amount of prestressed and non-prestressed reinforcement shall be adequate to develop an ultimate moment at the critical section at least 1.2 times the cracking moment M*cr.

jM n ³ 1.2M* cr where: M*cr = (fr + fpe)Sc - Md/nc(Sc/Sb - 1)

EQ 17-27

Appropriate values for Md/nc and Sb shall be used for any intermediate composite sections. Where beams are designed to be noncomposite, substitute Sb for Sc in the above equation for the calculation of M*cr. 17.19.2.2 The minimum amount of non-prestressed longitudinal reinforcement provided in the cast-inplace portion of slabs utilizing precast prestressed deck panels shall be 0.25 square inch per foot (530 mm2 per meter) of slab width.

SECTION 17.20 NON-PRESTRESSED REINFORCEMENT

1

3

Non-prestressed reinforcement may be considered as contributing to the tensile strength of the beam at design flexural strength in an amount equal to its area times yield strength, provided that: For rectangular sections: ( pf sy ¤ f¢ c )d t ¤ d + ( p*f* su ¤ f¢ c ) – ( p¢f¢ y ¤ f¢ c ) £ 0.36b 1

EQ 17-28

For flanged sections: ( A s f sy ) ¤ ( b¢df¢ c ) + ( A sr f* su ) ¤ ( b¢df¢ c ) – ( A¢ s f ¢ y ) ¤ ( b¢df¢ c ) £ 0.36b 1

EQ 17-29

Design flexural strength shall be calculated based on EQ 17-13 or EQ 17-15 if these values are met, and on EQ 17-25 or EQ 17-26 if these values are exceeded.

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AREMA Manual for Railway Engineering

8-17-29

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Concrete Structures and Foundations

SECTION 17.21 SHEAR 17.21.1 GENERAL (2001) 17.21.1.1 Prestressed concrete flexural members, except solid slabs and footings, shall be reinforced for shear and diagonal tension stresses. Voided slabs shall be investigated for shear, but shear reinforcement may be omitted if the factored shear force, Vu, is less than half the shear strength provided by the concrete jVc. 17.21.1.2 Web reinforcement shall consist of stirrups perpendicular to the axis of the member or welded wire fabric with wires located perpendicular to the axis of the member. Web reinforcement shall extend to a distance d from the extreme compression fiber and shall be carried as close to the compression and tension surfaces of the member as cover requirements and the proximity of other reinforcement permit. Web reinforcement shall be anchored at both ends for its design yield strength in accordance with the provisions of Article 2.21. 17.21.1.3 Members subject to shear shall be designed so that Vu £ j( Vc + Vs )

EQ 17-30

where Vu is the factored shear force at the section considered, Vc is the nominal shear strength provided by concrete and Vs is the nominal shear strength provided by web reinforcement. 17.21.1.4 When the reaction to the applied loads introduces compression into the end regions of the member, sections located at a distance less than h/2 from the face of the support may be designed for the same shear Vu as that computed at a distance h/2. An exception occurs when major concentrated loads are imposed between that point and the face of support. In that case sections closer than d to the support shall be designed for Vu at distance d plus the major concentrated loads.

17.21.2 SHEAR STRENGTH PROVIDED BY CONCRETE (2007) 17.21.2.1 For members with effective prestress force not less than 40 percent of the total tensile strength of flexural reinforcement, unless a more detailed calculation is made in accordance with 17.21.2.2, shear strength Vc shall be computed by: V u d pö V c = æ 0.6 f¢ c + 700 ------------- b d è M ø w

EQ 17-31

V u d pö æ f¢ V c = ç ---------c- + 5 -------------÷ b d Mu ø w è 20

EQ 17-31 (Metric)

u

but Vc need not be taken less than 2 f¢ c b w d

1 --- f¢ c b w d 6

Metric

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Prestressed Concrete

nor shall Vc be taken greater than 5 f ¢c bw d 0.4 f ¢ c b w d Metric

nor the value given in 17.21.2.3. The quantity Vudp/Mu shall not be taken greater than 1.0, where Mu is factored moment occurring simultaneously with factored shear force, Vu at the section considered. 17.21.2.2 For more precise analysis the shear strength provided by concrete, Vc, shall be taken as the lesser of the values Vci or Vcw. The shear strength, Vci, shall be computed by: V i M cr V ci = 0.6 f¢ c b¢d + V d + ---------------M max

V ci = 5 ´ 10

4

V i M cr f ¢ c b¢d + V d + ---------------M max

EQ 17-32

EQ 17-32 (Metric)

1

but Vci need not be less than 1.7 f¢ c b¢d 220 f¢ c b¢d

3 Metric

and d need not be taken less than 0.8h. The moment causing flexural cracking at the section due to externally applied loads, Mcr, shall be computed by: M cr = ( I ¤ y t ) ( 6 f¢ c + f pe – f d )

EQ 17-33

M cr = ( I ¤ y t ) ( 0.5 f¢ e + f pe – f d )

EQ 17-33 (Metric)

The maximum factored moment and factored shear at the section due to externally applied loads, Mmax and Vi, shall be computed from the load combination causing maximum moment at the section.

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4

Concrete Structures and Foundations 17.21.2.3 The shear strength, Vcw, shall be computed by: EQ 17-34

V cw = ( 3.5 f¢ c + 0.3f pc )b¢d + V p

5

V cw = 10 ´ 10 [ ( 0.29 f¢ c + 0.3f pe )b¢d ] + V p

EQ 17-34 (Metric)

but d need not be taken less than 0.8h. 17.21.2.4 In a pretensioned member in which the section at a distance h/2 from face of support is closer to the end of member than the transfer length of the prestressing steel, the reduced prestress shall be considered when computing Vcw. This value of Vcw shall also be taken as the maximum limit for EQ 17-31. The prestress force shall be assumed to vary linearly from zero at the end of prestressing steel, to a maximum at a distance from the end of prestressing steel equal to the transfer length, assumed to be 50 diameters for strand and 100 diameters for single wire. 17.21.2.5 In a pretensioned member where bonding of some tendons does not extend to the end of member, a reduced prestress shall be considered when computing Vc in accordance with 17.21.2.1 and 17.21.2.2. The value of Vcw calculated using the reduced prestress shall also be taken as the maximum limit for EQ 17-31. The prestress force due to tendons, for which bonding does not extend to the end of member, shall be assumed to vary linearly from zero at the point at which bonding commences to a maximum at a distance from this point equal to the transfer length, assumed to be 50 diameters for strand and 100 diameters for single wire. 17.21.2.6 The provisions for computing the shear strength provided by concrete, Vci and Vcw , apply to normal weight concrete. When lightweight aggregate concretes are used, (see definition, concrete, structural lightweight, Article 2.2.2), one of the following modifications shall apply: a.

When fct is specified, the shear strength, Vci and Vcw, shall be modified by substituting fct/6.7 (1.8 fct) for f¢ c but the value of fct/6.7 (1.8 fct) used shall not exceed f¢ c

b. When fct is not specified, Vci and Vcw shall be modified by multiplying each term containing f¢ c by 0.85 for “sand-lightweight” concrete.

17.21.3 SHEAR STRENGTH PROVIDED BY WEB REINFORCEMENT (2001) Shear reinforcement shall consist of stirrups perpendicular to axis of member or welded wire fabric with wires located perpendicular to axis of member. Shear reinforcement shall be anchored at both ends in accordance with Article 2.21.

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Prestressed Concrete 17.21.3.1 The shear strength provided by web reinforcement shall be taken as EQ 17-35

Vs = (Avfsyd)/s where Av is the area of web reinforcement within a distance s. Vs shall not be taken greater than 8 f¢ c b¢d 0.66 f¢ c b¢d

Metric

and d need not be taken less than 0.8h. 17.21.3.2 The spacing of web reinforcing shall not exceed 0.75h or 24 inches (600 mm). When Vs exceeds 4 f¢ c b¢d 0.332 f¢ c b¢d

Metric

this maximum spacing shall be reduced by one-half.

1

17.21.3.3 Minimum Shear Reinforcement A minimum area of shear reinforcement shall be provided in all flexural members, except: slabs, footings, and shallow beams, where factored shear force Vu exceeds ½ the shear strength provided by concrete jVc, (Beams with total depth not greater than either 10 in. (250 mm), 2-1/2 times the thickness of the flange, or one-half the width of web shall be considered shallow beams).

3

The minimum area of web reinforcement shall be: Av = (50 b's)/fsy

EQ 17-36

Av = (0.345 b's)/fsy

EQ 17-36 (Metric)

4 where

b' and

s are in inches (mm) and fsy is in psi (MPa).

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Concrete Structures and Foundations 17.21.3.4 The design yield strength of web reinforcement, fsy, shall not exceed 60,000 psi (420 MPa).

17.21.4 HORIZONTAL SHEAR DESIGN-COMPOSITE FLEXURAL MEMBERS (2001) 17.21.4.1 In a composite member, full transfer of horizontal shear forces shall be assured at contact surfaces of interconnected elements. 17.21.4.2 Design of cross sections subject to horizontal shear may be in accordance with provisions of Article 17.21.4.3 or 17.21.4.4, or any other shear transfer design method that results in prediction of strength in substantial agreement with results of comprehensive tests. 17.21.4.3 Design of cross sections subject to horizontal shear may be based on: EQ 17-37

V u £ jV nh

where Vu is factored shear force at section considered, Vnh is nominal horizontal shear strength in accordance with the following, and where d is for the entire composite section. a.

When contact surface is clean, free of laitance, and intentionally roughened, shear strength Vnh shall not be taken greater than 80bvd in pounds (0.552bvd in newtons).

b. When minimum ties are provided in accordance with Article 17.21.4.5, and contact surface is clean and free of laitance, but not intentionally roughened, shear strength Vnh shall not be taken greater than 80bvd, in pounds (0.552bvd in newtons). c.

When minimum ties are provided in accordance with Article 17.21.4.5, and contact surface is clean, free of laitance, and intentionally roughened to a full amplitude of approximately 1/4 in. (7 mm), shear strength Vnh shall not be taken greater than 350bvd, in pounds (2.413bvd in newtons).

d. For each percent of tie reinforcement crossing the contact surface in excess of the minimum required by Article 17.21.4.5, shear strength Vnh may be increased by (160fy/40,000)bvd, in pounds [(90fy/100,000) bvd in newtons]. 17.21.4.4 Horizontal shear may be investigated by computing, in any segment not exceeding one-tenth of the span, the change in compressive or tensile force to be transferred, and provisions made to transfer that force as horizontal shear between interconnected elements. The factored horizontal shear force shall not exceed horizontal shear strength jVnh in accordance with Article 17.21.4.3, except that length of segment considered shall be substituted for d. 17.21.4.5 Ties for Horizontal Shear a.

When required, a minimum area of tie reinforcement shall be provided between interconnected elements. Tie area shall not be less than 50 bvs/fy, and tie spacing “s” shall not exceed four times the least web width of support element, nor 24 in. (600 mm).

b. Ties for horizontal shear may consist of single bars or wire, multiple leg stirrups, or vertical legs of welded wire fabric. All ties shall be adequately anchored into interconnected elements by embedment or hooks. c.

All beam shear reinforcement shall extend into cast-in-place deck slabs. Extended shear reinforcement may be used in satisfying the minimum tie reinforcement.

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AREMA Manual for Railway Engineering

Prestressed Concrete

SECTION 17.22 POST-TENSIONED ANCHORAGE ZONES 17.22.1 GEOMETRY OF ANCHORAGE ZONE (2001) a.

The anchorage zone is geometrically defined as the volume of concrete through which the concentrated prestressing force at the anchorage device spreads transversely to a linear stress distribution across the entire cross section.

b. For anchorage zones at the end of a member or segment, the transverse dimensions may be taken as the depth and width of the section. The longitudinal extent of the anchorage zone in the direction of the tendon (ahead of anchorage) shall be taken as not less than the larger transverse dimension but not more than one and one-half times that dimension. c.

For intermediate anchorages in addition to the length of Article 17.22.1b the anchorage zone shall be considered to also extend in the opposite direction for a distance not less than the larger transverse dimension.

d. For multiple slab anchorages, both width and length of the anchorage zone shall be taken as equal to the center-to-center spacing between stressed tendons, but not more than the length of the slab in the direction of the tendon axis. The thickness of the anchorage zone shall be taken equal to the thickness of the slab. e.

For design purposes, the anchorage zone shall consist of two regions; the general zone as defined in Article 17.22.2.1 and the local zone as defined in Article 17.22.2.2.

1

17.22.2 GENERAL ZONE AND LOCAL ZONE (2001) 17.22.2.1 General Zone The geometric extent of the general zone is identical to that of the overall anchorage zone as defined in Article 17.22.1 and includes the local zone.

3

Design of general zones shall meet the requirements of Articles 17.15 and 17.22.3. 17.22.2.2 Local Zone The local zone is defined as the rectangular prism (or equivalent rectangular prism for circular or oval anchorages) of concrete surrounding and immediately ahead of the anchorage device and any integral confining reinforcement. The dimensions of the local zone are defined in Article 17.22.7. Design of local zones shall meet the requirements of Articles 17.15 and 17.22.7 or shall be based on the results of experimental tests required in Article 17.22.7.3 and described in Article 17.25.3.5. Anchorage devices based on these acceptance tests of Article 17.25.3.5, are referred to as special anchorage devices. 17.22.2.3 Responsibilities The Engineer is responsible for the overall design and approval of working drawings for the general zone, including the specific location of the tendons and anchorage devices, general zone reinforcement, and the specific stressing sequence. The Engineer is also responsible for the design of local zones based on Article 17.22.7.2 and for the approval of special anchorage devices used under the provisions of Article 17.22.7.3. All working drawings for the local zone must be approved by the Engineer.

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Concrete Structures and Foundations

Anchorage device suppliers are responsible for furnishing anchorage devices which satisfy the anchor efficiency requirements of Article 17.25.3.1. In addition, if special anchorage devices are used, the anchorage device supplier is responsible for furnishing anchorage devices that satisfy the acceptance test requirements of the Engineer. This acceptance test and the anchor efficiency test shall be conducted by an independent testing agency acceptable to the Engineer. The anchorage device supplier shall provide records of the acceptance test to the Engineer and to the constructor and shall specify auxiliary and confining reinforcement, minimum edge distance, minimum anchor spacing, and minimum concrete strength at time of stressing required for proper performance of the local zone. The responsibilities of the constructor shall be as specified by the Engineer.

17.22.3 DESIGN OF THE GENERAL ZONE (2001) 17.22.3.1 Design Methods The following methods may be used for the design of general zones: a.

Equilibrium based plasticity models (strut-and-tie models) (see Article 17.22.4)

b. Elastic stress analysis (finite element analysis or equivalent) (see Article 17.22.5) c.

Approximate methods for determining the compression and tension forces, where applicable (see Article 17.22.6).

Regardless of the design method used, all designs shall conform to the requirements of Article 17.22.3.4. The effects of stressing sequence and three-dimensional effects shall be considered in the design. When these three dimensional effects appear significant, they may be analyzed using three-dimensional analysis procedures or may be approximated by considering two or more planes. However, in these approximations the interaction of the planes’ models must be considered, and the model loadings and results must be consistent. 17.22.3.2 Nominal Material Strengths The nominal tensile strength of bonded reinforcement is limited to fsy for nonprestressed reinforcement and to fy for prestressed reinforcement. The nominal tensile strength of unbonded prestressed reinforcement is limited to fse + 15,000 psi (fse + 105 MPa). The effective nominal compressive strength of the concrete of the general zone, exclusive of confined concrete, is limited to 0.7 f 'c. The tensile strength of the concrete shall be neglected. The compressive strength of concrete at transfer of prestressing shall be specified on the construction drawings. Stress shall not be transferred to concrete until the compressive strength of the concrete as indicated by test cylinders, cured by methods identical with the curing of the member, meets the requirements of the drawings. 17.22.3.3 Use of Special Anchorage Devices Whenever special anchorage devices which do not meet the requirements of Article 17.22.7.2 are to be used, reinforcement similar in configuration and at least equivalent in volumetric ratio to the supplementary skin reinforcement permitted under the provisions of Article 17.25.3.5 shall be furnished in the corresponding regions of the anchorage zone.

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Prestressed Concrete 17.22.3.4 General Design Principles and Detailing Requirements Good detailing and quality workmanship are essential for the satisfactory performance of anchorage zones. Sizes and details for anchorage zones should respect the need: for tolerances on the bending, fabrication and placement of reinforcement; the size of aggregate; and, the placement and sound consolidation of the concrete. a.

Compressive stresses in the concrete ahead of basic anchorage devices shall meet the requirements of Article 17.22.7.2.

b. Compressive stresses in the concrete ahead of special anchorage devices shall be checked at a distance measured from the concrete bearing surface equal to the smaller of: (1) The depth to the end of the local confinement reinforcement. (2) The smaller lateral dimension of the anchorage device. These compressive stresses may be determined according to the strut-and-tie model procedures of Article 17.22.4, from an elastic stress analysis according to Article 17.22.5b, or by the approximate method outlined in Article 17.22.6.2. These compressive stresses shall not exceed 0.7 f 'ci. c.

Compressive stresses shall also be checked where geometry or loading discontinuities within or ahead of the anchorage zone may cause stress concentrations.

d. The bursting force is the tensile force in the anchorage zone acting ahead of the anchorage device and transverse to the tendon axis. The magnitude of the bursting force, Tburst , and its corresponding distance from the loaded surface, dburst, can be determined using the strut-and-tie model procedures of Article 17.22.4, from an elastic stress analysis according to Article 17.22.5c, or by the approximate method outlined in Article 17.22.6.3. Three-dimensional effects shall be considered for the determination of the bursting reinforcement requirements. e.

Resistance to bursting forces, j Asfsy and/or j A*s f*y, shall be provided by non-prestressed or prestressed reinforcement, in the form of spirals, closed hoops, or well anchored transverse ties. This reinforcement is to be proportioned to resist the total factored bursting force. Arrangement and anchorage of bursting reinforcement shall satisfy the following:

1

3

(1) Bursting reinforcement shall extend over the full width of the member and must be anchored as close to the outer faces of the member as cover permits.

4 (2) Bursting reinforcement shall be distributed ahead of the loaded surface along both sides of the tendon throughout a distance of 2.5 dburst for the plane considered, but not to exceed 1.5 times the corresponding lateral dimension of the section. The centroid of the bursting reinforcement shall coincide with the distance dburst used for the design. (3) Spacing of bursting reinforcement shall exceed neither 24 bar diameters nor 12 inches (300 mm). f.

Edge tension forces are tensile forces in the anchorage zone acting parallel and close to the transverse edge and longitudinal edges of the member. The transverse edge is the surface loaded by the anchors. The tensile force along the transverse edge is referred to as spalling force. The tensile force along the longitudinal edge is referred to as longitudinal edge tension force.

g.

Spalling forces are induced in concentrically loaded anchorage zones, eccentrically loaded anchorage zones, and anchorage zones for multiple anchors. Longitudinal edge tension forces are induced when the resultant of the anchorage forces considered causes eccentric loading of the anchorage zone. The edge

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Concrete Structures and Foundations

tension forces can be determined from an elastic stress analysis, strut-and-tie models, or in accordance with the approximate methods of Article 17.22.6.4. h. In no case shall the spalling force be taken as less than two percent of the total factored tendon force. i.

Resistance to edge tension forces, jAsfsy and/or jA*sf*y, shall be provided in the form of non-prestressed or prestressed reinforcement located close to the longitudinal and transverse edge of the concrete. Arrangement and anchorage of the edge tension reinforcement shall satisfy the following: • Minimum spalling reinforcement satisfying Article 17.22.3.4h shall extend over the full width of the member. • Spalling reinforcement between multiple anchorage devices shall effectively tie these anchorage devices together. • Longitudinal edge tension reinforcement and spalling reinforcement for eccentric anchorage devices shall be continuous. The reinforcement shall extend along the tension face over the full length of the anchorage zone and shall extend along the loaded face from the longitudinal edge to the other side of the eccentric anchorage device or group of anchorage devices.

17.22.3.5 Intermediate Anchorages a.

Intermediate anchorages shall not be used in regions where significant tension is generated behind the anchor from other loads. Whenever practical, blisters shall be located in the corner between flange and webs, or shall be extended over the full flange width or web height to form a continuous rib. If isolated blisters must be used on a flange or web, local shear, bending and direct force effects shall be considered in the design.

b. Bonded reinforcement shall be provided to tie back at least 25 percent of the intermediate anchorage unfactored stressing force into the concrete section behind the anchor. Stresses in this bonded reinforcement are limited to a maximum of 0.6fsy or 36 ksi (250 MPa). The amount of tie back reinforcement may be reduced using EQ 17-38, if permanent compressive stresses are generated behind the anchor from other loads. Tia = 0.25Ps - fcbAcb

EQ 17-38

where: Tia = the tie back tension force at the intermediate anchorage; Ps = the maximum unfactored anchorage stressing force; fcb = the compressive stress in the region behind the anchor; Acb = the area of the continuing cross section within the extensions of the sides of the anchor plate or blister. The area of the blister or rib shall not be taken as part of the cross section. c.

Tie back reinforcement satisfying Article 17.22.3.5b shall be placed no further than one plate width from the tendon axis. It shall be fully anchored so that the yield strength can be developed at a distance of one plate width or half the length of the blister or rib ahead of the anchor as well as at the same distance behind the anchor. The centroid of this reinforcement shall coincide with the tendon axis, where possible. For blisters and ribs, the reinforcement shall be placed in the continuing section near that face of the flange or web from which the blister or rib is projecting.

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Prestressed Concrete

d. Reinforcement shall be provided throughout blisters or ribs are required for shear friction, corbel action, bursting forces, and deviation forces due to tendon curvature. This reinforcement shall be in the form of ties or U-stirrups which encase the anchorage and tie it effectively into the adjacent web and flange. This reinforcement shall extend as far as possible into the flange or web and be developed by standard hooks bent around transverse bars or equivalent. Spacing shall not exceed the smallest of blister or rib height at anchor, blister width, or 6 inches (150 mm). e.

Reinforcement shall be provided to resist local bending in blisters and ribs due to eccentricity of the tendon force and to resist lateral bending in ribs due to tendon deviation forces.

f.

Reinforcement required by Articles 17.22.3.4d through 17.22.3.4i shall be provided to resist tensile forces due to transfer of the anchorage force from the blister or rib into the overall structure.

17.22.3.6 Diaphragms For tendons anchored in diaphragms, concrete compressive stresses shall be limited within the diaphragm in accordance with Articles 17.22.3.4a through 17.22.3.4c. Compressive stresses shall also be checked at the transition from the diaphragm to webs and flanges of the member. Reinforcement shall be provided to ensure full transfer of diaphragm anchor loads into the flanges and webs of the girder. The more general methods of Article 17.22.4 or 17.22.5 shall be used to determine this reinforcement. Reinforcement shall also be provided to tie back deviation forces due to tendon curvature. 17.22.3.7 Multiple Slab Anchorages a.

1

Minimum reinforcement meeting the requirements of Articles 17.22.3.7b through 17.22.3.7d shall be provided unless a more detailed analysis is made.

b. Reinforcement shall be provided for the bursting force in the direction of the thickness of the slab and normal to the tendon axis in accordance with Article 17.22.3.4d and 17.22.3.4e This reinforcement shall be anchored close to the faces of the slab with standard hooks bent around horizontal bars, or equivalent. Minimum reinforcement is two No. 10 (#3) bars per anchor located at a distance equal to one-half the slab thickness ahead of the anchor. c.

Reinforcement in the plane of the slab and normal to the tendon axis shall be provided to resist edge tension forces, T1, between anchorages (EQ 17-39) and bursting forces, T2, ahead of the anchorages (EQ 17-40). Edge tension reinforcement shall be placed immediately ahead of the anchors and shall effectively tie adjacent anchors together. Bursting reinforcement shall be distributed over the length of the anchorage zones (see Article 17.22.1d).

(

T1 = 0.10Pu 1- a/s

(

)

T2 = 0.20Pu 1 - a/s

EQ 17-39

)

EQ 17-40

where: Pu = the factored tendon load on an individual anchor; a = the anchor plate width; s = the anchorage spacing.

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d. For slab anchors with an edge distance of less than two plate widths or one slab thickness, the edge tension reinforcement shall be proportioned to resist 25 percent of the factored tendon load. This reinforcement shall preferably be in the form of hairpins and shall be distributed within one plate width ahead of the anchor. The legs of the hairpin bars shall extend from the edge of the slab past the adjacent anchor but not less than a distance equal to five plate widths plus development length.

17.22.4 APPLICATION OF STRUT-AND-TIE MODELS TO THE DESIGN OF ANCHORAGE ZONES (2001) 17.22.4.1 General The flow of forces in the anchorage zone may be approximated by a series of straight compression members (struts) and straight tension members (ties) that are connected at discrete points (nodes). Compression forces are carried by concrete compression struts and tension forces are carried by non-prestressed or prestressed reinforcement. The selected strut-and-tie model shall follow a load path from the anchorages to the end of the anchorage zone. Other forces acting on the anchorage zone, such as reaction forces, tendon deviation forces, and applied loads, shall be considered in the selection of the strut-and-tie model. The forces at the end of the anchorage zone can be obtained from an axial-flexural beam analysis. 17.22.4.2 Nodes Local zones which meet the provisions of Article 17.22.7 or Article 17.25.3.5 are considered as properly detailed, adequate nodes. The other nodes in the anchorage zone are adequate if the effective concrete stresses in the struts meet the requirements of Article 17.22.4.3 and the tension ties are properly detailed to develop the full yield strength of the reinforcement. 17.22.4.3 Struts The effective concrete compressive strength for the general zone shall usually be limited to 0.7jf 'ci. In areas where the concrete may be extensively cracked at ultimate due to other load effects, or if large plastic rotations are required, the effective compressive strength shall be limited to 0.6jf 'ci. In anchorage zones the critical section for compression struts is ordinarily located at the interface with the local zone node. If special anchorage devices are used, the critical section of the strut can be taken as that section whose extension intersects the axis of the tendon at a depth equal to the smaller of the depth of the local confinement reinforcement or the lateral dimension of the anchorage device. For thin members with a ratio of member thickness to anchorage width of no more than three, the dimension of the strut in the direction of the thickness of the member can be approximated by assuming that the thickness of the compression strut varies linearly from the transverse lateral dimension of the anchor at the surface of the concrete to the total thickness of the section at a depth equal to the thickness of the section. The compression stresses can be assumed as acting parallel to the axis of the strut and as uniformly distributed over its cross section. 17.22.4.4 Ties Tension forces in the strut-and-tie model shall be assumed to be carried completely by non-prestressed or prestressed reinforcement. Tensile strength of the concrete shall be neglected.

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Prestressed Concrete Tension ties shall be properly detailed and shall extend beyond the nodes to develop the full tension tie force at the node. The reinforcement layout must closely follow the directions of the ties in the strut-and-tie model.

17.22.5 ELASTIC STRESS ANALYSIS (2001) a.

Analyses based on assumed elastic material properties, equilibrium, and compatibility of strains are acceptable for analysis and design of anchorage zones.

b. If the compressive stresses in the concrete ahead of the anchorage device are determined from a linearelastic stress analysis, local stress maxima may be averaged over an area equal to the bearing area of the anchorage device. c.

Location and magnitude of the bursting force may be obtained by integration of the corresponding tensile bursting stresses along the tendon path.

17.22.6 APPROXIMATE METHODS (2001) 17.22.6.1 Limitations In the absence of a more accurate analysis, concrete compressive stresses ahead of the anchorage device, location and magnitude of the bursting force, and edge tension forces may be estimated by EQ 17-41 through EQ 17-42, provided that: a.

The member has a rectangular cross section and its longitudinal extent is at least equal to the largest transverse dimension of the cross section.

1

b. The member has no discontinuities within or ahead of the anchorage zone. c.

The minimum edge distance of the anchorage in the main plane of the member is at least one and onehalf times the corresponding lateral dimension, a, of the anchorage device.

3

d. Only one anchorage device or one group of closely spaced anchorage devices is located in the anchorage zone. Anchorage devices can be treated as closely spaced if their center-to-center spacing does not exceed one and one-half times the width of the anchorage devices in the direction considered. e.

The angle of inclination of the tendon with respect to the center line of the member is not larger than 20 degrees if the anchor force points toward the centroid of the section and for concentric anchors, and is not larger than 5 degrees if the anchor force points away from the centroid of the section.

17.22.6.2 Compressive Stresses a.

No additional check of concrete compressive stresses is necessary for basic anchorage devices satisfying Article 17.22.7.2.

b. The concrete compressive stresses ahead of special anchorage devices at the interface between local zone and general zone shall be approximated by EQ 17-41 and EQ 17-42.

f ca

æ ö 0.6P ç ÷ k u = æ ---------------ö ç ----------------------------------------÷ è A øç 1 1 b 1 + l c æ ---------- – ---ö ÷ èb øø è eff t

k = 1 + (2 - s/aeff) (0.3 + n/15)

EQ 17-41

for s < 2aeff

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Concrete Structures and Foundations

k=1

for

s ³ 2a eff

EQ 17-42

where: fca = the concrete compressive stress ahead of the anchorage device; k = a correction factor for closely spaced anchorages; Ab = an effective bearing area as defined in Article 17.22.6.2c; aeff = the lateral dimension of the effective bearing area measured parallel to the larger dimension of the cross section or in the direction of closely spaced anchors; beff = the lateral dimension of the effective bearing area measured parallel to the smaller dimension of the cross section; lc = the longitudinal extent of confining reinforcement for the local zone, but not more than the larger of 1.15 aeff or 1.15 beff; Pu = the factored tendon load; t = the thickness of the section; s = the center-to-center spacing of multiple anchorages; n = the number of anchorages in a row. If a group of anchorages is closely spaced in two directions, the product of the correction factors, k, for each direction is used in EQ 17-42. c.

Effective bearing area, Ab, in EQ 17-41 shall be taken as the larger of the anchor bearing plate area, Aplate, or the bearing area of the confined concrete in the local zone, Aconf, with the following limitations: (1) If Aplate controls, Aplate shall not be taken larger than ( 4 ¤ p )A conf (2) If Aconf controls, the maximum dimension of Aconf shall not be more than twice the maximum dimension of Aplate or three times the minimum dimension of Aplate. If any of these limits is violated the effective bearing area, Ab, shall be based on Aplate. (3) Deductions shall be made for the area of the duct in the determination of Ab.

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Prestressed Concrete 17.22.6.3 Bursting Forces Values for the magnitude of the bursting force, Tburst, and for its distance from the loaded surface, dburst, shall be estimated by EQ 17-43 and EQ 17-44. In the application of EQ 17-43 and EQ 17-44, the specified stressing sequence shall be considered if more than one tendon is present. T burst = 0.25SP u ( 1 – a ¤ h ) + 0.5P u sin a dburst = 0.5 (h - 2e) + 5e sin a

EQ 17-43 EQ 17-44

where: SP u = the sum of the total factored tendon loads for the stressing arrangement considered; a = the lateral dimension of the anchorage device or group of devices in the direction considered. e = the eccentricity (always taken as positive) of the anchorage device or group of devices with respect to the centroid of the cross section; h = the lateral dimension of the cross section in the direction considered; a = the angle of inclination of the resultant of the tendon forces with respect to the centerline of the member.

1

17.22.6.4 Edge Tension Forces For multiple anchorages with a center-to-center spacing of less than 0.4 times the depth of the section, the spalling forces shall be given by Article 17.22.3.4h. For larger spacings, the spalling forces shall be determined from a more detailed analysis, such as strut-and-tie models or other analytical procedures. If the centroid of all tendons considered is located outside of the kern of the section both spalling forces and longitudinal edge tension forces are induced. The longitudinal edge tension force shall be determined from an axial-flexural beam analysis at a section located at one half the depth of the section away from the loaded surface. The spalling force shall be taken as equal to the longitudinal edge tension force but not less than specified in Article 17.22.3.4h.

17.22.7 DESIGN OF THE LOCAL ZONE (2001)

4

17.22.7.1 Dimensions of the Local Zone a.

When no independently verified manufacturer’s edge distance recommendations for a particular anchorage device are available, the transverse dimensions of the local zone in each direction shall be taken as the larger of: (1) The corresponding bearing plate size plus twice the minimum concrete cover required for the particular application and environment. (2) The outer dimension of any required confining reinforcement plus the required concrete cover over the confining reinforcing steel for the particular application and environment.

b. When independently verified manufacturer’s recommendations for minimum cover, spacing and edge distance for a particular anchorage device are available, the transverse dimensions of the local zone in each direction shall be taken as the smaller of:

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(1) The bearing plate size plus twice the edge distance specified by the anchorage device supplier, (2) The center-to-center spacing specified by the anchorage device supplier. The manufacturer’s recommendations for spacing and edge distance of anchorages shall be considered minimum values. c.

The length of the local zone along the tendon axis shall be taken as the greater of: • The maximum width of the local zone. • The length of the anchorage device confining reinforcement. • For anchorage devices with multiple bearing surfaces, the distance from the loaded concrete surface to the bottom of each bearing surface plus the maximum dimension of that bearing surface. In no case shall the length of the local zone be taken as greater than one and one-half times the width of the local zone.

d. For closely spaced anchorages an enlarged local zone enclosing all individual anchorages shall also be considered. 17.22.7.2 Bearing Strength a.

Anchorage devices may be either basic anchorage devices meeting the bearing compressive strength limits of Articles 17.22.7.2b through 17.22.7.2d or special anchorage devices meeting the requirements of Article 17.22.7.3.

b. The effective concrete bearing compressive strength fb used for design shall not exceed that of EQ 17-45 or EQ 17-46 . Pr = jfb Ab

f b £ 0.7f ¢ ci A ¤ A g

EQ 17-45

f b £ 2.25f ¢ ci

EQ 17-46

but:

where: fb = the maximum factored tendon load, Pu, divided by the effective bearing area Ab; f 'ci = the concrete compressive strength at stressing; A = the maximum area of the portion of the supporting surface that is geometrically similar to the loaded area and concentric with it; Ag = the gross area of the bearing plate if the requirements of Article 17.22.7.2c are met, or is the area calculated in accordance with Article 17.22.7.2d;

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Ab = the effective net area of the bearing plate calculated as the area Ag minus the area of openings in the bearing plate. EQ 17-45 and EQ 17-46 are only valid if general zone reinforcement satisfying Article 17.22.7.3 is provided and if the extent of the concrete along the tendon axis ahead of the anchorage device is at least twice the length of the local zone as defined in Article 17.22.7.1c. c.

The full bearing plate area may be used for Ag and the calculation of Ab if the anchorage device is sufficiently rigid. To be considered sufficiently rigid, the slenderness of the bearing plate (n/t) must not exceed the value given in EQ 17-47. The plate must also be checked to ensure that the plate material does not yield. n ¤ t £ 0.08 3 E b ¤ f b

EQ 17-47

where: n = the largest distance from the outer edge of the wedge plate to the other edge of the bearing plate. For rectangular bearing plates this distance is measured parallel to the edges of the bearing plate. If the anchorage has no separate wedge plate, the size of the wedge plate shall be taken as the distance between the extreme wedge holes in the corresponding direction. t = the average thickness of the bearing plate. Eb = the modulus of elasticity of the bearing plate material.

1

d. For bearing plates that do not meet the stiffness requirements of Article 17.22.7.2c, the effective gross bearing area, Ag, shall be taken as the area geometrically similar to the wedge plate (or to the outer perimeter of the wedge hole pattern for plates without separate wedge plate) with dimensions increased by assuming load spreading at a 45 degree angle. A larger effective bearing area may be calculated by assuming an effective area and checking the new fb and n/t values for conformance with Articles 17.22.7.2b and 17.22.7.2c.

3

17.22.7.3 Special Anchorage Devices Special anchorage devices that do not meet the requirements of Article 17.22.7.2 as well as other devices that do not meet the requirements of Article 17.22.7.2 but which the Engineer requires to have tested may be used provided that they have been tested by an independent testing agency acceptable to the Engineer according to the procedures described in Article 17.24 (or equivalent) and meet the acceptance criteria specified in Article 17.25.3.5.3c. For a series of similar special anchorage devices, tests are only required for representative samples unless tests for each capacity of the anchorages in the series are required by the Engineer.

SECTION 17.23 PRETENSIONED ANCHORAGE ZONES In pretensioned beams, vertical stirrups acting at a unit stress of 20,000 psi (140 MPa) to resist at least 4 percent of the total prestressing force shall be placed within the distance of d/4 of the end of the beam. For at least the distance d from the end of the beam, nominal reinforcement shall be placed to enclose the prestressing steel in the bottom flange.

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For box girders, transverse reinforcement shall be provided and anchored by extending the leg into the web of the girder. Unless otherwise specified, stress shall not be transferred to concrete until the compressive strength of the concrete as indicated by test cylinders, cured by methods identical with the curing of the member, is at least 4,000 psi (28 MPa).

SECTION 17.24 CONCRETE STRENGTH AT STRESS TRANSFER Unless otherwise specified, stress shall not be transferred to concrete until the compressive strength of the concrete as indicated by test cylinders, cured by methods identical with the curing of the members, is at least 4,000 psi (28 MPa) for pretensioned members (other than piles) and 3,500 psi (24 MPa) for post-tensioned members and pretensioned piles.

SECTION 17.25 GENERAL DETAILING 17.25.1 FLANGE REINFORCEMENT (2001) Bar reinforcement for cast-in-place T-beam and box girder flanges shall conform to the provisions in Articles 2.23.10 and 2.23.11 except that the minimum reinforcement in bottom flanges shall be 0.3 percent of the flange section.

17.25.2 COVER AND SPACING OF REINFORCEMENT (2001) The minimum concrete cover to be provided for prestressing tendons and non-prestressing reinforcement shall conform to the requirements of Article 17.5.2. Drainage details shall dispose of chemical spill solutions without constant contact with the prestressed girders. Where such contact cannot be avoided, or in locations where members are exposed to salt water, salt spray, or chemical vapor, additional cover should be provided. The minimum clear spacing of prestressing tendons and post-tension ducts shall conform to the requirements of Article 17.5.1. Prestressing tendons in precast deck panels shall be spaced symmetrically and uniformly across the width of the panel. They shall not be spaced farther apart than 1 ½ times the total composite slab thickness or more than 18 inches (460 mm).

17.25.3 POST-TENSIONING ANCHORAGES AND COUPLERS (2001) 17.25.3.1 Anchorages, Couplers, and Splices Anchorages, couplers, and splices for bonded post-tensioned reinforcement shall develop at least 95 percent of the minimum specified ultimate strength of the prestressing steel, tested in an unbonded state without exceeding anticipated set. Bond transfer lengths between anchorages and the zone where full prestressing force is required under service and ultimate loads shall normally be sufficient to develop the minimum specified

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ultimate strength of the prestressing steel. Couplers and splices shall be placed in areas approved by the Engineer and enclosed in a housing long enough to permit the necessary movements. When anchorages or couplers are located at critical sections under ultimate load, the ultimate strength required of the bonded tendons shall not exceed the ultimate capacity of the tendon assembly, including the anchorage or coupler, tested in an unbonded state. 17.25.3.2 Anchorages, End Fittings, Couplers, and Exposed Tendons Anchorages, end fittings, couplers, and exposed tendons shall be permanently protected against corrosion. 17.25.3.3 Bonded Systems Bond transfer lengths between anchorages and the zone where full prestressing force is required under service and ultimate loads shall normally be sufficient to develop the minimum specified ultimate strength of the prestressing steel. When anchorages or couplers are located at critical sections under ultimate load, the ultimate strength required of the bonded tendons shall not exceed the ultimate capacity of the tendon assembly, including the anchorage or coupler, tested in an unbonded state. Housings shall be designed so that complete grouting of all the coupler components will be accomplished during grouting of tendons. 17.25.3.4 Unbonded Systems For unbonded tendons, a dynamic test shall be performed on a representative anchorage and coupler specimen and the tendon shall withstand, without failure, 500,000 cycles from 60 percent to 66 percent of its minimum specified ultimate strength, and also 50 cycles from 40 percent to 80 percent of its minimum specified ultimate strength. The period of each cycle involves the change from the lower stress level to the upper stress level and back to the lower. The specimen used for the second dynamic test need not be the same used for the first dynamic test. Systems utilizing multiple strands, wires, or bars may be tested utilizing a test tendon of smaller capacity than the full-sized tendon. The test tendon shall duplicate the behavior of the full-sized tendon and generally shall not have less than 10 percent of the capacity of the full-sized tendon. Dynamic tests are not required on bonded tendons, unless the anchorage is located or used in such a manner that repeated load applications can be expected on the anchorage.

1

3

Anchorages for unbonded tendons shall not cause a reduction in the total elongation under ultimate load of the tendon to less than 2 percent measured in a minimum gauge length of 10 feet (3 meters). All the coupling components shall be completely protected with a coating material prior to final encasement in concrete. 17.25.3.5 Special Anchorage Device Acceptance Test The test block shall be a rectangular prism. It shall contain those anchorage components which will also be embedded in the structure's concrete. Their arrangement has to comply with the practical application and the suppliers specifications. The test block shall contain an empty duct of size appropriate for the maximum tendon size which can be accommodated by the anchorage device. The dimensions of the test block perpendicular to the tendon in each direction shall be the smaller of the minimum edge distance or the minimum spacing specified by the anchorage device supplier, with the stipulation that the cover over any confining reinforcing steel or supplementary skin reinforcement be appropriate for the particular application and environment. The length of the block along the axis of the tendon shall be at least two times the larger of the cross-section dimensions.

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The confining reinforcing steel in the local zone shall be the same as that specified by the anchorage device supplier for the particular system. In addition to the anchorage device and its specified confining reinforcement steel, supplementary skin reinforcement may be provided throughout the specimen. This supplementary skin reinforcement shall be specified by the anchorage device supplier but shall not exceed a volumetric ratio of 0.01. The concrete strength at the time of stressing shall be greater than the concrete strength of the test specimen at time of testing. Either of three test procedures is acceptable: cyclic loading described in Article 17.25.3.5.1, sustained loading described in Article 17.25.3.5.2, or monotonic loading described in Article 17.25.3.5.3. The loads specified for the tests are given in fractions of the ultimate load Fpu of the largest tendon that the anchorage device is designed to accommodate. The specimen shall be loaded in accordance with normal usage of the device in posttensioning applications except that load can be applied directly to the wedge plate or equivalent area. 17.25.3.5.1 Cyclic Loading Test In a cyclic loading test, the load shall be increased to 0.8 Fpu . The load shall then be cycled between 0.1 Fpu and 0.8 Fpu until crack widths stabilize, but for not less than 10 cycles. Crack widths are considered stabilized if they do not change by more than 0.001 in. (0.025 mm) over the last three readings. Upon completion of the cyclic loading the specimen shall be preferably loaded to failure or, if limited by the capacity of the loading equipment, to at least 1.1 Fpu. Crack widths and crack patterns shall be recorded at the initial load of 0.8 Fpu at least at the last three consecutive peak loadings before termination of the cyclic loading, and at 0.9 Fpu. The maximum load shall also be reported. 17.25.3.5.2 Sustained Loading Test In a sustained loading test, the load shall be increased to 0.8 Fpu and held constant until crack widths stabilize but for not less than 48 hours. Crack widths are considered stabilized if they do not change by more than 0.001 in. (0.025 mm) over the last three readings. After sustained loading is completed, the specimen shall be preferably loaded to failure or, if limited by the capacity of the loading equipment, to at least 1.1 Fpu. Crack widths and crack patterns shall be recorded at the initial load of 0.8 Fpu, at least three times at intervals of not less than 4 hours during the last 12 hours before termination of the sustained loading, and during loading to failure at 0.9 Fpu. The maximum load shall also be reported. 17.25.3.5.3 Monotonic Loading Test a.

In a monotonic loading test, the load shall be increased to 0.9 Fpu and held constant for 1 hour. The specimen shall then be preferably loaded to failure or, if limited by the capacity of the loading equipment, to at least 1.2 Fpu.

b. Crack widths and crack patterns shall be recorded at 0.9 Fpu after the 1-hour period, and at 1.0 Fpu. The maximum load shall also be reported. c.

The strength of the anchorage zone must exceed: Specimens tested under cyclic or sustained loading............................................................1.0 Fpu Specimens tested under monotonic loading.........................................................................1.2 Fpu

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d. The maximum crack width criteria specified below must be met for moderately aggressive environments. e.

For higher aggressive environments the crack width criteria shall be reduced by at least 50 percent. (1) No cracks greater than 0.010 in. (0.254 mm) at 0.8 Fpu after completion of the cyclic or sustained loading, or at 0.9 Fpu after the 1-hour period for monotonic loading. (2) No cracks greater than 0.016 in. (0.406 mm) at 0.9 Fpu for cyclic or sustained loading, or at 1.0 Fpu for monotonic loading.

f.

A test series shall consist of three test specimens. Each one of the tested specimens must meet the acceptance criteria. If one of the three specimens fails to pass the test, a supplementary test of three additional specimens is allowed. The three additional test specimen results must meet all acceptance criteria of Article 17.25.3.5. For a series of similar special anchorage devices, tests are only required for representative samples unless tests for each capacity of the anchorages in the series are required by the Engineer.

g.

Records of the anchorage device acceptance test shall include: (1) Dimensions of the test specimen. (2) Drawings and dimensions of the anchorage device, including all confining reinforcing steel.

1

(3) Amount and arrangement of supplementary skin reinforcement. (4) Type and yield strength of reinforcing steel. (5) Type and compressive strength at time of testing of concrete. (6) Type of testing procedure and all measurements required in Articles 17.25.3.5.1 through 17.25.3.5.3c for each specimen.

3

17.25.4 EMBEDMENT OF PRESTRESSED TENDON (2001) Seven-wire pretensioning strand shall be bonded beyond the critical section for a development length in inches (mm) not less than (f*su - 2/3 f se)D

EQ 17-48

(f*su - 2/3 fse) D/7

EQ 17-48 (Metric)

where D is the nominal diameter in inches (mm), f*su and fse are in psi (MPa), and the parenthetical expression is considered to be without units. Investigations may be limited to those cross sections nearest each end of the member which are required to develop their full ultimate capacity. Where strand is debonded at the end of a member and tension at service load is allowed in the precompressed tensile zone, the development length required above shall be doubled.

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SECTION 17.26 GENERAL FABRICATION 17.26.1 GENERAL (2001) Precast concrete members shall be fabricated, erected and installed in accordance with the contract documents, except as may be modified by Contractor's drawings that have been reviewed and accepted by the Engineer.

17.26.2 CONTRACTOR’S DRAWINGS (2001) Such drawings shall be submitted to the Engineer for review and acceptance.

17.26.3 MATERIALS AND FABRICATION (2001) a.

Materials and manufacture shall conform to the requirements of Part 1 of this Chapter, except as modified by this Part.

b. The fabricator shall perform all tests required by the contract documents and ASTM Standards, and the Engineer or his representative shall be allowed access to observe all of this sampling and testing. The results of all tests shall be submitted to the Engineer for review and acceptance. c.

Precast members shall be cast on unyielding beds. Bearing surfaces shall be cast in accordance with the contract documents, so that they will join properly with other elements of the structure.

d. Precast members that are to be abutted together in the finished work shall be match-cast with adjacent segments. e.

Forms may not be removed until such time as the removal will not damage the member. A member shall not be lifted until its strength is sufficient to prevent damage.

f.

When cast-in-place concrete will later be cast against a precast member, mating surfaces shall be finished to a coarse texture as approved by the Engineer.

17.26.4 CURING (2001)1 Unless otherwise specified in the contract documents, precast members shall be cured by the water method or the steam or radiant heat method. Curing shall not be interrupted or compromised by the removal of forms.

17.26.5 STORAGE AND HANDLING (2001) a.

Care shall be taken during storage and handling to prevent damage to precast units. Units damaged during storage or handling shall be replaced at the Contractor's expense.

b. Precast girders shall be transported in an upright position with points of support as shown on the Contractor's drawings. c.

1

Prestressed concrete members shall not be shipped until tests demonstrate that the concrete has attained a compressive strength equal to the specified design compressive strength.

See C - 17.26.4 Curing (2001)

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17.26.6 ERECTION (2001) a.

The Contractor shall be responsible not to damage precast members during construction. Lifting devices shall be used in accordance with Contractor’s drawings that have been reviewed and accepted by the Engineer. Temporary supports shall be used as necessary to prevent damage.1

b. Where cast-in-place concrete is to be cast against precast members, forms shall be erected and sealed so that excessive leakage will not occur.

17.26.7 PLACEMENT OF DUCTS, STEEL, AND ANCHORAGE HARDWARE (2001) 17.26.7.1 Placement of Ducts Ducts shall be rigidly supported at the proper locations in the forms by ties to reinforcing steel which are adequate to prevent displacement during concrete placement. Supplementary support bars shall be used where needed to maintain proper alignment of the duct. Hold-down ties to the forms shall be used when the buoyancy of the ducts in the fluid concrete would lift the reinforcing steel. Joints between sections of duct shall be coupled with positive connections which do not result in angle changes at the joints and will prevent the intrusion of cement paste. After placing of ducts, reinforcement and forming is complete, an inspection shall be made to locate possible duct damage.

1 All unintentional holes or openings in the duct must be repaired prior to concrete placing. Grout openings and vents must be securely anchored to the duct and to either the forms or to reinforcing steel to prevent displacement during concrete placing operations. After installation in the forms, the ends of ducts shall at all times be covered as necessary to prevent the entry of water or debris.

3

17.26.7.1.1 Vents and Drains All ducts for continuous structures shall be vented at the high points of the duct profile, except where the curvature is small, as in continuous slabs, and at additional locations as shown on the plans. Where freezing conditions can be anticipated prior to grouting, drains shall be installed at low point in ducts where needed to prevent the accumulation of water. Low-point drains shall remain open until grouting is started. The ends of vents and drains shall be removed 1 inch (25 mm) below the surface of the concrete after grouting has been completed, and the void filled with mortar. 17.26.7.2 Placement of Prestressing Steel 17.26.7.2.1 Placement for Pretensioning Prestressing steel shall be accurately installed in the forms and held in place by the stressing jack or temporary anchors and, when tendons are to be harped or draped, by hold-down devices. The hold-down devices used at all points of change in slope of tendon trajectory shall be of an approved low-friction type.

1

See C - 17.26.6 Erection (2001)

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Prestressing steel shall not be removed from its protective packaging until immediately prior to installation in the forms and placement of concrete. Openings in the packaging shall be resealed as necessary to protect the unused steel. While exposed, the steel shall be protected as needed to prevent corrosion. 17.26.7.2.2 Placement for Post-Tensioning All prestressing steel preassembled in ducts and installed prior to the placement of concrete shall be accurately placed and held in position during concrete placement. When the prestressing steel is installed after the concrete has been placed, the Contractor shall demonstrate to the satisfaction of the Engineer that the ducts are free of water and debris immediately prior to installation of the steel. The total number of strands in an individual tendon may be pulled into the duct as a unit, or the individual strand may be pulled or pushed through the duct. Anchorage devices or block-out templates for anchorages shall be set and held so that their axis coincides with the axis of the tendon and anchor plates are normal in all directions to the tendon. The prestressing steel shall be distributed so that the force in each girder stem is equal or as required by the plans, except as provided herein. For box girders with more than two girder stems, at the Contractor's option, the prestressing force may vary up to 5 percent from the theoretical required force per girder stem provided the required total force in the superstructure is obtained and the force is distributed symmetrically about the center line of the typical section. 17.26.7.2.2.1 Protection of Steel after Installation Prestressing steel installed in members prior to placing and curing of the concrete, or installed in the duct but not grouted within the time limit specified below, shall be continuously protected against rust or other corrosion by means of a corrosion inhibitor placed in the ducts or directly applied to the steel. The prestressing steel shall be so protected until grouted or encased in concrete. Prestressing steel installed and tensioned in members after placing and curing of the concrete and grouted within the time limit specified below will not require the use of a corrosion inhibitor described herein and rust which may form during the interval between tendon installation and grouting will not be cause for rejection of the steel. The permissible interval between tendon installation and grouting without use of a corrosion inhibitor for various exposure conditions shall be as follows unless approved by the Engineer: Very Damp Atmosphere (Humidity > 70%) or Over Saltwater ..........................................7 days Moderate Atmosphere (Humidity from 40% to 70%)..........................................................15 days Very Dry Atmosphere (Humidity < 40%)............................................................................20 days After tendons are placed in ducts, the openings at the ends of the ducts shall be sealed to prevent entry of moisture. When steam curing is used, steel for post-tensioning shall not be installed until the steam curing is completed. Whenever electric welding is performed on or near members containing prestressing steel, the welding ground shall be attached directly to the steel being welded. All prestressing steel and hardware shall be protected from weld spatter or other damage.

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Prestressed Concrete 17.26.7.3 Placement of Anchorage Hardware The contractor is responsible for the proper placement of all materials according to the design documents of the Engineer and the requirements stipulated by the anchorage device supplier. The Contractor shall exercise all due care and attention in the placement of anchorage hardware, reinforcement, concrete, and consolidation of concrete in anchorage zones. Modifications to the local zone details verified under provisions of Section 17.22.7.3 and Section 17.26.3 shall be approved by both the Engineer and the anchorage device supplier.

17.26.8 APPLICATION AND MEASUREMENT OF PRESTRESSING FORCE (2005)1 Prestressing force shall be determined by both of the following methods: (1) Observation of jacking force on a calibrated gage or load cell or by use of a calibrated dynamometer. (2) Measurement of tendon elongation. Required elongation shall be determined from average load elongation curves for prestressing tendons used. Cause of any difference in force determination between Paragraph 1 and Paragraph 2 that exceeds 5% for pretensioned elements or 7% for post-tensioned construction shall be ascertained and corrected. Where transfer of force from bulkheads of pretensioning bed to concrete is accomplished by cutting prestressing tendons, cutting points and cutting sequence shall be predetermined to avoid undesired temporary stresses. Unless otherwise required by the Contract Documents long lengths of exposed pretensioned strand shall be cut near the member to minimize shock to concrete.

1

Wire failure in prestressing tendons is acceptable provided total area of broken wires does not exceed 2% of total area of tendons in member, and wire failure is not symptomatic of a more extensive distress condition.

3

SECTION 17.27 MORTAR AND GROUT 17.27.1 GENERAL (2001) This article governs mortars and grouts except as required for prestressing ducts.

4

17.27.2 MATERIALS AND MIXING (2001) a.

Grout shall consist of portland cement and water; or portland cement, water and approved admixtures.

b. Materials for mortar and grout shall conform to the requirements of Part 1 of this Chapter except as modified by this Part. c.

The grading of sand for use in grout or mortar shall be adjusted in accordance with Part 1 the use to which the mortar or grout is being put.

d. Air entraining Portland cement shall be used for grout whenever air entrainment is required for the concrete.

1

See C - 17.26.8 Application and Measurement of Prestressing Force (2005)

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e.

When non-shrink mortar or grout is specified in the contract documents or on the Contractor's drawings, a non-shrink admixture or an expansive hydraulic cement approved by the Engineer, shall be used.

f.

Six proportions for mortars and grouts shall be submitted to the Engineer for review and acceptance.

g.

Mortar or grout shall not be retempered by the addition of water and shall be placed within one hour of mixing.

17.27.3 PLACING AND CURING (2001) a.

Concrete areas to be patched shall be free of all loose material and shall be sprayed with water and allowed to surface dry immediately prior to placing the mortar or grout.

b. After placing all surfaces of mortar or grout shall be cured by the water method. c.

Locations to be grouted shall be mortar-tight before placing mortar.

SECTION 17.28 APPLICATION OF LOADS a.

Loads shall not be applied to prestressed members until the concrete has attained sufficient strength to prevent damage or until as specified on the accepted Contractor's drawings.

b. Application of loads to members that are to be post-tensioned shall only be done in accordance with construction sequences shown on the accepted Contractor's drawings. c.

Materials and equipment shall not be supported on the work except as shown on the accepted Contractor's drawings.

d. Earth loads shall be applied in such a way as not to cause movements or deformations during construction. e.

Railway loading shall not be permitted on the completed work until the concrete strengths and other requirements specified on the contract documents have been achieved.

SECTION 17.29 MATERIALS - REINFORCING STEEL1 17.29.1 GENERAL (2001) a.

Uncoated reinforcing steel shall conform to the requirements of Part 1 of this Chapter except that welded steel wire fabric for concrete reinforcement shall conform to the requirements of either ASTM Standard A185 or ASTM Standard A497, as shown on the contract documents.

b. Epoxy-coated reinforcing steel shall conform to the requirements of Part 1 of this Chapter except that when epoxy coating of reinforcing bars is shown on the contract documents, the coating materials and 1

See C - Section 17.29 Materials - Reinforcing Steel

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process, fabrication, handling, identification of the steel, and the repair of any damaged coating material that occurs during fabrication and handling shall conform to the requirements of ASTM Standard A775. c.

Contractor's Reports: (1) Whenever steel bars, other than bars conforming to ASTM A706 are to be welded, or when otherwise required by the contract documents a certified copy of the mill test report showing physical and chemical analysis for each heat or lot of reinforcing bars shall be provided to the Engineer for review and acceptance. (2) Shipments of epoxy-coated reinforcing steel shall include a certificate of compliance that the coated bars or coated wire conform to the applicable ASTM Standard.

17.29.2 BAR LISTS AND BENDING DIAGRAMS (2001) The Contractor shall provide bar lists and bending diagrams in accordance with the requirements of Part 1 of this Chapter to the Engineer for review and acceptance.

17.29.3 FABRICATION (2001) Steel reinforcement shall be cut and bent as shown on the bar lists and bending diagrams.

17.29.4 HANDLING, STORING AND SURFACE CONDITION OF REINFORCEMENT (2001) a.

1

Steel reinforcement shall be handled and stored in such a way as to meet the surface condition requirements of Part 1 of this Chapter.

b. Epoxy-coated reinforcing steel shall be handled and stored as not to damage the epoxy coating. Materials and equipment for handling epoxy-coated reinforcement shall have adequate padding to prevent damage. The requirements of Part 1 of this Chapter shall also be satisfied.

3

17.29.5 PLACING AND FASTENING (2001) 17.29.5.1 General a.

Steel reinforcement shall be placed as shown on the accepted Contractor's drawings and held firmly in position as required by Part 1 of this Chapter.

b. Tie wires and metal clips for epoxy-coated reinforcement shall be plastic or epoxy-coated. 17.29.5.1.1 Support Systems a.

Reinforcing steel shall be supported in position by mortar blocks, wire bar supports, supplementary bars or other devices subject to the acceptance of the Engineer. Supports shall prevent shifting of the reinforcement within the forms.

b. Mortar blocks shall have a compressive strength not less than that of the concrete in which they are to be embedded. c.

Wire bar supports shall meet the requirements of Part 1 of this Chapter.

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d. Any damage to the epoxy coating of reinforcing steel shall be repaired in accordance with Part 1 of this Chapter.

17.29.6 SPLICING OF BARS (2001) All reinforcement shall be furnished in the lengths indicated in the contract documents unless otherwise permitted by the accepted Contractor's drawings. Splices shall not be provided except as so approved.

SECTION 17.30 PRESTRESSED CONCRETE CAP AND/OR SILL FOR TIMBER PILE TRESTLE (2003)1 For guidelines for prestressed concrete cap and/or sill for timber pile structures, refer to Figure 8-17-2.

1

References, Vol. 78, 1977, p. 109.

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Figure 8-17-2. Prestressed Concrete Cap and/or Sill for Timber Pile Trestle

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COMMENTARY (2006)

C - SECTION 17.1 GENERAL REQUIREMENTS AND MATERIALS C - 17.1.1 SCOPE (2001) c.

For practical reasons a long span structure would be greater than 150 feet (50 m).

C - 17.4.4 GROUT FOR POST-TENSIONING TENDONS (2006) Several bridges have experienced corrosion of post-tensioning tendons because grout did not completely fill the tendon ducts allowing water to be entrapped. The primary cause of these grout voids in the tendon ducts has been attributed by investigators to construction methodology and to bleeding of the grout after it was installed. Substantial effort was expended by the Post-Tensioning Institute and the American Segmental Bridge Institute in cooperation with several State Departments of Transportation to develop an acceptable set of grout requirements and specifications to assist the correcting the deficiencies of the existing grout specifications. The result was the creation of the “Specification For Grouting Of Post-Tensioned Tendons” published by the PostTensioning Institute. All of the State Departments of Transportation have accepted and are using the new guide specifications. The specifications will remain guide specifications until such time as AASHTO accepts them for inclusion into the AASHTO bridge code publications. The guide specifications makes substantial revisions for materials, testing and prequalification of materials, certification of personnel, equipment requirements and installation procedures. The industry and the design community believe all post-tensioning tendons should be grouted in compliance with these guide specifications.

C - 17.5.1 SPACING OF TENDONS AND DUCTS (2006) With the increased use of High Performance Concrete and the desire to use 0.6 inch tendon to take advantage of the higher strength concrete being used, the U. S. D. O. T. - Federal Highway Administration had extensive tests performed relative to the bond and spacing of these new prestressing tendons. The test results indicated that the 0.6 inch tendon was “behaving fine: 2 inch (50 mm) spacing for 0.6 inch diameter tendons was acceptable”, and that designers could use 1/2 inch diameter tendons at 1-3/4 inch (45 mm) spacing. Subsequently, AASHTO adopted these criteria in the Standard Specifications for Highway Bridges. Since the prestressing industry has been using this strand at the 2 inch (50 mm) spacing with success, it is believed, in the interest of uniformity of facilities and economy, Part 17 should follow this criteria adopted by the industry.

C - 17.5.8 DEVELOPMENT OF PRESTRESSING STRAND (2001) EQ 17-2 gives the development length beyond which a three or seven wire prestressing strand is considered bonded. The formula can be divided into two components, the transfer length and the flexural bond length. In October 1988, the Federal Highway Administration (FHWA) issued a memorandum to all State Highway Departments expressing concern that the AASHTO Equation 9-32 was not conservative in determining the flexural bond length and thus the total development length. The memorandum has resulted in a great deal of research by a number of Universities, State Department's of Transportation, and the FHWA. Two documents are available from the FHWA giving more information on this issue. Publication No. FHWA-RD-93-076, “The

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History of the Prestressing Strand Development Length Equation”, and Publication No. FHWA-RD-94-049, “An Analysis of Transfer and Development Lengths for Pretensioned Concrete Structures”. Until research proves otherwise, the 1988 memorandum from the FHWA increased the required development length for fully bonded uncoated strand by 1.6 times the development length specified by AASHTO in Equation 9-32. For debonded strands, the factor was specified as 2.0 times the AASHTO Equation. There is a belief by industry representatives that this is not necessary and that further testing will indicate that to do so is extremely conservative.

C - SECTION 17.6 GENERAL ANALYSIS Where load or external forces, or geometry of the structure produces a torsion in the member the provisions of ACI 318 may be appropriate for use.

C - SECTION 17.9 FRAMES AND CONTINUOUS CONSTRUCTION When designing grade separations, solid cast-in-place conventionally reinforced or post-tensioned concrete spans may be used for continuous construction. Prior approval from the Engineer must be obtained. Most railroads normally do not utilize continuity in precast superstructures so that repairs can be made after derailments without the potential for overstressing members to remain.

1

For post-tensioned cast-in-place concrete continuous bridges, any benefits from the restraint moment should not be considered when checking the ultimate moment. At ultimate state, the slab may be cracked and there would be a redistribution of the restraint moment.

3 C - SECTION 17.11 FLANGE AND WEB THICKNESS-BOX GIRDERS Consideration should be given to the potential damage that may be caused to the top flange by track tampers being used on the bridge with insufficient ballast depth during the track installation. Increasing the flange thickness may mitigate this problem.

C - SECTION 17.12 DIAPHRAGMS It is suggested that intermediate diaphragms are not required for typical “I” beam structures. Temporary diaphragms are suggested during deck casting to provide stability.

C - 17.14.3 COMPOSITE FLEXURAL MEMBERS (2001) In structures with a cast-in-place slab on precast beams, the differential shrinkage tends to cause tensile stresses in the slab and in the bottom of the beams. Because the tensile shrinkage develops over an extended time period, the effect on the beams is reduced by creep. Differential shrinkage may influence the cracking load

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and the beam deflection profile. When these factors are particularly significant, the effect of differential shrinkage should be added to the effect of loads.

C - 17.16.2 CONCRETE (2001) The “auxiliary reinforcement” cited is additional mild steel reinforcement added to the member to resist part of the tension.

C - SECTION 17.18 FLEXURAL STRENGTH Strand A*s may be considered as non-prestressed reinforcement.

C - SECTION 17.26 GENERAL FABRICATION C - 17.26.4 CURING (2001) Curing of prestressed members shall be in accordance with the provisions of Section 17.1 of this chapter.

C - 17.26.6 ERECTION (2001) a.

It is recommended that lifting devices shall be designed with a safety factor to account for temporary stresses due to shipping and erection.

C - 17.26.8 APPLICATION AND MEASUREMENT OF PRESTRESSING FORCE (2005) Elongation measurements for prestressed elements should be in accordance with the procedures outlined in the “Manual for QUALITY CONTROL for Plants and Production of STRUCTURAL PRECAST CONCRETE PRODUCTS” published by the Precast/Prestressed Concrete Institute. Elongation measurements for post-tensioned construction are affected by several factors that are less significant, or that do not exist, for pretensioned elements. The friction along prestressing steel in posttensioning applications may be affected to varying degrees by placing tolerances and small irregularities in tendon profile due to concrete placement. The friction coefficients between the prestressing steel and the duct are also subject to variation. The 5 percent tolerance for pretensioned elements was proposed by ACI-ASCE Committee 423 in 1958, and primarily reflected experience with production of pretensioned concrete elements. Because the tendons for pretensioned elements are usually stressed with minimal friction effects, the 5 percent tolerance for such elements has been retained. Where differences are less than 5% for pretensioned elements or 7% for post-tensioned construction, the gage readings are to be used.

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C - SECTION 17.29 MATERIALS - REINFORCING STEEL A497 is already cited in Part 1, but A185 is not. A497 is for fabric made of deformed wire, and A185 is for fabric made of plain wire. This reference to A185 is from AASHTO. Article 17.29 now gives the designer a choice.

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Part 18 Elastomeric Bridge Bearings — 2001 —

This Part has now been eliminated. This material can now be found in Chapter 15, Steel Structures, Part 10, Bearing Design and Part 11, Bearing Construction.

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Part 19 Rating of Existing Concrete Bridges1 — 2005 — TABLE OF CONTENTS

Section/Article

Description

Page

19.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.1.1 Units (2000) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.1.2 Scope (2000) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-19-2 8-19-2 8-19-2

19.2 Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.2.1 General (2000) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.2.2 Normal Rating (2000) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.2.3 Maximum Rating (2000) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.2.4 Load Carrying Capacity (2000) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.2.5 Inspection (2000) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.2.6 Computation of Stresses or Strengths (2000) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-19-2 8-19-2 8-19-2 8-19-2 8-19-3 8-19-3 8-19-3

19.3 Loads and Forces. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.3.1 General (2000) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.3.2 Dead Load (2000). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.3.3 Live Load (2000) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.3.4 Impact (2000). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.3.5 Longitudinal Forces (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.3.6 Other Loads (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-19-4 8-19-4 8-19-4 8-19-4 8-19-4 8-19-5 8-19-5

19.4 Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.4.1 Concrete (2000) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.4.2 Reinforcing Steel (2000) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-19-5 8-19-5 8-19-6

19.5 Load Combinations and Rating Formulas. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.5.1 Loads and Forces (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.5.2 Notations (2000) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.5.3 Formulas (2005). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-19-8 8-19-8 8-19-9 8-19-9

19.6 Excessive Loading . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.6.1 Action to be Taken (2000). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-19-10 8-19-10

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References Vol. 67, 1966, pp. 355, 656; Vol. 71, 1970, p. 232; Vol. 90, 1989, pp. 53, 80.

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TABLE OF CONTENTS (CONT) Section/Article

Description

Page

Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-19-11

SECTION 19.1 GENERAL 19.1.1 UNITS (2000) a.

The values stated in metric (SI) units are to be used. The imperial values are approximate and are provided for information only.

b. Metric ASTM Standards are cited, where available. Corresponding imperial ASTM designations are cited only in the absence of a metric reference.

19.1.2 SCOPE (2000) a.

The provisions of Parts 2 and 17, this Chapter, should be followed except as modified by this Part.

SECTION 19.2 RATING 19.2.1 GENERAL (2000)1 a.

Concrete railway bridges shall be rated according to their load carrying capacity as determined by the rules specified herein.

b. The rating of the bridge shall be made either with reference to service loads and allowable service load stresses as provided in SERVICE LOAD RATING or, alternately, with reference to load factors and strength as provided in LOAD FACTOR RATING. The method to be used, SERVICE LOAD RATING or LOAD FACTOR RATING, shall be as directed by the Engineer. c.

Each bridge shall be assigned two ratings; NORMAL and MAXIMUM. The stated normal and maximum ratings of each bridge as a unit shall be the lowest of the ratings determined for the various components.

19.2.2 NORMAL RATING (2000) a.

Normal rating is the maximum load level which can be carried by an existing structure for an indefinite period of time.

19.2.3 MAXIMUM RATING (2000) a. 1

Maximum rating is the maximum load level which the structure can support at infrequent intervals.

See Commentary

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19.2.4 LOAD CARRYING CAPACITY (2000)1 a.

The load-carrying capacity of a bridge should be determined by the computation of stresses or strengths based on actual records of the design, details, materials, workmanship, and physical condition, including data obtained by inspection and load tests, if feasible.

19.2.5 INSPECTION (2000)2 a.

Inspection of the bridge shall be made in accordance with Part 21, this Chapter, with special attention to the following items: (1) Whether the actual sections and details conform to the plans. Dimensions of the concrete sections should be measured to nearest 5 mm (1/4 inch). Location and size of reinforcement should be checked at critical sections by use of a pachometer or other suitable device. (2) Any additions to the dead load not shown on the plans, such as heavier rail, deeper ballast section, concrete ties, walkways, pipelines, conduits, signal devices, and wire supports. (3) The position of the track with respect to the center line of the bridge. (4) Any loss of concrete. All loose concrete shall be removed before making this determination. (5) Any reduction in reinforcing steel area due to corrosion. This determination should be made by measurements after removal of corrosion.

1

(6) The physical condition, noting such conditions as excessive cracking at points of maximum moment and at points of maximum shear. If cracks are deemed critical, they should be observed during the passage of a train to determine whether live load stresses cause movement or growth in the cracks. (7) Uneven settlement of supports.

3

(8) Vertical or horizontal misalignment of spans or supports. (9) Superelevation of track.

19.2.6 COMPUTATION OF STRESSES OR STRENGTHS (2000)

4

19.2.6.1 General3 a.

The computation of stresses or strengths should be made for all load-carrying members and components, giving particular attention to the increased load carried by any member due to eccentricity.

19.2.6.2 Critical Sections a.

The critical sections at which computations are made should be approved by the Engineer. In addition to the main reinforcement, consideration shall be given to: (1) Sizes, spacing and development length of shear reinforcement.

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See Commentary See Commentary 3 See Commentary 2

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(2) Development length of and splices in longitudinal reinforcement. (3) Column moments due to continuous construction or eccentricity of loading. (4) The bond (development length) requirements in effect at the time the bridge was designed. 19.2.6.3 Redistribution of Moments1 a.

For continuous bridges, moments determined by elastic analysis may be redistributed by increasing or decreasing the negative moments by not more than 20 percent.

b. This redistribution of moments should follow that given in “Building Code Requirements for Reinforced Concrete–ACI 318-95M (ACI 318-95),” ART. 8.4 for nonprestressed members or ART 18.10.4 for prestressed members. 19.2.6.4 Maximum Reinforcement a.

For LOAD FACTOR RATINGS the area of tension steel to be used in computing the design moment strength should not exceed that available at the section. If the area of the tension steel exceeds the reinforcement required for balanced conditions, then a general analysis is required.

SECTION 19.3 LOADS AND FORCES 19.3.1 GENERAL (2000)2 a.

The loads and forces should be computed and are defined as follows:

19.3.2 DEAD LOAD (2000) a.

The dead load should be the mass of the bridge, including the track, ballast, and fill, together with that of any other loads, multiplied by the acceleration due to gravity (equivalent to a weight in imperial units).

19.3.3 LIVE LOAD (2000) a.

The live load should be one of the Cooper EM (E) series. Other standard loading criteria, or a load consisting of a specific locomotive or other equipment may be used, depending on the purpose for which the rating is being done.

b. The lateral and longitudinal distribution of the axle loads to the structure should be determined as outlined in Part 2, this Chapter.

19.3.4 IMPACT (2000)3 a.

The impact should be determined as outlined in Part 2, or Part 17, this Chapter, as applicable.

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See Commentary See Commentary 3 See Commentary 2

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b. Reduction of impact may be allowed as follows: for speeds less than 65 km/h (40 mph) the impact shall be reduced in a straight-line variation from full effect at 65 km/h (40 mph) to 0.5 of the full effect at 15 km/h (10 mph).

19.3.5 LONGITUDINAL FORCES (2005)1 Longitudinal forces shall be as specified in Part 2 Reinforced Concrete Design, Article 2.2.3(j). The EM360 (E80) loading is to be scaled proportionally to be consistent with the live load plus impact rating of the structure.

19.3.6 OTHER LOADS (2005) a.

Other loads shall be determined as given in Part 2, this Chapter.

SECTION 19.4 MATERIALS 19.4.1 CONCRETE (2000) 19.4.1.1 General2 a.

The compressive strength of the concrete shall be taken as the 28-day strength of the concrete, if records of same are available. If there is no record of the compressive strength of the concrete, it shall be assumed as 20 MPa (3,000 psi). For deteriorated concrete, the compressive strength should be assumed as not more than 17 MPa (2,500 psi), or a lower value should be used as required by the Engineer.

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19.4.1.1.1 Coring for Strength Tests3 a.

In the event that the concrete stress proves to be critical, the compressive strength of the concrete may be determined by “Standard Methods of Obtaining Testing Drilled Cores and Sawed Beams of Concrete,” ASTM Standard C42, or other methods as determined by the Engineer.

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19.4.1.1.2 Treatment of Core Holes a.

All core holes shall be filled with cementitious material having a 28-day specified compressive strength equal to or higher than that of the structure, or with a commercial grout approved by the Engineer. Epoxy bonding compound, meeting the approval of the Engineer, shall be used to bond the new concrete to the existing concrete.

19.4.1.2 Service Load Rating a.

The permissible stress for the concrete shall be taken as 1.2 fc, where fc is the allowable stress as specified in Part 2, this Chapter.

b. Modular ratio n shall be determined as the ratio of elasticity of steel to that of concrete, Es/Ec, as specified in Part 2, this Chapter.

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See Commentary See Commentary 3 See Commentary 2

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Concrete Structures and Foundations 19.4.1.3 Load Factor Rating a.

The applicable concrete design assumptions shall follow those in Part 2, this Chapter.

19.4.2 REINFORCING STEEL (2000) 19.4.2.1 Maximum Allowable Stresses a.

The following maximum allowable stresses should be used where fy is determined as indicated in Article 19.4.2.2. METRIC UNITS

IMPERIAL UNITS

0.8 fy 0.7 fy 0.6 fy 140 MPa

0.8 fy 0.7 fy 0.6 fy 20,000 psi

0.7 fy 230 MPa

0.7 fy 34,000 psi

All grades of steel. . . Wrought Iron. . .

165 MPa 140 MPa

24,000 psi 20,000 psi

Structural-grade steel bars. . . Intermediate-grade steel bars and Grade 280 (40) bars. . . Hard-grade steel bars and Grade 340 (50) or Grade 410 (60) bars. . . Wrought Iron. . .

0.6 fy 0.6 fy 0.5 fy 140 MPa

0.6 fy 0.6 fy 0.5 fy 20,000 psi

All grades of steel. . . Wrought Iron. . .

165 MPa 140 MPa

24,000 psi 20,000 psi

All grades of steel. . . Wrought Iron. . .

165 MPa 140 MPa

24,000 psi 20,000 psi

1. Tension reinforcement in flexural members: (with or without axial loads) Structural-grade steel bars. . . Intermediate-grade steel bars and Grade 280 (40) bars. . . Hard-grade steel bars and Grade 340 (50) or Grade 410 (60) bars. . . Wrought Iron. . . Wire mesh or cold-drawn steel wire not exceeding 12 mm (1/2 inch) in diameter when used in one-way solid slabs only. . . but not to exceed. . . 2. Tension in shear reinforcement:

3. Compression in column vertical reinforcement:

4. Compression reinforcement in flexural members:

5. Compression in composite column:

6. Compression in combination columns: Open-hearth or Bessemer steel (metric & imperial). . . [0.8fy/18,000][15,000-0.25(L2/r2)] Wrought Iron (metric & imperial). . . [0.8fy/15,000][12,500-0.21(L2/r2)] 7. Compression in pipe columns: Open-hearth or Bessemer steel (metric). . .

[124-0.48(L/r)](0.8fy2/38,500)

2 (imperial). . . [18,000-70(L/r)](0.8fy /810,000,000)

Where:

L is the unsupported length of the column. r is the radius of gyration of the steel section.

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Rating of Existing Concrete Bridges 19.4.2.2 Yield Strength 19.4.2.2.1 Known Yield Strengths1 a.

The yield strengths of the reinforcement shall be as shown on the plans unless mill test reports of the reinforcement used in the structure are available. If the reports are available, the yield strength of the reinforcement used in determining the rating shall be the lowest value shown for the size of bar used at the section being analyzed.

19.4.2.2.2 Unknown Yield Strengths a.

If the yield strength is unknown the following should be used: MINIMUM YIELD STRENGTH fy

REINFORCING BARS

METRIC

IMPERIAL

Structural Grade or unknown before 1968

230 MPa

33,000 psi

Intermediate Grade, Grade 300 (40) or unknown after 1967

300 MPa

40,000 psi

Hard Grade or Grade 350 (50)

350 MPa

50,000 psi

Grade 400 (60)

400 MPa

60,000 psi

Grade 500 (75)

500 MPa

75,000 psi

1

MINIMUM YIELD STRENGTH fpy

PRESTRESSING STEEL

METRIC

IMPERIAL

1) Low-Relaxation 2) Stress-Relieved

1675 MPa 1585 MPa

243,000 psi 230,000 psi

1) Low-Relaxation 2) Stress-Relieved

1550 MPa 1470 MPa

225,000 psi 213,000 psi

2. Wire ASTM A421M (ASTM A421) a. Low-Relaxation b. Stress-Relieved

1460 MPa 1380 MPa

212,000 psi 200,000 psi

3. High-Strength Bar ASTM A722M (ASTM A722) a. Low-Relaxation b. Stress-Relieved

880 MPa 825 MPa

128,000 psi 120,000 psi

1. Strands ASTM A416M (ASTM A416) a. Grade 1860 (270)

3

b. Grade 1725 (250)

1

4

See Commentary

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AREMA Manual for Railway Engineering

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Concrete Structures and Foundations

WELDED WIRE FABRIC OR COLD-DRAWN STEEL WIRE

METRIC

IMPERIAL

1. Plain Wire ASTM A82M (ASTM A82) a. 1961 & Before b. 1962 & After

440 MPa 480 MPa

64,000 psi 70,000 psi

2. Plain Welded Wire Fabric ASTM A185M (ASTM A185) a. Smaller than W1.2 b. W1.2 and larger

385 MPa 410 MPa

56,000 psi 60,000 psi

3. Deformed Wire ASTM A496M (ASTM A496)

515 MPa

75,000 psi

4. Deformed Welded Wire Fabric ASTM A497M (ASTM A497)

480 MPa

70,000 psi

SECTION 19.5 LOAD COMBINATIONS AND RATING FORMULAS 19.5.1 LOADS AND FORCES (2005) a.

The following notations represent the effect, due to the load or force specified, to be considered in the rating of a railroad bridge. The effects should be determined as stresses for service load rating and as forces for load factor rating. D = Dead Load L = Live Load I = Impact Load CF = Centrifugal Force E = Earth Pressure B = Buoyancy W = Wind Force on Structure WL = Wind Force on Live Load LF = Longitudinal Force from Live Load F = Longitudinal Force due to Friction or Shear Resistance at Expansion Bearings SF = Stream Flow Pressure

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8-19-8

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Rating of Existing Concrete Bridges

19.5.2 NOTATIONS (2000) SLN = Service Load Normal Rating Factor SLM = Service Load Maximum Rating Factor LFN = Load Factor Normal Rating Factor LFM = Load Factor Maximum Rating Factor Sf = Permissible Stress SN = Nominal Strength f = Strength Reduction Factor as specified in Part 2 or Part 17, this Chapter, whichever applies

19.5.3 FORMULAS (2005) 19.5.3.1 Service Load Rating 19.5.3.1.1 Normal Rating a.

The rating factor (SLN) shall be taken as the lesser of the values calculated using the following formulas: [ S f ¤ 1.2 ] – [ D + E + B + SF ] SLN = -------------------------------------------------------------------------[ L + I + CF ]

EQ 19-1

S f – [ D + E + B + SF + 0.5W + WL + F ] SLN = -------------------------------------------------------------------------------------------------------[ L + I + CF + LF ]

EQ 19-2

1

b. The rating expressed in terms of Cooper EM (E) Series shall be computed in accordance with the following expression. For example, if the live load in EQ 19-1 or EQ 19-2 were for a Cooper EM360 (E80) series, then the rating value would be: Normal Rating = SLN ´ 360 ( SLNx80 )

3

EQ 19-3

19.5.3.1.2 Maximum Rating a.

This rating factor (SLM) shall be taken as the lesser of the values calculated using the following formulas:

4

S f – [ D + E + B + SF ] SLM = -------------------------------------------------------[ L + I + CF ]

EQ 19-4

1.2S f – [ D + E + B + SF + 0.5W + WL + F ] SLM = ----------------------------------------------------------------------------------------------------------------[ L + I + CF + LF ]

EQ 19-5

b. The rating expressed in terms of Cooper EM (E) Series shall be computed in accordance with the following expression. For example, if the live load used in EQ 19-4 or EQ 19-5 were for a Cooper EM360 (E80) series, then the rating value would be: Maximum Rating = SLM ´ 360 ( SLMx80 )

EQ 19-6

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8-19-9

Concrete Structures and Foundations

This rating may be increased by reducing the speed over the structure. A reduction of impact as defined in 19.3.4 can then be used to recalculate the rating. 19.5.3.2 Load Factor Rating 19.5.3.2.1 Normal Rating a.

The rating factor (LFN) shall be taken as the lesser of the values calculated using the following formulas: fS N – 1.1 ( D + E + B + SF ) LFN = ---------------------------------------------------------------------1.3 [ 5 ¤ 3 ( L + I ) + CF ]

EQ 19-7

fS N – 1.1 [ D + E + B + SF + 0.5W + WL + F ] LFN = ----------------------------------------------------------------------------------------------------------------------1.3 [ L + I + CF + LF ]

EQ 19-8

b. The rating expressed in terms of Cooper EM (E) Series shall be computed in accordance with the following expression. For example, if the live load used in EQ 19-7 or EQ 19-8 were for a Cooper EM360 (E80) series, then the rating value would be: EQ 19-9

Maximum Rating = LFN ´ 360 ( LFNx80 ) 19.5.3.2.2 Maximum Rating a.

The rating factor (LFM) shall be taken as the lesser of the values calculated using the following formulas: fS N – 1.1 ( D + E + B + SF ) LFM = ---------------------------------------------------------------------1.3 ( L + I + CF )

EQ 19-10

fS N – 1.1 [ D + E + B + SF + 0.5W + WL + F ] LFM = ----------------------------------------------------------------------------------------------------------------------1.1 [ L + I + CF + LF ]

EQ 19-11

b. The rating expressed in terms of Cooper EM (E) Series for full speed shall be computed in accordance with the following expression. For example, if the live load used in EQ 19-10 or EQ 19-11 were for a Cooper EM360 (E80) series, then the rating value would be: Normal Rating = LFMx360 ( LFMx80 )

EQ 19-12

SECTION 19.6 EXCESSIVE LOADING 19.6.1 ACTION TO BE TAKEN (2000)1 a.

1

If the normal operating loads exceed those permissible under these rules, the speed and/or the loading should be restricted so that the permissible loads will not be exceeded; otherwise, appropriate action

See Commentary

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8-19-10

AREMA Manual for Railway Engineering

Rating of Existing Concrete Bridges

should be taken until the bridge is strengthened or replaced. When the operating loads are determined to be close to permissable loads, or when the physical conditions of the main members or components are marginal, the bridge should be frequently inspected as long as it is in service.

COMMENTARY The purpose of this Commentary is to provide additional information and explanation regarding various articles in Part 19 Rating of Existing Concrete Bridges. The numbers after the “C -” correspond to the Article or Section being explained.

C - SECTION 19.2 RATING C - 19.2.1 GENERAL (2005) a.

Protection of the investment made in a bridge facility through well programmed preventative maintenance, inspections, ratings, and repairs is second only to the overall safety of the structure and the traffic it carries. The procedure for rating requires careful evaluation of a number of complex and often conflicting factors in the continuing effort to extend the useful life of concrete railroad bridges. The evaluation of bridges should include a detailed inspection, a thorough structural analysis, and consideration of the degree of control the railroad can exercise over the bridge loading. This work is to be performed in the interest of obtaining the maximum safe and cost-effective utilization of the assets of the railroad facility.

1

b. Two methods of structural analysis are allowed. These methods should both account for the strength of the bridge in its current state, and the method used should be identified for future reference. c.

The MAXIMUM load rating is the higher level rating, and reflects the absolute maximum permissible load level to which the structure may be subjected on an infrequent basis. The NORMAL load rating reflects the load level that can safely utilize an existing structure on a regular basis. Both ratings need to be re-evaluated periodically to account for ongoing deterioration that may be detected in regular inspections.

C - 19.2.4 LOAD CARRYING CAPACITY (2005) a.

4

Field tests should be made and the results given due consideration in the assessment of the load carrying capacity if required by the Engineer. For a specific service, the location, history, and behavior of the bridge under investigation should be taken into account.

C - 19.2.5 INSPECTION (2005) a.

Rating of a bridge generally should start with a detailed field inspection. All physical features of the bridge having an affect upon its structural integrity should be examined. In some cases, a detailed physical inspection may be all that is required for the Engineer to make a judgment that the bridge is safe for normal, every-day loads. An example could be a sound concrete bridge carrying normal traffic for many years and shows no distress. Features other than the bridge itself that may affect the structure should also be observed and noted. For example, a rough or otherwise abrupt transition between the track on the embankment section and the track on the bridge may cause an increase in the impact above what would routinely be calculated.

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Concrete Structures and Foundations

C - 19.2.6 COMPUTATION OF STRESSES OR STRENGTHS (2005) C - 19.2.6.1 GENERAL a.

Generally, most bridges requiring load restrictions are either old, or are of insufficient strength as a result of damage. With some exceptions, the elements of older structures with insufficient strength are usually in the superstructures, not in the piers or abutments. The susceptibility of substructure elements to the effects of scour at bridges over waterways should be considered, as well as potential detrimental effects of longitudinal force from live load.

C - 19.2.6.3 REDISTRIBUTION OF MOMENTS a.

Under certain specific conditions, negative moments at interior supports of continuous beams may be reduced. Such reduction must be accompanied by an increase in the positive moments in the adjacent spans equal to the average decrease in negative moment. Moment redistribution is dependant upon adequate ductility in the plastic hinge regions to allow plastic hinges to develop. Often, the ductility required to allow redistribution of moments is not available in members designed by the Working Stress Method.

C - SECTION 19.3 LOADS AND FORCES C - 19.3.1 GENERAL (2005) a.

The total load in any member caused by dead load, live load, and other loads deemed applicable by the Engineer shall not exceed the member capacity. When it becomes necessary to reduce the allowable live load in order to avoid exceeding the capacity of the bridge, such a reduction is based upon the assumption that each axle load maintains a constant relation to the total load. For example, each axle of an E-60 live load is exactly three-fourths of the magnitude of each corresponding axle of an E-80 live load.

C - 19.3.4 IMPACT (2005) a.

A reduced speed of operation may be considered where it is desirable to reduce impact loads. In some cases, a reduction in speed of operation will reduce impact loads to the extent that decreasing the load rating will not be required. Consideration of a reduced speed of operation will require the judgment of the Engineer and much will depend upon the track alignment, the bridge location, as well as the type and volume of traffic. The condition of the approaching track and the transition from the embankment section to the bridge section may also influence the selection of an appropriate impact factor.

C - 19.3.5 LONGITUDINAL FORCES (2005) a.

Longitudinal forces due to train traffic on railway bridges are influenced by a number of factors including: 1) the type of motive power used, 2) train tonnage, 3) grades, 4) braking forces, 5) likelihood of starting or stopping a train at or near a particular bridge, and 6) individual railroad operating practices. For further information, see Chapter 8 commentary section on design for longitudinal forces (C -2.2.3(j)), and see related material in Chapter 15.

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8-19-12

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Rating of Existing Concrete Bridges

b. The longitudinal force in Article 2.2.3(j) is based on E-80 loading. For structures with a live load plus impact rating different from E-80, the longitudinal force used in the rating is to be reduced or increased by the ratio of the rating for live load plus impact to E-80. c.

It is important to trace the load path these forces will follow to the point at which they are taken out of the structure, and ensure the load path is consistent with compatibility of deflections and rotations.

d. Longitudinal forces are included in the Group III load case in design. The same load case is used to include longitudinal forces for rating purposes. e.

These rating cases cover the extreme events of emergency braking, and starting a train from a static state at maximum tractive effort. Longitudinal forces applied during normal train operations might be significantly lower. If the rating of a particular structure is too restrictive because of longitudinal forces, the methodology provided in Chapter 15, Part 7, may be considered and adapted to provide relief for normal train operations, at the discretion of the Engineer. Additionally, a reduction in impact may be considered, as the maximum longitudinal force due to tractive effort or braking occurs at speeds below 25 mph.

C - SECTION 19.4 MATERIALS C - 19.4.1 CONCRETE (2005)

1

C - 19.4.1.1 GENERAL a.

In some cases, such as with compression members or over-reinforced flexural sections, the strength of the concrete may be the controlling factor in the rating calculation of the member. In such cases, use of an assumed concrete strength may not be advisable.

3

C - 19.4.1.1.1 CORING FOR STRENGTH TESTS a.

Care must be exercised in gathering and interpreting the results of field and laboratory tests. Several issues may play a part in the evaluation, especially if the test results indicate incipient failure, the need for immediate repairs, or load rating reduction below acceptable levels. For example, was sampling done properly? Were the location, size, and number of samples adequate to represent the member being evaluated? Is there a pattern or consistency in the results? Are other tests or inspections needed to verify results, or to investigate other members in the bridge for similar defects? Is there a possibility or likelihood other structures on the system have similar problems that may not have been discovered yet?

C - 19.4.2 REINFORCING STEEL (2005) C - 19.4.2.2 YIELD STRENGTH C - 19.4.2.2.1 UNKNOWN YIELD STRENGTHS a.

These strengths are provided to facilitate rating of bridges with unknown steel reinforcement properties. Records should exist for most bridges, and these records should be researched in an effort to determine the most accurate data to use in the bridge rating. The yield strengths given in this section should only be used after an exhaustive search for the actual records proves unproductive. The values given in this section may also be used as a rough approximation prior to searching for the actual data. © 2011, American Railway Engineering and Maintenance-of-Way Association

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Concrete Structures and Foundations

C - SECTION 19.6 EXCESSIVE LOADING C - 19.6.1 ACTION TO BE TAKEN (2005) a.

All bridges should be included in a regular inspection program. More frequent inspections are required for any bridge with known deficiencies or which is in questionable condition. Also, bridges with no apparent deficiencies loaded at a level above their “NORMAL” rating should be subject to more frequent, competent inspections. Several factors may influence the selection of the load level. For example: (1) A higher safety factor for a bridge carrying a large volume of traffic may be desirable as compared with the safety factor for a bridge carrying very little traffic, especially if the bridge carrying the high traffic volume also carries a high percentage of heavy loads. (2) Bridges with extensive material losses may warrant a lower load level due to the greater uncertainty in evaluating the present strength of the bridge. This is especially true if the loss of material is in a highly stressed region. (3) The ratio of dead load to live load may have an influence on the selection of the appropriate load level. Structures with high dead load to live load ratios and no signs of distress may merit consideration of higher load levels.

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8-19-14

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8

Part 20 Flexible Sheet Pile Bulkheads — 1995 — TABLE OF CONTENTS

Section/Article

Description

Page

20.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.1.1 Scope (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.1.2 Types of Flexible Bulkheads (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-20-2 8-20-2 8-20-2

20.2 Information Required. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.2.1 Field Surveys and Records (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.2.2 Soil Investigation (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.2.3 Loads (1993). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.2.4 Drainage (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.2.5 Character of Backfill (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-20-3 8-20-3 8-20-3 8-20-3 8-20-3 8-20-3

20.3 Computation of Lateral Forces Acting on Bulkheads . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.3.1 Active Earth Pressure Due to the Weight of Backfill (1993) . . . . . . . . . . . . . . . . . . . . . . . 20.3.2 Active Earth Pressure Due to Surcharge Loads (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.3.3 Active Earth Pressure Due to Unbalanced Water Pressure (1993) . . . . . . . . . . . . . . . . . . 20.3.4 Passive Earth Pressure (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.3.5 Reduction of Weight in Passive Wedge Due to Upward Seepage (1993) . . . . . . . . . . . . . .

8-20-5 8-20-5 8-20-5 8-20-8 8-20-9 8-20-9

20.4 Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.4.1 Stability Calculations (1993). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-20-9 8-20-9

20.5 Design of Anchored Bulkheads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.5.1 Depth of Embedment (1993). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.5.2 Maximum Moment (1993). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.5.3 Anchor Pull (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.5.4 Flexibility of Anchorage (1993). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.5.5 Anchorages (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.5.6 Connections (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.5.7 Allowable Stresses (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-20-10 8-20-10 8-20-11 8-20-11 8-20-12 8-20-12 8-20-13 8-20-13

20.6 Cantilever Bulkheads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.6.1 Scope (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-20-13 8-20-13

20.7 Notations (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-20-15

Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-20-16

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8-20-1

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Concrete Structures and Foundations

LIST OF FIGURES Figure 8-20-1 8-20-2 8-20-3 8-20-4 8-20-5 8-20-6 8-20-7 8-20-8 8-20-9

Description

Page

Lateral Pressure Diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pressure Distribution for Strip Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pressure Distribution for Line Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pressure Distribution for Point Load. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Flow Net for Upward Seepage of Water After Rapidly Receding High Water. . . . . . . . . . . . . . Stability Analysis – Massive Earth Movements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Depth of Total Embedment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Maximum Moment Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Anchorage Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-20-5 8-20-6 8-20-7 8-20-8 8-20-9 8-20-10 8-20-11 8-20-12 8-20-14

LIST OF TABLES Table

Description

Page

8-20-1 Granular Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-20-2 Silt and Clay Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-20-3 Unit Weights of Soils, and Coefficients of Earth Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-20-4 8-20-4 8-20-4

SECTION 20.1 GENERAL 20.1.1 SCOPE (1995)1 a.

This part of the Manual provides a recommended practice for the design of flexible sheet pile bulkheads. The guidelines are intended for SERVICE LOAD DESIGN only.

b. Braced excavations and cofferdams are not within the scope of these recommended practices.

20.1.2 TYPES OF FLEXIBLE BULKHEADS (1995)2 a.

A sheet pile bulkhead is a structure designed to provide lateral support for a soil mass and derives stability from the passive resistance of the soil in which the bulkhead is embedded. Bulkheads are frequently referred to as retaining walls of the waterfront or as seawalls.

b. For purposes of this part of the Manual, the “bulkhead” is considered to include the sheet piling, the soil masses behind and in front of the sheet piling, and the various kinds of anchors. c.

Sheet pile bulkheads may be constructed of steel, concrete, or timber. They may be cantilevered; or they can be anchored by tie rods connected to deadman, pile foundations, or existing structures. Bulkheads may be anchored by batter piles secured to wales connecting the sheet piles.

d. Sheet piles bulkheads are generally designed as flexible structures which yield sufficiently to mobilize full active earth pressure and a portion of the passive pressure. For anchored bulkheads, movement at the anchor rod in the range of 0.001Hf to 0.002Hf is needed to develop full active pressure.

1 2

See Commentary See Commentary

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e.

Where adjacent structures would be endangered by a flexible bulkhead, a rigid type bulkhead not covered in this design guideline must be utilized.

f.

Braced excavations and cofferdams, not included in the scope of this design guideline, exhibit different types of deformation with resulting higher earth pressures.

SECTION 20.2 INFORMATION REQUIRED 20.2.1 FIELD SURVEYS AND RECORDS (1995) Sufficient information shall be furnished in the form of a profile and cross sections, or a topographical map to determine general design and structural requirements. Present and proposed grades and alignment of tracks and roads shall be indicated together with records of: reference datum, maximum and minimum high water, mean high water, minimum and mean low water, existing ground water level, location of utilities, construction history of the area, indication of any conditions which might hamper proper installation of the piling, depth of scour, allowance for overdredging, wave heights, and seiches.

20.2.2 SOIL INVESTIGATION (1995)1 The characteristics of the foundation soils shall be investigated as indicated in Part 22, Geotechnical Subsurface Investigation.

20.2.3 LOADS (1993) a.

1

All design criteria, temporary and permanent loading, boring and laboratory test results, and properties of construction materials, including yield stress, should be clearly stated in the design calculations and on the contract and record plans. Temporary loads include, but are not limited to: construction equipment, construction materials, lower water levels adjoining the bulkhead causing unbalanced hydrostatic pressure. Permanent loads include, but are not limited to: future grading and paving, railroads or highways, structures, material storage piles, snow and earthquake.

3

b. The allowable live load after construction should be clearly shown in the plans and painted on the pavements behind the bulkheads or shown on signs at the site and also recorded on the record plans. c.

The “loads” listed above are external to the total bulkhead system. There are also internal effects that are treated as loads in the design of individual members of the bulkhead system. These internal loads are active and passive soil pressures, acting separately or combined algebraically, saturated or dry as appropriate, for granular or cohesive soil or a combination thereof.

20.2.4 DRAINAGE (1993) a.

The drainage pattern of the site before and after construction should be analyzed, and adequate drainage provisions incorporated into the plans and specifications. Consideration should be given to underdrainage as well as surface drainage.

b. Drainage provisions for backfill should be compatible with the assumed water conditions in design.

20.2.5 CHARACTER OF BACKFILL (1993) a.

1

A reconnaissance survey should be made of cost and availability of local materials. At major structures, gradation, maximum and minimum density, specific gravity, and shear strength determinations should

See Commentary

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4

Concrete Structures and Foundations be performed and classified with reference to granular soils (Table 8-20-1) and Silt and Clay Soils (Table 8-20-2). b. Granular backfill is recommended where the depth of the bulkhead is great or the bulkhead deformation must be minimized. c.

The range of the unit weight of soils and the coefficients of active pressure, Ka, and passive pressure, Kp , for horizontal ground surface are shown in Table 8-20-3. Table 8-20-1. Granular Soils Descriptive Term for Relative Density Standard Penetration Test Blows per Foot “N” Very Loose

0–4

Loose

4 – 10

Medium

10 – 30

Dense

30 – 50

Very Dense

Over 50 Table 8-20-2. Silt and Clay Soils

Descriptive Term for Consistency

Unconfined Compressive Strength Tons per Square Foot

Very Soft

Less than 0.25

Soft

0.25 – 0.50

Medium

0.50 – 1.00

Stiff

1.00 – 2.00

Very Stiff

2.00 – 4.00

Hard

Over 4.00

Table 8-20-3. Unit Weights of Soils, and Coefficients of Earth Pressure

Type of Soil

Unit Weight of Moist Soil, g (Note 1)

Unit Weight of Submerged Soil, g ¢ (Note 1)

Minimum Maximum Minimum (1)

(2)

(3)

(4)

Coefficient of Active Earth Pressure, Ka For Backfill

Friction Angles For Soils (Note 2) in Place

Maximum (5)

(6)

(7)

f

d

(8)

(9)

Coefficient of Passive Earth Pressure, Kp For Soils in Place (10)

Friction Angles (Note 2)

f

d

(11)

(12)

Clean Sand: Dense

110

140

65

78

0.20

38

20

9.0

38

25

Medium

110

130

60

68

0.25

34

17

7.0

34

23

Loose

90

125

56

63

0.30

30

15

5.0

30

20

0.35

Silty Sand: Dense

110

150

70

88

0.25

7.0

Medium

95

130

60

68

0.30

5.0

Loose

80

125

50

63

0.50

0.35

3.0

1.00

qu 1 – ---------------p+gz

qu 1 + ---------------p+gz

Silt and Clay (Note 3) Note 1: Note 2: Note 3:

165 ( 1 + w ) ----------------------------1 + 2.65w

103 -------------------------1 + 2.65w

In pounds per cubic foot. These angles, expressed in degrees, are f, the angle of internal friction, and d, the angle of wall friction, and are used in estimating the coefficients under which they are listed. The symbol g represents g or g ¢ , whichever is applicable; p is the effective unit pressure on the top surface of the stratum; qu is the unconfined compressive strength; w is the natural water content, in percentage of dry weight; and z is the depth below the top surface of the stratum.

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SECTION 20.3 COMPUTATION OF LATERAL FORCES ACTING ON BULKHEADS 20.3.1 ACTIVE EARTH PRESSURE DUE TO THE WEIGHT OF BACKFILL (1993) a.

The active earth pressure due to the weight of the backfill may be computed by the Coulomb Theory, and is represented in the loading diagram by area I, Figure 8-20-1.

b. The active earth pressure at depth “z” is: pA = Kagz

20.3.2 ACTIVE EARTH PRESSURE DUE TO SURCHARGE LOADS (1993) 20.3.2.1 Uniform Load q The active earth pressure due to a uniform surcharge load q (pounds per square foot) is: pu = Kaq which is represented by area II, Figure 8-20-1.

1

3

4

Figure 8-20-1. Lateral Pressure Diagrams

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20.3.2.2 Strip Load q a.

A continuous strip of surcharge load q (pounds per square foot) parallel to the bulkhead is shown in Figure 8-20-2. The intensity of pressure at a given point may be computed by: 2 2 p s = 2q ------- ( b + sin b sin a – sin b cos a ) p

b. The Strip Load is not shown in Figure 8-20-1. Symbols and notations are shown in Figure 8-20-2. 20.3.2.3 Line Load a.

A very narrow strip surcharge load q¢ (pounds per linear foot) may be considered as a line load. The intensity of lateral pressure, p1, may be computed by the following semi-empirical formulas: 2

1.27q¢ m n p 1 = ----------------- ----------------------------- For ( m > 0.40 ) H 2 2 2 (m + n ) q¢ n p 1 = 0.203 ----- -------------------------------- For ( m £ 0.40 ) H 2

Figure 8-20-2. Pressure Distribution for Strip Load

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b. The pressure is represented by area IV, Figure 8-20-1. Symbols and notations are shown in Figure 8-20-3.

Figure 8-20-3. Pressure Distribution for Line Load 20.3.2.4 Point Load a.

The lateral pressure due to a point load, Q, Figure 8-20-4, varies with the depth as well as the horizontal distance from the load. The intensity of lateral pressure pq on line ab directly opposite the load may be computed by the following formulas: 2 2

1

Q m n p q = 1.77 ------- ----------------------------- For ( m > 0.40 ) 2 3 H m2 + n2 2

Q n p q = 0.28 ------- -------------------------------- For ( m £ 0.40 ) 2 2 3 H

3

b. The unit pressure on any other point, on both sides of ab is smaller than pq at the same depth, and may be computed by: p2 = pqcos2(1.1Y). c.

Point loading is not shown in the diagram in Figure 8-20-1. Symbols and notations are shown in Figure 8-20-4.

4

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d. A Trial Wedge analysis, Part 5, Retaining Walls, Abutments and Piers, Commentary, is accepted as an alternate solution for the loading obtained in Article 20.3.2.2, Article 20.3.2.3, or Article 20.3.2.4.

Figure 8-20-4. Pressure Distribution for Point Load

20.3.3 ACTIVE EARTH PRESSURE DUE TO UNBALANCED WATER PRESSURE (1993) a.

When bulkheads are used for waterfront construction, the bulkhead is subjected to a maximum earth pressure at the low water stage. During a rainstorm or a rapidly receding high water, the water level behind the bulkhead may be several feet higher than in front, as shown in Figure 8-20-5. The unbalanced water pressure is represented by area III in Figure 8-20-1.

b. Drained conditions in backfill apply when clean sand or clean sand and gravel, as defined in Article 20.2.5 are used and adequate permanent drainage outlets are provided. Where drained conditions exist, the design water level may be assumed at the drainage outlet elevation.

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20.3.4 PASSIVE EARTH PRESSURE (1993) The passive earth pressure, pp, in front of the bulkhead may also be computed by the Coulomb Theory. This pressure is also shown in Figure 8-20-1. pp = Kpg z

20.3.5 REDUCTION OF WEIGHT IN PASSIVE WEDGE DUE TO UPWARD SEEPAGE (1993) a.

During a rainstorm or rapidly receding high water, the water level behind the bulkhead may be several feet higher than in front. The receding water percolates downward through the backfill and then upward in front of the bulkhead as illustrated in Figure 8-20-5. The upward flow causes a significant reduction in the effective weight of the soil g ¢ and consequently must be considered in the design using passive pressure where applicable.

b. Piping under the sheeting may be a problem for bulkheads driven to a shallow depth.

1

Figure 8-20-5. Flow Net for Upward Seepage of Water After Rapidly Receding High Water

3

SECTION 20.4 STABILITY 20.4.1 STABILITY CALCULATIONS (1993) a.

4

The stability condition referred to herein concerns a local condition immediately under the bulkhead. Massive earth movements such as the type indicated in Figure 8-20-6 are not covered by this calculation. Massive movements may occur independently of the type and design of the bulkhead and constitute a slope stability problem.

b. The vertical effective pressure behind the bulkhead at the elevation of the mud line is denoted by p . It is made up of the effective submerged unit weight of the soil below the low water line, the weight of the soil above the low water line, the uniform surcharge load q as shown in Figure 8-20-1, and a distributional load of any line, point, and other loads. For purposes of this stability calculation line, strip, and point loads may be distributed uniformly over the area covered (behind the bulkhead only) by a 2:1 (horizontal:vertical) distribution to the elevation of the mud line. c.

The stability calculation is carried out by treating the area behind the bulkhead as though it were a spread footing resting on the surface of the soil at the elevation of the mud line. Generally, stability

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problems will arise only with weak silts and clays. To meet the stability requirements the passive pressure must satisfy the following: p £ 5.14c -------------FS where: c = the cohesion which can be taken as one-half the unconfined compressive strength of soft clays below the mud line FS = the factor of safety For well defined loading conditions and thoroughly determined soil parameters, the minimum factor of safety for permanent construction may be 1.50. If temporary loading is included, the minimum factor of safety may be reduced to 1.30. d. If weaker layers exist below, then the shear strength value applicable to these layers should be used in the above calculations. e.

If the above criteria for stability are not satisfied, then these design guidelines are not applicable. In such an event, a thorough soils investigation and analysis, combined with field observations, may lead to a satisfactory design, but this condition is considered beyond the scope of this Manual.

Figure 8-20-6. Stability Analysis – Massive Earth Movements

SECTION 20.5 DESIGN OF ANCHORED BULKHEADS 20.5.1 DEPTH OF EMBEDMENT (1993) a.

The total depth of embedment D is found by extending the active and passive pressures downward to the bottom of the pile as schematically shown in Figure 8-20-7. The total embedment D, is satisfactory when the moment about the elevation of the anchorage Ap, due to the passive pressure resultant Pp equals

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that due to the active pressure resultant Pa with a factor of safety of 2.0 for permanent construction and 1.5 if temporary loads are included. b. The designer should be on guard against shallow penetration of sheet piling into relatively strong soil layers. The moment summations described above are greatly affected when a relatively strong layer is encountered. It is suggested that arbitrary reductions in strengths, or assumption of the lowest probable elevation of the mudline, be made for such layers in order to avoid unrealistically short penetrations.

20.5.2 MAXIMUM MOMENT (1993)1 a.

It will usually be found that a maximum positive moment controls the selection of the sheet pile section. The maximum moment for design is to be not less than that calculated according to the assumed equivalent beam shown in Figure 8-20-8. The structure has been made statically determinate by assuming that a hinge occurs at the lowest elevation of the mud line. Naturally, the designer shall make a structural check for all loading conditions.

b. If a thin layer of relatively soft soil exists at the mud line, the point of contraflexure is moved to the base of said layer, but not deeper than 0.1D. It may be assumed that the maximum negative moment, below the dredge line as shown in Figure 8-20-8, is less than the maximum positive moment. In selecting a structural section, interlock friction is to be ignored. If materials other than steel are used, their flexural stiffness EI should not be greater than that for the required steel sheet pile section; otherwise, this part of the design procedure does not apply.

1

3

4

Figure 8-20-7. Depth of Total Embedment

20.5.3 ANCHOR PULL (1993)2 For design of the anchorage system, the anchor pull shall be increased arbitrarily by at least 20% when determined according to the equivalent beam theory given in Figure 8-20-8.

1 2

See Commentary See Commentary

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Figure 8-20-8. Maximum Moment Calculations

20.5.4 FLEXIBILITY OF ANCHORAGE (1993) The anchor, anchor rod, and the connecting details are to be sufficiently flexible that a deformation of 0.001 Hf to 0.002 Hf can develop at the wall without distress to the structural system. If the specified deformation cannot develop, then the active earth pressures should be recomputed as for a braced cut and the bulkhead redesigned accordingly.

20.5.5 ANCHORAGES (1993) a.

All reactions to the anchor pull are developed entirely beyond the active pressure wedge behind the face of the bulkhead as indicated in Figure 8-20-9. If batter piles are used as the anchorage, the piles are to develop the anchor pull entirely below and in back of the active earth pressure wedge. Deadman anchorages as shown in Figure 8-20-9 are designed utilizing passive earth pressures as resistance against anchor pull. (1) Deadman type anchorages are preferred. (2) Next in order of preference, is the A-Frame shown in Figure 8-20-9, utilizing a combination of tension and compression batter piles connected by a pile cap.

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(3) The least desirable anchorage is a tension pile as shown in Figure 8-20-9. The tension pile may be difficult to develop and costly. The flexibility requirements may be difficult to develop because of the high axial stiffness of the pile; further, this is frequently a very expensive anchorage. b. Corrosion protection of the anchor rods shall be provided consistent with the electrochemical properties of the soil and external factors affecting corrosion. c.

The probable settlement of the backfill should be estimated and the anchor rods designed to withstand the added loading. Alternately, the rods may be encased in tubes sufficient in size to enable the settlement to occur without adding loads to the rods.

d. Anchorages should never be proportioned for a factor of safety less than 2.0.

20.5.6 CONNECTIONS (1993) The walers, brackets, and all connections shall be designed in accordance with the provisions of Chapter 15, Steel Structures.

20.5.7 ALLOWABLE STRESSES (1993) a.

The allowable stresses shall be determined on the following basis: (1) Sheet Pile Sections:

1

• 1/3 compressive strength for concrete. • 2/3 tensile yield strength for steel. (2) Anchor Rods – 1/2 tensile yield strength for steel.

3

(3) Other structural Members: • According to the applicable section of the Manual. b. All connections shall be designed for the computed structural loads after allowances for wear and corrosion. The minimum corrosion allowance for anchor rods shall be 1/32 inch for each surface. Provision should be made to facilitate maintenance of structural elements subjected to significant wear and corrosion.

SECTION 20.6 CANTILEVER BULKHEADS 20.6.1 SCOPE (1993)1 Cantilever bulkheads are not covered within these design guidelines.

1

See Commentary

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Concrete Structures and Foundations

Figure 8-20-9. Anchorage Design

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SECTION 20.7 NOTATIONS (1993) Ap = Anchor Pull c= D= D¢ = EI = FS = H= Hf =

Cohesion Depth of embedment below mud line Minimum depth of embedment below mud line for equilibrium Flexural Stiffness Factor of Safety Length of sheet pile Length from top of sheet pile to mud line

Hu = Unbalanced head of water Ka = Active earth pressure coefficient Kp = Passive earth pressure coefficient m= n= N= Pa =

Horizontal distance from top of sheet pile as a percentage of H Vertical distance below top of sheet pile as a percentage of H Blows per foot, Standard Penetration Test Resultant horizontal active earth pressure

Pp = Resultant horizontal passive earth pressure pa = Horizontal active earth pressure

1

p1 = Horizontal active earth pressure due to a Line Load pp = Horizontal passive earth pressure p2 = Horizontal active earth pressure due to a Point Load Q ps = Horizontal active earth pressure due to a Strip Load of intensity q pu = Horizontal active earth pressure due to a Uniform Surcharge pq = Maximum horizontal active earth pressure due to a Point Load

3

p = Vertical effective pressure behind the bulkhead at elevation of mud line p = Vertical effective pressure behind the bulkhead at lowest elevation of the mud line Q = Point Load q = intensity of strip load or surcharge load q¢ = intensity of line load qu = Unconfined compressive strength of cohesive soil w= x= z= a= b= g= g¢ = d= f= y=

4

Water content Horizontal distance from top of wall Vertical distance from top of sheet pile Angle (in radians) from wall to center of a uniform strip load Article 20.3.2 Angle (in radians) made by a uniform strip load Article 20.3.2 Moist unit weight of soil Submerged unit weight of soil Angle of wall friction Angle of internal friction of soil Angle of point in question from maximum Article 20.3.2

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COMMENTARY The purpose of this part is to furnish the technical explanation of various articles in Part 20, Flexible Sheet Pile Bulkheads. In the numbering of articles of this section, the numbers after the “C-” correspond to the section/article being explained. See Reference 1, 22, 33, and 101.

C - SECTION 20.1 GENERAL C - 20.1.1 SCOPE (1995) a.

This part of the Manual has been prepared for permanent construction. Braced excavations and cofferdams are not included.

b. This part of the Manual is primarily based on the references listed in the References. c.

Tiebacks drilled into in situ soil are not included within the scope at this time.

C - 20.1.2 TYPES OF FLEXIBLE BULKHEADS (1995) a.

Most bulkheads or sheet pile walls are sufficiently flexible to meet the design criteria of a total deflection more than 0.0015 times the wall height. If this requirement is not satisfied, the magnitude and distribution of the earth pressures can be much greater and the loads must be calculated on the basis of a braced cut. See any major soil text for the pressure distribution for “braced excavations.”

b. This part of the Manual has been prepared assuming waterfront construction and designed backfill. The principles given are fully applicable to other situations, i.e. sheeting used for a retaining wall or wingwall. When natural soil is retained, consideration must be given to several other conditions: (1) Swelling soils. (2) Poor drainage which may result in higher pressures. (3) Difficulty in the tieback installation, including necessary shoring for this installation. (4) Unknown driving conditions for piling. Though some or all of the above conditions can be a part of any installation, they are more apt to occur where virgin ground is retained.

C - 20.2.2 SOIL INVESTIGATION (1995) a.

Consideration must be given to the importance of the structure and anchorages when planning geotechnical work. A thorough study may result in shorter piling lengths and/or lower anchor loads, and thus result in an economical design.

b. The present and future location of the water table is of great importance since water reduces the passive pressure, and increases the active pressure. c.

Corrosiveness of the soil shall be investigated. (See Reference 101.)

d. Considerations shall be given to possibility of liquefaction due to seismic loadings.

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C - 20.5.2 MAXIMUM MOMENT (1993) For sheeting in water, the elevation of mud line shall be considered at minimum 2¢-0² below the dredge line. If site investigation reveals that the mud and/or silt build-up is more than 2¢-0², the lowest elevation of mud and/or silt build-up shall be used as mud line elevation. Effect of sloping soil in front of the bulkhead which would reduce passive resistance should be investigated.

C - 20.5.3 ANCHOR PULL (1993) a.

The anchor pull is determined by an assumption that the sheet pile penetration below the mud line is sufficient to provide for fixed support of the piling at the bottom. Considerations should be given to future construction possibilities and design should be modified accordingly.

b. Since the pressure behind a bulkhead will build up if the deflection of the bulkhead is not sufficient to fully mobilize the active pressure, rigid anchorages can be a problem, and this condition should be recognized by the designer.

C - SECTION 20.6 CANTILEVER BULKHEADS C - 20.6.1 SCOPE (1993) a.

Since cantilever bulkheads are not recommended for permanent construction, they are not covered in these design guidelines.

1

b. Cantilever sheet pile bulkheads often undergo large lateral deflections which are not easily calculated. Erosion in front of the bulkhead materially affects the stability of the structure. For these reasons, cantilever sheet pile bulkheads are recommended only for temporary installations and not for permanent construction. Further, the use of cantilever sheet pile bulkheads is generally not recommended where a track will be located on the higher elevation behind the bulkhead. c.

Cantilever sheet pile bulkheads receive all of their lateral support from passive pressure exerted on the embedded portion of the bulkhead. For this reason, the depth of penetration can become very large, which can result in very high stresses and deflections in the sheet piling.

3

d. The recommended restrictions on cantilever sheet pile bulkheads are:

4

(1) Temporary construction only. (2) No track or railroad loads behind the bulkhead, except for very short cantilevers in medium to very dense or hard soil. (3) Maximum height not to exceed 12 feet.

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8

Part 21 Inspection of Concrete and Masonry Structures1 — 2006 — TABLE OF CONTENTS

Section/Article

Description

Page

21.1 General (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-21-1

21.2 Reporting of Defects (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-21-2

21.3 Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.3.1 General (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.3.2 Structural Protection (2006). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-21-2 8-21-2 8-21-5

Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-21-20

1

3 SECTION 21.1 GENERAL (2006)2 a.

All concrete and masonry structures and components should be given thorough, detailed condition inspections at scheduled intervals. For timber and steel components, refer to Chapter 7 and Chapter 15, respectively. The scope and detail of the inspection should be based on the condition and age of the structure, and traffic type and tonnage in order to determine that the physical condition of each structure is suitable for the imposed loading and to determine maintenance or rehabilitation needs. A record of physical conditions should be kept.

b. A special inspection may be required when the structure is subjected to abnormal conditions which may affect the capacity of the structure such as: floods, storms, fires, earthquakes, collisions, overloads and evidence of recent movement. Refer to Commentary for information related to inspection of fire damaged concrete. c.

1 2

The inspector should review prior inspection reports before making the inspection. Previously noted defects should be examined in the field and any changes in conditions recorded. Field book, sketch pad, inspection form, camera, monitoring gages, etc., should be used to record the inspection data. Appropriate personal safety equipment should be used throughout the inspection.

References, Vol. 71, 1970, p. 246; Vol. 86, 1985, p. 53. See Commentary

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SECTION 21.2 REPORTING OF DEFECTS (2006) a.

When the inspector finds defects that appear to be of such a nature as to make the passage of traffic unsafe, the condition should immediately be reported. After steps have been taken to protect traffic, the train dispatcher and appropriate officers should be notified, consistent with established policies, recommending a speed limit and briefly describing the conditions which prompted the action. The inspector should follow this immediately with a report so that a detailed investigation and recommendation for repair can be made.

b. Upon completion of the inspection, a written record covering the inspection should be forwarded to the engineer or other officer in charge of maintenance. Upon receipt of the report, a review should be made to determine the need for remedial action. c.

A sample inspection form for concrete and masonry structures is included at the end of this part.

SECTION 21.3 INSPECTION1 21.3.1 GENERAL (2006) a.

The inspection of concrete and masonry structures should be carried out in a methodical manner. Of primary importance in all structures is evidence of distress, misalignment, deflection, settlement, cracks, and general deterioration. Evidence of deterioration of concrete such as width and length of structural cracks, size and location of spalling and scaling, and location and extent of water-saturation of concrete should be recorded. Cleaning of the structure or component parts may be necessary prior to inspection.

b. The inspector should report indications of failure in any portion of the structure and any conditions which could contribute to a future failure. c.

Reference points should be established for monitoring misalignment, deflection, settlement, and cracks. The amount of tilt, separation between components, width and length of cracks, efflorescence and ruststaining and other measurements necessary for future checking should be recorded.

d. The inspection should include the structure and all related features. 21.3.1.1 Track2 The inspector should note the alignment, profile and surface of the track on the structure, its approaches and bridge ends. Any irregularities in line or surface should be noted along with their magnitude, location and any other information that may indicate the cause of the irregularities. Depth of ballast and condition of ballast, ties and hardware should be noted. 21.3.1.2 Site and Crossing3 a.

Where a structure crosses over a waterway, the inspector should note the condition and alignment of the waterway. The condition of the slopes and any slope protection (such as riprap) should be noted along with any indication of debris accumulation. The inspector should note any indication of damage from marine collision, ice or debris.

1

See Commentary See Commentary 3 See Commentary 2

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b. Where scour is possible, the channel bottom at piers and abutments should be checked by sounding, probing or other means. c.

Where a structure carries tracks over a roadway, waterway or another track, the inspector should note any indication of collision damage from high or wide loads. Roadway clearances should be measured and signage verified for accuracy.

d. The inspector should note any indication of collision damage from high or wide loads to the bridge superstructure, bearings and substructure. 21.3.1.3 Foundations, Piers and Abutments1 a.

The type of foundation and type and condition of material used in the various structural components should be noted. The inspector should note any settlement and/or rotation of foundations, piers, abutments or their component parts. Reference points should be established for monitoring of structural movement if appropriate.

b. Location and extent of exposed and/or corroded reinforcing steel should be reported. The condition of the structure at the bridge seats, bearings and near the waterline should also be investigated. c.

Crack width, orientation and location should be noted. Widths and lengths of structural cracks should be marked and dated to monitor crack progression. On masonry structures note cracked, shifted, or missing stones, and condition of mortar.

d. Location, size and description of unsound areas, spalling, scaling or other deterioration should be noted. e.

Condition of retained fill, drainage and slope protection at abutments should be inspected. Watersaturated masonry or concrete and extent of efflorescence and rust-staining should be noted. Check weepholes and drains for proper function.

1

21.3.1.4 Pile and Pile Bents a.

Inspection of piling and pile bents should be in general conformance with Article 21.3.1.3. For timber and steel components, refer to Chapter 7 and Chapter 15, respectively.

3

b. Alignment and condition of piling should be recorded. Impact damage from debris, vessels or vehicles should also be noted. c.

Condition of piles should be investigated for soundness. Loss of section and cracking should be noted. These may be especially severe in a marine environment, particularly in the tidal zone.

4

d. Condition of connections between cap and piling should be noted. e.

Condition of bracing members and their connections should be noted.

21.3.1.5 Underwater Inspections2 The need and frequency for underwater inspections should be evaluated for every structure having submerged components. These inspections should identify the channel bottom conditions and presence of any scour, extent of foundation exposure and any undermining, and all deterioration and damage below water. a.

Divers should be experienced in the inspection of bridge substructures.

b. Inspection data should be recorded by written description, sketches, reports, photography and/or video.

1 2

See Commentary See Commentary

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c.

During high water events when scour conditions may be expected, channel activity should be monitored, which may include the use of sonar readings, until inspections can be made.

21.3.1.6 Retaining Walls1 a.

Concrete inspection should be in general conformance with Article 21.3.1.

b. The inspector should note any settlement and/or rotation of retaining walls. Changes in wall alignment or cracks in earth embankment which parallel the wall should be noted. c.

Condition of retained fill and drainage at walls should be inspected. The extent of water-saturated concrete and exposed or corroded reinforcing steel should be recorded.

21.3.1.7 Slabs and Beams2 a.

Inspector should note if prestressed or conventionally reinforced concrete is used in the structure. Method of construction, cast-in-place or precast, simple or continuous, should also be recorded.

b. Any cracks that open and close under traffic, diagonal cracks near supports, or wide or numerous cracks in any location should be reported immediately to the proper authority. Acute corners of skewed bridges should be examined for cracks, delaminations and spalls. c.

Structural members should be inspected for excessive deflection, misalignment or collision damage.

d. Curbs, ballast retainers, walkways and handrails should be inspected, noting the condition as to soundness and security of fastening devices. Soundness, uniformity and condition of bearings and bearing areas should also be noted. Areas exposed to drainage should be checked for spalls and cracks. 21.3.1.8 Box Girders3 a.

Type of box construction (precast, cast-in-place, segmental, pre-tensioned, post-tensioned, simple or continuous spans) should be recorded.

b. General inspection guidelines should be as outlined in Article 21.3.1.7. Top flange, bottom flange and web walls should be inspected when accessible. Chamfers of boxes should be inspected for cracking which may extend along the sides or bottom of the girders. c.

Shear transfer devices between adjacent box girders should be inspected, where accessible. Condition of grout, hardware, tie rods, and other materials used in tying together adjacent box girders should be noted. Evidence of differential box deflections or misalignments should be recorded.

d. Condition of void drain holes and evidence of leakage between adjacent boxes should be noted. 21.3.1.9 Arches4 a.

Type of arch construction, such as segmental, open spandrel, closed spandrel, single or multiple span should be noted. Shape of arch span (circular, elliptical or parabolic) should be recorded, if known. Type and general condition of material (brick, stone, mortar or concrete) should also be recorded.

b. Arch foundations should be investigated for settlement, shifting, scour and undermining. c.

Arch ribs and bearing areas of arches at springings (spring lines) should be inspected for loss of cross section due to spalling or cracking.

1

See Commentary See Commentary 3 See Commentary 4 See Commentary 2

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d. Open spandrel columns and walls should be inspected with particular attention to areas near the interface with the arch rib and cap. e.

Arch ribs connected with struts should be inspected for diagonal cracking due to torsional shear.

f.

Floor systems of open spandrel arches and closed spandrel arches with no fill material should be inspected as outlined in Article 21.3.1.7.

g.

Inspect areas exposed to drainage and seepage for deteriorated and contaminated areas. For closed spandrel arches, note whether weepholes are working properly.

21.3.2 STRUCTURAL PROTECTION (2006) Structural protection devices including crash walls, cellular dolphins, pile clusters, shear fences, floating shear booms, anchored pontoons, fender systems, navigation lights and warning mechanisms should be inspected as part of the scheduled inspection of their related foundation or substructure element. The inspection should identify all deterioration, damage, displacement, misalignment, instability, undermining, and any other detrimental conditions which would inhibit these devices from protecting the structure or cause them to create an obstruction. All submerged portions of structural protection devices should be inspected underwater based on the recommendations set forth in Article 21.3.1.5. The inspection of structural protection devices should also note any aspects which may present a hazard to navigation, railroad or highway operations, and identify the necessary measures to correct the situation. 21.3.2.1 Culverts1 a.

Inspection of a concrete or masonry culvert in general should be in conformance with Article 21.3.1.3.

1

b. Inspector should note any settlement, variations in cross-sectional shape and misalignment along the horizontal axis of a culvert. All joints between end treatments and within the culvert itself should be examined for differential movement, and all transverse or longitudinal cracking within a culvert should be noted. c.

A culvert should be inspected for any scour or undermining at either end. Any embankment damage around the culvert openings and debris or vegetation within the culvert should be noted. All submerged portions of a culvert should be inspected underwater based on the recommendations set forth in Article 21.3.1.5.

3

21.3.2.2 Tunnels a.

Important features of a tunnel might be obscured by a shield or lining, therefore the inspector should review plans, if available, prior to the inspection. Note the structural configuration, provisions for drainage, ventilation and lighting. Note if secondary passageways that would provide additional access for inspection are present.

b. Concrete inspection should be in general conformance with Article 21.3.1.3. In exposed masonry construction, make special note of bulges in walls and displacement, shifting or loss of masonry or mortar. c.

Walls should be inspected for indications of water leakage or ice buildup. The condition and effectiveness of drainage systems should be noted.

d. Note whether ancillary systems for lighting, ventilation, and fire prevention are in working order, if discernible. e. 1

The accumulation of trash or foreign debris or the blockage of safety niches should be noted.

See Commentary

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f.

Any new construction above or adjacent to the tunnel should be noted.

g.

Horizontal and vertical clearances should be verified. Items causing changes in clearance should be noted.

h. The inspector should note the alignment, profile and surface of the track and clearance of the tunnel.

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RECORD OF INSPECTION OF CONCRETE AND MASONRY STRUCTURES Division __________________________________

Date: ____________________________________

Bridge No. ___________________________ (MP)

Inspector _________________________________

Weather __________________________________

Temperature _____________________________

Description of Structure:

NOTE: Remarks should include an estimate of the urgency to repair the structure. (i.e., Immediate, 1 or 2 years, over 2 years). TRACK CONDITION 1.Surface of track on structure and approaches

2.Alignment of track and its location with reference to the structure

1 3.Location, amount and probable causes of any track out of line or surface

3

4.Ballast, condition and depth

5.Remarks

4 SUBSTRUCTURE 1.

General:

Alignment of unit (horizontal, vertical)

Evidence of settlement

Evidence of scour (wingwalls, abutments, piers)

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RECORD OF INSPECTION OF CONCRETE AND MASONRY STRUCTURES (Continued) SUBSTRUCTURE (Continued) Condition of retained fill (drainage, slope protection)

Alignment of waterway and evidence of debris

Changes apparent since last inspection

2.

Piers and Abutments:

Material (brick, stone, concrete)

Condition of backwall (plumb, clearance of structure)

Condition of bridge seat

Condition of bearings (level, bedding)

Brick and Stone: Condition of mortar joints

Condition of bricks or stones

Conditions at waterline

Concrete: Cracks (location, size, description)

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RECORD OF INSPECTION OF CONCRETE AND MASONRY STRUCTURES (Continued) SUBSTRUCTURE (Continued) Spalling or cracking (location, size, description)

Condition of reinforcing steel (exposed, corroded – location)

Condition at waterline

3.

Bents and Pile Piers:

Type of Piles (prestressed concrete, conventional concrete, concrete filled, metal shells, steel H, timber, other)

Alignment of piles (horizontal and vertical)

1 Cracks, corrosion and decay (location, size, description)

Spalling or crazing (location, size, description)

3 Condition of reinforcing steel (exposed, corroded – location and description)

4

Condition of pile shells (corroded – location, size and description)

Condition of pile at waterline

Caps, Bracing and Collars Cracks (location, size and description)

Spalling and crazing (location, size and description)

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RECORD OF INSPECTION OF CONCRETE AND MASONRY STRUCTURES (Continued) SUBSTRUCTURE (Continued) Condition of reinforcing steel (exposed, corroded – location and description)

Condition of bridge seat

Condition of bearings (level, bedding)

4.

Remarks

PRESTRESSED AND REINFORCED CONCRETE BEAMS AND SLABS 1.

General:

Type of construction (prestressed or reinforced concrete)

Cracks (location, size and description)

Spalling and crazing (location, size and description)

Condition of reinforcing steel (exposed, corroded, rust around cracks – location and description)

Condition of end blocks (voids draining)

Condition of bearings

Condition of expansion joints

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RECORD OF INSPECTION OF CONCRETE AND MASONRY STRUCTURES (Continued) PRESTRESSED AND REINFORCED CONCRETE BEAMS AND SLABS (Continued) Condition of curbs (cracks, spalls)

Condition of handrail (fastenings)

Indications of movement

Other deterioration (location and description)

Changes apparent since last inspection

1 2.

Remarks

ARCHES – SOLID AND OPEN SPANDREL 1.

3

General:

Materials (stone or concrete)

Headwalls and wingwalls

4 Barrel of arch

Alignment of unit (horizontal, vertical)

Evidence of settlement

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RECORD OF INSPECTION OF CONCRETE AND MASONRY STRUCTURES (Continued) ARCHES – SOLID AND OPEN SPANDREL (Continued) Leakage through barrel of arch

Condition of expansion joints

Changes apparent since last inspection

2.

Headwalls and Wingwalls:

Condition of embankment (spilling over, drainage, cavities)

Indications of wingwall movement

Evidence of scour

Headwall pulling away from barrel of arch

Stone: Condition of mortar joints

Condition of stones

Concrete: Cracks (location, size and description)

Spalling and crazing (location, size and description)

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RECORD OF INSPECTION OF CONCRETE AND MASONRY STRUCTURES (Continued) ARCHES – SOLID AND OPEN SPANDREL (Continued) Condition of reinforcing steel (exposed, corroded – location and description)

3.

Stone Arch Barrel:

Condition of mortar joints

Condition of stones

4.

Concrete Arch Barrel:

Cracks (location, size and description)

Spalling and crazing (location, size and description)

1 Condition of reinforcing steel (exposed, corroded – location and description)

5.

3

Remarks

CULVERTS 1.

General:

4

Type (box, pipe, arch)

Material

Condition of channel (open)

Culvert undermined

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RECORD OF INSPECTION OF CONCRETE AND MASONRY STRUCTURES (Continued) CULVERTS (Continued) Indications of settlement

Cracks or open joints (location and description)

Condition of embankment (spilling over, drainage, cavities)

Condition of headwalls and wingwalls

Indications of wingwall movement

Water leaking into embankment

Changes apparent since last inspection

2.

Remarks

TUNNELS 1.

General:

Material

Portals

Lining (or unlined)

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RECORD OF INSPECTION OF CONCRETE AND MASONRY STRUCTURES (Continued) TUNNELS (Continued) Track alignment

Condition of side ditches and drainage

Changes apparent since last inspection

2.

Portals

Conditions of overburden (spilling over, drainage, cavities)

Sealing required

1 Evidence of washing

Portal pulling away from tunnel

3 3.

Tunnel lining

Lined: Bulges, cracks, open joints, flaking (location, size and description)

4 Seepage through walls (weep holes functioning)

Deterioration of lining material (location, size and description)

Unlined: Condition of rock (loose)

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RECORD OF INSPECTION OF CONCRETE AND MASONRY STRUCTURES (Continued) TUNNELS (Continued) Seepage into tunnel

Condition of rock anchors (if present)

4.

Remarks

RETAINING WALLS 1.

General:

Material

Indicated movement (settling, sliding, leaning)

Condition of fill (spilling over, cavities, stability)

Washing or scouring

Condition of drainage (weep holes functioning, ditches open)

Cracks, deterioration or open joints (location, size and description)

Condition of prefabricated members (broken, misaligned)

Changes apparent since last inspection (wall movement)

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RECORD OF INSPECTION OF CONCRETE AND MASONRY STRUCTURES (Continued) RETAINING WALLS (Continued) 2.

Remarks

PIER PROTECTION 1.

General:

Type

Materials

General condition of alignment

Collision damage

1

Evidence of scour

3

Condition of navigation channel

Condition of navigation aids (lighting, fog horn)

4 Debris trapped on system

Apparent ability to protect pier

Changes apparent since last inspection

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RECORD OF INSPECTION OF CONCRETE AND MASONRY STRUCTURES (Continued) PIER PROTECTION (Continued) 2.

Integral:

Condition of energy absorbing devices

Condition of rubbing strips (non-sparking)

Condition of fasteners and splicing materials

Condition of pier adjacent to fender

3.

Dolphins:

Pile clusters Type of piles

Condition of piles

Location relative to planned position

Condition of lashings or connections

Cellular dolphins: Type of construction (sheet piles, steel rings, etc.)

Condition of piles or rings

Type and condition of fill material

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RECORD OF INSPECTION OF CONCRETE AND MASONRY STRUCTURES (Continued) PIER PROTECTION (Continued) Location relative to planned position

4.

Floating shear booms:

Condition of floating material

Condition of boom material

Condition of anchoring system

Location relative to planned position

1 5.

Hydraulic devices:

Condition of suspended cylinder

3

Condition of suspension system

Condition of supporting piles, caissons, or piers

4 Changes in water level affecting cylinder engagement

6.

Independent Fenders:

Condition of pile supports

Condition of energy absorbers

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Concrete Structures and Foundations

RECORD OF INSPECTION OF CONCRETE AND MASONRY STRUCTURES (Continued) PIER PROTECTION (Continued) Condition of longitudinal wales

Condition of rubbing strips

Location relative to planned position

7.

Remarks

COMMENTARY The purpose of this part is to furnish the technical explanation of various articles in Part 21, Inspection of Concrete and Masonry Structures. In the numbering of articles of this section, the numbers after the “C-” correspond to the section/article being explained.

C - EVALUATING FIRE DAMAGED CONCRETE RAILWAY BRIDGES (2006) General Concrete structures exposed to fire may experience a permanent loss of strength, formation of structural cracks, surface spalling, and reinforcing damage. However, concrete structures exposed to fire generally perform well and usually are repairable. The heat conductivity of concrete is low and thus heat from a fire is usually confined to shallow depths. The extent of structural damage is related to the intensity and duration of the fire, and the mass and details of the concrete structure. The exposure of concrete to a temperature of 572°F (300°C) is significant for two reasons: • Below this temperature the effects of heat on concrete are likely to be insignificant. • Above this temperature concrete coloration changes may indicate permanent damage. Water directed on hot concrete may cause spalling, crack development and the embrittlement of steel. Fire fighting efforts should be directed to extinguishing the combustible material and not cooling the structure. Traffic should not cross the structure if significant deflection or distortion is noted or if there are reasons to doubt that adequate strength remains. Inspection

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a.

Prior to the inspection of a damaged concrete structure, it should be determined whether the site is safe for entry.

b. Damage may include the deflection of concrete beams and slabs, distortion of columns, cracking, spalling and unsightly appearance. c.

Inspection observations should include looking for and measuring any unusual component deflection, recording the location and extent of structural cracks, spalls and exposed reinforcing. Fire exposed surfaces should be mapped to indicate those areas having structural and cosmetic damage. If fire exposed surfaces exhibit colorations of pink, white or buff, those surfaces should be mapped and color noted. Surfaces may need to be cleaned of soot to make these observations.

d. Information concerning the combustible material, duration, intensity indicators and method for extinguishing should be obtained from eyewitnesses or other reliable sources for assistance in evaluating the damage. Although any concrete coloration from the fire may provide sufficient information concerning the intensity of the fire, if coloration is not evident, to a lesser degree other materials associated with the fire site may have melted and may provide some indication of the fire intensity, such as: lead 621°F (327°C), plastics 572-842°F (300–450°C), glass 752–932°F (400–500°C), aluminum 1218°F (660°C), and copper 1981°F (1083°C). Other information concerning the original concrete strength, age, reinforcing details and types of aggregates may be obtained from structural plans, specifications and construction records. Evaluation e.

Generally, all concrete that has coloration changes (pink, white, buff) is considered damaged. The pink coloration 572°F (300°C) experienced by heating concrete is the formation of ferrous salts and is more pronounced in concrete with siliceous aggregates. At approximately 1110°F (600°C), concrete may have a whitish coloration from the hydration of lime. At 1650°F (900°C) the coloration may be grey-buff.

f.

Indications of possible structural damage may be evident by visual examination, but the extent of damage will require tests and analysis. Evaluation tools for testing include: surface hammer sounding, impact hammers, coring and/or drilling and pulse-echo non-destructive testing. Sounding the concrete surface with hammers may be sufficient to determine if there is any internal concrete delamination. Calibrated impact hammers can give direct measurements of the concrete compressive strength and may be used on sound and unsound concrete for quick strength comparisons. Coring will assist in determining the depth of damage and corings destructively tested will ascertain accurate compressive strength. A petrographic analysis of cored samples will give a detailed analysis of the concrete condition but the analysis is time consuming. Pulse-echo testing can give a rapid and accurate determination of internal concrete conditions relative to micro-cracking and bond loss. Additional testing may be needed for prestressed and post-tensioned concrete.

g.

Concrete strength decreases as temperature is increased and further decreases on cooling as a result of micro-cracking. Approximately 75% residual strength remains in most concrete after exposure to fire. This loss may be offset by excess residual strength of mature concrete. Internal induced stresses from differential heating may result in the formation of cracks. Young concrete may experience more damage than mature concrete due to larger amounts of internal moisture that may convert to steam and increase internal tensile stresses.

h. Damage may result from aggregate spalls due to physical or chemical changes. Explosive spalling may occur from the release of tensile stresses by the formation of steam within aggregates. Slough-off or the detachment of layers of concrete may occur where reinforcement is restrained. Igneous aggregates (granite, basalt) generally perform well when exposed to fire, carbonate aggregates (limestone) perform well to about 1290°F (700°C), and siliceous aggregates (quartz) do not perform well due to expansion and cracking. © 2011, American Railway Engineering and Maintenance-of-Way Association

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i.

The absence of deflection or distortion in any element may indicate that the steel was not damaged. Reinforcing steel usually recovers in strength unless exposed to temperatures over 1110°F (600°C). Anchorages of post-tensioned members may require special evaluation. The tension in pretensioned steel or post-tensioned ducts exposed by spalling should generally be assumed to be zero. Prestressed members may suffer substantial relaxation losses, additional to those allowed by normal design. Low relaxation strands may have improved fire performance. At 572°F (300°C) the residual bond strength is approximately 85% and at 932°F (500°C) the bond strength is approximately 50% of initial bond. Bond strength losses of epoxy coated reinforcing steel subjected to fire may require special evaluation.

j.

Resins used in construction bonding of concrete elements and in repairs may not perform well in the presence of elevated temperatures.

k. Hydrochloric acid fumes occurring in fires involving PVC and other plastic ducts may react with hardened cement paste to form calcium chloride which may constitute a hazard to the reinforcement. A silver/chromate test can confirm the presence of calcium chloride ions. Repairs l.

Repair procedures, as applicable, are outlined in Part 14.

m. Pulse-echo or other nondestructive testing may be used to confirm that all damaged concrete is removed and can be used to confirm proper bonding of new concrete to old concrete and bonding to reinforcement.

C - 21.3 INSPECTION There are many common defects that occur on concrete bridges. The following definitions are provided as a guideline for consistency in reporting of defects. Abrasion — Abrasion damage is the result of external forces acting on the surface of the concrete member. Erosive action of silt-laden water running over a concrete surface and ice flow in rivers and streams can cause considerable abrasion damage to concrete. Cold joint displacement or deterioration — Unbonded concrete resulting from intended separate concrete placement or by lack of consolidation. Cracking — A crack is a linear fracture that may extend partially or completely through the concrete member. When recording cracks, the inspector should describe the type, width, depth, length, direction, location and appearance of the crack as appropriate for the inspection. Delamination — Delamination occurs when layers of concrete separate at or near the level of the top or outermost layer of reinforcing steel. The major cause of delamination is expansion of corroding reinforcing steel. Delaminated areas can generally be identified by a hollow sound when tapped with a hammer. Efflorescence — Efflorescence is a white deposit on concrete caused by crystallization of soluble salts (calcium chloride) brought to the surface by moisture in the concrete. Freeze-Thaw Damage — The deterioration of concrete, typically a crack or spall, due to introduction of moisture and the subsequent alternate freezing and thawing of the retained moisture. Honeycombs — Honeycombs are hollow spaces or voids that may be present within the concrete. Honeycombs are caused by improper consolidation during construction, resulting in the segregation of the coarse aggregates from the fine aggregates and cement paste.

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Pop-Outs — Pop-outs are conical fragments that break out of the surface of the concrete leaving small holes. Generally, a shattered aggregate particle will be found at the bottom of the hole, with a part of the fragment still adhering to the small end of the pop-out cone. Scaling — Scaling is the gradual and continuing loss of surface mortar and aggregate over an area. When reporting scaling, the inspector should note the location of the defect, the size of the area, and the depth of penetration of the defect. Spalling — A spall is a roughly circular or oval depression in the concrete. Spalls result from the separation and removal of a portion of the surface concrete, revealing a fracture roughly parallel to the surface. Spalls can be caused by corroding reinforcement and friction from thermal movement. Reinforcing steel is often exposed after spalling. When reporting spalls, the inspector should note the location of the defect, the size of the area, and the depth of the defect. C - 21.3.1.1 Track Line swings may be an indication of pier movement. Sags in the track over the structure may indicate settlement. Effects of creep and strand relaxation may affect track profile. C - 21.3.1.2 Site and Crossing a. The inspector should note any changes in the alignment of a waterway both upstream and downstream and the resulting effect that they may have on the structure. A major change in the alignment of a waterway may place it outside the spans intended for the crossing.

1 b. Sedimentation deposits may fill scour holes after high water events. Underwater investigations may be required as per Article C - 21.3.1.5. Structures located downstream of spillways or locks may be subject to increased scour potential. C - 21.3.1.3 Foundations, Piers and Abutments Concrete and masonry structures are placed on foundations of earth, piling, cribbing, rock or other similar material. Cracks may be evidence of settlement which has occurred during consolidation of the foundation. Settlement may occur without cracking. Noticeable changes in track surfaces and alignment, plumbness or elevation may indicate foundation settlement. Changes in backwall alignment or cracks in the earth embankment parallel to the backwall may indicate movement. Constant wetting may indicate swelling, premature loss of mortar, deterioration of facing or excessive water pressure behind backwalls. Exposure of timber mats or untreated timber piling may lead to rapid deterioration of the timber. C - 21.3.1.5 Underwater Inspections In evaluating the need for an underwater inspection, consideration should be given to type and depth of foundation, depth of water, normal and peak flow rates, nature of channel bottom and susceptibility to and history of scour, type of aquatic environment, typical extent of drift and ice accumulation, and amount and type of watercraft traffic. The inspections should be performed with sufficient frequency to provide early detection of any detrimental conditions, and between inspections, the measuring of water depths should be considered to monitor channel bottom activity. In the event of a high water and/or flow occurrence, an excessive accumulation of ice or drift, a watercraft collision, a significant change in channel bottom configuration, or any submerged component movement, consideration should be given to performing an emergency inspection as soon as conditions will safely permit. C - 21.3.1.6 Retaining Walls In addition to structural deficiencies, retaining wall failures may result from:

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a.

Softening of the supporting material by moisture.

b. Overloading of the embankment behind the wall. c.

Scour or erosion beneath the foundation.

d. Expansive backfills. e.

Hydrostatic pressure behind wall.

f.

Seismic event.

g.

Cracks in the earth embankment which parallel the wall may be signs of wall movement.

C - 21.3.1.7 Slabs and Beams a.

Transverse cracks in the bottom of simple span slabs and beams can indicate overload, particularly if cracks open and close during passage of a train. Hairline cracks on the tops of simple span prestressed beams are generally due to shrinkage of the concrete. Hairline cracks in the top or bottom of simple span reinforced concrete slabs and beams are generally not significant. Diagonal cracks running up the sides of the slab or beam from near the supports may indicate excessive shear stress in the member or the beginning of shear failure.

b. Transverse cracks in the top of continuous beams over support locations or in the bottom of continuous beams within the span can indicate overload. (1) Sagging or excess deflection may indicate a loss of prestress. Loss of prestress may be caused by strand slippage, which may be visible at the ends of beams. (2) End spalling can lead to a loss of bond in the prestressing tendons. Note any deterioration that has exposed or damaged prestressing tendons. C - 21.3.1.8 Box Girders a.

Horizontal or vertical cracks in the top of girder ends are frequently due to stresses created at the transfer of prestressing forces. Flexural cracks in the lower portion of the girders, particularly at midspan, may indicate a problem resulting from overload or loss of prestress.

b. Individual girder deflection under live load may indicate that shear keys between boxes have been broken and that boxes are acting independently of each other. C - 21.3.1.9 Arches a.

A true arch has an elliptical shape and functions in a state of pure compression. Many arches are not elliptical and resist loads by a combination of axial compression and bending moment.

b. Changes in horizontal alignment, sags in the arch crown, bulges in the sidewalls, transverse cracks, longitudinal cracks and expansion joint failures may be signs of settlement, overload or impending arch failure. c.

The area between the arches and the deck is called the spandrel. Open spandrel concrete arches receive traffic loads through spandrel bents which support a slab or tee beam floor system. Horizontal cracks in spandrel columns within several feet of the arch indicate excessive bending in the column, which may be caused by overloads and differential arch rib deflection. © 2011, American Railway Engineering and Maintenance-of-Way Association

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d. The spandrel area in closed spandrel arches is typically occupied by fill retained by vertical walls. Surface water should drain properly and not penetrate the fill material. C - 21.3.2.1 Culverts a.

Horizontal alignment of a culvert can be inspected by sighting along one of the culvert walls. Sag in the culvert axis may be identified by a location of sediment buildup on the culvert floor. Spalls or cracking in the vicinity of a joint may be a sign of movement at the joint. Both longitudinal and transverse cracking may be an indication of differential settlement. Longitudinal cracks can also be caused by a structural overloading of the culvert. Holes appearing in the track structure may be an indication of open culvert joints. For culvert extensions, integrity of connection should be noted.

b. Insufficient hydraulic capacity, either by design or due to obstructions, may cause upstream ponding and lateral flow movements which can erode the embankments and supporting material around the culvert end treatments. Culverts often convey short-term, high volume flows, and consequently, all culverts should be carefully inspected for scour and undermining. Tipping, cracking or separation of the headwalls, wingwalls or apron may indicate the presence of undermining. For arch and frame type culverts with earthen floors, undermining beneath the wall foundations along their full length should also be investigated.

1

3

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Part 22 Geotechnical Subsurface Investigation1 — 1992 — TABLE OF CONTENTS

Section/Article

Description

Page

22.1

General (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-22-2

22.2

Scope (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-22-2

22.3

Classification of Investigations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.3.1 Foundation Investigations (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.3.2 Failure Investigations (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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22.4

General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.4.1 Planning an Exploration Program (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.4.2 Number and Location of Borings (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.4.3 Depth of Borings (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.4.4 Equipment (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.4.5 Permits (1992). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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22.5

Exploration Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.5.1 Dry Sample Borings (1992). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.5.2 Test Pits (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.5.3 Core Borings in Rock (1992). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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22.6

Determination of Groundwater Level (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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22.7

Sampling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.7.1 Dry Samples (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.7.2 Rock Cores (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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22.8

Records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.8.1 Scope (1992). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.8.2 General (1992). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.8.3 Borings – Dry Sample (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.8.4 Core Borings (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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1

References Vol. 78, 1977, p. 102; Vol. 93, 1992, pp. 78, 98.

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3

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TABLE OF CONTENTS (CONT) Section/Article 22.9

Description

Page

Inspection (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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22.10 Geophysical Explorations (1992). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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22.11 In-Situ Testing of Soil (1992). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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22.12 Backfilling Bore Holes (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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22.13 Cleaning Site (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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SECTION 22.1 GENERAL (1992) a.

The intent of this part is to furnish the Engineer with certain guidelines for the formulation of specifications for a particular project. Subsurface investigation for structures only is addressed in this section. Site investigations for fills and cuts shall follow the requirements of Chapter 1, Roadway and Ballast, Part 1, Roadbed.

b. It is recommended that a qualified geotechnical engineer be retained to perform the investigation, conduct the laboratory and/or in-situ testing, and prepare the geotechnical analysis and report.

SECTION 22.2 SCOPE (1992) These specifications entail a procedure for performing borings through soil and into rock, to determine the nature and extent of the various soil and rock strata, location of groundwater level, as well as, to obtain samples for identification and tests for the purpose of development of the subsoil profile and determination of the engineering properties of the soil and rock.

SECTION 22.3 CLASSIFICATION OF INVESTIGATIONS 22.3.1 FOUNDATION INVESTIGATIONS (1992) 22.3.1.1 New Structure For a new structure, the site investigation shall provide sufficient information to determine: a.

Location of groundwater level, at least to the extent that it is within the zone of influence, beneath the footing.

b. Bearing capacity of the soil.

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c.

Data on soil and/or rock properties relative to shallow and deep foundations.

d. Settlement predictions. e.

Selection of alternative types and/or depth of foundations.

f.

In seismic areas, evaluation of liquefaction potential of various soil strata.

22.3.1.2 Existing Structure For an existing structure, if it is desired to make additions or increase the service loading (Ex: heavier rolling stock), then an investigation shall be conducted based on the increased loadings. The information obtained shall be employed in determining the ability of the existing foundation to carry additional loading, both in terms of bearing capacity and settlement.

22.3.2 FAILURE INVESTIGATIONS (1992) Failure investigations are made to obtain information for the failure analysis of a structure related to the foundation conditions.

SECTION 22.4 GENERAL

1

22.4.1 PLANNING AN EXPLORATION PROGRAM (1992) a.

Preliminary site reconnaissance and review of existing information will facilitate the understanding of the site subsurface information. Useful information includes:

3

(1) Topographic and geologic maps. (2) Aerial photographs. (3) Geologic and subsurface exploration reports. (4) Related articles in engineering and geologic journals.

4

(5) Study of local ground features. (6) Survey of existing or adjacent structures on site and their influence on ground type. (7) Condition of adjacent structures. (8) Information on previous and future planned use of the site. b. For buildings the Engineer should provide to the geotechnical engineer information on column spacing, column loads, dimensions, and use of the structure. For bridges, the geotechnical engineer should have access to type, span length, foundation loading, and controlling dimensions. c.

If project funding and scheduling permits, explorations can be conducted in a phase sequence as: reconnaissance investigation; and, explorations for preliminary design, followed by explorations for final design.

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d. Thorough research for details of any contaminated materials and associated appurtenances must be made. A Risk Management procedure needs to be in-place that conforms with federal, state and local government guidelines for removal of elements.

22.4.2 NUMBER AND LOCATION OF BORINGS (1992) The number and location of borings shall be such that the soil profiles obtained will permit an accurate estimate of the extent and character of the underlying soil and/or rock masses and will disclose important irregularities in the subsurface conditions. Borings shall be uniformly distributed or located in accordance with the loading pattern imposed by the structure. The number and location of the borings shall be determined by the Engineer.

22.4.3 DEPTH OF BORINGS (1992) a.

The depth of borings shall be based on the magnitude and distribution of the load imposed by the structure and the nature of the subsurface conditions. In all projects, the borings as a minimum, must extend to a depth sufficient to reveal the nature of all materials which could be significantly affected by the loads imposed by the structure and which by settlement and/or shear failure could affect the integrity of the structure.

b. As a rule of thumb, for spread footings the borings should extend to a depth such that from a Boussinesq (or similar) analysis the increase in pressure is 10% of the contact pressure, in other words the boring depth shall be 1.5 to 2 times the anticipated width of the footing. c.

For piles and other deep foundations the depth of borings should extend below the zone of influence and not less than 10 feet below the estimated tip elevation.

d. When a structure is to be founded on rock, one or more borings should be extended at least 15 feet into sound rock (defined as RQD1 equal to 90%) in order to determine the extent and character of the weathered zone of the rock and to ensure that bedrock and not boulders have been encountered. For failure investigations, borings shall extend to a depth sufficient to determine the limits of the failure.

22.4.4 EQUIPMENT (1992) Drill rigs shall be specifically designed and manufactured for drilling, coring and sampling soil and rock. Drill rigs shall have adequate capacity, be in satisfactory operating condition and have the power to accomplish the required work. The rigs shall be supplemented with the necessary auxiliaries, appurtenances, tools and other equipment required for proper operation. The operator in charge shall be thoroughly experienced in soil and rock boring.

22.4.5 PERMITS (1992) All necessary permits shall be secured before the work is started as provided by the contract.

1

Rock Quality Designation defined as the ratio of the total length of pieces 4 inches or greater to the length cored. In determining the length of 4 inch pieces, fresh fractures caused by the drilling process shall be ignored.

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SECTION 22.5 EXPLORATION METHODS 22.5.1 DRY SAMPLE BORINGS (1992) 22.5.1.1 Auger Borings Auger borings shall conform to current ASTM D1452 requirements and may be used for exploratory borings as a rapid means of obtaining a preliminary soil profile. a.

Procedure. Auger borings shall be made by turning a screw-type auger into the soil a short distance, either by hand or mechanical means, withdrawing the auger and the soil that clings to it, and removing the soil from the auger for examination. The auger shall not be less than 1-1/2 inches in diameter. Most cohesive soils above the water table will permit auger borings to a depth of 20 feet or more without casing to support the walls of the hole.

b. Casing. If the hole does not stand open because of caving or squeezing from the sides, it shall be lined with a casing the diameter of which is larger than that of the auger. The casing shall be driven to a depth not to exceed the top of the next sample. In lieu of casing, a continuous-flight hollow-stem auger may be used, sampling being done through the stem with a split-barrel sampler. Point closure devices shall be used where the soils have a tendency of flowing into the hollow stem. c.

Sampling. The soil auger can be used for both boring the hole and bringing up disturbed samples of the soil encountered. Other sampling methods shall be as specified in Article 22.7.1.

1

22.5.1.2 Wash Borings a.

Procedure. Casing shall be driven to the required sampling elevation and the inside cleaned partly by a chopping and twisting action of a light bit and partly by the jetting action of water which is pumped through the hollow drill rod and bit. Cuttings are removed from the hole by circulating water which passes down the drill rod and returns to the surface between the drill rod and the casing pipe. Wash borings shall conform to current ASTM D1586 requirements. (Split Barrel.)

3

b. Casings. Casings shall not be less than 1-1/2 inches inside diameter and shall be extra-heavy pipe. c.

Sampling. Whenever there is a change in the appearance of the mixture of wash water and soil that comes out of the hole, but not greater than at intervals of 5 feet, a sample shall be taken by one of the methods specified in Section 22.7, Sampling.

22.5.2 TEST PITS (1992) Test pits are preferable for shallow investigations where the surface material is extremely variable. Test pits are required when there is a need for load testing of the soil in-situ. They shall be made to the full depth of the layer. Excavation shall be by suitable methods and materials of each class shall be kept in separate piles as far as is practicable. Representative samples of the formations shall be taken progressively from the natural formation where requested by the Engineer, placed in suitable sample jars or containers and properly labeled.

22.5.3 CORE BORINGS IN ROCK (1992) 22.5.3.1 Equipment Drilling into bedrock shall be done with a double-tube, swivel-type core barrel equipped with a diamond, shot or other approved bit which will obtain a core, not less than 2-1/8 inches in diameter, from the rock penetrated. The drilling rig shall be capable of applying a constant hydraulic pressure on the bit during drilling. © 2011, American Railway Engineering and Maintenance-of-Way Association

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Concrete Structures and Foundations 22.5.3.2 Starting Core Bit Before starting the core bit in the hole, a chopping bit shall be used to break up and remove all disintegrated rock, and the casing shall be seated firmly on hard rock, by driving and washing out. 22.5.3.3 Procedure The core bit shall be in the hole and drilled to a depth of 5 feet. It shall then be withdrawn, the core removed, labeled as specified in Article 22.7.2, and stored. After the core is removed, the core bit shall be replaced in the hole and another 5 feet of depth drilled, the core bit withdrawn and the core removed as noted above. Drilling shall continue in this manner until the required depth has been reached. If the core bit becomes blocked, it shall immediately be withdrawn and cleaned before advancing further. Core borings in rock shall conform to current ASTM D2113 requirements.

SECTION 22.6 DETERMINATION OF GROUNDWATER LEVEL (1992) a.

The elevation of the groundwater at each boring location shall be accurately determined at a time when the groundwater table has stabilized.

b. When the hole is in a material that caves when the casing is withdrawn, a 1 inch diameter perforated plastic tubing shall be inserted in the casing before it is withdrawn. If long-term observations of the groundwater are desired, a short casing shall be installed and sealed to prevent inflow of surface water. The casing shall be threaded and capped at the upper end. The elevation of the groundwater can then be read in the plastic tube after the casing is withdrawn. If the boring is located where the groundwater level may be influenced by a tidal body of water, a record of the exact stage and direction of the tide at the time of taking the elevation of the groundwater shall also be made.

SECTION 22.7 SAMPLING 22.7.1 DRY SAMPLES (1992) 22.7.1.1 Split-Barrel Sampling of Soil a.

Scope. This procedure covers the method for recovering disturbed samples with a split-barrel sampler and to obtain a record of the resistance of the soil to the penetration of the sampler. Split-barrel sampling borings shall conform to current ASTM D1586 requirements.

b. Procedure. The casing shall be driven to the sampling elevation and the hole cleaned out by augering, washing or other methods insuring that the material to be sampled is not disturbed by the clean-out operation. Sampling shall either be continuous or at 5 feet intervals of depth and at all changes in strata. The split-barrel sampler shall be slowly lowered to the bottom of the hole, then driven into the soil a distance of 18 inches by a series of blows from a 140 lb hammer falling freely for a drop of 30 inches. The number of blows required to produce each 6 inches of penetration shall be recorded. Where the bottom of the boring is below the water table at the time of sampling, the water level in the hole should be at or above the groundwater level. The number of blows for the last 12 inches is termed the Standard Penetration Blow Count or N-Value. If blow counts for the last 6 inches are abnormally high, indicating a different layer, blow counts for the first 12 inches shall be used. If it is not possible to obtain 1 foot of penetration, the fraction of a foot penetrated and the corresponding number of blows shall be reported.

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c.

In cohesionless, or nearly cohesionless, soils located below the water table, a core catcher attached to the lower end of the sampler or a scraper bucket or other similar devices shall be used in order to prevent the sample from falling out before it can be brought to the surface. The soil shall be promptly removed from the sampler and immediately placed in airtight suitable containers of sufficient size to hold a section of the sample intact. The containers shall be marked to indicate the job designation, boring number, sample number and elevation or depth at which the soil was taken. The samples obtained by this methodology are disturbed samples. Strength or compressibility testing results should be viewed with caution.

22.7.1.2 Thin-Walled Tube Sampling of Soil a.

Scope. This procedure covers the method of obtaining relatively undisturbed samples of suitable size of cohesive soils for laboratory testing. The minimum size sample shall not be less than 3 inches outside diameter. Piston-type samples shall be used if satisfactory samples cannot be obtained with the thinwalled tube samplers. Thin-walled tube samplers shall conform to the current ASTM D1587 requirements.

b. Procedure. The casing shall be driven to the sampling elevation and the hole cleaned out by augering, washing, or other methods insuring that the material to be sampled is not disturbed by the clean-out operations. With the sampling tube resting on the bottom of the hole and the water level in the hole approximately at groundwater elevation, the tube shall be pushed into the soil with a continuous and rapid motion without impact or twisting by means of a hydraulic jack, for a distance about 6 inches less than the length of the tube. The sample shall then be rotated to shear the end of the sample and the sample tube slowly raised to the surface. Disturbed material at each end of the tube shall be completely removed. To insure laboratory test results that are representative of the in-situ conditions, it is necessary for the samples to be transported and delivered to the laboratory in an undisturbed condition and without loss of moisture. A recommended procedure is to fill the space in the tube with a minimum of 1 inch of micro-crystalline paraffin wax, cap and tape the ends and seal them with wax. If the samples are to be tested in the field, they can be carefully extruded from the tubes and tested. Each sample shall be labeled with the job designation, boring number, sampler number, elevation or depth at which the sample was taken and the orientation of the sample. Thin-walled tube sampling borings shall conform to current ASTM D1587 requirements. (Shelby Tube.)

1

3

22.7.2 ROCK CORES (1992) The rock cores shall be placed in wooden boxes in the order in which they were taken. These boxes shall be about 5 feet long, containing only one layer, capable of holding approximately 25 feet of core, and substantially made of 1/2 inch lumber. Each row of cores shall be separated from the adjacent row by a 1/4 inch wood strip. Cores from each run shall be separated from those of the next run by a wooden block nailed into place. If cores from more than one boring are placed in the same box, two wooden blocks shall be nailed between cores from adjacent borings. On each of these two blocks, the boring number referring to the adjacent core shall be marked. On the lid and ends of each box shall be clearly marked the job designation, boring number, core runs, and the elevation or depth for each run.

SECTION 22.8 RECORDS 22.8.1 SCOPE (1992) Full and complete records of all pertinent data shall be kept. All items listed in Article 22.8.2, Article 22.8.3 and Article 22.8.4 shall be included.

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22.8.2 GENERAL (1992) The following information shall be recorded: a.

Name of railroad, site and weather conditions.

b. Location and identifying number of test boring and reference to permanent survey data. c.

Date and time of start and completion of boring.

d. Name of contractor, names and titles of all boring crew members, inspectors, and engineer. e.

Ground surface elevation at each boring and datum used, preferably United States Geodetic Survey datum.

f.

Elevation of groundwater or surface of waterway and time of observation.

22.8.3 BORINGS – DRY SAMPLE (1992) The following information shall be recorded: a.

Diameter and description of casing (when used).

b. Weight and drop of hammer and number of blows used to drive the casing for each successive foot of elevation. c.

Depths at which major changes in the character of the soil take place.

d. Method and total force used to push sampler into soil. e.

If sampler is driven, height and weight of drop hammer used to drive sampler and number of blows required to drive it each 6 inches for each sample.

f.

Elevation of bottom of sampler at the start of taking each sample.

g.

Elevation to which sampler was forced into the soil.

h. The length of the sample obtained. i.

The stratum represented by the sample.

j.

Detailed description of the soil in each major stratum, to include: • Kind: top soil, fill, clay, sand, gravel, etc. • Color: Light, dark blue, red, etc. • Moisture: Dry, moist, wet, very wet, etc. • Consistency: Loose, soft, compact, stiff, etc.

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22.8.4 CORE BORINGS (1992) The following information shall be recorded: a.

Elevation of bottom of casing when seated according to Article 22.5.3.2.

b. Type of core drill, including size of core. c.

Length of core recovered for each 5 feet length drilled, with resulting percentage of recovery, and Rock Quality Designation.

d. Elevation of each change in type of rock. e.

Elevation of bottom of core hole.

f.

The rock shall be described in accordance with the following classifications. • Type: Shale, slate, limestone, sandstone, granite, etc. • Condition: Broken, fissured, laminated, solid, etc. • Hardness: Soft, medium hard, very hard, etc.

g.

Rate at which each 5 feet section was cored in minutes per foot.

1

SECTION 22.9 INSPECTION (1992) No drilling shall be done except in the presence of the Engineer or his representative (inspector). No more than two drilling crews working in the same vicinity at the same time shall be covered by one inspector. The Engineer or inspector shall identify bench marks for the determination of the required elevations, check the log of the boring to determine that the information designated in Section 22.8, Records is being obtained, and to establish its accuracy and see that all soil samples and cores are properly boxed and stored in a suitable place or shipped to its designated destination.

3

4 SECTION 22.10 GEOPHYSICAL EXPLORATIONS (1992) Two geophysical methods, seismic and electrical resistivity, have proven useful as rapid means of obtaining subsurface information and as economical supplements to borings in exploratory programs. These methodologies supply information for bedrock profiling, for locating firmer material underlying softer material and for yielding a general definition of subsurface conditions including the depth to groundwater. However, there are numerous limitations to the information obtained. All geophysical information should be used in conjunction with borings.

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SECTION 22.11 IN-SITU TESTING OF SOIL (1992) a.

Techniques for the measurement of soil properties by in-situ tests have developed rapidly during the decade of 1980-1990. Some of the advantages are: (1) Provides an almost continuous soil record with depth. (2) Ability to determine the properties of sands and offshore deposits which are difficult to sample undisturbed for laboratory testing. (3) Capacity of evaluating the properties of a much larger volume of soil and provides a cost effective technique because of large collection of data in a short time which is processed automatically. Some of the common methods are vane shear, sounding, dutch cone, and self-boring pressure meter test (SBPMT). Based on the nature and complexity of the project, the project schedule and funding availability, the geotechnical engineer shall make the judgement for use of the in-situ testing.

b. To determine values for shear use current ASTM D2573 requirements. (Field Vane Shear Test in Cohesive Soils.)

SECTION 22.12 BACKFILLING BORE HOLES (1992) Open bore holes, as well as open exploratory excavations, can be a safety hazard and shall be backfilled when they are no longer required. Backfilling with available local soil tamped in place will be adequate unless local or state regulations require backfilling with grout or other means. In certain cases to prevent movement of water from one stratum to another and to prevent piping of material through the bore hole or contamination of groundwater, the use of grout is appropriate.

SECTION 22.13 CLEANING SITE (1992) After completion of the work, the casing shall be withdrawn, all equipment removed and the site restored to its original condition as directed by the Engineer.

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Part 23 Pier Protection Systems at Spans Over Navigable Streams — 2010 — TABLE OF CONTENTS

Section/Article

Description

Page

23.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.1.1 Scope (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.1.2 Purpose (2001). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.1.3 Terms (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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23.2 Special Considerations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.2.1 Vessel (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.2.2 Waterway (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.2.3 Types of Construction (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.2.4 Permits (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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23.3 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.3.1 General (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.3.2 Design Loads (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.3.3 Suggested Design Procedure (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.3.4 Types of Protection (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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23.4 Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.4.1 General (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.4.2 Materials (2010). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.4.3 Handling and Storage of Materials (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.4.4 Framing of Timber (2010). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.4.5 Fabrication of Structural Steel (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23.4.6 Pile Driving (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Commentary (2010). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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3

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LIST OF FIGURES Figure

Description

Page

8-23-1 Energy Dissipation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-23-7 8-23-2 Pier Protection - Sheet Pile Dolphin - Deep Water, Poor River Bottom (For General Information Only) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-23-10 8-23-3 Pier Protection - Treated Timber Pile Dolphin (For General Information Only) . . . . . . . . . . . 8-23-11 8-23-4 Pier Protection - Hydraulic Type Hydrocushion Dolphin (For General Information Only). . . 8-23-12 8-23-5 Pier Protection - Floating Sheer Boom (For General Information Only) . . . . . . . . . . . . . . . . . 8-23-13 8-23-6 Pier Protection - Fender System Integral with Pier (For General Information Only) . . . . . . . 8-23-14 8-23-7 Pier Protection - Independent Fender System (For General Information Only) . . . . . . . . . . . 8-23-15 8-23-8 Pier and Swing Span Protection - Pivot Pier (For General Information Only). . . . . . . . . . . . . 8-23-16 8-23-9 Pier Protection (For General Information Only). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-23-17 8-23-10 Pier Protection - Modular Fender Systems (For General Information Only) . . . . . . . . . . . . . . 8-23-18 8-23-11 Rock Blanket Pier Protection (For General Information Only) . . . . . . . . . . . . . . . . . . . . . . . . . 8-23-20

SECTION 23.1 GENERAL 23.1.1 SCOPE (2010) These recommendations cover the design, construction, and maintenance of protective systems for railway bridge piers located in or adjacent to channels of navigable waterways. The details included in these recommendations may also be applied for the protection of railway bridge abutments. For inspection of protective systems, see Article 21.3.2.

23.1.2 PURPOSE (2001) The purpose of the protective systems is to prevent or minimize damage to supporting piers of railway bridges caused by accidental collision from floating debris and vessels. Such protection should be designed to eliminate or reduce the impact energy transmitted to the pier from the debris or vessel, either by redirection of the force, or by absorption or dissipation of the energy to nondestructive levels.

23.1.3 TERMS (2001) Following is a list of terms associated with this Part. These terms are defined in the Glossary at the end of this Chapter. Dolphin Fender Sheer Boom Wales

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SECTION 23.2 SPECIAL CONSIDERATIONS 23.2.1 VESSEL (2010) The size and type of vessel to be chosen as a basis for design of the pier protection should reflect the maximum vessel tonnage, type of cargo and velocity to be reasonably expected for the specific facility involved.

23.2.2 WATERWAY (2001) a.

Consideration should be given to the exposure of the structure in the waterway, including the alignment and width of the channel, skew of pier, visibility for approaching vessels, as well as effect of wind, ice, current, or tide in the vicinity.

b. The use of increased bridge span length to reduce the chance of ship collision, by constructing piers in shallow water or on land away from the waterway, may reduce or eliminate pier protection. c.

Depth of water, fluctuation of water level, and scour potential may dictate the type of protection to be chosen. If the depth is so great, or the character of the waterway bottom does not lend itself to proper anchorage and support for an independent protective system, it may be necessary to design a suspended or floating protective system.

23.2.3 TYPES OF CONSTRUCTION (2001) a.

The type of construction to be chosen for the protective system should be based on the physical site conditions and the amount of energy to be absorbed or deflected, as well as the size and ability of the pier itself to absorb or resist the impact.

1

b. Some of the more common types of construction are as follows. 23.2.3.1 Integral

3

Where the pier is considered to be stable enough to absorb the impact of floating vessels, it may be necessary to attach cushioning devices to the surfaces of the pier in the areas of expected impact to reduce localized damage to concrete surfaces and exposure of reinforcing steel, or damage to masonry and its jointing. Such cushioning may include strips of material attached to the face of the pier, such as solid or preformed rubber, timber, pneumatic, hydraulic or hydrocushion strips. 23.2.3.2 Dolphins Where depth of water and other conditions are suitable, the driving of pile clusters may be considered. Such clusters have the piles lashed together with cable to promote integral action. The clusters should be flexible to be effective in absorbing impact through deflection. Cellular dolphins may be filled with concrete, loose material or material suitable for grouting. Cells filled with uncemented materials may lose fill material in the event of rupture due to collision. 23.2.3.3 Floating Sheer Booms Where the depth of water or other conditions precludes the consideration of dolphins or integral pier protection, floating sheer booms may be used. These are suitably shaped and positioned to protect the pier and are anchored to allow deflection and absorption of energy. Anchorage systems should allow for fluctuations in water level due to stream flow or tidal action.

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Concrete Structures and Foundations 23.2.3.4 Hydraulic Devices Suspended cylinders engaging a mass of water to absorb or deflect the impact energy may be used under certain conditions of water depth or intensity of impact. Such cylinders may be suspended from independent caissons, booms projecting from the pier, or other supports. Such devices are customarily most effective in locations subject to little fluctuations of water levels. 23.2.3.5 Fenders Construction of fender systems, using piling with horizontal wales, is a common means of protection where water depth is not excessive and severe impacts are not anticipated. 23.2.3.6 Other Types Various other types of protective systems, such as earthen and riprap islands around piers, have been successfully used and may be considered by the designer.

23.2.4 PERMITS (2001) Proposed protective systems must receive approval of the appropriate regulating agencies prior to installation. Advance coordination with these agencies to determine waterway clearance, lighting and any other special requirements, is recommended.

SECTION 23.3 DESIGN1 23.3.1 GENERAL (2010) a.

Criteria for the design of protective systems cannot be specified to be applicable to all situations. Investigation of local conditions is required in each case, the results of which may then be used to apply engineering judgment to arrive at a reasonable solution.

b. In any type of pier protection system, general details should be designed to provide the following: (1) Adequate mass and resilience so that the railroad facility will not be vulnerable to damage from reasonably expected collision of marine traffic. (2) A smooth transition past the pier with particular attention to protrusions and details that could cause damage to a vessel. (3) Ease of replacement of damaged parts. (4) Elimination of sparking upon vessel impact. (5) Accessibility for inspection. c.

1

The effects of scour for the protective system and the adjacent structure being protected should be considered.

See Commentary (2010).

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23.3.2 DESIGN LOADS (2010) Design loads to be used shall be determined for each individual structure, based on factors unique to the location. Information may be available from ship owners and operators, port facility authorities, industry representatives, the U.S. Army Corps of Engineers, Federal Highway Administration, and the U.S. Coast Guard. a.

General factors to be considered in determining the desired degree of pier protection include, but are not limited to, the following: (1) Piers at the edge of a channel having a wide horizontal clearance may require only minimum protection. (2) The type of construction of the pier should be considered. (a) A massive pier may be capable of resisting most reasonably expected loads so that the additional resistance offered by a protective system may not be warranted. (b) A pier incapable of resisting reasonably expected loads should be provided with greater protection than a massive pier might require. (3) Piers may be especially vulnerable because of difficulty of navigation caused by high stream velocity or tidal flow, wind velocity, waterway traffic, poor visibility, limited horizontal clearances, channel curvature, proximity of other obstacles, or other similar factors.

1

(4) Foundation conditions will have a bearing on the resistance capability of the pier and on the practicality of providing the desired degree of protection. (5) The history of collisions with existing bridges or other obstacles in the vicinity should be considered. b. To estimate the actual collision forces which could be encountered, and their effects, the following items should be known:

3

(1) Maximum sizes and types of vessels. (2) Impact velocity of vessels. (3) Crushing resistance of hulls.

4

(4) Stream velocities. (5) High and low water elevations. (6) Impact angle. (7) Wind velocities. (8) Velocity and mass of floating ice. c.

The kinetic energy in the moving vessel may be determined as follows: KE = MV2/2

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where: KE = Kinetic energy M = Total mass of the vessel V = Velocity of the vessel relative to the pier d. Energy may be dissipated according to the following (see Figure 8-23-1): E=F´ d where: E = Energy dissipated F = Average force applied to the moving vessel d = Distance vessel moves (in the direction of F) during the time F is applied The distance (d) is measured after initial contact and is composed of deflection of the protective system, crushing of the system and vessel, or a combination thereof. System flexibility determines, to a large extent, the relative amounts of deflection and crushing, and is more fully discussed in the appended commentary. e.

The effects of stream flow forces, wind forces and ice forces, where applicable, and the probability of collision should be taken into consideration in the design of pier protection systems.

23.3.3 SUGGESTED DESIGN PROCEDURE (2010) As a practical matter, pier protection will not always be adequate to completely dissipate the kinetic energy of a vessel at high speed. However, in many cases, the protection will deflect a vessel, reducing damage that may otherwise occur. The outline presented here provides an approach to the problem of evaluating the effect on the kinetic energy of a vessel when a collision occurs: a.

Compute the kinetic energy (KE) based on the mass and impact velocity of the vessel.

b. Assume trial configuration of the pier protective device and estimate resistance force (F) of the pier protection for the following: (1) Assuming allowable stresses equivalent to 1.5 times basic allowable unit stress of the material. (2) Assuming ultimate strength of materials. c.

Equate kinetic energy (KE) with energy dissipated (E): MV2/2 = F ´ d solve for d to determine total movement required to dissipate energy (see Commentary (2010)).

d. The above outline provides a basis for evaluating the amount of energy that can be dissipated by the pier protection and the total resistance capability. e.

Vertical movement of the vessel can be considered in the dissipation of energy.

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3

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Figure 8-23-1. Energy Dissipation

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23.3.4 TYPES OF PROTECTION (2010) The various types of pier protection systems shown in this section are for general information only. For the most part, they have been taken from protection systems currently in use on both highway and railway bridges in the United States. Member sizes, numbers of units, types of material, and details of construction are those used for specific installations and cannot be considered standards since the design of pier protection systems depends on many parameters that may vary markedly from one installation to another. Each pier protection system must be chosen and designed to fulfill the unique requirements at the given location. The following types of protection are commonly used; however, other types may be considered. 23.3.4.1 Sheet Pile Cell Dolphins (Figure 8-23-2) a.

Sheet pile cells preferably should be of circular configuration. A typical cell includes interlocking steel sheet piles filled with concrete or grouted material. If loose fill materials are used, a concrete or grouted liner and a reinforced concrete top should be considered. The concrete top should be adequately anchored to the sheet piles. Desirable qualities of fill material include free draining characteristics, high unit weight, shear strength, and high coefficient of friction.

b. The designer should make an evaluation of the cell stability and resistance to overturning and sliding. Factors to be considered include characteristics of the underlying soil or rock and the cell fill material, interaction of the cell fill material with the cell walls, and friction of the sheet piles embedded in the underlying soil. c.

Additional resistance against overturning may be provided by driving and attaching additional piles around the perimeter of the cell. Increased penetration into the underlying soil may be obtained in this manner, in lieu of extension of all sheet piles.

d. The possibility of scour occurring near a dolphin or at the pier due to the dolphin, should be investigated and protection should be provided, if required. 23.3.4.2 Pile Cluster Dolphins (Figure 8-23-3) Pile cluster type dolphins should be composed of groups of battered and/or vertical piles which are held together at the top. The designer should evaluate the resistance to lateral forces, considering the effects of any battered piles, and the interaction of the piles and the surrounding soils. 23.3.4.3 Gravity Pendulum Dolphin (Hydrocushion Type) (Figure 8-23-4) a.

Typically, a heavy cylindrical mass of steel or concrete is suspended from a cantilevered supporting structure, which may be a part of the pier, or may be an independent support. Energy is dissipated by movement of the pendulum when a force is applied by a striking vessel.

b. The designer should evaluate the energy dissipated by the pendulum, taking the following items into account. (1) Movement of the pendulum. When the pendulum is suspended in water, the effective mass includes an amount of water which moves along with the pendulum; in the case of a ring, (as shown in Figure 8-23-4) the volume of water enclosed by the ring is part of the total mass to be moved. x (2) The resisting horizontal force component = W r æ -------------ö è L – yø

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where: Wr = Weight of the ring x = The horizontal displacement of the ring L = Length of hanger to the ring y = The amount the ring is lifted 23.3.4.4 Floating Sheer Booms (Figure 8-23-5) a.

The configuration of a sheer boom will depend upon the requirements of a particular location.

b. The designer should evaluate the capability of the device to dissipate energy, recognizing the following: (1) The mass to be considered as part of the moving element includes a volume of water which will be forced to move with the boom. (2) Deflection movements of supporting elements will account for some energy loss. (3) Frictional resistance is provided by the water adjacent to the moving elements.

1

23.3.4.5 Fenders (Figure 8-23-6, Figure 8-23-7, Figure 8-23-8, Figure 8-23-9, and Figure 8-23-10) a.

Pier fenders are intended to provide protection to the pier in the event of contact by a vessel. Fenders are usually positioned with the anticipated direction of impact from a vessel at a relatively small angle with respect to the fender line. A fender may be supported by the pier it is intended to protect, or it may be independently supported.

b. Independently supported fender systems typically consist of vertical and/or battered piles with horizontal members connecting the piles so the fender system acts as a unit. The horizontal members may be used as rubbing strips or separate rubbing strips may be attached to these members. c.

3

Pier-supported fenders vary in type from simple rubbing strips attached directly to the pier face to more elaborate installations which provide for some energy dissipation by the fender when struck by a vessel.

4

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Figure 8-23-2. Pier Protection - Sheet Pile Dolphin - Deep Water, Poor River Bottom (For General Information Only)

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11 WRAPS OF CABLE COMFORMING TO ARTICLE 23.4.2.10. EACH TURN SHOULD BE STAPLED TO EACH PERIMETER PILE

1

3

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Figure 8-23-3. Pier Protection - Treated Timber Pile Dolphin (For General Information Only)

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Figure 8-23-4. Pier Protection - Hydraulic Type Hydrocushion Dolphin (For General Information Only)

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3

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Figure 8-23-5. Pier Protection - Floating Sheer Boom (For General Information Only)

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Figure 8-23-6. Pier Protection - Fender System Integral with Pier (For General Information Only)

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3

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Figure 8-23-7. Pier Protection - Independent Fender System (For General Information Only)

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Figure 8-23-8. Pier and Swing Span Protection - Pivot Pier (For General Information Only)

Concrete Structures and Foundations

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Pier Protection Systems at Spans Over Navigable Streams

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Figure 8-23-9. Pier Protection (For General Information Only)

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Figure 8-23-10. Pier Protection - Modular Fender Systems (For General Information Only)

Pier Protection Systems at Spans Over Navigable Streams

d. The designer should consider the following items pertaining to fenders: (1) Fenders should preferably be detailed so that a maximum number of piles, or other supporting elements, will participate in resisting applied loads. (2) Fenders should have a somewhat flexible arrangement to provide for deflection of the fender and for energy dissipation. (3) The effects of battered piles and pile-soil interaction should be considered when evaluating the capability of the fender to resist lateral forces. (4) Consideration should be given to providing a weak point in the design, thus causing the unit to fail in a pre-planned manner when struck by a force in excess of the capacity. Details can then be arranged to facilitate the replacement of damaged elements. 23.3.4.6 Riprap Used as Pier Protection a.

Riprap may be mounted around a pier to prevent a vessel from making contact.

b. The designer should consider the following items pertaining to the use of riprap around piers: (1) The depth of water and resulting amount of fill required. (2) The effect on waterway opening required for navigation and hydraulics.

1

(3) The riprap should be designed to adequately dissipate the kinetic energy of the vessel prior to making contact with the pier. (4) Environmental and permitting concerns. (5) Overburden on the pier foundation. c.

3

The use of protective islands may be considered for pier protection for major bridges.

4

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Figure 8-23-11. Rock Blanket Pier Protection (For General Information Only)

SECTION 23.4 CONSTRUCTION 23.4.1 GENERAL (2010) a.

Construction permits from all federal, state and local regulatory bodies should be obtained prior to beginning construction.

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b. All construction should be performed in accordance with all applicable laws and regulations including navigational clearances, maintenance of marine traffic, environmental considerations, navigation lighting and temporary warning signs and devices. c.

All temporary construction facilities should be approved by the Engineer and the concerned regulatory bodies. Temporary construction should be removed upon completion of the work and the construction site returned to a condition acceptable to the regulatory bodies and the Engineer.

d. Excavated material and debris of demolition and of construction should be disposed of in accordance with all applicable laws and regulations. e.

Construction inspection safeguards should be provided to ensure that pier protection structures are constructed in the correct location with respect to the navigation channel. Underwater inspection services should be provided if necessary to determine conditions relevant to the construction. As-built plans should be furnished to the Engineer upon completion of the work.

23.4.2 MATERIALS (2010) 23.4.2.1 Timber1 a.

All new timber should meet the requirements of the current standard Methods for Establishing Structural Grades and Related Allowable Properties for Visually Graded Lumber, ASTM Designation D245. Timber should be Dense Structural 65 or Long-Leaf Structural 65, southern yellow pine, conforming to the Grading Rules of the Southern Pine Inspection Bureau; or No. 1 Douglas Fir conforming to the Standard Grading Rules for West Coast Lumber; or other species conforming to the flexural strength specified for Southern Pine and Douglas Fir, other requirements being comparable.

1

b. Timber for joists, planks, beams, wales and walkways should be square edge and shall be grade marked. c.

The preservative treatment should be in accordance with AREMA Chapter 30, Ties, Section 3.6, Wood Preserving and Section 3.7, Specifications for Treatment, and applicable environmental regulations. Alternative preservative treatment is subject to approval of the Engineer.

3

d. Timber should be treated with a fire retardant, if appropriate. 23.4.2.2 Concrete a.

Workmanship, materials and proportioning for concrete members used in pier protection structures should be in accordance with requirements for Part 1, Materials, Tests and Construction Requirements.

b. The design of concrete members used in pier protection structures should be in accordance with the requirements for Part 2, Reinforced Concrete Design. c.

The minimum cover on reinforcing steel in concrete faces subject to impact should be 3 inches (75 mm).

23.4.2.3 Structural Steel Structural steel shapes and plates should conform to the Standard Specification for Structural Steel, ASTM A36, or ASTM A709, with a minimum of 0.2% copper. Other steels may be used having greater strength and enhanced corrosion resistance as required by the design of the pier protection work. The recommended minimum thickness of all metal components to be used is 3/8 inch (10 mm). 1

See See Commentary (2010).

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Concrete Structures and Foundations 23.4.2.4 Composites and Other Materials Other materials that can be used for fender wales and other pier protection components include: composite plastic, low-friction rubber, high-density polyethylene (HDPE) and ultra high molecular weight polymers (UHMV). These materials come in various sections and lengths. 23.4.2.5 Timber Piles a.

Timber piles should be First Class piles in accordance with AREMA Chapter 7, Timber Structures, Part 1, Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Timber Bridge Ties and Recommendations for Fire-Retardant Coating for Creosoted Wood and Part 3, Rating Existing Wood Bridges and Trestles, and should conform to ASTM D25.

b. Preservative treatment is required and should conform to AREMA Chapter 30, Ties, Section 3.6, Wood Preserving and Section 3.7, Specifications for Treatment and be in accordance with applicable environmental regulations. 23.4.2.6 Steel Piles a.

W and H steel shapes should have minimum flange and web thicknesses of 3/8 inch (10 mm) and as appropriate should, conform to ASTM A36, A572, or A709, with a minimum 0.2% copper; or should conform to ASTM A588.

b. Steel pipe piles should have a minimum wall thickness of 3/8 inch (10 mm) and shall conform to ASTM A252, Grade 2, with minimum 0.2% copper. A weathering steel equivalent may also be considered. c.

Steel sheet piles should have a minimum thickness of 3/8 inch (10 mm) and shall conform to ASTM A328, with minimum 0.2% copper, or shall conform to ASTM A690. The designer should specify the minimum strength required in the interlock joint.

23.4.2.7 Composite Plastic Piles Composite plastic piles suitable for cluster dolphins and fenders are available in uniform diameters from 10 to 16 inches (250 to 400 mm) and of virtually any length that can be handled. The proprietary material is recycled plastic with either steel or fiberglass reinforcing strands. The material is high energy absorptive, low friction, ultraviolet light resistant, impervious to marine borers and can be cut and drilled with common construction tools. These pilings are generally used as a direct substitution (one-for-one) for timber piling. 23.4.2.8 Hardware Bolts, nuts, washers, spikes, lag bolts, staples, cable clamps and similar hardware items should be galvanized steel or stainless steel. In lieu of using galvanized or stainless steel hardware, other means of corrosion protection should be provided. a.

Galvanized standard carbon steel fasteners should conform to the standard Specification for Carbon Steel Externally and Internally Threaded Standard Fasteners, ASTM A307; or to the Standard Specification for High Strength Bolts for Structural Steel Joints, Including Suitable Nuts and Plain Hardened Washers, ASTM A325, Type I. Galvanizing should be in accordance with the requirements of ASTM A153, Class C. If galvanizing is not required, fasteners should conform to the Standard Specifications for High Strength Bolts for Structural Steel Joints, Including Suitable Nuts and Plain Hardened Washers, ASTM A325, Type 3.

b. Stainless steel hardware should be manufactured from material conforming to the Standard Specifications for Stainless and Heat-Resisting Steel Bars and Shapes, ASTM A276, Type 304 or 316. © 2011, American Railway Engineering and Maintenance-of-Way Association

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Type 316 should be used in a salt water atmosphere and treated with a positive corrosion resistant material. 23.4.2.9 Wrapping for Dolphins Cable for wrapping dolphins should be galvanized 6 ´ 7 steel rope; or galvanized 7 ´ 7 mild plow steel rope. Where enhanced corrosion resistance is required, 7 ´ 19 stainless steel wire rope should be used. The designer should evaluate the cost, expected life, usage, susceptibility to damage and other pertinent factors when choosing the dolphin wrapping cable. All wire ropes should have steel wire cores. 23.4.2.10 Corrosion Protection Consideration should be given to protecting submerged steel surfaces cathodically and exposed surfaces by means of suitable paint systems or by galvanizing.

23.4.3 HANDLING AND STORAGE OF MATERIALS (2010) a.

All timber, lumber, timber piles and associated hardware should be handled and stored in accordance with Chapter 7, Timber Structures, Part 4, Construction and Maintenance of Timber Structures, Section 4.4, Workmanship for Construction of Pile and Framed T restles and Part 1, Material Specifications for Lumber, Timber, Engineered Wood Products, Timber Piles, Fasteners, Timber Bridge Ties and Recommendations for Fire-Retardant Coating for Creosoted Wood, Section 1.5, Specifications for Timber Piles.

b. Concrete materials such as cement, aggregates and steel reinforcement, should be stored in accordance with Part 1, Materials, Tests and Construction Requirements, Section 1.8, Storage of Materials. c.

1

Handling and storage of steel items should be in accordance with Chapter 15, Steel Structures, Part 4, Erection, Section 4.8, Handling and Storing Materials.

d. Miscellaneous parts and materials should be handled in a manner as to prevent loss and damage, and should be stored on blocking or on platforms above the ground. Weather and fire protection should be provided as necessary.

3

23.4.4 FRAMING OF TIMBER (2010) a.

Timber should be cut and framed in accordance with Chapter 7, Timber Structures, Part 4, Construction and Maintenance of Timber Structures.

b. Bolt heads and washers on the navigation side should either be recessed below the rubbing surface of the fender or be of the dome-head type flush with the rubbing surface.

23.4.5 FABRICATION OF STRUCTURAL STEEL (2001) Fabrication of structural steel should be in accordance with the requirements of Chapter 15, Steel Structures, except as noted herein: a.

Substitution of stronger, but less energy absorbing members will not be permitted.

b. Substitution of higher grade, but less ductile steel will not be permitted. c.

Shop assembly will not be required.

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d. Field welding will not be permitted, unless specifically authorized by the Engineer. All field connections should be held to a minimum and should be made by means of bolts with appropriate washers and nuts. e.

Washers should be placed under both the heads and nuts of all bolts (except dome-head bolts) bearing on timber. Suitable lock nuts should be provided where fastenings may tend to loosen.

23.4.6 PILE DRIVING (2001) Pile driving should be performed in accordance with Part 4, Pile Foundations, Section 4.5, Installation of Piles or Chapter 7, Timber Structures, Part 3, Rating Existing Wood Bridges and Trestles. 23.4.6.1 Pile Driving Records An accurate record should be kept of all piles driven, on the form prescribed by the Engineer. The log should show date, type of pile driven, pile number, location, type of hammer used, water depth and elevation, pile depth into soil, and ultimate driving resistance. The form should be signed by the person recording the information, including their job title. The record should be made a permanent part of the job statistics.

COMMENTARY (2010) C - 23.3.2 DESIGN LOADS (2010) C - ENERGY DISSIPATION a.

A moving vessel has a certain amount of kinetic energy, which is dependent upon the mass of the vessel and its velocity. To redirect or stop a vessel in protecting the pier, a portion or all of its kinetic energy must be absorbed or dissipated. This energy is dissipated by applying a force to the vessel over a given distance. For the fender to function properly, this distance must be less than the distance from initial contact until the vessel would strike the pier. For large vessels, traveling at fair speeds, in deep water, the amount of kinetic energy provided is large and the resistance of the fender is relatively small and it is very difficult to design a fender that will completely protect a pier for such a collision if the vessel is headed directly at the pier.

b. The energy in any contact with the fender is dissipated by deflection of the fender itself, by lifting a portion of the fender, by lifting the vessel out of the water, by crushing of the fender, by crushing of the bow of the vessel, by displacement of the water adjacent to the vessel, by displacement of the ground or river bottom, etc. c.

Several general facts should be considered and are noted briefly: (1) It should be recognized that the total resisting force is not developed immediately upon impact, but requires some movement until it develops. (2) If the crushing force of the vessel is greater than the ultimate resisting force of the fender, then dissipation of the kinetic energy occurs. Initially, the impact creates a force between the vessel and the fender, which causes the vessel to decelerate and the fender to accelerate (F = mass ´ acceleration). At some point, the fender and the vessel reach the same velocity and move along together, being slowed by the resisting forces of the fender and/or the soil being acted upon. This will continue until either the vessel stops, the fender breaks or some combination of the two. (3) If the crushing force of the vessel is less than the total ultimate resisting force of the fender, then the velocity of the fender will increase from zero to a maximum and decrease to zero again without a © 2011, American Railway Engineering and Maintenance-of-Way Association

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common velocity being achieved. When the fender stops, the vessel continues to decelerate, acted upon by the crushing force.

C - FENDER FLEXIBILITY (2001) a.

An ideal pier fender would be constructed so that the fender itself absorbs all of the energy of the moving vessel in stopping the vessel before it hits the pier and then returns to its normal position without damage to either the fender or the vessel. Except for relatively small vessels and low speeds, design of such a fender is impractical due to the large required resisting force and the short distance in which to stop the vessel.

b. A flexible fender, one that acts elastically, will absorb energy with little or no damage to the vessel; however, the horizontal force that such a fender can resist is usually relatively small and may be insufficient to protect the pier. On the other hand, a rigid fender is capable of resisting a considerably larger force, although this force may only be applied over a small deflection before the member breaks, or is damaged locally. In this case, the total amount of energy absorbed may be far less than is absorbed in a flexible fender, although a considerable amount of energy is absorbed in breaking of the fender parts. In most cases, some compromise between a truly flexible and a very rigid fender is the better solution. c.

In fender systems, incorporating steel pipe piles or sheet pile cells, a concrete fill will provide a much more rigid device than will one filled with sand, stone or riprap. In the latter case, the energy absorbing qualities are improved due to the rubbing of the fill particles on each other, by friction in the interlocks of the sheet piles and the like. On the other hand, one must be extremely careful that the pile wall or the sheet pile wall is protected to prevent damage resulting in the loss of fill, which would materially reduce the effectiveness of the fender and its energy absorbing capability.

d. The type of fender used in any particular application must take into account the size and velocity of the vessel, flow of the stream, the depth of the water, the founding conditions, the distance between the pier protection and the pier, the strength of the pier itself and the types of cargo that are normally carried. The designer must normally use his discretion in selecting a pier protection design that best suits all of the parameters of the individual case considered.

1

3

C - 23.4.2 MATERIALS (2010) Timber, except walkway planking and handrails, may be preservative treated with creosote or other appropriate preservative subject to environmental regulations. Walkway planking and handrails may be treated either with creosote, pentachlorophenol or other preservative subject to environmental regulations. Pentachlorophenol or other appropriate treatments should be used if the member is to be painted with exterior paints. Creosoted members will generally not accept exterior paints.

C - SOURCES OF INFORMATION (2001) a.

Guide Specification and Commentary for Vessel Collision Design of Highway Bridges, Volume I: Final Report, American Association of State Highway and Transportation Officials, Washington, D.C., February, 1991.

b. Vessel Collision Design of Highway Bridges, NHI Course No. 13060, Publication No. FHWA HI-92-050July, 1992. c.

Stream velocities for various river stages on most navigable waters can be obtained from the U.S. Corps of Engineers. Channel locations, navigation maps and scour potential, may be available from the U.S. Corps of Engineers and the U.S. Coast Guard.

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d. Information regarding principal sizes, capacities and power of various vessels, as well as the type of cargo is usually available for navigable waters from the U.S. Corps of Engineers, the U.S. Coast Guard, the American Waterways Operators, Inc., port authorities, pilot associations and others. e.

Specific site parameters such as riverbed conditions, soil information, local wind and current effects on navigation usually must be developed by the design engineer, although local pilot associations and and waterway users associations may be able to help with the latter.

f.

References are located at the end of this Chapter. Refer to Reference 16, 19, 28, 48, 75, 77, 79, 81, 83, 84, and 102.

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Part 24 Drilled Shaft Foundations1 — 2010 — TABLE OF CONTENTS

Section/Article

Description

Page

24.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.1.1 Scope (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.1.2 Purpose and Necessity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.1.3 Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.1.4 Design Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-24-2 8-24-2 8-24-3 8-24-3 8-24-3

24.2 Information Required. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.2.1 Field Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.2.2 Subsurface Investigation (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-24-5 8-24-5 8-24-5

24.3 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.3.1 General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.3.2 The Transfer of Load from the Drilled Shaft to the Rock or Soil Bearing Strata (2010) . 24.3.3 Connection Between Supported Structure and Drilled Shaft. . . . . . . . . . . . . . . . . . . . . . . 24.3.4 Group Action of Drilled Shafts (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-24-5 8-24-5 8-24-5 8-24-7 8-24-7

24.4 Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.4.1 Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.4.2 Reinforcing Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.4.3 Permanent Steel Casing Material (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.4.4 Temporary Casing Material (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-24-9 8-24-9 8-24-9 8-24-9 8-24-9

24.5 Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.5.1 Contractor Qualifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.5.2 Shaft Excavation (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.5.3 Casing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.5.4 Bells or Underreams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.5.5 Sockets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.5.6 Tolerances (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.5.7 Dewatering. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.5.8 Inspection (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-24-9 8-24-9 8-24-9 8-24-10 8-24-10 8-24-10 8-24-10 8-24-11 8-24-11

1

References, Vol. 85, 1984, p. 29.

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TABLE OF CONTENTS (CONT) Section/Article 24.5.9 24.5.10 24.5.11 24.5.12 24.5.13

Description

Page

Placing Reinforcing Steel (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Placing Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Casing Removal (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Continuity of Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-24-11 8-24-11 8-24-11 8-24-12 8-24-12

24.6 Testing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.6.1 Material Testing (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.6.2 Capacity Testing (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24.6.3 Integrity Testing (2010)1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-24-12 8-24-12 8-24-12 8-24-12

C - Commentary (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-24-13

LIST OF FIGURES Figure

Description

Page

8-24-1 Drilled Shaft. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-24-4

SECTION 24.1 GENERAL 24.1.1 SCOPE (2010)1 a.

This part covers the description and general aspects of design, installation, inspection and testing of drilled shafts, also frequently referred to as drilled caissons, drilled piers, or bored piles.

b. This part is intended to serve as guidelines in developing specific designs and construction specifications on a project basis. c.

For the purpose of this part, the minimum diameter of these units shall be 30 inches (760 mm). Drilled shafts with smaller diameters have been constructed, but are not included in this specification.

d. This part relates primarily to single, vertical drilled shafts.

1

e.

Factors to be used in modifying the capacities of single drilled shafts for determination of the capacity of a group of drilled shafts which support a common rigid cap are included elsewhere in this part.

f.

The use of battered drilled shafts to accommodate lateral loads by the horizontal component of the shaft’s axial resistance is not recommended and is not addressed by this part. Lateral loads applied to drilled shafts are to be resisted by the effect of soil/rock interaction between the shaft and ground.

See C - Commentary (2010).

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24.1.2 PURPOSE AND NECESSITY a.

Drilled shafts are used to transmit loads through soils of poor bearing capacity into rock or soil formations having adequate bearing capacity. Generally, single drilled shafts have load capacities much larger than piling due to their larger size and capability of belling to increase the bearing area without enlarging either the footing or the drilled shaft.

b. The selection of foundation treatment for a given site should be determined by subsurface conditions, and by economic considerations as there is often a choice of several types of foundations for a structure.

24.1.3 TERMS Drilled Shaft — A machine and/or hand excavated shaft, concrete filled, with or without steel reinforcing, for the purpose of transferring structural loads to bearing strata below the structure. Protective Casing — Protective steel unit, usually cylindrical in shape lowered into the excavation to protect workmen and inspectors from collapse or cave-in of the side wall. Bell or Underream — An enlargement at the bottom of the drilled shaft made by hand excavation or mechanical underreaming with drilling equipment for the purpose of spreading the load over a larger area. Socket — A shaft of equal or smaller diameter extended into the bearing material.

1

Toe — Vertical section at bottom of bell. Permanent Casing — A steel cylinder that is installed for the purpose of excluding soil and water from the excavations. It is used as a form to contain concrete placed for the drilled shaft and remains in place. Temporary Casing — A cylinder that is installed for the purpose of excluding soil and water from the excavations. It may also be used as a form for the shaft concrete, but is withdrawn as the shaft concrete is placed.

3

24.1.4 DESIGN LOADS a.

Loading for drilled shafts shall be the design loads from the supported structure without application of load factors used for Load Factor design procedure. Design loads shall include the following:

4

• Primary Forces: – Dead Load – Live Load – Centrifugal Force – Earth Pressure – Buoyancy – Negative Soil Friction • Secondary Forces (Occasional): – Wind and Other Lateral Forces – Ice and Stream Flow

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Figure 8-24-1. Drilled Shaft – Longitudinal Forces – Seismic Forces

b. When drilled shaft foundations are designed for both primary and secondary forces, the allowable load on the drilled shafts may be increased by 25 percent, provided that the size or number of drilled shafts is not less than that required for primary forces alone. In soils where downward movements of surrounding soil relative to the drilled shaft are expected to occur, axial loads shall include negative soil friction

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forces, acting downward on the drilled shaft. Under special conditions swelling soils can produce upward forces, with fluctuation of the water table, which should also be considered in design.

SECTION 24.2 INFORMATION REQUIRED 24.2.1 FIELD SURVEY Sufficient information shall be furnished in the form of profile and cross sections to determine general design and structural requirements. The location of overhead and underground utilities, existing foundations, roads, tracks, or other structures shall be indicated. Records pertaining to high and low water levels and depth of scour shall be provided for stream crossings.

24.2.2 SUBSURFACE INVESTIGATION (2010) a.

Foundation material shall be investigated as specified under Part 22, Geotechnical Subsurface Investigation, in order to determine soil or rock properties, ground water elevations, and any other pertinent conditions.

b. Where a large portion of the required shaft capacity is to be generated from tip resistance of the shaft or rock socket, the geotechnical investigation shall be of sufficient scope to permit the determination that the strata in which the tip is founded is of sufficient depth and strength to carry the loads to which it is subjected. c.

1

Reference is also made to Article 4.3.1, Part 4, for additional information.

3 SECTION 24.3 DESIGN 24.3.1 GENERAL The design is divided into three basic parts: a.

4

The transfer of load from the drilled shaft to the rock and/or soil bearing strata.

b. The drilled shaft itself. c.

The connection between the supported structure and the drilled shaft.

24.3.2 THE TRANSFER OF LOAD FROM THE DRILLED SHAFT TO THE ROCK OR SOIL BEARING STRATA (2010)1 24.3.2.1 Drilled shafts transfer load to the bearing strata as follows: a.

1

An end bearing-type drilled shaft transfers essentially all of its load through weaker soils to a layer of soil or rock with adequate bearing capacity.

See C - Commentary (2010).

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b. A friction-type shaft is one whereby the drilled shaft load is transferred to the surrounding material primarily through friction between the shaft wall and the adjacent material. c.

A combination end bearing and friction-type drilled shaft is a shaft in which some of the load is transferred into the stratum by soil friction and the remainder by end bearing.

24.3.2.2 Lateral Loads and Moment When the drilled shaft is subjected to lateral load and moments, as well as axial load, the distribution of soil pressures and the variation of moments and shear in the shaft must be determined. 24.3.2.3 Belled Shafts a.

Where the bearing strata has insufficient strength to support the load on the base of the shaft, the shaft bottom may be enlarged by belling or underreaming to reduce the pressure by distributing the load over a greater area. Belled shafts shall be used only where the soil in which the bell is placed will not collapse due to the underreaming. Bells are normally unreinforced. The base diameter of the bell shall not exceed three times the shaft diameter and the sides shall not be less than 60 degrees from the horizontal. The toe height of bottom edge shall not be less than 6 inches (150 mm).

b. The ultimate axial capacity of a drilled shaft (Qult) shall be based on the summation of the ultimate shaft tip capacity and ultimate side resistance capacity minus the weight of the shaft. The allowable shaft capacity shall be the ultimate capacity divided by a factor of safety. c.

The ultimate shaft tip capacity (QT) shall be QT = qT · AT, where qT is the ultimate unit soil tip resistance determined by geotechnical analysis and AT is the area of the shaft tip.

d. The ultimate side resistance (QS) of the shaft in a layer of uniform unit side resistance (qS) shall be equal to the circumference of the shaft multiplied by the embedment length in a soil layer of uniform unit side resistance (qS) multiplied by qS. The value(s) of qS shall be determined by geotechnical analysis. Where a shaft passes through stratified soil having different values of qS for the various soil type layers, the value of QS shall be the shaft circumference multiplied by the summation of various qS values multiplied by the depth of the respective layer. In general, the top five feet (1,520 mm) of an embedded shaft and a bottom length equal to the diameter of the shaft tip or perimeter of the bell shall be considered as noncontributing to the side resistance of the shaft. Where the drilled shaft is located in scour susceptible areas, the probable depth of scour shall also be deducted when calculating the ultimate shaft side resistance. e.

Where rock sockets having a diameter equal to or less than the nominal diameter of the shaft are used, the ultimate tip capacity of the shaft shall be equal to the area of the socket tip multiplied by the uniaxial ultimate unit rock capacity. The ultimate socket side resistance shall be the product of the socket circumference, socket embedment and ultimate unit side shear resistance along the socket/rock interface.

f.

Unless an analysis is used which accounts for the load/deflection relationship of the various soil or rock strata encountered, the ultimate capacity of a drilled shaft which utilizes a rock socket shall be based on the sum of the ultimate tip and side resistance capacities of the rock socket only, neglecting side resistance of the shaft in the soil overburden.

24.3.2.4 Uplift Capacity The ultimate uplift capacity of a drilled shaft shall be equal to or less than the weight of the shaft plus 0.7 times the ultimate side resistance of the shaft. If belled, the uplift capacity of the shaft may be increased by taking

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into consideration the reinforcement details of the shaft and bell together with the strength characteristics of the adjacent soil. 24.3.2.5 Factors of Safety For drilled shafts in soil or socketed in rock, a minimum design factor of safety of 2.5 shall be used against bearing capacity failure. A factor of safety of 2.5 shall be used when designing for conditions which produce uplift. 24.3.2.6 Shafts Under Water1 a.

Wherever practicable, the drilled shaft shall be designed to permit the placing of the concrete in the dry, and for visual inspection of the hole, the bearing strata, and the rock socket.

b. When it is impractical to dewater the excavation for rock-socketed shafts, the concrete may be placed under water by means of a tremie or pumped concrete and appropriate allowances made in the concrete mix design. The water level shall have reached a static condition before concrete placement begins. c.

When concrete cannot be placed in the dry and a thorough visual inspection cannot be made by television or by divers, the Design Engineer shall reduce the allowable bearing and side resistance stress appropriately.

24.3.2.7 The Drilled Shaft a.

1

The drilled shaft is generally designed as a short column for axial loads due to the lateral support provided by the soil/rock. In muck or water, slenderness effects of the column must be taken into consideration.

b. When the drilled shaft is subjected to moment and lateral forces at the connection to the supported structure, the shaft must be designed for bending and shear in addition to axial force. Moment and shear along the length of the shaft must be calculated, and adequate reinforcement provided. c.

3

The shaft shall satisfy the design requirements of Part 2, Reinforced Concrete Design of this Chapter.

24.3.3 CONNECTION BETWEEN SUPPORTED STRUCTURE AND DRILLED SHAFT The connection between the drilled shaft and the supported structure (parts above the top of shaft) shall be capable of transferring the design loads, including direct load, shear and moment. This can be accomplished by the following means: a.

When the supported structure at the top of shaft is of concrete, the reinforcing steel cage shall be extended into the cap so that the load is transferred into the reinforcing steel of the drilled shaft by bond and into the concrete by compression.

b. When the cap section is a steel element, appropriate design shall be developed to transmit all loads, conforming to the requirements of Chapter 15, Steel Structures, Part 1, Design or Part 3, Fabrication.

24.3.4 GROUP ACTION OF DRILLED SHAFTS (2010) Evaluation of group shaft capacity assumes the effects of negative soil friction (if any) are negligible.

1

See C - Commentary (2010).

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Concrete Structures and Foundations 24.3.4.1 Cohesive Soil a.

Evaluation of group capacity of shafts in cohesive soil shall consider the presence and contact of a cap with the ground surface and the spacing between adjacent shafts.

b. If the cap is not in firm contact with the ground, or if the soil at the surface is loose or soft, the individual capacity of each shaft having a diameter B should be reduced by a reduction factor times QT for an isolated shaft. This factor equals 0.67 for a center-to-center (CTC) spacing of 3B and 1.0 for a CTC spacing of 6B. For intermediate spacings, the reduction factor may be determined by linear interpolation. The group capacity may then be computed as the lesser of: • the sum of the modified individual capacities of each shaft in the group, and • the capacity of an equivalent pier defined as the perimeter area of the group. For a shaft group with a cap in firm contact with the ground, Qult may be computed as the lesser of: • the sum of the individual capacities of each shaft in the group, or • the capacity of an equivalent pier as described above. For the equivalent pier, the shear strength of soil shall not be reduced by any factor to determine the QS component of Qult. The total base area of the equivalent pier shall be used to determine the QT component of Qult and the additional capacity of the cap shall be ignored. 24.3.4.2 Cohesionless Soil Evaluation of group capacity of shafts in cohesionless soil shall consider the spacing between adjacent shafts. Regardless of cap contact with the ground, the individual capacity of each shaft should be reduced by a reduction factor times QT for an isolated shaft. This factor equals 0.67 or a center-to-center (CTC) spacing of 3B and 1.0 for a CTC spacing of 8B. For intermediate spacings, the reduction factor may be determined by linear interpolation. The group capacity may be computed as the lesser of: a.

the sum of the modified individual capacities of each shaft in the group, or

b. the capacity of an equivalent pier circumscribing the group, including resistance over the entire perimeter and base areas. 24.3.4.3 Group in Strong Soil Overlying Weaker Soil a.

If a group of shafts which are embedded in a strong soil deposit overlies a weaker deposit (cohesionless or cohesive soil), consideration shall be given to the potential for a punching failure of the tip into the weaker soil strata.

b. If the underlying soil unit is a weaker cohesive soil strata, careful consideration shall be given to the potential for large settlements in the weaker layer.

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SECTION 24.4 MATERIAL 24.4.1 CONCRETE Unless otherwise stipulated in this specification, concrete shall be produced and placed in accordance with Part 1 of this Chapter. Concrete shall have a minimum compressive strength of 3,000 psi (21 MPa) in 28 days. Approved additives, such as set retarders, may be used to improve workability. Slump at time of placement shall be not less than 4 inches (100 mm), and not more than 6 inches (150 mm). If temporary casing is to be used, the slump should be not less than 5 inches (125 mm), and a set retarder may be necessary.

24.4.2 REINFORCING STEEL Unless otherwise stipulated in this specification, any required reinforcing steel shall conform to the requirements of Part 1 of this Chapter.

24.4.3 PERMANENT STEEL CASING MATERIAL (2010) If the steel casing is relied upon as a structural element, the steel casing material shall conform to the requirements of ASTM A252 or ASTM A709, Grade 36.

24.4.4 TEMPORARY CASING MATERIAL (2010) Casing that is not intended to be a structural element of the shaft or that is to be removed shall be considered temporary casing. Temporary casing may be metal, fiber or other material that possesses adequate strength for its intended purpose and is not detrimental to the design function of the shaft.

1

SECTION 24.5 CONSTRUCTION

3

24.5.1 CONTRACTOR QUALIFICATIONS Drilled shafts shall be installed by the Owner with experienced personnel, or by a Contractor or Subcontractor who specializes in such work. Availability of all required special equipment, tools, and experienced personnel are important items to be considered when determining Owner installation or selecting an installation contractor.

24.5.2 SHAFT EXCAVATION (2010) a.

When excavating a drilled shaft, earth walls shall be adequately and securely protected against cave-in, subsidence and/or displacement of surrounding earth, and for the exclusion of groundwater by means of temporary or permanent steel casings.

b. Whenever personnel are required to enter the shaft, a protective casing shall be used and there shall be adequate provisions for fresh air, light and protection from falling objects and toxic gases. c.

Rock grapples or special tools for removal of boulders or other obstructions must be readily available for use. Blasting will be permitted only upon obtaining written approval from the Engineer.

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Concrete Structures and Foundations

d. Inspection of the shaft base, and any socket, by a qualified inspector is highly recommended and should be omitted only with the approval of the Engineer. e.

No shaft excavation shall be made within 15 feet (4,570 mm) of an uncased shaft filled with concrete that is less than one day old. The construction procedure used shall be approved by the Engineer before commencing work.

24.5.3 CASING a.

Where called for, permanent steel casing shall be installed to the plan elevation or to the elevation designated by the Engineer in the field. When the top of the drilled shaft is below the surface of the ground, installation of additional large diameter casing may be required to extend above the working level to minimize the possibility of foreign materials or water entering the top of the shaft.

b. Casings shall be of adequate size and thickness to safely retain the adjacent earth materials and water from entering the shaft excavation, without exceeding allowable steel stresses, distortion, or collapse of the casing. c.

A protective casing is also to be provided, where required, to serve as protection for personnel entering the shaft excavations not provided with casings as specified above. Casing size and thickness shall meet the requirements stated above. The outside diameter of the protective casing shall be as large as possible, yet small enough to be lowered and removed without damage to the sides of the shaft.

d. If conditions are such that casing withdrawal will cause dislocation of the reinforcing steel or permit sloughing soils to enter the shaft, a double casing should be used. By this method, the shaft is drilled oversize and a temporary casing installed. A light gage permanent inner casing the same size as the required shaft diameter is then installed. This inner casing shall be of sufficient strength to serve as a form for the concrete shaft, but need not be designed for soil pressure. Concrete is then placed within the permanent inner casing. After the concrete has set, the annular space between the permanent casing and surrounding soil is filled with grout, lean concrete, sand or by another approved method and the temporary outer casing is withdrawn.

24.5.4 BELLS OR UNDERREAMS Before belling, the Engineer shall determine that the formation encountered at the plan elevation is adequate. When shafts are required to be belled, the bells shall be formed either by hand or by use of special belling equipment to the angle and slope called for on the drawings. The bottoms of bells shall be thoroughly cleaned of all loose materials and inspected before the concrete is placed.

24.5.5 SOCKETS When sockets are required, they shall be formed by machine or by hand to the proper size and depth called for in the plans. Sides and bottom of sockets must be thoroughly cleaned of all loose material since the bond of the concrete to the socket sides is used in design.

24.5.6 TOLERANCES (2010) The center of the top of each shaft shall not vary from its design location by more than 1/24 of the shaft diameter, or 3 inches (75 mm), whichever is less, and the shaft shall not be out of plumb by more than 1.5 percent of the length, not exceeding 12.5 percent of shaft diameter.

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24.5.7 DEWATERING Suitable dewatering procedures shall be as agreed upon between the Engineer and Contractor as determined at such time as conditions warrant. Unless otherwise agreed, the shaft at the time of placement of steel reinforcing cage, if any, and concrete shall be essentially free of standing water in excess of 2 inches (50 mm) deep.

24.5.8 INSPECTION (2010)1 Immediately prior to placement of any reinforcement or concrete, each shaft shall be thoroughly inspected as directed by the Engineer to ascertain that the shaft has been properly prepared, that the bearing material is compatible with design requirements, and whether additional investigation of the bottom is required. If conditions vary from the assumed conditions determined by the borings, additional investigation shall be conducted as directed by the Engineer.

24.5.9 PLACING REINFORCING STEEL (2010) Reinforcing steel shall be prefabricated and placed as a unit immediately prior to concrete operations. In order to minimize displacement of reinforcing steel cage when casing is pulled, the cage may be reinforced by welding horizontal bands to the cage at about 5 feet (1,520 mm) intervals. When concrete is placed by tremie methods, temporary hold-down devices shall be employed to prevent uplift of the cage during concrete placement.

24.5.10 PLACING CONCRETE

1

24.5.10.1 Dry Hole Prevent segregation of concrete through use of tube, sectionalized pipe or other means to direct the free fall of concrete, so that it does not strike the sides of reinforcement in the shaft. 24.5.10.2 Under Water

3

Utilize a tremie or pumped concrete in accordance with Part 1, Materials, Tests and Construction Requirements, Article 1.15.10 and Part 24, Drilled Shaft Foundations, Article 24.3.2.6. 24.5.10.3 Consolidation

4

Rodding or mechanical vibrating is necessary only for the top 5 feet (1,520 mm) of shaft. Any special requirements for concrete placement shall be approved by the Engineer.

24.5.11 CASING REMOVAL (2010) a.

In situations where temporary casing is to be removed, the head of concrete inside the casing must be adequate to preclude infiltration of water and sluffage of the shaft face and sides.

b. Elapsed time from beginning of concrete placement in cased portion of shaft, until extraction of casing is begun, shall not exceed one hour. c.

1

Extreme care shall be taken when a casing is removed to prevent subsidence of the surrounding ground.

See C - Commentary (2010).

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d. Elevation of top of the steel cage should be carefully checked before and after casing extraction. The top of the concrete shall not raise during extraction of the casing. e.

The exterior temporary casing, if a double-cased shaft, shall not be removed until three (3) days after the shaft is poured.

24.5.12 CONTINUITY OF WORK Drilled shaft construction work shall be planned so that all required operations proceed in a continuous manner until the shaft is complete. A precise time schedule agreement between the Contractor and the Engineer should be established. Provision shall be made for protecting the shaft and adjacent construction in case of unforeseen interruptions. Such provisions shall be approved by the Engineer before drilling begins.

24.5.13 RECORDS An accurate record shall be kept of each drilled shaft as installed. The record shall show the top and bottom elevations, shaft and bell diameters, depths of test holes if required, date the shaft is excavated, inspection report of the bearing stratum, depth of water in excavation at time of placing steel and concrete, quantity of concrete placed compared with theoretical quantity, and any other pertinent data. Records shall be made and signed by both the project superintendent and inspector and distributed to proper authorities daily.

SECTION 24.6 TESTING 24.6.1 MATERIAL TESTING (2010) Materials used in construction of drilled shafts should be sampled and tested as designated elsewhere in Part 1 of this Chapter. At least two (2) concrete test cylinders shall be taken for each shaft. When permanent steel casing is used in determining the capacity of the shaft, certified mill test reports in accordance with the provisions of Chapter 15 shall be provided to document the adequacy of the material properties of the casing.

24.6.2 CAPACITY TESTING (2010)1 Drilled shafts may be static load tested per ASTM D1143 “Standard Method of Testing Piles under Axial Compressive Load.” As an alternate, drilled shafts may be tested by use of a hydraulic load cell or other method as approved by the Engineer.

24.6.3 INTEGRITY TESTING (2010)1 It is essential that the excavation for drilled shafts, placement of permanent casing or placement and extraction of temporary casing, placement of reinforcing steel and placement of concrete be conducted in a manner such that all construction operations are under close supervision to verify that completed shaft will not contain any voids, deleterious or other extraneous material or other defects that may reduce the ability of the shaft to support its design loading. When shafts are constructed under conditions where all elements of the shaft’s construction cannot be reliably inspected, the use of Crosshole Sonic Log (CSL) testing shall be employed to verify the integrity of the shaft(s).

1

See C - Commentary (2010).

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CSL testing shall be performed by firms specializing in such testing and having a minimum of 5 years prior documented related experience. Prior to testing, testing personnel, their qualifications and all elements of the testing process shall be submitted to the Engineer for approval. All CSL testing procedures and equipment shall conform to the requirements of ASTM D6760. CSL testing shall not commence until a minimum of 24 hours has elapsed after placement of the shaft concrete.

C - COMMENTARY (2010) C - 24.1.1 SCOPE (2010) (Bibliography 79) f.

Vertical drilled shafts, adequately reinforced, can accommodate significant lateral loading. Internal moments and shears are highly dependent not only on the loading condition, but also on the physical properties of the material through which the shaft passes. For additional information see Handbook on Design of Piles and Drilled Shafts Under Lateral Load, U.S. DOT Report No. FHWA–IP-84-11 and Drilled Shafts: Construction Procedures and Design Methods, U.S. DOT Report No. FHWA-IF-99-025.

C - 24.3.2 THE TRANSFER OF LOAD FROM THE DRILLED SHAFT TO THE ROCK OR SOIL BEARING STRATA (2010) For drilled shafts it is very important that the engineer work closely with the geotechnical engineer in order that both have a clear understanding of what portion of the applied load to the drilled shaft is resisted by side friction and what is resisted by end bearing. The interaction of side friction with end bearing is often very complex and the possibility of large and possibly unsafe settlement occurring prior to complete mobilization of the anticipated end bearing resistance must be considered.

1

C - 24.3.2.6 SHAFTS UNDER WATER (2010) When drilled shafts are to be constructed under water the concrete as it is placed in the casing may carry miscellaneous debris (rock cuttings, sediment, diluted concrete, etc.) to the top of the shaft. Therefore, the top portion of the shaft in this situation may contain poor quality concrete. It is recommended for such conditions that concrete in the casing be carried 1 to 2 feet (300 to 600 mm) above the final top of shaft elevation to allow for the careful removal of that portion of the shaft which may contain such deleterious material.

3

C - 24.5.8 INSPECTION (2010)

4

For further information on the inspection of drilled shafts, the following document is available. Drilled Shaft Inspector’s Manual Deep Foundations Institute 326 Lafayette Avenue Hawthorne, NJ 07506

C - 24.6.2 CAPACITY TESTING (2010) In lieu of a static load test which may be inefficient due to the typical large capacity of drilled shafts relative to driven piles, consideration may be given to the use of a hydraulic load cell referred to as an Osterberg Cell®. This test method uses an instrumented hydraulic cell placed typically near the tip of the shaft. After placement and curing of the shaft concrete the cell is activated, loading the tip of the shaft and providing an upward force on the shaft above the cell. The use of the cell thus can provide a measurement of tip base capacity as well as the frictional force developed along the side of the shaft. After testing, the hydraulic fluid is replaced with a

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Concrete Structures and Foundations

high strength grout. Use of this test method should be reserved for experienced specialty contractors and requires the submission and approval of proposed test details.

C - 24.6.3 INTEGRITY TESTING (2010)1 In the past the taking of concrete cores of drilled shafts was the primary means of ascertaining the quality and consolidation of the shaft concrete. As an alternate to coring for determination of the quality of drilled shaft concrete, the measurement of the response of ultrasonic pulse waves as they pass from a signal source to a receiver source within the shaft concrete will provide an indication of the soundness of shaft. This method of testing is often referred to as Crosshole Sonic Log (CSL) Testing. This method utilizes a number of tubes placed within the shaft to allow for transmission and reception of the ultrasonic pulse waves. After testing, the tubes are fully grouted. As opposed to coring, which verifies the concrete quality in the immediate vicinity of the core only, CSL Testing provides for greater coverage of the shaft. CSL Testing is, however, limited to the area of the shaft within the arrangement of the CSL tubes and therefore does not provide an assessment of concrete quality outside of the interior of the reinforcing steel cage. Also the decision to use CSL Testing must be made before concrete placement. Therefore, if anomalies occur during the placement of the shaft concrete, which may lead to questioning of the concrete integrity, coring remains the only viable test for such situations. Use of Crosshole Sonic Log Testing should be reserved for specialty firms with satisfactory experience in the use of this method. Prior to testing, submittals detailing the materials to be used, the number of tubes, the vertical spacing of the tests and the procedures to be employed should be made to the engineer for review and approval, if acceptable. Where the CSL test indicates void or other anomalies present in the shaft, or when supplementary testing when the concrete for the shaft is placed under water or where the use of a slurry is employed, the use of sample cores of approximate 2 inches (50 mm) in diameter and extending the entire length of the shaft may be employed to verify the adequate consolidation and composition of the concrete. After coring, the hole shall be filled with a cement grout compatible with the shaft concrete. Reference: Osterberg, J.O. and S.F. Pepper, A New Simplified Method for Load Testing Drilled Shafts, Foundation Drilling, Association of Drilled Shaft Contractors, August 1984, pp.9-11.

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Part 25 Slurry Wall Construction1 — 2002 — TABLE OF CONTENTS

Section/Article

Description

Page

25.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.1.1 Purpose (2002). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.1.2 Scope (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.1.3 References (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-25-2 8-25-2 8-25-2 8-25-3

25.2 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.2.1 General (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.2.2 Qualifications (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.2.3 Subsurface Investigation (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.2.4 Construction Phase (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.2.5 Methods of Increasing Stability (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.2.6 Final Condition (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-25-3 8-25-3 8-25-3 8-25-3 8-25-3 8-25-6 8-25-6

25.3 Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.3.1 Slurry (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.3.2 Bentonite (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.3.3 Cement (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.3.4 Water (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.3.5 Additives (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.3.6 Backfill (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.3.7 Tremie Concrete (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.3.8 Precast Panels (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.3.9 Permanent Joint Beams (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.3.10 Materials Quality Control (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-25-7 8-25-7 8-25-7 8-25-7 8-25-8 8-25-8 8-25-8 8-25-9 8-25-9 8-25-9 8-25-9

25.4 Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.4.1 General (1988) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.4.2 Trench Excavation (2002). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.4.3 Slurry Material (2002). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.4.4 Wall Construction (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.4.5 Inspection (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-25-10 8-25-10 8-25-10 8-25-11 8-25-12 8-25-13

1

References, Vol. 89, 1988, p. 114. Adopted 1988.

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LIST OF FIGURES Figure

Description

Page

8-25-1 Forces in Non-Cohesive Soils . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-25-5

LIST OF TABLES Table

Description

Page

8-25-1 Backfill Gradation Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-25-2 Materials Quality Control Program . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-25-8 8-25-9

SECTION 25.1 GENERAL 25.1.1 PURPOSE (2002) These specifications apply to the use of bentonite slurry trenching techniques for the construction of underground foundations and cutoff walls. Other materials such as polymers may be considered as an alternative to bentonite.

25.1.2 SCOPE (2002) a.

The use of bentonite slurry to permit deep, unshored excavation work is an effective construction method when properly employed. The susceptibility to slurry trench techniques of any proposed site must be established by subsurface investigation.

b. In practice, excavations are kept constantly filled with a bentonite slurry during both digging and backfilling operations. The excavation is held open by the hydrostatic thrust of the slurry. Formation of an impermeable bentontitic seal, or filter cake, at the trench interface prevents slurry loss and allows the development of the hydrostatic head. Presence of slurry in the trench also prevents the drawdown of the ground water table, a frequent result of open excavation work. c.

Slurry applications include temporary and permanent construction of concrete foundation walls, both precast and cast-in-place, and flow-controlling cutoff walls. Critical procedures such as cleaning the slurry, cleaning the bottom of the trench and checking slurry density prior to placing tremie concrete should be considered.

d. The engineer’s decision to use the slurry trench method on an excavation project, and the design of the appropriate slurry, must be based on: (1) Analysis of subsurface investigations. (2) Soil stability analysis. (3) Risk assessment. (4) Site constraints.

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(5) Economic alternatives analysis. (6) Possible adverse effects of stray current on slurry quality.

25.1.3 REFERENCES (1988) References for Part 25, Slurry Wall Construction are found at the end of this chapter. Refer to Reference 6, 7, 9, 17, 36, 59, and 108.

SECTION 25.2 DESIGN 25.2.1 GENERAL (1988) a.

Slurry walls are designed in large part according to accepted foundation engineering practices; however, the interaction of the slurry and the surrounding soil affects the stability and functionality of the wall to a much greater degree than in most other structure types.

b. Slurry walls must be designed for both the construction and the final conditions. While the design for one condition affects the other, different forces and criteria apply.

1

25.2.2 QUALIFICATIONS (2002) It is highly recommended that the engineer for the design of the slurry wall have previous experience in the design of slurry trench construction.

25.2.3 SUBSURFACE INVESTIGATION (1988)

3

Subsurface investigation prior to the design of the slurry system shall be in accordance with Part 22, Geotechnical Subsurface Investigation. Additional information, such as permeability and pH of the soil, may also be required as part of this investigation.

25.2.4 CONSTRUCTION PHASE (2002)

4

25.2.4.1 Trench Design Design of the slurry trench for the construction phase has the following objectives: a.

Provide stability of the trench during excavation.

b. Prevent drawdown of groundwater. c.

Minimize settlement of surrounding soil and structures bearing thereon.

d. Minimize loss of the slurry into the groundwater of particular concern in very porous soils. e.

Assurance of integrity of adjacent structures.

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Concrete Structures and Foundations 25.2.4.2 Stability Analysis a.

The hydrostatic pressure from the slurry in the trench provides the main stabilizing force to offset the pressures acting on the trench walls. These include pressures due to: (1) Soil loads; (2) Surcharge loads, including structures and construction equipment; (3) Fluid pressures due to groundwater.

b. The factor of safety of the trench, with respect to stability based on these pressures, is calculated as follows: Pf F. S. = ------------------Pa + Ps (1) For cohesive soils 2

gH P a = ---------- – 2S u H 2 Ps = qs H Assuming f = 0 (2) For non-cohesive soils (Figure 8-25-1). Pa = P1 + P2 + P3 + Pw ( H – Hw ) P 1 = ( H – H w )gK a -----------------------2 P 2 = ( H – H w )gK a ( H w ) Hw P 3 = ( H w g¢K a )-------2 Hw P w = H w g w -------2 2

2 2 ( H – Hw ) ( Hw ) ( Hw ) gw P a = --------------------------( gK a ) + H w ( H – H w )gK a +---------------+ ( g¢K a ) ----------------------2 2 2

Ps = K a qs H

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where: Su = Undrained Shear Strength qs = Surcharge Loading H = Depth of Trench Hf = Depth of Slurry Hw = Depth of Water Table Above Bottom of Trench g = Unit Weight of Soil gf = Unit Weight of Slurry gw = Unit Weight of Water g’ = Unit Weight of Submerged Soil Ka = Active Coefficient Pa = Active Pressure Ps = Pressure Due to Surcharge Pf = Slurry Pressure f = Angle of Internal Friction c.

Fluctuations in groundwater elevations have a large effect upon the stability equation above. Therefore, in areas of porous soil adjacent to bodies of water or other locations where the water table may vary quickly, the water table shall be monitored.

d. In addition to the force from the fluid pressure of the slurry, the formation of the slurry cake which develops at the soil-slurry interface may contribute to the stability of the trench. Due to this, the minimum allowable factor of safety for slurry trenches is often lower than that used in the stability analyses of other systems where this interaction between the soil and the retaining substance does not occur. The appropriate factor of safety for the trench shall be determined by the Engineer, based upon previous experience with slurry walls, the soil type and an overall project risk assessment, including the risk involved to the surrounding track or structures.

1

3

4

Figure 8-25-1. Forces in Non-Cohesive Soils

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25.2.5 METHODS OF INCREASING STABILITY (1988) A number of measures may be taken to increase the stability of the trench: a.

Adjusting slurry level and density to increase the hydrostatic pressure within the trench.

b. The water table outside of the trench may be lowered by means of well points to decrease the hydrostatic pressure outside the trench. Lowering the water table may increase settlement outside of the trench. c.

Grouting to lessen loss of slurry into coarse gravel layers, to lessen sloughing off of wall surfaces into the trench in loose materials or to increase bearing capacity in areas with surcharge loads.

d. Adjusting the length of cut open at one time in order to increase the arching action in the soil.

25.2.6 FINAL CONDITION (2002) 25.2.6.1 Wall The design of the wall for the final condition is dependent upon the type and purpose of wall. 25.2.6.2 Cutoff Walls Slurry cutoff walls may be of either soil-bentonite or cement-bentonite construction. The design of either system shall be based, in part on the following factors: a.

Permeability. In order to be effective, cutoff walls must be keyed into an underlying aquaclude (impervious layer). The soil-bentonite or cement-bentonite mixture shall be designed and tested for the desired degree of permeability, as required to contain the lateral flow of the groundwater. It should be determined that chemical attack on the cutoff wall from toxic wastes or acids will not reduce the efficiency of the walls.

b. Strength. The cutoff wall shall have sufficient strength to withstand the hydraulic gradient across the wall, in addition to pressures from any embankment or surcharge. c.

Flexibility. The wall should be sufficiently flexible to withstand movements due to deformation of the adjacent soil under the loads listed in Article 25.2.4.2.

25.2.6.3 Foundation Walls Foundation walls should be designed (see Part 2, Reinforced Concrete Design) for the following applicable horizontal and vertical loads: a.

Earth pressure.

b. Hydrostatic pressure from the difference in water table on the opposite sides of the wall. c.

Live load and structure surcharges on the retained fill.

d. Direct live and dead loads on the wall.

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SECTION 25.3 MATERIALS 25.3.1 SLURRY (2002) 25.3.1.1 Bentonite-Water Slurry Slurry consists of a stable colloidal suspension of bentonite in water and shall be controlled in accordance with the most current American Petroleum Institute (API) Standard 13B, “Standard Procedure for Field Testing Drilling Fluids,” and the following requirements: a.

At the time of introduction of the slurry into the trench the slurry shall be a mixture of not less than 18 pounds (8.16 kg) of bentonite per barrel (42 gallons) (159 l) of water. Additional bentonite may be required, depending on the hardness and temperature of the water and the quality of the bentonite. The slurry shall have a minimum apparent viscosity of 15 centipoise or 40 seconds reading through a Marsh Funnel Viscosimeter at 68 F (20 C), a maximum filtrate loss of 30 cubic centimeters (1.83 in3) in 30 minutes at 100 psi (690 kPa), and a pH of not less than eight.

b. The slurry mixture in the trench shall have unit weight not less than 64 pcf (1.03 gm/cc) and not greater than 87 pcf (1.40 gm/cc). 25.3.1.2 Soil-Bentonite Slurry The slurry to be mixed with the soil should be either slurry taken from the trench or slurry meeting the requirements of slurry introduced into the trench. If slurry from the trench is used, it shall be cleaned of unsuitable excavated materials (lumps) and tested prior to reuse.

1

25.3.1.3 Cement-Bentonite Slurry The Cement-Bentonite slurry consists of a stable suspension of cement in a bentonite water slurry and shall be controlled in accordance with the most current API Standard 10A: “Well Cements” and the following requirements: a.

At the time of introduction of cement in the bentonite-water slurry, the bentonite slurry shall have a minimum 34 seconds reading through a Marsh-Funnel, 1,500 ml (91.5 in3) in and 1,000 ml (61.0 in3) out.

b. Cement should be weighed and added to the bentonite slurry to produce a cement-water ratio of 0.20 by weight. c.

At the time of introduction in the trench, the cement-bentonite slurry should be generally proportioned so as to have a viscosity corresponding to a Marsh Funnel reading not less than 40 seconds or more than 50 seconds, as measured at the batch plant. If a reading falls outside these limits, the next batch will be corrected to fall within the limits.

25.3.2 BENTONITE (2002) Bentonite used in preparing slurry shall be pulverized (powder or granular) premium grade sodium cation montmorillonite and shall meet the most current API Standard 13A “Drilling Fluid Materials.”

25.3.3 CEMENT (2002) a.

3

Cement used in Cement-Bentonite slurry shall conform to ASTM C150, “Requirements for Portland Type 1 Cement.”

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b. Cement used in tremie concrete shall conform to the requirements of Part 1, Materials, Tests and Construction Requirements.

25.3.4 WATER (1988) Fresh water, free of deleterious substances that adversely affect the properties of the slurry, shall be used to manufacture bentonite slurry. It is the responsibility of the Contractor that the slurry resulting from the water shall always meet the standards of this Specification.

25.3.5 ADDITIVES (2002) Additives such as softening agents, dispersants, retarders or plugging or bridging agents, may be added to the water or the slurry to permit efficient use of bentonite and proper workability of the slurry only with the approval of the Engineer.

25.3.6 BACKFILL (2002) a.

When consolidation of the trench backfill is a concern, the material for trench backfilling for a Soil/Bentonite slurry trench cutoff wall shall be composed of slurry and selected granular soils obtained from the excavation and/or designated borrow areas. The soil shall be friable and free from roots, organic matter, or other deleterious materials. The backfill shall be thoroughly mixed and reasonably wellgraded between the gradation limits found in Table 8-25-1. Table 8-25-1. Backfill Gradation Limits U.S. Standard (metric)

Percent Passing by Dry Weight

3/8 inches (9.5 mm)

65 to 100

No. 20 (850 micrometers)

35 to 85

No. 200 (75 micrometers)

15 to 35

b. When a coefficient of permeability for the backfill must be less than or equal to 1 ´ 10-7 cm/sec, the fines in the backfill mix shall have sufficient plasticity so that the material can be rolled into a 1/8 inch (3 mm) thread without crumbling. The water content of the backfill material shall not exceed 20% prior to blending with bentonite slurry. Laboratory permeability tests shall be run to verify the suitability of the mix. Dry bentonite may be added to further decrease the permeability if needed. c.

When consolidation of the backfill is not a concern and a coefficient of permeability in excess of 1 ´ 10-6 cm/sec for the wall is acceptable, the excavated soil, cleaned of deleterious material, should be used for economy.

d. The material used to backfill trenches where precast panels are used shall be composed of any fine grain soil of low plasticity capable of flowing in place between the precast panel and the walls of the trench excavation. Alternately, the void between panels can be filled with an approved grout mix such as cement-bentonite.

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25.3.7 TREMIE CONCRETE (2002) Unless otherwise stipulated in this Specification, concrete shall be produced and placed in accordance with Part 1, Materials, Tests and Construction Requirements. Concrete shall have a minimum compressive strength of 4,000 psi (28 MPa) in 28 days. Approved additives, such as set retarders, may be used to improve workability. Slump at time of placement shall not be less than 8 inches (200 mm).

25.3.8 PRECAST PANELS (2002) Design of precast panels shall meet all requirements of Part 2, Reinforced Concrete Design.

25.3.9 PERMANENT JOINT BEAMS (1988) If used with cast-in-place concrete walls, permanent joint beams shall be precast concrete or steel shapes.

25.3.10 MATERIALS QUALITY CONTROL (1988) a.

Proper quality control shall be maintained for the cutoff wall construction, under the direction of a qualified engineer. Testing requirements are summarized in Table 8-25-2.

b. Results of all tests performed in accordance with the Specification should be recorded.

1

Table 8-25-2. Materials Quality Control Program Subject Materials Water

Additives

Bentonite

Standard –

–

Type of Test

Minimum Frequency

– pH Per Water Source or As Required to Properly – Total Hardness as Changes Occur Hydrate Bentonite with Approved Additives Manufacturer Certificate of Compliance with Stated Characteristics

API Std. 13A Manufacturer Certificate of Compliance

Backfill Soils

–

Cement (for Cement– Bentonite Slurry Wall)

ASTM C150

Specified Values

As Approved by Engineer

Premium Grade Sodium Cation Montmorillonite

Selected Soils Obtained from a Borrow 65% to 100% Passing 3/8 Area Approved by the Engineer inches Sieve (9.5 mm) 35% to 85% Passing #20 Sieve (850 micrometers) 15% to 35% Passing #200 Sieve (75 micrometers) Roll to 1/8 inch (3 mm) Thread Manufacturer Certificate of Compliance

Portland, Type I

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8-25-9

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Concrete Structures and Foundations Table 8-25-2. Materials Quality Control Program (Continued) Subject Slurry

Backfill Mix

Prepared for Placement into the Trench

Standard

Type of Test

API Std. 13B – Unit Weight – Viscosity – Filtrate Loss – pH

Minimum Frequency

Specified Values

One Set per Shift or Unit Weight ³ 64 lb/cu. ft. Per Batch (Pond) (1.03 gm/cc) V ³ 15 Centipoise or 40 Sec-Marsh @ 68 degrees F (20 degrees C) Loss £ 30 cc in 30 min @ 100 psi (690 kPa) pH ³ 8

In Trench

API Std. 13B 1 – Unit Weight

One Set per Shift at Unit Weight = 64 - 87 Point of Trenching lb/cu. ft. (1.03 – 1.40 gm/cc) and Near the Bottom of Trench

At Trench

ASTM C143

– Slump – Gradation

One Set per 200 Cubic Yards (153 m3 )

Slump 2 inches to 6 inches (50 mm to 150 mm) 65% to 100% Passing 3/8 inches Sieve (9.5 mm) 35% to 85% Passing #20 Sieve (850 micrometers) 15% to 35% Passing #200 Sieve (75 micrometers)

– C/W Ratio – Viscosity

Each Batch Five per Shift

C/W = 0.20 V = 40 to 50 Sec-Marsh

Cement- Upon API Std. 13B Bentonite Introduction API Std. 10 Slurry in the Trench

SECTION 25.4 CONSTRUCTION 25.4.1 GENERAL (1988) The construction of precast, cast-in-place, and flow-controlling cutoff walls all generally follow the same construction techniques, i.e., trench excavation under the influence of a restraining bentonite slurry fluid, and fluid replacement by a wall or barrier material. Construction methods shall be such that slurry material is contained and controlled to prevent loss of trench excavation, leaks, spillage, and then properly disposed.

25.4.2 TRENCH EXCAVATION (2002) 25.4.2.1 General The trench shall be constructed to line and grade and tolerances as shown on the plans. Boring logs indicate the general type of materials to be excavated.

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Slurry Wall Construction 25.4.2.2 Pretrenching Pretrenching shall be performed to relocate, remove, or preserve utilities. Isolated additional excavations “in the dry” may be needed to remove obstructions. 25.4.2.3 Trenching Method a.

Trenching should be performed using suitable earth-moving equipment, such as grab or clamshell buckets, backhoe, chisels, drills, special patented equipment, or other means for the removal of material. Excavation shall be to full-depth at the point of start, proceed along the trench line full-depth and be performed under bentonite slurry. Methods and techniques are chosen to minimize over-excavation, loosening and/or caving of material outside the designated wall width.

b. Guide walls are commonly constructed ahead of the trenching operations to assist in the control of line and grade, protect the trench sides against sloughing and/or caving of material, support surcharge loads, and act as a reservoir for the slurry. c.

The distance of trench excavation at any one time should not exceed practical limits for placement of permanent wall material in a given period of time.

d. Additional equipment, such as an air lift, pump, or clamshell buckets, may be needed to clean the trench bottom of loose material. Means shall be provided to verify the trench depth and condition prior to wall construction. e.

Continuous trenching may be allowed in soil-bentonite wall construction, but individual panels with joints are required for reinforced concrete wall construction.

f.

Joints are very important and their design and detail should be carefully considered.

1

25.4.3 SLURRY MATERIAL (2002)

3

25.4.3.1 General Sufficient batch plant mixers, pumps, supply lines, ponds and tanks, and reserve material shall be provided to assure proper mixing and placement of the slurry. No slurry shall be prepared in the trench. Mixing of water and bentonite shall continue until bentonite particles are fully hydrated and the resulting slurry appears homogeneous. The slurry shall be agitated or recirculated in storage ponds or tanks as required to maintain a homogeneous mix. 25.4.3.2 Slurry Introduction At the start of trench excavation, the bentonite slurry shall be introduced into the excavation. 25.4.3.3 Slurry Maintenance The slurry shall be maintained in the excavated trench until the completion of the excavation and displacement of the wall construction. The slurry level shall meet the design requirements of Section 25.2, Design and be maintained within a reasonable distance from the top of excavation, generally within 3 feet (1 m), and at least 2 feet (0.7 m) above the groundwater level. The Contractor shall have sufficient personnel, equipment, and material ready to raise the slurry level at any time.

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Concrete Structures and Foundations 25.4.3.4 Quality Control The Contractor shall maintain his own quality control under the direction of a qualified engineer. Testing of the slurry shall be performed each working shift and shall include testing slurry pH, unit weight, filtration loss, and viscosity. 25.4.3.5 Slurry Disposal As the slurry is displaced by the construction of the wall, means shall be provided for holding the fluid or for its disposal. No slurry shall be left in ponds at the site. Proper disposal of the slurry shall be the Contractor’s responsibility.

25.4.4 WALL CONSTRUCTION (2002) 25.4.4.1 General In addition to the above general construction requirements and methods, the following should be considered by the designer: 25.4.4.2 Cutoff Wall (Soil-Bentonite) a.

Introduce and maintain bentonite-water slurry into the trench. It is essential that the bottom of the slurry trench be keyed a minimum specified penetration into the underlying aquaclude, as indicated by soil borings.

b. Prepare wall material per project requirements. Soil-bentonite wall material (backfill) shall be composed of slurry and selected soils obtained from designated borrow areas. The soil shall be free of organic or other deleterious materials. The backfill shall be thoroughly mixed to a homogeneous paste consistency and reasonably well-graded. c.

Place the wall material continuously, starting at the beginning of the trench in a manner that will produce a homogeneous wall free of voids or pockets of slurry. Before drying occurs, the top of the wall shall be capped.

25.4.4.3 Cutoff Wall (Cement-Bentonite) a.

Introduce and maintain cement-bentonite slurry into the trench. If, at any time, the slurry in the trench begins to set or gel before excavation is complete to the full-depth, or otherwise becomes unworkable, additional freshly prepared cement-bentonite shall be introduced. Addition of water to slurry in the trench shall not be permitted.

b. It is essential that the bottom of the slurry trench be keyed a minimum specified penetration into the underlying aquaclude, as indicated by soil borings. c.

After initial set, the top of the completed wall shall be checked for decantation. After the wall has been topped off and set, but before drying occurs, the wall shall be capped.

d. Any time that a wall segment is extended where the slurry in the previously excavated trench has taken a set, a minimum of 3 feet (1 m) overlap into the previously excavated trench shall be removed. 25.4.4.4 Cast-in-Place Concrete Wall a.

Trench to the line and grade shown on the plans, introducing water-bentonite slurry as trenching progresses. Trench length open at any one time should not exceed the capacity for placing concrete.

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b. Set panel end forms or joint material as required by the plans. c.

Place reinforcement (bars or structural steel) in slurry (for reinforced wall construction).

d. Place wall concrete by tremie (gravity flow or pump) using high slump concrete with 3/4 inches (2 cm) maximum size aggregate, of the compressive strength designated on the plans. The concrete placement shall be controlled to prevent segregation and not be allowed to fall through the slurry, but rather placed on the trench bottom and allowed to displace slurry in accordance with Part 1, Materials, Tests and Construction Requirements. e.

The wall top shall be finished to the grade designated on the plans.

f.

Additional requirements for cast-in-place concrete wall construction are beyond the scope of these specifications.

25.4.4.5 Precast Panel Wall a.

Trench to the line and grade shown on the plans, introducing water-bentonite slurry as trenching progresses. Trench length should not exceed the capacity for placing precast panels and tremie concrete.

b. Place precast panels in trench (held in position by guide restraints) displacing the slurry fluid. c.

Place tremie concrete at toe of set precast panels as shown on the plans.

d. Backfill with granular material between panel and trench after concrete has set. Remove panel restraints.

1

25.4.5 INSPECTION (2002) Only competent and experienced contractors, prequalified by the Railroad, should be engaged for slurry wall construction. Slurry trench specialists (as approved by the Railroad) shall supervise the construction, slurry preparation, and quality control. Documentation of all materials used shall be furnished to the Railroad, along with certification that the wall construction conforms to the requirements of the plans and all applicable environmental regulations.

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Part 26 Recommendations for the Design of Segmental Bridges1 — 1996 — TABLE OF CONTENTS

Section/Article

Description

Page

26.1 General Requirements and Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.1.1 General (1996). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.1.2 Notations (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.1.3 Terms (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.1.4 Concrete (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.1.5 Segmental Bridges, Design Reinforcement (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-26-4 8-26-4 8-26-4 8-26-7 8-26-8 8-26-8

26.2 Methods of Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.2.1 General (1996). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.2.2 Strut-and-Tie-Models (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.2.3 Effective Flange Width (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.2.4 Transverse Analysis (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.2.5 Longitudinal Analysis (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-26-8 8-26-8 8-26-8 8-26-8 8-26-11 8-26-12

26.3 Design Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.3.1 General (1996). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.3.2 Dead Loads (1996). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.3.3 Erection Loads (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.3.4 Thermal Effects (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.3.5 Creep and Shrinkage (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.3.5 Creep and Shrinkage (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-26-12 8-26-12 8-26-13 8-26-13 8-26-13 8-26-16 8-26-16

26.4 Load Factors. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-26-16 26.4.1 General (1996). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-26-16 26.4.2 Service Load Combinations for Part 2, Reinforced Concrete Design, Article 2.2.4 (1996)8-26-16 26.4.3 Strength Reduction Factors (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-26-17 26.4.4 Construction Load Combinations, Stresses and Stability (1996). . . . . . . . . . . . . . . . . . 8-26-18 26.5 Allowable Stresses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.5.1 Prestressing Steel (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.5.2 Prestressed Concrete (1996). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

8-26-21 8-26-21 8-26-21

References, Vol. 97, p. 60. Adopted 1996.

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TABLE OF CONTENTS (CONT) Section/Article

Description

Page

26.6 Prestress Losses (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-26-22

26.7 Flexural Strength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.7.1 General (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.7.2 Strain Compatibility (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.7.3 Center of Gravity Correction for Strand Tendons (1996) . . . . . . . . . . . . . . . . . . . . . . .

8-26-23 8-26-23 8-26-23 8-26-23

26.8 Shear and Torsion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-26-23 26.8.1 Scope (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-26-23 26.8.2 General Requirements (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-26-24 26.8.3 Traditional Shear and Torsion Design for Plane Section Type Regions (1996) . . . . . 8-26-27 26.8.4 Strut-and-Tie Truss Model Design for Either Beam Type or Discontinuity Regions (1996)8-26-29 26.8.5 Special Requirement for Diaphragms, Deep Beams, Corbels and Brackets (1996) . . . 8-26-31 26.8.6 Shear Transfer at Interfaces (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-26-32 26.8.7 T wo-way Punching Shear (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-26-32 26.9 Fatigue Stress Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.9.1 Fatigue Stress Limits for Bonded Nonprestressed Reinforcement (1996) . . . . . . . . . . 26.9.2 Fatigue Stress Limits for Prestressed Reinforcement (1996) . . . . . . . . . . . . . . . . . . . .

8-26-32 8-26-32 8-26-33

26.10 Design of Local and General Anchorage Zones, Anchorage Blisters and Deviation Saddles8-26-33 26.10.1 General (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-26-33 26.10.2 Forces and Reinforcement in General Anchorage Zones (1996) . . . . . . . . . . . . . . . . . . 8-26-34 26.10.3 Reinforcement (1996). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-26-34 26.10.4 Reinforcement Detailing (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-26-34 26.10.5 Anchorages in Special Blisters (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-26-35 26.10.6 Anchorages in Diaphragms (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-26-35 26.10.7 Anchorage Bearing Reaction Force (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-26-35 26.10.8 Deviation Saddles (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-26-35 26.11 Provisional Post-Tensioning Ducts and Anchorages . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.11.1 General (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.11.2 Bridges with Internal Ducts (1996). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.11.3 Provision for Future Dead Load or Deflection Adjustment (1996) . . . . . . . . . . . . . . . .

8-26-36 8-26-36 8-26-36 8-26-37

26.12 Duct Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.12.1 Material Thickness (1996). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.12.2 Duct Area (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.12.3 Minimum Radius of Curvature (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.12.4 Duct Supports (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.12.5 Duct Size, Clearance and Detailing (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.12.6 Duct Confinement Reinforcement (1996). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-26-37 8-26-37 8-26-37 8-26-37 8-26-38 8-26-38 8-26-39

26.13 Couplers (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-26-39

26.14 Connection of Secondary Beams (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-26-39

26.15 Concrete Cover and Reinforcement Spacing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.15.1 Cover and Spacing (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.15.2 Reinforcement Details for Erection Loads (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-26-41 8-26-41 8-26-41

© 2011, American Railway Engineering and Maintenance-of-Way Association

8-26-2

AREMA Manual for Railway Engineering

Recommendations for the Design of Segmental Bridges

TABLE OF CONTENTS (CONT) Section/Article

Description

Page

26.16 Inspection Access (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-26-41

26.17 Box Girder Cross Section Dimensions and Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.17.1 Minimum Flange Thickness (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.17.2 Minimum Web Thickness (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.17.3 Length of Top Flange Cantilever (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26.17.4 Overall Cross Section Dimensions (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-26-41 8-26-41 8-26-41 8-26-42 8-26-42

Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-26-42

LIST OF FIGURES Figure

Description

8-26-1 Cross Sections and Corresponding Effective Flange Widths, bm, for Bending and Shear. . . . . 8-26-2 Pattern of the Effective Flange Width bm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-26-3 Effective Flange Width bm/b Coefficients bf bs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-26-4 Effective Flange Widths bn for Normal Faces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-26-5 Normal Daily Minimum Temperatures (Degrees F) for January . . . . . . . . . . . . . . . . . . . . . . . . 8-26-6 Normal Daily Maximum temperatures (Degrees F) for July. . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-26-7 Negative Moment Region. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-26-8 Reinforcement Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-8-26-1Relative Joint Displacement Shear Key Behavior. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-8-26-2Stress Trajectories in a B-Region and Near Discontinuities (D-Regions)1 . . . . . . . . . . . . . . . . C-8-26-3Beam with Direct Supports1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-8-26-4T-beam1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-8-26-5Longitudinal Shear Transfer by Bottom Slab to Web Haunches1 . . . . . . . . . . . . . . . . . . . . . . . C-8-26-6Truss Model of a Beam with Cantilever1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-8-26-7The Two Most Frequent and Most Useful Strut-and-Tie Models1 . . . . . . . . . . . . . . . . . . . . . . C-8-26-8The Compression Strut in the Web with the Stirrups1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-8-26-9Examples of the Basic Types of Nodes1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-8-26-10Diaphragm of a Box Girder Bridge1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-8-26-11Fan Action1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-8-26-12Different Support Conditions Lead to Different Strut-and-Tie Models and Different Reinforcement Arrangements of Corbels1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-8-26-13Bursting Stresses Under Bearing Plate Anchorages1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-8-26-14A Typical D-Region1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-8-26-15Schematic Drawing of Different Types of “Hanger” Reinforcement1 . . . . . . . . . . . . . . . . . . . C-8-26-16Extent of the Intersection Zone for the Connection of Secondary Beams1 . . . . . . . . . . . . . . .

Page 8-26-9 8-26-10 8-26-10 8-26-11 8-26-14 8-26-15 8-26-23 8-26-40 8-26-46 8-26-48 8-26-48 8-26-49 8-26-49 8-26-52 8-26-53 8-26-54 8-26-55 8-26-56 8-26-57 8-26-58 8-26-60 8-26-60 8-26-64 8-26-64

LIST OF TABLES Table

Description

8-26-1 Strength Reduction Factor f . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-26-2 Allowable Tensile Stresses for Construction Load Combinations. . . . . . . . . . . . . . . . . . . . . . . .

Page 8-26-18 8-26-20

1 Republished through the courtesy of the Prestressed Concrete Institute PCI Journal, see individual figure for volume and page number.

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

8-26-3

1

3

4

Concrete Structures and Foundations

SECTION 26.1 GENERAL REQUIREMENTS AND MATERIAL 26.1.1 GENERAL (1996)1 The specifications of this part are intended for design of longitudinally and/or transversely post-tensioned bridges utilizing normal weight concrete constructed with either precast or cast-in-place box segments of single or multiple cells, or combinations thereof, as well as simple span and continuous segmental beam-type bridges. The specifications pertain to bridges of all sizes and are restricted to bridge span lengths of 200 feet or less. Unless otherwise stated or superseded by these specifications, the provisions of the AREMA Manual for Railway Engineering are intended to apply to the design of segmental concrete bridges.

26.1.2 NOTATIONS (1996) Notations are in accordance with Part 2, Reinforced Concrete Design and Part 17, Prestressed Concrete and the following: A

= area of concrete surrounding a bar, (see Article 26.15.2) square inch.

Ab

= bearing area of tendon anchorage, square inch.

A'

= maximum area of the portion of the concrete anchorage surface that is geometrically similar to and concentric with the bearing area of the tendon anchorage, square inch.

Acc

= area of concrete in compression chord, square inch.

Acn

= area of one face of a truss node region, square inch.

Acp

= area enclosed by outside perimeter of concrete cross section, square inch.

Acs

= area of inclined compression strut, square inch.

Ag

= gross area of concrete cross section, square inch.

Al

= total area of additional longitudinal reinforcement to resist torsion, square inch.

Ao

= area enclosed by shear flow path, See Article 26.8.2j, square inch.

As

= area of nonprestressed tensile reinforcement, square inch.

A's

= area of compression reinforcement, square inch.

A *s

= area of prestressed reinforcement in tension zone, square inch.

At

= area of one leg of continuous, closed transverse torsion reinforcement within a distances, square inch.

b

AV

= area of transverse shear reinforcement within a distance s, square inch.

a

= portion of single span, end span, or span adjacent cantilever arm subject to shear lag effects (see Figure C-8-26-2), feet.

b

= top or bottom flange width either side of web (see Figure C-8-26-1), feet.

be

= minimum effective shear flow web or flange width to resist torsional stresses, (see Article 26.8.2j, Article 26.8.2e and Article 26.8.3a), feet.

bf

= effective flange width coefficient for interior portion of span (see Figure C-8-26-2 and Figure C-8-263), unitless.

bm

= effective width of flange (see Figure C-8-26-2), feet.

bm1

= effective width of cantilever flange of box girder (see Figure C-8-26-1), feet.

bm2

= effective width of half of interior top flange of box girder (see Figure C-8-26-1), feet.

bm3

= effective width of half of bottom flange of box girder (see Figure C-8-26-1), feet.

bmf

= effective width for center portion of span (see Figure C-8-26-2 and Figure C-8-26-3), feet.

1

See Commentary

© 2011, American Railway Engineering and Maintenance-of-Way Association

8-26-4

AREMA Manual for Railway Engineering

Recommendations for the Design of Segmental Bridges

bms

= effective width at support or for cantilever arm (see Figure C-8-26-2 and Figure C-8-26-3), feet.

bn

= effective flange width for lateral distribution of post-tensioning force (see Figure C-8-26-4), feet.

bno

= web width at anchorage of post-tensioning force (see Figure C-8-26-4), feet.

bo

= web width (see Figure C-8-26-1), feet.

bs

= effective top or bottom flange width coefficient at supports and for cantilever arms (see Figure C-826-2 and Figure C-8-26-3), feet.

bw

= minimum web width, (see Article 26.8.2e), inches.

b1

= width of cantilever flange of box girder (see Figure C-8-26-1), feet.

b2

= width of half of interior top flange of box girder (see Figure C-8-26-1), feet.

b3

= width of half of interior bottom flange of box girder (see Figure C-8-26-1), feet.

CE

= weight of specialized construction equipment, kips.

CLE = longitudinal construction equipment load, kips. CLL = construction live load, psf, normally taken as 10 psf. c

= portion of continuous span adjacent to interior support subject to shear lag effects (see Figure C-826-2), feet.

D

= sum of dead load of structure (DL), superimposed dead load (SDL), and permanent effects of erection loads (EL), kips.

DIFF = differential (unbalanced) dead load from one cantilever, kips. DL

= dead load of structure only, kips.

DT

= thermal differential from centerline of top flange to centerline of bottom slab, degrees F.

d

= distance from the extreme compression fiber to the centroid of the longitudinal tension reinforcement, inches. For prestressed concrete members, the greater of the distance from the extreme compression fiber to the centroid of the prestressed tension reinforcement or 0.8h may be used, feet.

1

da

= depth of anchor plate, inches.

dc

= thickness of cover from tension fiber to center of bar, (see Article 26.15.2) inches.

do

= total depth of section (see Figure C-8-26-2), feet.

dON

= construction height of secondary beam (see Figure C-8-26-8), feet.

dOH

= construction height of main beam (see Figure C-8-26-8), feet.

dsp

= total depth of symmetric concrete prism above and below the anchor plate (also assumed to be the length of the anchorage zone), inches.

Ecm

= secant modulus of elasticity, psi or ksf.

Eeff

= effective modulus of elasticity for long term loads considering creep deformations, psi or ksf.

EL

= permanent effect of erection loads (final state), psi or ksf.

e

= base of Naperian logarithms

Fbst

= total bursting force (tensile) due to a tendon anchorage, kips.

Fr

= radial force due to tendon curvature, lb per foot.

f c'

= specified compressive strength of concrete, psi or ksf. f c'

f ci '

3

4

= square root of specified compressive strength of concrete, (see Article 26.8.2f for limit) psi or ksf. = compressive strength of concrete at time of initial prestress, psi or ksf.

fcn

= compressive stress in the concrete node regions, (see Article if) psi or ksf.

fcp

= permissible concrete compressive stress under anchorage, psi or ksf.

fcu

= crushing strength of diagonally cracked concrete, (see Article id) psi or ksf.

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

8-26-5

Concrete Structures and Foundations

fpc

= compressive strength in concrete after allowance for all prestress losses, psi or ksf. Critical stress to be determined at: (a) the centroid of the cross section resisting external loads, or (b) the junction of the web and compression flange when the centroid lies within the flange, or (c) in composite members, the stress at (a) or (b) for stresses due to both prestress and the moments resisted by the precast member acting alone.

fpm

= ultimate strength of prestressing steel, psi.

fs

= stress in nonprestressed reinforcement under erection loads, (see Article 26.15.2), psi.

f s'

= stress in compression reinforcement, psi.

fst

= steel stress at beginning of time intervals tl, psi.

* f su

= average stress in prestressed reinforcement at ultimate load, psi.

fsy

= specified yield strength of nonprestressed reinforcement, psi.

f y*

= yield point stress of prestressing steel, psi.

h

= overall thickness of member, inches.

IE

= impact load from equipment

K

=

f pc 1 + ---------------- , factor for torsional cracking moment (see Article 26.8.2j and l) 2 f¢ c

l

= span length, (see Figure C-8-26-2) feet.

li

= span length for use in determining effective flange width, (see Figure C-8-26-2) feet.

Mu

= factored moment at section, in-lb or ft-lb.

Nuc

= factored compressive axial force normal to cross section, lb.

Nut

= factored tensile axial force normal to cross section, lb.

P

= tendon force, (see Article 26.12.3 and Article 26.12.6.1) lb.

pcp

= outside perimeter of the concrete cross section, inches.

Pj

= tendon jacking force, kips.

ph

= perimeter of centerline of outermost continuous closed transverse reinforcement, inches.

R

= tendon radius of curvature, (Article 26.12.3) feet.

R

= rib shortening and creep effects, (see Article 26.4.2 and Article 26.4.4.1) kips.

Rlr

= loss of prestress due to steel relaxation, low relaxation strand, psi.

Rsr

= loss of prestress due to steel relaxation, stress relieved steel, psi.

S

= shrinkage effects, (see Article 26.4.4.1) kips.

Su

= force in a truss member due to factored ultimate loads, lb.

SDL = superimposed dead load, kips. s

= spacing of shear or torsion reinforcement measured parallel to the longitudinal axis of the member, inches.

s

= bar spacing, inches (see Article 26.15.2).

T

= sum of effects of thermal rise or fall (TRF) and thermal differential (DT), kips.

TRF = thermal rise or fall, degrees F. Tc

= torsional cracking moment, (see Article 26.8.2j) in-lb.

Tn

= nominal torsion resistance, in-lb.

To

= tendon stress at jacking end, psi.

Tu

= factored torsion at section, in-lb.

U

= load due to segment unbalance on opposite cantilever ends, kips.

© 2011, American Railway Engineering and Maintenance-of-Way Association

8-26-6

AREMA Manual for Railway Engineering

Recommendations for the Design of Segmental Bridges

Vc

= nominal shear strength provided by concrete, lb.

Vn

= nominal shear force resisted by member, lb.

Vp

= component of the effective prestressing which acts in the direction of the applied shear (see Article 26.8.1g and Article 26.8.2h).

Vs

= nominal shear resisted by the 45 degrees truss model as measured by the stirrup capacity, lb.

VU

= factored shear force at section, lb.

WTdl = area of concrete surrounding a bar, (see Article 26.15.2), square inch. WUP = wind uplift on cantilever, kips. Z

= correction dimension for location of center of gravity of tendon bundle in duct, (see Article 26.7.3) inch.

Z

= quantity for detailing of reinforcement to control flexural cracking during erection, (see Article 26.15.2) kips per inch.

so

= average compressive stress in the concrete section due to the post-tensioning anchorage force after the force is distributed over the depth, d, of the section, psi.

sy

= transverse tensile stress in the concrete section due to the post-tensioning anchorage force, psi (see Figure C-8-26-13).

f

= strength reduction factor (see Article 26.4.3).

fb

= strength reduction factor for bearing (see Article 26.4.3).

fc

= creep coefficient, ratio of creep strain to elastic strain.

ff

= strength reduction factor for flexure (see Article 26.4.3).

fv

= strength reduction factor for shear and diagonal tension (see Article 26.4.3).

m

= friction coefficient (per radian)

a

= total angular deviation from jacking end to point x, radians.

1

3 26

8

26.1.3 TERMS (1996) Terms are in accordance with Part 2, Reinforced Concrete Design and Part 17, Prestressed Concrete and the following. Refer to the Chapter 8 Glossary located at the end of the chapter for definitions. Anchorage Blister

General Zone

Secondary Moment

Closure

Internal Tendon

Strut-and-Tie Model

Confinement Anchorage

Local Zone

Temperature Gradient

Deviation Saddle

Launching Bearing

Type A Joints

External Tendon

Launching Nose

Type B Joints

General Bursting Forces

Low Relaxation Steel

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

8-26-7

4

Concrete Structures and Foundations

26.1.4 CONCRETE (1996) Structural concrete used in segmental construction shall have a minimum 28-day strength of 4,500 psi, or greater as specified by the Engineer. The required concrete strength at the time of stressing shall be determined in accordance with Article 26.5.2.

26.1.5 SEGMENTAL BRIDGES, DESIGN REINFORCEMENT (1996)1 26.1.5.1 Prestressing Steel As per Part 17, Prestressed Concrete. 26.1.5.2 Reinforcing Steel a.

ASTM Grade 60 unless otherwise specified.

b. All bridge deck reinforcement, including any reinforcement projecting from the web into the deck, shall be provided with a corrosion protective system in aggressive environments.

SECTION 26.2 METHODS OF ANALYSIS 26.2.1 GENERAL (1996)2 Elastic analysis and beam theory may be used to determine design moments, shears, and deflections. The effects of creep, shrinkage, and temperature differentials shall be considered, as well as the effects of shear lag. Shear lag shall be considered in accordance with the provisions of Article 26.2.3.

26.2.2 STRUT-AND-TIE-MODELS (1996)3 Strut-and-tie-models may be used for analysis when tensile stresses exceed the tensile strength of the concrete, and for areas where strain distribution is non-linear.

26.2.3 EFFECTIVE FLANGE WIDTH (1996) 26.2.3.1 General4 Effective flange width may be determined by elastic analysis procedures (Reference 87 and 88), by the provisions of Section 3-10.2 of the 1983 Ontario Highway Bridge Design Code (Reference 63) or by the provisions of Article 26.2.3.2. 26.2.3.2 Effective Flange Width for Analysis, and for Calculation of Section Capacity and Stresses5 a.

1 2 3 4 5

Section properties for analysis and for calculation of the effects of bending moments and shear forces may be based on the flange widths specified in this section, or may be based on flange widths determined by other procedures listed in Article 26.2.3.1. The effects of unsymmetrical loading on effective flange width may be disregarded. For flange width, b, less than or equal to 0.3 do, bm may be assumed equal to b, where do is taken as the web height in accordance with Figure C-8-26-1. For flange widths, b, greater than 0.3 do, the effective width may be determined in accordance with Figure C-8-26-2 and Figure C-8-

See Commentary See Commentary See Commentary See Commentary See Commentary

© 2011, American Railway Engineering and Maintenance-of-Way Association

8-26-8

AREMA Manual for Railway Engineering

Recommendations for the Design of Segmental Bridges

26-3. The value of bs shall be determined using the greater of the effective span lengths adjacent to the support. If bmf is less than bms in a span, the pattern of the effective width within the span may be determined by the connecting line of the effective width bms at adjoining support points. However, bm shall not be greater than b.

1

3

Figure 8-26-1. Cross Sections and Corresponding Effective Flange Widths, bm, for Bending and Shear

b. The section properties for normal forces may be based on the pattern according to Figure C-8-26-4, or may be determined by more rigorous analytical procedures. c.

Stresses due to bending, shear and normal forces may be determined by using their corresponding section properties.

d. For the superposition of the bending stresses of the main load-bearing structure over the slab bending stresses generated by local loads, the former may be assumed to have a straight line pattern in accordance with Figure C-8-26-1. The linear stress distribution is determined from the constant stress distribution under the condition that the flange force remains unchanged. e.

The capacity of a cross-section at the ultimate state may be determined by considering the full flange width effective.

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Concrete Structures and Foundations

Figure 8-26-2. Pattern of the Effective Flange Width bm

Figure 8-26-3. Effective Flange Width bm/b Coefficients bf bs

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AREMA Manual for Railway Engineering

Recommendations for the Design of Segmental Bridges

1

3

Figure 8-26-4. Effective Flange Widths bn for Normal Faces

26.2.4 TRANSVERSE ANALYSIS a.

4

(1996)1

The transverse design of box girder segments for flexure shall consider the segment as a rigid box frame. Flanges shall be analyzed as variable depth sections considering the fillets between the flange and webs. Combinations of track loads, if the structure may support more than one track, shall be positioned to provide maximum moments, and elastic analysis shall be used to determine the effective longitudinal distribution of wheel loads for each load location. Tracks shall be positioned on the structure in accordance with clearance policies. Consideration shall be given to the increase in web shear and other effects on the cross-section resulting from eccentric loading or unsymmetrical structure geometry.

b. Influence surfaces (Reference 41, 42 and 74) or other elastic analysis procedures may be used to evaluate live load plus impact moment effects in the top flange of the box section.

1

See Commentary

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Concrete Structures and Foundations

c.

Transverse elastic and creep shortening due to prestressing and shrinkage shall be considered in the transverse analysis.

d. The secondary effects due to prestressing shall be included in stress calculations at working load. In calculating ultimate strength moment and shear requirements, the secondary moments or shears induced by prestressing (with a load factor of 1.0) shall be added algebraically to the moments and shears due to factored ultimate dead and live loads.

26.2.5 LONGITUDINAL ANALYSIS (1996) 26.2.5.1 General1 a.

Longitudinal analysis shall be in accordance with the provisions of Article 26.2.1. Longitudinal analysis of segmental concrete bridges shall consider a specific construction method and construction schedule, as well as the time-related effects of concrete creep, shrinkage, and prestress losses.

b. The secondary effects due to prestressing shall be included in stress calculations at working load. In calculating ultimate moments and shear requirements, the secondary moments or shears induced by prestressing (with a load factor of 1.0) shall be added algebraically to moments and shears due to factored dead and live loads. c.

Internal Tendons shall be designed and constructed as bonded tendons. Details of construction methods resulting in unbonded or partially unbonded internal tendons are not allowed.

26.2.5.2 Erection Analysis Analysis of the structure during the construction stage, shall consider the construction load combinations, stresses, and stability considerations outlined in Article 26.4.4. 26.2.5.3 Analysis of the Final Structural System The final structural system shall be analyzed for redistribution of erection stage moments resulting from the effects of creep and shrinkage, and from any change in the statical system, including the closure of joints. Thermal effects on the final structural system shall be considered in accordance with Article 26.3.4. The effect of prestress losses occurring after closure shall be evaluated in accordance with Section 26.6, Prestress Losses (1996). The maximum moments resulting from the above analyses shall be utilized in conjunction with the combinations of loads specified in Article 2.2.4 for determination of required flexural strength.

SECTION 26.3 DESIGN LOADS 26.3.1 GENERAL (1996) All loadings shall be in accordance with the latest edition of the Manual For Railway Engineering except as provided below.

1

See Commentary

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Recommendations for the Design of Segmental Bridges

26.3.2 DEAD LOADS (1996)1 Unit weight of concrete (including reinforcing steel) – 155 pcf or as determined for the project. Weight of diaphragms, anchor blocks, or any other deviations from the typical cross section shall be included in the dead load calculations.

26.3.3 ERECTION LOADS (1996)2 a.

Erection loads comprise all loadings arising from the designer’s anticipated system of temporary supporting works and/or special erection equipment to be used in accordance with the assumed construction sequence and schedule. The assumed erection loads (magnitude and configuration) and acceptable closure forces due to misalignment corrections shall be stated on the drawings. Due allowance shall be made for all effects of any changes to the statical structural scheme during construction. The application, changes or removal of the assumed temporary supports or special equipment shall be considered by taking into account residual “built-in” forces, moments, deformations, secondary posttensioning effects, creep, shrinkage and any other strain induced effects.

b. All elements of the bridge shall be designed for the anticipated construction system assumed by the Engineer and shown on the plans. Any accepted contractor proposals which present differing construction loads shall be evaluated, by the Engineer, for effects upon the structure.

26.3.4 THERMAL EFFECTS (1996)

1

26.3.4.1 Normal Mean Temperature Unless more precise local data are available, normal mean temperature for the location shall be taken as the average of the January and July values from Figure C-8-26-5 and Figure C-8-26-6, (Reference 43) respectively. 26.3.4.2 Seasonal Variation a.

For the purposes of design of the structure, the minimum and maximum overall temperatures shall be taken from Figure C-8-26-5 and Figure C-8-26-6, respectively, unless more precise local data is available.

3

b. The temperature setting variations for bearings and expansion joints shall be stated on the bridge plans. 26.3.4.3 Thermal Coefficient3 The coefficient of thermal expansion used to determine temperature effects shall be taken as 6.0 ´ 10-6 per degree F, unless more precise data are available. 26.3.4.4 Differential Temperature4 Positive and negative differential superstructure temperature gradients shall be considered in accordance with Appendix A of National Cooperative Highway Research Program Report 276 “Thermal Effects in Concrete Bridge Superstructures.” (Reference 43) More precise data may be used if available.

1 2 3 4

See Commentary See Commentary See Commentary See Commentary

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Concrete Structures and Foundations

8-26-14

Figure 8-26-5. Normal Daily Minimum Temperatures (Degrees F) for January

Recommendations for the Design of Segmental Bridges

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AREMA Manual for Railway Engineering

8-26-15

Figure 8-26-6. Normal Daily Maximum temperatures (Degrees F) for July

Concrete Structures and Foundations

26.3.5 CREEP AND SHRINKAGE (1996)1 Effects due to creep and shrinkage strains shall be calculated in accordance with provisions of Article 26.2.5.3. The creep coefficient fc may be evaluated in accordance with the provisions of the ACI Committee 209 Report, (Reference 2) the CEB-FIP Model Code, (Reference 15) or by a comprehensive test program. Creep strains and prestress losses (Reference 14) which occur after closure of the structure causes a redistribution of the forces. Stresses shall be calculated for this effect based on an assumed construction schedule stated on the plans.

26.3.6 POST-TENSIONING FORCE (1996)2 The structure shall be designed for both initial and final post-tensioning forces. Prestress losses shall be calculated for the construction schedule stated on the plans. The final post-tensioning forces used in service load stress calculations shall be based on the most severe condition at each location along the structure.

SECTION 26.4 LOAD FACTORS 26.4.1 GENERAL (1996) In the final working condition, service or load factor load combinations shall be in accordance with Part 2, Reinforced Concrete Design as amended below. Allowable stresses shall be in accordance with Section 26.5, Allowable Stresses. When checking tensile stresses for service load, Groups II through IX, the variable load effects shall be divided by the allowable stress increases in Part 2, Reinforced Concrete Design, Article 2.2.4. Strength reduction factors, f, shall be in accordance with Article 26.4.3. During construction, load case combinations, allowable stresses and stability shall be in accordance with Article 26.4.4.

26.4.2 SERVICE LOAD COMBINATIONS FOR PART 2, REINFORCED CONCRETE DESIGN, ARTICLE 2.2.4 (1996) 26.4.2.1 Creep and Shrinkage a.

The permanent effects of creep and shrinkage shall be added to all specified loading combinations with a load factor of 1.0.

b. For the group loading combinations listed in Part 2, Reinforced Concrete Design, Article 2.2.4, the following abbreviations shall apply: D = DL + SDL + EL and OF = TRF + DT + R where: EL = Erection Loads (final state) NOTE:

See Article 26.4.2.2.

TRF = Thermal – Rise or Fall

1 2

See Commentary See Commentary

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AREMA Manual for Railway Engineering

Recommendations for the Design of Segmental Bridges

DT = Thermal – Differential R = Creep Effects NOTE:

Creep effects to be considered, in conjunction with any rib shortening, shrinkage and anticipated support settlement effects as loading designation R.

A thermal differential of 0.5DT is permissible when the load combination includes full live load + impact. 26.4.2.2 Erection Loads at End of Construction The final state erection loads are defined as the final accumulated “built-in” forces and moments resulting from the construction process. 26.4.2.3 Additional Thermal Loading Combination In addition to Group Loads IV, V, and VI at service load, the following combination and stress shall apply: (DL + SDL + EL) + E + B + SF + R + S + (DT) @ 100% Allowable Stress NOTE:

Letters in parenthesis are as per Article 26.1.2, others are as per Part 2, Reinforced Concrete Design, Article 2.2.3.

1

26.4.3 STRENGTH REDUCTION FACTORS (1996)1 a.

The basic strength reduction factors, ff and fv for flexure and shear, respectively, shall consider both the type of joint between segments and the degree of bonding of the post-tensioning system provided. The appropriate value of fv listed below shall be used for torsional effect calculations in Section 26.8, Shear and Torsion.

3

b. Since the post-tensioning provided may be a mixture of fully bonded tendons and unbonded or partially bonded tendons, the strength reduction factor at any section shall be based upon the bonding conditions for the tendons providing the majority of the prestressing force at the section. All internal tendons shall be designed and constructed as bonded tendons. c.

In order for a tendon to be considered as fully bonded to the cross-section at a section, it must be bonded beyond the critical section for a development length. The development length shall be calculated by a rational approach based upon tendon pull out tests.

d. Cast-in-place concrete joints and wet concrete joints shall be considered as Type A joints.

1

e.

Epoxy joints between precast units shall be considered as Type B joints.

f.

Dry joints between precast units shall be considered as Type B joints.

g.

Strength reduction factor, f, shall be taken as shown in Table 8-26-1.

See Commentary

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Concrete Structures and Foundations

Table 8-26-1. Strength Reduction Factor f ff Flexure

fv Shear

Type A Joints

0.95

0.85

Type B Joints

0.90

0.80

Type A Joints

0.90

0.90

Type B Joints

0.85

0.75

Type Fully Bonded Tendons

Unbonded or Partially Bonded External Tendons

NOTE:

The appropriate value of fv from Table 8-26-1 shall be used for torsional effect calculations in Section 26.8, Shear and Torsion.

h. The strength reduction factor for bearing, fb shall be taken as 0.70 for all types of construction. This value shall not be applied to bearing stresses under anchorage plates for post-tensioning tendons.

26.4.4 CONSTRUCTION LOAD COMBINATIONS, STRESSES AND STABILITY (1996) 26.4.4.1 Erection Loads During Construction1 a.

Erection Loads as defined by AREMA and as stated on the plans shall be as follows: (1) Dead load of structure (DL). Unit weight of concrete (including rebar) 155 pcf or as determined for the project. Weight of diaphragms, anchor blocks, or any other deviations from the typical crosssection shall be included in the dead load calculations. (2) Differential load from one cantilever (DIFF). This only applies to balanced cantilever construction. The load is 2% of the dead load applied to one cantilever. (3) Superimposed dead load (SDL). This does not normally apply during construction. If it does, it should be considered as part of the dead load (DL). (4) Distributed construction live load (CLL). This is an allowance for miscellaneous items of plant, machinery and other equipment apart from the major specialized erection equipment. The following magnitudes shall be used as minimum unless loads of different magnitudes can be verified. Distributed load allowance 10 psf. In cantilever construction, distributed load shall be taken as 10 psf on one cantilever and 5 psf on the other. For bridges built by incremental launching, construction live load may be taken as zero. (5) Specialized construction equipment (CE). This is the load from any special equipment such as a launching gantry, beam and winch, truss or similar major item. This also includes segment delivery trucks and the maximum loads applied to the structure by the equipment during the lifting of segments.

1

See Commentary

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Recommendations for the Design of Segmental Bridges

(6) Impact Load from equipment (IE). To be determined according to the type of machinery anticipated. For very gradual lifting of segments, where the load involves small dynamic effects, the impact load may be taken as 10%. (7) Longitudinal construction equipment load (CLE). The longitudinal force from the construction equipment. (8) Segment unbalance (U). This applies primarily to balanced cantilever construction but can be extended to include any “unusual” lifting sequence which may not be a primary feature of the generic construction system. The load “U” is the effect of any out of balance segments or other unusual condition as applicable. (9) Wind uplift on cantilever (WUP). 5 psf minimum (balanced cantilever construction applied to one side only). (10) Accidental release or application of a precast segment load or other sudden impact from an otherwise static segment load of WTd1. Force plus Impact = 2WT1. (11) Creep (R). In accordance with Article 26.3.5. Creep effects shall be considered as part of rib shortening (R). (12) Shrinkage (S). In accordance with Article 26.3.5. (13) Thermal (T). The sum of the effects due to thermal rise and fall (TRF) and differential temperature (DT) from Article 26.3.4.

1

26.4.4.2 Construction Load Combinations and Allowable Stresses a.

Stresses shall be checked under the service load combinations given in Table 8-26-2. The distribution and application of the individual erection loads (Article 26.4.4.1) appropriate to a construction phase shall be such as to produce the most unfavorable effects. Table 8-26-2 is a guide; if more unfavorable conditions may occur with the particular construction system, these shall be taken into account. The maximum allowable construction load compressive stress shall be 0.5 f c' .

3

b. Load factor design need not be used for construction conditions with the exception of Article 26.4.4.3. 26.4.4.3 Construction Load Combinations Load Factor Design Check

4 Using strength reduction factors (f) in accordance with Article 26.4.3, the strength provided shall not be less than required by the following load factor combinations: a.

For maximum forces and moments: 1.1 (DL + DIFF) + 1.3CE + 2A

b. For minimum forces and moments: DL + CE + 2A

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Live Loads

Superstructure Only

Wind Loads

DL DIFF U CLL CE IE CLE

W

Segmental Substructure Only

(1) (2) Allowable bE (3) (4) B SF (R+S+T) Including Stress (Note 3) Excluding Including (R+S+T) WUP WE (Note 4) (R+S+T) (R+S+T) Allowable Allowable Allowable Stress Stress Stress (Note 4)

Comments

Combination

Dead Loads

AREMA Manual for Railway Engineering

© 2011, American Railway Engineering and Maintenance-of-Way Association

a

1

1

0

1

1

1

0

0

0

0

6 f c'

1

7 f c'

bE

1

1

6 f c'

7 f c'

b

1

0

1

1

1

1

0

0

0

0

6 f c'

1

7 f c'

bE

1

1

6 f c'

7 f c'

c

1

1

0

0

0

0

0

0.7 0.7 (Note 1)

0

6 f c'

1

7 f c'

1

1

1

7 f c'

7 f c'

d

1

1

0

1

1

0

0

0.7 (Note 1)

1

0.7

7 f c'

1

7 f c'

bE

1

1

7 f c'

7 f c'

Equipment not working

e

1

0

1

1

1

1

0

0.3 (Note 2)

0

0.3

7 f c'

1

7 f c'

bE

1

1

7 f c'

7 f c'

Normal Erection

f

1

0

0

1

1

1

1

0.3 (Note 2)

0

0.3

7 f c'

1

7 f c'

bE

1

1

7 f c'

7 f c'

Moving Equipment

The allowable stresses in Columns (1) and (2) apply to the summation of all the loads multiplied by their tabulated coefficients in all the columns to the left. Similarly for Columns (3) and (4) with the exceptions of (R+S+T) as noted. Note 1: Reduction is to allow for lesser probability of maximum wind during construction period. Note 2: Reduction is to allow for limiting wind beyond which construction is halted. Note 3: The bE term is as defined in AASHTO Section 3.22. Note 4: When less than 50% of the tendon capacity is provided by internal tendons, the maximum allowable construction stresses shall be 3 f c' for Type A joints, and 0 for Type B joints.

Concrete Structures and Foundations

8-26-20

Table 8-26-2. Allowable Tensile Stresses for Construction Load Combinations

Recommendations for the Design of Segmental Bridges

SECTION 26.5 ALLOWABLE STRESSES 26.5.1 PRESTRESSING STEEL (1996) The allowable stresses for prestressing steel shall be in accordance with the provisions of Part 17, Prestressed Concrete.

26.5.2 PRESTRESSED CONCRETE (1996) 26.5.2.1 Temporary Stresses Before Losses Due to Creep and Shrinkage, at the Time of Application of the Prestress a.

Maximum Compression: 0.55 f ci' .

b. Longitudinal stresses in the PRECOMPRESSED tensile zone: (1) Type A joints with minimum bonded mild steel auxiliary reinforcement through the joints sufficient to carry the calculated tensile force at a stress of 0.5 fsy; internal tendons. 3 f ci' maximum tension

1

(2) Type A joints without the minimum bonded mild steel auxiliary reinforcement through the joints; internal or external tendons: 0 tension (3) Type B joints, external tendons not less than: 200 psi minimum compression (4) Tension in other areas without bonded nonprestressed reinforcement: 0 tension.

3

(5) Where the calculated tensile stress exceeds the allowable tensile value, bonded reinforcement shall be provided at a stress of 0.5 fsy to resist the total tensile force in concrete computed on the assumption of an uncracked section. In such cases, the maximum tensile stress shall not exceed 6 f ci' .

4

26.5.2.2 Stresses at the Service Level After Losses a.

Maximum Compression: 0.4 f c'

b. Longitudinal stresses in the PRECOMPRESSED tensile zone: (1) Type A joints with minimum bonded auxiliary reinforcement through the joints sufficient to carry the calculated tensile force at a stress of 0.5 fsy; internal tendons: 3 f c' maximum tension (2) Type A joints without minimum bonded auxiliary reinforcement through joints: 0 tension © 2011, American Railway Engineering and Maintenance-of-Way Association

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Concrete Structures and Foundations

(3) Type B joints, external tendons, not less than: 200 psi minimum compression (4) Tension in other areas without bonded reinforcement: zero tension (5) Where the calculated tensile stress exceeds this value, bonded reinforcement shall be provided at a stress of 0.5 fsy to resist the total tensile force in the concrete computed on the assumption of an uncracked section. In such cases, the maximum tensile stress shall not exceed 6 f c' . c.

Transverse tension in the precompressed tensile zone: 3 f c' maximum tension

26.5.2.3 Anchorage a.

The bearing stresses under the anchor plates shall be in accordance with the provisions of Part 17, Prestressed Concrete, Article 17.16.2.4 as modified by this section. The stresses calculated at application of the post-tensioning force and at the service load shall be limited to 5,000 psi and 6,250 psi, respectively.

b. Anchorage devices which function on the basis of confinement reinforcing need not conform to the bearing stress limitations for plate type anchorage devices specified in paragraph a. Acceptance of such anchorage devices shall be based on review of test data or on the basis of documented performance on major bridge projects.1 c.

The concrete splitting force shall be calculated in accordance with Article 26.10.2; by test results based on similar anchorages, tendon trajectory, and concrete section geometry; or by more rigorous analytical procedures.2

d. Reinforcement shall be provided to resist the anchorage splitting forces. e.

Tensile stress in anchorage splitting reinforcement at the time of application of the prestress: 0.6 fsy , where fsy shall not exceed 60,000 psi.

SECTION 26.6 PRESTRESS LOSSES (1996) Prestress losses shall be computed in accordance with the provisions of Part 17, Prestressed Concrete. Lump sum losses shall only be used for preliminary design purposes. Losses due to creep, shrinkage, and elastic shortening of the concrete as well as friction, wobble, anchor set and relaxation in the tendon shall be calculated for the construction method and schedule shown on the plans in accordance with time-related procedures for calculation of prestress losses.

1 2

See Commentary See Commentary

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Recommendations for the Design of Segmental Bridges

SECTION 26.7 FLEXURAL STRENGTH 26.7.1 GENERAL (1996)1 Flexural strength of segmental concrete bridges shall be calculated in conjunction with Part 17, Prestressed Concrete. The flexural capacity required by the load factor provisions of Article 26.4.1 shall be less than or equal to ff times the flexural capacity provisions of Part 17, Prestressed Concrete. The values of ff shall be taken from Article 26.4.3.

26.7.2 STRAIN COMPATIBILITY (1996) As an alternative to use of Part 17, Prestressed Concrete, flexural strength of bonded tendon bridges may be calculated in accordance with the strain compatibility provisions of Section 10.2 of the ACI 318 Building Code (Reference 4). Strain compatibility analysis may also be used for computation of bridges with unbonded tendons provided that the analysis correctly recognizes the differences in strain between the tendons and the concrete section, and provided that the analysis recognizes the effect of tendon anchorage lateral restraints and deflection geometry changes on the effective stress in the tendons.

26.7.3 CENTER OF GRAVITY CORRECTION FOR STRAND TENDONS (1996) Draped strand tendons shall be assumed to be at the bottom of the duct in negative moment areas, and at the top of the duct in positive moment areas. For both strength and allowable stress calculations, the location of the tendon center of gravity with respect to the center line of the duct shall be assumed as illustrated by Figure C8-26-7 (negative moment area shown).

1

3 z

4 Figure 8-26-7. Negative Moment Region

SECTION 26.8 SHEAR AND TORSION 26.8.1 SCOPE (1996)2 a.

1 2

The provisions of this section shall apply to the design of prestressed concrete segmental bridges subjected to shear or combined shear and torsion. Design for shear of combined shear and torsion shall

See Commentary See Commentary

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Concrete Structures and Foundations

be based on ultimate load conditions. The provisions of Article 26.8.2 shall apply to all parts of this section. b. Regions with one-way beam or thin plate type action or similar conditions in which the plane sections assumption of flexural theory can be applied shall be designed for shear or shear and torsion according to Article 26.8.1, and either the traditional approach of Article 26.8.3 or the strut-and-tie model approach of Article 26.8.4. Detailing of all shear and torsion reinforcement must meet the requirements of Article 26.8.2.1 c.

Discontinuity regions where the plane sections assumption of flexural theory is not applicable such as regions adjacent to abrupt changes in cross sections, openings, dapped ends, regions where large concentrated loads, reactions, or post-tensioning forces are applied or deviated, diaphragms, deep beams, corbels or joints shall be designed for the applied forces causing shear or shear and torsion according to Article 26.8.2 and the strut-and-tie model approach of Article 26.8.4. In addition, special discontinuity regions like deep beams, brackets and corbels should be designed for the applicable parts of Article 26.8.5.2

d. Interfaces between elements such as webs and flanges, between dissimilar materials, between concretes cast at different times, or at an existing or potential major crack shall be designed for shear transfer in accordance with Article 26.8.6.3 e.

Slab type regions subjected to local concentrated forces such as concentrated loads or column reactions shall be designed for two-way punching shear in accordance with Article 26.8.7.

f.

The applied shear on a cross section shall consist of the shear due to factored ultimate dead load (VuDL) including continuity effects, factored ultimate live load (VuLL) and any other factored ultimate load cases specified. Torsional moments (Tu) shall be included in design for factored ultimate load when their magnitude exceeds the value specified in Article 26.8.2j.4

g.

The applied shear due to the component of the effective longitudinal prestress force which acts in the direction of the section being examined (Vp) shall be considered as a load effect.

h. The vertical component of inclined tendons shall only be considered to reduce the applied shear on the webs for tendons which cross the webs and are anchored or fully developed by anchorages, deviators, or internal ducts located in the outer 1/3 of the webs.

26.8.2 GENERAL REQUIREMENTS (1996) a.

For members subjected to combined shear and torsion, the resulting shear forces in the different elements of the structure from the combined shear flows from shear and from torsion shall be considered. The individual elements shall be designed for the resultant shear forces.

b. The effects of axial tension due to creep, shrinkage and thermal effects in restrained members shall be considered wherever applicable. c.

1 2 3 4

The component of the effective prestressing force in the direction of the shear force shall be considered in accordance with Article 26.8.1f.

See Commentary See Commentary See Commentary See Commentary

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AREMA Manual for Railway Engineering

Recommendations for the Design of Segmental Bridges

d. The components of inclined flexural compression or tension in variable depth members shall be considered. e.

The effects of any openings or ducts in members shall be considered. In determining the effective web width, bw or be the diameters of ungrouted ducts or one-half the diameters of grouted ducts shall be subtracted from the web width at the level of these ducts.

f.

The values of

g.

The design yield strength of nonprestressed transverse shear or torsion reinforcement shall not exceed 60 ksi. The shear and torsion resistance contribution of prestressed transverse shear or torsion reinforcement shall be based on substitution of the effective stress after allowance for all prestress losses plus 60 ksi, but not to exceed f y* , in place of fsy in transverse reinforcement expressions.

f c' used in any part of this section shall not exceed 100 psi.1

h. In pretensioned elements, the reduced prestress in the transfer length of the prestressing tendons shall be considered when computing fpc and Vp. The prestress force due to a given tendon shall be assumed to vary linearly from zero at the point at which bonding commences to a maximum at a transfer length which may be assumed as 50 diameters for 1/2 inch diameter strand.2 i.

j.

Shear effects may be neglected in areas of members where the factored shear force Vu is less than fV c /2 (Vc is defined in this article (Reference 3). Nominal minimum stirrup capacity of not less than the equivalent of two No. 4 Grade 60 bars at 1 foot on centers shall be provided per web in such areas or the minimum shrinkage and temperature reinforcement required by Part 2, Reinforced Concrete Design, Article 2.12.3

1

Torsional effects may be neglected in members where the factored torsional moment Tu is less than fT c / 3 . In lieu of a more detailed calculation, Tc may be taken as T c = 2K f c' ( 2A o b e )

3 K shall be computed as 1 + ( f pc ¤ 2 f c' ) but K £2.0 However, K shall not exceed 1.0 at any section where the stress in the extreme tension fiber due to factored load and effective prestress force exceeds 6 f c' in tension. The influence of axial tension, Nut, shall be accounted for by replacing fpc by ( f pc – N ut / A g ) . The influence of axial compression, Nuc, shall be accounted for by replacing fpc by the term ( f p c + N uc / A g ) . Ao is the area enclosed by the shear flow path defined by the centroids of the longitudinal chords of the space truss model resisting the applied torsion. In lieu of a more precise analysis, Ao may be taken as 85% of the area enclosed by the centerline of the exterior closed transverse torsion reinforcement. be is the effective width of the shear flow path of the elements making up the space truss model resisting torsion. In box girders be may be taken as A c p / p c p , where Acp is the area enclosed by the outside perimeter of the concrete cross section and Pcp is the outside perimeter of the concrete cross section. The effects of openings and ducts must be considered as required in paragraph e.

1 2 3

See Commentary See Commentary See Commentary

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Concrete Structures and Foundations

k. In a statically indeterminate structure where significant reduction of torsional moment in a member can occur due to redistribution of internal forces upon cracking, the factored torsion moment Tu may be reduced to fTc [Tc is defined in paragraph j], provided that moments and forces in the member and in adjoining members are adjusted to account for the redistribution. In lieu of a more exact analysis, the torsional loading from a slab may be assumed as linearly distributed along the member. l.

Transverse reinforcement shall be provided in all elements except for slabs and footings, and elements where Vu is less than 0.5 fVc. In lieu of more detailed calculations, Vc may be taken as: V c = 2K f c' b w d K shall be computed in accordance with paragraph j.

m. Where transverse reinforcement is required, the minimum tensile capacity of the transverse reinforcement shall be 50 bws, where bw and s are in inches. Greater amounts may be required to carry shear and torsion to meet the requirements of Article 26.8.3 or Article 26.8.5. n. Transverse reinforcement may consist of: (1) Stirrups perpendicular to the axis of the member or making an angle of 45 degrees or more with the longitudinal tension reinforcement, inclined to intercept potential cracks. (2) Welded wire fabric sheets or cages with wires located perpendicular to the axis of the member. (3) Longitudinal bars bent to provide an inclined portion making an angle of 30 degrees or more with the longitudinal tension reinforcement and inclined to intercept potential diagonal cracks. (4) Well-anchored prestressed tendons which are carefully detailed and constructed to minimize seating and time dependent losses. (5) Combinations of stirrups, tendons, and bent longitudinal bars. (6) Spirals. o.

Transverse reinforcement shall be detailed so that the shear forces between the different elements or zones of a member are effectively transferred. Transverse shear or torsion reinforcement shall extend as a continuous tie from the extreme compression fiber (less cover) to the outermost tension reinforcement. All transverse reinforcement shall be fully anchored according to Part 2, Reinforced Concrete Design, Article 2.13.1.

p. Torsion reinforcement shall consist of longitudinal bars or tendons and: (1) closed stirrups or closed ties, perpendicular to the axis of the member; (2) a closed cage of welded wire fabric with transverse wires perpendicular to the axis of the member: (3) spirals. q. Transverse torsion reinforcement shall be made fully continuous and shall be anchored according to Part 2, Reinforced Concrete Design, Section 2.21b(1), where the concrete surrounding the anchorage is restrained against spalling by flange or slab or similar element. Anchorage shall be by 135 degrees standard hooks around longitudinal reinforcement where the concrete surrounding the anchorage is unrestrained against spalling. Spacing of closed stirrups or closed ties shall not exceed one-half of the shortest dimension of the cross section, nor 12 inches.

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r.

At any place on the cross section where the axial tension due to torsion and bending exceeds the axial compression due to prestressing and bending, either supplementary tendons to counter the tension must be added or local longitudinal reinforcement which is continuous across the joints between segments is required.

s.

If supplementary tendons are added, they shall be distributed around the perimeter of the precompressed tension zone inside the closed stirrups. At least one tendon shall be placed near each corner of the stirrups in the precompressed tension zone.

t.

If longitudinal reinforcement is added, the bars shall be distributed around the perimeter formed by the closed stirrups. Perimeter bar spacing shall not exceed 18 inches. At least one longitudinal bar shall be placed in each corner of the stirrups. The minimum diameter of the corner bars shall be 1/24 of the stirrup spacing but no less than that of a #5 bar.

u. Maximum spacing of transverse reinforcement shall not exceed 0.5d in nonprestressed elements, 0.75h in prestressed elements nor 36 inches. When Vu exceeds 6f f c' b w d , these maximum spacings shall be reduced by one-half. v.

Flexural reinforcement, including tendons, shall be extended beyond the theoretical termination or deviation points for a distance of at least h / 2. Transverse reinforcement for shear and torsion shall be provided for a distance at least h / 2 beyond the point theoretically required.1

w. Shear keys in webs of precast segmental bridges shall extend for as much of the web height as is compatible with other detailing requirements. Alignment shear keys shall also be provided in top and bottom flanges.

1

26.8.3 TRADITIONAL SHEAR AND TORSION DESIGN FOR PLANE SECTION TYPE REGIONS (1996)2 a.

The design of beam-type members or regions for shear and torsion may be carried out according to this article provided:

3

(1) Vn does not exceed 10 f c' b w d (2)

2

2

( V n ¤ b w d ) + ( T n ¤ 2A o b e ) does not exceed 15 f c' .

4

(3) There are no significant discontinuities such as abrupt changes in cross section or openings. (4) No concentrated load located within 2d of a support causes more than one-third of the shear at that support. (5) Where required, shear reinforcement consists of tendons and stirrups perpendicular to the axis of the member or welded wire fabric sheets or cages with wires perpendicular to the axis of the member, and conforms to Article 26.8.2. (6) Where required, torsion reinforcement consists of longitudinal bars, and closed stirrups perpendicular to the axis of the member, and conforms to Article 26.8.2. b. The design of cross sections subject to shear shall be based on Vu £fVn where Vu is the factored shear force and Vn is the nominal shear strength. Vu shall consider any unfavorable effects of prestressing and 1 2

See Commentary See Commentary

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may consider favorable effects of prestressing in accordance with Article 26.8.1f. For the purposes of this section, Vn may be computed as: Vn = Vc + Vs where: Vc = may be determined from Article 26.8.2l Vs = may be determined from paragraph d. In equations for Vc and Vs, d shall be the distance from the extreme compression fiber to the centroid of the prestressed reinforcement in the tension chord or 0.8h, whichever is greater. c.

The applied shear Vu in regions near supports may be reduced to the value computed at a distance h / 2 from the support when both of the following conditions are satisfied: (1) The support reaction, in the direction of the applied shear, introduces compression into the support region of the member, and (2) No concentrated load occurs within a distance h from the face of the support.

d. The nominal shear contribution of the truss model with concrete diagonals at 45 degrees inclination as determined by the shear reinforcement perpendicular to the axis of the member is V s = Avf syd / s e.

Where required by Article 26.8.2j, torsion reinforcement shall be provided in addition to the reinforcement required to resist the factored shear, flexure and axial forces that act in combination with the torsion.

f.

The longitudinal and transverse reinforcement required for torsion shall be determined from: Tu £fTn

g.

The nominal torsional resistance provided by a space truss with concrete diagonals at 45 degrees inclination and the indicated transverse reinforcement for torsion is: T n = 2 A oAtf sy/ s where: Ao = defined in Article 26.8.2j

h. The additional longitudinal reinforcement for torsion shall not be less than: Al = (Tnph) / (2Aofsy) where: ph = the perimeter of the polygon defined by the centroids of the longitudinal chords of the space truss resisting torsion.

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ph may be taken as the perimeter of the centerline of the outermost closed stirrups. Al shall be distributed around the perimeter of the closed stirrups in accordance with Article 26.8.2t.1 i.

The area of additional longitudinal torsion reinforcement in the flexural compression zone may be reduced by an amount equal to M u /(0. 9d f s y ) where Mu is the factored bending moment acting at that section except that the reinforcement provided shall not be less than required by Article 26.8.2t.

26.8.4 STRUT-AND-TIE TRUSS MODEL DESIGN FOR EITHER BEAM TYPE OR DISCONTINUITY REGIONS (1996)2 a.

The design of any region for shear and torsion may be carried out according to this article based on an analysis of the internal load paths for all forces acting on the member or region. The effects of the prestress force shall be included in accordance with Article 26.8.1f. The internal load paths shall be idealized using appropriate strut-and-tie or space truss models consisting of: (1) Concrete and compressive reinforcement compression chords. (2) Inclined concrete compressive struts. (3) Longitudinal reinforcement tension chords or ties.

1

(4) Transverse reinforcement tension members or ties. (5) Node regions at all joints of chords, struts and ties.3 b. The proportions of the elements and the reinforcement shall be selected so that the tension ties yield before the compression chords or struts crush. Chord capacities shall be based on underreinforced sections for flexure. c.

3

The size of the members and joint regions in the truss shall be chosen so that the computed forces in the struts, ties, and truss members, Su, due to factored loads shall satisfy: (1) Compression chords ff ( 085f c' A cc + A's f s' ) ³ S u

4

where: ff = the appropriate f value for flexure (2) Inclined compressive struts fv(fcuAcs) ³ Su where: fv = the appropriate f value for shear and diagonal tension 1 2 3

See Commentary See Commentary See Commentary

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fcu = the limiting strut compressive stress from paragraph d (3) Reinforcement tension chords * )³S ff ( A s f sy + A *s f su u

where: ff = the appropriate f value for flexure * = f su

the average stress in prestressing steel at ultimate load considering the anchorage and bonding conditions

(4) Transverse reinforcement tension members or ties: fv(Avfsy) ³ Su where: fv = the appropriate f value for shear and diagonal tension When such members or ties are prestressed, the effective stress after prestress losses shall be used in place of fsy. (5) Node regions fb(fcnAcn) ³ Su where: fb = the appropriate f value for bearing fcn = the limiting compressive stress in a node region from paragraph f d. The compressive stress in an inclined compressive strut, fcu shall not exceed: (1) For essentially undisturbed, uniaxial compressive stress states 0.6 f c' . (2) For compressive stress states where tensile strains in the cross-direction or transverse tensile reinforcement may cause cracking of normal crack width parallel to the strut 0.45 f c' . (3) For compressive stress states with skew cracking or skew transverse reinforcement 0.35 f c' . (4) For compressive stress states with very wide skew cracks when the strut orientation differs appreciably from the elastic orientation of the internal load path 0.25 f c' . e.

The tension chord and all tension ties shall be effectively anchored to transfer the required tension to the truss node regions in accordance with the ordinary requirements of Part 2, Reinforced Concrete Design

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for development of reinforcement (Section 2.14) and shall be detailed to satisfy the stress limits of paragraph f. f.

Unless special confining reinforcement is provided, the concrete compressive stress fcn in the node regions shall not exceed: (1) 0.85f c' in node regions bounded by compressive struts and bearing areas, (2) 0.70f c' in node regions anchoring only one tension tie, or (3) 0.60f c' in node regions anchoring tension ties in more than one direction.

26.8.5 SPECIAL REQUIREMENT FOR DIAPHRAGMS, DEEP BEAMS, CORBELS AND BRACKETS (1996) 26.8.5.1 General All discontinuity regions must be proportioned using the strut-and-tie model approach of Article 26.8.4. Special discontinuity regions like diaphragms, deep beams, corbels, brackets must also satisfy the special provision of Article 26.8.5. 26.8.5.2 Diaphragms and Deep Beams a.

Diaphragms are ordinarily required in pier and abutment superstructure segments to distribute the high shear forces to the bearings. Vertical and transverse post-tensioning shall be analyzed using the strutand-tie model of Article 26.8.4 and the effective prestress forces of Article 26.8.1f. The diaphragm tendons must be effectively tied into the diaphragms with bonded nonprestressed reinforcement to resist tendon forces at the corners of openings in the diaphragms.1

b. Deep beams are members in which the distance from the point of zero shear to the face of the support is less than 2d or members in which a load causing more than one-third of the shear at a support is closer than 2d from the face of the support.

1

3

(1) The strut-and-tie model of Article 26.8.4 shall be used to analyze and design deep beams.2 (2) The minimum tensile capacity of transverse reinforcement shall be 120bws, and s shall not exceed d/4 nor 12 inches. (3) Bonded longitudinal bars shall be well distributed over each face of the vertical elements in pairs. The minimum tensile capacity of this bonded reinforcement pair shall be 120bws. The vertical spacing between each pair, s, shall not exceed d/ 3 nor 12 inches. (4) In deep beam vertical elements with a width less than 10 inches, the pairs of bonded bars required by paragraph (3) may be replaced by a single bar with the required tensile capacity. 26.8.5.3 Brackets and Corbels a.

1 2 3

The strut-and-tie model of Article 26.8.4 shall be used to analyze and design brackets and corbels.3

See Commentary See Commentary See Commentary

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b. The depth at the outside edge of the bearing area shall be at least half the depth at the face of the support. c.

Corbels and brackets shall be designed to resist the calculated external tensile force Nut acting on the bearing area, but Nut shall not be less than 0.2 Vu unless special provisions are made to avoid tensile forces. Therefore, Nut shall be regarded as a live load even when tension results from creep, shrinkage or temperature change.

d. The steel ratio A s / b d at the face of the support shall be at least 0.04f c' ¤ f sy , where d is measured at the face of the support. e.

Closed stirrups or ties parallel to the primary tensile tie reinforcement, As, with a total area not less than 0.5 As shall be uniformly distributed within 2/3 of the effective depth adjacent to As.

f.

At the front face of a bracket or corbel, the primary tension reinforcement As shall be effectively anchored to develop the specified yield strength, fsy, by: (1) A structural weld to a transverse bar of at least equal size, or; (2) Bending the primary bars, As back to form a continuous loop, or; (3) Some other positive means of anchorage.

g.

The bearing area of the load on a bracket or corbel shall not project beyond the interior portion of the primary tension bars, As, nor project beyond the interior face of any transverse anchor bar.

26.8.6 SHEAR TRANSFER AT INTERFACES (1996) Shear transfer at interfaces shall be designed in accordance with Part 2, Reinforced Concrete Design, Article 2.35.4 using the f values found in this Part.

26.8.7 TWO-WAY PUNCHING SHEAR (1996) Two-way punching shear slab type elements shall be designed in accordance with Part 2, Reinforced Concrete Design, Article 2.35.6 using the appropriate f values from this Specification.

SECTION 26.9 FATIGUE STRESS LIMITS 26.9.1 FATIGUE STRESS LIMITS FOR BONDED NONPRESTRESSED REINFORCEMENT (1996)1 Design of bonded nonprestressed reinforcement for fatigue shall conform to the provisions of Part 2, Reinforced Concrete Design, Article 2.26.2.

1

See Commentary

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26.9.2 FATIGUE STRESS LIMITS FOR PRESTRESSED REINFORCEMENT (1996)1 Fatigue of prestressed reinforcement need not be considered for bridges designed in accordance with this Specification.

SECTION 26.10 DESIGN OF LOCAL AND GENERAL ANCHORAGE ZONES, ANCHORAGE BLISTERS AND DEVIATION SADDLES 26.10.1 GENERAL (1996)2 a.

Anchorage zones for post-tensioning tendons are regions of complex stresses. The post-tensioned anchorages zone may be considered as comprised of two zones.

b. The local zone is the region immediately surrounding each anchorage device. It may be taken as a cylinder or prism with transverse dimensions approximately equal to the sum of the projected size of the bearing plate plus the manufacturer’s specified minimum side or edge cover. The length of the local zone extends for the length of the anchorage device plus an additional distance in front of the anchor equal to at least the maximum lateral dimensions of the anchor. Performance of the anchorage device and furnishing of any supplementary reinforcement required in this local zone is the responsibility of the constructor and material suppliers. These responsibilities shall be set forth in the project plans and specifications. c.

The general zone is the region in front of the anchor which extends along the tendon axis for a distance equal to the overall depth of the member. The height of the general zone is taken as the overall depth of the member. In the case of intermediate anchorages which are not at the end of a member, the general zone shall be considered to also extend along the projection of the tendon axis for about the same distance before the anchor.

1

3

d. Design and specification of any supplementary reinforcement required in the general zone (in addition to the required local zone reinforcement) is the responsibility of the engineer of record. Proper installation of such supplementary reinforcement is the responsibility of the constructor.

1 2

e.

Reinforcement shall be provided for bursting, splitting, and spalling tensile stresses generated by tendon anchorages and deviation saddles in accordance with the following provisions of this Section. The method of analysis shall consider anchorage eccentricity, tendon inclination, and tendon curvature.

f.

The proportions and supplementary reinforcement of the local zone containing the tendon anchors must be adequate to transfer the tendon force into the mass of the concrete structure. The load transfer may be achieved by either bearing plate type anchors or by special anchorage devices which in combination with special anchor reinforcement (such as spirals, stirrups or other reinforcement) transfer the local zone loads from the anchors into the general anchorage zone of the structure.

See Commentary See Commentary

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26.10.2 FORCES AND REINFORCEMENT IN GENERAL ANCHORAGE ZONES (1996)1 a.

The general distribution of forces and the reinforcement required to provide the necessary general anchorage zone tensile capacity to counteract the bursting forces of the anchorages may be determined using the strut-and-tie model approach of Article 26.8.4.

b. In lieu of analysis using the strut-and-tie approach, the total bursting force, Fbst, for an individual anchorage shall be taken as: F bst = 0.30 ( 1 – d a ¤ d sp )P j

26.10.3 REINFORCEMENT (1996) 26.10.3.1 Local Zones The local zone shall be reinforced for the bursting forces as required for the anchor type used in accordance with the provisions of Article 26.5.2.3 and Article 26.10.2. The reinforcement may consist of stirrups, ties, spirals, or combinations of these. 26.10.3.2 General Anchorage Zone Bursting and Directional Forces2 The structure shall be reinforced with stirrups or ties to resist general anchorage zone bursting forces and directional forces due to total post-tensioning forces anchored at a section in accordance with the provisions of Article 26.5.2.3 and Article 26.10.2. 26.10.3.3 Stress in Reinforcement for Bursting Forces3 Reinforcement for bursting forces shall be designed for maximum jacking forces at time of stressing with fs = 0.6 fsy where fsy shall not exceed 60 ksi. 26.10.3.4 Post-Tensioning Post-tensioning may be provided to supplement reinforcement restraint against anchorage bursting or directional forces.

26.10.4 REINFORCEMENT DETAILING (1996) Reinforcement may be in the form of spirals, stirrups, orthogonal reinforcement, or combinations of these. Groups of anchorages shall be restrained by reinforcement stirrups or lateral post-tensioning enclosing the entire group. All orthogonal reinforcement must be mechanically anchored around reinforcement running parallel with tendons. All spirals, stirrups, or orthogonal reinforcement shall have sufficient extra length to develop full bond with the concrete, or shall be mechanically anchored by 135 degrees bends around reinforcement. The clear distance between bars or pitch of spirals used as anchorage zone reinforcement shall be at least the maximum size of the coarse aggregate plus 1/2 inch but not less than 1-1/2 inches.

1 2 3

See Commentary See Commentary See Commentary

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26.10.5 ANCHORAGES IN SPECIAL BLISTERS (1996) 26.10.5.1 Design In addition to reinforcements provided for tensile stresses perpendicular to the tendon trajectory, blisters shall also be designed for shear and bending between the blister and web/flange interface. For these purposes, the strut-and-tie models of Section 26.8, Shear and Torsion, or the rules for shear friction and special provisions brackets and corbels as set out in Part 2, Reinforced Concrete Design shall be applied. The reinforcement required for anchorage zone tensile stress may also be used for shear friction calculations if full bond development or mechanical anchorage within the web and slab is provided for the reinforcement. 26.10.5.2 Local Bending When blisters are used, a check shall be made for the localized bending induced into the web and/or flange in the region surrounding the anchorage. Reinforcement shall be provided equivalent to the force represented by the concrete tensile stress block proportioned at a stress of not more than 0.6 fsy, where fsy shall not exceed 60 ksi. 26.10.5.3 Local Tensile Stresses Behind Anchorage Blisters Blisters should preferably be located at the juncture of the flange and the web. Calculations shall be made to assure that sufficient residual compression exists behind anchorage blisters that no localized tensile stresses occur, or sufficient reinforcement shall be provided at an allowable stress of 0.6 fsy (maximum value of fsy to be 60 ksi) to take all the tensile force. Use of anchorage blisters projecting from one surface only, such as a flange, should preferably be restricted to anchorage of small tendons and bars. Blisters shall preferably be located sufficiently far from a joint to allow dispersal of local tensile stress effects through the reinforced slab. Minimum reinforcement shall be provided to carry 25-50% of the anchor load into the concrete behind the anchor. The amount of reinforcement provided shall be based on evaluation of the compressive stress level due to other tendons or loads in the local area behind the anchor, and shall increase to an amount of reinforcement sufficient to carry 50% of the tendon force whenever local net tensile stresses might be generated behind the anchorage.

1

3

26.10.6 ANCHORAGES IN DIAPHRAGMS (1996) Reinforcement shall be provided to ensure a full transfer of shear load from the diaphragm to the webs and flanges. The diaphragm shall be designed and reinforced for any localized bending effects due to concentrated anchorage loads. Anchorage zones in diaphragms shall be reinforced in accordance with Article 26.10.2.

26.10.7 ANCHORAGE BEARING REACTION FORCE (1996) In situations where the anchorage reaction force is not parallel to the longitudinal axis of the beam, it is necessary to take into account the magnitude and direction of the anchorage bearing reaction. Reinforcement or post-tensioning shall be provided as required to contain the component of the anchorage reaction perpendicular to longitudinal axis of the girder. The reinforcement stress may be taken as 0.6 fsy but not greater than 36 ksi (for Grade 60 steel).

26.10.8 DEVIATION SADDLES (1996) 26.10.8.1 General Deviation saddles are blisters external to the webs and flanges, normally on the inside of a box at the junction of web and flange where tendons placed external to the concrete are deviated in direction to produce the required tendon profile. © 2011, American Railway Engineering and Maintenance-of-Way Association

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Concrete Structures and Foundations 26.10.8.2 Design Reinforcement shall be provided in the form of fully anchored reinforcement and bent bars in webs or flanges * from the deviated tendon(s) at a service stress of 0.5 f . to take the resultant pull out force computed at f su sy Additional reinforcement shall be provided to take any out of balance longitudinal forces by shear friction action according to the ACI 318-86 Standard Building Code, Article 11.7. Reinforcement shall also be provided to take any localized bending and axial effects transmitted from the deviation saddles to the webs and/or flanges. 26.10.8.3 Detailing All reinforcements shall have a full effective development length measured from the tendon axis or shall otherwise be fully mechanically anchored around longitudinal reinforcement located at the outside of the (box) section. Consideration shall be given to constructibility and clearances between reinforcement for adequate concrete compaction. Not more than two reinforcing bars shall be bundled and the clear distance between reinforcement shall be at least 1/2 inch greater than the maximum coarse aggregate size and in no case less than 1-1/2 inches. 26.10.8.4 Localized Effects on Transverse Design The transverse design of the section shall be checked for the transverse force imparted through deviation saddles, including any unsymmetrical effects due to sequential post-tensioning. Additional bonded reinforcement proportioned at a tensile stress of 0.6 fsy, where fsy shall not be taken as greater than 60 ksi, or transverse post-tensioning shall be provided equivalent to the tensile force induced in the slab.

SECTION 26.11 PROVISIONAL POST-TENSIONING DUCTS AND ANCHORAGES 26.11.1 GENERAL (1996) In accordance with Article 26.11.2, the design of ducts and anchorages for bridges with internal tendons shall provide for increases in the post-tensioning force at selected locations along the bridge during construction to compensate for excessive friction and wobble losses during stressing. For bridges with either internal or external tendons, the design shall provide for future addition of external unbonded tendons in accordance with provisions of Article 26.11.3 as an allowance for addition of future dead load, or to adjust for deflection of the bridge.

26.11.2 BRIDGES WITH INTERNAL DUCTS (1996)1 At intervals of not more than three segments, provisional anchorage and duct capacity for negative and positive moment tendons located symmetrically about the bridge centerline shall provide for an increase in the posttensioning force. The total provisional force potential of both positive and negative moment anchorages and ducts shall not be less than 5% of the total positive and negative moment forces, respectively, and shall be distributed uniformly at three segment intervals along the length of the bridge. At least one empty duct per web shall be provided with anchorages at appropriate locations. Except for non-continuous bridges, and the minimum empty duct capacity noted above, provisional positive moment duct and anchorage capacity shall not be required for 25% of the span length either side of pier supports. Any provisional ducts not utilized for adjustment of the post-tensioning force shall be grouted at the same time as other ducts in the span.

1

See Commentary

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26.11.3 PROVISION FOR FUTURE DEAD LOAD OR DEFLECTION ADJUSTMENT (1996)1 Specific provisions shall be made for access and for anchorage attachments, pass through openings, and deviation block attachments to permit future addition of unbonded external tendons symmetrically about the bridge centerline for a post-tensioning force of not less than 5% of the total positive moment and negative moment post-tensioning force.

SECTION 26.12 DUCT DETAILS 26.12.1 MATERIAL THICKNESS (1996) 26.12.1.1 Metal Ducts2 Metal ducts shall be galvanized corrugated semi-rigid conduit. For strand and wire tendons, the duct thickness shall be 26 gage up to 2-5/8 inches diameter. Ducts larger than 2-5/8 inches diameter shall be 24 gage. For bar tendons, the duct thickness shall not be less than 31 gage. 26.12.1.2 Polyethylene Duct3 Polyethylene duct or rigid pipe used as external duct shall be high density polyethylene conforming to ASTM D3350. Internal polyethylene duct shall have spiral corrugations. Rigid pipe may be manufactured in accordance with ASTM D2447, ASTM F714, or ASTM D2239. Material thickness shall be as follows: a.

1

Internal polyethylene duct = 0.050 inches ± 0.010 inch.

b. External polyethylene duct shall have a minimum external diameter to wall thickness ratio of 21 or less.

26.12.2 DUCT AREA (1996)4

3

Duct for strand and wire tendons shall be sized so that the area of the duct is at least 2-1/2 times the area of the prestressing steel it contains.

26.12.3 MINIMUM RADIUS OF CURVATURE (1996)5 a.

Tendon ducts shall preferably be installed with a radius of curvature of 20 feet or more. Ducts with sharper curvature down to a minimum of 10 feet shall have confinement reinforcement detailed to tie the duct into the concrete. Duct curvature with radii less than 10 feet may be approved by the Engineer based on review of test data. The minimum radius for corrugated polyethylene duct shall be 30 feet. The confinement reinforcement shall be proportioned to resist radial forces calculated as: Fr = P/ R where: P = the tendon force in pounds per foot

1 2 3 4 5

See Commentary See Commentary See Commentary See Commentary See Commentary

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R = the radius of curvature, in feet Fr = the radial force in pounds per foot Confinement reinforcement shall be proportioned at 0.6 fsy where fsy shall not exceed 60 ksi. Spacing of confinement reinforcement shall not exceed 12 inches. Closer spacing shall be used for duct with radius of curvature less than 15 feet. b. When the tendon profile radius of curvature is less than 20 feet, design consideration shall also be given to lateral forces exerted by multistrand tendons on thin webs due to bunching of the strand at the top or bottom of circular ducts. Confinement reinforcement, preferably in the form of spirals, shall be provided whenever the nominal shear stress due to tendon jacking forces in the concrete cover beside the tendon exceeds 2 f c' .

26.12.4 DUCT SUPPORTS (1996) 26.12.4.1 Internal Supports1 a.

Internal ducts shall be rigidly supported by ties to reinforcing steel as follows: (1) Transverse slab tendons in metal duct: 2 feet. (2) Transverse slab tendons in polyethylene duct: 2 feet. (3) Longitudinal slab or web tendons in metal duct: 4 feet. (4) Longitudinal slab or web tendons in polyethylene duct: 2 feet.

26.12.4.2 External Ducts2 External ducts shall have a maximum unsupported length of 25 feet unless a vibration analysis is made.

26.12.5 DUCT SIZE, CLEARANCE AND DETAILING (1996) a.

Maximum size of ducts shall not exceed 0.4 ´ web thickness.

b. Where two curved tendons run parallel such that the outer one is bearing inwards toward the inner one, a minimum clearance of one duct diameter shall preferably be maintained between the ducts. If this is not possible, reinforcement shall be provided between the ducts to fully restrain the outer tendon if it has to be stressed before the inner tendon has been stressed and grouted. In cases where longitudinal tendons cross each other, at least one-half duct diameter but not less than 2 inches clear space shall be provided. This restriction does not apply to transverse ducts crossing longitudinal ducts at approximately 90 degrees. c.

1 2

Curved tendons should not be placed around re-entrant corners or voids. If this is unavoidable, then the tendons must be provided with well anchored, full reinforcement restraint proportioned as per Article 26.12.6.1. In no case shall the distance between the re-entrant corner or void and the edge of the duct be less than 1.5 duct diameters.

See Commentary See Commentary

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26.12.6 DUCT CONFINEMENT REINFORCEMENT (1996) 26.12.6.1 Ducts in Webs of Curved Bridges a.

When curved tendons are located in thin webs or close to internal voids reinforcement shall be provided to prevent the tendon from bursting through the concrete into the void whenever the nominal shear stress in the cover beside the tendon due to tendon jacking forces exceeds 2 f c' . The area of steel required may be estimated from: A s = P/ ( R ´ 0.6 f s y ) where: Asy = Area of steel required, inches2/foot

b. The lateral force exerted on the concrete by the tendons may be calculated by dividing the tendon force by the radius of curvature in accordance with Article 26.12.3. 26.12.6.2 Ducts in Flanges1 a.

Ducts in bottom slabs shall be located between top and bottom layers of transverse and longitudinal slab reinforcement. For ducts in the bottom flanges of variable depth segments, nominal confinement reinforcing shall be provided around the duct at each segment face. The reinforcement shall not be less than two rows of #4 hairpin bars at both sides of each duct with vertical dimensions equal to the slab thickness less top and bottom cover dimensions.

b. When closely spaced transverse or longitudinal ducts are located in top or bottom flanges, the top and bottom nonprestressed reinforcement mats shall be tied together with vertical reinforcement consisting of #4 hairpin bars with spacing not to exceed 18 inches or 1-1/2 times the slab thickness in each direction, whichever is the lesser.

1

3

SECTION 26.13 COUPLERS (1996)2 Not more than 50% of the longitudinal post-tensioning tendons shall be coupled at one section. The spacing between adjacent coupler locations shall not be closer than the segment length or twice the segment depth. The void areas around couplers shall be deducted from the gross section area and moment of inertia when computing stresses at the time of application of the post-tensioning force.

SECTION 26.14 CONNECTION OF SECONDARY BEAMS (1996)3 a.

1 2 3

The load from secondary beams connected to the main beam (indirect support) shall be resisted by suspension stirrups or inclined bars. Not less than 2/3 of this suspension reinforcement shall be located in the immediate area of the intersection. The entire load shall be transmitted within the intersection

See Commentary See Commentary See Commentary

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zone specified in Figure C-8-26-8. Existing shear reinforcement within the intersection zone may be considered as part of the suspension reinforcement provided that the secondary beam extends for the full height of the main beam. Suspension stirrups and inclined bars shall be anchored in accordance with Part 2, Reinforced Concrete Design, Section 2.21. b. Detailing of the connection may be accomplished by use of the strut-and-tie procedures outlined in Article i.

Figure 8-26-8. Reinforcement Details

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SECTION 26.15 CONCRETE COVER AND REINFORCEMENT SPACING 26.15.1 COVER AND SPACING (1996) Reinforcement cover and spacing shall conform to Part 2, Reinforced Concrete Design, Section 2.6 and to Article 26.15.2.

26.15.2 REINFORCEMENT DETAILS FOR ERECTION LOADS (1996)1 The transverse analysis of the box girder shall include an evaluation of the quantity Z of Part 2, Reinforced Concrete Design, Section 2.39, EQ 60, for any loads applied prior to attainment of full design strength. The value of Z calculated for flanges and webs shall not exceed 130 kips per inch.

SECTION 26.16 INSPECTION ACCESS (1996) Inspectability of the structure shall be assured by providing secured access hatches with minimum dimensions of 2¢ -6² ´ 4¢ -0² . Interior diaphragms shall be provided with openings larger than the dimensions specified for access hatches. The box section shall be vented by drains or screened vents in webs at intervals not greater than 50 feet. Such venting is to prevent the build up of potential hazardous gas which might endanger inspection personnel.

1

SECTION 26.17 BOX GIRDER CROSS SECTION DIMENSIONS AND DETAILS

3

26.17.1 MINIMUM FLANGE THICKNESS (1996)2 Top and bottom flange thickness shall not be less than any of the following: a.

1/30 the clear span between webs or haunches, a lesser dimension will require transverse ribs at a spacing equal to the clear span between webs or haunches.

b. Top flange, 9 inches where transverse post-tensioning is anchored. Transverse post-tensioning or pretensioning shall be used where the clear span between webs or haunches is 15 feet or larger. Strand used for transverse pretensioning shall be 0.5 inch diameter or less.

26.17.2 MINIMUM WEB THICKNESS (1996)3 a.

Webs with no longitudinal or vertical post-tensioning tendons – 8 inches.

b. Webs with only longitudinal (or vertical) post-tensioning tendons – 12 inches. c.

1 2 3

Webs with both longitudinal and vertical post-tensioning tendons – 15 inches.

See Commentary See Commentary See Commentary

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26.17.3 LENGTH OF TOP FLANGE CANTILEVER (1996) The cantilever length of the top flange measured from the centerline of web should preferably not exceed 0.45 the interior span of the top flange measured between the centerline of the webs.

26.17.4 OVERALL CROSS SECTION DIMENSIONS (1996)1 Overall dimensions of the box girder cross section should preferably not be less than required to limit live load plus impact deflection calculated using the gross section moment of inertia and the secant modulus of elasticity to 1/1800 of the span. The live loading shall be in accordance with Part 2, Reinforced Concrete Design, Article 2.2.3c. The live loading shall be considered to be uniformly distributed to all longitudinal flexural members.

COMMENTARY The purpose of this part is to furnish the technical explanation of various articles in Part 26, Recommendations for the Design of Segmental Bridges. In the numbering of articles of this section, the numbers after the “C-” correspond to the section/article being explained.

C - SECTION 26.1 GENERAL REQUIREMENTS AND MATERIAL C - 26.1.1 GENERAL (1996) a.

Segmental bridges contemplated under this Article include but are not limited to those erected by the following methods: (1) Balanced cantilever (2) Span-by-span with truss or falsework (3) Span-by-span lifting (4) Incremental launching (5) Progressive placement

b. The span length of bridges considered by these specifications ranges to approximately 800 feet. Bridges supported by stay cables are not specifically covered although many of the specification provisions are applicable to cable-stayed bridges. c.

1

Lightweight concrete has been infrequently used for segmental bridge construction. Provision for the use of lightweight aggregates represents a significant complication of both design and construction specifications. For these reasons, as well as questions concerning the economic benefit of use of lightweight aggregates for segmental bridges, their use is not explicitly covered in these specifications.

See Commentary

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C - 26.1.5 SEGMENTAL BRIDGES, DESIGN REINFORCEMENT (1996) a.

Special corrosion protection is considered necessary for all bridge deck reinforcement in areas of contamination or where de-icer or other harmful chemicals may be applied. Corrosion protection should also be provided for all reinforcement of bridges located in coastal areas or over sea water, or in heavily industrialized areas.

b. See the ACI Committee 222 report “Corrosion of Metals in Concrete” (Reference 3) for a comprehensive discussion of methods of corrosion protection.

C - SECTION 26.2 METHODS OF ANALYSIS C - 26.2.1 GENERAL (1996) Results of elastic analyses should be evaluated with consideration of possible variations in the modulus of elasticity of the concrete, and variations on the concrete creep and shrinkage properties, as well as the impact of variations in the construction schedule on these (and other) design parameters.

C - 26.2.2 STRUT-AND-TIE-MODELS (1996) Strut-and-tie models provide one means of analyzing areas near concentrated loads, bearing areas, diaphragms, corners, bends, openings, anchorage zones for post-tensioning tendons, and other areas where non-linear strains exist, as well as the cracked global structural system. Morsch proposed an extension of this concept in 1989. (Reference 18, 56 and 85)

1

C - 26.2.3.1 General The procedures of Article 3-10.2 of the 1983 Ontario Highway Bridge Design Code provides an equation for determining the effective flange width for use in calculating bending resistances and bending stresses. C - 26.2.3.2 Effective Flange Width for Analysis, and for Calculation of Section Capacity and Stresses a.

Note that b as used in this Article is the flange width on either side of the web. (b1, b2, or b3 in Figure C-8-26-1).

b. The pattern of stress distribution in Figure C-8-26-4 is intended only for calculation of stresses due to anchorage of post-tensioning tendons, and may be disregarded in the general analysis to determine design moments, shears and deflections. c.

Superposition of local slab bending stresses due to track loads (two-way slab action) and the primary longitudinal bending stresses is not normally required.

C - 26.2.4 TRANSVERSE ANALYSIS (1996) See references (Reference 73 and 86) for background on transverse analysis of concrete box girder bridges. C - 26.2.5.1 General a.

3

Analysis of concrete segmental bridges requires consideration of variation of design parameters with time, as well as a specific construction schedule and method of erection. This, in turn, requires the use of a computer program developed to trace the time-dependent response of segmentally erected prestressed concrete bridges through construction, and under service loads. Among the many programs developed

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for this purpose, several are in the public domain, and may be purchased for a nominal amount. (Reference 21, 46 and 90) b. A comprehensive series of equations for evaluating the time-related effects of creep and shrinkage is presented in the ACI Committee 209 report, “Prediction of Creep, Shrinkage and Temperature Effects in Concrete Structures.” (Reference 2) A procedure based on graphical values for creep and shrinkage parameters is presented in the CEB-FIP Model Code. (Reference 15) c.

Recent research results (Reference 14) have suggested that the ACI 209 predictions underestimate the creep and shrinkage strains for the large scale specimens used in segmental bridges. The ACI 209 creep predictions were consistently about 65% of the experimental results in these tests. The report suggests modifications of the ACI 209 equations based on the size or thickness of the members.

C - SECTION 26.3 DESIGN LOADS C - 26.3.2 DEAD LOADS (1996) a.

The use of lightweight concrete is not covered in these specifications for the reasons outlined in the commentary to Article 26.1.1.

b. The value of 155 pcf for the unit weight of concrete is intended to provide for more heavily reinforced sections than would be anticipated in more conventional concrete superstructures.

C - 26.3.3 ERECTION LOADS (1996) Erection loads may be imposed on opposing cantilever ends by use of the Formtraveler, diagonal alignment bars, a jacking tower, or by external weights. Cooling of one cantilever with water has also been used to provide adjustment of misalignment. Any misalignment of interior cantilevers should be corrected at both ends before constructing either closure. The frame connecting cantilever ends at closure pours should be detailed to prevent differential vertical movement between cantilevers due to forces including thermal gradient until the final structural connection is complete. The magnitude of closure forces should not induce stresses in the structure in excess of those stipulated in these specifications. C - 26.3.4.3 Thermal Coefficient For major bridges, tests or use of previous test data to determine more precise thermal coefficients is recommended. C - 26.3.4.4 Differential Temperature a.

Additional field research is recommended to verify the temperature gradients specified in the referenced NCHRP report for four temperature zones in the United States. Railroad bridges differ from highway bridges when the deck is ballasted and require special attention. While the need for consideration of thermal gradients in design of concrete box girder bridges has been clearly demonstrated, opinion is divided as to the need for use of complex gradients and relatively high temperature differentials outlined in NCHRP Report 276. However, the use of the provisions of Appendix A of NCHRP Report 276 is conservative and is recommended for unballasted decks until such time as additional research data on thermal gradients and temperature differentials becomes available.

b. Transverse analysis for the effects of differential temperature outside and inside box girder Articles is not considered generally necessary. However, such an analysis may be necessary for relatively shallow bridges with thick webs. (Reference 43, 49, 50 and 73) In that case, a ±10 degrees F temperature differential is recommended. Additional field research is recommended to determine temperature © 2011, American Railway Engineering and Maintenance-of-Way Association

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differentials between the inside and outside surfaces of segmental concrete box girder Articles in U. S. temperature zones.

C - 26.3.5 CREEP AND SHRINKAGE (1996) a.

A variety of computer programs and analytical procedures have been published to evaluate creep and shrinkage effects in segmental concrete bridges. (Reference 2, 15, 21, 27, 46 and 90)

b. For permanent loads, the behavior of segmental bridges after closure may be approximated by use of an effective modulus of elasticity, Eeff, which may be calculated as: E e f f = E c m / fc where: fc = the creep coefficient Ecm = the 28 day secant modulus of elasticity of the concrete calculated from: E cm = 57, 000 f c' where: Ecm, Eeff and f c' are all in psi.

1

C - 26.3.5 CREEP AND SHRINKAGE (1996) Prestress losses vary significantly with different values of the creep coefficient, type of prestressing steel (low relaxation steel is recommended), and with the creep model (ACI 209 or CEB-FIP). Further, the prestress losses vary significantly at different sections along the superstructure.

3

C - SECTION 26.4 LOAD FACTORS C - 26.4.3 STRENGTH REDUCTION FACTORS (1996) a.

The values of ff and fv presented in Article 26.4.3 are based on consideration of relatively limited test results (Reference 4, 47 and 76 and Figure C-8-26-1) and are considered interim provisions until further comprehensive tests, analyses, and experience with completed structures are obtained.

b. The proposed ff values for flexure for segmental bridges with fully bonded tendons with cast-in-place concrete joints, wet concrete joints or epoxy joints are based on the current AASHTO value of 0.95 for monolithic post-tensioned construction. This specification assumes the practice of requiring epoxy for all joints having internal tendons passing through them is valid. Comprehensive tests (Reference 95) of a large continuous three span model of a twin cell box girder bridge built from precast segments with fully bonded internal tendons and epoxy joints indicated that cracking was well distributed throughout the segment lengths, no epoxy joint opened at failure, and the load-deflection curve was identical to that calculated for a monolithic specimen. The complete ultimate strength of the tendons was developed at failure. The model had substantial ductility and full development of calculated deflection at failure. Recent tests (Reference 40 and 76) on single span segmental girders with varied tendon arrangements (internal, mixed and external tendons) and with dry joints indicate that the deflection at failure was less than would be expected for monolithic girders. Flexural cracking concentrated at joints, and final failure came with a central joint opening widely and crushing occurring at the top of the joint. The somewhat limited ductility is reflected in the reduced f factors for Type B (dry) joints as well as reduced f factors with unbonded tendons which allow the concentration of articulation at a single joint opening. The

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Figure C-8-26-1. Relative Joint Displacement Shear Key Behavior (Reference 4) reduction in nominal strength for unbonded construction is adequately reflected in the determination of unbonded tendon stress at ultimate using AREMA calculation procedures. c.

The proposed fv values for shear utilize the current AREMA value of 0.85 for monolithic construction as the accepted value for Type A joints (cast-in-place, wet concrete or epoxy joints) in bonded tendon construction based on the very favorable experience in the ultimate shear tests reported in Reference 95. Comparative shear tests of epoxy and dry joints indicate the epoxied joints develop the full strength of monolithically cast specimens. However, dry joints developed less strength and allowed appreciable slip along the joint. Because of this, lower fv factors are specified for dry joints (Type B).

d. The development length computation for defining a bonded tendon assumes that the duct is completely filled with grout and the grout completely surrounds all the strands. Therefore, the development length of a tendon is similar to that of an individual strand. C - 26.4.4.1 Erection Loads During Construction The differential load between cantilevers is to allow for possible variations in cross-section weight.

C - SECTION 26.5 ALLOWABLE STRESSES C - 26.5.2.3 paragraph b The bell anchor for threadbar tendons is an example of a confinement anchorage device that has demonstrated satisfactory performance over many years on major bridge projects. Other confinement anchorages which have demonstrated satisfactory performance utilize spiral reinforcement in conjunction with plate or casting type anchorages which do not comply with the bearing stress limitations of Article 26.5.2.3a.

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Recommendations for the Design of Segmental Bridges C - 26.5.2.3 paragraph c a.

NCHRP Project 10-29, “Anchorage Zone Reinforcement for Post-Tensioned Concrete Girders” is now underway at the University of Texas at Austin to develop more comprehensive recommendations for proportioning reinforcement for anchorage splitting stresses. Previous work at the University of Texas at Austin (Reference 70, 95 and 96) includes recommendations for design of anchorage zone reinforcement that may be utilized until NCHRP Project 10-29 is completed.

b. Bursting or splitting forces occur in front of individual anchors inside the local zone. The magnitude of these forces depends on the shape and design of the particular anchor. For plate type anchors these bursting forces and the required reinforcement can be determined by computation or by test. For confinement anchors, bursting forces in the local zone are normally not accessible by computations. Their adequacy can only be determined by representative tests. It is the suppliers responsibility to determine the required bursting reinforcement in the local zone for such special anchors. c.

General zone bursting forces exist beyond the individual tendon local zones. The general zone bursting forces are dependent primarily on the overall concrete dimensions and the magnitude, direction and location (eccentricity) of total prestressing force anchored and not on the particular anchor design. The reinforcement for these general zone bursting forces is part of the overall structural design, and is the responsibility of the Engineer. For design purposes, it may be conservatively assumed that any local zone reinforcement provided does not contribute to the strength of the general zone.

C - SECTION 26.7 FLEXURAL STRENGTH

1

C - 26.7.1 GENERAL (1996) a.

The minimum reinforcement provisions of Part 17, Prestressed Concrete were developed to avoid a brittle failure in a grossly under-reinforced simple span precast, prestressed section. Application to segmental concrete bridges results in requirements of more bonded reinforcement for bridges with more conservative (arbitrary) design tensile stress levels which is contrary to load requirements. Minimum reinforcement requirements are adequately covered by the allowable stresses and load factor requirements of these specifications.

3

* unbonded members. The German DIN b. Additional research is recommended to verify the value of f su Specification allows a stress increase of only 6 ksi for unbonded cantilever tendons, and no stress increase for fully continuous unbonded tendons.

4

C - SECTION 26.8 SHEAR AND TORSION C - 26.8.1 SCOPE (1996) All design for shear and torsion of prestressed concrete segmental bridges is based on ultimate load conditions because little information is available concerning actual shear stress distributions at working or service load levels. C - 26.8.1 paragraph b Regions with beam-type action are basically those where the Bernoulli hypotheses that linear strain profiles exist are valid. See B-regions in Figure C-8-26-2, Figure C-8-26-3, and Figure C-8-26-4.

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Figure C-8-26-2. Stress Trajectories in a B-Region and Near Discontinuities (D-Regions)1

Figure C-8-26-3. Beam with Direct Supports1

1

Republished through the courtesy of the Prestressed Concrete Institute, PCI Journal, V. 32, No. 3, May-June 1987, pp. 74-150.

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(a) real structure (b) loads and reactions applied in accordance with Bernoulli hypothesis (c) self equilibrating state of stress, and (d) real structure with B- and D-regions

Figure C-8-26-4. T-beam1

1

3

4

Figure C-8-26-5. Longitudinal Shear Transfer by Bottom Slab to Web Haunches1

1

Republished through the courtesy of the Prestressed Concrete Institute, PCI Journal, V. 32, No. 3 May-June 1987, p. 1.

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Concrete Structures and Foundations C - 26.8.1 paragraph c Discontinuity regions, where the assumption that strain profiles are linear is invalid, usually exist for about a distance h from a concentrated load or point of geometrical discontinuity. See D-regions in Figure C-8-26-2, Figure C-8-26-3, and Figure C-8-26-4. Moving wheel loads need not be considered as large concentrated loads. The use of strut-and-tie models in design is well described in “Towards a Consistent Design of Structural Concrete,” by J. Schlaich, K. Schafer, and M. Jennewein, Vol. 32, No. 3 PCI Journal, May/June 1987, pp. 74– 150. (Reference 85) Note that a structure can be made up of both beam-type and discontinuity regions. The strut-and-tie model procedures must be used in the discontinuity regions. Either the traditional beam approach of the strut-and-tie approach can be used in the beam-type regions. C - 26.8.1 paragraph d a.

In addition for obvious checks for shear transfer when dissimilar materials are utilized, adequate shear transfer reinforcement must be provided perpendicular to the vertical planes of web/slab interfaces to transfer flange longitudinal forces at ultimate conditions. This shear transfer shall account for the shear force, F, as shown in Figure C-8-26-5, as well as any localized shear effects due to prestress anchorages at that Article.

b. Article 11.7 of ACI 318 is generally termed the “shear-friction” method but does provide in Article 11.7.3 that a wide range of shear transfer design methods may be utilized. In some cases, the designer may find the strut-and-tie method of Article i useful in proportioning transverse reinforcement to assist in transfer of horizontal shear between elements. C - 26.8.1 paragraph f a.

The shear effect of moving vehicle loads may be considered by development of maximum factored shear envelopes and the use of these values in determining the factored ultimate live load shear on the section.

b. Prestressing is considered as an applied load with a carefully controlled magnitude and direction. The components of the prestress force can add to or subtract from the shear on a cross section. In cantilevered segmental construction, the prestress vertical component can reverse the applied shear direction near the supports.

C - 26.8.2 GENERAL REQUIREMENTS (1996) C - 26.8.2 paragraph f The limitation on the effective diagonal tension and aggregate interlock components of shear strength contributed by the concrete has been adopted by ACI Committee 318. C - 26.8.2 paragraph h Research is recommended on the transfer length of 0.6 inch diameter strand. C - 26.8.2 paragraph i A simplified determination of Vc is presented which eliminates the need to check Vci and Vcw as in the present AREMA Specifications and which eliminates the complex V ud / M u term. This expression has been checked against a wide range of test data and has been found to be a conservative yet simpler expression.

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Recommendations for the Design of Segmental Bridges C - 26.8.2 paragraph v In place of requiring additional longitudinal reinforcement for shear as indicated by the mechanics of the truss model, the requirement of extending all flexural reinforcement beyond the theoretical bend or cut off points for a distance of h / 2 automatically satisfies this need. Since actual shear and torsion may vary from the assumed calculation, it is also recommended that transverse reinforcement be provided for the same distance beyond the zone theoretically required.

C - 26.8.3 TRADITIONAL SHEAR AND TORSION DESIGN FOR PLANE SECTION TYPE REGIONS (1996) This Article is a simplified version of the present AREMA approach for section design in beam-type regions. It is based on the simplified Vc term introduced in Article 26.8.2l. Provision of a “traditional” but less complex approach for beam-type regions is desirable since designers may find its application easier than strut-and-tie models for moving loads. C - 26.8.3 paragraph h In determining the required amount of longitudinal reinforcement, the beneficial effect of longitudinal prestressing may be taken into account by considering it equivalent to an area of reinforcing steel with a yield force equal to the effective prestressing force. C - i. The area of additional longitudinal torsion reinforcement in the flexural compression zone may be reduced by an amount equal to M u / ( 0 . 9d f s y ) where Mu is the factored bending moment acting at that section except that the reinforcement provided shall not be less than required by Article 26.8.2t.

1

This Article combines the recommendations of Schlaich, Schafer, and Jennewein with recommendations of Marti (Reference 56) as developed by ACI Committee 318, Subcommittee E for a future edition of the ACI Building Code. The proposed stress limits on struts and nodes may be subject to further refinement.

3

C - i paragraph a Figure C-8-26-6 (Reference 85) and Figure C-8-26-7 (Reference 85) illustrate the analysis using strut-and-tie models. Figure C-8-26-8 (Reference 85) shows a compression strut in a web with a tension tie in the stirrups. Figure C-8-26-9 (Reference 85) gives examples of basic types of nodes. An inclination angle f (Figure C-8-26-6) of 30 to 35 degrees is recommended for the inclined compressive struts in prestressed members.

4

C - 26.8.5.2 Diaphragms and Deep Beams C - 26.8.5.2 paragraph a Figure C-8-26-10 (Reference 85) illustrates application of the strut-and-tie model to analysis of forces in the diaphragm of a box girder bridge. C - 26.8.5.2b paragraph (1) Figure C-8-26-11 (Reference 85) shows application of the strut-and-tie model to analysis of deep beams. C - 26.8.5.3 paragraph a Figure C-8-26-12 (Reference 85) illustrates application of strut-and-tie models to analysis of corbels.

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(a) Model (b) Distribution of inner forces (c) Magnitude of inner forces derived from equilibrium of a beam element

Figure C-8-26-6. Truss Model of a Beam with Cantilever1

1

Republished through the courtesy of the Prestressed Concrete Institute, PCI Journal, V. 32, No. 3, May-June 1987, pp. 74-150.

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1 (a) and (b) Most frequent and useful strut-and-tie Models (c), (d), and (e) variations of above

3

4

Figure C-8-26-7. The Two Most Frequent and Most Useful Strut-and-Tie Models1

1

Republished through the courtesy of the Prestressed Concrete Institute, PCI Journal, V. 32, No. 3, May-June 1987, pp. 74-150.

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Figure C-8-26-8. The Compression Strut in the Web with the Stirrups1

1

Republished through the courtesy of the Prestressed Concrete Institute, PCI Journal, V. 32, No. 3, May-June 1987, pp. 74-150.

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1

3

4

(a) CCC-nodes. Idealized “hydrostatic” singular nodes transfer the concentrated loads from an anchor plate (a1) or bearing plate (a2) into (bottle shaped) compression fields (b) CCT-nodes. A diagonal compression strut and the vertical support reaction are balanced by reinforcement which is anchored by an anchor plate behind the node (b1), bond with the node (b2), bond within and behind the node (b3), bond and radial pressure (b4) Figure C-8-26-9. Examples of the Basic Types of Nodes1

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(a) D-regions and model of the web near the diaphragm (b) Diaphragm and model (c) Prestressing of the web and the diaphragm Figure C-8-26-10. Diaphragm of a Box Girder Bridge1

1

Republished through the courtesy of the Prestressed Concrete Institute, PCI Journal, V. 32, No. 3, May-June 1987, pp. 74-150.

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1

3 (a) Strut-and-tie model of uniformly loaded deep beam (b) Fan-shaped stress field (c) Strut-and-tie system for equivalent single load R replacing distributed load q

4

(d) Continuous fan developed from discrete strut

Figure C-8-26-11. Fan Action1

1

Republished through the courtesy of the Prestressed Concrete Institute, PCI Journal, V. 32, No. 3, May-June 1987, pp. 74-150.

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Figure C-8-26-12. Different Support Conditions Lead to Different Strut-and-Tie Models and Different Reinforcement Arrangements of Corbels1

1

Republished through the courtesy of the Prestressed Concrete Institute, PCI Journal, V. 32, No. 3, May-June 1987, pp. 74-150.

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C - SECTION 26.9 FATIGUE STRESS LIMITS C - 26.9.1 FATIGUE STRESS LIMITS FOR BONDED NONPRESTRESSED REINFORCEMENT (1996) Calculation of fatigue stress limits in bonded reinforcement is necessary only for cracked sections.

C - 26.9.2 FATIGUE STRESS LIMITS FOR PRESTRESSED REINFORCEMENT (1996) Bridges designed under the allowable stresses of this specification should be uncracked at service load levels. Fatigue of prestressed reinforcement will not occur in uncracked sections due to the related small stress range. Fretting fatigue due to rubbing between duct and strand also does not occur in uncracked sections.

C - SECTION 26.10 DESIGN OF LOCAL AND GENERAL ANCHORAGE ZONES, ANCHORAGE BLISTERS AND DEVIATION SADDLES C - 26.10.1 GENERAL (1996) See Article 26.5.2.3a for allowable local zone bearing stresses under anchorage plates, and allowable general zone tensile stress in reinforcement for the anchorage splitting force. The Commentary to Article 26.5.2.3a provides references for anchorage zone analysis and design. The pattern of splitting stresses due to bearing plate anchorages the same width as the web is illustrated by Figure C-8-26-13. Note that the maximum splitting stress occurs at 1/4 d to 1/2 d in front of the anchor. The value of the total bursting force in Article 26.10.2a is an approximation of the area under the splitting stress curve in Figure C-8-26-13.

1

C - 26.10.2 FORCES AND REINFORCEMENT IN GENERAL ANCHORAGE ZONES (1996) a.

The strut-and-tie approach suggested by Schlaich et al. (Reference 85) will give a good approximation of the reinforcement quantity and distribution required to counteract the general anchorage zone tensile forces set up both directly in advance of the anchorages (see Figure C-8-26-7) and in the outer regions of general anchorage zones with eccentrically located anchorages (see Figure C-8-26-14). The anchorage local zone becomes a node for the strut-and-tie model and the adequacy of the node must be checked by appropriate analysis or full scale testing as required under Article 26.5.2.3b.

b. The center of the bursting force is located approximately 3/8 of the depth of the section in front of the anchorage (see Figure C-8-26-13). c.

Tendon inclination, tendon curvature, and the blockout to achieve tendon inclination at the face of the anchorage all increase the bursting stresses. (Reference 70)

C - 26.10.3.2 General Anchorage Zone Bursting and Directional Forces Local anchorage zone reinforcement supplied as part of a proprietary post-tensioning system shall be shown on post-tensioning system shop drawings. Adjustment of general anchorage zone tensile reinforcement due to reinforcement supplied as part of a proprietary post-tensioning system may be considered as part of the shop drawing approval process. The responsibility for design of general anchor zone reinforcement remains with the Engineer of Record.

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Concrete Structures and Foundations

Figure C-8-26-13. Bursting Stresses Under Bearing Plate Anchorages1

(a) Elastic trajectories (b) Elastic stresses (c) Strut-and-tie models Figure C-8-26-14. A Typical D-Region1 1

Republished through the courtesy of the Prestressed Concrete Institute, PCI Journal, V. 32, No. 3, May-June 1987, pp. 74-150.

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Recommendations for the Design of Segmental Bridges C - 26.10.3.3 Stress in Reinforcement for Bursting Forces For flange thickness ranging from 5 to 9 inches, an upper limit of 12 - 1/2 inches f 270 k strand is recommended for tendons anchored in blisters supported only by the flange. The anchorage force of 347 kips for a tendon of this size must be carefully distributed to the flange by reinforcement.

C - SECTION 26.11 PROVISIONAL POST-TENSIONING DUCTS AND ANCHORAGES C - 26.11.2 BRIDGES WITH INTERNAL DUCTS (1996) Excess capacity may be provided by use of oversize ducts and oversize anchorage hardware at selected anchorage locations.

C - 26.11.3 PROVISION FOR FUTURE DEAD LOAD OR DEFLECTION ADJUSTMENT (1996) This provides for future addition if internal unbonded post-tensioning tendons draped from the top of the diaphragm at piers to the intersection of the web and bottom slab at midspan. Tendons from adjacent spans have to be lapped at opposite faces of the diaphragm to provide negative moment capacity. The requirement of a force of 5% of the total positive moment and negative moment post-tensioning force is an arbitrary value. Provision for larger amounts of post-tensioning might be developed as necessary to carry specific amounts of additional dead load as considered appropriate for the structure.

1

C - SECTION 26.12 DUCT DETAILS C - 26.12.1.1 Metal Ducts Thickness of metal duct material is related to duct diameter and the method of installing the tendon. Strand tendons are normally installed in the duct after the concrete is placed, requiring a stiffer duct. Bar tendons are preassembled inside small diameter ducts and placed as a unit. The bar fills most of the void and helps to prevent duct damage. The use of epoxy coated metal duct is not recommended due to questionable bond characteristics.

3

C - 26.12.1.2 Polyethylene Duct a.

Ontario Ministry of Transportation tests indicate a tendency for air entrapment for ducts with concentric corrugations.

4

b. ASTM D2239 relates to rigid pipe manufactured by a process based on controlled inside diameter. ASTM D2447 and ASTM F714 relate to rigid pipe manufactured by a process based on controlled outside diameter. All three specifications produce pipe satisfactory for bridge applications.

C - 26.12.2 DUCT AREA (1996) Placement of tendons by the pull-through method requires duct area of 2-1/2 times the prestressing steel area specified for grouting.

C - 26.12.3 MINIMUM RADIUS OF CURVATURE (1996) Polyethylene duct abrades at curvature radii less than 30 feet.

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Concrete Structures and Foundations C - 26.12.4.1 Internal Supports It is recommended that duct support requirements be stipulated or shown in the contract documents. C - 26.12.4.2 External Ducts External ducts are normally polyethylene. C - 26.12.6.2 Ducts in Flanges a.

The hairpin bars tie the slab together in event of spalling forces at slab joints.

b. Ducts spaced closer than 12 inches on center in either direction should be considered as closely spaced. The hairpin bars are provided to prevent slab delamination along the plane of the post-tensioning ducts. The hairpin bars are not required in areas where duct congestion does not exist.

C - SECTION 26.13 COUPLERS (1996) European experience indicates that the prestressing force decreases locally in the region of a coupler. This is believed to result partially from increased creep caused by high compressive stresses in the reduced concrete Article due to coupling of tendons. Cracking has not been observed in bridges where the number of tendons coupled at an Article has been limited to 50% of the total number of tendons.

C - SECTION 26.14 CONNECTION OF SECONDARY BEAMS (1996) Figure C-8-26-15 and Figure C-8-26-16 (Reference 49) provides schematic illustration of various methods of transmitting load from secondary beams to the main beam.

C - SECTION 26.15 CONCRETE COVER AND REINFORCEMENT SPACING C - 26.15.2 REINFORCEMENT DETAILS FOR ERECTION LOADS (1996) The quantity Z provides reinforcement detailing that will reasonably control flexural cracking. Crack potentials are largest when handling and storing segments for precast construction and when stripping forms and supports from cast-in-place construction.

C - 26.17.1 MINIMUM FLANGE THICKNESS (1996) a.

The top flange thickness of 9 inches is preferable in the area of anchorages for transverse post-tensioning tendons.

b. Further research is recommended on the transfer length of 0.6 inch diameter strand before such strand is used for transverse pretensioning in thin sections of segmental bridges.

C - 26.17.2 MINIMUM WEB THICKNESS (1996) Ribbed webs may be reduced to 7 inches thickness.

C - 26.17.4 OVERALL CROSS SECTION DIMENSIONS (1996) Girder depth and web spacing determined in accordance with the following will generally provide satisfactory deflection behavior: © 2011, American Railway Engineering and Maintenance-of-Way Association

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Recommendations for the Design of Segmental Bridges

a.

Constant depth girder 1/15 > d o / L > 1/30

(optimum 1/18 to 1/20)

where: do = girder depth, feet L = span length between supports, feet In case of incrementally launched girders, the girder depth should preferably be between the following limits: L = 100 feet, = 1/15 < d o / L < 1/12 L = 200 feet, = 1/13.5 < d o / L < 1/11.5 L = 300 feet, = 1/12 < d o / L < 1/11 b. Variable Depth Girder with Straight Haunches at pier 1/16 > d o / L > 1/20

(optimum 1/18)

at center of span 1/22 > d o / L > 1/28 NOTE: c.

(optimum 1/24)

1

A diaphragm will be required at the point where the bottom flange changes direction.

Variable Depth Girder with Circular or Parabolic Haunches at pier 1/16 > d o / L > 1/20

(optimum 1/18)

3

at center of span 1/30 > d o / L > 1/50 d. Depth to Width Ratio A single cell box should preferably be used when d o / b ³ 1/ 6

4

A two cell box should preferably be used when d o / b < 1/6 where: b = width of the top flange If in a single cell box the limit of depth to width ratio given above is exceeded, a more rigorous analysis is required and may require longitudinal edge beams at the tip of the cantilever to distribute loads acting on the cantilevers. An analysis for shear lag should be made in such cases. Transverse load distribution is not substantially increased by the use of three or more cells.

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Concrete Structures and Foundations

Figure C-8-26-15. Schematic Drawing of Different Types of “Hanger” Reinforcement1

Figure C-8-26-16. Extent of the Intersection Zone for the Connection of Secondary Beams1

1

Republished through the courtesy of the Prestressed Concrete Institute, PCI Journal, V. 32, No. 3, May-June 1987, pp. 74-150.

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8

Part 27 Concrete Slab Track

8

— 2011 — TABLE OF CONTENTS

Section/Article

Description

Page

27.1 Scope and Notations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-27-3 27.1.1 Scope (2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-27-3 27.1.2 Notations (2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-27-3 27.2 Application and Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-27-3 27.2.1 Application (2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-27-3 27.2.2 Definitions (2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-27-5

1

27.3 General Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-27-6 27.3.1 Introduction (1999) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-27-6 27.3.2 Loading Conditions (1999) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-27-7 27.4 Materials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.4.1 General (1999) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.4.2 Subgrade (2011). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.4.3 Stabilized Subbase (1999) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.4.4 Concrete Slab (1999) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.4.5 Metal Reinforcement (1999) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-27-7 8-27-7 8-27-7 8-27-8 8-27-8 8-27-8

27.5 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.5.1 Design Considerations (1999) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.5.2 Subgrade (2011). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.5.3 Subbase (1999). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.5.4 Continuously Reinforced Concrete Slab (2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.5.5 Drainage (1999) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-27-8 8-27-8 8-27-9 8-27-9 8-27-9 8-27-10

27.6 Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.6.1 Subgrade (2011). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.6.2 Subbase (1999). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.6.3 Construction Methods (2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.6.4 Reinforcement Placement (1999) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.6.5 Concrete Placement (2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.6.6 Curing (1999) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.6.7 Construction Joints (1999) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.6.8 Installation of Fastener Inserts (1999). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-27-10 8-27-10 8-27-10 8-27-10 8-27-11 8-27-11 8-27-11 8-27-11 8-27-12

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TABLE OF CONTENTS Section/Article

Description

Page

27.6.9 Testing Anchor Inserts (2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-27-14 27.6.10 Placement of Rail Fasteners (1999) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-27-15 27.6.11 Installation of Running Rail (1999). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-27-15 27.7 Direct Fixation Fastening System. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.7.1 Rail Fastening Requirements (1999) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.7.2 Types of Rail Fasteners (2011). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.7.3 Design Features (2011). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.7.4 Laboratory Testing of Fasteners for Acceptance (1999). . . . . . . . . . . . . . . . . . . . . . . . . .

8-27-15 8-27-15 8-27-16 8-27-17 8-27-18

27.8 Special Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.8.1 Transition Areas (2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.8.2 Treatment at Slab Ends (1999) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.8.3 Continuity of Slab Track Over Bridge Deck (1999) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27.8.4 Modification of Existing Tunnel Concrete Invert to Slab Track (1999) . . . . . . . . . . . . . 27.8.5 New Tunnel - Slab Track (2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-27-18 8-27-18 8-27-18 8-27-21 8-27-21 8-27-22

Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-27-26

LIST OF FIGURES Figure 8-27-1 8-27-2 8-27-3 8-27-4 8-27-5 8-27-6 8-27-7 8-27-8

Description

Page

Continuously Reinforced Concrete Slab Track System (Typical) . . . . . . . . . . . . . . . . . . . . . . . . Fastener Insert Attachment to the Slab Track (Typical). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Restrained Test (Not to Scale). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A Typical Direct Fixation Fastener Envelope. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Detail for Termination of Slab Track at Approach to a Bridge . . . . . . . . . . . . . . . . . . . . . . . . . . Typical Direct Fixation Fastener System for Existing Tunnel Invert . . . . . . . . . . . . . . . . . . . . Single-Pour Method for New Tunnel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . New Tunnel Floating Slab Track . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-27-4 8-27-13 8-27-14 8-27-17 8-27-20 8-27-23 8-27-24 8-27-25

LIST OF TABLES Table

Description

Page

C-8-27-1 Example of Computer Static Analysis of Concrete Slab Track . . . . . . . . . . . . . . . . . . . . . . . .

8-27-28

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Concrete Slab Track

SECTION 27.1 SCOPE AND NOTATIONS 27.1.1 SCOPE1 (2011) a.

These recommendations for design and construction of continuously reinforced concrete slab track system provide guidelines to railroads, rail transit systems, public agencies, consultants, contractors and other interested professionals. A typical continuously reinforced concrete slab track system is shown in Figure 8-27-1.

27.1.2 NOTATIONS (2011) CWR

= Continuous Welded Rail

CRC

= Continuously Reinforced Concrete

ks

= Modulus of Subgrade Reaction, lb/in³ (N/mm³)

DFF

= Direct Fixation Fastener

K

= Fastener Vertical Spring Rate, lb/in (N/mm)

u

= Track Modulus, lb/in/in (N/mm/mm)

1

SECTION 27.2 APPLICATION AND DEFINITIONS 27.2.1 APPLICATION (2011) a.

The concrete slab track system described herein is suitable for:

3

(1) At-grade guideways (2) Existing or new embankments (3) Existing or new tunnels

4 b. These recommendations state minimum performance requirements and are applicable for both moderate rolling stock speed up to 125 mph (200 km/h), and high speed over 125 mph (200 km/h), low axle loads (light rail transit, rail transit system), medium axle loads (commuter rail-electric or diesel system) and heavy axle loads (freight). c.

Other types of concrete2 slab tracks which have been used but are not addressed in these recommendations include: (1) Cast-In-Place Unreinforced or Conventionally Reinforced (2) Cast-In-Place Post-Tensioned (3) Precast Reinforced

1 2

See Commentary See Commentary © 2011, American Railway Engineering and Maintenance-of-Way Association

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8-27-4

Figure 8-27-1. Continuously Reinforced Concrete Slab Track System (Typical).

Concrete Slab Track

(4) Precast Reinforced (5) Floating Slab (6) Embedded Slab (7) Independent Dual Block

27.2.2 DEFINITIONS (2011) The following terms are defined for general use in Part 27. BROKEN RAIL - The fracture of a continuous welded rail which has been directly fastened to the concrete slab. CROSS TIE - A transverse component of a track system whose functions are the control of track gage and the transmitting of rail loads to ballast. CONVENTIONAL TRACK - Two rails seated on tie plates or pads fastened to ties embedded in a ballast layer. CONCRETE SLAB TRACK SYSTEM - A continuously reinforced concrete (CRC) slab supported on a stabilized subbase and compacted subgrade. CONTINUOUS WELDED RAIL - Running rails that act as a continuous structural element as a result of full penetration welding and connection of individual sections of rail in lengths of 400 feet (122m) or longer. DIRECT FIXATION FASTENING SYSTEM - A group of components of track structure which directly attaches the rail to the concrete slab.

1

3

FLEXURAL STRENGTH - The maximum resistance to bending of a given cross section. INSERT - A component of the fastening system which is embedded in the concrete slab. The insert may be installed by presetting it in the formwork prior to placement of concrete, or inserting it in a hole either drilled, cored or formed in the slab, after concrete has hardened. LATERAL LOAD - A load or a component of a load at the gage side of the rail parallel to the transverse axis of the slab and perpendicular to the rail. The lateral load shall be assumed to be applied at the base of rail. LONGITUDINAL LOAD - A load acting along the longitudinal axis of a rail. The longitudinal load shall be assumed to be applied at the base of rail. MODULUS OF SUBGRADE REACTION (ks) - The modulus of subgrade reaction (also soil "spring" constant or coefficient of subgrade reaction) is expressed as: ks = q/y with units of force/length³, lb/in³ (N/mm³) where q = intensity of contact pressure, psi (MPa) y = soil deformation, in (mm)

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Concrete Structures and Foundations

The modulus of subgrade reaction can be obtained by performing a plate load test (ASTM D1196) and plotting a curve of q versus y. PRESTRESSED CONCRETE TIE - A tie utilizing precompressed concrete and prestressing tendons. RAIL SEAT - The area of the slab surface on which the rail rests. TRACK MODULUS (u) - is defined as: 1 u = --- 3 4

P 4 æ ------d-ö ¤ ( EI ) lb/in/in (N/mm/mm) è Y oø

where, Pd = Dynamic wheel load, lb (N) E = Modulus of elasticity of rail steel, psi (MPa) I = Moment of Inertia of Rail Section, in4 (mm4) Yo = Maximum rail deflection under single wheel load, in (mm).1 VERTICAL LOAD - A load or a component of a load at right angles to a line joining the two opposite rail seats, and normal to the longitudinal axis of the rail.

SECTION 27.3 GENERAL CONSIDERATIONS 27.3.1 INTRODUCTION2 (1999) a.

In supporting and guiding railway rolling stock, the track structure shall be adequate to sustain repeated longitudinal, vertical and lateral forces. Hence, in the design of a concrete slab track system, the concrete slab shall be considered interconnected with other components of the track structure.

b. Items to consider in the design of the concrete slab track system are: (1) The concrete slab, rail, fasteners, subbase and subgrade. (2) The quality of each component, method of manufacture, installation and maintenance. (3) The direction, magnitude and frequency of traffic induced loads, the effect of environmental factors such as temperature and weather. (4) The need to adequately support and safely guide railway rolling stock while sustaining repeated longitudinal, vertical and lateral forces. (5) Overall economics of installation and maintenance.

1 2

See Commentary See Commentary

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Concrete Slab Track

27.3.2 LOADING CONDITIONS (1999) 27.3.2.1 Load Distribution a.

A properly designed concrete slab track system shall distribute the load uniformly through a layered system of three distinct materials: compacted subgrade (low stiffness), stabilized subbase (medium stiffness), and reinforced concrete slab (high stiffness).

27.3.2.2 Rail, Lateral and Longitudinal Loads a.

Rail, lateral and longitudinal loads shall be as formulated in AREMA Manual Chapter 30, Part 4, Concrete Ties, and modified as deemed appropriate by the Engineer.

27.3.2.3 Slab Dimensions1 a.

The width of the slab is a function of the number of tracks, the distance between tracks, and the gage of the tracks. Other components such as third rail for electrification may affect the width of the slab. For a single track layout with standard gage, a minimum width dimension of 10.5 feet (3.2 m) is recommended. The thickness of the slab shall be based on requirements stated in Article 27.5.4.

27.3.2.4 Subbase Pressure a.

The subbase pressure on stabilized asphaltic subbase shall not exceed 30 psi (0.2MPa).

1

27.3.2.5 Subgrade Pressure2 a.

The subgrade pressure on well compacted subgrade shall not exceed 20 psi (0.14MPa).

27.3.2.6 Impact Factor3 a.

An impact factor of 200 percent shall be used for design of continuously reinforced concrete slab track.

3

SECTION 27.4 MATERIALS 27.4.1 GENERAL (1999) a.

The properties and characteristics of the existing foundation conditions shall be investigated as specified in Part 22, Geotechnical Subsurface Investigation.

27.4.2 SUBGRADE (2011) a.

1 2 3

The subgrade material shall preferably be cohesionless, gravel-sand well draining material. The top 24 inches (610 mm) shall be free from organic material, and be suitable to distribute the loads to stratum below. In case of construction on either existing or new embankment, it is recommended to limit the sandy material to a 1/4 inch (6 mm) maximum size. However, the No. 200 fines shall be limited to a maximum of 15 percent by weight to reduce possibility of pumping action and to mitigate frost heave in cold regions.

See Commentary See Commentary See Commentary

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27.4.3 STABILIZED SUBBASE (1999) a.

Stabilized subbases that have been used successfully include stabilized bituminous (asphalt). Some of the other types of subbase materials which have been used and may be appropriate, are the following: (1) Crushed Stone. (2) Granite Stone. (3) Lean Concrete. (4) Cement-Treated Gravel. (5) Cement-Treated Crushed Stone. (6) Expanded Polystyrene Concrete.

27.4.4 CONCRETE SLAB (1999) a.

The minimum 28-day compressive strength of concrete shall be 4000 psi (28MPa) as determined by ASTM C39.

b. Cement shall be portland cement and shall meet the requirements of ASTM Specification C150. Aggregates and mix water shall meet the requirements of Part 1, of Chapter 8. Air entraining admixtures shall be used in freeze-thaw environments. Admixtures containing chloride ions shall not be used. c.

Based on requirements of Part 1, consideration shall be given to selection of concrete ingredients and properties that affect the durability of the concrete slab. These include alkali-aggregate reaction, freezing and thawing, air entraining agents and other admixtures, and sulfate and adverse chemical reactions.

27.4.5 METAL REINFORCEMENT (1999) a.

Reinforcement shall meet the requirements as stipulated in Part 1, Materials, Tests and Construction Requirements.

b. When the concrete is subjected to aggressive environments, the top mat of reinforcing steel shall be provided with a corrosion protection system.

SECTION 27.5 DESIGN 27.5.1 DESIGN CONSIDERATIONS1 (1999) a.

1

The design procedures shall be as per Part 2, Reinforced Concrete Design. Moreover, the design of the continuously reinforced concrete (CRC) slab shall be based on the existing construction technology available in North America for CRC highway and airfield pavements.

See Commentary

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b. The design can be formulated by using the modulus of subgrade reaction (ks), and elastic theory analytical techniques. The slab track system generally involves three distinct materials. The compacted subgrade with a low stiffness is overlaid with a stabilized subbase followed by the CRC slab, which is a stiff structure. This will ensure that the stresses induced by the rolling stock are minimized in the various layers, enabling the entire track system to perform satisfactorily. However, in case of subgrade material being sound rock1, the subbase can be eliminated. c.

The following design considerations should be established for any concrete slab track system: (1) Track must be structurally adequate and capable of maintaining alignment and profile. (2) The system must be capable of being constructed efficiently and economically. (3) A fastening assembly with the capability of allowing lateral and vertical adjustments shall be utilized. (4) Concrete slab must have provision for attaching contact (third) rail assembly for electrification, if required or expected in the future.

27.5.2 SUBGRADE (2011) a.

A minimum of 350 lb/in³ (0.09 N/mm³) is suggested as the modulus of subgrade reaction (ks) for subgrade, on which the slab track is to be constructed.

1

27.5.3 SUBBASE2 (1999) a.

A subbase of one of the types listed in Article 27.4.3 shall be provided between the concrete slab and the finished subgrade.

27.5.4 CONTINUOUSLY REINFORCED CONCRETE SLAB3 (2011) a.

3

The thickness of the concrete slab shall be established by considering both the fatigue effect and the static wheel load, for 50,000 Cooper E-80 (EM-360) loadings for 50 years, or loading as deemed appropriate by the Engineer.

b. In calculating the longitudinal bending stiffness (EI) of the concrete slab about the neutral axis of the slab cross section, the tensile strength of concrete shall be assumed to be zero. c.

Slab thickness shall be computed so as to be adequate and rigid enough to withstand: (1) Bending and shear stresses produced by wheel loads (live load plus impact). (2) Longitudinal stresses induced as a result of anchoring continuous welded rail (CWR) to the concrete slab. (3) Warping stresses (temperature differential between the top and bottom of the slab).

1

Rock quality shall be as defined in Part 22, Geotechnical Subsurface Investigation, sub-article 22.4.3 (d), of Chapter 8.

2

See Commentary See Commentary

3

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d. Adequate reinforcement shall be provided to ensure that the cracks in concrete do not exceed 0.012 inch (0.30 mm), so that the passage of water or moisture to reinforcement is minimized. In addition, longitudinal reinforcement shall be sufficient to maintain aggregate interlock for transfer of the load at the crack locations.

27.5.5 DRAINAGE (1999) a.

The slab track shall be designed to provide for transverse drainage to the edges of the slab. To reduce infiltration of water under the slab, a paved ditch shall be provided between individual slab tracks.

b. Drainage water shall be collected in a paved ditch. Water shall be discharged through sub-invert pipes to an external discharge system for an at-grade concrete slab. c.

For concrete slab on embankment, drop inlets shall be provided in the embankment discharging to a positive drainage system. To reduce embankment erosion, paved ditches shall be installed adjacent to the slab.

d. In tunnel construction, a trough shall be provided in the center of the slab with a longitudinal slope to drain through sub-invert pipe(s), which discharge to a positive drainage system.

SECTION 27.6 CONSTRUCTION 27.6.1 SUBGRADE (2011) a.

All materials susceptible to frost heave shall be removed to at least 24 inches (610 mm) depth below subbase and replaced with frost free cohesionless material. The subgrade should be compacted in order to achieve a minimum ks value of 350 lb/in³ (0.09 N/mm³).

b. If the construction is on a new embankment, the top 24 inches (610 mm) at a minimum shall be granular material. Soil for embankment shall be placed in layers not thicker than 9 inches (230 mm) and compacted to 95 percent of maximum density obtained by the Standard Proctor Method (ASTM 698). Soils having a moisture content in excess of 2 percent above optimum moisture content as determined by Modified Proctor Method (ASTM 1557), shall be unacceptable as an embankment material. When the construction entails placement on an existing embankment, all load bearing soil material in the frost zone shall be removed and replaced with cohesionless granular material. The top 24 inches (610 mm) shall be compacted to achieve the specified ks value.

27.6.2 SUBBASE (1999) a.

A minimum 4 inches (100 mm) thick subbase material as determined by geotechnical evaluation, shall be laid over the finished subgrade. The subbase shall project 2 feet (610 mm) beyond each side of the concrete slab.

27.6.3 CONSTRUCTION METHODS (2011) a.

The contractor should be responsible for means and methods of construction. There are basically two types of construction methods used for installing direct-fixation fastener system on concrete surfaces: “Bottom-Up” and “Top-Down”.

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The bottom-up construction is generally used when the concrete slab track has already been poured. This conventional approach involves installing formwork and reinforcements in place, placing concrete, coring/drilling for fastener inserts, fitting rail fasteners to cast concrete and shimming/adjusting rail to final position. The top-down construction entails pre-assembling (skeletonized) track and setting the rail and the fasteners to a final line and surface on temporary supports, and then pouring the concrete as a final operation.

27.6.4 REINFORCEMENT PLACEMENT (1999) a.

Steel reinforcement shall be placed on chairs in two layers, with the main longitudinal reinforcement divided between the bottom and top layers. Longitudinal steel shall be spliced in tension only as specified under Part 2, Reinforced Concrete Design, of Chapter 8. Transverse bars shall be spaced as necessary in the top and bottom layers. Steel reinforcing bars shall be placed so as to be clear of the drilling/coring areas, using special templates for marking hole locations, both before and after concrete placement. This technique will minimize damage or cutting of reinforcing steel which may be encountered during the concrete drilling or coring operation.

27.6.5 CONCRETE PLACEMENT (2011) a.

It is recommended that in order to achieve the proper tolerances, conventional highway paving forms be utilized. For large projects, the use of slipform paving equipment may be warranted, for obtaining higher production rates for concrete placement. Paving equipment shall include vibrating screed and associated components necessary to obtain the required slab cross section. The paving equipment train can be mounted on adjustable screed rails, accurately set by a surveyor for both horizontal and vertical alignments. Concrete should be consolidated by internal vibrators.

b. In order to minimize shimming and/or grinding of concrete, it is recommended that tight vertical tolerance of +0 inches (+0 mm) and -1/4 inches (-6 mm) be required of the finished concrete. Careful attention should be paid to obtain the required finish tolerances when using slipform paving equipment. c.

27.6.6 CURING (1999) The curing of concrete shall be as specified under Part 1, Materials, Tests and Construction Requirements.

27.6.7 CONSTRUCTION JOINTS (1999) a.

3

The concrete can be placed either in a single pour method, a two separate pour sequence, or a recessed two pour method, which can maximize clearance in tunnel construction.

d. The two pours (sections) shall be adequately attached to each other by dowels and an adhesive bonding material.

a.

1

The following provisions shall be specified, when construction joints are required at the end of a day's concrete placement. (1) Construction joints shall not be closer than 5 feet (1.5 m) from splices in longitudinal reinforcement. (2) Transverse reinforcement shall be doubled for a 10 feet (3 m) distance each side of a construction joint.

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(3) Longitudinal reinforcement shall be increased by one third for a 10 feet (3 m) distance each side of a construction joint. (4) Formed keys or dowel bars can also be used to prevent differential settlement.

27.6.8 INSTALLATION OF FASTENER INSERTS (1999) a.

Inserts may be installed by presetting them in the formwork, by means of a template, prior to the placement of concrete. Accurately locate female inserts, into which fastener hold down bolts can be threaded, prior to casting the slab. After casting, the tops of the inserts must be flush with the slab surface. The surface around the inserts shall be smooth and flat, providing a satisfactory bearing area for the rail fasteners. A variation of this method would be, to cast-in-place rail holding devices (shoulders).

b. An alternative method is the installation of inserts after placement and curing of concrete, either by drilling or coring holes. Percussion drilling is not permitted. Precision must be exercised in locating and drilling/coring of holes, into which inserts (or anchor bolts) are installed. c.

It is recommended that slab drilling or coring for fastener inserts be performed after the initial shrinkage of the concrete has occurred and the 28 day specified compressive strength has been obtained. Slight adjustment in spacing of inserts may be permitted to avoid existing shrinkage cracks.

d. The inserts shall be held plumb in the hole, either by templates or other means, and the hole filled with an adhesive material. Fastener inserts may be epoxy coated to provide additional electrical insulation. e.

Figure 8-27-2 depicts fastener insert attachment to the slab track.

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3

4 Figure 8-27-2. Fastener Insert Attachment to the Slab Track (Typical).

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27.6.9 TESTING ANCHOR INSERTS (2011) a.

The inserts which attach the rail fastener to the slab track are subject to pull-out forces generated by bolt torque, vertical uplift forces produced by a passing train, and forces produced by thermal conditions.

27.6.9.1 Insert Pull-Out Testing a.

For rail fastener bolts, or female inserts that are embedded in concrete and rely on concrete tensile strength for pull-out resistance, the tensile stress in the concrete at maximum pull-out load shall not exceed 6 percent fc’, where fc’ = compressive strength of concrete, psi (MPa).

b. In order to determine the load capacity of an anchoring system, tests shall be performed in accordance with ASTM E1512. A mock-up test shall be required to simulate the in-situ conditions, with satisfactory results. c.

A minimum of 10 percent of the inserts shall be randomly tested for a pull-out force of not less than 14,000 lb (62,300 N). In case of inserts failing pull-out testing, the percentage of inserts being tested shall be increased, as per judgement of the Engineer. The test load shall be applied in three equal increments. The final load shall be held constant for one minute and the epoxy, concrete and insert inspected for distress.

d. If no drop in gage pressure occurs after one minute, the insert shall be accepted. If the insert fails to meet the pull-out strength, then it shall be cored out and replaced with a new insert. The pull-out tests shall be performed using the Restrained Test as shown in Figure 8-27-3.

Figure 8-27-3. Restrained Test (Not to Scale).

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Concrete Slab Track 27.6.9.2 Insert Torque Testing a.

Screw anchor bolt into insert, tight against lock nut. Apply 600 foot-pounds (813 N-m) torque to the anchor bolt head.

b. The insert shall be considered acceptable, if it shows no evidence of rotational movement in the concrete.

27.6.10 PLACEMENT OF RAIL FASTENERS (1999) a.

After installation of inserts, the finished surface of concrete shall be surveyed, and if necessary, grinding the high spots of concrete may be required. If the concrete finished surface is lower than that required, then shim pads up to a maximum height of 3/8 in (9 mm) can be placed under the fastener at the discretion of the Engineer. The inserts (anchor bolts) shall be checked for vertical plumbness and correct location prior to the placement of rail fasteners. Rail fasteners shall then be installed.

27.6.11 INSTALLATION OF RUNNING RAIL1 (1999) a.

Continuous welded rail (CWR), the weight and type to be determined by the individual agency, may be delivered on work trains with factory welded sections and shall be carefully placed on the fasteners. As an alternative, the rail can be entirely field welded at the project site to form continuous welded rails.

b. Changes in temperature of CWR will develop stresses in the rail and the concrete slab. Rail is typically installed at a high neutral temperature, to reduce the risk of rail buckling at high temperatures and rail pull-apart at low temperatures. c.

The suggested procedure, during low temperatures, is that each section of the CWR be heated at installation to a predetermined temperature, in order to ensure that the rail will remain in tension a large percentage of the time. The base of the rail shall be secured to the direct fixation fastener, with elastic clips.

d. It is suggested that the Engineer should refer to the detail guidelines of Chapter 5, Track, for the handling, transporting, laying and construction of CWR.

SECTION 27.7 DIRECT FIXATION FASTENING SYSTEM

Rail fasteners for installation under the continuous welded rail shall satisfy the following: (1) Allow for vertical and lateral adjustment, if required. (2) Provide resilience that will reduce the effect of dynamic impact on the track structure, minimize vibrations, absorb energy and reduce noise. (3) Maintain a consistent clamping force on the rail to provide resistance to rail creep, and maintain rail alignment.

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See Commentary

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27.7.1 RAIL FASTENING REQUIREMENTS (1999) a.

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(4) Provide the required electrical insulation for electrified and/or signalized railways. (5) Exhibit resistance to track environment (weather, oil, etc.).

27.7.2 TYPES OF RAIL FASTENERS1 (2011) a.

1

There are a variety of rail fasteners of different design and capabilities available. It is recommended that for slab track construction the direct fixation fasteners with satisfactory in-service performance history be installed. As an alternative, new direct fixation fasteners which have satisfactory passed extensive laboratory testing may be used.

See Commentary

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b. The type of direct fixation fastener to be specified shall be a function of the slab track operating environment (main line, yard, etc.), axle load, train speeds and maintenance considerations. Figure 827-4 shows a typical direct fixation fastener envelope.

1

3

4

Figure 8-27-4. A Typical Direct Fixation Fastener Envelope.

27.7.3 DESIGN FEATURES (2011) 27.7.3.1 Fastener Vertical Spring Rate1 a.

1

The vertical spring rate, K, of direct fixation fasteners normally ranges from 90,000 pounds/inch (15.8 kN/mm) which is considered as soft pad to 300,000 pounds/inch (52.5 kN/mm) which is considered a hard pad. The slope of the load-deflection curve (the fastener spring rate) shall be within 20 percent of a

See Commentary

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constant slope calculated at each 1000 pounds (4450 N) increment (secant modulus between two given load points). b. The selection of a spring rate for a fastener shall be determined by the individual railroad based on its operating needs, requirements and practice. 27.7.3.2 Elastic Clips1 a.

Elastic clips shall be used in combination with direct fixation fasteners, in order to attach the base of the rail to the fasteners.

b. The recommended toe load for elastic clips shall be in the range of 2200 pounds (9800 N) to 3200 pounds (14,240 N).

27.7.4 LABORATORY TESTING OF FASTENERS FOR ACCEPTANCE (1999) a.

The laboratory testing requirements are comprehensively covered in AREMA Manual for Railway Engineering, Chapter 30, Part 4, Concrete Ties.

b. It is recommended that the Engineer adhere to Chapter 30, with modifications as deemed appropriate.

SECTION 27.8 SPECIAL CONSIDERATIONS 27.8.1 TRANSITION AREAS2 (2011) a.

Transition areas such as behind abutments at bridge approaches or at change of track structure from slab track to wood tie track require special considerations.

b. Factors to be considered in the design of transition areas are: susceptibility of backfill soil material to settlement behind bridge abutments, difference in track modulus between stiff (concrete slab) track, and soft (wood tie) track, respectively. c.

In the case of bridge abutments, a sub-surface approach slab adequately reinforced and varying in thickness from 18 in (450 mm) at bridge abutment to 12 in (300 mm) at the opposite end, for a length of 25 feet (7.5 m), may be installed as detailed in Figure 8-27-5.

d. Where change of track structure from concrete slab to wood tie track occurs, a sub-surface concrete slab of similar design features as in (c) above, may be installed starting from the end of the concrete slab track and carried below the wood track structure a length of at least 20 ft (6 meters).

27.8.2 TREATMENT AT SLAB ENDS (1999) a.

Expansion joints are recommended at slab ends to handle slab movements at bridge sites and at ends of the slab track construction.

b. The slab track can be terminated 25 feet (7.5 m) from bridge abutment approaches, if the bridge is at the end of the slab track. Transverse reinforcing steel shall be doubled for a 15 feet (4.5 m) distance from 1 2

See Commentary See Commentary

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slab ends. A galvanized structural steel inverted T-section shall be installed in a 10 feet (3 m) long reinforced concrete slab that supports one end of the slab track. The structural steel inverted T-section shall have expansion joints that permit up to a 3 in (75 mm) expansion and a 2 in (50 mm) contraction. Expansion material shall be installed in the expansion joints. Refer to Figure 8-27-5 as one example for design details.

1

3

4

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Figure 8-27-5. Detail for Termination of Slab Track at Approach to a Bridge.

Concrete Slab Track

27.8.3 CONTINUITY OF SLAB TRACK OVER BRIDGE DECK1 (1999) a.

This section is applicable to straight, simply supported concrete deck bridges of spans up to 75 feet (23 m). If it is required to continue the concrete slab track over a bridge deck, the following provisions shall be addressed: (1) In order to minimize slab cracking and to permit sliding of bridge deck under the concrete slab track, it is imperative to reduce friction at the interface between the bottom of the slab track and top of the bridge deck concrete. (2) Provide two layers of bituminous material separated by two sheets of polyethylene between slab and bridge decking. (3) As an alternative, teflon may be used as a friction reducing material, if additional cost considerations are acceptable.

27.8.4 MODIFICATION OF EXISTING TUNNEL CONCRETE INVERT TO SLAB TRACK (1999) a.

In existing tunnels, the following two types of track structures are generally encountered: (1) Type (A) Concrete tunnel invert with ballast and ties.

1

(2) Type (B) Half wood ties embedded in concrete tunnel invert. b. The following reconstruction methodology can be used to modify the tunnel invert: (1) Type (A) Tunnel Invert: (a) Remove ballast and cross ties.

3

(b) If additional vertical clearance is required or the top section of concrete invert consists of unsuitable or deteriorated concrete, it shall be removed until sound matrix of concrete is reached. If reinforcing steel is encountered, remove the steel and replace it with new bars. (c) Apply bonding material. (d) If required by the Engineer, drill and grout vertical dowels into existing concrete for mechanical anchorage. (e) Place concrete grouting material to achieve the required elevation. (f) Drill or core holes for anchor bolts. (g) Install fasteners, lay rail and secure clips as stipulated in the previous sections. (2) Type (B) Tunnel Invert: (a) Remove the embedded ties and concrete section to at least one inch (25mm) below the ties. (b) Follow the same procedure as detailed above in Type (A) Concrete Tunnel Invert. 1

See Commentary

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One type of Direct Fixation Fastener System for modifying existing tunnel invert is depicted in Figure 8-27-6.

27.8.5 NEW TUNNEL - SLAB TRACK (2011) Slab Track in a new tunnel can be constructed in any of the following four ways: a.

Single-pour method

b. Recessed single-pour method c.

Two-pour method

d. Recessed two-pour method Figure 8-27-6 shows Direct Fixation Fastener System for modifying existing Tunnel Invert. Figure 8-27-7 shows Single-Pour method of construction of a new Tunnel Slab Track. Figure 8-27-8 shows a New Tunnel Floating Slab Track.

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3 Figure 8-27-6. Typical Direct Fixation Fastener System for Existing Tunnel Invert.

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Figure 8-27-7. Single-Pour Method for New Tunnel.

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Figure 8-27-8. New Tunnel Floating Slab Track.

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C - COMMENTARY C - 27.1.1 Scope (2011) A concrete slab track can provide improvements over a conventional track system, and solutions to the problems of costly track maintenance, increasing axle loads, and faster operating speed. A concrete slab track system consisting of a continuously reinforced concrete slab, supported on a subbase and compacted subgrade, is one example of an improved track structure. A slab track system provides the following advantages: (1) Elimination of those components with inherent weakness that require periodic maintenance such as ballast, ties, tie plates and spikes. (2) Rail fasteners with better lateral and longitudinal restraint characteristics are used. (3) Load is distributed more uniformly on the subgrade, thus settlement is reduced. (4) Proper line and surface are maintained, thus reducing need for surfacing and lining. (5) When combined with continuous welded rail, ride quality is improved, and faster operating speeds are possible. (6) Reduced maintenance results in less traffic disruption. (7) Due to improved track structure, rolling stock encounters less wear and tear, and thus, requires less maintenance. C - 27.2.1 (c) Other Types of Concrete Slab Tracks (2011) A Floating slab design incorporates elastomeric pads which separate, and therefore isolate and dampen, the rail support slab from the underlying concrete sub-slab. Floating slab track system as show in Figure 8-27-8 is an effective and reliable solution for mitigating mechanical vibrations and ground-borne noise generated by rolling stock. An Embedded Slab Track system, consists of dual tie blocks, set in rubber boots using microcellular pads locked-in with a second pour of concrete. Some of the slab track systems in use are proprietary in nature, such as: Individual Dual Block Track and Precast Reinforced and Precast Pretensioned both developed in Europe and used in various systems around the world. C - 27.2.2 Definitions (1999) Track Modulus (u) The value of modulus of elasticity of rail support (u) for directly fixed track is dependent upon the moment of inertia of the rail section and the amount of deflection obtained by the compression of the fastener pad. The allowable deflection of a rubber pad is limited to 15 percent of it’s uncompressed thickness. Direct fixation fasteners presently in service use 1/2 in (12 mm) pads. These pads allow a maximum deflection of 0.075 in (2 mm).

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Track Modulus for slab track systems are generally in the range of 8,000 lb/in/in (55 N/mm/mm) to 10,000 lb/in/in (70 N/mm/mm). C - 27.3.1 Introduction (1999) The concrete slab as part of the track structure system, is subjected to loads from the rails through the direct fixation fastening, and in turn concrete slab transfers loads to the subbase and subgrade. C - 27.3.2.3 Slab Dimensions (2011) The use of a 10.5-ft (3.2-m) wide slab is recommended. This will minimize or eliminate the development of punchout failure, which is predominantly due to edge loading. For the 10.5-ft. (3.2-m) wide slab track, the loading under the rail is about 34 inches (863 mm) from the slab edge and this loading is considered an interior loading condition, which is far less damaging than an edge load. Also, this loading is channeled, that is, the loading is always maintained along the same location within the slab. There is no lateral wander of the loading, for example, as for highway CRC pavements. However, if the slab width were less, a concern may develop due to the edge loading conditions. Edge loading conditions include higher concrete stresses and higher slab deflections. These may lead to progressive cracking in the slab and deflection related failures such as slab settlement. C - 27.3.2.5 Subgrade Pressure (1999) Due to the reduction of number of load pulses on subgrade, a well constructed slab track structure minimizes the subgrade pressure.

1

C - 27.3.2.6 Impact Factor (2011) The requirements are based on calculations including an assumed impact factor. This factor is a percentage increase over static vertical loads, intended to estimate the dynamic effect of wheel and rail irregularities. The Impact Factor is comparable to that used in Chapter 30, for Concrete Ties.

3

C - 27.5.1 DESIGN CONSIDERATIONS (2011) The following criteria provide a guideline for slab track system design: (1) Rail vertical deflection not to exceed 0.25 inches (6 mm).

4

(2) Rail bending stress not to exceed 11000 psi (77 MPa). (3) Subbase pressure not to exceed 30 psi (0.21 MPa). (4) Subgrade pressure not to exceed 20 psi (0.14 MPa).

C - 27.5.3 SUBBASE (1999) A subbase shall be provided to serve the following functions: (1) Prevent mud pumping (2) Increase the modulus of subgrade reaction. (3) Serve as a working platform for erection of concrete slab formwork.

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(4) Distribute pressure to subgrade more uniformly.

C - 27.5.4 CONTINUOUSLY REINFORCED CONCRETE SLAB TRACK (1999) Computer Analysis (1999) The static analysis of the concrete slab track is based on a longitudinal structure which is represented as a continuous beam (rail) on a continuous uniform support (resilient fasteners) in turn resting on another continuous beam (concrete slab) resting on another continuous uniform support (stabilized subbase and compacted subgrade). Reference numbers 26 and 57 in the References refer to the computer program which was written to facilitate the analysis. The outputs from the program include rail deflection and bending moment, fastener deflection and loads, slab deflection and bending moment, and subgrade deflection and bearing pressure. For illustration purpose, based on the computer program, in case of 35000lb (155,750 N) wheel load, 136 lb (61.2 kg) rail and 6 foot (1.8 m) axle spacing, the output in Table C-8-27-1 on the following page was obtained: Table C-8-27-1. Example of Computer Static Analysis of Concrete Slab Track Given: 8 foot (2.4 m) slab, ks = 500lb/in3 (0.135 N/mm3 ) Fastener spacing = 30 in (762mm)

Slab Depth inches (mm)

Slab Stiffness EI lb-in2 (N-m2)

6 (152)

516 x 107 (1.48 x107)

0.047 (1.19)

9600 (67.2)

0.022 (0.55)

1025 (7.17)

10.85 (0.076)

18 (457)

13,380 x107 (3.971 x107)

0.044 (1.11)

9150 (64.0)

0.018 (0.46)

800 (5.6)

9.15 (0.064)

Rail Peak Rail Slab Slab Slab Bearing Deflection Stress Deflection Stress Pressure inches psi inches psi psi (mm) (MPa) (mm) (MPa) (MPa)

Design Procedure (1999) The following is a guideline for a simplified design procedure for the major design elements: Background: A continuously reinforced concrete pavement (CRCP) is a portland cement concrete pavement with continuous longitudinal reinforcement and no intermediate expansion or contraction joints. Transverse reinforcement is also required at intervals corresponding to the rail fastener spacing to absorb the loads transmitted into the slab at the rail fastener attachment points. It also aids in construction by supporting and maintaining longitudinal reinforcement spacing. Slab thickness and longitudinal reinforcement design must be considered simultaneously in a continuously reinforced concrete pavement. If too small an amount of steel is used, transverse cracks will open an excessive amount and aggregate interlock will be lost, resulting in appreciable slab deflections and ultimate slab deterioration and failure.

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Concrete Slab Track

A properly designed CRC slab typically develops regularly spaced, hairline transverse cracks at 3 feet (0.9 m) to 10 feet (3 m) intervals. The resultant pavement is composed of a series of short slabs held tightly together by the longitudinal reinforcement. With a sufficient amount of reinforcement, a high degree of shear transfer across the cracks is assured because the cracks are held tightly closed.

Slab Bending Stiffness (EI) (1999) Compute bending stiffness, assuming slab width, depth, fc' and weight of concrete. Reference number 57 has additional information on bending stiffness trade-offs (deeper concrete section versus less percentage of reinforcement), and track structure cost as a function of bending stiffness. Stresses in Slab (2011) Assume: 50,000 Cooper E-80 (or equivalent) loading for 50 years. Say spacing between fasteners is 24 inches (610 mm) to 30 inches (760 mm). Use contact area between rail fastener and slab as 7 inches (178 mm) x 14 inchs (356 mm). Use fc' = 4000 psi (28 MPa), MR = 475 psi (3.3 MPa) Assume ks = 450 lb/in3 (12451.5 N/mm3), includes

1

4 in (102 mm) stabilized bituminous subbase. Using "Influence charts for concrete pavements", ASCE, Vol.116, and "Thickness design for concrete pavements", PCA, compute • pavement thickness

3

• stresses in slab Longitudinal Reinforcement (2011) Selection of percentage of steel should be based on the following considerations:

4

• The reinforcement should help the slab resist train loads. • Crack width not to exceed 0.012 inch (0.30 mm), in order to limit corrosion by minimizing passage of water or moisture to reinforcement. • Given contraction of the slab, the tensile stresses in the reinforcement should be within elastic range. a.

Longitudinal reinforcement to resist train loads. Use Mstatic, ft-lbs (N-m) Add 200% impact Therefore, M = (Mstatic)(3), ft-lbs (N-m) Say: fc' = 4000 psi (28 MPa), n = 7.5,

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total slab thickness = Say 12 inches (305 mm) d = 12 inches (305 mm) - 3 inches (76 mm) = 9 inches (229 mm) fs = 20,000 psi (140 MPa) Using trial and error: Say fc = 0.3 fc' f ck Compute k, p = -------- , As, and Moment M, ft-lbs (N-m) 2f s When Moment available = Moment Imposed Use that area of reinforcement (% steel) at the bottom of slab. Use 2/3 of lower reinforcement to resist negative moment at top. Total percent steel = percent steel at bottom + percent steelat top. b. Longitudinal reinforcement to prevent cracks from widening and reinforcement at the crack location must be less than its yield point, say fsy = 60,000 psi (420 MPa). Based on the axle loads, operating considerations, and if mitigation of noise and vibrations along the right-of-way is required, the use of softer pads may be more desirable However, if the track structure is subjected to higher axle loads, and the objective is to minimize fastener replacement cycles and associated costs, then the selection of harder pads may be more appropriate. C - 27.6.11 (b) Installation of Runnng Rail (2011) The neutral temperature is defined as the temperature at which the axial forces in a rail are zero. Usually it is the rail temperature at which the stressless rail is anchored to the track. Given that the rail in tunnels is not exposed to a wide range of temperature variations being underground as compared to at-grade or elevated structures, the thermal effects of CWR are considerably less.

C - 27.7.2 TYPES OF RAIL FASTENERS (2011) Proprietary products primarily developed for transit, commuter, and high speed application drive the direct fixation fastener market. These fasteners are comprised of elastomeric pads, steel plates, insulating components, and anchoring devices. Direct fixation fasteners are either unbonded or bonded. An unbonded fastener is made of a steel plate resting on an elastomeric pad. Whereas a bonded fastener utilizes one or two steel plates bonded to an elastomeric pad. Some of the new designs developed come from the containment design philosophy. Unlike the typical sandwich type DFF that depends on the rubber-to-metal bond to secure the top plate to the base plate, this design contains the top plate inside an outside containment frame. While the elastomer bonds the two castings together there are internal design features to restrain the top plate in all lateral and longitudinal directions. As a general criteria for slow speeds and light axle loads, a light duty single plate fastener with or without bonded elastomer can be used. However, for higher axle loads and faster operating speeds, it is recommended that heavy duty fasteners with a double plate and bonded elastomer be utilized. Elastic clips are recommended to hold the base of running rail to the fasteners.

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Concrete Slab Track C - 27.7.3.1 Fastener Vertical Spring Rate (1999) Based on the axle loads, operating considerations, and if mitigation of noise and vibrations along the right-ofway is required, the use of softer pads may be more desirable. However, if the track structure is subjected to higher axle loads, and the objective is to minimize fastener replacement cycles and associated costs, then the selection of harder pads may be more appropriate. C - 27.7.3.2 Elastic Clips (1999) In the selection of the elastic clips, it should be recognized that the clip toe load requirement must be adequate to longitudinally restrain the rail under braking or tractive forces of rolling stock wheels, and also in case of rail breakage be capable of resisting the pull-apart forces in continuous welded rail, and thus prevent a potential derailment condition.

C - 27.8.1 TRANSITION AREAS (1999) These installations will help in minimizing maintenance costs generally associated with these transition areas, and also provide continuity of ride comfort to train passengers.

C - 27.8.3 CONTINUITY OF SLAB TRACK OVER BRIDGE DECK (1999) In case of long bridges, horizontally curved bridges, etc. an independent analysis should be undertaken and appropriate design features incorporated.

1

C - 27.8.4 MODIFICATION OF EXISTING TUNNEL CONCRETE INVERT TO SLAB TRACK (2011) and C - 27.8.5 NEW TUNNEL - SLAB TRACK (2011) Some of the considerations in selection of the final design option are:

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(a) Clearances (b) Tolerances during construction (c) Construction equipment mobility (d) Maintenance considerations in terms of CWR and DFF renewals

4

FINAL ACCEPTANCE (2011) At the completion of slab track project, Rail properties having access to a Track Geometry Car (TGC), can employ the TGC as a quality control, as part of the final acceptance of slab track construction, to check track gauge, alignment, cross level, superelevation, and profile.

ADDITIONAL REFERENCES (2011) 1 Slab Track Field Test and Demonstration Program for Shared Freight and High Speed Passenger Service, PCA, R & D Serial No. 2988, 2007. 2 Performance of Direct-Fixation Track Structure, Design Guidelines, Battelle, Ohio, April 1999.

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3 Paving Alternatives to Ballasted Track, Heiner H. Moehren, AREA, Volume 98, Bulletin 762, December 1997.

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Part 28 Temporary Structures for Construction — 2002 —

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TABLE OF CONTENTS Section/Article

Description

Page

28.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.1.1 Scope (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.1.2 Criteria (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.1.3 Responsibility (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.1.4 Types of Temporary Structures (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-28-2 8-28-2 8-28-2 8-28-2 8-28-3

28.2 Information Required. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.2.1 Field Surveys and Records (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.2.2 Soil Investigation (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.2.3 Loads (2002). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.2.4 Drainage (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.2.5 Soil Properties (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-28-4 8-28-4 8-28-4 8-28-4 8-28-4 8-28-5

28.3 Computation of Lateral Forces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-28-5

28.4 Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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28.5 Design of Shoring Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.5.1 Design of Cantilever Sheet Pile Walls (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.5.2 Design of Anchored Sheet Pile Walls (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.5.3 Design of Cantilever Soldier Beam with Lagging Walls (2002) . . . . . . . . . . . . . . . . . . . . 28.5.4 Design of Anchored Soldier Beam with Lagging Walls (2002) . . . . . . . . . . . . . . . . . . . . . 28.5.5 Design of Braced Excavations (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.5.6 Design of Cofferdams (2002). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-28-5 8-28-5 8-28-6 8-28-7 8-28-8 8-28-10 8-28-10

28.6 Design of Falsework Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.6.1 Review and Approval of Falsework Drawings (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.6.2 Design Loads (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.6.3 Design Stresses, Loadings, and Deflections (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.6.4 Special Conditions (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.6.5 Falsework Construction (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.6.6 Removing Falsework (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-28-14 8-28-14 8-28-15 8-28-16 8-28-18 8-28-19 8-28-19

Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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LIST OF FIGURES Figure

Description

Page

8-28-1 Lateral Earth Pressure - Granular Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-28-2 Apparent Earth Pressure Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-28-6 8-28-9

SECTION 28.1 GENERAL 28.1.1 SCOPE (2002) a.

These specifications provide a recommended practice for the design of the most commonly used temporary structures. Other types of temporary structures may be used with the approval of the Engineer. These specifications are intended for SERVICE LOAD DESIGN only.

b. Temporary structures are defined as those structures used to facilitate the construction of a permanent structure. The temporary structures addressed by these specifications are primarily shoring and falsework systems. c.

All temporary structures anticipated to be in service for more than an 18-month period are not within the scope of these specifications.

d. Temporary bridges to carry railroad traffic shall be designed as permanent structures and are not included in these specifications.

28.1.2 CRITERIA (2002) a.

All temporary structures shall be designed and constructed to provide safe and adequate rigidity and support for the loads imposed.

b. All temporary structures shall be constructed with minimal interference to the operating tracks.

28.1.3 RESPONSIBILITY (2002) a.

The Contractor shall be solely responsible for the design, construction and performance of the temporary structure.

b. The Contractor shall submit to the Engineer working drawings and design calculations for the temporary structures. The drawings and calculations shall be signed and sealed by a registered professional engineer having a minimum of five years experience in the design of temporary structures and licensed in the jurisdiction in which the work is being constructed. The temporary structure(s) shall follow the lines, grades and location as shown on the plans. The temporary structure(s) shall be designed to conform to the right-of-way and easement restrictions provided and shall protect existing and proposed utilities shown on the plans. c.

Acceptance by the Engineer of the designs and working drawings shall in no way relieve the Contractor of full responsibility for the temporary structure, or its effect upon other adjacent structures.

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28.1.4 TYPES OF TEMPORARY STRUCTURES (2002) 28.1.4.1 Shoring Systems a.

A cantilever sheet pile wall is a structure designed to provide lateral support for a soil mass and derives stability from passive resistance of the soil in which the sheet pile is embedded.

b. An anchored sheet pile wall is a structure designed to provide lateral support for a soil mass and derives stability from passive resistance of the soil in which the sheet pile is embedded and the tensile resistance of the ground anchors. c.

A cantilever soldier beam with lagging wall is a structure designed to provide lateral support for a soil mass and derives stability from passive resistance of the soil in which the soldier beam is embedded.

d. An anchored soldier beam with lagging wall is a structure designed to provide lateral support for a soil mass and derives stability from passive resistance of the soil in which the soldier beam is embedded and the tensile resistance of the ground anchors. e.

For purposes of these specifications, soldier beams include steel H-piles, wide flange sections or other fabricated sections that are driven or set in concrete in drilled holes. Lagging refers to the members spanning between soldier beams.

f.

For purposes of these specifications, ground anchors shall be cement-grouted tiebacks designed, furnished, installed, tested and stressed in accordance with these specifications.

g.

1

Anchored soldier beam with lagging walls are generally designed as flexible structures which have sufficient lateral movement to mobilize active earth pressures and a portion of the passive pressure.

h. A braced excavation is a structure designed to provide lateral support for a soil mass and derives stability from passive resistance of the soil in which the vertical members are embedded and from the structural capacity of the bracing members. i.

j.

For purposes of these specifications, the vertical members of the braced excavation system include steel sheet piling or soldier beams comprised of steel H-piles, wide flange sections, or other fabricated sections that are driven or installed in drilled holes. Wales are horizontal structural members designed to transfer lateral loads from the vertical members to the struts. Struts are structural compression members that support the lateral loads from the wales. A cofferdam is an enclosed temporary structure used to keep water and soil out of an excavation for a permanent structure such as a bridge pier or abutment or similar structure. Cofferdams may be constructed of timber, steel, concrete or a combination of these. These specifications consider cofferdams primarily constructed with steel sheet piles.

28.1.4.2 Falsework a.

Falsework is defined in general terms as a temporary construction work on which a main or permanent work is wholly or partially supported until it becomes self-supporting.

b. Falsework for roll-in/roll-out construction methods is not covered in these specifications. 28.1.4.3 Types of Falsework Systems a.

Conventional falsework typically consists of timber posts and caps, timber bracing, and either timber or steel stringers and timber joists. Foundation support is usually provided by timber pads or sills set on © 2011, American Railway Engineering and Maintenance-of-Way Association

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the surface of the ground, although poor soil conditions may require the use of concrete footings, or by steel sills designed to distribute the loads to adequate timber pads or cribbing. b. Large-diameter, typically 20 inches (508 mm) or more, welded steel pipe columns are occasionally used to support steel caps and girders. When properly braced, pipe columns may provide an economical design when falsework is high and spans are long. c.

Patented steel shoring typically consists of individual components that may be assembled into modular units and erected in place to make any desired falsework configuration. When erected, the shoring consists of a series of internally-braced steel towers which, either directly or through a cap system, support the longitudinal load-carrying members.

d. Depending on load-carrying capacity, steel shoring systems are classified as pipe-frame shoring, heavyduty shoring or intermediate strength shoring. For bridge falsework the use of pipe-frame shoring is limited to installations where tower leg loads do not exceed 11 kips (49 kN). In contrast, a properly designed heavy-duty shoring system will be capable of supporting loads of 100 kips (490 kN) per tower leg. Intermediate strength shoring will have a load carrying capacity of up to 25 kips (111 kN) per tower leg. Typically, timber caps and stringers are used with pipe-frame intermediate strength systems, whereas rolled-beams or welded plate girders will be more economical for the longer spans which are possible with heavy-duty shoring. Pipe-frame shoring is usually supported on timber pads; however, the larger leg loads associated with heavy-duty shoring will require, depending on soil conditions, solid timber cribbing or reinforced concrete footings.

SECTION 28.2 INFORMATION REQUIRED 28.2.1 FIELD SURVEYS AND RECORDS (2002) a.

Sufficient information shall be furnished in the form of profiles and cross sections, or topographical maps to determine general design and structural requirements. Existing and proposed grades and alignment of tracks and roads shall be indicated together with records of: reference datum, maximum and minimum high water, minimum and mean low water, existing ground water level, location of utilities, construction history of the area, indication of any conditions which might hamper proper installation of the piling, soldier beams, ground anchors, depth of scour, allowance for overdredging, and wave heights.

28.2.2 SOIL INVESTIGATION (2002) a.

The characteristics of the foundation soils shall be investigated as indicated in Part 22, this Chapter with the investigation being done specifically for the temporary structure being designed.

28.2.3 LOADS (2002) a.

Loads shall be as indicated in Part 20, Article 20.2.3, this Chapter.

28.2.4 DRAINAGE (2002) a.

Drainage shall be as indicated in Part 20, Article 20.2.4, this Chapter.

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28.2.5 SOIL PROPERTIES (2002) a.

Soil properties shall be determined and soils classified as indicated in Part 20, Article 20.2.5, this Chapter.

SECTION 28.3 COMPUTATION OF LATERAL FORCES a.

Computation of lateral forces shall be as indicated in Part 20, Section 20.3, this Chapter.

SECTION 28.4 STABILITY a.

The stability of the system shall be investigated as indicated in Part 20, Section 20.4, this Chapter.

SECTION 28.5 DESIGN OF SHORING SYSTEMS

1

28.5.1 DESIGN OF CANTILEVER SHEET PILE WALLS (2002) 28.5.1.1 Restrictions of Use1 a.

Cantilever sheet pile walls shall not exceed 12 feet (3.7 m) in height and shall be used only in granular soils or stiff clays.

3

b. If used for shoring adjacent to an operating track the wall should be at least ten feet (3 m) away from the centerline of track, and its maximum height shall not exceed ten feet (3 m). 28.5.1.2 Depth of Embedment2 a.

1 2

The total depth embedment D shall be found by assuming rigid body rotation of the sheet pile wall about a point x located at a distance Z above the pile tip elevation. The resulting active and passive pressures are shown schematically in Figure 8-28-1 for a granular soil. The actual lateral pressure distributions shall be determined as specified in Part 20, Section 20.3 of this Chapter. The passive resistance shall include a factor of safety of 1.5 and be reduced by multiplying Kp by 0.66. The requirements for static equilibrium (the sum of the forces in the horizontal direction must be zero and the sum of the moments about, say the pile tip elevation, must be zero) may be expressed in terms of Z and D. The two equations obtained may be solved simultaneously for D, or a trial and error process may be used.

See Commentary See Commentary

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Figure 8-28-1. Lateral Earth Pressure - Granular Soil b. Conditions such as unrealistically short penetration requirements into relatively strong layers, potential for overall instability, scour or erosion shall be taken into account, and the depth of embedment increased to not less than the height of the wall. 28.5.1.3 Maximum Moment1 a.

Determine the depth at which the shear in the wall is zero by starting from the top of the wall and finding the point at which the areas of the driving and resisting pressure diagrams are equivalent. Calculate the maximum bending moment at the point of zero shear.

28.5.1.4 Allowable Stresses a.

The allowable stresses shall be determined on the following basis: (1) Sheet Pile Section: 2/3 tensile yield strength for new steel. Allowable stresses shall be reduced depending on the extent of usage for reused material. (2) All other structural material to comply with applicable parts of AREMA specifications.

28.5.2 DESIGN OF ANCHORED SHEET PILE WALLS (2002) a.

1

The design of anchored sheet pile wall systems shall be as indicated in Part 20, this Chapter. Requirements of Article 28.5.4.1, 28.5.4.2, 28.5.4.3, 28.5.4.5, and 28.5.4.6 shall be satisfied as applicable to the anchored sheet pile walls.

See Commentary

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28.5.3 DESIGN OF CANTILEVER SOLDIER BEAM WITH LAGGING WALLS (2002) 28.5.3.1 Restrictions of Use1 a.

Cantilever soldier beam with lagging walls shall not exceed 12 feet (3.7 m) in height and shall be used only in granular soils or stiff clays.

b. If used for shoring adjacent to an operating track the wall should be at least 13 feet (4.0 m) away from the centerline of track, and its maximum height shall not exceed eight feet (2.4 m). 28.5.3.2 Depth of Embedment2 a.

The total depth of embedment D shall be determined using the guidelines given in Article 28.5.1.2 except that the pressure distribution on the soldier piles below the excavation elevation shall be adjusted based on their equivalent width. The equivalent width shall be assumed to equal the width of the soldier pile multiplied by a factor of 3 for granular soils and a factor of 2 for cohesive soils. The width of the soldier piles shall be taken as the width of the flange or diameter for driven sections and the diameter of the concrete-filled hole for sections encased in concrete. Also, when determining the passive pressure distribution on the soldier piles, a depth of 1.5 times the width of the soldier pile in soil, and a depth of one foot in rock below the excavation elevation shall not be considered in providing passive lateral support.

b. Conditions such as unrealistically short penetration requirements into relatively strong layers, potential for overall instability, scour or erosion shall be taken into account, and the depth of embedment increased to not less than the height of the wall.

1

28.5.3.3 Maximum Moment a.

Determine the depth at which the shear in the soldier piles is zero by starting from the top of the wall and finding the point at which the areas of the driving and resisting pressure diagrams are equivalent. Calculate the maximum bending moment at the point of zero shear.

3

28.5.3.4 Allowable Stresses a.

The allowable stresses shall be determined on the following basis: (1) Sheet Pile Section: 2/3 tensile yield strength for steel. Allowable stresses shall be reduced depending on the extent of usage for reused material. (2) All other structural material to comply with applicable parts of AREMA specifications.

28.5.3.5 Lagging a.

The design load on the lagging is the theoretical pressure computed to act on it. When arch action can form in the soil behind the lagging (e.g., in granular or stiff cohesive soils where there is sufficient space to permit the in place soil to arch and the back side of the soldier piles bear directly against the soil) the moment computed based on simple end supports may be reduced by one third.

b. Well compacted fill shall be provided behind the lagging.

1 2

See Commentary See Commentary

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28.5.4 DESIGN OF ANCHORED SOLDIER BEAM WITH LAGGING WALLS (2002) 28.5.4.1 Qualifications a.

The performance of anchored soldier beam with lagging walls is strongly influenced not only by the methods and materials used but also the experience of the Contractor. The specifications presented herein are intended for evaluating earth pressure loading, tieback anchor design, wall facing design, stability considerations and corrosion protection requirements.

b. The Contractor or the Subcontractor selected for the design and construction shall be prequalified as a specialty Contractor for the design and construction of anchored soldier beam with lagging walls in order for the contract to be awarded. The Contractor shall submit proof of 5 anchored soldier beam with lagging walls successfully completed within the past 5 years. The Contractor's staff shall include an engineer with at least 5 years of experience in the design and construction of permanently tied back structures. The use of a manufacturer's representative by the contractor will not meet this qualification. 28.5.4.2 Submittals a.

The drawings shall include all details, dimensions, cross-sections, and sequence of construction necessary to construct the wall. The drawings and calculations shall include, but not be limited to: (1) A description of the tieback installation including drilling, grouting and stressing information. (2) Anchor capacity, type of tendon, anchorage hardware, minimum unbonded lengths, minimum anchor lengths, angle of installation and tieback locations and spacings. (3) Testing schedule and procedures for tiebacks. (4) An elevation view indicating the elevation at the top and bottom of the wall including all horizontal and vertical dimensions. (5) A plan view of the wall indicating the offset from the construction centerline to the face of the wall at all changes in horizontal alignment. (6) All details for construction of drainage facilities associated with the wall shall be clearly indicated. (7) Relationship between existing and proposed utilities.

28.5.4.3 Design Criteria a.

The lateral earth pressures shall be computed as indicated below: (1) For cantilevered conditions, and single tier anchored walls, lateral earth pressures shall be computed using Part 20. (2) For masses which do not have a history of sliding, the magnitude of lateral pressures on multi-tiered anchored walls shall be computed following the guidelines on Figure 8-28-2.

b. Where soldier beams are used, the width shall be assumed to be equal to the width of the flange for driven sections and the shaft diameter of the drilled sections. The resultant passive resistance of a soldier beam assumes that passive resistance is mobilized across an equivalent width described in Article 28.5.3.2, Paragraph a. The effects of backfill compaction and surcharge loads applied to the surface behind the wall shall be considered in the design earth pressure. The design stresses shall be in accordance with the current edition of Chapter 15. © 2011, American Railway Engineering and Maintenance-of-Way Association

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c.

The unbonded tendon length shall extend beyond the critical failure surface and be a minimum of 15 feet (4.6 m) in length. The critical failure surface starts at the bottom of the excavation. The wall-anchor system shall be checked for adequate stability. The overall stability of the earth mass being retained shall be checked and shall have a minimum factor of safety of 1.3.

1

Figure 8-28-2. Apparent Earth Pressure Diagram 28.5.4.4 Soldier Beam Installation a.

Installation Method (1) Soldier beams may be installed by driving with impact or vibration hammers or set in predrilled holes and encased with concrete below subgrade elevation and with lean concrete backfill above subgrade elevation. Encasement below subgrade level shall be concrete with a minimum 28-day compressive strength of 3,000 psi (20.7 MPa). Methods and equipment used for soldier beam installations shall be determined by the Contractor. (2) For driven soldier beams, leads or spuds shall be centered in such a manner as to afford freedom of movement to the hammer and shall be rigged to hold the soldier beam and hammer in alignment during driving. The soldier beam shall be driven with equipment which will ensure a properly distributed hammer impact on the soldier beam and prevent damage while driving. (3) For drilled-in soldier beams, side wall stability shall be maintained during drilling. If required by soil and water conditions, provide casing for hole excavation. Provide casing of sufficient strength to withstand handling stresses, lean concrete backfill pressure and surrounding earth and/or water pressure. Drilling mud may also be used to maintain side wall stability of soldier beam holes subject to the approval of the Railroad. Pump water from drill holes. Contractors may use tremie methods in lieu of pumping water. The soldier beam shall be fully encased in lean concrete backfill after completion of soldier beam hole excavation. The soldier beam may be set prior to, or after, lean concrete backfill placement at the option of the Contractor. Free fall lean backfill may be used. Vibrating of lean backfill mix is not required.

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Concrete Structures and Foundations

(4) Soldier beams may be furnished in full-length sections or may be spliced according to the method of splicing as shown on the plans. Field welding will be allowed only in accordance with the requirements for welding as specified in AWS D1.1, except as amended on the plans. (5) Structural welding of steel, steel reinforcement and soldier beams shall be made by personnel qualified to perform the type of welding involved in accordance with the qualification procedure of AWS D1.1, except as amended on the plans. (6) Any field welder will be required to present a certificate stating that he/she has been qualified in accordance with the requirements on these specifications within the previous 24-month period. A welder having a certificate which expired within the last 12 months may be permitted to commence welding provided a retest specimen is submitted immediately. The engineer may require a confirming qualification test during the progress of the work. 28.5.4.5 Ground Anchors (Tiebacks) a.

Unless otherwise directed, the Contractor shall select the tieback type and the installation method, and determine the bond length, anchor length and anchor diameter.

b. Ground anchor materials shall be in accordance with current "Recommendations for Prestressed Rock and Soil Anchors" from the Post-Tensioning Institute or as specified on the shoring plans. c.

Ground anchors shall be designed, fabricated, stored, handled, installed, tested and locked off in accordance with current "Recommendations for Prestressed Rock and Soil Anchors" from the PostTensioning Institute or as specified on the shoring plans.

28.5.4.6 Allowable Stresses a.

Ground anchor components shall comply with current "Recommendations for Prestressed Rock and Soil Anchors" from the Post-Tensioning Institute.

b. Allowable stresses and factors of safety for all other wall structural components shall be in accordance with the applicable sections of the Manual.

28.5.5 DESIGN OF BRACED EXCAVATIONS (2002) a.

Braced excavations shall be designed using the apparent earth pressure diagram shown in Figure 8-28-2.

28.5.6 DESIGN OF COFFERDAMS (2002) 28.5.6.1 General a.

This section deals primarily with cofferdams constructed with steel sheet piles. This section applies to the case where the water level lies above the soil or rock level such as in rivers, lakes and bays.

b. A single-wall cofferdam consists of a single wall of sheet piling driven in the form of a box. Single-walled cofferdams shall be designed as flexible sheet pile bulkheads or braced excavations. c.

A double-walled cofferdam consists of two rows of steel sheet piling driven parallel to each other and tied to each other with anchors and wales. Double wall cofferdams shall be designed similar to single-wall cofferdams. The two rows of sheet piles shall not be assumed to share equally in resisting the outside pressure unless concrete fill or rigid bracing is used between them. The need for double-wall cofferdams over single-wall cofferdams is usually to provide increased watertightness.

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d. A cellular cofferdam consists of soil-filled interconnected circular or diaphragm cells constructed of steel sheet piling. Cellular cofferdams are designed as gravity retaining structures. 28.5.6.2 Required Data a.

The required information about the site includes the following: •High water elevation •Velocity of water flow •Wave height and period •Ice conditions •Scour •Groundline cross-sections and profiles •Existing soil types, layer thicknesses, and properties •Properties of backfill materials •Flow net

1

•Vessel impact 28.5.6.3 Design Stresses and Factors of Safety a.

The maximum stresses for cofferdam materials shall not exceed 125% of the allowable stresses used for the design of permanent structures. The minimum factors of safety for stability of cofferdams shall be 1.25. The factors of safety shall be calculated as the sum of the resisting forces or moments divided by the sum of the driving forces or moments. The factors of safety may be calculated on a unit length of cofferdam. A flow net analysis shall be conducted to determine the stability of the bottom of the excavation.

3

28.5.6.4 Driving Forces

4 a.

In determining the stability of cofferdams, the driving forces shall include the following as applicable: •Hydrostatic water pressure •Seepage force •Stream flow pressure •Wave forces •Active earth pressure •Vessel impact •Ice forces

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Concrete Structures and Foundations 28.5.6.5 Equivalent Width a.

The stability of cellular cofferdams may be determined using an equivalent width. The equivalent width of a cofferdam is defined as the width of an equivalent rectangular section having an area equal to that of the actual cofferdam.

28.5.6.6 Saturation Line a.

The location of the line of saturation or phreatic surface within a cofferdam cell may be taken as a straight line sloping downward from the water surface level on the outboard side to the inboard side. The slope of the saturation line may be assumed as shown below. A horizontal line representing the average level of saturation may be assumed for stability calculations.

Cell Fill Material

Slope (Horizontal to Vertical)

Free draining coarse grained

1 to 1

Silty coarse grained

2 to 1

Fine grained

3 to 1

28.5.6.7 Sliding a.

Cofferdams shall be investigated for sliding at the base. The resisting forces shall consist of the frictional resistance of the soil along the bottom of the cofferdam, the passive resistance of soil on the inboard face, and the passive resistance of a berm, if any, on the inboard face. The unit weight of the soil below the saturation line shall be the submerged unit weight.

28.5.6.8 Overturning a.

Cofferdams shall be investigated for overturning about the inboard toe. The resultant of the driving forces and the cell weight shall lie within the middle one-third of the cofferdam.

28.5.6.9 Piling Uplift a.

Cofferdams shall be investigated for uplift of the outboard piling. The moments shall be summed about the inboard toe. The resisting moments shall be those due to the frictional forces on the inner and outer surfaces of the outboard sheeting plus the effective passive resistance of the soil and berm, if any, on the outboard face. The weight of the cell fill shall not be used for resisting moment.

28.5.6.10 Vertical Shear a.

Cofferdam cells shall be investigated for vertical shear failure on the centerline of the cells. The total shearing force, Q, on the neutral plane at the centerline of the cell shall be as follows: Q = 3M/2E Q

=

total shearing force per unit length of cofferdam

M

=

net overturning moment per unit length of cofferdam

E

=

equivalent width of cofferdam

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b. The shearing force, Q, shall be resisted by vertical shear within the cell fill and friction in the interlocks of the sheeting. In computing the vertical shear resistance of the fill material, the coefficient of earth pressure shall be as follows: 2

cos f K = -----------------------2 2 – cos f F = angle of internal friction of cell fill c.

The total centerline shear force resistance of the cell fill per unit length of cofferdam shall be the resultant lateral force due to soil fill material times tanF. The frictional resistance of the sheet pile interlocks per unit length of cofferdam shall be the interlock tension times the coefficient of friction of the interlocks.

28.5.6.11 Horizontal Shear a.

Cofferdam cells shall be investigated for tilting failure through horizontal shear in the cell fill material. The resisting moments shall be those due to the lateral resistance of the cell fill, the frictional resistance of the sheet pile interlocks, and the passive resistance of the berm if one is used.

b. The lateral resisting moment, M, of the cell fill about the base of the cofferdam shall be:

M = gs

c.

[

(H - EtanF) (EtanF)2 + (EtanF)3 2

3

M

=

resisting moment per unit length of cofferdam

H

=

height of cofferdam

E

=

equivalent width of cofferdam

gs

=

submerged unit weight of fill material

F

=

angle of internal friction of fill material

] 1

3

The resisting moment due to frictional resistance of the interlocks shall be the interlock tension times the coefficient of friction of the interlocks times the equivalent width of the cofferdam.

28.5.6.12 Interlock Tension a.

4

The hoop or interlock forces for circular cells and connecting arcs shall be calculated by the following equation: T =

PR

T

=

hoop or interlock force

P

=

maximum lateral pressure from cell fill and water

R

=

radius of circle or arc

b. The maximum lateral pressure may be taken as maximum at 1/4 the height from the mudline to the top of the cofferdam. c.

The interlock force at the connection of arc to circular cell shall be calculated by the following equation: © 2011, American Railway Engineering and Maintenance-of-Way Association

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Concrete Structures and Foundations

Tc =

PLsec F

Tc

=

hoop or interlock force at connection

P

=

maximum lateral pressure from cell fill and water

L

=

½ the center-to-center distance of full circular cells

F

=

angle between centerline of cells and a line from center of cell to point on cell periphery where connecting arc is attached.

d. The interlock tension shall not exceed the manufacturer's recommended values. e.

The maximum coefficient of friction of steel on steel at the interlocks shall not exceed 0.3.

28.5.6.13 Construction Requirements a.

Cofferdams for foundation construction shall be carried well below the bottom of the excavation or as near the bottom of the excavation as foundation conditions will permit and shall be well braced and as watertight as practical. The interior dimensions of cofferdams shall provide sufficient clearance inside the wales for constructing forms, driving piles, pumping outside the forms, and inspection.

b. Cofferdams which are tilted or moved out of position by any causes during the process of construction shall be righted or enlarged so as to provide the necessary clearances. c.

No shoring will be permitted in cofferdams which will induce stress, shock, or vibration in the permanent structure.

d. Cellular cofferdams with diaphragm walls shall be filled equally on each side of the diaphragm walls to avoid distortion of the cells. e.

After completion of the construction, the cofferdams with all sheeting and bracing shall be removed as directed by the Engineer or as shown on the plans. Such removal shall be done in a manner that will not disturb or mar the permanent structure.

SECTION 28.6 DESIGN OF FALSEWORK SYSTEMS 28.6.1 REVIEW AND APPROVAL OF FALSEWORK DRAWINGS (2002) a.

Falsework design drawings and calculations covering falsework adjacent to or over Railroad's operating tracks shall be certified to be complete and satisfactory to the submitting public agency prior to being submitted to the Railroad.

b. There shall be sufficient detail in the drawings to permit a complete stress analysis. In particular, the drawings shall show the size of all load-supporting members; all lateral and longitudinal bracing, including connections; the method of adjustment; and similar design features. c.

All design-controlling dimensions shall be shown, including, but not limited to, beam length; beam spacing; post location and spacing; vertical distance between connectors in diagonal bracing; overall height of falsework bents; and similar dimensions critical to the analysis.

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d. The falsework drawings shall include a superstructure placing diagram showing the concrete placing sequence and construction joint locations. When a schedule of placing concrete is shown on the contract plans, no deviation will be permitted without the approval of design engineer. e.

When footing type foundations are to be used, the Contractor shall determine the bearing value of the soil and shall show the values assumed in the design of the falsework on the falsework drawings.

f.

Anticipated total settlements of the falsework and forms shall be shown on the falsework drawings.

g.

Falsework footings shall be designed to carry the load imposed upon them without exceeding the estimated soil bearing values and anticipated settlements. Refer to Part 3 of this Chapter for allowable soil pressures of various material and settlements.

h. When falsework will be supported on pile bents, the required pile capacity and the maximum allowable driving tolerances shall be shown. i.

The support systems for form panels supporting concrete deck slabs and overhangs on girder bridges shall also be considered to be falsework and designed as such.

j.

The falsework drawings shall show all openings which are required through the falsework. Horizontal and vertical clearances shall be adequate and be shown on the plans.

k. Temporary bracing shall be provided to all falsework bents adjacent to the operating tracks, and shall be designed to withstand all imposed loads during erection, construction and removal. Wind loads shall be included in the design of such bracing. l.

In addition to the falsework drawings, the design engineer shall submit a copy of design calculations. The design calculations shall show the stresses and deflections of all load-supporting members, calculations furnished by the design engineer are for information only, rather than for review and acceptance. Accordingly, design and/or construction details which may be shown in the falsework in the form of sketches on the calculation sheets shall be shown on the falsework drawings as well; otherwise the drawings will not be complete.

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3

28.6.2 DESIGN LOADS (2002) a.

The design loads for falsework shall consist of the sum of dead and live vertical loads, and the assumed horizontal load. The minimum total design load for any falsework shall be not less than 100 pounds per square foot (4.8 kPa) for the combined live and dead load regardless of slab thickness.

b. Dead load shall include the weight of concrete, reinforcing steel, forms and falsework. The weight (mass density) of concrete, reinforcing steel and forms shall be assumed to be not less than 160 pounds per cubic foot (2563 kg/m3 ) for normal concrete. c.

Live loads shall consist of the actual weight of equipment to be supported by the falsework applied as concentrated loads at the points of contact and a uniform load of not less than 20 pounds per square foot (958 Pa) applied over the area supported, plus 75 pounds per linear foot (1095 N/m) applied at the outside edge of deck overhangs.

d. The assumed horizontal load to be resisted by the falsework bracing system shall be the sum of the actual horizontal loads due to equipment, construction sequence or other causes and an allowance for wind, but in no case shall the assumed horizontal load to be resisted in any direction be less than 2 percent of the total dead load.

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e.

The falsework shall be designed so that it will have sufficient rigidity to resist the assumed horizontal load without considering the weight of the concrete.

f.

The minimum horizontal load to be allowed for wind on each heavy-duty steel shore having a vertical load carrying capacity exceeding 30 kips (133 kN) per leg shall be the sum of the products of the wind impact area, shape factor, and the applicable wind pressure value for each height zone. The wind impact area is the total projected area of all the elements in the tower face normal to the applied wind. The shape factor for heavy-duty shoring shall be taken as 2.2. Wind pressure values shall be determined from the following table: WIND PRESSURE

g.

Height Zone Distance above ground

Shores Adjacent to Traffic Openings

At Other Locations

0 to 30 ft. (0 to 9 m)

20 psf (958 Pa)

15 psf (718 Pa)

30 to 50 ft. (9 to 164 m)

25 psf (1197 Pa)

20 psf (958 Pa)

50 to 100 ft. (164 to 30 m)

30 psf (1436 Pa)

25 psf (1197 Pa)

Over 100 ft. (30 m)

35 psf (1676 Pa)

30 psf (1436 Pa)

The minimum horizontal load to be allowed for wind on all other types of falsework, including falsework supported on heavy-duty shoring, shall be the sum of the products of the wind impact area and the applicable wind pressure value for each height zone. The wind impact area is the gross projected area of the falsework and any unrestrained portion of the permanent structure, excluding the areas between falsework posts or towers where diagonal bracing is not used. Wind pressure values shall be determined from the following table: WIND PRESSURE VALUE Height Zone (Feet above ground)

For Members over and Bents Adjacent to Traffic Openings

At Other Locations

0 to 30 (0 to 9 m)

2.0 Q psf (Pa)

1.5 Q psf (Pa)

30 to 50 (9 to 164 m)

2.5 Q psf (Pa)

2.0 Q psf (Pa)

50 to 100 (164 to 30 m)

3.0 Q psf (Pa)

2.5 Q psf (Pa)

Over 100 (30 m)

3.5 Q psf (Pa)

3.0 Q psf (Pa)

The value of Q in the above tabulation shall be determined as follows: Q = 1 + 0.2W (Q = 1 + 0.656W); but shall not be more than 10 In the preceding formula, W is the width of the falsework system in feet (meters), measured in the direction of the wind force being considered. h. The entire superstructure cross-section, except railing, shall be considered to be placed at one time. If the concrete is to be prestressed, the falsework shall be designed to support any increased or readjusted loads caused by the prestressing forces.

28.6.3 DESIGN STRESSES, LOADINGS, AND DEFLECTIONS (2002) a.

The maximum allowable design stresses and loadings listed are based on the use of undamaged, highquality structural grade material. Stresses and loadings shall be reduced by the design engineer if lesser quality materials are to be used.

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b. The maximum allowable stresses, loadings and deflections used in the design of the falsework shall be as follows: 28.6.3.1 Timber a.

Compression perpendicular to the grain 450 psi (3,100 kPa).

b. Compression parallel to the grain 480,000/(L/d)2 psi (33,000/(L/d)2 MPa), but not to exceed 1,600 psi (11.0 MPa). c.

Flexural stress 1,800 psi (12.4 MPa) reduced to 1,500 psi (10.3 MPa) for members with a nominal depth of 8 inches (20 mm) or less.

d. Horizontal shear 140 psi (965 kPa). e.

Axial tension 1,200 psi (8.3 MPa).

f.

Deflection due to the weight of concrete only L/240 of the span irrespective of the fact that the deflection may be compensated for by camber strips.

g.

In the foregoing formulas, L is the unsupported length, d is the least dimension of a square or rectangular column, or the width of a square of equivalent cross-sectional area for round columns.

h. The maximum modulus of elasticity, E, for timber shall be 1.6 x 106 psi (11.0 x 103 MPa).

1

i.

Timber piles, maximum loading 45 tons (400 kN).

j.

Timber connections shall be designed in accordance with the stress and loads allowed in the National Design Specification of Wood Construction, as published by the National Forest Products Association except that (1) reductions in allowable loads required therein for high moisture condition of the lumber and service conditions shall not apply, and (2) the design value of bolts in two member connections (single shear) when used for falsework bracing shall be 0.75 of the tabulated design value.

3

28.6.3.2 Steel a.

For identified grades of steel, design stresses, except stresses due to flexural compression, shall not exceed those specified in the Manual of Steel Construction as published by the AISC.

4 b. When the grade of steel cannot be positively identified, design stresses, except stresses due to flexural compression, shall not exceed either those specified in said AISC Manual for ASTM Designation A36 steel or the following: c.

Tension, axial and flexural 22,000 psi (151.7 MPa).

d. Compression, axial16,000-0.38 (L/r)2 psi (110.3-0.38(L/r)2 MPa) except L/r shall not exceed 120. e.

Shear on gross section of web 14,500 psi (100 MPa).

f.

Web crippling for rolled shapes 27,000 psi (186 MPa).

g.

For all grades of steel, design stresses and deflections shall not exceed the following:

h. Compression, flexural 12,000/(Ld/bt) psi (82,000/(Ld/bt) MPa), but not to exceed 22,000 psi (151.7 MPa) for unidentified steel or steel conforming to ASTM Designation A36 nor 0.6 Fy, for other identified steel. © 2011, American Railway Engineering and Maintenance-of-Way Association

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i.

Deflection due to the weight of concrete only L/240 irrespective of the fact that the deflection may be compensated for by camber strips.

j.

In the foregoing formulas, L is the unsupported length; d is the least dimension of rectangular columns, or the width of a square of equivalent cross-sectional area for round columns, or the depth of beams; b is the width and t is the thickness of the compression flange; and r is the radius of gyration of the member. All dimensions are expressed in inches (millimeters). Fy is specified minimum yield stress in psi (MPa), for the grade of steel used.

k. The modulus of elasticity, E, used for steel shall be 30x106 psi (2.07x103 MPa). 28.6.3.3 Manufactured Assemblies a.

The maximum loadings and deflections used on jacks, brackets, columns, joists and other manufactured devices shall not exceed the manufacturer's recommendations except that the dead load deflection of such joists used at locations other than under deck slabs between girders shall not exceed L/240. If requested by the Engineer, the design engineer shall furnish engineering data from the manufacturer verifying the manufacturer's recommendations or shall perform tests as necessary to demonstrate the adequacy of any such device proposed for use.

28.6.4 SPECIAL CONDITIONS (2002) a.

In addition to the minimum requirements specified in Section 28.6.2 falsework over or adjacent to the railroad tracks which are open to traffic shall be protected from impact by motor vehicles and construction equipment. The falsework design shall include, but not be limited to, the following minimum provisions:

b. The vertical load used for design of falsework posts and towers, but not footings, which support the portion of the falsework over openings, shall be the greater of the following: (1) 150 percent of the design load calculated in accordance with the provisions for the design load previously specified but not including any increased or readjusted loads caused by the prestressing forces, or (2) The increased or readjusted loads caused by the prestressing forces. c.

Falsework posts adjacent to railroads shall consist of either steel with a minimum section modulus about each axis of 9.5 inches cubed (155,700 mm3) sound timbers with a minimum section modulus about each axis of 250 inches cubed (4,097,000 mm3).

d. Each falsework post adjacent to railroad shall be mechanically connected to its supporting footing at its base, or otherwise laterally restrained, so as to withstand a force of not less than 2,000 pounds (8.90 kN) applied at the base of the post in any direction except toward the railroad track. Such posts also shall be mechanically connected to the falsework cap or stringer. Such mechanical connection shall be capable of resisting a load in any horizontal direction of not less than 1,000 pounds (4.45 kN). e.

For falsework spans over railroads all stringers shall be mechanically connected to falsework cap or framing. Such mechanical connections shall be capable of resisting a load in any direction, including uplift on the stringer, of not less than 500 pounds (2.22 kN).

f.

When timber members are used to brace falsework bents which are located adjacent to railroads, all connections for such timber bracing shall be bolted type using 5/8 inch (16 mm) diameter or larger bolt.

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g.

Falsework bents adjacent to tracks shall have a minimum horizontal clearance of twelve feet (3.7 m) from centerline of track. Falswork to be sheathed solid on the side adjacent to track between 3 feet (0.9 m) and 17 feet (5.2 m) above the top of rail elevation. Sheathing shall consist of plywood not less than 5/8 inch (16 mm) thick or lumber not less than one inch thick (25 mm), nominal. Bracing on such bents shall be adequate so that the bent will resist the required assumed horizontal load or 5,000 pounds (22.2 kN) whichever is greater. Collision posts and sheathing shall not be required if horizontal clearances to falsework is 18 feet (5.5 m) or greater.

h. A minimum vertical clearance of 22'-6" (6.9 m), or as established by the Railroad, above top of higher rail shall be maintained at all times.

28.6.5 FALSEWORK CONSTRUCTION (2002) a.

The falsework shall be constructed to conform to the falsework drawings. The materials used in the falsework construction shall be of quality necessary to sustain the stress required by the falsework design. The workmanship used in falsework construction shall be of such quality that the falsework will support the loads imposed on it without excessive settlement or take-up beyond that shown on the falsework drawings.

b. Falsework shall be founded on solid footings, safe against undermining, protected from softening, and capable of supporting the loads imposed on it. When requested by the Engineer, the Contractor shall demonstrate by suitable load tests that the soil bearing values assumed for the design of the falsework do not exceed the supporting capacity of the soil. c.

When falsework is to be supported on piles, the piles shall be driven until the required pile capacity is obtained as shown on the falsework drawings.

d. For falsework over or adjacent railroad tracks, all details of the falsework system which contribute to the horizontal stability and resistance to impact, except for bolts in bracing, shall be installed at the time each element of the falsework is erected and shall remain in place until the falsework is removed. e.

Falsework shall be designed to compensate for falsework deflection, vertical alignment and anticipated structure deflection.

f.

Contractor shall provide tell-tales attached to the soffit forms and readable from the ground in enough systematically placed locations to determine the total settlement of the entire portion of the structure where concrete is being placed.

28.6.6 REMOVING FALSEWORK (2002) a.

Falsework supporting any span of a simple span concrete bridge shall not be released before 10 days after the last concrete, excluding concrete above the bridge deck, has been placed in that span and in the adjacent portions of each adjoining span of a length equal to at least ½ the length of the span where falsework is to be released.

b. Falsework for cast-in-place prestressed portions of structures shall not be removed until after the prestressing tendons have been tensioned and released. c.

Falsework supporting any span of a continuous or rigid frame bridge shall not be removed until all required prestressing has been completed in that span and in the adjacent portions of each adjoining span for a length equal to at least ½ the length of the span where falsework is to be removed.

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Concrete Structures and Foundations

d. Falsework supporting overhangs, deck slabs between girders and girder stems which slope 45 degrees or more off vertical shall not be removed before 7 days after the deck concrete has been placed. e.

In addition to the above requirements, no falsework for bridge spans shall be removed until the supported concrete has attained a compressive strength of 2,600 pounds per square inch (17.9 MPa) or 80 percent of the specified strength, whichever is higher.

f.

When falsework piling are used to support falsework within the limits of the railroad right-of-way, such piling within this area shall be removed to at least 2 feet (0.6 m) below the finished grades.

g.

All debris and refuse resulting from the work shall be removed and the premises left in a neat and presentable condition.

COMMENTARY C - SECTION 28.5 DESIGN OF SHORING SYSTEMS C - 28.5.1 DESIGN OF CANTILEVER SHEET PILE WALLS (2002) C - 28.5.1.1 Restrictions of Use A cantilever wall derives support from the passive resistance below the excavation line to support the active pressure from the soil above excavation elevation without an anchorage. Cantilever walls undergo large lateral deflections, and the member stresses increase rapidly with height. Therefore, it is important to restrict the maximum height of the wall and require good quality soil below the excavation line that can provide adequate passive resistance. C - 28.5.1.2 Depth of Embedment The large moment and deflections that need to be resisted in cantilever type walls may require quite large penetration depths. C - 28.5.1.3 Maximum Moment See Steel Sheet Piling Design Manual, US Steel, 1975, for charts that may be used to obtain preliminary values for the depth of penetration D and the maximum moment for the case of a cantilever sheet pile wall in homogeneous granular soil and in a cohesive soil with granular soil behind above the excavation elevation. The D values obtained from the charts shall be increased by 20 percent.

C - 28.5.3 DESIGN OF CANTILEVER SOLDIER BEAM WITH LAGGING WALLS (2002) C - 28.5.3.1 Restrictions of Use A cantilever soldier pile wall behaves similarly to a cantilever sheet pile wall. The active soil pressure and surcharge loadings are transmitted through the lagging to the soldier piles above the excavation elevation. Below the excavation the soldier piles utilize the soils passive resistance to resist the driving pressures. Due to the rapid increase in deflections and moments with the wall height, maximum height restrictions needed to be imposed.

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Temporary Structures for Construction C - 28.5.3.2 Depth of Embedment The depth of embedment of the soldier piles must be sufficient to mobilize the passive resistance. The arching capability of soils allows the use of an equivalent width for the soldier pile below the excavation.

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Part 29 Waterproofing

8

— 2005 — TABLE OF CONTENTS

Section/Article

Description

Page

29.1 General Principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29-4 29.1.1 Purpose (2001). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29-4 29.1.2 Scope (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29-4 29.2 Waterproofing (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-29-4

29.3 Dampproofing (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-29-5

29.4 Specific Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.4.1 Abutments and Retaining Walls (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.4.2 Short Single-Span Arches and Box Culverts (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.4.3 Pedestrian Subways (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.4.4 Arches – Long Single-Span and Multiple-Span with Spandrel Fill (1994). . . . . . . . . . . . 29.4.5 Precast Slabs for Bridge Decks and Floors (2001). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.4.6 Cast-in-Place Concrete Bridge Decks or Floors (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.4.7 Pump Pits for Subways and Basements (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.4.8 Pipe Manholes and Pipe T unnels (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.4.9 Water Containers (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.4.10 Walls and Floors of Buildings (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.4.11 Platforms, Walkways and Roadways (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.4.12 Grain Elevator Pits and Similar Underground Structures (1994) . . . . . . . . . . . . . . . . . . 29.4.13 Scale Pits and Other Similar Structures Below Grade (1994) . . . . . . . . . . . . . . . . . . . . .

8-29-5 8-29-5 8-29-6 8-29-6 8-29-6 8-29-6 8-29-6 8-29-6 8-29-6 8-29-6 8-29-7 8-29-7 8-29-7 8-29-7

29.5 Terms (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-29-8

29.6 Applicable ASTM Designations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.6.1 General (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.6.2 ASTM D41 (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.6.3 ASTM D43 (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.6.4 ASTM D173 (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.6.5 ASTM D226 (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.6.6 ASTM D227 (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.6.7 ASTM D312 (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.6.8 ASTM D449 (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.6.9 ASTM D450 (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-29-8 8-29-8 8-29-8 8-29-8 8-29-8 8-29-8 8-29-9 8-29-9 8-29-9 8-29-10

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TABLE OF CONTENTS (CONT) Section/Article 29.6.10 29.6.11 29.6.12 29.6.13 29.6.14 29.6.15 29.6.16 29.6.17 29.6.18 29.6.19 29.6.20 29.6.21 29.6.22 29.6.23 29.6.24

Description

Page

ASTM D517 (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ASTM D692 (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ASTM D946 (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ASTM D1187 (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ASTM D1190 (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ASTM D1227 (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ASTM D1327 (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ASTM D1668 (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ASTM D2178 (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ASTM D2823 (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ASTM D3515 (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ASTM D4215 (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ASTM D4479 (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ASTM D4586 (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ASTM D6134 (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-29-10 8-29-10 8-29-10 8-29-10 8-29-11 8-29-11 8-29-11 8-29-11 8-29-11 8-29-11 8-29-12 8-29-12 8-29-12 8-29-12 8-29-12

29.7 General Practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29-12 29.7.1 Design (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29-12 29.7.2 Types (1996) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29-13 29.8 Primers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29-13 29.8.1 General (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29-13 29.8.2 Primer (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29-13 29.9 Membranes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29-14 29.9.1 Asphalt for Mopping (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29-14 29.9.2 Coal-Tar Pitch for Mopping (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29-14 29.9.3 Fabric (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29-14 29.9.4 Felt (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29-14 29.9.5 Butyl Rubber (Butyl-based IIR) or EPDM (Ethylene-propylene-diene-monomers) (2001)8-29-14 29.9.6 Adhesive (1994). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29-15 29.9.7 Cement (2001). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29-15 29.9.8 Butyl Gum Tape (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29-15 29.9.9 Rubberized Asphalt with Plastic Film or Preformed Board Membrane (2001) . . . . . . . 8-29-16 29.9.10 Cold Liquid-Applied Elastomeric Membrane (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29-16 29.10 Membrane Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.10.1 Portland Cement Concrete (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.10.2 Asphalt Plank (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.10.3 Asphaltic Panels (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-29-17 8-29-17 8-29-17 8-29-17

29.11 Sealing Compounds for Joints and Edges of Membrane Protection (2001) . . . . . . . .

8-29-20

29.12 Anti-Bonding Paper (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-29-20

29.13 Inspection and Tests (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-29-20

29.14 Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29-20 29.14.1 General (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29-20

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Waterproofing

TABLE OF CONTENTS (CONT) Section/Article

Description

Page

29.14.2 Primer (2001). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29-21 29.14.3 Membrane (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29-21 29.14.4 Protective Cover (2001). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29-26 29.15 Introduction to Damproofing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29-28 29.15.1 Damproofing Scope (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29-28 29.16 Materials for Damproofing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.16.1 Asphalt Primer (1994). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.16.2 Creosote Primer (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.16.3 Woven Cotton Fabrics (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.16.4 Coal-Tar Saturated Organic Felt (1994). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.16.5 Asphalt (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.16.6 Coal-Tar Pitch (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.16.7 Emulsified Asphalt Coatings (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.16.8 Emulsified Asphalt Protective Coating (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.16.9 Asbestos-Free Asphalt Roof Coatings (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.16.10 Asbestos-Free Asphalt Roof Coating (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.16.11 Inspection and Tests (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-29-28 8-29-28 8-29-28 8-29-28 8-29-28 8-29-28 8-29-28 8-29-28 8-29-28 8-29-29 8-29-29 8-29-29

29.17 Application of Damproofing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.17.1 Preparation of Surfaces (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.17.2 Temperature (2001). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.17.3 Method of Application (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

8-29-29 8-29-29 8-29-29 8-29-29

C - Commentary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29-30

LIST OF FIGURES Figure

Description

Page

8-29-1 Joint Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29-7 8-29-2 Lapping of Bituminous Membrane Waterproofing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29-22 8-29-3 Recommended Butyl Membrane Field Seam Assembly Recommended in Order Listed for Field Assembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-29-24

LIST OF TABLES Table 8-29-1 8-29-2 8-29-3 8-29-4

Description ASTM D6134 Physical Requirements for Vulcanized Rubber Sheets. . . . . . . . . . . . . . . . . . . . Performance Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Performance Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Degree of Resistance to Penetration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Page 8-29-15 8-29-16 8-29-17 8-29-19

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Concrete Structures and Foundations

SECTION 29.1 GENERAL PRINCIPLES 29.1.1 PURPOSE (2001) These recommended practices are intended to be used for work carried out by railroad companies or their selected contractors when requested by the Engineer. These recommended practices apply to bridges and other structures constructed of either concrete or steel.

29.1.2 SCOPE (2005) These recommended practices describe the selection, sampling and testing of materials to be used, material properties and construction requirements under specific conditions. They also apply to materials and construction methods for impervious membranes and auxilliary components to protect structures or parts of structures, except roofs of buildings, from the harmful effects of water.

SECTION 29.2 WATERPROOFING (2001) a.

Adequate and effective drainage should be provided to remove free water and lessen the possibilities of the development of a hydrostatic pressure head.

b. Where the range of temperature varies from above freezing to below freezing, the disintegrating effect of frost action on water-saturated concrete and masonry should be recognized and adequately protected against. c.

All surfaces of concrete, masonry, or steel structures that are or will be in contact with ballast, fill or water or will be inaccessible for inspection, shall be considered for waterproofing to eliminate the corrosive action of liquids upon the structural members.

d. All waterproofing materials shall be applied when surface and air temperature are both above 40 degrees F (4 degrees C) and rain is not likely before completion of material application, unless specifically recommended by the material manufacturer and with written approval of the Engineer. e.

The materials for waterproofing and the methods of application must ensure that the bond is permanently maintained to the concrete, masonry, or steel interface.

f.

Where the waterproofing membrane is subject to potential injury or violation from abrasion, pressure, puncture, or other job-site abuse, a protection course is required.

g.

Waterproofing shall be applied where required to protect and extend the service life of the structure.

h. The type of waterproofing should be determined by the use and probable life of the structure as related to the potential future cost of renewal of the waterproofing. i.

Waterproofing of the most durable and effective type should be used on all concrete, steel and masonry structures:1 (1) In locations subject to water or other liquids under a hydrostatic head.

1

See C - Commentary

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Waterproofing

(2) Where repair or removal is impractical or prohibitive in cost. (3) Where certainty of watertightness must be positive because of heavy damage if water enters. (4) For the protection of structural members from corrosive action caused by liquid infiltration. j.

Waterproofing specially designed for the purpose should be used where the structure must be protected against liquids containing corrosive or deleterious substances.

k. A waterproofing membrane on the surface adjacent to the water source is the most effective externally applied waterproofing.

SECTION 29.3 DAMPPROOFING (1994) a.

Dampproofing is effective in preventing the accumulation of surface moisture from condensation only in proportion to its temperature-insulating value.

b. Dampproofing is not effective where masonry is subject to moisture saturation accompanied by cycles of freezing and thawing. c.

Dampproofing is not effective where cracks may occur in concrete or masonry walls as it does not have the ability to bridge those cracks.

1

d. A frequent fault of one-coat dampproofing is failure to produce a continuous covering free from pin holes. This should be considered in deciding upon the number of coats that should be applied. e.

The purpose and character of dampproofing should not require special protection or covering. Where protection or covering is necessary, the conditions will usually warrant the use of a waterproofing membrane.

f.

A prime requisite of a dampproof coating is that it must remain in place. Bond with the surface is therefore essential.

g.

The selection of materials for dampproofing should include consideration of the effect of temperature extremes, the effect of ultraviolet exposure, and the physical and chemical effects of the liquid to which they will be subjected.

SECTION 29.4 SPECIFIC APPLICATION 29.4.1 ABUTMENTS AND RETAINING WALLS (2001) Once effective drainage has been provided, waterproofing on the back of an abutment or retaining wall is generally not necessary, but dampproofing should be provided above the footings. Where it is desired to prevent the passage of water through expansion joints, contraction joints or construction joints, a suitable waterstop shall be installed.

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29.4.2 SHORT SINGLE-SPAN ARCHES AND BOX CULVERTS (1994) Short single-span arches and box culverts should be dampproofed on the surfaces in contact with the fill.

29.4.3 PEDESTRIAN SUBWAYS (1994) Pedestrian subways should be waterproofed on surfaces in contact with the fill.

29.4.4 ARCHES – LONG SINGLE-SPAN AND MULTIPLE-SPAN WITH SPANDREL FILL (1994) Long single-span arches and arches of multiple span with spandrel fill should be fully waterproofed on all surfaces in contact with the fill, including the parapets. Special attention should be given to the drainage and to the position of the fill in order to prevent the pocketing of water.

29.4.5 PRECAST SLABS FOR BRIDGE DECKS AND FLOORS (2001) a.

The top surface of reinforced slabs and the backs of parapets should be dampproofed or waterproofed. When construction is over streets or walkways, waterproofing shall be applied.

b. Prior to the application of hot-poured rubberized asphalt joint sealing material in joints between precast units, a heat-resistant backer rod should be inserted to a minimum depth of 1/2 inch (13 mm) below the slab surface ss shown in Figure 8-29-1. The remaining reservoir should then be filled with hot-poured rubberized asphalt joint sealing compound. Fill flush with the slab surface. The joint width should be twice the joint depth.

29.4.6 CAST-IN-PLACE CONCRETE BRIDGE DECKS OR FLOORS (1994) a.

The top surface of slabs and the backs of parapets should be waterproofed or dampproofed and the construction joints closed with suitable waterstops, where the slab is an integral part of the structure, as in rigid frames or girderless flat slabs, or where it is the main load-carrying element, as in simple or continuous slabs.

b. When the slab is supported on steel beams, all construction joints should be closed with suitable waterstops and membrane waterproofing applied.

29.4.7 PUMP PITS FOR SUBWAYS AND BASEMENTS (1994) Pump pits should be waterproofed or dampproofed on all exterior surfaces.

29.4.8 PIPE MANHOLES AND PIPE TUNNELS (1994) Pipe manholes and concrete pipe tunnels should be dampproofed or waterproofed on all exterior surfaces.

29.4.9 WATER CONTAINERS (1994) The walls and floors of water containers, such as reservoirs and tanks, should be made of dense concrete to insure watertightness. Special attention should be given to the waterproofing of all joints and a suitable waterstop shall be installed.

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Figure 8-29-1. Joint Preparation

29.4.10 WALLS AND FLOORS OF BUILDINGS (2001) a.

The walls and floors of all buildings subject to hydrostatic pressure should be waterproofed on the pressure surfaces.

1

b. If not subject to hydrostatic pressure, all exterior walls should be dampproofed below ground. c.

Dampproofing should be applied to the back and top (under coping) of parapet walls and to the back and to the embedded surfaces of architectural masonry trim; also, to the inside of exterior masonry walls if plaster is to be directly applied.

3

d. Special attention should be given to all joints and to places where pipes or other facilities pass through walls.

29.4.11 PLATFORMS, WALKWAYS AND ROADWAYS (1994) Platforms, walkways and roadways over rooms or spaces used as adjuncts to building should be waterproofed.

29.4.12 GRAIN ELEVATOR PITS AND SIMILAR UNDERGROUND STRUCTURES (1994) Grain elevator pits and similar underground structures should be made watertight by design and construction and waterproofed on the exterior.

29.4.13 SCALE PITS AND OTHER SIMILAR STRUCTURES BELOW GRADE (1994) Scale pits and other similar structures below grade should be made watertight by design and construction as well as waterproofed or dampproofed, subject to the following conditions: • The walls and floors of all pits subject to hydrostatic pressure should be waterproofed. • If not subject to hydrostatic pressure, all exterior walls should be dampproofed below grade.

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Concrete Structures and Foundations

• Utility openings that pass through these walls shall be given special attention to prevent water infiltration or leakage.

SECTION 29.5 TERMS (2001) The following terms are defined in the Chapter 8 Glossary located at the end of this Chapter: Asphaltic Panels for Waterproofing Protection Butyl Rubber Cold Liquid-Applied Elastomeric Membrane EPDM Rubberized Asphalt with Plastic Film or Preformed Board Membrane

SECTION 29.6 APPLICABLE ASTM DESIGNATIONS 29.6.1 GENERAL (2001) These descriptions are offered as an assist to railway Engineers as a capsulized summary of their intended usage; whether it be on grade, above grade or whether they be used in structures horizontally or vertically, to include railway bridges and structures.

29.6.2 ASTM D41 (2001) Covers asphaltic primers suitable for use with asphalt in dampproofing and waterproofing below or above ground level, for application to concrete, masonry and metal surfaces.

29.6.3 ASTM D43 (2001) Covers coal tar primers suitable for use with coal-tar pitch in dampproofing and waterproofing below or above ground level, for application to concrete and masonry surfaces.

29.6.4 ASTM D173 (2001) Covers woven cotton fabrics saturated with either asphalt or coal-tar pitch and suitable for use with asphalts conforming to D449 or D312 and coal-tar pitch conforming to D450 in the membrane system of waterproofing.

29.6.5 ASTM D226 (2001) Covers asphalt-saturated organic felts, either with or without perforations, 36 inches (915 mm) in width, suitable for use with mopping asphalts conforming to D449 in the membrane system of waterproofing, and with mopping asphalts conforming to D312 in the construction of built-up roofs.

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29.6.6 ASTM D227 (1994) Covers coal-tar-saturated organic felt for use with coal-tar pitches conforming to the appropriate requirements of D450 in the construction of built-up roofs and in the membrane system of waterproofing.

29.6.7 ASTM D312 (2001) Covers four types of asphalt intended for use in built-up roofing construction. This is intended for general classification purposes only and does not imply restrictions on the slope in which an asphalt must be used. • Type I. Includes asphalts that are generally susceptible to flow at roof temperatures, with good adhesive and “self-healing properties.” They are generally used in slag or gravel surfaced roofs on inclines up to 2%, or 1/4 inch per foot (20 mm/m) slope. • Type II. Includes asphalts that are moderately susceptible to flow at roof temperatures. They are generally for use with built-up roof construction on inclines from approximately 2%, or 1/4 inch per foot (20 mm/m) to 8%, or 1 inch per foot (80 mm/m) slope. • Type III. Includes asphalts that are generally not susceptible to flow at roof temperatures for use in the construction of built-up roof construction on inclines from approximately 2%, or 1/4 inch per foot (20 mm/m) to 25%, or 3 inches per foot (250 mm/m) slope. • Type IV. Includes asphalts that are generally not susceptible to flow at roof temperature, for use in the construction of built-up roofing on inclines from approximately 2%, or 1/4 inch per foot (20 mm/m) to 50%, or 6 inches per foot (500 mm/m) slope. These asphalts may be useful in areas where relatively high year-round temperatures are experienced.

1

29.6.8 ASTM D449 (2001) Covers three types of asphalts suitable for use as a mopping coat in dampproofing; or as a plying or mopping cement in the construction of membrane waterproofing systems with felts conforming to D226; fabrics conforming to D173 or D1668 (asphalt types); asphalt-impregnated glass mat conforming to D2178 and with primer conforming to D41.

3

• Type I. A soft, adhesive, “self-healing” asphalt that flows easily and is suitable for use below grade under uniformly moderate temperature conditions both during the process of installation and during the service. NOTE:

4

Type I asphalt is suitable for foundations, tunnels, subways, etc.

• Type II. An asphalt somewhat less susceptible to flow than Type I with good adhesive and “selfhealing” properties, suitable for use above grade where it will not be exposed to temperatures exceeding 122 degrees F (50 degrees C). NOTE:

Type II asphalt is suitable for railroad bridges, culverts, retaining walls, tanks, dams, conduits, spray decks, etc.

• Type III. An asphalt less susceptible to temperature than Type II, with good adhesive properties, and suitable for use above grade on vertical surfaces exposed to direct sunlight or temperatures above 122 degrees F (50 degrees C).

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29.6.9 ASTM D450 (2001) Covers three types of coal-tar pitch suitable for use in the construction of built-up roofing, dampproofing and membrane waterproofing systems. • Type I. Suitable for use in built-up roofing, dampproofing, and membrane waterproofing systems with felts conforming to the requirements of D227 or as specified by the manufacturer. • Type II. Suitable for use in dampproofing and in membrane waterproofing systems with primers conforming to the requirements of D43, felts conforming to the requirements of D227, and fabrics with coal-tar saturant conforming to the requirements of D173, D1327, or D1668 or in systems using any combination of components specified by the manufacturer. • Type III. Suitable for use in built-up roofing, dampproofing, and membrane waterproofing systems but having less volatile components than Types I or II.

29.6.10 ASTM D517 (1994) Covers asphalt plank of two types as used for bridge floors: • Type I. Plain asphalt plank. • Type II. Mineral-surfaced asphalt plank.

29.6.11 ASTM D692 (1994) Covers crushed stone, crushed hydraulic-cement concrete, crushed blast-furnace slag, and crushed gravel suitable for use in bituminous paving mixtures, as described in D3515 or D4215.

29.6.12 ASTM D946 (1994) Covers asphalt cement for use in the construction of pavements and covers the following penetration grades: • 40 - 50. • 60 - 70. • 85 - 100. • 120 - 150. • 200 - 300.

29.6.13 ASTM D1187 (2001) Covers emulsified asphalt suitable for application in a relatively thick film as a protective coating for metal surfaces. • Type I. Quick-setting emulsified asphalt suitable for continuous exposure to water within a few days after application and drying. • Type II. Emulsified asphalt suitable for continuous exposure to the weather, only after application and drying.

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29.6.14 ASTM D1190 (2001) Covers concrete joint sealants of the hot-pour elastic type, intended for use in sealing joints and cracks in concrete pavements, bridges and other structures.

29.6.15 ASTM D1227 (2001) Covers emulsified asphalts suitable for use as a protective coating for built-up roofs and other exposed surfaces with inclines of not less than 4%, or 1/2 inch per foot (40 mm/m). • Types II and III. Emulsified asphalt prepared with mineral colloid emulsifying agents and not containing asbestos.

29.6.16 ASTM D1327 (2001) a.

Covers woven burlap fabrics, saturated with either asphalt or refined coal-tar, as specified by the Engineer, for use in the membrane system of roofing or waterproofing or as specified by the manufacturer.

b. Asphalt-saturated burlap fabric shall be used with asphalt-based cement; a mopping asphalt conforming to D312, D449, or appropriate solvent bearing bitumen materials. c.

Coal-tar-saturated burlap fabric shall be used with coal-tar-based cement; a coal-tar pitch conforming to ASTM D450, which is an appropriate solvent bearing bitumen material.

1

29.6.17 ASTM D1668 (2001) Covers finished treated (coated) woven glass fabrics, coated with either asphalt, coal-tar pitch, or an organic resin compatible with the waterproofing system, as specified by the Engineer.

3

• Type I, Asphalt Treated. Is suitable for use with all asphalts and asphalt based compounds. • Type II, Coal Tar Pitch Treated. Is suitable for use with all coal-tar pitches and coal tar based compounds. • Type III, Organic Resin Treated. The Engineer and supplier shall agree on an organic resin which is compatible with or suitable for the plying materials. The organic resins shall not be water soluble.

29.6.18 ASTM D2178 (2001) a.

Covers glass felts impregnated to varying degrees with asphalt, that may be used with asphalts conforming to the requirements of D312 in the construction of built-up roofs, and with asphalts conforming to the requirements of D449 in the membrane system of waterproofing.

b. Asphalt-impregnated glass felts, 36 inches (914 mm) wide, covered by this Designation are Types III, IV and VI.

29.6.19 ASTM D2823 (2001) Covers asphalt roof coatings of brushing or spraying consistency. • Type I. Is made from asphalts characterized as self-healing, adhesive and ductile, conforming to the requirements of D312, Type I; D449, Types I or II; or D946.

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• Type II. Is made from asphalts characterized by a high softening point and relatively low ductility, conforming to the requirements of D312, Type II or III; or D449, Type III.

29.6.20 ASTM D3515 (2001) Covers hot-mixed, hot-laid asphalt, tar, emulsified asphalt, and recycled bituminous paving mixtures for base, binder, leveling, and surface covers.

29.6.21 ASTM D4215 (2001) Covers cold-mixed, cold-laid and recycled cold-mixed, cold-laid bituminous paving mixtures for base, binder, leveling, and surface covers.

29.6.22 ASTM D4479 (1994) Covers asbestos-free asphalt roof coatings of brushing or spraying consistency. • Type I. Made from asphalts characterized as self-healing, adhesive, and ductile, and conforming to the requirements of D312, Type I; D449, Types I or II; or D946. • Type II. Is made from asphalts characterized by high softening point and relatively low ductility, conforming to the requirements of D312, Types II or III; or D449, Type III.

29.6.23 ASTM D4586 (2001) Covers asbestos-free asphalt roof cement suitable for trowel application to roofings and flashings. • Type I. Made from asphalt characterized as self-healing, adhesive, and ductile, conforming to the requirements of D312, Type I; D449, Types I or II; or D946. • Type II. Made from asphalt characterized by high softening point and relatively low ductility, and conforming to D312, Types II or III; or D449, Types II or III.

29.6.24 ASTM D6134 (2001) Covers unreinforced, vulcanized rubber sheets made from ethylene propylene diene terpolymer (EPDM) or butyl (IIR), used in waterproofing systems.

SECTION 29.7 GENERAL PRACTICES 29.7.1 DESIGN (2005)1 a.

1

Section 29.2, Waterproofing (2001) and Section 29.3, Dampproofing (1994) enumerate the principles which shall govern the waterproofing of railway structures. Structures which require waterproofing shall be designed so that they can be waterproofed by the methods and with the materials specified herein. Special care shall be taken to provide flexibility in the waterproofing membrane or in the joints between sections of membrane at expansion joints or at those locations where deflection deformation

See C - Commentary

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may cause excessive stretching of the membrane. Care shall be taken to seal effectively or flash all places where the waterproofing membrane terminates, such as along the webs of girders. b. Right-angle bends should be avoided by using rounded or chamfered edges on outside corners and suitable fillet on inside corners. An underlayment of portland cement concrete or bituminous mastic may be used under the membrane waterproofing on bridge deck to cover rough or uneven surfaces or to provide slope for drainage. c.

Requirements affecting details of waterproofing as may be included in this Chapter or in Chapter 6, Buildings and Support Facilities; Chapter 7, Timber Structures; Chapter 15, Steel Structures; AAR Scale Handbook (included in this manual) – should be observed in the design of the structure.

29.7.2 TYPES (1996) The membrane shall consist of one of the following types, as illustrated: a.

Two layers of bitumen-treated cotton fabric and three moppings of bitumen (Figure 8-29-2, Type A).

b. Three layers of bitumen-treated cotton fabric and four moppings of bitumen (Figure 8-29-2, Type B). c.

Two layers of bitumen-treated felt, one middle layer of bitumen-treated cotton fabric and four moppings of bitumen (Figure 8-29-2, Type C).

d. Four layers of bitumen-treated felt, one middle layer of bitumen-treated cotton fabric and six moppings of bitumen (Figure 8-29-2, Type D). e.

One layer of butyl rubber or EPDM secured as indicated with an approved adhesive (Figure 8-29-3).

f.

Rubberized asphalt with plastic film or preformed board membrane.

g.

Multiple layers of cold liquid-applied elastomeric membrane with an approved primer.

1

3

SECTION 29.8 PRIMERS

4

29.8.1 GENERAL (1994) Bitumen shall consist of asphalt or coal-tar pitch. The mopped-on material shall be asphalt for use with asphalt-saturated felt or fabric and coal-tar pitch for use with coal-tar-saturated felt or fabric.

29.8.2 PRIMER (2001) a.

Asphaltic Primer. Asphaltic primer shall meet the requirements of ASTM designation D41.

b. Coal Tar Primer. Coal tar for priming for use with coal-tar pitch shall meet the requirements of ASTM designation D43. c.

Cold Liquid-Applied Elastomeric Membrane Primer. Primer shall be of the type compatible with the substrate and membrane type as recommended by the manufacturer.

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d. Rubberized Asphalt with Plastic Film or Preformed Board. Primer shall be cold-applied as recommended by the manufacturer.

SECTION 29.9 MEMBRANES 29.9.1 ASPHALT FOR MOPPING (2001) Asphalt shall meet the requirements of ASTM designation D449. This Designation requires a choice of Types I, II or III based on conditions relating to use. Type II asphalt shall be used for membranes on ballasted-deck railroad bridges.

29.9.2 COAL-TAR PITCH FOR MOPPING (2001) Coal-tar pitch shall meet requirements of ASTM designation D450. The use of this Designation requires a choice of Types I, II or III based on conditions relating to use. Type I coal-tar pitch shall be used for membranes on ballasted-deck railroad bridges.

29.9.3 FABRIC (2001) Fabric shall meet the requirements of ASTM designation D173 covering woven cotton fabrics saturated with a bituminous substance. The use of this Designation requires a choice of asphalt meeting ASTM designation D449 or coal-tar pitch meeting the requirement of ASTM designation D450 as a saturant.

29.9.4 FELT (2001) a.

Felts for use with an asphalt mopping shall meet the requirements of ASTM designation D226. This Designation offers a choice of two types of felt. Type I shall be used for construction of membranes on ballasted-deck railroad bridges.

b. Felt for use with coal-tar pitch moppings shall meet the requirements of ASTM designation D227.

29.9.5 BUTYL RUBBER (BUTYL-BASED IIR) OR EPDM (ETHYLENE-PROPYLENE-DIENE-MONOMERS) (2001) a.

Membrane shall be 0.060 inch, 0.090 inch, or 0.120 inch (1.5, 2.3 or 3.1 mm) thick at the Engineer’s option.

b. Membrane shall conform to the properties found in Table 8-29-1.

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Table 8-29-1. ASTM D6134 Physical Requirements for Vulcanized Rubber Sheets Type

EPDM

Butyl

.054 (1.37)

.054 (1.37)

Hardness, durometer A

60 +/- 10

60 +/- 10

Tensile strength, minimum psi (MPa)

1,300 (9)

1,200 (8.3)

Elongation, ultimate minimum %

300

300

Tensile set, maximum %

10

10

150 (26.2)

150 (26.2)

-49 (-45)

-49 (-45)

1200 (8.3)

900 (6.2)

210

210

+/- 1

+/- 2

4

2

50 (8.8)

50 (8.8)

.06 (3.5)

.0025 (.14)

Breaking factory

10

10

Elongation at break

10

10

Puncture resistance lbs. (Kg)

70 (32)

95 (43)

Thickness, minimum inch (mm)

Tear resistance, minimum lbf./in. (kN/m) Brittleness temperature, maximum degress F (degrees C) Heat aging at 240 degrees F (116 degrees C): Tensile strength, minimum psi (MPa) Elongation, ultimate minimum % Linear dimensional change, maximum % Water absorption maximum, mass % Factory seam strength, minimum psi (MPa) Water vapor permeance, maximum perms

(mg/pasm2)

Resistance to soil burial (% change, maximum in original value):

1

29.9.6 ADHESIVE (1994)

3

Adhesive for securing membrane and the protective cover shall be in accordance with the recommendations of the membrane manufacturer.

29.9.7 CEMENT (2001) Cement for splicing either membrane shall be a self-vulcanizing butyl rubber compound conforming to the following requirements: a.

Viscosity at 77 degrees F (25 degrees C) Brookfield Viscometer (#3 Spindle at 10 rpm) 1,700-3,400 cps. Total Solids 30% (min).

b. Applied to both mating surfaces at 2 gallons/150 square foot (5.4 liters/m2).

29.9.8 BUTYL GUM TAPE (2001) Butyl gum tape for splicing either membrane shall be black, vulcanizable butyl rubber with an 8 mil (200 mm) polyethylene film backing. The tape shall be 30 (+4) mils (750 (+100) mm) thick, including the backing.

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29.9.9 RUBBERIZED ASPHALT WITH PLASTIC FILM OR PREFORMED BOARD MEMBRANE (2001) Rubberized Asphalt with Plastic film or preformed board membrane shall consist of a preformed layer of highly rubberized asphalt formed on plastic film or preformed board, with cold applied primer and/or mastic. a.

Performance Requirements, Properties. See Table 8-29-2. Table 8-29-2. Performance Requirements Property Membrane Thickness, minimum inches (mm) Permeability, maximum - perms (g.Pa-1.S -1.m-2)

Requirements

Test Methods

0.060 (1.5) 0.1 (5.72 x 10-10) ASTM E96

Accelerated aging, 400 h minimum (procedure 4)

no decline

ASTM D822 and ASTM G23

Exposure to fungi in soil, 16 weeks

unaffected

GSA-PBS-407121 (spec)

Peel Adhesion, 7 days dry, +7 days at l20 degrees F (49 degrees C), +7 days dry - lb/in (N/mm) of width minimum

5.0 (0.9)

TT-S-00230 Modified

Peel Adhesion - lb./inch of width (N/mm) after 7 days dry, and 7 days at 120 degrees F (49 degrees C), and 7 days of water immersion

5.0 (0.9) minimum

TT-S-00230 Modified

Crack bridging on Application 1/4 inch (6 mm) cycling at -15 degrees F (26 degrees C) (crack opened and closed from 0 to 1/4 inch (0 to 6 mm)) - minimum cycles

100

Puncture Resistance - minimum pounds (N)

40 (180)

TT-S-00230 Modified and TTS-227 Modified

ASTM E154

b. Certification. Manufacturer shall furnish certification that materials meet requirements. c.

Samples. A one square foot (0.1 m2) sample shall be furnished for testing, when required, from each production run of membrane to be supplied.

29.9.10 COLD LIQUID-APPLIED ELASTOMERIC MEMBRANE (2005)1 The membrane shall be 100% reactive spray-applied material. a.

Performance Requirements, Properties. See Table 8-29-3. For a product to be accepted, it must meet all tests detailed below within the manufacturer’s recommended thickness which is not to be less than 80 mils (2.0 mm) dry film thickness.

1

See C - Commentary

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Table 8-29-3. Performance Requirements Property

Requirements

Test Method

Water Vapor Transmission

Equal to or less than 0.2 perms, which is 0.1 grains/ft2/h (1.14x10-8g/Pa.s.m2)

ASTM E96, procedure B or BW

Elongation at Break

Minimum 80%

ASTM D638

Minimum Tensile Strength

930 psi (6.4 MPa)

ASTM D638

Adhesion to Steel

290 psi (2.0 MPa)

ASTM D4541

Adhesion to Concrete

100 psi (0.7 MPa)

ASTM D4541

Crack Bridging

Meet the low temperature flexibility ASTM C836 and crack bridging requirements of 10 cycles of 1/8 inch (3.2 mm) at -15 degrees F (-26 degrees C)

b. Certification. Manufacturer shall furnish certification from an approved independent testing agency that the supplied material meets designated test performance requirements. Manufacturer, if requested, shall supply the infrared spectrometer analysis (finger print) of the product from which the tests were conducted. The owner may, for quality assurance purposes, wish to corroborate material tested versus material received by means of sampling and further Infrared Spectrometer mapping.

1

SECTION 29.10 MEMBRANE PROTECTION1

3

29.10.1 PORTLAND CEMENT CONCRETE (2001) a.

Materials for portland cement concrete shall meet the requirements of Part 1, Materials, Tests and Construction Requirements. The concrete shall be air entrained, have a minimum cement content of 564 lbs. per cubic yard (334 kg/m3) and a maximum water to cement ratio of 0.53 by weight (mass). The maximum size of coarse aggregate shall be 3/4 inch (20 mm).

4 b. The concrete shall be reinforced with wire fabric which shall meet the requirements of ASTM A185. The minimum gage of wires shall be No. 12 (2.7 mm) and the wire shall have a maximum spacing of 6 inches (150 mm) in both directions.

29.10.2 ASPHALT PLANK (2001) Asphalt plank shall meet the requirements of ASTM D517. Asphalt plank used for protection of waterproofing membranes shall be plain and have a minimum total thickness of 1 inch (25 mm) using one or more layers. Edges of asphalt planks to be applied in a single layer shall be supplied with shiplapped joints.

29.10.3 ASPHALTIC PANELS (2001) Asphaltic panels shall meet the following requirements: 1

See C - Commentary

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Each panel is formed as a 5-layer member, including a core of a selected blend of asphalt and inorganic mineral filler particles, a bottom reinforcing cover of asphalt-saturated felt and on the top, a cover of asphalt-saturated felt or fiber glass mat that is weather coated and has bond breaking film or coating.

b. Asphalt and inorganic mineral filler particles shall be blended to form the core, with the asphalt forming the matrix of the blend to carry the particles. The mineral filler particles function to impart increased density and enhance stiffness and body in the core. c.

The inorganic mineral filler particles constitute an aggregate bound in the asphalt matrix which will permit points of ballast rock to penetrate a short distance into the core to secure a good seating position. The aggregate will then resist further penetration and will support the ballast rock.

29.10.3.2 Workmanship The protection course shall be free from defects affecting its serviceability and appearance; it shall have straight edges and square corners. 29.10.3.3 Properties a.

Asphaltic panels shall have the dimensions specified or shown on the plans. Tolerance of ± 1/ 16 inch (1.5 mm) in thickness, ± 1/ 8 inch (3 mm) in width and ± 1/ 4 inch (6.5 mm) in length shall be permitted.

b. Weight (mass) minimum for 0.375 inch (9.5 mm) thickness, 2.60 pounds per square foot (12.7 kg/m2). c.

Weight (mass) minimum for 0.50 inch (13 mm) thickness, 3.50 pounds per square foot (17.1 kg/m2).

d. Water absorption, max, ASTM D545, 1.0%. e.

Thickness of asphalt weather-coating, rivuleted average, 0.020 inch (0.5 mm) minimum.

f.

Asphalt saturated felt liners maximum 15 lb per 100 square foot (0.7 kg/m2) after saturation.

g.

Asphalt content 50-60% by weight (mass).

h. Inorganic mineral filler particle contents minimum 25% by weight (mass). i.

Resistance to deterioration from organisms and substances in contacting soil, ASTM E154. No effect.

j.

Flexibility, No cracking or breaking.

k. Brittleness at 39-43 degrees F (4 to 6 degrees C), ASTM D994. No cracking or shattering. l.

Heat distortion ASTM D994, 0.3125 inch (7.9 mm) maximum.

m. Mineral Filler, Carefully selected and graded inorganic mineral filler particles shall be blended with the asphalt to form the matrix of each panel. n. Weathercoating, Asphaltic weathercoating shall be flowed on the exterior top surface of the protection course. This coating shall be of sufficient thickness to provide complete dimensional stability to the material, when stored outdoors in direct sunlight. A suitable bond breaking film or coating shall be applied, to function as a release sheet. During installation, the asphalt-saturated felt side shall be placed against the membrane waterproofing; the side with the bond breaking film or coating shall be exposed to the ballast rock.

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o.

Resistance to Penetration, Dynamic Loading. (1) The degree of resistance to penetration, when tested in accordance with ASTM D1883, modified as described below, shall meet the requirements found in Table 8-29-3. Table 8-29-4. Degree of Resistance to Penetration Temperature

Dynamic Load

Penetration

Deg. F

Deg. C

lbs.

kN

ins., max.

mm, max.

100

38

225

1.00

0.10

2.54

77

25

350

1.56

0.10

2.54

40

4

600

2.67

0.10

2.54

(2) Pertinent modifications to ASTM D1883: (a) Section 5.1 Loading Machine – as described, except that the movable head is capable of traveling at a uniform rate of 0.025 inch per minute (0.61 mm/minute). (b) Section 5.7 Penetration Piston – as described, except that the diameter of the piston shall be 1.0 +/- 0.005 inch (25.4 +/- 0.13 mm).

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(c) Section 5.8 Gages - as described. (d) Section 6 Sample - Test three specimens 6 ´ 6 inches (152.4 x 152.4 mm), cut from each board sample. (e) Section 7 Preparation of Test Specimens - The test specimens shall be conditioned in a chamber maintained at the selected test temperature (±3 F degrees ±1.7 C degrees) for a minimum of 2 hours prior to testing.

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(f) Section 8.1 - The test specimen, after conditioning, shall be immediately placed on the platform of the loading machine and the piston placed in the center of the specimen. (g) Section 8.2 - As described. (h) Section 8.3 - Apply the load on the penetration piston so that the rate of penetration is approximately 0.025 inch per minute (0.61 mm/minute). The penetration shall be recorded at an applied load reading of 40 lb (178 kN) intervals, except where the load increases too fast to record (40 degrees F test (4 degrees C test)). p. Inspection. Sample from each lot shall be examined for appearance, straightness of edges and squareness of corners, and measured for width and length. They shall be calibered at four standard points each, with a micrometer having flat bearing surfaces at both contact points of not less than 3/4 inch (19 mm) diameter. The average of the readings shall be considered the thickness of the protection course. q. Flexibility Test (1) Three specimens 3 ´ 12 inches (75 x 305 mm) shall be conditioned at 770 ± 50 degrees F (400 ± 28 degrees C) for not less than 2 hours immediately prior to being subjected to test.

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(2) Place specimen with the 12 inch (305 mm) dimension perpendicular to and centered over the axis of a horizontal cylinder having a diameter of 19 ± 1 inch (483 ± 25 mm). (3) Clamp one end and grasp the other end of the samples and bend around the cylinder at the uniform rate to complete bend in 60 ± 10 seconds until the specimen is in full contact with the surface of the cylinder. (4) Examine for any cracking or breaking of the sample.

SECTION 29.11 SEALING COMPOUNDS FOR JOINTS AND EDGES OF MEMBRANE PROTECTION (2001) a.

Hot-poured elastic-type joint sealer shall meet the requirements of ASTM D1190.

b. Plastic cements for cold application for sealing joints and edges are generally proprietary products. The literature of the several manufacturers should be studied, and the Engineer shall select a material which will best serve the purpose as governed by conditions of use. c.

For types of plastic cement, refer to Section 29.16 for material description and conformance.

SECTION 29.12 ANTI-BONDING PAPER (2001) Anti-bonding paper shall be a tough paper that shall be impervious to the bituminous material applied to the membrane. It shall have a weight (mass) not less than 5 lb per 100 square foot (0.25 kg/m2).

SECTION 29.13 INSPECTION AND TESTS (1994) a.

Materials shall be sampled and tested by the current methods recommended by ASTM.

b. The acceptance of any material by the inspector shall not be a bar to their subsequent rejection if found defective. Rejected material shall be promptly removed from the job and replaced with acceptable material. c.

No material shall be used until it has been accepted by the Engineer.

SECTION 29.14 CONSTRUCTION 29.14.1 GENERAL (2001) a.

Bituminous membranes and Rubberized Asphalt with Plastic film or Preformed Board shall not be applied when atmospheric temperatures are below 50 degrees F (10 degrees C). Butyl Rubber Membrane

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shall not be applied when atmospheric temperature is below 10 degrees F (-12 degrees C) without written permission of the Engineer. Surfaces to be waterproofed shall be clean, smooth, dry, and free of fins, sharp edges, oil, grease and loose or foreign materials. New concrete shall have cured for a minimum of seven days, or for a longer period if recommended by the manufacturer, before applying the waterproofing system. Projections or depressions on the surface on which the membrane is to be applied that may cause injury to the membrane shall be removed or filled as directed by the Engineer. b. There shall be no depressions or pockets in horizontal surfaces of the finished waterproofing. The membrane shall be carefully turned into drainage fittings. Special care shall be taken to make the waterproofing effective along the sides and ends of girders and at stiffeners, gussets, etc. c.

Cold liquid-applied elastomeric membrane shall be applied when substrate temperatures are in the range of 32–104 degrees F (0–40 degrees C) providing that the substrate is above the dew point. The condition of the substrate shall meet the Manufacturer’s recommendations and be approved by the Engineer. Material shall be sprayed on horizontal or vertical surfaces up to, around or into details.

29.14.2 PRIMER (2001) a.

Surfaces to be protected with asphalt waterproofing shall be given one coat of asphaltic primer before the first mopping of asphalt. Surfaces to be protected with coal-tar-pitch waterproofing shall be given one coat of creosote primer before the first mopping of coal-tar pitch. A minimum of 1 gal of primer per 100 square foot (4 liters/10 m2) of surface shall be used. The primer shall be applied approximately 24 hr before applying the waterproofing membrane.

b. At expansion joints, the primer shall be omitted for a width of 9 inches (230 mm) of each side of the joint, and a strip of anti-bonding paper 18 inches (450 mm) wide laid thereon before the membrane is applied. c.

Surfaces to be protected with a cold liquid-applied elastomeric membrane shall be given one coat of Manufacturer approved primer prior to the application of the membrane. The primer shall be applied by either spray, brush, roller or a method approved by the Manufacturer.

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29.14.3 MEMBRANE (2001) 29.14.3.1 Bituminous Membrane a.

Coal-tar pitch shall not be heated above 300 degrees F (150 degrees C). Asphalt shall not be heated above 350 degrees F (177 degrees C).

b. The surface to be waterproofed shall be mopped in sections slightly wider than the strip of fabric or felt to be placed. While the mopping of bitumen is hot, a strip of cotton fabric or felt shall be laid on the mopping and pressed into place. The amount of bitumen used for each mopping shall not be less than 1/2 gallon per 100 square feet (18.3 liters/10 m2) of surface. c.

Lapping of layers of felt or fabric shall be in accordance with one of the types shown in Figure 8-29-2. Ends of fabric and felt shall be lapped a minimum of 12 inches (305 mm) where necessary to splice the material in a strip.

d. On surfaces that are vertical or nearly vertical, the strips of fabric or felt shall be laid vertical or in the direction of the slope. On other surfaces the strips shall be lapped in accordance with one of the types shown in Figure 8-29-2, beginning at the lowest part of the surface, to be waterproofed. Sufficient fabric or felt shall be allowed for suitable lap or anchorage at the upper edge of the surface to be waterproofed.

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Figure 8-29-2. Lapping of Bituminous Membrane Waterproofing. © 2011, American Railway Engineering and Maintenance-of-Way Association

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e.

At expansion joints of bridge decks protected with bituminous membrane waterproofing, a strip of antibonding paper 18 inches (450 mm) wide and a sheet of 22-gage (0.76 mm) galvanized metal a minimum of 12 inches (305 mm) wide shall be laid and centered on the joint both above and below the membrane before the protective cover is applied.

f.

The work shall be regulated so that at the end of the day, all fabric or felt that has been laid shall have been mopped.

g.

The waterproofing membrane shall be free from punctures or folds. Patching shall be done only with permission of the Engineer. Where patching is permitted for defective waterproofing, it shall extend a minimum of 12 inches (305 mm) beyond the outermost edge of the defective portion. The second and each succeeding ply of the patch shall extend at least 3 inches (75 mm) beyond the preceding ply.

29.14.3.2 Butyl Rubber or EPDM Membrane a.

For surfaces to be waterproofed with a membrane secured with adhesive, the adhesive shall be applied to ballast retainers and ends of deck in a solid area extending a minimum of 36 inches (915 mm). At the Engineer’s option, adhesive may be applied to the entire surface to be waterproofed. Adhesive should be applied in a thin layer (by using a roller or brush as recommended by the manufacturer) at a minimum rate of 1 gallon per 60 square foot (6.8 liters/10 m2) based on both mating surfaces.

b. Membrane sheets shall first be positioned and drawn tight without stretching. Half of the membrane is then uniformly rolled up in a direction away from the starting edge or subsequent splice. Adhesive is now applied to the exposed area. Allow adhesive to dry so as to not stick to a dry finger touch and all solvent is evaporated. The membrane is now unrolled and pressed firmly and uniformly in place, using care to avoid trapping of air. The same procedure is repeated for the remaining half of the membrane sheets. Wrinkles and buckles shall be avoided. Each succeeding sheet shall be positioned to fit the previously installed sheet and spliced. c.

Splices shall be of tongue-and-groove or lap type as specified by the Engineer. Splices shall be made as shown in Figure 8-29-3. All seam, lap and splice areas shall be cleaned with heptane, hexane, toluene, trichloroethylene or white gasoline, using a clean cloth, mop or similar synthetic cleaning device. Cement shall be spread continuously on seam, lap and splice areas at a uniform rate of not less than 2 gal per 150 square foot (5.4 liters/10 m2) based on both mating surfaces. After cement is allowed to dry until it will not stick to a dry finger touch, apply butyl gum tape to cemented area of membrane, pressing firmly into place, obtaining full contact. Bridging and wrinkles shall be avoided. Corner splices shall be reinforced with two continuous layers of rubber membrane over one layer of butyl tape.

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4 d. All projecting pipe, conduits, sleeves, etc., passing through membrane waterproofing shall be flashed with prefabricated or field-fabricated boots, fitted coverings, etc., as necessary to provide watertight construction. Butyl gum tape shall be used between layers of rubber membrane. e.

At expansion joints of bridge decks protected with butyl rubber membrane waterproofing, a strip of antibonding paper 18 inches (450 mm) wide and a sheet of 22-gage (0.76 mm) galvanized metal a minimum of 12 inches (305 mm) wide shall be laid and centered on the joint both above and below the membrane before the protective cover is applied.

f.

Any holes in the membrane sheeting shall be patched with a minimum overlap of 4 inches (100 mm) and in accordance with manufacturer’s instructions.

g.

During construction, care shall be exercised to prevent damage to the waterproofing membrane by men or equipment.

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Figure 8-29-3. Recommended Butyl Membrane Field Seam Assembly Recommended in Order Listed for Field Assembly

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Waterproofing 29.14.3.3 Rubberized Asphalt with Plastic Film or Preformed Board a. Surface Preparation. (1) All concrete or masonry surfaces shall be surface dry. Surfaces shall be broom cleaned, shall be free of voids, loose aggregate, sharp protrusions, form release agents or other contaminants. Horizontal concrete or masonry surfaces shall be wood float finished. (2) All concrete or masonry surfaces shall be primed with manufacturer’s recommended primer, applied by brush or roller at the rate of 100 to 250 square foot per gal (2.5 to 6.1 m2/liter). Primer shall be dried one hour or until tack free. Primed surfaces not covered within 36 hours shall be reprimed. Dense surfaces such as metal shall be primed, and shall be clean, dry and free of grease, oil, dust, or other contaminants before being primed. Wood shall be primed. b. Application Procedures. (1) Rubber Asphalt with Plastic Film shall be overlapped 2-1/2 inches (64 mm) to adjacent material surfaces. Rubber Asphalt with Preformed Board shall be butt-jointed with 6 inches (150 mm) gusset tape as recommended by the manufacturer applied directly over the joints. (2) All corners shall be double-covered with a double layer of membrane by applying an initial 12 inches (305 mm) strip centered along the axis of the corner. (3) Expansion joints shall be double covered with membrane. Prior to waterproofing over expansion joints, a minimum 12 inches (305 mm) wide galvanized 16 gage (1.52 mm) steel plate shall be placed and centered on the joint, then an inverted strip of membrane (plastic side down) 4 inches (100 mm) wider than the galvanized plate shall be centered on the galvanized plate. This should then be covered over with a full width of membrane, centered on the joint. (4) The perimeter of the membrane placed in any day’s operation and all outside edges of membrane shall have a trowelled bead of cold applied rubberized asphalt mastic applied after the membrane is placed.

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(5) Areas around drains, posts, bolts, or other protrusions shall have a double layer of membrane and shall be liberally coated with mastic adjacent to seams and protrusions after application of the membrane. (6) Immediately before covering the membrane, a careful inspection shall be made and any ruptures, misaligned seams or other discontinuities shall be patched with membrane. 29.14.3.4 Cold Liquid-Applied Elastomeric Membrane a. Surface Preparation. (1) All concrete surfaces shall be surface dry. Surfaces to be waterproofed shall be clean, smooth, dry and free of oil, grease and loose or foreign material. (2) The surface preparation shall be performed by means approved by the Engineer. The surface profile is not to exceed 1/4 inch (6.3 mm), peak to valley. Test method ASTM D4541 shall be used to verify that the surface preparation meets the required adhesion/pull off values of 100 psi (0.7 MPa) for concrete and 290 psi (2.0 MPa) for steel surfaces. (3) Steel substrates shall be cleaned and sand blasted to a near white SSPC SP-10 specification or to a condition that exceeds the Manufacturer’s minimum requirements. Special attention shall be given

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to welds, bolts, rivets, etc., so that preparation complies with Manufacturer’s recommendations. Primer is to be applied within 4 hours of preparation. (4) Other methods of surface preparation recommended by the manufacturer may be used as approved by the Engineer. b.

Application Procedures. (1) Immediately prior to the application of any component of the system, the surface shall be dry. Any remaining dust or loose particles shall be removed using a vacuum or clean, dry, oil-free compressed air. (2) Where the area to be waterproofed is vertical, the system shall be capable of being sprayed at the specified thickness. (3) The membrane shall be carefully sprayed around and into drainage fittings to ensure proper runoff of water. Special care shall be taken with the spraying of the system to get full coverage along the sides and ends of girders, stiffeners, gussets, and over welds, bolts or rivets, etc. (4) Where the membrane is to be joined to existing cured material the new application shall overlap the existing material by at least 4 inches (100 mm). (5) All overlap areas shall be wiped with a cleaner in accordance with manufacturer’s recommendation. (6) The membrane shall be applied in a methodical manner to ensure proper coverage. Wet film thickness shall be checked once every 100 square feet (9 m2). (7) If required by site conditions, or for application to small areas, or touch-up the membrane can be applied by brush or trowel in accordance with manufacturer’s recommendations. (8) The membrane shall be fully cured before it is covered. Membrane shall be inspected prior to covering and any surface defects or damage shall be repaired in accordance with manufacturer’s recommendations. (9) Protective cover in accordance with Article 29.14.4.1b shall be installed prior to ballast placement. (10)Other application procedures may be used as recommended by the manufacturer and approved by the Engineer.

29.14.4 PROTECTIVE COVER (2001) 29.14.4.1 General a.

Protective cover shall be placed over all waterproofing membranes to eliminate damage from ballast contact as soon as practicable within 24 hours after the membrane has been laid. Dirt and other foreign material shall be removed from the surface of the membrane before the protective cover is placed. Protective cover shall be shielded with permanent cover within 48 hours, unless a temporary cover, approved by the Engineer, is placed.

b. One of the following methods of protection shall be used: (1) A layer of reinforced portland cement concrete not less than 2 inches (50 mm) thick.

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(2) A layer of asphalt block or asphalt plank not less than 1 inch (25 mm) thick. (3) A layer or layers of asphaltic panels not less than 3/4 inch (19 mm) total thickness. 29.14.4.2 Portland Cement Concrete Protection Portland cement concrete shall be mixed in accordance with the requirements of Part 1, Materials, Tests and Construction Requirements. It shall be reinforced with one layer of wire fabric. Traffic shall not be allowed on the concrete until it is adequately cured as judged by the Engineer. 29.14.4.3 Asphalt Plank a.

Asphalt plank protection shall be laid in hot asphalt applied at not less than 5 gallons per 100 square foot (20 liters/10 m2). As successive planks are laid, the edges and ends of adjacent planks already laid shall be coated heavily with hot asphalt. This shall be the same asphalt as specified for mopping in Article 29.9.1. Planks shall be held tightly against those previously laid so that the asphalt will completely fill the joints and be squeezed out of the top. After all of the planks have been laid, any joints not completely filled shall be filled with hot asphalt.

b. Asphalt planks for use with a butyl rubber or EPDM membrane shall be laid in a coating of bonding adhesive as specified in Article 29.9.6. The adhesive shall be applied at a rate of not less than 1 gal per 100 square foot (4.1 liters/10 m2). Voids between the joints should be filled with a compatible material as described in Article 29.9.1.

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29.14.4.4 Asphaltic Panels a.

Asphaltic panels are available in various thicknesses. To obtain the thickness of 3/4 inch (19 mm), the recommended application is two layers with the joints staggered. The panels shall be laid tight jointed, with or without an approved adhesive. The adhesive shall be the same as specified in Article 29.9.1 when used with Bituminous membrane or in Article 29.9.6 when used with Butyl rubber or EPDM membrane. Any voids between the panels shall be filled with a material compatible to both the membrane and the panel.

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b. Where edges or protrusions of asphaltic panels are exposed to prolonged sunlight exposure, coat exposed areas with Fibre Aluminum Roof Coating meeting ASTM D2824, Type II at a rate of 12 square feet per gallon (3 m2/10 liter), for a 1/8 inch (3 mm) thickness.

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29.14.4.5 Sealing Joints and Edges a.

Joints shown on the plan to be filled with a joint sealing compound shall be filled where possible with a hot-poured elastic-type joint sealer or with an approved hot or cold elastic-type joint sealer. Steeply sloped or vertical areas shall be sealed with cold-applied mastic.

b. The following precaution (from ASTM D1190) should be observed in using hot-poured elastic-type joint sealer: Some, if not all, of the known materials conforming to these recommended practices may be damaged by heating to too high a temperature for too long a time. Care should be exercised to secure equipment for heating that is suitable for the purpose. The material should be heated in a kettle with mechanical agitation, constructed as a double boiler, with the space between the inner and outer shells filled with oil or other heat transfer medium. Thermostatic control for the heat transfer medium shall be provided and shall have sufficient sensitivity to maintain sealant temperature within the manufacturer’s specified application temperature range.

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SECTION 29.15 INTRODUCTION TO DAMPROOFING 29.15.1 DAMPROOFING SCOPE (2001) a.

Dampproofings are not to be used in any area where a hydrostatic head is anticipated.

b. Dampproofings are a surface coating intended to repel free water. c.

These recommended practices apply to materials and methods for dampproofing concrete surfaces.

SECTION 29.16 MATERIALS FOR DAMPROOFING 29.16.1 ASPHALT PRIMER (1994) Asphaltic primer shall meet the requirements of ASTM D41.

29.16.2 CREOSOTE PRIMER (2001) Coal tar primer for use with coal-tar pitch shall meet the requirements of ASTM D43.

29.16.3 WOVEN COTTON FABRICS (1994) Woven cotton fabrics saturated with either asphalt or coal-tar bitumen shall meet the requirements of ASTM D173.

29.16.4 COAL-TAR SATURATED ORGANIC FELT (1994) Coal-tar saturated organic felt shall meet the requirements of ASTM D227.

29.16.5 ASPHALT (1994) Asphalt shall meet the requirements of ASTM D449. Three types: I, II, or III are specified. Type II asphalt shall be used for dampproofing.

29.16.6 COAL-TAR PITCH (1994) Coal-tar pitch shall meet the requirements of ASTM D450. Three types: I, II, or III are specified. Type I coal-tar pitch shall be used for dampproofing.

29.16.7 EMULSIFIED ASPHALT COATINGS (2001) Emulsified asphalt coatings shall meet the requirements of ASTM D1187, Type I.

29.16.8 EMULSIFIED ASPHALT PROTECTIVE COATING (2001) Emulsified asphalt protective coating shall meet the requirements of ASTM D1227, Type II, Class 1.

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29.16.9 ASBESTOS-FREE ASPHALT ROOF COATINGS (1994) Asbestos-free asphalt roof coatings to be brush or spray applied shall meet the requirements of ASTM D4479. Two types: I and II are specified.

29.16.10 ASBESTOS-FREE ASPHALT ROOF COATING (1994) Asbestos-free asphalt roof coating to be trowel applied shall meet the requirements of ASTM D4586.

29.16.11 INSPECTION AND TESTS (1994) a.

Contractor shall supply certification that materials used are in full conformance to applicable ASTM designations. If requested by the Engineer, sampling and testing will be completed.

b. The acceptance of any material by the inspector shall not bar their subsequent rejection if found defective. Rejected materials shall be promptly removed from the job and replaced with acceptable material. c.

No material shall be used until it has been accepted by the Engineer.

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SECTION 29.17 APPLICATION OF DAMPROOFING1 29.17.1 PREPARATION OF SURFACES (2001) a.

The surfaces upon which a dampproofing coating is to be applied shall be cleaned of all dirt and loose or foreign material by sandblasting, the use of wire brushes, chisels or scrapers, or washing with water.

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b. Spalled, cracked, or honeycombed areas shall be repaired in accordance with Part 14, Repair and Rehabilitation of Concrete Structures. c.

All surfaces to be dampproofed shall be dry and free from sharp projections or porous places.

29.17.2 TEMPERATURE (2001)

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All dampproofing materials shall be applied when surface temperature is above 40 degrees F (4 degrees C) and rain is not likely before completion of the project, unless specifically recommended by the material manufacturer and with written approval of the Engineer.

29.17.3 METHOD OF APPLICATION (2001)2 a.

The primer shall be applied to the concrete surface at least 24 hours in advance of applying the first mopping of bitumen. The primer need not be heated but shall be applied in a uniform coat that completely covers the area to which the bitumen is to be applied.

b. The bitumen for mopping shall be heated to permit uniform covering; however, asphalt shall not be heated above 350 degrees F (177 degrees C) and coal-tar pitch shall not be heated above 300 degrees F 1 2

See C - Commentary See C - Commentary

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(150 degrees C). Two mop coats of bitumen shall be applied, using a total of approximately 8 gallons of bitumen for 100 square feet of dampproofing surface (32.6 liters/10 m2). If imperfections appear in the coating, additional coats shall be applied until the imperfections are corrected. c.

Cover or backfill within 72 hours after application. Backfill with care to avoid damage to dampproofed areas.

C - COMMENTARY The purpose of this part is to furnish the technical explanation of various articles in Part 29, Waterproofing. In the numbering of articles of this section, the numbers after the “C-” correspond to the section/article being commented upon.

C - SECTION 29.2 WATERPROOFING (2001) C - Paragraph i When doing remedial waterproofing on existing railway bridges, it is possible to encounter unusual materials used as the protection cover. These may include premoulded asphalt block, industrial or paving brick, mixedin-place asphalt or coar tar mastic with selected aggregates. These older methods of protection can be readily recognized and if being removed, should be replaced with current acceptable AREMA recommended materials and practices.

C - SECTION 29.7 GENERAL PRACTICES C - 29.7.1 DESIGN (2005) a.

Roll, sheet or liquid applied systems that, when applied to concrete and masonry surfaces, will prevent the ingress of moisture in both its liquid and gaseous forms. Systems are suitable for application on and below grade as well as railway structures of all types, including bridge structures.

b. Selected materials must be suitable for, and capable of handling, the inherent pressures of a hydrostatic head.

C - SECTION 29.9 MEMBRANES C - 29.9.10 COLD LIQUID-APPLIED ELASTOMERIC MEMBRANE (2005) The recommended waterproofing membrane thickness applied to the bridge deck is not to be less than recommended by the manufacturer. The minimum required dry film thickness of 80 mils at any location on the bridge deck is to ensure adequate coverage of substrate irregularities, and a greater thickness may be specified in order to insure that this minimum is achieved. The absence of pin holes should be verified in accordance with ASTM D4787. The thickness of membrane applied is to be at least equal to the thickness used by the manufacturer for the crack bridging test.

C - SECTION 29.10 MEMBRANE PROTECTION There has been a continuing debate on the use of protection board material over cold liquid applied membrane since cold liquid applied membrane was included in previous AREMA recommendations. The initial recommendations allowed cold liquid applied membrane to be used without protection board, provided the

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membrane material passed the ballast impact test. The use of protection board placed over cold liquid membrane material is an economic decision that an owner makes. The AREMA recommendation gives a standard practice, but does not prohibit the use of a cold liquid applied membrane without a protection board. The decision is a question of length of useful life (economical cost of replacement versus higher initial capital cost).

C - SECTION 29.17 APPLICATION OF DAMPROOFING Dampproofing is a surface coating applied to concrete or masonry that will prevent or repel water in its liquid form. May be applied in single or multiple layers, suitable for application above and below grade.

C - 29.17.3 METHOD OF APPLICATION (2001) Dampproofings are not to be used in any area where a hydrostatic head is anticipated.

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Chapter 8 Glossary — 2006 — The following Terms are listed in the various Parts of Chapter 8 Concrete Structures and Foundations and are defined here. These definitions apply only to those Parts in which they are cited as Terms since they may have different meanings where used in other Parts.

AASHTO American Association of State Highway and Transportation Officials, 444 North Capitol Street, Suite 249, Washington, D.C. 20001. www.aashto.org. Term cited in Part 1.

Absorption The process by which a liquid is drawn into and tends to fill permeable pores in a porous solid; also the increase in mass of a porous solid resulting from the penetration of a liquid into its permeable pores. Term cited in Part 1.

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Abutment Commonly consists of a retaining wall that incorporates a bridge seat in its face. It may also be of the spillthrough type, in which the bridge seat rests on horizontal beams supported by piles or columns between which the fill is permitted to extend. Term cited in Part 5.

ACI International American Concrete Institute, P.O. Box 9094, Farmington Hills, Michigan 48333. www.aci-int.org. Term cited in Part 1.

Admixture A material other than water, aggregates, hydraulic cement and fiber reinforcement, used as an ingredient of concrete or mortar, and added to the batch immediately before or during its mixing. Term cited in Part 1.

Admixture, Accelerating An admixture that causes an increase in the rate of hydration of the hydraulic cement, and thus shortens the time of setting, or increases the rate of strength development, or both. Term cited in Part 1.

Admixture, Air-Entraining An addition for hydraulic cement; also an admixture for concrete or mortar which causes entrained air to be incorporated in the concrete or mortar during mixing, usually to increase its workability and frost resistance. Term cited in Part 1.

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Admixture, Retarding An admixture which delays the setting of cement paste and hence of mixtures such as mortar or concrete containing cement. Term cited in Part 1.

Admixture, Water Reducing An admixture that either increases slump of freshly mixed mortar or concrete without increasing water content or maintains slump with a reduced amount of water, the effect being due to factors other than air entrainment. Also known as a plasticizer. Term cited in Part 1.

Admixture, Water Reducing (High Range) A water reducing admixture capable of producing large water reduction or great flowability without causing undue retardation or entrainment of air in mortar or concrete. Also known as a superplasticizer. Term cited in Part 1.

Admixture, Water Reducing and Accelerating An admixture that reduces the quantity of mixing water required to produce concrete of a given consistency and accelerates the setting and early strength development of concrete. Term cited in Part 1.

Admixture, Water Reducing and Retarding An admixture that reduces the quantity of mixing water required to produce concrete of a given consistency and retards the setting of concrete. Term cited in Part 1.

Agent, Bonding A substance applied to a sound substrate to create a bond between it and a succeeding layer or adjacent concrete placement, conforming to ASTM C881 Standard Specification for Epoxy-Resin-Base Bonding Systems for Concrete. Term cited in Part 1.

Aggregate Inert material such as sand, gravel or crushed stone used with a hydraulic cementing medium to produce either concrete or mortar. Term cited in Part 1.

Air, Entrained Microscopic air bubbles intentionally incorporated in mortar or concrete during mixing, usually by use of a surface-active agent; typically between 0.4 to 40 mils (10 and 1000 micrometers) in diameter and spherical or nearly so. Term cited in Part 1.

Anchorage Blister Build-out in the web, flange, or web-flange junction to provide area for one or more tendon anchorages. Term cited in Part 26.

Anchorage Seating Deformation of anchorage or seating of tendons in anchorage device when prestressing force is transferred from jack to anchorage device. Term cited in Part 17.

Approved or Approval Approved or approval shall be understood to mean written consent. Term cited in Part 1.

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Asphaltic Panels for Waterproofing Protection Asphaltic panels that are fortified in order to protect membrane waterproofing from ballast penetration and abrasion. They are furnished in sheet form, applied either dry or in asphalt mastic.

ASTM - International ASTM - International, 100 Barr Harbor Drive, West Conshohocken, Pennsylvania 19428-2959. www.astm.org Term cited in Part 1.

Bell or Underream An enlargement at the bottom of the drilled shaft made by hand excavation or mechanical underreaming with drilling equipment for the purpose of spreading the load over a larger area. Term cited in Part 24.

Blast-Furnace Slag The non-metallic product consisting essentially of silicates and alumino silicates of calcium and other bases, that is developed in a molten condition simutaneously with iron in a blast-furnace. Term cited in Part 1.

Blast-Furnace Slag, Ground Granulated The glassy granular material formed when blast furnace slag is rapidly chilled, as by immersion in water. Term cited in Part 1.

Bleeding The autogenous flow of mixing water within, or its emergence from, newly placed concrete or mortar (caused by the settlement of the solid materials within the mass) also called water gain. Term cited in Part 1.

1

Bonded Tendon See Tendon, Bonded. Term cited in Part 17.

Butyl Rubber An elastomeric membrane sheet formed of multiple plies of rubber factory-fabricated into a single ply for waterproofing bridge decks, foundations and tunnels. It is capable of being field spliced with appropriate adhesives, cements and butyl gum tape.

3

Casing, Permanent A permanent steel cylinder that is installed for the purpose of excluding soil and water from excavations. It is used as a form to contain concrete placed for a drilled shaft and remains in place. Term cited in Part 24.

Casing, Protective Protective steel unit, usually cylindrical in shape, lowered into the excavation to protect workmen and inspectors from collapse or cave-in of the side wall. Term cited in Part 24.

Casing, Temporary A temporary steel cylinder that is installed for the purpose of excluding soil and water from the excavations. It may also be used as a form for the shaft concrete but is withdrawn as the concrete shaft is placed. Term cited in Part 24.

Cement, Blended Hydraulic cement consisting essentially of an intimate and uniform blend of granulated blast-furnace slag and hydrated lime; or an intimate and uniform blend of portland cement and granulated blast-furnace slag; portland cement and pozzolan, or portland blast-furnace slag cement and pozzolan, produced by

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Concrete Structures and Foundations

intergrinding portland cement clinker and other materials or by blending portland cement with other materials, or a combination of intergrinding and blending. Term cited in Part 1.

Cement, Hydraulic A cement that sets and hardens by chemical interaction with water and is capable of doing so underwater.

Cement, Slag Hydraulic cement consisting mostly of an intimate and uniform blend of granulated blast-furnace slag and hydrated lime in which the slag constituent is more than a specified minimum percentage. Term cited in Part 1.

Cementitious Having cementing properties. Term cited in Part 1.

Centering Falsework that may be used in the construction of a continuous or other special structure, where the entire falsework is lowered (struck or decentered) as a unit. Term cited in Part 1.

Chemical Resistance The ability of the material to resist attack by chemicals such as caustics, chlorides or acids (e.g. salt or diesel fuel). Term cited in Part 1.

Closure Cast-in-place concrete segment or segments used to complete a span. Term cited in Part 26.

Coating Material used to protect prestressing tendons against corrosion, to reduce friction between tendon and duct, or to debond prestressing tendons. Term cited in Part 17.

Coefficient of Thermal Expansion Term cited in Part 1.

Cold Liquid-Applied Elastomeric Membrane A two component, resinous-based system that is brush, roll, or spray applied to form a seamless waterproof membrane, preventing the intrusion of moisture into the concrete or steel substrate. This type of membrane provides high bond strength to the substrate and excellent crack bridging capabilities.

Company Company shall be understood to mean the Railroad or Railway Company. Term cited in Part 1.

Compound, Curing A liquid that can be applied to the surface of newly placed concrete to retard the loss of water. Term cited in Part 1.

Compressive Strength See Strength, Compressive. Term cited in Parts 1 and 2.

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AREMA Manual for Railway Engineering

Glossary

Compressive Strength of Concrete (f 'c) See Compressive Strength. Terms cited in Parts 1 and 2.

Concrete A composite material that consists essentially of a binding medium within which are embedded particles or fragments of aggregate, usually a combination of coarse aggregate and fine aggregate; in portland-cement concrete, the binder is a mixture of portland cement and water. Term cited in Part 1.

Concrete Curing Compound See Curing Compound, Concrete. Term cited in Part 1.

Concrete, Cyclopean A term describing mass concrete in which large individual aggregates (cyclopean aggregates) each of 100 pounds (45 kg) or more are placed and embedded as concrete is deposited. Term cited in Part 1.

Concrete, Polymer Concrete in which an organic polymer serves as the binder; also known as resin concrete; sometimes erroneously employed to designate hydraulic cement mortars or concretes in which part or all of the mixing water is replaced by an aqueous dispersion of a thermoplastic copolymer. Term cited in Part 1.

Concrete, Polymer Cement A mixture of water, hydraulic cement, aggregate, and a monomer or polymer; polymerized in place when a monomer is used. Term cited in Part 1.

1

Concrete, Structural Lightweight A structural concrete made with lightweight aggregate; having an air-dry unit weight of not more than 115 lb/ft3 (1850 kg/m3). Term cited in Parts 1 and 2.

3

Confinement Anchorage Anchorage device for a post-tensioning tendon that functions on the basis of confinement of the concrete in the immediate anchorage zone by confinement reinforcing (stirrups, spirals or other devices to provide confinement to the concrete). Term cited in Part 26.

Contractor

4

The individual, partnership, corporation, or joint venturer undertaking performance of the work covered by the plans and specifications and in accordance with the terms of the contract. Term cited in Part 1.

Couplers (Couplings) Means by which prestressing force is transmitted from one partial-length prestressing tendon to another. Cited in Parts 17 and 26.

Creep of Concrete Time-dependent deformation of concrete under sustained load. Term cited in Part 17.

Crib Wall, Cribbing A Crib Wall consists of an earth filled assembly of individual structural units, which relies for its stability on the weight and strength of the earth fill. The design of such walls is treated in Part 6, Crib Walls.

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AREMA Manual for Railway Engineering

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Concrete Structures and Foundations

Term cited in Part 5. A Crib Wall is an earth-retaining structure made up of rigid members fabricated in the shape of open squares, open rectangles or other open shapes, or are assembled in the shape of square or rectangular cells, or cells of other shapes. The cells are filled with granular material. The structure of cells and soil infill act together as a gravity structure, obtaining safety and stability from the proper proportioning of its shape and weight (mass). Crib walls can be of traditional cribbing as described in Article 6.1.2.2, or of other units that behave in accordance with this definition. Crib wall members can be of concrete, metal, or timber. Cribbing also defines a traditional assembly of headers and stretchers, used to form the most common kind of crib wall. Term cited in Part 6.

Curing Compound, Concrete A chemical compound which is applied to a concrete surface to prevent the loss of moisture during early stages of cement hydration. Term cited in Part 1.

Curvature Friction Friction resulting from bends or curves in the specified prestressing tendon profile. Term cited in Part 17.

Cyclopean Concrete See Concrete, Cyclopean. Term cited in Part 1.

Debonding or Blanketing Wrapping, sheathing or coating prestressing tendon to prevent bond between strand and surrounding concrete. Term cited in Part 17.

Deformed Reinforcement See Reinforcement.

Design Load All applicable loads and forces or related internal moments and forces used to proportion members. For design by SERVICE LOAD DESIGN, design load refers to loads without load factor, for LOAD FACTOR DESIGN, design load refers to loads multiplied by appropriate load factors. Term cited in Part 2.

Design Strength Nominal strength multiplied by a strength reduction factor F – See Part 2 Reinforced Concrete Design, Article 2.30.2. Term cited in Part 2.

Development Length Length of embedded reinforcement required to develop the design strength of the reinforcement at a critical section. Term cited in Part 2.

Deviation Saddle Build-out in the web, flange, or web-flange junction to provide for change of direction of an external tendon. Term cited in Part 26.

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AREMA Manual for Railway Engineering

Glossary

Dolphin A stand-alone unit placed upstream or downstream of a substructure element, placed to protect portions of a bridge exposed to possible damage from impacts by floating debris or vessels. The dolphin may be a pile cluster, a filled cellular sheet pile structure, a reinforced concrete shaft or other structural unit intended to protect the bridge. Term cited in Part 23.

Drilled Shaft A machine and/or hand excavated shaft, concrete filled, with or without steel reinforcement, for the purpose of transferring structural loads to bearing strata below the shaft and/or through transfer of structural load through friction between the sides of the shaft and the adjacent material through which the shaft passes. Term cited in Part 24.

Duct Hole or void formed in prestressed member to accommodate tendon for post-tensioning. Term cited in Part 17.

Effective Prestress Stress remaining in concrete due to prestressing after all calculated losses have been deducted, excluding effects of superimposed loads and weight of member; stress remaining in prestressing tendons after all losses have occurred excluding effects of dead load and superimposed load. Term cited in Part 17.

Elastic Shortening of Concrete

1

Shortening of member caused by application of forces induced by prestressing. Term cited in Part 17.

Embankment Installation, Negative Projecting An embankment installation made over a pipe which is installed within a relatively narrow trench with the top of the pipe below the natural ground or compacted fill. Term cited in Part 10.

3

Embankment Installation, Positive Projecting An embankment installation made over a pipe which is installed on original ground or compacted fill with the top of the pipe above the ground or compacted fill. Term cited in Part 10.

Embedment Length Length of embedded reinforcement provided beyond a critical section. Term cited in Part 2.

4

Embedment Length, Equivalent (le) Term cited in Part 2.

End Anchorage Length of reinforcement, or a mechanical anchor or a hook, or combination thereof, beyond the point of zero stress in the reinforcement. Term cited in Parts 2 and 17.

End Block Enlarged end section of member designed to reduce anchorage stresses. Term cited in Part 17.

Engineer Engineer shall be understood to mean the Chief Engineer of the Company or the Chief Engineer’s duly authorized representative. Term cited in Part 1. © 2011, American Railway Engineering and Maintenance-of-Way Association

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Concrete Structures and Foundations

EPDM A sheet, elastomeric membrane formed of Ethylene-Propylene-Diene-Monomers for waterproofing bridge decks, foundations, and tunnels. It is capable of being field spliced with appropriate adhesive, cements, and butyl gum tape.

Expansion Joint A joint or dimensional gap between adjacent parts of a building, structure or concrete work which permits relative movement due to temperature changes (or other conditions) without rupture or damage. Term cited in Part 1.

External Tendon See Tendon, External. Term cited in Part 26.

Factored Load Load, multiplied by appropriate Load Factors, used to proportion member by the LOAD FACTOR DESIGN method. Term cited in Part 2.

Falsework A temporary structure erected to support concrete, formwork, machinery, workers or other loads during the process of construction; composed of shoring, posting and/or bracing. Term cited in Part 1.

Fender A protective structure or cover placed on or around a pier or abutment face, placed as a buffer to protect portions of bridge exposed to possible damage from impacts by floating debris or vessels. Fenders are frequently attached to the substructure element. Term cited in Part 23.

FHWA Federal Highway Administration, 1200 New Jersey Avenue, SE, Washington, D.C. 20590. www.fhwa.dot.gov. Term cited in Parts 1 and 4.

Fineness Modulus See Modulus, Fineness. Term cited in Part 1.

Fly Ash The finely divided residue resulting from the combustion of ground or powdered coal and which is transported from the firebox through the boiler by flue gases. Term cited in Part 1.

Form / Formwork The enclosures or panels which contain the fresh concrete and withstand the forces due to its placement and consolidation. Forms may in turn be supported on shores or falsework. Term cited in Part 1.

Friction (Post Tensioning) Surface resistance between tendon and duct in contact during stressing. Term cited in Part 17. See also Curvature Friction and Wobble Friction.

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AREMA Manual for Railway Engineering

Glossary

General Bursting Forces Bursting forces due to all of the tendons anchored at a cross section. Dependent on the overall concrete dimensions, and the magnitude, direction and location of the total prestressing force anchored. Term cited in Part 26.

Grout Opening or Vent Inlet, outlet, vent, or drain in post-tensioning duct for grout, water or air. Term cited in Part 17.

Heel That portion of the footing of a cantilever retaining wall which lies beneath the retained soil mass. Term cited in Part 5.

Honeycomb Voids left in concrete by failure of the mortar to effectively fill the spaces among coarse aggregate particles. Term cited in Part 1.

Internal Tendon See Tendon, Internal. Term cited in Part 26.

Jacked or Tunneled Installation A pipe installation that is made without removal of the ground above the pipe. Term cited in Part 10.

1

Jacking Force Temporary force exerted by device that introduces tension into prestressing tendons. Term cited in Parts 17 and 26.

Joint, Expansion

3

See Expansion Joint. Term cited in Part 1.

Joint, Type A Cast-in-place joint between previously cast concrete and wet concrete. Term cited in Part 26.

Joint, Type B

4

Epoxied joint or dry joint between precast units. Term cited in Part 26.

Laitance A layer of weak and nondurable material containing cement and fines from aggregates, brought by bleeding water to the top of overwet concrete. Term cited in Part 1.

Launching Bearing Temporary bearing with low friction characteristics used for launching of bridges constructed by the incremental launching method. Term cited in Part 26.

Launching Nose Temporary assembly attached to the front of an incrementally launched bridge to reduce superstructure moments during launching. Term cited in Part 26.

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Concrete Structures and Foundations

Local Zone The region immediately surrounding each anchorage device. It may be taken as a cylinder or prism with transverse dimensions approximately equal to the sum of the projected size of the bearing plate plus the manufacturer’s specified minimum side or edge cover. The length of the local zone may also extend the length of the anchorage device plus an additional distance in front of the anchor equal to at least the maximum lateral dimension of the anchor. Term cited in Part 26.

Loss of Prestress Reduction in prestressing force resulting from combined effects of strains in concrete and steel, including effects of elastic shortening, creep and shrinkage of concrete, relaxation of steel stress, friction, and anchorage seating. Term cited in Parts 17 and 26.

Low Relaxation Steel Prestressing strand in which the steel relaxation losses have been substantially reduced by additional manufacturing procedures (stretching at elevated temperatures). Terms cited in Parts 17 and 26.

Modulus, Fineness A factor obtained by adding the total percentages of material in the sample that are coarser than each of the following sieves (cumulative percentages retained), and dividing the sum by 100: No. 100 (150 micrometer), No. 50 (300 micrometer), No. 30 (600 micrometer), No. 16 (1.18 mm), No. 8 (2.36 mm), No. 4 (4.75 mm), 3/8 inch (9.5 mm), 3/4 inch (19 mm), 1-1/2 inch (37.5 mm), 3 inch (75 mm), 6 inch (150 mm). Term cited in Part 1.

Nominal Strength Strength of a member or cross section calculated in accordance with provisions and assumptions of the LOAD FACTOR DESIGN method before application of any strength reduction factors–See Part 2 Reinforced Concrete Design, Article 2.30.2. Term cited in Part 2.

PCI Precast/Prestressed Concrete Institute, 209 W. Jackson Blvd., Chicago, Illinois 60606. www.pci.org Term cited in Parts 1 and 26.

Permanent Casing See Casing, Permanent. Term cited in Part 24.

Plain Reinforcement See Reinforcement.

Plans The drawings, specifications and other contract documents prepared and approved by the Engineer. Term cited in Part 1.

Plasticizer See 'Admixture, Water Reducing'.

Post-Tensioning Method of prestressing in which tendons are tensioned after concrete has hardened. Term cited in Part 17.

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AREMA Manual for Railway Engineering

Glossary

Pozzolan A siliceous or siliceous and aluminous material, which in itself possesses little or no cementitious value but will, in finely divided form and in the presence of moisture, chemically react with calcium hydroxide at ordinary temperatures to form compounds possessing cementitious properties. Term cited in Part 1.

Precompressed Zone Portion of flexural member cross-section compressed by prestressing force. Term cited in Part 17.

Prestressed Concrete Reinforced concrete in which internal stresses have been introduced to reduce potential tensile stresses in concrete resulting from loads. Term cited in Part 17.

Prestressing Tendon Term cited in Parts 1, 17, and 26.

Pretensioning Method of prestressing in which tendons are tensioned before concrete is placed. Term cited in Part 17.

Protective Casing See Casing, Protective. Term cited in Part 24.

1

psi Pounds per square inch.

Reinforced Elastomeric Bearing Term cited in Part 18.

3

Reinforcement Bars, wires, or other slender members, excluding prestressing tendons unless specifically included, conforming to Part 1, Materials, Tests and Construction Requirements, which are embedded in concrete in such a manner that they and the concrete act together in resisting forces. 1. Reinforcement, Deformed. Reinforcement with a manufactured pattern of surface ridges which provide a locking anchorage with surrounding concrete. 2. Reinforcement, Plain. Reinforcement that does not conform to the definition of deformed reinforcement. Terms cited in Parts 1 and 2.

Relaxation of Tendon Stress Time-dependent reduction of stress in prestressing tendon at constant strain. Term cited in Part 17.

Required Strength Strength of a member or cross section required to resist factored loads or related internal moments and forces in such combinations as are stipulated in Part 2 Reinforced Concrete Design, Article 2.2.4c and Article 2.30.1. Term cited in Part 2.

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Concrete Structures and Foundations

Resistance, Chemical The ability of the material to resist attack by chemicals such as caustics, chlorides, sulphates or acids. Term cited in Part 1.

Rubberized Asphalt with Plastic Film or Preformed Board Membrane Consists of a layer of highly rubberized asphalt formed on plastic film or on preformed board for bridge deck, wall foundation and tunnel waterproofing. It is supplied in roll or sheet form, and is capable of field splicing using an appropriate primer, adhesive and/or gusset tape as recommended by the manufacturer.

Secondary Moment Restraint moments induced in continuous post-tensioned structures due to forces induced by the tendons at the time of stressing. The secondary moment changes with time only due to prestress losses. Term cited in Part 26.

Service Load Loads and forces without load factors. Term cited in Part 2.

Sheer Boom A longitudinal structural element or system of structural elements, generally positioned at a small angle to the direction of stream flow, placed to protect portions of a bridge exposed to possible damage from impacts by floating debris or vessels. Sheer booms are generally positioned and anchored to accomodate fluctuations in water level and deflect the debris or vessel past the substructure element. Term cited in Part 23.

Shore / Shoring Props or posts of timber or other materials used in the temporary support of formwork; the process of erecting shores. Term cited in Part 1.

Shrinkage of Concrete Time-dependent deformation of concrete caused by drying and chemical changes (hydration process). Term cited in Part 17.

Sieve A metallic plate or sheet, a woven-wire cloth, or other similar device, with regularly spaced apertures of uniform size, mounted in a suitable frame or holder for use in separating granular material according to size. Term cited in Part 1.

Sieve Analysis Particle size distribution; usually expressed as the weight percentage retained upon each of a series of standard sieves of decreasing size and the percentage passed by the sieve of smallest size. Term cited in Part 1.

Sieve Number A number used to designate the size of a sieve, usually the approximate number of openings per linear inch; applies to sieves with openings smaller than ¼ inch (6.3 mm). Term cited in Part 1.

Silica Fume Very fine noncrystalline silica produced in electric arc furnaces as a byproduct of the production of elemental silicon or alloys containing silicon; also known as condensed silica fume or microsilica. Term cited in Part 1.

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AREMA Manual for Railway Engineering

Glossary

Slump A measure of consistency of freshly mixed concrete or mortar; equal to the subsidence measured to the nearest 1/4 inch (5 mm) of the molded specimen immediately after removal of the slump cone. Term cited in Part 1.

Slump Cone Mold used to form a mass of concrete for measuring the slump of freshly mixed concrete. Term cited in Part 1.

Socket A shaft having a diameter equal or smaller to that of the main portion of a drilled shaft foundations, extended into the bearing material. Term cited in Part 24.

Soundness The freedom of a solid from cracks, flaws, fissures, or variations from an accepted standard; in the case of a cement, freedom from excessive volume change after setting; in the case of aggregate, the ability to withstand the aggressive action to which concrete containing it might be exposed, particularly that due to weather. Term cited in Part 1.

Spiral Continuously wound reinforcement in the form of a cylindrical helix. Term cited in Part 2.

1

Stirrup or Tie Lateral reinforcement formed of individual units, open or closed, or of continuously wound reinforcement. The term “stirrup” is usually applied to lateral reinforcement in horizontal members beams and the term “tie” to lateral reinforcement in vertical members columns. Term cited in Part 2.

Strength, Compressive

3

The measured maximum resistance of a concrete or mortar specimen to axial compressive loading, expressed as a force per unit cross sectional area; or the specified resistance used in design calculations. In the case of concrete, compressive strength (f’c) is the specified strength in psi (MPa). Wherever this quantity is under a radical sign, the square root of the numerical value only is intended, and the resultant is expressed as a force per unit cross sectional area. Term cited in Parts 1 and 2.

4

Strut-and-Tie Model A structural model used for analysis of shear, torsion and other forces based on a truss analysis by assuming compression struts in the concrete and tension ties in the concrete which must be reinforced. Term cited in Parts 17 and 26.

Superplasticizer See ‘Admixture, Water Reducing (High Range)’.

Temperature Gradient Variation of temperature of the concrete over the cross section. Term cited in Part 26.

Temperature Stick Calibrated crayon that melt at a predetermined temperature. Term cited in Part 1.

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Concrete Structures and Foundations

Temporary Casing See Casing, Temporary. Term cited in Part 24.

Tendon Wire, strand, or bar, or bundle of such elements, used to impart prestress to concrete. Term cited in Part 17.

Tendon, External Tendon located outside the flanges or webs of the structural member, generally inside the box girder cell. Term cited in Part 26.

Tendon, Internal Tendon located within the flanges or webs (or both) of the structural member. All internal tendons shall be designed and constructed as bonded tendons. Term cited in Part 26.

Toe That portion of the footing of a cantilever retaining wall which is typically in front of the retained soil mass and is the location of the highest soil bearing pressure. Term cited in Part 5. Vertical section at bottom of bell. Term cited in Part 24.

Transfer a.

Act of transferring stress in prestressing tendons from jacks or pretensioning bed to concrete member.

b. Transfer of stress in a pretensioned tendon to surrounding concrete. Term cited in Part 17.

Transfer Length Length over which prestressing force is transferred to concrete by bond in pretensioned members. Term cited in Part 17.

Trench Installation and Induced Trench Installation A pipe is installed by trench installation when it is installed in a relatively narrow trench excavated in undisturbed soil and then covered with backfill extending to the ground surface. A pipe is installed by induced trench installation when it is installed in a trench, backfilled with compressible material over the pipe, and then covered by a high embankment. Term cited in Part 10.

Tunneled Installation See Jacked or Tunneled Installation. Term cited in Part 10.

Type A Joint and Type B Joint See Joint. Terms cited in Part 26.

USDOT United States Department of Transportation, 1200 New Jersey Avenue, SE, Washington, D.C. 20590. www.dot.gov. Term cited in Part 1.

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AREMA Manual for Railway Engineering

Glossary

Wales Horizontal or generally horizontal structural members used to brace vertical members. Wales are often used in conjunction with struts or other bracing elements to form a structural system. Wales may be subject to axial and lateral loads. Term cited in Part 23.

Wall, Buttress A retaining wall which is similar to a counterfort wall except that the vertical members, called buttresses, are exposed on the face of the wall rather than buried in the backfill. Term cited in Part 5.

Wall, Cantilever A retaining wall which has a cross section resembling an L or an inverted T, and which requires extensive steel reinforcement. Term cited in Part 5.

Wall, Closed Face A crib wall with solid-surfaced walls. Term cited in Part 6.

Wall, Counterfort A retaining wall which consists of a reinforced vertical face slab supported laterally at intervals by vertical reinforced counterforts extending into the backfill and supported by a reinforced base slab which usually projects in front of the face slab to form a toe. Term cited in Part 5.

1

Wall, Gravity A retaining wall which is so proportioned that no reinforcement other than shrinkage and temperature steel is required. Term cited in Part 5.

Wall, Open Face A crib wall with slotted openings. Term cited in Part 6.

3

Wall, Retaining A structure used to provide lateral support for a mass of soil which, in turn, may provide vertical support for loads acting on or within the soil mass. Term cited in Part 5.

Wall, Semi-Gravity A retaining wall which is so proportioned that some steel reinforcement is required along the back and along the lower side of the toe. Term cited in Part 5.

Water Absorption See Absorption. Term cited in Part 1.

Water-Cementitious Material Ratio The ratio of the mass of water, exclusive only of that absorbed by the aggregate, to the amount of material having cementing properties in a concrete or mortar mixture. Term cited in Part 1.

Wobble friction Friction caused by unintended deviation of prestressing sheath or duct from its specified profile. Term cited in Part 17.

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Concrete Structures and Foundations

Workmanship Term cited in Part 1.

Wrapping or Sheathing Enclosure around a prestressing tendon to prevent bond between prestressing tendon and surrounding concrete. Term cited in Part 17.

Yield Strength or Yield Point (fy) Specified minimum yield strength or yield point of reinforcement in psi (MPa) generally to define the limit of elastic behavior. Term cited in Part 2.

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1 8

References1 — 2010 —

The following list of references used in Chapter 8, Concrete Structures and Foundations is placed here in alphabetical order for your convenience. 1. Anchored Bulkheads, Transactions ASCE 1954. 2. ACI Committee 209, Prediction of Creep, Shrinkage and Temperature Effects in Concrete Structures (ACI 209R-92). 3. ACI Committee 222, Corrosion of Metals in Concrete (ACI 222R-96). American Concrete Institute, Detroit. 4. ACI Committee 318. Building Code Requirements for Reinforced Concrete, (ACI 318-99), American Concrete Institute, Detroit.

1

5. ACI Report "Guide to Underwater Repair of Concrete, ACI 546.2R-98", American Concrete Institute. 6. API, Standard Procedure for Field Testing Water-Based Drilling Fluids, API RP 13B-1 Eleventh Edition, 1990.

3

7. API 1985 Specification for Oil-Well Drilling-Fluid Materials, API 13A Eleventh Edition. 8. AREMA Vol. I, Manual for Railway Engineering, Chapter 30, Part 12 - Concrete Ties 9. Bowles, J. E., 1982: Foundation Analysis and Design, McGraw-Hill, New York. 10. Bridge Inspectors Manual for Movable Bridges, by USDOT, FHWA. 11. Bridge Inspectors Training Manual 70, by USDOT, FHWA 12. Bridge Inspection Seminar Manual, American Railway Bridge and Building Association, Atlanta, Georgia, February 22-24, 1993. 13. Bridge Inspector’s Training Manual/90, FHWA-PD-91-015, U.S. Department of Transportation, Federal Highway Administration, May, 1991 14. Bryant, Anthony A. and Chayatit Vadhanavikkit. Creep, Shrinkage – Size, and Age at Loading Effects, ACI Materials Journal, March–April 1987. 15. CEB-FIP Model Code for Concrete Structures, Comité Euro-International de Beton (CEB), 1978, available from: Lewis Brooks, 2 Blagdon Road, New Malden, Surrey, KT3 4AD, England.

1

References, Vol. 97, p. 108.

© 2011, American Railway Engineering and Maintenance-of-Way Association

8-R-1

Concrete Structures and Foundations 16. Carson, A. Brinton, Foundation Construction 17. Clough, G. W., 1973: Analytical Problems in Modeling Slurry Wall Construction, FCP Res. Rev. Conf., San Francisco. 18. Collins, M.P., and D. Mitchell. Shear and Torsion Design of Prestressed and Non-Prestressed Concrete Beams, PCI Journal, Vol. 25, No. 5, Sept.–Oct. 1980. 19. Committee on Ship-Bridge Collisions, Marine Board, Commission on Engineering and Technical Systems, National Research Council, 1983; Ship Collisions with Bridges, The Nature of the Accidents, Their Prevention and Mitigation. 20. Continuously Reinforced Concrete Pavement, 16, National Cooperative Highway Research Program, 1973. 21. Danon, J. R., and W.L. Gamble. Time Dependent Deformation and Losses in Concrete Bridges Built by the Cantilever Method, Structural Research Series No. 437, University of Illinois at Urbana-Champaign, Urbana, Illinois, January 1977. 22. Davisson, M. T., (1975), “Pile Load Capacity,” Proceedings, Seminar Series, Design, Construction, and Performance of Deep Foundations, ASCE–U. of California, Berkeley. 23. Deadman Anchorages in Sand, J. E. Smith, Technical Report R199 U.S. Naval Civil Engineering Laboratory, Port Hueneme CA 1962. 24. "Design of Continuously Reinforced Concrete for Highways", CRSI, 1981. 25. Design of Terminals for Rigid Pavements to Control End Movements: State of the Art, Special Report 173, TRB, 1977. 26. "Design Report - Non-Conventional Track Structures-Kansas Test Track", Report to Santa Fe Railway Company and U.S. Department of Transportation, Westenhoff and Novick, Inc, Chicago, June, 1972. 27. Dilger, W. H. Creep Analysis of Prestressed Concrete Structures Using Creep-Transformed Article Properties, PCI Journal, Jan–Feb. 1982, Vol. 27, No. 1. 28. Dunham, Clarence W., Foundation of Structures. 29. FHWA "Underwater Evaluation and Repair of Bridges Components", Instructor's Guide, Demonstration Project 98, U.S. Department of Transportation, November, 1995. 30. Federal Highway Administration, Scour at Bridges, Technical Advisory T5140.20, 1988. 31. Federal Highway Administration, Countermeasures for Hydraulic Problems at Bridges, Publication RD 78162, 1978. 32. Fryba, Ladislav, Dynamics of Railway Bridges, Thomas Telford Services Ltd., London, 1996. 33. Foundation Design, Wayne C. Teng, Prentice Hall Inc. 1962. 34. Foutch, Douglas A., Tobias, Daniel H., and Otter, Duane E., Analytical Investigation of the Longitudinal Loads in an Open-Deck Through-Plate-Girder Bridge, Report R-894, Association of American Railroads, September 1996.

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AREMA Manual for Railway Engineering

References

35. Foutch, Douglas A., Tobias, Daniel H., Otter, Duane E., LoPresti, Joseph A., and Uppal A. Shakoor, Experimental and Analytical Investigation of the Longitudinal Loads in an Open-Deck Plate Girder Railway Bridge, Report R-905, Association of American Railroads, November 1997. 36. Gill, S. A., 1978: Applications of Slurry Walls in Civil Engineering Projects, ASCE Preprint 3355. 37. Goble, G. G. and Rausche, F. Wave Equation Analysis of Pile Driving, WEAP Program, User’s Manual, Vols. 1-4, U.S. Department of Transportation (Report No. FHWA-IP-76-14.l)., Springfield, VA, National Technical Information Service, 1976. 38. Guide specifications for concrete subject to Alkali-Silica Recations, PCA, Publication IS415, 1994. 39. Hanna, A.N., "Technical and Economic Feasibility Study of At-grade Concrete Slab Track for Urban Rail Transit Systems." UMTA Report UMTA-MA-06-0100-81-4, August, 1981. 40. Hoang, L. H., and M. Pasquignon. Essais de Flexion sur des Poutres en Beton Precontraintes par des Cables Exterieurs, Vols. 1 and 2, Contrat SETRA-CEBTP 1985, Dossiers de Recherche 910017, Service d’Etude des Structures, Saint Remy Les Chevreuse, November 1985. 41. Homberg, Helmut. Fahrbahnplatten Mit Verandlicher Dicke, Springer-Verlag, New York, 1968. 42. Homberg, Helmut, and Walter Ropers. Fahrbahnplatten Mit Veranderlicher Dicke, Springer-Verlag, New York, 1965.

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43. Imbsen, R.A., D.E. Vandershaf, R.A. Schamber and R.V. Nutt. Thermal Effects in Concrete Bridge Structures, National Cooperative Research Program Report 276, Transportation Research Board, Washington, D.C., September 1985. 44. "Influence Charts for Concrete Pavements", ASCE Transaction Vol. 116, 1951. 45. Joy, Richard, LoPresti, Joseph A., and Otter, Duane E., Longitudinal Forces in a Single-Span BallastedDeck Plate Girder Bridge, Technology Digest 99-026, Transportation Technology Center, Inc., July 1999.

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46. Ketchum, M.A. Redistribution of Stresses in Segmentally Erected Prestressed Concrete Bridges, Report No. UCB/SESM-86/07, Department of Civil Engineering, University of California, Berkeley, California, May 1986. 47. Koseki, K., and J.E. Breen. Exploratory Study of Shear Strength of Joints for Precast Segmental Bridges, Research Report 248-1, Center for Transportation Research, The University of Texas at Austin, September 1983. 48. Leonards, G. A., Foundation Engineering. 49. Leonhardt, Fritz, and Walter Lipproth. Conclusions Drawn from Distress of Prestressed Concrete Bridges, Beton und Stahlbetonbau, No. 10, Berlin, October 1970, Vol. 65, pp. 231–244. 50. Leonhardt, F., G. Kolbe and J. Peter. Temperature Differences Dangerous to Prestressed Concrete Bridges, Beton and Stahlbetonbau, 1965, No. 7, pp. 157–163. 51. Longi, M.S., "Innovations in Track Structures on Long Island Rail Road", Transportation Research Board, Transportation Research record 939, 1983. 52. Longi, M.S., "Concrete Slab Track on the Long Island Rail Road", American Concrete Institute SP93-20, 1986.

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Concrete Structures and Foundations 53. LoPresti, Joseph A., Otter, Duane E., Tobias, Daniel H., and Foutch, Douglas A., Longitudinal Forces in an Open-Deck Steel Bridge, Technology Digest 98-007, Transportation Technology Center, Inc., April 1998. 54. LoPresti, Joseph A., and Otter, Duane E., Longitudinal Forces in a Two-Span Open-Deck Steel Bridge at FAST, Technology Digest 98-020, Transportation Technology Center, Inc., August 1998. 55. Manual for Maintenance Inspection of Bridges – 1978 by AASHTO. 56. Marti, P., Basic Tools of Reinforced Concrete Beam Design, ACI Journal, Jan.–Feb. 1985, Vol. 82, No. 1. 57. Meacham, H.C., et al, "Studies For Rail Vehicle Track Structures", Federal Railroad Administration, Washington, D.C., Report No. FRA-RT-71-45. 58. Mettler, A.R., et al, "Design, Construction, and Performance of At-grade Guideways", Concrete International, July, 1980. 59. Millet, R. A., and Perez, J. Y., 1981: Current USA Practice: Slurry Wall Specifications, Proc. ASCE, Aug. 1981. 60. NCHRP Report 226, "Damage Evaluation and Repair Methods for Prestressed Concrete Bridge Members, November, 1980. 61. NCHRP Report 280, "Guidelines for Evaluation and Repair of Prestressed Concrete Bridge Members, December, 1985. 62. Noble, C-S, McCollough, B.F., and Ma, J.C., "Nomographs for the Design of CRP Steel Reinforcement", Research Report No. 177-16, Center for Highway Research, University of Texas, Austin, Aug, 1979. 63. Ontario Highway Bridge Design Code, Ontario Ministry of Transportation and Communications, Toronto, Ontario, Canada. 64. Osterberg, J.O. and S.F. Pepper, A New Simplified Method for Load Testing Drilled Shafts, Foundation Drilling, Association of Drilled Shaft Contractors, August 1984, pp. 9-11. 65. Otter, Duane E., LoPresti, Joseph, Foutch, Douglas A., and Tobias, Daniel H., Longitudinal Forces in an Open-Deck Steel Deck Plate-Girder Bridge, Technology Digest 96-024, Association of American Railroads, November 1996. 66. Otter, Duane E., LoPresti, Joseph, Foutch, Douglas A., and Tobias, Daniel H., "Longitudinal Forces in an Open-Deck Steel Deck Plate-Girder Bridge," Volume 98, Bulletin 760, American Railway Engineering Association, May 1997, pp. 101-105. 67. Otter, Duane E., and LoPresti, Joseph, "Longitudinal Forces in an Open-Deck Steel Deck Plate-Girder Bridge," Railway Track & Structures, May 1997, pp. 14-15. 68. Otter, Duane E., and LoPresti, Joseph A., "Longitudinal Forces in Three Open-Deck Steel Bridges," Proceedings, AREMA Technical Conference, September 1998. 69. Pavement Design and Continuously Reinforced Concrete Pavement Performance, Transportation Research Record, 485, TRB, 1974. 70. PCI Committee on Prestress Losses. Recommendations for Estimating Prestress Losses, PCI Journal, Vol. 20, No. 4, July–Aug. 1975.

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References 71. Peck, R. B., Hanson, W.E., and Thornburn, T. H., Foundation Engineering, John Wiley and Sons, 2nd Ed., New York, 1974. 72. Portland Cement Association, "Concrete Supported Railway Track", April, 1941. 73. Precast Segmental Box Girder Bridge Manual, Post-Tensioning Institute and Prestressed Concrete Institute, Phoenix, Arizona, Chicago, Illinois, 1978. 74. Pucher, Adolf. Influence Surfaces of Elastic Plates, Fourth Revised Edition, Springer-Verlag, New York. 75. Quinn, Alonzo DeF., Design and Construction of Ports and Marine Structures 76. Rabbat, Basile G., and Koz Sowlat. Testing of Segmental Concrete Girders with External Tendons, Journal of the Prestressed Concrete Institute, Vol. 32, No. 2, March/April 1987. 77. Ramakrishnan, V., Ultimate Energy Design of Prestressed Concrete Fender Piling, Am Soc Civil Engr J Waterways and Harbors, Nov 71; Vol 97, No WW 4, Proc Paper 8527, pp. 647-662, 4 Fig, 2 Tab,; 10 REF 78. Recording Coding Guide for Structure Inventory and Appraisal of the Nations Bridges, January, 1979, by USDOT, FHWA. 79. Reese, L.C. Handbook on Design of Piles and Drilled Shafts Under Lateral Load, U.S. Department of Transportation, Report No. FHWA-IP-84-11, Springfield, VA, National Technical Information Service, 1984.

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80. Reese, L.C., and Wright, S.L., Drilled Shaft Manual Vols. I and II, U.S. Department of Transportation, Office of Research and Development, Implementation Package 77-21, July 1977. 81. Renard, J., Energy Considerations on the Design of Dolphins, Acier-Stahl-Steel, No. 2-1966 pp. 80-89 82. Roadways and Airport Pavements, Publication SP-51, American Concrete Institute, 1975.

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83. Rooryck, ir. R., ir. J. Renard, Dimensions and Design of Protection and Braking Systems at the Entrances and Exits of Large Modern Locks 84. Saurin, Brendan F.1, Design Criteria for Fenders and Berthing Structures, Summary of Lecture, July 29, 1965 85. Schlaich, J., K. Schafer, and M. Jennewain. Towards a Consistent Design of Reinforced Concrete Structures, PCI Journal, May–June 1987, Vol. 32, No. 3. 86. Schlaich, J. and H. Scheef. Concrete Box Girder Bridges, International Association for Bridge and Structural Engineering, Zurich, Switzerland, 1982. 87. Scordelis, A.C. Analysis of Continuous Box Girder Bridges, SESM-85/02, Department of Civil Engineering, University of California, Berkeley, November 1987. 88. Scordelis, A.C., E.C. Chan, M.A. Ketchum and P.P. Van Der Walt. Computer Programs for Prestressed Concrete Box Girder Bridges, SESM-85/02, Department of Civil Engineering, University of California, Berkeley, March 1985.

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Interpretation from notes by J. T. O’Brien and B. W. Wilson

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89. Seed, H. Bolton and Idriss, Izzat M. “Simplified Procedure for Evaluating Soil Liquefaction Potential,” Journal of the Soil Mechanics and Foundation Division Proceedings of the American Society of Civil Engineers, Vol. 97, No. SM9, September 1971. 90. Shushkewich, K.M. Time Dependent Analysis of Segmental Bridges, Computers and Structures (Great Britain), Vol. 23, No. 1, 1986. 91. Smith, E. A. L. “Pile Driving Analysis by the Wave Equation,” Journal of the Soil Mechanics and Foundations Division Proceedings of the American Society of Civil Engineers, Vol. 86, No. SM4, April 1960. 92. Standard Specification for End Bearing Drilled Piers (ACI 336. 1-79) J, ACI, Sept. 1978. 93. Standard Specifications for Highway Bridges, Sixteenth Edition, 1996; American Association of State Highway and Transportation Officials. 94. Standard Specifications for Seismic Design of Highway Bridges, American Association of State Highway and Transportation Officials, Washington, D.C. 1991. 95. Stone, W.C., W. Paes-Filha and J.E. Breen. Behavior of Post-Tensioned Girder Anchorage Zones, Research Report 108-2, Center for Transportation Research, The University of Texas at Austin, April 1981. 96. Stone, W.C., and J.E. Breen. Design of Post-Tensioned Girder Anchorage Zones, Research Report 208-3F, Center for Transportation Research, The University of Texas at Austin, June 1981. 97. Structure Inventory and Appraisal Sheet – Abridged (Short Form) for Bridges not on the Federal Aid System, January, 1979, by USDOT and FHWA. 98. Subgrades and Subbases for Concrete Pavements, PCA/ACPA, Publications ISO29.03P/TB-011.OD, 1991. 99. Suggested Design and Construction Procedures for Pier Foundations Reported by ACI Committee 336 – Title No. ACI 69-42. J, ACI, Aug. 1972 100."Thickness Design for Pavements", PCA, 1966. 101.Tiebacks, U.S. Department of Transportation, FHWA, Report No. FHWA/RD-82/047 dated July 1981. 102.Tobias, Daniel, Foutch, Douglas, Lee, Kihak, Otter, Duane E., and LoPresti, Joseph A., Experimental and Analytical Investigation of Longitudinal Forces in a Multi-span Railway Bridge, Report R-927, Association of American Railroads, Transportation Technology Center, Inc., March 1999. 103.Tschebotarioff, Gregory P., Foundations, Retaining and Earth Structures, The Art of Design and Construction and its Scientific Basis in Soil Mechanics. 104.Underwater Inspection and Repair of Bridge Substructures National Cooperative Highway Research Program (NCHRP) Synthesis of Highway Practice 88, Dec. 1981 – TRB. 105.Underwater Inspection of Bridges, FHWA-DP-80-1, Federal Highway Administration, November, 1989. 106.U.S. Department of Transportation, The Performance of Pile Driving Systems: Inspection Manual, Report No. FHWA RD-86-l60, Springfield, VA, National Technical Information Service, 1978. 107.Winterkorn, H. F. Fang, H.Y., "Foundation Engineering Handbook", Van Nostrand Reinhold Company, 1975.

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References 108.Xanthakos, P. P., 1979: Slurry Walls, Published by McGraw-Hill, New York. 109.Zia, Paul, Preston, H. Kent, Scott, Norman L, Workman, Edwin B. Estimating Prestress Losses, ACI Concrete International, June 1979, pp. 32-38

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CHAPTER 9 SEISMIC DESIGN FOR RAILWAY STRUCTURES1 TABLE OF CONTENTS

Part/Section 1

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1

Description

Page

Seismic Design for Railway Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 Introduction (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 Post-Seismic Event Operation Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 General Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 New Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5 Existing Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6 Other Facilities and Infrastructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7 Construction of Others (2007). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.8 Retired Facilities (2007). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Commentary to Seismic Design for Railway Structures . . . . . . . . . . . . . . . . . . . . . . . . . . C - Section 1.2 Post-Seismic Event Operation Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C - Section 1.3 General Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C - Section 1.4 New Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C - Section 1.5 Existing Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C - Section 1.6 Other Facilities and Infrastructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Chapter 9 Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Notations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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The material in this and other chapters in the AREMA Manual for Railway Engineering is published as recommended practice to railroads and others concerned with the engineering, design and construction of railroad fixed properties (except signals and communications), and allied services and facilities. For the purpose of this Manual, RECOMMENDED PRACTICE is defined as a material, device, design, plan, specification, principle or practice recommended to the railways for use as required, either exactly as presented or with such modifications as may be necessary or desirable to meet the needs of individual railways, but in either event, with a view to promoting efficiency and economy in the location, construction, operation or maintenance of railways. It is not intended to imply that other practices may not be equally acceptable.

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INTRODUCTION The Chapters of the AREMA Manual are divided into numbered Parts, each comprised of related documents (specifications, recommended practices, plans, etc.). Individual Parts are divided into Sections by centered headings set in capital letters and identified by a Section number. These Sections are subdivided into articles designated by numbered side headings. Page Numbers – In the page numbering of the Manual (9-2-1, for example) the first numeral designates the Chapter number, the second denotes the Part number in the Chapter, and the third numeral designates the page number in the Part. Thus, 9-2-1 means Chapter 9, Part 2, page 1. In the Glossary and References, the Part number is replaced by either a “G” for Glossary or “R” for References. Document Dates – The bold type date (Document Date) at the beginning of each document (Part) applies to the document as a whole and designates the year in which revisions were last made somewhere in the document, unless an attached footnote indicates that the document was adopted, reapproved, or rewritten in that year. Article Dates – Each Article shows the date (in parenthesis) of the last time that Article was modified. Revision Marks – All current year revisions (changes and additions) which have been incorporated into the document are identified by a vertical line along the outside margin of the page, directly beside the modified information. Proceedings Footnote – The Proceedings footnote on the first page of each document gives references to all Association action with respect to the document. Annual Updates – New manuals, as well as revision sets, will be printed and issued yearly.

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Part 1 Seismic Design for Railway Structures1 — 2011 — TABLE OF CONTENTS

Section/Article

Description

Page

1.1 Introduction (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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1.2 Post-Seismic Event Operation Guidelines. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2.1 General (2001) R(2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2.2 Guidelines (2009). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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1.3 General Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.1 Approach (2004) R(2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.2 Ground Motion Levels (2004) R(2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.3 Performance Criteria (1998) R(2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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1.4 New Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4.1 Scope (2004) R(2009). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4.2 Design Approach (2001) R(2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4.3 Conceptual Design (2001) R(2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4.4 Structure Response (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4.5 Analysis Procedures (2003). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4.6 Load Combinations and Response Limits (2002) R(2007) . . . . . . . . . . . . . . . . . . . . . . . . . 1.4.7 Detailing Provisions (2001) R(2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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1.5 Existing Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.1 Scope (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.2 Inventory (1995) R(2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.3 History (1995) R(2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.4 Assessment and Retrofit (2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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1.6 Other Facilities and Infrastructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6.1 Scope (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6.2 T rack and Roadbed (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6.3 Culverts (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6.4 Retaining Walls (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6.5 Tunnels and Track Protection Sheds (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6.6 Buildings and Support Facilities (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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References, Vol. 94, 1994, p.110; Vol. 96, p. 64, Vol. 97, p. 113.

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TABLE OF CONTENTS (CONT) Section/Article 1.6.7 1.6.8

Description

Page

Utilities, Signal and Communication Facilities (2007). . . . . . . . . . . . . . . . . . . . . . . . . . . . Rail Transit (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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1.7 Construction of Others (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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1.8 Retired Facilities (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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LIST OF FIGURES Figure 9-1-1 9-1-2 9-1-3 9-1-4 9-1-5

Description

Page

Plate 1 – 100-year Return Period – United States. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Plate 2 – 475-year Return Period – United States. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Plate 3 – 2,400-year Return Period – United States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Plate 4 – 100-year Return Period – Canada . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Plate 5 – 475-year Return Period – Canada . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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LIST OF TABLES Table 9-1-1 9-1-2 9-1-3 9-1-4 9-1-5 9-1-6 9-1-7 9-1-8 9-1-9

Description

Page

Specified Response Radii. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Damage Criterion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Seismic Performance Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ground Motion Levels. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Weighting Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Site Coefficient. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Analysis Procedure Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Load Combinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Response Limits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9-1-4 9-1-4 9-1-8 9-1-8 9-1-11 9-1-20 9-1-22 9-1-24 9-1-24

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AREMA Manual for Railway Engineering

Seismic Design for Railway Structures

SECTION 1.1 INTRODUCTION (2004) The railroad industry is vitally interested in maintaining reliability in its infrastructure to assure safety for its employees, passengers, customers’ goods and the public at large. These guidelines have been developed specifically for Railroad facilities to help reduce damage from earthquakes. While many structures, such as culverts, retaining walls and buildings, may not be substantially different because of use on railroads, North America’s railroad bridges are functionally and behaviorally different from highway and other types of bridges. This document provides a framework of considerations and methodologies for seismic design of new bridges, roadbed and other railroad facilities. This document also addresses retrofit and post-seismic event response and inspection considerations. Railroad bridges historically have performed well in seismic events with little or no damage. Contributing to this ability are several factors, unique to railroad bridges, which are consistent throughout North America. First, bridges are traversed by track structure that functions as a restraint against longitudinal and lateral movement during earthquakes. Second, configurations of railroad bridges typically differ from other types of bridges. Third, the controlled operating environment permits different seismic performance requirements for railroad bridges compared to highway bridges.

1

SECTION 1.2 POST-SEISMIC EVENT OPERATION GUIDELINES 1.2.1 GENERAL (2001) R(2006) The responses of track and structures to seismic events vary greatly with respect to each other and to the various types of construction, geotechnical conditions and other seismic parameters such as importance and risk factors, structural importance and value, etc.

3

1.2.2 GUIDELINES (2009) Unless more appropriate guidelines have been developed as a result of experience with significant earthquakes in the affected area and/or consideration of other local conditions, the following are recommended: 1.2.2.1 Operations

1

After an earthquake is reported to the Railroad, Train Dispatcher shall notify all trains and engines within a 100 mile radius of the reporting area to run at restricted speed until magnitude and epicenter have been determined by proper authority. Inspection of track, structures, signal and communication systems shall be initiated. Upon determination of the magnitude and epicenter, the following response levels will govern operations within the specified radius from the epicenter:

1

See Part 2 Commentary to Seismic Design for Railway Structures

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Seismic Design for Railway Structures

Table 9-1-1. Specified Response Radii Earthquake (Richter)

Response Level

0.0 - 4.99

I

5.0 - 5.99

II

6.0 - 6.99 7.0 or greater

California and Baja California

Remainder of North America

50 miles (80 km)

100 miles (160 km)

III II

100 miles (160 km) 150 miles (240 km)

200 miles (320 km) 300 miles (480 km)

III II

As directed, but not less than for 6.0 - 6.99. As directed, but not less than for 6.0 - 6.99.

1.2.2.2 Response Levels I

Resume maximum operating speed. The need for the continuation of inspections will be determined by proper Maintenance of Way authority.

II

All trains and engines will run at restricted speed within a specified radius of the epicenter until inspections have been made and appropriate speeds established by proper authority.

III

All trains and engines within the specified radius of the epicenter must stop and may not proceed until proper inspections have been performed and appropriate speed restrictions established by proper authority. For earthquakes of 7.0 (Richter) or greater, operations shall be as directed by proper authority, but the radius shall not be less than that specified for earthquakes between 6.0 and 6.99.

The associated damage philosophy with respect to the above operating procedures can be correlated with the damage criterion shown in Table 9-1-2.

Table 9-1-2. Damage Criterion Response Ground Level Motion Level

Expected Damage to Track, Structure, Signal and Communications

I

0

Very low probability of damage or speed restrictions.

II

1

Moderate damage which may require temporary speed restrictions.

III

2

Heavy damage which can be economically repaired. Track or structures may be out of service for a short period of time.

III

3

Severe damage or failure requiring new construction or major rehabilitation. Track or structures may be out of service for an indefinite period of time.

The post-seismic event response will be affected by the individual Railroad’s operating requirements based in part on the risk factor, return periods, required factor of safety, structural occupancy, signal and communication systems and appurtenances such as highways, building types and waterways.

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Seismic Design for Railway Structures 1.2.2.3 Post Earthquake Inspection Inspection procedures and modifications of facilities to expedite the inspection process should be established before the seismic event. The following list provides a general guideline that may be used for developing an inspection procedure: 1.2.2.3.1 Track and Roadbed Line, surface and cross level irregularities caused by embankment slides or liquefaction, track buckling or pull aparts due to soil movement, offset across fault rupture, etc. Disturbed ballast Cracks or slope failures in embankments Slides and/or potential slides in cuts, including loose rocks that could fall in an aftershock Scour due to tsunami in coastal areas Potential for scour or ponding against embankment due to changes in water courses 1.2.2.3.2 Drainage Blockage of cut ditches or other changes in drainage patterns. (While these conditions will not usually prevent restoration of service, they will require correction.)

1

1.2.2.3.3 Bridges NOTE:

a.

Following an earthquake, inspectors may need to travel by rail between bridges. The time required for bridge inspection will be critical and normally dry stream beds may be flooded when inspection is required. Therefore, provisions should be made beforehand to permit quick access to bearing areas and other critical points from the track rather than from the ground.

3

Steel Displaced or damaged bearings

4

Stretched or broken anchor bolts Distress in viaduct towers Buckled columns or bracing Tension distress in main members or bracing Displaced substructure elements b. Concrete Displacement at bearings Displaced substructure elements Cracks in superstructure © 2011, American Railway Engineering and Maintenance-of-Way Association

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Seismic Design for Railway Structures

Cracks in substructure c.

Timber Trestles Line, surface and cross level of track. (Movements that do not affect line, surface or cross level are unlikely to be damaging, especially in open deck trestles). Displaced timbers, particularly in framed bents Broken bracing Bent bolts or drift bolts

d. Movable Spans Damage to counterweight guides Open draw span shifted on pivot pier Relative movement of piers that prevents opening or closing, including mis-alignment of track girders and segmental girders of rolling lift spans. 1.2.2.3.4 Culverts Damage is unlikely if line and surface of track are good and no slides or embankment spreading are observed. 1.2.2.3.5 Retaining Walls Increased tilt in walls which may be caused by footing rotation or cracking at base of stem. (Walls with surcharge above top of wall appear particularly vulnerable.) 1.2.2.3.6 Tunnels Fallen material or loose material that may fall in an aftershock New cracks or failures in lining Offsets due to displacement across fault Unusual flow of water within tunnel 1.2.2.3.7 Other Structures1 Structural and/or non-structural damage to essential buildings that would prevent or inhibit use. NOTE:

Inspect promptly, with concurrence of local building authorities, to prevent outside inspectors from “red tagging” buildings that are damaged but not unsafe.

Leaks and/or structural damage to fueling facilities, including tanks and pipelines. Look for evidence of leaks in buried fuel lines. Catenary support structures and tension-regulating systems of electrified lines. 1

See Part 2 Commentary to Seismic Design for Railway Structures

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AREMA Manual for Railway Engineering

Seismic Design for Railway Structures NOTE:

Substations should be inspected by a qualified individual.

1.2.2.3.8 Structures That May Fall on Track a.

Overpasses Reduced support for span at bearings Column damage Damage to any span restraint system

b. Adjacent Buildings Structural damage affecting ability to resist aftershocks Clearance infringements Power lines that may be vulnerable to aftershocks 1.2.2.3.9 Signal and Communication Facilities Signal and communications facilities must be inspected by qualified personnel. However, others involved in inspection should note damage to pole lines and other obvious damage to equipment. Signal masts, signal bridges or instrument housings observed to be out-of-plumb should be reported immediately.

1

1.2.2.4 Tsunamis1 After a tsunami warning is issued to the Railroad, Train Dispatchers shall notify all trains and engines within the areas vulnerable to the tsunami to move out of those areas before the estimated arrival of the tsunami. To the extent possible all other equipment should also be moved. The movement should be to the closest location at an elevation deemed to be safe. This movement may be in reverse of the train’s normal direction.

3

Railroad offices within potential tsunami affected areas and railroad dispatch centers shall be included on the email notification system provided by The National Weather Service. All railroad employees in those offices and those working on line with equipment in such areas shall be notified by their respective offices to move out of areas vulnerable to the tsunami when a warning is received.

4 Following a large earthquake near the coast, trains should not enter areas vulnerable to tsunamis until it is determined that the tsunami danger has passed. Trains already in vulnerable areas should not be stopped if the track is passable, but should proceed to protected or higher areas if possible.

1

See Part 2 Commentary to Seismic Design for Railway Structures

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Seismic Design for Railway Structures

SECTION 1.3 GENERAL REQUIREMENTS 1.3.1 APPROACH (2004)1 R(2009) Structures shall be designed to satisfy the specified performance criteria. The main objectives of the required performance criteria are to ensure the safety of trains and to minimize the costs of damage and loss of use caused by potential earthquakes. In order to provide a framework for evaluating seismic effects on railroad structures, a three-level ground motion and performance criteria approach consistent with the railroad post-seismic event response procedures is employed. The ground motion levels, the structure performance requirements and the railroad response levels are as shown in Table 9-1-3.

Table 9-1-3. Seismic Performance Criteria Railroad Response Level Ground Motion Level Performance Criteria Limit State II

1

Serviceability

III

2

Ultimate

III

3

Survivability

1.3.2 GROUND MOTION LEVELS (2004) R(2009) The ground motion levels reflect the seismic hazard at the site. They are defined in terms of peak ground acceleration levels associated with a given average return period. The average return period for each ground motion level may be determined based on seismic risk considerations (see Paragraph 1.3.2.1) and structure importance classification (see Paragraph 1.3.2.2), using the range of average return periods shown in Table 9-1-4.

Table 9-1-4. Ground Motion Levels Ground Motion Level

Frequency

Average Return Period (Yrs.)

1

Occasional

50-100

2

Rare

200-500

3

Very Rare

1000-2400

Level 1 Ground Motion represents an occasional event with a reasonable probability of being exceeded during the life of the structure. Level 2 Ground Motion represents a rare event with a low probability of being exceeded during the life of the structure. Level 3 Ground Motion represents a very rare or maximum credible event with a very low probability of being exceeded during the life of the structure.

1

See Part 2 Commentary to Seismic Design for Railway Structures

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AREMA Manual for Railway Engineering

Seismic Design for Railway Structures 1.3.2.1 Risk Factors1 Earthquakes are extreme events associated with a great amount of uncertainty and risk factors are an integral part of seismic design. To achieve a balance between seismic risk and costs associated with risk reduction, a certain amount of risk must be accepted. If there is a severe social penalty associated with structure failure, the acceptable level of risk will be greatly reduced. The greatest amount of uncertainty is associated with the seismic hazard at the site. Therefore, the overall seismic risk of a bridge is strongly affected by the design ground motion used. The acceptable risk criteria with respect to Level 1 Ground Motion shall consider the safety and continuing operation of trains with speed restrictions. For Ground Motion Levels 2 and 3, the acceptable risk criteria may be based mainly on economic considerations unless the bridge has a high passenger train occupancy rate. Train traffic is stopped per Railroad Response Level III for Ground Motions Levels 2 and 3 until bridge inspections are completed. 1.3.2.2 Structure Importance Classification2 The purpose of the structure importance classification system is to assist the engineer in determining the appropriate average ground motion return period for each of the three limit states: serviceability, ultimate and survivability. The importance of a structure is determined by three measures: Immediate Safety, Immediate Value and Replacement Value. These three measures are combined in Article 1.3.2.2.4 to determine the appropriate return period for each of the limit states.

1

1.3.2.2.1 Immediate Safety3 Immediate safety is a measure of the magnitude of earthquake a structure should be able to survive without any interruption of service. Factors to be considered are occupancy, hazardous material and community life lines. These factors should be summed to obtain the immediate safety factor. The immediate safety factor should not exceed 4. a.

3

Occupancy Factor Freight Service only . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Less Than 10 Passenger Trains per Day. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 More than 10 Passenger Trains per Day. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

4

b. Hazardous Material Factor The value of the hazardous material factor should be determined by the engineer by considering the type of material being handled, the volume and the proximity of the structure to population. The hazardous material factor should be a value between 0 and 4. c.

Community Life Lines Factor The community life line factor should reflect the danger to community if the structure fails during a seismic event. The community life line factor should be a value between 0 and 4. The nature of the structure should be taken into account when determining the community life line factor. If the structure is over a route that is critical for post seismic evacuation, a high community life line factor should be used. A high community life line factor should also be used when the structure is over a community’s

1 2 3

See Part 2 Commentary to Seismic Design for Railway Structures See Part 2 Commentary to Seismic Design for Railway Structures See Part 2 Commentary to Seismic Design for Railway Structures

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Seismic Design for Railway Structures

water supply. The potential disruption of telephone, electric, and water lines attached to the bridge and the importance of continued rail service should also be considered when determining the community life line factor. 1.3.2.2.2 Immediate Value1 Immediate Value is a measure of the magnitude of earthquake a structure should be able to survive with an interruption of service but with the ability to return to service after minor repairs. The factor is based on the railroad’s utilization of the structure and the ability to detour around the structure. The utilization of the structure by others should also be taken into account. a.

Railroad Utilization Factor Under 10 million gross tons annual traffic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Between 10 million and 50 million gross tons annual traffic . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Over 50 million gross tons annual traffic. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

b. Detour Availability Factor No Detour Available . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.00 Inconvenient Detour Route. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.50 Detour Route Readily Available . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.25 The Immediate Value factor should be determined by multiplying the railroad utilization factor by the detour availability factor. Usage by outside parties should be taken into account after this railroad utilization and detour availability is taken into account. 1.3.2.2.3 Replacement Value2 Replacement value is a measure of the magnitude of the ultimate earthquake the structure should be able to survive. The factor is determined by the difficulty of replacing the structure. a.

Span Length Factor Span length less than 35 feet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Span length between 35 feet and 125 feet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Span length between 125 feet and 250 feet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Span length greater than 250 feet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1 2 3 4

b. Bridge Length Factor Bridge length less than 100 feet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.0 Bridge length between 100 feet and 1,000 feet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.5 Bridge length greater than 1,000 feet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2.0 c.

Bridge Height Factor Bridge height less than 20 feet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.75 Bridge height between 20 feet and 40 feet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.00 Bridge height greater than 40 feet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1.25

1 2

See Part 2 Commentary to Seismic Design for Railway Structures See Part 2 Commentary to Seismic Design for Railway Structures

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Seismic Design for Railway Structures

The replacement value factor is determined by multiplying the span length, bridge length and bridge height factors, but should not exceed 4.0. The replacement value should be increased for conditions that would increase the difficulty of replacement such as multiple track, movable structures, difficult foundation and substructure reconstruction conditions, urban location and difficult access. 1.3.2.2.4 Conversion of Factors to Return Periods The importance classification factor for each limit state is calculated using the following weighting factors. Individual railroads may decide to change the weighting factors to better represent the conditions that they operate under.

Table 9-1-5. Weighting Factors Weighting Factors

Limit State

Immediate Safety Immediate Value Replacement Value 0.80

0.20

0.00

Serviceability

0.10

0.80

0.10

Ultimate

0.00

0.20

0.80

Survivability

To calculate the importance classification factor for each limit state, add the Immediate Safety, Immediate Value and Replacement Value factors together after multiplying them by the appropriate weighting factor. a.

1

Return Periods The return period for each limit state is calculated using a linear relationship between the appropriate average return period limits shown in Table 9-1-4. To calculate the return period, multiply the importance classification factor by the difference between the maximum and minimum return periods and divide by 4. Add this result to the minimum return period to get the final value.

3

1.3.2.3 Base Acceleration Coefficient Maps1 Several base acceleration coefficient maps are provided in this Article to help define the earthquake hazard. Figures 9-1-1, 9-1-2 and 9-1-3 show base accelerations in the United States for return periods of 100 years, 475 years and 2400 years. Figures 9-1-4 and 9-1-5 illustrate base accelerations in Canada for return periods of 100 years and 475 years. Other maps or site-specific procedures may be used to define the base accelerations as long as they are based on accepted methods. Base acceleration coefficients for locations in the United States with return periods other than those provided in Figures 9-1-1 through 9-1-3 may be determined based on the following formulas: • Acceleration for return period, R, less than 475 years R n A R = A 475 æ ---------ö è 475ø A 100 ln æ ------------ö è A 475ø n = -----------------------– 1.558

1

See Part 2 Commentary to Seismic Design for Railway Structures

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Figure 9-1-1. Plate 1 – 100-year Return Period – United States

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AREMA Manual for Railway Engineering

Figure 9-1-2. Plate 2 – 475-year Return Period – United States

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Figure 9-1-3. Plate 3 – 2,400-year Return Period – United States

Seismic Design for Railway Structures

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Figure 9-1-4. Plate 4 – 100-year Return Period – Canada

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Figure 9-1-5. Plate 5 – 475-year Return Period – Canada

Seismic Design for Railway Structures

• Acceleration for return period, R, between 475 years and 2400 years AR = en n = ln(A475) + [ln(A2400) - ln(A475)] x [0.606 x ln(R) - 3.73] AR = Base acceleration coefficient for return period = R A100 = Base acceleration coefficient for return period = 100 years (Figure 9-1-1) A475 = Base acceleration coefficient for return period = 475 years (Figure 9-1-2) A2400 = Base acceleration coefficient for return period = 2400 years (Figure 9-1-3)

1.3.3 PERFORMANCE CRITERIA (1998) R(2009)1 The requirements for each of the following limit states shall be satisfied. 1.3.3.1 Serviceability Limit State2 The serviceability limit state contains restrictions on bridge stresses, deformations, vibrations and track misalignments due to a Level 1 Ground Motion. Critical members shall remain in the elastic range. Only moderate damage that does not affect the safety of trains at restricted speeds is allowed. The structure shall not suffer any permanent deformation due to deformations or liquefaction of the foundation soil.

1

1.3.3.2 Ultimate Limit State3 The ultimate limit state ensures the overall structural integrity of the bridge during a Level 2 Ground Motion. The strength and stability of critical members shall not be exceeded. The structure may respond beyond the elastic range, but displacement, ductility and detailing requirements shall be satisfied to reduce damage and loss of structure use. The damage should occur as intended in design and be readily detectable and accessible for repair. The structure shall not suffer any damage which threatens the overall integrity of the bridge due to deformations or liquefaction of the foundation soil.

3

1.3.3.3 Survivability Limit State4 The survivability limit state ensures the structural survival of the bridge after a Level 3 Ground Motion. Extensive structural damage, short of bridge collapse, may be allowed. Structural and geometric safety measures that add redundancy and ductility shall be used to reduce the likelihood of bridge collapse. Failures of the foundation soil shall not cause major changes in the geometry of the bridge. Depending on the importance and the replacement value of a bridge, an individual railroad may allow irreparable damage for the survivability limit state, and opt for new construction.

1 2 3 4

See Part 2 Commentary to Seismic Design for Railway Structures See Part 2 Commentary to Seismic Design for Railway Structures See Part 2 Commentary to Seismic Design for Railway Structures See Part 2 Commentary to Seismic Design for Railway Structures

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SECTION 1.4 NEW BRIDGES 1.4.1 SCOPE (2004) R(2009) This article applies to bridges with spans not exceeding 500 feet in length. Movable bridges, arch type bridges and bridges with spans exceeding 500 feet in length may require additional analysis and design considerations, which are beyond the scope of this article.

1.4.2 DESIGN APPROACH (2001) R(2006) Bridge design for seismic loads should start with conceptual considerations to select the appropriate bridge type and configuration. The conceptual phase should be followed by analysis for Level 1 Ground Motion to size the various structure members. Finally, appropriate detailing provisions should be incorporated to allow the bridge to respond well during the Level 2 and 3 Ground Motions. Structures located in areas of low ground motion levels need not meet the conceptual design requirements and detailing provisions provided they are capable of withstanding the full Level 3 Ground Motion loadings within the elastic range.

1.4.3 CONCEPTUAL DESIGN (2001) R(2006)1 Conceptual design provisions contained herein should be followed as much as practical. The design should maintain a balance between functional requirements, cost and seismic resisting features. 1.4.3.1 Configuration2 The preferred configuration should be incorporated as shown below when possible. Special design and detailing considerations may be necessary for other configurations.

PREFERRED CONFIGURATION

SPECIAL CONSIDERATION

Straight bridge alignment

Curved bridge alignment

Normal piers

Skewed piers

Uniform pier stiffness

Varying pier stiffness

Uniform span stiffness

Varying span stiffness

Uniform span mass

Varying span mass

1.4.3.2 Superstructure3 The preferred superstructure characteristics should be incorporated as shown below when possible. Special design and detailing considerations may be necessary for other superstructure characteristics.

1 2 3

See Part 2 Commentary to Seismic Design for Railway Structures See Part 2 Commentary to Seismic Design for Railway Structures See Part 2 Commentary to Seismic Design for Railway Structures

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PREFERRED SUPERSTRUCTURE

SPECIAL CONSIDERATION

Simple spans

Continuous spans

Short spans

Long spans

Light spans

Heavy spans

No hinges

Intermediate hinges

1.4.3.3 Substructure1 The preferred substructure characteristics should be incorporated as shown below when possible. Special design and detailing considerations may be necessary for other substructure characteristics.

PREFERRED SUBSTRUCTURE

SPECIAL CONSIDERATION

Wide seats

Narrow seats

Seat bent caps

Integral bent caps

Multiple column

Single column

1.4.3.4 Ground Conditions2

1

Structures should be founded on competent, stable soils or otherwise designed to satisfy the performance requirements during soil instability.

1.4.4 STRUCTURE RESPONSE (2003) 1.4.4.1 Site Coefficient3

4

The Site Coefficient (S) shall be determined from Table 9-1-6 based on the foundation soil characteristics.

1 2 3

See Part 2 Commentary to Seismic Design for Railway Structures See Part 2 Commentary to Seismic Design for Railway Structures See Part 2 Commentary to Seismic Design for Railway Structures

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Table 9-1-6. Site Coefficient Site Coefficient

Soil Type

Description

1

Rock of any characteristic, either shale-like or crystalline in nature, that may be characterized by a shear wave velocity greater than 2,500 feet per second, or stiff soil conditions where the soil depth is less than 200 feet and the soil types overlying the rock are stable deposits of sand, gravel, or stiff clays.

1.0

2

Deep cohesionless or stiff clay conditions where the soil depth exceeds 200 feet and the soil types overlying rock are stable deposits of sands, gravel, or stiff clays.

1.2

3

20 to 40 feet of soft to medium-stiff clays with or without intervening layers of cohesionless soils.

1.5

4

Soil containing more than 40 feet of soft clays or silts, that may be characterized by a shear wave velocity of less than 500 feet per second.

2.0

1.4.4.2 Damping Adjustment Factor1 The Damping Adjustment Factor (D) may be calculated from the following formula. In the absence of more definitive information, a damping adjustment factor of 1.0 shall be used. 1.5 D = æ --------------------------- + 0.5ö è ( 0.4x + 1 ) ø

D= Damping Adjustment Factor

x = Percent Critical Damping (e.g. 5%) 1.4.4.3 Seismic Response Coefficient2 The Seismic Response Coefficient (Cm) to be used in the methods of analysis recommended in Paragraph 1.4.5, shall be calculated from the following formula. For areas with soft soil conditions and high seismicity, or close proximity to known faults, use of a site-specific response spectrum is preferred. 1.2ASD £2.5AD C m = --------------------2¤ 3 Tm Cm= Seismic Response Coefficient for the mth mode A= Base Acceleration Coefficient determined in accordance with Paragraph 1.3.2.3 S= Site Coefficient determined in accordance with Paragraph 1.4.4.1

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See Part 2 Commentary to Seismic Design for Railway Structures See Part 2 Commentary to Seismic Design for Railway Structures

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D= Damping Adjustment Factor determined in accordance with Paragraph 1.4.4.2 Tm= Period of vibration of the mth mode in seconds 1.4.4.4 Low Period Reduced Response1 a.

The seismic response of the bridge may be reduced in accordance with Paragraph 1.4.4.4b if the following provisions are satisfied. (1) The period, T, of the bridge is determined using the effective moment of inertia, Ie, for reinforced concrete substructure members. The effective moment of inertia may be calculated using EQ 2-12 in Chapter 8, Part 2, Paragraph 2.23.7c. (2) The period, T, of the bridge is determined including the effects of foundation flexibility. (3) The bridge response considers the lateral flexibility of the spans between piers. (4) The effects of foundation rocking are accounted for if the moment due to seismic loads exceeds the overturning moment of the footing.

b. The seismic response coefficient, Cm, for bridge structures with periods less than the initial transition period, To, may be determined as follows: Cm = A for T £0.03 seconds

1

( T – 0.03 ) ( 2.5D – 1 ) C m = A 1 + ------------------------------------------------------ for0.03 < T < T o sec onds ( T o – 0.03 ) To = initial transition period = 0.096S A = Base acceleration coefficient from Paragraph 1.3.2.3 T = Period of vibration D = Damping adjustment factor from Paragraph 1.4.4.2 S = Site coefficient from Paragraph 1.4.4.1

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1.4.5 ANALYSIS PROCEDURES (2003)

4

1.4.5.1 General 1.4.5.1.1 Serviceability Limit State2 Methods based on elastic analysis shall be used to determine stresses and deformations for the serviceability limit state. The methods recommended include: (1) Equivalent Lateral Force Procedure that is applicable to regular bridges and (2) Modal Analysis Procedure for multi-span irregular bridges. 1.4.5.1.2 Ultimate and Survivability Limit State3 Conceptual design methods shall be used to ensure satisfactory performance for both the ultimate and the survivability limit states. Recommendations for the selection of an appropriate bridge type, geometry and

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See Part 2 Commentary to Seismic Design for Railway Structures See Part 2 Commentary to Seismic Design for Railway Structures See Part 2 Commentary to Seismic Design for Railway Structures

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materials and requirements for ductility, redundancy and good detailing, as described in Article 1.4.2, Article 1.4.3, and Article 1.4.7, shall be incorporated. Non-ductile, non-redundant primary load carrying elements of structures shall be designed to satisfy the performance criteria with respect to Level 2 and/or Level 3 Ground Motions. The design forces shall be the lesser of the seismic loads or the maximum forces which can be transmitted to the element. The seismic loads may be computed by increasing the Level 1 Ground Motion forces by the ratio of the Base Acceleration Coefficients. 1.4.5.2 Procedure Selection1 The selection of the analysis procedure for the serviceability limit state shall be based on the bridge configuration as shown in Table 9-1-7.

Table 9-1-7. Analysis Procedure Selection Bridge Configuration Analysis Procedure1 Single-span

No analysis required

Two-span

ELF or MA Procedure

Multi-span regular Multi-span

2

irregular2

ELF or MA Procedure MA Procedure

Notes: 1. ELF denotes Equivalent Lateral Force Procedure, MA denotes Modal Analysis Procedure. 2. Irregular bridges are those structures with significantly irregular configuration or support stiffness. 1.4.5.3 Equivalent Lateral Force Procedure2 The Equivalent Lateral Force Procedure may be used for two-span bridges or multi-span regular bridges as described in Paragraph 1.4.5.2. The procedure is described below. a.

Calculate the Seismic Response Coefficient (Cm) for each of the two principal directions of the structure as follows. (1) Calculate the natural period of vibration (Tm) for each of the two principal directions of the structure using any commonly accepted method. (2) Calculate the Seismic Response Coefficient (Cm) for each of the two principal directions of the structure from Paragraph 1.4.4.3 “Seismic Response Coefficient.”

b. Perform static analysis on the bridge in each of the two principal directions. (1) Calculate the distributed seismic load in each direction from the following formula.

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See Part 2 Commentary to Seismic Design for Railway Structures See Part 2 Commentary to Seismic Design for Railway Structures

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p ( x ) = Cm w ( x ) p(x) = distributed seismic load per unit length of bridge Cm= Seismic Response Coefficient w(x) = distributed weight of bridge per unit length (2) Distribute the seismic load to individual members based on the stiffness and support conditions. c.

Combine the loads in each of the two principal directions of the structure to get the final seismic design loads. (1) Combination 1: Combine the forces in principal direction 1 with 30% of the forces from principal direction 2. (2) Combination 2: Combine the forces in principal direction 2 with 30% of the forces from principal direction 1.

1.4.5.4 Modal Analysis Procedure1 The Modal Analysis Procedure may be used for any structure configuration. The procedure is described below. a.

Develop elastic response spectra from Paragraph 1.4.4.3 “Seismic Response Coefficient.”

b. Perform dynamic analysis on the structure in each of the two principal directions using the elastic response spectra to determine the individual member loads.

1

(1) A mathematical model should be used to calculate the mode shapes, frequencies and member forces. The model should accurately represent the structure mass, stiffness and support conditions. (2) An adequate number of modes should be included so that the response in each principal direction includes a minimum 90% mass participation. c.

Combine the loads in each of the two principal directions of the structure using one of the following methods to get the final seismic design loads. (1) SRSS Method - Combine forces in individual members using the square root of the sum of the squares from each principal direction.

4

(2) Alternate Method - Perform two load combinations for investigation. (a) Combination 1: Combine the forces in principal direction 1 with 30% of the forces from principal direction 2. (b) Combination 2: Combine the forces in principal direction 2 with 30% of the forces from principal direction 1.

1

3

See Part 2 Commentary to Seismic Design for Railway Structures

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1.4.6 LOAD COMBINATIONS AND RESPONSE LIMITS (2002)1 R(2007) a.

The loads shall be combined in accordance with the formulas in Table 9-1-8 based on the structure material. These combinations shall be used in lieu of those specified in Chapter 8 Concrete Structures and Foundations, Part 2 Reinforced Concrete Design and Chapter 15 Steel Structures, Part 1 Design for seismic loads. Table 9-1-8. Load Combinations Material

Design Method

Combination1, 2

Steel

Allowable Stress Design

D + E + B + EQ

Concrete

Load Factor Design

1.0D + 1.0E + 1.0B + 1.0PS + 1.0EQ

D= Dead Load E= Earth Pressure B= Buoyancy PS= Secondary Forces from Prestressing EQ= Earthquake (Seismic) NOTE: (1) Effects of other loads, such as stream flow pressure, live load and friction shall be included if they have a significant likelihood of acting concurrently with earthquake loads. (2) Buoyancy loads should be based on the water level that has a significant likelihood of occurring concurrently with earthquake loads and produces the most conservative load combination. b. The response limits given in Table 9-1-9 shall be satisfied for each structure material. Table 9-1-9. Response Limits Material

Stress

Steel

The allowable stresses used in Chapter 15, Steel Structures, Part 1, Design may be increased by 50%.

Concrete

The design strengths should be used as specified in Chapter 8, Concrete Structures and Foundations.

1.4.7 DETAILING PROVISIONS (2001) R(2006)2 Appropriate detailing provisions shall be incorporated into the structure to meet the performance requirements for the Level 2 and 3 Ground Motion.

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See Part 2 Commentary to Seismic Design for Railway Structures See Part 2 Commentary to Seismic Design for Railway Structures

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Seismic Design for Railway Structures 1.4.7.1 Continuity Provisions1 The structure shall be designed with an uninterrupted load path to transfer lateral forces from the superstructure to the ground. 1.4.7.1.1 Superstructure2 The superstructure shall be designed to carry the lateral forces to the bearings or shear connectors. The lateral forces from the span may be carried to the end supports by the following load paths: a.

Lateral bracing system.

b. Lateral bending of the girders, including torsional effects as applicable. c.

Diaphragm action of concrete decks or steel ballast pans provided that the deck is adequately connected to the girders.

End cross frames or diaphragms shall be designed to carry the lateral forces to the bearings or shear connectors. 1.4.7.1.2 Bearings3 The bearings shall be designed to transfer the lateral forces to the substructure. Bearings may be supplemented by shear connectors to help transfer the lateral forces provided that the movement required to engage the shear connectors does not cause failure of the bearing device.

1

1.4.7.2 Ductility Provisions4 The ductility provisions contained herein shall be incorporated into the structure design. 1.4.7.2.1 Longitudinal Reinforcing Confinement5

3

Longitudinal reinforcing in concrete columns, pier walls and piles shall be adequately confined to allow the member to respond in the post-yield range. This requirement may be met by the following provisions. a.

Concrete columns and concrete piles fixed at the pile cap shall meet the following requirements: (1) The volumetric ratio of spiral or circular hoop reinforcement in the plastic hinge zone shall not be less than: f¢ c r s ³ 0.12 -------fy r s ³ that required by Chapter 8, Article 2.11.2

1 2 3 4 5

See Part 2 Commentary to Seismic Design for Railway Structures See Part 2 Commentary to Seismic Design for Railway Structures See Part 2 Commentary to Seismic Design for Railway Structures See Part 2 Commentary to Seismic Design for Railway Structures See Part 2 Commentary to Seismic Design for Railway Structures

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(2) The total cross-sectional area of rectangular hoop reinforcement in the plastic hinge zone shall not be less than: f¢ c A g A sh ³ 0.3 æ sh c --------ö æ ---------- – 1ö ø è f y ø è A ch f¢ c A sh ³ 0.09sh c -------fy Ach = cross-sectional area of a member measured out-to-out of confinement reinforcement. Ash = total cross-sectional area of hoop reinforcement, including cross-ties. hc = cross-sectional dimension of member core measured center-to-center of confinement reinforcement. (3) The longitudinal spacing of the confinement reinforcement in the plastic hinge zone shall not be greater than: s £ that required by Chapter 8, Article 2.11.2 s £ one-quarter of the minimum member dimension s £ six times the diameter of the longitudinal reinforcement s £ 6” (150 mm)

14 – h x 350 – h x ì ü s £ 4² + æ -------------------ö inches í s £100 + æ ----------------------ö mm ý è 3 ø è ø 3 î þ hx = maximum transverse spacing (inches or mm) of hoop or cross-tie legs (4) The transverse spacing of hoop or cross-tie legs in the plastic hinge zone shall not exceed 14 inches (350 mm). (5) The length of the plastic hinge zone from the joint face shall not be less than: l o ³ the depth of the member l o ³ one-sixth of the clear span of the member l o ³ 18” (450 mm) lo = length of plastic hinge zone from the joint face

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(6) The longitudinal spacing of the column confinement reinforcement outside the plastic hinge zone shall not be greater than: s £ six times the longitudinal reinforcement diameter s £ 6” (150 mm) s £ that required by Chapter 8, Article 2.11.2 (7) The design shear force shall be determined from consideration of the maximum forces that can be generated at the faces of the joints at each end of the member. These joint forces shall be determined using the member strength defined in Paragraph 1.4.7.3.1.b. (8) The confinement reinforcement in the plastic hinge zone shall be proportioned to resist shear assuming the nominal concrete shear strength is zero when the shear force determined in Paragraph 1.4.7.2.1.a.(7) is greater than one-half the maximum required shear strength in this area and the factored axial compressive force for the seismic load condition is less than Agf 'c/20. b. Reinforced concrete pier walls with axial loading below the lesser of 0.4Pb or 0.1f 'cAg may be exempted from the column transverse reinforcing requirements if the ratio of the Level 3 Ground Motion acceleration to the Level 1 Ground Motion acceleration is less than or equal to 2. The reinforcing shall meet the following requirements:

1 (1) Minimum percent of horizontal reinforcing is 0.25%. (2) Cross ties shall have a minimum cross sectional area of 0.2 in2 (129 mm2) with a 135° hook on one end and a 90° hook on the opposite end and shall be placed so that the 90° and 135° hooks of adjacent ties shall be alternated both horizontally and vertically. (3) Spacing of all horizontal bars and cross ties shall not exceed 12 inches (300 mm) in any direction, except vertical spacing shall not exceed 6 inches (150 mm) in plastic hinge zones.

3

1.4.7.2.2 Splices in Reinforcing1 Lap splices are not allowed in a main load carrying member within a distance “d” (effective depth) of any area designed to respond in the post-yield range. 1.4.7.3 Provisions to Limit Damage2 The following provisions shall be incorporated into the design to limit damage. 1.4.7.3.1 Weak Column Provisions3 Reinforced concrete columns which are designed to respond in the post-yield range shall be detailed to prevent damage to adjacent superstructure, bent cap and foundations. This requirement may be met by the following provisions:

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See Part 2 Commentary to Seismic Design for Railway Structures See Part 2 Commentary to Seismic Design for Railway Structures See Part 2 Commentary to Seismic Design for Railway Structures

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a.

Concrete column longitudinal reinforcement shall comply with ASTM A706. ASTM A615 reinforcement shall be permitted if the actual yield strength based on mill tests does not exceed the specified yield strength by more than 18000 psi (124 MPa) and the ratio of the actual ultimate tensile strength to the actual tensile yield strength is not less than 1.25.

b. The bent cap and foundation shall be designed for the lesser of 1.3 times the nominal column strength or the Level 3 ground motion load. c.

The plastic hinge zone should be designed to occur in locations that can be inspected.

1.4.7.3.2 Concrete Joints1 The joint shall be configured and reinforced to reduce the likelihood of damage to the superstructure and bent cap and foundation. This requirement may be met by the following provisions: a.

Concrete column joints with superstructure, bent cap and foundation shall be designed in accordance with the following provisions: (1) Column longitudinal reinforcement shall extend as close as practical to the far face of the adjoining member, but not less than: For hooked bars in tension: l dh ³ that required by Chapter 8, Section 2.17 l dh ³ 8d b l dh ³ 6² ( 150mm ) fy db fy db æ ö l dh ³ ------------------- inches ç l dh ³ --------------------- mm÷ 65 f¢ c 5.4 f¢ c è ø For straight bars: l d ³ that required by Chapter 8, Sections 2.14 through 2.16 l d ³ 2.5 times that required in this Article for hooked bars in tension (2) Confinement reinforcement shall be provided throughout the joint to the end of the longitudinal column reinforcement in an amount equal to the greater of that specified in Article 1.4.7.2.1a or Paragraph b of this Article. (3) The nominal shear strength of the joint shall not be taken greater than: 20 f c ¢ psi ( 1.7 f¢ c MPa )

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See Part 2 Commentary to Seismic Design for Railway Structures

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b. Concrete column joints where the column is integral with the bent shall meet the following requirements: (1) Vertical stirrups with a total area of 0.16 times the area of longitudinal column reinforcement shall be placed on each moment resisting side of the column within a distance of half the column width from the column face. (2) Vertical stirrups with a total area of 0.08 times the area of longitudinal column reinforcement shall be placed within the column width. (3) The top and bottom bent cap and integral superstructure flexural reinforcement in the area of the joint shall be increased by 0.08 times the area of longitudinal column reinforcement and adequately developed or hooked beyond the columns at the ends. (4) The volumetric ratio of column transverse reinforcement carried into the cap shall not be less than 0.4 times the area of longitudinal column reinforcement divided by the square of the longitudinal column reinforcement embedment length into the cap. 1.4.7.3.3 Steel Joints Joints in main lateral load carrying steel members shall be designed to be stronger than the adjoining member. This requirement may be met by designing the connections for the lesser of 1.3 times the connecting member yield strength or the Level 3 ground motion load. Slip-critical bolts may be designed to carry the higher ground motion loads by bearing rather than friction.

1

1

1.4.7.4 Redundancy Provisions

The redundancy provisions listed below are suggested to increase survivability during the higher level ground motion events. 1.4.7.4.1 Bearing Seats2

3

Bearing seats should be proportioned to accommodate the maximum relative movements caused by earthquakes. This requirement may be met by the following provision: Bearing seats supporting the ends of girders which are allowed to move relative to the seat during an earthquake shall be designed to provide a minimum support width, N, measured normal to the face of the abutment or pier, not less than that specified below: N = (12 + 0.03L + 0.12H)(1+0.000125S2) inches {N = (305 + 2.5L + 10H)(1+0.000125S2) mm}

L = length (ft or m) of the bridge deck to the adjacent movement joint, or to the end of the deck. S = angle of skew (degrees) measured from a line normal to the span. H = At abutments, H is the average height (ft or m) of piers supporting the bridge deck to the next movement joint, or H = 0 for single span bridges. At piers, H is the pier height (ft or m).

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See Part 2 Commentary to Seismic Design for Railway Structures See Part 2 Commentary to Seismic Design for Railway Structures

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Seismic Design for Railway Structures 1.4.7.4.2 Shear Connectors1 Shear connectors may be provided to resist the maximum seismic loads. The shear connectors should be positioned so that they are engaged prior to failure of the bearing device. 1.4.7.4.3 Span Ties Span ties may be used to reduce the likelihood of unseating during the higher level ground motion events. The spans may be tied together by alternate means through the bent caps such as by anchor bolts, shear rods or common bearing plates provided the load path is adequately verified. The span ties shall be designed to allow for the effects of thermal movement of the span. 1.4.7.4.4 Foundation Rocking2 Foundation rocking response may be used to satisfy the performance requirements for the Level 3 Ground Motion for non-ductile single pier foundations. The analysis should be conducted in accordance with well established procedures. New bridge design using rocking response shall have bearing blocks at the toe and heel of the footing with elastomeric material placed between the footing and bearing blocks. 1.4.7.4.5 Continuous Welded Rail3 Continuous welded rail (CWR) may be evaluated as a redundant load path for seismic loads or to increase bridge damping provided the following requirements are satisfied: a.

No expansions joints are allowed in the CWR over the bridge length and at least 200 feet (60 meters) onto the embankments.

b. CWR shall be adequately anchored to the ties over the bridge length and at least 200 feet (60 meters) onto the embankments.

SECTION 1.5 EXISTING BRIDGES 1.5.1 SCOPE (2004) This part of the chapter will address the extent to which existing bridges should be reviewed for resistance to seismic forces. In those areas where the horizontal acceleration shown in Figure 9-1-2 exceeds 10% of gravity, existing bridges should be reviewed for resistance to seismic forces.

1.5.2 INVENTORY (1995)4 R(2004) Of first importance is recognizing what existing bridges are in areas subject to seismic events. Equally important is knowing what construction of others is on, over and under the operating property in these areas. The accumulation of this information is found, or best contained, in inventory or inspection records. All such records, not so noting, should be modified to provide for indicating the bridge is in a seismic activity zone. 1 2 3 4

See Part 2 Commentary to Seismic Design for Railway Structures See Part 2 Commentary to Seismic Design for Railway Structures See Part 2 Commentary to Seismic Design for Railway Structures See Part 2 Commentary to Seismic Design for Railway Structures

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Further, these records should note constructions which have been designed, or analytically shown, to be seismic resistant. A reference to the level of resistance might be included.

1.5.3 HISTORY (1995)1 R(2004) Existing bridges in areas of seismic activity can be expected to have a history of response to various levels of seismic activity. To a large extent, the need for and direction of analytical investigation can be based on the response of the bridges to past events. In order to take advantage of past experience, it is necessary to develop and correlate event and results histories. A detailed history of seismic events, based on public records, could be developed for each area of interest to the railway, The length of the history would be determined by the oldest in-service structure within the area. Statistical analysis of the data might be used to reduce the volume to more manageable ranges of values. A history of the results of seismic activity would be assembled from railway inventory records or inspection reports, and other sources such as news media archives and witness oral accounts. Further, current inspection routines could be modified to specifically make observations designed to detect evidence of past seismic events.

An investigator developing a seismic history would be expected to have experience in the field of seismology. An investigator correlating seismic history and results records would be expected to have experience in the field of engineering forensics.

1

1.5.4 ASSESSMENT AND RETROFIT (2011) 1.5.4.1 General All bridges supporting track, except certain timber trestles, and all other bridges owned by the railway which support pedestrian or human operated vehicle traffic should be screened, evaluated or analyzed for resistance to seismic loads, except in areas where the value on Figure 9-1-2 is 10 or less.

3

1.5.4.2 Timber Trestles Exclusion Timber trestles may be screened and eliminated from further evaluation if they are free of conditions that would require attention in the near future to permit continuation of normal railroad traffic. Seismic evaluation of timber trestles not eliminated by screening should focus on the potential effect of a seismic event on deficient conditions or details. 1.5.4.3 Investigation of Railway Owned Bridges The analysis of an existing bridge for its response to a seismic load shall be conducted in accordance with the applicable provisions of Section 1.4, New Bridges. The results of this investigation will determine the level of seismic load the structure is capable of withstanding. The Engineer may, when justified by historic event/results data, declare a bridge structure resistant to a specific level of seismic load.

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See Part 2 Commentary to Seismic Design for Railway Structures

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Seismic Design for Railway Structures 1.5.4.4 Investigation of Bridges Owned by Others The Engineer may require that the Owner of a bridge over the operating right-of-way of the railway certify that the structure is of a design resistant to a specific level of seismic load. Such certification shall be furnished in a form determined by the Engineer and shall be attested to by a professional licensed to render such judgment. 1.5.4.5 Retrofit Designs Railroads may decide to retrofit bridges to minimize the potential for human casualties and major property loss in the event of an earthquake, or to expedite restoration of service following an earthquake. It is recognized that few structures can be made totally resistant to the effects of an earthquake of great magnitude. The likelihood and severity of loss must therefore be balanced against the cost of retrofit. a.

Many different schemes of retrofit are available for various types of bridges. These schemes generally accomplish their purposes by one or a combination of the following: (1) Changing characteristic frequencies of response to reduce seismic forces in the structure. (2) Strengthening components of the structure to accommodate the seismic loads. (3) Providing alternate paths for seismic forces within the structure. (4) Accommodating displacements with catchers, stoppers, enlarged bearing areas or other devices. (5) Providing for “yielding type response” at non-crictical points of the structure to relieve seismic stresses.

b. The following factors should be considered in any retrofit design: (1) Retrofit design must be site specific and must consider the condition and stability of the existing structure, including soils and foundation. (2) Attachments of substructure to superstructure must permit normal movement of the structure. (3) Behavior of the retrofit system shall not cause damage to the primary structure which would preclude promptly returning the structure to service after a seismic event. (4) Retrofits must permit both routine and post-seismic inspection, repair, and component replacement. c.

Primary retrofit designs would provide catchment areas with stop blocks to retain dislocated bearing areas. The design would consider guides to return vertically separated members to the foundation area, and provide for returning the structure to its design location.

SECTION 1.6 OTHER FACILITIES AND INFRASTRUCTURE 1.6.1 SCOPE (2007) Considerations for seismic effects on new and existing railroad facilities and infrastructure, other than bridges, are provided in this section. These facilities and infrastructure include, but are not limited to, track and roadbed, culverts, retaining walls, tunnels, track protection sheds, stations, office and shop buildings,

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locomotive fueling facilities, utilities, signal and communication facilities. Rail transit facilities and infrastructure are also addressed herein. General considerations include assumptions of seismic resistance, areas of seismic vulnerability and recommendations to improve seismic performance. Detailed procedures for performing seismic design of other railroad facilities and infrastructure are beyond the scope of this section. In those areas where the horizontal acceleration for the 475-year return period does not exceed 10% of gravity, no consideration for seismic effects on these other facilities and infrastructure is deemed necessary.

1.6.2 TRACK AND ROADBED (2007)1 The largest potential danger to track and roadbed in an earthquake is from failures in the subgrade due to slumping or liquefaction of the soils. This potential can be significantly reduced by eliminating excess water from ballast pockets and saturated embankments. French drains or drainpipes can be very effective. The track and ballast can also be disturbed in earthquakes, but the potential for extensive damage to track is low. During the shaking process the stability of the ties and ballast will be momentarily weakened and if the rail is in compression it can buckle. The shaking may also result in surface and alignment deviations, loss of welded rail neutral temperature, jointed rail gapping or the loss of superelevation in curves. Primarily, the nature of concern with track following an earthquake is the availability of equipment to reestablish surface and line and welded rail neutral temperature or jointed rail gaps where track has been disturbed. 1.6.2.1 Track Structure

1

The existing track structure and all manner of special trackwork, including the rail, cross ties, other track material, and the ballast section is presumed resistant to all levels of seismic forces, but not to displacements caused by offset across a fault or other gross ground movements, including liquefaction. Existing track facilities constructed by direct fixation of rail to a continuously reinforced concrete slab is presumed equally resistant to all levels of seismic forces.

3

1.6.2.2 Fills and Earth Cuts Variations in soil materials and soil moisture contents found within existing fills and earth cuts in any areas in general, economically precludes adequate data collection for analysis of the site conditions. The Engineer may, based on the geometry, the applicable standards of construction and a conservative estimate of existing soil properties, make an analysis of slope stability for the general case. The magnitude of the seismic force should be calculated as a function of the vertical acceleration component of the design event. The combination will affect both magnitude and direction of the resultant force exerted by the mass above the failure (sliding) surface. This load would be applied as a uniform dead load surcharge at the level of the centroid of the mass. The Factor of Safety against sliding would be determined based on risk factors, and a value close to unity may be acceptable. Fills founded on sloping strata or on strata of high moisture content should be given special attention. Retrofit designs for fills would include stabilization by piling, toe berms and revised side slope run-to-rise ratios. Earth cut retrofit designs include stabilization by piling and revised side slope run-to-rise ratios.

1

See Part 2 Commentary to Seismic Design for Railway Structures

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Seismic Design for Railway Structures 1.6.2.3 Rock Cuts Analytical investigation of rock cuts, as groups or as individual structures, is generally not practical. The Engineer should review the history of rock scaling programs for evidence of an extraordinary frequency of work at a specific site. Retrofit designs include increased scaling efforts, rock stabilization by bolting or other means, increasing existing bench catchment capacity and selective rebenching.

1.6.3 CULVERTS (2007) Drainage structures are subject to damage from distortion of the soils in which they are embedded. The most important consideration with culverts is that they maintain their ability to function following an event. Slumping and slope failures of the embankments can result in the ends of culverts becoming constricted, obstructed and/or buried. Consideration should therefore be given on new construction or during major maintenance projects protect or to lengthen the ends where this appears to be of practical benefit. Culverts are presumed to be of a design generally resistant to seismic forces, but not to displacements due to fault rupture at the site, and to other large ground movements such as those caused by soil liquefaction. One method to improve resistance to failure due to ground displacement is the provision of flexible joints. Retrofit designs include installation of structural linings throughout the culvert. New construction may be required.

1.6.4 RETAINING WALLS (2007)1 There are few, if any, unique railroad-specific issues related to retaining wall seismic design. There are a number of precautions to be taken in designing and constructing earth retaining structures in high seismic areas. The primary need is to minimize potential for the retained earth to absorb and retain excess moisture. If the soil moisture increases appreciably above the optimum level used for good compaction, there can exist a potential for the soil to liquefy in an earthquake. This would immediately increase lateral loads which could result in lateral displacement, tilting or complete failure of the retaining wall. Gravity-type structures should be designed to fail by sliding rather than by overturning, thereby taking advantage of active earth pressures developed by the sliding, and also thereby reducing the seismic induced earth pressures. Rigidly fixed structures could be subjected to very high soil forces that could only be reasonably predicted through an intensive soils investigation and analysis. Unless supported by a pile foundation, cantilever walls should be designed so that the design failure mode is sliding rather than overturning or collapse. In summary, designers should minimize any potential for tilting in their design, take full advantage of active earth pressures and drain the retained earth or use other methods, such as capping, to minimize or eliminate any potential for liquefaction.

1

See Part 2 Commentary to Seismic Design for Railway Structures

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1.6.5 TUNNELS AND TRACK PROTECTION SHEDS (2007) 1.6.5.1 Tunnels1 Tunnels are presumed to be of a design generally resistant to seismic forces, but not to displacements due to fault rupture at the site, and to other large ground movements such as those caused by soil liquefaction. Existing tunnel conditions should be reviewed to determine susceptibility to damage in a seismic event. Specific attention should be paid to the design of and conditions at the portal structure. The Engineer should review the history of tunnel maintenance programs for evidence of an extraordinary frequency of work at specific locations. New tunnel design is beyond the scope of this chapter. Retrofit designs include increased scaling efforts, rock stabilization by bolting or other means, and the installation of linings at unlined sites. 1.6.5.2 Track Protection Sheds The superstructures of track protection sheds are, by the nature of their function, presumed to be of a design generally resistant to seismic forces. In active seismic regions, consideration should be given to review existing sheds for resistance to seismic forces, particularly in the transverse direction, applying the appropriate design accelerations. Primary retrofit designs would provide catchment areas with stop blocks to limit the dislocation of column and beam bearing areas. The design should consider guides to return vertically separated members to the foundation area, and purchase points or jacking blocks for returning the structure to its design location.

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1.6.6 BUILDINGS AND SUPPORT FACILITIES2 (2007) Seismic design loads and other requirements for railroad building and support facilities should be governed by the Uniform Building Code or other applicable local, state or federal regulations.

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Building codes address the structural adequacy of the building with regard to life-safety but do not necessarily address functionality of railroad facilities. In addition to the safety of occupants, continuing function of the building and the equipment, which it contains, can be of great importance to the railway. The fact that a structure situated in a seismic activity zone currently exists in an acceptable state of maintenance does justify the presumption that a level of seismic-resistant design is inherent to the construction. It does not, however, permit the presumption that the structure has been subjected to the maximum seismic loading anticipated for the zone.

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The fact that a structure of a specific structural design performed successfully at a given level of seismic loading does not justify the presumption that all structures of that design will perform equally at that level of loading. The foundation conditions of a structure are of primary importance in determining resistance to seismic forces. Seismic load analysis of a structure is site specific. The results of one analysis may not be transferred to a second structure except in the case where each and every design parameter is exactly equal.

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See Part 2 Commentary to Seismic Design for Railway Structures See Part 2 Commentary to Seismic Design for Railway Structures

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Appurtenances associated with these facilities, such as storage racks, tanks, machinery, and stand-by generators, need specific attention. These need to be attached to the structure to resist overturning and shear in order to remain safe and operable.

1.6.7 UTILITIES, SIGNAL AND COMMUNICATION FACILITIES (2007) Seismic design and maintenance of railroad utility services shall be governed by the Uniform Building Code or other applicable local state or federal regulations. Utility services includes, but is not limited to, electric power supply, water, gas, fuel pipe lines, fire sprinkler system, heating and air conditioning, waste water treatment, water treatment, fuel storage, oil storage and distribution systems. Design and maintenance of environmental facilities should consider seismic forces and other requirements as provided for by the Uniform Building Code and the applicable environmental regulatory agency. Additional consideration shall be made with respect to failure-risk factors and potential impact in high environmentally sensitive areas. Some facilities may be required to have spill prevention, containment and countermeasure plans in case of a seismic event. The following measures are currently practiced to reduce the possibility of damage to the signal system. In new instrument bungalows, shelf-type relays are suspended with coil springs, providing additional seismic force reduction to reduce the possibility of overturning and of electrical relays setting. In existing instrument bungalows, a process has been initiated for securing the relays to shelves with straps.

1.6.8 RAIL TRANSIT (2007) AREMA Committee 12, Rail Transit, deals primarily with transit systems. As with other topics, Chapter 12 Rail T ransit, will include references to this chapter on seismic guidelines for bridges, buildings, support facilities, track and roadbed items. The Structure Importance Classification of Rail Transit Facilities will be high due to a maximum value for Immediate Safety and Immediate Value.

SECTION 1.7 CONSTRUCTION OF OTHERS (2007) Existing construction by others on the operating right-of-way should be reviewed for compliance with seismic code governing the type of construction involved. The Engineer may require the Owner of such construction to certify that the structure is of a design resistant to a specific level of seismic force. Such certification should be furnished in a form determined by the Engineer and should be sealed by a professional licensed to render such judgments.

SECTION 1.8 RETIRED FACILITIES (2007) To the extent possible, abandoned railroad right-of-way structures, such as bridges, buildings and facilities should be removed to their foundation level as soon as possible after the time they are removed from service. Economic justification of expenditures for this work should include avoidance of analytical costs necessary to

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show the structure is stable and the reduced exposure to liability arising from failure of the retired construction during a seismic event.

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Part 2 Commentary to Seismic Design for Railway Structures1 — 2009 — FOREWORD

The purpose of this part is to furnish the technical explanation of various Articles in Part 2, Commentary to Seismic Design for Railway Structures. In the numbering of Articles of this Section, the numbers after the “C-” correspond to the Section/Article being explained.

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TABLE OF CONTENTS Section/Article

Description

Page

C-

Section 1.2 Post-Seismic Event Operation Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . C -1.2.2 Guidelines (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9-2-2 9-2-2

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Section 1.3 General Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C -1.3.1 Approach (2004) R(2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C -1.3.2 Ground Motion Levels (2004) R(2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C -1.3.3 Performance Criteria (2006) R(2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

9-2-4 9-2-4 9-2-5 9-2-9

C-

Section 1.4 New Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C -1.4.3 Conceptual Design (2001) R(2006). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C -1.4.4 Structure Response (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C -1.4.5 Analysis Procedures (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C -1.4.6 Load Combinations and Response Limits (2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C -1.4.7 Detailing Provisions (2001) R(2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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C-

Section 1.5 Existing Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C -1.5.2 Inventory (1995) R(2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C -1.5.3 History (1995) R(2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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C-

Section 1.6 Other Facilities and Infrastructure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C -1.6.2 Track and Roadbed (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C -1.6.4 Retaining Walls (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C -1.6.5 Tunnels and Track Protecting Sheds (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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References, Vol. 94, 1994, p.110; Vol. 96, p. 64, Vol. 97, p. 113.

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TABLE OF CONTENTS (CONT) Section/Article Description C -1.6.6 Buildings and Support Facilities (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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LIST OF FIGURES Figure Description 9-C-1 Acceleration vs. Return Period . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-C-2 Normalized Response Spectra with Low Period Reduced Response . . . . . . . . . . . . . . . . . . . . . . 9-C-3 Normalized Response Spectra. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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LIST OF TABLES Table Description 9-C-1 Damping Values for Structural Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-C-2 Exceptions to Seismic Response Coefficient . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-C-3 FRA Horizontal Track Alignment Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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C - SECTION 1.2 POST-SEISMIC EVENT OPERATION GUIDELINES C - 1.2.2 GUIDELINES (2009) C - 1.2.2.1 Operations The post-seismic event operation guidelines are intended for use where experience or adequate knowledge of regional attenuation rates is not available. The response guidelines are based primarily on decades of experience with earthquakes in California. They provide the basis for a policy for areas where attenuation rates are relatively high, such as California. A more conservative policy is appropriate in areas where seismic experience is limited and/or attenuation rates are relatively low. These conditions exist in most of central and eastern North America. Seismic attenuation models were used to extend the California guidelines to cover other areas of North America. Where justified by adequate experience and/or analysis, a less conservative policy may be appropriate. For earthquakes of 6.0 (Richter) and greater, a two-level response is recommended. In areas closer to the epicenter, operations are more restricted. In areas further from the epicenter, a zone of less restrictive response is recommended. This less restrictive zone may be useful for moving trains away from the affected zone. Further information on the response levels is found in Reference 23. In 1998, the Association of American Railroads (AAR) conducted a study of seismic attenuation rates in various regions in North America, primarily the United States and Canada (Reference 23). The study reviewed the response policies of four railroads, the various seismological regions in North America, and the corresponding seismic attenuation models. The seismic attenuation models were used to extend California-based policies to cover other areas of North America, based on equivalent levels of acceleration. The development of one railroad’s response policies, including extension of California-based policies to other regions, is described in Reference 6. Examples of findings in post-earthquake inspections of railroad infrastructure can be found in Reference 7, 16, 19 and 22.

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Commentary to Seismic Design for Railway Structures C - 1.2.2.3.7 Other Structures It may be desirable to have an arrangement with a technically and legally qualified engineer to inspect essential buildings immediately after an earthquake so that their safety can be determined and certified to avoid unnecessary evacuations and/or restrictions on building use. Essential buildings would include, among others, dispatching centers, yardmaster’s towers, shop facilities, fueling facilities, buildings containing certain communications facilities, and, for lines with commuter service, passenger stations. C - 1.2.2.4 Tsunamis Tsunamis are associated with large offshore, and some near-shore, earthquakes. In some cases, they have been a primary source of earthquake-associated damage. Of about 100 earthquakes known to have damaged railroads, fewer than 40 have occurred in locations where they could possibly have caused tsunamis. Tsunamis associated with eight of these caused significant railroad damage. They washed out embankments, washed spans off bridges and overturned rolling stock along coasts near the earthquakes. Because of its very long wavelength, a tsunami behaves as a shallow surface wave. Its amplitude in mid-ocean is very small; as it approaches land, the amplitude builds up and all the energy of the original disturbance is concentrated into a few wavelengths with devastating results, erroneously called a tidal wave. In addition to damage in the immediate area of the earthquake, tsunamis have caused damage at large distances from the earthquake. The tsunami generated by the December 26, 2004 magnitude 9.0 earthquake off the coast of Sumatra washed a train off a track adjacent to the coast in southern Sri Lanka, killing a large number of passengers. Alaskan earthquakes have caused damage and loss of life in Hawaii and California and significant damage in Oregon and Washington. Earthquakes near Chile have caused damage and loss of life in Japan. Hawaii, Japan and some other islands in the Pacific appear particularly vulnerable to tsunamis from distant earthquakes. Evaluation of the potential hazard to coasts of North America is appropriate. Some railroad lines are adjacent to the coast in Alaska, Washington, California, and a few locations in Mexico, and the Alaska Railroad was damaged by a tsunami in 1964. The Washington coast and west coast of Mexico are subject to earthquakes that could generate large tsunamis. Tsunamis have been generated by submarine landslides due to earthquakes in California. There is a small, but definite, risk of tsunamis affecting the Atlantic coast. Tsunami hazard can be considered in two scenarios: tsunamis generated by nearby earthquakes, and those generated by distant earthquakes. An earthquake near Santa Barbara, CA in 1812 caused a tsunami that produced a run-up (increase in the water surface elevation) of about 10 feet at the coast in the area. Tsunamis from northern California earthquakes in 1859 and 1868 caused local run-ups of between 10 and 15 feet along the coast and in San Francisco Bay. The March 28, 1964 Alaska earthquake caused a tsunami that produced run-ups in the 10 foot to 15 foot range at locations in Washington, Oregon and northern California. About 1100 years ago, a tsunami with wave heights in the 15 to 20 foot range apparently occurred in Puget Sound due to a magnitude 7, or larger, earthquake on the Seattle fault (Reference 17). A study prepared for the U.S. Nuclear Regulatory Commission indicates maximum tsunami wave heights for distant earthquakes of about 4 feet, in deep water off the coast, for both Washington and southern California, and up to 7 feet for northern California, with the height increasing dramatically as the wave moves into more shallow coastal waters. In the case of Washington, the narrow channels and islands between the open ocean and the Puget Sound coast could reduce the wave height from the height at the outer coast. In the case of California, the coast is exposed. Advance warnings would be issued by the West Coast & Alaska Tsunami Warning Center of the National Weather Service one to several hours before arrival of the first wave, with identification of vulnerable coastal areas. The waves generated by a nearby earthquake will arrive shortly after the earthquake with the time between the earthquake and the arrival of the tsunami depending on the distance, by water, between the location of © 2011, American Railway Engineering and Maintenance-of-Way Association

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concern and the source of the tsunami. For a large earthquake, the wave height could be much greater than for a comparable distant earthquake. The strike-slip earthquakes that occur in California are relatively unlikely to produce a large tsunami unless they cause submarine landslides. On the other hand, a large interplate subduction zone earthquake, similar to the 1964 Alaska earthquake, which can occur near the coast in Washington, is likely to produce a major tsunami. There is good evidence that a large earthquake near the Washington-Oregon coast caused a tsunami in Japan in January of 1700. A very crude estimate of the time interval between such an earthquake off the Washington coast and the arrival of the first wave at the coast in Puget Sound is in the order of one hour. If the generating earthquake occurred in Puget Sound, the travel time would be a matter of minutes. Characteristics of the tsunami generated by the June 23, 2001 magnitude 8.4 earthquake in southern Peru, although affecting the open coast, which is a different environment from the rail lines along Puget Sound in Washington, are of interest as the generating earthquake is similar to what could occur in Washington. At a location near the earthquake, the first wave arrived about 6 minutes after the earthquake. At a location near the end of the tsunami damage, the first wave arrived about 35 minutes after the earthquake. At most locations, the second and third waves were larger than the first wave. The earthquake occurred at low tide, which resulted in a smaller area of damage than would have been produced at high tide. The maximum run-up was about 30 feet. In a relatively flat area where the run-up was about 16 feet, inundation extended nearly a mile inland from the coast (Reference 10). The tsunami produced extreme scour. If a tsunami-generating earthquake and landslide were to occur off the California coast, travel times would be similar to those observed in Peru. The appropriate response for a tsunami with a distant source would be movement of trains and, to the extent possible, other equipment out of areas designated in a tsunami warning before the estimated arrival of the tsunami. In the case of a nearby earthquake, advance warning may not be possible. Although most earthquakes do not cause tsunamis, the possibility does exist for large earthquakes in coastal areas. Vulnerable areas are close to the coast and have relatively low elevations. Wave run-up heights are rarely greater than 30 to 35 feet although extreme values in the order of 100 feet have been estimated and local variations due to ocean floor topography and focusing effects can be large. The crest to trough measurements for the December 26, 2004 tsunami at points on the Pacific coast of North and South America were generally in the 6 to 20 inch range but the crest to trough at Manzanillo, Mexico was about 9 feet (Reference 24). Although most information on tsunami effects is related to vertical run-up, distance from the coast without significant increase in elevation would provide a degree of protection. A first approximation of the maximum inland penetration of a tsunami wave in a very flat region, based on the 2001 southern Peru earthquake and a 30 to 35 foot vertical run-up, would be in the order of two miles.

C - SECTION 1.3 GENERAL REQUIREMENTS C - 1.3.1 APPROACH (2004) R(2009) The vulnerability of a bridge is determined by the risk associated with the earthquake ground motion and the specified performance criteria. The risks associated with the magnitude of the ground motion at a given location are defined by the acceleration coefficient maps in Paragraph 1.3.2.3. The performance criteria specified in this Section is consistent with the post seismic event operating procedures described in Section 1.2, Post-Seismic Event Operation Guidelines. Together, they aim to minimize consequences of earthquakes.

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Commentary to Seismic Design for Railway Structures

C - 1.3.2 GROUND MOTION LEVELS (2004) R(2009) C - 1.3.2.1 Risk Factors There are many sources of uncertainty involved in seismic design. The greatest source of uncertainty is associated with the regional seismicity and the expected ground motion characteristics at the site. The response of the bridge, which is affected by both the soil and the structure dynamic characteristics, and also the methods of analysis used, add to the overall degree of uncertainty. Even when conservative earthquake magnitudes and assumptions are used in design, during its life a bridge may be subjected to maximum earthquake loads that exceed the desired performance criteria. The design of a bridge for extreme ground motion is economically undesirable, unless there is a severe social penalty associated with bridge failure. Therefore, a certain amount of risk must be accepted so that a balance between the probability of large earthquakes and the costs of overdesign can be achieved. Determining “acceptable seismic risk” is a very complex task that must consider both social and economic aspects. Obviously the amount of risk that may be accepted for some bridges is greater than for others. Factors such as the volume and the type of train traffic, the value and the importance of the bridge and the cost of loss of use have to be considered when establishing acceptable seismic risk levels (see Paragraph 1.3.2.2). The acceptable seismic risk levels must also be consistent with the risks due to other extreme events such as flood waters, fire and ship collision. A relatively simple approach is to adjust the acceptable seismic risk levels used by seismic design codes of other structures, such as buildings and highway bridges to railroad bridges. Buildings and highway bridge design codes put a major emphasis on life safety. This is primarily due to their high occupancy rate and the social implications of a large loss of life at one location. Also, some highway bridges are part of lifelines that must remain open even after severe earthquakes. When the occupancy rate of most railroad bridges is compared to the occupancy rate of buildings and highway bridges the very large difference between the levels of risk of loss of life becomes apparent. In addition to this, the movement of trains is controlled by signalization and dispatchers, so that in the event of an earthquake trains may be stopped. Thus, lower ground motion return periods may be used for railroad bridge design, and more emphasis can be put on the economic aspects that are more rational and easier to express in a quantitative way. Another approach is to perform a probability-based overall seismic risk or cost-benefit analysis. A probabilistic approach can account for uncertainties in the ground motion, the performance of the bridge during a given ground motion and the methods of analysis used. Seismic risk analysis may be performed in three steps: (1) Seismic Hazard Analysis, that yields a probability distribution function of ground motion parameters at the bridge site, (2) Seismic Performance Analysis, that yields probabilistic statements of the risks of the bridge exceeding the specified limit states, conditioned upon specified levels of ground motion, (3) Seismic Risk Analysis, that integrates the first two steps to yield the overall risk of the bridge exceeding the specified limit states. This approach, however, is only recommended for special bridge projects and is limited by the uncertainty involved in seismic hazard estimates. C - 1.3.2.2 Structural Importance Classification Examples of Determining Structural Importance Classification

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Example 1 The proposed structure is a 130’ concrete trestle consisting of 5 spans each 26’ long. The bridge has a height of 30’. The structure is located on a branchline that has 12 million gross tons of traffic a year. There is no detour around the bridge. Approximately 25% of the traffic is hazardous material. There is not any passenger service on the line and the structure does not cross a community life line. Immediate Safety Occupancy Factor= Hazardous material Factor = Community Life Line Factor =

1 1 0 2

Replacement Value Span Length Factor =

1

Bridge Length Factor = 1.50 Bridge Height Factor = 1.00 1.50

Immediate Value Utilization Factor = 2 Detour Factor = 1.00 2 Serviceability Immediate Safety 2 Immediate Value 2 Replacement Value 1.5

Weighing Factor 0.80 0.20 0.00

Weighted Value 1.60 0.40 0.00 2.00

Return Period = 50 +2.00(100-50)/4 = 75 years Ultimate Immediate Safety 2 Immediate Value 2 Replacement Value 1.5

Weighing Factor 0.10 0.80 0.10

Weighted Value 0.20 1.60 0.15 1.95

Return Period = 200 + 1.95(500-200)/4 = 346 years Survivability Immediate Safety 2 Immediate Value 2 Replacement Value 1.5

Weighing Factor 0.00 0.20 0.80

Weighted Value 0.00 0.40 1.20 1.60

Return Period = 1000 + 1.60(2400-1000)/4 = 1560 years

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Example 2 The proposed structure is a 500’ steel bridge consisting of 2 trusses each 250’ long. The bridge has a height of 50’. The structure is located on a mainline that has over 50 million gross tons of traffic a year. There is no detour around the bridge. Approximately 25% of the traffic is hazardous material There are two passenger trains per day on the line. The structure does not cross a community life line. Immediate Safety Occupancy Factor= Hazardous material Factor = Community Life Line Factor =

2 1 0 3

Immediate Value Utilization Factor = 4 Detour Factor = 1.00 4 Serviceability Immediate Safety Immediate Value Replacement Value

3 4 4

Replacement Value Span Length Factor =

3

Bridge Length Factor = 1.50 Bridge Height Factor = 1.25 5.63 Note: the factor cannot exceed 4 Replacement Value = 4.00

Weighing Factor 0.80 0.20 0.00

Weighted Value 2.40 0.80 0.00 3.20

1

Return Period = 50 +3.20(100-50)/4 = 90 years Ultimate Immediate Safety Immediate Value Replacement Value

3 4 4

Weighing Factor 0.10 0.80 0.10

Weighted Value 0.30 3.20 0.40 3.90

3

Return Period = 200 + 3.90(500-200)/4 = 493 years Survivability Immediate Safety Immediate Value Replacement Value

3 4 4

Weighing Factor 0.00 0.20 0.80

4 Weighted Value 0.00 0.80 3.20 4.00

Return Period = 1000 + 4.00(2400-1000)/4 = 2400 years

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Seismic Design for Railway Structures C - 1.3.2.2.1 Immediate Safety Immediate safety is divided into three factors; occupancy, hazardous materials and community life lines to represent the three most likely risks during and immediately after a seismic event. These risks are: Occupancy:

Risk to train crews and passengers due to damage to the structure

Hazardous Materials:

Risk to the community caused by the possible release of hazardous materials

Community Life Lines: Risk to the community caused by the damaged structure disrupting a community lifeline The engineer should factor in any additional hazards that may be caused by the structure becoming unserviceable during a seismic event. The immediate safety factors are added together because the threat that each factor represents to railroad personnel and the public is independent of each other. C - 1.3.2.2.2 Immediate Value Immediate Value evaluates the railroads’s need to return the structure to service after a seismic event. The utilization factor is multiplied by the detour factor because the need to return a structure to service is reduced when a detour route is available. The engineer should examine the possibility of the detour route also being damaged in a seismic event when determining the detour availability factor. C - 1.3.2.2.3 Replacement Value Replacement Value evaluates the costs associated with replacing the structure. Replacement Value accounts for three of the major factors that affect replacement cost: span length, bridge length and bridge height. These factors are designed to be multiplied together to obtain a value which reflects the difficulty associated with replacing the structure. These factors may not represent the total cost to replace the structure. Other factors that should be considered are double track structures, movable structures, urban location, difficult access, environmental and political concerns. C - 1.3.2.3 Base Acceleration Coefficient Maps Acceleration coefficient maps reflect the seismic hazard at a site. They account for both maximum ground motion intensity expected and frequency of occurrence. The maps give ground acceleration levels with a uniform probability of being exceeded in all areas of the country. The steps involved in the development of these maps include: (1) the definition of the nature and location of earthquake sources, (2) magnitude-frequency relationships for the source, (3) attenuation of ground motion with distance from the source and (4) determination of ground motion parameters at the site having the required probability of exceedance. The base acceleration maps for return periods of 100 years, 475 years and 2400 years in the United States were obtained from Reference 4. More recent maps are available from U.S.G.S. for the higher return periods, however, this is the latest report that includes the 100-year return period map. Likewise more recent Canadian maps are available, however, they do not include the 100-year return period. The Level 1 seismic analysis procedure defined in this Chapter is based on earthquakes with return periods less than 100 years, therefore it is important that the 100-year return period maps are included. Formulas are included to determine base accelerations in the United States for return periods other than those shown on the maps. These formulas are based on the procedure shown in Article 2.6.1.3 of Reference 14. The FEMA 273 formulas were simplified for use with the AREMA base acceleration maps. The FEMA 273 formula for return periods less than 475 years has an exponent that is based on the acceleration level and site location. © 2011, American Railway Engineering and Maintenance-of-Way Association

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This exponent can be determined more directly using the AREMA acceleration maps for return periods of 100 and 475 years. Section C2.6.1.3 of Reference 15 indicates that the acceleration-return period curves are nearly linear on a log-log plot between return periods of 475 years and 2400 years, therefore a single formula is used in this range. Example acceleration vs. return period curves, developed using the formulas shown in this Article, are shown in Figure 9-C-1 for various cities throughout the United States. These curves were developed for example purposes only using specific latitude and longitude values and should not be used for design. 0.80

0.70

Acceleration (G's)

0.60

0.50 Los Angeles, CA Seattle, WA Butte, Montana Memphis, TN New York, NY

0.40

0.30

0.20

1 0.10

0.00 0

500

1000

1500

2000

2500

Return Period (years)

3

Figure 9-C-1. Acceleration vs. Return Period

C - 1.3.3 PERFORMANCE CRITERIA (2006) R(2009) A three-level ground motion and performance criteria approach is employed to ensure train safety and structure serviceability after a moderate earthquake, minimize the cost of damage and loss of structure use after a large earthquake and prevent structure collapse after a very severe earthquake. Considering all the limit states can account for the unique structural and operating characteristics of railroad structures, and the specific needs of railroad bridge owners. Also, the performance based format used allows for future updates as the state of the art in earthquake engineering advances. Railroad bridge owners may use alternate seismic design criteria or waive certain requirements contained herein provided that adequate precautions are taken to protect the safety of trains and the public following an earthquake. C - 1.3.3.1 Serviceability Limit State The primary aim of the serviceability limit state is to ensure the safety of trains. After Level 1 earthquakes, trains are allowed to proceed at a reduced speed until inspections are completed, and the track is cleared. The stresses and deformations are limited to immediate use of the structure after a Level 1 earthquake. The allowable deformations of the structure and track may be related to the train speed restrictions after a Level 1 earthquake. Vibration of flexible bridges with natural periods in the transverse direction around 1 second may cause derailments even in the elastic response range.

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Seismic Design for Railway Structures C - 1.3.3.2 Ultimate Limit State The primary aim of the ultimate limit state is to minimize the extent of damage and to ensure the overall structural integrity of the bridge. After Level 2 earthquakes, trains are stopped until inspections are completed. Structural damage that can be readily detected and economically repaired may be allowed. By allowing the structure to respond beyond the elastic range and undergo inelastic deformations, the earthquake resistance capacity of bridges with good ductility is significantly increased. C - 1.3.3.3 Survivability Limit State The survivability limit state aims to prevent overall bridge collapse. After Level 3 earthquakes, the expected track damage would prevent immediate access to the bridge. The performance of the bridge during such earthquakes will mainly depend on the ductility and redundancy characteristics of the bridge and on the additional safety measures designed to prevent bridge collapse.

C - SECTION 1.4 NEW BRIDGES C - 1.4.3 CONCEPTUAL DESIGN (2001) R(2006) The behavior of bridges during past earthquakes has shown that the structure type, configuration and structural details have a significant effect on seismic performance. At many locations certain bridge types have survived earthquakes with relatively minor damage, while other bridges in the same vicinity have sustained extensive damage or collapsed. The survival or failure of bridges of a similar type has been linked to their configuration and the particular design and detailing criteria used. For example, bridges with skewed or irregular configurations have experienced extensive damage, often at locations where other bridges remained unharmed. The conceptual approach recommended for satisfying the ultimate and survivability limit states consists of seismic design guidelines based on conceptual principles regarding structure type, configuration and details. Incorporating conceptual seismic design principles, especially during the early stages of bridge planning and design, can significantly improve seismic behavior at low additional costs. Also, such an approach is less sensitive to the uncertainties involved in the ground motion description, the numerical analysis of structure response in the post-yield range, and the limited analytical and experimental seismic research data on railroad bridges that is currently available. The recommendations provided are intended to reduce the seismic demands by selecting an appropriate structure type for the existing site conditions. Following basic requirements for simplicity, symmetry and displacement capability will increase the seismic resistance by providing adequate strength, stability, ductility, redundancy, energy dissipation and deformation capability. Strength and stability are important attributes for satisfying the serviceability limit state, while ductility and redundancy have a significant effect on the ultimate and the survivability limit states. Displacement and deformation capacity is quite important for structures on poor soil conditions or near a fault line. The conceptual design phase for railroad bridges should consider the soil conditions and the seismic hazard at the site and incorporate appropriate means to cope with the seismic induced forces that affect superstructure, substructure (including foundation) and load bearing strata. Since the nature and direction of gravity and seismic induced forces are significantly different, it is incumbent upon the design engineer to consider both types of loading conditions in the conceptual design phase in order to meet the performance requirements of the structure.

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Commentary to Seismic Design for Railway Structures C - 1.4.3.1 Configuration Bridge vulnerability to seismic effects is determined by the ability to resist earthquake forces and/or to withstand large relative movements. The selection of an appropriate structure type and configuration should take into account the seismic hazard at the site, the soil conditions and the bridge performance requirements. In general, sites near active faults, sites with potentially liquefiable or unstable soil conditions, and sites with unstable sloping ground conditions should be avoided, if practical, and measures to improve the soil conditions should be considered as an alternative. Conventional bridge structures are difficult to design to resist the load magnitudes generated by large ground displacements and possible settlement or shifting of foundations. Therefore, where the extent of poor soil conditions is relatively large, a structure type that can accommodate large ground displacements is recommended. For example, simple span structures with ample bearing support length can accommodate large movements, without accumulating loads. Criteria for determining adequate structure configuration and layout include simplicity, symmetry and regularity, integrity, redundancy, ductility and ease of inspection and repair. Bridges should be simple in geometry and structural behavior. Simple structures provide a direct and clear load path in transmitting the inertial forces from superstructure to ground. The bridge behavior under seismic loads can be predicted with more certainty and accuracy with fewer dominant modes of vibration. To the extent possible, the preferred configuration characteristics of Article 1.4.3.1 should be incorporated. The horizontal strength and stiffness of substructure elements should not vary much along the bridge and the placement of the fixed and expansion bearings should be such that a balanced seismic load distribution to all piers can be achieved. Severe skews should be avoided even at the expense of providing longer spans or making changes in alignment. Bridges with features such as extreme curvature or skew, varying stiffness or mass and abrupt changes in geometry require special attention in analysis and detailing to avoid premature damage or failure. The use of integral crash walls with piers in high seismic areas requires special considerations, since it creates an abrupt change in the pier stiffness. Alternative crash wall configurations, such as separate walls or piers of heavy construction as defined in Chapter 8, Article 2.1.5.1c, are recommended. Redundancy and ductility considerations should also be taken into account when establishing the bridge configuration. In addition, it is desirable to have a certain degree of deformation capability within the seismic load transfer path, since seismic demands are reduced when controlled movements are allowed. Bridges with rigid superstructures and rigid substructures could benefit from some allowance for movements at the bearing location. However, adequate bridge seat widths are needed to ensure that movements can be accommodated without potential for span loss. A strong and stiff superstructure to substructure connection is more appropriate when the substructure is not too rigid or when the end diaphragms or cross frames of spans are designed and detailed to undergo ductile deformations during a strong earthquake.

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C - 1.4.3.2 Superstructure Simple spans of standard configuration are preferred by railroads since they have performed well during past earthquakes and can be returned to service or replaced. Continuous spans may reduce the likelihood of unseating at the piers. This feature can be incorporated in simple spans by providing wider seat widths or span ties. Long spans produce higher load demands on fewer foundations which will increase foundation vulnerability and reduce redundancy. Heavy ballasted concrete spans will produce higher load demands on the foundation with subsequent increases in foundation cost. These costs should be compared to the increase in material and maintenance costs of steel to determine the optimum superstructure type. Excessive ballast and other non-structural weight should be avoided as much as practical. Intermediate hinges attract high seismic demands and require special detailing to provide the lateral load paths required to withstand seismic loads. C - 1.4.3.3 Substructure Wide seat widths at the abutments and piers allow for large displacements without unseating the bridge spans. Integral bent caps have performed poorly during large earthquakes and require extensive detailing to reduce © 2011, American Railway Engineering and Maintenance-of-Way Association

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Seismic Design for Railway Structures

the likelihood of superstructure damage. Multiple columns provide redundancy in the substructure which is needed to survive the higher level ground motions. Battered piles tend to attract most of the lateral load during an earthquake. C - 1.4.3.4 Ground Conditions The foundation soil should be investigated for susceptibility to liquefaction and slope failure during the seismic ground motion. To the extent possible, bridges in regions of high seismicity should be founded on stiff, stable soil layers. Consideration should be given to ground improvement techniques when the extent of soil instability threatens the performance of the bridge or approach embankments. It may be possible to satisfy the performance requirements by other means, such as designing the foundation to survive the soil instability. Large diameter pile foundations may be used to withstand a slope failure or carry the bridge loads through liquefiable soil layers to competent material. In some cases, ground improvement or design for soil instability may be impractical. Approach embankments may be allowed to fail during the higher level ground motion events provided that they can be quickly repaired using earth moving equipment. Retaining walls founded on deep liquefiable soils may require costly ground improvement to ensure stability. The effects of wall failure on rail operations should be carefully evaluated and weighed with the costs to improve the soils.

C - 1.4.4 STRUCTURE RESPONSE (2003) C - 1.4.4.1 Site Coefficient The site coefficients are consistent with those in Reference 2 and Reference 12. A default site coefficient is not given, as this would require a judgment based on little to no knowledge of the soils. Current seismic codes have default site coefficients ranging from 1.2 to 2.0. Experience has shown that most railroad bridge failures that have occurred in seismic events were due to soil failures such as lateral spreading or liquefaction. Because of this, it is recommended that the foundation investigation should include soil borings or test pits taken to an adequate depth to determine the soil profile. It should be emphasized that the need for adequate foundation investigation is necessary to determine the appropriate foundation type for the structure. C - 1.4.4.2 Damping Adjustment Factor The Damping Adjustment Factor provides a simplistic method for scaling the seismic response coefficient to account for different structure types and conditions. The seismic response coefficient is given for 5% critical damping without the damping adjustment factor. The percent critical damping varies based on the structure material and system, effect of structure attachments (i.e., track and ballast), whether the structure responds in the elastic-linear or post-yield range, and whether or not the structure response is dominated by the foundation or abutment response. The percent critical damping (x) preferably should be based on actual test data from similar structure types. A table of damping values for different structural (building) systems from Reference 11 is included below for information and guidance.

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Commentary to Seismic Design for Railway Structures Table 9-C-1. Damping Values for Structural Systems Structural System

Elastic-Linear

Post-Yield

Structural Steel

3%

7%

Reinforced Concrete

5%

10%

Masonry Shear Walls

7%

12%

Wood

10%

15%

Dual Systems

See note 1

See note 2

Notes: 1. Use the value of the primary, or more rigid, system. If both systems are participating significantly, a weighted value, proportionate to the relative participation of each system, may be used. 2. The value for the system with the higher damping value may be used. C - 1.4.4.3 Seismic Response Coefficient The Seismic Response Coefficient is the basis for determining the structure design loads for both the Equivalent Lateral Force Procedure and the Modal Analysis Procedure. The Equivalent Lateral Force Procedure only uses a single value based on the natural period of vibration of the structure for each of the two principal directions of the structure. The Modal Analysis Procedure combines values for multiple modes of vibration in each of the two principal directions of the structure. For areas with soft soil conditions and high seismicity, or close proximity to known faults, or for special bridge projects, a site-specific hazard analysis is preferred. The analysis should be based on accepted practice using the ground motion return period determined in accordance with Paragraph 1.3.2.2 “Structure Importance Classification.” A good discussion of site-specific hazard analysis is contained in Reference 11. The formula for the Seismic Response Coefficient is adopted from Reference 12 without the exceptions and modified by the Damping Adjustment Factor from Reference 11. The coefficient is based on 5% critical damping. The exceptions to the formula were not included since they differ from code to code and unnecessarily complicate the Seismic Response Coefficient. The values obtained using the basic formula are conservative compared to all the exceptions but one. The exceptions from various codes are listed below for information. If the bridge designer believes that the exceptions are needed for his site, he may include them or preferably use site-specific response spectra.

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Seismic Design for Railway Structures Table 9-C-2. Exceptions to Seismic Response Coefficient Source

Exception

Reference 12 & The limiting value of 2.5A is not applicable to important structures in areas with A ³ Reference 13 0.2 with a period of 0.7 seconds or greater located on Type 4 soils. Reference 12 & For soil profiles 3 and 4, and for modes other than the fundamental mode which have Reference 13 periods less than 0.3 seconds, Cm = A(1.0 + 5.0Tm) Reference 2

For soil profiles 3 and 4, and for modes other than the fundamental mode which have periods less than 0.3 seconds, Cm = A(0.8 + 4.0Tm)

Reference 2, For buildings where any modal period of vibration (Tm) exceeds 4.0 seconds, the Reference 12 & Seismic Response Coefficient for that mode is permitted to be determined by the 3 AS Reference 13 following equation: C = -----------m 4¤3 T C - 1.4.4.4 Low Period Reduced Response Railroad bridges are often more rigid than typical multi-level buildings or highway bridge structures. Therefore the response of railroad bridges in the low period range needs to be thoroughly addressed. Most general response spectra curves, such as those defined in Reference 14 have reduced responses in the low period range. Typically, these curves vary linearly from the peak ground acceleration at zero period to a maximum constant acceleration response at the initial transition period, To as shown in Figure 9-C-2. Other response spectra curves, such as those given in Reference 5 show a flat region for very low periods that represent perfectly rigid response. The AREMA seismic response coefficient defined in Article 1.4.4.3 does not include the reduced response at low periods since it was felt that typical railroad bridge analysis underestimates the actual period of the bridge. Underestimation of the structure period can result in unconservative response for low period structures when the reduced response region of the response spectra is used. This section was developed to allow the bridge designer to take advantage of the reduced response for low period structures when appropriate. The provisions listed in Article 1.4.4.4 account for the most common sources of flexibility in the structure, however, the bridge designer should consider any other component that will increase the structure period. Typical railroad bridge analysis uses the gross moment of inertia for reinforced concrete members to determine the stiffness and load distribution. Use of the gross moment of inertia for a reinforced concrete substructure member will underestimate the structure period when the flexural tension stress exceeds the concrete modulus of rupture. The effective moment of inertia, as determined from EQ 2-12 in Chapter 8, Part 2, Article 2.23.7c, of reinforced concrete members will provide a more representative structure period. The cracked moment of inertia used in EQ 2-12 may be determined from moment-curvature analysis of the member using the following relationship.

My1 = Moment at first yield of reinforcing steel fy1 = Curvature at first yield of reinforcing steel Ec = Concrete modulus of elasticity (Chapter 8, Part 2, Article 2.23.4) It is common practice to model bridge foundations as either pinned or fixed. If the foundation stiffness is overestimated, then the structure period will be underestimated. Foundation flexibility for spread footings may be accounted for by including a rotational footing stiffness calculated in accordance with accepted procedures, such as those defined in Section 5.3 of Reference 18. Lateral translation flexibility of a spread footing need not be considered provided that the base soil friction is not exceeded. Foundation flexibility for pile footings may be

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Commentary to Seismic Design for Railway Structures

accounted for by using accepted procedures, such as including a rotational pile cap stiffness that is derived from realistic pile load-deflection (t-z) data. When vertical piles are used, the lateral translation foundation stiffness should be determined from realistic pile lateral load-deflection (p-y) data, supplemented, if appropriate, by lateral soil resistance on the pile cap. If either of these foundation types is founded on sound rock, the effects of foundation flexibility can be neglected. Lateral flexibility of the bridge spans may amplify the seismic response between the bridge piers. For example, a point in the middle of the span may have a higher response acceleration than the point at the top of the pier. This effect is typically accounted for by performing modal analysis of the bridge using a model with at least four elements making up the span length. Foundation rocking is a response that occurs when the applied moment on a spread footing exceeds the overturning moment resistance. Rocking response will increase the period of the foundation and most likely take it out of the low period reduced response range. The low period reduced response defined in this Article has been developed based on review of the response spectra from other codes along with visual inspection of a number of response spectra generated from actual strong motion records. The perfectly-rigid period limit of 0.03 seconds corresponds to a frequency of 33 Hz and has generally been considered appropriate for this type of response. Evaluation of response spectra generated from actual strong motion records indicates that this is conservative except for sites very close (< 10 miles or 16 km) to the fault. The only structures that are expected to fall in the perfectly-rigid range are rigid piers with spread footings or piles founded on rock. Other rigid piers will generally fall in the low period linear transition region due to foundation flexibility.

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Seismic Design for Railway Structures

0.00 < T £ 0.03

Perfectly-rigid region

0.03 < T £ To

Low period linear transition region

To < T £ Ts

Constant acceleration region

To = Initial transition period = 0.096S Ts = Constant acceleration transition period = (0.48S)3/2 S = Site coefficient from Paragraph 1.4.4.1 T = Period of vibration Figure 9-C-2. Normalized Response Spectra with Low Period Reduced Response

C - 1.4.5 ANALYSIS PROCEDURES (2003) C - 1.4.5.1 General C - 1.4.5.1.1 Serviceability Limit State Within the serviceability limit state the response of a bridge is limited to its elastic range. Therefore, methods based on elastic analysis are most appropriate. The methods specified depend on the bridge configuration. The Equivalent Lateral Force Procedure expresses earthquake loads in terms of structure mass and Seismic Response Coefficient for the site. It will probably be applicable to the majority of the existing railroad bridges. The Modal Analysis Procedure is a more accurate approach that can evaluate irregular bridges, effects of higher modes of vibration and specific ground motion characteristics. Other analysis procedures such as time-

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Commentary to Seismic Design for Railway Structures

history analysis or deformation-based methods may be appropriate for certain structures and/or site conditions, but are not addressed herein. C - 1.4.5.1.2 Ultimate and Survivability Limit State The response of a bridge near its ultimate limit state is highly nonlinear and uncertain due to incomplete knowledge of inelastic structural action. Seismic highway bridge design codes specify the use of elastic analysis for the ultimate loads, and response modification factors that account for nonlinear behavior. Satisfying the ultimate state criteria is practically the main requirement of these codes, and there is on-going research to improve the analysis models and to get more reliable estimates of the response modification factors recommended. Using a similar approach for the evaluation of railroad bridges for the ultimate limit state would require more research into nonlinear response of railroad bridges to extreme horizontal loads. Also, for railroad bridges, satisfying the serviceability limit state, that is concerned with the continuing operation of trains after a seismic event, is the main design condition. The serviceability limit state criteria is associated with very low risk levels of being exceeded, and it will most likely be more restrictive than the other limit states. Using a conceptual design approach for the ultimate and the survivability limit states can overcome the high level of uncertainties involved in numerical analysis of the nonlinear bridge response. Conformance with the ultimate and the survivability limit states is based on requirements for type, geometry, materials, ductility and redundancy. The conceptual design methods recommended to ensure satisfactory performance for the ultimate and the survivability limit states are based primarily on experience from past earthquakes and from research and testing results applicable to railroad bridges. Commonly accepted detailing provisions and guidelines for a specific seismic region which are consistent with railroad practices may be used until more specific requirements for adequate details, connections, ductility and redundancy are developed herein. The requirement for non-ductile, non-redundant primary load carrying elements of structures to be designed for higher seismic loads is necessary to ensure survivability of some structures during an extreme event. The design forces to be used in this case are the lesser of the seismic forces or the maximum load which can be transmitted to the element. Non-ductile, non-redundant primary load carrying elements are bridge components whose failure can cause structure collapse. An example of such a component is a poorly reinforced single column concrete bent.

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C - 1.4.5.2 Procedure Selection The procedure used to analyze the structure is based on the bridge configuration. Single-span bridges do not require formal analysis, however they should be investigated using commonly accepted empirical formulations to ensure that the abutment seat widths are adequate to prevent span collapse. Two-span bridges are considered regular since they have only one bent, which precludes stiffness irregularity. Irregular bridges may be those with bridge vulnerability aspects as listed in Paragraph 1.4.3.1. A more specific description of bridge irregularity may be found in other codes such as Reference 2. C - 1.4.5.3 Equivalent Lateral Force Procedure The Equivalent Lateral Force Procedure is included as a simple method of analysis that may be used for regular bridges. The calculations for this procedure are appropriate for hand calculation methods in most cases, though static computer analysis may be used to determine the load distribution to the individual members. The two principal directions of the structure are typically the longitudinal and transverse directions of the bridge. For curved bridges, the longitudinal direction may be taken as a straight line connecting the centerline of the bridge at the beginning and end. The natural period of vibration (Tm) for each of the two principal directions of the structure may be calculated using any commonly accepted method. The following simple formulation may be used.

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Seismic Design for Railway Structures

W T m = 2p -------gK

W= Total weight of the bridge. g= Acceleration due to gravity (length/time2) K= The total structure stiffness including the stiffness of the superstructure, supporting members and surrounding soil. The seismic response coefficient, Cm, applied to the substructure of single level bridges may be reduced to the average of the Cm value calculated in Paragraph 1.4.5.3a for the superstructure and the base acceleration coefficient, A, determined in accordance with Paragraph 1.3.2.3 for the ground, but shall not be less than the base acceleration coefficient, A. The actual seismic response coefficient, Cm, varies throughout the structure in proportion to the relative lateral movement. A common method of equivalent lateral force analysis assumes that one-half the weight of the substructure is lumped at the superstructure level for the period calculation and the foundation load is calculated using the complete bridge weight with the seismic response coefficient determined for the superstructure. This analysis approach is accurate when the substructure weight is small relative to the superstructure weight, but may be too conservative for heavy pier substructures. Rather than using the more accurate modal analysis approach, a simple modification to the equivalent lateral force procedure may be used to minimize the foundation demand for bridges supported by large pier substructures. It is conservative to assume that the actual seismic response coefficient, Cm, varies linearly from the base acceleration coefficient, A, at the ground level to the seismic response coefficient calculated at the superstructure level as long as the response at the superstructure level exceeds the base acceleration. Therefore the average of these two acceleration values may be applied to the weight of the pier to more accurately determine the demand at the foundation. The seismic load should be distributed to the individual members based on the stiffness and support conditions. For a regular structure with uniform weight per unit length and simple supports, this reduces to a simple beam calculation for the superstructure between supports and a single lateral load calculation for the supporting bents. C - 1.4.5.4 Modal Analysis Procedure The Modal Analysis Procedure is included as a general method of analysis that may be used for any bridge configuration. The calculations for this procedure are appropriate to be performed by any commonly available finite element computer program. The response spectra is developed from Paragraph 1.4.4.3 “Seismic Response Coefficient.” The value of the Seismic Response Coefficient (Cm) should be calculated for a range of period (Tm) values to adequately define the spectral shape for the range of period (Tm) values needed to represent the structure. Figure 9-C-3 gives a typical normalized spectral shape for values of A, S and D all equal to 1.0.

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Commentary to Seismic Design for Railway Structures

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Figure 9-C-3. Normalized Response Spectra

C - 1.4.6 LOAD COMBINATIONS AND RESPONSE LIMITS (2002) The load combination used for the level 1 ground motion should be consistent with the probability of occurrence of the earthquake. For this reason, live load is usually not included in the load combination. Certain situations, such as long viaducts with high traffic volume or bridges in yard and terminal areas, may require consideration of combinations which include live loading. Extreme loads, such as wind and stream flow pressure, are not normally combined with the seismic loading. In cases where a certain minimum level of stream flow is constant, that minimum level should be included in the earthquake load combination. Friction forces can vary significantly due to contact surface conditions and vertical earthquake accelerations, therefore the use of friction should be carefully considered if it reduces the effects of the earthquake load. The stress limits are provided to satisfy the performance requirements of the serviceability limit state. The seismic loads are calculated at the yield level rather than at the working stress level, so it is appropriate to use a 50% allowable stress increase for steel and a 1.0 load factor for concrete. Specific lateral deflection limits are not provided, however, the bridge must satisfy the performance requirements of Section 1.3.3. PD effects should be considered if they are significant enough to affect the performance of the bridge. Columns designed in accordance with Article 1.4.7.3.1 may account for PD effects using conventional methods for the level 1 earthquake, however, this is not appropriate for the higher level earthquakes. The only reliable way to account for PD effects in the inelastic range of the columns for the higher level earthquakes is to perform nonlinear time history analysis. A practical limit from Reference 9 may be used which requires that the PD moment should not exceed 20% of the plastic moment capacity of the column for the maximum credible earthquake. To perform a similar comparison, the column PD moment for the level 1 earthquake should be multiplied by the ratio of the level 3 base acceleration coefficient divided by the level 1

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Seismic Design for Railway Structures

base acceleration coefficient and should not exceed 20% of 1.3 times the nominal moment capacity of the column. The lateral deflection of the bridge must not preclude train operations outlined in Article 1.2.2.1. Because the fixed steel rails are the riding surface over which rail equipment operates, railroad bridges have inherently strict limitations on the tolerable, permanent displacement and distortion they can undergo in a seismic event, and still remain serviceable. After a level 1 ground motion event, the trains are allowed to continue at restricted speed. For most bridges, there is a very low probability that the train will be on the bridge during the earthquake. Therefore the track deflection to be considered is the permanent deflection which will remain after the earthquake has occurred. It is the responsibility of the bridge designer to determine how much permanent track deformation will result from the elastic deflection of the structure. For bridges where a train is considered to be on the bridge during the earthquake, the deflection limitations must be satisfied directly. The Code of Federal Regulations, Title 49, Part 213, Section 55 (49 CFR 213.55) provides alignment requirements based on the class of track and 49 CFR 213.9 defines the speed limits for each class of track. Table 9-C-3 includes the information from the 49 CFR and is provided herein as an indication of order of magnitude limits to track misalignment tolerable for 'safe' conditions at various speeds. However, the designer must establish with the railroad(s) the tolerable limits for permanent track deformations used in the design. The individual railroads may have maintenance limits on various railways for horizontal, vertical and superelevation alignments that are more restrictive than the FRA standards. Table 9-C-3 can be used to determine the track alignment requirements for a given train speed. For example, the track on a bridge supporting a freight train operating at a restricted speed, which cannot exceed 20 mph (32 kph) after an earthquake, would have to satisfy the alignment requirements of a class 2 track, which is no more than a 3" (76 mm) mid-offset on a 62 ft. (18.9 m) long tangent section of track. Table 9-C-3. FRA Horizontal Track Alignment Requirements Class of Track

Maximum Operating Speed mph (km/h)

Maximum Horizontal Track Deviation from Alignment, in (mm)

Freight

Passenger

Tangent track1

Curved track2

1

10 (16)

15 (24)

5 (127)

5 (127)

2

25 (40)

30 (48)

3 (76)

3 (76)

3

40 (64)

60 (97)

1.75 (44)

1.75 (44)

4

60 (97)

80 (129)

1.5 (38)

1.5 (38)

5

80 (129)

90 (145)

0.625 (16)

0.625 (16)

NOTE: (1) The deviation of the mid-offset from 62 foot (18.9 m) line. The ends of the line must be at points on the gage side of the line rail, five-eighths of an inch (16 mm) below the top of the railhead. (2) The deviation of the mid-ordinate from 62 foot (18.9 m) chord. The ends of the chord must be at points on the gage side of the outer rail, five-eighths of an inch (16 mm) below the top of the railhead.

C - 1.4.7 DETAILING PROVISIONS (2001) R(2006) The detailing provisions are required to meet the performance requirements of the Level 2 and 3 Ground Motion. These provisions are based on accepted practice in high seismic areas and recent research. The structure design need not meet the required provisions provided that the structure is capable of resisting the Level 3 Ground Motion loadings in the elastic range.

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Commentary to Seismic Design for Railway Structures C - 1.4.7.1 Continuity Provisions Continuity provisions for transferring lateral forces from the superstructure to the ground are necessary to ensure structural integrity during a seismic event. All portions of the load path must be investigated to see that the lateral forces can be transferred. This is especially true for the load path from the superstructure span to the substructure, which is often not investigated for static loads. Friction should be neglected as a means to transfer lateral forces where there is a potential for uplift. At locations where movements are allowed, they should be accommodated or limited. C - 1.4.7.1.1 Superstructure Critical members which transfer lateral forces from the superstructure to the substructure and are non-ductile must be designed for the Level 3 Ground Motion forces or the maximum loads which can be transmitted to the member. Lateral bending of the girders is the load path for concrete box girders. Lateral bending resistance may also be used for other structures as long as the loads are investigated. For example, shorter open deck steel girders will often have the capability to transfer lateral loads without additional bracing since the live load is usually not combined with the seismic load. C - 1.4.7.1.2 Bearings Bearings are often the critical component in transferring seismic loads to the substructure. They shall be configured to transfer the lateral loads to the substructure or accommodate movement while allowing access for maintenance and replacement.

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C - 1.4.7.2 Ductility Provisions The importance of ductility during bridge response to large magnitude earthquakes is well recognized. During large earthquakes stresses in bridge members and connections exceed the elastic range and structures could experience large inelastic deformations. The ductility of a structure is usually defined in terms of the ratio between maximum deformation without failure and yield deformation. It depends on the individual member ductility and their loading condition, the ductility of the connection details and also on the structure configuration. For example, nonductile and poorly braced members loaded in compression may experience sudden failure even prior to reaching yield stresses. A ductile structure can undergo large inelastic deformations without significant strength degradation. Ductile behavior reduces seismic loads and provides an energy dissipation mechanism. To achieve good ductility, locations that are expected to experience plastic deformations need to be adequately designed and detailed, and instability or brittle failure modes need to be prevented. At the same time the structure should have sufficient stiffness to maintain stability and avoid excessive drift. The ductility provisions are required to ensure that the structure will meet the performance requirements of the Level 2 and 3 Ground Motion. These provisions are based on accepted practice in high seismic areas and recent research. The requirements for structure ductility for reinforced concrete, steel or timber structures are different, since they must take into account the inherent material properties and the typical structural configurations. The requirements for reinforcement details in concrete structures in seismically active regions are well established in design codes and State guidelines for seismic design of highway bridges. These requirements should be followed in a manner consistent with railroad design and detailing practices. In general, these requirements are intended to increase ductility and reduce the likelihood of brittle shear failures. The ductility requirements for steel structures are intended to prevent buckling and fracture and provide adequate connections and details. Due to differences in geometry, stiffness, ductility, mass and damping characteristics, the seismic behavior of steel bridges is fundamentally different from that of concrete bridges. © 2011, American Railway Engineering and Maintenance-of-Way Association

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One main difference is that steel bridges can yield and dissipate energy at various locations throughout the structure, and therefore plastic hinge regions do not need to be restricted only to the columns. Also, in steel members, the shear yielding mechanism is preferable, since it provides substantial stable energy dissipation, which is different from concrete members where flexural failure modes are desired and shear failure is avoided. Seismic design and detailing requirements for steel bridges are not as well established and codified as those for concrete bridges. This is probably because of the inherent ductility of structural steel and the relatively good performance of steel bridges during past earthquakes. In addition, by following relatively simple design and detailing guidelines, significant ductility levels can be achieved. Such guidelines include the following recommendations: • Limit the width to thickness (b/t) ratios for plates in compression; • Limit the slenderness ratio for main compression and bracing members; • Avoid using details susceptible to fracture in areas expected to respond in the plastic range; • Avoid field welds and other fatigue prone details; • Design steel members such that yielding of the gross section occurs before local buckling or fracture; • Avoid triaxial tension stress conditions that may occur at locations such as near the intersection of welds in thick elements. They can inhibit the ability of steel to exhibit ductility. • Use stiffeners that are more rigid than the minimum needed to prevent buckling. • Limit the axial compression load in columns to a percentage of their yield capacity; • Provide means for an alternative load path in case of damage; • Ensure that when damage occurs, the damage is confined to secondary, non-gravity carrying elements, such as bracing members; • Consider using the end diaphragms or cross frames as locations for ductile behavior. C - 1.4.7.2.1 Longitudinal Reinforcing Confinement The provisions in this Article were adapted from Sections 21.4.4 and 21.4.5 of Reference 3 with minor changes in notation and terminology to be consistent with Chapter 8 notation and railroad bridge terminology. Notation which is not defined in this section is defined in Chapter 8, Article 2.2.1 and additional commentary is contained in Sections R21.4.4 and R21.4.5 of Reference 3. Longitudinal reinforcing confinement is critical to ensuring that the concrete column will respond well in the post-yield range. Concrete piles with fixed heads will develop high bending moments at the cap interface, therefore they should be adequately confined to reduce the possibility of permanent damage. Extended concrete piles should be treated as regular columns above the ground. The reduced requirements for concrete pier walls with low axial loading have been shown by testing to exceed a ductility factor of 2. C - 1.4.7.2.2 Splices in Reinforcing The concrete cover tends to spall off of concrete members responding in the post-yield range. This eliminates the load transfer of lap splices and can cause premature failure.

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Commentary to Seismic Design for Railway Structures C - 1.4.7.3 Provisions to Limit Damage To limit damage during Level 2 Ground Motion, the distribution of strength and stiffness should be such that damage occurs at predetermined locations, and certain critical load carrying members are “protected” from inelastic response. The predetermined damage locations must be well detailed to sustain large inelastic deformations without strength degradation, and at the same time they should be the weakest links within their respective load paths in order to restrict damage to other members. In addition, the distribution of stiffness and strength should be such that plastic response or damage does not occur in locations inaccessible for inspection and repair. Since seismic demands are reduced when movements and ductile deformations are allowed, such damage control criteria can achieve good and reliable seismic performance at relatively low costs. The use of sacrificial elements, which could be easily replaced in the event of damage, may also offer a cost-effective way of enhancing the bridge seismic response and providing protection to other members. Knowledge of likely failure locations and modes also allows for the design of connection details and jacking locations for temporary support during repairs. C - 1.4.7.3.1 Weak Column Provisions Bridges in high seismic areas are typically designed so that plastic hinging is allowed in the reinforced concrete columns. The provisions for reinforcing steel material with maximum yield strength are adapted from Chapter 21, Section 21.2.5 of Reference 3, and are necessary to limit the post-yield loads delivered to the adjacent bent cap and foundation. The bent cap and foundation may be designed for 1.3 times the nominal column strength to ensure that they will not be damaged during plastic hinging. This requirement is also applicable for the superstructure when it is built integrally with the bent cap, as with cast-in-place box girder structures. Extended pile columns are not allowed to yield below the ground, since the area is inaccessible for inspection and repair.

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C - 1.4.7.3.2 Concrete Joints The provisions in this Article were adapted from Section 21.5 of Reference 3 with changes in notation and terminology to be consistent with Chapter 8 notation and railroad bridge terminology. Some of the ACI 318 provisions were modified or omitted to be consistent with the other provisions of this Chapter. For example, provision 21.5.1.1 of Reference 3 is omitted since it conflicts with the column overstrength requirements of Paragraph 1.4.7.3.1b and provision 21.5.3.1 of Reference 3 is modified since the joint shear reinforcement requirements of this Article allow for higher joint stresses. Notation which is not defined in this section is defined in Chapter 8, Article 2.2.1 and additional commentary is contained in Section R21.5 of Reference 3.

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4 Concrete joints must be adequately detailed to reduce the likelihood of damage extending into the superstructure and bent cap. The additional so called “joint shear” requirements for integral bent caps and superstructure have been used on California bridges since the Northridge earthquake. Further details on these requirements may be obtained from Reference 20. C - 1.4.7.4 Redundancy Provisions Redundancy provisions are suggested to provide additional safety against failure during the Level 3 ground motion event. These provisions are particularly important when the Level 3 ground motion acceleration is much greater than the Level 1 ground motion acceleration. C - 1.4.7.4.1 Bearing Seats The provisions in this Article were adapted from Division I-A, Section 7.3.1 of Reference 1 with minor changes in terminology to be consistent with railroad bridge terminology. Some of the AASHTO provisions were

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omitted since they are already addressed with the other provisions of this Chapter. For example, the AASHTO linkage provisions are omitted since they are already addressed in Article 1.4.7.4.3. Wide bearing seats will provide additional redundancy if bearing anchor bolts or shear rods fail during a high level ground motion. The AASHTO requirements provide an empirical equation for determining the minimum seat width as a function of the bridge length, height and skew. Seismic analysis of the bridge may also be used to determine the maximum relative movements. The bearing seat width requirements are not necessary if the superstructure is adequately connected to the substructure to prevent relative movement. C - 1.4.7.4.2 Shear Connectors Shear connectors are often used in high seismic areas to transfer the seismic loads from the superstructure to the substructure. Reinforced concrete shear keys should be placed as close to the girders as practical so that the bearings do not fail before shear key engagement. Shear connectors may also take the form of rods or pipes embedded through the superstructure of concrete box girder structures supported on elastomeric bearings. C - 1.4.7.4.4 Foundation Rocking Rocking response is a form of seismic isolation which reduces the response frequency of the bridge while dissipating energy. Bearing blocks are required on new bridge construction to reduce the permanent soil deformation which will result at the toe and heel of the rocking footing. This response mode is especially useful for evaluating existing bridges with large, non-ductile, single pier foundations. Further information on foundation rocking may be obtained from Reference 21. C - 1.4.7.4.5 Continuous Welded Rail The presence of track on railroad bridges has long been considered a distinguishing characteristic between the seismic response of highway bridges and railroad bridges. Properly detailed continuous welded rail will provide a continuous load path for longitudinal loads on the bridge. Further research into the load transfer mechanisms is required to adequately quantify the effect of CWR at this time, however, the presence of CWR is considered a desirable feature to add redundancy and increase damping in the longitudinal direction of short, straight bridges. Reference 8 allows an increase in damping of between 10 and 15 percent for straight bridges less than 300 feet if the abutments are capable of mobilizing the soil and are well tied into the soil. This increase in damping may be applied to straight railroad bridges less than 300 feet in length with CWR to reduce the seismic loading.

C - SECTION 1.5 EXISTING BRIDGES C - 1.5.2 INVENTORY (1995) R(2004) Most railroads have a good inventory of their own facilities. However, in several earthquakes where damage to railroad facilities was minor, structures owned by others, including structures over or adjacent to tracks, have collapsed. The presence of any structures whose collapse could adversely affect operations should be determined and recorded. Underground structures subject to seismic failure and buried utilities, including pipelines, should also be identified.

C - 1.5.3 HISTORY (1995) R(2004) Areas with frequent significant seismic activity are more appropriate for historical analysis than areas that have rare, but severe, earthquakes, such as parts of central and eastern North America.

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Commentary to Seismic Design for Railway Structures

C - SECTION 1.6 OTHER FACILITIES AND INFRASTRUCTURE C - 1.6.2 TRACK AND ROADBED (2007) Although the track structure, with the possible exception of the ballast, is rarely affected by shaking, the distortion of the underlying ground may severely impact track geometry. Longitudinal distortion can cause track buckling, or high tensile stresses in the rails with the resulting risk of the track pulling apart. Lateral movements and/or settlement due to liquefaction or embankment failure can cause serious defects in line, surface and cross-level. Fills supporting track are subject to two types of failures as a result of seismic activity. They are horizontal or vertical misalignment of the embankment and loss of fill materials by soil liquefaction. Misalignment could result from: a.

Movement associated with tectonic plate acceleration differentials at, or near, fault lines.

b. Local soil shear failure from forces generated by earth mass acceleration differentials. c.

Slope failures of the fill embankment.

d. Soil liquefaction. (Liquefaction requires the existence of a specific set of soil grain sizes and soil moisture conditions at the time a vibratory energy source is applied.)

1 e.

Water damage caused by failed retaining structures, distribution systems or redirected water courses.

Track in earth cuts is subject to the same misalignment from tectonic plate movements as is track on fills. Local soil shear failures and liquefaction may also occur, resulting in covering the track structure with debris. It is suggested that efforts to analytically predict these failures is of little value, as there is no practical design of retrofit that would prevent the movement. Whatever the type of movement imposed on the track it is likely the disturbance will affect the rail’s neutral temperature, for continuously welded rail (CWR), or the joint gapping for jointed rail, thus reducing the rail’s resistance to buckling at high temperatures (sun kinks). When realigning the track to the pre-earthquake alignment, CWR must be cut and stressed to the neutral temperature, and jointed rail regapped to the requirements specified by the railroad.

C - 1.6.4 RETAINING WALLS (2007) Design of retaining walls to fail by sliding instead of overturning or failure of the stem of cantilever walls is analogous to the use of strong column-weak beam moment resisting frames in buildings. If a wall supporting the railway embankment slides during an earthquake, a large amount of energy is absorbed and track damage is limited to loss of line and surface in amounts that may be readily corrected. If a wall supporting a hillside above the track slides, the resulting reduction of clearance may be corrected by realigning the track. In either case, restoration of service will likely be considerably faster than in the case of collapse or overturning of the wall.

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C - 1.6.5 TUNNELS AND TRACK PROTECTING SHEDS (2007) C - 1.6.5.1 Tunnels Tunnels usually are subjected to less severe loading from earthquakes than structures on the surface of the ground. However, they have been damaged by shaking and severely damaged by displacements at locations where they were intersected by fault ruptures. Tunnel lining damage, possibly due to earthquake accelerations even at some distance from the seismic event, has occurred where the tunnel floor slab has been removed to increase vertical clearances within the tunnel.

C - 1.6.6 BUILDINGS AND SUPPORT FACILITIES (2007) Structures located near the fault rupture are likely to suffer serious damage in a major earthquake. Safety of operation ultimately depends on post-event inspection of facilities in areas subjected to major ground movements and/or severe shaking. Proper design can reduce, but not totally eliminate, the probability of significant damage.

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Chapter 9 Glossary The following terms are used in Chapter 9 Seismic Design for Railway Structures and are placed here in alphabetical order for your convenience.

Amplitude Maximum value of a function as it varies with time.

Attenuation A decrease in amplitude of the seismic waves with distance due to geometric spreading, energy absorption and scattering.

Collapse Major change in the geometry of a bridge rendering it unfit for use.

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Damping Resistance which reduces vibrations by energy absorption.

Ductility Property of a member or connection that allows inelastic response.

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Ductility Ratio The ratio between the maximum displacement for elastoplastic behavior and the displacement corresponding to yield point.

Dynamic Magnification An increase in the induced lateral forces in a structure due to frequency matching between the ground and structure.

Elasticity The ability of a material to return immediately to its original form or condition after removal of the loads.

Elastoplastic Implies elastic behavior for a force that does not exceed a maximum value and plastic behavior above this maximum.

Epicenter The point on the Earth’s surface located vertically above the point where the first rupture and the first earthquake motion occur.

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Fault A fracture or fracture zone in the earth along which there has been displacement of the two sides relative to one another and which is parallel to the fracture.

Flexible Structure A structure that will sustain relatively large displacements without failure.

Fundamental Period The longest period (duration in time of one full cycle of oscillatory motion) of vibration of a structure which has several modes of vibration, each with a different period.

Ground Movement Term that refers to all aspects of ground motion, e.g. particle acceleration, velocity, displacement due to earthquakes.

Hoop Reinforcement Circular or rectangular transverse reinforcement capable of confining the concrete core after the concrete cover has spalled off. Circular hoop reinforcement shall either be welded or mechanically coupled with no lap splices. Rectangular hoop reinforcement shall consist of single or multiple overlapping stirrups which are closed by 135° hooks around a longitudinal reinforcing bar with no lap splices and cross-ties consisting of single-leg stirrups with a 90° hook around a longitudinal reinforcing bar on one end and a 135° hook around a longitudinal reinforcing bar on the other end. Cross-ties shall be alternated end for end along the longitudinal reinforcement.

Inelastic Behavior Behavior of a member beyond its elastic limit.

Intensity Qualitative or quantitative measure of the severity of seismic ground motion at a specific site. The most common intensity scale used in the United States today is the Modified Mercalli, 1956 version.

Limit State A condition beyond which a bridge, member or connection ceases to satisfy the performance requirements for which it was designed.

Liquefaction Transformation of a granular soil from a solid state into a liquefied state as a consequence of increased porewater pressure induced by vibrations.

Magnitude Qualitative measure of the size of an earthquake, related indirectly to the energy released, which is independent of the place of observation, e.g. Richter Magnitude Scale.

Mean Return Period, T The average time (in years) between occurrences of an event of a given size or a condition associated with a given severity. The inverse of the mean return period is the average annual probability of exceedance. For an estimate of the probability of exceedance, p, during an exposure time, t (in years), the following relation may

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Glossary be used: p = 1–(1–1/T)t. An event with a particular mean return period has a 63% probability of being exceeded during an exposure time equal to that return period.

Natural Frequency The frequency (number of cycles per second) of free vibration of a structure if damping effects are neglected. Sometimes expressed in radians per second.

Natural Period The time interval (in seconds) for a vibrating structure in free vibration to do one oscillation. The inverse of the natural period is the natural frequency.

Occupancy Rate Average number of persons occupying a structure each 24-hour day of the year.

Predominant Periods The most significant periods of the earthquake ground motion.

Regular Bridge A bridge that has no abrupt or unusual changes in mass stiffness or geometry along its span and has no large differences in these parameters between adjacent supports.

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Resonance A state of maximum amplitude of vibration caused by the matching of the excitation frequency with the natural frequency of the structure itself.

Response Spectrum A plot showing maximum earthquake response with respect to natural period or frequency of the structure for a given damping. It reflects the response of an infinite series of single-degree-of-freedom systems subjected to a time history of earthquake ground motion.

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Richter Magnitude Scale A measure of the magnitude of an earthquake. The measure is determined by taking the common logarithm (base 10) of the largest ground motion amplitude observed and applying a standard correction for distance to the epicenter.

Seismic Hazard The probability that given ground motion parameters at the site of a given bridge will be exceeded during a specified exposure time. May also be expressed in terms of average annual probability of exceedance of mean return period.

Seismicity Frequency of occurrence of earthquakes per unit area in a given region.

Serviceability Limit State Limit state that relates to maximum stresses and deformations within the elastic range that ensures safety of trains traveling at reduced speeds.

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Survivability Limit State Limit state that relates to bridge collapse.

Tsunami A sea-wave caused by an earthquake, or a submarine landslide or eruption.

Ultimate Limit State Limit state that relates to ultimate strength of material and stability of critical members. Structural damage that can be repaired within a short period of time is allowed.

Vulnerability Amount of damage induced by a given degree of hazard.

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Notations A = base acceleration coefficient, G’s. See Article 1.3.2.3 A100 = base acceleration coefficient for return period = 100 years. See Article 1.3.2.3 A475 = base acceleration coefficient for return period = 475 years. See Article 1.3.2.3 A2400 = base acceleration coefficient for return period = 2400 years. See Article 1.3.2.3 Ach = cross-sectional area of a member measured out-to-out of confinement reinforcement, in2 (mm2). See Article 1.4.7.2.1 Ag = gross area of section, in2 (mm2). See Article 1.4.7 AR = base acceleration coefficient for return period = R

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Ash = total cross-sectional area of hoop reinforcement, including cross-ties, in2 (mm2). See Article 1.4.7.2.1 B = buoyancy. See Article 1.4.6 Cm = seismic response coefficient for the mth mode, G’s. See Article 1.4.4.3

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d = distance from extreme compression fiber to centroid of tension reinforcement, inches (mm). See Article 1.4.7.2.2 db = diameter of reinforcing bar or wire, inches (mm). See Article 1.4.7.3.2 D = damping adjustment factor. See Article 1.4.4.2 D = dead load. See Article 1.4.6 E = earth load. See Article 1.4.6 Ec = concrete modulus of elasticity. See Paragraph C -1.4.4.4 EQ = earthquake (seismic). See Article 1.4.6 f ‘c = specified compressive strength of concrete, psi (MPa). See Article 1.4.7 fy = specified yield strength of reinforcement, psi (MPa). See Article 1.4.7 g = acceleration due to gravity. See Paragraph C -1.4.5.3 hc = cross-sectional dimension of member core measured center-to-center of confinement reinforcement, inches (mm). See Article 1.4.7.2.1

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hx = maximum transverse spacing of hoop or cross-tie legs, inches (mm). See Article 1.4.7.2.1 K = Total structure stiffness. See Paragraph C -1.4.5.3 H = height of piers, feet (m). See Article 1.4.7.2.1 Icr = cracked moment of inertia. See Paragraph C -1.4.4.4 ld = development length, inches (mm). See Article 1.4.7.3.2 ldh = development length of standard hook in tension, inches (mm). See Article 1.4.7.3.2 lo = length of plastic hinge zone from the joint face, inches (mm). See Article 1.4.7.2.1 L = length of the bridge deck to the adjacent movement joint, or to the end of the deck, feet (m). See Article 1.4.7.4.1 My1 = moment at first yield of reinforcing steel. See Paragraph C -1.4.4.4 N = minimum support width, inches (mm). See Article 1.4.7.4.1 p(x) = distributed seismic load per unit length of bridge. See Article 1.4.5.3 Pb = nominal axial load strength of a section at balanced strain conditions. See Article 1.4.7.2.1 PS = secondary forces from prestressing. See Article 1.4.6 s = longitudinal spacing of confinement reinforcing, inches (mm). See Article 1.4.7.2.1 S = site coefficient. See Article 1.4.4.1 S = angle of skew measured from a line normal to the span, degrees. See Article 1.4.7.4.1 T = period of vibration, seconds. See Article 1.4.4.4 To = initial transition period, seconds. See Article 1.4.4.4 Tm = period of vibration of the mth mode, seconds. See Article 1.4.4.3 Ts = constant acceleration transition period, seconds. See Paragraph C -1.4.4.4 W = total weight of bridge. See Paragraph C -1.4.5.3 w(x) = distributed weight of bridge per unit length. See Article 1.4.5.3 rs = ratio of volume of spiral or circular hoop reinforcement to total volume of concrete core (measured out-toout of spirals or hoops). See Article 1.4.7.2.1 x = percent critical damping (e.g. 5%). See

fy1 = curvature at first yield of reinforcing steel. See Paragraph C -1.4.4.4

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19 1 7 9

References — 2009 —

The following list of references used in Chapter 9, Seismic Design for Railway Structures is placed here in alphabetical order for your convenience. 1. AASHTO (1996), Standard Specifications for Highway Bridges, 16th edition, American Association of State Highway and Transportation Officials, Washington, D.C. 2. AASHTO (1994), AASHTO LRFD Bridge Design Specifications, Customary U.S. Units, 1st edition, American Association of State Highway and Transportation Officials, Washington, D.C. 3. ACI (1999) , Building Code Requirements for Structural Concrete (ACI 318-99) and Commentary (ACI 318R-99), American Concrete Institute, Farmington Hills, MI.

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4. Algermissen, S.T., D. M. Perkins, P. C. Thenhaus, and B. L. Bender (1982), “Probabilistic Estimates of Maximum Acceleration and Velocity in Rock in the Contiguous United States”, Open File Report 82-1033, U. S. Geological Survey, Reston, VA. 5. ATC (1996), “Improved Seismic Design Criteria for California Bridges: Provisional Recommendations”, ATC-32 Report , Applied Technology Council, Redwood City, CA. 6. Byers, William G., “Evolution of a Railroad’s Earthquake Response”, Lifeline Earthquake Engineering, Michael J. O’Rourke, ed., ASCE, 1995, pp 445-460. 7. Byers, William G., “Railroad Bridge Behavior During Past Earthquakes”, Building an International Community of Structural Engineers, S. K. Gosh & Jamshid Mohammadi, eds., ASCE, 1996, pp 175-182. 8. Caltrans (1995), “Memo to Designers 20-4: Earthquake Retrofit Guidelines for Bridges”, Memos to Designers, California Department of Transportation, Sacramento, CA. 9. Caltrans (2001), Caltrans Seismic Design Criteria, Version 1.2, California Department of Transportation, Sacramento, CA. 10. Dengler, Lori et al., Tsunami, Earthquake Spectra, Supplement A to Vol. 19, pages 115-144, 2003. 11. Departments of the Army, Navy and Air Force (1986), “Seismic Design Guidelines for Essential Buildings”, Technical Manual TM 5-809-10-1, NAVFAC P-355.1, AFM 88-3, Chapter 13, Section A, Joint Departments of the Army, Navy and Air Force, Washington, D.C. 12. FEMA (1991a), “NEHRP Recommended Provisions for the Development of Seismic Regulations for New Buildings”, 1991 Edition, Part 1 Provisions, FEMA 222 Report, Federal Emergency Management Agency, Washington, D.C.

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13. FEMA (1991b), “NEHRP Recommended Provisions for the Development of Seismic Regulations for New Buildings”, 1991 Edition, Part 2 Commentary”, FEMA 223 Report, Federal Emergency Management Agency, Washington, D.C. 14. FEMA (1997a), “NEHRP Guidelines for the Seismic Rehabilitation of Buildings”, FEMA 273 Report, Federal Emergency Management Agency, Washington, D.C. 15. FEMA (1997b), “NEHRP Commentary on the Guidelines for the Seismic Rehabilitation of Buildings”, FEMA 274 Report, Federal Emergency Management Agency, Washington, D.C. 16. Kealey, T.R., and Lewis, D.J., “Railroad Bridges inthe Loma Prieta Earthquake”, Bulletin, American Railway Engineering Assocation, No. 727, Vol. 91, October 1990, pp. 263-271. 17. Koshimura, Shunichi et al., Modeling the 1100 bp paleotsunami in Puget Sound, Washington, Geophysical Research Letters, Vol. 29, No. 20, pages 9-1 to 9-4, 2002. 18. Lam, I. And Martin, G. (1986), “Seismic Design of Highway Bridge Foundations”, Volume II, FHWA-RD-86102 Report, Federal Highway Administration, Washington, D.C. 19. McCulloch, David S. & Bonilla, Manuel G., “Effects of the Earthquake of March 27, 1964 on the Alaska Railroad”, USGS Professional Paper 545-D, U.S. Govt. Printing Office, Washington, DC, 1970. 20. Priestley, M. J. N. (1993), “Assessment and Design of Joints for Single-Level Bridges with Circular Columns”, Report No. SSRP-93/02, University of California, San Diego, CA. 21. Priestley, M.J.N., Seible, F. and Calvi, G.M. (1996), Seismic Design and Retrofit of Bridges, John Wiley & Sons, New York, N.Y. 22. Priestly, M.J Nigel, Singh, J.P., Youd, T. Leslie, and Rollins, Kyle M., “Costa Rica Earthquake of April 22, 1991 Reconnaissance Report, Chapter 6 - Bridges”, Earthquake Spectra, Supplement B to Volume 7, Publication 91-02, Earthquake Engineering Research Institute, October 1991, pp. 59-91. 23. Rogers, Peter D., Otter, Duane E., and Uppal, A. Shakoor, Development of Seismic Response Criteria for North American Railroads, Report No. R-923, Association of American Railroads, Transportation Technology Center, Inc., Pueblo, Colorado, November 1998. 24. Tsunami Bulletin No. 003, Pacific Tsunami Warning Center/NOAA/NWS, December 27, 2004. 25. Wammel, Kenneth L., Prucz, Zolan, and Boraas, Roger S., “The Philosophy and Development of AREA Seismic Design Criteria”, Bulletin, American Railway Engineering Association, No. 760, Vol. 98, May 1997, pp. 77-79. A comprehensive bibliography regarding seismic design and performance of railroads can be found at www.asce.org/inside/bibliography/ Information about the National Weather Services system for email notification of a potential Tsunami can be found at http://wcatwc.arh.noaa.gov/watcher.php (web site address subject to change).

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151

CHAPTER 15 STEEL STRUCTURES1 FOREWORD

Part 1 through Part 7 formulate specific and detailed recommendations for the design, fabrication, erection, maintenance, inspection, and rating of steel railway bridges for: • Spans up to 400 feet, • Standard gage track,

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• Normal North American passenger and freight equipment, and • Speeds of freight trains up to 80 mph and passenger trains up to 90 mph. The requirements, however, apply to spans of any length, but special provisions for spans longer than 400 feet should be added by the company as may be required. Part 8 covers miscellaneous items. Part 10, Bearing Design, and Part 11, Bearing Construction, formulate specific and detailed recommendations for the design and construction of bearings for nonmovable railway bridges. Recommendations for the design and construction of special bearings for movable railway bridges are included in Part 6, Movable Bridges. Part 9 is a commentary, including references, for explanation of various articles in the other parts. This chapter is presented as a consensus document by a committee composed of railroad engineers, engineers in private practice, engineers involved in research and teaching, and other industry professionals having substantial and broad-based experience designing, evaluating, and investigating steel structures used by railroads. The recommendations contained herein are based upon past successful usage, advances in the state of knowledge, and changes in design and maintenance practices. These recommendations have been developed and are intended for routine use and may not provide sufficient criteria for infrequently encountered conditions. Therefore, professional judgment must be exercised when applying the recommendations of this chapter as part of an overall solution to any particular issue. In general, this chapter is revised and published anew on an annual basis. The latest published edition of the chapter should be used, regardless of the age of an existing structure. For purposes of determining historical recommendations under which an existing structure may have been built and maintained, it can prove useful to 1

The material in this and other chapters in the AREMA Manual for Railway Engineering is published as recommended practice to railroads and others concerned with the engineering, design and construction of railroad fixed properties (except signals and communications), and allied services and facilities. For the purpose of this Manual, RECOMMENDED PRACTICE is defined as a material, device, design, plan, specification, principle or practice recommended to the railways for use as required, either exactly as presented or with such modifications as may be necessary or desirable to meet the needs of individual railways, but in either event, with a view to promoting efficiency and economy in the location, construction, operation or maintenance of railways. It is not intended to imply that other practices may not be equally acceptable.

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examine previously published editions of the chapter. However, when historical recommendations differ from the recommendations contained in the latest published edition of the chapter, the recommendations of the latest published edition of the chapter shall govern. Grateful acknowledgment is hereby made to the American Association of State Highway and Transportation Officials and the American Welding Society for having made available their Bridge Welding Code (AWS D1.5) for use by reference in these recommended practices. In applying AWS D1.5, the term “allowable stresses” is to be construed as those allowed herein. Certain other modifications and exceptions to the Code are also recommended. Grateful acknowledgement is also made to the Society of Protective Coating (SSPC) for use of their publications by reference in the recommendations cited in Part 8, Section 8.7, regarding the cleaning and painting of existing steel railway bridges. Part 2, Design – High Strength Steels was combined with Part 1, Design in 1993. Part 5, Special Types of Construction was combined with Part 1, Design in 2008.

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TABLE OF CONTENTS Part/Section Description Special Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1 Proposals and Drawings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2 General Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3 Loads, Forces and Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4 Basic Allowable Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5 General Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6 Members Stressed Primarily in Axial Tension or Compression . . . . . . . . . . . . . . . . . . . . . . . . 1.7 Members Stressed Primarily in Bending . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.8 Floor Members and Floorbeam Hangers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.9 Riveted and Bolted Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.10 Welded Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.11 Bracing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.12 Pins and Pin-Connected Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.13 Continuous and Cantilever Steel Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.14 Fracture Critical Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.15 Live Load Moments, Shears and Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-1-1 15-1-5 15-1-7 15-1-14 15-1-39 15-1-44 15-1-49 15-1-55 15-1-67 15-1-68 15-1-69 15-1-71 15-1-73 15-1-74 15-1-77 15-1-80

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Fabrication. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 Riveted and Bolted Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3 Welded Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4 Shop Painting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5 Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6 Shipment and Pay Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-3-1 15-3-3 15-3-10 15-3-21 15-3-22 15-3-22 15-3-23

Erection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 General (1992) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Definitions of Terms (1992) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 Work to be Done (2002) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 Drawings or Special Provisions to Govern (1992) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5 Plant (1992) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6 Plans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.7 Delivery of Materials (1992) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.8 Handling and Storing Materials (1992) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.9 Establishment of Lines and Elevations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.10 Bearings and Anchorage (2002) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.11 Erection Procedure (1992) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.12 Reinforcement of Members (1992) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.13 Falsework (1991) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.14 Allowable Stresses During Erection (1991) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.15 Drift or Traffic Pins (1991) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.16 Field Assembly of Members (1991) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.17 Fitting-up of Field Connections (1991) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.18 Riveted Field Connections (1991) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.19 High Strength Bolted Field Connections (1991) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.20 Field Welding (1991) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.21 Field Connections Using Pins (1991) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.22 Field Inspection (1991) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-4-1 15-4-2 15-4-3 15-4-3 15-4-3 15-4-3 15-4-3 15-4-4 15-4-4 15-4-4 15-4-4 15-4-5 15-4-5 15-4-5 15-4-5 15-4-6 15-4-6 15-4-6 15-4-7 15-4-7 15-4-7 15-4-7 15-4-7

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3

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TABLE OF CONTENTS (CONT) Part/Section Description 4.23 Misfits (1991) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.24 Field Cleaning and Painting (2002) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.25 Deck (1991) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.26 Removal of Old Structure and Falsework, and Cleanup (1991) R(2008). . . . . . . . . . . . . . . . . 4.27 Interference with Traffic (1983) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.28 Company Equipment (1983) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.29 Work Train Service (1983) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.30 Risk (1983) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.31 Laws and Permits (1983) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.32 Patents (1983) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Page 15-4-8 15-4-8 15-4-8 15-4-9 15-4-9 15-4-9 15-4-10 15-4-10 15-4-10 15-4-10

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Movable Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1 Proposals and General Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2 General Features of Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3 Loads, Forces and Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4 Basic Allowable Stresses and Hydraulic Pressures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5 General Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6 Wire Ropes and Sockets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7 Power Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8 Workmanship . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.9 Erection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-6-1 15-6-5 15-6-13 15-6-18 15-6-28 15-6-33 15-6-71 15-6-75 15-6-99 15-6-104

7

Existing Bridges. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1 General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2 Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3 Rating. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4 Repair, Strengthening and Retrofitting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5 Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-7-1 15-7-2 15-7-4 15-7-13 15-7-24 15-7-32

8

Miscellaneous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-8-1 8.1 Turntables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-8-3 8.2 Method of Shortening of Eyebars to Equalize the Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-8-10 8.3 Anchorage of Decks and Rails on Steel Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-8-12 8.4 Unloading Pits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-8-18 8.5 Walkways and Handrails on Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-8-29 8.6 Guidelines for Evaluating Fire Damaged Steel Railway Bridges . . . . . . . . . . . . . . . . . . . . . . . 15-8-30 8.7 Guide to the Preparation of a Specification for the Cleaning and Coating of Existing Steel Railway Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-8-34

9

Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Part 1 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Part 3 Fabrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Part 6 Movable Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Part 7 Existing Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Part 8 Miscellaneous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Part 10 Bearing Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Part 11 Bearing Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Welding Index (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-9-1 15-9-6 15-9-46 15-9-48 15-9-52 15-9-60 15-9-72 15-9-77 15-9-77

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TABLE OF CONTENTS (CONT) Part/Section

Description

Page

10 Bearing Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2 Basic Allowable Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3 Steel Bearing Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4 Bronze or Copper-Alloy Sliding Expansion Bearings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.5 PTFE Sliding Bearing Surfaces. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.6 Elastomeric Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.7 Multi-Rotational Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-10-1 15-10-3 15-10-10 15-10-11 15-10-17 15-10-18 15-10-21 15-10-32

11 Bearing Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Steel Bearing Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.3 Bronze or Copper-Alloy Sliding Expansion Bearings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.4 PTFE Sliding Bearing Surfaces. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.5 Elastomeric Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.6 Multi-Rotational Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-11-1 15-11-2 15-11-3 15-11-8 15-11-9 15-11-12 15-11-17

Chapter 15 Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-G-1

References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-R-1

1

INTRODUCTION The Chapters of the AREMA Manual are divided into numbered Parts, each comprised of related documents (specifications, recommended practices, plans, etc.). Individual Parts are divided into Sections by centered headings set in capital letters and identified by a Section number. These Sections are subdivided into Articles designated by numbered side headings.

3

Page Numbers – In the page numbering of the Manual (15-3-1, for example) the first numeral designates the Chapter number, the second denotes the Part number in the Chapter, and the third numeral designates the page number in the Part. Thus, 15-3-1 means Chapter 15, Part 3, page 1. In the Glossary and References, the Part number is replaced by either a “G” for Glossary or “R” for References. Document Dates – The bold type date (Document Date) at the beginning of each document (Part) applies to the document as a whole and designates the year in which revisions were last published somewhere in the document, unless an attached footnote indicates that the document was adopted, reapproved, or rewritten in that year. Article Dates – Each Article shows the date (in parenthesis) of the last publication of revisions to that Article. Reaffirmed Dates - Each Article is being reviewed and reaffirmed every 6 years beginning with the year 2002. If no technical changes are made, the publication date of the last reaffirmation is shown following the title of the Article and the Article Date. Revision Marks – All current year revisions (changes and additions) which have been incorporated into the document are identified by a vertical line along the outside margin of the page, directly beside the modified information.

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Proceedings Footnote – The Proceedings footnote on the first page of each document gives references to all Association action with respect to the document. Annual Updates – New manuals, as well as revision sets, will be printed and issued yearly.

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Special Index This special index is provided for assistance in the preparation of plans and other contract papers for the construction of new bridges. It covers Part 1, Design and Part 3, Fabrication, with limited references to other chapters and parts. Subject

Article Number

Abutting joints

3.1.13

Accessibility of parts

1.5.5

Advance material

3.6.2

Alignment of finished holes

3.2.12

Allowable bearing pressure on concrete

Part 10

Allowable bearing pressures, masonry

1.4.4 & Part 10

Allowable fatigue stress range

1.3.13

Allowable load, HS bolts, special surface treatment

Table 15-9-2

Allowable stresses, basic

Part 1, Section 1.4

Allowable stresses, cast steel

1.4.3

Allowable stresses, end floorbeams

1.8.1

Allowable stresses, structural steel, rivets, bolts and pins

1.4.1

Allowable stresses, weld metal

1.4.2

Anchor bolts

Part 10 & Part 11

Angles or tees, effective section

1.6.5

Angles, size of fasteners

1.9.5

Assembly

3.2.10

Attachments, welded

1.10.4

Authority of inspector

3.5.2

AWS Structural Welding Code application

1.2.2

Ballasted deck structures, distribution of live load

1.3.4.2

Base and cap plates, fitting

3.1.16

Base plates

Part 10 & Part 11

Bearing area effective for rivets and pins

1.5.3

Bearing plates and pedestals, surfaces

Part 10 & Part 11

Bearing stiffeners

1.7.7

Bearings, end

Part 10 & Part 11

Bearings inclined

Part 10 & Part 11

Bent bracing

1.11.5

Bibliography

Part 9

Bolts, high strength, installation

3.2.3

Bolts, nuts and washers, high strength

3.2.2

Box members, drainage

1.5.15

Bracing between compression members

1.3.11

1

3

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

15-vii

Subject

Article Number

Bracing of top flange of through girders

1.11.1

Bracing of viaduct towers and bents

1.11.5

Bracing, lateral

1.11.2

Bracing, portal and sway

1.11.3

Built-up member, connection of components

1.5.14

Butt joints, width or thickness transition for welding

1.10.1

Camber

1.2.10

Cambering of girder webs

3.1.6

Cantilever spans

Part 1, Section 1.13

Cast steel, allowable stresses

1.4.3

Categories for fatigue stresses, examples

Table 15-1-9

Categories of stress for fatigue consideration

Table 15-1-9

Centrifugal force

1.3.6

Clearance diagram

Figure 15-1-1

Clearances

1.2.6

Clearances for electrified operation

1.2.6

Clearances for pins

3.1.14

Combinations of welds, high strength bolts, rivets

1.5.12

Combined axial compression and bending, allowable stresses

1.3.14.1

Combined axial tension and bending, allowable stresses

1.3.14.2

Composite steel and concrete spans

1.7.9

Compression members

1.6.1

Compression members, bracing between

1.3.11

Compression members, forked ends

1.12.4

Concrete deck design

1.3.4.2.2d

Concrete, allowable bearing pressures

Part 10

Conflict between drawings and specifications

1.1.4

Connections and splices

1.5.9

Connections of components of built-up members

1.5.14

Connections, field

1.5.10

Consultant use on public works projects

1.1.8

Contact surfaces not to be painted

3.4.1c

Continuous spans

Part 1, Section 1.13

Cooper E series live load

1.3.3

Cover plates on rolled beams

1.7.2.2

Cross frames for deck spans

1.11.4

Cycles of stress for fatigue considerations

Table 15-1-7

Dead load

1.3.2

Deck design, concrete

1.3.4.2.2d

© 2011, American Railway Engineering and Maintenance-of-Way Association

15-viii

AREMA Manual for Railway Engineering

Subject

Article Number

Deck design, timber

1.3.4.2.2d

Deck spans, cross frames and diaphragms

1.11.4

Deck thickness, minimum for various materials

1.3.4.2.2c

Definitions, FCM provisions

1.14.2

Definitions, general

1.1.1

Deflection

1.2.5

Detail categories for fatigue consideration

Table 15-1-9

Development of fillers

1.5.11

Diaphragms for deck spans

1.11.4

Dimensional tolerances

3.1.7

Dimensional tolerances for truss and viaduct tower members

3.1.7.2

Dimension for stress calculations

1.2.7

Direct tension indicators for use with high strength bolts

3.2.3

Dissimilar fasteners in a connection

1.5.12

Distribution of live load

1.3.4

Distribution of live load, ballasted deck structures

1.3.4

Distribution of live load, open deck structures

1.3.4

Drainage of pockets

1.5.6

Drawings

1.1.3

Drawings govern over specifications

1.1.4

Drifting during assembly

3.2.13

Earthquake forces

1.3.17

Eccentric connections

1.5.7

Edge distance, base and masonry plates

Part 10 & Part 11

Edge distance, fasteners

1.9.4

Effective diameter of fasteners

1.5.2

Effective dimensions of base and masonry plates

Part 10 & Part 11

Effective dimensions of rollers and rockets

Part 10 & Part 11

Effective dimensions of shoes and pedestals

Part 10 & Part 11

Effective dimensions, base and masonry plates

Part 10 & Part 11

Effective section of angles or tees

1.6.5

End bearings

Part 10 & Part 11

End floorbeams

1.8.1

Erection

Part 4

Existing bridges

Part 7

Expansion

1.2.13

Fabricated material, marking, shipping and loading

3.6.1

Fabricator qualification

3.1.1

Fabricator qualification, fracture control plan

1.14.4

1

3

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

15-ix

Subject

Article Number

Facilities for inspection

3.5.1

Facing floorbeams, stringers and girders

3.1.12

Fastener sizes in angles

1.9.5

Fasteners for field use, quantity to be supplied

3.2.4

Fasteners in indirect splices

1.9.6

Fasteners, dissimilar types in a connection

1.5.12

Fasteners, edge distance

1.9.4

Fasteners, effective diameter

1.5.2

Fasteners, minimum number per connection plane

1.5.9

Fasteners, pitch and gage defined

1.9.1

Fasteners, spacing

1.9.3

Fatigue loading on high strength bolts

1.3.13.1

Fatigue, classification of members for E80 loading

Table 15-1-7

Fatigue, dissimilar fasteners in a connection

1.5.12

Fatigue, general

1.3.13

Fatigue, stress categories

Table 15-1-9

Fatigue, stress ranges allowed

Table 15-1-10

Field connections

1.5.10

Field welds for live load stress prohibited

1.5.10

Fillers, development

1.5.11

Fillet welds

1.10.3

Fit of stiffeners

3.1.10

Fitting for shop riveting or bolting

3.2.13

Fitting of base and cap plates

3.1.16

Flange sections of girders

1.7.2

Flanges splices, girders

1.7.5

Flange-to-web connection, girders

1.7.4

Flange-to-web welds

3.3.3

Floor members, end connections

1.8.3

Floorbeam reactions for E80 live load

Part 9

Floorbeams and Floorbeam hangers

1.8.2

Floorbeams, end

1.8.1

Floorbeams, end connections

1.8.3

Forked ends of compression members

1.12.4

Fracture control plan

1.14.1

Fracture critical members or member components definitions

1.14.2

Fracture critical members, design responsibilities

1.14.3

Fracture critical members

Part 1, Section 1.14

General rules

Part 1, Section 1.5

© 2011, American Railway Engineering and Maintenance-of-Way Association

15-x

AREMA Manual for Railway Engineering

Subject

Article Number

Girder flanges, riveted or bolted construction

1.7.2.1

Girder flanges, welded construction

1.7.2.2

Girders and beams, proportioning

1.7.1

Girders, through, bracing of top flanges

1.11.1

Guard (inner) rails, steel

1.2.12

Guard timbers

1.2.12

Gusset plates of trusses, minimum thickness

1.5.4

Height of rail

1.2.6

High strength bolted joints, inspection

3.5.4

High strength bolts fatigue tension loading on

1.3.13.1

High strength bolts, installation

3.2.3

High strength bolts, installation tension required

Table 15-1-12

High strength bolts, nuts and washers

3.2.2

High strength bolts, re-use

3.2.3(3)

High strength bolts, special surface treatment

Part 9, Section 9. 1.4

High strength structural steel

Table 15-1-1

Hole Alignment

3.2.12

Holes for field fasteners

3.2.7

Holes for shop fasteners

3.2.6

Holes, oversize, short slotted, long slotted

9. 3.2.6

Holes, size and workmanship

3.2.5

Impact load

1.3.5

Impact load, girder flange-to-web connections

1.7.4

Impact tests, FCM material

1.14.5

Impact test, non-FCM material

Table 15-1-14

Impact test, non-FCM material

Table 15-1-2

Inclined bearings

Part 10 & Part 11

Indirect splices, fasteners

1.9.6

Inspection facilities

3.5.1

Inspection of high strength bolted joints

3.5.4

Inspection of welded fabrication

3.5.5

Inspector authority

3.5.2

Installation of high strength bolts

3.2.3

Interaction formula for combined compression and bending

1.3.14.1

Intermediate stiffeners

1.7.8

Intermittent field welds prohibited

1.10.2

Jacking provisions applied to end floorbeams

1.8.1

Lacing

1.6.4.2

Lacing bars, round ends required

3.1.9

1

3

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

15-xi

Subject

Article Number

Lacing, shear force

1.6.4.1

Lateral bracing

1.11.2

Lateral forces from equipment

1.3.9

Live load

1.3.3

Live load distribution, ballasted deck structures

1.2.3

Live load distribution, open deck structures

1.3.4

Load, live

1.3.3

Loads and forces

1.3.1

Longitudinal beams or girders, design

1.3.4.2.4

Longitudinal force

1.3.12

Machined surfaces, shop painting

3.4.2

Map for service temperature, Canada

Figure 15-9-2

Map for service temperatures, USA

Figure 15-9-1

Marking fabricated material

3.6.1

Masonry plates

Part 10 & Part 11

Masonry allowable bearing pressures

1.4.4 & Part 10

Match marking

3.2.11

Material orders and shipping statements

3.1.2

Material storage

3.1.4

Material weldability

1.10.6

Materials

1.2.1

Moment, shear, pier reaction table, E80

Part 9

Movable bridges

Part 6

Multiple tracks, live load

1.3.3

Nameplates

1.2.11

Net section

1.5.8

Non-destructive testing personnel qualification, FCM work

1.14.1

Notch toughness for weld metal, fracture control plan

1.14.1

Notch toughness, FCM material

1.14.5 and Table 15-1-14

Notch toughness, other than FCM material

Table 15-1-2

Notice of beginning fabrication

3.1.3

Notice to Engineer

1.1.6

Open deck structures, distribution of live load

1.3.4.1

Oversize holes

9. 3.2.6

Painting of interiors of closed box members not required

1.5.15

Patented devices

1.1.5

Pay weight

3.6.3

Pedestals

Part 10 & Part 11

Perforated cover plates

1.6.4.3

© 2011, American Railway Engineering and Maintenance-of-Way Association

15-xii

AREMA Manual for Railway Engineering

Subject

Article Number

Perforated cover plates, shear force

1.6.4.1

Permits

1.1.7

Pier reactions for E80 live load

Part 9

Pin clearance

3.1.14

Pin holes, reinforcing plates

1.12.3

Pin holes, section

1.12.2

Pins

1.12.1

Pins and rollers

3.1.15, Part 10 & Part 11

Planning sheared edges

3.1.8

Plug and slot welds prohibited

1.10.2

Portal bracing

1.11.3

Preferred types of bridges

1.2.3

Preparation of material for welding

3.3.2

Prohibited types of joints and welds

1.10.2

Prohibited weld, tack welding on tension flanges

3.3.3

Proportioning girders and beams

1.7.1

Proportioning truss web members

1.3.16

Proposals

1.1.2

Prying action on high strength bolts

1.3.13.1

Public works projects

1.1.8

Qualification of fabricator, fracture critical members

1.14.1 and 3.1.1

Qualification of fabricators

3.1.1

Qualification of welders and welding operators

3.3.5

Qualification of welders, fracture critical members

1.14.1

Quality control and assurance, fracture critical members

1.14.1

Quantity of field fasteners

3.2.4

Radial force from welded rail

Part 8, Section 8.3

Rail height

1.2.6

Re-entrant corners, thermal cutting

3.1.6

Reaming and drilling after assembly

3.2.10

Reaming and drilling templates

3.2.8

Reaming and drilling through templates

3.2.9

Reinforcing plates at pin holes

1.12.3

Rejection of shop fabrication

3.5.3

Reuse of high strength bolts

3.2.3(3)

Rigid frame structures

1.7.10

Rivet grip, taper and extra rivet requirements

1.9.2

Riveting requirements and riveting

3.2.1

Rivets and pins, effective bearing area

1.5.3

1

3

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

15-xiii

Subject

Article Number

Rockers

Part 10 & Part 11

Rocking effect

1.3.5

Sealing

1.5.13

Secondary stress

1.3.15

Secondary stress floorbeam hangers, subverticals

9. 1.3.15

Service temperature map, Canada

Figure 15-9-2

Service temperature map, USA

Figure 15-9-1

Shear force in lacing or perforated cover plates

1.6.4.1

Sheared Edges, planning

3.1.8

Shears for E80 live load

Part 9

Shipping fabricated material

3.6.1

Shoes

Part 10 & Part 11

Ship drawings

1.1.3

Shop painting

3.4.1

Shop painting of machined surfaces

3.4.2

Size and workmanship of holes

3.2.5

Skew bridges

1.2.8

Slenderness ratio

1.5.1

Slotted holes

9. 3.2.6

Spacing of fasteners

1.9.3

Spacing of trusses, girders, and stringers

1.2.4

Specifications governed by drawings

1.1.4

Splices, abutting joints

3.1.13

Splices, girder flanges

1.7.5

Splices, girder webs

1.7.6

Splicing compression members

1.5.9

Squaring up bridge ends

1.2.8

Stability of spans and towers

1.3.10

Stay plates

1.6.3

Steel, structural

Table 15-1-1

Stiffener fit

3.1.10

Stiffeners, bearing

1.7.7

Stiffeners, intermediate

1.7.8

Stiffeners, intermediate, welded to girder webs

1.10.4

Storage of material

3.1.4

Straightening material

3.1.5

Stress categories for fatigue consideration

Table 15-1-9

Stresses allowed, basic

Part 1, Section 1.4

Stringers, end connections

1.8.3

© 2011, American Railway Engineering and Maintenance-of-Way Association

15-xiv

AREMA Manual for Railway Engineering

Subject

Article Number

Structural steel

Table 15-1-1

Structural steel, high strength

Table 15-1-1

Surfaces of bearing plates and pedestals

Part 10 & Part 11

Sway bracing

1.11.3

Tack welding, prohibited on tension flanges

3.3.4

Templates for reaming and drilling

3.2.8

Tension required in installed high strength bolts

Table 15-1-12

Thickness of compression members elements

1.6.1

Thickness of girder web plates

1.7.3

Thickness of metal

1.5.4

Thickness outstanding elements of compression members

1.6.2

Through girders, bracing of top flanges

1.11.1

Ties for open deck bridges

1.2.9

Timber bridge tie requirements

Chapter 6

Timber deck design

1.3.4.2.2d

Timber guards

1.2.12

Thermal cutting

3.1.6

Tolerances of dimensions

3.1.7

Tolerances of dimensions, truss and viaduct tower members

3.1.7.2

Tolerances, sweep and camber

3.1.7.1e paragraph (2)

Tower and span stability

1.3.10

Transition of thickness or width in welded butt joints

1.10.1

Transverse beams without stringers, diaphragm requirements

1.11.4h

Transverse beams, design

1.3.4.2.3

Turn-of-nut method for installing HS bolts, nut rotation

Table 15-3-3

Turn-of-nut method of installing high strength bolts

3.2.3d

Turntables

Part 8, Section 8.1

Types of bridges preferred

1.2.3

Unloading pits

Part 8, Section 8.4

Uplift on anchor bolts

Part 10 & Part 11

Viaduct tower bracing

1.11.5

Walkways and handrails on bridges

Part 8, Section 8.5

Web members of trusses, proportioning

1.3.16

Web plate thickness, girders

1.7.3

Web splices, girders

1.7.6

Webs of riveted or bolted girders, control of edge position

3.1.11

Weight of fabricated material for payment purposes

3.6.3

Weights of material shipped

3.1.2

Weld metal, allowable stresses

1.4.2

1

3

4

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

15-xv

Subject

Article Number

Weldability of material

1.10.6

Welded attachments

1.10.4

Welded butt joints

1.10.1

Welded closed box members

1.5.15

Welded fabrication

Part 3, Section 3.3

Welded fabrication, inspection

3.5.5

Welded rail on bridges

Part 8, Section 8.3

Welders and welding operators, qualification

3.3.5

Welding index

Part 9

Welding requirements, fracture critical members

1.14.1

Welding requirements, general

1.2.2

Welding, general

3.3.1

Welds and joints, prohibited types

1.10.2

Welds, fillet

1.10.3

Welds, intermediate stiffeners to girder webs

1.10.4

Width of outstanding elements of compression members

1.6.2

Wind combined with other loads, allowable stresses

1.3.14.3

Wind force on loaded bridge

1.3.7

Wind force on unloaded bridge

1.3.8

Wind force only, allowable stresses

1.3.14.3

© 2011, American Railway Engineering and Maintenance-of-Way Association

15-xvi

AREMA Manual for Railway Engineering

15 15310

Part 1 Design1 — 2011 — FOREWORD

The purpose of this part is to formulate specific and detailed rules as a guide for the design of fixed spans using structural steel.

1

TABLE OF CONTENTS Section/Article

Description

Page

1.1 Proposals and Drawings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.1 Definition of Terms (1984) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.2 Proposals (1984) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.3 Shop Drawings (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.4 Drawings to Govern (1993) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.5 Patented Technologies (1993) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.6 Notice to Engineer (1993) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.7 Permits (1993) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.1.8 Design of Public Works Projects (1993) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-1-5 15-1-5 15-1-5 15-1-6 15-1-6 15-1-6 15-1-6 15-1-6 15-1-6

1.2 General Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2.1 Materials (2010). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2.2 Welding (2003) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2.3 Types of Bridges (1995) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-1-7 15-1-7 15-1-10 15-1-11

1

References, Vol. 4, 1903, pp. 130, 141, 253; Vol. 5, 1904, p. 581; Vol. 6, 1905, pp. 218, 447; Vol. 7, 1906, pp. 185, 235; Vol. 11, 1910, part 1, pp. 115, 160; Vol. 21, 1920, pp. 493, 1398; Vol. 25, 1924, pp. 1072, 1262; Vol. 35, 1934, pp. 1021, 1196; Vol. 36, 1935, pp. 633, 987; Vol. 39, 1938, pp. 153, 891; Vol. 41, 1940, pp. 408, 858; Vol. 42, 1941, pp. 356, 874; Vol. 43, 1942, pp. 365, 737; Vol. 44, 1943, pp. 400, 670, 685; Vol. 45, 1944, pp. 180, 605; Vol. 47, 1946, pp. 245, 647; Vol. 48, 1947, pp. 391, 930; Vol. 49, 1948, pp. 199, 666; Vol. 50, 1949, pp. 425, 749; Vol. 51, 1950, pp. 443, 904; Vol. 53, 1952, pp. 508, 1061; Vol. 54, 1953, pp. 905, 1346; Vol. 55, 1954, pp. 586, 1020; Vol. 56, 1955, pp. 590, 1085; Vol. 57, 1956, pp. 554, 998; Vol. 58, 1957, pp. 685, 1191; Vol. 59, 1958, pp. 700, 702, 1194, 1195; Vol. 60, 1959, pp. 506, 508, 1098, 1100; Vol. 61, 1960, pp. 560, 1127; Vol. 62, 1961, pp. 545, 550, 551, 876, 877; Vol. 63, 1962, pp. 382, 699; Vol. 64, 1963, pp. 361, 630; Vol. 65, 1964, pp. 382, 775; Vol. 66, 1965, pp. 292, 653; Vol. 67, 1966, pp. 341, 697; Vol. 68, 1967, p. 350; Vol. 70, 1969, p. 241; Vol. 71, 1970, p. 375; Vol. 72, 1971, p. 153; Vol. 73, 1972, p. 176; Vol. 74, 1973, p. 137; Vol. 75, 1974, p. 334; Vol. 76, 1975, p. 240; Vol. 77, 1976, p. 249; Vol. 78, 1977, p. 77; Vol. 79, 1978, p. 45; Vol. 80, 1979, p. 188; Vol. 82, 1981, p. 78; Vol. 83, 1982, p. 372; Vol. 84, 1983, p. 100; Vol. 86, 1985, p. 90; Vol. 87, 1986, p. 103; Vol. 88, 1987, p. 87; Vol. 90, 1989, p. 98; Vol. 91, 1990, p. 121; Vol. 92, 1991, 67; Vol. 94, 1994, p. 131; Vol. 96, p. 66; Vol. 97, p. 171. Reapproved with revisions 1996.

© 2011, American Railway Engineering and Maintenance-of-Way Association

15-1-1

3

Steel Structures

TABLE OF CONTENTS (CONT) Section/Article 1.2.4 1.2.5 1.2.6 1.2.7 1.2.8 1.2.9 1.2.10 1.2.11 1.2.12 1.2.13

Description

Page

Spacing of Trusses, Girders, and Stringers (1995) R(2008) . . . . . . . . . . . . . . . . . . . . . . . Deflection (2001) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Clearances (1995) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Dimensions for Calculations of Stresses (2004) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . Skew Bridges (1994) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Open Deck Bridge Ties (1994) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Camber (1995) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nameplates (1995) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Steel Inner Guard Rails and Guard Timbers (1995) R(2008) . . . . . . . . . . . . . . . . . . . . . . Provision for Expansion (2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-1-11 15-1-11 15-1-12 15-1-13 15-1-14 15-1-14 15-1-14 15-1-14 15-1-14 15-1-14

1.3 Loads, Forces and Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.1 Loads and Forces (1995) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.2 Dead Load (1995) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.3 Live Load (1995) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.4 Distribution of Live Load (1993) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.5 Impact Load (2007) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.6 Centrifugal Force (2002) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.7 Wind Forces on Loaded Bridge (2003) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.8 Wind Forces on Unloaded Bridge (2006) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.9 Lateral Forces from Equipment (1993) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.10 Stability Check (2005) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.11 Bracing Between Compression Members (2000) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.12 Longitudinal Forces (2005) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.13 Fatigue (2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.14 Combined Stresses (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.15 Secondary Stresses (1994) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.16 Proportioning of Truss Web Members (2004) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.3.17 Earthquake Forces (1994) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-1-14 15-1-14 15-1-15 15-1-15 15-1-16 15-1-18 15-1-20 15-1-21 15-1-21 15-1-22 15-1-22 15-1-23 15-1-23 15-1-23 15-1-37 15-1-38 15-1-39 15-1-39

1.4 Basic Allowable Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4.1 Structural Steel, Rivets, Bolts and Pins (2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4.2 Weld Metal (1994) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4.3 Cast Steel (1994) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4.4 Masonry (2002) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4.5 Timber Bridge Ties (1994) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-1-39 15-1-39 15-1-43 15-1-44 15-1-44 15-1-44

1.5 General Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.1 Slenderness Ratio (2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.2 Effective Diameter of Fasteners (1993) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.3 Effective Bearing Area of Bolts, Rivets and Pins (1993) R(2008) . . . . . . . . . . . . . . . . . . . 1.5.4 Thickness of Material (2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.5 Accessibility of Parts (1993) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.6 Drainage of Pockets (1993) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.7 Eccentric Connections (1993) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.8 Net Section (2005) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.9 Connections and Splices (2003) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.10 Field Connections (1994) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.5.11 Development of Fillers (1993) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Description

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Combinations of Dissimilar Types of Connections (1993) R(2008) . . . . . . . . . . . . . . . . . . Sealing (1993) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Connections of Components of Built-up Members (1993) R(2008) . . . . . . . . . . . . . . . . . . Welded Closed Box Members (1993) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-1-48 15-1-48 15-1-48 15-1-48

1.6 Members Stressed Primarily in Axial Tension or Compression . . . . . . . . . . . . . . . . . . 1.6.1 Compression Members (2004) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6.2 Outstanding Elements in Compression (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6.3 Stay Plates (1994) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6.4 Lacing and Perforated Cover Plates for Tension and Compression Members (2009) . . . 1.6.5 Effective Net Area for Tension Members - Strength (2008) . . . . . . . . . . . . . . . . . . . . . . . . 1.6.6 Effective Area for Tension Members - Fatigue (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-1-49 15-1-49 15-1-50 15-1-50 15-1-51 15-1-53 15-1-55

1.7 Members Stressed Primarily in Bending. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7.1 Proportioning Girders and Beams (2004) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7.2 Flange Sections (1994) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7.3 Thickness of Web Plates (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7.4 Flange-to-Web Connection of Plate Girders (2009). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7.5 Flange Splices (1994) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7.6 Web Splices (1994) R(2002). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7.7 Stiffeners at Points of Bearing (1994) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7.8 Web Plate Stiffeners (Intermediate Transverse and Longitudinal) (2010) . . . . . . . . . . . . 1.7.9 Composite Steel and Concrete Spans (2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7.10 Rigid Frame Structures (2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-1-55 15-1-55 15-1-56 15-1-56 15-1-57 15-1-57 15-1-58 15-1-58 15-1-59 15-1-61 15-1-65

1.8 Floor Members and Floorbeam Hangers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.8.1 End Floorbeams (1993) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.8.2 Floorbeams and Floorbeam Hangers (1993) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.8.3 End Connections of Floor Members (1993) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-1-67 15-1-67 15-1-67 15-1-67

1.9 Riveted and Bolted Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.9.1 Pitch and Gage of Fasteners (1993) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.9.2 Grip of Rivets (1993) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.9.3 Minimum Spacing of Fasteners (1993) R(2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.9.4 Edge Distance of Fasteners (2005) R(2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.9.5 Sizes of Fasteners in Angles (1993) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.9.6 Fasteners in Indirect Splices (1993) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-1-68 15-1-68 15-1-68 15-1-68 15-1-68 15-1-69 15-1-69

1.10 Welded Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.10.1 Transition of Thickness or Widths in Welded Butt Joints (1993) R(2003) . . . . . . . . . . . . 1.10.2 Prohibited Types of Joints and Welds (2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.10.3 Fillet Welds (1993) R(2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.10.4 Welded Attachments (2004) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.10.5 Fracture Critical Members (1994) R(2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.10.6 Material Weldability (2006) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-1-69 15-1-69 15-1-70 15-1-70 15-1-70 15-1-71 15-1-71

1.11 Bracing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.11.1 Bracing of Top Flanges of Through Girders (2000) R(2008) . . . . . . . . . . . . . . . . . . . . . . . 1.11.2 Lateral Bracing (1994) R(2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Portal and Sway Bracing (1994) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cross Frames and Diaphragms for Deck Spans (1994) R(2002) . . . . . . . . . . . . . . . . . . . . Bracing of Viaduct Towers and Bents (1994) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bracing Members Used as Ties or Struts Only (1994) R(2008). . . . . . . . . . . . . . . . . . . . .

15-1-71 15-1-72 15-1-72 15-1-73

1.12 Pins and Pin-Connected Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.12.1 Pins (1994) R(2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.12.2 Section at Pin Holes (1993) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.12.3 Reinforcing Plates at Pin Holes (1993) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.12.4 Forked Ends of Compression Members (1993) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-1-73 15-1-73 15-1-73 15-1-73 15-1-73

1.13 Continuous and Cantilever Steel Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.13.1 Definition (2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.13.2 Basic Design Assumptions (2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.13.3 Deflection (2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.13.4 Camber (2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.13.5 Impact Load (2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.13.6 Uplift (2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.13.7 Bracing (2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.13.8 Longitudinal Stiffeners (2010). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.13.9 Cover Plates (2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.13.10 Splices in Flexural Members (2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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1.14 Fracture Critical Members. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.14.1 Scope (2001) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.14.2 Definitions (1997) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.14.3 Design and Review Responsibilities (1997) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.14.4 Special Welding Requirements (1997) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.14.5 Notch Toughness of Steel in Fracture Critical Members (2010) . . . . . . . . . . . . . . . . . . . .

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1.15 Live Load Moments, Shears and Reactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.15.1 Tabulated Values for Simple Spans (2003) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.15.2 Supplemental Formulas for Simple Spans (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-1-80 15-1-80 15-1-81

LIST OF FIGURES Figure 15-1-1 15-1-2 15-1-3 15-1-4 15-1-5

Description

Page

Minimum Railway Bridge Clearances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cooper E 80 Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Alternate Live Load on 4 Axles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Location of Eccentric Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Determination of x . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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LIST OF TABLES Table

Description

15-1-1 Structural Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-1-2 Impact Test Requirements for Structural Steel – Other than Fracture Critical Members. . . . 15-1-3 Equivalent Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-1-4 Curved Track Clearance Increases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-1-5 Unit Weights for Dead Load Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-1-6 Impact Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-1-7 Number of Stress Cycles, N . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-1-8 Assumed Mean Impact Load Percentages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-1-9 Detail Categories for Load Induced Fatigue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-1-10 Allowable Fatigue Stress Range, SRfat (ksi) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-1-11 Structural Steel, Rivets, Bolts and Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-1-11a Allowable Stress for Slip-Critical Connections (Slip Load per Unit of Bolt Area, psi). . . .. . . 15-1-12 Minimum Tension of Installed Bolts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-1-13 Allowable Stress on Welds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-1-14 Impact Test Requirements for Structural Steel - Fracture Critical Members . . . . . . . . . . . . . . 15-1-15 Maximum Moments, Shears and Pier (or Floorbeam) Reactions for Cooper E 80 Live Load or Alternate Live Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-1-16 Calculation of Maximum Moments on Short, Simple Spans (15-1-15) . . . . . . . . . . . . . . . . . . . .

Page 15-1-8 15-1-9 15-1-10 15-1-13 15-1-15 15-1-20 15-1-24 15-1-25 15-1-26 15-1-36 15-1-40 15-1-43 15-1-43 15-1-44 15-1-79 15-1-80 15-1-81

1 SECTION 1.1 PROPOSALS AND DRAWINGS 1.1.1 DEFINITION OF TERMS (1984) R(2008) The term “Company” means the railway company party to the contract. The term “Engineer” means the chief engineering officer of the Company or this individual’s authorized representative. The term “Inspector” means the inspector representing the Company. The term “Contractor” means the manufacturing, fabricating or erecting contractor party to the contract.

1.1.2 PROPOSALS (1984) R(2008) a.

4

Bidders shall submit proposals conforming to the terms in the letter of invitation. The proposals shall be based on plans and specifications furnished by the Company. Such plans and specifications shall show the conditions determining the design of the bridge, the general dimensions, force and stress data and typical details.

b. When the invitation requires the Contractor to furnish the design, the invitation shall state the design criteria and the general conditions at the site, such as the track spacing, foundation soil conditions, presence of old structures and traffic conditions.

1.1.3 SHOP DRAWINGS (2009) a.

After the contract has been awarded, the Contractor shall submit to the Engineer, for review and approval as to conformity to contract requirements, prints from checked plans in the number required, of stress sheets, shop drawings and erection procedures, unless such sheets, drawings and procedures have been prepared by the Company.

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Steel Structures

b. The original drawings shall be legible. They shall be delivered to and become the property of the Company upon completion of the contract. c.

Alternately, electronic drawings may be submitted in an approved format and via a method approved by the Engineer.

d. Shop drawing size shall be preferably 24 inches by 36 inches, including left margin 1-1/2 inches wide and 1/2 inch margin on other edges. An approved title shall be in the lower right corner. e.

Where any changes or corrections are required by the Engineer, one print, with changes shown thereon, shall be returned to the Contractor either electronically or by conventional method. Prints from corrected plans shall be submitted to the Engineer for review, and this procedure shall continue until each drawing, etc., is approved.

f.

No additional change shall be made to such approved drawings without the consent of the Engineer.

g.

The Contractor shall furnish to the Company as many prints of the drawings as required to carry out the work.

h. The Contractor shall be wholly responsible for the accuracy and completeness of the drawings, regardless of the approval by the Engineer. i.

Any work performed or material ordered prior to approval by the Engineer shall be at the sole risk of the Contractor.

1.1.4 DRAWINGS TO GOVERN (1993) R(2008) Where the drawings and the specifications conflict, the drawings shall govern.

1.1.5 PATENTED TECHNOLOGIES (1993) R(2008) The Contractor shall protect the Company against claims arising from the use of patented technologies or parts proposed by the Contractor.

1.1.6 NOTICE TO ENGINEER (1993) R(2008) No material shall be rolled or any work performed before the Engineer has been notified in writing where the orders have been placed.

1.1.7 PERMITS (1993) R(2008) All permits required for the location and construction of the structure shall be obtained as directed by the Company.

1.1.8 DESIGN OF PUBLIC WORKS PROJECTS (1993)1 R(2008) a.

1

The design, plans, special provisions and specifications for railroad bridges to be built as a public works project and paid for with public funds administered by a public agency shall be prepared by the engineering staff of the Company involved or by a consulting engineer or the staff of a public agency whose selection has been mutually approved by the Company and the public agency. Selection of

See Part 9 Commentary

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Design

consultants shall be limited to those who are familiar with the design of railroad bridges, and particularly with the special requirements and operating conditions of the Company concerned. b. When a consulting engineer is engaged, the contract for services may be administered either by the public agency or by the Company. In either case, the technical aspects of the work of the consulting engineer shall be under the direction of the Company and the final plans and specifications shall be subject to the approval of the Company.

SECTION 1.2 GENERAL REQUIREMENTS 1.2.1 MATERIALS (2010)1 a.

The design requirements of these recommended practices, contained in this part are based on the use of materials conforming to the current requirements of the following ASTM specifications: Structural Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Table 15-1-1 Where this material is to be used for applications in which improved notch toughness is important, such as welded main load carrying components subject to tensile stress other than Fracture Critical Members, defined in Article 1.14.2, the impact test requirements of Table 15-1-2 shall be met. Notch toughness requirements for Fracture Critical Members shall be in accordance with Table 15-1-14. Components requiring these toughness requirements shall be designated on the design drawings and/or in the specifications. For bridge construction, the material shall not be rimmed or capped steel.

1

Rivet steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A 502, Grade 1, 2, or Grade 3 High strength bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A 325 and A 490 Carbon and Alloy Steel Nuts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A 563

3

Washers, Steel, Hardened . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F 436 Direct Tension Indicators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . F 959 High Strength “Twist Off” Type Tension Control Bolts . . . . . . . . . . . F 1852 Machine bolts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A 307 Cast steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A 27, Grade 65–35 or A 148

4

Forged steel, for large pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A 668 Welding electrodes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . See AWS D1.5 For A709, Grade HPS 70W see Article 1.2.2c

1

See Part 9 Commentary

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Steel Structures Table 15-1-1. Structural Steel (Note 1)

ASTM Designation

Fu Fy - Min Ultimate Tensile Yield Point or Strength or Tensile Yield Strength Strength psi psi

Thickness Limitation For Plates and Bars, inches

Applicable to Shapes

A36

36,000 min

58,000 min 80,000 max

To 8 incl.

All (Note 3)

A709, Grade 36

36,000 min

58,000 min 80,000 max

To 4 incl.

All (Note 3)

A588 (Note 2) A709, Grade 50W (Note 2) A709, Grade HPS 50W (Note 2)

50,000 min

70,000 min

To 4 incl.

All

A588 (Note 2)

46,000 min

67,000 min

Over 4 to 5 incl.

None

A588 (Note 2)

42,000 min

63,000 min

Over 5 to 8 incl.

None

A992 (Note 4) A709, Grade 50S (Note 4)

50,000 min 65,000 max (Note 5)

65,000 min Yield to Tensile Ratio, 0.85 max

None

All

A572, Grade 50 A709, Grade 50

50,000 min

65,000 min

To 4 incl.

All

A572, Grade 42

42,000 min

60,000 min

To 6 incl.

All

A709, Grade HPS 70W (Note 2)

70,000 min

85,000 min 110,000 max

To 4 incl.

None

Note 1: These requirements are current as of May 2009. Refer to ASTM specifications for additional requirements. Note 2: A588 and A709, Grade 50W, Grade HPS 50W, and Grade HPS 70W have atmospheric corrosion resistance in most environments substantially better than that of carbon steels with or without copper addition. In many applications these steels can be used unpainted. Note 3: For wide flange shapes with flange thickness over 3 inches, the 80,000 psi maximum tensile strength limit does not apply. Note 4: The yield to tensile ratio shall be 0.87 or less for shapes that are tested from the web location; for all other shapes, the requirement is 0.85 maximum. Note 5: A maximum yield strength of 70,000 psi is permitted for structural shapes that are required to be tested from the web location.

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Design Table 15-1-2. Impact Test Requirements for Structural Steel – Other than Fracture Critical Members (See Notes 1 and 5)

ASTM Designation

Thickness Inches, (mm)

Minimum Average Energy, Ft-lb, (J) and Test Temperatures Zone 1

Zone 2

Zone 3

A36/A36M

To 6(150)incl.

15(20)@ 70°F(21°C)

15(20)@ 40°F(4°C)

15(20)@ 10°F(-12°C)

A709/A709M, Grade 36T(250T) (Note 6)

To 4(100)incl.

15(20)@ 70°F(21°C)

15(20)@ 40°F(4°C)

15(20)@ 10°F(-12°C)

15(20)@ 70°F(21°C)

15(20)@ 40°F(4°C)

15(20)@ 10°F(-12°C)

20(27)@ 70°F(21°C)

20(27)@ 40°F(4°C)

20(27)@ 10°F(-12°C)

To 2(50)incl. A992/A992M (Note 2) A709/A709M, Grade 50ST (Grade 345ST) (Notes 2 and 6) Over 2(50)to A588/A588M (Note 2) 4(100)incl. A572/A572M, Grade 42 (Grade 290) (Note 2) A572/A572M, Grade 50 (Grade 345) (Note 2) A709/A709M, Grade 50T (Grade 345T) (Notes 2 and 6) A709/A709M, Grade 50WT (Grade 345WT) (Notes 2 and 6)

1

A572/A572M, Grade 42 (Grade 290) (Note 2)

Over 4(100) to 6(150)incl.

20(27)@ 70°F(21°C)

20(27)@ 40°F(4°C)

20(27)@ 10°F(-12°C)

A588/A588M (Note 2)

Over 4(100) to 5(125)incl.

20(27)@ 70°F(21°C)

20(27)@ 40°F(4°C)

20(27)@ 10°F(-12°C)

A709/A709M, Grade HPS 50WT To 4(100)incl. (Grade HPS 345WT) (Notes 2 and 6)

20(27)@ 10°F(-12°C)

20(27)@ 10°F(-12°C)

20(27)@ 10°F(-12°C)

A709/A709M, Grade HPS 70WT To 4(100)incl. (Grade HPS 485WT) (Notes 3 and 6)

25(34)@ -10°F(-23°C)

25(34)@ -10°F(-23°C)

25(34)@ -10°F(-23°C)

0°F(-18°C)

–30°F(-34°C)

–60°F(-51°C)

Minimum Service Temperature (Note 4)

3

Note 1: Impact tests shall be in accordance with the Charpy V-Notch (CVN) tests as governed by ASTM Specification A673/A673M with frequency of testing H for all grades except for A709/A709M, Grade HPS 70WT (Grade HPS 485WT), which shall be frequency of testing P. Note 2: If the yield point of the material exceeds 65,000 psi (450 MPa) the test temperature for the minimum average energy required shall be reduced by 15°F (8°C) for each increment or fraction of 10,000 psi (70 MPa) above 65,000 psi (450 MPa). Note 3: If the yield strength of the material exceeds 85,000 psi (585 MPa) the test temperature for the minimum average energy required shall be reduced by 15°F (8°C) for each increment or fraction of 10,000 psi (70 MPa) above 85,000 psi (585 MPa). Note 4: Minimum service temperatures of 0°F (-18°C) corresponds to Zone 1. –30°F (-34°C) to Zone 2 –60°F (-51°C) to Zone 3, referred to in Article 9.1.2.1. Note 5: Impact test requirements for structural steel of Fracture Critical Members are specified in Table 15-1-14. Note 6: The suffix T is an ASTM A709/A709M designation for non-fracture critical material requiring impact testing, with Supplemental Requirement S83 applying. A numeral 1, 2 or 3 should be added to the T marking to indicate the applicable service temperature zone.

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Steel Structures

b. For the properties of steel used in this Manual unless otherwise provided use: Modulus of Elasticity, E = 29,000,000 psi Poisson’s Ratio, m = 0.3 Shear Modulus, G = 11,200,000 psi c.

Throughout this chapter, the equivalent materials of Table 15-1-3 may be used interchangeably. A36 and A588 plate and bar over 4 inches in thickness have no equivalent A709 grade.

d. A588/A588M material in thickness of 5 in. (125 mm) to 8 in. (200 mm) shall be used in compression or other non-toughness applications. e.

Material over 4 inches (100mm) in thickness shall not be used as a Fracture Critical Component.

f.

The design requirements for materials of Fracture Critical Members shall further comply with the Fracture Control Plan specified in Section 1.14, Fracture Critical Members. The Engineer shall designate on the plans which members or member components fall in the category of Fracture Critical Members. Table 15-1-3. Equivalent Materials Applicable Thickness

ASTM A709

ASTM Designation for Equivalent Material

Plates and Bars

Shapes

Grade 36

A36

To 4 inches incl.

All

Grade 50

A572 Grade 50

To 4 inches incl.

All

Grade 50W

A588

To 4 inches incl.

All

Grade 50S

A992

None

All

1.2.2 WELDING (2003)1 R(2008) a.

Welding shall conform to the applicable provisions of the Bridge Welding Code ANSI/AASHTO/AWS D1.5 of the American Association of State Highway and Transportation Officials and the American Welding Society, herein referred to as AWS D1.5, unless otherwise modified or supplemented by these recommended practices.

b. In applying the AWS D1.5 the following substitutions shall be made: (1) Wherever the designation AASHTO is used it shall be construed to refer to AREMA. (2) Wherever the term AASHTO Specification or AASHTO Standard Specification for Highway Bridges is used, it shall be construed to refer to this chapter’s recommended practices. (3) Wherever the word “highway” (as in highway bridge) appears, it shall be interpreted to mean railway or railroad.

1

See Part 9 Commentary

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(4) Wherever the word “State” (as in State approval, State specification, State inspector, etc.) appears, it shall be construed to refer to the Company as defined in Article 1.1.1 herein. (5) The terms “Engineer,” “Inspector” and “Contractor” shall have the definitions given in Article 1.1.1 herein. (6) Wherever AASHTO Material Specifications or AASHTO-M specifications are referenced, the corresponding ASTM specification shall be used. (7) The term “allowable stresses” is to be construed as those allowed herein. (8) In addition to the herein referenced specifications, the welding of Tubes and Pipes shall conform to the applicable provisions of the Structural Welding Code–Steel ANSI/AWS D1.1 of the American Welding Society. c.

Welding of ASTM A709, Grade HPS 70W shall conform to the latest edition of the AASHTO document “Guide for Highway Bridge Fabrication with HPS 70W Steel”. This document shall be used as a supplement to AWS D1.5 until such time as A709, HPS 70W is specifically included therein.

d. Until such time that AWS D1.5 adopts ASTM A709, Grade 50S and Grade HPS 50W, the prequalified procedures of AWS D1.5 for A709, Grade 50 and A709, Grade 50W, respectively, shall be used.

1.2.3 TYPES OF BRIDGES (1995) R(2008) a.

1

The preferred types of bridges are as follows: • Rolled or welded beams for spans of 50 feet or less. • Bolted or welded plate girders for spans over 50 feet to 150 feet.

3

• Bolted or welded trusses for spans over 150 feet. b. Pin connected trusses may be used for unusual conditions, but special provisions applicable to their design and construction shall be prepared and furnished by the Engineer.

1.2.4 SPACING OF TRUSSES, GIRDERS, AND STRINGERS (1995) R(2008) a.

The distance between centers of outside trusses or girders shall be sufficient to prevent overturning by the specified lateral loads. In no case shall it be less than 1/20 of the span for through spans, nor 1/15 of the span for deck spans.

b. Where the track is supported by a pair of deck girders or stringers, the distance center to center shall be not less than 6¢-6². If multiple girders or stringers are used, they shall be arranged as nearly as possible to distribute the track load uniformly to all members.

1.2.5 DEFLECTION (2001)1 R(2010) a.

1

The deflection of the structure shall be computed for the live loading plus impact loading condition producing the maximum bending moment at mid-span for simple spans. The computation of component stiffness shall be based on the following assumed behavior:

See Part 9 Commentary

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Steel Structures

• For flexural members use the gross moment of inertia. • For truss members without perforated cover plates use the gross area. • For truss members with perforated cover plates use the effective area. The effective area shall be the gross area reduced by the area determined by dividing the volume of a perforation by the distance center to center of perforations. b. The structure shall be so designed that the computed deflection shall not exceed 1/640 of the span length center to center of bearings for simple spans. c. Lateral deflection of spans shall be limited to 3/8 inch (10 mm) for tangent track as measured on a 62 foot (19 meter) chord. On curved track, lateral deflection shall be limited to 1/4 inch (6 mm) as measured on a 31 foot (9.5 meter) chord. Allowable lateral deflection for spans shall be calculated based on these limits taken in squared proportion to the span length under consideration. The lateral deflection calculated is to be the maximum lateral deflection at track level due to all applicable lateral forces and loads specified in Section 1.3 excepting those due to earthquake (seismic) or wind on unloaded bridges. The maximum lateral deflection at track level shall be referenced to the point on a vertical plane below which lateral deflection is restrained (i.e. base of structure, span bearings, bottom flange of girder; depending on the lateral deflection being considered).

1.2.6 CLEARANCES (1995)1 R(2008) a.

The clearances on straight track shall be not less than those shown in Figure 15-1-1. On curved track, the lateral clearance each side of track centerline shall be increased 1-1/2 inches per degree of curvature. When the fixed obstruction is on tangent track, but the track is curved within 80 feet of the obstruction, the lateral clearance each side of track centerline shall be increased as shown in Table 15-1-4.

b. Where legal requirements specify greater clearances, such requirements shall govern. c.

The superelevation of the outer rail shall be specified by the Engineer. The distance from the top of rail to the top of tie shall be assumed as 8 inches, unless otherwise specified by the Engineer.

d. Where there are plans for electrification, the minimum vertical clearance shall be increased to that specified in Chapter 28, Clearances. e.

1

The clearances shown are for new construction. Clearances for reconstruction work or for alterations are dependent on existing physical conditions and, where reasonably possible, should be improved to meet the requirements for new construction.

See Part 9 Commentary

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NOTE: See Article 1.2.6a for curve corrections. Figure 15-1-1. Minimum Railway Bridge Clearances Table 15-1-4. Curved Track Clearance Increases Distance from Obstruction to Curved track in Feet

1

Increase per Degree of Curvature in Inches

0–21

1-1/2

21–40

1-1/8

41–60

3/4

61–80

3/8

3

1.2.7 DIMENSIONS FOR CALCULATIONS OF STRESSES (2004) R(2008) a.

For calculation purposes the distance between the center of rails shall be taken as 5’-0” for standard gage track.

b. The length of span or member shall be assumed as follows: • For trusses and girders, the distance between centers of bearings. • For truss members, the distance between centers of joints. • For floorbeams, the distance between centers of trusses or girders. • For stringers, the distance between centers of floorbeams. c.

The depth shall be assumed as follows: • For trusses, the distance between gravity axes of chords. © 2011, American Railway Engineering and Maintenance-of-Way Association

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1.2.8 SKEW BRIDGES (1994) R(2008) At the ends of skew bridges, the ends of the supports for each track shall be perpendicular to the centerline of track.

1.2.9 OPEN DECK BRIDGE TIES (1994) R(2008) Timber bridge ties shall meet the requirements of Chapter 7, Timber Structures and be not less than 10 feet long and spaced such that the gap between the ties is not more than 6 inches. They shall be secured against bunching and uplift.

1.2.10 CAMBER (1995) R(2008) The camber of trusses shall be equal to the deflection produced by the dead load plus a live load of 3,000 lb per foot of track. The camber of plate girders more than 90 feet in length shall be equal to the deflection produced by the dead load only. Plate girders 90 feet or less in length and rolled beams need not be cambered.

1.2.11 NAMEPLATES (1995) R(2008) An approved nameplate showing the name of the fabricator and the year of construction shall be attached to one end of each span at a point convenient for inspection.

1.2.12 STEEL INNER GUARD RAILS AND GUARD TIMBERS (1995) R(2008) Recommendations pertaining to the use of steel inner guard rails and guard timbers are contained in Chapter 7, Timber Structures; Part 3, Rating Existing Wood Bridges and Trestles.

1.2.13 PROVISION FOR EXPANSION (2008) The design shall be such as to allow for the change in length of the spans resulting from change in temperature, at the minimum rate of 1 inch in 100 feet. Provision shall be made for change in length of the span resulting from live load. In spans more than 300 feet long, allowance shall be made for expansion of the floor system. For specific provisions for bearings, see Part 10 and Part 11.

SECTION 1.3 LOADS, FORCES AND STRESSES 1.3.1 LOADS AND FORCES (1995) R(2008) a.

Bridges shall be proportioned for the following: (1) Dead load. (2) Live load. (3) Impact load. (4) Wind forces. (5) Centrifugal force.

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(6) Forces from continuous welded rail – See Part 8, Miscellaneous; Section 8.3, Anchorage of Decks and Rails on Steel Bridges. (7) Other lateral forces. (8) Longitudinal forces. (9) Earthquake forces. b. Member forces and stresses shall be shown separately on the stress sheet.

1.3.2 DEAD LOAD (1995) R(2008) a.

In estimating the weight for the purpose of computing dead load stresses, the unit weights found in Table 15-1-5 shall be used. Table 15-1-5. Unit Weights for Dead Load Stresses Type

Pounds per Cubic Foot

Steel

490

Concrete

150

Sand, gravel, and ballast

120

Asphalt-mastic and bituminous macadam

150

Granite

170

Paving bricks

150

Timber

1

60

b. The track rails, inside guard rails, and their rail fastenings shall be assumed to weigh 200 lb per linear foot for each track.

3

1.3.3 LIVE LOAD (1995)1 R(2008) a.

The recommended live load in lb per axle and uniform trailing load for each track is the Cooper E 80 load shown in Figure 15-1-2 or the Alternate Live Load on 4 axles spaced as shown in Figure 15-1-3, whichever produces the greater stresses.

b. The Engineer shall specify the live load to be used, and such load shall be proportional to the recommended load, with the same axle spacing. c.

For bridges on curves, provision shall be made for the increased proportion carried by any truss, girder, or stringer due to the eccentricity of the load.

d. For members receiving load from more than one track, the design live load on the tracks shall be as follows: • For two tracks, full live load on two tracks.

1

See Part 9 Commentary

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Steel Structures

• For three tracks, full live load on two tracks and one-half on the other track. • For four tracks, full live load on two tracks, one-half on one track, and one-quarter on the remaining one. • For more than four tracks, as specified by the Engineer. • The selection of the tracks for these loads shall be such as will produce the greatest live load stress in the member.

Figure 15-1-2. Cooper E 80 Load

Figure 15-1-3. Alternate Live Load on 4 Axles

1.3.4 DISTRIBUTION OF LIVE LOAD (1993)1 R(2008) 1.3.4.1 Open Deck Structures a.

Timber bridge ties shall be designed in accordance with the requirements of Chapter 7, Timber Structures, based on the assumption that the maximum wheel load on each rail is distributed equally to all ties or fractions thereof within a length of 4 feet, but not to exceed 3 ties, and is applied without impact.

b. For the design of beams or girders, the live load shall be considered as a series of loads as shown in Figure 15-1-2 or Figure 15-1-3. No longitudinal distribution of such loads shall be assumed.

1

See Part 9 Commentary

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c.

Where two or more longitudinal beams per rail are properly diaphragmed, in accordance with Article 1.11.4, and symmetrically spaced under the rail, they shall be considered as equally loaded.

1.3.4.2 Ballasted Deck Structures 1.3.4.2.1 Design The designated lateral and longitudinal distribution of live load is based on the following assumptions: a.

Standard ties shall be used which are not less than 8 feet long, approximately 8 inches wide, and spaced at not over 24 inches on centers. If another type of tie or greater spacing is used, the design shall be modified for the greater load concentrations, or increased thickness of ballast used, or both.

b. Not less than 6 inches of ballast shall be provided under the ties. c.

The designated widths for lateral distribution of load shall not exceed 14 feet, the distance between track centers of multiple track structures, nor the width of the deck between ballast retainers.

d. The effects of track eccentricity and of centrifugal force shall be included. 1.3.4.2.2 Deck a.

Each axle load shall be uniformly distributed longitudinally over a length of 3 feet plus the minimum distance from bottom of tie to top of beams or girders, but not to exceed 5 feet nor the minimum axle spacing of the load system used.

1

b. In the lateral direction, the axle load shall be uniformly distributed over a width equal to the length of the tie plus the minimum distance from bottom of tie to top of beams or girders. c.

The thickness of the deck shall not be less than 1/2 inch for steel plate, 3 inches for timber, or 6 inches for reinforced or prestressed concrete.

3

d. Timber and concrete decks shall be designed in accordance with the applicable provisions of Chapter 7, Timber Structures and Chapter 8, Concrete Structures and Foundations, respectively. 1.3.4.2.3 Transverse Steel Beams a.

For ballasted decks supported by transverse steel beams without stringers, the portion of the maximum axle load on each beam shall be as follows: 1.15AD P = --------------------S æ ö 1 H 1 For moment: D = d ç ------------------÷ æ 0.4 + --- + ---------ö è ç ÷ d ø d 12 ø è 1 + ------aH but not greater than d or S. For end shear: D = d.

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Steel Structures

where: P = load on a beam from one track A = axle load S = axle spacing, feet d = beam spacing, feet a = beam span, feet n = the ratio of the modulus of elasticity of steel to that of concrete Ib = moment of inertia of beam, inch4 h = thickness of concrete deck slab, inches nI b H = ---------3ah D = effective beam spacing, feet b. The load P shall be applied as two equal concentrated loads on each beam at each rail, equal to P/2. No lateral distribution of such loads shall be assumed. c.

D = d for bridges without a concrete deck; or for bridges where the concrete slab extends over less than the center 75% of the floorbeam.

d. Where d exceeds S, P shall be the maximum reaction of the axle loads, assuming that the deck between the beams acts as a simple span. e.

For bridges with concrete decks, the slab shall be designed to carry its portion of the load.

1.3.4.2.4 Longitudinal Steel Beams or Girders a.

Where beams or girders are spaced symmetrically about the centerline of tangent track, the axle loads shall be distributed equally to all beams or girders whose centroids are within a lateral width equal to the length of tie plus twice the minimum distance from bottom of tie to top of beams or girders. Distribution of loads for other conditions shall be determined by a recognized method of analysis.

b. For the design of beams or girders, the live load shall be considered as a series of loads as shown in Figure 15-1-2 or Figure 15-1-3. No longitudinal distribution of such loads shall be assumed.

1.3.5 IMPACT LOAD (2007)1 R(2008) a.

Impact load, due to the sum of vertical effects (Paragraph c) and rocking effect (Paragraph d) created by passage of locomotives and train loads, shall be determined by taking a percentage of the live load specified in Article 1.3.3 and shall be applied vertically at top of each rail.

b. For open deck bridges the percentage of live load to be used shall be determined in accordance with Paragraph c and Paragraph d below. For ballasted deck bridges the impact load to be used shall be 90% of that specified for open deck bridges. These formulas do not cover direct fixation decks. c.

1

Impact load due to vertical effects, expressed as a percentage of live load applied at each rail, shall be determined by the applicable formula below:

See Part 9 Commentary

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Design

(1) Percentage of live load for rolling equipment without hammer blow (freight and passenger cars, and locomotives other than steam): 2

(a) For L less than 80 feet:

3L 40 – -----------1600

.

(b) For L 80 feet or more:

600 16 + ---------------L – 30

.

(2) Percentage of live load for steam locomotives with hammer blow: (a) For beam spans, stringers, girders, floorbeams, posts of deck truss spans carrying load from floorbeam only, and floorbeam hangers: 2

L 60 – --------500

• For L less than 100 feet:

• For L 100 feet or more:

(b) For truss spans:

1800 10 + ---------------L – 40

4000 15 + ----------------L + 25

.

.

.

1

where: L = length, feet, center to center of supports for stringers, transverse floorbeams without stringers, longitudinal girders and trusses (main members), or L = length, feet, of the longer adjacent supported stringers, longitudinal beam, girder or truss for impact in floorbeams, floorbeam hangers, subdiagonals of trusses, transverse girders, supports for longitudinal and transverse girders and viaduct columns. d. Impact load due to rocking effect, RE, is created by the transfer of load from the wheels on one side of a car or locomotive to the other side from periodic lateral rocking of the equipment. RE shall be calculated from loads applied as a vertical force couple, each being 20 percent of the wheel load without impact, acting downward on one rail and upward on the other. The couple shall be applied on each track in the direction that will produce the greatest force in the member under consideration. e.

For members receiving load from more than one track, the impact load shall be applied on the number of tracks designated in Table 15-1-6.

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4

Steel Structures

Table 15-1-6. Impact Loads

Span Length, L

Impact

Load Received From Two Tracks For L less than 175 feet

Full impact on two tracks

For L from 175 feet to 225 feet

Full impact on one track and a percentage of full impact on the other as given by the formula, 450 – 2L

For L greater than 225 feet

Full impact on one track and none on the other

Load Received From More than Two Tracks For all values of L

Full impact on any two tracks that creates the largest load effect

1.3.6 CENTRIFUGAL FORCE (2002)1 R(2008) a.

On curves, a centrifugal force shall be applied horizontally through a point 8 feet above the top of rail measured along a line perpendicular to the plane at top of rails and equidistant from them.

b. Where a maximum design speed is not specified by the Engineer, the centrifugal force shall correspond to 15 percent of each axle load without impact. The superelevation of the outer rail used in determining the point of application of the force shall be assumed as 6 inches. c.

Where the maximum design speed and superelevation are specified by the Engineer, the relationship among curvature, speed, and superelevation shall be determined in accordance with Chapter 5, Track, Section 3.3, Elevations and Speeds for Curves (1962), of this Manual. The resulting centrifugal force shall correspond to the percentage of each axle load, without impact, determined by the following formula:

C = 0.00117S2D where: C = centrifugal factor, percent S = speed, miles per hour D = degree of curve (central angle of curve subtended by a chord of 100 ft.) The superelevation of the outer rail used in determining the point of application of the force shall be as specified by the Engineer. 1

See Part 9 Commentary

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Design

d. On curves, each axle load on each track shall be applied vertically through the point defined above. Impact load shall be applied as specified in Article 1.3.5. e.

On curves, the forces in a stringer, girder or truss toward the outside and inside of curve shall be determined separately, and the greater section required shall be used on both sides. For members toward the outside of curve, the full impact load of Article 1.3.5 and the centrifugal force as defined in Paragraph a shall apply. For members toward the inside of curve, any effect of the centrifugal force shall be omitted.

1.3.7 WIND FORCES ON LOADED BRIDGE (2003)1 R(2008) In general, the wind force shall be considered as a moving load acting in any horizontal direction. As a minimum, the bridge shall be designed for laterally and longitudinally applied wind forces acting independently as follows: a.

On the train, the lateral wind force shall be taken at 300 lb. per linear foot applied normal to the train on one track at a distance of 8 feet above top of rail.

b. On the bridge, lateral wind pressure shall be taken at 30 lb. per square foot normal to the following surfaces: (1) For girder spans, 1.5 times the vertical projection of the span. (2) For truss spans, the vertical projection of the span plus any portion of leeward trusses not shielded by the floor system.

1

(3) For viaduct towers and bents, the vertical projection of all windward and leeward columns and bracing. c.

The lateral wind force on girder and truss spans, however, shall not be taken as less than 200 lb. per foot for the loaded chord or flange and 150 lb. per foot for the unloaded chord or flange, neglecting the wind force on the floor system.

3

d. The longitudinal wind force on spans shall be taken as: (1) For girder spans, 25 percent of the lateral wind force.

4

(2) For truss spans, 50 percent of the lateral wind force. (3) For viaduct towers and bents, 30 lb. per square foot on the vertical projection of all windward and leeward columns and bracing.

1.3.8 WIND FORCES ON UNLOADED BRIDGE (2006)2 R(2008) In general, the wind force shall be considered as a moving load acting in any horizontal direction. As a minimum, the bridge shall be designed for laterally and longitudinally applied wind forces acting independently as follows: a.

1 2

The lateral wind force on the unloaded bridge shall be taken as 50 lb per square foot of surface as defined in Article 1.3.7b.

See Part 9 Commentary See Part 9 Commentary © 2011, American Railway Engineering and Maintenance-of-Way Association

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Steel Structures

b. The longitudinal wind force on the unloaded spans shall be taken as: (1) For girder spans, 25 percent of the lateral wind force. (2) For truss spans, 50 percent of the lateral wind force. (3) For viaduct towers and bents, 50 lb per square foot on the vertical projection of all windward and leeward columns and bracing.

1.3.9 LATERAL FORCES FROM EQUIPMENT (1993) R(2008) a.

A single moving concentrated lateral force equal to one-quarter of the weight of the heaviest axle of the specified live load, without impact, shall be applied at the base of rail in either direction and at any point along the span in addition to the other lateral forces specified. On spans supporting multiple tracks, the force shall be applied on one track only.

b. The only resulting stresses to be considered are axial stresses in members bracing the flanges of stringer, beam and girder spans, axial stresses in the chords of truss spans and in members of cross frames of such spans, and stresses from lateral bending of flanges of longitudinal flexural members having no bracing system. The effects of lateral bending between braced points of flanges, axial forces in flanges, vertical forces and forces transmitted to bearings shall be disregarded.

1.3.10 STABILITY CHECK (2005)1 R(2008) a.

In calculating the stability of spans and towers, the live load on one track shall be 1,200 lb per linear foot applied without impact. On multiple track bridges, this live load shall be on the leeward track.

b. For beam and girder deck spans requiring lateral bracing in accordance with Article 1.11.2 an eccentric load is to be applied as a check to cross frames, diaphragms and anchor rods only. This is in addition to the requirements of Article 1.11.4. The permissible maximum resulting stress in these elements is to be 1.5 times that listed in Section 1.4. This check is not required on floor systems and anchor rods of through truss spans and through girder spans. A single line of wheel loads (Q) equal to the design load per rail (Article 1.3.3) including full design impact is to be applied at an eccentricity of 5 feet from the centerline of track as shown in Figure 15-1-4, but no further than the edge of the deck or, for open decks, the bridge ties.

Figure 15-1-4. Location of Eccentric Load

1

See Part 9 Commentary

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Design

1.3.11 BRACING BETWEEN COMPRESSION MEMBERS (2000) R(2008) The lateral bracing of the compression chords or flanges of trusses, deck girders and through girders and between the posts of viaduct towers shall be proportioned for a transverse shear force in any panel equal to 2.5% of the total axial force in both members in that panel, in addition to the shear force from the specified lateral loads.

1.3.12 LONGITUDINAL FORCES (2005)1 R(2008) a.

The longitudinal force for E-80 loading shall be taken as the larger of: Force due to braking, as prescribed by the following equation, acting 8 feet (2500 mm) above top of rail: Longitudinal braking force (kips) = 45 + 1.2 L (Longitudinal braking force (kN) = 200 + 17.5 L)

Force due to traction, as prescribed by the following equation, acting 3 feet (900 mm) above top of rail: Longitudinal traction force (kips) =

25 L

(Longitudinal traction force (kN) =

200 L )

1

3 where: L is length in feet (meters) of the portion of the bridge under consideration. For design loads other than E-80, these forces shall be scaled proportionally. The points of force application shall not be changed. b. The longitudinal force shall be distributed to the various components of the supporting structure, taking into account their relative stiffness. The soil resistance of the backfill behind the abutments shall be utilized where applicable. The mechanisms (rail, bearings, load transfer devices, etc.) available to transfer the force to the various components shall also be considered. c.

For multiple track structures, longitudinal forces shall be applied as per Article 1.3.3d.

1.3.13 FATIGUE (2011)2 a.

1 2

Members and connections subjected to repeated fluctuations of stress shall meet the fatigue requirements of this article as well as the strength requirements of Section 1.4, Basic Allowable Stresses.

See Part 9 Commentary See Part 9 Commentary

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Steel Structures

b. The major factors governing fatigue strength at a particular location of a member or connection are the number of stress cycles, the magnitude of the stress range, and the relevant Fatigue Detail Category. c.

The number of stress cycles, N, to be considered shall be selected from Table 15-1-7, unless traffic surveys or other considerations indicate otherwise, N depends on the span length in the case of longitudinal members, and on the number of tracks in the case of floorbeams, hangers, and certain truss members.

d. Mean Impact Load shall be taken as the Table 15-1-8 percentages of the impact load specified in Article 1.3.5. e.

The live load for fatigue design is specified in Article 1.3.3.

f.

The stress range, SR, is defined as the algebraic difference between the maximum and minimum calculated stress due to dead load, live load, mean impact load, and centrifugal load. Where live load, impact load and centrifugal load result in compressive stresses and the dead load stress is compression, fatigue need not be considered. The stress range, SR, shall be computed on the basis of the effective net area or the effective gross area as defined in Article 1.6.6.

g.

Examples of various construction details are illustrated and categorized in Table 15-1-9.

h. The stress range shall not exceed the allowable fatigue stress range. SRfat, listed in Table 15-1-10. i.

The prime focus on Fracture Critical Members must be on quality of the material and fabrication. Using low fatigue resistant details should be avoided. Detail Category E and E’ details shall not be used on fracture critical members, and Detail Category D details shall be discouraged and used only with caution.

j.

For span lengths exceeding 300 feet, a special analysis of the number of relevant cycles is required (see Part 9, Commentary). Table 15-1-7. Number of Stress Cycles, N

Member Description

Span Length, L of Flexural Member or Truss or Load Condition

Constant Stress Cycles, N

Classification I Longitudinal flexural members and their connections. Truss chord members including end posts, and their connections

L > 100 feet

2,000,000

L £ 100 feet

> 2,000,000

Classification II Floorbeams and their connections. Truss hangers and sub-diagonals that carry floorbeam reactions only, and their connections. Truss web members and their connections. Note:

Two Tracks Loaded

2,000,000

One Track Loaded

> 2,000,000

This table is based on bridges designed for the live loading specified in Article 1.3.13e. For bridges designed for other live loadings see Part 9, Commentary, Article 9.1.3.13.

k. Load paths that are sufficiently rigid to transmit all forces shall be provided by connecting all transverse members to appropriate components comprising the cross-section of the longitudinal member to deal © 2011, American Railway Engineering and Maintenance-of-Way Association

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with distortion-induced fatigue. To control web buckling and elastic flexing of the web, the provision of Article 1.7.3 must be satisfied. Table 15-1-8. Assumed Mean Impact Load Percentages

Member Members with loaded Lengths £ 10 feet (3m) and no load sharing Hangers Other Truss members Beams, Stringers, Girders and Floor Beams

Percentage 65% 40% 65% 35%

Note: Where bridges are designed for operation of trains handling a large percentage of cars with flat or out of round wheels which increase impact and/or poor track which increases impact, and the loaded length of the member is less than 80 feet (24m), the mean impact should be 100% of the design impact.

1.3.13.1 High Strength Bolts Subjected to Tensile Fatigue Loading Fully pretensioned high strength bolts subjected to tensile fatigue loading shall be designed for the combined external load and prying force using the following allowable tensile stress ranges: A 325 Bolts in axial tension: 31,000 psi on the tensile stress area (see table 15-1-9, section 8.2) at the threads

1

A 490 Bolts in axial tension: 38,000 psi on the tensile stress area (see table 15-1-9, section 8.2) at the threads In no case shall the prying force exceed 20% of the total externally applied load.

3

4

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Steel Structures Table 15-1-9. Detail Categories for Load Induced Fatigue

Description

Category

Constant Threshold A SRfat (ksi3) (Ksi)

Potential Crack Initiation Point

Illustrative Examples

SECTION 1 - PLAIN MATERIAL AWAY FROM ANY WELDING 1.1 Base metal, except nonA 24 Away from 250 x 108 coated weathering steel, with all welds or rolled or cleaned surfaces. structural Flame-cut edges with surface connections roughness value of 1,000 min. or less, but without reentrant corners.

1.2 Non-coated weathering steel base metal with rolled or cleaned surfaces detailed in accordance with (Reference 33). Flame-cut edges with surface roughness value of 1,000 m-in. or less, but without re-entrant corners.

B

120 x 108

16

Away from all welds or structural connections

1.3 Member with re-entrant corners at copes or other geometrical discontinuities made to the requirements of AASHTO/AWS D1.5, except weld access holes. A 1 inch minimum radius shall be provided at any cope.

C

44 x 108

10

At any external edge

1.4 Rolled cross sections with weld access holes made to the requirements of AASHTO/AWS D1.5, Article 3.2.4. A 1 inch minimum radius shall be provided at any cope.

C

44 x 108

10

In the base metal at the edge of the access hole.

1.5 Open fastener holes in members (Reference 19).

D

22 x 108

7

In the net section originating at the side of the hole

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Design Table 15-1-9. Detail Categories for Load Induced Fatigue (Continued)

Description

Category

Constant Threshold A SRfat (ksi3) (Ksi)

Potential Crack Initiation Point

Illustrative Examples

SECTION 2 - CONNECTED MATERIAL IN MECHANICAL FASTENED JOINTS B 16 Through the 120 x 108 gross section near the hole

2.1 Base metal at the gross section of high-strength bolted joints designed as slip-critical connections; i.e., with pre-tensioned highstrength bolts installed - e.g. bolted flange and web splices, bolted stiffeners, bolted lateral bracing members and bolted lateral connection plates.

2.2 Base metal at the net section of high-strength bolted joints designed as bearing-type connections, but fabricated and installed to all requirements for slipcritical connections; i.e., with pre-tensioned high strength bolts installed.

B

2.3 Base metal at the net section of all bolted connections in hot dipped galvanized members (Reference 19, 64), and at the net section of other mechanically fastened joints, except for eyebars and pin plates; e.g., joints using A 307 bolts, rivets, or non pre-tensioned high strength bolts.

D

2.4 Base metal at the net section of eyebar heads or pin plates (Note: for base metal in the shank of eyebars or through the gross section of pin plates, see Condition 1.1 or 1.2, as applicable).

E

120 x 108

22 x 108

16

7

In the net section originating at the side of the hole

1

3

In the net section originating at the side of the hole

4

11 x 108

4.5

In the net section originating at the side of the hole

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Steel Structures Table 15-1-9. Detail Categories for Load Induced Fatigue (Continued)

Description

Category

Constant Threshold A SRfat (ksi3) (Ksi)

Potential Crack Initiation Point

Illustrative Examples

SECTION 3 - WELDED JOINTS JOINING COMPONENTS OF BUILT-UP MEMBERS From surface B 16 120 x 108

3.1 Base metal and weld metal in members without attachments built-up of plates or shapes connected by continuous longitudinal complete joint penetration groove welds back-gouged and welded from the second side, or by continuous fillet welds parallel to the direction of applied stress.

or internal discontinuities in the weld away from the end of the weld

3.2 Base metal and weld metal in members without attachments built-up of plates or shapes connected by continuous longitudinal complete joint penetration groove welds with backing bars not removed, or by continuous partial joint penetration groove welds parallel to the direction of applied stress.

B’

61 x 108

12

From surface or internal discontinuities in the weld, including weld attaching backing bars

3.3 Base metal and weld metal at the termination of longitudinal welds at weld access holes made to the requirements of AASHTO/AWS D1.5, Article 3.2.4 in built-up members. (Note: does not include the flange butt splice). 3.4 Base metal and weld metal in partial length welded cover plates connected by continuous fillet welds parallel to the direction of applied stress.

D

22 x 108

7

From the weld termination into the web or flange.

B

120 x 108

16

From surface or internal discontinuities in the weld away from the end of the weld

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Design Table 15-1-9. Detail Categories for Load Induced Fatigue (Continued)

Description

Category

Constant Threshold A SRfat (ksi3) (Ksi)

Potential Crack Initiation Point

Illustrative Examples

SECTION 3 - WELDED JOINTS JOINING COMPONENTS OF BUILT-UP MEMBERS In the flange at the toe of the end weld or in the flange at the termination of the longitudinal weld or in the edge of the flange with wide cover plates E 4.5 11 x 108 Flange thickness < 0.8 in. 3.5 Base metal at the termination of partial length welded cover plates having square or tapered ends that are narrower than the flange, with or without welds across the ends, or cover plates that are wider than the flange with welds across the ends:

Flange thickness > 0.8 in.

E’

3.9 x 108

2.6

3.6 Base metal at the termination of partial length welded cover plates with slip-critical bolted end connections designed to transfer the full strength of the cover plate.

B

120 x 108

16

1 In the flange at the termination of the longitudinal weld

3

4 3.7 Base metal at the termination of partial length welded cover plates that are wider than the flange and without welds across the ends.

E’

3.9 x 108

2.6

In the edge of the flange at the end of the cover plate weld

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Steel Structures Table 15-1-9. Detail Categories for Load Induced Fatigue (Continued)

Description

Category

Constant Threshold A SRfat (ksi3) (Ksi)

Potential Crack Initiation Point

Illustrative Examples

SECTION 4 - WELDED STIFFENER CONNECTIONS 4.1 Base metal at the toe of transverse stiffener-to-flange fillet welds and transverse stiffener-to-web fillet welds. (Note: includes similar welds on bearing stiffeners and connection plates.)

C’

44 x 108

12

Initiating from the geometrical discontinuity at the toe of the fillet weld extending into the base metal

4.2 Base metal and weld metal in longitudinal web or longitudinal box - flange stiffeners connected by continuous fillet welds parallel to the direction of applied stress.

B

120 x 108

16

From the surface or internal discontinuities in the weld away from the end of the weld

4.3 Base metal at the termination of longitudinal stiffener-to-web or longitudinal stiffener-to-box flange welds: With the stiffener attached by fillet welds and with no transition radius provided at the termination: Stiffener thickness < 1.0 in.

E

11 x 108

4.5

Stiffener thickness > 1.0 in.

E’

3.9 x 108

2.6

B C D E

120 x 108 44 x 108 22 x 108 11 x 108

16 10 7 4.5

In the primary member at the end of the weld at the weld toe

With the stiffener attached by welds and with a transition radius R provided at the termination with the weld termination ground smooth: R > 24 in. 24 in. > R > 6 in. 6 in. > R > 2 in. 2 in. > R

In the primary member near the point of tangency of the radius.

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Design Table 15-1-9. Detail Categories for Load Induced Fatigue (Continued)

Description

Category

Constant Threshold A SRfat (ksi3) (Ksi)

Potential Crack Initiation Point

Illustrative Examples

SECTION 5 - WELDED JOINTS TRANSVERSE TO THE DIRECTION OF PRIMARY STRESS 5.1 Base metal and weld metal in or adjacent to complete joint penetration groove welded butt splices, with weld soundness established by NDT and with welds ground smooth and flush parallel to the direction of stress. Transitions in thickness or width shall be made on a slope no greater than 1:2.5.

From internal discontinuities in the filler metal or along the fusion boundary or at the start of the transition

Fy < 100 ksi

B

120 x 108

16

Fy > 100 ksi

B’

61 x 108

12

5.2 Base metal and weld metal in or adjacent to complete joint penetration groove welded butt splices, with weld soundness established by NDT and with welds ground parallel to the direction of stress at transitions in width made on a radius of not less than 2 ft with the point of tangency at the end of the groove weld.

B

108

5.3 Base metal and weld metal in or adjacent to the toe of complete joint penetration groove welded T or corner joints, or in complete joint penetration groove welded butt splices, with or without transitions in thickness having slopes no greater than 1:2.5 when weld reinforcement is not removed. (Note: cracking in the flange of the ‘T’ may occur due to out-of-plane bending stresses induced by the stem.)

C

120 x

16

1 From internal discontinuities in the filler metal or discontinuities along the fusion boundary

3

4 44 x 108

10

From the surface discontinuity at the toe of the weld extending into the base metal along the fusion boundary

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Steel Structures Table 15-1-9. Detail Categories for Load Induced Fatigue (Continued)

Description

Category

Constant Threshold A SRfat (ksi3) (Ksi)

Potential Crack Initiation Point

Illustrative Examples

SECTION 5 - WELDED JOINTS TRANSVERSE TO THE DIRECTION OF PRIMARY STRESS Initiating 10 44 x 108

5.4 Base metal and weld C or as metal at details where adjusted by loaded discontinuous plate Note 4 elements are connected with a pair of fillet welds or partial joint penetration groove welds on opposite sides of the plate normal to the direction of primary stress.

from the geometrical discontinuity at the toe of the weld extending into the base metal, or initiating at the weld root subject to tension extending up and then out through the weld.

SECTION 6 - TRANSVERSELY LOADED WELDED ATTACHMENTS 6.1 Base metal in a Near point longitudinally loaded of tangency component at a transversely of the radius loaded detail (e.g. a lateral at the edge connection plate) attached of the by a weld parallel to the longitudinally direction of primary stress loaded and incorporating a component transition radius R with the weld termination ground smooth. See Notes 1 & 2.

R > 24 in.

B

120 x 108

16

24 in. > R > 6 in.

C

44 x 108

10

6 in. > R > 2 in.

D

22 x 108

7

2 in. > R

E

11 x 108

4.5

E

11 x 108

4.5

With the weld termination not ground smooth: (Note: Condition 6.2, 6.3 or 6.4, as applicable, shall also be checked.)

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Design Table 15-1-9. Detail Categories for Load Induced Fatigue (Continued)

Description

Category

Constant Threshold A SRfat (ksi3) (Ksi)

Potential Crack Initiation Point

Illustrative Examples

SECTION 6 - TRANSVERSELY LOADED WELDED ATTACHMENTS 6.2 Base metal in a transversely loaded detail (e.g. a lateral connection plate) attached to a longitudinally loaded component of equal thickness by a complete joint penetration groove weld parallel to the direction of primary stress and incorporating a transition radius R, with weld soundness established by NDT and with the weld termination ground smooth:

1 With the weld reinforcement removed:

R > 24 in. 24 in. > R > 6 in. 6 in. > R > 2 in. 2 in. > R

B C D E

120 x 108 44 x 108 22 x 108 11 x 108

16 10 7 4.5

With the weld reinforcement not removed:

R > 24 in. 24 in. > R > 6 in. 6 in. > R > 2 in. 2 in. > R

C C D E

44 x 108 44 x 108 22 x 108 11 x 108

10 10 7 4.5

Near points of tangency of the radius or in the weld or at the fusion boundary of the longitudinally loaded component or the transversely loaded attachment

3

4

At the toe of the weld either along the edge of the longitudinally loaded component or the transversely loaded attachment

(Note: Condition 6.1 shall also be checked.)

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AREMA Manual for Railway Engineering

15-1-33

Steel Structures Table 15-1-9. Detail Categories for Load Induced Fatigue (Continued)

Description

Category

Constant Threshold A SRfat (ksi3) (Ksi)

Potential Crack Initiation Point

Illustrative Examples

SECTION 6 - TRANSVERSELY LOADED WELDED ATTACHMENTS At the toe of the weld along the edge of the thinner plate

6.3 Base metal in a transversely loaded detail (e.g. lateral connection plate) attached to a longitudinally loaded component of unequal thickness by a complete joint penetration groove weld parallel to the direction of primary stress and incorporating a weld transition radius R, with weld soundness established by NDT and with the weld termination ground smooth:

In the weld termination of small radius weld transitions At the toe of the weld along the edge of the thinner plate

With the weld reinforcement removed: R > 2 in. R < 2 in. For any weld transition radius with the weld reinforcement not removed:

D

22 x 108

7

E

11 x 108

4.5

E

11 x 108

4.5

(Note: Condition 6.1 shall also be checked.) 6.4 Base metal in a transversely loaded detail (e.g. a lateral connection plate) attached to a longitudinally loaded component by a fillet weld or a partial joint penetration groove weld, with the weld parallel to the direction of primary stress

See Condition 5.4

(Note: Condition 6.1 shall also be checked.)

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AREMA Manual for Railway Engineering

Design Table 15-1-9. Detail Categories for Load Induced Fatigue (Continued)

Description

Category

Constant Threshold A SRfat (ksi3) (Ksi)

Potential Crack Initiation Point

Illustrative Examples

SECTION 7 - LONGITUDINALLY LOADED WELDED ATTACHMENTS 7.1 Base metal in a In the longitudinally loaded primary component at a detail member at with a length L in the the end of direction of the primary the weld at stress and a thickness t the weld toe attached by groove or fillet welds parallel or transverse to the direction of primary stress where the detail incorporates no transition radius: See Notes 1 & 2. L < 2 in. 2 in. < L < 12t or 4 in. L > 12t or 4 in. t < 1.0 in. t > 1.0 in. 8.1 Base metal at studtype shear connectors attached by fillet or automatic stud welding

44 x 108 22 x 108

C D E E’ C

1

10 7

11 x 108 4.5 8 2.6 3.9 x 10 SECTION 8 - MISCELLANEOUS At the toe of 10 44 x 108 the weld in the base metal

At the root of the threads extending into the tensile stress area

8.2 Non pretensioned high-strength bolts, common bolts, threaded anchor rods and hanger rods with cut, ground or rolled threads. Use the stress range acting on the tensile stress area due to live load plus prying action when applicable. Finite Life

E’

3.9 x 108

N/A

Infinite Life

D

N/A

7

3

4

D

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AREMA Manual for Railway Engineering

15-1-35

Steel Structures Table 15-1-9. Detail Categories for Load Induced Fatigue (Continued)

Description

Category

Constant Threshold A SRfat (ksi3) (Ksi)

Potential Crack Initiation Point

Illustrative Examples

Notes 1. Transversely loaded partial penetration groove welds are prohibited except as permitted in Article 1.7.4. 2. Gusset plates attached to girder flange surfaces with only transverse fillet welds are prohibited. 3. The Detail Constant ‘A’ can be used to calculate the fatigue life of the detail (N) for any stress range less than the SRfat using the relationship: N = (A)/(SRfat)3. 4. The nominal fatigue resistance for base metal and weld metal at details where loaded discontinuous plate elements are connected with a pair of fillet welds or partial joint penetration groove welds on opposite sides of the plate normal to the direction of primary stress shall be taken as:

Where: SRC Constant amplitude fatigue limit of 10 ksi for category C SR allowable design stress range tp thickness of the loaded plate (in) w the leg size of the reinforcement or contour fillet if any in the direction of the thickness of the loaded plate (in) 2a the length of the non-welded root face in the direction of the thickness of the loaded plate (in). For fillet welded connections, the quantity (2a/t p) shall be taken as 1.0.

Table 15-1-10. Allowable Fatigue Stress Range, SRfat (ksi) (See Notes 1 and 2)

Detail Category A B B¢ C C’

No. of Constant Stress Cycles 2,000,000

Over 2,000,000

24 18 14.5 13

24 16 12 10 12

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AREMA Manual for Railway Engineering

Design Table 15-1-10. Allowable Fatigue Stress Range, SRfat (ksi) (See Notes 1 and 2) (Continued)

Detail Category D

No. of Constant Stress Cycles 2,000,000

Over 2,000,000

10

7Note 3

E 8 4.5 E¢ 5.8 2.6 F 9 8 Note 1: This Table is based on bridges designed for live loading specified in Article 1.3.13e. For bridges designed for other live loadings see Part 9, Commentary, Article 9.1.3.13. Note 2: For Fracture Critical Members, See Article 1.3.13i Note 3: For base metal in members with riveted or bolted connections with low slip resistance, use the variable amplitude stress range of 6.

1.3.14 COMBINED STRESSES (2005)1 1.3.14.1 Axial Compression and Bending Members subject to both axial compression and bending stresses shall be proportioned to satisfy the following requirements:

1

fa when -----£ 0.15 Fa

3

f a f b1 f b2 + --------- + --------- £ 1.0 -----F a F b1 F b2 fa when -----> 0.15 Fa

4

fa f b1 f b2 + -----------------------------------------------------------------------+ -----------------------------------------------------------------------£ 1.0 -----fa k1 l1 ö 2 fa k2 l2 ö 2 Fa æ æ F b1 1 – -------------------------- ----------F b2 1 – -------------------------- ----------ø ø 2 è 2 è 0.514p E r 1 0.514p E r 2 and, in addition, at points braced in the planes of bending, fa f b1 f b2 + --------+ --------- £ 1.0 -----------------0.55F y F b1 F b2

1

See Part 9 Commentary

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AREMA Manual for Railway Engineering

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Steel Structures

where: E = modulus of elasticity of the material Fy = yield point of the material as specified in Table 15-1-1 Fa = axial stress that would be permitted if axial force alone existed Fb1 and Fb2 = compressive bending stress about axes 1–1 and 2–2, respectively, that would be permitted if bending alone existed fa = calculated axial stress fb1 and fb2 = calculated compressive bending stress about axes 1–1 and 2–2, respectively, at the point under consideration k1 l1 k2 l2 ----------- and ---------- = ratios of the effective length in inches to the radius of gyration in inches, of the r1 r2 compression member about axes 1–1 and 2–2, respectively 1.3.14.2 Axial Tension and Bending Members subject to both axial tension and bending stresses shall be proportioned so that the total of the axial tensile stress and the bending tensile stresses about both axes shall not exceed the values indicated in Table 151-11. The compressive stress, if any, resulting from combining the compressive stress with respect to either axis and the minimum simultaneous axial tension stress shall not exceed the value indicated by Table 15-1-11 for compression in the extreme fibers of flexural members. 1.3.14.3 Allowable Stresses for Combinations of Loads or Wind Forces Only a.

Members subject to stresses resulting from dead load, live load, impact load and centrifugal force shall be designed so that the maximum stresses do not exceed the basic allowable stresses of Section 1.4, Basic Allowable Stresses, and the stress range does not exceed the allowable fatigue stress range of Article 1.3.13.

b. The basic allowable stresses of Section 1.4, Basic Allowable Stresses shall be used in the proportioning of members subject to stresses resulting from wind forces only, as specified in Article 1.3.8. c.

Members, except floorbeam hangers, which are subject to stresses resulting from longitudinal forces and/or lateral forces other than centrifugal force may be proportioned for stresses 25% greater than those permitted by paragraph a. However, the section of the member shall not be less than that required to meet the provisions of paragraph a or paragraph b alone.

d. Increase in allowable stress permitted by paragraph c shall not be applied to allowable stress in high strength bolts.

1.3.15 SECONDARY STRESSES (1994)1 R(2008) The design and details shall be such that secondary stresses will be as small as practicable. Secondary stresses due to truss distortion usually need not be considered in any member the width of which, measured parallel to the plane of distortion, is less than one-tenth of its length. If the secondary stress exceeds 4,000 psi for tension members and 3,000 psi for compression members, the excess shall be treated as a primary stress.

1

See Part 9 Commentary

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Design

1.3.16 PROPORTIONING OF TRUSS WEB MEMBERS (2004)1 R(2010) Web members and their connections shall be proportioned such that an increase in the specified live load that will increase the total stress in the most highly stressed chord by one-third will produce total stresses in the web members and their connections not greater than one and one-third times the allowable stresses.

1.3.17 EARTHQUAKE FORCES (1994) R(2008) Members and connections subjected to earthquake forces shall be designed in accordance with the requirements of Chapter 9, Seismic Design for Railway Structures.

SECTION 1.4 BASIC ALLOWABLE STRESSES The basic allowable stresses to be used in proportioning the parts of a bridge shall be as specified below. When the allowable stress is expressed in terms of Fy , Fy = yield point of the material as specified in Table 15-1-1. Fu = lowest ultimate strength of the material as specified in Table 15-1-1.

1.4.1 STRUCTURAL STEEL, RIVETS, BOLTS AND PINS (2011)2 See Table 15-1-11.

1

3

4

1 2

See Part 9 Commentary See Part 9 Commentary

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AREMA Manual for Railway Engineering

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Steel Structures

Table 15-1-11. Structural Steel, Rivets, Bolts and Pins Stress Area

Pounds per square inch

Axial tension, structural steel, gross section

0.55Fy

Axial tension, structural steel, effective net area (See Articles 1.5.8 and 1.6.5) 0.47Fu Axial tension, structural steel, effective net area at cross-section of pin hole of 0.45Fy pin connected members Tension in floorbeam hangers, including bending, gross section: Using rivets in end connections Using high strength bolts in end connections Tension in floorbeam hangers, including bending, effective net area at crosssection of pin hole of pin connected members Tension in floorbeam hangers, including bending, on effective net section:

0.40Fy 0.55Fy 0.45Fy 0.50Fu

Tension in extreme fibers of rolled shapes, girders and built-up sections, subject to bending, net section

0.55Fy

Tension on fasteners, including the effect of prying action: A325 bolts, gross section A490 bolts, gross section

44,000 54,000

Axial compression, gross section: For stiffeners of beams and girders For splice material For compression members centrally loaded, when kl ¤ r £ 0.629 ¤ when 0.629 ¤

Fy¤ E

F y ¤ E < kl ¤ r < 5.034 ¤

when kl ¤ r ³ 5.034 ¤

See Article 1.7.7c 0.55Fy 0.55Fy

F 3 ¤ 2 kl 0.60F y – æ 17, 500 ------yö ----è Eø r

Fy ¤ E

2

Fy ¤ E

where: kl is the effective length of the compression member, inches, under usual conditions k = 7/8 for members with pin-end connections, k = 3/4 for members with riveted, bolted or welded end connections, k to be evaluated for each gusset plate on the effective width, Lw, (See Commentary Figure 15-9-5), and r is the applicable radius of gyration of the compression member, inches. Compression in extreme fibers of I-type members subjected to loading perpendicular to the web

0.514p E -------------------------2 ( kl ¤ r )

0.55Fy

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AREMA Manual for Railway Engineering

Design Table 15-1-11. Structural Steel, Rivets, Bolts and Pins (Continued) Stress Area

Pounds per square inch

Compression in extreme fibers of flexural members symmetrical about the principal axis in the plane of the web (other than box-type flexural members) that are rolled beams or welded built-up members with solid rectangular flanges, the larger of the values computed by the following formulas. where: l = distance between points of lateral support for the compression flange, inches. ry = minimum radius of gyration of the compression flange and that portion of the web area on the compression side of the axis of bending, about an axis in the plane of the web, inch. Af = area of the smaller flange excluding any portion of the web, inch2. d = overall depth of the member, inches. Compression in extreme fibers of standard rolled channels.

2

0.55 ( F y ) æ l ö 2 0.55F y – -------------------------- è -----ø 2 6.3p E r y or 0.131pE --------------------------------------( ld 1 + m ) ¤ A f but not to exceed 0.55Fy

0.131pE --------------------------------------( ld 1 + m ) ¤ A f but not to exceed 0.55Fy

2 Compression in extreme fibers of riveted or bolted built-up flexural members 0.55F y æ l ö 2 0.55F – ------------------ ----symmetrical about the principal axis in the plane of the web (other than y 2 èr ø y 6.3p E box-type flexural members)

1

Compression in extreme fibers of box type welded, riveted or bolted flexural 2 members symmetrical about the principal axis midway between the webs 0.55F y æ l ö 2 - -and whose proportions meet the provisions of Article 1.6.1 and Article 1.6.2 0.55F y – -----------------2 è ø 6.3p E r e where (l/r)e is the effective slenderness ratio of the box type flexural member as determined by the following formula:

1.105plS x Ss ¤ t --------------------------------------------Iy A ----------------(1 + m)

3

where: l = distance between points of lateral support for the compression flange, inches. Sx= Section modulus of the box type member about its major axis, inch3 A= total area enclosed within the center lines of the box type member webs and flanges, inch2 s/t = ratio of width of any flange or depth of web component to its thickness. (Neglect any portion of the flange which projects beyond the box section.) Iy= moment of inertia of the box type member about its minor axis, inch4

4

Diagonal tension in webs of girders and rolled beams at sections where maximum shear and bending occur simultaneously

0.55Fy

Stress in extreme fibers of pins

0.83Fy

Shear in webs of rolled beams and plate girders, gross section

0.35Fy

Shear in A 325 bolts (slip critical connection)

17,000 (Note 1)

Shear in A 490 bolts (slip critical connection)

21,000 (Note 1)

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AREMA Manual for Railway Engineering

15-1-41

Steel Structures Table 15-1-11. Structural Steel, Rivets, Bolts and Pins (Continued) Stress Area

Pounds per square inch

Shear in power driven A 502 Grade 1 rivets

13,500

Shear in power driven A 502 Grade 2 rivets

20,000

Shear in hand driven A 502 Grade 1 rivets

11,000

Shear in pins

0.42Fy

Bearing on power driven A 502 Grade 1 rivets, in single shear in double shear

27,000 36,000

Bearing on power driven A 502 Grade 2 rivets, on material with a yield point of Fy in single shear but not to exceed in double shear but not to exceed (Rivets driven by pneumatically or electrically operated hammers are considered power driven.)

0.75Fy 40,000 Fy 50,000

Bearing on hand driven A 502 Grade 1 rivets

20,000

Bearing on pins 0.75Fy Fy = yield point of the material on which the pin bears, or of the pin material, as specified in Table 15-1-1 whichever is less Bearing on A 325 and A 490 bolts (Note 2) LF u ----------- or 1.2F u where: 2d L = Distance, inches, measured in the line of force from the center line of a bolt to the nearest edge of an adjacent bolt or to the end of the connected part toward which the force is directed. (whichever is smaller) d = Diameter of bolts, inch. Fu = lowest specified minimum tensile strength of the connected part, ksi, as specified in Table 15-1-1. Bearing on milled stiffeners and other steel parts in contact

0.83Fy

Bolts Subjected to Combined Tension and Shear where: Fv = Allowable shear stress, reduced due to combined stress, psi Sa = Allowable shear stress, when loaded in shear only, psi ft = Average tensile stress due to direct load, psi Ab = Nominal bolt area, inch2 Tb = Minimum tension of installed bolts, Table 15-1-12, lb

Fv £ Sa (1 – ftAb/Tb)

Note 1: Applicable for surfaces with clean mill scale free of oil, paint, lacquer or other coatings and loose oxide for standard size holes as specified in Part 3, Fabrication, Article 3.2.5. Where the Engineer has specified special treatment of surfaces or other than standard holes in a slip-critical connection, the allowable stresses in Table 15-1-11a. may be used if approved by the Engineer. Note 2: For single bolt in line of force or connected materials with long slotted holes, 1.0 Fu is the limit. A value of allowable bearing pressure Fp on the connected material at a bolt greater than permitted can be justified provided deformation around the bolt hole is not a design consideration and adequate pitch and end distance L are provided according to F p = LF u ¤ 2d £ 1.5F u

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15-1-42

AREMA Manual for Railway Engineering

Design Table 15-1-11a. Allowable Stress for Slip-Critical Connections (Slip Load per Unit of Bolt Area, psi) Hole Type and Direction of Applied Application Contact Surface of Bolted Parts

Any Direction

Class A (Slip Coefficient 0.33) Clean mill scale and blast-cleaned surfaces with Class A coatings (Note 1), (Note 2)

Transverse

Parallel

Standard

Oversize and Short Slot

Long Slot

Long Slot

A325

A325

A325

A325

A490

A490

17,000 21,000 15,000 18,000 12,000

Class B (Slip Coefficient 0.50) Blast-cleaned surfaces and blast28,000 34,000 24,000 29,000 20,000 cleaned surfaces with Class B coatings (Note 1), (Note 2) Class C (Slip Coefficient 0.40) Hot-dip Galvanized and roughened surfaces (Note 3)

22,000 27,000 19,000 23,000 16,000

A490

A490

15,000 10,000

13,000

24,000 17,000

20,000

19,000 14,000

16,000

Note 1: Coatings classified as Class A or Class B include those coatings which provide a mean slip coefficient not less than 0.33 or 0.50, respectively, as determined by Testing Method to Determine the Slip Coefficient for Coatings Used in Bolt Joints (Appendix A of Reference 113). Note 2: For Classes A and B, uncoated, contact surfaces shall be free of oil, paint, lacquer, or other coatings and loose oxide. Note 3: Contact surfaces shall be lightly scored by wire brushing or blasting after galvanizing and prior to assembly.

1

Table 15-1-12. Minimum Tension of Installed Bolts

3 Nominal Bolt Size Inches

Minimum Tension in Kips A325 Bolts

A490 Bolts

1/2

12

15

5/8

19

24

3/4

28

35

7/8

39

49

1

51

64

1-1/8

56

80

1-1/4

71

102

1-3/8

85

121

1-1/2

103

148

4

1.4.2 WELD METAL (1994)1 R(2008) See Table 15-1-13. In the formulas, Fy = yield point of base metal as specified in Table 15-1-1. 1

See Part 9 Commentary

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AREMA Manual for Railway Engineering

15-1-43

Steel Structures Table 15-1-13. Allowable Stress on Welds Type of Weld and Stress

Pounds per square inch

Groove Welds Tension or compression

0.55Fy 0.35Fy

Shear Fillet Welds Shear, regardless of direction of applied force. Electrodes or electrode-flux combinations with: 60,000 psi tensile strength 70,000 psi tensile strength 80,000 psi tensile strength

16,500 (Note 1) 19,000 (Note 1) 22,000 (Note 1)

Note 1:but not to exceed 0.35 Fy , shear stress on base metal.

1.4.3 CAST STEEL (1994)1 R(2008) For cast steel, the allowable stresses in compression and bearing shall be the same as those allowed for structural steel with the same yield point or yield strength. Other allowable stresses shall be three-quarters of those allowed for structural steel with the same yield point or yield strength.

1.4.4 MASONRY (2002) R(2008) Refer to Part 10 and Part 11.

1.4.5 TIMBER BRIDGE TIES (1994) R(2008) Timber ties shall conform to the requirements of Chapter 7, Timber Structures.

SECTION 1.5 GENERAL RULES 1.5.1 SLENDERNESS RATIO (2011) The slenderness ratio (ratio of length to least radius of gyration) shall not exceed: • 100 for main compression members. • 100 for gusset plates (see Article 9.1.5.4.a). • 120 for wind and sway bracing in compression. • 140 for single lacing. • 200 for double lacing. 1

See Part 9 Commentary

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Design

• 200 for tension members.

1.5.2 EFFECTIVE DIAMETER OF FASTENERS (1993) R(2008) The nominal diameter of fasteners shall be considered the effective diameter.

1.5.3 EFFECTIVE BEARING AREA OF BOLTS, RIVETS AND PINS (1993) R(2008) The effective bearing area of bolts, rivets and pins shall be the diameter multiplied by the length in bearing: except that for countersunk bolts and rivets, one-half the depth of the countersink shall be deducted from the length.

1.5.4 THICKNESS OF MATERIAL (2011)1 a.

Metal, except for fillers, shall not be less than 3/8 inch thick. Parts subject to marked corrosive influences shall be of greater thickness than otherwise or else protected against such influences.

b. The thickness of gusset plates connecting the chords and web members of a truss shall be proportioned for the force to be transferred but not less than 1/2 inch. c.

If the unsupported length of an edge of a gusset plate exceeds its thickness times E 2.06 ------ the edge shall be stiffened. Fy

1

1.5.5 ACCESSIBILITY OF PARTS (1993) R(2008) Details shall be such that all exposed parts will be accessible for inspection, cleaning and painting. Preferably not less than 18 inches clear shall be provided between the flanges of parallel lines of beams having depths in excess of 38 inches.

3

1.5.6 DRAINAGE OF POCKETS (1993) R(2008) Pockets or depressions that would hold water either shall have effective drain holes or shall be filled or caulked with an approved permanent-type waterproof caulking compound. Structural members shall not be caulked by welding except as approved by the Engineer.

1.5.7 ECCENTRIC CONNECTIONS (1993) R(2008) a.

Eccentricity between intersecting parts and between gravity axes of members intersecting at a panel point shall be avoided, insofar as practicable. If eccentric connections are unavoidable, adequate provision shall be made for the bending stresses resulting from the eccentricity.

b. For members having symmetrical cross sections, the connecting welds or fasteners shall be arranged symmetrically about the axis of the member, or proper allowance shall be made for unsymmetrical distribution of stresses.

1

See Part 9 Commentary

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4

Steel Structures

1.5.8 NET SECTION (2005)1 R(2008) a.

The net section of a riveted or bolted tension member, An, is the sum of the net sections of its component parts. The net section of a part is the product of the thickness of the part multiplied by its least net width.

b. The net width for any chain of holes extending progressively across the part shall be obtained by deducting from the gross width the sum of the diameters of all the holes in the chain and adding, for each space in the chain, the quantity: 2

s -----4g where: s = pitch of the two successive holes in the chain, in the direction of tensile stress g = gage of the same holes, in the transverse direction The net section of the part is obtained from that chain which gives the least net width, except that the net width shall in no case be considered as more than 85% of the corresponding gross width. c.

For angles, the gross width shall be the sum of the widths of the legs less the thickness. The gage for holes in opposite legs shall be the sum of the gages, measured from back of angle, less the thickness.

d. For splice material, the effective thickness shall be only that part of the material which has been developed by rivets or bolts. e.

The diameter of the hole shall be taken as 1/8 inch greater than the nominal diameter of the rivet or bolt.

1.5.9 CONNECTIONS AND SPLICES (2003)2 R(2008) a.

Connection and splices, except as used in paragraph d below for milled splices in compression, shall be in accordance with the following provisions: (1) Splices of main members shall have a strength not less than the capacity of the member and shall satisfy the requirements of Article 1.7.5 and Article 1.7.6. End connections of main members receiving load from the combined effect of floor system and truss action shall have a strength not less than the capacity of the member. End connections of members carrying direct load from one floorbeam only shall be proportioned for at least 1.25 times their computed reactions. End connections of simply supported floorbeams, stringers, and other beams and girders acting and framed similarly, shall be proportioned for at least 1.25 times their computed shear. Alternatively, these connections shall be proportioned for the combined effect of moment and shear. (2) Secondary and bracing members shall have a strength of the lesser of the strength of the member based on the allowable unit stress or 1.5 times the maximum computed stress.

1 2

See Part 9 Commentary See Part 9 Commentary

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Design

The requirement of Article 1.3.13 shall be satisfied. Bracing members used only as ties or struts to reduce the unsupported length of a member to which they connect need not be connected for more than the force specified in Article 1.11.6. b. All groove welds shall have full penetration, and shall satisfy the requirements of Article 1.3.13. c.

Bolted or riveted connections shall have not less than three fasteners per plane of connection or equivalent strength in welding. The weld shall preferably be a fillet weld and be parallel and symmetrical to the direction of force.

d. Members subject to compression only, if faced for bearing, shall be spliced on 4 sides sufficiently to hold the abutting parts accurately and securely in place. The splice shall be as near a panel point as practicable and shall be designed to transmit at least one-half of the force through the splice material. Where such members are in full milled bearing on base plates, there shall be sufficient bolted or riveted connecting material, or welding, to hold all parts securely in place. e.

Block shear shall be evaluated at beam end connections where the top flange is coped, at the end connections of tension members, in connections utilizing gusset plates and all other connections where failure by block shear is a concern. The allowable block shear rupture strength in pounds is as follows: (1) When FuAnt ³ 0.60FuAnv:

0.35FyAgv + 0.50FuAnt

(2) When FuAnt < 0.60FuAnv:

0.30FuAnv + 0.55FyAgt

(3) But no greater than:

0.30FuAnv + 0.50FuAnt

1

where: Agv = gross area subject to shear Agt = gross area subject to tension Anv = net area subject to shear Ant = net area subject to tension

3

1.5.10 FIELD CONNECTIONS (1994)1 R(2008) Field connections, including splices, shall be made using rivets or high strength bolts except that field welding may be used for minor connections not subject to live load force, and for joining sections of deck plates, etc., which do not function as part of the load carrying structure. Otherwise, welding shall not be used for field connections.

1.5.11 DEVELOPMENT OF FILLERS (1993) R(2008) a.

For high strength bolted construction, no additional bolts are necessary for the development of fillers.

b. For riveted construction, when rivets subject to force pass through fillers, the fillers shall be extended beyond the connected member and the extension secured by enough rivets to distribute the total force to the member uniformly over the combined sections of the member and the fillers, except that fillers less than 1/4 inch thick shall not be extended beyond the splicing material, and additional rivets are not required. c.

1

For riveted construction, eccentricity must be considered on short, thick fillers.

See Part 9 Commentary

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Steel Structures

1.5.12 COMBINATIONS OF DISSIMILAR TYPES OF CONNECTIONS (1993)1 R(2008) a.

Rivets and high strength bolts in the same connection plane may be considered as sharing the force. When such a connection plane is subjected to fatigue conditions, the requirements of Article 1.3.13 applicable to rivets shall be satisfied for both types of fasteners.

b. Welds acting in the same connection with rivets and/or bolts shall be proportioned to carry the entire force.

1.5.13 SEALING (1993)2 R(2008) a.

Where two or more plates or shapes are in contact, provision shall be made for sealing their edges for protection against the entrance of moisture between them.

b. For riveted and bolted members, sealing shall be accomplished by limiting the spacing of the fasteners connecting component parts. The pitch on a single line adjacent to a free edge of an outside plate or shape shall not exceed 4 + 4t, where t is the thickness of the thinnest outside plate or shape in inches, nor 7 inches. Where there is a second line of fasteners uniformly staggered with those in the line adjacent to the free edge, at a gage, g, less than 1-1/2 + 4t inches, therefrom, the staggered pitch of the fasteners in the two lines shall not exceed 4 + 4t – 3/4 g inches, nor 7– 3/4 g inches, but need not be less than one-half the requirement for a single line. c.

For welded members, longitudinal sealing may be accomplished by the use of continuous welds at exposed edges of contact surfaces, of such dimensions and made by such procedure as will ensure weld soundness throughout.

1.5.14 CONNECTIONS OF COMPONENTS OF BUILT-UP MEMBERS (1993)3 R(2008) a.

Where two or more plates or shapes are in contact, they shall be connected adequately to make them act in unison.

b. For riveted and bolted members, stitch fasteners shall be used to make component parts of the member act in unison. The pitch of stitch fasteners in compression members on any single line shall not exceed 12t, where t is the thickness of the thinnest outside plate or shape, except that, if the fasteners on adjacent lines are staggered and the gage, g, between the line under consideration and the farther adjacent line is less than 24t, the staggered pitch in such two lines shall not exceed 12t, nor 15t – 3/8 g. The gage between adjacent lines of such stitch rivets shall not exceed 24t. At the ends of compression members, the pitch of stitch fasteners on any single line in the direction of stress shall not exceed 4 times the diameter of the fasteners for a distance equal to 1.5 times the width of the member. In tension members, the pitch of stitch fasteners shall not exceed twice that specified for compression members, and the gage shall not exceed that specified for compression members. c.

The requirements of Article 1.5.13 and this Article are not additive, but both must be satisfied by the detail used.

1.5.15 WELDED CLOSED BOX MEMBERS (1993) R(2008) a.

Absolute airtightness of box members is not required.

1

See Part 9 Commentary See Part 9 Commentary 3 See Part 9 Commentary 2

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b. Box members shall be closed to the elements so as to inhibit access of water or moisture to the interior. c.

Crevices in areas where standing water may be drawn into the box member as a result of interior pressure changes shall be sealed with an approved permanent-type waterproof caulking compound; or, alternatively, such crevices may be sealed by welding if the details are approved by the Engineer.

d. Effective drain holes shall be provided to prevent accumulation of any water inside the member. e.

The interiors of box members meeting the requirements of this article need not be painted.

SECTION 1.6 MEMBERS STRESSED PRIMARILY IN AXIAL TENSION OR COMPRESSION 1.6.1 COMPRESSION MEMBERS (2004)1 R(2008) a.

Compression members shall be so designed that the main elements of the section are connected directly to the gusset plates, pins, or other members.

b. In members consisting of segments connected by lacing or by solid cover plates, the thickness of the web plate, inches, shall not be less than F 0.90b ------y E --------------------------- ; P ------c f

1

P ------c not to exceed 2 f

3

and the thickness of the cover plate, inches, shall not be less than F 0.72b ------y E --------------------------- ; P ------c f

P ------c not to exceed 2 f

4

where: b = unsupported distance between the nearest lines of fasteners or welds, or between the roots of rolled flanges, inches Pc = allowable stress for the member of axial compression, as determined by the applicable formula of Article 1.4.1, psi. f = calculated stress in compression, psi. Fy = yield point as specified in Table 15-1-1 for the material, psi. c.

1

For the thickness requirements for perforated plates, see Article 1.6.4.3.

See Part 9 Commentary

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1.6.2 OUTSTANDING ELEMENTS IN COMPRESSION (2004)1 a.

The width of outstanding elements of members in compression shall not exceed the following, where t, inches, is the thickness of the element: (1) Legs of angles or flanges of beams or tees: E 0.35t ------ for stringers and girders where ties rest on the flange Fy

E 0.43t ------ for main members subject to axial force, and for stringers and girders F y where ties do not rest on the flange

E 0.50t ------ for bracing and other secondary members Fy (2) Plates: E 0.43t -----Fy (3) Stems of tees: E 0.56t -----Fy where: Fy = yield point as specified in Table 15-1-1 for the material. b. The width of plates shall be measured from the free edge to the center line of the first row of fasteners or welds. The width of legs of angles, and the stems of tees, shall be considered as the full nominal dimension. The width of flange of beams and tees shall be measured from the free edge to the toe of the fillet. c.

Where a projecting element exceeds the width-to-thickness ratio prescribed above, but would conform to that ratio and would satisfy the stress requirements with a portion of its width considered as removed, the member will be acceptable.

1.6.3 STAY PLATES (1994) R(2008) a.

1

On the open sides of compression members, the segments shall be connected by lacing bars, and there shall be stay plates as near each end as practicable. There shall be stay plates at intermediate points where the lacing is interrupted. In main members, the length of the end stay plates shall not be less than

See Part 9 Commentary

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1.25 times the distance between the lines of connections to the outer flanges. The length of intermediate stay plates shall not be less than three-quarters of that distance. b. The segments of tension members composed of shapes shall be connected by stay plates. The length of the stay plates shall not be less than two-thirds of the lengths specified for stay plates on compression members. c.

The thickness of stay plates shall not be less than 1/50 of the distance between the lines of connections to the outer flanges for main members, or 1/60 of that distance for bracing members.

d. For riveted or bolted stay plates, the fasteners shall not be spaced more than four diameters on centers, and at least 3 fasteners shall be used in a line. For welded stay plates, 5/16 inch minimum continuous fillet welds shall be used along their longitudinal edges.

1.6.4 LACING AND PERFORATED COVER PLATES FOR TENSION AND COMPRESSION MEMBERS (2009)1 1.6.4.1 Shear Force The shear force normal to the member in the planes of lacing or continuous plates with or without perforations shall be assumed divided equally among all such parallel planes. The total shear force shall include any force due to weight of member and to other forces and, for compression members, 2.5% of the compressive axial force but not less than:

1 AF ----------y150 where: A = member area required for axial compression, square inches (axial compressive force divided by allowable compressive stress).

3

Fy = yield point of member material as specified in Table 15-1-1 1.6.4.2 Lacing a.

Lacing bars of compression members shall be so spaced that the slenderness ratio of the portion of the flange included between lacing-bar connections will not be more than 40 nor more than 2/3 of the slenderness ratio of the member.

b. The section of the lacing bars shall be determined by the formula for axial compression in which l is taken as the distance along the bar between its connections to the main segments for single lacing, and as 70% of that distance for double lacing. c.

Where the distance across the member between connection lines in the flanges is more than 15 inches and a bar not over 3-1/2 inches wide is used, the lacing shall be double and connected at the intersections.

d. The angle between the lacing bars and the axis of the member shall be approximately 45 degrees for double lacing and 60 degrees for single lacing.

1

See Part 9 Commentary

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e.

Lacing bars may be shapes or flat bars. For main members, the minimum thickness of flat bars shall be 1/40 of the distance along the bar between its connections for single lacing, and 1/60 for double lacing. For bracing members the limits shall be 1/50 for single lacing and 1/75 for double lacing.

f.

For riveted or bolted construction, the diameter of the fasteners in lacing bars shall not exceed 1/3 the width of the bar. There shall be at least two fasteners in each end of lacing bars fastened to flanges more than 5 inches width.

g.

For welded construction, fillet welds comparable in strength to that required for riveted or bolted construction shall be used.

1.6.4.3 Perforated Cover Plates a.

Perforations shall be ovaloid or elliptical.

b. The length of perforation shall not be more than twice its width. For compression members the ratio of the length of perforation to the radius of gyration of the half-member at the center of perforation about its own axis shall not be more than 20 nor more than one-third of the slenderness ratio of the member about its axis perpendicular to the perforation. c.

The clear distance between perforations shall not be less than the distance between the nearer lines of connections.

d. For tension members the thickness of the perforated plate shall not be less than 1/50 of the distance between the nearer lines of connections. For compression members the thickness shall not be less than F 1/50 of such distance nor less than 2.34 ------y times the distance from such a line of connections to the E edge of the perforation at the center of perforation, where Fy = the yield point as specified in Table 15-11 for the material, nor less than that specified in Article 1.6.1b for solid plates. Also, for all members, the thickness shall not be less than that required by the formula: 3cV t = ----------------------------2vh ( c – a ) where: t = thickness of plate, inches c = spacing of perforations, inches V = maximum transverse shearing force in the plane of the plate, kips v = basic allowable unit stress for shear in webs of plate girders, ksi h = width of plate, inches a = length of perforation, inches c – a = distance between perforations e.

Where the plate is spliced for transfer of force, the clear distance between the end perforation and the end of the plate shall not be less than the distance between the nearer lines of connections, except that one-half such distance may be used for compression members which are faced for bearing. Where the plate is not spliced for transfer of force, an open perforation may be used at the end of the plate provided that its length does not exceed one-half the distance between the nearer lines of connections.

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f.

The gross section of the plate through the perforation for compression members and the net section of the plate through the perforation for tension members shall be considered as a part of the area of the member.

1.6.5 EFFECTIVE NET AREA FOR TENSION MEMBERS - STRENGTH (2008)1 a.

When a tension load is transmitted directly to each of the elements of the cross section of a member by fasteners or welds, the effective net area, Ae, is equal to the net area as described in Article 1.5.8.

b. When a tension load is transmitted directly to some, but not all of the elements of the cross section of a member, the effective net area Ae of that member shall be computed as follows: (1) When the tension load is transmitted by bolts or rivets:

Ae = UAn where An = Net area of member, per Article 1.5.8 U = Shear lag reduction coefficient U = (1 - x/L) x = distance from the centroid of the connected area to the shear plane of the connection. (See Figure 15-1-5) L = Connection length in the direction of the loading, between the first and last fasteners.

1

3

4

1

See Part 9 Commentary

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For rolled or built-up shapes, the distance x is to be referenced to the center of gravity of the material lying on either side of the centerline of symmetry of the cross-section.

Figure 15-1-5. Determination of x. In lieu of calculated values, the reduction coefficient, U, for angles shall be taken as 0.80 for members with four or more bolts or rivets per line, and 0.60 for members with less than four bolts or rivets per line. (2) When the tension load is transmitted by only longitudinal welds to other than plate members, or by longitudinal welds in combination with transverse welds:

Ae = UAg where Ag = Gross area of member U = Shear lag reduction coefficient, as in (1) (3) When the tension load is transmitted by only welds transverse to the direction of loading: Ae = Area of directly connected elements

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(4) When the tension load is transmitted to a plate by longitudinal welds, welds shall be on both edges, for a length not less than the distance between the welds: Ae = UA For L

³ 2w . . . . . . . . . . . . . . . . . . . . . . U = 1.00

For 2w > L

³ 1.5w . . . . . . .. . . . . . . . .U = 0.87

For 1.5w >L

³ w . . . . . . . . . . . . . . . . .U = 0.75

where A= area of plate L= length of weld w= distance between welds

1.6.6 EFFECTIVE AREA FOR TENSION MEMBERS - FATIGUE (2007)1 a.

When a tension load is transmitted directly to all of the elements of the cross section of a member by fasteners or welds, the effective net area, Ae, is equal to the net area, An, as described in Article 1.5.8.

b. When a tension load is transmitted directly to some, but not all, of the elements of the cross section of a member, the effective net area, Ae, of that member shall be taken as the sum of the net areas of the component parts directly loaded. c.

1

When a tension load is transmitted directly to some, but not all, of the elements of the cross section of a member, the effective gross area of that member shall be taken as the sum of the gross areas of the component parts directly loaded.

3 SECTION 1.7 MEMBERS STRESSED PRIMARILY IN BENDING 1.7.1 PROPORTIONING GIRDERS AND BEAMS (2004)2 R(2008) a.

Plate girders, I-beams, and other members subject to bending that produces tension on one face, shall be proportioned by the moment of inertia method. The neutral axis shall be considered as the center of gravity of the gross section. The tensile stress shall be computed from the moment of inertia of the entire net section and the compressive stress from moment of inertia of the entire gross section.

b. Where the compression flange is not fully supported laterally, the flexural member shall be proportioned so that the ratio of the distance between points of lateral supports and the radius of gyration of the compression flange, including that portion of the web area on the compression side of the axis of bending about an axis in the plane of the web, shall not exceed: E 5.55 -----Fy

1 2

See Part 9 Commentary See Part 9 Commentary

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where: Fy = the yield point as specified in Table 15-1-1 for the material.

1.7.2 FLANGE SECTIONS (1994)1 R(2002) 1.7.2.1 Riveted or Bolted Construction a.

Flanges of plate girders preferably shall be made without side plates.

b. Where flanges of plate girders are subjected to transverse local bending from bridge ties, the minimum angle thickness shall be 5/8 inch where cover plates are used and 3/4 inch where cover plates are not used. c.

Where cover plates are used, at least one plate of each flange shall extend the full length of the girder or beam. Any cover plate which is not full length shall extend beyond the theoretical end far enough to develop the capacity of the plate, or shall extend to a section where the stress in the remainder of the girder or beam flange is equal to the allowable fatigue stress, whichever extension is greater. The term “theoretical end of cover plate” refers to the section where the stress in the flange without the cover plate equals the allowable stress, exclusive of fatigue considerations.

1.7.2.2 Welded Construction a.

Flanges of welded plate girders shall be made using only one plate in each flange, i.e. without cover plates. Side plates shall not be used in welded construction. The thickness and width of the flange plate may be varied by butt welding parts of different thickness or width with transitions conforming to the requirements of Article 1.10.1.

b. Not more than one cover plate may be used on each flange of a rolled beam. Such cover plates shall be full length and of uniform thickness and width, and shall be connected to the flange of the rolled beam with continuous fillet welds of sufficient strength to transmit the horizontal shear into the cover plate. The thickness of a cover plate shall not be greater than 1.5 times the thickness of the flange to which it is attached.

1.7.3 T HICKNESS OF WEB PLATES (2004)2 a.

The thickness of the webs of plate girders without longitudinal stiffeners shall not be less than: F 0.18 ------y E of the clear distance between the flanges, except that if the extreme fiber stress in the compression flange is less than the allowable, the above calculated thickness may be divided by the factor: Pc -----f

1 2

See Part 9 Commentary See Part 9 Commentary

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where: Pc = allowable stress in the compression flange, as determined by the applicable formula of Article 1.4.1, psi. f = the calculated extreme fiber stress in the compression flange, psi. Fy = yield point as specified in Table 15-1-1 for the material b. The thickness of the webs of plate girders with longitudinal stiffeners, proportioned in accordance with Article 1.7.8, shall not be less than 1/2 that determined in paragraph a. c.

The thickness of the webs of plate girders with or without longitudinal stiffeners shall not be less than 1/6 the thickness of the flange.

1.7.4 FLANGE-TO-WEB CONNECTION OF PLATE GIRDERS (2009)1 a.

The flanges of plate girders shall be sufficiently connected to the web to transmit to the flange the horizontal shear force at any point together with the force from any load that is applied directly on the flange. Where the ties bear directly on the flange, one wheel load, including 80% impact, shall be assumed to be distributed over 3 feet. On ballasted deck girders, the wheel load, including 80% impact, shall be assumed to be distributed over 5 feet.

b. Flange to web joints of welded plate girders:

1 (1) Flange to web joints on welded plate girders shall be identical welds for both compression and tension flanges. (2) Deck plate girders and stringers. For open and non-composite, non-ballasted decks, the flange-to-web joints shall be made using continuous, complete joint penetration (CJP) or if directed by the engineer, partial joint penetration (PJP) groove welds or fillet welds. If PJP groove welds or fillet welds are used, the root opening and/or fillet weld reinforcement shall be proportioned such that the fatigue strength of the joint is controlled by weld toe cracking and not throat cracking as calculated using the provisions of detail description 5.4 in Table 15-1-9.

3

For ballasted, welded steel plate or composite concrete decks, the flange to web joint may be continuous, CJP groove welds, PJP groove welds or fillet welds. (3) Through plate girders. The flange-to-web joints may be continuous, CJP, PJP, or fillet welded connections.

1.7.5 FLANGE SPLICES (1994) R(2002) a.

Flange members that are field spliced, or that are shop spliced by riveting and/or bolting, shall be covered by extra material not less in section than the member spliced. There shall be enough fasteners on each side of the splice to transmit to the splice material the force in the part cut. Flange angles shall be spliced with angles. No two elements in the same flange shall be spliced at the same cross section.

b. In shop welded construction, flange members may be shop spliced by riveting or bolting as in paragraph a or by welding as in paragraph c.

1

See Part 9 Commentary

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c.

Welded shop splices shall be made with full penetration groove welds. They shall preferably be made in the same cross section except when made before webs and flanges are joined to each other they may be located in the same or different cross sections.

d. Welded shop splices of rolled beams shall be made with full penetration groove welds at the same cross section, and shall be made without cope holes, i.e. the entire cross section shall be welded.

1.7.6 WEB SPLICES (1994) R(2002) a.

Splices in the webs of plate girders or rolled beams shall be designed to meet both of the following conditions: (1) Full shear strength of the web, gross section. (2) The combination of the full moment strength of the web, net section, with the maximum shear force that can occur at the section where the splice is located.

b. Shop or field web splices in riveted or bolted construction and field web splices in welded construction shall be made using splice plates on each side of the web, of the strength required by paragraph a. The net moment of inertia of these web splice plates shall not be less than that of the web. c.

Shop web splices in welded construction may be made as indicated in paragraph b, or may be welded. Welded shop splices shall be made with full penetration groove welds, and the entire cross section shall be welded.

1.7.7 STIFFENERS AT POINTS OF BEARING (1994) R(2002) a.

Stiffeners shall be placed in pairs at end bearings of plate girders and beams, and at points of bearing of concentrated loads. They shall extend as nearly as practicable to the edges of the flange to give effective distribution and shall be connected to the web by enough rivets, bolts or welds, to transmit the load. Where angle stiffeners are used, they shall not be crimped. Where plate stiffeners are used, they shall be clipped at 45 degrees at upper and lower ends to clear fillet of flange angle or weld connecting flange plate to web, as applicable.

b. The outstanding portion of a bearing stiffener shall meet the width-thickness ratio requirements for outstanding elements in compression. c.

Bearing stiffeners shall be designed as columns, assuming the column section to comprise the pair of stiffeners and a centrally located strip of the web whose width is equal to 25 times its thickness at interior stiffeners or a width equal to 12 times its thickness when the stiffeners are located at the end of the web. The effective length shall be taken as three-quarters of the length of the stiffeners in computing the ratio l/r.

d. Bearing stiffeners shall also be designed for bearing, without considering any part of the web. Only that part of the outstanding leg of an angle stiffener or that part outside the corner clip of a plate stiffener, which is in contact with the flange angle or flange plate, shall be considered effective in bearing. Where bearing stiffeners are welded to the flange in compliance with Part 3, Fabrication, Article 3.1.10a, an area equal to the length of the full penetration groove weld multiplied by the stiffener thickness shall be considered effective in bearing.

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1.7.8 WEB PLATE STIFFENERS (INTERMEDIATE TRANSVERSE AND LONGITUDINAL) (2010)1 a.

Where the depth of the web between the flanges or side plates of a riveted, bolted or welded plate girder exceeds 2.12 ( E ¤ F y ) times its thickness, it shall be transversely stiffened by pairs (except as noted in paragraph c) of angles riveted or bolted, or of plates welded, to the web. The actual clear distance, da, between intermediate transverse stiffeners shall not exceed 96 inches, nor the clear distance between flanges or side plates, nor d. The maximum clear distance, d, inches, between intermediate transverse stiffeners to preclude web shear buckling is given by the formula: E d = 1.95t ---S where: t = thickness of web, inches S = calculated shear stress in the gross section of the web at the point under consideration, psi Fy = minimum yield point as specified in Table 15-1-1 for the web material, psi The moment of inertia of the intermediate transverse stiffeners shall not be less than:

I =

1

2 3æ 2.5d a t ç D ------è 2

ö – 0.7 ÷ ø d

taken about the centerline of the web plate in the case of stiffeners furnished in pairs (on each side of web plate) and taken about the face of the web plate in contact with the stiffener in the case of single stiffeners.

3

where: da = actual stiffener spacing

4

I = moment of inertia, inches 4 D = depth of web between flanges or side plates, inches b. For intermediate transverse stiffeners, the width of the outstanding leg of each angle, or the width of the welded stiffener plate, shall not be more than 16 times its thickness nor less than 2 inches plus 1/30 of the depth of the girder. c.

Intermediate transverse stiffeners used on one side of the web plate only (single stiffeners), shall be connected to the outstanding portion of the compression flange.

d. All intermediate stiffeners on the track side of through plate girders shall be fastened to the compression flange in order to minimize out-of-plane deformations in the web caused by rotations of the ends of the floorbeam.

1

See Part 9 Commentary

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e.

Intermediate stiffeners on through plate girders located within a distance equal to the depth of the girder from the bearing shall be fastened to the tension flange.

f.

Where the depth of the web between the flanges or side plates of a riveted, bolted, or welded plate girder exceeds 4.18 ( E ¤ f ) times its thickness (where f = the calculated compressive bending stress in the flange, psi), it shall be stiffened by intermediate transverse stiffeners in accordance with paragraphs a, b, and c; and by a longitudinal stiffener. Longitudinal stiffeners are usually placed on one side of the web plate with the transverse stiffeners on the other side. Where longitudinal stiffeners and intermediate transverse stiffeners are on the same side and intersect, the longitudinal stiffener should be continuous and the intermediate transverse stiffener should be discontinuous. The stress in the stiffener (from participation in the girder stress) shall not be greater than the basic allowable bending stress for the material used in the stiffener. See Article 9.1.10.2 for further guidance on detailing intersecting stiffeners.

g.

The centerline of a plate longitudinal stiffener or the gage line of an angle longitudinal stiffener shall be D/5 from the inner surface or leg of the compression flange component.

h. The longitudinal stiffener shall be proportioned so that:

2

da ö 3æ I E = Dt ç 2.4 -------- – 0.13÷ 2 è ø D

where: da = actual clear distance between intermediate transverse stiffeners, inches IE = minimum required moment of inertia of longitudinal stiffeners about the edge in contact with the web plate, inches4, for stiffeners used on one side of the web or about the centerline of the web plate for stiffeners used on both sides of the web. i.

The thickness of the longitudinal stiffener (inches) shall not be less than: f 2.39b¢ ---E where: b¢ = width of outstanding leg of longitudinal stiffener, inches f = calculated compressive bending stress in the flange, psi

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1.7.9 COMPOSITE STEEL AND CONCRETE SPANS (2008)1 1.7.9.1 Definition (1986) R(2005) The term “composite steel and concrete spans” refers to simple span bridges in which steel beams and concrete deck slab are designed, and are so constructed, on the assumption that the two materials act as an integral unit. 1.7.9.2 Basic Design Assumptions (1986) R(2005) a.

Composite steel beams and concrete deck slab shall be proportioned by the moment-of-inertia method, using the net composite section.

b. The design of the concrete deck shall conform to the requirements of Chapter 8, Concrete Structures and Foundations, except that the live load and impact load shall be as specified in Article 1.3.3 and Article 1.3.5, respectively. c.

The effective width of flange on either side of any beam shall not exceed the following: (1) One-half of the distance to the center line of the adjacent beam. (2) One-eighth of the span length of the beam. (3) Six times the thickness of the slab.

d. For exterior beams, the effective width of flange on the exterior side shall not exceed the actual overhang. When the exterior beam has a flange on one side only, the requirements of paragraph c shall be modified to limit the total effective flange width to one-twelfth of the span length of the beam. e.

Composite construction shall not be used for isolated beams.

f.

The value of n, the ratio of the modulus of elasticity of steel to the modulus of elasticity of concrete of various design strengths, shall be as given in Chapter 8, Concrete Structures and Foundations.

g.

Composite sections preferably shall be proportioned so that the neutral axis lies below the top surface of the steel beam. Where concrete is on the tension side of the neutral axis, it shall not be considered in computing moments of inertia or resisting moments.

h. Where no temporary intermediate supports are provided for the beams during casting and curing of the concrete slab, then the steel and concrete dead loads shall be considered as acting on the steel beams alone, and all subsequent loads as acting on the composite section. Where the beams are provided with effective temporary intermediate supports which are kept in place until the concrete has attained 75% of its required 28-day strength, then the concrete dead load and all subsequent loads shall be assumed as acting on the composite section.

1

i.

The effect of creep shall be considered in the design of composite beams which have the dead loads acting on the composite section. Stresses and horizontal shear produced by such dead loads shall be taken as the greater of those computed for the value of n or for 3 times that value.

j.

Horizontal shear at the point under consideration between steel beam and concrete slab shall be computed by both the following formulas:

See Part 9 Commentary

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3

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VrQ VmQ and S m = ------------S r = ----------I I where: Sr = the range of horizontal shear, lb per linear inches Sm = the maximum horizontal shear, lb per linear inches Vr = the range of vertical shear due to live load and impact load. At any section, the range of shear shall be taken as the difference in the minimum and maximum shear envelopes, lb Vm = the maximum vertical shear due to live load and impact load combined with any portion of dead load superimposed on the composite span after the concrete slab is cured, including its weight if temporary intermediate supports during casting and curing are provided, lb Q = the static moment of the transformed compressive concrete area about the neutral axis of the composite section, inch3 I = the moment of inertia of the composite section. If the dead load shear is included in Sm, the horizontal shear resulting therefrom shall be computed separately as specified in paragraph i and added to the horizontal shear from the other loads, inch4 k. The vertical shear shall be considered to be resisted entirely by the web of the steel beam. 1.7.9.3 Shear Transfer Devices (2006) a.

Resistance to horizontal shear at the junction of the slab and beam shall be provided by studs or channels welded to the beam flange.

b. The spacing of the shear transfer devices shall be the smaller of the two values determined by dividing the resistance value of the individual device, as specified in Article 1.7.9.3.1, by the value of Sr or Sm as defined in Article 1.7.9.2j. The maximum spacing shall be 2 feet. c.

The shear connectors shall be so spaced that the concrete can be thoroughly compacted and in direct contact with all surfaces of the shear connectors.

d. The clear depth of concrete cover over the top of the shear connectors shall be not less than 2 inches Shear connectors shall penetrate at least 2 inches above the bottom of the slab. e.

The clear distance between the edge of the beam flange and the edge of the shear connector shall be not less than 1 inch for channels and 1-1/2 inches for studs.

f.

When stud shear connectors are used, a maximum variation of 1 inch from the location shown on the plans shall be accepted provided that this does not reduce the center to center distance to the nearest stud to less than 2-1/2 inches, or the edge distance required in paragraph e.

1.7.9.3.1 Design Force for Shear Connectors a.

The allowable horizontal design force range per shear connector for fatigue (Sr) when channels are used shall be 2,400(w) lb and 2,100(w) lb for 2,000,000 cycles and over 2,000,000 cycles respectively. The maximum allowable horizontal design force per shear connector (Sm) when channels are used shall be taken as 3,600(w) lb. In the equations for horizontal design force, w is the length of the channel in inches measured in a transverse direction to the flange of the beam.

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b. The allowable horizontal design force range per shear connector for fatigue (Sr) when studs are used shall be 10,000(As) lb and 7,000(As) lb for 2,000,000 cycles and over 2,000,000 cycles respectively. The maximum allowable horizontal design force per shear connector (Sm) when studs are used shall be taken as 20,000(As) lb. In the equations for horizontal design force, As is the nominal cross sectional area of the stud, inch2. c.

Where either stud or channel shear connectors are used, fatigue due to primary bending stress range must be checked on the base metal of the member to which the shear connectors are attached as per Table 15-1-9 for longitudinally loaded fillet welded attachments.

1.7.9.3.2 Channels as Shear Transfer Devices When channels are used as shear transfer devices they shall be from the American Standard series and of ASTM A 36 steel. They shall be placed transverse to the beam and with one channel flange welded all around to the flange of the beam with at least 3/16 inch fillet welds. 1.7.9.3.3 Studs as Shear Transfer Devices a.

Where welded studs are used as shear transfer devices they shall be headed, and shall be 3/4 inch or 7/8 inch nominal diameter, and their overall length after welding shall be at least 4 times their diameter.

b. Studs shall conform to the requirements of ASTM A108, grades 1010 through 1020, either semi- or fullykilled. c.

Tensile properties as determined by tests of bar stock after drawing or of finished studs shall conform to the following requirements:

1

Tensile strength (min) . . . . . . . . 60,000 psi Elongation (min). . . . . . . . . . . . . 20% in 2 inches Reduction of area (min) . . . . . . . 50%

3

Tensile properties shall be determined in accordance with the applicable sections of ASTM A370. Where fracture occurs outside of the middle half of the gage length, the test shall be repeated. d. Finished studs shall be of uniform quality and condition, free from laps, fins, seams, cracks, twists, bends or other injurious defects. Finish shall be as produced by cold drawing, cold rolling or machining. However, cracks or bursts in the heads of shear connectors do not adversely affect the structural strength or other functional requirements of shear studs, and are not to be considered cause for rejection of the stud, except that where they are deeper than one-half the distance from the periphery of the head to the shank, they may be cause for rejection. Cracks or bursts, as here used, apply to an abrupt interruption of the periphery of the head of the stud by radial separation of the metal. e.

The Contractor shall, upon request by the Engineer, furnish the stud manufacturer’s certification that the studs that are delivered are in accordance with the applicable requirements of this article. Certified copies of the stud manufacturer’s test reports of the last completed set of in-plant quality control mechanical tests of the diameters of studs to be provided, made not more than six months prior to the delivery of the studs, shall be furnished to the Engineer on request.

f.

The Engineer may select, at the Contractor’s expense, studs of each type and size used, as necessary for checking the requirements of this article. The cost of these check tests shall be at the Company’s expense.

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g.

Stud shear connectors shall be of a design suitable for end welding, and shall be end welded to the steel beams with automatically timed stud welding equipment. The equipment and procedure followed in making the welds shall be as recommended by the manufacturer of the type of stud used. The flux and the ceramic arc shield utilized in this procedure shall be furnished by the manufacturer, and shall be compatible with the equipment and procedure used.

h. Before installation, the Contractor shall submit to the Engineer for approval information on the studs to be furnished as follows: (1) The name of the manufacturer. (2) A detailed description of the stud and arc shield. (3) A certification from the manufacturer that the stud weld base is qualified as specified in paragraph g. Qualification test data shall be retained in the files of the manufacturer. i.

The first two stud shear connectors welded on each member, after being allowed to cool, shall be bent 45 degrees by striking the stud with a hammer. If failure occurs in the weld zone of either stud, the procedure shall be corrected and two more studs shall be welded to the member and tested. Two consecutive studs shall be satisfactorily welded and tested before any more production studs are welded to the member. The foregoing testing shall be performed after any change in the welding procedure. If failure occurs in the stud shank, an investigation shall be made to ascertain and correct the cause before further welds are made. Studs tested that show no sign of failure shall be left in the bent position.

j.

Where the automatically made weld joining the stud to the beam is not a full 360 degrees, the stud shall be removed and replaced, or, at the option of the Contractor, the weld may be repaired by adding a 3/16 inch fillet weld in place of the lack of weld, using the shielded metal- arc process with low-hydrogen welding electrodes.

k. Before welding a new stud where a defective one has been removed, the area shall be ground smooth and flush, or in the case of a pullout of metal, the pocket shall be filled with weld metal using the shielded metal-arc process with low-hydrogen welding electrodes and then ground flush. l.

In addition to the inspection requirements of paragraph i, the Inspector shall visually inspect all studs after all studs have been welded to a beam, and shall give each stud a light blow with a hammer. Any stud which does not have a complete weld, any stud which does not emit a ringing sound when given the light blow with the hammer, any stud which has been repaired by welding or any stud which has less than normal reduction in height due to welding, shall be struck with a hammer and bent 15 degrees from the correct axis of installation, and, in the case of a defective or repaired weld, the stud shall be bent 15 degrees in the direction that will place the defective portion of the weld in the greatest tension. Studs that crack either in the weld or in the shank shall be replaced. Studs tested that show no sign of failure shall be left in the bent position.

m. If during the progress of the work, inspection and testing indicate that the shear connectors are not satisfactory, the Contractor will be required at his expense to make such changes in welding procedure, welding equipment and type of shear connector as necessary to secure satisfactory results. 1.7.9.4 Deflection (1983) R(2005) Composite spans shall be designed so that the deflection, computed using the composite section, for the live load plus impact load condition does not exceed 1/640 of the span length center to center of bearings.

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Design 1.7.9.5 Camber (1983) R(2005) Beams in composite construction shall be cambered when the dead load deflection exceeds 1 inch. Dead load deflection in composite construction, where the beams are provided with falsework or other effective intermediate supports during casting and curing of the concrete slab, shall be computed using the composite section, but including the effect of creep as specified in Article 1.7.9.2i. If such supports are not provided, the dead load deflection shall be computed using the steel beams alone.

1.7.10 RIGID FRAME STRUCTURES (2008)1 1.7.10.1 Definition (1983) R(2005) The term “rigid frame” is used to denote a load-carrying frame in which the horizontal member is structurally integral with the upright supports; either or both may vary in section. 1.7.10.2 Basic Design Assumptions (1983) R(2005) a.

Moments, shears and reactions shall be determined by recognized methods of analysis based on gross moments of inertia and gross areas of members. If the structure has a box type cross section, with perforated cover plates, the effective area of the cover plates, as defined in Article 1.2.5, shall be used in calculating deformations caused by axial stress.

b. Hinged bearings for the upright supports are preferred. Where hinged bearings are not practicable, or where details may render them inoperative, the analysis of the rigid frames shall be made assuming (1) fixed bases, (2) hinged bases, and the design shall be based on the larger stress so determined. c.

Loads and forces shall include those specified in Article 1.3.1a, except that the longitudinal forces as specified in Article 1.3.12 shall be applied at the mid height of the horizontal member of the frame. In addition to the loads and forces specified in Article 1.3.1a, rigid frame structures shall be proportioned for the most unfavorable combinations of those loads and forces with loads and forces resulting from the following:

1

3

(1) Earth pressure, which shall be assumed to act on both ends, on one end only, or be omitted, whichever requires the largest section. Where granular back fill is used behind the cut off walls, only active pressure at both ends shall be included. Earth pressure shall be determined in accordance with the recommendations given in Chapter 8, Concrete Structures and Foundations. (2) Temperature change, which shall be based on a range of from plus 40 degrees F to minus 60 degrees F from the temperature expected at time of closure. Closure must be effected when the actual temperature is within 10 degrees F of the assumed figure; where this is not possible, the adequacy of the structure must be investigated for the actual temperature, and reinforcement added if necessary. (3) Rib-shortening and elastic yielding of the supports, which must be investigated and their effect included, if larger sections would be required thereby. 1.7.10.3 Foundations (1983) R(2006) a.

1

Footings shall be founded on rock, on substantially unyielding material, or on piles driven to an unyielding stratum. If the footings are founded on piles, there shall be a sufficient number of battered piles to provide the necessary resistance to the horizontal thrust.

References, Vol. 44, 1943, pp. 413, 670, 685; Vol. 60, 1959, pp. 506, 1098; Vol. 63, 1962, pp. 386, 699; Vol. 70, 1969, p 241.

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b. Where conditions make it impracticable to provide resistance to the horizontal thrust by means of direct bearing or by battered piles, steel tie rods may be used. Such tie rods shall be encased in concrete with a minimum cover on all sides of 6 inches. 1.7.10.4 Spacing (1983) In addition to the requirements of Article 1.2.4, the distance between frames shall be great enough to facilitate the attachment of bracing between them, and for painting. 1.7.10.5 Deflection (1983) R(2005) The structure shall be so proportioned and designed that the computed total elastic deflection at the mid span of the horizontal member for live load plus impact load shall not exceed 1/640 of the distance center to center of the upright supports. 1.7.10.6 Camber (1983) R(2005) Rigid frame structures in which the distance center to center of upright supports is 60 feet or less need not be cambered. Rigid frame structures in which that length exceeds 60 feet shall have camber equal to the deflection produced by the dead load plus a load of 3,000 lb per foot of track. 1.7.10.7 Impact Load (1983) R(2005) In computing impact load in accordance with Article 1.3.5, L shall be considered as the length, in feet, center to center of the upright supports for longitudinal rigid frames, and, for transverse rigid frames, L shall be considered as the length in feet of the longer adjacent supported longitudinal beam or girder. 1.7.10.8 Stresses (1983) The stresses resulting from earth pressure, temperature change, rib shortening and elastic yielding of supports shall be combined with the stresses resulting from the loadings of Article 1.3.14.3a, and the member shall be proportioned for the stresses specified in Article 1.3.14.3a. The provisions of Article 1.3.14.3b for combinations including stresses resulting from other lateral loads and/or longitudinal load shall apply. 1.7.10.9 Bracing (1983) a.

Bracing for rigid frames shall conform to the requirements of Section 1.11, Bracing, with the modifications of this section. There shall be continuous bracing in the planes of the compression flanges of both horizontal and vertical members. If the top flanges are rigidly connected to a steel deck plate, or laterally restrained by a cast-in-place reinforced concrete deck, only such top lateral bracing as is required for erection purposes need be provided.

b. There shall be cross frames or diaphragms between the main members of the rigid frames so placed as to act with the horizontal bracing to provide lateral support for the compression flange. 1.7.10.10 Stiffeners at Points of Bearing (1983) R(2005) a.

Where the bottom flange of the horizontal member in a rigid frame extends across the upright members and bears thereon, there shall be bearing stiffeners directly above the flanges of the upright members, milled to fit tight against the bottom flange of the horizontal member and designed to transmit the stress in the flanges of the vertical members to the web of the horizontal member.

b. Where the inner flanges of the upright members are made continuous up to the top flange of the horizontal member, the ends of the bottom flange of the horizontal member shall be milled to bear © 2011, American Railway Engineering and Maintenance-of-Way Association

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against the inner flanges of the upright members. There shall be bearing stiffeners on the webs of the vertical members opposite the milled ends of the bottom flange of the horizontal member, designed to transmit the force from that flange to the webs of the vertical members. c.

Where rounded corners at the junction of horizontal and vertical members are used, they shall be proportioned by recognized methods of analysis and adequately stiffened.

1.7.10.11 Splices (1983) R(2005) Splices in any component of the rigid frame structure shall be designed to develop the full strength of that component.

SECTION 1.8 FLOOR MEMBERS AND FLOORBEAM HANGERS 1.8.1 END FLOORBEAMS (1993) R(2008) Spans with floor systems shall have end floorbeams unless otherwise specified. Except where other means are provided, end floorbeams shall be proportioned for lifting the span without exceeding the basic allowable stresses by more than 50%.

1

1.8.2 FLOORBEAMS AND FLOORBEAM HANGERS (1993) R(2008) a.

Floorbeams preferably shall be perpendicular to the center line of the track.

b. The main material of floorbeam hangers shall not be coped or notched. Built-up hangers shall have solid or perforated web plates, or lacing. The minimum thickness of main material of floorbeam hangers shall be 1/2 inch.

3

1.8.3 END CONNECTIONS OF FLOOR MEMBERS (1993)1 R(2002) a.

Beams in solid floor construction, stringers and floorbeams shall have end connection angles to ensure the necessary flexibility in the connection. Welding shall not be used to connect the flexing leg.

b. The flexing legs of the connection angles shall not be less than 4 inches width and 1/2 inch finished thickness. c.

For stringers, the gage from back of angle to first line of fasteners in the flexing legs of the connection angles over the top one-third of the stringer depth shall not be less than the quantity: lt ---8 where: l = length of stringer span, inches t = thickness of angle, inches

1

See Part 9 Commentary

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SECTION 1.9 RIVETED AND BOLTED CONSTRUCTION 1.9.1 PITCH AND GAGE OF FASTENERS (1993) R(2008) The pitch of fasteners is the distance, inch, between centers of adjacent fasteners, measured along one or more lines of fasteners. The gage of fasteners is the distance, inches, between adjacent lines of fasteners, or the distance from the back of angle or other shape to the first line of fasteners.

1.9.2 GRIP OF RIVETS (1993) R(2008) Where the grip of rivets carrying calculated stress exceeds 4.5 times the diameter, the number of rivets shall be increased at least 1% for each additional 1/16 inch of grip. Where the grip equals or exceeds 6 times the nominal diameter, the body shall be tapered from the head for a distance not less than 3.42 times the nominal diameter, but not more than 4-3/4 inches. The body diameter at the head shall be 1/32 inch greater and where not tapered, 1/64 inch less than the nominal diameter.

1.9.3 MINIMUM SPACING OF FASTENERS (1993) R(2011) a.

The distance between centers of fasteners shall not be less than 3 times the diameter of the fasteners.

b. The distance between high strength bolts measured in the line of force from the center line of a bolt to the center line of an adjacent bolt shall not be less than: 2df p d ------------- + --2 Fu where: d = diameter of bolt, inches fp = calculated bearing stress due to design load, ksi Fu = lowest specified minimum tensile strength of the connected part, ksi

1.9.4 EDGE DISTANCE OF FASTENERS (2005)1 R(2011) a.

The distance from the center of a fastener to a sheared edge shall not be less than 1.75 times the diameter of the fastener. The distance from the center of a fastener to a rolled, planed, or thermally-cut edge shall not be less than 1.5 times the diameter of the fastener. The minimum edge distance may be decreased to 1.25 times the diameter of the fastener in flanges of rolled beams and channels if necessary to meet required clearances.

b. The distance from the free edge of an outside plate or shape to the first line of fasteners shall not exceed: 1-1/2 + 4t, nor 6 inches where: t = thickness, inches, of the plate or shape

1

See Part 9 Commentary

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c.

The distance between the center of the nearest bolt and that end of the connected member towards which the pressure of the bolt is directed shall not be less than: 2df p ------------Fu where: d = diameter of bolt, inches fp = calculated bearing stress due to design load, ksi Fu = lowest specified minimum tensile strength of the connected part, ksi

1.9.5 SIZES OF FASTENERS IN ANGLES (1993) R(2008) In angles, the size of which is determined by calculated stress, the diameter of the fasteners shall not exceed one-quarter of the width of the leg in which they occur. In angles, the size of which is not so determined, 1 inch fasteners may be used in 3-1/2 inch legs, 7/8 inch fasteners in 3 inch legs, and 3/4 inch fasteners in 2-1/2 inch legs.

1.9.6 FASTENERS IN INDIRECT SPLICES (1993) R(2008) For riveted construction only, where splice plates are not in direct contact with the parts which they connect, there shall be rivets on each side of the joint in excess of the number required in the case of direct contact, to the extent of two extra lines for each intervening plate. Where high strength bolts are used, no additional bolts need be added for indirect splices, nor for connections or splices with fillers.

1

3 SECTION 1.10 WELDED CONSTRUCTION 1.10.1 TRANSITION OF THICKNESS OR WIDTHS IN WELDED BUTT JOINTS (1993)1 R(2003) a.

Where butt joints subject to axial or flexural tensile stress, or to flexural compressive stress, are used to join material of different thicknesses, there shall be a smooth transition between offset surfaces at a slope not greater than 1 in 2.5 with the surface of either part. The thickness of the thicker plate shall not be more than twice that of the thinner plate. The transition of thickness may be accomplished by sloping weld faces or by chamfering the thicker part, or by a combination of the two methods.

b. Where butt joints subject to axial or flexural tensile stress, or to flexural compressive stress, are used to join material of different widths, there shall be a common longitudinal axis of symmetry, and there shall be smooth transition between offset edges at a slope of not greater than 1 in 2.5 with the edge of either part. c.

1

Where butt joints subject to axial compressive stress are used to join material of different thickness, the face of the weld shall have a slope of not greater than 1 in 2.5 with the surface of the thinner part.

See Part 9 Commentary

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d. Where butt joints subject to axial compressive stress are used to join material of different widths, reduction in width of the wider plate to effect a smooth transition is preferable, but is not mandatory.

1.10.2 PROHIBITED TYPES OF JOINTS AND WELDS (2008)1 a.

Those listed as such in AWS D1.5.

b. Plug or slot welds (This does not prohibit the use of fillet welds in holes or slots.) c.

Intermittent welds.

d. Butt joints of plates with transition of both thickness and width, and transmitting other than axial compressive stress. e.

Partial joint penetration groove welds transverse to the direction of stress.

f.

Transverse tack welds on tension flanges of flexural members.

g.

Highly constrainted joints. Welded connections shall be detailed to avoid welds that intersect or overlap. Welded attachments should be detailed so that the welds parallel to the primary stresses are continuous and the transverse welded connection is discontinuous. If unavoidable, welds in low stress range areas that are interrupted by intersecting members shall be detailed to allow a minimum gap of at least one inch between weld toes and weld terminations and shall be properly designed for the applicable fatigue limit state. (See Commentary)

1.10.3 FILLET WELDS (1993) R(2011) a.

Fillet welds which resist a tensile force which is not parallel to the axis of the weld, or which are proportioned to resist repeated stress, shall not terminate at corners of parts or members, but shall be returned continuously, full size, around the corner for a length equal to twice the weld size where such return can be made in the same plane. End returns shall be indicated on design and detail drawings.

b. Fillet welds in holes or slots may be used to transmit shear in lap joints or to prevent buckling or separation of lapped parts. Fillet welds in a hole or slot shall not overlap.

1.10.4 WELDED ATTACHMENTS (2004)2 R(2008) a.

Where stiffeners, brackets, gussets, clips, or other detail material are welded to members or parts subjected to fatigue conditions, the stress range in base material adjacent to the welds shall not exceed that permitted by Article 1.3.13.

b. An intermediate stiffener shall not be welded to the web of girder for a minimum distance of 6 times the thickness of web starting from the toe of the tension flange to web weld. c.

1 2

Wrap-around welds should not be used when an intermediate stiffener is fillet welded to a girder web or flange.

See Part 9 Commentary See Part 9 Commentary

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1.10.5 FRACTURE CRITICAL MEMBERS (1994) R(2003) Welding of Fracture Critical Members shall be in accordance with Section 1.14, Fracture Critical Members.

1.10.6 MATERIAL WELDABILITY (2006) R(2010) a.

When a grade of structural steel is to be supplied and the grade meets the chemical and mechanical properties of ASTM A709, the applicable prequalified procedures of AWS D1.5 shall apply.

b. When a steel listed in Table 15-1-1 is to be supplied, other than a steel described in Paragraph a above or in AWS D 1.5 Article 1.2.2, weldability and weld procedure qualification shall be established by the contractor in accordance with AWS D1.5 Article 5.4.3. Until such time that AWS D1.5 adopts ASTM A709, Grade 50S, the prequalified procedures of AWS D1.5 for A709, Grade 50 shall be used. For weldability and weld procedure qualification of ASTM A709, Grade HPS 70W, the latest edition of the AASHTO document “Guide for Highway Bridge Fabrication with HPS 70W Steel” shall be used as a supplement to AWS D1.5. The contractor, rather than the company, shall assume additional costs described in AWS D1.5 Article 5.4.3.2. c.

Welding procedures qualified in accordance with AWS D1.5 for materials 4 inches thick also qualify materials permitted in Table 15-1-1 over 4 inches thick.

1

SECTION 1.11 BRACING 1.11.1 BRACING OF TOP FLANGES OF THROUGH GIRDERS (2000) R(2008) The top flanges of through plate girders shall be braced at the panel points by brackets with web plates (knee braces). The brackets shall extend to the top flange of the main girder and be as wide as clearance will allow. They shall be attached securely to a stiffener on the girders and to the top flange of the floorbeam. On solid floor bridges the brackets shall not be more than 12 feet apart. The brackets shall be designed for the bracing force specified in Article 1.3.11.

3

1.11.2 LATERAL BRACING (1994) R(2003) a.

There shall be bottom lateral bracing in all spans greater than 50 feet long, except that such bracing shall not be required for deck spans having four or more beams per track and a depth of beam less than 72 inches in which either adequate shear transfer to a reinforced concrete deck is provided or the concrete is cast in place to engage not less than 1 inch of the beam flange thickness. There shall be top lateral bracing in all deck spans and in through spans that have enough head room.

b. Where the construction of the floor is such as to afford the specified lateral resistance, the floor shall be taken as the lateral bracing required in its plane. c.

Where the bracing is a double system and the members meet the requirements for both tension and compression members, both systems may be considered effective simultaneously.

1.11.3 PORTAL AND SWAY BRACING (1994) R(2008) a.

In through truss spans there shall be portal bracing, with knee braces, as deep as the clearance will allow. There shall be sway bracing at the intermediate panel points if the trusses are high enough to

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allow a depth of 6 feet or more for such bracing. Where there is not sufficient clearance to allow that depth, the top lateral struts shall be of the same depth as the chord, and there shall be knee braces as deep as the clearance will allow. b. In deck truss spans there shall be sway bracing at the panel points. The top lateral forces shall be carried to the supports by means of a complete system of bracing.

1.11.4 CROSS FRAMES AND DIAPHRAGMS FOR DECK SPANS (1994)1 R(2002) a.

Cross frames and diaphragms, and their connections, shall be adequate to resist forces induced by out of plane bending and the lateral distribution of loads. Connection plates for cross frames and diaphragms between beams or girders shall be adequately fastened to the web and both the top and bottom flanges of the beams or girders. Connection angles for diaphragms between rolled beams in single track spans, without skew and on tangent alignment, need not be fastened to the flanges.

b. Longitudinal girders or beams having depth greater than 3¢-6² and spaced more than 4 feet on centers shall be braced with cross frames. The angle of cross frame diagonals with the vertical shall not exceed 60 degrees. c.

Longitudinal girders or beams not requiring cross frames shall be braced with I-shaped diaphragms which are as deep as girders or beams will permit. Connections to the girder or beam webs for such diaphragms shall be designed to carry shear at least equal to one-half of the shear capacity of the diaphragm.

d. Cross frames or diaphragms shall be used at the ends of spans (except where the girders or beams are framed into floorbeams), and shall be proportioned for centrifugal and lateral forces. e.

In open deck construction, cross frames or diaphragms shall be used at intervals not exceeding 18 feet.

f.

Where steel plate, timber or precast concrete decking is utilized in ballasted deck construction, cross frames or diaphragms without top lateral bracing shall be used at intervals not exceeding 12 feet; or with top lateral bracing, at intervals not exceeding 18 feet.

g.

Where poured-in-place concrete decking is used in ballasted deck construction, cross frames or diaphragms shall be used at intervals not exceeding 24 feet. For girders or beams up to 4¢-6² deep, concrete diaphragms with reinforcement extending through the girders or beams may be used instead of steel diaphragms.

h. Where ballast and track are carried on transverse beams without stringers, the beams shall be connected with at least one line of longitudinal diaphragms per track.

1.11.5 BRACING OF VIADUCT TOWERS AND BENTS (1994) R(2008) a.

The bracing of bents and towers shall consist of double systems of diagonals with struts at caps and bases and at intermediate panel points. In towers supporting two or more tracks there shall be horizontal bracing at the top of the tower to transmit horizontal loads.

b. The bottom struts shall be proportioned for either the calculated forces or force in tension or compression equal to one-quarter of the dead load reaction on one pedestal, whichever is greater. The column bearings shall be designed to allow for the expansion and contraction of the tower bracing.

1

See Part 9 Commentary

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1.11.6 BRACING MEMBERS USED AS TIES OR STRUTS ONLY (1994) R(2008) Bracing members used only as ties or struts, to reduce the unsupported length of a member to which they connect, need not be designed for more than 2.5% of the force in that member.

SECTION 1.12 PINS AND PIN-CONNECTED MEMBERS 1.12.1 PINS (1994) R(2003) a.

Pins more than 7 inches in diameter shall be forged and annealed.

b. In pins more than 9 inches in diameter, there shall be a hole not less than 2 inches in diameter bored longitudinally on the center line. c.

The turned bodies of pins shall be long enough to extend at the ends 1/4 inch beyond the outside faces of the parts connected. The pins shall be secured by recessed pin nuts or by solid nuts and washers. If the pins are bored, through rods with cap washers may be used. The screw ends shall be long enough to allow burring the threads.

1.12.2 SECTION AT PIN HOLES (1993) R(2008)

1

The net section beyond the pin hole, parallel with the axis of the member, shall not be less than the required net section of the member. The net section through the pin hole, transverse to the axis of the member, shall be at least 40% greater than the required net section of the member. The ratio of the transverse net width through the pin hole to the thickness of the segment shall not be more than eight.

1.12.3 REINFORCING PLATES AT PIN HOLES (1993) R(2008)

3

Where necessary for the required section or bearing area, the section at pin holes shall be increased on each segment by plates so arranged as to reduce the eccentricity of the segment to a minimum. One plate on each side shall be as wide as the outstanding flanges will allow. At least one full width plate on each segment shall extend to the far edge of the stay plate, and the others not less than 6 inches beyond the near edge. These plates shall be connected adequately to transmit the bearing pressure and so arranged as to distribute it uniformly over the full section.

4

1.12.4 FORKED ENDS OF COMPRESSION MEMBERS (1993) R(2008) Forked ends of compression members shall be permitted only where unavoidable. There shall be enough pin plates on forked ends to make the section of each jaw equal to that of the member. The pin plates shall be long enough to develop the pin plate beyond the near edge of the stay plate, but not less than the length required by Article 1.12.3.

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SECTION 1.13 CONTINUOUS AND CANTILEVER STEEL STRUCTURES1 1.13.1 DEFINITION (2008) a.

A continuous steel structure is one in which the principal load-carrying beams, girders, or trusses have moment-carrying capacity without interruption throughout at least two adjacent spans. The calculation of reactions and forces involves the deformations due to stress in the member or members of the structure, and the structure is therefore said to be statically indeterminate.

b. A cantilever steel structure is one in which the principal load-carrying beams, girders or trusses have moment carrying capacity throughout one span without interruption, and project or cantilever over at least one support of that span into the adjacent span or spans, with an interruption in the momentcarrying capacity of the structure within the adjacent span or spans. The calculation of reactions and forces, except in the case where two projections or cantilever arms are joined by a shear connection without a suspended span between them, are independent of the deformations due to stress in the member or members in the structure, and the structure is therefore said to be statically determinate. In the exception stated, the structure is statically indeterminate, as noted for continuous structures in paragraph a.

1.13.2 BASIC DESIGN ASSUMPTIONS (2008) a.

Moments, shears and reactions shall be determined by recognized methods of analysis. In the case of the statically indeterminate structures described under Article 1.13.1, the gross moments of inertia for flexural members, and the gross and effective areas, as defined in Article 1.2.5a, for truss members, shall be used in the calculations.

b. Bearing supports preferably shall be constructed so that the supports may be considered to be unyielding. When such construction is not practical, provision shall be made in the design to allow for settlement of the supports based on reasonable assumptions as to the magnitude of the settlement. c.

A portion or portions of the live load specified in Article 1.3.3 and positioning on the structure shall be selected so as to produce maximum effects. In case of discontinuous loading not more than two separated loaded lengths shall be used, with one of the lengths subjected to uniform load only, and with the other subjected to the load headed in either direction.

1.13.3 DEFLECTION (2008) a.

The deflections of the individual spans of continuous or cantilever structures shall be computed for live load plus impact load, placed so as to produce maximum downward deflection in that span. In this computation, gross moment of inertia shall be used for flexural members, and gross or effective area, as defined in Article 1.2.5a, shall be used for truss members.

b. The structure shall be proportioned and designed so that the computed downward deflection within any span which has moment-carrying capacity throughout its length shall not exceed 1/640 of that span length. In the case of cantilever structures, the computed downward deflection at the end of the cantilever arm shall not exceed 1/250 of the length of that arm and the downward deflection of a suspended simple span shall not exceed 1/640 of the length of that span.

1

References, Vol. 58, 1957, pp. 694, 1203; Vol. 59, 1958, pp. 705, 1196; Vol. 63, 1962, pp. 386, 699; Vol. 70, 1969, p. 241; Vol. 79, 1978, p. 45; Vol. 97, p. 172.

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Design

1.13.4 CAMBER (2008) The camber of trusses shall be equal to the deflection produced by dead load plus a continuous uniform load of 3,000 lb per foot of track. The camber of plate girders shall be equal to the deflection produced by the dead load only. Rolled beams shall not be cambered, but shall be fabricated and erected so that any natural camber in the beam is upward.

1.13.5 IMPACT LOAD (2008) In computing impact load in accordance with Article 1.3.5, L shall be taken as the length, in feet, of the longest span, center to center of supports within the structure; except that, in the case of simple suspended spans in cantilever structures, the length of that span shall be used as L in computing impact loads in that span.

1.13.6 UPLIFT (2008) Span lengths preferably shall be selected so that the dead load reaction at any support of the group will be at least 1.5 times the uplift from live load and impact load. Should net calculated uplift occur, that end shall be securely anchored in a vertical direction. Anchorage against uplift shall engage a substantial mass of masonry, and shall be designed for at least 1.5 times the net calculated uplift.

1.13.7 BRACING (2008) Bracing for continuous spans shall be as required by Section 1.11, Bracing, and, in addition, top flanges of through plate girder spans in regions of negative moment as well as in regions of positive moment shall be braced as required in Article 1.11.1, and bottom flanges of all beam and girder spans, regardless of length, shall have a continuous lateral bracing system.

1

1.13.8 LONGITUDINAL STIFFENERS (2010)1 a.

Longitudinal stiffeners shall be placed as specified by Article 1.7.8f to provide flexural stiffness to the web plate over supports of continuous or cantilever deep girders, where there is negative moment. Longitudinal stiffeners are usually placed on one side only of the web plate with transverse stiffeners on the other side. Where bearing stiffeners are placed on both sides of the web and the longitudinal stiffeners intersect with bearing stiffeners, the longitudinal stiffener should be discontinuous with the bearing stiffener. The stress in the stiffener (from participation in the girder stress) shall not be greater than the basic allowable bending stress for the material used in the stiffener. Longitudinal stiffeners shall also be used at other locations as specified by Article 1.7.8f. See Article 9.1.10.2 for further guidance on detailing intersecting stiffeners.

b. The center line of a plate longitudinal stiffener or the gage line of an angle longitudinal stiffener shall be D/5 from the inner surface or leg of the compression flange component. c.

The longitudinal stiffener shall be proportioned so that: 2 3æ d – 0.13ö I E = D t ç 2.4 -----÷ 2 è ø D

1

See Part 9 Commentary

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where: IE = minimum required moment of inertia of longitudinal stiffeners about the edge in contact with the web plate, inch4 D = clear distance between flange, inches t = thickness of the web plate, inches d = clear distance between the transverse stiffeners, inches d. The thickness of the longitudinal stiffener shall not be less than b¢ f ---------------b 2250 where: b¢ = width of stiffeners, inches fb = calculated compressive bending stress in the flange, psi

1.13.9 COVER PLATES (2008) The requirements for cover plates in Article 1.7.2 shall apply except as modified in Article 1.13.9.1 and Article 1.13.9.2 wherein the term “theoretical end of cover plate” refers to the section where the stress in the flange without that cover plate equals the allowable stress, exclusive of fatigue considerations. 1.13.9.1 For Riveted or Bolted Construction Partial length cover plates shall extend beyond the theoretical end far enough to develop the capacity of the plate, or shall extend to a section where the stress in the remainder of the girder flange is equal to the allowable fatigue stress, whichever extension is greater. 1.13.9.2 For Welded Construction a.

Flanges of welded plate girders shall be made using only one plate in each flange (i.e. without cover plates).

b. Partial length cover plates may be used on rolled beam spans under the following conditions: (1) Partial length cover plates preferably shall be limited to one on any flange. The maximum thickness of the cover plate (or total thickness of all cover plates) on a flange shall not be greater than 1.5 times the thickness of the flange to which the cover plate is attached. (2) Cover plates may be wider or narrower than the beam flange to which they are attached. (3) Any partial length cover plate shall extend beyond the theoretical end by the terminal distance, or it shall extend to a section where the stress range in the beam flange is equal to the allowable fatigue stress range for base metal adjacent to or connected by fillet welds, whichever extension is greater. The terminal distance is 2 times the nominal cover plate width for cover plates not welded across their ends, and 1.5 times for cover plates welded across their ends. The width at ends of tapered cover plates shall be not less than 3 inches. All welds connecting the cover plate to the flange in its

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Design

terminal distance shall be of sufficient size to develop a total stress of not less than the computed stress in the cover plate at its theoretical end.

1.13.10 SPLICES IN FLEXURAL MEMBERS (2008) a.

Splices in continuous or cantilever flexural members shall be designed for maximum moment and simultaneous shear, or for maximum shear and simultaneous moment.

b. Splices preferably shall be located at points of dead load contraflexure in the case of continuous structures. c.

Bolted or riveted flange splices shall have a minimum strength equal to 75% of the strength of the flange component spliced.

SECTION 1.14 FRACTURE CRITICAL MEMBERS 1.14.1 SCOPE (2001)1 R(2008) Fracture Critical Members and member components (FCMs) have special requirements for materials, fabrication, welding, inspection and testing. The provisions of Section 12, AWS D1.5 “Fracture Control Plan” (FCP), shall apply to FCMs, except as modified herein. For ASTM A709, Grade HPS 70W, the latest edition of the AASHTO document “Guide for Highway Bridge Fabrication with HPS 70W Steel” shall be used as a supplement to AWS D1.5 with regard to the “Fracture Control Plan” until such time as A709 HPS 70W is specifically included therein.

1

1.14.2 DEFINITIONS (1997)2 R(2008) a.

Fracture Critical Members or member components (FCM’s) are defined as those tension members or tension components of members whose failure would be expected to result in collapse of the bridge or inability of the bridge to perform its design function.

b. Tension components of steel bridges include all portions of tension members and those portions of flexural members subjected to tension stress. Any attachment having a length in the direction of the tension stress greater than 4 inches that is welded to a tension component of a FCM shall be considered part of the tension component and, therefore, shall be considered Fracture Critical.

1.14.3 DESIGN AND REVIEW RESPONSIBILITIES (1997)3 R(2008) a.

The Engineer is responsible: for the suitability of the design of the railway bridge; for the selection of the proper materials; for choosing adequate details; for designating appropriate weld requirements; and for reviewing shop drawings and erection plans to determine conformance with the contract documents.

b. The Engineer is also responsible: for determining which, if any, bridge members or member components are in the FCM category; for evaluating each bridge design to determine the location of any FCM’s that may exist; for the clear delineation on the contract plans of the location of all FCM’s; for reviewing shop drawings to determine that they correctly show the location and extent of FCM’s; and for verifying that 1

See Part 9 Commentary See Part 9 Commentary 3 See Part 9 Commentary 2

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Steel Structures

the Fracture Control Plan is properly implemented in compliance with contract documents at all stages of fabrication and erection. c.

Welding procedure specifications are considered an integral part of shop drawings and shall be reviewed for each contract.

1.14.4 SPECIAL WELDING REQUIREMENTS (1997) R(2008) The Submerged Arc Welding (SAW) process shall be used for flange and web butt splices, flange to web welds, and box member corner welds unless otherwise authorized by the Engineer.

1.14.5 NOTCH TOUGHNESS OF STEEL IN FRACTURE CRITICAL MEMBERS (2010)1 Charpy V-notch (CVN) impact test requirements for steels in FCM’s shall be as given in Table 15-1-14 except as shown in Note 6.

1

See Part 9 Commentary

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Design Table 15-1-14. Impact Test Requirements for Structural Steel - Fracture Critical Members (See Note 1)

ASTM Designation

Thickness In.(mm)

Minimum Test Value Energy Ft-lb(J)

Minimum Average Energy, Ft-lb(J) and Test Temperatures Zone 1

Zone 2

Zone 3

A36/A36M (Note 6) To 4(100) incl. 20(27) 25(34) @ 25(34) @ 25(34) @ A709/A709M, Grade 36F(Grade 70°F(21°C) 40°F(4°C) 10°F(-12°C) 250F) (Notes 5 and 6) A992/A992M (Note 2) To 2(50) incl. 20(27) 25(34) @ 25(34) @ 25(34) @ A709/A709M, Grade 50SF(Grade 70°F(21°C) 40°F(4°C) 10°F(-12°C) 345SF) (Notes 2, 5 and 6) Over 2(50) to 4(100) 24(33) 30(41) @ 30(41) @ 30(41) @ A572/A572M, Grade 50(Grade incl. 70°F(21°C) 40°F(4°C) 10°F(-12°C) 345) (Notes 2 and 6) A709/A709M, Grade 50F(Grade 345F) (Notes 2, 5 and 6) A588/A588M (Notes 2 and 6) A709/A709M, Grade 50WF(Grade 345WF) (Notes 2, 5 and 6) A709/A709M, Grade HPS 50WF To 4(100) incl. 24(33) 30(41) @ 30(41) @ 30(41) @ (Grade HPS 345WF) (Notes 2 and 10°F(-12°C) 10°F(-12°C) 10°F(-12°C) 5) A709/A709M, Grade HPS 70WF To 4(100) incl. 28(38) 35(48) @ 35(48) @ 35(48) @ (Grade HPS 485WF) (Notes 3 and -10°F(-23°C) -10°F(-23°C) -10°F(-23°C) 5) Minimum Service Temperature (Note 4) 0°F(-18°C) -30°F(-34°C) -60°F(-51°C) Note 1: Impact tests shall be Charpy V-notch (CVN) impact testing, “P” plate frequency, in accordance with ASTM Designation A673/A673M except for plates of A709/A709M Grades 36F(250F), 50F(345F), 50WF(345WF), HPS 50 WF (HPS 345 WF) and HPS 70 WF (HPS 485 WF) and their equivalents in which case specimens shall be selected as follows: (1) As-rolled plates shall be sampled at each end of each plate-as-rolled. (2) Normalized plates shall be sampled at one end of each plate-as-heat treated. (3) Quenched and tempered plates shall be sampled at each end of each plate-as-heat-treated. Note 2: If the yield point of the material exceeds 65,000 psi(450 MPa), the test temperature for the minimum average energy and minimum test value energy required shall be reduced by 15°F(8°C) for each increment or fraction of 10,000 psi(70 MPa) above 65,000 psi(450 MPa). The yield point is the value given on the certified “Mill Test Report”. Note 3: If the yield strength of the material exceeds 85,000 psi(585 MPa), the test temperature for the minimum average energy and minimum test value energy required shall be reduced by 15°F(8°C) for each increment of 10,000 psi(70 MPa) above 85,000 psi(585 MPa). The yield strength is the value given on the certified “Mill Test Report”. Note 4: Minimum service temperature of 0°F(-18°C) corresponds to Zone l, –30°F(-34°C) to Zone 2, –60°F(51°C) to Zone 3 referred to in Part 9, Commentary, Article 9.1.2.1. Note 5: The suffix “F” is an ASTM A709/A709M designation for fracture critical material requiring impact testing, with supplemental requirement S84 applying. A numeral l, 2 or 3 shall be added to the F marking to indicate the applicable service temperature zone. Note 6: Steel backing for groove welds joining steels with a minimum specified yield strength of 50,000 psi(345 MPa) or less may be base metal conforming to ASTM A36/A36M, A709/A709M, A588/A588M and/or A572/A572M, at the Contractor’s option, provided the backing material is furnished as bar stock rolled to a size not exceeding 3/8 in(10mm) by 1-1/4 in(32mm). The bar stock so furnished need not conform to the Charpy V-Notch impact test requirements of this table.

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Steel Structures

SECTION 1.15 LIVE LOAD MOMENTS, SHEARS AND REACTIONS 1.15.1 TABULATED VALUES FOR SIMPLE SPANS (2003) R(2008) For the maximum moments, shears and pier (or floorbeam) reactions for Cooper E 80 live load (Figure 15-1-2) or alternate live load (Figure 15-1-3) refer to Table 15-1-15. Table 15-1-15. Maximum Moments, Shears and Pier (or Floorbeam) Reactions for Cooper E 80 Live Load or Alternate Live Load All Values are for one rail (one-half track load)

Span Length Ft

Maximum Moment Ft–Kips

Maximum Moment Quarter Point Ft–Kips

Maximum Shears Kips At End

E-80

Alt.

E-80

Alt.

E-80

Alt.

5

50.00

62.50

37.50

46.88

40.00

50.00

6

60.00

75.00

45.00

56.25

46.67

7

70.00

87.50

55.00

68.75

8

80.00

100.00

70.00

87.50

At Quarter Point

At Center

Maximum Pier Reaction Kips (2)

E-80

Alt.

E-80 20.00

25.00

40.00

50.00

58.33

30.00

37.50

20.00

25.00

53.33

58.33

51.43

64.29

31.43

39.29

20.00

25.00

62.86

71.43

55.00

68.75

35.00

43.75

20.00

25.00

70.00

81.25

Alt.

E-80

Alt.

9

93.89

117.36

85.00

106.25

57.58

72.22

37.78

47.23

20.00

25.00

75.76

88.89

10

112.50

140.63

100.00

125.00

60.00

75.00

40.00

50.00

20.00

25.00

80.00

95.00

11

131.36

164.20

115.00

143.75

65.45

77.27

41.82

52.28

21.82

27.28

87.28

100.00

12

160.00

188.02

130.00

162.50

70.00

83.33

43.33

54.17

23.33

29.17

93.33

108.33

13

190.00

212.83

145.00

181.25

73.84

88.46

44.61

55.76

24.61

30.76

98.46

115.39

14

220.00

250.30

165.00

200.00

77.14

92.86

47.14

57.14

25.71

32.14

104.29 121.43

16

280.00

325.27

210.00

250.00

85.00

100.00

52.50

62.50

27.50

34.38

113.74 131.25

18

340.00

400.24

255.00

318.79

93.33

111.11

56.67

68.05

28.89

36.11

121.33 138.89

20

412.50

475.00

300.00

362.50 100.00 120.00

60.00

72.50

28.70

37.50

131.10 145.00

24

570.42

668.75

420.00

500.00 110.83 133.33

70.00

83.33

31.75

41.67

147.92 154.17

28

730.98

866.07

555.00

650.00 120.86 142.86

77.14

92.86

34.29

46.43

164.58

32

910.85

1064.06

692.50

800.00 131.44 150.00

83.12

100.00

37.50

50.00

181.94

36

1097.30

1262.50

851.50

950.00 141.12 155.56

88.90

105.56

41.10

55.56

199.06

40

1311.3

1461.25 1010.50 1100.00 150.80 160.00

93.55

110.00

44.00

60.00

215.90

45

1601.2

1710.00 1233.60 1287.48 163.38 164.44 100.27 114.45

45.90

64.45

237.25

50

1901.80

1959.00 1473.00 1481.05 174.40

106.94 118.42

49.73

68.00

257.52

55

2233.10

1732.30

185.31

113.58 120.91

52.74

70.91

280.67

60

2597.80

2010.00

196.00

120.21 123.33

55.69

73.33

306.42

70

3415.00

2608.20

221.04

131.89

61.45

77.14

354.08

80

4318.90

3298.00

248.40

143.41

67.41

80.00

397.70

90

5339.10

4158.00

274.46

157.47

73.48

82.22

437.15

100

6446.30

5060.50

300.00

173.12

78.72

84.00

474.24

120

9225.40

7098.00

347.35

202.19

88.92

544.14

140

12406.00

9400.00

392.59

230.23

101.64

614.91

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AREMA Manual for Railway Engineering

Design Table 15-1-15. Maximum Moments, Shears and Pier (or Floorbeam) Reactions for Cooper E 80 Live Load or Alternate Live Load (Continued) All Values are for one rail (one-half track load)

Span Length Ft

Maximum Moment Ft–Kips

E-80

Alt.

Maximum Moment Quarter Point Ft–Kips

E-80

Alt.

Maximum Shears Kips At End

E-80

Alt.

At Quarter Point

E-80

Alt.

At Center

E-80

Alt.

Maximum Pier Reaction Kips (2)

E-80

160

15908.00 (1)

11932.00

436.51

265.51

115.20

687.50

180

19672.00 (1)

14820.00

479.57

281.96

128.12

762.22

200

23712.00 (1)

17990.00

522.01

306.81

140.80

838.00

250

35118.00 (1)

27154.00

626.41

367.30

170.05

1030.40

300

48800.00 (1)

38246.00

729.34

426.37

197.93

1225.30

350

65050.00 (1)

51114.00

831.43

484.64

225.51

1421.70

400

83800.00 (1)

65588.00

933.00

542.40

252.44

1619.00

Alt.

Note (1) - Values for Cooper E-80 Live Load. Moment values taken at center span. Note (2) - Maximum pier reactions are for equal span lengths.

1.15.2 SUPPLEMENTAL FORMULAS FOR SIMPLE SPANS (2009)

1

Units are in feet and kips. All values are for one rail (one-half track load). Table 15-1-16. Calculation of Maximum Moments on Short, Simple Spans (15-1-15)

1At

Span, L

Location of Mmax

0.00 ft. < L £ 8.54 ft. 8.54 ft. < L £ 11.12 ft. 11.12 ft. < L £ 18.66 ft. 18.66 ft. < L £ 27.61 ft. 27.61 ft. < L £ 34.97 ft. 34.97 ft. < L £ 38.72 ft. 38.72 ft. < L £ 49.56 ft. 48.31 ft. < L £ 53.54 ft. 53.54 ft. < L £ 58.47 ft. 58.47 ft. < L £ 63.42 ft. 63.42 ft. < L £ 75.15 ft. 75.15 ft. < L £ 79.831

L/2 L/2 +/-1.25 ft L/2 L/2 +/-1.25 ft L/2 +/-0.389 ft L/2 +/-0.961 ft L/2 +/-0.211 ft L/2 +/-1.45 ft L/2 +/-0.127 ft L/2 +/-1.374 ft L/2 +/-0.068 ft L/2 +/-0.088 ft

Maximum Moment (Cooper E-80)

3

Mmax = 10L Mmax = 20L - 100 + 125/L Mmax = 30L - 200 Mmax = 40L - 400 + 250/L Mmax = 45L - 530 + 27.2/L Mmax = 51.5L - 762 + 190/L Mmax = 58L - 1009 + 10.35/L Mmax = 64.5L - 1334 + 542.2/L Mmax = 71L - 1672 + 4.6/L Mmax = 77.5L - 2062 + 585.4/L Mmax = 84L - 2465 + 1.6/L Mmax = 97L - 3442 + 3/L

4

L = 80 ft., the last formula will give a value which is 99.98% of the value given in Table 15-1-15. Span, L

Location of Mmax

Max Moment (Alt LL: 4 - 100k Axles)

0.00 ft. < L £ 8.54 ft. 8.54 ft. < L £ 12.94 ft. 12.94 ft. < L £ 20.24 ft. L > 20.24 ft.

L/2 L/2 +/-1.25 ft L/2 +/-0.167 ft L/2 +/-1.5 ft

Mmax = 12.5L Mmax = 25L - 125 + 156.25/L Mmax = 37.5L - 275 + 4.17/L Mmax = 50L - 550 + 450/L

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For L ³ 288: M 0.5 = 0.5L + 3800 4398 For L ³ 101: V e = 2L + 144 – ------------L 4238 For L ³ 134.67: V 0.25 = 1.124L + 103 – ------------L 4238 For 202 ³ L ³ 296: V 0.5 = 0.5L + 62 – ------------L For L > 296: V 0.5 = 0.5L + 66 – 5422 ------------L For L ³ 144: R = 4L + 7600 ------------L where: L = span length Mmax = maximum moment M0.5 = maximum moment at center Ve, V0.25 and V0.5 = maximum shear at end of span, at 1/4 point and at center, respectively R = maximum pier reaction from two adjoining spans each of length L

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Part 3 Fabrication1 — 2010 — FOREWORD

The purpose of this part is to formulate specific and detailed rules as a guide for the fabrication of railway bridges.

TABLE OF CONTENTS Section/Article

Description

Page

3.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.1 Quality of Workmanship (1995) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.2 Material Orders and Shipping Statements (1987) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . 3.1.3 Notice of Beginning Work (2002) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.4 Storage of Material (1987) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.5 Straightening Material (1987) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.6 Thermal Cutting, Copes, and Access Holes (2005) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . 3.1.7 Dimensional Tolerances for Structural Members (2006) R(2008) . . . . . . . . . . . . . . . . . . . 3.1.8 Planing Sheared Edges (1994) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.9 Lacing Bars (1994) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.10 Fit of Stiffeners (1994) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.11 Flexural Member Web Plates, Riveted and Bolted Construction (1994) R(2008) . . . . . . . 3.1.12 Facing Floorbeams, Stringers, and Girders (1994) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . 3.1.13 Abutting Joints (1994) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.14 Pin Clearances (1994) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.15 Pins and Rollers (1994) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.16 Fitting of Base and Cap Plates (1994) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.17 Surfaces of Bearing Plates and Pedestals (2002) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . 3.1.18 Bent Plates (2007) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-3-3 15-3-3 15-3-3 15-3-3 15-3-3 15-3-3 15-3-3 15-3-4 15-3-7 15-3-7 15-3-7 15-3-8 15-3-8 15-3-8 15-3-8 15-3-8 15-3-8 15-3-8 15-3-9

3.2 Riveted and Bolted Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.1 Rivets and Riveting (1995) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.2 High Strength Bolts, Nuts and Washers (1995) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . .

15-3-10 15-3-10 15-3-10

1

References, Vol. 70, 1969, p. 241; Vol. 71, 1970, p. 376; Vol. 72, 1971, p. 153; Vol. 74, 1973, p. 132; Vol. 75, 1974, p. 336; Vol. 76, 1975, p. 241; Vol. 77, 1976, p. 249; Vol. 79, 1978, p. 45; Vol. 80, 1979, p. 188; Vol. 81, 1980, p. 129; Vol. 82, 1981, p. 78; Vol. 84, 1983, p. 100; Vol. 86, 1985, p. 90; Vol. 88, 1987, p. 87; Vol. 91, 1990, p. 121; Vol. 92, 1991, p. 78; Vol. 93, 1992, p. 124; Vol. 94, 1994, p. 142; Vol. 96, p. 69; Vol. 97, p. 171. Reapproved with revisions 1996.

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3

Steel Structures

TABLE OF CONTENTS (CONT) Section/Article 3.2.3 3.2.4 3.2.5 3.2.6 3.2.7 3.2.8 3.2.9 3.2.10 3.2.11 3.2.12 3.2.13 3.2.14

Description

Page

Installation of High Strength Bolts (2004) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Quantity of Field Fasteners (2003) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Size and Workmanship of Holes (2010). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Preparation of Holes for Shop Fasteners (1995) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . Preparation of Holes for Field Fasteners (2007) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . Templates for Reaming and Drilling (1983) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reaming and Drilling Through Templates (1995) R(2008). . . . . . . . . . . . . . . . . . . . . . . . Reaming and Drilling After Assembly (1995) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . Match Marking (1995) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Alignment of Finished Holes (1995) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Fitting for Shop Riveting or Bolting (1995) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Testing and Documentation of ASTM A325 and A490 Bolts (1995) R(2008). . . . . . . . . .

15-3-10 15-3-14 15-3-14 15-3-15 15-3-16 15-3-17 15-3-17 15-3-17 15-3-17 15-3-18 15-3-18 15-3-18

3.3 Welded Construction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.1 General (2002) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.2 Preparation of Material for Welding (1995) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.3 Flange-to-Web Welds of Flexural Members (1995) R(2008) . . . . . . . . . . . . . . . . . . . . . . . 3.3.4 Tack Welds (1995) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3.5 Welder and Welding Operator Qualifications (1997) R(2008) . . . . . . . . . . . . . . . . . . . . . .

15-3-21 15-3-21 15-3-21 15-3-21 15-3-21 15-3-21

3.4 Shop Painting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.1 Shop Painting of Structural Steel (2003) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4.2 Shop Painting of Machined Surfaces (1995) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-3-22 15-3-22 15-3-22

3.5 Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.1 Facilities for Inspection (1991) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.2 Inspector Authority (1991) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.3 Rejection (1991) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.4 Inspection – High Strength Bolted Joints (2003) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . 3.5.5 Inspection – Welded Work (2002) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-3-22 15-3-22 15-3-22 15-3-22 15-3-23 15-3-23

3.6 Shipment and Pay Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6.1 Marking, Packaging and Loading (1995) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6.2 Advance Material (1995) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6.3 Pay Weight (2003) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-3-23 15-3-23 15-3-24 15-3-24

LIST OF TABLES Table 15-3-1 15-3-2 15-3-3 15-3-4 15-3-5

Description

Page

Minimum Radii for Cold Bending of Plates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Minimum Tension of Installed Bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nut Rotation from Snug Tight Condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Contractor Acceptable Substitutes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Minimum Required Turn Test Tension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-3-9 15-3-11 15-3-12 15-3-15 15-3-19

© 2011, American Railway Engineering and Maintenance-of-Way Association

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AREMA Manual for Railway Engineering

Fabrication

SECTION 3.1 GENERAL 3.1.1 QUALITY OF WORKMANSHIP (1995) R(2008) a.

Structural steel fabricators shall be certified for the type of structure being fabricated under the AISC Quality Certification Program (SBR - Simple Steel Bridge Structures or CBR - Major Steel Bridges [all bridge structures other than unspliced rolled beam bridges]) or another suitable program as determined by the Engineer. Evidence of certification shall be submitted to the Engineer for his approval before beginning any work.

b. Structural steel fabricators of Fracture Critical Members shall be certified under the AISC Quality Certification Program, with a Fracture Critical Endorsement (F) or another suitable program as determined by the Engineer. The fabricator shall also meet the additional requirements for Fracture Critical Members specified in Part 1, Design, Section 1.14, Fracture Critical Members. c.

The workmanship and finish shall be equal to the best general practice in modern bridge shops.

3.1.2 MATERIAL ORDERS AND SHIPPING STATEMENTS (1987) R(2008) The Contractor shall furnish to the Engineer as many copies of material orders and shipping statements as the Engineer may require. The weights of the individual members shall be shown on the statements.

1

3.1.3 NOTICE OF BEGINNING WORK (2002) R(2008) The Contractor shall give the Engineer ample written notice of the beginning of work in the shop, in order that inspection may be provided. Work shall not be done in the shop before the Engineer has been so notified.

3.1.4 STORAGE OF MATERIAL (1987) R(2008)

3

Structural material, either plain or fabricated, shall be stored properly above the ground upon platforms, skids, or other supports. It shall be kept free from dirt, grease and other foreign matter, and shall be protected as far as practicable from corrosion.

3.1.5 STRAIGHTENING MATERIAL (1987) R(2008) Rolled material, before being laid off or worked, shall be straight within the tolerances allowed by ASTM Specification A 6. If straightening is necessary, it shall be done by methods which will not adversely affect the behavior of the material.

3.1.6 THERMAL CUTTING, COPES, AND ACCESS HOLES (2005)1 R(2008) 3.1.6.1 Thermal Cutting a.

1

The steels covered by these recommended practices may be thermally-cut, provided that a smooth surface free from cracks and notches is secured and provided that an accurate profile is secured by the use of a mechanical guide. Freehand cutting shall be done only when specifically approved by the Engineer.

See Part 9 Commentary

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Steel Structures

b. Cutting shall be done in such a manner as to avoid cutting inside the prescribed lines. The Surface Roughness value of cut surfaces, as defined in “ASME B46.1-1995 Surface Texture (Surface Roughness, Waviness and Lay), an American National Standard” published by The American Society of Mechanical Engineers, shall not exceed 1,000 min (25 mm) for material up to 4 inches (100 mm) thick and 2,000 min (50 mm) for material 4 inches (100 mm) to 8 inches (200 mm) thick. Member ends not subjected to calculated stress may have a surface roughness value up to 2,000 m in (50 mm). The procedure described below shall be used to correct roughness exceeding the applicable value or occasional notches or gouges. Roughness exceeding the applicable value and occasional notches or gouges not more than 3/16 inch (5 mm) deep, on otherwise satisfactory surfaces, shall be removed by machining or grinding. Cut surfaces and edges shall be left free of adhering slag. Corrections of defects shall be faired to the oxygen-cut surfaces with a slope not exceeding 1 in 10. Defects in oxygen-cut edges shall not be repaired by welding except occasional notches or gouges up to 7/16 inch (11 mm) deep in material up to 4 inches (100 mm) thick if so approved by the Engineer. The procedure for such weld repair shall be subject to the Engineer’s approval, shall ensure sound metal free from cracks, and shall produce a workmanlike finish. c.

Re-entrant corners shall be filleted to a radius of not less than 1 inch (25 mm). The fillet and its contiguous cuts shall meet without offset or cutting past the point of tangency.

d. Edges of built-up beam and girder webs shall be cut to prescribed camber with suitable allowance for shrinkage due to cutting and welding. However, moderate deviation from the specified camber tolerance may be corrected by a carefully supervised application of heat. 3.1.6.2 Copes and Access Holes a.

The re-entrant corners of copes shall be shaped with a radius of not less than 1 inch (25 mm) with a smooth transition that meets the adjacent edges without offset or cutting past the point of tangency.

b. In hot rolled shapes and built up shapes all beam copes and weld access holes shall be shaped free of notches or sharp re-entrant corners, except when web-to flange fillet welds are used on built-up shapes access holes are permitted to terminate perpendicular to the flange. Thermal cut edges shall meet the requirements of Paragraph 3.2.2 of AWS D1.5. c.

The thermal cut surfaces of holes and re-entrant cuts in primary members and their connections shall be ground to bright metal. For ASTM A6 Group 4 and 5 shapes and built-up shapes with web material thickness greater than 1-1/2 inch (38 mm), the thermal cut surfaces shall be inspected by either magnetic particle or dye-penetrant methods. If the curved transition portion of holes and beam copes are formed by predrilled or sawed holes, that portion of the hole or cope need not be ground. Unless specified by the Engineer, holes and copes in other members need not be ground nor dye-penetrant or magnetic-particle inspected.

d. All weld access holes required to facilitate welding operations shall have a length from the toe of the weld preparation of not less than 1-1/2 times the thickness of the material in which the hole is made. The height of the access hole shall be adequate for the deposition of sound weld metal in the adjacent plates and shall provide clearance for the weld tabs for the weld in the material in which the hole is made, but shall not be less than the thickness of the material.

3.1.7 DIMENSIONAL TOLERANCES FOR STRUCTURAL MEMBERS (2006) R(2008) 3.1.7.1 General Provisions a.

Members and parts of members shall be straight, true to line, and free from twists and bends. In determining acceptability under these general requirements, the tolerances stated hereinafter shall be applied as indicated. When more accurate conformance to detailed dimensions is required for any member or part of a member, it shall be specifically stated on the contract plans.

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Fabrication

b. Surfaces intended to be in a common plane at connections, joints, splices and bearings shall have no offset greater than 1/8 inch unless properly accommodated by fillers. c.

For rolled shapes or plates, the tolerance for any dimension shall conform with the requirements of ASTM A 6 except as otherwise shown on the contract drawings.

d. The tolerances stated hereinafter have been established to apply primarily to members fabricated by welding. Riveted and bolted members shall be well within these specified tolerances, as shall rolled members to the extent not excepted by paragraph c above. e.

Allowable deviations. (1) Deviation from detailed length: For members with ends milled for bearing and members with end connection angles faced ±1/32 inch For framed members not milled or faced: Lengths of 30 feet and under

±1/16 inch

Lengths over 30 feet

±1/8 inch

For other members

±1/4 inch

(2) Deviation from detailed straightness or curvature, that is, sweep or deviation from camber:

1

No. of feet of length between points ±1/16 inch ´ -------------------------------------------------------------------------------------------------10 or ±1/4 inch, whichever is greater. (3) Deviation from parallelism between corresponding elements of the same part at different crosssections along the length of the member (i.e. twist):

3

No. of feet of length between sections For box sections 1/16 inch in 12 inches bevel ´ ------------------------------------------------------------------------------------------------------10

4

of feet of length between sections For I sections 1/8 inch in 12 inches bevel ´ No. ------------------------------------------------------------------------------------------------------10 (4) Deviation from detailed depth or width, measured at the centerline of each web or flange: D ö ± æ 1 ¤ 8 inch + --------è 500 ø where: D = the dimension, inch, being considered (5) Out of square for box-shaped members. The deviation of parts on opposite sides of a member measured transverse to the principal axis of the cross-section shall not exceed:

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AREMA Manual for Railway Engineering

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Steel Structures

D 3/16 inch +------------1000 where: D = the nominal distance, inch, between the opposite sides. (6) Lateral deviation between the centerline of flanges measured transverse to the theoretical center line of web of I-shaped members at splice points and contact points of connection shall not exceed: D 3/16 inch + ------------1000 where: D = the nominal distance, inch, between the flanges (7) Combined warpage and tilt of flange at any cross section of welded I-shaped beams or girders shall be determined by measuring the offset at toe of flange from a line normal to the plane of the web through the intersection of the centerline of web with the outside surface of the flange plate. This offset shall not exceed 1/100 of total width of flange or 1/4 inch, whichever is greater, at any point along the member and 1/32 inch at any bearing. (8) The tolerances for out of flatness of seats and bases shall be as specified in Article 11.2.6. (9) Deviation from flatness or detailed curvature of panels of plate elements shall be determined by measuring offsets perpendicular to a template, edge having the detailed straightness or curvature and a length not less than the smaller of d1 or d2 as defined below and not more than 1.5 times the smaller of d1 or d2. The measurements shall be taken between points of contact of the template edge with the plate. The template edge may be placed anywhere within the panel of plate. The maximum offset shall not exceed the applicable values computed as follows: d (a) For girder webs without intermediate stiffeners ---------------but not greater than 0.75 ´ t. 200 t d (b) For all stiffened plate elements ---------------but not greater than 1.5 ´ t. 100 t where: d = the least dimension, inch, of: d1 the maximum transverse distance between longitudinal flanges edges or stiffeners, inch, d2 the maximum longitudinal distance between transverse edges or stiffeners, inch, or d3 the clear distance between points of contact of the template with the plate or web, inch t = the minimum thickness of the plate within the panel, inch (10) Deviation from detailed position of secondary parts and connections. (The detailed position is defined as the detailed distance from the member connection, centerline of bearing, or other primary working point or line):

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Fabrication

(a) For each secondary part not used for connection of other members except bearing stiffeners. (That is, a part such as a plain stiffener plate or bar.) ±1/4 inch. (b) For each secondary part used for connection of secondary members, and also for bearing stiffeners. (That is, a part used for connections in which the holes would be permitted to be punched full size if the connections were bolted.) ±1/8 inch. (11) Deviations from full surface contact: (a) At least 70% of the surfaces specified to be in bearing contact shall have the contact surfaces within 0.005 inch of each other. No remaining portion of the surfaces specified to be in bearing contact shall have a separation exceeding 0.03 inch. Any element of the main material which is composed of multiple elements shall have a minimum of 60% of its bearing area in contact. (b) Contact surfaces specified to be prepared by milling, grinding, or planing shall have a surface roughness value not to exceed 250 µin (ANSI/ASME) B46.1 Surface Texture. 3.1.7.2 Special Provisions for Trusses and Viaduct-Tower Main Members a.

Abutting joints of compression members which have been faced for bearing, when assembled, shall conform to Article 3.1.7.1e(11).

b. For member connections or splices, whether at joints or between joints, the clearance between the in-toin dimension of the gusset plates or splice plates and the out-to-out dimensions of the entering member shall not exceed 3/16 inch or as otherwise indicated by the Engineer for joints with thick or multiple gusset plates, long diaphragms, or other special framing conditions. c.

The use of squaring-up diaphragms may be necessary to meet the tolerances established in Article 3.1.7.1 and this Article. Design details of squaring-up diaphragms and any design restrictions on their use shall be shown on the design plans. Unless designated otherwise, their use will be optional with the contractor. All squaring-up diaphragms shall be shown on the shop drawings.

1

3

3.1.8 PLANING SHEARED EDGES (1994)1 R(2008) Sheared edges of ASTM A 36 main material over 5/8 inch thick and all high strength main material shall be planed to a depth of 1/4 inch. Web plates and pin plates (regardless of thickness) of pin connected tension members shall be universal mill plates or shall have edges planed 1/4 inch and the ends back of pins planed 1/4 inch.

3.1.9 LACING BARS (1994) R(2008) The ends of lacing bars shall be rounded unless otherwise required.

3.1.10 FIT OF STIFFENERS (1994) R(2008) a.

1

The ends of stiffeners on flexural members at points of bearing, as defined in Part 1, Design, Article 1.7.7, shall be milled or ground to bear against the flange, or shall be welded to the flange with a full penetration groove weld. Refer to Article 3.1.7.1e(7) and Article 3.1.7.1e(11) for combined warpage and tilt of flange and deviation from full surface contact.

See Part 9 Commentary

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Steel Structures

b. The fit of intermediate stiffener ends against the flange shall be such as to exclude water after being painted, except that for welded flexural members the ends of stiffeners adjacent to the tension flange may be cut back as appropriate to comply with the requirements of Part 1, Design, Article 1.10.4. c.

Fillers and splice plates under angle stiffeners shall be made to fit within 1/4 inch at each end.

3.1.11 FLEXURAL MEMBER WEB PLATES, RIVETED AND BOLTED CONSTRUCTION (1994) R(2008) a.

The edges of web plates of riveted or bolted flexural members that have no cover plates shall not be more than 1/8 inch above or below the backs of the top flange angles. Web plates of such members with cover plates may be 1/2 inch less in width than the distance back to back of flange angles.

b. In riveted or bolted splices of web plates there shall not be more than 3/8 inch opening between the plates.

3.1.12 FACING FLOORBEAMS, STRINGERS, AND GIRDERS (1994) R(2008) Floorbeams, stringers, and girders having end connection angles shall be made to exact length with tolerance as allowed in Article 3.1.7.1e(1). If facing is necessary, the thickness of the end connection angles shall not be reduced more than 1/8 inch at any point.

3.1.13 ABUTTING JOINTS (1994) R(2008) Where splice material at joints and splices in compression members or girder flanges is designed to transmit force as specified in Part 1, Design, Article 1.5.9d, all main material at that joint or splice shall be milled and brought to an even bearing in one plane across the end of each abutting piece at the joint or splice. When so specified on the drawings, this requirement shall also apply to tension members. When the abutting surfaces are not milled, the opening shall not be more than 1/4 inch. Note: Refer to Article 3.1.7.1e(11) for deviations from full surface contact.

3.1.14 PIN CLEARANCES (1994) R(2008) The difference in diameter between the pin and the pin hole shall be 1/50 inch for pins up to 5 inches diameter, and 1/32 inch for larger pins.

3.1.15 PINS AND ROLLERS (1994) R(2008) Pins and rollers shall be turned accurately to gage and shall be straight, smooth, and free from flaws. For additional information on pins and rollers see Part 10 and Part 11.

3.1.16 FITTING OF BASE AND CAP PLATES (1994) R(2008) Both top and bottom surfaces of base and cap plates of columns shall be planed or straightened and the parts of the members in contact with them faced to fit. Connection angles for base plates and cap plates shall be connected to compression members before the members are faced. Note: Refer to Article 3.1.7.1e(11) for deviations from full surface contact.

3.1.17 SURFACES OF BEARING PLATES AND PEDESTALS (2002) R(2008) Refer to Part 10 and Part 11.

© 2011, American Railway Engineering and Maintenance-of-Way Association

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AREMA Manual for Railway Engineering

Fabrication

3.1.18 BENT PLATES (2007)1 R(2008) a.

Bending procedures shall be such that no cracking of the plate occurs. Large dents or upsets shall be avoided. All bends shall receive at least visual inspection. Material that does not form satisfactorily when fabricated in accordance with the requirements of this Article shall be subject to rejection.

b. The bend radius and the radius of the male die should be as liberal as the finished part will permit. The width across the shoulders of the female die should be at least 8 times the plate thickness for ASTM A36/A36M and ASTM A709/A709M, Grade 36 (250). Higher strength steels may require larger die openings. The surface of the dies in the area of radius should be smooth. c.

Where the concave face of a bent plate must fit tight against another surface, the male die shall be sufficiently thick and have the proper radius to ensure that the bent plate has the required concave surface.

d. Bent plates for connections should preferably be oriented so that the bend line will be essentially perpendicular to the direction of rolling. If the bend line is parallel to the direction of rolling, the suggested minimum radii in Table 15-3-1 should be multiplied by 1.5. Table 15-3-1. Minimum Radii for Cold Bending of Plates Material

1

Plate Thickness

ASTM

Grade

Up to 1 in. (25 mm) incl.

A36/A36M A572/A572M A709/A709M

-42 (290) 36 (250)

1.5t

A572/A572M A588/A588M A709/A709M A709/A709M

50 (345) -50 (345) 50W (345W)

A572/A572M A709/A709M

55 (380) HPS 70W (485W)

Over 1 in. (25 mm) to 2 in. (50 mm) incl.

Over 2 in. (50 mm)

1.5t

2.0t

1

3 1.5t

2.0t

2.5t

1.5t

2.5t

3.0t

4

e.

In the area where bending is to occur, the edges of the plate should be ground smooth and the corners rounded before bending.

f.

Suggested minimum bend radii for cold bending (i.e. at room temperature), measured to the concave face of the plate, are given in Table 15-3-1. If a shorter radius is required, then heat may need to be a part of the bending procedure. Heat may also be applied to facilitate bends with radii meeting or exceeding those listed in Table 15-3-1. The temperature of the heated plate shall not exceed 1200 °F (650 °C) or 1100 °F (600 °C) in the case of ASTM A709/A709M, Grade HPS 70W (485W). Heat should be essentially uniform through the thickness of the plate.

See Part 9 Commentary

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AREMA Manual for Railway Engineering

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Steel Structures

SECTION 3.2 RIVETED AND BOLTED CONSTRUCTION 3.2.1 RIVETS AND RIVETING (1995) R(2008) a.

Rivet dimensions shall conform to the current requirements of the American National Standards Institute for large rivets, 1/2 inch in nominal diameter and larger, ANSI Standard B 18.4.

b. Rivets shall be heated uniformly to a light cherry red and driven while hot to fill the holes completely. They shall be free from slag, scale and carbon deposit. Loose, burned, or otherwise defective rivets shall be replaced. In removing rivets, care shall be taken not to injure the adjacent metal and, if necessary, the rivets shall be drilled out. Caulking or recupping shall not be done. c.

Rivets shall be driven by direct-acting riveters where practicable. The pressure shall be continued after the upsetting has been completed.

d. Where rivets are driven with a pneumatic riveting hammer, a pneumatic bucker shall be used where practicable. e.

Driven rivet heads shall be fully formed, neatly made, concentric with the rivet holes, and in full contact with the member.

f.

Rivets of ASTM A 502, Grade 2, shall not be driven by hand.

3.2.2 HIGH STRENGTH BOLTS, NUTS AND WASHERS (1995)1 R(2008) High strength bolts, nuts and washers shall conform to Part 1, Design, Article 1.2.1a. Other types of fasteners may be used provided all requirements of Article 2.8 of the Specification of the Research Council on Structural Connections are met and provided further it can be shown that the tension of installed fasteners meets the tensile requirements of Table 15-3-2 after installation.

3.2.3 INSTALLATION OF HIGH STRENGTH BOLTS (2004)2 R(2008) a.

After compacting the joint to the snug-tight condition, bolts shall be tensioned so as to obtain, when all the bolts in the joint are tight, at least the minimum tension per bolt shown in Table 15-3-2 for the grade and size of bolt using either the turn-of-nut method, twist-off-type tension-control bolts, or directtension-indicators as described in paragraphs d, e, or f. The calibrated wrench method may also be used.

b. Snug Tightening: All bolt holes shall be aligned to permit insertion of the bolts without undue damage to the threads. Bolts shall be placed in all holes with washers provided as required in paragraph c and the nuts installed to complete the assembly. Compacting the joint to the snug-tight condition shall progress systematically from the most rigid part of the joint in a manner that will minimize relaxation of previously snugged bolts. The snug-tight condition is the tightness that is attained with a few impacts of

1 2

See Part 9 Commentary See Part 9 Commentary

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15-3-10

AREMA Manual for Railway Engineering

Fabrication Table 15-3-2. Minimum Tension of Installed Bolts Minimum Tension in Kips

Nominal Bolt Size–Inches

A325 Bolts

A490 Bolts

1/2

12

15

5/8

19

24

3/4

28

35

7/8

39

49

1

51

64

1-1/8

56

80

1-1/4

71

102

1-3/8

85

121

1-1/2

103

148

an impact wrench or the full effort of an ironworker using an ordinary spud wrench to bring the connected plies into full contact. c.

ASTM F436 washers are required under the turned element. When ASTM A490 bolts are used with connected material having a specified yield strength of less than 40 ksi, ASTM F436 washers shall be used under both the bolt head and the nut. Special washer requirements when using direct-tensionindicator tensioning are given in paragraph f. Beveled washers shall be used where an outer face of the bolted parts has a slope of more than 1:20 with respect to a plane normal to the bolt axis.

1

d. Turn-of-Nut Tensioning: An installation verification test specified in paragraph g shall be performed prior to bolt installation. All bolts shall be installed in accordance with the requirements of paragraph b with washers installed as required in paragraph c. Subsequently, the nut or head rotation specified in Table 15-3-3 shall be applied to all fastener assemblies in the joint, progressing systematically from the most rigid part of the joint in a manner that will minimize relaxation of previously tensioned bolts. The part not turned by the wrench shall be prevented from rotating during this operation.

3

4

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AREMA Manual for Railway Engineering

15-3-11

Steel Structures Table 15-3-3. Nut Rotation from Snug Tight Condition Condition of Outer Faces of Bolted Parts Bolt Length Both faces (as measured from underside of normal to head to extreme end of point) bolt axis.

One face normal to bolt axis and other sloped not more than 1:20 (bevel washer not used)

Bolt faces sloped to bolts axis not more than 1:20 from normal (bevel washer not used)

Up to and including 4 diameters

1/3 turn

1/2 turn

2/3 turn

Over 4 diameters but not exceeding 8 diameters

1/2 turn

2/3 turn

5/6 turn

Over 8 diameters but not exceeding 12 diameters (Note 2)

2/3 turn

5/6 turn

1 turn

Note 1: Nut rotation is relative to bolt regardless of the element (nut or bolt) being turned. For bolts tightened by one-half turn or less, the tolerance is ± 30 degrees; for bolts tightened by two-thirds turn or more, the tolerance is ± 45 degrees. Note 2: Where the bolt length exceeds 12 diameters, the required rotation shall be determined by actual tests in a suitable tension device simulating actual conditions. e.

Twist-Off-Type Tension-Control Bolt Tensioning: If the use of twist-off-type tension-control bolt assemblies is permitted by the Engineer, the following provisions shall apply. (1) Twist-off-type tension-control bolt assemblies that meet the requirements of ASTM F1852 shall be used. (2) An installation verification test specified in paragraph g shall be performed prior to bolt installation. (3) All fastener assemblies shall be installed in accordance with the requirements of paragraph b without severing the splined end and with washers positioned as required in paragraph c. If a splined end is severed during snugging, the fastener assembly shall be removed and replaced. Subsequently, all the bolts in the joint shall be tensioned with the twist-off-type tension-control bolt installation wrench, progressing systematically from the most rigid part of the joint in a manner that will minimize relaxation of the previously tensioned bolts.

f.

Direct-Tension-Indicator Tensioning: If the use of direct-tension-indicators is permitted by the Engineer the direct-tension-indicators shall meet the requirements of ASTM F959. The pre-installation verification procedure in paragraph g shall be performed before the indicators are used in the work to establish the job inspection gap. Direct-tension-indicators shall be installed with protrusions bearing against a hardened washer or the unturned nut or bolt head. All bolts shall be installed in accordance with paragraph b with the washers positioned as follows: (1) When the nut is turned and the direct-tension-indicator is located under the bolt head, an ASTM F436 washer shall be used under the nut; (2) When the nut is turned and the direct-tension-indicator is located under the nut, an ASTM F436 washer shall be used between the nut and the direct-tension-indicator; (3) When the bolt head is turned and the direct-tension-indicator is located under the nut, an ASTM F436 washer shall be used under the bolt head;

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Fabrication

(4) When the bolt head is turned and the direct-tension-indicator is located under the bolt head, an ASTM F436 washer shall be used between the bolt head and the direct tension indicator. The installer shall verify that the direct-tension-indicator protrusions have not been compressed to a gap that is less than the job inspection gap during the snug tightening of the connection, and if this has occurred, the direct tension indicator shall be removed and replaced. Subsequently, all bolts in the joint shall be tensioned, progressing systematically from the most rigid part of the joint in a manner that will minimize the relaxation of the previously tensioned bolts. The installer shall verify that the directtension-indicator protrusions have been compressed to a gap that is less than the job inspection gap. g.

A Skidmore-Wilhelm Calibrator or an acceptable equivalent tension-measuring device shall be required at each job site during erection. The device shall be used to confirm the suitability of the complete fastener assembly, including lubrication, for installation and confirm the procedure and proper use by the bolting crew of the tensioning method to be used. The required testing consists of: (1) A representative sample of not fewer than three complete fastener assemblies of each combination of diameter, length, grade, and lot to be used in the work shall be checked at the site of installation in a tension calibrator to verify that the tensioning method develops a tension that is equal to or greater than 1.05 times that specified in Table 15-3-2. Washers shall be used in the pre-installation verification assemblies as required in the work in accordance with the requirements in paragraphs c and f. If the actual tension developed in any of the fastener assemblies is less than 1.05 times that specified in Table 15-3-2, the cause(s) shall be determined and resolved before the fastener assemblies are used in the work. Cleaning, lubrication, and retesting of these fastener assemblies, except for ASTM F1852 twist-off-type tension-control assemblies, are permitted, provided all assemblies are treated in the same manner.

1

(2) When direct-tension-indicators are used, five fastener assemblies of each combination of diameter, length, grade, and lot to be used in the work shall be tightened to 1.05 times the tension specified in Table 15-3-2. The measured gap shall not be less than the job inspection gap. The position of the direct-tension-indicator, the ASTM F436 washer, and the turned element shall match the conditions in the work.

3

(3) When the calibrated wrench method is used periodic testing shall be performed at least once each working day and when conditions change. h. A490 bolts and galvanized A325 bolts shall not be reused after having once been fully tensioned. These same type bolts may be used for both fitting up and final bolting if tightened to no more than snug-tight during fitting up. Other A325 bolts that have been tensioned beyond snug-tight condition only once may be reused if approved by the Engineer. i.

Fasteners shall be protected from dirt and moisture at the job site. Only as many fasteners as are anticipated to be installed and tightened during a work shift shall be taken from protected storage. Fasteners not used shall be returned to protected storage at the end of the shift. Fasteners shall not be cleaned of lubricant that is present in as-delivered condition. Fasteners for slip critical connections which accumulate dirt shall be cleaned and relubricated prior to installation, except that ASTM F1852 twistoff-type tension control assemblies shall be discarded or returned to the manufacturer.

j.

The rotational-capacity test for ASTM A325 and A490 high strength bolts described in Article 3.2.14 shall be performed on each rotational-capacity lot at the site prior to the start of bolt installation. Hardened steel washers are required as part of the test although they may not be required in the actual installation procedures.

k. Lubrication:

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Steel Structures

(1) Galvanized nuts shall be checked to verify that a visible lubricant is on the threads. (2) Black bolts shall be “oily” to the touch when delivered and installed. (3) Weathered or rusted bolts or nuts, except as noted below in (4), shall be cleaned and relubricated prior to installation. Recleaned or relubricated bolt, nut and washer assemblies shall be retested in accordance with paragraph j prior to installation. (4) ASTM F1852 twist-off-type tension control assemblies that are not in the as-delivered condition shall not be relubricated in the field, they shall be discarded or returned to the manufacturer. l.

Bolt, nut and washer (when required) combinations as installed shall be from same rotational-capacity lot.

3.2.4 QUANTITY OF FIELD FASTENERS (2003) R(2008) a.

The number of field rivets of each size and length furnished in excess of the nominal number required shall be 10% plus 10.

b. The number of field high strength bolts of each size and length furnished in excess of the nominal number required shall be 5% plus 10. The number of nuts and washers of each size and type furnished in excess of the nominal number required shall be 5% plus 10.

3.2.5 SIZE AND WORKMANSHIP OF HOLES (2010) a.

The diameter of standard holes punched full-size and of standard holes reamed or drilled shall be 1/16 inch greater than the nominal diameter of the rivets or high strength bolts.

b. The diameter of the punch shall be the diameter of the hole to be punched. c.

Holes shall be cylindrical, unless punched full-size; also they shall be perpendicular to the member, clean cut, and free of cracks and ragged edges. All burrs shall be removed either by chamfering no more than 1/16 inch or by grinding. For riveted construction where the grip exceeds 4-1/2 inches the holes shall be chamfered 1/32 inch.

d. At locations approved by the Engineer, oversize holes, short slotted, or long slotted holes may be used with high strength bolts 5/8 inch in diameter or larger in accordance with the following requirements. NOTE:

Refer to Table 15-1-11a.

(1) Oversize holes may have nominal diameters up to 3/16 inch larger than bolts 7/8 inch and less in diameter, 1/4 inch larger than bolts 1 inch in diameter, and 5/16 inch larger than bolts 1-1/8 inch and greater in diameter. They may be used in any or all plies of connections. Hardened washers shall be installed over oversized holes in an outer ply. Where A490 bolts over 1 inch in diameter are used in oversized holes in external plies, a single hardened washer conforming to ASTM F436, except with a 5/16 inch minimum thickness, shall be used under both the head and the nut in lieu of standard thickness hardened washers. Multiple hardened washers with combined thickness equal to or greater than 5/16 inch do not satisfy this requirement. (2) Short slotted holes are nominally 1/16 inch wider than bolt diameter and have a length which does not exceed the oversized diameter provisions for oversize holes by more than 1/16 inch. They may be used in any or all plies of connections without regard to direction of loading. Hardened washers shall be installed over short slotted holes in an outer ply. Where A490 bolts over 1 inch diameter are used in short slotted holes in external plies, a single hardened washer conforming to ASTM F436, except © 2011, American Railway Engineering and Maintenance-of-Way Association

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AREMA Manual for Railway Engineering

Fabrication

with a 5/16 inch minimum thickness, shall be used under both the head and the nut in lieu of standard thickness hardened washers. Multiple hardened washers with combined thickness equal to or greater than 5/16 inch do not satisfy this requirement. (3) Long slotted holes are nominally 1/16 inch wider than the bolt diameter and have a length more than allowed for short slotted holes, but not more than 2.5 times the bolt diameter. The slots may be used without regard to direction of loading. Long slotted holes may be used in only one of the connected parts at an individual faying surface. Where A325 bolts of any diameter or A490 bolts equal to or less than 1 inch in diameter are to be installed and tightened in a long slotted hole in an outer ply, a plate washer or continuous bar of at least 5/16 inch thickness with standard holes shall be provided. These washers or bars shall have a size sufficient to completely cover the slot after installation and shall be of structural grade material, but need not be hardened except as follows. When A490 bolts over 1 inch in diameter are to be used in long slotted holes in external plies, a single hardened washer conforming to ASTM F436 but with 5/16 inch minimum thickness shall be used in lieu of washers or bars of structural grade material. Multiple hardenend washers with combined thickness equal to or greater than 5/16 inch do not satisfy this requirement. If hardened washers are required to satisfy Specification provisions, the hardened washers shall be placed over the outer surface of the plate washer or bar.

3.2.6 PREPARATION OF HOLES FOR SHOP FASTENERS (1995)1 R(2008) a.

For meeting the requirements of this article, the tabulation of acceptable substitutes, for use at contractor’s option Table 15-3-4 shall apply:

1 Table 15-3-4. Contractor Acceptable Substitutes Requirement

Acceptable Substitute

Punching full-size

Drilling full size or subpunching and reaming to size with or without all parts assembled.

Subpunching

Subdrilling

Reaming with parts assembled

Drilling full size with parts assembled or, if approved by the Engineer, drilling full size without assembly, provided the drilling is done by suitable numerically controlled (N/C) drilling equipment, subject to the specific limitations contained in Article 3.2.7f and Article 3.2.7g.

Subpunching 1/8 inch less dia. than the finished hole.

Subpunching 1/4 inch less dia. than that of the finished hole.

3

b. Holes to be reamed shall be subpunched or subdrilled. c.

1

Except as prohibited by paragraph f, holes may be punched full size in A36 material not more than 7/8 inch thick and in high strength material not more than 7/8 inch thick for fasteners which are not stressed by vertical live load. This provision applies to, but is not limited to, holes for stitch fasteners; lateral, longitudinal or sway bracing or their connecting material; lacing stay plates; diaphragms which do not transfer shear or other force; inactive fillers; and stiffeners not at bearing points.

See Part 9 Commentary

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Steel Structures

d. Holes in rolled beams and plate girders, including stiffeners and active fillers at bearing points, in material not thicker than the nominal diameter of the fastener less 1/8 inch shall be subpunched 1/8 inch less diameter than that of the finished hole, and reamed to size with parts assembled. e.

Holes in A36 material thicker than 7/8 inch and in high strength material thicker than 3/4 inch shall be subdrilled 1/4 inch less diameter than that of the finished hole, and reamed to size with parts assembled.

f.

Where matching holes in two or more plies of material are required to be reamed with parts assembled and the assembly consists of more than five plies with more than three plies of main material, the matching holes in other plies shall also be reamed with parts assembled, with holes in these other plies subpunched 1/8 inch less diameter than that of the finished hole.

g.

Other holes for shop fasteners shall be subpunched 1/4 inch less in diameter than that of the finished hole, and reamed to size with parts assembled.

h. If approved by the Engineer, the contractor shall have the option to drill full size through individual pieces or any combination of pieces held tightly together, the holes designated to be sub-punched or subdrilled and reamed in paragraph d, paragraph e, paragraph f and paragraph g, provided the drilling is done by suitable numerically controlled (N/C) drilling equipment, subject to the specific limitations contained in Article 3.2.7f and Article 3.2.7g.

3.2.7 PREPARATION OF HOLES FOR FIELD FASTENERS (2007)1 R(2008) a.

Field splices in plate girders and in truss chords shall be reamed or drilled full size with the members assembled. Truss chord assemblies shall consist of at least three abutting sections, and milled ends of compression chords shall have full bearing.

b. Holes for field fasteners where assembly is not required shall be either: (1) subpunched or subdrilled 1/4 inch less in diameter than that of the finished holes and reamed to size through steel templates with hardened steel bushings, or (2) drilled full size through steel templates with hardened steel bushings. c.

Holes in A 36 material thicker than 7/8 inch and in high strength material thicker than 3/4 inch shall be either: (1) subdrilled 1/4 inch less in diameter than that of the finished holes and reamed to size with parts assembled, or (2) drilled full size with parts assembled.

d. Holes for field fasteners in lateral, longitudinal or sway bracing shall conform to the requirements for shop fastener holes in such members. e.

1

If approved by the Engineer, the fabricator shall have the option to drill full size into unassembled pieces, the holes designated in paragraph a, paragraph b, or paragraph c to be assembled reamed or drilled full size, provided the drilling is done by suitable numerically controlled (N/C) drilling equipment, subject to the specific limitations contained in paragraph f and paragraph g.

See Part 9 Commentary

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Fabrication

f.

Where N/C drilling equipment is used, the fabricator shall, if required by the Engineer, demonstrate by means of check shop assemblies that the drilling equipment will consistently produce holes and connections meeting all of the requirements of Article 3.2.5 and Article 3.2.12.

g.

Where check shop assemblies are designated, paragraph a shall be modified to require a check shop assembly for either one line of plate girders or for three abutting chord sections, one each for the top and bottom chords, of one truss including representative web members which connect to these chord assemblies. Composition of check shop assemblies shall be based on the proposed order of erection, joints in bearing, special complex points and similar considerations. The fabricator shall submit his designation of members to be shop assembled to the Engineer for approval. If the shop assembly fails to produce holes and connections meeting the requirements of Article 3.2.5 and Article 3.2.12, the Engineer may require further shop assemblies or may rescind his approval for the use of N/C drilling equipment.

h. When a span, intended to carry an active track, is to be erected during a work window between trains, all connections necessary for the erected span’s ability to carry traffic shall be checked by shop assembly unless exempted by the Engineer.

3.2.8 TEMPLATES FOR REAMING AND DRILLING (1983) R(2008) Each steel template shall have hardened steel bushings accurately positioned with respect to connection centerlines inscribed on the template.

1

3.2.9 REAMING AND DRILLING THROUGH TEMPLATES (1995) R(2008) a.

Reaming or drilling full size of field connections through templates shall be done only after the templates have been positioned with the utmost care, and firmly clamped or bolted. Templates used for the reaming of matching members, or of the opposite faces of one member, shall be exact duplicates. Templates for connections which duplicate shall be so accurately positioned that like members are duplicates and require no match-marking.

3

b. Where templates are used to ream or drill field connections of truss web members, at least one end of each such member shall be milled or scribed normal to the long axis of the member, and the templates shall be accurately set at both ends with respect to this milled or scribed end. Templates for reaming or drilling truss gusset plates shall be accurately positioned to the geometric dimensions shown on the shop plans. c.

Templates for field connector holes for joining floor sections to girders or trusses shall be positioned so as to space the field connectors correctly from the floor expansion joints.

3.2.10 REAMING AND DRILLING AFTER ASSEMBLY (1995) R(2008) Reaming, or drilling full size, of assembled parts shall be done only after the parts are firmly clamped together with the surfaces in close contact. If necessary, parts shall be separated before riveting or bolting for removal of shavings.

3.2.11 MATCH MARKING (1995) R(2008) Parts assembled in the shop for reaming or drilling holes for field connectors shall be match marked before disassembly. Diagrams showing match marks shall be furnished to the Engineer.

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Steel Structures

3.2.12 ALIGNMENT OF FINISHED HOLES (1995) R(2008) a.

The offset in any hole reamed 1/4 inch in any ply of material measured from an outer ply after the hole has been finished for riveting or bolting, shall not exceed 1/16 inch. Not more than 10% of the holes shall be offset as much as 1/16 inch and not more than 20% shall be offset as much as 1/32 inch.

b. The offset in any hole reamed 1/8 inch or punched full size, in any ply of material, measured from an outer ply after the hole has been finished for riveting or bolting, shall not exceed 1/8 inch. Not more than 10% of the holes shall be offset as much as 1/8 inch, and not more than 20% shall be offset as much as 1/16 inch. c.

Where approved by the Engineer, holes may be overreamed to meet these requirements, and larger rivets or bolts installed.

3.2.13 FITTING FOR SHOP RIVETING OR BOLTING (1995) R(2008) The parts of riveted or bolted members shall be adequately pinned and firmly drawn together in close contact with bolts before riveting or final bolting is begun. Tack welding shall not be used. The drifting done during assembly shall be only such as to bring the parts into position and shall not enlarge the holes or distort the metal.

3.2.14 TESTING AND DOCUMENTATION OF ASTM A325 AND A490 BOLTS (1995) R(2008) 3.2.14.1 Bolt Testing a.

Bolts: (1) Proof load tests in accordance with Method 1 of ASTM F606 are required. Minimum frequency of tests shall be as specified in ASTM A325 and A490 per the production lot method. (2) Wedge tests on full size bolts (ASTM F606 paragraph 3.5) are required. If bolts are to be galvanized, tests shall be performed after galvanizing. Minimum frequency of tests shall be as specified in ASTM A325 and A490 per the production lot method. (3) If galvanized bolts are supplied, the thickness of the zinc coating shall be measured. Measurements shall be taken on the wrench flats or top of bolt head.

b. Nuts: (1) Proof load tests (ASTM F606 paragraph 4.2) are required. Minimum frequency of tests shall be as specified in ASTM A563 paragraph 9.3. If nuts are to be galvanized, tests shall be performed after galvanizing, overtapping and lubricating. (2) If galvanized nuts are supplied, the thickness of the zinc coating shall be measured. Measurements shall be taken on the wrench flats. c.

Washers: (1) If galvanized washers are supplied, hardness testing shall be performed after galvanizing. (Coating shall be removed prior to taking hardness measurements.) (2) If galvanized washers are supplied, the thickness of the zinc coating shall be measured.

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Fabrication

d. Assemblies: (1) Rotational-capacity tests are required and shall be performed on all black or galvanized (after galvanizing) bolt, nut and washer assemblies by the manufacturer or distributor prior to shipping. Washers are required as part of the test procedure. (2) The following shall apply: (a) Except as modified herein, the rotational-capacity test shall be performed in accordance with the requirements of ASTM A325. (b) Each combination of bolt production lot, nut lot and washer lot shall be tested as an assembly. Where washers are not required by the installation procedures, they need not be included in the lot identification. (c) A rotational-capacity lot number shall be assigned to each combination of lots tested. (d) The minimum frequency of testing shall be two assemblies per rotational-capacity lot. (e) The bolt, nut and washer assembly shall be assembled in a Skidmore-Wilhelm Calibrator or an acceptable equivalent device (note- this requirement supersedes the current ASTM A325 requirement that the test be performed in a steel joint). For short bolts which are too short to be assembled in the Skidmore-Wilhelm Calibrator, see paragraph (i). (f) The minimum rotation, from a snug tight condition (10% of the specified proof load) shall be: 240 degrees (2/3 turn) for bolt lengths

< 4 diameters

360 degrees (1 turn) for bolt lengths

> 4 diameters and < 8 diameters

480 degrees (1-1/3 turn) for bolt lengths

> 8 diameters

(g) The tension reached at the above rotation shall be equal to or greater than 1.15 times the required installation tension. The installation tension and the tension for the turn test are shown in Table 15-3-5.

1

3

Table 15-3-5. Minimum Required Turn Test Tension Diameter (Inch)

1/2

5/8

3/4

7/8

1

1-1/8

1-1/4

1-3/8

1-1/2

Req. Installation Tension (Kips)

A325

12

19

28

39

51

56

71

85

103

A490

15

24

35

49

64

80

102

121

148

Turn Test Tension (Kips)

A325

14

22

32

45

59

64

82

98

118

A490

17

28

40

56

74

92

117

139

170

(h) After the required installation tension listed above has been exceeded, one reading of tension and torque shall be taken and recorded. The torque value shall conform to the following: Torque £ 0.25PD where: Torque = measured torque (foot-pounds)

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Steel Structures

P = measured bolt tension (pounds) D = bolt diameter (feet) (i) Bolts that are too short to test in a Skidmore-Wilhelm Calibrator may be tested in a steel joint. The tension requirement of paragraph (e) need not apply. The maximum torque requirement of paragraph (g) shall be computed using a value of P equal to the turn test tension shown in Table 15-3-5. e.

Reporting: (1) The results of all tests (including zinc coating thickness) required herein shall be recorded on the appropriate document. (2) Location where tests are performed and date of tests shall be reported on the appropriate document.

f.

Witnessing. The tests need not be witnessed by an inspection agency; however, the manufacturer or distributor that performs the tests shall certify that the results recorded are accurate.

3.2.14.2 Documentation a.

Mill Test Report(s) (MTR): (1) MTR shall be furnished for all mill steel used in the manufacture of the bolts, nuts, or washers. (2) MTR shall indicate the place where the material was melted and manufactured.

b. Manufacturer Certified Test Report(s) (MCTR): (1) The manufacturer of the bolts, nuts and washers shall furnish test reports (MCTR) for the item furnished. (2) Each MCTR shall show the relevant information required in accordance with Article 3.2.14.1e. (3) The manufacturer performing the rotational-capacity test shall include on the MCTR: (a) The lot number of each of the items tested. (b) The rotational-capacity lot number as required in Article 3.2.14.1d(2)(c). (c) The results of the tests required in Article 3.2.14.1d. (d) The pertinent information required in Article 3.2.14.1e(2). (e) A statement that MCTR for the items are in conformance to this recommended practice. (f) The location where the bolt assembly components were manufactured. c.

Distributor Certified Test Report(s) (DCTR): (1) The DCTR shall include MCTR above for the various bolt assembly components. (2) The rotational-capacity test may be performed by a distributor (in lieu of a manufacturer) and reported on the DCTR.

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(3) The DCTR shall show the results of the tests required in Article 3.2.14.1d. (4) The DCTR shall also show the pertinent information required in Article 3.2.14.1e(2). (5) The DCTR shall show the rotational-capacity lot number as required in Article 3.2.14.1d(2)(c). (6) The DCTR shall certify that the MCTRs are in conformance with this recommended practice.

SECTION 3.3 WELDED CONSTRUCTION 3.3.1 GENERAL (2002) R(2008) a.

These recommended practices cover requirements for welding practices and inspection to ensure that the resulting structure will be satisfactory for service. The AWS D1.5 shall be used for all requirements not specifically covered in these recommended practices. Until such time as AWS D1.5 specifically includes welding of ASTM A709 Grade HPS 70W, use the latest edition of the AASHTO document “Guide for Highway Bridge Fabrication with HPS 70W” as a supplement to AWS D1.5.

b. Electroslag and electrogas welding processes shall not be used. c.

Welding of Fracture Critical Members shall be in accordance with the requirements of Part 1, Design, Section 1.14, Fracture Critical Members.

1

3.3.2 PREPARATION OF MATERIAL FOR WELDING (1995) R(2008) Surfaces within 2 inches of any weld location shall be free from any paint or other material which would prevent proper welding or produce objectionable fumes while welding.

3

3.3.3 FLANGE-TO-WEB WELDS OF FLEXURAL MEMBERS (1995)1 R(2008) Flange-to-Web welds of flexural members shall be made by machine welding.

3.3.4 TACK WELDS (1995)2 R(2008)

4

Transverse tack welds on tension flanges of flexural members are prohibited.

3.3.5 WELDER AND WELDING OPERATOR QUALIFICATIONS (1997) R(2008) Welds shall be made only by welders, welding operators and tack welders currently qualified, in accordance with AWS D1.5, to perform the type of work required.

1 2

See Part 9 Commentary See Part 9 Commentary

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SECTION 3.4 SHOP PAINTING 3.4.1 SHOP PAINTING OF STRUCTURAL STEEL (2003) R(2008) a.

Steel surfaces for new structural steel fabrication, shall be prepared and painted in accordance with the “Standard Specification for Coating Systems with Inorganic Zinc-Rich Primer” (AASHTO/NSBA Steel Bridge Collaboration publication S8.1) as prepared by the AASHTO/NSBA Steel Collaboration Task Group 8, Coatings, unless another coating system is specified by the Company.

b. For welded construction, slag shall be cleaned from all welds. Welded joints shall not be painted until after the work has been completed and accepted. The surfaces to be painted shall be cleaned of spatter, rust, loose scale, oil and dirt. c.

Shop and field contact surfaces shall not be painted unless required by the Engineer.

d. Weathering steels, ASTM A588, A709, Grade 50W, Grade HPS 50W, and Grade HPS 70W need not be shop painted provided the shop painting requirement is waived in the contract documents or is otherwise deleted by the Engineer.

3.4.2 SHOP PAINTING OF MACHINED SURFACES (1995) R(2008) a.

Machine finished surfaces of steel (except abutting joints and base plates) shall be protected against corrosion by a rust-inhibiting coating which can be removed readily prior to erection, or which has characteristics which make removal unnecessary prior to erection. This coating shall be applied as soon as the surfaces have been finished and approved by the Inspector.

b. Abutting joints and base plates shall be painted as required by Article 3.4.1a.

SECTION 3.5 INSPECTION 3.5.1 FACILITIES FOR INSPECTION (1991) R(2008) The Contractor shall provide to the Inspector, without charge, facilities for the inspection of materials and workmanship. The Inspector shall be allowed free access to the fabricating areas.

3.5.2 INSPECTOR AUTHORITY (1991) R(2008) The Inspector shall have authority to reject materials or workmanship that do not meet the requirements of the contract documents. In case of dispute, the Contractor may appeal to the Engineer, whose decision shall be final.

3.5.3 REJECTION (1991) R(2008) a.

The acceptance by the Inspector of material or finished members shall not prevent their rejection later if found defective.

b. Rejected material and workmanship shall promptly be replaced or made good by the Contractor.

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3.5.4 INSPECTION – HIGH STRENGTH BOLTED JOINTS (2003) R(2008) a.

The Inspector shall observe the installation and tightening of bolts to determine that the specified tightening procedure is properly used, and shall determine that all bolts have been tightened.

b. When there is disagreement concerning the results of tension in the turn-of-nut method of installation, the arbitration procedure described in the current Specification for Structural Joints using A325 and A490 Bolts approved by the Research Council on Structural Connections (RCSC) shall be used, unless a different procedure is specified in the inquiry and order for the work. Required fastener tension shall be as specified in Part 1, Design, Table 15-1-12 (not as specified in the RCSC specifications).

3.5.5 INSPECTION – WELDED WORK (2002)1 R(2008) a.

All weld inspection shall be performed by the Inspector, or shall be witnessed by him. The Contractor shall place pieces so that the Inspector has ready access. When specified on the design plans or in special provisions covering the work, the Contractor may be required to perform specific non-destructive testing work, such as radiography, etc., but this must be witnessed by the Inspector. The Inspector must not unnecessarily delay such inspection by refusing to be present when this work must be done.

b. All groove welds carrying live-load stress in flanges of flexural members and in tension members shall be inspected by radiographic, ultrasonic or another nondestructive testing method which will satisfactorily present evidence to the Engineer that the welds meet the quality requirements of the AWS D1.5. At least 10% of all other groove welds, except flange-to-web full penetration welds, shall be similarly inspected. At least 10% of the flange-to-web complete joint penetration groove welds shall be inspected by the ultrasonic method or they may be inspected by the magnetic particle method if so authorized by the Engineer. If rejectable discontinuities are found, the provisions of AWS D1.5 for additional testing shall apply. c.

At least 10% of flange-to-web fillet welds shall be inspected by the magnetic particle method unless such inspection is waived by a statement in the design plans or special provisions. If rejectable discontinuities are found, the provisions of AWS D1.5 for additional testing shall apply.

1

3

d. Inspection of welded work for Fracture Critical Members shall be in accordance with Part 1, Design, Section 1.14, Fracture Critical Members. e.

Time delay prior to NDT of weld repairs to groove welds of ASTM A588 or A709, Grade 50W, or A709, Grade HPS 50W, or A709, Grade HPS 70W material over 2 inches in thickness, subject to tensile stress, shall be 16 hours minimum.

SECTION 3.6 SHIPMENT AND PAY WEIGHT 3.6.1 MARKING, PACKAGING AND LOADING (1995) R(2008) a.

1

Erection marks shall be painted on all members. Members weighing more than 10 tons shall have their weight marked thereon. Marks on weathering steel shall be placed in suitable inconspicuous places.

See Part 9 Commentary

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Steel Structures

b. The responsibilities of the shipper shall include proper loading, positioning, supporting and stabilizing of structural members in accordance with the carrier’s instructions and in case the material is damaged proper correction of the damage. The fabricator shall make certain that structural members are loaded for shipment in a manner that will ensure that they will not be damaged in shipment. The method of loading must not adversely affect the potential life of the permanent structure. Welding of tie-down attachments to a member is prohibited. The Engineer may request that loading diagrams be furnished to him for unusual or special members. The Engineer may also request the fabricator to notify the Engineer when any member is ready for shipment so that the method of loading can be observed. c.

Rivets and bolts, except ASTM A325 and A490 high strength bolts shall be packaged separately according to length and diameter. Loose nuts and washers shall be packaged separately according to size.

d. Pins and other small parts and packages of rivets, bolts, except ASTM A325 and A490 high strength bolts, nuts and washers shall be shipped in boxes, crates, kegs, or barrels, none of which shall exceed 300 lb gross weight. A list and description of material contained therein shall be firmly secured to or marked on the outside of each container. e.

ASTM A325 and A490 high strength bolts, nuts, and washers (where required) from each rotationalcapacity lot shall be shipped in the same container. If there is only one production lot number for each size of nut and washer, the nuts and washers may be shipped in separate containers. Each container (not the lid) shall be permanently marked with the rotational-capacity lot number such that identification will be possible at any stage prior to installation. The appropriate Mill Test Report(s) (MTR), Manufacturer Certified Test Report(s) (MCTR) and Distributor Certified Test Report(s) (DCTR) for high strength bolts as required in Article 3.2.14.2 shall be supplied to the Engineer.

f.

Long girders shall be so loaded that they can be delivered to the site in position for erection without turning. Instructions for such delivery shall be furnished to the carrier.

g.

Special precautions may be needed where girders are supported at points other than permanent support points, and where girder intermediate stiffeners are not in contact with flanges.

3.6.2 ADVANCE MATERIAL (1995) R(2008) Anchor bolts and washers and other anchorage or grillage materials to be built into the masonry shall be shipped in time therefore.

3.6.3 PAY WEIGHT (2003)1 R(2008) Payment in unit price contracts shall be based on the weight determined in accordance with the Code of Standard Practice of the American Institute of Steel Construction.

1

See Part 9 Commentary

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Part 4 Erection1 — 2008 — FOREWORD

The purpose of this part is to formulate general rules as a guide for the erection of railway bridges. Part 1, Design is applicable to erection of steel railway bridges except as modified by Part 4, Erection.

TABLE OF CONTENTS Section/Article Description 4.1 General (1992) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Page 15-4-2

4.2 Definitions of Terms (1992) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-4-3

4.3 Work to be Done (2002) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-4-3

4.4 Drawings or Special Provisions to Govern (1992) R(2008) . . . . . . . . . . . . . . . . . . . . . . .

15-4-3

4.5 Plant (1992) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-4-3

4.6 Plans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6.1 Steel Structure Supplied by Company (2002) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6.2 Steel Structure Fabricated by Contractor (2002) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . .

15-4-3 15-4-3 15-4-3

4.7 Delivery of Materials (1992) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-4-4

4.8 Handling and Storing Materials (1992) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-4-4

4.9 Establishment of Lines and Elevations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.9.1 Substructure Constructed by Company (2003) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.9.2 Substructure Constructed by Contractor (2003) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . .

15-4-4 15-4-4 15-4-4

4.10 Bearings and Anchorage (2002) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-4-4

4.11 Erection Procedure (1992) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-4-5

4.12 Reinforcement of Members (1992) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-4-5

1

References, Vol. 13, 1912, pp. 83, 935; Vol. 24, 1923, pp. 146, 1143; Vol. 38 1937, p. 630; Vol. 49, 1948, pp. 206, 669; Vol. 57, 1956, pp. 555, 998; Vol. 62, 1961, pp. 550, 877; Vol. 63, 1962, pp. 386, 699; Vol. 68, 1967, p. 351; Vol. 70, 1969, p. 241; Vol. 76, 1975, p. 241; Vol. 80, 1979, p. 188; Vol. 92, 1991, p. 78; Vol. 93, 1992, p. 124; Vol. 94, p. 1. Reapproved with revisions 1993.

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TABLE OF CONTENTS (CONT) Section/Article

Description

Page

4.13 Falsework (1991) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-4-5

4.14 Allowable Stresses During Erection (1991) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-4-5

4.15 Drift or Traffic Pins (1991) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-4-6

4.16 Field Assembly of Members (1991) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-4-6

4.17 Fitting-up of Field Connections (1991) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-4-6

4.18 Riveted Field Connections (1991) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-4-7

4.19 High Strength Bolted Field Connections (1991) R(2008) . . . . . . . . . . . . . . . . . . . . . . . .

15-4-7

4.20 Field Welding (1991) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-4-7

4.21 Field Connections Using Pins (1991) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-4-7

4.22 Field Inspection (1991) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-4-7

4.23 Misfits (1991) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-4-8

4.24 Field Cleaning and Painting (2002) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-4-8

4.25 Deck (1991) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-4-8

4.26 Removal of Old Structure and Falsework, and Cleanup (1991) R(2008). . . . . . . . . . . .

15-4-9

4.27 Interference with Traffic (1983) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-4-9

4.28 Company Equipment (1983) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-4-9

4.29 Work Train Service (1983) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-4-10

4.30 Risk (1983) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-4-10

4.31 Laws and Permits (1983) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-4-10

4.32 Patents (1983) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-4-10

SECTION 4.1 GENERAL (1992) R(2008) These recommended practices establish general rules for the erection of railway bridges. For work of a special nature, or work to be done under unusual conditions, these recommended practices may be modified, or supplemented, to adapt them to special requirements. When applicable these general rules apply to contracted work or work to be done by Company forces.

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SECTION 4.2 DEFINITIONS OF TERMS (1992) R(2008) The term “Engineer” refers to the chief engineering officer of the Company or his subordinates in authority. The term “Inspector” refers to the inspector or inspectors representing the Company. The term “Company” refers to the railway company or railroad company party to the agreement. The term “Contractor” refers to the erection contractor party to the agreement.

SECTION 4.3 WORK TO BE DONE (2002) R(2008) The Contractor shall erect the metalwork including erecting and removal of special erecting devices and falsework as required and shall make all connections and adjustments, and do all the work required to complete the bridge superstructure, in accordance with the plans, special contract provisions, and these recommended practices, and as required by the terms of the contract.

SECTION 4.4 DRAWINGS OR SPECIAL PROVISIONS TO GOVERN (1992) R(2008) Where the drawings, special provisions and/or these recommended practices differ, the drawings, special provisions and these recommended practices shall govern in that order.

1

SECTION 4.5 PLANT (1992) R(2008)

3 The Contractor shall provide all tools, equipment, temporary connectors, special erecting devices, and erecting falsework as required for the expeditious handling of the work and for completion within the time specified.

4

SECTION 4.6 PLANS 4.6.1 STEEL STRUCTURE SUPPLIED BY COMPANY (2002) R(2008) a.

The Company will be responsible for furnishing, if available, the complete detail plans for the steel structure or structures to be erected, including shop drawings, shop details, camber diagrams, erection diagrams, match marking diagrams, list of field fasteners, and shipping statements showing a full list of parts and weights.

b. The Contractor shall prepare erection procedures and submit them for review and acceptance by the Company.

4.6.2 STEEL STRUCTURE FABRICATED BY CONTRACTOR (2002) R(2008) a.

The Company will be responsible for furnishing the design drawings and special provisions for the steel structure or structures to be fabricated and erected. © 2011, American Railway Engineering and Maintenance-of-Way Association

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b. The Contractor shall prepare shop drawings, shop details, camber diagrams, erection diagrams, match marking diagrams, list of field fasteners, erection procedures, and shipping statements showing a full list of parts and weights; and shall submit them for review and acceptance by the Company.

SECTION 4.7 DELIVERY OF MATERIALS (1992) R(2008) Where the contract indicates that materials are to be furnished by the Company, the Contractor shall receive all such materials at the place and under the terms specified in the contract documents.

SECTION 4.8 HANDLING AND STORING MATERIALS (1992) R(2008) a.

Where the contract requires unloading of the materials, the Contractor shall unload promptly on delivery. Demurrage charges, when unloading is delayed for reasons within the control of the Contractor, shall be his responsibility.

b. Stored material shall be piled securely at least 12 feet clear from the center line of the track. Material shall be placed on blocking, above the ground. It shall be kept clean and properly drained. Long members, such as columns, chords and girders, shall be supported on blocking placed close enough together to prevent injury from deflection. The Contractor shall check all material turned over to him against shipping lists and report promptly in writing any shortage or damage discovered. The Contractor will be held responsible for the loss of any material while in his care, or for any damage resulting from his work.

SECTION 4.9 ESTABLISHMENT OF LINES AND ELEVATIONS 4.9.1 SUBSTRUCTURE CONSTRUCTED BY COMPANY (2003) R(2008) The Company will be responsible for the construction of the substructure to correct lines and elevations, and for the establishment of the lines and elevations required by the Contractor for setting the steelwork.

4.9.2 SUBSTRUCTURE CONSTRUCTED BY CONTRACTOR (2003) R(2008) The Contractor shall be responsible for the construction of the substructure to correct lines and elevations, and for the establishment of the lines and elevations requred for setting the steelwork.

SECTION 4.10 BEARINGS AND ANCHORAGE (2002) R(2008) Refer to Part 10 and Part 11.

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SECTION 4.11 ERECTION PROCEDURE (1992) R(2008) a.

To assure the Company that erection will proceed in an orderly sequence and that it will be completed within the contract time, the Contractor shall advise the Engineer fully as to the procedure which will be followed and the amount and kind of equipment which he proposes to use. When required by the nature of the structure and so stipulated in the special provisions of the contract, erection procedure plans shall be prepared by the Contractor.

b. The Engineer will review the information and plans submitted in accordance with paragraph a, and his approval shall be obtained before field erection may be started. This approval shall not be considered as relieving the Contractor of his responsibility for the safety of the procedure and equipment, or from carrying out the work in compliance with the contract requirements.

SECTION 4.12 REINFORCEMENT OF MEMBERS (1992) R(2008) Where the approved erection procedure requires the reinforcement or modification of any members of the permanent structure, the Contractor shall make such arrangements as are necessary with the fabricator for having this done. Such reinforcement or modification shall be at the Contractor’s expense, and shall be subject to the approval of the Engineer. Such approval shall not relieve the Contractor from responsibility for avoiding damage or detrimental overstress in the permanent member of the structure at all times during erection.

1

SECTION 4.13 FALSEWORK (1991) R(2008) Where the approved erection procedure involves the use of falsework, the Contractor shall prepare and submit to the Engineer for review, plans for the falsework. The falsework shall be properly designed and substantially constructed for the loads to which it will be subjected. Review by the Engineer of the Contractor’s plans shall not be considered as relieving the Contractor of full responsibility.

4

SECTION 4.14 ALLOWABLE STRESSES DURING ERECTION (1991) R(2008) a.

During erection, members and connections subject to erection loads shall not be stressed to more than 1.25 times the basic allowable stress. When the erection loads are combined with wind loads, members and connections shall not be stressed to more than 1.33 times the basic allowable stress.

b. The allowable shear stress for drift or traffic pins in a fitted-up connection shall be 20,000 psi. c.

Fully torqued high-strength bolts and drift or traffic pins in the same connection plane may be considered as sharing the stress.

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Steel Structures

SECTION 4.15 DRIFT OR TRAFFIC PINS (1991) R(2008) a.

Drift or traffic pins (cylindrical body pins with tapered ends to facilitate driving) shall be used to line up the open holes in a connection. They shall have the same nominal diameter as that of the open hole into which they are driven.

b. Drift or traffic pins shall be of hardened steel with a minimum yield strength of 50,000 psi. c.

Drift or traffic pins shall not be driven to deform the material but only to line up the holes. High strength bolts or temporary fit-up bolts shall be used in combination with the pins to hold the plies of material together during the fit-up process.

SECTION 4.16 FIELD ASSEMBLY OF MEMBERS (1991) R(2008) a.

Members shall be accurately assembled as shown on the plans and carefully handled so that no parts will be bent, broken or otherwise damaged. Hammering which will injure or distort the members will not be permitted. Bearing surfaces and surfaces to be in permanent contact shall be cleaned just before the members are assembled as required by Section 4.24a.

b. Unless erected by the cantilever method, truss spans shall be erected on blocking or falsework so placed as to accommodate proper truss camber. c.

Beams and girders which are field spliced shall be erected on blocking, falsework, or held in the falls until sufficient holes in the splices can be made fair and have been fitted-up as required by Section 4.17.

SECTION 4.17 FITTING-UP OF FIELD CONNECTIONS (1991) R(2008) a.

The Contractor shall furnish the Company information showing the erection and/or erection plus erection wind forces in all members, and shall show his proposed provisions for withstanding these forces and procedure for fitting-up the connections.

b. All connections shall be accurately aligned by driving sufficient drift or traffic pins in a pattern to fair-up the holes. Light drifting will be permitted to effect this fairing-up of the holes, but heavy drifting which would deform the material shall not be permitted. Unfair holes may be reamed or drilled oversize and corresponding high strength bolts or rivets used in such holes, subject to review and approval by the Engineer. Sufficient fitting-up bolts shall be used with pins as necessary to bring the parts into contact and to stabilize the joint during alignment. c.

Following fairing-up of the holes, fitting-up of the connection shall be completed with fitting-up bolts and pins in a pattern suitable to hold the joint material together and to withstand calculated erection stresses until final bolting or riveting is accomplished.

d. Where plain A325 high strength bolts are used as the field connectors the same bolts may be used both for fitting-up and for final bolting. Where galvanized A325 high strength bolts or A490 high-strength bolts are used as the field connectors, the same bolts, if tightened to no more than snug-tight fitting-up, may be used for final bolting. Galvanized A325 high strength bolts and A490 bolts shall not be re-used after having been once fully tightened. © 2011, American Railway Engineering and Maintenance-of-Way Association

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e.

Snug-tight is the tightness attained by a few impacts of an impact wrench or the full effort of a man using an ordinary spud wrench.

SECTION 4.18 RIVETED FIELD CONNECTIONS (1991) R(2008) a.

Where rivets are used in field connections, they shall be driven with pneumatic riveting hammers, and when practical, shall be bucked with pneumatic buckers.

b. The requirements for the rivets, and for the general procedure of heating and driving, shall be as specified in Part 3, Fabrication, Article 3.2.1.

SECTION 4.19 HIGH STRENGTH BOLTED FIELD CONNECTIONS (1991) R(2008) a.

Where high strength bolts are used in field connections, they shall meet the requirements of Part 3, Fabrication, Article 3.2.2.

b. The installation procedure for permanent high strength bolts and for fully tightened high strength fitting-up bolts shall be as specified in Part 3, Fabrication, Article 3.2.3.

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SECTION 4.20 FIELD WELDING (1991) R(2008) Field welding, where permitted by the provisions of Part 1, Design, Article 1.5.10, shall be done in accordance with the provisions of Section 3.3.

SECTION 4.21 FIELD CONNECTIONS USING PINS (1991) R(2008)

4

Pins may be driven or jacked into place. Pin nuts shall be screwed tight, and the threads burred, unless another means of retaining the pin nut is specified.

SECTION 4.22 FIELD INSPECTION (1991) R(2008) a.

The work shall be subject at all times to inspection by the Engineer or the Inspector.

b. The requirements for inspection and procedures to be followed for each type of work shall be as specified in Section 3.5.

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SECTION 4.23 MISFITS (1991) R(2008) a.

The correction of non-repetitive minor misfits shall be done by the Contractor without additional compensation.

b. Any error in shop work which prevents the proper assembling and fitting up of parts by the moderate use of drift or traffic pins or a moderate amount of reaming and slight chipping or cutting, shall immediately be reported to the Inspector, and his approval of the method of correction obtained. The correction shall be made in the presence of the Inspector, who will check the time and material. Where material requiring correction is furnished by the Company, the Contractor shall render to the Company within 30 days an itemized bill for such work of correction for the approval of the Engineer.

SECTION 4.24 FIELD CLEANING AND PAINTING (2002) R(2008) a.

Unpainted field contact surfaces shall be thoroughly wire brushed to remove loose rust and loose mill scale, and any grease or shop paint on such surfaces shall be removed with proper solvents.

b. Where the rust-inhibiting coating on machined surfaces required by Part 3, Fabrication, Article 3.4.2a is of a type which must be removed prior to erection, such coating shall be removed immediately prior to field assembly of mating surfaces so that rust will not form. c.

The intermediate and finish coats of field paint shall be in accordance with the system selected and specified by the Engineer from Table 1 – General Painting Guide for Steel Structures of the Steel Structures Painting Council Manual, Vol. 2.

d. Steel work inaccessible after placing of deck shall be field painted before the deck is placed. e.

Weathering steels, ASTM A588, and A709 Grade 50W, Grade HPS 50W, and Grade HPS 70W, need not be field painted provided the field painting requirement is waived in the contract documents or is otherwise deleted by the Engineer.

SECTION 4.25 DECK (1991) R(2008) Where required by the special provisions and the terms of the contract, the ties, guard timbers, guard rails, fire decking, concrete decking, waterproofing, ballast, deck planking, track rails, and tie plates, and other specified deck appurtenances shall be placed and, when applicable, fastened by the Contractor in accordance with the plans, specifications, and special provisions furnished by the Company. Unless otherwise specified, all such material will be delivered by the Company to the Contractor. If treated timber is used, the Company will deliver it properly framed to the Contractor. Untreated ties shall be framed by the Contractor to give a full and even bearing on girders or stringers and under the rails. Where necessary to do any framing or cutting of treated timber, the resulting surfaces shall be treated with wood preservatives as directed by the Engineer.

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Erection

SECTION 4.26 REMOVAL OF OLD STRUCTURE AND FALSEWORK, AND CLEANUP (1991) R(2008) a.

Where required by special provisions and terms of the contract, the Contractor shall dismantle the old structure and either load the material on cars for shipment or pile it neatly at a site immediately adjacent to the tracks with clearance specified in Section 4.8b, and at an elevation convenient for future handling, as specified. Where the old structure is to be used again, it shall be dismantled without unnecessary damage and the parts match marked according to diagrams furnished by the Company.

b. Where the falsework is the property of the Company, the Contractor shall follow the same procedure as specified by paragraph a. c.

Where the falsework is the property of the Contractor, he shall dismantle it and remove it completely from the site.

d. The Contractor shall cut off piling at the surface of the ground, or at a lower elevation, or shall completely remove it as required by the special provisions and terms of the contract. e.

On completion of his work, the Contractor shall remove all debris and refuse from the site, and leave the premises in good condition.

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SECTION 4.27 INTERFERENCE WITH TRAFFIC (1983) R(2008) a.

The special provisions and terms of the contract will state definitely the procedures to be followed by the Contractor to minimize interference with the movement of trains where the structure is being erected under traffic.

b. The special provisions and terms of the contract will stipulate any special requirements which may apply to interference with water-borne traffic when the structure is erected over a navigable body of water. c.

3

The special provisions and terms of the contract will stipulate any special requirements which may apply to interference with vehicular or railroad traffic above or below the structure being erected.

4 SECTION 4.28 COMPANY EQUIPMENT (1983) R(2008) When the special provisions and terms of the contract provide that the Company will furnish equipment to the Contractor, such as flat cars, water cars, bunk cars, etc., the Contractor shall repair all damage to such equipment furnished for his use and return it in as good condition as when he received it, less normal wear and tear.

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SECTION 4.29 WORK TRAIN SERVICE (1983) R(2008) Where the special provision and terms of the contract provide that work train or engine service is furnished to the Contractor without charge, the Contractor shall state in his bid the number of days such service will be required. Any excess over the time specified in this bid shall be paid for by the Contractor at the Company’s schedule of rates.

SECTION 4.30 RISK (1983) R(2008) The Contractor shall be responsible for loss or damage to materials, for all damage to persons or property, and for casualties of every description caused by his operations during the progress of the work. Injuries or losses due to events beyond the control of the Contractor shall not be borne by him unless they occurred because he was dilatory in handling the work, with the result of extending the time beyond the limit designated in the contract.

SECTION 4.31 LAWS AND PERMITS (1983) R(2008) a.

Permits for the location and construction of the structure shall be obtained as directed by the Company.

b. The Contractor shall comply with Federal, State and local laws, regulations and ordinances, and shall obtain at his expense the necessary permits for his operations.

SECTION 4.32 PATENTS (1983) R(2008) The Contractor shall protect the Company against claims on account of patented technologies used by him on the work.

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Part 6 Movable Bridges1 — 2011 — FOREWORD

The purpose of this part is to supplement or modify preceding parts of this manual in order to formulate specific and detailed rules as a guide for the design, fabrication and erection of movable railway bridges. Part 1, Design, Part 3, Fabrication and Part 4, Erection are applicable to movable railway bridges except as modified by this part. References used in this part are found at the end of this chapter. See Reference 15, 31, 57, 58, 62, 63, 73, 74, 86, 109, 142, 143, and 147.

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TABLE OF CONTENTS Section/Article

Description

6.1 Proposals and General Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.1 General (1986) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.2 Abbreviations (1996) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.3 Time of Opening (1986) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.4 Machinery and Hydraulic Drawings (1996) R(2010). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.5 Machinery and Hydraulic Design (1997) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.6 Weight and Center of Gravity (1986) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.7 Houses (1986) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.8 Signals and Interlocking (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.9 Warning Lights (1986) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.10 Communication (1997) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.11 Wrenches (1986) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.12 Wiring Diagrams, Operator’s Instructions, Electrical, Hydraulic and Mechanical Data Manuals, and Lubrication Charts (2010) . . . . . . . . . . . . . . . . . . . . . . . . 6.1.13 Classification of Bridge Work (2003) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.14 Parts Included in Classes (2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.1.15 Optional Requirements (1986) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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References, Vol. 23, 1922, pp. 169, 1051; Vol. 36, 1935, pp. 632, 986; Vol. 51, 1950, pp. 445, 606; Vol. 52, 1951, pp. 447, 869; Vol. 53, 1952, pp. 522, 1064; Vol. 54, 1953, pp. 906, 1346; Vol. 57, 1956, pp. 555, 998; Vol. 62, 1961, pp. 548, 876; Vol. 63, 1962, pp. 383, 699; Vol. 65, 1964, pp. 383, 775; Vol. 66, 1965, pp. 292, 653; Vol. 67, 1966, pp. 342, 697; Vol. 70, 1969, p. 241; Vol. 75, 1974, p. 257; Vol. 78, 1977, p. 75; Vol. 79, 1978, p. 45; Vol. 81, 1980, p. 130; Vol. 84, 1983, p. 100; Vol. 86, 1985, p. 90; Vol. 87, 1986, p. 105; Vol. 88. 1987, p. 89; Vol. 92, 1991, p. 79; Vol. 93, 1992, p. 124; Vol. 94, p. 1; Vol. 97, p. 172. Reapproved with revisions 1996. See Part 9 Commentary

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TABLE OF CONTENTS (CONT) Section/Article

Description

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6.1.16 Guarantees (2003) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-6-13 6.2 General Features of Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.1 Material (1997) R(2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.2 Types of Bridges (1997) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.3 Counterweights (1997) R(2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.4 Aligning and Locking (1986) R(2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.5 Emergency Operation (1986) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.6 Standby Power (1986) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.7 Interlocking (1986) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.8 Insulation of Track (1986) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.9 Houses for Operators, Machinery, Hydraulic Equipment, Electrical Equipment and Signal Devices (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.10 Stairways, Walks, and Elevators (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.11 Materials for Machinery and Similar Parts (1993) R(2003) . . . . . . . . . . . . . . . . . . . . . . . 6.2.12 Rail Ends (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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6.3 Loads, Forces and Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.1 Live Load (1993) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.2 Impact Load (2003). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.3 End Ties (1983) R(2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.4 Fatigue (1983) R(2010). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.5 Wind Forces and Ice Load (2011). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.6 Power Requirements and Machinery Design (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.7 Machinery Resistances (1983) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.8 Machinery Losses (1983) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.9 Brakes, and Machinery Design for Braking Forces (2003) . . . . . . . . . . . . . . . . . . . . . . . . 6.3.10 Machinery Design (1983) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.11 Machinery Supports (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.12 Anchorage (1983) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.13 Special Provisions for Swing Bridges (1983) R(2002). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.14 Special Provisions for Bascule Bridges (1984) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.3.15 Special Provisions for Vertical Lift Bridges (2004) R(2010) . . . . . . . . . . . . . . . . . . . . . . .

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6.4 Basic Allowable Stresses and Hydraulic Pressures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.1 Structural Parts (1993) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.2 Machinery Parts (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.3 Bearing (1997) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.4 Heating and Seizing (1992) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.5 Line Bearing Load (1984) R(2003). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.6 Shafts (1984) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.7 Bolts in Tension (1984) R(2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.4.8 Hydraulic Systems and Components (1984) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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6.5 General Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5.1 Fits and Surface Finishes (1984) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5.2 Rail End Connections (1984) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5.3 Air Buffers (1997) R(2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.5.4 Counterweights (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Movable Bridges

TABLE OF CONTENTS (CONT) Section/Article 6.5.5 6.5.6 6.5.7 6.5.8 6.5.9 6.5.10 6.5.11 6.5.12 6.5.13 6.5.14 6.5.15 6.5.16 6.5.17 6.5.18 6.5.19 6.5.20 6.5.21 6.5.22 6.5.23 6.5.24 6.5.25 6.5.26 6.5.27 6.5.28 6.5.29 6.5.30 6.5.31 6.5.32 6.5.33 6.5.34 6.5.35 6.5.36 6.5.37

Description

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Concrete (1984) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Machinery in General (1984) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Journal Bearings (1984) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Linings (1984) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Step Bearings (1984) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Roller Bearings for Heavy Loads (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Roller and Ball Bearings (1997) R(2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Speed Reducers (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Lubrication (2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Shafts (1983) R(2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Shaft Couplings (1983) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Longitudinal Thrust (1983) R(2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Collars (1997) R(2003). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Gear Teeth (1983) R(2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Strength of Gear Teeth (1983) R(2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Worm Gearing (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Screw Gearing and Cams (1983). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hubs (1983) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Keys and Keyways for Machinery Parts (2003) R(2010). . . . . . . . . . . . . . . . . . . . . . . . . . . Keys for Trunnions (1983) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bolts and Nuts (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Set Screws (1997) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tapped Holes (1983) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Springs (1983) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Equalizers (1983) R(2002). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Covers (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Safety Devices (1983) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Drain Holes (1983) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Compressed Air Devices (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Special Provisions for Swing Bridges (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Special Provisions for Bascule Bridges (2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Special Provisions for Vertical Lift Bridges (1997) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hydraulic Systems (2000) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-6-35 15-6-36 15-6-36 15-6-36 15-6-37 15-6-37 15-6-37 15-6-37 15-6-38 15-6-39 15-6-40 15-6-40 15-6-40 15-6-41 15-6-41 15-6-43 15-6-43 15-6-43 15-6-43 15-6-44 15-6-44 15-6-46 15-6-46 15-6-46 15-6-46 15-6-46 15-6-46 15-6-46 15-6-46 15-6-47 15-6-49 15-6-50 15-6-53

6.6 Wire Ropes and Sockets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6.1 Manufacturer (1984) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6.2 Diameter of Rope (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6.3 Construction (2010). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6.4 Lay (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6.5 Lubrication During Fabrication (1983) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6.6 Splices (1983) R(2010). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6.7 Wire – Physical Properties (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6.8 Ultimate Strength (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6.9 Rejection (1985) R(2010). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6.10 Prestretching (1985) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6.11 Sockets (1985) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6.12 Facilities for Testing (1985) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6.13 Rope Length (1985) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.6.14 Operating Ropes (1985) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Steel Structures

TABLE OF CONTENTS (CONT) Section/Article

Description

Page

6.6.15 Shipping (1985) R(2010). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-6-74 6.7 Power Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7.1 Power Operation (1984) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7.2 Manpower Operation (1984) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7.3 Machines (1984) R(2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7.4 Internal Combustion (1997) R(2002). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7.5 Electric (1997) R(2003). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7.6 Brakes for Span Operation (1983) R(2002). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7.7 Air Brakes (1997) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7.8 Hand Brakes and Foot Brakes (1983) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.7.9 Audible Navigation Signals (1983) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-6-75 15-6-75 15-6-75 15-6-75 15-6-75 15-6-77 15-6-98 15-6-98 15-6-99 15-6-99

6.8 Workmanship . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8.1 Machinery Manufacture in General (1983) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8.2 Racks (1983) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8.3 Shafts (1983) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8.4 Journals (1983) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8.5 Linings (1983) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8.6 Bearings (1983) R(2010). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8.7 Couplings (1983) R(2010). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8.8 Hubs (1983) R(2010). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8.9 Gears and Pinions (1983) R(2010). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8.10 Bevel Gears (1983) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8.11 Machine Molding (2003) R(2010). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8.12 Worms and Worm Wheels (1983) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8.13 Keys and Keyways (1983) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8.14 Bolts and Holes (1996) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8.15 Assembling Machinery in Frames (1983) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8.16 Balancing of Gears (1983) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8.17 Assembling Machinery on Structural Supports (2003) R(2010) . . . . . . . . . . . . . . . . . . . . 6.8.18 Grooves in Journals and Linings (1983) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8.19 Air Buffers (1983) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8.20 Special Provisions for Swing Bridges (2003) R(2010). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8.21 Special Provisions for Bascule Bridges (2003) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.8.22 Special Provisions for Vertical Lift Bridges (1983) R(2010) . . . . . . . . . . . . . . . . . . . . . . .

15-6-99 15-6-99 15-6-100 15-6-100 15-6-100 15-6-100 15-6-101 15-6-101 15-6-101 15-6-101 15-6-101 15-6-101 15-6-101 15-6-101 15-6-101 15-6-102 15-6-102 15-6-102 15-6-102 15-6-102 15-6-102 15-6-103 15-6-104

6.9 Erection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.9.1 Erection of Machinery (1996) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.9.2 Erection of Trunnion Bearings and Counterweight Sheave Bearings (1983) R(2010) . . 6.9.3 Protection of Parts (1983) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.9.4 Lubrication (2008) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.9.5 Erection of Wire Ropes (1983) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.9.6 Painting (1983) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.9.7 Counterweights (1983) R(2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.9.8 End Lifting Devices for Swing Spans (1983) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.9.9 Channel Lights (1983) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.9.10 Testing (1983) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.9.11 Bridge Operator (1983). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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LIST OF TABLES Table 15-6-1 15-6-2 15-6-3 15-6-4 15-6-5 15-6-6

Description Machinery Resistances. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Allowable Machinery Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Trunnion Bending Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Roller Maximum Bearing Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Surface Finishes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Torque Ratio. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Page 15-6-21 15-6-28 15-6-29 15-6-31 15-6-34 15-6-75

SECTION 6.1 PROPOSALS AND GENERAL REQUIREMENTS 6.1.1 GENERAL (1986)1 R(2010) a.

The structural, mechanical, hydraulic and electrical design will be furnished by the Company, unless it is stated in the invitation for bids that such designs, or specified portions of them, are to be furnished by the Contractor,

b. The Company will furnish, with its invitation for bids, a copy of the contract form together with site plans and a full description of the requirements for the structure. These requirements will make clear the division of responsibility between Company and Contractor for designing, furnishing and erecting or installing all components of the structure, and will specify or describe all of such components which are the responsibility of or affect the work of the Contractor, c.

The Contractor shall furnish and erect the structure ready for operation and to receive trains, except for such components as are specified to be furnished and/or installed by the Company.

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3

d. All shop drawings, assembly drawings and other papers prepared for the purpose of meeting the governing conditions and specifications of the contract shall be subject to the approval of the Engineer.

6.1.2 ABBREVIATIONS (1996) R(2010) a.

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4

The following abbreviations are used herein: AAR

Association of American Railroads

ABMA

American Bearing Manufacturers Association

AGMA

American Gear Manufacturers Association

AISE

Association of Iron and Steel Engineers

AISI

American Iron and Steel Institute

ANSI

American National Standards Institute

ASME

American Society of Mechanical Engineers

ASTM

American Society for Testing and Materials

AWG

American Wire Gage

See Part 9 Commentary

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

15-6-5

Steel Structures

IEEE

Institute of Electrical and Electronics Engineers

IPCEA

Insulated Power Cable Engineers Association

NEC

National Electrical Code

NEMA

National Electrical Manufacturers Association

NFPA

National Fluid Power Association

SAE

Society of Automotive Engineers

b. The National Fire Protection Association shall be referenced herein by full name only.

6.1.3 TIME OF OPENING (1986) R(2010) The time required for opening the bridge after the ends are released will be specified on the Plans for both normal and emergency operations. The times assumed for acceleration and deceleration will be given on the Plans with a cautionary note that shorter times, particularly during braking, may seriously overstress elements in the drive train.

6.1.4 MACHINERY AND HYDRAULIC DRAWINGS (1996) R(2010) a.

The Contractor shall make an assembly drawing and detail drawings of the machinery. These drawings shall be sufficiently complete that the machinery parts may be duplicated without reference to patterns, other drawings, or individual shop practice.

b. The Contractor shall make hydraulic control circuit and piping diagrams, hydraulic power unit layouts, and all assembly and detail drawings including the electrical schematic wiring diagrams and conduit diagrams that are needed for the complete hydraulic system. The drawings shall be so complete that the hydraulic components can be replaced without having the original stock numbers of the equipment. The drawings shall also conform to the requirements of the ANSI (NFPA/JIC) T2.24.1 Section 6.3 Standards. c.

The Contractor shall make a drawing or chart showing all bearings, electrical equipment, and other elements of the bridge which require lubrication, and designating the lubricants to be used and the frequency of lubrication. Framed, sealed copies of the lubrication drawing shall be mounted in appropriate places on the bridge.

6.1.5 MACHINERY AND HYDRAULIC DESIGN (1997) R(2010) a.

Where the machinery design is prepared by the Contractor, he shall furnish complete calculations for all parts of the machinery. The calculations shall include the operating shaft torques for all pump drive motors and drive engines, hydraulic motors and rotary actuators and rod forces for hydraulic cylinders and intensifiers along with hydraulic system pressures. Calculations shall be for the following conditions: (1) Acceleration and for retardation. (2) Frictional resistance. (3) Any unbalanced condition of the bridge. (4) Wind loads.

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(5) The greatest resultant combinations of resistances acting at one time under the various design conditions herein specified. The torque for starting friction shall not be combined with the torque for acceleration. b. Where operation is by electric motor, these calculations shall consider the speed-torque characteristics of the system to be provided. The rated full-load torque and the maximum starting torque of the motor, including the effect of its control system, shall be considered. The overload relay setting shall be provided for operation of the span under Conditions A, B and C of Article 6.3.6. The speed-torque curves shall be shown on the drawings.

6.1.6 WEIGHT AND CENTER OF GRAVITY (1986) R(2010) The Contractor shall determine the weight and the location of the center of gravity of the moving span, including parts attached thereto; also of the counter-weights, including their framework. These determinations shall be based on accurate weights computed from shop plans. The computations, accompanied by the weight bills, shall be submitted to the Company in form for review.

6.1.7 HOUSES (1986) R(2010) The Contractor shall furnish and build the machinery house or houses. The house or houses for the operator, the hydraulic equipment, the electrical equipment and the signal devices shall be built by the Contractor unless otherwise specified.

1

6.1.8 SIGNALS AND INTERLOCKING (2003) a.

Unless otherwise specified, the Company will furnish and install the railway signal system, including the master control and the devices necessary for interlocking the signal system with the moving span. The Contractor shall furnish and install the devices necessary for interlocking the parts of the bridge machinery with each other and for connection to the master control. The operating machinery and the hydraulic and electrical parts shall be so designed that the signal system may readily be installed and attached.

3

b. Rail locks shall be used on movable bridges when specified by the Company or where required by law or safety regulations. They shall be so designed that they cannot be locked closed with the rails more than 1/4 inch out of correct alignment. c.

When rail locks are not used, rail detectors shall be provided. There shall be a rail detector for each running rail, actuated directly by the rail, which will automatically set all signals to stop rail traffic whenever any rail is more than 1/4 inch out of correct alignment.

d. Shoes for aligning the rails shall be provided.

6.1.9 WARNING LIGHTS (1986) R(2010) The Contractor shall furnish and install (including wiring) on the moving span and piers, navigation lights and other signals or markings required by the United States Government or other authorities, and shall provide suitable means of access to such lights and signals.

6.1.10 COMMUNICATION (1997) R(2010) a.

Telephones shall be provided for communication between all points where routine maintenance or adjustment of the mechanical, hydraulic or electrical components is required. There shall be a

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permanent station at or near the control console, each panelboard, and each set of span operating machinery. There shall also be jack boxes at or near each span lock, rail lock, wedge drive, and submarine cable terminal cabinet, and at or near any other location where communication would simplify maintenance and adjustment. Three headsets with plug-in jacks shall be furnished at locations specified. A ringing system shall be provided at the permanent stations where specified by the Company. b. As an alternative to a telephone system, three sets of two-way radios may be provided. The sets shall be capable of operating satisfactorily from all locations outlined in paragraph a above. The sets shall be the same as used by the Company for railroad operations, but shall operate at a different frequency.

6.1.11 WRENCHES (1986) R(2010) Two sets of wrenches to fit heads and nuts of all bolts for the machinery and hydraulic equipment shall be furnished by the Contractor, together with a suitable work bench, machinist’s vise, pipe vise, and suitable wall racks for the storage of equipment and spare parts.

6.1.12 WIRING DIAGRAMS, OPERATOR’S INSTRUCTIONS, ELECTRICAL, HYDRAULIC AND MECHANICAL DATA MANUALS, AND LUBRICATION CHARTS (2010) a.

The Contractor shall furnish six bound copies of a manual containing descriptive leaflets and drawings covering all items of the electrical equipment, with catalog numbers indicated; printed or typewritten statements prepared by the manufacturers of the equipment covering the proper methods of adjusting, lubricating, and otherwise maintaining each item; speed-torque-current curves for the span-operating motors for each point of control; a concise statement of the necessary operating functions in proper sequence; a detailed description of the functions of each item in connection with the various operating paragraphs; reduced reproduced copies of all wiring and conduit diagrams and of all drawings of the control console and switchboards; and a list of spare parts furnished. The manual shall contain a table of contents and shall designate each wire and item of equipment by means of numbers on the wiring diagrams.

b. The Contractor shall also furnish six bound copies of a similar manual for the mechanical equipment, which shall include lubricating charts showing the locations of all lubricating fittings and other points of lubrication, in accordance with Article 6.1.4c. c.

The Contractor shall also furnish six bound copies of a similar manual for the hydraulic equipment. The manual shall provide the purchaser with maintenance data for all hydraulic equipment that clearly: (1) Describes start-up and shut down procedures where improper procedures could cause damage to the equipment. (2) Describes adjustment procedures. (3) Indicates external lubrication points and the type of lubricant required. (4) Identifies equipment parts by name and/or number. (5) Identifies seals and packing by the component manufacturer’s part number. (6) States service procedures for unique assemblies. (7) Locates fluid level indicators, fillpoints, drains, filters, strainers, magnets, etc. that require regularly scheduled maintenance.

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(8) Lists the model and serial number of each special cylinder or rotary actuator. This information shall also appear on the graphical (circuit) diagram. Where parts in the hydraulic components are commerically available and manufactured to an established standard that provides for uniform coding, further identification as provided by the standard’s code should be given.

6.1.13 CLASSIFICATION OF BRIDGE WORK (2003) R(2010) a.

Bridge work shall be classified as follows and, unless otherwise stipulated, paid for as indicated: • Class 1. Structural steel, by the lb. • Class 2. Machinery, lump sum. • Class 3. Counterweight sheaves, shafts, and bearings, lump sum. • Class 4. Trunnions and their bearings, lump sum. • Class 5. Tread plates and castings, by the lb. • Class 6. Wire ropes and sockets, by the lb. • Class 7. Balancing chains, by the lb. • Class 8. Metal in counterweights, by the lb. • Class 9. Concrete in counterweights, by the cu. yd.

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• Class 10. Reinforcing steel, by the lb. • Class 11. Internal combustion engines and tanks, lump sum. • Class 12. Electrical equipment, lump sum.

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• Class 13. Hydraulic equipment, lump sum. • Class 14. Houses for operators, machinery, electrical equipment, hydraulic equipment, and signal devices, lump sum. • Class 15. Railway deck and track, by the linear foot of full-width deck. • Class 16. Miscellaneous lumber, by the thousand foot board measure.

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• Class 17. Communication facilities, lump sum. • Class 18. Elevators, lump sum. • Class 19. Removals, lump sum. • Class 20. Salvage credits, lump sum. • Class 21. Concrete-Structural, by the cubic yard. • Class 22. Pier Protection System, lump sum. • Class 23. Items not classified in the foregoing. b. Payment quantities shall be determined as follows: • Class 1, by the provisions of Part 3, Fabrication, Article 3.6.3.

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• Classes 5 through 8, by scale weight; except that for Class 5, scale weight in excess of 5% above the computed weight shall not be included. • Class 10, by the computed weight of the plain or deformed bars of the specified sizes. • Classes 9, 16 and 21 by the Engineer’s measurement.

6.1.14 PARTS INCLUDED IN CLASSES (2008) Parts included in the various classes shall be as follows. 6.1.14.1 Class 1, Structural Steel a.

In addition to the moving span, any parts of rolled, forged, or cast steel which can be fabricated by the common shop methods of punching, reaming, drilling, boring, shearing, planing, bending, welding, etc., usual for stationary structures, except structural steel parts which function as machinery parts which shall be classified under the appropriate machinery items.

b. The following shall be classified as structural steel: rim girders in swing bridges, segmental girders in rolling bascule bridges and the girders on which they roll, parts supporting the machinery, machinery housing, counterweight frames, counterweight trusses, counterweight boxes, operating struts, rope attachment brackets or hangers, towers, steel framing and plates in houses and in elevator hoistways, handrails, stairways and ladders, and steel ties. 6.1.14.2 Class 2, Machinery Includes the following: Axles Bars Bearings Bells Brakes (unless part of electrical equipment) Bridge locks Buffers Cables and wires (non-electrical) for push-pull devices Cams Capstans Center-pivot stands Couplings Cranks

Deflector castings and plates Disks Eccentrics Gears Gear covers and guards Hooks Indicators Levers Lockbars Lubrication devices Pipes Pistons and their cylinders Pivots Racks Screws

Shafts Sheaves (except counterweight sheaves) Shims Speed reducers Spools Toggles Wedges Wedge bases Wedge Guides Wheels Whistles Winding drums Worm gearings Wrenches

6.1.14.3 Class 3, Counterweight Sheaves, Shafts, and Bearings Cast or fabricated sheaves, along with their shafts, bearings, shims and connecting bolts. 6.1.14.4 Class 4, Trunnions and their Bearings Trunnions for moving leaves and counterweights of bascule bridges, together with their bearings, sleeves, supporting pedestals, and connecting bolts. © 2011, American Railway Engineering and Maintenance-of-Way Association

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Movable Bridges 6.1.14.5 Class 5, Tread Plates and Castings Tread plates and castings for segmental girders, and track girders for rolling-lift bridges, along with their shims and connecting bolts. 6.1.14.6 Class 6, Wire Ropes and Sockets Wire ropes and their sockets, shims, attachments, and socket pins. 6.1.14.7 Class 7, Balancing Chains Chains and their fastenings used for balancing the counterweight ropes. 6.1.14.8 Class 8, Metal in Counterweights Cast iron used as counterweights; along with scrap metal or steel punchings used to increase the unit weight of counterweight concrete. 6.1.14.9 Class 9, Concrete in Counterweights Concrete or mortar used in counterweights, including concrete balance blocks, and concrete in pockets of column bases and similar places. No deductions shall be made for embedded reinforcing steel, drain pipes, scrap metal, or steel punchings.

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6.1.14.10 Class 10, Reinforcing Steel All reinforcing bars and mesh for concrete. Unless otherwise provided, no direct payment will be made for clips, spacers, ties, chairs, or other fastenings and supports for reinforcing steel, but their cost shall be included in the price per lb paid for reinforcing steel. 6.1.14.11 Class 11, Internal Combustion Engines and Tanks

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Internal combustion engines with tanks, compressors, starters, and interrelated piping to and including the clutch shaft, but not the clutch for delivery of power, and to but not including the valve for delivery of air, and not including such engines used as prime movers for standby electric power. 6.1.14.12 Class 12, Electrical Equipment

4 a.

High-voltage equipment and transformers as specified, the switchboard and control console with their attachments, and electrical parts beyond (whether on or off the moving span), such as motors, gearmotors, controllers, resistances, electric brakes, solenoids, circuit breakers, fuses, relays, contactors, switches, electric indicators, synchronizing and leveling equipment, limit switches, blow-outs, cut-offs, meters, trolley poles, trolley wheels and contact shoes, service and indicating lights, navigation lights and signals, electric heaters, conductors, wiring, submarine, aerial and other cables, and conduits and their fittings, as specified for the operation of the moving span and accessories, and the lighting and comfort conditioning of the houses; and engine-generators for the purpose of standby electric power.

b. Unless otherwise noted in the invitation to bid, this item and this contract shall include no parts or appurtenances of the signal interlocking system, except that the control panel and control console shall be of ample size to accommodate the interlocking equipment as specified by the Engineer.

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All hydraulic equipment, including hydraulic fluid and portable filtration units used during reservoir filling, necessary to provide the operating system specified, whether directly or indirectly associated with the system, shall be considered as a part of this work.

b. Hydraulic equipment shall also include mechanical and electrical equipment normally mounted on the power unit such as electric motors, couplings, coupling guards, and accessories such as pressure, temperature and fluid level switches, immersion heaters and gages. c.

All hydraulic hoses, piping, fittings, attachments, and their supports (not including structural steel paid elsewhere) are included in this class.

6.1.14.14 Class 14, Houses for Operators, Machinery, Hydraulic Equipment, Electrical Equipment and Signal Devices All parts of such houses, except steel framing and plating if any; all furniture, heaters other than electric, cranes, fire extinguishers supplies and similar items, as specified in the invitation to bid. 6.1.14.15 Class 15, Railway Deck and Track a.

The complete timber deck, footwalks at deck level, and permanent track with all permanent fastenings in place, but not specially fabricated track rails, special rail joints and rail locks; and sheet metal or other track coverings and fire stops.

b. Unless otherwise specified in the invitation to bid, the Company will furnish all of these materials and their fastenings f.o.b. the bridge site, ready for installation, and the Contractor shall unload, place and fasten these materials and their fastenings for the unit price per linear foot under this class. c.

When specified in the invitation to bid, the Contractor shall furnish to the Company the distribution of charges for material and construction covered by this item in accordance with Interstate Commerce Commission requirements.

6.1.14.16 Class 16, Miscellaneous Lumber Any lumber not allocated to another class by the foregoing definitions, along with nails, bolts and other fastenings. Measurement of lumber shall be based on nominal sizes. 6.1.14.17 Class 17, Communication Facilities Radio, telephone and any other communication facilities, including wiring therefor. 6.1.14.18 Class 18, Elevators The complete elevator system including cars, gates, motors and other operating machinery, guide rails and shoes, counterweights, buffers, hoisting cables, governors or other speed control devices and wiring. 6.1.14.19 Class 19, Removals All parts of the existing structure required to be removed. 6.1.14.20 Class 20, Salvage Credits The value of any components becoming the property of the contractor. © 2011, American Railway Engineering and Maintenance-of-Way Association

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6.1.15 OPTIONAL REQUIREMENTS (1986) R(2010) Wherever optional requirements are stated, the determination will be made by the Engineer, and will be indicated in the invitation to bid if bidders are to prepare plans or on the plans prepared by the Company which accompany the invitation to bid.

6.1.16 GUARANTEES (2003) R(2010) 6.1.16.1 Defects If any defects due to faulty workmanship or erection, or defective material, or design for which the Contractor is responsible, are found within one year after the date of final acceptance of the structure, the Contractor shall remedy such defects at his own expense. The Company will notify the Contractor, in writing, of any defects. If the Contractor does not remedy such defects within 15 days, the Company may remedy same at the Contractor’s expense. 6.1.16.2 Machinery, Etc. Machinery, hydraulic and electrical or other similar equipment which are the usual manufactured types such as diesel engines, electric motors, speed reducers, electrical apparatus, etc., shall be tested for the specified requirements to the satisfaction of the Engineer, and shall be fully guaranteed by the Contractor to fulfill these requirements for one year from date of final acceptance of the structure. If the manufacturer of any item normally provides a warranty in excess of one year, such warranty shall be assigned to the Company.

1 SECTION 6.2 GENERAL FEATURES OF DESIGN 6.2.1 MATERIAL (1997) R(2004) a.

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Structural materials used for machinery parts or assemblies shall meet the requirements of Part 1, Design, Article 1.2.1.

b. The materials used in machinery and similar parts, as described in Article 6.2.11, shall conform to the requirements of the ASTM Specifications current at the time proposals for the work are received.

4 Structural Steel . . . . . . . . . . . . . . . . . . . A 36 or A 709, Grade 36 Rolled Steel . . . . . . . . . . . . . . . . . . . . . . A 675, Grade 75 Cast Steel . . . . . . . . . . . . . . . . . . . . . . . . A 27, Grade 65-35 Forged Carbon Steel . . . . . . . . . . . . . . . A 668, Class D Forged Alloy Steel . . . . . . . . . . . . . . . . . A 668, Class G Forged Hardened Steel . . . . . . . . . . . . . A 668, Class F Cast Iron . . . . . . . . . . . . . . . . . . . . . . . . A 48, Class 25 Bronze . . . . . . . . . . . . . . . . . . . . . . . . . . B 22 Babbitt Metal. . . . . . . . . . . . . . . . . . . . . B 23, Grade No. 2 Bolts . . . . . . . . . . . . . . . . . . . . . . . . . . . . A 307, Grade A High Strength Bolts . . . . . . . . . . . . . . . A 449

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High Strength Studs . . . . . . . . . . . . . . . . A 449 c.

The above specifications show the minimum quality that shall be used for stress-carrying machinery parts, and the appropriate basic allowable stresses therefor are specified in Article 6.4.2. Any other material of the strength and durability required for its intended use may be used by the Company.

d. Where the testing of materials, in addition to those tests required by the ASTM Specifications, is considered necessary by the Engineer, such additional tests will be specified by the Company.

6.2.2 TYPES OF BRIDGES (1997) R(2002) a.

Movable bridges preferably shall be of the following types: (1) Swing. (2) Single leaf bascule. (3) Vertical lift.

b. Pin-connected trusses shall not be used.

6.2.3 COUNTERWEIGHTS (1997) R(2003) a.

As nearly as practicable the counterweights shall be sufficient to balance the movable span and its attachments in any position, except that there shall be small positive reactions at the supports when the bridge is seated. For vertical lift bridges having a vertical movement exceeding 40 feet, the counterweight ropes preferably shall be balanced by auxiliary counterweights or other devices unless specified. Rope unbalance shall be considered when sizing the operating machinery.

b. Provision shall be made for unbalanced conditions in the design of the machinery and the power equipment. c.

Provision shall be made for independent supports for the counterweights of vertical lift bridges, for the purpose of replacing counterweight ropes.

6.2.4 ALIGNING AND LOCKING (1986) R(2004) a.

Movable bridges shall be equipped with suitable mechanisms to surface and align the bridge and track accurately and to fasten them securely in position so that they cannot be displaced either horizontally or vertically under the action of traffic. Effective end wedges shall be used for swing bridges, and span locks for bascule and vertical lift bridges.

b. Span locks on movable bridges shall be designed so that locking cannot be initiated unless the movable parts are within 1/2 inch of proper alignment. c.

The operating mechanisms of end lifts and rail locks shall be independent.

d. The installation shall meet the applicable requirements of the Office of Safety, the Federal Railroad Administration, the U.S. Department of Transportation. e.

For swing, bascule and vertical lift bridges normally left in the open position, span locks shall be provided to hold the span in the fully opened position.

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6.2.5 EMERGENCY OPERATION (1986) R(2002) a.

Power-operated bridges shall be provided with a means of emergency operation in the event of failure of the normal drive or its controls. The prime mover for emergency operation may be an electric motor, internal-combustion engine, air motor, or manual drive, as specified by the Company. Where electric motors are used, emergency motors and their associated motor control equipment shall be provided, independent of those components used for normal operation.

b. Emergency operation of auxiliary devices such as span locks, rail locks and derails should preferably be manual.

6.2.6 STANDBY POWER (1986) R(2002) When the regular power source for electric operation of a movable bridge is not reliable, standby electric power shall be provided either from an independent primary source or from an engine-generator set. Where emergency operation of the movable span is by internal combustion engine, air motor, or manual drive, standby electric power need not be provided except as necessary for the operation of navigation and other warning signals.

6.2.7 INTERLOCKING (1986) R(2002) The bridge operating devices shall permit interlocking with the signal system and shall be so designed that Communication and Signal Division, AAR, interlocking apparatus may be used. They shall be so interlocked with each other that the operations, both for opening and closing the bridge, must be performed in the predetermined order, and so that the movable span, tracks, and switches within interlocking limits are locked in proper position.

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6.2.8 INSULATION OF TRACK (1986) R(2002) The connections of parts in contact with the track shall be such as to prevent all possibility of short circuiting of signal or other circuits.

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6.2.9 HOUSES FOR OPERATORS, MACHINERY, HYDRAULIC EQUIPMENT, ELECTRICAL EQUIPMENT AND SIGNAL DEVICES (2003) a.

Where mechanical or hydraulic power is to be used for operating the bridge, houses shall be provided for the operators, machinery, hydraulic equipment, electrical equipment including engine-generator sets, and signal devices. Houses shall be large enough for easy access to all machinery and apparatus to facilitate inspection, maintenance and repair. Houses shall be weather-tight and shall be constructed of non-combustible materials, Machinery rooms and rooms containing electrical apparatus and hydraulic equipment shall preferably be heated to maintain the temperature above 50 degrees F. Where climatic conditions warrant, the operator’s room shall be heated to maintain winter temperature above 70 degrees F and shall be air-conditioned to maintain summer temperature below 80 degrees F. Provision shall be made for the comfort conditioning system to be installed in the operator’s house by the Company or by the Contractor, as may be specified. All windows shall be glazed with safety glass and movable sash shall be screened. At least one opening shall be provided to permit passage of the largest unit of machinery or apparatus. Housing floors shall be of concrete, steel, or other non-combustible material, as specified. Floors shall be smoke-tight and have a non-slip surface. Floors in operator’s houses shall be insulated if exposed to the weather. Floors in rooms containing electrical equipment, such as control panels and control consoles, shall be covered with linoleum, asphalt tile, or rubber mats on areas surrounding such electrical equipment. Houses shall be designed and constructed so as to prevent undesirable vibration or deflection due to machinery loads or live loads.

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b. Where the bridge is hand-operated, or where the operator is not located in the machinery house, an operator’s house shall be provided. The type of construction shall be the same as that specified for the machinery house, except that for hand-operated bridges with the house located off the bridge structure, non-combustible construction will not be required. c.

Where practicable, the operator’s house shall be located so as to afford a clear view of operations on the railway and on the waterway. If such positioning is not practical, the system shall provide for closedcircuit television or other means to visually monitor these operations.

d. Where specified, a hand-operated overhead traveling crane, of sufficient capacity for handling the heaviest piece of machinery, shall be installed in the machinery house.

6.2.10 STAIRWAYS, WALKS, AND ELEVATORS (2003) a.

Stairways, platforms, and walks with railings shall be provided to give safe access to the operator’s house, machinery, trunnions, counterweights, navigation lights, bridge seats, and all points requiring lubrication or electrical maintenance. Ladders may be installed only where stairways are not feasible, and shall be provided with appropriate fall protection. For vertical lift bridges, ladders and walks shall be installed to give access to the moving span in any position from either tower. Hand railings shall be made of galvanized copper-bearing steel, or rust resistant metal pipe not less than l-1/2 inches size, or of structural shapes. Stairways, platforms and walks shall be of metal or concrete. Ladders shall be of metal. Stairway treads may be channels filled with concrete.

b. An elevator shall be provided at each tower of vertical lift bridges for all tower drive bridges and for span drive bridges where service platforms are 50 feet or more above track level. Elevators shall be capable of carrying personnel and maintenance equipment from track level to the machinery level at the tops of the towers. The elevator cars shall be fully enclosed with solid sides and roof. They shall have a net floor area of not less than 12 square feet and a capacity of not less than 1,200 lb. c.

Elevators shall be power operated, with single automatic control permitting the car to be called from a station at any landing and sent to any landing from the car station.

d. Elevators shall meet the requirements for passenger elevators of the ANSI Safety Code for Elevators, Escalators and Dumbwaiters, and of the applicable local codes.

6.2.11 MATERIALS FOR MACHINERY AND SIMILAR PARTS (1993) R(2003) Materials in machinery and similar parts shall be as follows; 6.2.11.1 Rolled Steel or Forged Steel a.

For trunnions, shafts, axles, bolts, nuts, keys, cotters, pins, screws, worms, piston rods, equalizing levers, and crane hooks.

b. Trunnions, shafts and axles up to 6 inches diameter may be either rolled or forged; those of larger diameter shall be forged. Shafts larger than 3-1/2 inches diameter shall not be cold finished. 6.2.11.2 Rolled Steel, Forged Steel, or Cast Steel For rim, segmental, and track girder treads and rollers. 6.2.11.3 Forged Steel or Cast Steel For levers, cranks, and connecting rods.

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Movable Bridges 6.2.11.4 Forged Steel For pinions and rope attachments. 6.2.11.5 Cast Steel For pivot stands, couplings, wedges, wedge bearings, toggles, trailing wheels, end shoes, pedestals, pistons and their cylinders, buffers, eccentrics, valves, spools, winding drums, racks, tracks, gears, brake wheels, clutches, lock castings, trunnion bearings, shaft bearings and hangers, and sheaves for vertical lift bridges. 6.2.11.6 Hardened Steel For parts which require hardening or oil tempering, such as pivots, friction rollers, ball and roller bearings, and springs. 6.2.11.7 Bronze For pivot disks, worm wheels, linings of the trunnion bearings of bascule and vertical lift bridges, linings of other large bearings carrying heavy loads, linings for wedges for swing spans and such gears and nuts as are required to be of bronze. 6.2.11.8 Bronze or Babbitt Metal For the linings of journal bearings and of other rotating or sliding parts. 6.2.11.9 Weldments Welded assemblies of structural steel or of structural steel and cast or forged steel may be employed instead of cast steel for such parts as may be specified in the invitation or approved by the Engineer. Such weldments shall conform to the requirements for welded construction included under Part 1, Design and Part 3, Fabrication of these recommended practices. Where such weldments are used as components of the moving machinery, they shall be stress-relieved before machining. 6.2.11.10 Cast Iron

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3

Cast iron may be used only for the parts of motors, engines and standard manufactured components that are usually made of cast iron, for balance chains on vertical lift bridges, and for counterweights.

6.2.12 RAIL ENDS (2003) a.

Rails at the ends of movable spans shall be either mitered or cut square.

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b. Where rail ends are cut square, they shall be connected by sliding sleeve or joint bars or by easer rails to carry the wheels over the opening between the ends of the bridge and approach rails. c.

Where rail ends are mitered, they shall be provided with seats that will secure them against transverse displacement, and with devices that will bring the mitered surfaces nearly into contact and hold them in such position. Mitered rails shall retain the full thickness of the web to the points. The points shall be trailing to normal traffic where possible; otherwise they shall be trailing to traffic entering the moving span.

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SECTION 6.3 LOADS, FORCES AND STRESSES 6.3.1 LIVE LOAD (1993) R(2010) The live load shall be as specified in Part 1, Design, Article 1.3.3, and for continuous spans as further specified in Part 1, Design, Article 1.13.2c.

6.3.2 IMPACT LOAD (2003) a.

Except as modified in this Article, the impact load shall be as specified in Part 1, Design, Article 1.3.5, and for continuous spans as further specified in Part 1, Design, Article 1.13.5.

b. Dead load stresses in structural parts which support dead loads during movement of the span shall be increased 20% to allow for impact or vibratory effect. Such parts include, but may not be limited to, swing span trusses or girders, vertical lift bridge trusses or girders, vertical lift bridge towers, bascule span trusses and girders, and supports for bascule trunnions and rolling lift span track girders. This impact allowance shall not be combined with live load stresses. c.

Stresses in structural parts caused by machinery or by loads applied for moving or stopping the span shall be increased 100% as an allowance for impact load.

d. The end floorbeams of the moving span and the adjacent floorbeams of the fixed spans shall be proportioned for a concentrated load on each track of 1.25 times the maximum weight on one axle of the specified live load, without impact load, in addition to the specified live load and impact load. e.

Allowance has been made for impact load in trunnions, wire ropes, wire rope attachments, and machinery parts in the basic allowable stresses specified herein for such parts.

6.3.3 END T IES (1983) R(2003) The ties which support the rail joint shoes at the ends of the moving span and at the adjacent ends of the fixed spans shall be supported throughout their length, so that they will not be subjected to bending. The supports for these ties, if other than end floorbeams, shall be proportioned for a concentrated total live load plus impact load on each track of 2.75 times the heaviest axle load of the specified live load series.

6.3.4 FATIGUE (1983) R(2010) Where the design stress in a structural part is affected by the movement of the span, the allowable stress range shall be determined from Part 1, Design, Article 1.3.13 using the applicable number of stress cycles.

6.3.5 WIND FORCES AND ICE LOAD (2011) a.

In proportioning the members and determining the stability of swing, bascule, and vertical lift spans, and their towers, wind forces shall be assumed acting either transversely, longitudinally, or diagonally at an angle of 45 degrees with the bridge axis. Exposed areas for transverse wind forces on the spans shall be determined as provided in Part 1, Design, Article 1.3.7b. Exposed areas for longitudinal wind forces on the spans shall be taken as one-half those for transverse wind, except for bascule bridges for spans when open where they shall be modified as specified below for forces acting normal to the floor. Exposed areas for transverse and longitudinal wind forces on houses and counterweights shall be their vertical projections. Exposed areas for transverse and longitudinal wind forces on towers and their bracing shall be the vertical projections of all columns and bracing not shielded by the counterweights and houses. For

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diagonal wind, the equivalent simultaneous transverse and longitudinal wind forces shall be taken as 70% of the values for winds acting transversely and longitudinally, respectively. b. The following wind forces and stresses shall be used in proportioning and determining the stability of members: (1) Movable span closed: Structure to be considered a fixed span insofar as lateral forces and increased allowable stresses are concerned. (See Part 1, Design, Article 1.3.7, Article 1.3.8 and Article 1.3.14.3.) (2) Movable span open: Where the movable span is normally left in the closed position, 30 lb per square foot on the structure, combined with dead load, and 20% of dead load to allow for impact load, at 1.25 times normal allowable stresses. For swing bridges provision shall also be made for 30 lb per square foot on one arm and 20 lb per square foot on the other arm, applied simultaneously in the same direction. Where the movable span is normally left in the open position, 50 lb per square foot on the structure, combined with dead load, at 1.33 times normal allowable stresses. For swing bridges provision shall also be made for 50 lb per square foot on one arm and 35 lb per square foot on the other arm, applied simultaneously in the same direction. c.

For open-deck bridges, the area exposed to ice and to wind acting normal to the floor shall be taken at 85% of the area of a quadrilateral whose width is the distance center-to-center of the trusses and whose length is that of the span. For bridges with solid floors or footwalks, the actual exposed floor surface shall be used.

6.3.6 POWER REQUIREMENTS AND MACHINERY DESIGN (2003) a.

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The machinery shall be proportioned and power provided to move the span under the following conditions: (1) Condition A.

3

(a) Bascule bridges and vertical lift bridges – Frictional resistances, rope bending, unbalanced conditions (Article 6.2.3), inertia, and a wind load of 2-1/2 lb per square foot on the area specified in Article 6.3.5, acting normal to the floor. For vertical lift spans, this wind load shall be considered to include frictional resistances from span and counterweight guides caused by horizontal wind on the moving span. (b) Swing bridges – Frictional resistances, inertia, and a wind load of 2-1/2 lb per square foot on the vertical projected area of one arm. (2) Condition B. Bascule bridges and vertical lift bridges–Ice load of 2-1/2 lb per square foot on the area specified in Article 6.3.5, in addition to the loads specified in A. (3) Condition C. Bascule bridges and swing bridges against frictional resistances, unbalanced conditions (Article 6.2.3), inertia, a wind load of 10 lb per square foot on any vertical projection of the open bridge, and an ice load of 2-1/2 lb per square foot on the area specified in Article 6.3.5. For swing bridges provision shall also be made for a wind load of 10 lb per square foot on the vertical projected area of one arm and 5 lb per square foot on the other arm. b. The normal operating time for opening or closing the moving span shall be computed under Condition A above. The operating time under Condition B shall not be more than 1.5 times the normal operating time. The operating time under Condition C shall not be more than 2.0 times the normal operating time.

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c.

The maximum bridge-starting torque shall be determined under Condition C using the friction coefficient for starting and neglecting inertia.

d. Where the excess of starting torque from the prime mover over the torque of Condition C is not sufficient to accelerate the span, the size of the prime mover shall be increased. This will usually be a factor only on swing bridges. e.

Where the movable span is normally left in the closed position, the machinery for bascule and swing bridges shall also be proportioned to hold the span in the fully open position against a wind load of 20 lb per square foot on any vertical projection of the open bridge. For swing bridges normally left in the closed position, provision shall be made for a wind load of 20 lb per square foot on one arm and 25 lb per square foot on the other arm. In proportioning the machinery for these conditions, 1.5 times the allowable stresses may be used.

f.

Where the moving span is normally left in the open position, the machinery for bascule and swing bridges shall also be proportioned to hold the span in the fully open position against the wind loads specified in Article 6.3.5b(2). If desired, the machinery may be proportioned as specified in the preceding Article and the difference between the wind loads specified in Article 6.3.5b(2), and those specified in the preceding Article, shall then be accommodated for by separate holding devices. In proportioning the machinery for these conditions, 1.5 times the allowable stresses shall be used.

6.3.7 MACHINERY RESISTANCES (1983) R(2010) a.

When calculating the resistances to be overcome by the machinery, the resisting forces shall be reduced to a single force acting between the pinion and the operating rack, or in the operating rope. In determining this force, the coefficients shown in Table 15-6-1 shall be used.

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Movable Bridges Table 15-6-1. Machinery Resistances Coefficient For Starting

Coefficient For Motion

Sliding bearings, one or more complete rotations

0.135

0.090

Sliding bearing, less than one complete rotation

0.180

0.120

Roller bearings

0.004

0.003

Type For trunnion friction:

NOTE:

For manually operated bridges, the coefficients for motion given above shall be increased 25%

For friction on center disks

0.150

0.100

For rolling friction of solid rollers without flanges where: r = radius of roller, inch

0.008 -------------r

0.008 -------------r

For rolling friction of bridges having rollers with flanges, or built-up segmental girders

0.009

0.006

For collar friction at ends of conical rollers

0.150

0.100

For 180 degrees bending of wire ropes, on each sheave, the coefficient of direct tension in rope where: d = diameter of rope, inch D = diameter of sheave, inch

d 0.3 ---D

d 0.3 ---D

1

b. In designing the machinery for holding the span against the wind pressure specified in Article 6.3.6, and for determining the required capacity of the brakes both for holding the span against the wind pressure and for stopping the span when in motion, 0.4 of the above mentioned coefficients for motion shall be used. Rope bending, solid roller friction, and machinery friction shall be disregarded. In determining the effect of the brakes on the machinery while stopping the span, full machinery friction shall be considered. c.

3

The coefficient of sliding friction between plane surfaces intermittently lubricated shall be taken as 0.08.

6.3.8 MACHINERY LOSSES (1983) R(2010)

4

The following coefficients shall be used in computing the machinery losses between the operating rack, or the operating rope, or a similar point, and a prime mover: For journal friction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.05 For efficiency of any pair of gears, bearing friction not included: Spur gears and helical gears . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.98 Bevel gears, collar friction included . . . . . . . . . . . . . . . . . . . . . 0.90 Np For efficiency of worm gearing, collar friction not included. . . . ------------------Np + R where: N = number of threads of lead of worm

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p = circular pitch of teeth on wheel R = radius of worm

6.3.9 BRAKES, AND MACHINERY DESIGN FOR BRAKING FORCES (2003) a.

Manually operated bridges shall be provided with one set of brakes.

b. Mechanically operated bridges, except as otherwise specified by the Engineer, shall be provided with two sets of brakes (see Articles 6.7.5.14 and 6.7.5.15). The machinery brakes shall be as near the operating ropes or operating racks as practicable. c.

Where only one set of brakes is provided for manually operated bridges, the brakes shall have sufficient capacity to stop the span in 10 sec when it is moving under the influence of the unbalanced loads specified in Article 6.3.6a, and to hold the span against the wind loads specified in Article 6.3.6e and Article 6.3.6f.

d. Where two sets of brakes are provided, they shall have the following capacities: (1) The motor brakes shall have sufficient capacity to stop the span in 10 sec when it is moving under the influence of the greatest unbalanced loads specified in Article 6.3.6a(1) for swing bridges, and Article 6.3.6a(2) for bascule and vertical lift bridges. (2) The machinery brakes for vertical lift bridges shall have a capacity, as measured at the shafts of the motor brakes, equal to or greater than one-half that of the motor brakes. The machinery brakes for bascule bridges and swing bridges shall be such that the combined motor and machinery brakes will have sufficient capacity to stop the span in 10 sec when it is moving at Condition A speed under the influence of the greatest unbalanced loads specified in Article 6.3.6a; and to hold the span against the wind loads specified in Article 6.3.6e and Article 6.3.6f. e.

Braking forces provided by friction, mechanical brakes and/or the deceleration torques, if any, from the motor control system shall be adjusted so that the time for decelerating from full speed to full stop is not less than the deceleration time given on the plans.

f.

Where specified by the Engineer, three separate brakes, all of equal torque as measured at the motor output shaft, may be used to prevent loss of more than one-third the braking force in case of failure of any one brake. The three brakes shall be electrically operated, controlled, interlocked and set to be applied in delayed sequence. Combined retarding torque for the No. 1 and No. 2 brakes shall be as specified in paragraph d(1). Retarding torque for No. 3 brake shall be as specified in paragraph d(2). Two of the brakes shall be located as close to the final drive as practicable; such as on the input shafts of the main reducer unit. The third brake shall be preferably so located as to permit utilization of the brake with either the main or auxiliary motors removed.

g.

The coefficient of friction for selecting brakes shall be taken as 0.3, but a coefficient of 0.45 shall be used for designing all other machinery. Where practicable, the pressure on the rubbing surface of the brake shall not exceed 30 psi and the product of the pressure on the rubbing surface times the velocity of the brake wheel rim in feet per minute shall not exceed 90,000.

h. Machinery, including operating ropes, shall be designed at basic allowable stresses for the machinery brake on any two brakes of the three brake system acting. When both motor and machinery brakes are applied simultaneously an overload stress of 1.5 times the basic allowable stresses may be used. i.

For calculating the strength of the machinery parts under the action of manually operated brakes, the force applied at the extreme end of a hand lever shall be assumed as 150 lb and the force applied on a foot

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pedal shall be assumed as 200 lb. Under this condition, 1.5 times the basic allowable stresses may be used.

6.3.10 MACHINERY DESIGN (1983) a.

The machinery for moving the span shall be designed at basic allowable stresses for the following percentages of full-load rated torque of the prime mover at the speed corresponding to normal operating time: Electric motors. . . . . . . . . . . . . . . . . . . . 150% Internal combustion engines. . . . . . . . . 100%

b. For manual operation, the machinery shall be designed as specified in Article 6.7.2. c.

The machinery shall also be designed for the braking loads, and at the stresses specified in Article 6.3.6 and Article 6.3.9.

6.3.11 MACHINERY SUPPORTS (2003) Structural parts subject to stresses from machinery loads or from loads applied for moving or stopping the span, shall be proportioned for stiffness. Beams subject to such stresses should preferably have a depth not less than one-eighth of their span; where shallower beams are used, the section shall be increased so that the deflection will not be greater than if this limiting depth had not been exceeded. Deflections and stiffness shall be investigated sufficiently to insure that they will not affect proper machinery operation.

1

6.3.12 ANCHORAGE (1983) R(2010) Anchor bolts or other anchorages that take uplift shall be designed at basic stresses to carry and engage a mass of masonry the weight of which is at least 1.5 times the uplift. Anchor bolts shall be tightened to an initial tension equal to at least 1.5 times the uplift force.

3

6.3.13 SPECIAL PROVISIONS FOR SWING BRIDGES (1983) R(2002) 6.3.13.1 Stress Combinations a.

4

The stresses in trusses or girders of swing bridges continuous on three or four supports shall be calculated for the bridge in the following conditions: • Condition 1 – Bridge open, or closed with ends just touching. • Condition 2 – Bridge closed with ends lifted.

b. The computation of stresses shall be divided into the following cases: • Case I – Condition 1, dead load. • Case II – Condition 2, dead load, ends lifted to give positive reaction equal to the maximum negative reaction of the live load and impact load plus 50% of their sum. • Case III – Condition 1, live load plus impact load on one arm as a simple span. • Case IV – Condition 2, live load plus impact load on one arm, bridge as a continuous structure. © 2011, American Railway Engineering and Maintenance-of-Way Association

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• Case V – Condition 2, live load plus impact load on both arms, bridge as a continuous structure. c.

The following combinations of these cases shall be used in determining the maximum stresses: • Case I alone, plus 20%. • Case I with Case III. • Case I with Case V. • Case II with Case IV. • Case II with Case V.

d. The stress sheet shall show the stresses in the various members for each of the foregoing cases, together with the combinations which give the greatest positive and negative stresses in each member. 6.3.13.2 End Wedge and Center Wedge Reactions a.

The end wedges, or equivalent devices, shall lift the ends of the swing bridge an amount sufficient to produce a positive reaction at either end equal to 1.5 times the maximum negative reaction at that end due to live load and impact load.

b. The end lifting machinery shall be proportioned to exert a lifting force equal to the greater of: (1) the lifting load stipulated in Article 6.3.13.2(a) plus the reaction due to a temperature difference of 20 degrees F between the top and bottom chords of truss spans or of 15 degrees F between the top and bottom flanges of girder spans, or, (2) the lifting load required to raise the ends of the span 1/2 inch or 0.1% of the length of one arm, whichever is greater. c.

End wedges and their supports shall be designed for the maximum positive reaction including live load, impact load and temperature differential.

d. Center wedges shall be designed for the maximum live load plus impact load. 6.3.13.3 Rollers a.

The rollers of rim bearing or combined rim and center bearing swing bridges shall be proportioned for the dead load when the bridge is swinging, and for the dead, live, and impact loads when the bridge is closed.

b. In computing the load on the rollers, the rim girder shall be considered as distributing the load uniformly over a distance equal to twice the depth of the girder out to out of flanges. This distance shall be taken as symmetrical about the vertical through the point of application of the concentrated load. 6.3.13.4 End Wedge and Center Wedge Machinery In designing the machinery for the end wedges and center wedges of swing bridges, the requirements specified for the machinery for driving the moving span shall apply.

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6.3.14 SPECIAL PROVISIONS FOR BASCULE BRIDGES (1984) R(2010) 6.3.14.1 Stress Combinations a.

The stresses in trusses or girders of bascule bridges shall be calculated for the bridge in the following conditions: • Condition 1 – Bridge open in any position. • Condition 2 – Bridge closed. • Condition 3 – Bridge closed, with counterweights independently supported.

b. The computation of stresses shall be divided into the following cases: • Case I – Condition l, dead load. • Case II – Condition 2, dead load. • Case III – Condition 3, dead load. • Case IV – Condition 2 or 3, live load plus impact load. c.

The following combinations of these cases shall be used in determining the maximum stresses:

1

• Case I alone, plus 20%. • Case II with Case IV. • Case III with Case IV. d. The stress sheet shall show the stresses in the different members for each of the foregoing cases, together with the combinations which give the greatest positive and negative stresses in each member. e.

In the proportioning of members, stresses 25% greater than the basic allowable stresses may be used for the combination of Case III with Case IV. Members subject to reversal of stress under this combination of cases or in consideration of this combination with any other combination shall be proportioned for the maximum tensile and compressive stresses without consideration of fatigue.

6.3.15 SPECIAL PROVISIONS FOR VERTICAL LIFT BRIDGES (2004) R(2010) 6.3.15.1 Stress Combinations a.

The stresses in trusses or girders of vertical lift bridges shall be calculated for the bridge in the following conditions: • Condition 1 – Bridge open. • Condition 2 – Bridge closed. • Condition 3 – Bridge closed, with counterweights independently supported.

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b. The computation of stresses shall be divided into the following cases: • Case I – Condition 1, dead load. • Case II – Condition 2, dead load. • Case III – Condition 3, dead load. • Case IV – Condition 2 or 3, live load plus impact load. c.

The following combinations of these cases shall be used in determining the maximum stresses: • Case I alone, plus 20%. • Case II with Case IV. • Case III with Case IV.

d. The stress sheet shall show the stresses in the different members for each of the foregoing cases, together with the combinations which give the greatest positive and negative stresses in each member. e.

In the proportioning of members, stresses 25% greater than the basic allowable stresses may be used for the combination of Case III with Case IV. Members subject to reversal of stress under this combination of cases or in consideration of this combination with any other combination shall be proportioned for the maximum tensile and compressive stresses without consideration of fatigue.

6.3.15.2 Wire Ropes The maximum force in counterweight ropes shall not exceed 2/9 of the specified ultimate strength of the rope, nor shall the force from the direct load only exceed 1/8 of the specified ultimate strength. For operating ropes, the respective maximum forces shall be 3/10 and 1/6 of these values. 6.3.15.3 Bending Stress and Maximum Force Over Sheave a.

Where a wire rope is bent over a sheave, the bending stress and permissible force in the rope shall be calculated as follows: where: P = permissible force in rope, lb K = bending stress in extreme fiber of largest individual wire E = modulus of elasticity of the wire = 29,000,000 psi a = metallic cross-sectional area of rope, inch2 d = diameter of outer wire, inch D = diameter of sheave, center to center of rope, inch (See Article 6.3.15.4) S = maximum tension allowable, psi L = angle of helical wire with axis of strand, deg B = angle of helical strand with axis of rope, deg c = diameter of rope, inch then: © 2011, American Railway Engineering and Maintenance-of-Way Association

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2

2

Lcos B K = 0.8Edcos ------------------------------------------------D 2

2

0.7Ed cos Lcos B æ S – 0.8 Ed -----------------------------------------öø = a æè S – ---------------- öø è D D

P=a

b. For rope having 6 strands of 19 main wires each (6 ´ 25 filler wire construction) and assuming: c d = ----16 , 300, 000c P = aæS – 1 -------------------------------- öø è D Values of P shall not exceed the values in Article 6.3.15.2. 6.3.15.4 Small Sheave Over Short Arc a.

Where a rope is in contact with a small sheave over a short arc (angle between the rope directions greater than 130 degrees), the actual radius of curvature of the rope may be greater than that of the sheave.

1

where: R = the actual radius of curvature of the rope, inch q = the angle between the directions of the rope, deg; for 130 deg < q < 180 deg W = force in individual wire (equals P divided by the number of wires if all wires are of equal diameters), lb

3

then: 2

E d R = ----------------------------- ---- W 4.25 cos  ---  2

4

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b. If R is greater than the radius of the sheave, 2R should be used in place of D in the formulas of Article 6.3.15.3.

SECTION 6.4 BASIC ALLOWABLE STRESSES AND HYDRAULIC PRESSURES 6.4.1 STRUCTURAL PARTS (1993) R(2010) Structural parts shall be proportioned by the requirements of Part 1, Design.

6.4.2 MACHINERY PARTS (1993)1 a.

Table 15-6-2 shows the allowable stresses, psi, which shall be used for machinery and similar parts, except as modified by paragraph d.

b. Table 15-6-3 shows the allowable bending stresses, psi, which shall be used for trunnions. Table 15-6-2. Allowable Machinery Stresses Tension or Bending

Compression (Note 1)

Fixed Bearing

Shear

Structural carbon steel, ASTM A 36 or A709 Grade 36

12,000

l 12, 000 – 55 -r

16,000

6,000

Forged carbon steel, ASTM A 668, Class D, except for keys

15,000

l 15, 000 – 65 -r

18,000

7,500

–

–

15,000

7,500

16,000

l 16, 000 – 70 -r

21,000

8,000

15,000

l 15, 000 – 65 -r

9,000

10, 000 – 45 -lr

Cast iron, ASTM A 48, Class 25

2,000

10,000 (Note 2)

Bronze, ASTM B 22, Alloy 905

7,000

7,000

Material

Forged carbon steel, ASTM A 668, Class D, for keys Forged alloy steel, ASTM A 668, Class G Rolled steel Cast steel, ASTM A 27, Grade 65-35

7,500 13,000

5,000

Note 1: Where l is the unsupported length of the member, inch and r is the least radius of gyration, inch Note 2: For struts whose -l- is 20 or less. r c.

1

For rotating parts, and for frames, pedestals, and other components which support rotating parts, the computed stresses shall be multiplied by the impact factor K.

See Part 9 Commentary

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Movable Bridges Table 15-6-3. Trunnion Bending Stresses Rotation More Rotation 90 Than 180 Degrees Degrees or Less

Type

Fixed Trunnions

Forged carbon steel, ASTM A 668, Class D

10,000

15,000

17,000

Forged alloy steel, ASTM A 668, Class G

10,000

20,000

22,000

where: K = 1.0 for trunnions and for counterweight sheaves and their shafts. K = 1.0 + 0.03 n for other parts where: n = rpm of rotating part. d. The stresses specified in this article provide appropriate safety factors against static failure and against failure by fatigue with and without reversal of stresses. In the determination of the safety factor against fatigue failure, provision was made for stress-raisers which would produce local stress concentrations of 140% of the computed stress. For trunnions and counterweight sheave shafts, the stress concentration factors shall be estimated for the actual geometry of the trunions or sheave shafts and suitable adjustments in size or detail shall be made when the estimated factors exceed 1.4; for gear arms this provides for the increase in stress near the hub; for integral shafts and pinions this provides for the increase in stress at the faces of the pinion; and for key-ways this provides for one or two keys 120 degrees apart, each having a width not more than one-quarter and a depth not more than one-eighth the shaft diameter. In the absence of keyways or other stress-raisers in a shaft, the allowable stress for torsion and flexure in a shaft may be increased 20%.

1

6.4.3 BEARING (1997) R(2010) a.

The allowable bearing pressures on the diametral projected area, psi, for rotating and sliding surfaces shall be as follows, except as modified by paragraph b and paragraph d

3

(1) For intermittent motion and for speeds not exceeding 50 feet per min: Pivots of swing bridges, hardened steel on ASTM B 22, Copper Alloy UNS No. C9l300 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,000

4

Pivots of swing bridges, hardened steel on ASTM B 22, Copper Alloy UNS No. C91100 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2,500 Trunnion bearings and counterweight sheave bearings, rolled or forged steel on ASTM B 22, Copper Alloy UNS No. C91100 bronze: For loads while in motion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1,500 For loads while at rest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2,000 Shaft journals, rolled or forged steel on ASTM B 22, Copper Alloy UNS No. C93700 bronze . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1,000 Wedges, cast steel on cast steel or structural steel . . . . . . . . . . . . . . . 1,500 Wedges, cast steel or structural steel on ASTM B 22, Copper Alloy UNS No. C86300 bronze . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1,500 Acme screws which transmit motion, rolled or forged steel on ASTM B 22, Copper Alloy UNS No. C90500 bronze. . . . . . . . . . . . . . 1,500

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(2) For speeds exceeding 50 feet per min: Shaft journals, rolled or forged steel, on ASTM B 22, Copper Alloy UNS No. C93700 bronze . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Shaft journals, rolled or forged steel on babbitt metal . . . . . . . . . . . . . . . . . . . . . . . . . . . . Shaft journals, rolled or forged steel on cast iron . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Thrust, collars, rolled or forged steel on ASTM B 22, Copper Alloy UNS No. C93700 bronze . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cross-head slides (speed not exceeding 600 feet per min). . . . . . . . . . . . . . . . . . . . . . . . . . Step bearing for vertical shafts Hardened steel shaft end on ASTM B 22, Copper Alloy UNS No. C91100 bronze . . . . Hardened steel shaft end on ASTM B 22, Copper Alloy UNS No. 93700 bronze. . . . . .

600 400 400 200 50 1,200 600

b. The allowable bearing pressures for the various bearings named in paragraph a(2) above also shall not exceed those specified in Article 6.4.4. c.

The slow-moving journals, as on trunnions, counterweight and deflector sheave bearings, and operating drum bearings, the bearing area shall be taken as the net area with the effective areas of oil grooves being deducted from the gross bearing area.

d. For crank pins and similar joints with alternating application and release of pressure, the bearing values given above may be doubled.

6.4.4 HEATING AND SEIZING (1992) R(2010) a.

To avoid heating and seizing at high speeds, the bearing pressures, psi, on shaft journals, step bearings for vertical shafts, thrust collars, and Acme thread power screws shall not exceed the following, except as modified by paragraph b, paragraph c and paragraph d: 250, 000 Shaft journals, rolled or forged steel on bronze . . . . p = ---------------------nd 60, 000 Step bearings, hardened steel on bronze . . . . . . . . . p = ------------------nd 50, 000 Thrust collars, rolled or forged steel on bronze . . . . p = ------------------nd 220, 000 Acme screws, rolled or forged steel on bronze . . . . . p = ---------------------nd where: p = pressure on projected area, psi n = number of revolutions per min d = diameter of journal or step bearing, or mean diameter of collar or screw, inch

b. For crank pins and similar joints with alternating application and release of pressure, the bearing values given by the foregoing formulas may be doubled. c.

Where pressures given by the foregoing formulas exceed those specified for similar parts in Article 6.4.3 the values in Article 6.4.3 shall be used. © 2011, American Railway Engineering and Maintenance-of-Way Association

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d. The pressures given by the foregoing formulas shall not be exceeded under the provisions of Article 6.3.10.

6.4.5 LINE BEARING LOAD (1984) R(2003) a.

The maximum bearing load in lb per linear inch of rollers is found in Table 15-6-4.

Table 15-6-4. Roller Maximum Bearing Load Diameters Up to 25 inches

Diameters From 25 inches to 125 inches

For rollers in motion: F y – 15, 000 -------------------------------- multiplied by 20, 000

400d

2, 000 d

For rollers in rest: F y – 15, 000 -------------------------------- multiplied by 20, 000

600d

3, 000 d

Type

1

3

where: Fy = yield point of the material, psi d = diameter of roller, inch b. The foregoing values are for rollers and bearing surfaces of the same materials. If the rollers and bearing surfaces are of different materials, the lower value of Fy shall be used. c.

For rollers of trunnion and counterweight sheave roller bearings, the maximum bearing stress in lb per linear inch of roller shall be 3,000 d, where d is the diameter of the roller, inch. One-fifth of the rollers shall be taken as effective in carrying the load.

6.4.6 SHAFTS (1984) R(2010) a.

Bending stresses in circular shafts, trunnions, and axles shall be determined by the following formulas: f = 16K ----------- æèM + M 2 + T 2 öø 3 pd S = 16K ----------- M 2 + T 2 3 pd

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where: f= S= d= M= T=

extreme fiber stress in tension or compression, psi shear, psi diameter of shaft at the section considered, inch simple bending moment computed for the distance center to center of bearing, inch lb simple torsional moment, inch lb

b. For values of K and allowable stresses with and without keyways, or other stress-raisers, see Article 6.4.2.

6.4.7 BOLTS IN TENSION (1984) R(2003) a.

Bolts in tension in machinery parts shall be designed by assuming the effective area of the threaded portion to be: A = An – (a ´ 2D) where: A = effective area of threaded portion, square inch An = net area at root of thread, square inch a = net area of 1/2 inch bolt at root of thread, square inch D = nominal diameter of threaded portion, inch

b. This formula takes account of the fact that the initial stress in a 1/2 inch bolt, produced by tightening the nut, frequently equals or exceeds the yield point of the material. c.

For ANSI coarse threads, the formula reduces to: 1 A = A n – --- D 4

6.4.8 HYDRAULIC SYSTEMS AND COMPONENTS (1984)1 R(2010) 6.4.8.1 Allowable System Pressures a.

The hydraulic system shall be designed and hydraulic components proportioned such that the maximum allowable system pressures shall not exceed the following, except as otherwise permitted by prior written approval of the Company. Normal operation. . . . . . . . . . . . . . . . . . . . . . . . . . . 1,000 psi Operation against maximum specified loads . . . . . 2,000 psi Holding against maximum specified wind loads . . 3,000 psi

b. Normal operation shall be defined as operation against loads specified in Article 6.3.6a(1). Operation against maximum specified loads shall be defined as operation against loads specified in Article 6.3.6a(2) 1

See Part 9 Commentary

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and Article 6.3.6a(3). Holding against maximum specified wind loads shall be defined as holding the movable span in the fully open position, static condition, against the loads specified in Article 6.3.6e. 6.4.8.2 Pressure Ratings for Hydraulic Components a.

Minimum working pressure ratings for hydraulic components shall be as follows, except as otherwise permitted by prior written approval of the Company. Pipe, tubing and their fittings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3,000 psi Flexible hose and hose fittings: For pressure lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5,000 psi For drain lines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2,000 psi Cylinders, pumps, valves and all other components . . . . . . . . . . . . . 3,000 psi

b. Working pressure rating shall be defined as the maximum allowable continuous operating pressure for the component. For pipe, tubing, flexible hose and fittings the working pressure ratings are equal to the burst pressure rating divided by a minimum factor of safety of 4. For cylinders the working pressure rating shall be equal to the NFPA theoretical static failure pressure rating as required by Article 6.5.37.11 divided by a minimum factor of safety of 3.33. For pumps, valves and other components the working pressure rating is equal to the maximum allowable peak (intermittent) pressure rating divided by a minimum factor of safety of 1.5. c.

The minimum factors of safety designated in paragraph b apply to systems having light to moderate operating shock loads during operation resulting in short duration peak system pressures no greater than two times the allowable maximum operating pressure against Conditions B or C loads, whichever is greater. For systems having higher shock load pressures, the factors of safety shall be increased proportionally.

1

3 SECTION 6.5 GENERAL DETAILS 6.5.1 FITS AND SURFACE FINISHES (1984) R(2002) a.

The fits and surface finishes for parts found in Table 15-6-5 shall be in accordance with ANSI B4.1, Preferred Limits and Fits for Cylindrical Parts, and ANSI B46.1, Surface Texture.

b. Surface finishes are given as the roughness height in microinches; if additional limits are required for waviness and lay, they shall be specified by the Engineer. c.

The fits for cylindrical parts found in Table 15-6-5 shall also apply to the major dimensions of noncylindrical parts.

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Fit

Finish

Machinery base on steel

–

250

Machinery base on masonry

–

500

Shaft journals

RC6

8

Journal bushing

RC6

16

Split bushing in base

LC1

125

Solid bushing in base (to 1/4 inch wall)

FN1

63

Solid bushing in base (over 1/4 inch wall)

FN2

63

Hubs on shafts (to 2 inch bore)

FN2

32

Hubs on shafts (over 2 inch bore)

FN2

63

Hubs on main trunnions

FN2

63

Turned bolts in finished holes

LT1

63

Sliding bearings

RC6

32

Key and keyways

FN2

63

–

125

Machinery parts in fixed contact Teeth of open spur gears: Under 1 inch circular pitch

32

1 inch to 1-3/4 inch circular pitch

63

Over 1-3/4 inch circular pitch

125

6.5.2 RAIL END CONNECTIONS (1984) a.

Designs for rail end connections will be furnished by the Engineer.

b. Where the connections are of the sliding rail lock type, the ends of the bridge rails shall be fixed, cut square, and connected with the approach rails by sliding sleeves or joint bars, to carry the wheels over the openings between the rail ends. The distance from the center of the track to the inside of the rail lock wheel tread shall be not less than 2¢-6², and not more than 2¢-6-1/2² with the heads of the rails being planed off on the outside if necessary. c.

Where the connections are of the miter type, the two sections shall be held positively in a transverse direction by guides, to prevent spreading at the miter joint.

d. Provisions shall be made so that the rail locks can be closed only when the span is seated and the rail end sections properly engaged. e.

The edges of all drilled holes in rail locks and in the rail ends adjacent thereto shall be chamfered approximately 1/16 inch. All reentrant angles in these appurtenances shall be filleted.

6.5.3 AIR BUFFERS (1997) R(2003) a.

Air buffers to aid in seating the movable span shall be provided as specified in Article 6.5.35.4, Article 6.5.36.4, and Article 6.8.19.

b. The inside diameter of the cylinder of the air buffer shall not be less than 10 inches, and the travel of the piston not less than 24 inches.

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c.

There shall be three cast iron packing rings for each piston.

d. Each air buffer shall be provided with a needle valve and a check valve, and these shall be suitable for sustaining for short intervals air pressures of 1,000 psi and temperatures of 800 degrees F. e.

As an alternative to air buffers, industrial type shock absorbers may be provided, if specified by the Engineer in the contract documents.

f.

Air buffers or shock absorbers may be omitted if the control system is designed to seat the span smoothly at a slow speed which will not create undue impact.

6.5.4 COUNTERWEIGHTS (2003) a.

Counterweights normally shall be made of concrete, supported by a steel frame or, preferably, enclosed in a steel box. Boxes shall be rigidly braced and stiffened to prevent warping or bulging. All surfaces of the boxes in contact with the concrete shall be provided with open holes (about l square inch to each 10 square feet of surface) to permit escape of water from the box as the concrete cures, or otherwise a lowslump concrete shall be used and any excess water drawn off as the concrete is placed. In the design of counterweight attachments, details which may produce fatigue due to vibration of the structure shall be avoided.

b. Concrete counterweights not enclosed in steel boxes shall be adequately reinforced. c.

Counterweights shall be made so as to be adjusted easily for variations in the weight of the span and in the unit weight of the concrete. Usually this shall be done by adding or taking off properly located cast iron or concrete balance blocks. Pockets shall be provided in the counterweights to house the balance blocks necessary to care for not less than 3.5% underrun and 5% overrun in the weight of the span. Each completed counterweight shall contain not less than 1% of its weight in balance blocks, arranged so as to be readily removable for future adjustment. Additional balance blocks for future adjustment in the amount of 0.5% of the weight of the counterweight shall also be provided and shall be stored at the site as directed by the Engineer. All balance blocks shall be firmly held in place so that they will not move during the operation of the bridge. Balance blocks shall be provided with recessed handles or recesses on the underside of the blocks for projecting handles and shall weigh not more than 100 lb each. Balance blocks shall be furnished only as necessary to meet the specified requirements for future adjustment and to secure the required balance of the span and counterweights.

d. Pockets in counterweights shall be provided with drain holes of not less than 2 inches diameter. The pockets shall be covered. The cover, its fastenings and frame shall be of metal. The cover shall be weatherproof.

6.5.5 CONCRETE (1984) R(2002) a.

Concrete, unless otherwise stipulated, shall conform to the requirements of Chapter 8, Concrete Structures and Foundations, shall be made with Type II cement, and shall be proportioned as directed by the Engineer, with not more than 6 gal of water per sack of cement. Where heavy concrete is required for counterweights, the coarse aggregate shall be trap rock, magnetic iron ore, or other heavy material, or the concrete may incorporate steel punchings or scrap metal, and mortar composed of 1 part of cement and 2 parts of fine aggregate. The maximum weight of heavy concrete shall be 315 lb per cubic foot but preferably not more than 275 lb per cubic foot. Heavy concrete shall be placed in layers and consolidated with vibrators or tampers. Methods of mixing and placing shall be such as to give close control of the unit weight of the concrete and uniformity of unit weight throughout the mass. Counterweights containing punchings or scrap metal or iron ore aggregates shall be enclosed in steel boxes. Concrete for counterweights preferably shall be non air-entrained to permit better control of density.

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b. Concrete counterweights of the revolving type shall be poured continuously where practicable. c.

For ascertaining the weight of the concrete, test blocks having a volume of not less than 4 cubic feet for ordinary concrete, and 1 cubic foot for heavy concrete, and 1 cubic foot for the mortar for heavy concrete, shall be cast at least 30 days before concreting is begun. Two test blocks of each kind shall be provided, and one weighed immediately after casting and the other after it has seasoned.

6.5.6 MACHINERY IN GENERAL (1984) R(2002) a.

Machinery shall be simple, and of substantial construction. The configuration and arrangement of the components shall permit easy erection, adjustment, inspection, lubrication, cleaning, painting, and replacement of worn or defective parts.

b. Fastenings shall be adequate to hold the parts in place under all conditions of service. Mounting bolts shall be of such size that they may be preloaded to not less than 150% of the maximum operating design load. c.

Where practicable, machinery units shall be assembled in enclosed rigid housings or castings, or shall be shop assembled on rigid steel bases.

6.5.7 JOURNAL BEARINGS (1984) R(2002) a.

Bearings shall be placed close to the points of loading and located so that the bearing pressure shall be as nearly uniform as possible.

b. Journal bearings shall be of the split type with one half recessed into the other half. The length of a bearing shall be not less than its diameter. The base halves of bearings for gear trains and for mating gears and pinions shall be in one piece. The caps of bearings shall be secured to the bases with turned bolts with square heads recessed into the base and with double hexagonal nuts. The nuts shall bear on finished bosses or spot-faced seats. Fits and finishes for caps and bolts shall be as specified in Article 6.5.1. c.

Provision shall be made for the aligning of bearings during erection by means of shims and for the adjustment of the caps by means of laminated liners or other effective device.

d. Large bearings shall be provided with effective means for cleaning without dismantling the parts.

6.5.8 LININGS (1984) R(2002) a.

Journal bearings normally shall have bronze linings; other lightly loaded bearings may have bronze or babbitt metal linings. For split bearings, the lining shall be in halves and shall be provided with an effective device to prevent its rotation under load. The force tending to cause rotation shall be taken as 1/16 of the maximum load on the bearing and as acting at the outer circumference of the lining. There shall be 1/4 inch clearance between the lining of the cap and the lining of the base into which laminated liners shall be placed. The inside longitudinal corners of both halves shall be rounded or chamfered, except for a distance of 3/8 inch from each end or shaft fillet tangent point.

b. Linings for solid bearings shall be in one piece and shall be pressed into the bearing bore and effectively held against rotation.

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6.5.9 STEP BEARINGS (1984) R(2002) The bearing ends of vertical shafts running in step bearings shall be of hardened steel, and shall bear on bronze disks.

6.5.10 ROLLER BEARINGS FOR HEAVY LOADS (2003) a.

Roller bearings may be used to support the trunnions of bascule bridges, the counterweight sheave shafts of vertical lift bridges, and similar shafts carrying heavy loads. Roller bearings shall not be used on trunnions of bascule bridges that are subject to uplift due to live load. Each roller bearing shall be of a type, or shall be so mounted, that the deflection of the shaft will produce no overloading of any part of the bearing or housing. The bearing rollers shall be relatively short for their diameter, shall be closely spaced in bronze cages, and shall run between hardened-steel races, mounted in the housing and on the shaft. The bearing mountings on each shaft shall be such that the shaft shall be restrained from axial movement by one mounting, and shall be free to move in the other mounting.

b. The ratio of length to diameter of any roller or roller segment shall not exceed 3.25. For segmented rollers the ratio of total length of roller to diameter shall not exceed 6.5. c.

Cylindrical roller bearings shall be provided with anti-friction thrust bearings capable of restraining an axial thrust equal to l5% of the total radial load on the shaft or trunnion. Spherical or tapered roller bearings shall be proportioned for an axial load equal to 15% of the total radial load on the shaft or trunnion combined with the radial load on the bearing.

1 d. Each roller bearing shall be mounted in an oil- and water-tight steel housing, which shall be provided with means for replenishing the lubricant and arranged for convenient access for thorough cleaning of the operating parts. e.

Rollers and races shall be of special steel proposed by the manufacturer, which shall have Rockwell C hardness not less than 58 for the rollers and not less than 56 for the races. Bearings shall be made by a manufacturer of established reputation who has had bearings of comparable size of the same materials and type in successful service for at least 10 years.

3

6.5.11 ROLLER AND BALL BEARINGS (1997) R(2003) a.

Roller and ball bearings shall be so sized that under the loads and resistances specified in Section 6.3, Loads, Forces and Stresses, and at the average running speed at which the bearing is applied, the B-10 life shall be at least 40,000 hours. (B-10 life shall be as defined by the ABMA and shall be the time for which 90% of a group of identical bearings will survive under the given loading conditions).

b. Bearings separately mounted in pillow blocks shall be self-aligning. Housings shall be cast steel and may be one piece or split on the center line. Where pillow blocks are exposed to dirt or moisture, seals shall be provided. Split housings shall have positive means to align the cap with the base. When loads are in a direction other than directly into the base, the housings, cap bolts, alignment devices for split housings, and the base mounting bolts shall have adequate strength and stiffness to resist the lateral and uplift components of the loads without adverse effects on the roller and ball bearing elements.

6.5.12 SPEED REDUCERS (2010) a.

Main drive train helical, herringbone and bevel gear speed reducers shall be designed and manufactured in accordance with the requirements of AGMA Standard 6010. © 2011, American Railway Engineering and Maintenance-of-Way Association

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b. Gears shall be finished to AGMA 2000 quality 10 or better. c.

Gear teeth shall be through hardened.

d. Anti-friction bearings shall be used on all shafts and shall have a minimum B-10 rating of 40,000 hours. They shall be automatically and continuously lubricated. An independently driven lubrication system shall be provided when the operating speed of the reducer is too slow for normal integral lubrication. e.

Housings shall have provisions for filling, draining and ventilation.

f.

Provision shall be made for indicating the oil level by means of a sight gage. The recommended oil level shall be permanently marked on the housing, adjacent to the sight gage.

g.

A gasketed inspection cover, preferably located above the static oil level, shall be provided.

h. The reducer shall be able to withstand a momentary overload equal to three times the normal full load torque of the driving motor(s) without any component reaching yield. To achieve this, the minimum service factors shall be 1.0 for durability and 1.5 for strength (bending) based on the full load torque/horsepower of the electric motor(s). i.

Reducers driven by internal combustion engines or hydraulic motors shall be selected considering the speed-torque characteristics of the engine or motor.

j.

Pinions shall be proportioned so that the root diameter of the pinion is not smaller in diameter than the diameter of the journals for the pinion shaft.

k. Base plates for the reducers shall be large enough to give unobstructed access for drilling and reaming the mounting holes.

6.5.13 LUBRICATION (2008)1 a.

Provision shall be made for effective lubrication of sliding surfaces and of roller and ball bearings. Lubricating devices shall be readily accessible.

b. Each sliding bearing requiring lubrication shall have a high pressure grease fitting, containing a small receiving ball or cone check valve, made of steel, that will receive the grease and close against back pressure. These fittings shall be connected to the linings of bearings by means of corrosion resisting pipe, which shall be screwed into the lining through a hole in the cap. Where the bearings are not readily accessible, the fittings shall be placed where they will be accessible, and shall be connected to the bearings by means of corrosion resisting pipe. c.

Grease ducts shall be so located that the lubricant will tend to flow, by gravity, toward the bearing surface. Grooves shall be provided, wherever necessary, for the proper distribution of the lubricant.

d. Grooves for trunnion bearings may be cut in either the shaft or the lining. Such grooves shall be straight, parallel to the axis of the shaft, and for large bearings no fewer than three shall be provided. Grooves shall be so located that the entire bearing surface will be swept by lubricant in one movement of opening or closing the bridge, or in 90 degree rotation of the shaft, whichever is less. Each such groove shall be served with lubricant by a separate pressure fitting. The grooves shall be of such size that a 5/16 inch diameter wire will lie wholly within the groove and their bottoms shall be rounded to a 1/4 inch radius. The grooves shall be accessible for cleaning with a wire. 1

See Part 9 Commentary

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e.

Grooves for counterweight sheave sleeve bearings may be in accordance with the requirements of the foregoing paragraph but preferably shall be spiral grooves cut in the lining and served with pressure fittings. A cleanout hole shall be provided in the bearing base and connected to the lowest point of the spiral grooves so that the journal surface can be cleaned and the grooves flushed out.

f.

In disk bearings, straight grooves shall be cut in the upper of the two rubbing surfaces in contact. The grooves shall be not less than 1/4 inch wide and deep, and the corners shall be rounded to a radius not less than half the width of the groove. The corners at the bottom of the grooves shall be filleted to eliminate all sharp corners.

g.

Small bearings with light bearing pressures and slow or intermittent motion, and not readily accessible, may be lubricated with self-lubricating bushings. Such bushings shall be of a type which will not be injured by the application of oil. The bearings shall be provided with oil holes for emergency lubrication, and the oil holes shall be fitted with readily removable screw plugs.

h. Hand-operated grease guns having a capacity of 12 oz shall be provided to service all lubrication fittings. There shall also be provided portable loaders of 25-lb capacity and a loader for use with 100-lb grease drums. All necessary adapters shall be provided for the equipment. i.

Two guns shall be furnished for each swing and bascule span, and three guns for each lift span. One portable loader and one drum loader shall be furnished for each movable bridge.

j.

All lubricants for a given component shall be chemically compatible, including the lubricant used in manufacture and the lubricant that will be field applied. For any component on which a new lubricant is to be applied that is not chemically compatible with the existing lubricant, all traces of the existing lubricant shall be thoroughly cleaned and flushed from the component before applying the new lubricant.

1

6.5.14 SHAFTS (1983) R(2003) a.

For shafts supporting their own weight only, the unsupported length of the shaft shall not exceed: L = 80 ( d

2¤3

3

)

where:

4

L = length of shaft between bearings, inch d = diameter of shaft, inch b. Shafts likely to be thrown out of line by the deflection of the supporting structure shall be made in noncontinuous lengths. The arrangement preferably shall be such that only angular misalignment need be provided by the couplings with offset misalignment provided for by a floating shaft. Each length of shaft preferably shall rest in not more than two bearings. c.

Shafts shall be proportioned so that the angular strain in degrees per foot of length under the maximum loads will not exceed the following limits: (1) For shafting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.6 -------d (2) For more rigid drives where less spring is desirable, as in shafts driving end-lifting devices. . . . . . . . . . . . . . . . . . . 0.08 © 2011, American Railway Engineering and Maintenance-of-Way Association

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where: d = the shaft diameter, inch NOTE:

Where the diameter exceeds 7.5 inches, requirement 1 governs.

d. Line shafts connecting the machinery at the center of the bridge with that at the ends shall be designed to run at fairly high speed, the speed reduction being made in the machinery at the end. The maximum speed of line shafts shall not exceed 2/3 of the critical speed of any section of the shaft. e.

Shafts transmitting power for the operation of the bridge, and shafts 4 feet or more in length forming part of the operating machinery of rail locks and bridge locks, shall not be less than 2-1/2 inches dia.

f.

Journals on cold-rolled shafting shall not be turned down. Pinions may be forged integral with their shafts.

6.5.15 SHAFT COUPLINGS (1983) a.

Where practicable, all couplings used in connection with the machinery shall be standard manufactured flexible couplings placed close to the bearings.

b. Couplings between machinery units preferably shall be of the gear type, providing for angular misalignment or for both angular and offset misalignment. c.

Couplings connecting machinery shafts to electric motor or internal combustion engine shafts shall be flexible couplings, transmitting the torque through metal parts and providing for both misalignment and shock.

d. Machinery shafts supported and assembled so as to avoid any misalignment between the shafts may be connected by flange couplings. The bolt heads and nuts shall be seated in recesses or protected by flanges. The couplings shall be cylindrical. e.

Couplings used to connect instrument drives or other small units to large units shall preferably have short floating shafts between the units to minimize participation stresses in the small units.

f.

All coupling and shaft fits and finishes shall meet the requirements of Article 6.5.1 for hubs on shafts. Couplings shall be keyed to the shafts. The couplings shall in all cases be fitted to their shafts in the shop.

6.5.16 LONGITUDINAL THRUST (1983) R(2003) Wheels and similar parts shall be securely fastened, to prevent longitudinal movement, by set screws through the hub, or by clamps around the shaft. Provision shall be made to hold bevel gears and worm wheels against movement along the shaft. The axial thrust from bevel gears shall be taken by the shaft bearing by means of a loose bronze washer between the gear hub and the face of the bearing, or by an equivalent means.

6.5.17 COLLARS (1997) R(2003) Collars shall be provided wherever necessary to prevent the shaft from moving axially. There shall be at least two set screws, 120 degrees apart, in each collar. The set screws shall have dog points, and the shafts shall be counterbored for the set screws. The edges of the holes shall be peened over the set screws after the collars are

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adjusted. Where a shaft or trunnion receives an axial force, a thrust bearing shall be provided to prevent axial movement.

6.5.18 GEAR TEETH (1983) R(2003) a.

Gear teeth, unless specifically specified otherwise, shall be machine cut, shall be of the involute type, and shall have a pressure angle of 20 degrees. Gears in general shall have straight spur teeth of full depth. For special applications, stub teeth may be used. For tooth speeds over 1200 feet per min, and for tooth speeds over 500 feet per min, where quiet operation is desired, helical gears shall preferably be used. Helical gears shall be assembled in a common frame, shall be fully enclosed in a metal housing, and shall run in oil; they shall be assembled so that one gear of each pair of mating gears may have a slight axial movement to permit operation at the correct location relative to the other gear. Unless otherwise specified, all gear teeth shall be cut from solid rims.

b. For full-depth spur gear teeth, the addendum shall be not more than 0.3183 of the circular pitch and the tooth thickness measured on the pitch circle shall be 0.495 of the circular pitch. For stub teeth, the addendum shall be not more than 0.2546 of the circular pitch. c.

The face width of a spur gear shall be not less than 1.5 times the circular pitch. The face width of a bevel gear shall be not more than one-third of the slant height of the pitch cone, nor more than 3 times the circular pitch at the middle section of the tooth.

d. The circular pitch of spur gears, other than motor pinions, transmitting power for moving the span, shall be not less than 1 inch, and for motor pinions not less than 3/4 inch. The circular pitch for main rack teeth shall be not less than 1-1/2 inches. e.

Pinions shall have not less than 15 teeth. Rack pinions preferably shall have not less than 17 teeth. Motor pinions preferably shall have not less than 19 teeth.

f.

Helical gear teeth shall be cut to the same normal profile as spur gear teeth. The helical angle shall be not less than 23 degrees and not more than 30 degrees. The net width of face, measured parallel to the axis of the bore, shall be not less than 3 times the circular pitch nor more than 1.5 times the pitch diameter of the pinion.

1

3

6.5.19 STRENGTH OF GEAR TEETH (1983) R(2003) a.

In the design of spur gears, bevel gears, and helical gears, the load shall be taken as applied to only one tooth.

b. The tooth profile for spur, bevel and helical gears shall be the 20 degrees, full depth or stub, involute and shall be of the proportions stated in Article 6.5.18. c.

The allowable load on gear teeth shall conform to the following formulas: (1) Spur gears and bevel gears: (a) For full-depth involute teeth: 0.912 600 W = psf æ 0.154 – --------------ö -------------------è n ø 600 + V (b) For stub involute teeth:

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1.033 600 W = psf æ 0.178 – --------------ö -------------------è n ø 600 + V (2) Helical teeth, full depth: 1200 W = 0.7psf æ 0.154 – 0.912 --------------öø -----------------------è n 1200 + V where: W = allowable tooth load, lb p = circular pitch, inch s = permissible unit stress, psi f = effective face width, inch n = number of teeth in gear V = velocity of pitch circle, feet per min. d. The effective face width for spur and bevel gears shall be the full face width up to 3 times the circular pitch; for greater face widths, the effective width shall be 3 times the circular pitch but not less than onehalf the full width. e.

The effective face width for helical gears shall be the net active width of face measured parallel to the axis of the bore.

f.

For calculating the strength of bevel gear teeth, the middle section of the tooth shall be taken. The number of teeth “n” in the above formulas for bevel gear teeth shall be the formative number which, for the pinion, is determined as follows: np 2 n = np 1 + æ -------ö è ngø where: np = actual number of teeth in pinion ng = actual number of teeth in gear

g.

The basic allowable stresses, psi, for cut gear teeth of all types shall be: Bronze . . . . . . . . . . . . . . . . . . . . . . . . 9,000 Cast steel . . . . . . . . . . . . . . . . . . . . . . 16,000 Class C forged carbon steel . . . . . . . 20,000 Class D forged carbon steel . . . . . . . 22,500 Forged alloy steels . . . . . . . . . . . . . . 60% of tensile yield point, but not more than 1/3 of ultimate tensile strength.

h. The basic allowable stress, psi, for machine molded teeth shall be:

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Cast steel . . . . . . . . . . . . . . . . . . . . . 8,000 i.

For racks and their pinions and for all other mating gears and pinions which are not supported in and shop-assembled in a common frame, the basic allowable stresses shall be decreased 20%.

6.5.20 WORM GEARING (2003) a.

Except for the end and center wedges of swing bridges, worm gearing preferably shall not be used for transmitting power. In calculating the strength of worm gear teeth, the load transmitted shall be taken as equally distributed between two teeth. If used for span operating machinery, worm gearing shall be designed to be back driven without damage.

b. Worm gear reducers for transmitting power preferably shall be commercial units selected on the basis of their rating under the American Gear Manufacturers Association recommended practice. The helix angle of the worm shall be not less than 20 degrees. The worms shall be heat-treated alloy steel forgings and the gear shall be bronze. The thread of the worm shall be ground and polished, and the teeth of the gear shall be accurately cut to the correct profile. The worm and gear-thrust loads shall be taken by antifriction bearings, mounted in water and oil tight housings. The unit shall be mounted in a steel or cast iron housing and the lubrication shall be continuous while in operation. c.

Worm gear units used for end and center wedges of swing bridges shall be self-locking.

6.5.21 SCREW GEARING AND CAMS (1983) a.

1

Except for end lifts and center wedges of swing bridges, screw gearing preferably shall not be used for transmitting power.

b. Screws and nuts for transmitting power shall be cut with 29 degree general purpose Acme thread. Antifriction bearings shall be provided to carry all thrust loads. The unit shall be mounted in an oil and watertight housing and provided with continuous lubrication. The screw and nut shall be made of dissimilar metals, preferably steel and bronze. c.

3

Cams and similar devices transmitting power by line or point contact shall not be used.

6.5.22 HUBS (1983) R(2010) a.

Where practicable, the length of all hubs shall be not less than the diameter of the bore, and for gears also not less than 1.25 times the width of the teeth. The thickness of the hub preferably shall not be less than 0.4 of the diameter of the bore.

b. Unless otherwise specified, all hub and shaft fits and finishes shall meet the requirements of Article 6.5.1. Hubs shall be provided with keys designed to carry the total torque. c.

Bascule trunnion hubs that are to fit tightly into structural parts shall have an ANSI Class FN2 fit therein, and shall be secured against rotation by keys or bolts.

6.5.23 KEYS AND KEYWAYS FOR MACHINERY PARTS (2003) R(2010) a.

Keys for securing machinery parts to shafts shall be parallel-faced, square or flat, except that tapered keys may be used to meet special requirements. All keys shall be fitted into keyways sunk into the hub and shaft. Preferably, the keyways in the shaft shall have closed ends, which shall be milled to a semicircle equal to the width of the key. Keyways shall not extend into any bearing.

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b. Keys that are not set into closed-end keyways shall be held by safety set screws, or other effective means; in vertical shafts, collars clamped about the shafts, or similar devices, shall be used. c.

In hubs of spoked wheels, the keyways shall be located in the centers of the spokes. If two keys are required, they shall be placed 120 degrees apart.

d. All keys shall have a width not greater than one-quarter of the shaft diameter and the thickness of flat keys shall be approximately three-quarters of their width. e.

Details of keys and keyways shall conform to ANSI B17.1 except for the fit of keys which is covered in Table 15-6-5.

6.5.24 KEYS FOR TRUNNIONS (1983) R(2010) a.

The foregoing requirements for keys and keyways are for machinery parts, whose use is intended to develop the full torsional strength of the shaft.

b. For trunnions and similar parts which are designed chiefly for bending and bearing, the keys and keyways shall be proportioned simply to hold the trunnion from rotating. The force tending to cause rotation shall be taken as one-fifth of the load on the trunnion acting at the circumference of the trunnion.

6.5.25 BOLTS AND NUTS (2003) a.

Bolts for connecting machinery parts to each other or to steel supporting members shall conform to one of the following types: (1) Finished, high-strength bolts. (2) Turned bolts, turned cap screws, and turned studs. (3) High-strength turned bolts, turned cap screws, and turned studs.

b. Finished high-strength bolts shall meet the requirements of ASTM A449. High-strength bolts shall have finished bodies and regular hexagonal heads. Holes for high-strength bolts shall be not more than 0.01 inch larger than the actual diameter of individual bolts and will require drilling holes to match the tolerances for each bolt. The clearance shall be checked with 0.011 inch wire. The hole shall be considered too large if the wire can be inserted in the hole together with the bolt. c.

Turned bolts, turned cap screws, and turned studs shall have turned shanks and cut threads. Turned bolts shall have semi-finished, washer-faced, hexagonal heads and nuts. Turned cap screws shall have finished, washer-faced, hexagonal heads. Finished shanks of turned fasteners shall be 1/16 inch larger in diameter than the diameter of the thread, which shall determine the head and nut dimensions. The shanks of turned fasteners shall have Class LT1 fit in the finished holes in accordance with ANSI Standard B4.1. The material for the turned shank fasteners shall meet the requirements of ASTM A307, Grade A.

d. High-strength turned bolts, turned cap screws, and turned stud details shall be as specified in paragraph c, except that the material shall meet the requirements of ASTM A449. e.

Elements connected by bolts shall be drilled or reamed assembled to assure accurate alignment of the hole and accurate fit over the entire length of the bolt within the specified limit.

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f.

The dimensions of bolt heads, nuts, castle nuts, and hexagonal head cap screws shall be in accordance with ANSI Standard B18.2, Square and Hexagon Bolts and Nuts.

g.

Heads and nuts for turned bolts, screws, and studs shall be heavy series.

h. The dimensions of socket-head cap screws and socket flathead cap screws shall conform to ANSI Standard B18.3. The screws shall be made of heat-treated alloy steel, cadmium-plated, and furnished with a self-locking nylon pellet embedded in the threaded section. i.

Threads for bolts, nuts, and cap screws shall conform to the coarse thread series and shall have a Class 2 tolerance for bolts and nuts or Class 2A tolerance for bolts and Class 2B tolerance for nuts in accordance with ANSI Standard B1.1, Unified Inch Screw Threads.

j.

Bolt holes through unfinished surfaces shall be spotfaced for the head, nut, and washer, square with the axis of the hole.

k. Unless otherwise called for, bolt holes in machinery parts or connecting these parts to the supporting steel work shall be subdrilled at least 1/32 inch smaller in diameter than the bolt diameter. They shall be reamed for the proper fit at assembly or at erection with the steel work after the parts are correctly and finally assembled and aligned and the supporting steel work subdrilled. l.

Holes in shims and fills for machinery parts shall be reamed or drilled to the same tolerances as the connected parts at final assembly.

m. Positive locks of an approved type shall be furnished for nuts, except those of ASTM A449 bolts which are tensioned at installation to at least 70% of their required minimum tensile strength. If double nuts are used, they shall be used for connections requiring occasional opening or adjustment. If lock washers are used for securing, they shall be made of tempered steel and shall conform to the SAE regular dimensions. The material shall meet the SAE tests for temper and toughness. n. High-strength bolts shall be installed with a hardened plain washer meeting ASTM F436 at each end. o.

1

3

Wherever possible, high-strength bolts connecting machinery parts to structural parts or other machinery parts shall be inserted through the thinner element into the thicker element.

p. Cotters shall conform to the SAE standard dimensions and shall be made of half-round stainless steel wire, ASTM A276, Type 316.

4 q. Anchor bolts connecting machinery parts to masonry shall be ASTM A307, Grade A or Grade C material, hot-dipped galvanized per ASTM A153. Bolts shall be as shown on the masonry drawings. Anchor bolts for new construction preferably shall be cast-in-place and not drilled. The Engineer shall specify the material and loading requirements for the given design condition. When these fasteners connect a mechanical component directly to the concrete, filler material must be put in the annular space between the bolt and the bolt hole in the machinery component. The filler material may be a non-shrink grout, tin based babbitt metal, or zinc. r.

Nuts shall be of material and grade to match or exceed the strength of the bolts on which they are used.

s.

Fasteners shall be of North American manufacture and shall be clearly marked with the manufacturer’s designation.

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6.5.26 SET SCREWS (1997) R(2010) Set screws shall not be used for transmitting torsion; they may be used for holding keys or light parts in place. They shall be safety-type headless set screws with dog points, set in counterbored seats. Unless otherwise ordered, they shall be secured in position by peening over the holes, or by welding.

6.5.27 TAPPED HOLES (1983) R(2010) Machinery parts shall not be joined together or mounted on structural supports by means of bolts or studs in tapped holes, except by special permission of the Engineer. This does not apply to joints in component parts of standard manufactured items.

6.5.28 SPRINGS (1983) R(2010) Springs preferably shall not be used to actuate any moving part. For electric parts, preference will be given to those having the fewest springs.

6.5.29 EQUALIZERS (1983) R(2002) The net section back of the pinhole in equalizing levers shall be not less than the net section in tension required to carry the load on the pin. The net section through the pinhole shall be not less than 140% of the required net section in tension.

6.5.30 COVERS (2003) a.

Dust covers shall be provided where necessary to protect sliding and rotating surfaces and prevent dust from mixing with lubricants.

b. Gear safety guards shall be provided for gears in machinery houses. c.

Shaft safety guards shall be provided for shafts in machinery houses.

d. Where gears or sheaves are located where falling objects may foul them, they shall be protected by easily removed metal covers. e.

Counterweight sheave rims shall be covered to protect them from the weather.

6.5.31 SAFETY DEVICES (1983) R(2002) Safety devices such as hand rails, chains and cages shall be installed where needed. Applicable safety regulations shall be observed.

6.5.32 DRAIN HOLES (1983) R(2002) Drain holes not less than 1 inch diameter shall be provided at places where water is likely to collect.

6.5.33 COMPRESSED AIR DEVICES (2003) Mechanical devices powered by compressed air may be used for the operation of center wedges, end lifts, centering devices, and sliding rail locks. Air motors may be used for emergency power for span operating machinery. Means shall be provided to keep compressed air systems free of condensed moisture and ice.

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6.5.34 SPECIAL PROVISIONS FOR SWING BRIDGES (2003)1 6.5.34.1 Center Bearing Center-bearing swing bridges shall be so designed that when the bridge is swinging, the entire weight of the moving span is carried on a center pivot, and when the bridge is closed, the trusses or girders rest at the center on wedges. Adjustment for height shall be provided. 6.5.34.2 Rim Bearing a.

The load on the rim girder of a rim-bearing or combined rim- and center-bearing swing bridge shall be distributed equally among the bearing points, which shall be spaced equally around the rim girder.

b. Rigid struts firmly anchored to the rim girder shall connect the rim girder to a center pivot. A strut shall be attached to the rim girder at each bearing point, and at intermediate points where required. No fewer than eight struts shall be used in any case. c.

The rim girder shall be designed so that the load will be properly distributed over the rollers. For designing the girder, the loads shall be assumed to be distributed equally to all rollers. The span length shall be taken as the developed length of the girder between adjacent bearing points, and this length shall be considered fixed at both ends. The girder shall be designed in accordance with the requirements for plate girders.

d. The lower track shall be designed to distribute the roller load uniformly over the masonry.

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6.5.34.3 Combined Bearing In a combined rim and center-bearing swing bridge, a definite portion of the load, not less than 15%, shall be carried to the center pivot by radial girders attached rigidly to the center pivot and to the rim. 6.5.34.4 Shear Over Center

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In swing bridges having a center truss panel, this panel shall be so designed that shear will not be carried past the center. The web members of such a panel shall be strong enough to secure the bridge against longitudinal wind pressure when it is open. 6.5.34.5 End Wedges and Center Wedges End wedges of swing bridges shall be arranged to center the closed bridge accurately, unless a separate device is used to center the bridge. The end and center wedges shall be so designed that the action of the moving load cannot cause displacement of the end supports and wedges in case of failure or disconnection of the mechanism which actuates the end lift. The end and center wedges shall be so designed as to permit adjustment, and may be operated by the same mechanism. (See Commentary) 6.5.34.6 Rim Girders a.

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Rim girders shall be provided with stiffeners on both sides of the web at points of concentrated loading. These stiffeners shall be milled or ground to fit tightly against both flanges. The distance between adjacent intermediate stiffeners shall not exceed 2 feet. On rim girders exceeding 5 feet depth, alternate intermediate stiffeners may extend only one-half the depth of the girder, unless required to be of full depth to stiffen the web. The thickness of the stiffeners shall be not less than one-eighth of their width. The tread plate for the rollers shall be securely fastened to the rim girder and shall be from 2 inches to 3

See Part 9 Commentary

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inches thick, depending on the weight of the bridge. The rim girder flange angles shall be not smaller than 6²´4²´3/4². For welded construction, the flange plates shall not be less than 1 inch thick. b. Provisions shall be made for jacking the entire span. 6.5.34.7 Center Pivots a.

Center pivots shall consist of disk bearings, upon which the span revolves, and supporting pedestals. Disk bearings shall consist of two disks, one of phosphor bronze and one of hardened steel.

b. Center pivots shall be so designed that the disks may be taken out and replaced while the bridge is closed, without interfering with the operation of trains over the bridge. The disks shall be so anchored that sliding will take place only at the surface of contact. 6.5.34.8 Balance Wheels a.

For power operated center bearing bridges, no fewer than eight wheels, running on a circular track, shall be provided to limit the tilting of the bridge and to carry the wind load to the track while the bridge is swinging. The balance wheel bearings shall be adjustable for height, preferably by shims between the superstructure and the seats of the bearings. For short, single track, hand operated bridges, four wheels may be used.

b. Fits and finishes for wheel hubs on shafts shall meet the requirements of Article 6.5.1. The axles shall rotate in bronze lined bearings, with means for lubrication. 6.5.34.9 Rack and Track The rack and track of swing bridges shall be made in sections, preferably not less than 6 feet long. The track shall be deep enough to ensure good distribution of the balance wheel or roller loads to the masonry, and not less than 4 inches for rim-bearing bridges. If a cast track is used and the loads are light, as in center bearing bridges, the rack and track segments preferably shall be cast in one piece. In rim bearing bridges, the rack shall be cast separately from the track, so that the parts may be easily removed for repairs. The joints in the rack and track shall be staggered. The track shall be anchored to the masonry by bolts not less than 1-1/2 inches diameter, extending at least 12 inches into the masonry, and set in non-shrink grout. The track of hand operated, center bearing bridges shall have an ample number of anchor bolts so that the mortar or grout in which they are set will not be crushed by the tractive force developed when turning the bridge. Where center bearing bridges are operated by mechanical power, the track shall be anchored down by bolts, and the tractive force developed when turning the bridge shall be taken by lugs extending down into the masonry and set in non-shrink grout or concrete. 6.5.34.10 Main Pinion Shaft Bearings a.

Where two main pinions are used they shall be placed diametrically opposite, and where four pinions are used, they shall be placed in pairs which shall be diametrically opposite.

b. Each main pinion shaft shall be supported in a double bearing, which shall be provided with bolted caps, split linings, and liners, to permit easy removal of the pinion shaft and to provide adjustment for wear. A bronze thrust collar shall be provided at the top bearing to carry the weight of the pinion, shaft and gear. The double bearing and its supports shall have ample strength and stiffness for the maximum pinion load, including effects of maximum acceleration and deceleration forces, and shall be rigidly attached to the rim girder or superstructure. c.

Sufficient shims shall be provided between the bearing base and the steelwork to provide for any necessary adjustment in position of the bearing. Where practicable, the bearings shall be shipped assembled to the steelwork, with the shims in place. © 2011, American Railway Engineering and Maintenance-of-Way Association

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Movable Bridges 6.5.34.11 Equalizing Devices Power operated swing spans shall have no fewer than two main pinions. These pinions shall be connected by mechanical devices which will equalize the torques at the pinions, unless such equalization is provided by other means acceptable to the Engineer.

6.5.35 SPECIAL PROVISIONS FOR BASCULE BRIDGES (2008) 6.5.35.1 Rail End Connections Where rail end connections are of the sliding-lock type, the sliding locks at the heel end of the bridge shall be on the approach. 6.5.35.2 Centering Devices Bascule bridges shall be equipped with self centering devices at the toe end. Transverse centering shall be accomplished by a device preferably located on the centerline of the bridge as near the track level as practicable, with a clearance not to exceed 1/16 inch. 6.5.35.3 Locking Devices There shall be a locking device at the end for each girder or truss to force down and hold down the toe end to its seats.

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6.5.35.4 Air Buffers Power operated bridges shall be equipped with air buffers to aid in stopping the span smoothly in either the open or closed positions. Single track bridges having girders or trusses not more than 10 feet center to center shall have one air buffer at the toe end of the bridge. All other bridges shall have two air buffers at the toe end of the bridge.

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6.5.35.5 Segmental Girders and Track Girders a.

The flanges of segmental and track girders of rolling lift bridges shall be symmetrical about the central planes of the webs. Central planes of webs of segmental girders shall coincide with the central planes of webs of the track girders. The treads attached to the segmental girders and track girders shall be steel castings, steel forgings or rolled steel plates, and shall not be considered as part of the flanges of these girders.

b. The allowable line bearing load per linear inch between treads for segments having a diameter of 120 inches or more shall not exceed: ( F y – 15, 000 ) ( 12 , 000 + 80D ) -----------------------------------20, 000 where: D = the diameter of the segment, inch Fy = the yield point of the material, psi c.

The thickness of solid tread plates shall not be less than 3 inches plus 0.004 D. The effective length of line bearing for solid tread plates shall not exceed the thickness of the web of the segmental or track

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girder, plus the thickness of the side plates, plus 1.6 times the thickness of the tread plate. The edges of the webs and side plates, and the backs of the flange angles, shall be machined so as to bear continuously on the tread plate. d. The bearing stress of the tread plates on the web plate shall not exceed one-half the yield point of the material. The length of the area in bearing shall be taken as 2.0 times the least thickness of the tread and the width as the thickness of the web plus the effective thickness of the side plates for calculation purposes. Flange angles shall not be considered as transmitting any load from the web to the treads, and the bearing value of side plates shall not exceed the strength of those fasteners or welds connecting them to the web which are included between diverging lines in the plane of the web that intersect in the line contact between the treads and that make an angle with the normal to the rolling surfaces at that point whose tangent is 0.8. The load, as used in this paragraph, shall be the dead weight of the structure alone. e.

Tread plates may be flange and web castings. The edge thickness of the rolling flange shall be not less than 3 inches and the flange thickness at the face of the web of the casting shall be such that the bearing stress on the web of the casting shall not exceed one-half the yield point of the material, the length of bearing being taken as 2.0 times the depth from the rolling face to the plane under consideration.

f.

Solid tread plates on segmental girders shall have a radius slightly smaller than the segmental girders in order to secure tight contact with the girders throughout their length when drawn up with the attaching bolts.

g.

Where not otherwise specified on the plans, all tread plates shall be made as long as practicable. Where tread plates are made in segments, the faces of the tread plates at the joints between the segments shall be in planes at right angles to the rolling surface and preferably at an angle of 45 degrees to 60 degrees with the longitudinal centerline of the tread plate.

h. Those portions of the segmental and track girders, which are in contact when the bridge is closed, shall be designed for the sum of the dead load, the live load, and an impact load equal to the live load. Under this loading, the allowable line bearing shall be 150% of that given in paragraph b above. i.

The segmental and track girders shall be reinforced with stiffeners and diaphragms.

6.5.35.6 Location of Machinery The machinery preferably shall be located on the stationary part of the bridge. 6.5.35.7 Equalizing Devices There shall be mechanical devices on bascule bridges to equalize the torques at the two main pinions, unless such equalization is provided by other means acceptable to the Engineer.

6.5.36 SPECIAL PROVISIONS FOR VERTICAL LIFT BRIDGES (1997)1 6.5.36.1 Centering Devices Bridges shall be equipped with self centering devices at each end. Transverse centering shall be accomplished by devices located on the center line of bridge, as near the track level as practicable, with a clearance not to exceed 1/16 inch. For truss bridges these centering devices shall be supplemented by close transverse centering of the unloaded chords, accomplished by special centering devices or by the span guides.

1

See Part 9 Commentary

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Movable Bridges 6.5.36.2 Locking Devices Vertical lift bridges shall be equipped with locking devices to prevent the span from rising after it has been seated by the operating machinery. At each end there shall be a locking device on the center line of bridge for single track bridges, and a locking device at each outside girder or truss for multiple track bridges. 6.5.36.3 Span Guides The lift span and its counterweights shall be held in position transversely and longitudinally during movement by means of guides engaging guide flanges on the towers. Truss spans shall have transverse guides at both top and bottom chords. Guides may be of either the sliding or the rolling type. The ends of guide flanges shall be planed smooth. The guides shall be adjustable, and shall preferably be set to provide a normal running clearance of 3/8 inch. For the seated position of the span, the clearance may be reduced to 1/8 inch. 6.5.36.4 Air Buffers a.

Power operated vertical lift bridges shall be equipped with air buffers, except as permitted in Article 6.5.3, to aid in seating the span smoothly. Single track bridges having girders or trusses not more than 10 feet center to center, shall have an air buffer at each end of the bridge. All other bridges shall have two air buffers at each end of the bridge.

b. Power-operated bridges shall be equipped with air buffers, except as permitted in Article 6.5.3, to aid in stopping both the moving span and counterweights without damage to the structure, in the event that the span is raised above the prescribed limit.

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6.5.36.5 Counterweight Pockets The balance-block pockets shall be placed as near the ends of the counterweights as practicable, in order to aid in securing the required balance between the lift span and the counterweights at each of the four corners of the span.

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6.5.36.6 Clearance Below Counterweights The counterweights shall clear the track rails by not less than 5 feet when the span is fully open. In computing this clearance the counterweight ropes shall be assumed to stretch 1% of their length in addition to the elastic elongation.

4

6.5.36.7 Equalizing Devices Vertical lift spans operated through pinions engaging racks on the counterweight sheaves shall have devices to equalize the torques at the rack pinions when two counterweight sheaves and two pinions are used at each corner of the span. Equalizing devices shall not be used between pinions on opposite sides of the span, but adjusting devices shall be provided between such pinions, to permit transverse leveling of each end of the span. 6.5.36.8 Counterweight Sheaves a.

For main counterweight ropes, the pitch diameter of the sheave, center to center of ropes, shall be not less than 72 times the rope diameter, and preferably not less than 80 times. For auxiliary counterweight ropes, the pitch diameter of the sheave shall be not less than 60 times the rope diameter.

b. Counterweight sheaves shall have shrink fits on their shafts, and shall be secured by driving-fit dowels set in holes drilled after the sheave is shrunk onto the shaft.

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c.

The shape of the grooves shall conform as closely as feasible to the rope cross-section so that the ropes run freely in the grooves without flattening. The distance center to center of grooves shall not be less than 1/4 inch more than the diameter of the rope.

6.5.36.9 Operating Drums and Deflector Sheaves a.

For operating ropes, the diameter of the drums and deflector sheaves shall be not less than 45 times the rope diameter, and preferably not less than 48 times, except for deflector sheaves with small angles of contact between rope and sheave.

b. Operating drums shall have pressed fits on their shafts, and in addition shall have keys designed to carry the total torque to be transmitted to the shafts. c.

The shape of the grooves shall conform as closely as feasible to the rope cross section. The distance center to center of grooves shall not be less than 1/8 inch more than the diameter of the rope.

d. Deflector sheaves shall generally have the same diameter as the drums. Intermediate deflector sheaves shall be provided as necessary to prevent rubbing of the ropes on other parts and to avoid excessive rope sag. When operating ropes have small angles of contact with deflector sheaves, the sheaves shall be supported on roller or ball bearings and shall be designed as light as practicable to ensure easy turning and minimum rope slippage in starting and stopping. e.

All deflector sheaves shall have deep grooves to prevent displacement of the ropes.

6.5.36.10 Welded Sheaves a.

Sheaves fabricated by welding shall be made of structural steel, ASTM A 36 or A 709 Grade 36 or of forged carbon steel, ASTM A 668, Class D. The rim shall be fabricated from not more than three pieces of plate. It shall be welded into a complete ring and the welds ground flush on all four sides before being welded into the sheave assembly. Each web shall be fabricated from not more than two pieces of plate. Web welds, if used, shall be ground flush on both sides. The hub shall be made from a one-piece forging.

b. In addition to the strength requirements of Section 6.4, Basic Allowable Stresses and Hydraulic Pressures, the calculated fatigue stress range, SRfat, of welds and base metal, under conditions of impact load, shall not exceed the allowable values given in Part 1, Design, Table 15-1-10. c.

All welds shall be full-penetration groove welds and made with low hydrogen procedures. Automatic submerged arc welding shall be used to the greatest extent practicable. After completion of the weldment and before final machining, the sheave shall be stress relieved.

6.5.36.11 Counterweight Ropes a.

The connections of the counterweight ropes to the lift span and counterweights shall be so made as to permit ready replacement of any one rope without disturbing the other ropes. Provision shall also be made for replacement of all the ropes simultaneously, preferably by supporting the counterweights from the towers.

b. On the lift span side, the counterweight ropes shall be separated sufficiently to prevent objectionable slapping of the ropes against each other while the span is in the closed position. This may be accomplished either by use of widely spaced grooves on the sheaves, by using deviations of the ropes from a vertical plane, or by other approved means.

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c.

The transverse deviation of a counterweight rope from a vertical plane through the center of the groove on the sheaves, preferably shall not exceed one-half the spacing of the grooves, shall be the same for all the ropes on a sheave, and shall not exceed 1 in 40. The longitudinal deviation of a counterweight rope leading from the sheave, measured from a vertical plane tangent to the pitch diameter of the sheave, shall not exceed l in 30, and shall be the same for all the ropes on a sheave. These deviations shall not be exceeded on the span side for the lift span in its highest possible position, and on the counterweight side for the span in the closed position.

d. The several ropes of a group shall have equal loads, accomplished either by adjustment during erection, by fabrication of the ropes in the shop to the exact required lengths without tolerance with provision for future adjustment if required, or by use of equalizers. e.

The connections of ropes shall be so made that the centerline of the rope adjacent to the socket is at all times at right angles to the socket pin axis for pin sockets and to the socket bearing face for block sockets. Rope deflector castings or plates, or equivalent devices, shall be provided near the sockets, where necessary, to accomplish this result.

6.5.36.12 Operating Ropes a.

The transverse rope deviation from a plane through the groove of a drum or sheave at right angles to the axis of its shaft of the drum or sheave shall not exceed 1 in 30, and preferably shall not exceed 1 in 40.

b. There shall be at least two full turns of the rope on the operating drum when the span is in the closed or fully open position and the end of the rope shall be securely clamped to the drum in such a way as to avoid sharp bends in the wires. c.

1

Turnbuckles or other devices shall be provided for taking up slack in the ropes. The take-ups shall not permit any rotation of a rope about its axis. Take-ups shall be readily accessible for operation by one man.

6.5.36.13 Balance Chains

3

Chains for balancing counterweight ropes shall be made of cast iron links, connected by rust-resistant steel pins, placed in bored or reamed holes. The holes shall be of uniform size, carefully located, and at right angles to the length of the links. The chains shall hang freely in vertical planes without twists. The pins shall be fitted with washers and round cotter pins.

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6.5.37 HYDRAULIC SYSTEMS (2000) R(2002) 6.5.37.1 Drawings a.

Design drawings and specifications shall conform to ANSI(NFPA/JIC) T2.24.2-1990 System Standard, hereinafter referred to as the “ANSI System Standard”, Section 6.3, and will be furnished by the Company or, if stated in the invitation for bids, by the Contractor.

b. Design drawing originals shall be on reproducible material, preferably Mylar. c.

As-built changes made by the Contractor shall be recorded by the Contractor in accordance with ANSI System Standard, Section 6.4.3.

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Steel Structures 6.5.37.2 Identification All hydraulic components shall be identified in accordance with ANSI System Standard, Section 6.5, including those located within manifolds, mounting plates, pads or fittings. 6.5.37.3 Accessibility a.

All hydraulic components shall be mounted, located and arranged to be readily accessible for adjustment and maintenance.

b. Hydraulic components shall be located such that the adjustment and maintenance of one component does not disturb the adjustment or maintenance of another. c.

Connections of flexible lines, fabricated pipe, and tubing runs shall be accessible. Where flexible lines and/or piping runs terminate in a fitting cluster, clearances should permit securing each threaded joint without disturbing adjacent piping or equipment. Flexible lines, fabricated pipe, and tubing runs shall be removable without disturbing the terminal components.

6.5.37.4 Safety Included are the safety-related requirements from other articles of this section, which have been repeated below primarily for those interested in this important phase of hydraulic application. 6.5.37.4.1 Safe Circuitry Hydraulic circuits shall be designed and components selected, applied, mounted, and adjusted to safely provide uninterrupted operation, extended life, and shall be fail-safe. Circuits shall: (1) Operate within the component maufacturer’s specifications. (2) Be protected against overpressure. (3) Be so designed and applied that surge pressure, overpressure, and loss of pressure do not cause hazard or damage to the equipment. (4) Be so designed and constructed that components attached to the equipment are located where they can be safely serviced. 6.5.37.4.2 Control Station Nameplates A nameplate shall be provided for each control station component and shall be located where it can be easily read by the equipment operator. The nameplate information shall be pertinent and easily interpreted, providing positive identification of the control component and its function. 6.5.37.4.3 Emergency Stop and Return Controls All equipment shall incorporate an emergency stop or return control. Duplicate emergency controls shall be provided at each operator station. Emergency stops and return controls: (1) Shall be readily accessible from the operator’s working position. (2) Shall not release any locating pin, index drive engagement, latch, lock, or clamping device. (3) Shall operate immediately. © 2011, American Railway Engineering and Maintenance-of-Way Association

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(4) Shall be independent and unaffected by the adjustments of other controls or flow restrictions. (5) Shall provide a blocking valve upstream in the supply line of the servo valve(s) for emergency stop. (6) Shall not require energizing any control element. (7) Shall not require operation of more than one manual control for all emergency functions. (8) Shall not create an additional hazard. 6.5.37.4.4 Two Hand Control Where pinch points and other movement hazards are exposed to the operating personnel, two-hand manual controls shall be provided each operator, which: (1) Require maintained actuation of each control throughout the equipment cycle or until the point in the cycle is reached where the hazard ceases. (2) Are so located and guarded that operation by means other than both hands is prevented. (3) Are so designed that the equipment cannot be operated unless both manual controls at each control stations are released between cycles. 6.5.37.4.5 Location of Manual Controls

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The location and mounting of manual controls shall: (1) Place the controls within reach of the equipment operator from the operator’s normal working position(s). (2) Not require the operator to reach past rotating or moving equipment elements or work in the process to operate the controls.

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(3) Not interfere with the equipment operator’s required working movements. 6.5.37.4.6 Manual Control Levers Manually activated levers shall move in the same direction as the resulting motion of the related equipment element. 6.5.37.4.7 Control Media Failure Hydraulic devices controlled electrically, pneumatically, and/or hydraulically shall be selected and so applied that failure of the control media does not cause a hazard or damage to the equipment. 6.5.37.4.8 Uncontrolled Movement The circuits shall be designed to prevent uncontrolled movement and improper sequencing of the hydraulic acuators during all phases of the equipment cycle, including pump idling, starting, and stopping. 6.5.37.4.9 Counterbalancing On vertical and inclined equipment slides, rams, and other similar equipment elements, means shall be provided to prevent their rapid drop. © 2011, American Railway Engineering and Maintenance-of-Way Association

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Steel Structures 6.5.37.4.10 Accumulator Safety 6.5.37.4.10.1 Automatic Vent Hydraulic circuits incorporating accumulators shall automatically vent the accumulator when equipment is shut off. Isolation shall prevent uncontrolled movement of the actuators in case manual overrides on associated equipment are operated. 6.5.37.4.10.2 Pressure Isolation Where deviation is agreed to or a circuit application utilizes accumulator liquid pressure isolation only (not vented) when the equipment is shut off, complete information for proper servicing shall be given on or near the accumulator in a visible location. The information shall include the statement: CAUTION - PRESSURIZED VESSEL. Duplicate information shall be provided on the graphical diagram. 6.5.37.4.10.3 Discharge Rate Accumulator discharge rates shall be restricted to the demands of the intended service. 6.5.37.4.10.4 Charging Medium Gas accumulators shall be charged with nitrogen or an inert gas. 6.5.37.4.11 Flexible Hose Failure Flexible hose shall be restrained or confined where its failure would constitute a hazard. 6.5.37.5 Hydraulic System Controls 6.5.37.5.1 Methods of Operator Control a.

Hydraulic system controls shall be designed to permit the bridge operator to control, from the control station, the rate and direction of fluid flow for span movement and the operation of auxiliary equipment such as rail locks, span locks, wedges, barriers and other devices associated with the movement of the span. Controls shall be of the type that will automatically maintain constant fluid flow, within 5% of maximum flow during full load change, without operator assistance regardless of normal operating pressure fluctuations, except during periods of acceleration and deceleration. Requirements for hydraulic system controls shall conform with the ANSI System Standard, Section 7.

b. Methods of operating the hydraulic system shall be classified as manual, semiautomatic or automatic control, as follows: (1) Manual control shall be defined as any system in which the operator must manually control the rate of fluid flow for span acceleration and deceleration in addition to the initiation of each of the several major interlocked functions in sequence. (2) Semi-automatic control shall be defined as any system where the fluid flow automatically increases from zero to normal volume and back to zero again for span acceleration and deceleration by the single operation of a push-button or hand lever. However, the operator must initiate each of the several major interlocked functions in sequence. (3) Automatic control shall be defined as any system where the operator can actuate the several major interlocked functions in sequence and the hydraulic system fluid flow automatically increases from

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zero to normal volume and back to zero again for span acceleration and deceleration, all by the operation of a single pushbutton or hand lever. Requirements for the sequencing of bridge functions, span speed control and interlocking shall be in conformance with Article 6.7.5. c.

Flows produced by fixed displacement pumps shall preferably be controlled by varying the speed of the pump drive motors. If pressure compensated flow controls are provided to control fixed displacement pump flow, the hydraulic system shall be designed to minimize heat build-up.

d. Variable displacement pump flows shall be directly controlled by manual stroking, or if remotely controlled, preferably by closed loop servo control systems. e.

Closed loop servo control systems shall be analyzed by the manufacturer of the servo control components to verify that the control system will perform as required. The servo component manufacturer shall furnish all necessary instructions on how to trim (adjust) and maintain the servo control system.

6.5.37.5.2 Control Stations 6.5.37.5.2.1 Location and General Requirements a.

The Operator’s control station shall be located for either direct (valve station) or remote (control console) operation of the hydraulic system. Direct operation shall be defined as hydraulic system control from the power unit or separate valve stand, by the use of manually operated directional or flow control valves, or the manual stroking of variable displacement pumps. Remote control shall be defined as hydraulic system control from a control console. Remote control shall be accomplished with pushbuttons or hand levers (joysticks) to operate solenoid controlled directional and flow control valves for fixed displacement pumps, or electrically operated servo valves or gear-motors for the stroking of variable displacement pumps.

b. Indicating lights, gages and other warning devices shall be provided at the control stations to monitor and protect the hydraulic system from damage due to low pressure, high pressure, low fluid level, high fluid level, low temperature, high temperature and pump servo valve malfunction. Requirements for pressure gages shall conform to Article 6.5.37.20.

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6.5.37.5.2.2 Valve Stations a.

4

Nameplates shall be provided for each control in accordance with Article 6.5.37.4.2.

b. Control valves for manual control shall be located as shown on the drawings or, if not shown, at a comfortable working height and oriented in such a way that water and railroad traffic can be readily observed by the operator. c.

Control valve handles for manual span operation shall be located for right handed operation by the operator. If separate control valves are provided for manual brake, lock or wedge operation, they shall be located for left handed operation by the operator.

d. When valves are to be controlled by the operator’s right and left hands simultaneously they shall preferably be located no more than 3 feet apart and in no case more than 4 feet apart. e.

Pressure gages shall be provided to monitor hydraulic system pressures and shall be located where they can be easily observed by the operator during bridge operation.

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Requirements for control consoles, instruments, position indicators and indicating lights shall conform with Article 6.7.5. 6.5.37.5.3 Pressure Controls Adjustable pressure control valves shall be provided in the hydraulic system to maintain desired pressure levels and to protect equipment from damage due to excessive operating and static pressures. 6.5.37.5.4 Shock and Surge Suppression a.

The hydraulic system and its controls shall be designed to minimize shock loads from pressure surges during system operation.

b. Automatic or pre-programmed acceleration and deceleration shall preferably be provided for span operation. Span movement controls shall preferably be designed such that if the operator tries to change direction of the span while it is moving, the span will decelerate smoothly to standstill and then smoothly accelerate to the same set speed in reverse. c.

Directional control valves and blocking valves shall be equipped with adjustable pilot control chokes for shock and surge pressure control if the velocity of the hydraulic fluid in the piping exceeds 20 feet per second.

d. Flexible hose may be used between fixed components to help control shock and surge pressures. When used for this purpose flexible hose and hose fittings shall have a minimum factor of safety as defined in Article 6.4.8.2. e.

Deceleration valves and/or accumulators shall be used in hydraulic systems with moderate to severe shock and surge pressures.

f.

Piping clamps shall have cushioned inserts to reduce vibration and noise and help to absorb shock in the piping system.

6.5.37.5.5 Temperature Control a.

Any unusual high or low temperature that affects hydraulic equipment operation shall be noted in the Special Provisions.

b. Reservoir hydraulic fluid temperature shall not be permitted to fall below 45 degrees F during periods of hydraulic system inactivity. Immersion and/or unit heaters controlled by automatic thermostats shall be provided where ambient temperatures fall below 45 degrees F. c.

Reservoir hydraulic fluid temperature shall not be permitted to rise above 140 degrees F during periods of hydraulic system operation. Reservoirs shall be sized large enough to dissipate heat and be located to have an adequate amount of free air circulation. If reservoir sizing and free air circulation will not control heat build-up, then heat exchangers shall be provided. Requirements for heat exchanges shall conform with ANSI System, Section 15.

d. Hydraulic systems originally not requiring heat exchangers but using fixed displacement pumps and relief valves, or pressure compensated flow control valves, for purposes of pump unloading, shall have provisions at the power units for the addition of heat exchangers at a later time, after the system has been installed at the bridge, if heat build-up during operation becomes excessive.

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Movable Bridges 6.5.37.5.6 Synchronization of Actuators Flow dividing devices or other means shall be provided in the hydraulic-system for the synchronous operation of end lifting devices or other equipment which is not mechanically connected but which must be synchronized for proper operation. 6.5.37.6 Hydraulic Power Units 6.5.37.6.1 General Requirements a.

Hydraulic power units shall conform to NFPA Standard T3.16.3M Requirements for Non-Integral Industrial Fluid Power Hydraulic Power Units.

b. The Contractor shall make assembly drawings, drawn to scale, of the hydraulic power unit. Each component of the hydraulic power unit, including piping, shall be identified. Nameplates shall preferably be shown on the assembly drawings at their actual locations on the hydraulic power unit. If nameplates cannot be shown on their actual locations a keyed nameplate list shall be provided on the power unit drawing. The Contractor shall submit the assembly drawings to the Company for approval. c.

Work shall not begin on the power unit until the shop drawings have been approved. Shipment of the hydraulic power unit to the bridge site for installation will not be permitted until it has been demonstrated to the Company that the unit has the ability to perform as specified. Power units shall be tested in conformance with Article 6.5.37.25.2.

d. Where the bridge operator is to operate the hydraulic system directly at the power unit, the overall height and location of the power unit shall not interfere with visibility of navigation or trains. e.

Requirements for piping, fittings and manifolds for power units shall conform with Article 6.5.37.10.

f.

Requirements for couplings to connect pumps to drive motors shall conform with Article 6.5.37.16.

g.

Hydraulic fluid shall be filtered as it is placed into the reservoirs, both during original reservoir filling and during the addition of make-up fluid. The fluid shall be filtered while being pumped from its original containers using portable filtration units. The degree of filtration shall be equal to 10 microns or the same as that used during normal hydraulic system operation, whichever is finer.

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6.5.37.6.2 Pumps

4 a.

Requirements for pumps shall conform with the ANSI System, Section 10.

b. Pumps shall be positive displacement of either the variable or fixed displacement type. Pumps shall be equipped with integral or add-on relief valves to prevent damage to pump and hydraulic system from high pressure. Relief valves shall not discharge into pump intake ports. c.

Piston type or gear type pumps shall be used in hydraulic systems where maximum operating pressures, as defined in Article 6.4.8, exceed 2000 psi.

d. Where noise control is an important consideration, such as when the hydraulic power unit is to be located in the bridge house, piston pumps shall be used. 6.5.37.6.3 Pump Actuators a.

Servo valve pump actuators shall be of the type which automatically return the pump to the neutral or zero pumping position in the event of pump control system malfunction, loss of electrical power or loss of © 2011, American Railway Engineering and Maintenance-of-Way Association

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hydraulic control pressure. Valves capable of by-passing 100% of pump volume shall be provided in the hydraulic circuit to by-pass fluid flow in the event of loss of servo control and the servo actuator does not return to neutral. b. Pump actuators shall have provisions for manual operation of the pump. c.

The use of pneumatically operated actuators for pump control shall not be permitted.

6.5.37.6.4 Fluid Reservoirs a.

Fluid reservoirs shall conform to ANSI System Standard Section 11, Nonintegral Industrial Fluid Power Hydraulic Reservoirs, except where noted herein.

b. Reservoirs shall be of heavy-duty welded steel construction. They shall be structurally rigid to resist warpage and damage from the mounting of equipment on the reservoir top, handling during shipping and erection at the bridge site. c.

Reservoirs interior and exterior surfaces shall not be galvanized. Painting of interior surfaces shall not be permitted. Interior surfaces shall be coated with a vapor-phase rust inhibitor specially formulated to prevent rust. Rust inhibitor shall be added to the hydraulic fluid by the hydraulic power unit manufacturer prior to testing and shipment from the factory.

d. Bladder-type breathers to prevent the mixing of outside air and reservoir air shall be provided for fluid reservoirs located in environments having airborne contaminants such as dust, chemicals and condensing water vapor which can damage the hydraulic system. e.

Reservoirs shall have drains which permit a complete fluid change without disconnecting any hydraulic components.

f.

Reservoirs equipped with large removable covers shall have separate filler openings to permit the adding of fluid to the reservoir without removal of the cover.

g.

Reservoirs shall either be equipped with accessories as specified in Article 6.5.37.6.6 or shall have provisions for future installation of these accessories. The reservoirs shall be constructed to permit the addition of accessories, without disturbing existing equipment, after the hydraulic system has been put into operation.

6.5.37.6.5 Electric Motors a.

The general requirements for electric motors, control and overload components shall conform with Article 6.7.5 except where noted herein.

b. Electric motors used for driving of hydraulic pumps, except as required in paragraph d, shall preferably be squirrel cage induction types. Motors shall be 1,800 or 1,200 rpm, TEFC or TENV, types with embedded winding temperature-sensitive devices, as specified in the contract documents. Motors shall have grease-lubricated antifriction shaft bearings and shall be equipped with lubrication fittings. c.

Electric motors for the driving of variable displacement pumps or fixed displacement pumps utilizing pressure compensated flow control valves shall be squirrel cage type, NEMA design B and shall have manual across-the-line or simple reversing starters.

d. Electric motors for the driving of fixed displacement pumps, where there is no provision for controlling the rate of fluid flow, shall be AC wound rotor induction motors or direct current motors. Speed controls for these motors shall be provided in conformance with Article 6.7.5.

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Movable Bridges 6.5.37.6.6 Accessories a.

Hydraulic power units shall be equipped with the required accessories to protect the hydraulic equipment from damage and ensure the safety of maintenance and operating personnel. Accessories shall include but not be limited to such items as gages and transmitters for pressure, temperature and fluid level monitoring, immersion heaters, fluid conditioning filters and magnets, heat exchangers and air dryers or coalescing filters for reservoir vents.

b. Requirements for pressure gages shall conform to Article 6.5.37.20. c.

Requirements for filters shall conform to Article 6.5.37.18.

d. Requirements for heat exchangers shall conform with ANSI System Standard, Section 15. e.

Immersion heaters shall be electric resistance type and controlled so as not to cause deterioration of the hydraulic fluid from overheating. Preferably dry-well type immersion heaters shall be used. Steam or hot-water coils shall not be used for immersion heating.

f.

Cold-water coils shall not be used for reservoir oil cooling.

6.5.37.7 Internal Combustion Engine Pump Drives a.

Internal combustion engines, for the driving of pumps, shall be permitted only for emergency operation, or at locations where suitable electric power cannot be provided.

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b. Requirements for internal combustion engines shall conform to Article 6.7.4. c.

Manual or electrically operated clutches shall be provided for the coupling of engines to pumps. Clutches shall be of the type that engage gradually and smoothly, and will slip during equipment overloads, to prevent damage to pumps or engines.

d. Electrically operated clutches shall be normally disengaged and shall have electric power applied to engage and remain engaged. Electric clutches shall have provisions for manual operation. e.

Requirements for pumps, reservoirs, pump actuators, accessories and piping shall conform to Article 6.5.37.6 and Article 6.5.37.10.

6.5.37.8 Valve Stands a.

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Valve stands for the mounting of manifolds, valves and gages may be either integral parts of the hydraulic power units, or separate floor-mounted units. Separate floor-mounted valve stands shall be provided when the overall size or weight of the hydraulic power units with integral valve stands is so great that shipping, erection or maintenance may be difficult.

b. Valve stands shall be of heavy duty construction, rigidly constructed to resist deflection and warpage during shipping, erection or operation of the system. c.

Where the bridge operator’s control station is located at the valve stand, the overall height and location of the valve stand shall not interfere with visibility of navigation or trains.

6.5.37.9 Valves a.

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Requirements for valves shall conform with the ANSI System Standard, Section 13.

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b. Adjustable valves shall be equipped either with protective caps, or with locking nuts on the adjusting screws, to prevent unintentional misadjustment. c.

Directional control valves and blocking valves shall be provided with adjustable pilot control chokes to increase valve opening and closing time, for shock and surge pressure control.

d. Flow dividing valves used for actuator synchronization shall be of the type that will always permit flow to all actuators simultaneously, regardless of the magnitude of pressure differential between the actuators being loaded. 6.5.37.10 Piping, Fittings and Manifolds 6.5.37.10.1 General Requirement a.

Piping shall include all pipe, tubing and flexible hose. Requirements for piping, fittings, manifolds and the piping system in general shall conform with the ANSI Standard, Section 17, except as otherwise noted herein.

b. Piping, fittings and manifolds shall be made of carbon steel or stainless steel. The materials used shall be consistent with the pressures and environmental conditions to which the hydraulic system will be subjected. Steel fittings shall be used with steel piping, and stainless steel fittings shall be used with stainless steel piping. Use of flutings which are softer than the piping shall not be permitted. Piping, fittings and manifolds shall not be galvanized. c.

Fittings used for piping connections shall be of the type to permit rapid assembly and disassembly of all components. Fittings shall also permit repeated disassembly and reassembly of a connection without loss of sealing quality or strength.

d. Pipe shall preferably have welded flange fittings. Use of threaded pipe fittings in pressure lines above 200 psi shall not be permitted without prior written approval of the Company. e.

Tubing shall have flared, flareless or welded flange fittings. Use of flared fittings shall be limited to tubing of 1-1/2 inch nominal outside diameter or smaller. Flareless fittings may be used for tubing sizes up through 2 inches nominal outside diameter. Welded flange fittings shall be used for tubing of greater than 2 inches nominal outside diameter.

f.

Fluid velocity in pressure and return line piping shall not exceed 15 feet per second and pump suction line velocity shall not exceed 5 feet per second unless approved in writing by the Company by the time shop drawings are reviewed.

g.

The Contractor shall make piping layouts and assembly drawings for the hydraulic system. These drawings shall clearly indicate the type and spacing of piping supports. The Contractor shall submit the drawings, and they must be approved by the Company, before field erection will be permitted. Support spacing and type shall conform to ANSI System Standard, Section 17.5.

h. Test ports shall be provided to bleed the system of air, and to check system pressure at control valves as well as other locations where a pressure governing component is not so equipped. i.

Flexible hose shall be provided to connect the hydraulic power unit to the rigid piping system. Where separate valve stands are provided, flexible hose shall be used to connect the valve stands to the hydraulic power unit and to the rigid piping system.

j.

Piping shall be connected to hydraulic component ports by means of SAE Straight Thread o-ring fittings for piping sizes up to 7/8 inch nominal outside diameter, and by means of SAE split flange fittings for © 2011, American Railway Engineering and Maintenance-of-Way Association

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larger size piping. The use of tapered pipe thread fittings to connect piping to components will not be permitted. 6.5.37.10.2 Pipe a.

Pipe shall be seamless with plain ends. Use of threaded pipe ends will not be permitted, without prior written approval of the Company.

b. Carbon steel pipe shall conform to the following ASTM specifications: • A 53 – Type S, Grade B. • A 106 – Grade B. • A 714 – Type S. c.

Stainless steel pipe shall conform to ASTM specification A 312–Grades TP304 or TP316. NOTE:

The foregoing materials are of the minimum quality that shall be used for pipe. Other materials of greater strength and durability may be specified by the Company.

6.5.37.10.3 Pipe Fittings a.

Welded flange fittings shall be SAE 4-bolt minimum flanges; utilizing a captive o-ring pressure sealing system. Socket weld flanges shall preferably be used. Use of threaded flanges will not be permitted without prior written approval of the Company. Carbon steel flanges shall be manufactured from low carbon steel to facilitate welding. Stainless steel flanges shall be type 304 or 316 and be suitable for welding. Flange connecting bolts shall be hardened and have sufficient strength for the working pressure rating of the flanges. Stainless steel bolts shall be used with stainless steel flanges. A lockwasher shall be used at every bolt.

b. Threaded fittings and threaded flange fittings, used for field connections and field erected piping systems, when approved for use above 200 psi, by the Company, shall have Dryseal Pipe Threads to permit pressure-tight joints without the use of pipe sealing compound, or PTFE sealant tape.

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6.5.37.10.4 Tubing a.

Tubing shall be seamless, have a low carbon content and be annealed to facilitate bending and flaring. Tubing to be used with flareless fittings shall have a maximum hardness of 65 Rockwell B.

b. Carbon steel tubing shall conform to the following ASTM specifications: • A 519 – Grades 1010, 1020 and 4130. • A 423 – Grades 1 and 2. c.

Stainless steel tubing shall conform to the following ASTM specifications: • A 269 – Grade TP304 or TP316. • A 789. NOTE:

The foregoing materials are of the minimum quality that shall be used for tubing. Other materials of the strength and durability required may be specified by the Company. © 2011, American Railway Engineering and Maintenance-of-Way Association

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Steel Structures 6.5.37.10.5 Tube Fittings a.

Flared fittings shall have a 37 degree angle of flare and conform to SAE specifications.

b. Flareless fittings shall conform to SAE specifications and be of the type that bites into the outside surface of the tubing when the fitting assembly is tightened. c.

Welded flange fittings shall be SAE 4-bolt flanges utilizing a captive o-ring pressure sealing system. Socket weld flanges shall preferably be used. Use of threaded flanges will not be permitted without prior written approval of the Company. Carbon steel flanges shall be manufactured from low carbon steel to facilitate welding. Stainless steel flanges shall be grade 304 or 316 and be suitable for welding. Flange connecting bolts shall be hardened and have sufficient strength for the working pressure rating of the flanges. Stainless steel bolts shall be used with stainless steel flanges. A lockwasher shall be used at every bolt. Threaded flange fittings, when approved for use by the Company, shall have Dryseal Pipe Threads to permit pressure-tight joints without the use of pipe sealing compound or sealant tape.

6.5.37.10.6 Flexible Hose and Fittings a.

Only extra-high or high pressure hose conforming to SAE specifications and having the working pressure ratings specified in Article 6.4.8.2a shall be used. Hose shall be seamless, oil and weather resistant and have steel wire reinforcement.

b. Hose fittings shall be made of steel and be of the pressed-on (non-reusable) type conforming to SAE specifications. Hose fittings shall have either 37 degree SAE flare or flange style ends for connection to other hydraulic components. Flange head style fittings shall use SAE split flanges with hardened bolts and 0-ring sealing. Threaded fittings may only be used for connection to threaded drain ports. 6.5.37.10.7 Special Fittings a.

Special fittings of the swivel, rotating or self-sealing type shall not be used without prior written approval of the Company.

b. Quick-disconnect type fittings shall not be used except for the temporary connection of portable gages to test ports and the temporary connection of hand or air operated hydraulic pumps for emergency or maintenance operation of the hydraulic system. 6.5.37.10.8 Manifolds Requirements for manifolds shall conform with the ANSI System Standard, Section 17.4. 6.5.37.11 Cylinders and Linear Actuators a.

Requirements for cylinders and linear actuators shall conform to the ANSI System Standard, Section 8. Cylinders and Linear Actuators shall have a minimum theoretical failure pressure rating of 11 (10,000 psi), as defined by NFPA Standare T3.6.5M.

b. Cylinders shall have engraved permanent nameplates which are securely attached to the head of the cylinder. The nameplates shall clearly indicate the manufacturer, model number, cylinder bore, rod diameter, stroke length, theoretical static failure pressure rating symbol, and all features which are nonstandard.

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c.

Protective flexible rod boots shall be provided for all cylinders that are oriented such that the rods are normally extended.

d. Piston rod seal assemblies shall be replaceable without cylinder disassembly. e.

The use of rotating type or telescoping cylinders shall not be permitted without prior written approval of the Company.

6.5.37.12 Intensifiers a.

The use of intensifiers or pressure boosters shall not be permitted without prior written approval of the Company. Intensifiers shall only be used to assist in the operation of auxiliary equipment such as locks, lifting devices, wedges, brakes and barriers. Intensifiers shall only be used for holding or clamping purposes and shall not be operated continuously as a pump.

b. The maximum output pressure from an intensifier shall be 3,000 psi and components subjected to the boosted operating pressure shall be designed to withstand the pressure with a factor of safety as defined in Article 6.4.8. Relief valves shall be provided in the boosted circuits to protect equipment and personnel. c.

The use of air-air or air-oil intensifiers shall not be permitted.

6.5.37.13 Fluid Motors and Rotary Actuators a.

Requirements for fluid motors shall conform with the ANSI System Standard, Section 9, except as otherwise noted herein.

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b. Fluid motors shall be of the fixed displacement type. Speed control of the motors shall be accomplished by controlling the volume of fluid to the motors. c.

Gear type fluid motors shall be of the hydraulically balanced type.

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d. Where hydraulic systems use fluid motors in which the operating pressure, as defined in Article 6.4.8, exceeds 2,000 psi, only piston type fluid motors shall be used. e.

f.

High speed fluid motors shall be coupled to driven equipment in a manner that eliminates overhung loads on the fluid motor’s shaft bearings. The magnitude of overhung loads on low speed, high torque (LSHT) fluid motor shafts shall preferably be limited to provide a minimum shaft bearing B-10 life rating of 20,000 hours. (B-10 life shall be as defined by the AFBMA and shall be the time for which 90% of a group of identical bearings will survive under the given loading condition). Requirements for couplings to connect fluid motors to other equipment, for purposes of transmitting fluid motor operating torques, shall comply with Article 6.5.37.16.

6.5.37.14 Rotary Actuators a.

Rotary actuators are devices which produce output torque over a limited range of rotation, usually less than 360 degrees. Actuators shall self-lock when the flow of pressurized fluid to the actuator is stopped or operating pressure is lost due to line leakage or breakage. Provision for manual operation of actuators shall be provided. Vane type rotary actuators shall be hydraulically pressure balanced.

b. Actuators shall have keyed output shafts and be connected to driven equipment with couplings conforming to Article 6.5.37.16.

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c.

Cylinder type rotary actuators having internal chain and sprocket mechanisms shall have automatic chain tensioning devices incorporated into the actuators.

d. Actuators shall be coupled to driven equipment in a manner that eliminates overhung and thrust loads on the actuator shaft bearings. 6.5.37.15 Self-Contained Hydraulic Actuators a.

A self-contained hydraulic actuator unit shall consist of a heavy duty cylinder or other type of actuator, electric motor, pump, reservoir and control valving. Units shall be completely closed systems, requiring no external piping to supply or remove hydraulic fluid.

b. Self-contained hydraulic actuators shall not be used for span operation. Such actuators may be used only to operate auxiliary equipment such as locks, lifting devices, wedges and barriers. c.

Cylinders shall conform to NFPA standards.

d. Electric motors shall conform to the general requirements of Article 6.7.5. e.

Protective rod boots shall be provided for cylinder rods which are normally extended.

6.5.37.16 Couplings a.

Requirements for couplings, connecting pumps to drive motors and connecting fluid motors or rotary actuators to speed reducers or other equipment, shall conform to ANSI System Standard 10.1.3.

b. Coupling guards shall be provided that conform to the requirements of NFPA Standard T3.l6.3M. c.

The use of belts for coupling purposes will not be permitted.

d. Rigid coupling of equipment will not be permitted without prior written approval of the Company. e.

Chain casings shall be provided for chain-type couplings. Casings shall be designed to seal in lubrication, and protect sprocket teeth and chains from abrasives.

f.

The use of shock resistant couplings, with non-metal torque transmitting components, will be permitted only where the coupling design is such that normal operating torques can be transmitted by the coupling in the event of non-metal component failure.

6.5.37.17 Brakes a.

Machinery brakes or counterbalance valving, for span driving cylinders, shall be provided to hold the span stationary against unbalanced loads and the wind pressures specified in Article 6.3.6e and Article 6.3.6f.

b. If the hydraulic system does not provide sufficient braking to stop the span in 10 seconds or less, dynamic brakes shall be provided. c.

Machinery brakes shall have the capacities as specified in Article 6.3.9. Dynamic brake capacity shall be the same as specified for motor brakes in Article 6.3.9. Electrically operated brakes shall conform to the requirements of Article 6.7.5.

d. Spans normally left in the open position shall also be provided with locking devices to hold the span stationary at the fully open position, against the wind loads specified in Article 6.3.5b(2).

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Movable Bridges 6.5.37.18 Filtration and Fluid Conditioning a.

Requirements for filtration of hydraulic fluid shall conform with the ANSI System Standard, Section 12.

b. Full flow filtration shall be provided. c.

Filters, including pump intake strainers, shall be equipped with an indicator to show when the filter needs servicing.

d. The degree and quality of filtration shall be as recommended by the manufacturer of the hydraulic components. The Beta 10 rating system as defined by ANSI standard B93.3l shall be used to determine filter performance. Filtration performance shall never be allowed to deteriorate, at time of filter change, below a Beta 10 rating of 15 for servo controlled hydraulic systems, and a Beta 10 rating of 5 for nonservo controlled hydraulic systems. e.

Filter flow capacity ratings shall be as recommended by the pump manufacturer. As a general guide, such capacity shall be equal to at least 10% of high pressure pump capacity for hydrostatic (nondifferential) drives, at least 30% of high pressure pump capacity for a normal industrial type differential system, and 100% of high pressure pump capacity for differential system operating in a contaminated atmosphere.

f.

Bypass valves shall be provided on filters to limit the differential pressure across the filter elements. Bypass valves shall be sized for the maximum flow that can be expected through the filter without excessive differential pressure. Non-bypass type filtration shall be used only where required by the hydraulic equipment manufacturer, and shall be equipped with warning devices to provide remote indication at the operator’s station of an impending clogged condition.

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6.5.37.19 Accumulators a.

Requirements for accumulators shall conform with the ANSI System Standard, Section 14, and the NFPA standards.

3

b. Gas accumulators shall be charged with an inert gas such as dry nitrogen or helium. The use of oxygen, air or other active gases will not be permitted for accumulator charging. c.

Clamps or straps used for accumulator mounting shall not restrict thermal expansions, or distort the shell of the accumulator.

4

6.5.37.20 Pressure Gages a.

Gages shall be of durable construction. Dial faces shall be clearly calibrated for pressure ranges 50% and beyond the maximum design operating pressures of the hydraulic system. Gages shall be accurate and permit continuous monitoring. They shall have a minimum diameter of 4 inches, and preferably 6 inches. Shutoff valves shall be provided at each gage.

b. Portable gages shall be provided for maintenance and adjustment of the hydraulic system. The pressure ranges shall cover all possible values that will be needed for the system. c.

One gage shall be provided for each pressure range such that the test pressure will be within the midhalf of the total pressure range of the gage.

d. Connections for portable gages shall be of the quick-disconnect type. Test ports in the hydraulic system shall be equipped with removable, protective caps, secured by chains to the component. Shutoff valves shall be provided at each test port.

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Hydraulic fluid shall be suitable for the operating pressure, temperature and lubrication requirements of the system. The selection of the hydraulic fluid shall be based on performance data or actual experience in other heavy duty hydraulic systems subjected to similar operating pressures and temperatures and having similar hydraulic equipment. The fluid shall be that recommended by the pump manufacturer and shall be compatible with all hydraulic components and seals.

b. Hydraulic fluid shall be either petroleum based oil type, or oil-water emulsion type fire resistant fluid which is compatible with the same type of seals used with petroleum based oils. Straight synthetic, high water content fluids, synthetic blends or water-glycol mixtures shall not be permitted without prior written approval of the Company. c.

Hydraulic fluid shall have the correct viscosity range for the operating requirements of the hydraulic system; shall have a high enough viscosity index to resist changes in viscosity due to anticipated temperature ranges, prevent wear on working parts, resist foaming, oxidation and the formation of sludges; shall retain original properties in use; and shall have a long service life and protect parts against rust.

6.5.37.22 Seals and Sealing Devices 6.5.37.22.1 Sealing Principles Sealing devices for hydraulic circuts shall be of the pressure sealing type. 6.5.37.22.2 Sealing Materials Sealing device materials shall; (1) Not be adversely affected by the hydraulic fluid. (2) Be of compatible materials where adjacent contact materials are metals. (3) Be of an elastomeric material where no leakage other than that required for lubrication can be tolerated, e.g., for reciprocating and rotating elements. 6.5.37.22.3 Seal Quality Seals shall be adequate in size and in number for the service intended. 6.5.37.22.4 Availability Packings, seals, and sealing devices used in hydraulic circuits shall be commercially available. 6.5.37.22.5 Seal Replacement Where continuous ring packages and seals are used, the component and the actuated equipment designs shall facilitate servicing and replacement of seals and packings. 6.5.37.22.6 Seal Gland Clearance Clearances in seal glands shall prevent extrusion of the sealing material(s).

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Movable Bridges 6.5.37.22.7 Adjustable Seal Glands Where seal glands are adjustable, seal and packing gland chambers shall be so designed that they cannot be adjusted beyond thier functional limits. 6.5.37.23 Workmanship 6.5.37.23.1 Piping Systems a.

Piping runs shall be as short and free of bends as possible. At least one bend shall be provided in pipe runs where thermal expansion and contraction may be a problem.

b. Piping bends shall be of good quality without excessive flattening or creasing. Minimum bend radius shall be 3 times the inside diameter of the pipe. Each leg of a piping bend shall have a length of not less than 10 pipe outside diameters. c.

Tubing flares shall preferably be formed with roller type flaring tools.

d. Bending and flaring shall be done with suitable portable equipment at the bridge site. e.

Bolted flange connections shall be evenly assembled by the use of feeler gages and torque wrenches to ensure equal bolt tightening. 0-rings shall be lubricated before flanged connections are assembled.

f.

The use of pipe compound or sealant tape to facilitate the assembly of threaded fittings will not be permitted.

1

6.5.37.24 Field Painting a.

Nameplates on all hydraulic components shall not be painted. Protective tape shall be placed over all nameplates prior to field painting, and subsequently removed.

b. The final coat of paint, for field erected piping systems, shall preferably have a color such that hydraulic fluid leakage will be easily observed. c.

3

Flexible hoses and hose guards shall not be painted.

6.5.37.25 Testing

4

6.5.37.25.1 Components a.

Pumps and fluid motors shall be tested by the manufacturer before hydraulic power units are assembled, and catalog rating certification shall be provided to the Company. Tests for pumps and fluid motors shall be conducted for 15 minutes continuously, at a minimum test pressure equal to the maximum peak or intermittent pressure rating of the component.

b. Pumps shall be checked during testing for external leakage, charge pump pressure and flow (where charge pumps are provided), and main pump pressure and flow. Integral relief valves shall be set at 3,000 psi maximum, and checked for proper operation. c.

Fluid motors shall be checked during testing for external leakage, pressure and flow.

d. Cylinders shall be tested by the manufacturer before shipment to the bridge site. Testing shall include a 30 minute static pressure test at a minimum pressure of 4,000 psi. The leakage rate past the piston during the static pressure test shall be no greater than 5 cubic inches per minute for span driving © 2011, American Railway Engineering and Maintenance-of-Way Association

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cylinders. Certified test data for span driving cylinders and catalog rating certification for all other cylinders shall be provided to the Company. 6.5.37.25.2 Power Units a.

Assembled power units shall be shop tested for proper operation, and certified test data submitted to the Company for approval before shipment to the bridge site.

b. Power units shall be shop tested at full drive motor speed under conditions of maximum design pressure at minimum fluid flow, and reduced pressure at maximum fluid flow. The maximum pressure test shall be conducted for one hour continuously. c.

During all tests, the power units shall be checked for fluid leakage, excessive fluid temperature, proper relief valve operation and proper operation of charge pumps.

d. Pump controls shall be tested for correct speed regulation, response time and direction of rotation. 6.5.37.25.3 Shipment a.

Power units, valve stands and cylinder assemblies shall be shipped fully assembled to the bridge site and installed at their final positions. Pumps, motors and couplings shall be checked for proper alignment and realigned if necessary. Disassembly of power units, valve stands and cylinder assemblies will not be permitted for shipment, storage or during installation.

b. Hydraulic equipment fluid ports shall be securely sealed prior to shipment and shall remain sealed until final assembly of the hydraulic system. Seals shall not be removed until just before the connection of components. 6.5.37.25.4 Final Tests at Bridge a.

After final installation, but before connection to the piping system or valve stands, power units shall be checked for correct rotation of drive motors and pumps.

b. Reservoirs shall be filled with fluid to the correct level. Portable filtration units shall be used during reservoir filling in conformance with Article 6.5.37.6.1g. c.

When the entire installation is completed, the span, including all accessories, shall be operated by the Contractor through not less than three complete cycles using normal power, prime movers, and controls; and through at least two cycles using auxiliary or emergency power, prime movers, and controls. These tests shall be repeated for alternate operating modes if provided.

d. During these tests, equipment shall be inspected for external fluid leakage, and to determine whether all features are in proper working order and adjustment, and whether they meet the requirements of the drawings and specifications. e.

Portable pressure gages shall be used at all test stations of the hydraulic system, including the power unit.

f.

During all tests, the level of the hydraulic fluid in the reservoir shall be closely monitored. Proper fluid level shall be maintained at all times to prevent pump cavitation. Air shall be bled from the hydraulic system and make-up fluid added to the reservoir as required, using portable filtration units in conformance with Article 6.5.37.6.1g.

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g.

In the event tests show that any features are defective or inadequate, or function improperly, the Contractor shall make all necessary corrections, adjustments, or replacements at his own expense.

h. When all the components are in proper working order and adjustment, the pressure readings taken at each test station shall be recorded, and provided to the Company. i.

After completion of final tests hydraulic fluid shall be removed, properly discarded, replaced with new fluid, and air bled from the entire hydraulic system. New fluid shall be added using portable filtration units in conformance with Article 6.5.37.6.1g. In lieu of fluid replacement, the Contractor may take fluid samples from each reservoir for analysis by the fluid supplier. The fluid shall be changed if sample contamination levels are greater than Class 3, as defined by specification SAE ARP-598. New fluid, where required, shall be added using portable filtration units in conformance with Article 6.5.37.6.1g.

j.

After completion of final hydraulic testing, and either fluid replacement or the continued use of fluid which has passed contamination level testing, filter elements shall be replaced and strainers and magnets cleaned.

SECTION 6.6 WIRE ROPES AND SOCKETS

1

6.6.1 MANUFACTURER (1984) R(2010) Wire rope shall be made by a manufacturer whose facilities and experience are approved by the Engineer.

6.6.2 DIAMETER OF ROPE (2010)1 a.

The nominal diameter of counterweight ropes shall not be less than l inch. For counterweight ropes with a nominal diameter larger than 2-3/8 inch, a wire rope manufacturer shall be consulted during the design phase of the project, before the construction contract is awarded. Operating ropes shall not be less than 3/4 inch in diameter.

b. The actual diameter of a wire rope (the diameter of the circumscribed circle) shall be measured when the rope is unstressed.

6.6.3 CONSTRUCTION (2010)2 a.

Wire rope shall be improved plow steel (IPS) grade or extra improved plow steel (EIP) grade. All ropes shall be of preformed construction. The wire rope may be manufactured from uncoated (bright), drawngalvanized, or drawn-zinc aluminum mischmetal alloy (Zn5Al-MM) wire. On any structure, the use of different types of wire rope construction shall not be permitted for the same type of component. The type of wire rope construction shall be stated on the shop drawings.

b. Counterweight ropes of 2-3/8 inch diameter or less shall conform to ASTM A-1023 and shall be of either Class 6x19 or Class 6x36 construction. They may be made of only circular wires with either fiber or independent wire rope cores (IWRC), as listed in Tables 12, 13, 14, and 15 of ASTM A-1023. Fiber cores shall be of natural or synthetic fibers as defined in Article 5.2.1 of ASTM A-1023, except that jute shall 1 2

See Part 9 Commentary See Part 9 Commentary

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not be used. The ropes may be of compacted strand construction (CS) as listed in Tables 28 and 29 of ASTM A-1023. Counterweight ropes greater than 2-3/8 inch diameter shall be Class 6x61 per Federal Specification RRW-410F with either fiber core or IWRC as listed in Tables XVII through XIX. Wire strand core shall not be permitted. They shall be of Construction 4, 5, or 6. Fiber cores shall be of natural or synthetic fibers as defined in Article 3.2.1 of Federal Specification RR-W-410F except that jute shall not be used. c.

Ropes shall be laid in accordance with the best practice. Every effort shall be made to obtain ropes of uniform physical properties. The ropes shall be fabricated in the greatest lengths practicable, and all similar ropes for any one bridge shall be cut from ropes manufactured with one setting of one stranding machine and one setting of one closing machine.

6.6.4 LAY (2010) a.

All wire ropes, unless otherwise specified, shall be right regular lay. Where required by the design, counterweight wire ropes may be right or left lay, with all other construction, and lay length, identical. The maximum length of lay shall be as follows: (1) Operating ropes – 6.75 times nominal rope diameter. (2) Counterweight ropes – 7.25 times nominal rope diameter.

b. The lay of the wires in the strands shall be such as to make the wires approximately parallel to the axis of the rope where they would come in contact with a circular cylinder circumscribed on the rope.

6.6.5 LUBRICATION DURING FABRICATION (1983) R(2010) Manila and sisal fiber cores shall be thoroughly impregnated by the cordage manufacturer with a suitable lubricating compound free from acid. All portions of wire rope core, wires and strands shall be lubricated during manufacture with a lubricant containing a rust inhibitor approved by the Engineer.

6.6.6 SPLICES (1983) R(2010) No splicing of the ropes or individual strands will be permitted. Wire splices shall be securely and properly made by electric welding, and no two joints in any one strand shall be closer than 25 feet apart, except for filler wires.

6.6.7 WIRE – PHYSICAL PROPERTIES (2010)1 The wire from which wire ropes are made shall be tested in the presence of an inspector designated by the Engineer. Excepting that filler wires may be made to the manufacturer’s standards, the physical properties of the bright (uncoated) individual wires before manufacture into rope shall be as follows: a.

The tensile strength of the wires shall meet the requirements of Table 1 - Wire Tensile Strength Grades or Levels for Wire Rope Grades, of ASTM A-1023. Wire tensile strength is related to wire level in Articles 8.1.3 and Table 3 of ASTM A-1007.

b. The wire ductility shall be evaluated per Article 3.13.1 of ASTM A-1023, which refers to Article 9.2 and Table 3 of ASTM-A1007.

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See Part 9 Commentary

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c.

All of the tests specified above shall be made upon fair samples which may be taken from either end of any coil of wire, and such samples shall be taken from not less than 10 percent of the number of coils.

d. Wire rope for operating ropes obtained from stock may be accepted upon certification by the manufacturer that all provisions of the specifications are met; tensile strength and torsion tests may be waived, where test data are not available, but the tension test on the rope as specified in Article 6.6.8 is required.

6.6.8 ULTIMATE STRENGTH (2010)1 In order to demonstrate the strength of the rope and its socket, test pieces with a length between the sockets of not less than 25 rope diameters, and preferably not less than 50 rope diameters, shall be cut, and shall have sockets, selected at random from the job lot, attached to their ends. The sockets used for these tests shall not be used in the structure. The number of test pieces shall be not less than two from each manufactured length of rope, but not more than 10 percent of the total number of finished assemblies of rope to be fabricated. The test pieces shall be taken from both ends of the manufactured lengths of rope. A suitable mark shall be placed around the rope near the base of the socket, so that any relative movement of the latter can be readily detected. These test pieces are to be tested to destruction per ASTM A-931 Test Methods for Tension Testing of Wire Rope and Strand, in the presence of an inspector designated by the Engineer. Wire ropes 2-3/8 inch diameter or less shall develop the minimum breaking force given in ASTM A-1023 for the particular size, construction, grade and coating (if any). Wire ropes larger than 2-3/8 inch diameter shall develop the minimum breaking force given in Federal specification RR-W-410F for the particular size, grade and coating (if any).

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6.6.9 REJECTION (1985) R(2010) Where the physical properties of the rope or of its individual wires do not meet those specified, the manufacturer shall replace the entire manufactured length with a new length, the physical properties of which conform to those specified.

6.6.10 PRESTRETCHING (1985) R(2010)

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Each counterweight rope shall be prestretched using the following procedure: a.

Tension the rope to 40% of its ultimate strength as given in Article 6.6.8 and hold that load for 5 minutes.

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b. Reduce the load to 5% of the ultimate strength. c.

Repeat this load-unload cycle two more times.

d. Release the load.

6.6.11 SOCKETS (1985) R(2010) a.

1

Sockets for wire ropes shall conform to the requirements of Federal Specification RR-S-550, latest revision, except that sockets for 2-1/2-inch diameter ropes may be cast steel conforming to ASTM A 148, Grade 80-50. Sockets shall be attached to the ropes by using zinc of a quality not less than that defined in the current Specifications for Slab Zinc (Spelter), ASTM B 6 High Grade. Maximum socket slip or seating of the zinc cone, with the rope, when tensioned to 80% of its specified ultimate strength under

See Part 9 Commentary

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the test specified in Article 6.6.8, shall be 1/6 the nominal diameter of the rope. If a greater slip should occur, the socketing method shall be changed until satisfactory results are obtained. b. Variations or substitute designs of sockets will be considered acceptable if they meet or exceed the functional requirements for strength, materials, and other applicable provisions of the Federal Specification. c.

Sockets shall be stronger than their ropes. If a socket should break during the test specified in Article 6.6.8, two other job sockets shall be selected at random and attached to another piece of rope, and the test repeated, and this process shall be continued until the Inspector is satisfied of socket reliability, whereupon the lot shall be accepted. However, if 10% or more of the tested sockets fail at a load less than the specified minimum ultimate strength of the rope, the entire lot of sockets shall be rejected, and new ones shall be furnished which meet specification requirements.

d. Pin and socket fits different from those specified by the Federal Specification may be specified by the Engineer. e.

Sockets shall be shop painted as specified for structural steel.

6.6.12 FACILITIES FOR TESTING (1985) R(2010) The manufacturer shall provide proper test facilities, and shall make, at his own expense, the required tests. Tests shall be made in the presence of an inspector representing the Engineer.

6.6.13 ROPE LENGTH (1985) R(2010) a.

The Contractor shall verify the exact lengths to which the counterweight ropes shall be fabricated.

b. The fabricated length, after prestretching, of each counterweight rope bearing-to-bearing of sockets shall be determined, and stamped on a metal tag securely attached to the rope. While being measured, each rope shall be twisted to the correct lay, supported throughout its length at points not more than 25 feet apart, and tensioned 12% of its ultimate strength. Variation from the required length shall be not more than 1/4 inch in 100 feet. For ropes having bearing sockets, this permissible length variation shall be corrected in the shop by permanently fastening, by a method approved by the Engineer, the appropriate thickness of steel shims to the bearing face of one socket. No shim shall be less than 3/8 inch thick. c.

Each rope shall have a stripe painted along its entire length at the time of length measurement, to facilitate its correct alignment upon installation in the bridge.

d. Ropes shall be suitably marked or tagged for identification prior to shipment.

6.6.14 OPERATING ROPES (1985) R(2010) Ends of non-socketed operating ropes shall be seized and shall have the end wires composing the ropes welded together. Seizing shall be removed prior to rope installation. Lengths of operating ropes shall be verified by the Contractor.

6.6.15 SHIPPING (1985) R(2010) Ropes shall be shipped on reels, the drum diameter of which is not less than 25 times the rope diameter, unless coil shipment is specified in the order.

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SECTION 6.7 POWER EQUIPMENT 6.7.1 POWER OPERATION (1984) R(2002) If the bridge is to be operated by mechanical power, the type of power will be specified by the Company. The internal combustion engine, electric motor, or other type of power specified shall be of ample capacity to move the bridge at the required speed. Where the design is made by the Contractor, the type of prime mover and the name of the manufacturer shall be given in the proposal.

6.7.2 MANPOWER OPERATION (1984) R(2002) a.

Where the bridge or parts thereof are to be hand-operated, the required number of men and the time of operation shall be calculated on the following basis: (1) One man can exert continuously on a capstan lever a force of 40 lb while walking at a speed of 160 feet per min. (2) One man can exert continuously on a crank a force of 30 lb at a radius of 15 inches with rotation at 15 rpm.

b. For calculating the strength of the machinery parts, the design load per man applied to a lever shall be taken as 150 lb, and to a crank as 50 lb. Under these loads, the allowable stresses may be increased 50%.

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6.7.3 MACHINES (1984) R(2003) Machines of the usual manufactured types, such as internal combustion engines, electric motors, pumps, and air compressors, shall be factory-tested for the specified requirements to the satisfaction of the Engineer, and shall be guaranteed by the Contractor to fulfill operating requirements for one year.

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6.7.4 INTERNAL COMBUSTION (1997) R(2002) 6.7.4.1 Engine Torque for Span Operation a.

The ratio of rated engine torque to the maximum bridge starting torque shall not be less than the found in Table 15-6-6.

4

Table 15-6-6. Torque Ratio No. of Cylinders

Minimum Ratio

Less than 4

1.50

4 or more

1.33

b. The rated engine torque, as referred to above, shall be measured at the flywheel at the operating speed with all metal housings, radiator, fan, and all other power consuming accessories in place, and shall be taken as not more than 85% of the rated torque of the stripped engine. 6.7.4.2 Engines a.

These requirements apply to separately mounted engines and to engines forming part of an enginegenerator set (see Article 6.7.5.12 for generators). Internal combustion engines shall be of the truck or marine type and of the most substantial kind. The engines shall operate at a speed of not more than 2200

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rpm but preferably not more than 2000 rpm unless a higher speed is recommended by the manufacturer, and shall be equipped with a governor to limit the maximum speed to the designated value. Unless otherwise specified, the engine shall have not less than 4 cylinders. The engines shall be tested by the manufacturer at his plant to demonstrate that they will develop the rated torque as defined in Article 6.7.4.1, where used for span operation. b. The engine shall be equipped with reversing gears, preferably of the helical type, and preferably in a separate gear unit, having a gear ratio of not less than 2 to 1. Reversing shall be controlled by an approved friction clutch or clutches on the countershaft operated by a lever or other approved device. The machinery shall be operable in either direction without stopping the engine. c.

Engines having a rating of 20 hp or more shall be equipped with an electric starter with generator and storage battery. Where electric current is available at the bridge, a battery charging unit shall also be provided. Engines having a rating of 60 hp or less shall also be provided with a hand cranking device, where feasible.

d. Engines shall be cooled by means of a radiator and fan. A corrosion-resisting metallic exhaust pipe shall be provided, discharging outside the engine room and fitted with an effective muffler. Air inlets, including louvers, shall be arranged to ensure an adequate air supply to the engines. e.

The fuel tank shall be located outside the engine room, below the level of the intake. The tank shall be made of corrosion resisting metal and shall be large enough to hold fuel for 30 days of normal operation where the engine is used for span operation, and at least one day where used for standby service. The tank shall be protected from the sun. It shall be equipped with an automatic gage to show the quantity of fuel in the tank. The fuel pipe and fittings shall be of copper or brass, arranged and supported to provide for temperature and vibration movements tending to produce fracture and leakage. Protective fill and vent seal units shall be included to prevent accidental vapor ignition. A day tank, including pumps, shall be provided for engines over 60 hp. The installation shall be in accordance with the requirements of the National Fire Protection Association.

f.

A small control board containing throttle and choke controls, ignition switch, starter button, and oil and temperature gages shall be provided at the engine, in addition to other controls that may be required for remote starting.

g.

Where suitable, the ignition shall be of the jump-spark kind, so that a low voltage primary current of not more than 24 v will be sufficient for the secondary coil. For other fuel, the best device available shall be used.

h. The engine shall either be enclosed in a readily removable metal housing or located in a protected space, and, together with reversing gears and all other engine accessories, shall be mounted in the shop on a rigid steel frame so as to form a complete unit ready for installation. i.

The room containing span operating engines shall have indicators to show the position of the moving span and, if specified, of the lifting and locking apparatus.

j.

Where low ambient temperatures may affect starting reliability, a water jacket heater or other suitable means shall be provided having such protective features as low oil pressure cut-out, high water temperature cut-out, and engine overspeed shut-down; and overcranking protection, if applicable.

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6.7.5 ELECTRIC (1997) R(2003) 6.7.5.1 Basis of Specification Requirements a.

The specification requirements given herein are based on the use of either direct current or 60-Hz alternating current motors. Where specified, the bridge shall be operated by direct current motors using variable-voltage control or adjustable voltage control or with alternating current motors with control by semiconductor elements; in such cases the specification requirements shall be modified as specified by the Company.

b. For the operation of a vertical lift bridge, these requirements are based on the use of one hoisting machine to operate the bridge, or on the use of two hoisting machines mechanically connected. Provisions are also given for tower drive vertical lift bridges using independent hoisting machines at the ends of the span operated by synchronized alternating-current motors. Where specified, such independent hoisting machines shall maintain the span in level position during operation by means of synchronizing controls; in such cases the specification requirements shall be modified as specified by the Company. 6.7.5.2 General Requirements for Electrical Installation a.

The Company will state the electric power service which is available and will give the location of the point at which such service shall be obtained. The Contractor shall provide the electrical installation complete from this service point, including all equipment, wiring, and cables, except as otherwise specified by the Company.

1

b. The electrical equipment shall conform to the standardization rules of IEEE and NEMA. c.

The NEC and local ordinances shall apply to the electrical material, construction, and installation, except as otherwise provided herein. In general, total voltage drops shall not exceed 5% at rated load for all electrical equipment.

d. Insofar as practicable, all major items of electric equipment shall be products of the same manufacturer in order to secure single responsibility and the most satisfactory service. All electrical equipment shall be equal to the best grade of that particular type of equipment made by the leading manufacturers. e.

The Contractor shall provide all grounds required for the electrical equipment and service.

f.

In order to prevent deterioration due to corrosion of parts of the electrical installation other than electrical apparatus, all bolts, nuts, studs, pins, screws, terminals, springs, and similar fastenings and fittings shall be, where practicable, of an approved corrosion resisting material, such as brass, bronze or stainless steel, or of a material treated in an approved manner to render it adequately resistant to corrosion. Hot-dip galvanizing of materials in compliance with ASTM Specifications for such materials shall be considered such approved treatment. Corrosion preventive treatment of electrical apparatus shall be as specified by the Company to suit the conditions of exposure.

g.

Except as otherwise approved by the Company, all metal parts of the electrical equipment, including all conduits not furnished with a fused coating of polyvinylchloride, shall be painted as specified for structural steel. For conduits and similar parts where it is not practicable or convenient to apply paint in the shop, the shop coat may be applied in the field, and followed by the required field coats.

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h. The Contractor shall take insulation resistance readings on all circuits installed, with electronic equipment disconnected, and shall furnish a complete record of the results. These circuits shall preferably include connected motors when tested. Conductors rated 600 v or more shall be tested with a 500 volt instrument, and shall register at least one megohm. Defective circuits shall be replaced at the Contractor’s expense. i.

Provisions for emergency operation of power operated bridges, and for standby power for electrically operated bridges, shall be as specified in Article 6.2.5 and Article 6.2.6, respectively.

6.7.5.3 Working Drawings a.

In addition to furnishing the data required in Article 6.1.12, the Contractor shall provide complete working drawings for the electrical equipment. The tracings, or translucent copies thereof on cloth or polyester film, shall be corrected to show the work as constructed and shall then become the property of the Company. These drawings shall include the following: (1) Wiring interconnection diagrams, giving termination identification of wires and cables, sizes and numbers of wires and cables, and the make and capacity of all apparatus, including the ratings of impedances. Schematic diagrams shall include three-line power diagrams showing the connection schemes including detailed apparatus and control schematic diagrams, which shall include the control panels and console. The number of each wire and designation for each electrical device or piece of apparatus shall be shown on the control schematic diagram. This device designation shall be used to identify each piece of apparatus on the assembly and installation drawings, which shall show locations to scale of all external and internal components including terminal blocks for the control panels, terminal boxes, and control console. (2) Conduit drawings showing the routing and size of each conduit, the number and size of each wire therein, and the location and method of support of all conduits, ducts, boxes and expansion fittings. Each conduit shall be given an individual conduit designation. (3) The requirements of paragraph (1) and paragraph (2) may be partially fulfilled by use of a suitably coordinated conduit and cable schedule. (4) Installation drawings giving the location of all cables, conduits, control panels, control consoles, resistances, lamps, switches, and other apparatus. (5) Sectional drawings of all cables showing component parts, their dimensions, and the material used. (6) Drawings showing the general construction and dimensions of the control console and all control panels and the arrangement of all apparatus thereon. (7) Certified dimension prints of all electrical apparatus. (8) Detailed construction drawings of all boxes, troughs, ducts, and raceways other than conduit. (9) Curves for each span driving motor showing the variation in motor speed and motor currents with output torque, and within the torque intervals determined by test (as specified in Article 6.7.5.4), for each power point on the controller.

b. Special apparatus shall be designated by the manufacturer’s name and catalog reference.

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Movable Bridges 6.7.5.4 Motor and Generator Tests a.

One span driving motor of each size or type used shall be subjected to a complete test in accordance with the latest requirements of NEMA Standards for Motors and Generators. At the option of the Company, certified test data of a motor of identical design may be accepted in lieu of tests of the actual motors.

b. For alternating current motors the tests shall also include the determination of the variation in speed and motor currents with motor torques from zero to the maximum designed torque for the drive system. Where stipulated by the Company, the speed-current-torque curve shall also be determined for overhauling torque and including the effects of the motor control equipment. In addition, for wound rotor motors the speed-current-torque relationship shall be determined with a rotor shorted condition. At the option of the Company, some of these curves may be developed by computation. c.

Direct current motors shall also be tested to determine the speed-current-torque relationship for each power point on the controller, from an overhauling torque of 100% of full load to a driving torque of 200% of full load.

d. Unless otherwise specified by the Company, all other span driving motors shall be subjected to a short commercial test. Should the results indicate characteristics differing materially from those of the motor completely tested, the Contractor shall be required, at his own expense, to make the necessary alterations, and to run complete tests to demonstrate the final characteristics. e.

For tower drive vertical lift bridges with synchronizing motors, these motors shall be subject to the test requirements for span-driving motors; except that where the synchronizing motors are of the same size and type as the span-driving motors, only the short commercial test is required.

f.

Each electric motor other than the span driving motors shall be subjected to a short commercial test.

g.

Each generator shall be subjected to a short commercial test.

h. Except as otherwise approved by the Company, all motor and generator tests shall be made in the presence of the Company’s Inspector. i.

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The Contractor shall furnish six certified copies of reports of motor tests and of all other required tests.

6.7.5.5 Motor Torque for Span Operation a.

The required locked rotor and breakdown torques for a-c motors shall be those specified by NEMA.

b. Motor torques shall be as follows: (1) One-motor installation. The rated full load motor torque shall be not less than 80% of the maximum bridge starting torque, and the maximum torque peaks that occur when the bridge is accelerated to the required speed, using the specified bridge control, shall preferably not exceed 180% of the rated full load motor torque. (2) Two-motor installation with no provision for operating of the bridge with a single motor. The two motors jointly shall meet the requirements given in paragraph a for one motor. (3) Two-motor installation with provision for operating the bridge with a single motor in not more than 1.5 times the opening times specified in Article 6.3.6. c.

Where specified or approved by the Company, the power requirements of motors may be less than specified in Article 6.3.6.

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d. The maximum bridge-starting torque shall be determined in accordance with the requirements of Article 6.3.6. 6.7.5.6 Number of Motors a.

Where the total power necessary at the motor shaft to move the bridge according to Article 6.3.6a(1) at the required speed exceeds 50 hp, the use of two similar span driving motors, with provision for operation of the bridge by one motor shall be considered.

b. Except as otherwise specified by the Company, the rail locks, the span locks, and the end and center wedges of swing spans, shall be operated by one or more motors separate from and independent of the span-driving motors. 6.7.5.7 Synchronizing Motors for Tower Drive Vertical Lift Bridges Where synchronizing motors are used on tower drive vertical lift bridges to maintain the bridge in level position during operation, the total full load rated torque of these motors on each tower shall not be less than 50% of the total full load rated torque of the span driving motors on each tower. 6.7.5.8 Speed of Motors The speed of span driving motors shall not exceed 900 rpm. The speed of integral horsepower motors that operate rail locks, bridge locks and wedges shall not exceed 1,200 rpm. The speed of gear motors of 10 hp or less, fractional horsepower motors, and motor generator sets shall not exceed 1,800 rpm. 6.7.5.9 Motors – General Requirements a.

Motors shall be of the totally enclosed crane, hoist or mill type, except where the size specified cannot be obtained, or unless authorized by the Company. Motors shall be as nearly waterproof as practicable. Motors subjected to atmospheric conditions shall be totally enclosed and waterproof; and non-ventilated if subjected to reduced-speed duty. Motors installed in weather-protected houses may be either drip proof or protected type. Unless otherwise specified by the Company, motor windings shall be impregnated with a moisture resisting compound to increase the resistance to excessive moisture, and span drive motors shall have embedded winding temperature sensitive devices. A drain hole shall be provided in the bottom of the motor frame and, where feasible, heaters shall be built in. Motors whose frames tilt during the operation of the bridge shall have ball or roller bearings arranged with provisions for flushing. Span motors shall be capable of stalled operation for two minutes with the motor control equipment functioning normally for seating torque. Primary and secondary conduit boxes for span drive motors shall be split cast and fully gasketed, with a lead bushing and a threaded conduit hole sized 2 inches or more in diameter.

b. Direct current motors shall be series, compound, or shunt wound, as determined by the performance specified, and shall have commutating poles. Motors to be used for dynamic or regenerative braking shall perform that function without injurious sparking or temperature rise. Span driving motors shall conform to the requirements of AISE standards for mill motors. c.

Alternating current motors shall be induction motors, suitable for the service characteristics specified, and conforming to the requirements of NEMA. Span driving motors shall be of the wound rotor crane type when AC variable voltage control or secondary resistance control is utilized. All other motors shall be of the squirrel cage type.

6.7.5.10 Heating Requirements for Motors a.

All alternating current span driving motors and motors used directly or indirectly in conjunction with the span driving motors shall be capable of delivering their rated output continuously for at least 30 min.

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without exceeding 80 degrees C rise in temperature for Class B insulation measured by resistance, or 70 degrees C rise if specified by the Company. b. All direct current motors shall be capable of delivering their rated output continuously for at least 30 min without exceeding 80 degrees C rise in temperature measured by resistance, or 70 degrees C rise if specified by the Company. c.

Motors other than span driving motors shall be rated on the basis of 15 minutes, provided that their running time during a single opening of the bridge does not exceed 30 seconds.

d. Where the maximum one hour ambient temperature exceeds 40 degrees C, the temperature rise requirements of this Article shall be adjusted accordingly. 6.7.5.11 Gear Motors Gear motors shall preferably be provided with an extension of the high speed shaft to allow hand operation. Electrical operation of the gear motor shall be prevented by a suitably wired limit switch when the hand crank is inserted. Gears shall be lubricated by immersion in the lubricant, and effective seals shall be provided to prevent the lubricant from reaching the motor windings. Gear motors shall have not less than a Class II rating as defined by the AGMA and shall carry an AGMA nameplate stating the horsepower, service rating and service factor. 6.7.5.12 Engine-generators a.

Engine-generators sets, either for primary or emergency power, shall consist of an internal combustion engine and an electric generator, direct connected and mounted on a common base. Separate units may be provided for supplying power for span operation and for auxiliary services such as lights and signals. Where used as emergency power source, the lighting generator unit shall start automatically and transfer the load automatically upon failure of the normal power. The span operating power unit shall be started manually by a remote control switch.

b. Engines shall, in general, conform to the applicable requirements of Article 6.7.4.2 with additional controls as specified in paragraph c. The engines shall develop adequate power to supply the maximum load, including motor starting load, while maintaining speed within the specified range. c.

Engine instruments and controls shall be mounted in a cabinet on the unit and shall include gages indicating water temperature, oil pressure and temperature, vacuum for diesel engines, throttle control, start/stop switch for manual control, manual emergency shut-down and indicating lights for low oil pressure, high water temperature, overspeed and overcrank, and an alarm contact for sounding a remote alarm in case of high water temperature, low lubricating oil pressure or failure to start after four cranking cycles.

d. Engine governor shall be of the centrifugal type providing 3% to 5% regulation from no load to maximum load. e.

The generator shall be capable of supplying the maximum load, including motor starting load, with regulated voltage drop within limits specified. It shall have a continuous rating of 70 degrees C rise in temperature for Class B insulation over 40 degrees C ambient, shall have drip-proof construction, and shall conform to ANSI and IEEE standards.

f.

The exciter shall be the direct connected, brushless type sized to furnish 10% excess excitation required at full generator operating load.

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g.

The generator control panel shall be suitable for wall mounting and shall contain the following devices: Three-position control switch “Off-Auto-Manual” for automatic starting units; air circuit breaker; Voltmeter, Ammeter, and their switches; Frequency Meter; Elapsed time meter; Automatic voltage regulator, Voltage adjustment rheostat; alarm contacts for remote indication; and automatic starting device when in “Auto” position for automatic power transfer switch, if required.

6.7.5.13 Automatic Electric Power Transfer a.

Where two sources of electric power are available, power for continuous services, such as lights, and navigation signals, shall be transferred automatically from the normal feeder to the standby or emergency source upon failure of the normal supply. Upon return of the normal power to at least 90% of rated voltage, the load shall be retransferred after an adjustable time delay of not less than five minutes. Should the emergency source fail, the retransfer shall be instantaneous upon return of normal power. The automatic transfer switch shall be electrically operated and mechanically held, with a single solenoid or motor mechanism and separate arcing contacts, and shall be enclosed in a wall-mounted cabinet, with circuit diagram on inside of door.

b. Where both power sources are external, one designated “Normal,” the other “Stand-by,” an auxiliary switch shall be provided to permit using either of the two as the preference source. c.

Where the standby source is an engine-generator set, the automatic transfer switch shall be equipped with a pilot contact for remote automatic starting of the engine 3 sec after normal source failure or after drop of any phase to 70% or less of the rated voltage. The normal load circuits should remain connected during this 3 sec delay. When the standby generator delivers not less than 90% rated voltage and frequency, the load shall be automatically transferred. After transfer, the engine shall run five min and then automatically shut down. The transfer switch shall have a test button so that normal source failure can be simulated.

6.7.5.14 Electrically Operated Motor Brakes a.

“Motor” brakes (Article 6.3.9) for the span driving motors, shall be base mounted shoe brakes which are held in the set position by springs with such force as to provide the required retarding torques (Article 6.3.9). Brake wheels for the motor brakes shall be mounted on the motor pinion shaft, or on a motor shaft extension.

b. Brakes shall be designed for intermittent duty for the required retarding torques. The brakes shall be designed to release when the current is on, and to apply automatically when the current is cut off. Brakes for the span operation shall be provided with hydraulic, mechanical or electrical escapements, such that the brakes will not be applied at the same time. c.

The brakes shall be equipped with a means for adjusting the torque and shall be set in the shop for the specified torque. Each brake shall be provided with a nameplate which shall state the torque rating of the brake, and the actual torque setting where it differs from the torque rating. Shoe type brakes shall be so designed that it is possible to adjust the brakes or replace the shoe linings without changing the torque settings.

d. Direct current brakes shall be released by thruster units or shunt-coil solenoids. Shunt coils shall have discharge resistors or surge suppressors so that opening the shunt-coil circuit does not cause high transient voltage. e.

Alternating current brakes shall be released by thruster units, or motor operators if so specified. Thruster motors exposed to the atmosphere shall be totally enclosed and non- ventilated with weatherproof insulation of both the motor and conduit box.

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f.

For shoe type brakes the releasing mechanism shall be capable of exerting a force of not less than 130% of the force actually required to release the brake when set at the specified torque setting and at the minimum expected ambient temperature.

g.

Brakes for other motors shall be solenoid released shoe type brakes or dry type disk brakes, and shall have an intermittent rating not less than the full load torque of the motors.

h. Brakes shall be of a construction which ensures uniform wear, and shall have independent provisions for adjusting lining wear, equalizing clearance between friction surfaces, and adjusting the retarding torque. The brake linings shall not be affected by moisture. Solenoids, thruster units, and motor operators shall be moisture proof. Fittings shall be corrosion resisting. Thrusters for shoe type brakes shall be provided with year around oil. i.

Shoe type brakes shall be provided with a permanent manual release lever suitable for one man operation. Means shall be provided for latching the lever in the set and released positions. Disk type brakes shall be provided with a manual release which can be latched in the released position; the manual release shall automatically reset when the brake is energized.

j.

Where brakes are located outside the machinery house, they shall be of weatherproof construction or shall be provided with a weatherproof housing. The housing shall be arranged to permit operation of the hand release lever from outside the housing.

k. Brakes installed on the moving span, shall operate satisfactorily with the span in any position. l.

Where specified by the Company, brakes shall be provided with heating elements to prevent the accumulation of moisture and frost, and shall have provision for the addition of limit switches for control, and of lights to indicate the position of the brakes and their hand release levers.

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6.7.5.15 Electrically Operated Machinery Brakes a.

Machinery brakes (Article 6.3.9) for the span-operating machinery shall meet the requirements for the “motor” brakes, except as otherwise herein provided.

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b. Brake wheels shall be shipped to the manufacturer of the machinery who shall press them onto the shafts. 6.7.5.16 Design of Electrical Parts

4 a.

For lift bridges electrical parts, including wiring, switches, circuit breakers, controllers, and contactors, shall be designed for operation of the bridge using either normal or emergency power for the span loads (as specified in Article 6.3.6) and for the operating cycles and durations (as specified in Article 6.9.10). For bascule and swing bridges these parts shall be similarly designed for bridge operation for the specified span loads (Article 6.3.6) and for 30-minutes continuous operating cycles of Condition B load for bascule bridges and 30-minutes continuous operating cycles of Condition A load for swing bridges.

b. The temperature rise of electrical parts under such operation shall not exceed that for which the part is normally rated including those of Article 6.7.5.10 and Article 6.7.5.38. 6.7.5.17 Electrical Control a.

Methods of span electrical control may be classified as either “Master Switch Control” and “Automatic Sequenced Control.” Except for these differences, the following general features shall apply:

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(1) Separate controllers shall be provided for the span driving motors, the rail lock motors, the span lock motors and the wedge motors. (2) Where there are two main direct current motors powering one output, the control shall be series, parallel, or series parallel as required, except that where the current is furnished by a storage battery, the control shall be of the series parallel type. b. The following features shall apply to master switch control: (1) Where each span driving motor is rated at more than 75 HP, the control shall be of the full magnetic type. Where the rated horsepower of each span driving motor rated at is 75 HP or less, the control shall be of the full magnetic, or semi-magnetic type, as stipulated by the Company. (2) For full magnetic control, all span driving and span brake circuits shall be energized by magnetic contactors opened and closed by control circuits wired through and operated by the master switch. Speed of span shall be controlled by accelerating contactors. (3) Semi-magnetic controls shall be as specified for full magnetic controls except that the speed of span operation shall be controlled in whole or in part by opening and closing the motor circuits directly by means of the master switch. (4) Motor brakes shall be controlled through contacts on the master switches so arranged that all motor brakes shall be held released when power is applied to the span driving motors. (5) Where two motor brakes are used on a hoisting machine, a control point for each motor brake shall be provided for each direction of travel so that the motor brakes may be applied separately. (6) For tower drive vertical lift bridges, two points of motor brake control shall be provided for each direction of travel where two motor brakes are used for the hoisting machine in each tower. (7) Electrically operated machinery brakes may be controlled either through contacts on the master switch, or by a separate switch. (8) Where the machinery brakes are controlled by the master switch, the contacts shall be so arranged that all machinery brakes are held released when power is applied to the span driving motors, except when the seating switch is used, as hereinafter described. The sequence of the master switch contacts shall be so arranged that the machinery brakes may be applied by the operator whenever the span is coasting. One point of machinery brake control shall be provided for each direction of travel for all machinery brakes on a hoisting machine. (9) Where the machinery brakes are controlled by a separate switch, they shall normally be set, and shall be so arranged, that they must be released by the operator before starting the bridge. They shall be held in release during the entire operation unless the operator desires to use them while coasting, or unless an emergency condition arises requiring brake power in excess of that offered by the motor brakes, when they may be applied instantly by the operator. This portion of the equipment shall be designed so that it will not be injured if left in release indefinitely. Where so specified, the brakes shall be provided with not less than three steps of retarding torque to permit partial application of the brakes. The machinery brake circuits shall be independent of the general interlocking system, and may be an electrically operated interlocking device which will prevent the use of the span driving motors and the machinery brakes one against the other, except by the use of the seating switch hereinafter described.

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(10) A seating switch shall be provided for applying the machinery brakes while power is still on the motors, in order that the span may be drawn tightly to its seat and held in that position. The seating switch shall be convenient to the operator and shall be hand or foot operated. (11) For tower drive vertical lift bridges, one control point for each direction of travel shall be provided for all machinery brakes. In addition, all machinery brakes shall be applied automatically if the span should exceed a predetermined skew. (12) Motors for rail locks, span locks, wedges, and other devices associated with the movement of the span shall be controlled through magnetic contactors energized by control switches independent of the master switch. c.

The following features pertaining primarily to span operation shall apply to automatic sequenced control: (1) The normally required action by the operator consists of the initiation, by one movement of a single pushbutton or hand lever, each of the several major interlocked functions in sequence. Examples of sequenced steps include: • actuate railroad signals. • pull rail locks. • pull span locks.

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• raise span. (2) Emergency actions by the operator could include operation of bypass switches, selection of emergency mode of span operation, and skew correction following skew limit switch operation. (3) Span motor controls shall include all components required to protect the motor against abnormal conditions, automatically controlled acceleration and deceleration, modulated speed control where applicable (such as for tower drives without power synchronizing motors), adequate controlled speed regulation to accommodate overhauling loads (negative torque or regenerative braking loads), and other features as required to ensure satisfactory performance following a single movement of the initiating control switch.

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(4) Selection of motor and machinery brake types, and control arrangements shall ensure time sequenced brake application under all conditions.

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(5) Two modes of stopping span movement shall be provided: (a) normal stop, with controlled electrical deceleration followed by brake application, and (b) emergency stop, with immediate power cutoff and application of brakes, initiated by an emergency stop button. (6) Limit switch actions shall initiate deceleration prior to the “nearly open” and “nearly closed” span positions. The control system shall be designed to accomplish reduction to slow speed when those positions are passed. Speed limit switches shall be provided to detect span speed at the “nearly open” and “nearly closed” positions. Where span speed is within the normal limit of the span, movement shall continue to completion; where not, power shall be cut off and brakes applied, and a reset operation of the overspeed circuit shall be required before span movement can be resumed.

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(7) During final seating, the motor torque shall be reduced and the brakes shall remain in released position until the span is tightly seated, after which the brakes shall set and the motors disconnected. (8) Tower drive lift bridges arranged for automatic sequenced control shall have two independent skew limit switches, in effect for each span mode of operation, connected in series. (9) As specified by the Company, the drive system may include alternating current or direct current motors controlled by semiconductor devices. 6.7.5.18 Speed Control for Span Driving Motors (a) Master switch control for span driving motors shall provide for speed control. In general, not less than six steps of acceleration shall be provided, such that the motor torque will differ as little as practicable from the average torque required for uniform acceleration from zero speed to full speed. The acceleration steps shall be such that the bridge will start slowly and will accelerate and decelerate smoothly and without excess torque when under the smoothest friction conditions and without wind or other unbalanced load; and such that the bridge will accelerate and decelerate similarly when the motors are carrying their maximum loads. Separate resistors shall be provided for each motor. (b) Solid state variable speed drives for control of AC or DC span driving motors shall provide for smooth, stepless speed control over a speed range of at least 10 to 1. Speed regulation shall be 2 percent or better up to rated motor speed. A closed-loop feedback type speed control system with overspeed detection shall be used. Speed and torque control shall be four-quadrant regenerative, with static (contactorless) reversing. Dynamic braking may be utilized as a supplement to regeneration, but shall not be the primary means of controlling overhauling loads. Acceleration and deceleration ramping shall be field adjustable from 2 to 20 seconds. A minimum of two adjustable speed settings shall be provided, one covering a range of approximately 50% to 100%, and one covering a range of approximately 5% to 25% of rated speed. Two independent adjustable settings of torque limiting shall be provided, each covering the minimum range of 50% to 150% rated motor full load torque. Automatic drive shutdown with fault indication, shall be provided for loss of feedback signal. Each variable speed drive shall be provided with a disconnect circuit breaker and an isolation contactor mounted in the drive cabinet to remove power from the solid state switching components and/or the connected motors when the span driving motors are not being operated. The solid state speed control shall be a standard product of the manufacturer. For two motor installations, drives shall be arranged to provide equal torque from each of the motors. 6.7.5.19 Magnetic Control For Span Driving Motors a.

The following features shall apply to full magnetic control with master switch: (1) Master switches Master switches for the span driving motors shall be cam operated reversing switches with a single handle, and provided with necessary contacts and contact fingers for operating the magnetic contactors. Contacts and wearing parts shall be easily removable and replaceable. The controller shall provide for speed control of the motors. (2) Parallel or series-parallel operation For parallel operation for alternating current motors, and for constant potential parallel or seriesparallel operation for direct current motors, there shall be separate reversing contactors and

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separate resistors for each motor. Where two motors are connected to one hoisting machine, accelerating contactors shall be common to both motors, unless otherwise specified by the Company. For three-phase alternating current motors, each phase shall have its own resistors, so designed as to give balanced current in all three phases. Certain of the acceleration contactors shall be controlled by acceleration relays, such that the specified torques in Article 6.7.5.5 are not exceeded. Where common accelerating contactors are not used, the acceleration contactors shall be so designed, or electrically or mechanically connected, that corresponding circuits in each motor control will be made simultaneously, and that in the event one motor is cut out, the control for the motor in service will operate satisfactorily. (3) Acceleration relays Adjusting plugs, screws, and nuts, including time limit adjustments, shall be easily accessible to allow for adjustment of relays to the proper timing intervals between acceleration steps. The contacts shall be removable without disturbing the setting of the relays. (4) Reversing of motors Magnetic shunt type contactors for reversing the motors shall be installed with a forward and a reverse pole for each motor conductor. b. The following features shall apply to semi-magnetic control: (1) For semi-magnetic control, a drum type master switch shall be provided for reversing the motors by contactors controlled by contacts on the master switch. The master switch accelerating contacts shall carry the secondary current at the step applied without exceeding a 30° C temperature rise, and when the motors are operating a full load torque, or at stalled torque if it is less. Reversing contactors, and accelerating contactors used in conjunction with the accelerating contacts of the master switch, shall meet the requirements of Article 6.7.5.27.

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(2) For control of motors in parallel the switches shall be interconnected so that all switches will be operated simultaneously by one handle. The controllers shall be so arranged that the operation of one motor may be cut out without affecting the operation of any other motor.

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6.7.5.20 Programmable Logic Controllers a.

Programmable logic controllers (PLC) may be used for the sequential control and continuous monitoring of bridge operations. The PLC’s shall be manufactured and tested in accordance with applicable IEEE and NEMA standards. The PLC’s shall be installed and grounded in accordance with the manufacturer’s recommendations and the requirements of NEC.

b. The following features shall apply to bridge control with programmable logic controllers: (1) Cold Backup PLC. Cold backup shall generally be the preferred backup method. For cold backup, two identical PLC’s (CPU’s only) shall be provided, and shall be wired in place. One PLC shall normally be de-energized and electrically isolated from power source and input/output (I/O) racks via transfer switches or relays until selected for operation. Separate, dedicated power supplies shall be provided for each PLC. Common I/O modules and racks shall be shared by both PLC’s, but only electrically connected to the active one. (2) Hot Backup PLC.

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In certain situations, where momentary interruption to the PLC system cannot be tolerated, hot backup may be utilized. For hot backup, two identical PLC’s shall be connected so as to be operating simultaneously, with PLC processor error and fault checking, memory and register updating. (3) Power Conditioning. All PLC’s and I/O racks shall be protected against power source surge and noise problems by the use of a power conditioning system, including surge suppression, in the power line ahead of all power supplies and ahead of all power connections to I/O modules and any other devices, connected to the PLC’s. Consideration shall also be given to the use of surge suppression terminal blocks for all conductors connecting to PLC inputs. (4) System De-energizing. The PLC system shall be provided with a master control power switch on the control console which directly interrupts all power feeds to I/O modules when control power is turned off. A standby mode may be utilized with such switch in which input modules remain energized. (5) Emergency Stop. A maintained-contact Emergency Stop pushbutton shall be provided which interrupts the PLC logic sequence, and simultaneously and immediately directly interrupts all output module power feeds associated with all bridge operating machinery and all other bridge-related moving equipment including roadway gates and barriers if present. c.

A PLC programming terminal shall be furnished with each PLC system. The PLC programming terminal shall be a compact, portable computer with all necessary PLC programming software, hardware, and communications link cables and adapters specific to the PLC installed. All software registrations and product warranties shall be in the Company’s name.

6.7.5.21 Resistances and Reactors a.

Resistors for motor control shall, unless otherwise specified, be non-breakable, corrosion resistant, edgewise wound or punched grid resistor units. The resistors for the span operating motors, unless otherwise specified, shall be of a capacity equal to NEMA intermittent cycle rating providing for 15 sec on out of each 45 sec. The resistors shall be mounted on a steel frame so as to be free from injurious vibration and to permit free circulation of air; and shall be furnished so that any unit or part of a unit may be removed and replaced without disturbing the others. The units shall be insulated from their supports.

b. For wound rotor motors with secondary resistance control, the controller shall be so arranged that a small amount of resistance shall always be left in the rotor circuits of each motor. This permanent resistance section shall be adjustable after installation, and shall be proportioned for continuous duty. c.

Reactors for secondary control of wound rotor motors shall be arranged to present the same reactance to each motor phase, and they shall be mounted so as to be free from injurious vibration, to permit free circulation of cooling air, and to be protected from any dripping liquids.

6.7.5.22 Switches for Limiting Travel and Speed a.

Limit switches which will stop the motors and set the brakes automatically at the end of travel shall be provided for the span lock, rail lock, end wedge and wedge motors. The term limit switch includes all types of mechanical switches as well as encoders, resolvers and proximity switches.

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b. Limit switches shall be provided for the movable span with master switch control which will cut off the current from the span driving motors and set the brakes so as to stop the span in the “nearly closed” and “nearly open” positions. It shall then be necessary to return the controller handle to the “off” position to bypass the limit switch contacts and regain control of the span to fully close or fully open the bridge. Where specified, relays shall be provided which will prevent the bypass from functioning until a predetermined time after the brakes have set. Additional limit switch contacts shall be provided to stop the span in the “fully open” position, and for swing bridges, where specified, in the “fully closed” position. Unless otherwise specified, the “nearly closed” and “nearly open” positions shall be taken to be 6 feet from the “fully closed” and “fully open” positions, respectively. c.

Fully seated switches shall be provided for vertical lift and bascule bridges which shall indicate to the operator when the bridge is fully closed.

d. “Skew” limit switches mechanically connected to the machinery on the two towers, or equally effective devices of other type, shall be provided for tower drive vertical lift bridges which will cut off the current from the main motors and set the brakes so as to stop the span whenever it is more than a prescribed amount out of level. e.

Limit switches exposed to the weather shall be watertight and all exposed parts shall be corrosion resisting. Where plunger type limit switches are used for fully seated switches, they shall be weatherproof and shall be provided with cast or malleable iron enclosures and stainless steel operating rods.

f.

Electrically operated bridges, shall include an over-speed limit switch to stop the span whenever normal span speed is exceeded by 10 percent or more.

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6.7.5.23 Interlocking a.

The operating mechanisms of all movable bridges shall be so interlocked that the operation of all devices can be performed only in the prescribed sequence.

b. Emergency bypass switches shall be provided which will free the various motors from the prescribed interlocking in case of emergency. These switches shall be conveniently mounted on the control desk or on the main switchboard. Each such emergency switch shall be sealed in the “off” position. c.

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Auxiliary power units and main power units shall be interlocked to make each one inoperative while the other is in service.

4 d. Motor and machinery brakes shall be provided with limit switches so arranged that the bridge shall be inoperable whenever any brake or combination of brakes shall be released by hand, such that the available braking torque left in service would be insufficient to meet the requirements in Article 6.3.9. e.

Motors equipped with a shaft extension for hand operation shall be provided with a suitably wired limit switch to prevent electrical operation of the motors when the hand crank is inserted.

6.7.5.24 Switches a.

An enclosed switch or circuit breaker shall be provided as a disconnect for the supply feeder, with a pole for each ungrounded conductor. A similar switch, or a circuit breaker capable of being operated as a switch, shall be provided as a disconnect for each motor, light, signal or other circuit.

b. Main disconnect switches shall not be less than 60 amp capacity.

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c.

Toggle and tumbler switches shall be of corrosion resistant construction and they shall not be less than 20 amp capacity.

6.7.5.25 Circuit Breakers and Fuses a.

An automatic circuit breaker shall be placed in the supply line and be arranged with undervoltage release or trip coils to permit provision of undervoltage, reversal, and loss of phase protection. Where the supply has very large short circuit capability, suitably rated current limiting fuses may be provided in a disconnect switch ahead of the automatic circuit breaker, or otherwise incorporated into its design to accomplish alternate suitability. Where practicable, circuit breakers shall be used to provide short circuit protection for all wiring circuits. Molded case circuit breaker selection shall include a comparison of either the short circuit interrupting ability of the I2t rating (the integral of the square of the short circuit current, I, with respect to time, t, for the period of interrupting time duration), with the respective short circuit capacity of the I2t rating of the supply source connection. They shall not be applied to circuits with possible short circuit duty in excess of 60% of their rated interrupting ability or, if preceded by current limiting fuses, their permissible I2t source rating shall be at least 125% of the rated I2t letthrough of the preceding fuses for the particular application. Such a protective device shall be provided in each motor, brake, light, signal, indicator or other circuit. Where fuses are used, they shall generally be of the dual element or current limiting type.

b. All circuit breakers shall be air break type for 600 v and less. For circuits above 600 v, either air break, vacuum break, or oil immersed circuit breakers shall be used as required by the service conditions. Breakers shall have a pole for each phase wire feeding through the breaker, an overload device consisting of a thermal or magnetic element for each pole, and a common trip. c.

Circuit breakers shall not be used for motor overload protection or for limiting the travel of any mechanism.

6.7.5.26 Contact Areas For custom designed electrical equipment such as slip rings for swing bridges, line contacts shall be avoided where practicable. The current per square inch of contact area shall not exceed 50 amp for spring held contact, or 100 amp for bolted or clamped contact. 6.7.5.27 Magnetic Contactors Magnetic contactors shall have an 8 hr rating not less than the current through the contactor when the connected apparatus is operating at rated load. Magnetic contactors shall be of the shunt type, and shall be quick acting. Contacts shall be well shielded to prevent arcing between them and other metal parts near and shall be designed so as to be readily accessible for inspection and repair. Copper contacts shall have a wipe. Contactors shall have double-break features or shall have magnetic blowouts or equivalent means for rapidly quenching the arc and shall have a minimum number of parts, and all steel parts shall be corrosion resistant. Magnetic motor starters shall have no less than 25 amp rating. 6.7.5.28 Overload Relays a.

Overload relays, automatic or hand reset as specified, shall be used in each phase or d-c circuit for overload protection of all motors.

b. Instantaneous magnetic overcurrent relays shall also be provided in motor circuits to de-energize all motors when the safe torque is exceeded, unless other means are provided for limiting the maximum torque.

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Movable Bridges 6.7.5.29 Shunt Coils Where shunt coils are used, in particular with brakes and magnetic contactors, the insulation shall be capable of withstanding the induced voltage caused by cutting off the current. 6.7.5.30 Instruments A line voltmeter, ammeters for span driving motors, and a power bus wattmeter, shall be provided and mounted on the control console. A voltmeter switch shall be provided for measuring the voltage between any two phases and between any phase and ground. Instruments shall be of the rectangular illuminated type, and flush mounted and back connected. 6.7.5.31 Protection of Apparatus Electrical apparatus shall be protected from the weather and from accumulations of dirt. 6.7.5.32 Cast Iron in Electrical Parts Where cast iron is used in switches and small electrical parts, it shall be of the malleable type. 6.7.5.33 Position Indicators Synchronous moving span position indicators of the high accuracy type guaranteed within ± 1 degree shall be provided. Transmitters shall be geared to trunnion shafts, counterweight sheave shafts, or machinery shafts, whichever is most suitable for the particular installation, and the receivers in the control console shall be geared to the indicators. Gearing shall be arranged so as to give the greatest practicable accuracy.

1

6.7.5.34 Indicating Lights a.

Indicating lights of suitable colors shall be furnished and installed on the control console to show span positions, especially the fully closed, fully open, nearly closed, and nearly open positions, and also the positions of the span locks, rail locks, and end wedges. Indicating lights shall also be provided to show the released position of each span brake, the overload or overheat tripping of span drive motors, and the status of other emergency functions.

3

b. Where specified, indicating lights may be oil-tight “push-to-test” type.

4

6.7.5.35 Control Console a.

The span control console shall contain switches for the span operating motors and for the lock, end lift and wedge motors; seating switches; bypass switches, instruments; position indicators; indicating lights; and all other control devices and apparatus necessary or pertinent to the proper operation and control of the span and its auxiliaries by the operator.

b. The control console shall be located so as to afford the operator a clear view in all directions. The console shall be of cabinet type construction with a horizontal front section about 36 inches above the floor and an inclined rear instrument panel set at such a slope that the meters can be read from average eye level without parallax and without reflection from the glass instrument cover. The console plan dimensions and the arrangement of equipment shall be such that all control devices are within easy reach. The top of the console shall be a laminated phenolic compound not less than 1 inch thick, with edges beveled and neatly finished. Where specified by the Company, the top of the console may be of No. 10 U.S. Standard gage stainless steel with a non-reflecting finish. The horizontal and sloping sections of the top shall be accurately cut to ensure a close fit.

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c.

The console frame shall be constructed of sheet steel of not less than No. 11 U.S. Standard gage. All corners and edges of the console shall be rounded, and the sheet steel shall be reinforced by flanging the metal into angle and channel sections. Connecting sections shall be properly joined by either continuous seam welding or spot welding to provide a rigid free-standing structure. Outside surfaces shall be smooth and without visible joints, seams or laps. The bottom of the console shall be left open. The supporting flange on the inside of the console frame at the bottom shall be provided with suitable holes for bolting the console to the floor. Suitable brackets and angles shall be provided on the inside of the console to support the top and the equipment mounted thereon.

d. The control console shall be provided with hinged doors on the front, and with doors, removable panels, or fixed panels on the back and sides, as specified by the Company, to suit the requirements of the installation. Doors shall have well-rounded flanged edges, and shall be flush mounted on concealed hinges, and shall incorporate jambs to limit the swing. Doors shall be fitted with sturdy, three point latches operated by flush type, chromium plated handles, and shall be assembled accurately and shall have a clearance not exceeding 1/8 inch at any point. e.

The “off” position of master switch handles shall be toward the front of the console. For bascule and swing bridges, the direction of rotation of each master switch shall be such that when it is moved from the “off” position, the span, as seen by the operator, will move in the same direction as the master switch handle. For double leaf bascule bridges, the switches shall rotate opposite. For vertical lift bridges, clockwise rotation shall raise the bridge.

f.

Seating switches, where foot-operated, may be supported by the outside of the console or may be set in a suitable recess at the bottom of the console. Foot recess shall be rounded at the top to a l-1/4 inch radius.

g.

Outgoing control connections from the console shall be brought to suitably marked barrier type terminal boards supported on straps securely attached to the console frame. Terminal boards shall be located so that they do not interfere with door access to the inside of the console. Wires shall be copper and shall be brought from the terminal boards to their respective terminals in a neat and orderly arrangement, properly bunched and tied.

h. The console when finished shall be given one coat of moisture-resisting primer and one coat of filler on all surfaces. The outside surfaces shall be given a finished coat of dull lacquer of a color specified by the Company. The horizontal console top shall not be painted. i.

The console interior shall be equipped with suitable lights controlled from a switch on the console.

j.

Each piece of equipment and each indicating light on the control console shall have a properly engraved metal or lamicoid nameplate showing white characters on a black background or black characters on a white background. The designation on the nameplates shall correspond with that shown on the wiring diagrams.

6.7.5.36 Control Panels a.

Control panels shall be of enclosed, dead front, free standing construction, NEMA Type 1 or better. All disconnect switches, circuit breakers, contactors, relays, rectifiers, instrument transformers, and other electrical equipment for the control of the span and its auxiliaries shall be mounted on or in the control panels.

b. The control panels shall be constructed of sheet steel of not less than No. 11 U.S. Standard gage, generally as described in Article 6.7.5.35 for the control console. Equipment mounted at the bottom of the panel boards shall clear the floor by at least 6 inches. Except for front connected or wall mounted panels, there shall be a distance of at least 2-1/2 feet between the wall and the back of the panelboard. Open control panels, where specified, shall be installed in a separate room provided with a lockable door. © 2011, American Railway Engineering and Maintenance-of-Way Association

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c.

Control panels shall be designed and installed with a view to the safety of the operator. The equipment shall be so arranged as to be easily reached and operated and to give a neat and attractive appearance.

d. Control panels shall be either back wired or front wired. Interconnections shall be made by either copper bus bars or insulated cables of equivalent current-carrying capacity. Control panel wiring shall terminate in terminal strips supported in a substantial manner, and all conductors shall be copper. e.

Each piece of equipment on the control panel shall have a properly engraved nameplate, as specified for the control console.

6.7.5.37 Control Panel Enclosures Enclosures for panels shall, unless otherwise specified by the Company, be general purpose enclosures conforming to the NEMA requirements for Type 1 general purpose enclosures. The cabinet shall be provided with suitably arranged doors to give access to the front of the control panels, and either doors or removable panels to give access to the back. The cabinet, including doors and panels, shall be of sheet steel of not less than No. 11 U.S. Standard gage, welded and flanged in a manner that will result in a rigid free standing structure, and shall be treated to resist corrosion, and finished in the manner specified for the control console. 6.7.5.38 Electric Wires and Cables a.

The quality of the wires and cables, and their insulation and covering, shall conform to the IPCEANEMA Standards. Where these requirements do not apply, wires and cables shall conform to ASTM requirements.

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b. In general, unless otherwise specified, wires external to the control console and control panels, shall be protected by conduit, armor, or be suitably jacketed. Wire shall be type RHW, use or XHHW with class XLP or EPR insulation, rated for 75°C and 600 volts. c.

Insulated wire for connections made on terminal boards and completely inside control panels and control consoles shall conform to the Underwriters’ Laboratories requirements for Type SIS or THWN Wire, 600 volts.

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d. Insulated wires for connections to motor resistance grids shall be high temperature appliance or motor lead wire rated 250° C, 600 volts, Type TFE, TGGT, or TKGT. High temperature wires preferably shall be connected to the general purpose type wires within approximately, but not less than, five feet, and they shall be run between this connection and the resistors in separate conduits.

4 e.

All wires shall be stranded copper. No wires smaller than No. 12 AWG shall be used except that No. 14 AWG will be permitted for connection to internal control components where the use of No. 12 AWG would be impractical for control console, control panel, or interlocking device wiring.

f.

The ends of all wires No. 8 AWG gage and smaller shall have solderless high compression indent type terminals where they terminate at control panels, control consoles, terminal strips, lighting panels, junction boxes, and similar locations. The ends of larger wires shall be similar and shall terminate in pressure lugs or screw-type solderless connectors.

g.

Vertical runs of metal-clad cable should be limited to 30 feet.

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Steel Structures 6.7.5.39 Tagging of Wires Wires shall be numbered and the numbers permanently marked on durable fiber tags, or on metal or plastic bands with protective heat-shrunk protective sleeving, so that any wire may be traced from terminal to terminal, or as specified. The numbers used shall correspond with those shown on the wiring diagrams. 6.7.5.40 Wire Splices Wires shall be continuous from terminal to terminal. Splices may be used only where the terminations specified in Article 6.7.5.38f would be impractical; and shall be neatly and carefully made and mechanically and electrically secure before soldering. They shall be wrapped with rubber tape and friction tape and painted with waterproof insulating varnish. Splices shall not be used inside conduits. 6.7.5.41 Raceways, Metal Conduits, Conduit Fittings and Boxes a.

Except as otherwise specified by the Company, conduits shall be hot-dip-galvanized, standard weight steel or alloy steel pipe, with a factory-fused and bonded polyvinylchloride plastisol coating if specified, and shall be not less than 3/4 inch dia. All couplings, locknuts and bushings shall be standard screw type; setscrew type couplings, locknuts and bushings shall not be used. Bushings shall be the insulating type. Conduit entrances to sheet metal enclosures shall have sealing 0-rings or liquid tight hub fittings.

b. Conduit size shall be such that the total areas of the wires, including insulation, shall not exceed the percentage of the area of the conduit specified by the NEC. Phase wires in alternating current motor circuits shall be placed close together in one conduit to lessen the inductive effects. The circuits for not more than three alternating current motors may be in one conduit. c.

Suitable conduit outlet boxes, junction and pull boxes, ells, and other fittings shall be used with conduits except as otherwise provided herein. Boxes, outlets and other fittings shall be of cast iron or malleable iron of sufficient thickness to permit the conduit to be threaded into the fitting, and shall be hot-dipgalvanized. Boxes and other fittings must be weather-proof throughout, in particular at conduit connections, be free from rough edges and rough surfaces, and unless otherwise specified shall be of NEMA Type 4 construction unless housed in a room. Large boxes, for which cast iron or malleable iron is not practicable, may be built of steel plates and angles not less than 3/16 inch thick, with all joints continuously welded and shall be provided with drain holes.

d. Bends in conduits shall be used sparingly. The total angle of all bends in one conduit run shall not exceed 270 degrees and preferably 180 degrees. Where the conduit is bent, the radius of the bend to the center of the conduit shall be not less than 8 times the inside diameter of the conduit except for factory ells. Conduits shall have drain holes placed in tee-connections located at the low points. So far as possible, conduits shall be run in lines parallel and perpendicular to the principal lines of the house and structure. Embedded conduits shall be carefully rodded after placing, with a device that will ensure that the whole interior surface of the conduit is free and clear of obstruction. The conduit shall be temporarily protected by conduit closures or pipe caps until wires are pulled and conduit is permanently closed. e.

Conduits shall be so placed that dirt will not accumulate around them, and shall be firmly clamped to the structure to prevent rattling, by means of supports on not more than 6 foot centers. There shall be at least 1 inch clearance between conduits, and at least 4 inches clearance between conduits and the supporting structure. Adequate provision for the conduit movement shall be made wherever conduits cross expansion joints in the supporting structure, and conduit runs between the bridge and solidly based structures, such as piers and operator’s houses, shall include at least 1 foot of liquid tight flexible metal conduit at the interface.

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f.

Conduit connections to motors, generators, limit switches, brakes, and other devices as otherwise specified, shall include a minimum of 18 inches of liquid tight flexible metal conduit.

g.

Where bridges have a relatively large amount of equipment and an extensive control system, consideration shall be given to the use of wireways or continuous rigid cable supports instead of exclusive use of conduits above the control panels and connecting with the control console. Where wireways are used, they shall be full lay in type of at least 8²´8² cross-section and preferably 12²´12² to adequately accommodate recommended bending radii of all cables. Where continuous rigid cable supports are used, all cables so supported shall meet the NEC requirements. Wireways and trays shall not be used outside the operator’s house.

6.7.5.42 Electrical Connections Between Fixed and Moving Parts Electrical connections for carrying current between fixed and moving parts shall be made as specified or approved by the Company for each particular installation, and may be by means of flexible cables, collector rings, sliding or rolling trolleys, as generally indicated below, or by other suitable methods. 6.7.5.42.1 Flexible Cables Conductors in flexible cables shall have extra-flexible stranding. In general, the cables shall be connected to terminal strips in junction boxes at which the wiring in conduits terminate. Short cables with relatively small movement of the moving part with reference to the fixed part, such as cables extending from a fixed pier to a fender not rigidly attached to the pier, shall be extra flexible round portable cable covered with a neoprene jacket or protected with corrosion resistant metal armor. Long cables with relatively large movement of the moving part with reference to the fixed part, such as vertical cables hanging in a loop between the end of a vertical lift span and a tower, shall be special, rubber insulated flexible cables covered with a special neoprene jacket internally reinforced with cotton twine. Such cables shall be suspended from segmental supports arranged to ensure against any sharp bends in the cables as the span moves.

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6.7.5.42.2 Collector Rings On swing bridges the connection between the fixed part and the swing span may be made through shoes sliding on circular collector rings attached to the center pivot. The collector rings shall be protected by a removable metal casing.

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6.7.5.42.3 Sliding and Rolling Trolleys On vertical lift bridges, the connection between the lift span and the towers may be made through trolleys with sliding or rolling shoes moving along vertical tracks supported on the towers. For sliding shoes, the track for each conductor shall consist of a flat copper contact strip not less than 1/4 inch thick supported continuously on a rolled steel section of adequate size and so supported from the tower as to secure a rigid track during operation. For rolling shoes, the track for each conductor shall consist of a grooved copper trolley wire supported at close intervals on a continuous wood strip attached to a steel section. Means shall be provided to put the trolley wire in tension so as to secure a rigid track during operation. The rolling shoes shall be standard trolley wheels. Twin sliding or rolling shoes shall be provided for each conductor in order to secure good contact under conditions of ice or sleet. Twin shoes shall be supported on a trolley arm so designed as to hold the shoes against the track by a spring or by gravity and to provide full contact between the shoes and the track under extreme lateral and longitudinal movements of the span. 6.7.5.43 Electrical Connections Across the Navigable Channel Electrical connections for carrying current across the navigable channel shall be made as specified or approved by the Company for each particular installation. They shall preferably be made by means of submarine cables but may be made by overhead cables, particularly for vertical lift bridges. The voltage, the number of © 2011, American Railway Engineering and Maintenance-of-Way Association

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conductors in each cable, the size and number of strands in each conductor, the construction of the cable, and other such data shall be as specified by the Company. In general, each cable shall provide a number of spare conductors. Installations shall conform to the following general requirements. 6.7.5.43.1 Submarine Cables Submarine cables shall be armored with spiral wound galvanized steel wire armor and, if specified, covered with a neoprene jacket. Individual wires shall meet the requirements of Article 6.7.5.38. Submarine cables may be lead-covered but preferably shall be provided with conductor insulation suitable for submarine use without the use of a lead sheath. Unless otherwise specified, submarine cables shall be placed at least 5 feet below the bed of the channel. Cables shall be long enough to provide ample slack. 6.7.5.43.2 Overhead Cables a.

Overhead cables shall be jacketed with neoprene or other superior jacketing compounds resistant to weather and aging. Individual wires shall meet the requirements of Article 6.7.5.38.

b. Each cable shall be suspended from a messenger strand at intervals of not more than 18 inches. Messenger strands shall be strung with such a sag as required to safely support the entire construction under various conditions of ice, wind, and temperature, appropriate for the location of the bridge and shall be of high strength material and shall be adequately anchored to steel framework at their ends. Messenger strands, cable hangers, and all accessories shall be protected against corrosion in such manner as to ensure a service life not less than that of the overhead cable. 6.7.5.44 Service Lights a.

A complete electric lighting system shall be installed for the operator’s house, machinery house, stairways, vertical lift span tower tops, signals, machinery, the end lifting and locking apparatus, and at all other points where periodic inspection or maintenance of equipment is required. Lighting systems shall be designed to produce at least the following intensities: operator’s house, 30 fc; machinery house, 20 fc; unhoused machinery, 15 fc; and walkways and stairways, 20 fc.

b. Lighting may be fluorescent, incandescent, or mercury vapor type. All fixtures fitted with incandescent lamps smaller than 100 w shall be so equipped that lamps up to 100 w can be used, and the sizes of conductors shall be based on a minimum of 100 w per fixture. c.

The lights in the control house shall preferably have dimming adjustment from the control console. In machinery houses, there shall be fixed pendants of suitable length with enclosed fixtures or fireenameled steel dome reflectors. Vapor-tight, fire-enameled steel dome reflectors or enclosed mercury vapor fixtures shall be provided for exterior lighting. Lampholders generally shall have shock-absorbing porcelain sockets.

d. Convenience outlets shall be provided in each room of the operator’s house; in machinery houses; at bridge lock, rail lock, and wedge machinery; at submarine cable terminal cabinets; and at all locations where occasional inspection or maintenance of equipment is required. They shall be of the twinreceptacle, 3-wire, grounding type. Exposed outlets to the weather shall be weatherproof, and all exposed parts shall be corrosion resisting. Two extension cords shall be furnished, each about 30 feet long of heavy rubber-jacketed cord, incorporating hand lamps and guards fitted with a 100 w lamp and with a plug to fit the receptacles specified heretofore. 6.7.5.45 Navigation Lights a.

Navigation lights shall be provided in compliance with the requirements of Article 6.1.9.

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b. All navigation light units on the movable span and on fenders shall be capable of withstanding shocks and rough treatment, and shall be completely weatherproof. Unless otherwise specified, light bodies shall be bronze, aluminum or fiberglass and the lenses shall be fully gasketed. Lights shall be provided with shock-absorbing porcelain sockets and preferably shall have lamps rated below 15 v. 6.7.5.46 Circuits a.

Circuits shall be classified as follows: (1) Power circuits: – Motors. – Other. (2) Control circuits: – Span. – Rail locks. – Bridge locks. – Wedges.

1

– Other. (3) Lighting circuits: – Navigation lights. – Service lights.

3

– Convenience outlets. – Other. b. An independent circuit shall be provided for each motor, each control circuit, the navigation lights, each group of service lights, and each group of convenience outlets. Common return wires will not be allowed. Each circuit shall be protected and controlled by its own circuit breakers, fuses, and switches, located on the panelboards or at an equally convenient point. 6.7.5.47 Grounding and Lightning Protection a.

Grounding and lightning protection systems shall be provided to meet or exceed the NEC requirements. The power supply shall preferably be solidly grounded, but otherwise may be resistance grounded or ungrounded. Where either of the latter types are used, a solidly grounded system, ground indicating lights shall be provided.

b. The bridge metallic structure shall have grounding conductors connected to low resistance grounding electrodes. An electrical system ground bus, and connections to all major electrical equipment including each motor, brake, and land-based navigation light shall be provided. 6.7.5.48 Spare Parts The Contractor shall furnish the following spare parts as a part of the electrical equipment:

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a.

Six fuses of each size and kind.

b. One complete set of stationary and moving contacts for each size of each master switch and limit switch. c.

One indicating light unit, complete with lamp, fitted with colored cap for each size, type, and color.

d. One complete navigation pier light for each size and color of lens used; and six lamps for each type and size of navigation light. e.

One control relay and two extra sets of contacts for each type.

f.

One complete set of contacts and one operating coil for each size and type of magnetic contactor and motor starter.

g.

One brake coil or thruster motor for each size of brake, or one complete brake.

h. One spare motor of each size and type, including gearmotors, and one set of brushes for each size and type of motor. i.

Spare parts shall be furnished as specified by the Company for engines, engine-generator sets, skew and positioning indicating devices, electronic control components, tachometers, motor secondary impedance elements, and other parts.

j.

One complete set of replacement solid state power modules and one replacement circuit board of each type used for each size and type of solid state variable speed drive.

k. One input and one output module of each type installed, and one spare resolver and encoder of each type installed.

6.7.6 BRAKES FOR SPAN OPERATION (1983) R(2002) a.

Brakes shall be provided in accordance with the requirements of Article 6.3.9. For electrically operated bridges, one or more electrically operated brakes shall be provided for each main motor; and the machinery brakes shall also be operated electrically or, when so specified, by air, by hand, or by foot. Where specified, electrically operated machinery brakes shall be provided with three steps of retarding torques.

b. Brakes for bridges operated by power other than electricity shall be operated by air, by hand, or by foot, or, where so specified by an auxiliary electric generator.

6.7.7 AIR BRAKES (1997) R(2002) a.

Where air brakes are used, they shall be controlled from the operator’s house. The air compressor shall be electrically operated, and shall have a capacity of 11 cubic feet of free air per minute at a tank pressure of 90 psi. The pressure lost through the compressor valves of the compressor shall be not more than 1-1/2 psi in 10 min. The tank pressure shall be maintained automatically between 60 and 90 psi.

b. The air tank shall be cylindrical with a minimum capacity of 10 cubic feet. It shall be built up of steel plate sides welded to pressure vessel heads, and shall be capable of withstanding without rupture a pressure of 250 psi. It shall have an adjustable safety valve and blowout plug. The tank shall show no leaks when tested to a pressure of 160 psi.

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c.

The brake cylinder shall be not less than 6 inches diameter with a stroke of not more than 6 inches, and shall have a spring release capable of placing the brake in the released position automatically as soon as the air is exhausted.

d. The line carrying air to the brake cylinder shall have, at a convenient place, a union with a choke which will introduce a period of at least 5 sec for establishing the tank pressure in the cylinder. e.

Where the air in the brake cylinder is controlled electrically, the brake shall be applied automatically in case of any power failure.

6.7.8 HAND BRAKES AND FOOT BRAKES (1983) R(2002) Hand brakes and foot brakes shall preferably be arranged so that the brake is applied by means of a weight or spring, and released manually.

6.7.9 AUDIBLE NAVIGATION SIGNALS (1983) R(2002) a.

An audible navigation signal, such as an air whistle, electric horn or, electric sirens, or other devices, shall be provided, as specified.

b. Audible navigation signals shall conform to all legal requirements for the waterway. c.

Electrically operated bridges, except as otherwise specified, shall have two electric compressor-type air trumpets of weatherproof construction and protected from sleet and snow, with minimum rating of 120 db at 10 feet reference 0.0002 microbar, and two smaller auxiliary electric trumpets or sirens having approximately 100 db output. Trumpets or sirens shall be installed in approved locations, and pointing upstream and downstream. Pushbuttons for their control shall be provided on the control console.

d. Where so specified a whistle shall also be provided. The whistle bell shall be not less than 3 inches dia and 9 inches long. Where the whistle is air operated, the compressor shall be power driven with the motor and compressor mounted on one frame. The working parts shall be enclosed and self-lubricating. The compressor shall have a capacity of from 25 cubic feet to 30 cubic feet a min when working against a tank pressure of 90 psi, and shall have an automatic governor and switch to start and stop the compressor automatically at any predetermined tank pressure. e.

f.

The air receiving tank shall be 36 inches dia and 8 feet long, or of equivalent capacity, and shall sustain a working pressure of 125 psi. It shall be provided with pressure gage, pop valve, and drain cock, and shall have standard flanges bushed for 1-1/2 inch pipe. The Contractor shall furnish and install pipe, pipe fittings and valves, all adequate for a working pressure of 125 psi. Where the bridge is electrically operated, whistle may be controlled by an electrically operated solenoid valve, operated from the control console.

SECTION 6.8 WORKMANSHIP 6.8.1 MACHINERY MANUFACTURE IN GENERAL (1983) R(2010) a.

Machinery shall be manufactured, finished, assembled, and adjusted in an approved manner and according to the best machine shop practice. The tolerances for machining the work and the allowances for all metal fits shall be placed on the Contractor’s working drawings, which shall show the working © 2011, American Railway Engineering and Maintenance-of-Way Association

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allowances for the journals and their bearings. Differences between journal and bearing diameters shall be within the prescribed limits. Measurements for roller bearing assemblies, as specified in Article 6.8.21.4b and Article 6.8.22.2b shall be taken and recorded. b. Machinery parts in contact with other parts or with supports shall be machined so as to provide even true bearings, and surfaces in sliding or rotating contact with other surfaces shall be finished true to dimensions and finished in accordance with the requirements of Article 6.5.1a. c.

Castings shall have fins and other irregularities removed so that they will have suitable clean, smooth surfaces. Unfinished edges of flanges and ribs shall be neatly made with rounded corners. Inside angles shall have suitable fillets. Suitable drainage holes shall be provided in all places where water might collect.

d. Finished rubbing surfaces shall be coated as soon as possible after being accepted with an approved rust inhibitive grease before removal from the shop. Other surfaces shall be cleaned and painted in the shop as specified for structural metal. Finished rubbing surfaces which are not assembled in the shop for shipment shall be adequately protected during shipment by burlap or canvas wrapping secured by wooden bats securely wired together. All grease holes shall be adequately plugged for shipment. e.

Careful attention shall be given to the protection of all machinery parts during shipment. Inlet and exhaust ports in air buffers shall be plugged at assembly and protected until installed.

6.8.2 RACKS (1983) R(2010) a.

Where racks are built in segments, the segments shall be accurately fitted together and match marked. Particular care shall be taken to have the pitch of the teeth at the joints accurate. The periphery of rack teeth shall be planed. The pitch line shall be scribed on both ends of the teeth.

b. The backs of racks which bear on metal surfaces and the surfaces in contact with them shall be planed.

6.8.3 SHAFTS (1983) R(2010) a.

Shafts shall be straight, true to gage, and turned or otherwise well finished throughout their lengths. Shafts shall be filleted where abrupt changes in section occur.

b. Shafts more than 8 inches dia shall have a hole bored lengthwise through the center. The hole diameter shall be about one-fifth of the shaft diameter.

6.8.4 JOURNALS (1983) R(2010) a.

Shaft journals, including their shoulders, shall be accurately machined and polished. Particular care shall be taken to secure a high polish on the journals of trunnion and counterweight sheave shafts.

b. Unless otherwise specified, machinery journals and those of trunnion and counterweight sheave shafts shall have the corners at their ends rounded and, except for cold-rolled shafts, their ends shall be of slightly less diameter than the remainder of the shaft.

6.8.5 LININGS (1983) R(2010) a.

Linings shall be bored, finished smooth, and scraped to a true fit so that the journals will run without excess friction or heating.

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6.8.6 BEARINGS (1983) R(2010) Rubbing and bearing surfaces and the joints between bearing caps and bases shall be finished. Holes in caps and bases shall be drilled. Holes in bearings for bolts fastening them to their supports shall be drilled.

6.8.7 COUPLINGS (1983) R(2010) Faces of flange couplings shall be machined to fit.

6.8.8 HUBS (1983) R(2010) Holes in hubs, including those of sheaves, drums, gears, and pinions, shall be bored concentric with the pitch circle or rolling surface and, unless otherwise specified, so as to give a press or shrink fit to the shaft. Such hubs shall be properly keyed to the shafts. Where the hub performs the function of a collar, the end next to the bearing shall be machined and polished.

6.8.9 GEARS AND PINIONS (1983) R(2010) Teeth of gears and pinions, unless specified otherwise, shall be machine cut. The periphery and the ends of teeth and gears shall be finished and the pitch circle scribed on both ends of the teeth.

6.8.10 BEVEL GEARS (1983) R(2010)

1 Teeth of bevel gears shall be cut by a planer having a rectilinear motion in lines through the apex of the cone. Rotating milling cutters shall not be used for making bevel gears.

6.8.11 MACHINE MOLDING (2003) R(2010) All gear teeth shall be machine cut. Machine molded teeth shall not be permitted.

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6.8.12 WORMS AND WORM WHEELS (1983) R(2010) Threads on worms shall be machine cut and the teeth of worm wheels shall fit the worm accurately with surface on line contact.

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6.8.13 KEYS AND KEYWAYS (1983) R(2010) Keys shall be planed and keyways machine cut. The finish of the keys and keyways shall be such as to give the key a driving fit on the sides. Tapered keys shall bear on the top, bottom and sides; parallel-faced keys on the sides only.

6.8.14 BOLTS AND HOLES (1996) R(2010) a.

Bolts for minor machinery parts may be unfinished and shall have drilled or reamed holes not more than 1/16 inch larger diameter than the bolts if approved by the Engineer.

b. All fasteners and their mounting holes not included in paragraph a shall conform to the requirements of Article 6.5.25.

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6.8.15 ASSEMBLING MACHINERY IN FRAMES (1983) R(2010) Shafts, gears, pinions, and other parts supported by machinery frames shall be assembled in the shop in their several frames, tested by operation, and shipped to the field ready to be set in place. Each assembly shall be operated continuously for a period of not less than 4 hr in the shop before shipment at a speed of operation not less than that of the assembly under normal bridge operation.

6.8.16 BALANCING OF GEARS (1983) R(2010) In order to reduce running noise to the minimum, gears shall be shop assembled on their shafts with keys in place, and each shaft assembly balanced for any position of rotation of the shaft. Gears shall be cast so that compensation can be obtained after assembling.

6.8.17 ASSEMBLING MACHINERY ON STRUCTURAL SUPPORTS (2003) R(2010) a.

Where specified on the plans, machinery parts shall be assembled on supporting members in the shop, and holes shall be drilled with components in correct alignment and relative position. Members shall be match marked, both to the supports and to each other, and erected in the field in the same relative positions.

b. Where the foregoing assembly is not specified, holes in machinery parts shall be shop drilled and holes in supports shall be left blank and drilled in the field after the machinery parts are assembled and aligned. Where undersize holes are permitted to aid in field alignment of the machinery, they shall be reamed to fit the permanent bolts after all other holes have been drilled and their bolts placed.

6.8.18 GROOVES IN JOURNALS AND LININGS (1983) R(2010) Lubrication grooves in the surfaces of shaft journals and bearing linings shall be machine cut. Small inequalities may be removed by chipping and filing. Grooves and rounded corners shall be smooth.

6.8.19 AIR BUFFERS (1983) R(2010) Workmanship on air buffers shall be so accurate that the weight of the cylinder and its attachments will be sustained by the confined air for 6 min, with a piston travel not more than that which occurs during the closure of the bridge. Valves must be closed and the buffers balanced so that the whole weight is carried by the piston rod.

6.8.20 SPECIAL PROVISIONS FOR SWING BRIDGES (2003) R(2010) 6.8.20.1 Rim Girders The edges of the webs and side plates and the backs of the flange angles in the bottom flanges of riveted rim girders of rim-bearing swing spans, shall be so planed as to secure full bearing on the tread plates. Bottom flanges of welded rim girders shall have complete penetration welds connecting the webs to the flanges. 6.8.20.2 Rack and Track a.

Track segments shall be planed on the top and bottom and at the ends. Surfaces on which conical rollers bear shall be planed to the true bevel and centerline shall be scribed on the surface.

b. The rack and track shall be completely assembled in the shop to their correct centerlines, fitted, drilled, and the parts match marked. © 2011, American Railway Engineering and Maintenance-of-Way Association

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Movable Bridges 6.8.20.3 Bearings for Rack Pinion Shafts Bearings for rack pinion shafts shall be bolted to the bracket supporting them and bored while so fastened to ensure perfect alignment. 6.8.20.4 Rollers The faces and sides of rollers and balance wheels shall be finished, the corners rounded, and the centerline of the rollers and balance wheels scribed on the faces. Hubs shall be bored accurately and faced on both ends. 6.8.20.5 Pivots Pivot stands and center castings of swing bridges shall be finished and fitted accurately. The base shall be truly faced at right angles to the axis, and shall be turned on the circumference concentric with the axis. 6.8.20.6 Disks Steel disks shall be fitted accurately, finished to gage, and ground accurately to the final finish. Disk centers shall be assembled, fitted accurately and match marked. Sliding surfaces of steel and phosphor-bronze disks shall be polished. 6.8.20.7 Assembling Centers For rim bearing swing spans, the complete center, including rim girders, center pivot, radial members, rack, track and rollers, shall be shop-assembled, aligned, fitted, drilled and tested, and the parts match marked.

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6.8.21 SPECIAL PROVISIONS FOR BASCULE BRIDGES (2003) R(2010) 6.8.21.1 Segmental Girders and Track Girders For rolling lift bridges, the bottom flanges of riveted segmental girders and top flanges of riveted track girders shall have the edges of the web and side plates and the backs of the flange angles so planed as to secure full bearing on the tread plates. Flanges of the segmental girders shall be so accurately bent to the required radius so that planing will reduce their thickness by no more than 1/8 inch. Bottom flanges or welded segmental girders and top flanges of welded track girders shall have complete penetration welds connecting the webs and flanges.

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6.8.21.2 Racks

4

Where specified on the plans, all circular racks shall be shop-assembled on their supporting members, including all parts up to and including the trunnion shaft or its supporting member, the parts then aligned and adjusted so that the pitch of the rack throughout its length is at the prescribed radius from the center of the trunnion shaft, the holes drilled, and the parts match marked. Where any temporary radial members are required to properly align the rack, they shall be furnished and match marked. 6.8.21.3 Tread Plates a.

For rolling lift bridges, the top and bottom surfaces of the tread plates shall be planed. Where tread plates are built in segments, their ends shall be faced.

b. Tread plates shall be shop-assembled with their segmental girders and track girders, aligned, fitted, drilled, and the parts match marked.

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In journal bearing installations, each trunnion shaft shall be shop-assembled with its bearings, and the linings shall be scraped to a true fit with the journals.

b. For roller bearing installations, two sets of exact diameter measurements shall be taken at 90 degree angles on the contact faces between the trunnion shaft and the inner race. Each component shall be permanently marked and the measurements taken at locations near the ends and at the corner of the inner race. Measurements shall be recorded and included in the maintenance manual.

6.8.22 SPECIAL PROVISIONS FOR VERTICAL LIFT BRIDGES (1983) R(2010) 6.8.22.1 Sheaves and Drums a.

Grooves in sheaves and drums shall be turned. Particular care shall be taken to secure uniformity of pitch diameter for all grooves of a counterweight sheave. The variation from the required diameter shall not exceed 0.01 inch.

b. Built sheaves shall be assembled and permanently riveted, or welded and stress-relieved, before the grooves are turned. 6.8.22.2 Assembly of Counterweight Sheave Shafts and Bearings a.

For journal bearing installations, each sheave shaft shall be shop-assembled with its bearings, and the linings scraped to a true fit with the journals.

b. For roller bearing installations, two sets of exact diameter measurements shall be taken at 90 degree angles on the contact faces between the sheave shaft and the inner race. Each component shall be permanently marked and the measurements taken at locations near the ends and at the center of the inner race. Measurements shall be recorded and included in the maintenance manual.

SECTION 6.9 ERECTION 6.9.1 ERECTION OF MACHINERY (1996)1 R(2002) a.

The installation and adjustment of all machinery shall be by competent mechanics experienced in this class of work. They shall be provided with all necessary gages, straightedges, and other precision instruments required to ensure accurate installation.

b. The final alignment and adjustment of machinery parts, whose relative position is affected by the deflection or movement of the supports under full dead load, or of the span under full dead load, shall not be made until such deflection or movement has taken place. c.

1

Machinery parts shop-assembled on their supporting members, with connection holes shop drilled, shall be erected according to the match marking diagrams. Frames carrying machinery assemblies, individual bearings, and other machinery parts, which have not been assembled with their supports in the shop, shall be assembled in the field and adjusted to proper elevation and alignment on the supporting steel parts, by means of full length shims, the holes through the supporting steel parts for the connecting bolts

See Part 9 Commentary

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shall be drilled while the parts are so assembled. Where any small placement holes are provided to aid in field alignment of machinery, they shall be reamed to fit the permanent bolts after all other holes have been drilled and their bolts placed. d. Open gearing shall be aligned such that backlash is within tolerance so that at least the center 50% of the face width of each pair of meshing teeth is in contact. The cross mesh shall not exceed 0.01 inch per 6 inches face width. Open gear measurements shall be submitted to the Engineer for approval. The measurements shall include backlash, cross mesh alignment, tooth valley gap and face contact. The type of bluing or lubricant used for face contact measurements shall be submitted to the Engineer for approval prior to any measurements. These measurements shall be performed at a minimum of eight (8) equally spaced span positions ranging from fully open to fully closed. e.

Careful attention shall be given to the protection of all machinery parts during unloading and while stored before erection. Before erection, all finished surfaces which were shop coated with a protective rust inhibitive grease shall have such grease removed with an appropriate solvent.

6.9.2 ERECTION OF TRUNNION BEARINGS AND COUNTERWEIGHT SHEAVE BEARINGS (1983) R(2010) a.

Trunnion bearings and counterweight sheave bearings shall be aligned with the utmost accuracy. After they have been adjusted by the use of full length shims, to proper elevation, and position on the supporting steel parts, with due allowance for movement of the bearings which may result from the dead load to be placed on the bearings, the holes through the supporting steel parts for the connecting bolts shall be drilled through the previously drilled holes in the bearings.

1

b. The exact methods to be used in securing the required alignment of trunnion and counterweight sheave bearings shall be shown on the Contractor’s working drawings. c.

Installation of roller-type sheave bearings shall be supervised by a qualified and experienced technician furnished by the bearing manufacturer.

3

d. Before ropes are placed over counterweight sheaves, the bearings shall be lubricated and the sheave shall be turned to verify that the shaft turns freely in the bearings. If the shaft does not turn freely, the alignment of the bearings shall be corrected as necessary.

6.9.3 PROTECTION OF PARTS (1983) R(2002) a.

Parts, particularly electrical parts, which are protected from the weather in the finished structure shall be protected in the field during erection, by housing or equivalent means.

b. Wire ropes shall be housed and stored at least 18 inches above the ground, and shall be kept free from dirt, cinders, and sand.

6.9.4 LUBRICATION (2008)1 R(2010) a.

1

The Contractor shall furnish at his own expense, grease, oil, fuel and all other lubricants and supplies as necessary for satisfactory operation of the movable span until it has been accepted by the Company, excepting only that for electric-motor-operated spans the Company will pay for electric current obtained from the power line. Greases and oils must be suitable for the operating service and pressures and shall meet the approval of the Engineer.

See Part 9 Commentary

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b. When the movable span is in operating condition, the Contractor shall thoroughly clean all counterweight ropes and operating ropes of foreign material and, when weather conditions become suitably dry and the atmospheric temperature above 40 degrees F, shall furnish and apply hot, one coat of approved wire rope dressing. c.

All lubricants for a given component shall be chemically compatible, including the lubricant used in manufacture and the lubricant that will be field applied. For any component on which a new lubricant is to be applied that is not chemically compatible with the existing lubricant, all traces of the existing lubricant shall be thoroughly cleaned and flushed from the component before applying the new lubricant.

6.9.5 ERECTION OF WIRE ROPES (1983) R(2010) a.

Wire ropes shall be carefully removed from reels and coils by revolving them, and shall be erected so as to avoid any sharp kinks or bends. The ropes shall be kept clean during erection.

b. Operating ropes for vertical lift spans shall be adjusted to equal tensions at the four corners of the span, and in such manner as to give only slight tension in the slack side of the rope. c.

Counterweight ropes, where not fabricated to exact lengths, and when not connected by equalizers, shall be adjusted in the field so as to secure equal loads on all of the ropes at a corner of the span. The stripe shop painted on each rope shall be straight after the rope is erected.

6.9.6 PAINTING (1983) R(2010) a.

Surfaces of machinery parts, except rubbing surfaces, shall be cleaned and painted in the field as specified for structural metal.

b. Exposed concrete surfaces of counterweights shall be coated with approved waterproofing material. c.

Care shall be taken to prevent the painting of nameplates of electrical and mechanical equipment. Any painted nameplates shall be replaced with new plates.

6.9.7 COUNTERWEIGHTS (1983)1 R(2003) a.

The Contractor shall prepare calculations showing the required dimensions and weights of counterweights based on weights computed from the shop drawings of structural steel and machinery, and on estimated unit weights of concrete, timber, and all other parts of the span. These calculations shall be submitted to the Engineer, in suitable form, for verification. These calculations shall include summarized tabulations showing, for each kind of material, the total quantity of the material, its estimated unit weight, and its total estimated weight. Before pouring the counterweights, the Contractor shall verify these estimated and computed weights by comparison with shipping weights of steel, and by weighing suitable portions of non-metal parts, and shall submit to the Engineer for approval, supplemental summarized tabulations based on actual weights.

b. The Contractor shall adjust and correct the counterweights, shall provide the required balance blocks, and shall secure the required balance of the counterweights and span. Approval by the Engineer of any balance tabulations or of any materials or processes shall not relieve the contractor of the entire responsibility for securing such balance.

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See Part 9 Commentary

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6.9.8 END LIFTING DEVICES FOR SWING SPANS (1983) R(2010) End lifting devices shall be adjusted, when the span is at uniform temperature, to produce a lift equal to the greatest of the following: a.

1.5 times the computed deflection which would result from the negative end reaction of the live load plus impact load,

b. 0.10% of the length of one arm, or c.

One-half inch.

6.9.9 CHANNEL LIGHTS (1983) R(2002) During construction of a new span and/or removal of and old span, the Contractor shall place and maintain navigation lights and signals, in accordance with government requirements for navigation and for the protection of the falsework.

6.9.10 TESTING (1983) R(2010) a.

Before the main operating machinery is connected for transmitting power, it shall be given an idle run for four hours.

b. When the entire installation is completed, the span, including all accessories, shall be operated through not less than three complete cycles using normal power, prime movers, and control and through at least two cycles using auxiliary or emergency power, prime movers, and control. These tests shall be repeated for the auxiliary drive system and alternate operating modes where provided. During these runs, the entire equipment shall be inspected to determine whether all features are in proper working order and adjustment, and meet fully the requirements of the plans and specifications. Electrically powered bridges shall be completely checked with recording type electrical instruments, and the temperature rise of electrical parts, during the specified duration of continuous testing, shall not exceed design ratings. Should tests show that any features are defective or inadequate, or function improperly, the Contractor shall make any corrections, adjustments, or replacements required at his own expense. c.

Lift bridges shall be tested per Article 6.3.6a(1) and Article 6.3.6a(2) loads, simulated by placing equal weights at each end of the span. Unless otherwise specified, the total continuous duration of the operating cycles under Article 6.3.6a(2) load shall be at least 30 minutes for the main drive system. Where there is an auxiliary drive system, it shall be similarly tested.

d. Bascule and swing bridges shall be tested without any additional load to simulate ice or wind. Unless otherwise specified, the total continuous duration of the operating cycles shall be taken as 30 min for the main drive system. Where there is an auxiliary drive system, it shall be similarly tested.

6.9.11 BRIDGE OPERATOR (1983) For a power-operated bridge, the Contractor shall provide, at his own expense, competent persons to supervise the operation of the bridge for a period of 14 calendar days after the span is completely operable; and for an additional 14-day period, he shall provide one person. These persons shall be competent to operate the bridge, to supervise its operation, and to make any adjustments or corrections that may be required in the mechanical or electrical equipment of the bridge. They shall instruct and qualify the employees of the Company in the operation of the bridge. Any adjustments or corrections required during the two 14-day periods shall be at the expense of the Contractor.

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Part 7 Existing Bridges1 — 2011 — FOREWORD

Part 1, Design; Part 3, Fabrication; Part 4, Erection; and Part 6, Movable Bridges are applicable to the strengthening, rating and inspection of existing bridges, except as modified by this part. As information, Title 49 Code of Federal Regulations, Part 214 Railroad Workplace Safety, is applicable to personnel engaged in inspection, repair or maintenance of most railroad bridges in the USA. Similar regulations also exist in other jurisdictions.

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TABLE OF CONTENTS Section/Article

Description

Page

7.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.1 Classification (1995) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.2 Division of Subject (1994) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.3 Rating of Bridges (1994) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.4 Rating of Equipment (1994) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.1.5 Form of Presentation (2002) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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7.2 Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.1 General (2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.2 Bridge Inspection Procedure (2002) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.3 Periodic Inspections (2002) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.4 Special Inspections (2011). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.5 Emergency Inspections (2002) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.6 Conditions to Report (2002) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.7 Rating Inspection (2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2.8 Inspection Sketches for Identification of Members (2002) R(2008) . . . . . . . . . . . . . . . . . .

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7.3 Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.1 General (1998) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.2 Loads and Forces (2007) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.3 Stresses (2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.3.4 Action to Be Taken (2002) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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References, Vol. 25, 1924, pp. 228, 1262; Vol. 49, 1948, pp. 206, 666; Vol. 60, 1959, pp. 507, 1098; Vol. 63, 1962, pp. 367, 699; Vol. 70, 1969, p. 241; Vol. 84, 1983, p. 100; Vol. 92, 1991, p. 79; Vol. 93, 1992, p. 124; Vol. 94, 1994, pp. 1, 143; Vol. 96, p. 73; Vol. 97, p. 175. Reapproved with revisions 1996.

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TABLE OF CONTENTS (CONT) Section/Article

Description

Page

7.4 Repair, Strengthening and Retrofitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4.1 General (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4.2 Plate Girders or Rolled Beams (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4.3 Floor Systems (1993) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4.4 Trusses (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4.5 Other Structures (1983) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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7.5 Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5.1 General (1984) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5.2 Maintenance of Structural Elements (1984) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5.3 Maintenance Painting (2001) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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LIST OF FIGURES Figure

Description

Page

15-7-1 Typical Through Truss Bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-7-2 Typical Through Girder Bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-7-3 Typical Deck Girder Bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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LIST OF TABLES Table

Description

Page

15-7-1 Allowable Stresses for Maximum Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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SECTION 7.1 GENERAL 7.1.1 CLASSIFICATION (1995) R(2008) a.

The classification of a bridge with regard to carrying capacity is based on the heaviest moving load of specification type which may be operated over it in regular service without subjecting it to such severe stresses, vibration or wear of parts as to impair its safety or serviceability. Loads in excess of design loads will, if continuously operated, shorten the useful life of the bridge.

b. Iron and steel bridges shall be classified according to their rated carrying capacity as determined by Section 7.3, Rating.

7.1.2 DIVISION OF SUBJECT (1994) R(2008) The work of classifying bridges consists of three steps: a.

The determination of the capacity and rating of the bridges.

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b. The determination in corresponding terms of the effect and rating of each type and size of equipment used, in order that the territorial operating limits of each class of equipment may be assigned. c.

The presentation of such data in a format convenient for the operating personnel.

7.1.3 RATING OF BRIDGES (1994) R(2008) 7.1.3.1 Plans and Records Complete plans and records of each bridge, including design live load, impact load and material specifications shall be made. Record plans shall be prepared and maintained. 7.1.3.2 Bridge Sketches For ready reference, a sketch, or line diagram, of each bridge shall be prepared. 7.1.3.3 Record of Bridge Material The records shall show the materials of which each bridge is constructed. If necessary, the character of the material shall be determined from small specimens obtained in the field. 7.1.3.4 Assignment of Ratings Each bridge shall be analyzed on the basis of the rating rules and specification loading in effect. Significant loss in section shall be recorded and accounted for in the rating of a member. The strength of each member, including connections and other details, shall be determined and the capacity of the bridge ascertained. The bridge shall then be given a rating corresponding to the lowest rated member.

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7.1.3.5 Filing of Calculations

3

The calculations shall be made in permanent form and filed for future reference. 7.1.3.6 Bridge Rating Lists Lists of all bridges shall be prepared and arranged in territorial groups, showing for each bridge the identifying number or name, location, lengths and number of spans, type, number of tracks carried, material of which constructed, date built, capacity and rating.

7.1.4 RATING OF EQUIPMENT (1994) R(2008) 7.1.4.1 Definition of Equipment Equipment, as used in this section, is defined as one or more engines and/or cars which can be operated on their own wheels in a train. 7.1.4.2 Line Diagrams of Equipment A line diagram of equipment shall be obtained and filed for reference. This diagram shall show the axle loads, axle spacings and coupled length.

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Steel Structures 7.1.4.3 Loading Effects The effect of equipment loading shall be ascertained by calculating the associated bending moments, shears and pier reactions. The calculations shall be such that the maximum loading effect on each member may be determined or estimated. 7.1.4.4 Equipment Rating The rating of equipment for operating purposes shall be expressed in terms of equipment for which the bridges are rated, and for that span length on which it produces its maximum effect. 7.1.4.5 List of Equipment Ratings A list of equipment shall be prepared, giving its number, class, type, total weight, rating for operating purposes and rating for each span length. 7.1.4.6 Relation of Loads to Specification Loading For each bridge span length for which moments, shears and pier reactions are determined, the effect of the load in terms of specification loading shall be ascertained.

7.1.5 FORM OF PRESENTATION (2002) R(2008) 7.1.5.1 Common Standard for Rating By following the procedure outlined, each bridge and all equipment will be assigned a rating based on a common standard. 7.1.5.2 Cooper Series The Cooper series is used as a standard of railroad bridge loading. 7.1.5.3 Format for Use of Operating Department The capacities of the various lines shall either be shown by means of a diagrammatic map, or arranged geographically in a table, or both. 7.1.5.4 Special Cases Special conditions involving particular bridges on a line, or the operation of special loads in certain territories, may be covered by means of notes calling attention to exceptions to a general rule.

SECTION 7.2 INSPECTION 7.2.1 GENERAL (2011)1 a.

1

The inspection of steel bridges may be classified as periodic inspections, special inspections and emergency inspections. All steel bridge inspections should be performed in accordance with the

See Part 9 Commentary

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Company established bridge inspection procedure to ensure that every steel bridge is inspected at the prescribed frequency. b. Periodic inspections are regular, scheduled inspections. Their purpose is to ensure the integrity of the bridge and to note any condition or change that requires investigation or attention. Periodic inspection of all steel bridges should be performed at least once each year. c.

Special inspections are detailed inspections made for the purpose of obtaining accurate information for determining the capacity rating and/or for determining required repairs. Special inspections may also be performed on bridges with unique requirements, such as movable bridges, bridges with fracture critical members or those with fatigue susceptible details that require special inspection procedures.

d. Emergency inspections are inspections performed on bridges that have sustained an unusual occurrence potentially affecting the ability of the bridge to support the loads imposed upon it. e.

Formulation of and general oversight for the bridge inspection procedure should be performed by a competent railroad bridge engineer who should prescribe the minimum frequency and levels of inspection and resolve exceptions.

7.2.2 BRIDGE INSPECTION PROCEDURE (2002) R(2008) The bridge inspection procedure shall establish the method(s) and format(s) to be used to record observations and document each inspection. An accurate inventory of bridges shall be established and maintained to ensure that inspections occur as required by the procedure. The procedure should include the title and a description of the responsibilities of each employee or contract agent in the inspection process. Additionally, the frequency and level of inspection for each bridge shall be prescribed. The frequency and level of inspection should be based on the condition and age of the bridge, any other unique characteristics of the bridge, the type of traffic and the tonnage.

7.2.3 PERIODIC INSPECTIONS (2002) R(2008) a.

3

Periodic inspections should be performed by a competent Inspector whose training and experience enable the Inspector to identify and record defects, deterioration and indications of distress.

b. The Inspector should maintain an accurate record of the observed physical condition of the bridge and prepare an inspection report for each bridge inspected. This inspection report should provide a description of the structure, the date of inspection, the Inspector’s name and changes noted in the condition of the superstructure, substructure and surrounding conditions since the last inspection. The inspection report should state the condition of all bridge components; note defects, deterioration and conditions of distress; and identify items in need of maintenance or repair. The Inspector should review prior inspection reports and should examine previously noted defects in the field. c.

1

The Inspector should identify those bridges that need to be further evaluated by the Engineer.

d. If a condition is noted during inspection which may impair operating over the bridge, the Inspector should immediately take action to protect traffic as prescribed by the Railroad’s rules and should notify the Engineer. The Engineer should evaluate the condition and, as warranted, take immediate action to modify the traffic protection and/or order any required emergency repairs. Other reported deficiencies should be evaluated by the Engineer to determine appropriate action.

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7.2.4 SPECIAL INSPECTIONS (2011) a.

Special inspections provide additional detailed information not contained in the periodic inspection report. This information may be needed to rate the existing bridge or to design a repair plan. Special inspections should be performed and reported as requested by the Engineer.

b. Movable bridges require inspection procedures for items such as cables, electrical and hydraulic equipment, machinery, or miter rails and shoes. c.

Bridges with fracture critical members (FCM) may require inspection that includes procedures outlined to address detailed evaluation of these members. (Reference 34) (1) In advance of field inspection, the Engineer may review archival materials (as-built plans, shop drawings, etc.) to identify all FCMs and the fatigue prone details of all FCMs. (2) The Engineer may establish the inspection protocol to be used by the inspection team including hands-on inspection and employment of non-destructive testing (NDT) procedures such as dyepenetrant, ultrasonic, acoustic emission, or magnetic particle testing. NDT technicians shall possess proper certification for the type of testing they will perform. (3) The Engineer may develop an inspection plan and frequency for individual bridges which possess FCMs.

7.2.5 EMERGENCY INSPECTIONS (2002) R(2008) Unusual occurrences, such as floods, derailments, collisions, fires, or earthquakes, may damage the structure and affect its ability to support the loads imposed upon it. Emergency inspections are initiated after such unusual occurrences to evaluate the structure for any changes. Immediate actions, such as operating restrictions or emergency repairs, may be required. Operating restrictions may be needed until the emergency inspection is performed.

7.2.6 CONDITIONS TO REPORT (2002) R(2008) Of primary importance in all structures is evidence of distress, misalignment, excessive deflection, settlement, cracks, corrosion and general deterioration. The Inspector should report indications of overload or failure in any part of the bridge. The general behavior of the bridge should be observed during passage of live load, where practical, noting unusual vibration, deflection, side sway, opening of cracks or movements at piers and/or abutments. Evidence of deterioration of steel components such as location, length and growth of cracks, amount and location of section loss, and the location and extent of impact damage should be recorded. Reference points should be established for monitoring misalignment, deflection, settlement, and cracks. The amount of tilt, separation between components, length of cracks, and other measurements necessary for future monitoring should be recorded. The following items should be covered in detail: a.

Track: • Surface of track on bridges and approaches. • Alignment of track and its location with reference to the steel structure, at ends and center of each span. • Location, amount, and probable causes of any track out of line or surface.

b. Deck:

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• Size, spacing and minimum depth of ties. • Size and condition of guard timbers and guard rails. • Condition of walks and railings. • Condition of ballasted deck, and depth of ballast measured from base of rail at each end of bridge. • Condition of waterproofing. c.

Anchors, bearings and bridge seats: • Whether superstructure is securely anchored to masonry. • Whether expansion bearings are functioning properly. • Whether bed plates, rollers, rockers, and pedestals are clean, in correct position and have full bearing. • Whether bed plates are wearing into masonry and if so, how much.

d. Expansion: • Clearance between expansion ends and masonry or adjoining spans. Temperature at time of measurement. • Whether there is any apparent movement of masonry during train passage. e.

1

Straightness and alignment of members: Condition of individual members as to bends and kinks. Alignment of trusses, girders, floor members and towers. Slackness of eyebars and adjustment of counters. • Parts damaged by blows from equipment, lading, or floating objects.

f.

Cracks and breaks: • Stringer connection angles, stringer and girder flange angles under the bearings, hangers, pin plates, fillets of angles of flanges and posts, end sections of lower chords or flanges over or near bearings, and ends of cut-off cover plates.

3

• Webs of floorbeams where bottom flange angles do not extend under end connection angles. • Lateral bracing and cross frames, especially those of spans on curves.

4

• Welds on lateral bracing and cross frames, stiffeners and other welded details. • Where parts or welds to be examined for cracks or breaks are in dark or poorly lighted places, examination should be made with flashlight or other artificial light and with the aid of a mirror, if necessary. g.

Rivets, bolts, pin holes and nuts: • Location and number of rivets and bolts that are loose and of rivets that have badly corroded heads, particularly for floor connections. • Movement and wear of pins and pin holes. • Pins should be observed under traffic if practicable, especially those at or near center panels of trusses where counters are slack and at hip vertical connections.

h. Corrosion:

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• Loss of section from corrosion, noting exact location and extent of such action, with measurements of remaining section if members are badly corroded, paying close attention to loss of metal in girder and beam flanges and webs, and parts of lateral bracing systems. • Distortion caused by rust between rivets and built-up members. • Damage to overhead structures from engine blast in spans. • Pockets at bearing locations and at bottom of bearing stiffeners. i.

Paint and cleanliness: • Condition of paint, date of last painting, and number of coats and kinds of paint. • Need for spot painting or repainting. • Dirt collection on steel surfaces.

7.2.7 RATING INSPECTION (2011) When the findings of the inspection are to be used for purposes of rating the bridge, the following items should be reported in detail: a.

Whether the actual sections and details conform to the drawings.

b. Any additions to the dead load not shown on the plans, such as heavier deck or rail, walks, pipelines, conduits, signal devices, and wire supports. c.

The position of the track with respect to the bridge centerline, and actual ballast depth.

d. Any loss of metal due to corrosion and wear. This determination should be made by measurement after removal of scale. e.

The physical condition, noting, for example, such defects as loose tension members, loose or missing fasteners, worn pins, crooked or damaged members, and cracked parts.

f.

The condition of specific members and details, including: • Braces intended to limit the slenderness ratio of compression members or flanges. • Pin plates of tension members, especially those inside other members. • Gusset and splice plates, particularly any reduced section, cracking, buckling or other distortion. • Slender tension members, such as eyebars, with special reference to the effects of member vibration caused by passing trains or by wind. • Floorbeams and their connections, particularly where the connection has been shaped to clear eyebar heads, or the bottom chord or flange. • Stringer connections, especially for shallow stringers.

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7.2.8 INSPECTION SKETCHES FOR IDENTIFICATION OF MEMBERS (2002) R(2008) Typical sketches are shown of a through truss span (Figure 15-7-1), a through girder span (Figure 15-7-2), and a deck girder span (Figure 15-7-3), for the guidance of the Inspector.

1

3

4

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Figure 15-7-1. Typical Through Truss Bridge

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Figure 15-7-2. Typical Through Girder Bridge

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Figure 15-7-3. Typical Deck Girder Bridge

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SECTION 7.3 RATING1 7.3.1 GENERAL (1998)2 R(2008) a.

Rating of existing bridges in terms of carrying capacity shall be determined by the computation of stresses based on authentic records of the design, details, materials, workmanship and physical condition, including data obtained by inspection (and tests if the records are not complete). If deemed advisable, field determination of stresses shall be made and the results given due consideration in the final assignment of the structure carrying capacity. For a specific service, the location of the bridge and its behavior under load shall be taken into account.

b. Bridges may be assigned two types of ratings; NORMAL and MAXIMUM. The rating or ratings to be assigned, with any corresponding service limitations, shall be as directed by the Engineer. 7.3.1.1 Normal Rating a.

Normal rating is the load level which can be carried by the existing structure for its expected service life. The rating is dependent on a specified speed, as impact reductions are allowed for reduced speeds per Article 7.3.2.3. The speed or speeds to be used shall be as directed by the Engineer. Allowable stresses for normal rating shall be those specified in Part 1, Design; Section 1.4, Basic Allowable Stresses, supplemented by Part 1, Design, Article 1.3.14.3. The fatigue requirements of Article 7.3.3.2 shall be included, unless a remaining fatigue service life calculation is made.

b. When the allowable stress in Part 1, Design; Section 1.4, Basic Allowable Stresses is expressed in terms of Fy , Fy = yield strength of the material as explained in Article 7.3.3.3a. c.

1

If the normal rating is greater than the maximum rating, the lesser rating shall govern.

7.3.1.2 Maximum Rating a.

Maximum rating is the load level which the structure can support at infrequent intervals, with any applicable speed restrictions. Allowable stresses for maximum rating shall be those specified in Article 7.3.3.3. The provisions of Article 7.3.3.2, Fatigue need not be considered when determining Maximum Rating.

b. The Engineer may authorize load levels up to maximum rating at more frequent intervals, recognizing that the remaining useful life of the bridge may be significantly shortened. See Part 9, Commentary Article 9.7.3.1.2.

7.3.2 LOADS AND FORCES (2007)3 R(2008) Bridges shall be analyzed for the following loads and resulting forces: a.

Dead load.

b. Live load.

1

References, Vol. 22, 1921, pp. 379, 1006; Vol. 37, 1936, pp. 266, 729, 1024; Vol. 39, 1938, pp. 165, 891; Vol. 41, 1940, pp. 411, 858; Vol. 42, 1941, pp. 358, 874; Vol. 44, 1943, pp. 403, 670, 685; Vol. 50, 1949, pp. 428, 749; Vol. 51, 1950, pp. 444, 904; Vol. 52, 1951, pp. 446, 868; Vol. 59, 1958, pp. 701, 1195; Vol. 60, 1959, pp. 507, 1098; Vol. 63, 1962, pp. 387, 699; Vol. 68, 1967, p. 351; Vol. 73, 1972, p. 176; Vol. 92, 1991, p. 79; Vol. 94, 1994, p. 144; Vol. 97, p. 176. 2 See Part 9 Commentary 3 See Part 9 Commentary

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c.

Impact load.

d. Centrifugal force. e.

Wind forces.

f.

Other lateral forces.

g.

Longitudinal forces.

h. Forces from continuous welded rail (see Part 8, Miscellaneous; Section 8.3, Anchorage of Decks and Rails on Steel Bridges). 7.3.2.1 Dead Load The dead load shall be the weight of the bridge including the deck and track, together with any other fixed loads. 7.3.2.2 Live Load a.

The live load shall be one of the Cooper E series or a load of specific equipment, depending on the purpose for which the rating is desired.

b. Where the live load is specific equipment, complete data shall be obtained, including the spacing of axles and the static load on each axle. 7.3.2.3 Impact Load a.

Impact load shall be in accordance with the impact percentage equations and other provisions of Part 1, Design, Article 1.3.5 except that under the following conditions, reductions may be made in the vertical effects of such equations, as follows. (1) For train speeds below 60 mph, for all spans carrying equipment without hammer blow and for all spans other than truss spans carrying equipment with hammer blow, the values of the vertical effects of the impact equations shall be multiplied by the factor: 2 0.8 1 – ------------- ( 60 – S ) ³ 0.2 where S = speed in mph 2500

(2) For all truss spans carrying equipment with hammer blow that is limited to speeds less than synchronous speed, the values of the vertical effects of the impact percentage equations shall be multiplied by a factor which increases in a straight line from 0.2 at 10 mph to 1.0 at synchronous speed. Synchronism occurs when the revolutions per second of equipment drive wheels equals the natural frequency of the span, in cycles per second, which is given approximately by the following equation: 12 -------------d+D

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where: d and D = the central deflections, in inches, for dead load and for the static live load, respectively, placed in the position for maximum moment. b. Impact on steel or concrete decks with direct fixation of the rail is not covered by the formulas in this Chapter and requires special evaluation. Measured attenuation properties need to be considered. (See Commentary Article 9.1.3.5) 7.3.2.4 Centrifugal Force Centrifugal force shall be as specified by Part 1, Design, Article 1.3.6. 7.3.2.5 Wind Force a.

The wind force shall be considered as a moving load in any horizontal direction. Wind force on the train shall be taken as 200 lb per linear foot on one track applied 8 feet above the top of rail. Wind force on the bridge shall be taken as 20 lb per square foot of the following surfaces: (1) For girder spans, 1.5 times the vertical projection of the span. (2) For truss spans, the vertical projection of the span plus any portion of the leeward trusses not shielded by the floor system.

1

(3) For viaduct towers and bents, the vertical projections of all columns and tower bracing. b. These loadings are based on the assumption that when the wind velocity exceeds 70 mph a train will operate at reduced speed, if it operates at all. c.

Where considered justifiable by the Engineer, the wind forces on bridge and train may be reduced to not less than one-half of those specified above.

3

7.3.2.6 Lateral Forces from Equipment Lateral forces from equipment shall be as specified by Part 1, Design, Article 1.3.9. 7.3.2.7 Bracing Between Compression Members (2002) a.

4

For Normal Rating, use the requirements of Section 1.3.11 unless reduced by the Engineer.

b. For Maximum Rating where the sum of the total displacement and the out-of-straightness of the braced component is not greater than L/320 (where L is the unbraced length), the lateral bracing of the compression chords or flanges of trusses, deck girders, and through girders and between the posts of viaduct towers shall be analyzed for a transverse shear force in any panel not less than 1.25% of the total axial force in both members in that panel, in addition to the shear force from the specified lateral forces. For cases of out-of-straightness greater than L/320, see Commentary Article 9.7.3.2.7b. 7.3.2.8 Longitudinal Force a.

Longitudinal forces shall be as specified by Part 1, Design, Article 1.3.12. The E-80 loads may be scaled proportionally to be consistent with the live load rating of the structure.

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b. The longitudinal forces from Paragraph a shall be used where maximum locomotive tractive effort at speeds below 25 mph (40 km/h) is likely to occur. This includes locations where maximum braking effort is likely to be used to hold train speed below 25 mph (40 km/h), or to bring trains to a stop. c.

For structures not covered by Paragraph b, the longitudinal force from Paragraph a due to locomotive traction may be reduced by the ratio of the actual locomotive tractive effort used at that location to the maximum tractive effort rating of locomotives used system-wide.

d. Members whose main function is to carry longitudinal force, wind force (7.3.2.5), lateral force from equipment (7.3.2.6), and, where appropriate, bracing force between compression members (7.3.2.7) shall be checked for the combination of these forces with allowable stresses equal to the allowable stresses for rating. e.

Members whose main function is to carry vertical loads in combination with longitudinal forces shall be checked for dead load (7.3.2.1), live load (7.3.2.2), impact load (7.3.2.3), and centrifugal force (7.3.2.4) in combination with the forces listed in Paragraph d with allowable stresses equal to 1.25 times those otherwise recommended for rating.

f.

At all locations, the bridge must be capable of sustaining the full design longitudinal force, proportioned to the live load rating as indicated in Paragraph a, at 1.5 times the allowable stresses for rating.

7.3.3 STRESSES (2011)1 7.3.3.1 Computation of Stresses Stresses shall be computed for the details as well as for the main members, giving particular attention to: a.

The increased load carried by any truss, girder, or floor member due to load eccentricity. (This will occur where bridges are on tangent and the tracks are off center, and where bridges are on curves.)

b. Spacing of web stiffeners, lacing and forked ends of compression members, eccentricity of riveted joints and connections, unequal stress in tension members, and secondary stresses. Where web stiffener spacing exceeds that required by Part 1, Design, Article 1.7.8a, the Engineer may use a more detailed analysis in assessing the adequacy of the girder. c.

Gusset plates (1) showing signs of distress such as distortion, buckling, cracking, tearing or localized corrosion holes or perforations or other unusual behavior and/or (2) where an average thickness through the critical section has been reduced by more than 25 percent or (3) with free edges that have ripples or buckles that deviate visibly and/or measurably from a flat surface or (4) with a field measured unsupported length to average thickness ratio greater than E 2.06 -----Fy

.

d. Pin plates of tension members and eyebars. The following rules are given as a guide for those cases where the body of the member is carrying the limiting stress; 1

See Part 9 Commentary

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(1) The net section through the pin hole transverse to the axis of the member should be 40% greater than the net section of the member. (2) The net section beyond the pin hole on any line parallel to the axis of the member should be not less than three-fourths of the net section of the member. (3) In the event that the net section at the pin does not conform to Paragraph (1) or Paragraph (2) above, the net section of the member should be reduced proportionately for rating purposes. 7.3.3.2 Fatigue NOTE: Also see Part 9, Commentary, 9.7.3.3.2. a.

Fatigue evaluation can be a multi-step process that becomes more involved for details that have marginal fatigue capacity, and may require a remaining fatigue life estimation.

b. For a bridge carrying less than 5 million gross tons per annum of usual mixed traffic (see Commentary) throughout its existing and projected life and without details with an allowable stress range lower than Detail Category D, a fatigue evaluation is not necessary. If the bridge does contain details with an allowable stress range lower than Detail Category D, a fatigue evaluation should be conducted unless adequate inspection procedures are in place for those details. c.

Using the live load plus impact stress range calculated under Normal Rating (Article 7.3.1.1) as modified by the reduction of impact for fatigue (Article 1.3.13d) and as modified by the reduction of impact for speed as per Article 7.3.2.3, check the fatigue capacity as follows:

1

(1) For fatigue life evaluation of multiple track structures, consideration should be given to the frequency of simultaneous loading of tracks, as well as types of loading on the tracks. (2) Welded or rolled members and welded and high strength bolted connections subject to repeated fluctuations of stress: fatigue requirements of Part 1, Design, Article 1.3.13 shall be considered. (3) Members with riveted or bolted connections with low slip resistance, subject to repeated stress fluctuations: the requirements of Detail Category D of Part 1, Design, Article 1.3.13 shall be considered with a variable amplitude stress range fatigue limit of 6 ksi up to 100 million cycles. Where the Engineer can verify that the fasteners are tight and have developed a normal level of clamping force, Detail Category C may be used provided the Normal Rating Live Load plus Impact stress range does not exceed 9 ksi. If Detail Category C is used, the variable amplitude stress range fatigue limit is 6 ksi, up to 100 million cycles (see Part 9, Commentary, Figure 15-9-8). (4) Riveted and bolted connections and members that do not satisfy the requirements of Paragraph (3): These requirements may be waived at the discretion of the Engineer if the Normal Rating Live Load plus Impact stress range does not exceed 9 ksi and if the connections or members will retain their structural adequacy in the event one of the elements cracks. The connection and/or member of the span must have adequate capacity to carry the redistributed load, and a frequency of inspection which will permit timely discovery of any local failure and need for corrective action. This paragraph shall not be applied if there is insufficient and/or inadequate lateral bracing of the potentially cracked member. (5) Wrought iron riveted connections shall be considered to have Detail Category D fatigue strength with a variable amplitude stress range fatigue limit of 6 ksi, up to 100 million cycles (see Part 9, Commentary, Figure 15-9-8). (6) Eyebars and pin plates subject to repeated fluctuations of stress: the requirements of Detail Category E of Part 1, Design, Article 1.3.13, for the nominal stress range acting on the net section of

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the eyebar head or pin plate, shall be considered, unless analysis or testing shows that a less restrictive Detail Category is appropriate. Where a less restrictive Detail Category is determined using analysis or testing, the effect of bending stresses must be included. When total dead load, live load plus impact bending stresses in main chord members are of the order of secondary stresses, the resulting live load plus impact bending stress range may be ignored. (See Commentary) (7) Where the thickness of any component has been reduced by corrosion to less than 50% of its original thickness causing a local discontinuity, a Detail Category E detail shall be assumed to exist at that location. d. If the detail being examined does not meet the requirements above, the remaining safe fatigue life needs to be estimated based on past and future traffic. Use Paragraphs (1), (2) and (3) below in place of Article 7.3.3.2c(3) and (4). (See Commentary for further suggestions.) (1) Members with riveted or bolted connections with low slip resistance, subject to repeated stress fluctuations: the requirements of Detail Category D of Part 1, Design, Article 1.3.13 shall be considered with a variable amplitude stress range fatigue limit of 6 ksi up to 100 million cycles. Where the Engineer can verify that the fasteners are tight and have developed a normal level of clamping force, Detail Category C may be used provided the Root-Mean-Cube (RMC) stress range (SRe) does not and will not exceed 9 ksi. If Detail Category C is used, the variable amplitude stress range fatigue limit is 6 ksi, up to 100 million cycles (See Part 9, Commentary, Figure 15-9-8). (2) Riveted and bolted connections and members that do not satisfy the requirements of Paragraph (1): These requirements may be waived at the discretion of the Engineer if the Root-Mean-Cube (RMC) stress range (SRe) does not and will not exceed 9 ksi and if the connections or members will retain their structural adequacy in the event one of the elements cracks. The connection and/or member of the span must have adequate capacity to carry the redistributed load, and a frequency of inspection which will permit timely discovery of any local failure and need for corrective action. This paragraph shall not be applied if there is insufficient and/or inadequate lateral bracing of the potentially cracked member. (3) Riveted connections where the holes for these connections were drilled or reamed may be evaluated using the criteria given in Part 9, Commentary, Figure 15-9-8. e.

Where the actual stress cycles can be estimated from traffic records and future estimated traffic, an effective stress range can be determined for the total number of variable stress cycles, Nv, as 3

S Re = a ( Sg i S Ri )

1¤3

The combination of SRe and Nv for the applicable fatigue detail must be less than the fatigue strength

curves shown in Part 9, Commentary, Figure 15-9-3 and/or Figure 15-9-8. The appropriate value of a shall be taken from Part 9, Table 15-9-1, unless an appropriate analysis provides a more accurate estimate. The terms gi, SRi and a are defined in Part 9, Commentary, Article 9.1.3.13l. f.

For Non-Welded Details: For Detail Category D details and better: If the number of cycles with stress ranges above the Constant Amplitude Fatigue Limit (CAFL) exceeds 0.1% of the spectrum considered, the CAFL is deemed not to exist and the detail line is extended below the CAFL. (See Part 9, Commentary, Figure 15-9-8). Stress ranges that fall below a value of 0.5 of the CAFL should be ignored.

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For Detail Category E and E’ details: If the number of cycles with stress ranges above the CAFL exceeds 0.1% of the spectrum considered, the CAFL is deemed not to exist and the detail line is extended below the CAFL. (See Part 9, Commentary, Figure 15-9-8). Stress ranges that fall below a value of 0.25 of the CAFL should be ignored. For Riveted Details: Stress ranges that cause the RMC stress range to fall below the Variable Amplitude Fatigue Limit (VAFL) of 6 ksi should be ignored provided the total number of relevant cycles does not exceed 100 million. g.

For Welded and Heat Treated Details (Reference 40): For Detail Category C details and better: If the number of cycles with stress ranges above CAFL exceeds 0.05% of the spectrum considered, the CAFL is deemed not to exist and the detail line is extended below the CAFL. (See Part 9, Commentary, Figure 15-9-8). Stress ranges that fall below a value of 0.5 of the CAFL should be ignored. For Detail Category D details: If the number of cycles with stress ranges above the CAFL exceeds 0.01% of the spectrum considered, the CAFL is deemed not to exist and the detail line is extended below the CAFL. (See Part 9, Commentary, Figure 15-9-8). Stress ranges that fall below a value of 0.5 of the CAFL should be ignored. For Detail Category E and E’ details: If the number of cycles with stress ranges above the CAFL exceeds 0.01% of the spectrum considered, the CAFL is deemed not to exist and the detail line is extended below the CAFL. (See Part 9, Commentary, Figure 15-9-8). Stress ranges that fall below a value of 0.25 of the CAFL should be ignored.

1

h. Fracture Critical Members with Detail Category D, E and E’ details shall be given special attention. Inspection procedures shall be adequate to identify Fracture Critical Members and to detect flaws or cracks before serious damage occurs from uncontrolled propagation. The actual loads and load history shall be considered for computing stress ranges and corresponding stress cycles as opposed to theoretical loads.

3

7.3.3.3 Allowable Stresses for Maximum Rating a.

Allowable maximum rating stress shall be based on either the minimum yield strength or the minimum ultimate tensile strength of the material as determined from tests or records. In the absence thereof, The yield strength shall be taken as 30,000 psi for open-hearth or Bessemer steel, 25,000 psi for wrought iron, 45,000 psi for silicon steel and 50,000 psi for nickel steel. The ultimate tensile strength shall be taken as 60,000 psi for open-hearth, 50,000 psi for Bessemer steel, 45,000 psi for wrought iron, 62,000 psi for silicon steel and 90,000 psi for nickel steel.

b. Allowable unit stresses resulting from the loads and forces described in the preceding articles are shown Table 15-7-1. in Where: E=

modulus of elasticity of the material, psi

Fy =

yield strength of the material, psi

Fu =

ultimate tensile strength of the material, psi

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Steel Structures

For open-hearth steels (including A7, A36 and similar subsequent steels), High Performance Steels (HPS), and wrought iron: K=

0.8 Fy

K1 = 0.67 Fu For Bessemer, silicon and high strength steels other than High Performance Steels (HPS): K=

0.7 Fy

K1 = 0.58 Fu For nickel steel: K=

0.65 Fy

K1 = 0.54 Fu For weld steel: K=

0.7 Fy

All other nomenclature is as defined in Part 1 Design, Article 1.4.1 and Article 1.3.14.1.

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Existing Bridges Table 15-7-1. Allowable Stresses for Maximum Rating Pounds Per Square Inch

Type Axial tension, structural steel, gross section Axial tension, structural steel, effective net area (See Article 1.6.5) Axial tension, structural steel, effective net area at cross-section of pin hole of pin connected members Tension in floorbeam hangers, including bending, gross section: Using rivets in end connection but not to exceed Using high-strength bolts in end connection but not to exceed Tension in floorbeam hangers, including bending, effective net area at crosssection of pin hole of pin connected members: but not to exceed Tension in floorbeam hangers, including bending, on effective net section:

K K1 0.82 K

0.75 K 21,600 K 28,800 0.60 K 17,300 K1

Tension in extreme fibers of rolled shapes, girders and built-up sections, subject to bending net section

K

Tension in A325 bolts including the tension resulting from prying action produced by deformation of the connected parts, gross section

55,000

Tension in A490 bolts including the tension resulting from prying action produced by deformation of the connected parts, gross section

67,500

Axial compression, gross section: For stiffeners of beams and girders, and splice material For compression members centrally loaded, where: kl/r £ 3388 ¤ 3388 ¤

K

K

Fy

F y < kl ¤ r < 27111 ¤

kl ¤ r ³ 27111 ¤

1

Fy

Fy

3

K F kl 1.091 K – ------------------y- ----37, 300 r K 147, 000, 000 ------------------ ----------------------------------2 0.55F y ( kl ¤ r )

Compression in extreme fibers of I-type members subjected to loading perpendicular to web

4

K

Compression in extreme fibers of welded built-up or rolled beam flexural KF y 2 K – ----------------------- ( l ¤ ry ) members symmetrical about the principal axis in the plane of the web (other 9 than box type flexural members), and compression in extreme fibers of rolled 1.8 ´ 10 channels, the larger of the values computed by the following formulas (Note 1) or K ö 10, 500, 000 æ -----------------è 0.55F ø ------------------------------ld ¤ A y

f

but not to exceed: K

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Steel Structures Table 15-7-1. Allowable Stresses for Maximum Rating (Continued) Pounds Per Square Inch

Type Compression in extreme fibers of riveted or bolted built-up flexural members symmetrical about the principal axis in the plane of the web (other than box type flexural members) Compression in extreme fibers of box type welded, riveted or bolted flexural members symmetrical about principal axis midway between the webs and whose proportions meet the provisions of Part 1, Design, Article 1.6.1 and Article 1.6.2 Diagonal tension in webs of girders and rolled beams at sections where maximum shear and bending occur simultaneously

KF y 2 K – ----------------------- ( l ¤ ry ) 9 1.8 ´ 10 KF y æ l ö 2 K – ----------------------- -9è rø e 1.8 ´ 10 K

Tension in extreme fibers of pins, assuming loads concentrated at centers of bearings: Open hearth or bessmer steel, A7 or A36 steel, wrought iron, silicon 2K steel and nickel steel High strength steels 1.8K NOTE: If the members are packed close together on the pin, the bending stress may be disregarded unless the tension in the extreme fiber exceeds 60,000 psi for A7, A36 or open hearth steel, 50,000 psi for wrought iron or Bessemer steel or the ultimate strength for high strength steels. Shear in webs of plate girders and rolled beams, gross section

0.75K

Shear in A325 bolts

25,200

Shear in A490 bolts

31,800

Shear in rivets: Carbon Steel: Including A141 and A502 Grade 1 Carbon Manganese Steel: Including A502 Grade 2 Weathering Steel: Including A502 Grade 3

20,000 28,800 28,800

NOTE:The allowable values for shear shall be reduced 20% for countersunk rivets and floor connection rivets. Shear in pins

0.9K

Bearing: Bearing on rivets, pins, outstanding legs of stiffeners, and other steel parts in contact, may be disregarded unless there is visible deformation of parts in contact. Stresses in welds, where material, details and procedures conform to good practice: Tension or compression in groove welds Shear in groove welds Shear in fillet welds, regardless of direction of applied force where: K = the value for base metal or for weld metal, whichever is smaller.

K 0.625K 0.625K

Note 1: Applicable only for members with solid rectangular flanges and standard I-beams. c.

Members subject to both axial compression and bending stresses shall satisfy the following requirements:

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Existing Bridges

fa where -----£ 0.15 : Fa f a f b1 f b2 + --------- + --------- £ 1.0 -----F a F b1 F b2 fa > 0.15 : where -----Fa f b1 fa f b2 + -----------------------------------------------------------------------+ -----------------------------------------------------------------------£ 1.0 -----Fa fa fa k1 l1 ö 2 k2 l2 ö 2 æ æ F b1 1 – -------------------------- ----------F b2 1 – -------------------------- ----------ø ø 2 è 2 è 0.741p E r 1 0.741p E r 2 and, in addition, at points braced in the planes of bending, f a f b1 f b2 ----- + --------- + --------- £ 1.0 K F b1 F b2 For nomenclature, see Paragraph (b) above. d. For members subject to both axial tension and bending, the total of the axial tensile stress and the combined bending tensile stresses about both axes shall not exceed K. However, the compression stresses, if any, in the extreme fibers of flexural members resulting from the combined bending compressive stresses about both axes and the minimum simultaneous axial tension stress shall not exceed the values allowed by the formulas of paragraph b above. e.

Secondary stresses due to truss distortion usually need not be considered in any member the width of which, measured parallel to the plane of distortion, is less than 1/10 of its length. Where the secondary stress exceeds 4,000 psi for tension members and 3,000 psi for compression members, the excess shall be treated as primary stress.

1

3

7.3.4 ACTION TO BE TAKEN (2002) R(2008) a.

When the stresses under load are found to exceed allowable values for the selected type of rating (see Article 7.3.1), one or both of the following actions shall be taken: (1) The train speed, load intensity, or load configuration, or a combination of these, shall be restricted to that which does not develop stresses in excess of allowable. (2) The bridge shall be strengthened or replaced.

b. When the stresses under load are found to closely approach allowable values for the selected type of rating (see Article 7.3.1), or when the physical condition of main members or details is not satisfactory, the bridge shall be inspected at an increased frequency prescribed by the Engineer, with particular attention given to the critical members or details.

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SECTION 7.4 REPAIR, STRENGTHENING AND RETROFITTING1 7.4.1 GENERAL (2009) a.

The repair, strengthening, or retrofitting of existing bridges is usually brought about by one or more of the following conditions: • Category 1 – Accidental Damage. Sudden unexpected damage resulting from vehicular collision, marine collision, derailment, wide loads, fire, vandalism, seismic activity, or other emergency event. • Category 2 – Deterioration Damage. Damage resulting from corrosion, fatigue, settlement, past improper repair of the structure, etc. • Category 3 – Capacity or Geometric Deficiency. Insufficient capacity to carry current loads, vertical or horizontal clearance deficiency, non-compliance with current standards and practices, and/or poor structural details. • Category 4 – Natural Hazard Deficiency. Potential damage resulting from future seismic events, increased flood levels, or increased wind loads. The methods used to accomplish the repair, strengthening, or retrofitting of steel structures for the four categories of damage or deficiency may be different in terms of acceptable details, allowable stresses, and acceptable results. What may be acceptable for the emergency repair of accidental damage to a structure to restore traffic may not be acceptable for permanent repairs.

b. The decision to repair, strengthen, retrofit, or to replace a structure should take into account the condition of the structure, the age of the structure, the material of which the various members are made, the fatigue effect of the live loads that have been operated over the structure, the comparative estimated costs, the added length of life to be obtained from the modified bridge, and the possible future increase in the live loading. 7.4.1.1 Physical Condition a.

The physical condition of the structure shall be determined by inspection.

b. The materials of which the members are made shall be determined together with their relevant properties. While this information may be determined by examining the drawings, specifications, or test records, in some situations it may be necessary to obtain test coupons from the structure or to employ appropriate field testing methods such as the emery wheel/spark test and portable Brinell testing. 7.4.1.2 Stresses a.

The permissible stresses in repaired, strengthened, or retrofitted members shall be in compliance with the design stresses specified in Part 1, Design, except that in certain circumstances, rating stresses as specified in Section 7.3, Rating, or other stress levels, may be used as determined by the Engineer.

b. In adding metal to stringers, floorbeams or girders, or to members of trusses and viaducts, the new material shall be considered effective in carrying its proportion of live loads only, unless the dead load stress can be removed temporarily, or some other means is provided to introduce the proper dead load

1

References, Vol. 36, 1935, pp. 685, 1008; Vol. 39, 1938, pp. 165, 891; Vol. 53, 1952, pp. 511, 1063; Vol. 63, 1962, pp. 387, 699; Vol. 64, 1963, pp. 367, 633; Vol. 70, 1969, p. 241; Vol. 96, p. 73; Vol 97, p 175.

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stress in the new metal when it is applied. Connections of adequate strength shall be provided for the added metal. c.

Where the added material carries its proportion of the live load only, the stresses in the remaining portion of the original members, which is carrying the total dead load as well as its portion of live load, shall be investigated for the live load for which the bridge is being repaired or strengthened. The added material may be considered fully effective in computing the radius of gyration for determination of allowable stress in axially loaded compression members.

d. Members to be repaired or strengthened shall be investigated for any decrease in strength or stability resulting from the temporary removal of rivets, bolts, lacing, batten plates, cover plates or other parts. Bolts required for sealing only may be omitted temporarily during the repair process. In some cases, falsework or temporary members may be required. Where compression members are being reinforced, lacing bars, batten plates or tie plates, if removed, shall be restored to an acceptable level before allowing traffic over the bridge. 7.4.1.3 Eccentricity The added material shall be applied so as to produce a balanced section, eliminating or minimizing the effect of eccentricity on the strengthened member. Where balanced section cannot be obtained economically the eccentricity of the member shall be taken into account in determining the stresses. 7.4.1.4 Fasteners a.

Existing rivets that are removed to effect a repair or strengthening shall be replaced on a one for one basis with high strength bolts of equal or greater diameter.

b. Where remaining safe fatigue life is a controlling limit state, existing rivet holes shall be reamed after removal of the rivets, and the replacement high strength bolt shall be one size larger in nominal diameter than the replaced rivet or if of the same diameter shall satisfy the requirements for an oversize hole unless the hole is examined and found to contain no significant flaws or stress raisers. c.

Rivet heads may be removed by either mechanical means or careful use of oxygen-fuel gas cutting methods. If the oxygen-fuel gas method is used, use of a rivet cutting tip is recommended. Where existing material is to be preserved for reuse, rivet shanks shall be removed by mechanical means only, with coring permitted to assist the mechanical removal; the coring process shall not penetrate the surface of the rivet shank. Where existing material is to be discarded, rivets may be removed by any appropriate means acceptable to the Engineer.

d. If a rivet hole has been scored or otherwise damaged, the hole shall be reamed and the replacement high strength bolt shall be one size larger in nominal diameter than the replaced rivet, or if of the same diameter shall satisfy the requirements for an oversize hole. e.

Existing high strength bolts removed to effect a repair or strengthening may be reused only under conditions approved by the Engineer. If unacceptable to the Engineer, they shall be replaced with new high strength bolts of equivalent diameter.

f.

The extent of contamination of the faying surfaces by damage, mill scale, paint, grease, etc. shall be considered by the Engineer in assigning the allowable shear values for high strength bolts used in repair, strengthening or retrofitting applications.

g.

Type 3 high strength bolts shall be used with weathering steel. Galvanized bolts shall not be used with uncoated steel.

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Steel Structures 7.4.1.5 Welding a.

Electric arc welding may be employed subject to the approval of the Engineer.

b. In general, welds shall not be assumed to act together with rivets or bolts. c.

Where welds are added to existing riveted or bolted connections, the welds shall be designed to transmit the entire force, except that in such members where the existing material carries the entire dead load force, the welds shall be designed to carry the entire live load force in the member. Where some of the existing rivets in a member are loose or defective, they shall be replaced with high-strength bolts properly installed, unless otherwise directed by the Engineer, and such bolts may be considered to carry the dead load stress of the replaced rivets provided they are installed prior to the welding. Loose rivet heads shall not be welded.

d. Welding shall be in accordance with the applicable sections of Part 1, Design, and may be used only where specifically permitted by the Engineer. e.

When welding existing material where mill scale, rust, and dirt are present, and standard surface preparation cannot be accomplished, low hydrogen electrodes shall be used.

f.

When difficult-to-weld material must be welded to effect a repair, use of global pre-heats and post-heats shall be considered. Refer to Alternative Pre-Heat Requirements of AWS.

7.4.1.6 Jacking and Temporary Support a.

Jacks shall be placed so that the line of action is as nearly as possible, concentric with the gravity axis of the existing member(s). If jacks must be placed on an eccentric axis, an analysis of the effects of such eccentricity shall be made.

b. The rated capacity of a jack shall be a minimum of 50% greater than the computed required jacking force. c.

When choosing member sizes for jacking, strongbacks, or other temporary support, the allowable stress may be increased by 50%. Attention shall be paid to slenderness ratios and buckling allowables.

d. Live loads of locomotives, cars or similar equipment shall not be supported hydraulically. Other live loads may not be supported hydraulically without prior approval of the engineer. 7.4.1.7 Repair of Cracks and Defects a.

An actively propagating fatigue crack, either load-induced or distortion-induced, may be temporarily repaired by drilling a hole in the member to encompass the crack tip, provided the remaining net section of the member has sufficient stress-carrying capacity. The hole size shall be at least equal to the thickness of the material, but not less than ³⁄₄ inch (19 mm) diameter. Permanent repairs shall consist of measures to reduce the stress range in the case of load-induced fatigue cracking, and to eliminate the causes of the distortion in the case of distortion-induced fatigue cracking.

b. Defects from Category 1 Damage, such as gouges, nicks, burrs, etc., on the surface of fracture critical members shall be repaired by grinding smooth or peening. No weld repair of such surface defects shall be permitted.

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Existing Bridges 7.4.1.8 Heat Straightening a.

Heat straightening may consist of either flame straightening used alone, flame straightening with an auxiliary force, or hot mechanical straightening.

b. Heat straightening of damaged steel members shall not be undertaken by unskilled or inexperienced persons. c.

Heat straightening of damaged steel members shall be undertaken only after due consideration of the stability of the individual member, the stability of the overall structure, and possible redistribution of stresses as a consequence of the heat straightening process.

d. The temperature of the heated steel shall not exceed 1200 degrees F for carbon and low alloy steels, nor 1050 degrees F for quenched and tempered steels. No artificial means of cooling shall be applied until the steel has cooled to below 600 degrees F. e.

Mechanisms to apply auxiliary forces during heat straightening shall be of the type that reduce the magnitude of these auxiliary forces as the member displaces.

7.4.1.9 Bearings a.

Where expansion bearings are frozen in position by accumulated corrosion, they shall not be freed without prior investigation of the stability of the superstructure and substructure elements.

b. Where a bearing has been pounded into the bearing seat, the bearing may be restored to correct elevation by filling the void under the bearing with a suitable grout. If the restoration of the bearing shoe to correct elevation requires an extension above the seat, steel shim plates may be used.

1

7.4.2 PLATE GIRDERS OR ROLLED BEAMS (2010)

3

7.4.2.1 Reinforcing Reinforcing may be required in practically any part of plate girders. 7.4.2.2 Stiffeners a.

The bearing stiffeners may be reinforced by adding angles or plates, grinding the bearing ends of the new parts to make them fit closely, or welding them to the flanges.

b. Intermediate stiffeners may be added by high-strength bolting, or welding, but they shall not be welded to the tension flange. 7.4.2.3 Flanges and Webs a.

The flange section may be increased by adding cover plates or by replacing the existing cover plate with a new cover plate providing adequate section. Where the exposed surfaces of old cover plates are rough or uneven from the effects of corrosion or tie wear, they shall be discarded and new plates provided. When more than one cover plate must be renewed due to wear, etc., consideration should be given to replacing the defective plates with one plate of adequate size. Cover plates added to plate girders without existing cover plates shall be full length and connected to the flange angles with continuous fillet welds, or high strength bolts.

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Steel Structures

b. Cover plates added to rolled sections shall be full length and shall be connected by continuous fillet welds, or high strength bolts. Intermittent welds shall not be used. Welded cover plates shall be of sufficient thickness to prevent buckling without intermediate fasteners. c.

In open deck bridges where ties rest directly on the flange angles, worn or inadequate size flange angles may be renewed by bolting in place, new flange angles of sufficient size. Cover plates may be added, where required because of inadequate size flange angles, only when the surface to which they are to be attached has not been severely reduced by corrosion.

d. Where the cost of removal and replacement of the deck would be excessive, as in ballasted-deck bridges, flange sections may be increased by adding full-length longitudinal angles, plates, or channels just below the flange angles, first removing the stiffener angles and then finally replacing them with new stiffeners. e.

Where flange material is added, the existing flange fasteners may be insufficient. This may be corrected by replacing the existing fasteners with high strength bolts of equal or larger diameter.

f.

Holes in flange material may be drilled full size in the shop or in the field or subpunched in the shop and reamed in the shop or in the field. See Articles 3.2.6, 3.2.7 and associated commentary.

g.

Where fasteners are removed from two or more plies of material which are to remain in contact, holes shall be filled with a bolt snug tightened before any adjacent fastener is removed, unless otherwise authorized by the Engineer.

h. Where the web was not originally spliced to resist moment, it may be so spliced by adding cover plates or side plates. 7.4.2.4 Initial Tension Initial tension may be placed in a new bottom cover plate by welding one end of the plate to the flange angles and then heating the plate until it has expanded to some predetermined length, welding the other end of the plate, and then allowing it to cool, after which the welding can be completed. 7.4.2.5 Effective Span Where the bridge seat is wide, the effective span may be shortened somewhat by moving the bearings nearer to the edge of the seat and providing new end stiffener angles over them, provided that a thorough analysis of the abutments indicates that excessive soil pressure or pile loadings will not be created. 7.4.2.6 Laterals, Cross Frames and Connections Inadequate lateral systems, especially those composed of rods or bars, should be replaced with lateral members of the required strength and stiffness connected with high strength bolts. Cross frame members, diaphragms and their connections shall be checked for adequacy to carry shear due to unequal distribution of wheel loads and strengthened, if necessary. 7.4.2.7 Doubling Up Girders In strengthening deck plate girder bridges where there are several identical spans, one method is to double up the spans, and then provide additional spans to complete the bridge. Where girders are so arranged, the spacing should be such as to equalize the load on the girders and to allow inspection, cleaning and painting of the interior surfaces. An adequate system of laterals and cross frames shall be provided.

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Existing Bridges 7.4.2.8 Substitution Where extensive strengthening is to be done on a number of identical girder spans, one new span may be provided and substituted for one of the spans which will then be removed and strengthened. Each span in turn can be replaced by a span that has been removed and strengthened, until the entire bridge has been strengthened.

7.4.3 FLOOR SYSTEMS (1993) R(2008) 7.4.3.1 Stringers and Floorbeams a.

Strengthening of riveted or high-strength-bolted plate girder sections shall be done in accordance with applicable requirements of Part 1, Design.

b. Stringer systems may be strengthened by adding cover plates to existing stringers, by adding additional stringers, or by stringer replacement with new sections of adequate strength. Where possible, additional or new stringers shall be standard rolled sections without cover plates rather than built-up sections. Where additional stringers are used they shall be connected to the existing stringers so that they will deflect together. Stringer spacing shall be such as to allow inspection, cleaning and painting of interior surfaces. c.

The floorbeams webs are likely to be overstressed at the ends, especially in pin-connected truss spans where the ends have been recessed to clear the pin-nuts and eyebars. Floorbeam details shall be analyzed for both flange and web stresses and adequate reinforcement provided.

1

7.4.3.2 End Connections The end connection of a stringer may sometimes be strengthened by using longer connecting angles and adding high strength bolts, by reaming the holes and using larger high strength bolts, or by welding. Brackets may be placed under the ends of the stringers to give additional support.

3

7.4.3.3 Lateral Connections Lateral plates attached to the tension flange of short-span stringers and floorbeams decrease their fatigue strength, and the addition of such plates should be avoided, particularly near points of maximum bending. 7.4.3.4 Substitution

4

The procedure of Article 7.4.2.8 may be followed where applicable.

7.4.4 TRUSSES (2009) The strengthening of trusses is more difficult and requires considerably more analysis of the connections and their details than is required for the strengthening of girders or floor systems. The connections often determine the strength of the truss span. 7.4.4.1 Tension Members a.

Tension members of pin-connected trusses may often be reinforced by the addition of adjustable bars. These may be of several types, such as loop bars, or single bars attached to a loop or forging that fits over and bears on the pin. Care must be taken to form the position of the bar or forging in contact with the pin so that full bearing will be secured. This may be accomplished by providing sufficient metal in this portion for boring the pin holes. Where a bar of uniform section is bent around a pin, the cross section is

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likely to be reduced by the stretching and narrowing of the outer edge of the bar, for which allowance shall be made. Where space is limited, bars sometimes are placed over the heads of existing eyebars, but this method gives doubtful results, because the edges of the eyebar heads are not finished to a true surface. b. Except where a single bar can be placed in the exact center of the pin, two additional bars or members equally spaced from the center of the pin, shall be used to strengthen each panel. The resultant stresses in the pins under the revised loading condition must be investigated. c.

After the new members have been installed, the entire panel shall be adjusted to properly distribute the dead load tension to all members. Eyebars or rods that do not have adjustable provisions shall be adjusted in accordance with Part 8, Miscellaneous; Section 8.2, Method of Shortening of Eyebars to Equalize the Stress.

d. Elongated eyebars may be adjusted in accordance with Part 8, Miscellaneous; Section 8.2, Method of Shortening of Eyebars to Equalize the Stress. e.

Rolled or built-up sections may be effectively reinforced by the addition of cover plates in the planes of the gusset plates. These plates may be high strength bolted or welded to the flange of the member and butt welded to the gusset plates, provided that the strength of the gusset plate and its connections is adequate. Care shall be taken to protect against notches or other severe stress concentrations at the connections of the cover plates to the gussets. Unless the dead load force in the original member is relieved, new metal so added shall be considered effective in carrying its portion of the live load stress only.

f.

Floorbeam hangers are frequently highly stressed from a combination of bending and direct axial tension. To reduce the probability of fatigue cracking in these highly stressed hangers, sharp copes or reentrant cuts should be eliminated or modified. The replacement of all rivets with high strength bolts at the top connection of the floorbeam hangers to improve the transfer of force to the gusset plates should also be considered.

7.4.4.2 Compression Members a.

The reinforcement of compression members requires careful investigation. The chord members of many old bridges are unsymmetrical in section and are eccentrically loaded. This condition may be corrected by adding metal in the proper location. A small amount of metal placed in this way will often increase the rating of the member considerably.

b. Where a substantial increase in the strength of a compression member is required, special analysis is needed. The solution will depend on the type of section, the details at or near the pins, and other conditions. Metal sometimes may be added to the cover plate, usually between the existing lines of rivets. This should be balanced by placing additional metal on the lower flanges in the manner described in the preceding paragraph. Full length side plates may be added to the web plates of the section, between the vertical legs of the upper and lower angles, provided that adequate means of transferring this stress into the connection or adjacent member can be obtained. Where the cover plate in the original design is so wide in proportion to its thickness that it has little resistance to buckling, this may be achieved by adding a cover plate connected by fasteners along the center line in addition to the fasteners through the angles. c.

One of the problems encountered in reinforcing compression members is the introduction of the dead load stress into the additional material. Where this is not done, full value cannot be obtained from the new material. For instance, assuming that the new material gets no dead load stress, that the dead load stress in the old material is 10,000 psi, and that the total allowable stress is 26,000 psi, then the new material will be carrying only 16,000 psi stress from live load only. This is the maximum stress to which © 2011, American Railway Engineering and Maintenance-of-Way Association

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the new metal can be worked, since any higher stress would cause overstress in the old metal. Several methods may be used to induce dead load stress in the new material. The new material may be temporarily shortened by cooling or compressing before connecting to the old material or the old material may be temporarily relieved of dead load while adding the new material. d. The cover plates of large upper chords and end posts may be thin compared with their unsupported width and it may be desired to bring all of the old metal into full use. The reinforcement, in this case, may be provided in the form of a new central web with top and bottom flange angles; and is divided into two segments, each occupying one-half of the panel length. The segments are designed to receive a wedge between their adjacent ends. The segments are placed inside the member with ends bearing against the pins and the center wedge. To introduce compression into the segments, the new material is first seated for proper bearing against the pins or connections; by pulling the wedge up tight by means of a large bolt. The wedges are drawn up a predetermined amount to develop the desired dead load stress in the new metal. The bolts holding the wedges are left in place permanently. The flanges of the new segments are then bolted to the top cover plate and to the lower lacing bars, thus making the new center segment an integral part of the chord, carrying the same stress per square inch as the old metal. 7.4.4.3 Adding a Center Truss a.

The reinforcement of deck truss spans frequently is accomplished by the addition of a center truss. In a single track bridge, this is comparatively simple, as ample bracing may be applied to make the three trusses deflect alike. The center truss should not be too stiff but should have the same deflection under load as the old trusses. Otherwise excessively heavy cross bracing will be required or else excessive stresses will be induced in the center truss before the outer trusses have deflected enough to stress the members up to their safe carrying capacity.

b. In a double-track deck truss span that has only two trusses, the addition of a center truss creates difficult problems. The tracks may be loaded either separately or simultaneously, and it may not be economical to introduce enough bracing between the trusses to make them act together. The floorbeams will be continuous over the new truss. Where the center truss is too stiff, the outer truss will have the greater deflection under a single-track load, and the outer rail will be low under load. When both tracks are loaded, however, the center truss must be strong enough to carry its share of the load from both tracks. Thus the truss deflections and the distribution of stresses through the floorbeams for various conditions of loading must be determined and a design chosen in which the various members will be as stressed as nearly equally as possible under equal stress without introducing objectionable deflections and poor-riding-track. The reinforcement should be designed and erected in such a way that the new center truss may be swung under its own dead load before making the final connections between the new and the old trusses. 7.4.4.4 Auxiliary Truss Supports It is sometimes possible to shorten the effective length of a truss span by the installation of auxiliary piers or bents at the first or second interior panel points. However, since this converts a simple span truss to a threespan continuous truss, changing its stress characteristics, a thorough analysis of the altered span must be made. Members having insufficient capacity must be strengthened to carry the revised loading prior to the installation of the new supports. 7.4.4.5 Auxiliary Truss Members Girders, lattice trusses, floorbeams and stringers may sometimes be reinforced by adding auxiliary truss members underneath.

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7.4.5 OTHER STRUCTURES (1983) R(2008) Viaduct towers and structures of other types not specifically mentioned herein may be strengthened by methods similar to the foregoing.

SECTION 7.5 MAINTENANCE1 7.5.1 GENERAL (1984) R(2008) a.

All steel structures are subject to gradual deterioration due to corrosion, mechanical wear, and impact and fatigue damage from moving loads, and require periodic maintenance throughout their service life.

b. The class of maintenance to be used for each structure shall be determined by the Engineer, based upon the importance of the structure to the operations of the railroad, the cost and difficulty of repair or replacement, and the probable remaining service life required. c.

The extent of maintenance shall be classified as follows: (1) Class A. The structure is maintained in a condition comparable to new construction, except weathering and any deterioration which affects appearance only. (2) Class B. Main members are maintained to the extent that the rated capacity of the bridge will not be reduced, but secondary members are maintained only as necessary to preclude extensive structural repairs. (3) Class C. Main members are maintained to the extent necessary to carry the prevailing traffic, and secondary members are maintained only as immediately necessary.

7.5.2 MAINTENANCE OF STRUCTURAL ELEMENTS (1984) R(2008) a.

Where inspection reveals that a structural element has been weakened, the Engineer shall determine whether the element shall be replaced or reinforced, based on the extent of loss of strength and the class of the maintenance as defined in Article 7.5.1c.

b. The procedures to be followed in replacing or reinforcing a structural element shall be the same as specified in Section 7.3, Rating.

7.5.3 MAINTENANCE PAINTING (2001) R(2008) a.

Except in those cases where appearance is an important consideration, the purpose of maintaining the paint or other corrosion protection system on a structure is to protect the structure from deterioration which may affect its rated capacity.

b. The extent of maintenance painting for each structure shall be determined by the Engineer as part of a system bridge maintenance program and shall be consistent with the general class of maintenance as defined in Article 7.5.1c, with consideration being given to the local environment and factors such as relative humidity and type of atmosphere. 1

References: Vol. 75, 1974, p. 338.

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Existing Bridges

c.

Steel surfaces to be painted shall be prepared and painted in accordance with the applicable articles of Section 8.7, Guide to the Preparation of a Specification for the Cleaning and Coating of Existing Steel Railway Bridges.

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15

Part 8 Miscellaneous — 2011 — FOREWORD

Part 1, Design, Part 3, Fabrication, Part 4, Erection and Part 6, Movable Bridges are applicable to turntables except as modified by Section 8.1, Turntables.

1

TABLE OF CONTENTS Section/Article

Description

Page

8.1 Turntables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1.1 General Features of Design (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1.2 Loads and Stresses (2009). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1.3 Basic Allowable Stresses and Deflections (2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1.4 General Details (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-8-3 15-8-3 15-8-4 15-8-6 15-8-7

8.2 Method of Shortening of Eyebars to Equalize the Stress . . . . . . . . . . . . . . . . . . . . . . . . 8.2.1 General (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-8-10 15-8-10

8.3 Anchorage of Decks and Rails on Steel Bridges. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3.1 Foreword (2010). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3.2 Anchorage of Decks to Bridge Spans (2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3.3 Anchorage of Rail (2011). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3.4 Rail Expansion Joints (1983) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3.5 Maintenance of Bridges with Continuous Welded Rail (1983) R(2002) . . . . . . . . . . . . . . .

15-8-12 15-8-12 15-8-14 15-8-14 15-8-16 15-8-17

8.4 Unloading Pits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4.1 Scope and Purpose (1993) R(2002). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4.2 General (1993) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4.3 Operating Limitations (1993) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4.4 Loads (1993) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4.5 Unsupported Running Rail (1993) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4.6 Rail as Supporting Beams (1993) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4.7 Structural Supporting Beams (1993) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4.8 Concrete Pit (1993) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-8-18 15-8-18 15-8-18 15-8-18 15-8-18 15-8-27 15-8-27 15-8-27 15-8-28

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TABLE OF CONTENTS (CONT) Section/Article

Description

Page

8.4.9 Construction Drawings (1993) R(2002). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4.10 Applicant’s Responsibilities (1983) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-8-28 15-8-28

8.5 Walkways and Handrails on Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5.1 Locations (1983) R(2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5.2 Clearances and Minimum Dimensions (1983) R(2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5.3 Loads (1984) R(2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5.4 Materials (1984) R(2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-8-29 15-8-29 15-8-29 15-8-29 15-8-30

8.6 Guidelines for Evaluating Fire Damaged Steel Railway Bridges . . . . . . . . . . . . . . . . . 8.6.1 Introduction (1986) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.6.2 T ypes of Fires (1986) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.6.3 Temperature Effects (2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.6.4 High Strength Steels (1985) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.6.5 Fasteners (1985) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.6.6 Evaluation of Bridge (1986) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.6.7 Conclusion (1986) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.6.8 References (1986) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-8-30 15-8-30 15-8-31 15-8-31 15-8-32 15-8-32 15-8-32 15-8-33 15-8-33

8.7 Guide to the Preparation of a Specification for the Cleaning and Coating of Existing Steel Railway Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-8-34 8.7.1 General (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-8-34 8.7.2 Surface Preparation (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-8-42 8.7.3 Application (2009). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-8-46 8.7.4 Coating Systems (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-8-52 8.7.5 Safety and Environmental Considerations (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-8-54 8.7.6 Quality Control and Quality Assurance (2009). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-8-60 8.7.7 Final Inspection and Warranty (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-8-61

LIST OF FIGURES Figure

Description

Page

15-8-1 Turntable Clearances . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-8-2a Recommended Live Load Turntable Design Case a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-8-2b Recommended Live Load Turntable Design Case b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-8-3 Clamp Plates, Rods, and Trammels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-8-4 Dead Load Eyebar Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-8-5 Unloading Pit – Four Foot Maximum Span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-8-6 Unloading Pit – Fifteen Foot Maximum Span . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-8-7 Unloading Pit – Fifteen Foot Maximum Span Reinforcing Details . . . . . . . . . . . . . . . . . . . . . .

15-8-3 15-8-5 15-8-6 15-8-11 15-8-13 15-8-20 15-8-22 15-8-25

LIST OF TABLES Table

Description

Page

15-8-1 Properties of Structural Carbon Steel Related to Temperature. . . . . . . . . . . . . . . . . . . . . . . . . 15-8-2 Color of Steel vs. Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-8-31 15-8-33

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Miscellaneous

SECTION 8.1 TURNTABLES1 8.1.1 GENERAL FEATURES OF DESIGN (2005) 8.1.1.1 General a.

These provisions cover the following types of turntables: (1) Balanced (2) Continuous three-point support

b. Turntables shall preferably be of deck construction, but they may be made with through girders or trusses. 8.1.1.2 Length a.

The nominal length of the turntable is the overall length of the girders. The length shall preferably be a multiple of 5 feet.

b. The length shall be such that no part of the locomotive to be turned will project beyond the ends of the turntable.

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8.1.1.3 Clearances a.

Turntable clearances shall preferably be in accordance with a diagram prepared by the purchaser and submitted with information given to bidders. Otherwise, clearances shall not be less than those shown in Figure 15-8-1.

b. Clearances shall conform with legal requirements for turntables.

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4

Figure 15-8-1. Turntable Clearances 1

References, Vol. 25, 1924, pp. 225, 231, 1262; Vol. 44, 1943, pp. 406, 670, 685; Vol. 54, 1953, pp. 907, 1347; Vol. 63, 1962, pp. 386, 699; Vol. 70, 1969, p. 241. Reapproved with revisions 1993.

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Steel Structures 8.1.1.4 Power Operation a.

Turntables shall be power operated unless otherwise specified. Power equipment shall be the kind specified by the purchaser and shall conform with the applicable requirements of Part 6, Movable Bridges.

b. For the calculation of power requirements and of forces for turning or braking, the position of the live load on three-point-support tables shall be taken as the one most unfavorable. c.

The maximum speed at the circle rail shall be 200 feet per minute.

8.1.1.5 Locking Device A locking device system shall be provided, preferably at each end of the turntable, which will hold it in line with any approach track. The locking device shall engage the approach track rather than the pit wall. The locking device may or may not be connected to a signal. The locking device shall be electrically interlocked with the driving system.

8.1.2 LOADS AND STRESSES (2009) 8.1.2.1 Loads a.

The turntable shall be designed for the live load and length as specified by the purchaser in information given to the bidders. Recommended design live loads per axle for turntables of various lengths are shown in Figure 15-8-2a and Figure 15-8-2b. For turntables designed for steam locomotives only, the recommended live loads shall be those shown in Figure 15-8-2a multiplied by 72/80. For turntables designed for diesel locomotives, the recommended design live loads shall be those shown in Figure 15-82a and Figure 15-8-2b. The live load specified shall be placed on either one or both arms of the turntable in such position(s) as will produce maximum stresses in each component, maximum reactions on the center pivot and end trucks, and maximum end uplift for continuous three-point-support turntables.

b. The stresses from these loads and forces shall be shown separately on the stress sheet. 8.1.2.2 Live Loads for Design a.

The turntable shall be designed for the live load and length as specified by the purchaser in information given to bidders. Recommended design live loads for turntables of various lengths are shown in Figure 15-8-2a and Figure 15-8-2b. The live load specified shall be placed on either one or both arms of the turntable in such positions as will produce maximum stresses in each component, maximum reactions on the center pivot and end carriages, and maximum end uplift for continuous three-point-support turntables.

b. In addition to the specified live loads, the end of the turntable, including main girders, end floorbeams, trucks, and other components above the foundation similarly affected, shall be proportioned for an axle load of 150,000 lb placed in the most unfavorable position. c.

The center pivot shall be proportioned for 125% of the specified live load and the center cross girder assembly with its connections to the main girders, down to and including the bearing of the cross girder on the top of the center casting, shall be proportioned for 175% of the specified live load.

d. In considering the loads to be turned on the table, the 150,000 lb load and the 25% and 75% additions to the live load mentioned in the preceding two paragraphs shall not be included.

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Figure 15-8-2a. Recommended Live Load Turntable Design Case a

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Figure 15-8-2b. Recommended Live Load Turntable Design Case b

8.1.3 BASIC ALLOWABLE STRESSES AND DEFLECTIONS (2008)1 8.1.3.1 Structural Components a.

Structural components shall be proportioned by applicable requirements of Part 1, Design, Part 3, Fabrication, Part 4, Erection, and Part 6, Movable Bridges, except for components which determine the deflection of balanced turntables. Such components shall be so proportioned that live load deflection at the ends will not exceed 1/2 inch for an 80 foot turntable; and for longer turntables, 1/8 inch more for each 10 feet of length beyond 80 feet.

b. If a balanced turntable designed for Diesel locomotives is turned by separate tractors and has a length between 95 feet and 110 feet, the calculated deflection from 2 four-axle units with 80 kip axle loads and a combined wheel base equal to the length of the turntable shall not result in the turntable wheels contacting the circle rail. c.

Three-point-support turntables shall be designed for a variation of 1 inch either way in the relative elevations of the circle rail and the center support.

d. In three-point-support turntables, vertical stiffness is not essential; rather a degree of flexibility is desirable. Such turntables shall be proportioned to provide positive reactions at all three supports, i.e. to avoid uplift, regardless of the position of the live load.

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See Part 9 Commentary

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Miscellaneous

8.1.4 GENERAL DETAILS (2009) 8.1.4.1 Center Cross Girders Center cross girders shall be as deep as practicable, and their webs shall be made to bear over the center, to minimize their deflection and ensure uniform bearing over the full length of their center contact. 8.1.4.2 Bracing a.

Horizontal bracing shall be provided to permit turning the table by means of power applied at either end. Both top and bottom lateral bracing systems shall be provided where practicable. Balanced turntables shall be braced to prevent warp. Bracing shall be of such pattern that the center cross girders cannot be stressed under torque loading.

b. The minimum thickness of bracing material shall be 1/2 inch. 8.1.4.3 Footwalks There shall be footwalks along both sides of the track. Footwalks on deck tables shall be protected by railings. 8.1.4.4 Collector Ring Support Where feed wires of an electrically operated turntable are over the pit, a structural steel frame shall be attached to the main girders to support the wires and the collector ring over the center.

1

8.1.4.5 Protection and Components a.

The center, center cross girders, and machinery shall be protected (preferably by metal housing) against the entry of water, cinders, dirt, etc.

b. The thickness of any full length top cover plate of deck girders, stringers, floorbeams, and center cross girders shall be increased 1/8 inch over the computed thickness. The section of other components subject to excessive corrosion shall be increased appropriately over the computed section.

3

8.1.4.6 Inspection Turntables shall be so designed as to facilitate inspection and making repairs. Jacking brackets on the steel superstructure and foundations in the pit paving, shall be provided for raising the turntable off the center and the circle rail. A pair of stiffeners shall be provided on the outside of each main girder near one end. Their outstanding legs shall be 3 inches apart and shall extend at least 1 inch beyond the girder flange to provide nonslip sling position for lifting the end of the turntable with a crane. 8.1.4.7 Center a.

The center pivot shall be of the disk type.

b. The point of application of the load on the pivot shall be directly over the center of the pivot. The rotating portion of the center pivot shall be equipped with a saddle or pin to allow longitudinal rocking of the main girders. The center cross girder assembly shall be secured to the center in such a way as to prevent the turntable from being forced off-center by a blow of locomotive wheels on the ends of the turntable rails, and where this force is resisted by a pin in a half-round bearing, the pin shall be 4 inches dia or less. The whole center, including the foundation, shall be constructed to resist any unbalanced lateral force resulting from turning the turntable.

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c.

The entire unit shall be as nearly dustproof and waterproof as practicable. It shall be equipped with substantial and effective lubricating devices and be so designed that it may be readily removed, taken apart, inspected, cleaned, repaired, lubricated and replaced. There shall be provision for height adjustment.

d. The disk pivot shall be one disk of phosphor bronze or be comprised of two disks, one of phosphor bronze and one of hardened steel, set in oil-tight recesses. The disks shall be so secured that sliding will take place only at the surfaces of a single disk or the contact surfaces between two disks. e.

Sliding surfaces shall be finished accurately and polished.

8.1.4.8 End Trucks a.

The end trucks shall be of substantial construction. They shall be braced to hold the wheel axles in lines radiating from the center of rotation. The end trucks shall be completely assembled in correct alignment on the main girders and the correct lengths of braces determined. The braces then shall be connected. The braces shall have provisions for small length adjustments to be made, preferably by shims.

b. Bolts connecting trucks to balanced turntables shall be ASTM A 325. c.

There shall be either two or four wheels at each end of the turntable. Where there are only two, they shall be placed outside the main girders and mounted in a single truck frame connected rigidly to the main girders. Where there are four wheels, they shall be mounted in pairs in separate trucks attached to the main girders so as to equalize loads transmitted to the wheels.

d. Trucks having either traction equipment built in them or separate tractors connected to them shall be adequately connected to the main girders to transmit the traction force. e.

Provisions for height adjustment shall be furnished.

f.

For turntables that are turned by power to end trucks in an emergency, the truck at either end shall have sufficient power to rotate the turntable with the design load.

8.1.4.9 Wheels and Axles a.

Wheels shall be AAR multiple-wear wrought steel wheels or equal, of as large diameter as practicable, and shall not be conical. Treads shall not be flanged and the webs preferably shall be straight. Wheels shall be bored for tight fit and mounted on steel axles under heavy pressure. In addition, wheels used as drivers shall be keyed to the axles.

b. Wheel material shall conform to ASTM A 504, Class C. The rims only shall be heat treated. Axle material shall conform to ASTM A 236, Class G. 8.1.4.10 Bearings a.

These provisions cover the following types of axle bearings: (1) Journal Bearings with Boxes (Old Construction) (2) Roller Bearings (New, Rebuilt and Old Construction)

b. It is recommended that roller bearings be installed on newly constructed and rebuilt turntables.

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Miscellaneous

c.

It is recommended that balanced beam tables be converted during rebuilding to three-point bearing turntables using redesigned trucks.

d. Bearing boxes for journal bearings shall be of cast or rolled steel with removable phosphor bronze bushings or bearings. Other suitable types of bearing material may be specified. e.

Bearing boxes for journal bearings shall be compact, with lids which can be opened readily, and of such construction as to facilitate effective lubrication and to exclude water and dirt.

f.

Bearing boxes of continuous three-point-bearing turntables shall be preferably equipped with roller bearings.

8.1.4.11 Brakes A braking system shall be installed on the end trucks, with controls located in the operator’s house. 8.1.4.12 Circle Rail a.

The circle rail shall be of a section not less than the heaviest standard rail used by the purchaser and preferably not less than 132 lb per yd.

b. Provisions shall be made for adjustment of the elevation and the radius of the circle rail and for drainage. c.

All or most of the joints in the circle rail shall preferably be butt welded. Where bolted rail joints are used, they shall not interfere with rail anchorage. The top of the circle rail shall be in a horizontal plane.

d. The circle rail shall preferably be supported on steel beams embedded in the concrete foundation, or on bearing plates not less than 2 inches thick set directly on the concrete foundation. Where timber ties are used for supporting circle rails, they shall be treated hardwood, sized to the same dimensions, and held in position while the concrete is being placed. The circle rail shall be securely anchored to its support to hold it in alignment and to prevent creeping. e.

Circle rail shall be set level within 1/16 inch, truly circular and concentric with the turntable center within +/- 1/8 inch.

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3

8.1.4.13 Radial Tracks a.

A track layout with tangents extending from face of pit wall a distance at least equal to the locomotive wheel base is desirable. (Anything less will result in side kick at the end of the table.)

b. Radial track rails ending at the circle wall shall not be less than 39 feet long. The radial tracks shall be box anchored for a distance of 200 feet extended outward from the pit wall to prevent longitudinal movement. c.

The top of rails of radial tracks shall be at the same elevation as the top of rails on ends of turntable, with the end truck wheels bearing. The ends of rails in radial tracks shall be held securely in line and elevation. Where wood supports are used over the circle wall under ends of radial tracks, adequate steel bearing plates shall be provided.

d. There shall be 3/4 inch clearance between the ends of the radial track rails and rails on turntable. 8.1.4.14 Rails on the Turntable a.

The rails on turntable shall be anchored securely in line and elevation and anchored to prevent longitudinal movement. The purchaser’s heaviest standard rail and steel tie plates may be used

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throughout, except at ends of table where there should be larger steel bearing plates with sufficient depth to prevent bending. b. Rails at ends of turntables shall preferably be full length. 8.1.4.15 Pads Consideration shall be given to the use of pads at locations subject to impact loads, to improve rail bearing conditions for rails on the turntable, approach track rails, and circle rail. 8.1.4.16 Pit a.

The bottom of turntable pit preferably shall be paved. Ample clearance for snow shall be provided between turntable steelwork and paving. Suitable pit drainage shall be provided, and where conditions warrant there shall be an adequate drainage system behind the circle wall. An inspection pit shall be provided in the circle wall, of sufficient size to permit removal of a truck.

b. There shall be a clearance of not more than 3 inches between the circle wall and the ends of the turntable.

SECTION 8.2 METHOD OF SHORTENING OF EYEBARS TO EQUALIZE THE STRESS1 8.2.1 GENERAL (2006)2 Detail of the clamp plates, rods and trammel suitable for use in flame shortening to tighten loose eyebars is shown in Figure 15-8-3. The general procedure shall be as follows: a.

Remove paint from those eyebar areas where clamp plates are to be fastened and from the 12 inch length of eyebar to be heated.

b. Bolt the clamp plates to the eyebar with the V-grooves on the centerline of the bar, allowing ample thread length on the clamp rods so that nuts will have plenty of room to turn when the eyebar is upset. Keep the nuts on the clamp rods close (eyebar will expand during heating). c.

Attach block and falls to inclined eyebars about 6 feet above clamp plates to take possible sag out of the bar and to insure that no sag results after the eyebar is heated. Do not put excessive uplift on the bar.

d. Provide a canvas shield to protect the heated area of the eyebar from wind.

1 2

e.

Measure the decrease in length of the eyebar with trammel points by placing punch marks or scratches on the bar above and below the clamp plates before the bar is heated.

f.

Check the train traffic schedule and allow about 1 hr between trains for heating, upsetting and cooling of the eyebar.

g.

Unless a lower temperature is specified by the Engineer, heat both sides of the bar to a temperature of 1,300 to 1,400 degrees F for a length of 12 inches midway between the upper and lower clamp plates with two torches using heating tips. These temperatures are not recommended for use with quenched and

References, Vol. 49, 1948, pp. 231, 666; Vol. 60, 1959, pp. 507, 1098; Vol. 62, 1961, pp. 548, 876; Vol. 70, 1969, p. 241. See Part 9 Commentary

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Miscellaneous

1

Figure 15-8-3. Clamp Plates, Rods, and Trammels tempered steels. Apply the heat uniformly on both sides of the bar, which can be done by moving the torches in unison as the heating progresses.

3

h. Measure the temperature of the heated area with a non-contact thermometer or temperature sensing crayons. i.

When the 12 inches area is fully heated, tighten nuts on the clamp rods simultaneously and upsetting the heated area a very small amount. Take considerable care, especially on large eyebars, that the interior of the bar is fully heated. It is essential that nuts on both clamp rods are tightened the same amount. By a side push on the eyebar close to the head, it can be determined whether the heads are tight against the pins.

j.

Kinking of the heated portion of the eyebar can be held to a minimum if the reduction in length is kept below 1/4 inch for each heating. A maximum of two heatings, or 1/2 inch total reduction, should be allowed at any one location on the eyebar. If more reduction is needed, move to a different location on the eyebar, preferably several feet away from the first location.

k. If the eyebar shows a tendency to buckle or delaminate, eyebar shortening shall stop. The buckling or delamination may be caused by attempting too much reduction in one heating or by trying to upset the eyebar before the correct temperature is reached. To straighten a buckled eyebar, place a 2 or 3 foot length of 8 inch steel channel on each side of the bar and cinch with heavy C clamps, striking the channel with a maul if necessary.

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4

Steel Structures

l.

Where it is desired to keep initial or dead load eyebar stress low, reduce the amount of heat applied and keep a 3 or 4 inch length of bar in the middle of the 12 inch heated area at a temperature specified in Article 8.2.1(g) for 3 or 4 minutes. This short section of heated bar allows elongation in this area while the remainder of the heated area is cooling and contracting. Where it is necessary to reduce initial or dead load stress in an eyebar after adjustment has been made and the eyebar has fully cooled, heat a shorter length of the eyebar to the temperature specified in Article 8.2.1(g) with clamps still in place and nuts on the clamp rods loose. The weight of lower portion of eyebar or pull on the pins when the eyebar is hot will again lengthen it and then cooling will place a smaller initial tension in the bar.

m. The upset eyebar should cool to ambient temperature gradually and unassisted. If necessary for passage of trains, the eyebar may be spray cooled with water after its temperature falls below 600 degrees F. n. Traffic may be resumed over the bridge after the heated eyebar area has cooled to 300 degrees F. o.

Approximate dead load eyebar stress may be determined by measuring the frequency of vibration of the bar, about its minor axis, and the stress F, from Figure 15-8-4.

p. Frequency of vibration of the eyebar can be measured in the following manner: (1) Remove clamp plates and bolts. (2) Mount a sheet of paper or cardboard to a small piece of wood clamped to the edge of the eyebar. (3) Place the bar in vibration about its weak axis. (4) Hold a pencil on the paper or cardboard and then move the pencil slowly parallel to the eyebar for a definite interval of time, say 10 sec. The pencil will then trace the number of cycles for this time interval. NOTE:

For a comprehensive discussion of the flame shortening of eyebars, see Proceedings, Vol. 48, 1947, pages 969 to 986, incl.

SECTION 8.3 ANCHORAGE OF DECKS AND RAILS ON STEEL BRIDGES1 8.3.1 FOREWORD (2010)2 a.

In the absence of definitive data, there is no satisfactory way to predict behavior of rail on bridges under the influence of temperature changes, braking and traction of trains, and creep. Recommendations which follow are based on experience and research work done by the Transportation Technology Center, Inc. and the UIC (International Union of Railways) (Reference 6, 7, 48, 51, and 68).

b. Effectiveness of deck and rail anchorage systems on bridges is dependent upon proper anchorage and maintenance of track on the roadbed approaches. 1 2

References, Vol. 76, 1975, p. 338; Vol. 77, 1976, p. 250; Vol. 79, 1978, p. 49. See Part 9 Commentary

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Figure 15-8-4. Dead Load Eyebar Stress

Miscellaneous

15-8-13

Steel Structures

8.3.2 ANCHORAGE OF DECKS TO BRIDGE SPANS (2011)1 8.3.2.1 Open Deck Bridges a.

Ties shall be anchored to bridge spans to control lateral, vertical and longitudinal movement. Each anchorage shall consist of two fasteners, each equivalent to a 3/4 inch dia bolt. Maximum longitudinal spacing of such anchorages shall be at every 4th tie, but not to exceed 4’-8” centers, on spans where rivet or bolt heads protrude into the ties, or other spans where the ties are fixed in longitudinal position.

b. For spans exceeding 300 feet see Articles 1.2.13 and 8.3.4.2. c.

Where hook bolts are used for anchorage of ties, the Engineer may also require that ties be dapped to fit top flanges of girders or stringers or that other suitable lateral restraining devices be installed. Such tie daps shall not be less than 1/2 inch deep nor more than 1/2 inch wider than girder or stringer flange.

d. A spacer timber of section not less than 4² ´ 8² nominal or a metal spacer plate shall be placed on the deck outside of each rail and secured to each tie with lag bolts or drive spikes of not less than 5/8 inch dia. e.

Bolts fastening timber ties to open deck bridges shall preferably use a fastening system with a method to prevent bolt loosening. Such methods might include the use of double nuts, threaded fastener adhesive, locking clips, locking nuts, as well as combinations thereof. Consideration should be given to the possible need to adjust or tighten the fasteners to account for settling or shrinkage of the deck ties.

8.3.2.2 Ballasted Deck Bridges a.

Timber ballasted decks and precast concrete slab decks shall be anchored to bridge spans with fasteners having total capacity equivalent to that specified for open decks.

b. Cast-in-place concrete decks shall be anchored to steel spans either by shear connectors or by making the bottom of the concrete slab flush with the bottom surface of top flanges of girders or stringers.

8.3.3 ANCHORAGE OF RAIL (2011)2 8.3.3.1 Longitudinal Anchorage of Rail on Bridge Approaches On roadbed approaches to bridges of length over 50 feet, rail shall be box anchored longitudinally at each tie a distance of 200 feet unless otherwise specified by the Engineer. 8.3.3.2 Lateral and Vertical Rail Anchorage Tie plates and spikes manufactured and installed in accordance with the Company’s standard specifications shall be considered adequate as lateral and vertical anchorage of rails to timber ties. 8.3.3.3 Anchorage of Rail to Concrete Slabs, Concrete Ties, or Directly to Steel Spans Such fastening systems are special applications and shall be approved by the Engineer. 8.3.3.4 Longitudinal Anchorage of Conventional Jointed Rail a. 1 2

On open deck bridges, rail anchors shall be installed as specified by the Engineer.

See Part 9 Commentary See Part 9 Commentary

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b. On ballasted deck bridges, rail anchors shall be installed in accordance with the Company’s standard specifications for track not on bridges unless otherwise specified by the Engineer. 8.3.3.5 Anchorage Requirements for Continuous Welded Rail (CWR) without Expansion Joints on Open Deck Bridges For bridges with CWR not longitudinally anchored, the provisions of 8.3.3.5.1 shall apply. For bridges with CWR longitudinally anchored, the provisions of 8.3.3.5.2 shall apply (See Commentary). 8.3.3.5.1 Continuous Welded Rail without Expansion Joints on Open Deck Bridges, Rail Not Longitudinally Anchored Rail may be unanchored on bridges having a total length of 400 feet or less on tangent track and on curved track with curvature less than 1 degree, or as directed by the Engineer, provided there is a rail flaw management program in place. Unanchored rail shall not be placed on individual spans exceeding 300 feet unless rail expansion joints are installed (See Articles 1.2.13 and 8.3.4.2). 8.3.3.5.2 Continuous Welded Rail without Expansion Joints on Open Deck Bridges, Rail Longitudinally Anchored a.

For individual spans of 100 feet or less, rail anchors shall be applied throughout the span at all ties anchored to bridge spans (See Article 8.3.2.1 and Commentary).

b. For individual spans exceeding 100 feet, rail anchors shall be applied at ties anchored to the span in the first 100 feet from the fixed end (See Article 8.3.2.1 and Commentary). c.

Rail anchors and hook bolts or similar fastening of the deck to spans should be placed in accordance with Article 8.3.2.1 (See Commentary).

d. Bolted joints connecting strings of continuous welded rail shall not be located on bridges nor on roadbed approaches within 200 feet of the ends of bridges. e.

1

3

Forces in continuous welded rail may be computed from the following equations: I.F. = 38 WT WDT R.F. = -------------150

4

where: I.F. = internal force in 2 rails, lb; compression for temperature rise, tension for temperature fall R.F. = radial force in 2 rails, lb per foot of bridge; acting toward outside of curve for temperature rise, toward inside for temperature fall W = weight of one rail, lb per yd T = temperature change, degrees F D = degree of curvature

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AREMA Manual for Railway Engineering

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Steel Structures 8.3.3.6 Longitudinal Anchorage of Continuous Welded Rail without Expansion Joints on Ballasted Deck Bridges Rail anchors shall be installed in accordance with the Company’s standard specifications for track not on bridges unless otherwise specified by the Engineer. 8.3.3.7 Longitudinal Anchorage of Continuous Welded Rail with Expansion Joints a.

Rail anchors shall be applied to secure fixed parts of rail expansion joints.

b. Rail anchors shall be applied at the center of rail strings having movable parts of rail expansion joints at the ends.

8.3.4 RAIL EXPANSION JOINTS (1983)1 R(2002) Movement of rail due to changes in temperature or to train action sometimes produces adverse effects. The magnitudes of the movement and of resulting forces are difficult to forecast. Rail expansion joints may be used in order to reduce the likelihood of rail breakage, to relieve rail radial forces where they cannot feasibly be resisted, and to facilitate track maintenance where track and fastenings must be disturbed. 8.3.4.1 Movable Bridge Spans a.

In addition to rail joints that provide for expansion and contraction of the movable span and its rails, consideration shall be given to placing one pair of rail expansion joints immediately off each end of the span.

b. Deck and rails shall be anchored to the movable span as specified by the Engineer to prevent their displacement during opening and closing of the span. 8.3.4.2 Long Individual Bridge Spans For individual simple bridge spans of 300 feet or greater, rail expansion joints shall preferably be installed at or near the expansion end of the span, as specified by the Engineer or, alternatively, rail expansion joints may be installed as specified in Article 8.3.4.4. When rail expansion joints are used at the expansion end of long bridge spans, rail anchors may be installed near the fixed bearings to control creep. 8.3.4.3 Open Deck Bridges on Curves with Continuous Welded Rail Rail expansion joints shall preferably be used for each bridge having total length greater than 50 feet located on curve exceeding 2 degrees. Where feasible, joint location should be off the curve. 8.3.4.4 Number and Positioning of Rail Expansion Joints on Bridges with Continuous Welded Rail a.

Rail expansion joints shall be used in pairs, which shall be installed closely or directly opposite to each other, depending on type of joint used.

b. Where two pairs of joints are used, they shall preferably be located near the center of the bridge. c.

1

Where an even number of pairs of expansion joints is used greater than two pairs, they shall preferably be placed in groups of two pairs, with the fixed parts of one pair connected to fixed parts of the other pair.

See Part 9 Commentary

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Miscellaneous

d. Where an odd number of pairs of expansion joints is used, the odd pair shall preferably be at one end of bridge, and either entirely on or off the bridge. In absence of other controlling conditions, the odd pair shall preferably be at the lower end of a bridge on grade and the remaining pairs shall be placed as in paragraph c. e.

The spacing and design of joints shall be such that the maximum length L, in feet of rail, causing movement through each joint shall be as follows, except that L shall not exceed 1,500 feet. ( J – K1 ) eLT = -----------------------12K 2

EQ 1

where: e = coefficient of rail thermal expansion = 0.0000066 T = temperature range, deg F (140 degrees recommended in the absence of a substantiated value) J = total permissible range of movement in joints, inch K1 = creep allowance, inch (3 inches recommended in absence of a substantiated value) K2 = safety factor (1.5 recommended) For recommended values, formula EQ 1 reduces to L = ( J – 3 )60

EQ 2

L J = ------ + 3 60

EQ 3

1

or

f.

Rail expansion joints shall be assembled in such a manner that they are at the approximate midpoint of the range of movement at a temperature midway between expected extremes.

g.

Design and details of rail expansion joints shall be such as to minimize resistance to expansion and contraction.

8.3.4.5 Rail Expansion Joints in Track with Bolted Rail Joints

4

Where rail expansion joints are used in track having bolted rail joints, consideration shall be given to the possibility and consequences of bolted joint failure and excessive longitudinal movement of rail through the expansion joint. All such installations shall require approval by the Engineer.

8.3.5 MAINTENANCE OF BRIDGES WITH CONTINUOUS WELDED RAIL (1983) R(2002) a.

Suitable measures shall be taken to prevent buckling of track or rails during maintenance operations. The most favorable rail temperatures for such work are those below that of the rail when it was laid. The probability of rail compression resulting from creep and other causes shall be considered.

b. On curved track, the effect of radial forces shall be considered and measures taken to hold the track in line during maintenance operations. Work shall not be done during periods of extreme high or low temperatures.

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Steel Structures

c.

Maintenance operations involving removal of fastenings of rail to ties, or ties to bridge steel shall be carried out in short sections; and, where practicable, on alternate ties in a first phase and on the remaining ties in a second phase.

SECTION 8.4 UNLOADING PITS1 8.4.1 SCOPE AND PURPOSE (1993) R(2002) This section gives recommended practice for the design and detailing of small undertrack structures for handling of materials unloaded through the bottom of a railroad car. Representative detail and data are included to assist industries in preparing plans for submittal to railroads operating on tracks involved and to facilitate a railroad’s consideration of such submissions.

8.4.2 GENERAL (1993) R(2002) a.

Design of supporting beams for unloading pits shall conform to the requirements of Part 1, Design, Part 3, Fabrication and Part 4, Erection, except as modified herein.

b. Design of the pit structure shall conform to the requirements of Chapter 8, Concrete Structures and Foundations. c.

Typical designs are shown in Figure 15-8-5, Figure 15-8-6 and Figure 15-8-7 and design criteria are listed in Article 8.4.3 and Article 8.4.4.

d. Track running rails shall be attached directly, without ties, to supporting beams or rails except in the case of very short spans where the running rails may be adequate to carry wheel loads without supporting beams.

8.4.3 OPERATING LIMITATIONS (1993) R(2002) a.

This section applies to pits located on tracks where speed does not exceed 10 mph.

b. Where train speed exceeds 10 mph, the design requirements of Chapter 8, Concrete Structures and Foundations, Part 2, Reinforced Concrete Design and Part 1, Design, Part 3, Fabrication and Part 4, Erection of this chapter shall apply, and the pit shall be designed accordingly.

8.4.4 LOADS (1993) R(2002) a.

Supporting beams shall be proportioned for the sum of the following loads: (1) Dead load. (2) Live load. (3) Impact load.

b. The pit structure shall be proportioned for the sum of the following loads: (1) Dead load.

1

References, Vol. 78, 1977, p. 90.

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Miscellaneous

(2) Live load, without impact load. (3) Horizontal earth pressure. (4) Horizontal live load surcharge.

1

3

4

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Steel Structures

Figure 15-8-5. Unloading Pit – Four Foot Maximum Span (Sheet 1 of 2) © 2011, American Railway Engineering and Maintenance-of-Way Association

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Miscellaneous

Unsupported Running Rail Maximum Clear Span

Minimum Weight of Rail

1¢ -3²

90 (Note 1)

1¢ -8²

100 (Note 1)

2¢ -1²

110 (Note 1)

2¢ -4²

115 (Note 1)

2¢ -6²

119 (Note 1)

3¢ -0²

131 (Note 1)

Wall Height “H” 4¢ –0² Maximum for Dimensions and Reinforcing Shown. Supported Running Rail (Note 1) Maximum Clear Span

Running Rail

Support Rail

4¢ -0²

90 Minimum (Note 1)

115 Minimum But Not Less Than Running Rail (Note 1)

Note 1: To be used only at discretion of Railroad’s Chief Engineer.

1 General Notes: 1. Spec.: Design, material and workmanship shall be in accordance with Chapter 8, Concrete Structures and Foundations and this chapter. 2. Live Load: Cooper E80 with 28% impact. 3. Concrete shall be proportioned to provide a minimum 28 day compressive strength of 3,000 psi. 4. Reinforcing steel shall be deformed bars conforming to A.S.T.M. A615, Grade 40 or Grade 60. 5. Foundation material shall be adequate to support a load of 2.0 ton per square foot. 6. No rail joints will be permitted over the pit opening. 7. This drawing is intended as a guide in preparing a construction drawing. If pit is to be constructed under traffic, include plans for supporting the track. If pit is located adjacent to an operating track, include sheeting plans to support the operating track. All plans shall be submitted to the railway’s chief engineer for approval. 8. No traffic will be allowed over pit until concrete has reached 2500 psi compressive strength. 9. Pits are to be located on tracks having a maximum speed of 10 mph. 10. Horizontal equivalent fluid pressure on wall from backfill is 30 psf plus 11 feet of live load surcharge. 11. Ground water pressure was not considered in the design and provisions must be made for drainage if necessary. 12. Only new or good quality second hand rail free of all defects shall be used. 13. The reinforcement shown represents a conservative design using safe but not unreasonable loadings. 14. The owner should retain a qualified structural engineer to design a pit for the actual soil conditions at the site. Suggested plan only. Plan must be adjusted to local conditions. Construction plans must be submitted to railroad’s chief engineer for approval.

Figure 15-8-5. Unloading Pit – Four Foot Maximum Span (Sheet 2 of 2)

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4

Steel Structures

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© 2011, American Railway Engineering and Maintenance-of-Way Association

Figure 15-8-6. Unloading Pit – Fifteen Foot Maximum Span (Sheet 1 of 3)

Miscellaneous

Table of Beam Requirements Span Feet 5 or less

Beam

Size of 1 Inch Bearing Plate Inches

Width of 1/2 Inch Stiffeners Inches

Number Interior Diaphram

38.6

W8 ´ 58 HP10 ´ 42

6 ´ 14 6 ´ 16

3 3

0

6´ 6´ 6´ 6´

14 16 16 18

3 3 3 4

0

Required Required Web Area S Inches2 Inches3 4.1

6

4.8

46.4

W8 ´ 67 HP10 ´ 57 W10 ´ 68 HP12 ´ 53

7

5.3

54.2

W8 ´ 67 W10 ´ 77 HP12 ´ 53

6 ´ 14 6 ´ 16 6 ´ 18

3 3 4

1

8

5.7

62.0

W10 ´ 77 HP12 ´ 74

6 ´ 16 6 ´ 18

3 4

1

9

6.0

72.8

W10 ´ 88 HP12 ´ 74

6 ´ 16 6 ´ 18

3 4

1

87.2

W10 ´ 88 HP12 ´ 74 HP14 ´ 73 W14 ´ 74 W16 ´ 57

6´ 6´ 7´ 7´ 7´

16 18 16 16 16

3 4 4 4 3

1

101.9

W12 ´ 96 HP14 ´ 73 W16 ´ 67

6 ´ 18 6 ´ 20 8 ´ 16

4 5 5

1

7´ 6´ 6´ 8´

18 21 21 16

4 5 5 4

1

10

11

6.2

6.7

1

12

7.2

124.5

W12 ´ 106 HP14 ´ 89 W14 ´ 109 W16 ´ 89

13

7.6

148.0

W14 ´ 120 W16 ´ 89 W18 ´ 86

6 ´ 21 7 ´ 18 9 ´ 15

5 4 5

2

14

8.0

171.5

W14 ´ 120 W18 ´ 97

7 ´ 21 8 ´ 18

5 5

2

15

8.3

194.9

W18 ´ 106 W21 ´ 101

8 ´ 18 9 ´ 15

5 5

2

3

4

Figure 15-8-6. Unloading Pit – Fifteen Foot Maximum Span (Sheet 2 of 3)

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Steel Structures General Notes: 1. Spec.: Design, material and workmanship shall be in accordance with Chapter 8, Concrete Structures and Foundations and this chapter. 2. Live Load: Cooper E80 with 28% impact. 3. Structural steel shall conform to A.S.T.M., A36. 4. Concrete shall be proportioned to provide a minimum 28 day compressive strength of 3,000 psi. 5. Reinforcing steel shall be deformed bars conforming to A.S.T.M. A615, Grade 40 or Grade 60. 6. Foundation material shall be adequate to support a load of 2.0 ton per square foot. 7. This drawing is intended as a guide in preparing a construction drawing. If pit is to be constructed under traffic, include plans for supporting the track. If pit is located adjacent to an operating track, include sheeting plans to support the operating track. All plans shall be submitted to the railway’s chief engineer for approval. 8. No traffic will be permitted over pit until concrete has reached 2500 psi compressive strength. 9. Pits are to be located on tracks having a maximum speed of 10 mph. 10. Ground water pressure was not considered in the design and provisions must be made for drainage if necessary. 11. See Figure 15-8-7 for reinforcing steel details. 12. Suggested plan only. 13. Plan must be adjusted to local conditions. 14. Construction plans must be submitted to railroad’s chief engineer for approval. Note “A”: Bolted rail clips may be used as alternate provided there is sufficient flange width and provision is made for loss of section in the holes.

Figure 15-8-6. Unloading Pit – Fifteen Foot Maximum Span (Sheet 3 of 3)

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Miscellaneous

1

3

Notes: 1. Bars A and B are noted in the table. 2. All other bars shall be #5@12 inch centers. 3. End wall bars shall be the same as side wall bars. 4. The reinforcement shown in the tables represents a conservative design using safe but not unreasonable loadings. 5. The owner should retain a qualified structural engineer to design a pit for the actual soil conditions at the site.

4

Work with Figure 15-8-6.

Figure 15-8-7. Unloading Pit – Fifteen Foot Maximum Span Reinforcing Details (Sheet 1 of 2)

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Steel Structures

Span Length – “L” in Feet L

5

H

5

Wall Height – “H” in Feet

6

7

8

6

9

10

11

12

13

14

15

Mark

10

10

10

10

10

10

10

10

10

12

T

11

11

11

11

11

12

12

13

13

13

15

S

#6@6

#6@6 #6@8

A

#5@12 #6@12 #6@9 #7@12 #7@6 #7@6 #8@6 #8@6 #8@6 #9@6 #9@6

B

10

10

10

10

10

10

10

10

10

10

T

11

11

11

11

11

12

12

13

13

13

S

#7@6

A

#5@12 #6@12 #6@12 #7@12 #7@6 #7@6 #8@6 #8@6 #8@6 #9@6

B

12

12

12

12

12

12

12

12

12

T

13

13

13

13

13

13

13

13

13

S

#7@6

A

#5@12 #5@12 #5@9 #6@12 #7@9 #7@6 #7@6 #8@8 #8@6

B

12

12

12

12

12

12

12

12

T

13

13

13

13

13

13

13

13

S

#7@6

A

#5@12 #6@12 #7@9 #7@9 #7@6 #8@8

B

#7@6

#7@6

#7@6

14

14

14

14

14

14

14

T

15

15

15

15

15

15

15

S

#7@6

A

#5@12 #7@12 #7@9 #7@9

B

#7@6 #5@12

10

8

10

#5@12

9

7

16

16

16

16

16

16

T

17

17

17

17

17

17

S

#7@6

A

#5@12 #6@12 #7@12

B

#7@6 #5@12

T and S are inches. Figure 15-8-7. Unloading Pit – Fifteen Foot Maximum Span Reinforcing Details (Sheet 2 of 2)

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8.4.5 UNSUPPORTED RUNNING RAIL (1993) R(2002) a.

The maximum clear span length for unloading pits without supporting beams or rails shall be as shown in Figure 15-8-5.

b. The design span shall be taken as clear span plus 6 inches. c.

No running rail joints shall be permitted over the pit.

d. The top of the concrete pit walls shall be true and level to provide full bearing for the running rails.

8.4.6 RAIL AS SUPPORTING BEAMS (1993) R(2002) a.

The maximum clear span length for unloading pits with rail supporting beams shall be 4 feet. See Figure 15-8-5 for details.

b. Supporting rails shall extend a minimum of 6 inches into the concrete side walls and shall be in place when the walls are poured. c.

No joints shall be permitted in the supporting or running rail over the pit.

d. The running rail shall be attached to the supporting rail with pairs of 7/8 inch hook bolts located at the center of the span.

1 e.

Welding on running or support rails shall not be permitted.

8.4.7 STRUCTURAL SUPPORTING BEAMS (1993) R(2002) a.

This article is applicable to a maximum span length of 15 feet. See Figure 15-8-6 for details. Spans longer than 15 feet shall be designed as bridges in accordance with Part 1, Design, Part 3, Fabrication and Part 4, Erection.

3

b. Running rails shall normally be attached to the supporting beam with pairs of 7/8 inch hook bolts spaced at 2 feet. However, where the width of flange is adequate, rail clips at 2¢ -6² centers may be used in lieu of hook bolts to attach the running rail to the supporting beam. Welding of rails to beams shall not be permitted. c.

The supporting beam shall be provided with end bearing stiffener plates fillet welded to the web and ground to bear against both top and bottom flanges or welded with full penetration groove welds at top and bottom flanges.

d. Beams shall be provided with masonry plates between beams and concrete pit walls. Beams shall be welded to the masonry plates. Should the owner desire, sole plates can be provided between beam and masonry plate. The sole plate shall be welded to the beam flange and may be beveled on the bottom surface from the inside edge to within 1 inch of the center line of bearing. Elastomeric bearing pads 1/4 inch thick under masonry plates are recommended. e.

Two anchor bolts for each masonry plate shall be provided. Anchor bolts shall be 1 inch minimum diameter, swedged, and shall extend 12 inches into the masonry. Anchor bolts may be preset, or drilled and grouted into place after steel is erected.

f.

Interior diaphragms shall be used at a maximum of 6 foot centers. Diaphragms shall be channel sections as deep as the beam will allow.

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g.

End diaphragms of the same section as the interior diaphragms shall be connected to end stiffener plates at each end of the beam. Where ends of the beam are to be encased in concrete, end diaphragms may be omitted.

8.4.8 CONCRETE PIT (1993) R(2002) a.

A minimum of 2 inches shall be provided from edge of bearing plate to face of pit wall.

b. The design and details of the pit structure as shown in Figure 15-8-5, Figure 15-8-6 and Figure 15-8-7 will be adequate for most conditions. Soil borings to determine actual conditions are desirable. Determination of soil conditions prior to the design of the pit is the owner’s responsibility.

8.4.9 CONSTRUCTION DRAWINGS (1993) R(2002) a.

Figure 15-8-5, Figure 15-8-6 and Figure 15-8-7 are intended as a guide in preparing construction drawings and are not themselves construction drawings. Where these details are not considered applicable, alternate details may be submitted. Note that beams shown in table of beam requirements are applicable for details and allowable loads shown. Where additional holes are made in the flange or web for bolted connections or rail clips, or where there is additional dead weight of mechanical equipment or unloading devices, design of beams must be reviewed. A complete construction drawing should show the following: (1) Location of structure relative to existing tracks. (2) Plan, elevation, and sections. (3) Complete details including dimensions, reinforcing, beam details, and cover details. (4) Where pit is to be constructed under traffic, provisions for temporary support of the track shall be included. (5) Where pit is located adjacent to an operating track, provisions for sheeting to support the operating track during construction shall be included.

b. Complete construction plans shall be submitted to the Engineer for approval prior to initiation of construction. Only approved plans shall be used for construction.

8.4.10 APPLICANT’S RESPONSIBILITIES (1983) R(2002) a.

The applicant shall contact the Company in advance to determine the acceptability of the chosen location with respect to movement of rail traffic and to determine requirements for construction, including but not limited to need for falsework to maintain rail traffic, need for sheeting and shoring to protect rail traffic on adjacent tracks and variations in specified loadings (and impact).

b. The applicant shall make adequate provision for disposal of drainage water. c.

The applicant shall obtain permits as required.

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SECTION 8.5 WALKWAYS AND HANDRAILS ON BRIDGES 8.5.1 LOCATIONS (1983) R(2011) Those bridges on which walkways and handrails are required will be designated by the Engineer.

8.5.2 CLEARANCES AND MINIMUM DIMENSIONS (1983) R(2011) Clearances shall not be less than specified in Part 1, Design, Article 1.2.6. A guide to legal requirements in the various states may be found in Chapter 28, Clearances, Section 3.6, Legal Clearance Requirements. 8.5.2.1 Handrails a.

In through structures, handrail need not provide more clearance than the structural members.

b. Top of handrail shall be not less than 3¢ -6² above surface of walkways. An intermediate rail, or rails, shall be provided, with clear space between rails, or between rail and top of walkways, not to exceed 1¢ -9² . c.

The ends of rails shall not overhang terminal posts except where such overhang does not constitute a projection hazard.

8.5.2.2 Walkways a.

1

In general, walkways shall not be less than 2¢ -0² wide and shall extend to the inner face of the handrail. On ballasted deck bridges the ballast may be used as the walkway, or a separate walkway may be provided. On open deck bridges, not more than 2 inches gap shall be allowed between the line of the ends of ties and edge of walkways.

b. On bridges with two or more tracks, walkway may be located between the tracks, without handrails. c.

3

Structural members (such as floorbeam brackets) shall not be considered an obstruction to the walkway.

d. Walkways on bridges over highways or other locations where spillage of ballast or lading is a consideration shall be solid material (i.e. not grating) and shall be provided with a curb or toe board.

8.5.3 LOADS (1984) R(2011)

4

8.5.3.1 Handrails a.

Each railing and its fastening shall be designed for a single load of 200 lb, applied either laterally or vertically, and at any point in the span.

b. Where steel cable is used for railing, sag at middle of any span shall not exceed 2 inches. c.

Posts shall be designed for a single load of 200 lb acting either laterally or vertically, applied at point of attachment of top railing.

8.5.3.2 Walkways a.

Walkways shall be designed to support a uniformly distributed load of not less than 85 lb per square foot.

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b. The walkway deflection under a single concentrated live load of 250 lb applied at midspan, shall not exceed 1/160 of the span length. c.

Where off-track equipment may be driven across the bridge, walkways should be designed for the appropriate wheel loads. Deflection may be disregarded.

8.5.4 MATERIALS (1984) R(2011) 8.5.4.1 Stresses Walkways and handrails may be designed for higher stresses than allowed for members subject to railroad live loading, as approved by the Engineer. 8.5.4.2 Handrails a.

Rails or posts of timber shall have minimum thickness of 2 inches nominal. Rail material shall be surfaced.

b. Rails or posts of structural steel shall have minimum thickness of 1/4 inch. c.

Cable rails shall be of minimum 3/8 inch diameter, 7-wire galvanized steel strand. Cut ends shall be suitably protected to prevent injury to personnel.

d. Posts connected to a structural member and the connection shall be designed to fail under overload without damaging the member. 8.5.4.3 Walkways a.

Walkways shall have a suitable walking surface.

b. Timber walkways material shall have a minimum nominal thickness of 2 inches, with the walking surface rough. Walkway timbers shall be fastened to each support with the equivalent of 2–20d spikes. c.

Structural steel plate used for walkway material shall have a roughened tread surface (checker plate), with a minimum thickness of 1/4 inch.

d. Metal grating used as walkway material shall be of galvanized steel or other corrosion resistant material. Fastenings shall be adequate to prevent longitudinal movement (which may result in loss of bearing).

SECTION 8.6 GUIDELINES FOR EVALUATING FIRE DAMAGED STEEL RAILWAY BRIDGES1 8.6.1 INTRODUCTION (1986) R(2008) The evaluation of a railway bridge after a fire has one primary goal, and that is to determine the ability of the structure to continue to carry railroad loading. To do this, an examination of what has happened to the steel during a fire must be made. The reaction of steel to a fire can be broken down into two areas. The first area

1

References, Vol. 86, 1985, p. 90; Vol. 87, 1986, p. 105.

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consists of temporary changes that occur while the steel is at elevated temperatures, and the second area is made up of permanent changes. It is these permanent changes that are of the most concern.

8.6.2 TYPES OF FIRES (1986) R(2008) A railway bridge may be subject to three basic types of fires: a deck fire consisting of ties and timber guardrail; a brush fire or fire from an adjacent structure; or a cargo fire. A deck fire or brush fire is usually of short duration, and is unlikely to cause serious damage to the bridge except possibly for the stringers supporting the deck. A fire in an adjacent structure or a cargo fire is potentially the most hazardous because of the possible high temperatures developed for a long period.

8.6.3 TEMPERATURE EFFECTS (2008) a.

The temporary changes in steel due to elevated temperatures include decreased strength, decreased modulus of elasticity and increased coefficient of expansion. These temporary effects can, however, combine into the permanent effect of distortion. Table 15-8-1 lists the properties of structural carbon steel relative to temperature. These effects, while temporary, can cause the bridge to collapse during the fire. Table 15-8-1. Properties of Structural Carbon Steel Related to Temperature Temperature

Yield Strength

Tensile Strength

Modulus of Elasticity

Coefficient of Expansion

Atmospheric

100%

100%

100%

100%

400°F

90%

100%

95%

106%

800°F

75%

85%

85%

117%

1000°F

60%

60%

65%

123%

1200°F

35%

30%

55%

129%

1400°F

15%

15%

–

–

1

3

b. Included in the permanent effects on steel due to elevated temperatures are member distortion and decrease in strength. (1) The strength lost by a member due to heating above approximately 1,100 degrees F is only that extra strength imparted to it during rolling. The basic strength of the structural steel is not lost. Finally, if steel is heated to very high temperatures for long enough periods, the surface of the steel will oxidize. This is evidenced by a heavy scaling and pitting and indicates a loss of strength in the steel. The amount of time necessary to oxidize steel is dependent on temperature, with less time being needed at the higher levels of temperature. At 1,200 degrees F, 6 to 7 hours are required. At 2,000 degrees F only approximately one half an hour is needed. While the temperature of a fire may be quite high, it does not necessarily follow that the steel reached that temperature. It takes approximately one hour per inch thickness of steel for thorough heating. (2) Distortion occurs in two basic forms: buckling of small light members and warping or buckling of large heavy members. A small light member such as bracing is constrained at both ends. Heating such a member produces compressive stresses in the member. The associated loss of strength allows buckling to occur, and the decrease in elasticity makes this buckling permanent. A large heavy member such as a girder cannot be uniformly heated. This uneven heating causes warping or buckling. This same effect can cause distortion during welding and is also the principle behind flame straightening or cambering. Distortion can occur after temperatures as low as 450 degrees F and is, therefore, not a precise indication of the maximum temperature reached by the steel during a fire. When steel is heated above its transformation temperature (1,300 to 1,550 degrees F) and quickly

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cooled, it will lose some of its ductility. If steel is heated above approximately 1,100 degrees F and cooled slowly, it will lose part of its as-rolled strength. It is these last two changes, which are not readily discernible, that cause the most concern. However, the quick rate of cooling needed to harden steel is virtually impossible to achieve at a fire site. The use of water from a fire hose is usually insufficient to cause hardening, but may increase the distortion experienced by a member.

8.6.4 HIGH STRENGTH STEELS (1985) R(2008) The comments of Article 8.6.3 on the effect of temperature do not necessarily apply to high strength steels which have achieved their strength through heat treatment. Such steels must be given individual consideration and may require laboratory study.

8.6.5 FASTENERS (1985) R(2008) a.

Fasteners, either rivets or bolts, will begin to lose their clamping force at approximately 600 degrees F. They should be carefully inspected and if there is any indication that the fasteners have been affected by the fire, they should be replaced. This is normally a simple routine, and one that should be followed to ensure long term reliability.

b. Fasteners in connections of distorted members may also be subjected to high tensile forces which can result in popped rivet heads or broken bolts. This condition may occur away from the fire zone. c.

All welds should be visually inspected for signs of distress. In some cases more sophisticated inspection may be warranted.

8.6.6 EVALUATION OF BRIDGE (1986) R(2008) a.

To evaluate a railway bridge after a fire the following data are useful: (1) Maximum temperature reached by the steel. (2) Length of time maximum temperature was maintained. (3) Information on the physical condition of the steel. (a) distortions. (b) scaling, pitting, etc. (c) hardness. (4) Laboratory test results of specimens taken from structure.

b. Items 1 and 2 are usually not available, or if available are only estimates. The information in Item 3 can be obtained by an examination of the steel in the field and is the most important. Item 4 is often impractical within the time frame to restore service but may be conducted later to eliminate any doubts regarding long term service. c.

The most obvious physical change resulting from fire is distortion. While distortion may be grounds for rejection, it is not necessarily an indication of a lessening of the strength of the steel. If a member can be straightened economically, it usually can be reused. A member with only minor distortions may be usable without repair.

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d. Scale will start to form on steel at approximately 900 degrees F. From approximately 900 to 1,000 degrees F the resulting scale will be red in color. A black scale will form from approximately 1,200 degrees to 1,400 degrees F. If oxidation has occurred a heavy dark gray scale will form. It is only this heavy scaling that indicates damage to the steel and is cause for rejection. Such heavy scaling will be accompanied by pitting and loss of section, and is easily identifiable. e.

The maximum temperature reached during the fire may be estimated by testimony of competent observers as to the color of the steel during the height of the fire. Such temperature estimates would be accurate only within the range of a few hundred degrees. Table 15-8-2 may be used to correlate color with temperature. An alternate guide is the Heat-Color Poster available from the ASM International, formerly the American Society for Metals. Table 15-8-2. Color of Steel vs. Temperature Temperature

Color

750°F

Red heat, visible in the dark

900°F

Red heat, visible in twilight

1000°F

Red heat, visible in daylight

1300°F

Dark red

1500°F

Dull cherry red

1800°F

Bright cherry red

1 8.6.7 CONCLUSION (1986) R(2008) a.

In conclusion, if the steel is undistorted, or can be economically straightened, it is generally safe for reuse. The only exceptions are members showing evidence of heavy oxidation, which is usually recognizable, and fasteners. Fasteners will start losing a substantial amount of their clamping force at approximately 600 degrees F and should be thoroughly investigated. Generally speaking, it is advisable to replace any fasteners showing evidence of having been affected by the fire.

b. This conclusion is drawn for the simpler types of railroad bridge structures. If a complex structure having interacting framing, continuity, and/or indeterminate characteristics is involved, the possibility of high locked in tensile stress in restrained elements that have yielded and cooled must be considered. This condition can result in brittle fracture when subsequently exposed to cold weather conditions. It can also subject connections and fasteners to large forces.

8.6.8 REFERENCES (1986) R(2008) References used in this part are found at the end of this chapter. See Reference 27, 75, 108, 112, 141 and 144.

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SECTION 8.7 GUIDE TO THE PREPARATION OF A SPECIFICATION FOR THE CLEANING AND COATING OF EXISTING STEEL RAILWAY BRIDGES 8.7.1 GENERAL (2009) 8.7.1.1 Purpose Generally coatings applied in the shop and field prior to the mid-1980’s contain lead which is now considered to be hazardous material when removed. The methods and materials recommended in this guide meet the existing U.S. Environmental Protection Agency (EPA) requirements and are based on the current technology and research to produce a cost effective, environmentally acceptable steel protection system. The user of this guide is advised to consult current regulatory agency requirements governing any particular project based scope of work and project location. This guide addresses the selection of the surface preparation and coating systems for both shop and field maintenance coating of the structure by total removal and replacement of the existing coating or by spot repair, spot touch-up, or full overcoating. This guide is intended for use in the selection of coating systems to provide atmospheric corrosion protection. Enclosures required for cleaning and coating structures previously coated with lead based coatings are subject to damage from coatings, transportation, erection, wind, etc. and the workers are at risk to lead exposure if proper ventilation and industrial hygiene practices are not followed. Using current technology, the costs of procedures associated with coating removal may be of such magnitude that bridge replacement would be a less expensive option. The best strategy may be to do the minimum maintenance coating necessary to maintain structural integrity and cosmetic acceptability. This guide is written using the Society for Protective Coating (SSPC) philosophy and the references listed therein. Reference to the National Association of Corrosion Engineers (NACE) is only appropriate when SSPC and NACE requirements are exactly the same.

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Miscellaneous 8.7.1.2 Abbreviations a. AASHTO

American Association of State Highway and Transportation Officials

b. ASTM

American Society for Testing and Materials

c. ATP

Acceptance Testing Plan

d. CFR

Code of Federal Regulations

e. DFT

Dry Film Thickness

f. EPA

Environmental Protection Agency

g. FRA

Federal Railroad Administration

h. IH

Industrial Hygienist

i. NACE

The National Association of Corrosion Engineers

j. NIOSH

National Institute of Occupational Safety and Health

k. OSHA

Occupational Safety and Health Adminstration

l. PEL

Permissible Exposure Limit for toxic metals

m. QCP

Quality Control Plan

n. SAE

Society of Automotive Engineers

o. SSPC

The Society for Protective Coatings (Formerly Steel Structures Painting Council)

p. TLV

Threshold Limit Value established for toxic metals

q. VOC

Volatile Organic Compound

1

8.7.1.3 Definitions a.

The term “Company” refers to the railway company or railroad company party to the Contract.

b. The term “Engineer” refers to the chief engineering officer of the Company or his authorized representative. c.

3

The term “Contractor” refers to the coating contractor party to the Contract.

d. The term “Inspector” refers to the inspector or inspectors representing the Company. e.

Refer to Protective Coatings Glossary. Terms from Coating of Industrial Steel and Concrete Structures, Failure Analysis, and Regulations SSPC 00-07 ISBN 1-889060-47-X

8.7.1.4 Reference Standards a.

General: The standards referenced in this guide are listed in the sections that follow. The latest issue, revision, or amendment of the reference standards in effect on the date of invitation to bid shall govern unless otherwise specified.

b. SSPC Standards and NACE Joint Standards Guide 6

Guide for Containing Debris Generated During Paint Removal Operations

Guide 7

Guide for the Disposal of Lead-Contaminated Surface Preparation Debris

AB 1

Specifications for Mineral and Slag Abrasives

AB 2

Cleanliness of Recycled Ferrous Metallic Abrasives

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AB 3

Newly Manufactured or Re-Manufactured Steel Abrasives

PA 1

Shop, Field, and Maintenance Painting of Steel

PA 2

Measurement of Dry Paint Thickness with Coating Gages

PA Guide 4

Guide to Maintenance Repainting with Oil Base or Alkyd Painting Systems

QP 1

Standard Procedure for Evaluating Painting Contractors (Field Application of Complex Industrial Structures)

QP 2

Standard Procedure for the Qualification of Painting Contractors (Field Removal of Hazardous Paint)

RP 87-02 (NACE) Recommended Practices SSPC 00-07

Protective Coatings Glossary. Terms from Coating of Industrial Steel and Concrete Structures, Failure Analysis, and Regulations

SP 1

Solvent Cleaning

SP 2

Hand Tool Cleaning

SP 3

Power Tool Cleaning

SP 5/NACE No. 1

White Metal Blast Cleaning

SP 6/NACE No. 3

Commercial Blast Cleaning

SP 7/NACE No. 4

Brush-Off Blast Cleaning

SP 10/NACE No. 2 Near-White Blast Cleaning SP 11

Power Tool Cleaning to Bare Metal

SP 12/NACE No. 5 Surface Preparation and Cleaning of Metals by Waterjetting Prior to Recoating SP 14/NACE No. 8 Industrial Blast Cleaning TU 4

Field Methods for Retrieval and Analysis of Soluble Salts on Substrates

VIS 1

Guide and Reference Photographs for Steel Structures Prepared by Dry Abrasive Blast Cleaning

VIS 2

Standard Method of Evaluating Degree of Rusting on Painted Steel Structures

VIS 3

Guide and Reference Photographs for Steel Surfaces Prepared by Hand and Power Tool Cleaning

VIS 4/NACE VIS 7 Guide and Reference Photographs for Steel Structures Prepared by Waterjetting c.

American Society for Testing and Materials (ASTM) Standards D 610

Standard Test Method for Evaluating Degree of Rusting on Painted Surfaces

D 2621

Test Method for Infrared Indentification of Vehicle Solids from SolventReducible Paints

D 3359

Test Methods for Measuring Adhesion by Tape Test

D 4138

Standard Test Methods for Measurement of Dry Film Thickness of Protective Coating Systems by Destructive Means

D 4214

Test Methods for Evaluating the Degree of Chalking of Exterior Paint Films

D 4414

Standard Practice for Measurement of Wet Film Thickness by Notch Gages

D 4417

Standard Test Method for Field Measurements of Surface Profile of Blast Cleaned Steel

D 4541

Test Method for Pull-Off Strength of Coatings Using Portable Adhesion Testers

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D 5064

Practice for Conducting a Patch Test to Assess Coating Compatibility

D 5065

Guide for Assessing the Condition of Aged Coatings on Steel Surfaces

d. Federal Standard (Code of Federal Regulations) 29 CFR 1920.55

Gases, Vapors, Fumes, Dusts and Mists Construction Industry Standard

29 CFR 1926.1118 Inorganic Arsenic (Construction Industry Standard) 29 CFR 1926.1127 Cadmium (Construction Industry Standard) 29 CFR 1926.51

Sanitation

29 CFR 1926.55

Gases, Vapors, Fumes, Dust, and Mists

29 CFR 1926.62

Lead (Construction Industry Standard)

8.7.1.5 Determine Requirements for Maintenance Coating Prior to Request for Proposals a.

General: A written description of the structure(s) requiring maintenance coating should be obtained or prepared. The description should include location, dimensions, type of substrate, configuration, process (if applicable), coating history (if known), life expectancy of the structure, and any other pertinent information. Examples of the latter would include proximity to sensitive areas, planned new construction or other activities nearby, proposed time of application for new coating system, and types of exposures (e.g., acid fallout). (See SSPC Publication 94-18, Project Design.) It is usually most economical to consider all structures in a similar condition within a given area for maintenance at the same general time.

b. Hazardous Substance Determination: Laboratory testing, unless previous coating history/specifications are known, shall be performed to determine whether any hazardous elements are present. These elements include but are not limited to lead, cadmium, chromium, and arsenic. OSHA requirements for worker exposure and local agency requirements for disposal with its implied containment should be incorporated into the contract to protect workers and the environment and lessen the potential for claims. SSPC-Guide 6, for containment of hazardous debris, and Guide 7, for classification and disposal of hazardous wastes, provide details relevant to containment and disposal. OSHA regulation 29 CFR 1926.62 details worker protection requirements for lead. (See SSPC publication 94-18, Project Design.) In addition, regional, state, or local regulations may apply and should be identified. c.

Structural Inspection: Coating inspection should be included as part of a general inspection for loss of metal, broken connections, or other structural defects. (1) Degree of Corrosion: Evaluated in accordance with ASTM D 610. The numerical scale ranges from 0 to 10. Rust Grade 10 indicates no rust and Grade 1 represents 50 percent rust. Surfaces with 10 percent or more rust (Grades 4,3,2 and 1) are normally not considered candidates for overcoating, although with the cost of total removal being so high, spot cleaning of structures with a high percentage of rust, with a focus on corroded areas, may be an alternate to total removal. Budget comparisons should be done by the Engineer before a final decision is made. (2) Any areas of severe corrosion, especially crevice corroded joints and connections, should be identified and their dimensions recorded. The depth of corrosion pits should be measured with a pit gage. (3) Replacement of components or the entire structure could be a more effective solution than cleaning, repairing, strengthening, and coating existing components. (See Chapter 15, Section 7.2 for additional information regarding structural inspections.)

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d. Existing Coating Condition: A condition assessment should be planned and conducted on the existing coating systems. The assessment may vary considerably in the extent and detail of information required. Among the types to be considered are: (1) General Overview Coating Survey: In this survey, usually only one or two parameters are rated, (e.g., general condition or rusting). The structure is normally observed from the ground (i.e., without scaffolding). The survey produces, at best, a qualitative rating of the condition (e.g., good, fair, poor). Only the major features of the structure are rated (e.g., a full span of a bridge). This type of survey is usually done in a few hours or less and is suitable for distinguishing severe condition trends. (2) Detailed Visual Inspection: This type of survey also relies exclusively on visual observations, but these are done more systematically than for a general overview survey. Numerous structural elements (e.g., support beams, connections, edges) are separately rated and combined to provide an overall structure coating rating. Often, several condition parameters (e.g., loss of topcoat, cracking, rust staining) and several corrosion parameters (e.g., rusting, blistering, scaling, loss of metal) are recorded. With this survey one can obtain a semi-quantitative rating of the percent of surface deteriorated. This type of survey may assist in the development of preliminary cost estimates for the recoating or overcoating. (3) Physical Coating Testing: Physical testing, visual inspection, and the general survey are often performed simultaneously. Visual inspection gives no information on the film adhesion, thickness, brittleness, or underfilm corrosion. Physical testing is necessary to determine whether the coating can be overcoated or repaired, or whether it is too weak to accept another coating layer. This inspection should be performed prior to specifying the corrective actions and requires direct access to the surface at several locations on the structure. (a) Number of Coats: Tested in accordance with ASTM D 4138. Using a Tooke gage each layer of coating and the thickness of each layer can be observed. (b) Dry Film Thickness: Tested in accordance with ASTM D 5065. The dry film thickness (DFT) may be measured nondestructively using a DFT gage, or destructively using a Tooke gage. The DFT should be measured in a number of locations to obtain averages at each location in accordance with SSPC-PA2. (c) Adhesion: Tested in accordance with ASTM D 3359 (Method A, crosscut adhesion test). It requires some simple tools such as a knife or an adhesion test kit. An “X” is scribed through the coating to the substrate. A specific reinforced tape is applied to the scribe and then removed. The results of the area tested are classified as follows: 5A No peeling or removal 4A Trace peeling or removal along incisions 3A Jagged removal along incisions up to 1/16 inch 2A Jagged removal along incisions up to 1/8 inch 1A Removal from most of the area of the “X” 0A Removal beyond the area of the “X” Tensile adhesion testers (ASTM D 4541) also provide semi-qualitative results. The adhesion rating should also be taken at numerous locations with several readings taken at each location to provide a statistical average.

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(d) Presence of Chlorides: When the presence of chloride or other soluble salts is suspected, the surface should be tested for their presence in accordance with SSPC-TU 4. (e) Existing Finish Coat: If the generic identity of the existing finish coat is unknown, it should be washed with water to remove contamination, permitted to dry, and lightly sanded to obtain a sample for laboratory identification. e.

Coating Options (1) Shop Coating: Under certain situations, it may be advisable to remove components or groups of components and transport them to a temporary or permanent shop facility for cleaning, repairing, and recoating the steel prior to reinstallation. In some cases new steel will be fabricated for retrofitting in the existing structure. Under these circumstances, the recommendations for coating of new steels in Chapter 15, Part 3 shall apply, except that the coating system shall be compatible with the proposed coating system for the existing members that will be coated in the field. (2) Spot Coating: For this option, cleaning and coating are limited to those areas exhibiting coating deterioration or steel corrosion. It is necessary to specify the degree of cleanliness for the corroded areas and areas adjacent to or surrounding the corroded areas. Typically, all loose coating material shall be removed and all corroded areas shall be cleaned to bare steel. The degree and method of cleaning will depend on the surface preparation requirements of the coating system. All prepared areas shall be treated with penetrant or primed and finish coated to blend with the existing coating. (3) Spot Repair and Overcoating: For this option, special attention is required for areas exhibiting coating deterioration or steel corrosion. Typically, all loose coating material shall be removed and all corroded areas shall be cleaned to bare steel. The entire surface to be coated must then be cleaned to remove all contaminants. Where salts from a marine environment or deicing chemicals are present, power washing is necessary and a soluble salt remover may be required. Then all areas of coating removal or bare steel shall be treated with penetrant or primed. Finally the total surface area shall be coated with the overcoat system. (4) Total Removal and Recoat: This option involves complete removal of the existing coating, preparation of the steel substrate to the surface condition specified, and application of a new coating system. When project conditions permit (e.g., deck removal and replacement projects), any or all of the steel members may be removed and work conducted in a permanent or temporary shop environment as noted in (1). (5) Zone Coating: This option involves special treatment of highly vulnerable portions or zones of a structure that may warrant topcoating at more frequent intervals, possibly before the existing coating has started to deteriorate. Spot repairs, as noted in (3), may also be necessary. These zones should be considered for topcoating at intervals of about five years. Typical vulnerable zones would include crevice corroded joints and connections, bearings and up to 5 feet on each side of expansion joints and bottom chords of through trusses.

f.

Demolition, Alteration, Repair or Renovation of Steel Coated With Hazardous Materials (1) General: When it is necessary to either remove, retrofit or widen structures that involve working on steel surfaces that are coated with materials containing hazardous substances (in particular lead based coatings), the following provisions shall be satisfied. (a) Cutting or Welding Steel: Prior to cutting or welding steel coated with hazardous materials, a width of at least 6 inches from the cut or weld, and on all sides of the subject work (cut or weld), shall be cleaned of the hazardous coating to a condition equivalent to SSPC - SP2, Hand Tool Cleaning, or SP3, Power Tool Cleaning. © 2011, American Railway Engineering and Maintenance-of-Way Association

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(b) Removal and Handling of Hazardous Materials: During the removal of the hazardous material, and thereafter, the provisions of Article 8.7.5.4 of this guide shall be satisfied. (c) Worker Protection: This portion of the document will establish the purpose for worker protection (safety and health hazards, including lead); “acceptance criteria” for pre-bid, preconstruction, and construction phase submittals; and guidelines on the areas that must be addressed in the Contractor’s resulting program. This section should be written in “performance” language so that goals and objectives are established while the means of compliance are left to the Contractor. 8.7.1.6 Recommended Project Requirements a.

The Engineer shall arrange for project documents to contain a Project Location Map: The project documents should contain a map that clearly defines the location and extent of the bridges that are to be coated and their relationships to other site features. Potential bidders should be required to visit the project site as a condition of their bids.

b. Project/Site Conditions (1) Ordinarily, an actual visit to the structures to be coated should be required prior to bidding. (2) Pre-Bid Meeting: All prospective or qualified bidders should be invited to attend a meeting with the owner’s representative to review the bid package. This review would normally include an explanation of the surface cleaning and the application requirements, the nature of the structure, its condition, access to the structure, special restrictions (e.g., on blast cleaning safety requirements), and answers to any questions the Contractors might have. For major and critical projects, pre-bid attendance is mandatory because it minimizes problems. c.

Protection of Surrounding Property and the Public (1) Protect adjacent properties, landscaping, watercourses and the public from any damage due to operations. (2) The Contractor shall provide flagmen to protect vehicular and pedestrian traffic during his operations at the time when his forces or equipment could endanger such traffic. (3) The Contractor shall be held responsible for any damage to vehicles and damage and injury to pedestrians and occupants of vehicles resulting from his operations or the operating of equipment by others.

d. Maintenance of Traffic: The number and type of trains per day and the anticipated work windows should be communicated to the prospective bidders. Passenger train movement usually require special attention. All traffic controls, detours, protection, etc. required shall be determined by communication with the appropriate authority, and complying with these requirements shall be the responsibility of the Contractor. e.

Lighting Equipment The Contractor shall be required to: (1) Maintain as fully operational throughout the project all existing navigational and anti-collision lighting systems that are attached to the structure. If existing lighting will be concealed, install © 2011, American Railway Engineering and Maintenance-of-Way Association

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temporary lighting. A Navigational Lighting Plan may need to be submitted for approval to the waterway authority. (2) Make all efforts to maintain existing aerial, roadway, and parking lot lighting, or provide suitable substititions as approved by the Engineer. (3) Maintain light intensity inside containments, by natural or artificial means, at a minimum of 20 foot-candles on the surface preparation and coating activities. Maintain a minimum of 50-foot candles at the surface for inspection activities. Provide auxiliary lighting as necessary. Use explosive-proof lighting. f.

Protection of Drainage Systems The Contractor shall be required to: (1) Protect storm sewers and drains from debris from project activities. Keep all protective systems clean and operational throughout the project. At the end of each shift, at a minimum, remove all visible debris from the protective devices or from areas where rain water could carry the debris into drains or storm sewers. Conduct more frequent cleaning as directed by the Engineer. (2) Identify the methods that will be used to route run-off from the existing deck drains through the containment enclosure prior to construction. Do not close any bridge deck drains without the explicit approval of the Engineer.

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8.7.1.7 Special Safety and Environmental Requirements a.

Personal Protective Equipment and Hygiene Facilities (1) At each site the Contractor shall provide all personal protective clothing and equipment needed to protect Contractor workers, railway company employees and other agents that have permission or authority to visit the site.

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(2) Provide climate-controlled decontamination facilities. (a) Supply the number of facilities as dictated by 29 CFR 1926.51, site conditions, the Contractor’s sequence of operations, and as approved by the Contractor’s IH and the Engineer. (b) Provide facilities which contain a “clean” area where workers can remove and store their street clothing when they arrive on the site, a shower room with hot and cold running water, soap, and clean towels; and a “dirty” area where workers can remove their work clothing at the end of their work shift. The “clean” area and the “dirty” area shall each have a separate entrance. (3) Provide all water required for drinking and hygiene purposes. b. Enclosure Ventilation: Provide ventilation equipment for containment areas in accordance with the approved containment drawings. c.

Personal Vehicles: Provide a parking area for employee cars where they will not be contaminated with lead. Relocate the parking area as necessary throughout the course of the project.

d. Control Zones (1) Establish zones (regulated areas) around project locations or activities that might generate airborne emissions of lead, cadmium, chromium, inorganic arsenic, or other toxic metal in excess of the © 2011, American Railway Engineering and Maintenance-of-Way Association

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Regulatory Action Level (e.g., coating removal and cleanup locations, dust collector staging areas, waste storage areas). (2) Use ropes, ribbons, tape, or other visible means to define the areas. Prohibit entrance into the regulated areas by unprotected or untrained personnel to ensure that they are not exposed to toxic metals from project activities. (3) Use signs that are a minimum of 8-1/2 inches by 11 inches in size with black block lettering on a white, yellow or orange background. Do not use caution ribbons as a substitute for signs.

8.7.2 SURFACE PREPARATION (2009) 8.7.2.1 General a.

Introduction: Surface preparation is the most critical procedure for successful performance of a coating system. Surface preparation consists of cleaning the bare steel or previously coated surface. It includes establishing an appropriate profile of bare steel or an acceptable surface condition of the previously coated surface. Cleaning and surface profile are both critical to the performance of the coating system. Cleaning the surface includes removing by whatever means necessary all loose materials, soluble salts, oil, grease, dirt, dust, and any other contaminants that will adversely affect the adhesion of the coating to the surface, coated or not, and may include power washing the entire structure. Ensuring that recontamination does not occur, such as from airborne dusts, is also critical to a successful project.

b. Preparation Methods and Specifications (1) Methods: Cleaning of surfaces to be coated may consist of use of hand or power tools, power washing, water jetting, use of solvents, abrasive blasting or a combination thereof, to remove contaminants and establish an acceptable profile. (2) Surface Preparation Specifications (a) Solvent Cleaning - SSPC-SP1 (b) Hand Tool Cleaning - SSPC-SP2 (c) Power Tool Cleaning - SSPC-SP3 (d) White Metal Blast Cleaning - SSPC-SP5 (e) Commercial Blast Cleaning - SSPC-SP6 (f) Brush-Off Blast Cleaning - SSPC-SP7 (g) Near-White Blast Cleaning - SSPC-SP10 (h) Power Tool Cleaning to Bare Metal - SSPC-SP11 (i) Surface Preparation and Cleaning of Metals by Waterjetting Prior to Recoating - SSPCSP12/NACE No. 5 (j) Guide and Reference Photographs for Steel Structures Prepared by Dry Abrasive Blast Cleaning SSPC-VIS-1

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(k) Guide and Reference Photographs for Steel Surfaces Prepared by Waterjetting - SSPC-VIS4/NACE VIS-7 c.

Abrasives (1) Abrasives used shall be free of oil, moisture, hazardous substances (i.e., lead, chromium, mercury, etc.) and corrosive constituents (i.e., chlorides, sulphates, salts, etc.). Non-steel abrasives shall be in accordance with SSPC-AB1, “Specifications for Mineral and Slag Abrasives.” Abrasives with “free” silica contents in excess of 1 percent shall not be used. (2) Surface profile, as defined in d(2) below, is critical to coating system performance. It must be controlled at the time it is produced; i.e., when the blasting work is conducted. This can be accomplished by controlling the range of particle size and shape of the abrasive used for blasting. (3) When using automated recycling blasting equipment with steel shot or grit, it is important to consider that a working mix is developed through use, then maintained by addition of suitable quantities of steel abrasive of the correct size range. This mixture of sizes is commonly called the work mix. It is important to emphasize that this is indeed a mixture of a range of particle sizes, shape and hardness that is necessary to produce the correct profile. Larger particle sizes are suitable for removing heavy build-ups of mill scale or rust. Smaller size ranges increase productivity of removal of corrosion products through an increased number of impacts. (4) When using abrasives, the “right mix” can be obtained through consultation with the abrasive supplier.

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(5) Steel shot/steel grit abrasives, with maximum recycling, are strongly recommended when blasting steel. When recycled, the abrasives shall be visibly cleaned to meet SSPC AB 2 Cleanliness of Recycled Ferrous Metallic Abrasives specifications. d. Surface Profile (1) Surface profile for steel surfaces shall be obtained using abrasives or equipment meeting the requirements herein. Where repairs to previously applied coatings are required, the proper surface condition of the repair area shall be obtained by power tool cleaning, spot-blasting or other acceptable means. (2) Surface profile is measured as the difference between the average depth of the bottom of the pits to the average tops of the highest peaks created by the blasting. (3) The profile is dependent upon the size, type, and hardness of the abrasive, the angle of impact and hardness of the surface. (4) Durability of Bridge Coating Systems: Too great a profile can result in inadequate coverage of the peaks by the initial application of the coating system leading to premature rust-through of the coating system. For most coatings up to about 8 mils thickness, a surface profile of 1 mil minimum to 3 mils maximum is adequate for new surfaces (note: all references to coating film thickness are based on Dry Film Thickness (DFT) measurements). For maintenance coating, actual profiles may be substantially greater due to pitting caused by corrosion. Selection of a coating system must consider the actual profile present. The user is advised to follow the recommendations of the coating manufacturer for a particular product. (5) Surface profile measurements shall be determined in accordance with ASTM Specification D4417, Standard Test Method for Field Measurements of Surface Profile of Blast Cleaned Steel. Method A, B, or C may be used. Method A is a visual comparison between the blasted surface and a standard. © 2011, American Railway Engineering and Maintenance-of-Way Association

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Method B entails actual measurement of the depth of profile and determining the authentic mean. Method C involves use of a composite plastic tape that is impressed on the surface to form a reverse image of the profile. The peak-to-valley height is then measured with a micrometer. 8.7.2.2 Total Removal of the Existing Coating a.

General (1) Surface preparation of coated surfaces may involve specific collection, containment and disposal requirements of materials as detailed in Articles 8.7.5.4, 8.7.5.5, and 8.7.5.6. (2) Where the surface is contaminated with marine salts, deicing chemicals or other contaminants, the surface to be coated should be washed or, if necessary, power washed to remove all contaminants before any other cleaning operations are begun. Surfaces should be tested to insure all salts have been removed. (3) At the beginning of the surface cleaning and preparation stage of the project, the coating applicator shall clean and prepare a minimum 2 foot by 2 foot area on the existing structure to demonstrate that the proposed methods will obtain the specified surface preparation requirements. The test area shall include both portions of bare steel and exposed portions of all existing coatings. This area shall be preserved during the preparation stage for reference purposes. (4) The surface of each coat to receive a subsequent coating shall be clean, dry and prepared in accordance with the manufacturer’s recommendations. (5) At a minimum the surface preparation shall satisfy the coating manufacturer’s recommendations. (6) Re-Cleaning: Prepared surfaces shall be coated before any visible rusting occurs and, preferably, within 24 hours after preparation. The occurence of contamination from any source shall be cause for requiring re-cleaning of the surface.

b. Cleanliness (1) Steel surfaces to be coated shall be free of oil, dirt, dust, soluble salts or any other contaminant that will affect the adherence of the coating and shall conform to the required surface preparation specification. When blast cleaning is used to prepare the surface, the compressed air used to propel the abrasive shall be tested periodically to insure it is free of oil and moisture, and is a sufficient volume and pressure to clean the surface in a productive manner to the required profile. (2) For inorganic zinc prime coatings, surfaces shall be cleaned as specified by the coating manufacturer but not less than SSPC-SP10. For other primer coats, the surface should be prepared as per the coating manufacturer’s recommendations. c.

Surface Profile Surfaces shall be prepared to have a profile as recommended by the manufacturer or specified herein, whichever is the more stringent.

d. Abrasives Abrasives shall be in accordance with the following specifications: (1) Non-metallic - SSPC AB 1

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(2) Metallic - SAE J27 or SSPC AB 3 e.

Surface Defects (1) Prior to applying coatings, surface defects of bare steel or previously coated surfaces shall be repaired to an acceptable condition that will not affect adhesion of the coating. Surface defects, including weld spatter, burrs, slivers, etc., shall be repaired. (2) Repaired surfaces shall have a profile equal to the specifications or as required by the manufacturer, whichever is the more stringent. No matter what method is used to reestablish the profile, the remaining surfaces shall be cleaned as necessary to remove dust or other contaminants generated by the repair operation.

8.7.2.3 Maintenance of Existing Coating a.

Refer to Article 8.7.2.2a for existing structure surface preparation caveats and minimum requirements.

b. Spot Cleaning for Spot Coating (1) Where only spot cleaning of corroded areas is specified, all areas of loose coating shall be removed and the bare steel cleaned to the condition specified or required by the manufacturer and equivalent to the SSPC Standards SSPC SP-1, Solvent Cleaning, SP-6 for abrasive cleaning, SP-2 for hand tool cleaning, SP-3 for conventional power tool cleaning, and/or SP-11 for special power tool cleaning, SSPC SP-12 WJ4 - High Pressure Water Cleaning or SSPC SP-12 WJ3 - Ultra-High Pressure Water Jetting. (2) Primers requiring a bare metal profile may be cleaned by abrasive blast cleaning to SSPC-SP 6 or by needle guns and rotary peening tools to SSPC SP-11. Care must be exercised when spot blasting to avoid damaging the intact coating around the blasting areas. This may require use of low-angle blasting and small particle size abrasives. Interfaces (edges) between the existing intact coating and the cleaned area must be feathered to provide a smooth tightly adhered edge for spot priming. The bare steel areas shall have an ideal surface profile of 1 mil to 3 mils. However, corroded areas will generally be rougher than this, which must be considered in selection of the coating system to prevent early rust-through at the profile peaks.

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(3) Coating that is to remain in place around the corroded areas shall be thoroughly cleaned by washing and roughened, if necessary, by sandpaper or power tools to insure adhesion to the new coating.

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Cleaning for Overcoating Damaged or corroded areas of the existing coating shall be prepared in accordance with Paragraph a. The surface of areas with intact coatings shall be thoroughly washed to remove all contaminants that will adversely affect coating adhesion. Surface preparation procedures may need to be modified to prevent early rust breakthrough. Roughening of the entire surface by sanding, brush-off blasting (SSPC-SP7), or power tools may be necessary to achieve proper adhesion.

d. Zone Cleaning Intact coatings in zones of the bridge specified to be coated shall be prepared in accordance with Paragraph c and the manufacturer’s recommendations. Deteriorated areas shall be prepared in accordance with Paragraph b. Where total removal of the existing coating system is specified, surface preparation shall be in accordance with Article 8.7.2.2.

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8.7.3 APPLICATION (2009) 8.7.3.1 General a.

Apply coatings in accordance with contract requirements, SSPC-PA 1, and the manufacturer’s instructions. In case of conflict, the most stringent requirements will govern.

b. The applicator or a designated representative is required to conduct and document an on-going quality inspection of the coating. 8.7.3.2 Delivery, Handling and Storage a.

Conformance certificates and product data sheets shall be obtained from the manufacturer or material supplier upon receipt of materials.

b. Inventory control must be utilized to ensure that components are used within the shelf life prescribed by the manufacturer. The coating batch numbers from the containers, the amount and type of thinner used, along with the date applied shall be recorded in the application log. c.

Storage temperatures of coating materials are to be recorded daily and verified for conformance with the coating manufacturer’s product data sheet.

8.7.3.3 Weather Limitations a.

Unless otherwise authorized by the Engineer, coating shall not be applied when: (1) Surface and air temperatures are below 40 degrees F or when temperature is expected to drop to 40 degrees F (4 degrees C) before paint is dried. Follow the manufacturer’s recommendations if more stringent. (2) Temperature of the steel surface to be coated is less than 5 degrees F above the dew point temperature. (3) Fog or mist occur at the site; it is raining or snowing; there is danger of snow or rain. (4) Temperature of the steel surface is over 105 degrees F (40 degrees C). (5) Relative humidity is above 85 percent. (6) Previous coats are not thoroughly dry. (7) Sustained wind speeds of 30 mph or more that could cause the release of waste material to the surrounding environment are forecast. All work activities should be stopped and the containment area immediately cleaned of waste materials.

b. Any coating that is exposed to unacceptable conditions (e.g., rain or dew, freezing temperatures) prior to adequate curing shall be removed and replaced. 8.7.3.4 Mixing a.

Verification shall be made to ensure that the coating to be mixed has not exceeded its shelf life.

b. Ingredients in the container are to be mechanically mixed before use to ensure breakup of lumps, complete dispersion of settled pigment, and uniform composition. © 2011, American Railway Engineering and Maintenance-of-Way Association

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c.

Mix the coating often enough during application to keep the pigment in suspension and the composition uniform.

d. The mixing or keeping of coating in suspension by means of an air stream bubbling under the coating surface should not be permitted. e.

Where a skin has formed in the container, the skin shall be cut loose from the sides of the container, removed and discarded. If the volume of such skin is more than 2 percent of the remaining coating, the coating shall not be used.

f.

Coatings shall not be thinned unless approved by the coating manufacturer and the Engineer. If thinning is required and authorized, only those steps, brands, and amounts of thinner stipulated by the coating manufacturer shall be used. Compliance with VOC limits shall be observed after thinning.

g.

Coatings shall always be mixed in the original pail or clean pails.

8.7.3.5 Equipment a.

General: The coating shall be applied by brushing, rolling or spraying, or a combination of each. In places of difficult access, sheepskins or daubers shall only be used when no other method is practical.

b. Spray Application (1) Equipment shall be provided and maintained that is suitable for the intended purpose, capable of properly atomizing coatings to be applied, and equipped with suitable pressure regulators and gages.

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(2) Traps or separators shall be provided to remove oil and water from compressed air and shall be drained periodically during operations. (3) Coating ingredients shall be kept properly mixed in spray pots or containers during coating application either by continuous mechanical agitation or by intermittent agitation as frequently as necessary.

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(4) Coating shall be applied in a uniform layer, with overlapping at edge of spray pattern. (5) Runs or sags shall be brushed out immediately. (6) Brushes shall be used to work coating into crevices and blind spots which are not adequately coated by spray. In areas not accessible to a spray gun, brushes, daubers or sheepskins shall be used. (7) Air Spray (a) The air caps, nozzles, and needles shall be those recommended by the manufacturer of the material being sprayed and the equipment being used. (b) Traps or separators shall be provided to remove oil and condensed water from the air. The traps or separators shall be of adequate size and shall be drained periodically during operations. The air from the spray gun impinging against a clean surface shall show no sign of condensed water or oil. The pressure on the material in the pot, and of the air in the gun, shall be adjusted for optimum spraying effectiveness. The pressure on the material in the pot shall be adjusted when necessary for changes in elevation of the gun above the pot. The atomizing air pressure at the gun shall be high enough to properly atomize the coating, but not so high as to cause excessive fogging of coating, excessive evaporation of solvent or loss by overspray.

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(8) Airless Spray (a) Fluid tip shall be of proper orifice size and fan angle, and the fluid control gun of proper construction, as recommended by the manufacturers of the material being sprayed and the equipment being used. Fluid tips shall be of the safety type with shields. (b) The air pressure to the coating pump shall be adjusted so that the coating pressure to the gun is proper for optimum spraying effectiveness. This pressure shall be sufficiently high to properly atomize the coating. Pressures considerably higher than those necessary to properly atomize the coating should not be used. (c) Spraying equipment shall be kept clean and shall utilize proper filters in the high pressure line so that dirt, dry coating, and other foreign materials are not deposed in the coating film. Any solvents left in the equipment shall be completely removed before applying coating. (d) Airless coating spray equipment shall always be provided with an electric ground wire in the high pressure line between the gun and the pumping equipment. Further, the pumping equipment shall be suitably grounded to avoid the build-up of any electrostatic charge on the gun. The manufacturer’s instructions are to be followed regarding the proper use of the equipment. c.

Roller Application (1) Roller application may be used on flat or slightly curved surfaces and shall be in accordance with the recommendations of the coating manufacturer and roller manufacturer. Paint rollers shall be of a style and quality that will enable proper application of coating having the continuity and thickness required in Section 6.7 and 6.8 of SSPC-PA 1. (2) Roller application should not be used on irregular surfaces such as rivets, bolts, crevices, welds, corners, or edges, unless otherwise specified. When permitted, however, the coating applied by roller on these surfaces shall be subsequently brushed out to form a continuous and unbroken film.

d. Brush Application (1) Coating shall be worked into all crevices and corners. Spray, daubers, or sheepskins shall be used on surfaces not accessible to brushes. (2) Runs or sags shall be brushed out. (3) A minimum of brush marks shall be left in the applied coating. 8.7.3.6 Quality Assurance Inspection a.

The Company shall have the right, but without obligation, to inspect all phases of the work to determine that it is in conformance with the requirements of the specifications. The inspection shall be coordinated and facilitated as required, including allowing ample time for the inspections and access to the work. Inspections may include, but are not limited to, surface preparation, pre-coating cleanliness, coating application, dry film thickness, film appearance and continuity, and adhesion. Subsequent phases of the work shall not proceed until the preceding phase has been approved by the Company.

b. The inspection by the Company in no way relieves the Contractor of the responsibility to comply with all requirements as specified in the contract and to provide comprehensive inspections of its own to assure compliance with the approved quality control inspection plan.

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c.

Until final acceptance of the coating system, all equipment and instrumentation needed to inspect all phases of the work shall be furnished by the Contractor.

8.7.3.7 Time for Application a.

No coating shall be applied until the preceding coat has dried. The coating shall be considered ready for recoating when the first coat is firm and tack free and the coating is within the recoat window specified by the coating manufacturer.

b. The maximum practical time shall be allowed for coating to dry before recoating. Some coatings may be too hard for good adhesion of subsequent coats; these shall be recoated within the time period in accordance with the manufacturer’s instructions. If not recoated within the specified time, the previously applied coatings shall be roughened prior to recoating. c.

No coating shall be force dried under conditions which will cause checking, wrinkling, blistering, or formation of pores, or which will detrimentally affect the protective properties of the coating.

d. No drier shall be added to coatings on the job unless specifically called for in the manufacturer’s instructions. e.

The coating shall be protected from rain, condensation, contamination, snow, and freezing until dry to the fullest extent possible.

f.

No coating shall be subject to immersion before it is thoroughly dried and cured.

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8.7.3.8 Thickness and Color a.

To the maximum extent possible, each coat shall be applied as a continuous film of uniform thickness, free of pores. Any thin spots or areas missed in application shall be recoated and permitted to dry before the next coat is applied.

b. Each coat shall be provided in a contrasting color to distinguish it from previously applied or existing coats. Coating shall be delivered ready mixed to approved tints and colors. Construction site tinting shall not be permitted. c.

Each coat shall be applied at the proper consistency in a workmanlike manner to assure thorough wetting of the substrate or underlying coat to achieve a smooth, streamline surface relatively free of spray, overspray, and orange peel. Shadow through, pinholes, bubbles, blisters, fish eyes, skips, misses, lap marks between applications, or other visible discontinuities in any coat are unacceptable and must be repaired. Runs or sags may be brushed out while the material remains wet.

d. All surfaces shall be thoroughly coated with special attention to hard-to-reach areas and irregular surfaces such as lacing bars. When coating these complex configurations, the material shall be applied from multiple directions to assure complete coverage. e.

If the coating system has an active penetrating sealer designed for crevice corroded joints and connections and for gaps around rivets and bolt threads, it should be applied as per the manufacturer’s instructions or as specified by the Engineer.

f.

If the system has a rust penetrating sealer designed to bind up the rust before coating, a full stripe coat of the rust penetrating sealer shall be applied to all edges, corners, welds, crevices, rivets, bolt heads, and other surface irregularities before a full wet coat is applied. The stripe coat of the intermediate coating material shall be applied prior to the application of the full intermediate coat. The stripe coat shall

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extend a minimum of one inch from surface edges using a color that contrasts with previously applied primer layers. g.

Wet film gages shall be used in accordance with ASTM D 4414 to verify the thickness of each film coat at the time of application.

h. Special attention shall be given to assure that surfaces such as edges, corners, crevices, welds, and lacing bars receive a dry film thickness equivalent to that of flat surfaces. i.

The thickness of each coat shall be measured using non-destructive dry film thickness gages compatible with the coating system used. Comply with SSPC-PA2 for the calibration and use of magnetic gages and the frequency of thickness measurements. Spot readings both 20 percent above and 20 percent below the specified thicknesses are permitted, provided the average thicknesses are within the specified tolerances.

j.

An additional coating of the same type shall be applied to areas of insufficient thickness. Care shall be used during application to assure that all repairs blend in with the surrounding surfaces.

k. Unless directed otherwise by the Engineer in writing, excessive coating thicknesses shall be removed and the affected coat(s) reapplied. l.

All coats shall be applied in such a manner as to assure that they are well adhered to each other and to the substrate. If the application of any coat causes uplifting of an underlying coat or if there is poor adhesion between coats or the substrate, the coating shall be removed in the affected area to the adjacent sound, adherent coating and the material reapplied.

m. If adhesion is suspect, adhesion tests shall be conducted in accordance with ASTM D 3359 or ASTM D 4541 as directed by the Company, and all test areas shall be repaired. The acceptance criteria for the testing will be established by the Company and the coating manufacturer. All defective coating as identified by the herein specified testing shall be replaced. 8.7.3.9 Damaged Areas a.

Surface Preparation of Localized Areas (1) Localized damage, corrosion, and unacceptable coatings shall be repaired. (2) The surface shall be prepared by solvent cleaning in accordance with SSPC-SP 1 followed by power tool cleaning. A solvent that is acceptable to the manufacturer shall be used. (3) In areas previously blast cleaned to SSPC-SP 6 or SP 7, if the damage exposes the substrate, all loose material shall be removed and the steel prepared in accordance with SSPC-SP 11. (4) In areas originally prepared by methods specified to remove loose material or if the substrate is not exposed in those areas previously blasted, all loose material shall be removed and the surface prepared in accordance with SSPC-SP 2 or SP 3.

b. Surface Preparation of Extensive Areas (1) Extensive areas of damage or unacceptable coatings shall be repaired. (2) The surface shall be prepared by blast cleaning. The Company will stipulate the degree of blast cleaning required based on the nature of the defect.

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(3) Extreme care shall be used to avoid damage to the surrounding coating due to overblasting. c.

Feathering of Repair Areas (1) When the bare substrate is exposed in the repair area, all coats of the system shall be applied to the specified thickness. (2) When the damage does not extend to the bare substrate, only the affected coats shall be applied. (3) The thickness of the system in overlap areas shall be maintained within the specified total thickness tolerances.

8.7.3.10 Protection of the Public and Work a.

Unless approved by the Company in writing, all coats shall be applied within an enclosure. The enclosed environment shall be maintained within the temperature limits specified by the coating manufacturer during application and drying.

b. Continuous ventilation shall be provided during all coating and drying activities to evacuate the solvent fumes, to maintain a safe working environment, and to facilitate the evaporation of the solvents for proper curing of the coating. c.

When the coating enclosure is not weather-tight, the coating shall not be applied when the National Weather Bureau, or other agency approved by the Engineer, forecasts precipitation which would commence prior to the drying of the coating system.

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8.7.3.11 Coating System Requirements Before and After Shutdowns a.

When the coating operations are to be concluded for shutdowns, all coated surfaces must have received the full intermediate and finish coats.

b. The coating shall be terminated with “tie-in” areas consisting of a 6 inch step back of each successive coating layer scheduled to be applied. c.

Prior to completing work for the shutdown, the area being coated shall be “squared up” so that the ending point is not visually apparent. Individual members shall be complete or work stopped at a point such as the end of an individual member or a gusset plate. Work shall be completed such that the squared areas are no farther apart than two panel points (e.g., coating work above a bridge deck cannot finish more than two panel points ahead or behind deck coating work).

d. Upon resumption of operations after shutdown, adjacent surfaces shall be sufficiently roughened and the 6 inch bands of the exposed previously applied coating system prepared. e.

When coating the adjacent surface with the full coating system, the coating layer being applied shall be overlapped at the tie-in area only at the corresponding step back layers established when coating was previously terminated.

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8.7.4 COATING SYSTEMS (2009)1 8.7.4.1 General a.

Coatings include paints, penetrating sealers, galvanizing and metalizing. Coatings are used to protect steel structures from deterioration due to environmental effects and for cosmetic appearance. Galvanizing is a shop applied procedure and there are piece size limitations. Metalizing can be field applied but requires specialized equipment and procedures. Although not required, galvanizing and metalizing can be overcoated with paints for enhanced appearance and added protection.

b. Paint coatings basically consist of a pigment and a vehicle. Pigments generally contribute to the coating qualities such as color, hiding and rust inhibition of the dried film, while the vehicle or resin provides the delivery system for the pigment and the overall resistance characteristics of the film. c.

All coats of the coating system shall be compatible coatings of the same manufacturer.

8.7.4.2 Coating Selection a.

The Engineer defines the method of coating failure which exists on the project structure(s). The Engineer establishes a minimum performance standard for the proposed systems with prequalification criteria. These criteria can be based on existing standards, or the Engineer can develop criteria based on his specific requirements using the Company’s own personnel or by contracting with a coatings research and consulting firm for assistance. The Engineer then makes this information available to the coating manufacturers and Contractors. The Engineer may ask that any system which the coating manufacturer/Contractor applicator proposes be backed by a performance warranty which particularly addresses the failure modes present on the structure. The warranty should include both material and labor. A minimum warranty period of 5 years is suggested.

b. The selection of the coating system often involves two phases: selection of the generic system (e.g., zincrich/epoxy/polyurethane), followed by selection of proprietary materials for this generic system. c.

Selection of the system previously used should be considered for complete recoating strategies, if it performed well in the past. However, environmental or health restrictions may prevent its use. Factors to consider when selecting a coating system for complete recoating include: (1) Service history under similar conditions (2) Application under (potentially adverse) field conditions (3) Application to structural configurations, often from locations that are difficult to access (4) Complexity of requirements for field mixing (5) Acceptable times for drying, overcoating, or exposure to rain or cold (6) Documented durability and protection afforded in specific exposure environments (7) Ease of repair and touch up (8) Cost of materials and application

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(9) Track record and reliability of supplier (10)Capabilities and qualifications of the Contractor (11)Potential environment, safety, or health hazards of coating materials 8.7.4.3 Materials/Systems a.

Penetrants for treating crevice corrosion and pack rusted joints that cannot be cleaned are as follows: (1) Low molecular weight epoxies (2) Moisture cured urethanes (3) High Ratio Co-Polymerized Calcium Sulfonates

b. Coatings used as primers for new steel or existing steel with coating totally removed are as follows: (1) Alkyds (2) Modified Alkyds (a) Vinyl Alkyds

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(b) Silicone Alkyds (c) Calcium Sulfonate Modified Alkyds (3) Zinc-Rich Coatings - 3 coat system (4) Moisture-Cured Urethanes

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(5) Epoxy Coatings (6) Epoxy Mastic Coatings (7) Water Borne Acrylic Coatings

4 (8) High Ratio Co-Polymerized Calcium Sulfonates (9) Galvanizing (10)Metalizing (11)Polyurea Coatings c.

Coatings for Overcoating Existing Coatings and Stable Substrates are as follows: (1) Alkyd Coatings (2) Modified Alkyds (a) Vinyl Alkyds

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(b) Silicone Alkyds (c) Calcium Sulfonate Modified Alkyds (3) Epoxy Mastic Coatings (4) Moisture Cured Urethanes (5) Epoxy Penetrating Sealer (total surface preprimers) (6) Water Borne Acrylics (7) High Ratio Co-Polymerized Calcium Sulfonates (8) Urethane Systems 8.7.4.4 Volatile Organic Compound (VOC) Content VOC refers to the transportation vehicle that the coating manufacturer uses to control the rheology of the coating material. This material does not remain in the film and evaporates into the atmosphere. The VOC run the gamut of hazardous to non-hazardous and various rules apply to them. The amount of VOC allowed into the air is controlled by the Environmental Protection Agency (EPA) in the USA (federal) and state and local governments who may have special requirements. The specification should refer the Contractor to the specific rules that apply in the area that the coating is being applied or, if the Engineer deems it necessary, the level the Engineer requires. The more restrictive level will govern. The level of VOC may limit the types of coatings available for use on the structure. 8.7.4.5 Data Sheets a.

The coating manufacturer is responsible to supply the Engineer with current product data sheets, technical data sheets, and material safety data sheets which supply a minimum of information required by law.

b. The data presented on all data sheets must be verifiable by the testing methods used to produce the information on the data sheets as they are submitted to the Engineer. The Engineer, at his option, may pull samples from the site to verify that the material on the site is equal to the material described on the data sheets.

8.7.5 SAFETY AND ENVIRONMENTAL CONSIDERATIONS (2009) 8.7.5.1 General This portion of the specification shall address those submittals required from the Contractor at the time of bid, pre-construction, and periodically throughout the performance of the contract. The required submittals shall be based upon the performance guidelines established in each of the preceding sections of the specification. These submittals can be used to determine the responsiveness of prospective bidders and form the final criteria for monitoring the project for effective implementation of worker protection, environmental protection, waste management plans, and containment system performance. 8.7.5.2 Worker Protection a.

General

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(1) The work shall be conducted in strict accordance with the Federal FRA or OSHA, state, and local government regulations governing worker protection. If the bridge carries a railroad track, or the bridge is located on an active railroad right-of-way, applicable provisions of the Title 49 Code of Federal Regulations, Part 214, the FRA Railroad Workplace Safety Rule, will govern for bridge workers safety and for protection against railroad traffic. (2) When disturbing coatings, institute engineering and work practice controls to reduce worker exposures to lead and other toxic metals to as low a level as feasible and in accordance with legal requirements. (3) The Contractor shall employ an Industrial Hygienist (IH) on staff or through subcontract to develop the Worker Protection Plan, and review all exposure monitoring and medical surveillance results. The IH shall be required to conduct a monthly site visit and issue a monthly summary of activities and monitoring results. (4) The worker protection requirements shall apply to all personnel of the Contractor and subcontractors working for the Contractor. (5) The requirements identified in this section regarding exposure to toxic metals are based on CFR 1926.62, but the Contractor must protect the employees from exposure to any of the toxic metals which may be present in the coating and/or abrasive, as applicable, in addition to lead. b. Bird Droppings (1) In addition to controlling exposures to lead and other toxic metals, the Contractor shall be required to take special precautions when working in areas where birds have nested.

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(2) The Worker Protection Plan should, at a minimum, require the use of gloves, whole body protective clothing and a respirator while inspecting or removing debris, followed by thorough washing of hands, face, and forearms before eating, drinking or smoking. c.

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Worker Protection Plan (1) Develop a written Worker Protection Plan under the direction of the IH, if required by the contract, to establish and implement practices and procedures for protecting the health and safety of employees from project hazards in accordance with applicable requirements. (2) The Worker Protection Plan must include provisions for protection of workers from exposures to toxic metals when exposures to lead or other toxic metals are above the Action Level. The Worker Protection Plan must address the protection of workers from all project hazards, such as those cited in Paragraph b. (3) The Worker Protection Plan shall be updated at least every six months during the portion of the project which involves the disturbance of toxic metals. (4) The Worker Protection Plan shall establish methods for complying with the project specifications and any OSHA standards published for the toxic metals present in the coating (e.g., 29 CFR 1926.62 for lead, 29 CFR 1926.1127 for cadmium, and 29 CFR 1926.1118 for inorganic arsenic). Toxic metals may be present in the coating for which OSHA has not developed a comprehensive health and safety standard (e.g., chromium). In these cases, include statements that appropriate measures will be taken to assure that the workers will not be exposed above the Permissible Exposure Limit (PEL) or Threshold Limit Value (TLV) established for the metal as identified in 29 CFR 1926.55.

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(5) The Worker Protection Plan shall identify methods of compliance that will be used to reduce worker exposure to toxic metals. Respiratory protection should be relied on only after feasible engineering and work practice controls have been first implemented to reduce airborne exposures. d. Medical Surveillance (1) Provide all employees with initial and periodic medical surveillance as required by published OSHA health and safety standards for the metal of concern, except that the frequency of blood testing in the case of lead is increased. Conduct blood lead and zinc protoporhyrin (ZPP) sampling and analysis prior to exposure to lead and at monthly intervals thereafter. In addition, exit blood tests should be conducted for each worker within five working days upon completion of their project activities that involve exposure to lead. The exit tests should be conducted even if the departure of the employee occurs prior to the completion of the Contractor’s work on the project, and at any time that project activities involving lead exposure will be halted for 30 days or more (e.g., winter shut down). (2) Verify that all medical tests are completed by or conducted under the supervision of a licensed physician. Verify that the blood analysis is conducted by qualified laboratories. Provide the specialized medical surveillance and X-rays required by CFR 1926.1118 for employees exposed to inorganic arsenic. (3) Do not use workers with initial blood lead levels of 40 mg/dl for any work activities involving exposure to lead above the Action Level. (4) Provide for intervention by the IH if a blood level >25 mg/dl occurs for two or more workers or if there is an increase of 10 mg/dl or more between consecutive tests for any individual worker. Intervention consists of an on-site investigation by the IH, implementation of corrective action, and notification of the Engineer in the next monthly report. (5) Provide all exam information and test results to employees in writing within 10 calendar days after the completion of each month signed by the IH that summarizes all examination and biological monitoring results. (6) For employees who are offered an examination and biological monitoring but choose not to participate or fail to respond, the Contractor shall provide documentation that the examination and monitoring were offered. This shall be in the form of a written declination signed by the employee or, for employees who are no longer on the payroll, a registered letter to the employee’s last known address. (7) The Contractor shall identify and address safety practices required by his operations. They include, but are not limited to, confined space procedures, clothing and personal protection equipment, storage, breathing air and respiratory requirements, grounding, ventilation, scaffolding, and training. He should be familiar with “right-to-know” laws. The Contractor should be advised of all hazards specific to the structure and all safety procedures, including work tag requirements. Projects removing lead-based coating will have increased safety requirements. 8.7.5.3 Environmental Surveillance a.

Environmental monitoring such as air, water, soil, and sediment sampling is to be conducted throughout the project as appropriate to characterize and prevent releases outside of the containment area.

b. All environmental monitoring should be conducted by a third party consultant hired by, but independent of the Contractor.

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Miscellaneous 8.7.5.4 Hazardous Waste and Debris Containment a.

General (1) Use a containment system that maintains the work area free of emissions of dust and debris in accordance with all provisions of the specifications. (2) Install and use a containment system for the project based on the coating removal methods that will be utilized and in compliance with SSPC Guide 6.

b. Use Class 1A for abrasive blast cleaning of the bridge steel when the existing coating contains lead. All abrasive, dust, coating chips, and debris must be contained and collected. c.

Use Class 3P for washing and vacuum-shrouded power tool cleaning for all other steel that will be overcoated when the existing coating does not contain lead.

d. The performance of the containment system should be inspected at least weekly for compliance with the approved containment submittals, and a report of the observations prepared. The information should be maintained at the project site and made available to the Engineer or environmental consultant for review at any time. e.

Containment Drawings and Submittals (1) Provide containment drawings, calculations, and assumptions, including ventilation criteria, signed and sealed by a Professional Engineer licensed in the locality where the work is performed.

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(2) Do not conduct any work until the drawings, calculations, and containment submittals have been reviewed and accepted by the Engineer. f.

Certification of Containment Installation (1) After the containment system is installed, have the Professional Engineer, as described in Paragraph e(1), or a designee working under his/her direction, conduct a site inspection to verify that the containment system has been assembled as shown on the approved, signed and sealed drawings. Have the Professional Engineer described in Paragraph e(1) submit a letter to the Engineer attesting to the above. The Engineer must receive the letter before any coating removal work within the containment can begin.

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4 (2) If the containment system is not installed in accordance with the design drawings, reinstall the containment, or issue supplemental calculations for the new design for Engineer review and acceptance in accordance with the original submittal requirements. g.

Containment Flooring System and Additional Collectors (1) If the floor or ground beneath the structure being prepared serves as the base of the containment, cover it with air and dust impenetrable materials such as solid panels of plywood or flexible materials such as tarpaulins. Maintain the materials throughout the project to avoid loosing debris through rips, tears, or breaks in the coverings. (2) If a suspended or elevated platform is constructed to serve as the base of the containment, use rigid and/or flexible materials, and cover as needed to create an air and dust impenetrable enclosure. Verify that the platform and its components are designed and constructed to support at least 4 times their maximum intended load without failure, with cables capable of supporting 6 times their

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maximum intended load without failure. Strictly follow all applicable regulations regarding scaffolding. (3) When required by the contract or directed by the Engineer, ground covers around and beneath the containment area shall be provided to capture inadvertent spills or leaks of debris. Extend the covers a minimum of 10 feet beyond the area covered by the containment. Increase this distance based on the height of the work above the ground as directed by the Engineer. The Contractor shall remove debris from the covers at least once per shift, or as directed by the Engineer. h. Containment and Ventilation System Components: The basic components that make up the containment systems are defined below. The components shall be in accordance with SSPC Guide 6 to establish the requirements for each method of removal. (1) Rigidity of Containment Materials: Rigid containment materials consist of solid panels of plywood, aluminum, rigid metal, plastic, fiberglass, composites, or similar materials. (2) Permeability of Containment Materials: The containment materials are identified as air impenetrable if they are impervious to dust or wind such as provided by rigid panels, coated solid tarps, or plastic sheeting. Air penetrable materials are those that are formed or woven to allow air flow. Water impenetrable impermeable materials are those that are capable of containing and controlling water when wet methods of preparation are used. (3) Support Structure: Rigid support structures consist of scaffolding and framing to which the containment materials are affixed to minimize movement of the containment cocoon. Flexible support structures are comprised of cables, chains, or similar systems to which containment materials are affixed. Minimal support structures involve the cables or connections necessary to attach the material to the structure being prepared and/or the ground. (4) Containment Joints: Fully sealed joints require that mating surfaces between the containment materials and the structure being prepared are completely sealed. Sealing measures include tape, Velcro, clamps, or similar material capable of forming a continuous, impenetrable or impermeable seal. (5) Entryway: An airlock entryway involves a minimum of one stage that is fully sealed to the containment and which is maintained under negative pressure using the ventilation system of the containment. Resealable door entryways involve the use of flexible or rigid doors capable of being repeatedly opened and resealed. Sealing methods include the use of zippers, Velcro, clamps, or similar fasteners. Overlapping door tarpaulin entryways consist of three overlapping door tarpaulins. Open seam entryways involve entrance into the containment through any open seam. (6) Mechanical Ventilation: The requirement for mechanical ventilation is to ensure that adequate air movement is achieved to reduce worker exposure to toxic metals to as low a level feasible, and to enhance visibility. Design the system with proper exhaust ports or plenums, adequately sized ductwork, adequately sized discharge fans and air cleaning devices (dust collectors) and properly sized and distributed make-up air points. Natural ventilation does not require the use of mechanical equipment for moving dust and debris through the work area. It relies on natural air flow patterns, if any, through the containment. (7) Negative Pressure: Negative pressure is specified for abrasive blast cleaning. Verify its performance through instrument monitoring to achieve a minimum of 0.03 inch water column (WC) relative to ambient conditions. In addition, verify through visual assessments for the concave appearance of the containment system.

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(8) Exhaust Ventilation: Mechanical ventilation systems are required for abrasive blast cleaning. Provide filtration of the exhaust air to prevent airborne particulate from the containment being exhausted directly into the surrounding air. Provide a filter that is at least 99.9 percent efficient in removing a mono-dispersed aerosol at 0.5 micrometers in diameter. 8.7.5.5 Hazardous Waste Collection All coating debris containing hazardous substances, contaminated abrasives, unused coating, thinners, or any other materials used on the project site shall be collected and properly stored prior to disposal in accordance with SSPC Guide 6, “Guide for Containing Debris Generated During Paint Removal Operations.” 8.7.5.6 Hazardous Waste Disposal a.

Hazardous wastes collected in accordance with Article 8.7.5.5, shall be disposed of in accordance with SSPC Guide 7, “Guide for Disposal of Lead Contaminated Surface Preparation Debris”. Where the contract documents provide for shipment of hazardous wastes to another location for stabilization and reuse, such as in asphaltic concretes, the Contractor is fully responsible for proper transport to the designated location. Transport of hazardous wastes shall be done only by licensed hazardous waste transporters.

b. The Contractor shall institute procedures to prevent spilling of all coating materials. Spills that occur shall be cleaned up immediately and all contaminated material, including soil, shall be disposed of as a hazardous material. All trash generated during the Contractor’s operation that becomes contaminated in any way with hazardous substances shall be disposed of as a hazardous material.

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8.7.5.7 Air Quality a.

The Contractor must maintain temporary pollution control features installed under the contract.

b. The Contractor must control emissions from equipment and plant to local authority’s emission requirements. c.

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The Contractor must prevent extraneous materials from contaminating air beyond the application area by providing temporary enclosures.

d. The Contractor must cover or wet down dry materials and rubbish to prevent blowing dust and debris. Provide dust control for temporary roads and unprotected ground surfaces.

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8.7.5.8 Volatile Organic Compounds The contract documents shall specify the maximum allowable VOC limits for coatings used for the project. 8.7.5.9 Owner’s Responsibility For projects involving wastes containing hazardous materials, the Company is considered to be the “generator” even if the work is accomplished by contract. As such, the Company is responsible to insure that all regulations relating to removal, containment, and disposal are met. The Company must obtain an EPA identification number and insure that the regulations are being followed. The requirements are outlined in SSPC - Guide 7, “Guide for Disposal of Lead-Contaminated Surface Preparation Debris.”

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8.7.6 QUALITY CONTROL AND QUALITY ASSURANCE (2009) 8.7.6.1 General a.

The goal of the contract is to ensure that a durable coating system, applied in accordance with all of the local and national regulations and specifications included herein, is obtained. To achieve this there are responsibilities that the Company, coating manufacturer, and Contractor must meet. The Company must insure that the contract documents adequately cover the regulatory requirements that the bidders will be asked to cover by their proposal. The Company must also insure that the coating system(s) specified is (are) compatible with the existing coatings, if applicable, and that the Contractor is properly preparing the surface. The Contractor is responsible for supplying only acceptable materials and trained workers, supplying properly maintained equipment whether the coating is applied in the shop or the field, and full compliance with the regulatory requirements contained in the contract documents. The coating manufacturer is responsible to supply only the level of quality of materials that meet the contract requirements, including adequate instructions to the Contractor and Company of the environmental and application requirements to safely obtain a long-lasting coating.

b. The Contractor shall submit, with the contract proposal, a Quality Control Plan (QCP), including manufacturer’s data sheets, and indicating how the above responsibilities will be met. The Company reserves the right to reject any bids not containing an adequate QCP. c.

The Company will institute an Acceptance Testing Plan (ATP) that will provide for verification of compliance with the QCP and contract documents.

d. Prior to bidding, the Contractor shall be qualified in accordance with SSPC-QP 1, “Standard Procedure for the Evaluation of Painting Contractors: Field Application to Complex Structures,” or approved equal. The SSPC Painting Contractor Certification Program provides an industry sponsored certification program to pre-qualify contractors. If potential Contractors are not certified under the SSPC program, a minimum of 5 years of successful experience in applying coating systems to steel structures may, at the Company’s discretion, be considered a minimum acceptance alternate level of pre-qualification. e.

For projects involving removal of coatings containing hazardous substances, the Contractor shall be qualified in accordance with SSPC Qualification Procedure SSPC-QP 2, “Standard Procedure for Evaluating the Qualifications of Contractors to Remove Hazardous Paint from Industrial Structures.” The SSPC Certification Program provides an industry sponsored certification program for Contractors involved in lead based coating removal projects which the Company may implement to insure a minimum acceptance level of Contractor qualifications.

f.

Verification of a Contractor’s current status as it relates to the SSPC Certification Programs can be obtained by contacting SSPC.

8.7.6.2 Quality Control Plan (QCP) a.

The QCP shall, as a minimum, contain the following: (1) Coating manufacturer and type of coating proposed for each coat (2) Manufacturer’s certification that the coating meets the project requirements, including VOC limitations (3) Equipment maintenance procedures (4) Worker safety procedures and equipment to be utilized

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(5) Identification of site safety officer for projects involving lead based coating removal (6) Procedures for containment and disposal of hazardous wastes (7) Procedures to contain site generated dust if required by the contract documents (8) Designated Quality Control Officer responsible for insuring the above procedures are maintained (9) A plan for taking thickness measurements of the initial surface (if coated) and each coat in accordance with SSPC-PA 2 (10)All required product data (material, safety and technical) sheets 8.7.6.3 Acceptance Testing Plan a.

The Company will assign properly trained Inspectors to the project to determine if the Contractor has met the contract requirements.

b. The Company reserves the right to sample and test coatings supplied for the project at any time, before or during the project, whether accepted by certification or not. c.

The Company will make random checks of surface preparation, surface profile and coating film thickness following the procedures outlined in SSPC-PA 2 after the Contractor submits the QCP test measurements for acceptance.

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d. The Company reserves the right to check any equipment for proper operation, including abrasives for particle size distribution, cleanliness and other required properties.

8.7.7 FINAL INSPECTION AND WARRANTY (2009)

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8.7.7.1 Final Acceptance When the project is complete, the Contractor shall make arrangements for a joint final inspection. 8.7.7.2 Warranty/Guarantee a.

The most common warranty for coating work is a two-year warranty against defective materials and workmanship. Extended period performance warranties are becoming more common and, when utilized, should be formulated to correlate with the specific coating systems selected. When warranties are utilized, they should clearly state who is to be responsible for the warranty and what conditions will trigger the warranty work.

b. The Contractor shall provide with his performance bond, a maintenance bond to cover any or all defects/failures in material and/or workmanship for a period of two years or as specified by the Engineer. This maintenance bond shall cover the warranty period and will start on the date indicated on the Construction Completion Certificate issued by the Company. The cost of the maintenance bond can be included as a separate bid item on the bid form. c.

The surety shall be licensed to conduct business in the state or province of jurisdiction.

d. If the surety on any bond furnished is declared bankrupt or becomes insolvent, its right to do business is terminated in any state or province where any part of the project is located, or is revoked, the Contractor

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shall within five days thereafter substitute another bond and surety, both of which shall be acceptable to the Company. e.

The warranty forms shall be jointly executed by the Contractor and the coating manufacturer and forwarded to the Company as called for herein.

f.

During the warranty period, the Company will inspect the coating system at least 60 days prior to warranty expiration. The Contractor and coating manufacturer are required to attend this inspection. The Company will advise the Contractor, coating manufacturer, and surety in writing of any defects/failures.

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Part 9 Commentary1 — 2011 — FOREWORD

The purpose of this part is to furnish the technical explanation of various articles in Part 1, Design, Part 3, Fabrication, Part 4, Erection, Part 6, Movable Bridges, Part 7, Existing Bridges, Part 8, Miscellaneous, Part 10, Bearing Design and Part 11, Bearing Construction and to furnish supplemental recommendations for use in special conditions. In the numbering of articles of this part, the second and succeeding digits in each article number represent the article being explained.

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TABLE OF CONTENTS Section/Article

Description

Page

Part 1 Design 9.1.1 Proposals and Drawings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.1.8 Design of Public Works Projects (1993) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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9.1.2 General Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.2.1 Materials (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.2.2 Welding (2003) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.2.5 Deflection (2001) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.2.6 Clearances (1995) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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9.1.3 Loads, Forces and Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.3.3 Live Load (1995) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.3.4 Distribution of Live Load (1993) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.3.5 Impact Load (2007) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.3.6 Centrifugal Force (2002) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.3.7 Wind Forces on Loaded Bridge (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.3.8 Wind Force on Unloaded Bridge (2005) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.3.10 Stability Check (2005) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.3.12 Longitudinal Forces (2005) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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1

References, Vol. 71, 1970, p. 379; Vol. 72, 1971, p. 153; Vol. 73, 1972, p. 176; Vol. 75, 1974, p. 336; Vol. 76, 1975, p. 240; Vol. 77, 1976, p. 249; Vol. 78, 1977, p. 75; Vol. 80, 1979, p. 188; Vol. 81, 1980, p. 132; Vol. 82, 1981, pp. 78-87, incl; Vol. 84, 1983, p. 100; Vol. 90, 1989, p. 98; Vol. 91, 1990, p. 121; Vol. 92, 1991, p. 80; Vol. 93, 1992, p. 124; Vol. 94, 1993, p. 1; Vol, 94, 1994, p. 145; Vol. 96, p. 74; Vol. 97, p. 177. Reapproved with revisions 1996.

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9.1.3.13 Fatigue (2011). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.3.14 Combined Stresses (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.3.15 Secondary Stresses (1994) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.3.16 Proportioning of Truss Web Members (2004) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-9-16 15-9-22 15-9-22 15-9-23

9.1.4 Basic Allowable Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.4.1 Structural Steel, Rivets, Bolts and Pins (2011). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.4.2 Weld Metal (1994) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.4.3 Cast Steel (1994) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-9-23 15-9-23 15-9-27 15-9-27

9.1.5 General Rules. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.5.4 Thickness of Material (2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.5.8 Net Section (2005) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.5.9 Connections and Splices (2003) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.5.10 Field Connections (1994) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.5.12 Combinations of Dissimilar Types of Connections (1993) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.5.13 Sealing (1993) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.5.14 Connections of Components of Built-up Members (1993) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . .

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9.1.6 Members Stressed Primarily in Axial Tension or Compression. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.6.1 Compression Members (2004) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.6.2 Outstanding Elements in Compression (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.6.4 Lacing and Perforated Cover Plates for Tension and Compression Members (2009) . . . . . . . . . . . . . 9.1.6.5 Effective Net Area for Tension Members - Strength (2007) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.6.6 Effective Area for Tension Members - Fatigue (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-9-29 15-9-29 15-9-30 15-9-30 15-9-31 15-9-31

9.1.7 Members Stressed Primarily in Bending . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.7.1 Proportioning Girders and Beams (2004) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.7.2 Flange Sections (1994) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.7.3 Thickness of Web Plates (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.7.4 Flange-to-Web Connection of Plate Girders (2009). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.7.8 Web Plate Stiffeners (Intermediate Transverse and Longitudinal) (2010). . . . . . . . . . . . . . . . . . . . . . 9.1.7.9 Composite Steel and Concrete Spans (2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-9-32 15-9-32 15-9-32 15-9-32 15-9-33 15-9-34 15-9-35

9.1.8 Floor Members and Floorbeam Hangers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.8.3 End Connections of Floor Members (1993) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-9-35 15-9-35

9.1.9 Riveted and Bolted Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.9.4 Edge Distance of Fasteners (2005) R(2011). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-9-36 15-9-36

9.1.10 Welded Construction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.10.1 Transition of Thickness or Widths in Welded Butt Joints (1993) R(2003) . . . . . . . . . . . . . . . . . . . . 9.1.10.2 Prohibited Types of Joints and Welds (2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.10.4 Welded Attachments (2004) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-9-36 15-9-36 15-9-36 15-9-39

9.1.11 Bracing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.11.4 Cross Frames and Diaphragms for Deck Spans (1994) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-9-39 15-9-39

9.1.13 Continuous and Cantilever Steel Structures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.13.8 Longitudinal Stiffeners (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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9.1.14 Fracture Critical Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.14.1 Scope (2001) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.14.2 Definitions (1997) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.14.3 Design and Review Responsibilities (1997) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.14.5 Notch Toughness of Steel in Fracture Critical Members (2006) R(2008) . . . . . . . . . . . . . . . . . . . . . .

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Part 3 Fabrication 9.3.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3.1.6 Thermal Cutting, Copes, and Access Holes (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3.1.8 Planing Sheared Edges (1994) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3.1.18 Bent Plates (2000) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-9-46 15-9-46 15-9-46 15-9-46

9.3.2 Riveted and Bolted Construction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3.2.2 High Strength Bolts, Nuts, and Washers (2005) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3.2.3 Installation of High Strength Bolts (2005) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3.2.6 Preparation of Holes for Shop Fasteners (1995) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3.2.7 Preparation of Holes for Field Fasteners (1983) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-9-47 15-9-47 15-9-47 15-9-47 15-9-47

9.3.3 Welded Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3.3.3 Flange-to-Web Welds of Flexural Members (1995) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3.3.4 Tack Welds (1995) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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9.3.5 Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3.5.5 Inspection – Welded Work (2002) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-9-47 15-9-47

9.3.6 Shipment and Pay Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.3.6.3 Pay Weight (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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3

Part 6 Movable Bridges Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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9.6.1 Proposals and General Requirements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6.1.1 General (1986) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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9.6.4 Basic Allowable Stresses and Hydraulic Pressures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6.4.2 Machinery Parts (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6.4.8 Hydraulic Systems and Components (1984) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-9-49 15-9-49 15-9-49

9.6.5 General Details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6.5.13 Lubrication (2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6.5.34 Special Provisions for Swing Bridges (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6.5.36 Special Provisions for Vertical Lift Bridges (1997). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-9-49 15-9-49 15-9-49 15-9-50

9.6.6 Wire Ropes and Sockets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6.6.2 Diameter of Rope (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6.6.3 Construction (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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9.6.6.7 Wire – Physical Properties (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6.6.8 Ultimate Strength (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-9-51 15-9-51

9.6.9 Erection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6.9.1 Erection of Machinery (1996) R(2002) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6.9.4 Lubrication (2008) R(2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.6.9.7 Counterweights (1983) R(2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-9-51 15-9-51 15-9-52 15-9-52

Part 7 Existing Bridges 9.7.2 Inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.7.2.1 General (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-9-52 15-9-52

9.7.3 Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.7.3.1 General (1998) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.7.3.2 Loads and Forces (2007) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.7.3.3 Stresses (2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-9-52 15-9-52 15-9-53 15-9-54

Part 8 Miscellaneous 9.8.1 Turntables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.8.1.3 Basic Allowable Stresses and Deflections (2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-9-60 15-9-60

9.8.2 Method of Shortening of Eyebars to Equalize the Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.8.2.1 General (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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9.8.3 Anchorage of Decks and Rails on Steel Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.8.3.1 Foreword (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.8.3.2 Anchorage of Decks to Bridge Spans (2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.8.3.3 Anchorage of Rail (2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.8.3.4 Rail Expansion Joints (2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-9-61 15-9-61 15-9-62 15-9-62 15-9-63

9.8.7 Guide to the Preparation of a Specification for the Cleaning and Coating of Existing Steel Railway Bridges ...................................................................................... 15-9-64 9.8.7.4 Coating Systems (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-9-64 Part 10 Bearing Design 9.10.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.10.1.2 General Requirements (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.10.1.5 Bearing Selection Criteria (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-9-72 15-9-72 15-9-72

9.10.2 Basic Allowable Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.10.2.1 Structural Steel, Bolts and Pins (2000) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.10.2.6 Polyether Urethane Disc Bearings (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-9-75 15-9-75 15-9-76

9.10.3 Steel Bearing Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.10.3.3 Shoes and Pedestals (1997) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Commentary

TABLE OF CONTENTS (CONT) Section/Article

Description

Page

9.10.4 Bronze or Copper-Alloy Sliding Expansion Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.10.4.3 Design (2001) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-9-76 15-9-76

9.10.5 PTFE Sliding Bearing Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.10.5.3 Design (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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9.10.7 Multi-Rotational Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.10.7.1 Scope (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.10.7.3 Design (2007) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Part 11 Bearing Construction 9.11.3 Bronze or Copper-Alloy Sliding Expansion Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.11.3.1 General (2001) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-9-77 15-9-77

9.11.4 PTFE Sliding Bearing Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.11.4.1 General (2002) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Welding Index (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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References (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-9-79

LIST OF FIGURES Figure

Description

3 Page

15-9-1 15-9-2 15-9-3 15-9-4 15-9-5 15-9-6

Isolines for First-Percentile Minimum Temperatures (USA). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-9-7 January Design Temperature 1 Per Cent Basis (Canada). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-9-8 Stress Range vs. Number of Cycles for Various Detail Categories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-9-20 Bolted and Riveted Gusset Plates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-9-28 Examples of details at intersection of longitudinal stiffeners and transverse plates welded to web. . . . . . . 15-9-38 Examples of welded Fatigue Category E details at certain locations at the intersection of transverse connection plates and gusset plates welded to web. Both of these fatigue resistant details are difficult to fabricate. Bolted gussets are recommended. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-9-39 15-9-7 Schematic Showing Relation Between Static and Dynamic Fracture Toughness . . . . . . . . . . . . . . . . . . . . 15-9-45 15-9-8 Riveted Bridge Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-9-57

LIST OF TABLES Table

Description

15-9-1 Parameters Used to Develop Table 15-1-7 and Table 15-1-10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-9-2 Constant A and Thresholds for Detail Categories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Steel Structures

PART 1 DESIGN 9.1.1 PROPOSALS AND DRAWINGS 9.1.1.8 DESIGN OF PUBLIC WORKS PROJECTS (1993) R(2008) The purpose of requiring consulting engineers to be familiar with the design of railroad bridges is to ensure compliance with the Company’s standards and operating procedures with minimum time involvement of the Company’s engineering staff.

9.1.2 GENERAL REQUIREMENTS a.

The safety and reliability of a bridge is governed by material properties, design, fabrication, inspection, erection and usage.

b.

The following are contributing factors in bridge failures: inadequate inspection and non-destructive testing; design details resulting in notches or high stresses due to secondary effects; joints which are difficult to weld and inspect; hydrogen-induced cracks; improper fabrication, welding and weld repair; lack of base metal and weld metal toughness. Excessive attention to a single preceding item will not overcome the effects of a deficiency in any other item.

c.

The fatigue provisions of the AREMA specifications are based on a design loading which minimizes the possibility of fatigue crack growth under regular traffic (see Article 9.1.3.13).

9.1.2.1 MATERIALS (2009) a.

Prior to 1969, these recommended practices were based on the use of materials defined in a special section and differing to some extent from ASTM specifications. Developments of materials and acceptance of these materials by ASTM have made it unnecessary for AREMA to specify special requirements for materials additional to those of the ASTM Specifications so that since 1969, most materials are specified in terms of such specifications.

b.

Based on commonly accepted approximate values for E and μ obtained from test results, the approximate value for G is derived using the following theoretical Equation: G = E ⁄ (2(1 + μ)) .

c.

Table 15-1-2 and Table 15-1-14 make provisions for materials with improved notch toughness. ASTM A709, Grade HPS 70W and Grade HPS 50W steels have such high toughness that when they were included in the ASTM A709 Specification, the Zone 3 requirements, which are the most severe, were specified for all zones for both Non Fracture Critical, Table 15-1-2, and for Fracture Critical, Table 15-1-14. Because of their high toughness it was decided to eliminate the need to choose the appropriate zone when using HPS 50W or HPS 70W and treat all zones alike.

d.

Refer to Table 15-1-2 and Table 15-1-14: “Service Temperature” shall be taken to be the lowest ambient temperature expected for the area in which a structure is to be located or to which a structure is to be exposed while in service. The testing zones correspond with those chosen by AASHTO and imply the service temperatures listed in the tables. Zone 1 implies a minimum service temperature of 0 degrees F; Zone 2 implies a minimum service temperature of –30 degrees F; Zone 3 implies a minimum service temperature of –60 degrees F.

e.

For guidance in determining the Lowest Anticipated Service Temperature for a particular location in the United States or Canada, Figure 15-9-1 and Figure 15-9-2 may be used. Both figures show temperatures in degrees Fahrenheit. Figure 15-9-1 (U.S. and Alaska) shows isolines for which there is a 99% chance that the daily minimum temperature will be no lower than shown. Figure 15-9-2 (Canada) shows isolines for which the temperature during January will be no lower than shown for 99% of the time.

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Commentary

1

3

Figure 15-9-1. Isolines for First-Percentile Minimum Temperatures (USA)

4

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Steel Structures

Figure 15-9-2. January Design Temperature 1 Per Cent Basis (Canada) f.

Refer to Table 15-1-2: The recommended practice is silent on energy requirements for material thicker than 4 inches even though some of the materials listed are available in greater thicknesses. Table 15-1-2 will normally apply to welded main load carrying components subject to tensile stress and such applications will be rare for thicknesses exceeding 4 inches. Nevertheless, if an engineer wishes to use a greater thickness, the notch toughness requirement for these materials not listed in Table 15-1-2 should be specified.

g.

Fracture Critical Members require additional consideration. This includes increased material toughness as specified in Section 1.14, Fracture Critical Members.

h.

Refer to Table 15-1-1, Note 2: There is a potential for atmospheric corrosion rates to increase in applications that subject weathering grade steels to frequent alternating wet and dry or continuously moist conditions for prolonged periods of time; or to corrosive chemicals, including deicing salts. Guidelines for proper application of unpainted weathering steels in bridges may be found in FHWA Technical Advisory T5140.22 “Uncoated Weathering Steel in Structures”, dated October 3, 1989.

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Commentary

9.1.2.2 WELDING (2003) R(2008) a.

Prior to 1990, these recommended practices stipulated that welding of structural steel should conform to the American Welding Society Structural Welding Code Steel ANSI/AWS D1.1. With the introduction of the Bridge Welding Code ANSI/AASHTO/AWS D1.5 in 1988, under a joint development effort of the American Association of State Highway and Transportation Officials (AASHTO) and the American Welding Society (AWS), the AREMA had available a welding specification that specifically addresses bridge construction. The development of the AWS D1.5 code represents a landmark of cooperative industry action to address the proliferation of costly and sometimes contradictory regulations. While some specifications of AWS D1.5 may appear unorthodox to members of the welding community, AWS has agreed that AASHTO should play a deciding role in determining the specifics of the code.

b.

Since AWS D1.5 is directed toward the construction of highway bridges constructed in accordance with standard State Specifications, several terminology and definition substitutions must be made in order to render the bridge code applicable to the construction of railroad bridges.

c.

ASTM A709, Grade HPS 70W steel was developed starting in 1994. By 1997 the material was ready for use in bridge structures. The existing AWS D1.5 Bridge Welding Code has many provisions for welding materials with yield strengths of 70 ksi (former A852 and A709 70W); however, these provisions have significant limitations with reference to A709 HPS 70W. As a result, the “Guide Specification for Highway Bridge Fabrication with HPS 70W Steel” was developed by the industry and subsequently adopted by AASHTO. This guide recommends procedures that will result in economical high quality fabrication using A709 HPS 70W steel. The guide is intended to be used as a supplement to AWS D1.5 until such time as A709 HPS 70W is included therein.

d.

Due to a time lag in the updating of the AWS D1.5 Specification, some of the newer steels are not specifically referenced. Until AWS D1.5 includes these grades, guidance is provided on the proper weld procedures to follow.

1

9.1.2.5 DEFLECTION (2001) R(2010) a.

b.

Prior to 1969, the deflection limitation was covered by an article headed “Depth Ratios.” Structures built with depth ratios meeting the requirements of that article were satisfactorily stiff for railroad operations since the stresses allowed for A 36 (or A 7) steel were used in the design. Since the 1969 edition of these recommended practices introduced and permitted the use of a variety of higher strength steels, it became necessary to define more accurately the degree of stiffness which is desirable in terms of the deflection of the structure rather than in terms of the depth ratio. Relating deflection to live loading also gives a more appropriate basis for ballasted deck bridges, for which the live load is generally a lesser percentage of total load than for open deck bridges. Waddell (1916) recommended a vibration load of 700 lb. per linear foot for loaded chords to ensure sufficient lateral rigidity in members (Reference 143). Furthermore, observations and tests at CN determined that lateral forces on bridges from equipment can exceed the forces given in Article 1.3.9. Nevertheless, experience indicates that the provisions for lateral forces of this Chapter have generally resulted in satisfactory structures with sufficient lateral rigidity when all the recommended loads and lateral forces are considered. The lateral deflection limits recommended are 50% of the FRA allowable limits for alignment deviation for Class 5 Track. Therefore, at least 50% of the allowable limit remains to account for variations in track alignment, rail wear and track fastener wear or movement.

9.1.2.6 CLEARANCES (1995) R(2008) The requirements for clearances were changed in the 1983 edition to be slightly more severe than in previous editions (previously changed in 1969). This was done to be consistent with the recommendations of AREMA Committee 28 to accommodate the increased dimensions of cars and of higher and wider loads.

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Steel Structures

9.1.3 LOADS, FORCES AND STRESSES 9.1.3.3 LIVE LOAD (1995) R(2008) a.

The recommended live load of Cooper E 80 for the design of steel structures was adopted in 1967 by Committee 15. While locomotives with weights greater than Cooper E 72, the previously recommended design live load, are not likely to be found on any railroad in the United States, there is a trend toward heavier locomotives, and some of the heavy cars produce loads equivalent to Cooper E 80 or greater.

b.

Heavy double stack cars with axle loads of 78,750 lb per axle and 4–axle 315,000 lb gross weight cars (both using the so-called 120 or 125 ton truck) accepted in regular service on certain railroads produce the equivalent of nearly E 80 Loading on shorter spans. In 1995, an alternate loading was introduced with a spacing similar to coupled typical 4–axle cars with an axle load 25% higher than the Cooper E 80 load to address problems associated with fatigue on shorter span lengths.

c.

For members receiving load from more than one track, the proportions of full live load on the tracks to be used for design are determined by use of the theory of probability to determine the frequency with which stresses of various magnitudes might occur. Consideration was given to the fact that most of the trains which pass over a bridge will produce lower stresses than the recommended design live load on each track (Reference 125).

9.1.3.4 DISTRIBUTION OF LIVE LOAD (1993)1 R(2008) 9.1.3.4.2 Ballasted Deck Structures The recommendation for distribution of load to ballasted deck structures is based on tests performed by the AAR and reported in AREA Proceedings, Vol. 56, 1955, page 45, other prior tests, and Report No. ER-5 of Engineering Research Division of AAR of February, 1961. 9.1.3.4.2.3 Transverse Steel Beams a.

The above noted studies show the beneficial effects of the concrete slab in distributing the applied load for decks supported by transverse steel beams without stringers. This is now reflected in Article 1.3.4.2.3.

b.

The equation for D shown for moment has been introduced to account for the load carrying and load distributing effects of the concrete slab. The first term in parentheses, ⎛ ⎞ 1 ⎟ ⎜ ---------------⎜ d ⎟⎠ ⎝ 1 + -----aH indicates the amount of the total load that is carried by the beams. The remainder is assumed to be carried by the slab. However, for this effect to be obtained, the slab must extend over at least the center 75% of the length of the floorbeam. If there is no slab, or the slab is less than the center 75% of the length of the floorbeam (and thus essentially ineffective) then, as designated in Article 1.3.4.2.3c, the effective beam spacing becomes d, the actual spacing, and the equation for P is essentially the same as specified prior to the 1969 edition. The second term in the parentheses, ⎛ 0.4 + --l- + -------H -⎞ ⎝ d 12 ⎠

1

Reference 104

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Commentary accounts for the effect of the slab in distributing the load. The effect of beam spacing, and slab beam stiffness is shown in this term. c.

In special situations, it may be necessary to design decks with transverse beams without ballast. Although the criteria outlined in Article 1.3.4.2.3 are intended for use with ballasted deck structures, the criteria are acceptable for use with decks without ballast.

9.1.3.4.2.4 Longitudinal Steel Beams or Girders a.

For ballasted deck structures with longitudinal beams or girders, the test data are limited. It is, therefore, inappropriate at this time to attempt to refine significantly the criteria for distribution of live loads to these members.

b.

The data indicate that lateral distribution of live load to longitudinal beams or girders is improved by increasing the ballast thickness or increasing the floor stiffness, or both. The lateral distribution is also affected by the beam stiffness. Widely spaced diaphragms consisting of beams or plates and angles are relatively ineffective in improving lateral load distribution but improve stability and rigidity of the floor support system. For groups of beams, the live load carried by beams more than approximately 7 feet from center line of track is of relatively low magnitude and difficult to predict because of several factors involved in addition to those mentioned above. A primary objective of this article is to ensure the placement of the main track supports where they are most effective.

c.

For design purposes, it is assumed that all supports within a width defined by a line with a 1:1 slope down from the end of tie through the ballast and deck, are equally loaded, even though the slope of such a line is usually limited to 1/2:1, especially through ballast. Using the total depth and the flatter slope recognizes the additional distribution effect due to bending and shear of the timber or concrete floor and is reasonably consistent with field test results. For floors of timber or steel the supports generally will be spaced closer together which will reduce the required floor thickness and result in concentrating the supports in a narrower width. It is undesirable to complicate the formula by introducing the modulus of elasticity of the floor material, since the available test data do not justify this refinement at this time.

d.

In design, all beams outside of the width defined above are assumed to carry only dead load, live load of off-track equipment and similar loads. For simplicity of details and construction, and for possible future widening, such additional beams should be of the same section as the main supports.

1

3

9.1.3.5 IMPACT LOAD (2007) R(2008) a.

b.

The impact loads specified are based on investigations and tests of railroad bridges in service under passage of locomotives and train loads. The early tests, prior to 1935, were made with mechanical instruments and included measurements of deflections and strains. In general and particularly for shorter spans, the instruments were subject to considerable error due to vibration. Later tests (Reference 102) were made with electrical instruments which permitted more accurate measurements without disturbance from vibrations. The impact load due to rocking effect, RE, is due to a couple created by 20% of the wheel load acting down on one rail and up on the other rail, which effect was called roll prior to 1967. By service tests (Reference 136), it was established that the roll effect was essentially the same for all speeds. In 1967, the term 100/S (S in feet) was introduced as a downward load only (Reference 137), which approximates the effect of roll used in previous recommended practices. S was defined as the distance between centers of single or groups of longitudinal beams, girders or trusses; or the length between supports of floorbeams or transverse girders. Because of inconsistent interpretations of the term 100/S (S in feet) the term RE was introduced in 1991. In accordance with Article 1.3.5a, impact load due to rocking effect, RE shall be determined as a percentage of live load applied vertically at each rail. RE is then added to the impact load due to vertical effects (Article 1.3.5c) to determine the total impact load expressed as a percentage of the specified live load.

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4

Steel Structures The impact load due to rocking effect, RE, is created by a rocking load equal to the applied force couple of 20% of the wheel load acting vertically at each rail. Vertical loads in members due to the rocking load can be calculated for steel bridge span members based on the distribution of the rocking load to members supporting the track. RE can then be expressed as a percentage of specified live load by determining the ratio of the vertical load due to rocking to the vertical due to otherwise specified vertical live loads in each member supporting the track (for example, if the distribution of rocking load to members supporting the track is assumed to be the same as the distribution of vertical live load, RE expressed as a percentage of live load, will be equal for all members supporting the track). For spans with one longitudinal beam, girder or truss per rail the impact load due to rocking effect, RE, is (100/S)% of the vertical live load applied at each rail, where S, feet, is the distance between the centers of the longitudinal beams, girders or trusses. The constant of 100 represents the effective rail spacing of 5 feet times the load factor of 20 percent. For spans with more than one longitudinal beam, girder or truss per rail the impact load due to rocking effect, RE, (expressed as a percentage of live load) depends on the distribution of rocking load and specified vertical loads to the members supporting the track. Vertical loads shall be distributed to members supporting the track in accordance with Article 1.3.4. The distribution of rocking loads to members supporting the track shall be based on the configuration and spacing of members supporting the track. For floorbeams and transverse girders the impact load due to rocking effect, RE, is (100/S)% of the vertical live load applied at each rail, where S, feet, is the distance between the supports of floorbeams or transverse girders. Tests (Reference 95) have shown that the impact load on ballasted deck bridges can be reduced to 90% of that specified for open deck bridges because of the damping which results from the mass and resiliency of the ballast on a ballasted deck bridge. c.

The requirements specified for members receiving load from more than one track are based on judgement. For a double track span, the shortest span for which the impact load for only one track is to be used is 225 feet. For an open deck through span of this length the use of the impact load for the second track would add approximately 5% to the total design load of the truss. The probability that full impact load effects will occur simultaneously for both tracks is remote, but should this happen, the resulting increase in total load is small.

d.

The impacts calculated by the formulas given in this article do not include the effect of impulsive loads that are not substantially attenuated between the rail and the structure. For example, direct fixation of the rail to a steel deck without some appropriately designed attentuation device is not covered. Such impacts have been measured to be as high as 600%. (References 32, 66)

9.1.3.6 CENTRIFUGAL FORCE (2002) R(2008) a.

The centrifugal force defined in Section 1.3.6 is a function of curvature and speed. The centrifugal force contributes to the horizontal forces applied to the bridge through the outer rail of a curve, and affects the proportion of the vertical force taken by each rail.

b.

In cases where the maximum train speed for the expected life of the bridge on a curve is not limited by other conditions, it is constrained by a practical maximum superelevation of 6 inches (150) and a maximum underbalance of 3 inches (75), which equates to equilibrium speed for a superelevation of 9 inches (225). At that point, regardless of the actual curvature and corresponding speed, the proportion of centrifugal to vertical force is very close to 0.15. Article 1.3.6(b) is based upon the assumptions that, at some time in the life of the bridge, a superelevation of 6 inches (150) could be applied to the track, and trains could be operated at the corresponding maximum speed, with superelevation underbalance of 3 inches (75).

c.

In cases where the maximum train speed for the expected life of the bridge is limited by other factors, the design speed may be reduced to that specified by the Engineer in accordance with the provisions of Chapter 5 of this Manual, with the centrifugal force factor and superelevation adjusted accordingly.

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Commentary d.

On superelevated curves, the point of application of the vertical load will be offset horizontally toward the center of the curvature. Article 1.3.6(d) accounts for this offset.

e.

Article 1.3.6(e) accounts for the application of the entire horizontal centrifugal force at the flange of the wheel on the outer rail, combined with the proportion of vertical load, with full impact, taken by the outer rail. No horizontal force is assumed at the inner rail, as any horizontal wheel forces applied at the inner rail are normally canceled by the other wheels at the same side of that truck.

9.1.3.7 WIND FORCES ON LOADED BRIDGE (2009) a.

The specified basic wind pressure of 30 lb per square foot on a structure carrying live load has a long historic background in railroad specifications. It was assumed that the maximum wind velocity under which train operations would be attempted would produce a load of 30 lb per square foot on a flat surface normal to the wind. The provisions of Article 1.3.7b (1), (2), and (3) were selected to make provisions for the effect of the wind on the portions of the structure which are behind, and partly shielded by, the portion of the structure directly exposed to the wind pressure.

b.

The recommended use of 300 lb per linear foot for wind force on a train on a bridge as contained in Article 1.3.7a is adequate for use on lines where double stack equipment is not operated. The engineer should consider increasing this force in areas where double stack equipment, or other equipment with a large vertical projection operates, and strong wind gusts are known to occur.

c.

Article 1.3.7c promotes proper proportioning of affected members in order to attain rigidity for the structure as a whole. It does not actually address wind loads, but rather a “notional” load which was once termed “vibration load” in earlier bridge specifications (Reference 143). This load is included in the section on wind load because it is applied as an alternative to wind load. The affected members are to be proportioned for the greater force of either the wind load or this “notional” load.

1

9.1.3.8 WIND FORCE ON UNLOADED BRIDGE (2005) R(2008) The specified basic wind force of 50 lb per square foot on an unloaded structure has a long historic background in railroad specifications. It was assumed that a hurricane wind, during which train operations would not be attempted, could produce a load of 50 lb per square foot on such surfaces.

3

9.1.3.10 STABILITY CHECK (2005) R(2008) a.

For wind, nosing, and centrifugal forces, the vertical weight of a train on a tower or pier usually improves the lateral stability of the structure, so it is prudent to model the least weight train that would be present with the applicable lateral overturning load. A uniform vertical loading of 1,200 lbs/ft applied to the leeward track represents a consist of empty cars. For multiple track structures supported by the same pier(s) only the leeward track is loaded.

b.

This stability check is designed to ensure that a load equal to half the full design load on the verge of incipient roll will not cause the span to roll over. It is not intended to prevent damage to the structure, nor is it intended for deck design.

9.1.3.12 LONGITUDINAL FORCES (2005) R(2008) The longitudinal force used in previous editions of this Manual of recommended practice has changed over time. In the 1905 edition, the force was 20 percent of the specified total live load. By the 1920 edition reductions were permitted for ballast deck spans and for short structures. In the 1932 edition, the additional force of 25 percent of the driving axles of the Cooper’s series was introduced, and the braking force of 15 percent of the Cooper’s train was introduced.

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Steel Structures The AAR conducted a number of tests with the secondary objective of measuring longitudinal forces in the 1940’s and 1950’s. None of these tests were conducted under conditions that would have approached the maximum possible longitudinal force available at that time. It became the practice of some railroads to use one half the specified force which by this time was 25 percent of the Cooper’s driving axles or 15 percent of the Cooper’s train on the appropriate loaded length. In the 1968 edition of the Manual, a factor L/1200 was introduced to be applied to the 15 percent of the Cooper’s train with an exception for bridges with discontinuous rail (e.g.: movable bridges and those with sliding joints or switches). This resulted in a vastly reduced longitudinal force requirement. The traction force of 25 percent of the weight on driving axles was eliminated. A similar change was made to Chapter 8, Concrete Structures and Foundations. Committee 7, Timber Structures, did not make changes to the recommended practice in Chapter 7. With the introduction of high-adhesion locomotives, load/empty brakes, and ECP brakes, concern was expressed that recommended forces were not high enough. Several railroads have acknowledged component failures in bridges due to longitudinal forces, and several structures have been replaced due to distress caused by high longitudinal forces. In 1996, the AAR conducted a test specifically to investigate longitudinal forces under the newly developed AC diesel-electric freight locomotives. The test demonstrated that a longitudinal force of about 100 kips (440 kN) on a 50-foot (15-meter) opendeck span was more than 25 times the design force in the 1996 edition of the Manual. Under direction from the Board of Directors, and with the concurrence of the chairmen of the structural committees (7, 8 and 15) who formed the nucleus of a quickly gathered ad-hoc committee, AREA revised its recommended practice for the 1997 edition to conform to this test result. Chapter 7 was thought to be appropriate and not warrant the emergency change. The AAR followed this test with further tests, all of which confirmed the much higher longitudinal forces, and the far greater percentage of those forces which went into the structure. On a four-span, 400-foot (122-meter) open-deck steel bridge, longitudinal forces up to 330 kips (1470 kN) were measured in the entire structure, with up to 220 kips (980 kN) in a 210-foot (64-meter) truss, and up to 110 kips (490 kN) in a 42-foot (13-meter) beam span. On a two-span, 121-foot (37-meter) opendeck steel DPG bridge, forces up to 140 kips (620 kN) were measured in the entire structure, with up to 96 kips (430 kN) in a 55.5-foot (17-meter) span. On a single-span, 60-foot (18-meter) ballast-deck steel DPG bridge, forces up to 115 kips (510 kN) were measured. All tests used sets of two or three AC locomotives, operated near their maximum tractive effort capabilities of 180 kips (800 kN) to 200 kips (890 kN) per locomotive. Further information about these tests can be found in Reference 46, 47, 69, 77, 78, 90, 91, 92, 93 and 138. The results of these tests indicated the following: (1) Ballast deck spans do not have lower longitudinal forces (2) Short spans do not have significantly lower longitudinal forces (3) Half the force is not always dissipated through the rails (4) There has been considerable confusion over the difference between the force and its distribution and path (5) High longitudinal forces are not necessarily grade related (6) High longitudinal forces are related to lower speeds for tractive effort and dynamic braking situations. When a train is maintaining a speed that exceeds 15 mph (25 km/h) it cannot exert the maximum tractive effort. To cover future developments, the recommended practice has used 25 mph (40 km/h).

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AREMA Manual for Railway Engineering

Commentary (7) High longitudinal forces due to braking can occur at any location, particularly if an emergency brake application occurs (8) The ability of the approach embankments to resist longitudinal forces from the superstructure is reduced as longitudinal forces are also applied to the approach embankments. This would be the case with several locomotives passing over a short bridge, or a train braking. Analytical confirmation of the above behaviors has been done by Foutch et al (Reference 46, 47, 138), and is also explained by Fryba (Reference 48). Unfortunately, these formulations are too cumbersome for routine work. The problem can be envisioned as the rails being continuously supported in the longitudinal direction. The longitudinal stiffness of the connection between the rails and the bridge is similar to the stiffness of the connection between the rails and fixed ground on the approach embankments. With regard to braking force, the maximum adhesion between wheel and rail is about 15 percent. This level of braking would typically be reached with an emergency application of the train air brakes. The equation for train braking is derived using 15 percent of the Cooper live loading. Longitudinal force due to braking acts at the center of gravity of the live load. Center of gravity height is taken as 8 feet (2500 mm) above the top of rail. This force is transferred from vehicle to rail as a horizontal force at the top of rail and a vertical force couple transmitted through the wheels. Longitudinal force due to locomotive traction acts at the drawbar. Drawbar height is taken as 3 feet (900 mm) above top of rail. As with braking, this force is transferred from vehicle to rail as a horizontal force at the top of rail and a vertical force couple transmitted through the wheels.

1

Longitudinal forces transmitted by tractive effort of locomotives or the braking action of trains will be distributed to bridge members in accordance with their relative stiffness and orientation with respect to the force path between the applied longitudinal force and the supporting substructure. The length “L” in Article 1.3.12 is to be taken as the appropriate length for the structure or portion of the structure under consideration. The length selected should be the one that produces the maximum force in the structure or portion of the structure under consideraton.

3

In bridges with stringer and floorbeam floor systems, longitudinal forces are first applied to the stringers. The force must then be transferred to the members to which stringers are connected, usually the floor beams. Traction bracing can be used to directly transfer the longitudinal force from the stringers to truss or girder panel points. In bridges with transverse floorbeam floor systems (such as through girder spans), traction bracing can be used to transfer the longitudinal force to the bridge members supporting the floorbeams (typically girders). It is generally considered good practice to design traction bracing to be the same depth as the member being braced. However, when traction bracing isn’t used, the floorbeams should be designed for transverse bending and torsion where applicable. See Reference 52. It is generally considered good practice to provide traction bracing rather than design floorbeams or transverse members for lateral bending and torsion. Fixed bearings and their anchorages should be designed to transfer the longitudinal force from superstructure to substructure. In addition to designing the fixed bearings to take all the longitudinal forces, it is the practice of some engineers, given that bearings tend to become frozen or stuck with time, to design the area around and below expansion bearings for a percentage of the longitudinal forces going through those bearings as though the expansion bearings were partially fixed. Longitudinal forces are of importance in railway trestle bridges and may govern the economic span length considering requirements for longitudinal bracing and column sizes in towers.

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Steel Structures

9.1.3.13 FATIGUE (2011) a.

Fatigue is now covered in a sufficient number of texts so a basic explanation is no longer needed in this Commentary. It was removed in 2009. Between 1910 and 1969, inclusive, this Manual required an increase of each stress by 50% of the smaller stress for members subject to reversal of stress. Fatigue damage prior to the introduction of 263,000 lb. cars (100 ton capacity) in the 1960’s was primarily the result of the passage of heavier locomotives. With 20 trains a day for 60 years, the number of damaging cycles caused by locomotives would be less than 500,000. Most freight cars were light enough to cause little if any damage due to fatigue. In 1969, methods were introduced based on the R ratio, the ratio of minimum to maximum stress, and a distinction was made between cases of more than 500,000 cycles of load or less. Consideration of the methods used to fabricate and connect members was included. Fatigue problems accelerated in the 1970s, with the introduction of heavy and frequent unit train service where the influence of each car produces a significant effect. With the same 20 trains a day with 60 cars per train causing damage, 500,000 cycles could accumulate in one year for some members. Fatigue design for this Chapter has been based entirely on the nominal stress range concept since the 1978 Edition. Other factors, such as mean stress and steel strength have negligible effect in the types of fabricated structures used in the railroad industry. The type of load distribution has been revised as new knowledge has been developed. Structures designed to the fatigue criteria of Article 1.3.13 should be adequate for: (1) continuous unit trains with axle loads not exceeding 80,000 lb for loaded lengths less than 100 feet, (2) continuous unit trains with equivalent uniform load not exceeding 6,000 lb per foot of track and axle loads not exceeding 80,000 lb, or other variations of higher load with fewer cycles on longer spans (see Article 9.1.3.13.c). This should be adequate for mainlines of Class I railroads, and for most heavy haul lines. The Chapter recommends special consideration for spans exceeding 300 feet (see Article 9.1.3.13j).

b.

The major factors governing fatigue strength are the number of stress cycles covered in section c, the magnitude of the stress range, section h, and the type of constructional detail, section g.

c.

The derivation of the design criteria for fatigue did not consider Rail Transit or other Light Rail facilities. For such cases, unless demonstrated otherwise, the Mean Impact Load shown in Article 1.3.13d should be 100% of the impact load specified in Article 1.3.5 for all member span lengths, and in Table 15-1-7, the number of constant stress cycles, N, should be > 2,000,000. For typical North American freight railroads the number of cycles used for design were derived assuming 315,000 lb. cars in 110 car trains at a frequency of 60 trains per day over an 80-year period. The number of cycles per train is the result of extensive work done by G. Oommen, S. Beisler and R.A.P. Sweeney as reported to Committee 15 in 1987 and 1988 (See Table 15-9-1). This criterion will theoretically provide infinite life for all loaded lengths less than 100 feet and will accommodate longer and more frequent trains. Existing cars (1988) with gross weights of 315,000 lb and certain double stack cars are approaching E 80 loading values on short spans. In order to provide sufficient fatigue capacity under solid, or “unit” trains of these types of vehicles the number of design cycles shown in Table 15-1-7 was derived by prorating the fatigue curve formula, N = Nv x (α x SE60/SE80)3

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AREMA Manual for Railway Engineering

Commentary to an equivalent number of cycles of E 80 loading. In this formula N is the number of cycles, α i s a constant, and SE60 and SE80 are respectively the stress ranges characteristic of E 60 and E 80 loading. The total projected number of variable stress cycles, Nv, shown in Column 5 of Table 15-9-1, is obtained by multiplying columns 2, 3 and 4. The value of alpha is to be taken as one unless a test on the member being evaluated indicates that a lower value is appropriate. Table 15-9-1 is based on 110-vehicle train. Critical characteristic load is assumed to be ¾, i.e. 60/80, of design load E 80. On spans exceeding 100 feet it may be necessary to increase the number of cycles per train if a consistent operating pattern of loaded cars followed by empty cars is repeated throughout the design train, throughout the service life of the bridge. It is theoretically possible to get 55 cycles on spans close to 100 feet if the pattern is 2 loaded cars followed by 2 empty cars. Nevertheless, the committee assumed 3 cycles of loaded-empty combinations in its design 110-car train as a more likely maximum on spans exceeding 100 feet. Table 15-9-1. Parameters Used to Develop Table 15-1-7 and Table 15-1-10 Classification I 1

2

Span Length Life L in Days Ft 80 Yr

3

4

5

6

7

8

No. of Daily Trains

Stress Cycles per Train Crossing

Projected Nv Million

Alpha (α)

N Col. 5 × (Alpha x 6/8)3 Million

N used in Table 15-1-7 Million

L > 100

29,200

60

3

5.3

1.0

2.2

2

100 ≥ L > 75

29,200

60

6

10.5

1.0

4.4

>2

75 ≥ L > 50

29,200

60

55

96

1.0

41

>2

50 ≥ L

29,200

60

110

193

1.0

82

>2

Keep in mind that the number of variable cycles leading to the greater-than-2-million category in Table 15-1-10 is different for each category of detail, varying from 3 to 31 cycles per 110-car train on spans exceeding 100 feet. d.

Impact values used in design are estimated to have a probability of occurrence of 1% or less. Considering that a railroad bridge is normally designed for an 80-year period, this level of impact is quite likely to occur at least once during the bridge life and probably more frequently. For fatigue design the mean value of impact is more appropriate. Nevertheless, the note to Table 15-1-8 covers cases of consistent and continuous poor maintenance practice with regard to wheel or track maintenance or places where there are joints in the rail due to switches or rail expansion or other joints where higher impact is a frequent occurrence. This is likely to include but is not restricted to locations where there is "FRA Excepted Track" or "FRA Class 1 Track." In locations where a structural member supports or is influenced by a “Conley” or similar style joint or where there are rail break castings, a rail end connection or similar style joint or switch, the reduction in impact shown in Table 15-1-8 should not be used. For members supporting end ties on movable spans and at the adjacent ends of fixed spans, use the full impact outlined in Article 6.3.3, unless test results show a lower permissible impact. Observations on 37 spans with span lengths between 30 and 140 feet, summarized by W. G. Byers (Reference 20), indicates that mean impact values fall below 65% of the values used for design. Tests included results obtained with poor wheels and on poor track.

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1

3

4

Steel Structures Tests on 15 bridges on Canadian National Railways done between 1975 and 1988 (reported to Committee 15, May 1988, by R. A. P. Sweeney) indicated mean values of 34% on spans less than 80 feet, and 65% on longer spans. A further presentation by Dr. Sweeney made to the committee in 2002 based on tests on over 100 bridges confirmed the numbers in revised Table 15-1-8, and confirmed that alpha should be assumed to be 1 unless a particular structure was tested and alpha proved to be lower for that structure. The mean impact is a function of the geometry of the track and how well it is maintained up to and across the bridge, along with the maintenance standards for out-of-roundness of wheels and for wheel flats. The more restrictive limitations placed on short members without load sharing is based on the probability that a single wheel may cause such values relatively frequently. This is based on a one-year sample of wheel impact data at 10 Wheel Impact Load Detector (WILD) Sites on CN (Reference 22). e.

The fatigue criteria is based on continuous unit trains with equivalent uniform load not exceeding 6,000 lb per foot of track and axle loads not exceeding 80,000 lb and has been adjusted so that the Standard Cooper load specified in Article 1.3.3 may be used for design purposes.

f.

For the usual design condition of members subjected to bending, only SR derived from bending needs to be considered for details, such as transverse stiffeners, which are subjected to shear stresses as well. The design detail categories have taken shear into account; therefore, principal stresses need not be considered in the usual design condition. For unusual design conditions, the principal stresses may need to be considered. Residual and/or locked-in stresses induced during welding, fabrication or erection shall not be considered in investigating fatigue. Residual stresses due to welding are implicitly included through the specification of stress range as the sole dominant stress parameter for fatigue design. This same concept of considering only stress range has been applied to rolled, bolted, and riveted components or details where far different residual stress fields exist. The application to nonwelded components or details is conservative. It has been shown that the level of total applied stress is insignificant to fatigue design for a welded steel component or detail in structures typically designed using this Manual. A complete stress range cycle may include both a tensile and compressive component. Only the live load plus impact stresses need be considered when computing a stress range cycle; dead load does not contribute to the stress range. Tensile stresses propagate fatigue cracks. Material subjected to a cyclical loading at or near an initial flaw will be subject to a fully effective stress cycle in tension, even in cases of stress reversal, because the superposition of the tensile residual stress elevates the entire cycle into the tensile stress region. These provisions shall be applied only to components or details subjected to a net applied tensile stress. In regions where the permanent loads produce compression, fatigue shall be considered and these provisions applied only if the tension component of the live load plus impact stress range cycle due to fatigue exceeds the permanent-load compressive stress in the component or at the detail under consideration. Fatigue design criteria need only be considered for components or details subject to effective stress cycles in tension and/or stress reversal. If a component or detail is subject to stress reversal, fatigue is to be considered no matter how small the tension component of the stress cycle is since a flaw in the tensile residual stress zone could still be propagated by the small tensile component of stress. Hence, the entire stress range cycle (which may include compression) is used in computing the stress range. In addition, for fatigue to be considered, the component or detail must be subject to a net applied tensile stress under an appropriate combination of the permanent loads and the fatigue live load. The tensile component of the stress range cycle resulting from live load and its appropriate impact combination acting in conjunction with the compressive stress due to the permanent loads are used to establish the presence of a net applied tensile stress in the component or at the detail under consideration. Cross-frames and diaphragms connecting adjacent girders are stressed when one girder deflects with respect to the adjacent girder. The sense of stress is reversed depending on which way roll is applied and this usually creates the largest stress range in these members. To cause one cycle of the stress range so computed requires two vehicles to roll in opposite direction. This has been observed in practice. For cases where the force effects in these members are available from an analysis, such as in horizontally curved or sharply skewed bridges, it may be desirable in some © 2011, American Railway Engineering and Maintenance-of-Way Association

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Commentary instances to check fatigue-sensitive details on a bracing member subjected to a net applied tensile stress. In no case should the calculated range of stress be less than the stress range caused by full live load and appropriate impact load. g.

Components and details susceptible to load-induced fatigue cracking have been grouped into nine categories, called detail categories, of similar fatigue resistance established through full scale testing (Reference 17). Table 15-1-9 illustrates many common details found in bridge construction and identifies potential crack initiation points for each detail. In Table 15-1-9, “Longitudinal” signifies that the direction of applied stress is parallel to the longitudinal axis of the detail. “Transverse” signifies that the direction of applied stress is perpendicular to the longitudinal axis of the detail. Where fasteners and connected material are proportioned in accordance with Article 1.3.13 and Section 1.4, Basic Allowable Stresses, the fasteners will have greater fatigue life than the connected material. Thus, no categories for bolts or rivets in shear or bearing are required to replace the 1969 formulas. For information on Partial Penetration (PJP) joints see Article 1.7.4 and its commentary. Research on end-bolted cover plates is discussed in Reference 145.

h.

The requirement that the maximum stress range experienced by a detail be less than the constant-amplitude fatigue threshold provides a theoretically infinite fatigue life for all loaded lengths less than 100 feet. For longer spans see Article 9.1.3.13c. For cases where different criteria are appropriate, the fatigue resistance above the constant amplitude fatigue threshold, in terms of cycles, is inversely proportional to the cube of the stress range, e.g., if the stress range is reduced by a factor of 2, the fatigue life increases by a factor of 23. This is reflected in the equation shown below and shown in Figure 15-9-3.

1

(Sr) = (A/N)1/3

3

4

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Steel Structures

Figure 15-9-3. Stress Range vs. Number of Cycles for Various Detail Categories Sr-N curves in Figure 15-9-3 were developed (Reference 17, 35 & 37) by using 95% confidence limits for 97.5% survival applied to full-scale test data. Table 15-9-2. Constant A and Thresholds for Detail Categories DETAIL CATEGORY

CONSTANT, A TIMES 108 (KSI3)

THRESHOLD (CAFL) ksi

A

250.0

24

B

120.0

16

B’

61.0

12

C

44.0

10

C’

44.0

12

D

22.0

7

E

11.0

4.5

E’

3.9

2.6

F

9.0

8.0

A 325 Bolts in Axial Tension

17.1

31

A 490 Bolts in Axial Tension

31.5

38

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Commentary Detail Category F is for the allowable shear stress range on the throat of a fillet weld. When fillet welds are properly sized for strength considerations, Detail Category F should not govern. Fatigue will be governed by cracking in the base metal at the weld toe and not by shear on the throat of the weld. i.

Detail Category E and E’ details shall not be used on fracture critical members, and Detail Category D details shall be discouraged and used only with caution. Such details are highly susceptible to fatigue damage. Eye bars and pin plates are design details which are not recommended except for very long truss spans where live load stress ranges are very low. In the event of their use, see Article 7.3.3.2 and the appropriate Commentary Article 9.7.3.3.2.

j.

For span lengths exceeding 300 feet an analysis is required for each bridge component using influence lines and the preceding car types and load frequencies, accounting for the effect of lightly loaded vehicles interspaced within the design train.

k.

When proper detailing practices are not followed, fatigue cracking has been found to occur due to strains not normally computed in the design process. This type of fatigue cracking is called distortion-induced fatigue. Distortion-induced fatigue often occurs in the web near a flange at a welded connection plate for a cross-frame where a rigid load path has not been provided to adequately transmit the force in the transverse member from the web to the flange. These rigid load paths are required to preclude the development of significant secondary stresses that could induce fatigue crack growth in either the longitudinal or the transverse member (Reference 38). It is emphasized that the stiffness of this connection is critical to prevent relative displacement between the components.

l.

List of symbols:

1 N = Number of occurrences of constant stress cycles which would cause fatigue damage equivalent to the fatigue damage caused by a larger number, Nv, of variable stress cycles ni = Number of stress cycles for each of the stress range values represented in the distribution being considered

Nv or Σn = Total number of variable stress cycles in the distribution or life

3

SR = Stress range, the algebraic difference between the maximum stress and the minimum stress for a stress cycle SRact = Stress range actually created at a given location in the structure by a moving load SRfat = Allowable fatigue stress range as listed in Table 15-1-10

4

SRi = Stress range of cyclic stress corresponding to the number of occurrences, ni SRe = Effective cyclic stress range for the total number of variable stress cycles, Nv . SRRMC = (Root Mean Cube Stress Range)

3

3

Σ ( n i S Ri ) -----------------------Σn i

α = SRact/SR or Eact/Eapplied ratio when SR is calculated by using the same load which was applied when SRact was measured. Field measurements have shown the measured SR is equal to a factor, α, times the calculated SR. This reduction reflects the beneficial effects of participation by the bracing, floor system, or other three-dimensional response of the structure and, also, the fact that full impact does not occur for every stress cycle. Since SR at a given location is directly proportional to the loading used, Eact/Eapplied also equals this ratio. γi = The ratio of the number of occurrences of SRi to the total number of variable stress cycles, Nv

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Steel Structures

SRmin = stress range or lower limit value for the starting point of the function being considered SRN = Stress range which corresponds to N constant stress cycles for a given detail 9.1.3.13.1 High Strength Bolts Subjected to Tensile Fatigue Loading Previous versions of this article were based on the 1969 edition of the Manual and distinguished between connections subject to less than or more than 500,000 cycles and were based on maximum applied stress. The current limits are based on applied stress range with a maximum set at the constant amplitude fatigue limit for these bolts. Prying force was taken as 20% pending further testing. The formula for the tensile stress area or effective bolt area is: 0.75 * cross-sectional area based on nominal bolt diameter (Reference 140, page 381).

9.1.3.14 COMBINED STRESSES (2005) 9.1.3.14.1 Axial Compression and Bending a.

f f f f The straight line interaction formula ----a- + -----b ≤ 1.0 is acceptable for small values of ----a- , but for values of ----a- greater Fa Fb Fa Fa than 0.15, the deflection of the column and the resulting increase in bending stresses caused by the axial load being made eccentric must be taken into account. The formula accomplishes this by applying a magnification factor f 1 1 ----------------------------------------------------- to -----b . This factor is similar in form to the formula -------------- (Reference 50) in which F′ e is 2 F 1 – f fa kl b -------------a 1 – ----------------------- ⎛ ----- ⎞ 2 ⎝ ⎠ F′ e 0.514π E r the elastic (Euler) buckling stress of the column loaded axially, divided by the applicable factor of safety, or 2

0.514π E ----------------------- in these specifications (see Article 1.4.1). 2 ⎛ kl ----- ⎞ ⎝r⎠ b.

When a member is braced in the plane of bending, at a panel point for example, there is no column deflection and, therefore, the magnification factor does not apply. Furthermore, the allowable axial stress here may be based on kl ⁄ r = 0 . The applicable formula then becomes f a ⁄ 0.55F y + f b ⁄ F b ≤ 1.0 . It should be noted that this formula does not apply at a connection point which is coincident with the location of maximum curvature of the deflected column axis, because such a point is not, in effect, braced.

c.

The above remarks cover bending about one axis only. For bending about both axes, the three-term formulas obtained by expansion are sufficiently accurate for use.

9.1.3.15 SECONDARY STRESSES (1994) R(2008) This article provides that secondary stresses due to truss distortion usually need not be considered in any member of the width of which, measured parallel to the plane of distortion, is less than 1/10 of its length. An exception to this general provision should be the effects of secondary truss members, such as floorbeam hangers and subverticals; these may produce excessive secondary stresses in the chord unless adjustment is made in lengths of the verticals.

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Commentary

9.1.3.16 PROPORTIONING OF TRUSS WEB MEMBERS (2004) R(2010) In determining whether it is safe to keep an old structure in service, the rules of Part 7, Existing Bridges, Section 7.3 Rating, govern. Experience with older structures designed for lighter live loads, shows that in such structures the web members of trusses reach their capacity sooner than other portions. This situation can be remedied either by providing an initial design of all members for an increased live load at higher stresses or by providing a truss design under which the web members reach their safe live load capacity at substantially the same increased live load as the remainder of the truss. The latter method is more economical and is provided by the recommended practices requirements (Reference 76).

9.1.4 BASIC ALLOWABLE STRESSES 9.1.4.1 STRUCTURAL STEEL, RIVETS, BOLTS AND PINS (2011) a.

In determining the allowable stresses, the value of 1.82, which is equal to 1/0.55, has been adopted as the usual factor of safety in tension, based on the minimum yield point of the material. The same value has been used for such compression applications as are not affected by axial combined with bending effects.

b.

Yielding of the gross area and fracture of the effective net area are considered the failure limit states. Yielding of the gross area can lead to excessive elongation of the member. This uncontrolled elongation can precipitate failure of the overall structural system. Fracture of the effective net area was proposed by Munse and Chesson (Reference 87) and has been long since adopted as a limit state by both the AISC (References 81, 82, 83) and AASHTO (Reference 120). The allowable stress of 0.47 Fu has been adopted by AREMA to align with AASHTO and to provide an additional factor of safety due to the sudden nature of this failure state.

c.

The more conservative design approach for pin connected members is based on the results of experimental research (Reference 67).

d.

Since there have been more failures in floor beam hangers with riveted connections than in other members, a greater apparent factor of safety has been adopted for such members.

e.

From 1935 to 1969, the secant formula, and parabolic type formula approximating it, formed the basis for the column formula of these recommended practices. It has been somewhat difficult to use and an assumed value of ec/r2 such that reasonable values result for intermediate column lengths makes the allowable stress on short columns less than necessary. For these reasons, and because long columns and eccentrically loaded columns can be provided for by Euler type formulas and interaction formulas, respectively, without resort to the secant formula, the use of the secant formula was discontinued.

f.

The column curve of the Column Research Council (now titled Structural Stability Research Council) (Reference 54) which can be expressed in the symbols adopted in these recommended practices: 2

F y ⎛ kl ⎞ 2 f = F y – ------------ ----2 ⎝ r⎠ 4π E was selected as the basic curve for the development of the formulas used in these recommended practices. Studies were made which included plots of this curve with variable factors of safety such as that used by AISC (Reference 4), and with constant factors of safety 1.8, 1.9 and 2.0. Many varieties of column curves were plotted on the chart on which these Column Research Council curves had been plotted, and it was decided that the most practical form to be used was one involving the three formulas of the recommended practice. g.

The difficulty of evaluating k in railroad bridge compression members may lead to allowable stresses that are too high, especially in the approximate range of kl/r between 40 and 100, where a slight variation in k will have a large effect on

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3

4

Steel Structures the allowable stress. Some protection against this danger is provided by the adopted straight line formula as compared to the Column Research Council curve. h.

The formula to be used in determining the allowable compressive stress in the extreme fibers of welded built-up or rolled beam flexural members symmetrical about the principal axis in the plane of the web (other than box-type members) is based on theoretical studies made by Professors George Winter and Bruno Thürliman. In Professor Winter’s discussion of a paper by Karl de Vries, he developed formula (Reference 39) for fc, the critical stress for failure of the beam. This formula may be written: 2 2 ⎧ ⎫1 ⁄ 2 2 KI y ⎪ Eπ 2 ⎛ I y ⎞ 2 Eπ l ⎞ 2⎪ ⎛ f c = ⎨ --------------- ------- + --------------- ----------------------------- ------ ⎬ ⎝ 2I ⎠ ⎝ ⎠ ⎪ ⎛ l⎞2 x l 2 2 ( 1 + μ )I x 2 πd ⎪ 2 ⎛ --- ⎞ ⎩ 2 ⎝ --- ⎠ ⎭ ⎝ d⎠ d

where: K = torsional constant μ = Poisson’s ratio Professor Thürliman (Reference 11) has shown that this formula may be expressed in the form of fc =

2

σw + σv

2

where: σw = extreme fiber stress resulting from warping torsion, where the compression flange bends and the beam warps σv = extreme fiber stress resulting from pure torsion. Thus, the critical extreme fiber stress may be considered to be represented by the length of the hypotenuse of a right triangle, whose sides are σw and σv , and to be equal to or greater than either of them. Under certain conditions, one or the other may be negligible, so that the value of fc cannot be less than the greater value. If σv , is assumed negligible (i.e. = 0), then the critical stress is 2

fc =

2 2 Iy ⎞ ry ⎞ Eπ - ⎛ ------Eπ - ⎛ --------σ w = ------------= -------------⎟ ⎜ ⎝ ⎠ l ⎞ 2 2I x l ⎞ 2 ⎝ 2r 2 ⎠ ⎛ ⎛ 2 --2 --x ⎝ ⎠ ⎝ ⎠

d

d

For I shaped members, rx = 0.4d (approx.), so that 2

1.56Eπ f c = -------------------2 ( l ⁄ ry )

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Commentary Based on a factor of safety of 1.8, the allowable stress becomes 2

0.87Eπ -------------------2 ( l ⁄ ry )

This formula is of the Euler type, and the allowable stress so determined must be modified so that it will be limited by the yield point of the material involved. A parabolic transition curve of the form Fb = A–B (l/ry)2 from the value Fb = 0.55 Fy at l/ry = 0, and tangent to the Euler type formula curve, is the most acceptable form for this transition curve. This parabola intersects, and is tangent to, the Euler curve at E l ⁄ r y = 5.55 ----- , and the values of A and B are such that Fy 2

0.55F y ⎛ l ⎞ 2 0.55F y – ------------------ ---2 ⎝ ⎠ 6.3π E r y is the first expression applying to this case in Article 1.4.1. Since Article 1.7.1b limits flexural members to those with E , the Euler type formula is not part of the requirements. an l/ry not greater than 5.55 ----Fy i.

The second compression formula in Article 1.4.1 applying to this case is based on the Winter formula with the assumption that σw is negligible (i.e. = 0), so that the critical stress is

1

2 KI y ⎞ 1 ⁄ 2⎛ l ⎞ Eπ ⎛ -----f c = --------------- ⎜ ----------------------------- ⎟ ⎝ πd ⎠ 2 l ⎞ 2 ⎝ 2 ( 1 + μ )I x ⎠ ⎛ 2 --⎝ d⎠

and, with only minor error.

3

2 3 K = --- bt 3 3

tb I y = 2 ------12 I x = 2bt ( d ⁄ 2 )

4

2

μ = 0.3 so that

Eπbt 0.207πE f c = ----------------------------- = --------------------ld ⁄ bt 2 l 2 ⎛ --- ⎞ 2.42d ⎝ d⎠

0.115πE and the allowable stress, based on a factor of safety of 1.8 and with bt = Af, is --------------------ld ⁄ Af which is the second of the formulas in Article 1.4.1 applying to this case.

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Steel Structures j.

Since tests have shown that the pure torsional (σv) effect on a riveted member is modified considerably by slip in the riveted connections, only the first type formula is considered suitable for use with riveted construction, and Article 1.4.1 so limits this case.

k.

For box type flexural members, the stiffness of the member is usually such that the full allowable stress (= 0.55 Fy) can be used for both flexural tension and compression, without reduction. However, very slender and deep box type flexural members may require reduction comparable to that of a single plane I type flexural member, and it is necessary to determine the effective slenderness ratio (defined herein as (l/r)e) of such members by calculating the (l/r)e) value as defined in Article 1.4.1. This effectiveness slenderness ratio is also the slenderness ratio determining the critical stress in the formula derived above 2

1.56π E f c = -------------------2 ⎛ -l⎞ ⎝ r⎠ e for beams in which the pure torsion effect is negligible. This critical stress for box girders is calculated to be (Reference 55): π f c = ------- JGEl y lS x 2

4A where J = torsional constant = ----------Σs ⁄ t E G = --------------------2(1 + μ ) I, Sx, A, Iy and s/t defined in Article 1.4.1. Equating these two values for fc: 2

1.56π E π -------------------- = ------- JGEl y lS 2 x ⎛ -l⎞ ⎝ r⎠ e and making the indicated substitutions, the value of the effective slenderness ratio shown in Article 1.4.1 is solved to be: ⎛ -l⎞ = ⎝ r⎠ e

l.

1.105πlS x Σs ⁄ t ----------------------------------------Iy A ----------------(1 + μ)

The allowable stress in bearing between rockers and rocker pins was adapted from editions prior to the 1969 edition and the low value of 0.375 Fy was retained to minimize pin wear. Pin wear had historically been a cause of trouble when higher values for this condition were permitted. Refer to Part 10 and Part 11 for additional information.

m. The allowable shears in A325 and A490 bolts are based on recommendations of the Research Council on Structural Connections of the Engineering Foundation. Also see Reference 42 and 115.

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Commentary n.

The allowable stress in bearing on expansion rollers and rockers was based on static and rolling tests on rollers and rockers (Reference 14). The average vertical pressures over calculated contact areas for loads substantially less than allowable design values are in excess of the yield point, causing a flow of the material. It was concluded that the resulting “spread” of the roller and base, measured parallel to the axis of the roller at points near the surfaces in contact, was the most satisfactory phenomenon to use in determining design values. Such “spreads” or deformations were measured in units of 0.001 to, per inch per 1,000 strokes, each stroke corresponding to a roller movement of 4 inches and an equal movement back. Design values according to the tests would give total deformations varying from about 3 units to less than 1.

9.1.4.2 WELD METAL (1994) R(2008) The allowable stresses on weld metal specified in Article 1.4.2, Table 15-1-13 are close to those permitted by AWS D1.5.

9.1.4.3 CAST STEEL (1994) R(2008) In the 1969 edition, because of better control over casting practices, the allowable unit stresses for cast steel in bearing or compression were increased from 0.9 to 1.0 of those for rolled steel, and for all other types of stress, from 2/3 to 3/4 those for rolled steel.

9.1.5 GENERAL RULES 9.1.5.4 THICKNESS OF MATERIAL (2011) a.

The 0.335 inch thickness limitation was introduced in 1969 to accommodate the use of certain wide flange beam sections as timber stringer replacements given that the assumed life of a timber structure was less than the assumed life of a typical steel structure. It is not the intention of this article to preclude this application on timber trestles.

b.

The usual design checks for a gusset plate and each member framing into the gusset plate are: • Normal Loads on a Section (t Lw), often referred to as the Whitmore Section as shown in Figure 15-9-4, where Lw is the effective width and t is the thickness of the gusset plate.

1

3

• Block shear, for compression and tension loads. • Shear on critical shear planes. • Buckling on the average of L1, L2, L3, as shown in Figure 15-9-4 with buckling factor of k to be evaluated for the gusset plate (k might be greater than 1.0). • All edge distance and end distance requirements for fasteners should be followed. • Gusset plates should be as compact as possible. • Check various critical sections using an acceptable method. • Check fastener prying action. • Each gusset plate is unique and must be designed based on specific forces, geometry and details.

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Steel Structures

Figure 15-9-4. Bolted and Riveted Gusset Plates

For further information on bolted and riveted gusset plates see Reference 65. Design of gusset plates using the procedure in Section 13 of “Structural Steel Designers Handbook” Third Edition, edited by R L Brockenbrough and F S Merritt, written by Prickett, Leroy and Kulicki, provides a reasonable approach.

9.1.5.8 NET SECTION (2005) R(2008) Net section is discussed by Chapin (Reference 21). He gives the history of this method of obtaining the net section of a riveted tension member to take account of the weakening effect of staggered open holes. He gives the rather complicated formula which represents the theoretically correct solution of the problem, and states that the simplified formula used in the recommended practices gives approximately the same results. The application of the formula to bolted fabrication and the 85% limit were based on later tests. A chart for use with the formula is included with his discussion.

9.1.5.9 CONNECTIONS AND SPLICES (2003) R(2008) In 2003, provisions to evaluate block shear were added to the Manual. Tests indicate that it is reasonable to add the yield strength on one plane(s) of a connection to the rupture strength on the other plane(s) of a connection to predict the block shear strength of a connection (References 56, 97). The controlling equation is the one that produces the larger rupture force (Reference 3).

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Commentary

9.1.5.10 FIELD CONNECTIONS (1994) R(2008) Welding under field conditions cannot always be satisfactorily performed and inspected to ensure the high quality needed for welds in railroad structures. Rivets or high strength bolts are therefore required for all main stress carrying connections made under field conditions.

9.1.5.12 COMBINATIONS OF DISSIMILAR TYPES OF CONNECTIONS (1993) R(2008) Welds are more rigid than rivets or bolts. Where used in combination, the welds will be overstressed before the rivets or bolts become effective.

9.1.5.13 SEALING (1993) R(2008) The requirements of Article 1.5.13b were adopted in 1943 and were based on experience and judgment. The maximum gage at which a second line of fasteners is considered effective was arbitrarily made the same as the maximum edge distance (See Article 1.9.4b) recognizing that the maximum gage should increase somewhat with the thickness of the material.

9.1.5.14 CONNECTIONS OF COMPONENTS OF BUILT-UP MEMBERS (1993) R(2008) The requirements for stitch fasteners in compression members, that the maximum pitch in a single line shall not exceed 12t nor the gage 24t, had been in force for many years prior to 1943 and were considered satisfactory. However, when it was not practical to have a gage as large as 24t, because the material was not wide enough, or not so disposed as to permit it, the requirements often led to an extravagant number of fasteners. The 1943 provisions with respect to staggered pitch permit the use of a reasonable number of fasteners in such cases. A study of the possible fastener patterns that might result from these provisions indicated that they would give greater security against buckling than the permissible pattern without stagger, using pitch of 12t and gage of 24t.

1

9.1.6 MEMBERS STRESSED PRIMARILY IN AXIAL TENSION OR COMPRESSION 9.1.6.1 COMPRESSION MEMBERS (2004) R(2008) a.

3

The basic formula for determining the minimum permissible thickness of webs and cover plates of compression members as stated in Article 1.6.1b was derived by Hovey (Reference 61). This basic formula for the determination of the minimum thickness, t, of plate of width, b, at which buckling of the plate when the plate is simply supported at both edges and is stressed to the yield point, Fy in compression is:

4

Fy t = b ---------------3.616E Hovey then reduced the constant 3.616 by 25% to provide for small initial buckles in the plate as rolled, and the resulting formula is: F t = 0.61b -----y E b.

In order to be conservative, the minimum permissible thickness values in these recommended practices have been F F established as 0.90b -----y for webs and 0.72b -----y for cover plates. E E

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Steel Structures c.

Where the calculated stress, f, is less than the allowable, Pe, the denominator of the formula determining the P permissible minimum thickness may be increased by ---------e with an arbitrary maximum limit of 2 for the value of this f radical.

d.

For commentary on Article 1.6.1c regarding the minimum thickness of perforated cover plates, see Article 9.1.6.4.

9.1.6.2 OUTSTANDING ELEMENTS IN COMPRESSION (2004) a.

The basic formula derived by Bleich for the thickness-width (t/b) ratio at which buckling of the angle leg will occur when an equal legged angle is stressed to the yield point, Fy , is (Reference 16): t --- = b

Fy F ------------------ = 1.61 -----y E 0.384 E

b.

For unequal legged angles, for plates supported on one edge, for stems of tees, and for flanges of beams, the Bleich formula is conservative.

c.

In determining the values specified in Article 1.6.2 conservative modifications in the denominator constant have been made. These modifications were based on experience, judgement and values used currently in other specifications.

9.1.6.4 LACING AND PERFORATED COVER PLATES FOR TENSION AND COMPRESSION MEMBERS (2009) a.

The probable maximum shears on column lacing were analyzed by Hardesty (Reference 59). He listed the causes producing shear on column lacing as follows: (1) Transverse loads acting on the column. (2) Moments at the end of the column, or eccentric application of loads. (3) Initial curvature of the column. (4) The springing of the column as a result of Causes 2 and 3. (5) Local defects in the column and initial stresses set up in the column during fabrication.

b.

Analyses in 1935 of Causes 2, 3 and 4 by Hardesty (Reference 59) led to the adoption of a column shear formula that remained in use until 1993. For derivation of this shear formula, the 1935 analyses used the secant formula which resulted in unnecessarily reduced allowable axial stresses in short columns, as noted in Article 9.1.4. This use of the secant formula led to unusually high shear forces for short columns. The subsequent abandonment of the secant formula in these recommended practices (see Article 9.1.4) permits the use of a uniform percentage of axial load for shear load for Causes 2 through 5. The AFy /150 expression for minimum shear force is included to keep the shear resisting elements from being too light for columns of length approaching or in the Euler range. Without such a limit, long columns could be designed with very little relative shear resisting steel since the column area is greatly increased on account of the L/R stress reduction applied for determination of the column area for axial load, with no corresponding reduction in allowable stress for the shear steel. Furthermore, the application of the limit to columns in the Euler range makes the shear resisting steel area requirement the same for steels of all yield strengths, the same as applies to the axial steel area. The limit will not affect columns having customary L/R ratios unless the yield strength is unusually high.

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Commentary c.

The formula represents average conditions. For end conditions not properly covered by the assumptions made in the analyses, special investigation can be made by means of the appropriate formulas given. This design formula covers only shears due to accidental eccentricities and usual column imperfections, and does not include shears caused by transverse loads (Cause l) or by eccentricity of load.

d.

Thürliman and White made a study and conducted tests of columns with perforated cover plates which demonstrated that the formula given for shear on lacing is also adequate for shear on perforated cover plates of structural steels. (Reference 148) Other specification requirements given for perforated plates are also based on this study and these tests.

e.

The formula given in Article 1.6.4.3d for the determination of the thickness of the perforated cover plate is based on the calculation of the net area required along the center line of perforations to resist the longitudinal shear. Using the nomenclature of that article, 3V/2ht is the maximum transverse shearing stress at the center line of the cover plate, and is also the maximum longitudinal shearing stress at that location. The total longitudinal shear in a length equal to the distance center to center of perforations which must be resisted by the cover plate is (3 V/2ht) ct = 3cV/2h. The net area of the plate center to center of perforations is (c – a) t; so that the shearing stress, v, on this area is 1 - or t = -------------------------3cV v = 3cV ---------- × ----------------2h ( c – a )t 2vh ( c – a )

f.

The shearing stress in the transverse section through the center of a perforation is usually not critical and can be calculated according to accepted methods, taking account of all of the section of the member outside of the perforation.

9.1.6.5 EFFECTIVE NET AREA FOR TENSION MEMBERS - STRENGTH (2007) R(2008)

1

Research (Reference 87) has shown that failure by rupture through a tension member is a function of the effective net section of the tension member. The effective net section of a member is a function of the geometry of the member and the connection(s) transferring load into or out of that member. In bolted and riveted connections, due to the presence of holes, the concept of effective net section is characterized by rupture across the net section. It is important to note that when evaluating a bolted or riveted connection, the shear lag reduction coefficient should only be used in conjunction with the net section rupture failure mode (Fa=0.50Fu) and not the yielding of the net section failure mode (Fa=0.55Fy). In welded connections, due to the absence of holes, the concept of effective net section is characterized by rupture across the gross section. In welded connections, both the rupture failure mode and the yielding failure mode occur across the gross section. Again, the shear lag reduction factor should only be used in conjunction with the allowable stress against rupture (0.50Fu) and not the allowable stress against yielding (0.55Fy). It should be noted that shear lag is present only when tension is being transferred into or out of a member. Some members, such as lower chords of trusses, are incrementally loaded across the length of the member. In the case of a lower chord of a truss, the loads are transferred into and out of the chord at panel points. Engineering judgement should be used in applying the shear lag reduction coefficient in cases such as this. Depending on the details of the connections, the shear lag factor may or may not need to be applied to that portion of the tension force transferred through the panel point from chord segment to chord segment. The shear lag factor should be applied to that portion of the tension force transferred from the diagonal members to the chord segment.

9.1.6.6 EFFECTIVE AREA FOR TENSION MEMBERS - FATIGUE (2007) For the purpose of calculating the stress range in a member, the effective area (gross or net) of a member that receives load through a connection shall be the sum of the areas (gross or net) of its component parts which receive load directly through the connection. An example of this would be an I-shaped member that receives load through a connection to gusset plates fastened only to the flanges and not the web of the member. The effective area (gross or net) of this member, for fatigue calculations, should be the sum of the areas (gross or net) of its flanges only. If the connection is made through the use of rivets or bolts in a bearing type connection, the area of the holes shall be deducted in accordance with Article 1.5.8. If the

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Steel Structures connection is made through the use of bolts in a slip-resistant connection or through the use of welds, no deduction for holes shall be made and the gross section of the component parts shall be used. The purpose of utilizing the effective area (gross or net) for the calculation of a fatigue stress range is to account for the shear lag effect which occurs when load is transferred through a connection to a member where not all of the component parts of the member are directly connected. The effective area that is used in the calculation of fatigue stress range is different than that used in the calculation of stress for a strength evaluation. The shear lag reduction coefficient described in Article 1.6.5 is based on a level of stress consistent with fracture of the member. Although limited information is available concerning the magnitude of shear lag at stress levels less than that associated with fracture, researchers agree that the sum of the areas (gross or net) of the directly connected parts is an appropriate estimate of the effective area that should be used in a fatigue evaluation.

9.1.7 MEMBERS STRESSED PRIMARILY IN BENDING 9.1.7.1 PROPORTIONING GIRDERS AND BEAMS (2004) R(2008) a.

These articles provide for proportioning flexural members, whether rolled or built up, by the moment of inertia method, using a neutral axis along the center of gravity of the gross section, and using the moment of inertia of the entire net section for the determination of the extreme fiber stress in tension, and the moment of inertia of the entire gross section for the determination of the extreme fiber stress in compression.

b.

This procedure is not subject to question in the case of welded built up or of rolled members. In the case of built up members of riveted or bolted construction, the neutral axis for a section taken through rivet or bolt holes in the tension area will not be along the neutral axis of the gross section, but will be somewhat nearer the compression flange. If such a section is analyzed taking account of the lack of symmetry of the section and consequent differences in distances from the neutral axis to the two flanges in determining the section moduli for the two flanges, the section moduli for the two flanges will agree very closely with those prescribed in these articles.

c.

The requirement that the ratio of the unsupported distance between points of lateral support and the radius of gyration E of the compression flange in paragraph b shall not exceed 5.55 ----- is based on the derivation of the parabolic Fy formula for the allowable stress in the compression flange as explained in Article 9.1.4. The parabolic formula becomes tangent to the basic Euler type formula at that point.

9.1.7.2 FLANGE SECTIONS (1994) R(2002) The 1969 edition of these recommended practices dropped the requirements for riveted and bolted construction which had appeared in earlier editions specifying relative thicknesses for flange angles and cover plates, and specifying the maximum percentage of the total flange area permitted in the cover plates. These requirements had no theoretical basis, but had been included because of what had historically been considered good practice. Present requirements for the length of partial length cover plates in riveted and bolted construction control the stress at the end of the cover plate, which is a critical section for fatigue.

9.1.7.3 T HICKNESS OF WEB PLATES (2004) a.

The specified thickness of web plates for flexural members is based on work done by Hovey (Reference 61). Hovey showed that the buckling of the web of a flexural member on the compression side of the neutral axis can be prevented either by the use of horizontal (longitudinal) stiffeners or by making the web of such thickness that stability against buckling is ensured. Vertical (intermediate transverse) stiffeners are not effective in resisting buckling caused by bending. Assuming the actual extreme fiber stress in the compression flange is 0.55 Fy, and that the compression stress in the web adjacent to the flange is less than this by an assumed percentage, the ratio of the thickness of the web to the

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Commentary clear distance between flanges, for a web without horizontal stiffeners, to ensure the stability of the web against F flexural buckling may be expressed by the formula 0.18 -----y . E Where the extreme fiber stress in compression is less than the allowable, then the ratio may be modified as specified. b.

For web plates stiffened by a horizontal (longitudinal) stiffener located at 0.20 of the web depth from the compression flange, work by Rockey and Leggett (Reference 98) has shown that, to ensure the stability of the web against flexural buckling, the web plate thickness required is only 43% of that required without a horizontal stiffener. It is specified that the web plate thickness shall not be less than 1/2 that determined for a web plate without a horizontal stiffener.

9.1.7.4 FLANGE-TO-WEB CONNECTION OF PLATE GIRDERS (2009) a.

The recommendation to use continuous, full penetration groove welds for the flange-to-web connection of open and non-composite, non-ballasted decks is to prevent fatigue cracking in the top flange welds from the direct application of cyclic wheel loads. Full penetration groove welds ensure complete fusion between flange and web. Fillet welds may crack through their throat from the transfer of repetitive concentrated loads unless they have been designed for that loading condition. For ballasted, welded steel plate or composite concrete decks, and through plate girders, either continuous, partial joint or complete joint penetration groove welds or fillet welds can be used as the concentrated loads are distributed such that the loading on the flange and web plate is not as critical for fatigue. Any of these types of connections will provide comparable performance. When webs less than 1/2 inch thick are used, fillet welded connections are preferable as they result in less web out-of-plane distortion from weld shrinkage. Fillet welds on the bottom flange should never be subjected to concentrated wheel loads.

b.

Fatigue cracking has been known to originate from the lack-of-fusion plane which exists between the web and flange joints where fillet welds were used in open and non-composite, non-ballasted decks. The driving force producing the cracking is from the direct application of wheel loads which apply vertical cyclic stresses to the welded joint perpendicular to the lack-of-fusion plane. Although the applied vertical cyclic stress ranges are compressive, the welds actually undergo cyclic tensile stress ranges due to the residual tensile stresses from welding. Previous editions of the manual required the flange-to-web joints be made using continuous, complete joint penetration (CJP) welds. Partial joint penetration (PJP) groove welds were acceptable if permitted by the engineer, though no guidance on how to design the PJP joint for fatigue was provided in manual. As a result, CJP were typically specified. The provisions to include PJP groove welds at the flange-to-web weld in Article 1.7.4b were added to allow the use of the more economical weld details in lieu of the CJP welds previously required. When properly proportioned, PJP groove welds will perform as well as CJP groove welds to resist such cracking if sufficient penetration is achieved and/or if sufficient fillet reinforcement is provided. In such cases, the fatigue strength of the PJP weld subjected to transverse or vertical loads is controlled by weld toe cracking and not throat cracking. Hence, the performance will be the same as the CJP but with the lower cost PJP. This can be achieved by using the equation in the provisions of detail description 5.4 in Table 15-1-9. The costs to fabricate CJP are greater than PJP connections due to the increased requirements on inspection and increased overall fabrication costs. If a PJP weld is used for the flange-to-web connection, the connection shall be considered a Fatigue Detail Category B’ for checking the longitudinal bending stresses in the girder.

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Steel Structures

9.1.7.8 WEB PLATE STIFFENERS (INTERMEDIATE TRANSVERSE AND LONGITUDINAL) (2010) a.

Hovey showed that the ratio of web clear depth to thickness for which stiffeners are not needed is determined by the formula

4.83E -------------- , where Fys is the yield point in shear of the web material (Reference 61). With Fys = 0.636 Fy , the F ys

E E formula became 2.75 ----- . The formula 2.12 ----- , used in Article 1.7.8, makes allowance for lack of flatness in the Fy Fy web plate. b.

Where stiffeners are required, their spacing is dependent on the web thickness and the shearing stress in the web. The development of the formula is based on work by Moisseiff and Leinhard and is based on a factor of safety of 1.5 against buckling of the web (Reference 85). This factor of safety is lower than the basic factor of safety generally used throughout these recommended practices, but is considered adequate because elastic buckling of the web does not cause failure. When elastic buckling of the web occurs, its share of additional diagonal compression is transferred to the flange and vertical (intermediate transverse) stiffeners.

c.

The 96 inches maximum spacing of the stiffeners is specified in order to provide stiffeners at reasonably close intervals so as to aid in eliminating the effect of any small out of flatness that may exist in the web. The 96 inch maximum spacing is based on work done by Basler indicating that for fabrication, handling and erection purposes the maximum stiffener spacing should not exceed 260t, where t is the web thickness in inches (Reference 13). The distance between vertical (intermediate transverse) stiffeners shall not exceed the distance between the flanges (web depth) because the E formula for stiffener spacing, 1.95t --- , is developed from the theory of elastic stability with this assumption (i.e. S critical buckling coefficient in shear always less than 9.35).

d.

The equation for minimum required moment of inertia “I” of the transverse stiffener is a modification of that developed by Bleich (Reference 16). In prior editions of the Manual the term “da”, the actual clear distance between intermediate transverse stiffeners, was used in the formula for “I” instead of the present “d”. The effect of using “da” was that the stiffeners were sized to develop the elastic shear buckling capacity of the web for that “da”. For various reasons, transverse stiffeners are sometimes spaced closer than the spacing required by Article 1.7.8a. This close spacing results in a web shear buckling capacity (based on elastic behavior) much greater than the web shear yielding capacity. Hence, for such cases of arbitrary stiffener spacing, the stiffener sizes computed from the formula for “I” were excessive. The use of “d” in the equation for “I” results in more consistent stiffener sizes for girders having stiffener spacings dependent on other factors in addition to shear.

e.

The web plate depth criteria of ⎛ 4.18 E ---⎞ t specified in Paragraph f, relates to the web plate depth required to preclude ⎝ f⎠ flexural elastic buckling of the web plate without horizontal (longitudinal) stiffeners.

f.

The recommended practice for placing the centerline of the longitudinal stiffener at 1/5 the web depth from the compression flange is from work by Rockey and Legett (Reference 98) showing this to be near optimum location to resist flexural buckling of a simply supported plate. Where longitudinal and intermediate transverse stiffeners intersect, the preferred detail is to interrupt the transverse stiffener since terminations in the longitudinal stiffener create details that are more prone to fatigue. Article 9.1.10.2g provides additional guidance and preferred detailing practices for intersecting stiffeners.

g.

The recommended practice for longitudinal stiffener size is taken as a reasonable upper bound for girders of practical proportions based on the work by Dubas (Reference 29).

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Commentary h.

The recommended practice for the thickness requirements for longitudinal stiffeners is based on the local buckling behavior of the stem of a tee section.

9.1.7.9 COMPOSITE STEEL AND CONCRETE SPANS (2008) a.

The two types of shear connectors included, i.e. manually welded channels and automatically welded studs, are those most commonly used (Reference 113). Other types may be satisfactory.

b.

Recommended practice requirements are generally based on performance, allowing the manufacturer and fabricator considerable leeway as to details and procedures.

9.1.7.9.2 Basic Design Assumptions (1986) R(2005) and 9.1.7.9.3.1 Design Force for Shear Connectors a.

The calculations for the value of the horizontal shear between the steel beam and the concrete slab in Article 1.7.9.2 j involve the determination of the values Sm of the maximum horizontal shear and the value of Sr of the range of the horizontal shear.

b.

The effect of repeated stress variations was studied at Lehigh University by making fatigue tests on composite spans (Reference 113). The results indicated that the range of horizontal shear resulting from live load and impact load, rather than the maximum horizontal shear from dead load combined with live load and impact load, controls fatigue capacity. The allowable design load per shear connector, based on maximum range as specified in Article 1.7.9.3.1, is therefore less than is specified in that same article for maximum shear.

c.

1

It is noted that the fatigue check Article 1.7.9.3.1(c) is different from that required in Articles 1.7.9.3.1(a) and 1.7.9.3.1(b). The checks in Articles 1.7.9.3.1(a) and 1.7.9.3.1(b) are to ensure that fatigue cracking in the weld used to attach the shear connector to the flange does not occur through the weld throat due to cyclic shear stresses. The requirement to check fatigue in the base metal of the member to which the shear connectors are attached (Article 1.3.13) is to ensure toe cracking does not develop at the weld and lead to cracking of the member due to primary bending stress range. The shear connectors are considered a short attachment on the flange. It is unlikely this check will ever control, as live load stress ranges will be very small due to the high location of the neutral axis.

3

9.1.8 FLOOR MEMBERS AND FLOORBEAM HANGERS

4

9.1.8.3 END CONNECTIONS OF FLOOR MEMBERS (1993) R(2002) a.

The requirements for the connection angles of stringers were developed by Wilson after a study of the bending stresses in such angles resulting from the lengthening of the bottom chords of through truss bridges under live and impact loads, and from the deflection of the stringers themselves under such loadings (Reference 149).

b.

Although the flexural stresses in the stringer and connection angles resulting from the lengthening of the bottom chord of through truss bridges are small, making these connection angles more flexible reduces the rather large bending stresses in the floorbeams resulting from bottom chord elongation.

c.

The flexural stress in the top portion of the leg of the stringer connection angles connected to the floorbeam may be high as a result of the deflection of the stringer under load and in the case of thick angles may cause fatigue cracks. For a given deflection in the top portion of the angle, the stress induced in the angle leg varies directly with the angle thickness, and inversely as the square of the gage. This deflection is essentially proportional to the length of the stringer. These three factors have been combined empirically in the requirements of this article.

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Steel Structures

9.1.9 RIVETED AND BOLTED CONSTRUCTION 9.1.9.4 EDGE DISTANCE OF FASTENERS (2005) R(2011) Based on a review of various textbooks, specifications, and design guides it has been found that there is not a solid “engineering” reason for the various limits on edge distance. The limits which have been set are more related to detailing issues. The rationale for various edge conditions is as follows: • Sheared edges From the Cyclopedia of Civil Engineering, Vol 3, Steel Construction, 1920, a reason for a limit on edge distance is given based on the tendency of the material to bulge between the edge of the hole and the edge of the plate due to the punching process. To prevent this, it is stated that a minimum edge distance is required. The limit is decreased for smaller size rolled shapes only to allow punching in the material rather than for any engineering reason. The third edition of the AISC LRFD Manual of Steel Construction (2003) indicates similar reasoning in the Commentary contained in Chapter J of that publication. (References 25, 84) • Rolled edges of plates, shapes, bars or thermally cut edges Limitations on the clearance for making the hole, as well as the fact that the rolled and thermally cut edges have a much better tolerance in terms of workmanship, justifies a lower limit for these type edges. The limit is reduced for flanges of beams and channels to 1.25 times the diameter of the fastener, but only because there may be clearance issues with the equipment used to make the hole in these sections with smaller flanges. Similar reductions are also permitted by the AISC Manual. (Reference 84) • Fatigue The difference in the edge distance requirements is not related to fatigue. Although a sheared edge is almost always a lower quality than a rolled or thermally cut edge, the fatigue strength of a plate that is sheared cannot be improved by slightly increasing the edge distance. The micro cracks produced by the process are present regardless and under large enough cyclic stresses will grow into fatigue cracks. For a base metal condition to apply at the gross section of the element (i.e., Category A), there are specific surface quality standards that must be met as per AREMA Table 15-1-9, AASHTO LRFD, and others. Rolled edges will typically meet these criteria. For thermally cut edges, it may be necessary to grind the surface of the cut to meet the required surface quality. However, sheared edges will not meet the requirements due to the destructive nature of shearing the plate material, and some surface preparation will be required. (Reference 2)

9.1.10 WELDED CONSTRUCTION 9.1.10.1 T RANSITION OF THICKNESS OR WIDTHS IN WELDED BUTT JOINTS (1993) R(2003) The requirements of Article 1.10.1 are similar to those in AWS D1.5 with additions to cover flexural conditions.

9.1.10.2 PROHIBITED TYPES OF JOINTS AND WELDS (2008) Because of fatigue considerations, several types of joints and welds are added to types prohibited by AWS D1.5. g.

Highly Constrained Joints:

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Commentary Welded structures are to be detailed to avoid conditions that create highly constrained joints and crack-like geometric discontinuities that are susceptible to Constraint-Induced-Fracture (CIF). Avoid intersecting welds by using a preferred detail (see Figure 15-9-5) or by using high strength bolted connections. However, the avoidance of intersecting welds is not intended to apply to the intersection of flange splice welds with flange-to-web welds. Constraint-Induced-Fracture is a form of brittle fracture that can occur without any perceptible fatigue crack growth and more importantly, without any apparent warning. This type of failure was documented during the Hoan Bridge failure investigation (Reference 151) as well as in other bridges that have exhibited very similar fractures (References 23 & 24). Criteria have been developed to identify and retrofit bridges susceptible to this failure mode (References 23 & 79). Although it is common to start and stop an attached element parallel to primary stress (e.g., gusset plate or longitudinal stiffener) when intersecting a full-depth transverse member, the detail is more resistant to fracture (and fatigue) if the attachment parallel to the primary stresses is continuous and the transverse connection is discontinuous. (See Figure 15-9-5 and Figure 15-9-6) High strength bolted connections are not susceptible to Constraint-Induced-Fracture and should be considered where practical and economical.

1

3

4

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Figure 15-9-5a. Preferred detail Figure 15-9-5b. Acceptable detail

Figure 15-9-5c. Less desirable detail

Figure 15-9-5d. Very poor detail

Figure 15-9-5. Examples of details at intersection of longitudinal stiffeners and transverse plates welded to web

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Commentary

Figure 15-9-6. Examples of welded Fatigue Category E details at certain locations at the intersection of transverse connection plates and gusset plates welded to web. Both of these fatigue resistant details are difficult to fabricate. Bolted gussets are recommended.

9.1.10.4 WELDED ATTACHMENTS (2004) R(2008)

1

The requirements of Article 1.10.4 are based on fatigue considerations.

9.1.11 BRACING 9.1.11.4 CROSS FRAMES AND DIAPHRAGMS FOR DECK SPANS (1994) R(2002)

3

a.

Paragraph a provides the means to accomplish the lateral distribution specified in Article 1.3.4.2.4 (Reference 89 and 146).

b.

Out of plane bending may result from restraint provided by cross frames or diaphragms where there is differential deflection of adjacent beams or girders. This may be expected to occur in spans with curved alignment, skews or multiple tracks and has also been observed in single track spans, without skew, on tangent alignment. Out-of-plane bending may cause high stresses in non-stiffened web gaps, unless rigid type connections are provided to stabilize these gaps.

c.

Determination of whether a cross frame or diaphragm should be used is covered by paragraph b.

d.

Requirements for diaphragms are specified in paragraph c to assure suitable lateral distribution of live load.

e.

Paragraph d, paragraph e, paragraph f and paragraph g concern the spacing of cross frames and diaphragms for various types of deck construction. Spacing of 18 feet for cross frames and diaphragms in open deck construction has been specified since 1920; has been found to be satisfactory; and is used as a guide in specifying the spacing of these members for spans where steel plate, timber or precast concrete decking is utilized in ballasted deck construction and no top lateral bracing is used, as well as for spans with poured in place decking. The lack of lateral bracing requires close spacing of these members, whereas poured in place concrete decking will allow greater spacing, as evidenced by tests conducted at the University of Illinois on diaphragms for highway deck spans (Reference 89 and 146).

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Steel Structures f.

The diaphragms required in paragraph h are primarily for tying the transverse beams together and to some extent for distributing loads longitudinally.

9.1.13 CONTINUOUS AND CANTILEVER STEEL STRUCTURES 9.1.13.8 LONGITUDINAL STIFFENERS (2010) The requirements of this article correspond to specifications of the American Association of State Highway Officials 1977 edition, with some modifications. A continuously welded stiffener is best for design and performance, but at the intersection of two stiffeners continuity of one must be sacrificed. In such cases, it is generally better to interrupt the transverse stiffener since terminations in the longitudinal stiffener create details that are more prone to fatigue. For continuous or cantilever spans, however, the intersection between longitudinal stiffeners and transverse bearing stiffeners are an exception since bearing stiffener continuity is necessary for bearing loads and fatigue demand on the longitudinal stiffener termination detail is lower at bearing locations. Article 9.1.10.2g provides additional guidance and preferred detailing practices for intersecting stiffeners.

9.1.14 FRACTURE CRITICAL MEMBERS 9.1.14.1 SCOPE (2001) R(2008) The implementation of the AWS D1.5 Fracture Control Plan for Fracture Critical Members will help to ensure that a steel bridge with critical tension components will serve a useful and serviceable life over the period intended in the original design. Some bridges do not have fracture critical members. However, it is most important to recognize them when they do exist. The Fracture Control Plan should not be used indiscriminately by designers to circumvent good engineering practice. Section 1.14, Fracture Critical Members should be used as an extension of and supplement to the current requirements for welding as specified throughout Chapter 15, Steel Structures and the AWS Specifications. Where not specifically replaced by Section 1.14, Fracture Critical Members, all provisions of Chapter 15, Steel Structures and AWS D1.5 still apply. In 1995, AWS D1.5 was issued, including Section 12 that specifically addresses additional requirements for FCM’s. The D1.5 code contains the latest provisions to ensure reliable control of weld quality. Major changes from the 1978 AASHTO plan (and modifications) include: a.

Alternative to lot testing criteria for filler metals (D1.5)

b.

Extension of WPS qualification testing period of validity from one to three years (D1.5)

c.

Prequalification of SMAW WPS’s for use with electrodes with a tensile strengths 80 ksi (D1.5)

d.

Testing of welding consumables for FCAW and SAW in accordance with AWS A4.3 versus the glycerine method (D1.5)

e.

More extensive controls on exposure of welding consumables to atmospheric moisture (D1.5)

f.

Preheat levels based upon heat input, diffusible hydrogen levels, as well as steel grade and thickness (D1.5)

g.

New tack welding requirements (D1.5)

h.

Qualification testing of WPS’s for FCM’s is fully consistent with D1.5 requirements for WPS’s used on non-fracture critical members (D1.5)

The following commentary applies to the provisions of D1.5 Section 12 FCP as applied to railroad bridges: © 2011, American Railway Engineering and Maintenance-of-Way Association

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Commentary Fabricator Qualification Certification [AWS D1.5] Quality workmanship requires fabrication capability, trained workmen and effective and knowledgeable supervision. The AISC Quality Certification Program evaluates a plant on general management, engineering, drafting, procurement, operations and quality. Each of these areas is divided into sub areas and evaluated for policy statement, organization and personnel, procedures, facilities and equipment, and past record. Welding Inspector Qualification and Certification [AWS D1.5] Although requirements for welder qualification have long been established, little, if anything, was done to determine the competence of welding inspectors. The AWS Standard for Qualification and Certification of Welding Inspectors, QC-1, was developed to ensure that inspection personnel will have the ability to determine if welding is in compliance with requirements of the contract specifications. Non-Destructive Testing Personnel Qualification and Certification [AWS D1.5] Personnel performing non-destructive testing shall be qualified as NDT Level II or Level III, in accordance with ASNT Recommended Practice SNT-TC-1A. This practice has been upgraded for the non-destructive testing of FCM’s by only permitting the testing to be performed by individuals qualified as NDT Level II and working under the supervision of an NDT Level III person or an NDT Level III person to perform the testing. To ensure the capability of the Level III persons, they must be certified by the ASNT or equivalent as determined by the Engineer. The term “under the supervision” is intended to mean that the NDT Level III person will be available, as necessary, and will personally check the NDT Level II person's work on a periodic basis.

1

Preheat and Interpass Temperatures [AWS D1.5] The minimum preheat and minimum interpass temperatures required in D1.5 are based upon the requirements of the 1978 AASHTO FCP, but modified to incorporate the effects of the heat input of welding, and different levels of diffusible hydrogen in deposited weld metal. The actual minimum preheat and interpass temperature listed on the WPS is selected from the applicable table in D1.5 based upon the grade of steel being welded, the thickness(es) of steel involved, the computed value of welding heat input, and the maximum diffusible hydrogen content in deposited weld metal. While more complex than other systems to determine preheat, this method is considered more accurate and appropriate for fabrication of FCM’s.

3

Welding Consumables [AWS D1.5] All welding consumables used for fabrication of FCM’s must be of controlled quality. D1.5 accomplishes this by either requiring lot testing of consumables, or requiring the manufacturer to have a quality assurance program audited and approved by one of the independent agencies listed. It is not essential that each heat and lot of welding consumables be pretested in the combination that will be actually used in the work. Accepted heats and lots of welding consumables that conform to the same specification and that are made by the same manufacturer may be interchanged without concern that the weld metal produced will be unacceptable. Backing [AWS D1.5] Steel backing for groove welds using rolled bar stock of limited cross sectional area is considered superior to backing produced by stripping from plate. Bar stock is uniform in cross section and has light mill scale in most instances. Studies of the effects of backing chemistry on weld metal properties indicates that A36 steel is suitable backing for all groove welds in steels with a minimum specified yield stress of 50 ksi or less. The Charpy V-Notch toughness of backing bars of limited dimension will not have a significant influence on the fracture resistance of the groove welds.

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Steel Structures It is absolutely essential that all weld backing be continuous and that welds used to join segments of backing be made before the backing is applied to the weld. All joints in backings should be subject to the same weld quality standards and nondestructive tests specified for similar groove welds in the structure. Welding Procedures [AWS D1.5] Current AWS filler metal specifications recognize the weld metal properties may vary widely, depending on electrode size, flux used, amperage, voltage, plate thickness, joint geometry, preheat and interpass temperature, surface condition, base metal composition and admixture with the deposited metal. Because of the profound effect of the variables, a test procedure is included in these filler metal specifications intending to reproduce “good practice” welding conditions reasonably well and, at the same time, minimize the effect of the more important variables on weld metal properties. Although the above requirements are adequate for most applications, they are not considered sufficient for Fracture Critical Members. Therefore, D1.5 requires all welding procedures to be qualified by test, except for SMAW performed with specific electrodes. This is to help ensure that the weld metal deposited, using the procedure and base metal to be used in production, provides the required toughness. The deposited weld metal toughness of 25 ft-lb @ –20 degrees F is greater than the toughness of the base metal which it connects. This recognizes the possibilities of discontinuities (porosity, slag inclusions, etc.,) as permitted by AWS D1.5 and that the weld metal may have strength significantly greater than the base metal. It is the intent of these specifications that a fabricator that has properly completed welding procedure qualification tests within the last 3 years, not be required to repeat the tests for individual railroads unless the railroad has made it a Contract requirement prior to bidding. The A588 steel test plates and backing specified as an alternative to other steels have been subjected to a metallurgical evaluation that revealed the strength, ductility, and toughness of weld metal produced using this test base metal can be relied upon to indicate whether or not a Welding Procedure Specification will successfully join any of the approved steels with a yield stress of 50 ksi or less. Approval of a single grade of steel will reduce unnecessary testing of base metals and combinations of metals that have no significant effect on the acceptability of the Welding Procedure Specification. Hydrogen Control [AWS D1.5] D1.5 requires measurement of the SMAW coating moisture, and the diffusible hydrogen content of weld metal deposited by SAW and FCAW. These measurements are made by the filler metal manufacturer. Testing of diffusible hydrogen must be done in accordance with AWS A4.3 which recognizes the latest methods to measure diffusible hydrogen. The glycerine method, previously required by the AREA FCP, is no longer permitted as the results obtained by this method were highly variable, often resulting in artificially low values. The A4.3 methods are more consistent and more accurately represent actual hydrogen values. Welder Qualification [AWS D1.5] It is intended that welders, welding operators, and tackers be qualified by test within six months prior to the start of fabrication or regularly requalified on the annual basis. Once welders are qualified on the basis of mechanical and radiographic tests, yearly examination of radiographs is considered an acceptable method of assuring that welders and welding operators remain qualified. Repair Welding [AWS D1.5] Repair welding consists of deposition of additional weld metal to correct a surface condition, such as insufficient throat or undercut, or procedures which require removal of weld or base metal preparatory to correcting defects in materials or workmanship. The latter are divided into noncritical and critical repairs as determined by type and size of defect. Because virtually all weld repairs are made under conditions of high restraint, the minimum preheat/interpass temperatures requirements are generally higher than specified for the original welding. In addition, the minimum preheat for the repair area must be continued after completion of the repair until a post weld heating of 400° to 500° degrees F has been completed. This post weld heating is to enhance diffusion of any hydrogen that might be present. © 2011, American Railway Engineering and Maintenance-of-Way Association

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Commentary Again, because of the possible high restraint situation in repair welding, a longer time interval is required between completion of the weld repair and final non-destructive testing than in original welding. Documentation of both non-critical and critical repair welding is required. This is to enable these areas to be given special attention when inspections are made after the bridge is in service.

Non-Destructive Testing of Fracture Critical Members [AWS D1.5] The FCP recognizes that control of quality is the responsibility of the fabricator. However, it is the prerogative of the Engineer to assure that the quality of the product is as specified. This latter includes Quality Assurance (QA), witnessing of Quality Control (QC), testing, review of the fabricator’s documentation of visual and non-destructive testing and duplicating any such work as is deemed necessary. For production schedules to be maintained, it is essential that all QA work be carried out in a timely manner to minimize interference with production. The effectiveness of radiographic testing and ultrasonic testing is determined by the size, shape and orientation of discontinuity. The Plan requires that both methods of testing be used in determining the quality of all transverse tensiongroove welds. When the configuration of the material utilizing tension-groove welds is not in the same plane, only ultrasonic testing is required. The penetrating power and intensity of X-rays can be controlled by the user, but these same factors cannot be controlled by the user of gamma rays. The penetrating power of cobalt 60, 1.2 and 1.3 MEV, is so much higher than required for material thicknesses normally used in bridge construction that it is difficult to discern the small changes in thickness due to discontinuities. Iridium 192, however, has a lower and broader equivalent voltage, 0.2 to 0.6 MEV, and more closely approaches the operating characteristics of X-rays. Therefore, the use of cobalt is restricted to material thickness over 3 inches and is permitted because available sources for the thicker material are limited.

1

9.1.14.2 DEFINITIONS (1997) R(2008) a.

b.

c.

Fracture Critical Members (FCM) are defined as those tension members or tension components of members whose failure would be expected to result in collapse of the bridge or inability of the bridge to perform its design function. The identification of such components must, of necessity, be the responsibility of the bridge designer since virtually all bridges are inherently complex and the categorization of every bridge and every bridge member is impossible. However, to fall within the fracture critical category, the component must be in tension. Further, a fracture critical member may be either a complete bridge member or it may be a part of a bridge member. Some examples of critical complete bridge members are girders of two-girder bridges and tension chords in truss bridges, provided a failure would cause loss of serviceability of the bridge. Some bridges do not depend on any single member, be it in tension or in compression, for structural integrity. Critical tension components of structures usually occur in flexural members. The tension flange of a flexural member is a critical component if a failure of the specific flexural member would cause loss of serviceability of the bridge. The web of a flexural member, adjacent to the tension flange, can be a critical component. Members or member components whose failure would not cause the bridge to be unserviceable are not considered fracture critical. Compression members and member components in compression may, in themselves, be critical but do not come under the provisions of this Plan. Compression components do not fail by crack formation and extension but rather by yielding or buckling. Similarly, riveted and bolted members, even though in tension, may not come under the provisions of this Plan. The Plan provides for additional quality of material and provides for increased care in the fabrication and use of the materials to lessen the probability of fracture of tension components from crack formation and extension under static and fatigue loading.

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Steel Structures

9.1.14.3 DESIGN AND REVIEW RESPONSIBILITIES (1997) R(2008) a.

A critical part of any complete Fracture Control Plan must deal with design and detailing. These two sections are not addressed in Section 1.14, Fracture Critical Members or in this commentary primarily because they are already included in other parts of this chapter. Fatigue requirements are extensively covered in Article 1.3.13 and, where necessary, are made more conservative for fracture critical members (see Article 1.3.13i). Fatigue categories for various bridge details also are extensively covered. However, it remains a prime responsibility of the designer to examine each detail in the bridge for compliance with the fatigue requirements and to ensure that the detailing will allow effective joining techniques and non-destructive testing of all welded joints. It is emphasized that the Fracture Control Plan must begin with the designer and that without proper design, details and specifications, the Plan will fail.

b.

The designer is the only one with sufficient knowledge of the design to determine if fracture critical members are present and to specifically delineate those members or member components. It is, therefore, his responsibility to designate on the plans those members or member components which are fracture critical. Further, he also is responsible for the review of the shop drawings to determine whether the plans and specifications have been properly interpreted and that the fracture critical members are identified and properly fabricated.

9.1.14.5 NOTCH TOUGHNESS OF STEEL IN FRACTURE CRITICAL MEMBERS (2006) R(2008) a.

For comments relating to Table 15-1-14 see Article 9.1.2.1.

b.

The notch toughness requirements for steels in railroad bridges are similar to those used in steel highway bridges as specified by AASHTO. The requirements developed by AASHTO were adopted after considerable research and deliberation between representatives of the AASHTO Subcommittees on Bridges and on Materials, the Federal Highway Administration, the American Iron and Steel Institute, the American Institute of Steel Construction and various consultants. These requirements were based on numerous technical considerations that include the following: (1) An understanding of the effects of constraint and temperature on the fracture toughness behavior of steels that were established by testing fracture mechanics specimens. (2) An understanding of the effects of rate of structural loading on the fracture toughness behavior of structural steels. (3) The development of a correlation between impact fracture toughness values (KId obtained by testing fracture toughness type specimens under impact loading) and impact energy absorption for Charpy V-notch (CVN) impact specimens. (4) Specification of CVN impact toughness values that ensure elastic-plastic initiation behavior for fracture of fatigue cracked specimens subjected to minimum operating temperatures and maximum in-service rates of loading. (5) A verification of the selected toughness values by the testing of fabricated bridge girders that were subjected to the maximum design fatigue life, followed by testing at the minimum operating temperature and the maximum inservice rate of loading. (6) An awareness of the extensive satisfactory service experience with steels in bridges and an understanding of the factors that have occasionally led to brittle fractures in bridges.

c.

The safety and reliability of steel bridges are governed by material properties, design, fabrication, inspection, erection and usage. Both the AASHTO and AREMA Fracture Control Plans recognize that attention to all of these factors is essential and that excessive attention to any single item will not necessarily overcome the effects of a deficiency in any other item.

d.

Neither the AASHTO nor the AREMA fracture toughness requirements are sufficient to prevent brittle fracture propagation under certain possible combinations of poor design, fabrication or loading conditions. To accomplish that

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Commentary fact would require intermediate or upper-shelf dynamic toughness levels (also called crack arrest) and these levels of fracture-toughness are not needed to ensure the safety and reliability of the steel bridges. e.

The general difference in initiation and propagation behavior as related to fracture toughness test results is shown schematically in Figure 15-9-7. The curve labeled “static” refers to the fracture toughness obtained in a KId test under conditions of slow loading. (The curve for intermediate loading rate tests, which are extremely complex to run, would be shifted slightly to the right of the static curve. The AASHTO material toughness requirements were developed using an intermediate loading rate found applicable to actual bridge structures.) The impact curve is from KId or other dynamic test under conditions of impact loading. The difference between these two is the temperature shift, which is a function of yield strength for structural steels. In an actual structure loaded at temperature A, initiation may be static and propagation dynamic. However, there is no apparent difference between the two because both initiation and propagation are by cleavage. If a similar structure is loaded slowly to failure at temperature B, there will be some localized shear and a reasonable level of static fracture toughness at the initiation of failure. However, for rate sensitive materials, such as structural steels used in bridges, once the crack has initiated, the notch toughness is characterized by the dynamic toughness level on the impact curve and the fracture appearance for the majority of the fracture surface is cleavage. If the structure is loaded slowly to fracture initiation at temperature C, the initiation characteristics will be full shear initiation with a high level of plane stress, crack toughness Kc. However, the fracture surface of the running crack may still be predominately cleavage, but with some amount of shear as shown in the lower impact curve at temperature C in Figure 15-9-7.

1

3

4

Figure 15-9-7. Schematic Showing Relation Between Static and Dynamic Fracture Toughness f.

The use of impact or dynamic fracture tests in fracture control would predict no difference in actual resistance to fracture between temperatures A and B and only a modest difference between B and C. In fact, however, there is a considerable increase in resistance to fracture initiation between A and B and between B and C, as is indicated by slow loading tests such as KIc or crack opening displacement tests. However, there is essentially no difference in the resistance to fracture propagation (i.e., crack arrest behavior) between A and B, and the difference between B and C is modest. Thus, to prevent brittle fracture propagation in a structure by using material toughness alone (i.e., without proper control of design, fabrication, inspection and usage), the impact toughness must be quite high, e.g., approaching full shear propagation behavior temperature D. Even then, there may be situations where crack growth still occurs.

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Steel Structures g.

In summary, application of the AREMA material toughness requirements should provide a high level of elastic-plastic or plastic initiation behavior for steels with fatigue cracks loaded to maximum in-service rates of loading at the minimum service temperature. Because the AREMA Fracture Control Plan addresses all aspects that may lead to brittle fractures or fatigue failure (i.e., material properties, design, fabrication, inspection, erection and usage), these material toughness requirements should be satisfactory in the context of the total AREMA Fracture Control Plan.

h.

The prime focus on Fracture Critical Members must be on quality of the material and fabrication. Using low fatigue resistant details should be avoided. Category E and E’ details shall not be used on Fracture Critical Members, and Category D details shall be discouraged and used only with caution.

PART 3 FABRICATION 9.3.1 GENERAL 9.3.1.6 THERMAL CUTTING, COPES, AND ACCESS HOLES (2009) There are a number of thermal cutting techniques that are suitable for steel railroad bridge fabrication including, primarily, oxyfuel cutting and plasma cutting. Plasma cutting is generally preferred by fabricators because it is faster and offers improved quality (such as squarer corners, less hardness variability, and less distortion), but it is limited to thinner sections. The thickness limit depends upon the equipment, but typically about two inches is the reasonable thickness limit for plasma cutting. The provisions of this paragraph are similar to those in the AASHTO/AWS D1.5 Bridge Welding Code.

9.3.1.8 PLANING SHEARED EDGES (1994) R(2008) a.

Any sheared edge may have incipient cracks resulting from the shearing operation, which literally tears the material apart. Since such cracks might be harmful, the requirements for edge planing of sheared material have been included in these recommended practices and other specifications for many years.

b.

The planing requirements need not be applied to thin A 36 material because the shearing operation does not produce structurally damaging defects therein.

9.3.1.18 BENT PLATES (2000) R(2008) In fabrication, plates are often bent to a radius in a press brake or die. When conducted at room temperature, these processes are known as “cold bending”. To avoid cracking the plate during bending, it is necessary to adopt a suitable minimum inside bend radius, which typically varies with plate thickness and grade. Over the years, many new grades of steel have come into existence. A concern in the steel industry was that current limits dealing with this subject may not have been developed on a consistent basis. As a result, the American Iron and Steel Institute (AISI) initiated a project to develop rational limits for cold bending plates. Initially, AISI retained Concurrent Technologies Corporation (CTC) to conduct an experimental research program, augmented by inelastic analysis, to investigate the forming characteristics of five plate steels. At the conclusion of that effort in January 1997, AISI then retained R. L. Brockenbrough & Associates to extend the CTC findings to all steel plate specifications referenced in ASTM A6. That work was accomplished and reported in the document “Fabrication Guidelines for Cold Bending” dated June 29, 1998. ASTM A6 has adopted the recommendations of this work as well as some supplemental workmanship language for achieving quality bent plates. Article 3.1.18 Bent Plates, is derived from both the “Fabrication Guidelines for Cold Bending” and the ASTM A6 document.

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Commentary

9.3.2 RIVETED AND BOLTED CONSTRUCTION 9.3.2.2 HIGH STRENGTH BOLTS, NUTS, AND WASHERS (2005) R(2008) AND

9.3.2.3 INSTALLATION OF HIGH STRENGTH BOLTS (2005) R(2008) High strength bolts can be adequately installed by methods that control either the bolt deformation (strain) or the applied torque. Previous editions of this recommended practice adopted turn-of-nut as the primary installation method because deformation control procedures are typically more reliable and consistent than control by torque measurement. In addition to turn-of-nut, the current provisions also permit the use of direct-tension indicators (strain-control), tension-control twist-off bolts (torque-control) and the calibrated wrench (torque-control) methods of high strength bolt installation. Further details on these methods can be found in the Specification of the Research Council on Structural Connections (Reference 12 and 103).

9.3.2.6 PREPARATION OF HOLES FOR SHOP FASTENERS (1995) R(2008) Holes in members subject to live load stress are required to be drilled or reamed in order to avoid the incipient peripheral cracking at holes punched full size through thick material and the resultant lower resistance against fatigue failures.

9.3.2.7 PREPARATION OF HOLES FOR FIELD FASTENERS (1983) R(2008) The same comments as for Article 3.2.6 regarding cracks in the periphery of punched holes apply also to holes for field connections, and, in addition, there must be provision for accurate alignment of field connection holes. This article calls for field connection holes to be so located that they will register exactly when the structure is in its geometric configuration. This requires that truss members, as erected under a no stress (or practically so) condition, must be bent and forced to fit the end connections, thus introducing an initial reverse secondary stress which will theoretically disappear when the structure assumes the loading for which it is cambered.

1

9.3.3 WELDED CONSTRUCTION

3

9.3.3.3 FLANGE-TO-WEB WELDS OF FLEXURAL MEMBERS (1995) R(2008) Only properly selected machine welding is considered to be acceptable for flange-to-web weld of flexural members. In order to make such welds having the necessary uniformity and quality by any other method, elaborate and costly inspection procedures would be required.

4

9.3.3.4 TACK WELDS (1995) R(2008) The requirements of this Article are based on fatigue considerations.

9.3.5 INSPECTION 9.3.5.5 INSPECTION – WELDED WORK (2002) R(2008) The requirements of paragraph b and paragraph c take into account the generally high shear to moment ratio in railway flexural members and the common circumstance of heavy concentrated direct loading of flanges.

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Steel Structures

9.3.6 SHIPMENT AND PAY WEIGHT 9.3.6.3 PAY WEIGHT (2009) Editions of the AREA Manual prior to that of 1969 permitted payment for pound-price contracts to be based on either scale weight or computed weight. Consequently, it was necessary to specify a method of computing the weight which is compatible with scale weight. Since it is practically impossible in many cases to determine an accurate scale weight, and since the procedure of computing a weight compatible with a scale weight serves no practical purpose, the 1969 edition of the AREA Manual adopted the procedure reflected in the then current edition of the American Institute of Steel Construction Manual of STEEL CONSTRUCTION for computing weight.

PART 6 MOVABLE BRIDGES FOREWORD See the Foreword for References for Movable Bridges.

9.6.1 PROPOSALS AND GENERAL REQUIREMENTS 9.6.1.1 GENERAL (1986) R(2010) The history of movable bridge design specifications can be traced back at least as far as 1901 to the Baltimore & Ohio Railroad Company specification for swing bridges. C.C. Schneider’s Paper No. 1071 in the June 1908 ASCE Transactions, Volume LX, Page 258 appears to be the earliest specification giving allowable loads and stresses for individual components. The basic content of the Schneider specification appears in the first edition (1922) of the AREA Movable Bridge Specification. Many changes and additions have been made over the years to that specification and this recommended practice. Early movable bridges, designed using the requirements outlined inthe Schneider paper, have proved to be durable. In contrast, certain proprietary movable bridge designs using less stringent requirements have not been as durable. It thus appears that the Schneider specification and the succeeding editions of the AREA Movable Bridge Specification have successfully defined adequate design standards for typical movable bridge machinery. Nevertheless, failures have occurred in bridges designed to these specifications. Some of these failures may have occurred because of lack of good engineering judgment in the application of the specifications. Others may have occurred because of lack of good engineering judgment in using components and/or details not covered in the specifications, as well as errors in construction, faulty operation and inadequate maintenance. These recommended practices contain no criteria for the anticipated number of openings expected over the life of the bridge. Two basic categories of machinery components are covered in the recommended practices. The first category includes components which always or nearly always operate under maximum design loads. These are the components which support the dead load of the movable span. Examples of these are counterweight sheaves for vertical-lift spans, trunnions for bascule spans, treads for rolling lift spans, center pivots, rim bearings and end wedges for swing spans. The second category includes components whose loading consists of friction, inertia, wind, ice, and other transient loads, during operation of the movable span. Machinery in the first category carries maximum or near maximum loads at all times. Machinery in the second category seldom carries maximum design loads and normally operates at a relatively small fraction of design load.

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Commentary The basis of the recommended practice is textbook mechanical engineering methods and allowable stresses for the design of heavy machinery developed prior to 1940. The bridge machinery design philosophy should be simple and normally not be based on overly-sophisticated methodology for several reasons. They include: a.

Bridge machinery is heavy, low-speed machinery intended to last 50-100 years.

b.

The real loading conditions and number of cycles of operation are difficult to establish.

c.

The level of maintenance over the life of the bridge is difficult to establish at the time of design.

d.

Future replacement of sophisticated components can be difficult.

9.6.4 BASIC ALLOWABLE STRESSES AND HYDRAULIC PRESSURES 9.6.4.2 MACHINERY PARTS (1993) Some allowance for stress concentration factors is included in the basic allowable design stresses. Stress concentration factors for unusual configurations are not covered and must be recognized by the designer. Some counterweight sheave trunnions have failed due to fatigue as the sheaves exceeded 500,000 revolutions. The combined effects of high-cycle complete reversals, small fillet radii at changes in trunnion diameter and section discontinuities resulting from termination of grease grooves close to the fillets have produced fatigue cracking in the area of the fillets. Journals with a length to diameter ratio exceeding 1.2 may result in high bending stresses in the area of the fillets.

1

9.6.4.8 HYDRAULIC SYSTEMS AND COMPONENTS (1984) R(2010) Consideration should be given in the design of hydraulic systems for the effect of the large inertia of the moving span and the compressability of the hydraulic fluid.

3

Provision should be made to contain any hydraulic fluid leakage to avoid contamination of the waterway or surrounding areas.

9.6.5 GENERAL DETAILS 9.6.5.13 LUBRICATION (2008) j.

4

Due to the variety of lubricants available, this article provides a warning to Designers, Owners, and Erectors to verify that all lubricants are compatible. Experience has shown that serious damage can occur when lubricants are incompatible.

9.6.5.34 SPECIAL PROVISIONS FOR SWING BRIDGES (2003) 9.6.5.34.1 Center Bearing Center bearing swing spans are generally preferable to rim bearing swing spans because of simpler fabrication and erection, and more reliable operation. 9.6.5.34.2 Rim Bearing See 9.6.5.34.1 Center Bearing.

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Steel Structures 9.6.5.34.5 End Wedges and Center Wedges Wedges with sliding surfaces which must operate under load may be designed with steel against bronze to minimize galling.

9.6.5.36 SPECIAL PROVISIONS FOR VERTICAL LIFT BRIDGES (1997) 9.6.5.36.10 Welded Sheaves Welded counterweight sheaves must be designed with special care to assure adequate fatigue life in both the sheaves and the trunnions. 9.6.5.36.12 Operating Ropes The minimum tension in the slack rope should preferably be not less than 10% of the maximum operating tension and can be determined by measuring the sag in the rope.

9.6.6 WIRE ROPES AND SOCKETS 9.6.6.2 DIAMETER OF ROPE (2010) a.

The diameter of counterweight ropes had been limited by the specification to 2-1/2 inches since 1922. Wire ropes of larger diameter are now available for use on vertical lift bridges.

b.

Prior editions of the Manual listed tolerances for rope diameters from 5/8 inch to 2-1/2 inches.

9.6.6.3 CONSTRUCTION (2010) a.

Improved plow steel (IPS) was the only grade of wire rope permitted by the Manual since 1922. Advances in wire rope technology have led to the wide use, in other industries, of the higher strength grade ropes listed in ASTM A-1023 and Federal Specification RR-W-410F. The higher strength rope grades are; extra improved plow steel (EIP) and extra extra improved plow steel (EEIP). Each step upward in grade represents an increase of approximately 10 percent of minimum breaking force, compared with the next lower grade. Extra improved plow steel wire rope (EIPS) is now permitted by the Manual, as well as the improved plow steel rope (IPS) that was formerly required. The specifier is alerted to the fact that there is no known published data regarding the relative performance of extra improved plow steel rope compared to improved plow steel rope over many years of service in a bridge application. The Manual now requires that all wire rope for movable bridges be preformed in accordance with the strong recommendation of the Wire Rope Technical Board (April 2007). Prior editions of the Manual required wire rope to be made of bright (uncoated) carbon steel wires. The use of rope made with drawn-galvanized or drawn-zinc mischmetal (Zn5/Al-MM) wire is now permitted. However, wires coated with zinc or Zn5/Al-MM by hot-dipping are not permitted because the hot-dipping process relieves some of the residual stresses in the wire from prior cold drawing, thereby reducing the strength of the wire. Drawn-galvanized and drawn-(Zn5/Al-MM) ropes are used in other industries where long life under adverse environmental conditions is required. Even if the zinc layer is “partly damaged”, the steel remains protected as the electro-chemical process results in the zinc corroding first. Zinc is more resistant to wear than Zn5/Al-MM. For these reasons, drawn-galvanized ropes are preferred over bright (uncoated).

b.

Only one classification of counterweight wire rope had been permitted by the specification since 1922. It is 6x19 with a fiber core. Since 1938, or earlier, only the subclass 6x25FW has been specified. This construction has generally given acceptable service when the ropes are draped over counterweight sheaves with sheave diameter (D) to rope diameter (d) ratios of approximately 80. The 6x25FW characteristics have been found to be an acceptable

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Commentary compromise between flexibility and wear resistance for counterweight ropes of 2-1/2 inch diameter or less. For situations where wear resistance is of importance, the subclass 6x26WS (Warrington Seale) is considered advantageous. However, for specific situations consultation with a wire rope manufacturer may disclose that other subclasses of 6x19 are more suitable. Vertical lift bridges have recently been designed with larger diameter ropes and smaller D/d ratios. For these situations 6x25FW and 6x26WS may be too stiff because the diameter of the wires in the outer layer are larger for the larger diameter ropes. Hence, the Manual now permits the use of Class 6x36 and Class 6x61 wire rope, which have greater flexibility. Only one subclass of 6x36 rope is manufactured for most rope sizes. Counterweight ropes may be stationary for long periods under the design tension. They are subjected to lateral compression along the length draped over the sheaves. These forces tend to deform the rope from a circular cross section. The deformation is resisted by the core, which supports the strands in the radial direction. Fiber cores deteriorate if the ropes are not properly maintained and lose their effectiveness as strand supports. Independent wire rope cores (IWRC) do not deteriorate in the same way as fiber cores and are considered better supports for the strand. However, IWRC are generally stiffer than fiber cores and there is metal-to-metal contact between the strands and the core. In addition, the Manual now permits the use of compacted strand (CS) for wire ropes. The strands of these ropes are subjected to mechanical work after they have been closed. The mechanical work changes the cross sectional shape of the outer wires, thereby increasing the contact area between wires and increasing the external metallic surface area. These ropes also have more metallic cross sectional area than ropes with only circular wires of the same diameter and class. CS ropes are stronger than circular wire ropes of the same class, grade, and diameter and have much greater resistance to wear and fatigue.

1

9.6.6.7 WIRE – PHYSICAL PROPERTIES (2010) The prior versions of the Manual covered one grade and subclass of wire rope and listed the required properties of the wire and described wire tests. Because of the expansion to other grades and classes, reference is now made to ASTM A-1023 and ASTM A-1007, which are cross-referenced by Federal Specification RR-W-410F.

3

9.6.6.8 ULTIMATE STRENGTH (2010) Prior versions of the Manual listed the required ultimate strengths of the 6x19 IPS ropes with fiber cores. Because of the expansion to other grades and classes of rope, reference is made to ASTM A-1023 for ropes 2-3/8 inch diameter or less. For rope sizes larger than those listed in ASTM A-1023, the designer is referred to Federal Specification RR-W-410F. Although the term “ultimate strength” has been retained in the heading of this article, and elsewhere in Section 6.6, it should be noted that the synonym in ASTM is “minimum breaking force” and in Federal Specification RR-W-410F “Minimum Breaking Strength (force)”. A new requirement is that rope tests to destruction be conducted per ASTM A-931 Test Methods for Tension Tests of Wire Rope and Strand, in the presence of an inspector designated by the Engineer.

9.6.9 ERECTION 9.6.9.1 ERECTION OF MACHINERY (1996) R(2002) Bridge machinery erection generally should be started with alignment of the lower speed components and working back to the prime mover. This gives the best flexibility to correct misalignments.

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Steel Structures

9.6.9.4 LUBRICATION (2008) R(2010) c.

Due to the variety of lubricants available, this article provides a warning to Designers, Owners, and Erectors to verify that all lubricants are compatible. Experience has shown that serious damage can occur when lubricants are incompatible.

9.6.9.7 COUNTERWEIGHTS (1983) R(2003) For satisfactory balance, the movable span should have a slight closing force present when seated and either a neutral or very slight opening force present when fully open. Balance can be checked in the field by the following procedures: a.

Compare motor currents during opening and closing of the span.

b.

Compare power meter (kw) readings during opening and closing of the span.

c.

Run a drift test in the mid range of travel in both the opening and closing direction. Compare the drift in each direction with power off and the brakes released.

d.

Measure the torque in the drive train during opening and closing of the bridge.

e.

Compare the grease patterns on the main pinion teeth.

f.

For vertical lift bridges, weigh the imbalance between the span and the counterweights.

The above tests should be run under minimum wind velocity and with equal speed in the opening and closing direction. Periodic retesting of the balance of the movable span can reveal changes in operational characteristics.

PART 7 EXISTING BRIDGES 9.7.2 INSPECTION 9.7.2.1 GENERAL (2010) The Bridge Inspection Handbook published by AREMA in 2008 (Reference 9) provides additional information on the inspection of steel railway bridges.

9.7.3 RATING 9.7.3.1 GENERAL (1998) R(2008) 9.7.3.1.1 Normal Rating (2011) a.

The intent of the normal rating is to limit the stresses in the structure to those for which it would be designed given the yield strength of the steel in question and the design recommendations of Part 1, Design. The normal rating will ensure a consistent factor of safety and prolong the useful life of the structure. For older structures which were generally not designed for current fatigue criteria, rather than reduce the rating by requiring use of current fatigue allowables, a remaining fatigue service life calculation may be made. It is then up to the Engineer to consider the trade-off between the resulting higher normal rating and the consequent reduced remaining fatigue service life.

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Commentary The correct section for tension yielding has always been the gross section. Nevertheless, it was the practice to use the net section prior to 2006 to introduce an additional factor of safety and provide consistency with certain test practices particularly in the area of fatigue. For structures designed starting in 2006, an additional requirement of checking the effective net section against the ultimate tensile stress was introduced to cover a concern with High Performance Steels (HPS). With the reintroduction of this criterion (dropped many years ago) it is now possible to be consistent with the actual behavior of structures in checking tension yielding on the gross section and ultimate tensile strength on the effective net section. Traditionally, bridge structures that have been designed and rated in accordance with AREA and AREMA procedures have used yielding of the net section for tension calculations. Given that there are thousands of bridges already rated based on these assumptions and with a desire that there not be a sudden change in the calculated rating of railroad bridges, the Committee felt that yielding of the net section for tension calculations may continue to be used for structures designed before 2006. This will tend to give conservative results for traditional steels. Ratings should indicate the rating criteria used (e.g. AREMA Rating 2005) so as to clarify comparisons between ratings based on different methodologies. b.

The allowable rating stresses, when wind forces are included, can be increased to 25% greater than basic allowable stresses, but in no case greater than the allowable stresses for Maximum Rating. The 25% increase is included so that, for members such as truss chords where wind forces may be significant, the Normal Rating will not be less than the loading for which the member was designed.

9.7.3.1.2 Maximum Rating R(2008) a.

Maximum rating recognizes that loads producing stresses higher than design values may be imposed on a structure. However, to maintain a consistent factor of safety and to reduce the effects of fatigue, it is recommended that loads up to the maximum rating be allowed only infrequently.

b.

Paragraph b permits the Engineer to authorize more frequent maximum rating loads with the caution that the useful life of the structure will be thereby reduced. If frequent maximum rating loads are contemplated, it is appropriate that either a more detailed inspection be made of fracture critical members or a fatigue analysis be conducted per Article 7.3.3.2 and Article 9.7.3.3.2 to predict the remaining useful life of the structure and preclude the continued application of loads beyond the stage where the potential for member failure is high. Another alternative is to predict the theoretical remaining useful life and when this predicted life has expired, continue using the structure by making more detailed inspections of fracture critical members.

c.

3

It should also be remembered that maximum rating stress results in a reduced factor of safety.

4

9.7.3.2 LOADS AND FORCES (2007) R(2008) 9.7.3.2.7 Bracing Between Compression Members (2002) R(2008) a.

A lateral bracing force of 1.25% of the total axial force is based on an initial out of straightness of L/500 plus a total load displacement of L/900 or equivalent combination. These two, when combined, are approximately L/320.

b.

For other cases of greater deviation from the straight, the following formula may be used: Lateral Bracing Percentage = 400 (Initial Deviation + Total Maximum Deformation Under Load)/L.

9.7.3.2.8 Longitudinal Force R(2008) a.

1

Longitudinal forces due to train traffic on railway bridges are influenced by a number of factors including: (1) the type of motive power used

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Steel Structures (2) train tonnage (3) grades and curves (4) type of braking system (5) likelihood of starting or stopping a train at or near a particular bridge (6) individual railroad operating practices. For further information, see AREMA Manual for Railway Engineering, Chapter 16 Economics of Railway Engineering and Operations, and the commentary section on design for longitudinal forces (9.1.3.12). The longitudinal force in Article 1.3.12 is based on E-80 loading. For structures with a live load rating different from E-80, the longitudinal force used in rating is to be reduced or increased by the ratio of the rating for live load to E-80. b.

The longitudinal force due to locomotive traction is to be used in locations where train operations may include either of the following conditions: (1) Application of maximum tractive effort below 25 mph (40 km/h) (2) Application of maximum dynamic braking effort with actual train speed less than 25 mph (40 km/h)

c.

In other locations, the longitudinal force due to locomotive traction may be reduced in proportion to the larger of the actual locomotive tractive effort or the dynamic braking effort. The actual locomotive tractive effort or dynamic braking effort used at a location can be obtained either from actual train operations, or estimated using the methods in AREMA Manual for Railway Engineering, Chapter 16 Economics of Railway Engineering and Operations. The maximum tractive effort and dynamic braking effort ratings of locomotives are typically listed in the operating timetable, or may be obtained from the operating department of the Railroad.

f.

The recommended practice also covers the extreme events of emergency braking, or starting a train from a stationary position at maximum tractive effort, at locations where other longitudinal forces are expected to be low, with an allowance of 1.5 times the allowable stresses for rating. For a maximum rating calculation, this will allow stresses that exceed the yield point for this rare extreme event. In the event that longitudinal forces are higher than the calculated capacity of the structure, operating restrictions for the bridge need to be discussed with operating and mechanical personnel. It is important to trace the load path that these forces will follow to the point at which they are taken out of the structure, and ensure that the load path is consistent with the compatibility of deflections and rotations.

9.7.3.3 STRESSES (2011) 9.7.3.3.1 Computation of Stresses b.

The provisions for intermediate stiffener spacing in Article 1.7.8 are derived from the equations for elastic and inelastic buckling of a flat web under shear stress, using suitable reduction factors. See Article 9.1.7.8. Those equations are critical load solutions for thin flat plates based on small deflection theory and do not consider post-buckling conditions in the web plate. The detailed analysis referred to in Article 7.3.3.1b is a more refined elastic/inelastic critical load analysis of a flat plate subjected to shear and bending (Reference 49 and 105). The Engineer is advised to apply a reduction factor to the computed critical load to account for web plate out-of-flatness and other imperfections. These comments do not consider the effect of stiffeners to support the top flange.

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Commentary c.

It has been common practice not to rate gusset plates under the assumption they would rate as strong as the main members. This sub-article was added to identify the gusset plates that need to be evaluated. Clearly under-designed gusset plates and any other components that are under designed relative to the rest of the structure should be evaluated. Refer also to Article 9.1.5.4.

9.7.3.3.2 Fatigue a.

The intent of evaluating a structure for fatigue in this Article is to minimize the probability of failure as a result of fatigue crack growth. This primarily affects the maximum service life for which the structure is designed. If a reduced life is acceptable, higher loads are permissible providing the serviceability is not impaired throughout the shortened useful life. There are two ways to deal with fatigue. The first is to ensure that a structure is fail safe, and the second is to limit the usable life to one that is shown to be safe for a certain period of use (Safe Life). Given that most details in older bridges were developed before fatigue became a major concern, only a few structures could possibly be regarded as fail safe. Even these are only fail safe within a risk management framework. Where waivers of the need to make a safe life calculation are permitted in the Manual, it is felt that these structures are at least as safe as the general level of safety provided by typical civil engineering structures. In the more common case for railroad bridges, that of ensuring a safe usable life, there are again two major alternatives to consider. One can limit the load to a very low value and obtain a long usable fatigue safe life, or one can use a higher load (usually the normal rating) but accept a reduced usable fatigue safe life. The latter alternative has been chosen for this Manual, based on economics. A multi-step method has been selected which is designed to first screen the overall bridge population for bridges with details with potential fatigue problems, followed by more sophisticated evaluation methods where the Engineer deems them to be needed and appropriate. The intent is to avoid detailed fatigue calculations when experience has shown that a class of structures clearly has adequate fatigue life. In this case, calculating a fatigue rating is not appropriate, although an estimation of remaining fatigue life may be needed. The fatigue strengths used throughout this section are the latest available and are based on the results of full scale testing on relevant bridge-sized components. The failure criterion used, where a safe life must be estimated, is that of a 2.5% probability of failure of a component based on simple calculations.

b.

For lines carrying low volumes of traffic, fatigue is generally not a problem. In Article 7.3.3.2b for a bridge carrying less than 5 million gross tons per annum throughout its existing and projected life, a fatigue check is waived for usual mixed traffic. The term “usual mixed traffic” refers to normal North American equipment and is intended to exclude solid unit train traffic and unusual heavy loads such as heavy molten metal cars or heavy transformers in frequent service. For lines carrying less than 15 million gross tons per annum historically and projected in the future for usual mixed traffic, the fatigue requirements may be waived if so decided by the Engineer. The decision should be made on the basis of the individual railroad’s traffic loading patterns, bridge management criteria, fatigue details, inspection procedures, and failure history. A special analysis is needed for non-freight traffic to establish the appropriate parameters for the relevant number of cycles.

c.

The first step in an evaluation of any detail is to check the detail against the design requirements for the Normal Rating stress ranges. This Article also provides guidance on details not fully covered in the design section of this Manual and for wrought iron riveted connections. The purpose of Article 7.3.3.2c is to flag members with less than ideal fatigue strength. The various parts of Article 7.3.3.2c, except Article 7.3.3.2c(4), are intended as a preliminary screening tool to see if there is a potential

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3

4

Steel Structures fatigue problem. Article 7.3.3.2c(4) is intended to eliminate the need for calculation where adequate inspection within the limited circumstances mentioned should find a fatigue crack before it becomes critical (a very necessary part of this Fail Safe assumption). Any structure that meets the requirements of Article 7.3.3.2c, except Article 7.3.3.2c(4), is deemed adequate from a fatigue standpoint because it has met a very stringent criterion, that of calculated infinite, or at least very long, life. This criterion is appropriate for newly designed structures. (1) On multiple track structures, the incidence of more than one track being loaded frequently by heavy freight loads is low. This section allows the use of probability evaluations to estimate the occurrence of more than one track being loaded simultaneously. (2) Welded structures do not have the inherent redundancy of riveted or bolted construction. Hence, the consequences of fatigue crack growth are more serious for most welded connections and members than for riveted or bolted structures with built-up sections. Severe corrosion may reduce the advantage of redundancy in riveted or bolted members. Experience with welded highway bridges that have experienced fatigue cracking has demonstrated that the members usually fail before the crack is discovered (Reference 41 and 44). As a result, it appears prudent to use the requirements of Article 1.3.13 when rating welded bridge members. High strength bolted joints provide improved fatigue resistance. (3) The fatigue resistance of members with riveted or other mechanically fastened connections with low slip resistance is defined by Detail Category D as a result of review of available test data (References 5, 36, 45, 94 and 153). The most recent research indicates a variable amplitude stress range fatigue limit of 6 ksi, extending to at least 100 million cycles (Reference 153). Referring to Figure 15-9-8, it is apparent that nearly all test data on riveted joints with normal levels of clamping force fall to the right of the line defined by Detail Category C between 6 ksi and 9 ksi. The existing test data (References 36, 45, 94 and 153) show failures at high numbers of cycles below the constant amplitude stress range fatigue limit for Detail Category C, 10 ksi, but above the variable amplitude stress range fatigue limit value of 6 ksi. Hence, any evaluation using Detail Category C must extend on to 6 ksi. For stress ranges above 9 ksi, the test results for riveted connections typical for railroad bridges fall to the right of the line defining Detail Category D.

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Commentary

1

For riveted bridge components For design only:

For optional evaluation of drilled or reamed bridge components

N=2.183 x 109 Sr-3 Sr > 9 ksi For evaluation: N=2.183 x 109 Sr-3 Sr > 9 ksi N=4.446 x 109 Sr-3 9 ksi > Sr > 6 ksi Fatigue limit: (Sr)fl = 6ksi

(see 9. 7.3.3.2 Fatigue) N=2.183 x 109 Sr-3 Sr > 9 ksi N=4.446 x 109 Sr-3 9 ksi > Sr > 7.65 ksi N=2.465 x 1015 Sr-9.5 7.65 ksi > Sr > 6 ksi Fatigue limit: (Sr)fl = 6 ksi

3

4

Figure 15-9-8. Riveted Bridge Components It is reasonable to permit a higher fatigue stress range for Root-Mean-Cube (RMC) stress ranges below 9 ksi if the connection or member in question has tight riveted joints. Where the rivets are tight and rivet holes are smooth, having been correctly drilled or subpunched and reamed, a further refinement in the allowable stress range is permissible. A line on the rivet S-N plot extending from Detail Category C at 7.65 ksi to 6 ksi at 100 million cycles may be used in lieu of the horizontal line at 6 ksi (Reference 5 and 153). This discretion has been left to the Engineer dependent on his verifying the tightness of the rivets or bolts and the adequacy of the clamping force. This refinement does not apply to punched holes. For riveted construction where the members are fabricated from multiple elements, the immediate consequences of fatigue cracking may not be as serious as in welded structures. Riveted construction often has built-up members and connections, so that if one element fails there is normally sufficient capacity and redundancy for the force to be redistributed. The members will usually survive long enough for the crack to be detected by routine inspection thereby permitting corrective action before more serious damage develops. If no immediate repair action is to be taken, the probable time between first detectable cracking and uncontrolled propagation should be taken into

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Steel Structures account when setting up inspection frequency. Where the constant amplitude stress range exceeds 9 ksi, test results indicate that not much time elapses between easily detectable cracking and member failure. (4) Article 7.3.3.2c(4) permits waiver of the fatigue provisions when the Engineer can show that the structure has an adequate level of redundancy, so that should cracking develop it can be accommodated. The requirement that sufficient lateral resistance be provided by bracing or diaphragms to ensure that existing crack tips will not be subjected to unaccounted secondary stresses is consistent with test results (Reference 45). (5) Wrought iron riveted connections exhibit a fatigue strength represented by Detail Category D with a variable amplitude stress range fatigue limit of 6 ksi (Reference 5 and 153). (6) For eyebars and pin plates, the critical section is at the pin hole normal to the applied load. Several studies have indicated that the stress concentration factor at such a location is in excess of 4 (Reference 36 and 139). Detail Category E is intended to provide a conservative estimate of fatigue resistance at such connections. Particular attention should be given to any forge seams or other unusual flaw-like conditions that may exist at the bore of the eyebar normal to the applied load. Suitable analytical and/or experimental studies may show that a lower stress concentration exists if pin fit and the component geometry are favorable. If the stress concentration factor is less than 4, Detail Category D can be used to assess fatigue resistance. Detailed analysis or full size testing may be used to demonstrate that an even more favorable category is appropriate. The inclusion of bending stresses is intended to apply primarily to hangers and similar members where pin connections may develop large bending stresses due to configuration, corrosion, wear or other causes. For advice on secondary stresses, see Article 1.3.15 and Commentary Article 9.1.3.15. (7) Test results (Reference 45 and 94) indicate that severe corrosion may lead to the initiation of cracks. If the thickness of a component is reduced by 50% or more, the member at that location is best categorized by Detail Category E. Until more conclusive test results are available, no advice can be given in this Manual on sections with less than 50% loss of thickness. d.

A structure that does not pass Article 7.3.3.2c may still be adequate, but only if further evaluation demonstrates that this is the case. There are two generic ways to check this, as noted in Paragraph e.

e.

The first method is to ascertain as accurately as possible the actual damage done by traffic to date and to estimate the remaining life based on future projected traffic. This requires the records of the operating railroad, if they are available, and a calculation using the concepts outlined in Article 7.3.3.2d, e and f with a full spectrum rain flow analysis of actual tested trains crossing the bridge, or a short cut method using the AAR bridge fatigue charts as an approximation. When the actual stress cycles can be estimated from known traffic, the total variable stress cycles can be estimated and the effective stress range calculated by the formula given in Article 7.3.3.2e. The resulting coordinates can be compared with Figure 15-9-8 and Article 1.3.13 for the applicable fatigue detail. The values of α for various spans and member classifications are tabulated in Table 15-9-1. The factor gi is the ratio of the number of occurrences of SRi to the total number of occurrences of cyclic stress Nv. The second method is to refine the model of the structure by more sophisticated analytical means, or by field-testing using the structure itself as the model. In the event that calculated stress ranges give a low estimated remaining safe fatigue life, it is suggested, if economically justified, to obtain stress range data by strain gaging under traffic that is at the upper weight range of traffic expected on the structure. In this instance, if the actual strains are less than the analytical model strains, either a rechecking of fatigue capacity using Article 7.3.3.2c or a more thorough analysis as per Article Article 7.3.3.2d, e and f will result in a longer useful calculated fatigue life.

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Commentary Clearly, in the most pressing case, these methods may be combined, i.e. real traffic data and the most accurate model possible. Caution must be exercised in the application of these articles in order to avoid erroneous conclusions. For example, the use of these articles to evaluate a floor beam or stringer without being cognizant of the effect of potential end fixity, or the application of these articles to the midsection of such a member while ignoring the real stress variation at the end connections, could lead to wrong conclusions. When the procedures above result in a deficient remaining life estimation, several alternatives are available. Depending on the economics, consider: Closing the structure or restricting traffic; Repairing, strengthening or retrofitting the deficient details or replacing the structure; Initiating frequent and very rigorous inspections, being very cognizant of fracture critical considerations; Installing strain gages to establish actual stress ranges related to the traffic handled, to permit a more accurate analysis; Using more sophisticated techniques, such as acoustic emission verification and fracture mechanics. f & g.The limits and the stress ranges outlined in Article 7.3.3.2f and 7.3.3.2g on fatigue details being sufficient to eliminate the existence of the Constant Amplitude Fatigue Limit (CAFL) Stress Ranges are approximate and are based upon a small number of tests (Reference 39). h.

This paragraph draws attention to details that have low fatigue capacity with particular reference to Fracture Critical Members.

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9.7.3.3.3 Allowable Stresses for Maximum Rating (2011) a.

Traditionally, bridge structures that have been designed and rated in accordance with AREA and AREMA procedures have used yielding of the net section for tension calculations. Given that there are thousands of bridges already rated based on these assumptions and with a desire that there not be a sudden change in the calculated rating of railroad bridges, the Committee felt that yielding of the net section for tension calculations may continue to be used for structures designed before 2006. This will tend to give conservative results for traditional steels. Ratings should indicate the rating criteria used (e.g. AREMA Rating 2005) so as to clarify comparisons between ratings based on different methodologies. Nevertheless, it is imperative that steels with allowable maximum rating stresses based on Fy greater than 0.5 Fu be evaluated differently, particularly because some High Performance Steels (HPS) have low ultimate to yield ratios. Applying the ultimate tensile strength to the effective and/or net section and the yield strength to the gross section in axial tension more correctly represents the behavior at failure. Because test results have been reported on the net section for some fatigue studies, the fatigue limits recommended in other articles of this Chapter may not be consistent with this provision. Since there have been many failures in floorbeam hangers, and since an increase in allowable stress for high strength steels in such applications is not acceptable, the allowable stress for such members has been established as that permitted for members of A36 steel, and a greater apparent factor of safety has been adopted, in line with past experience, for such members.

b.

The allowable values represented in Table 15-7-1 for Shear in Rivets are intended to provide maximum rating parameters that cover current and historic rivet steel specifications. The current ASTM Specification for Carbon Steel Rivets is A502 Grade 1. The current ASTM Specification for Carbon Manganese Steel Rivets is A502 Grade 2. The current ASTM Specification for Weathering Steel Rivets is A502 Grade 3.

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Steel Structures

PART 8 MISCELLANEOUS 9.8.1 TURNTABLES 9.8.1.3 Basic Allowable Stresses and Deflections (2008) 9.8.1.3.1 Structural Components b.

The second diagram in Figure 15-8-2b. consists of two 4-axle diesel locomotives and may be used to apply this article by changing the 25 foot distance to ensure that all 8 axles are on the turntable.

9.8.2 METHOD OF SHORTENING OF EYEBARS TO EQUALIZE THE STRESS 9.8.2.1 General (2006) A recommended practice for shortening eyebars to equalize their stress was originally published in the AREA Manual in 1948 following completion of a 1943 Committee 15 assignment on shortening of eyebars to equalize stress. This procedure involved heating a short length of the bar, which was restrained between clamps, to 1600 to 1800 degrees Fahrenheit, low in the range of forging temperatures, and drawing the clamps together to upset and shorten the bar. Since eyebar heads were formed by forging, these temperatures were considered appropriate. Current practice relies more on restrained thermal expansion of the heated area to produce upsetting followed by shortening as the bar cools. A detailed report comparing the effects on strength of various methods used to tighten loose eyebars and recommending the procedure for flame shortening, which was adopted as a recommended practice by the AREA in 1948, can be found in AREA Proceedings Vol. 48, 1947, pages 969-986. Fatigue tests were run on three bars in each condition. A summary of data from these tests is tabulated below. Considering the variability of test results and limited field experience when compared with shortening steel eyebars, extreme caution should be exercised if the method is applied to wrought iron eyebars. In heat shortening wrought iron eyebars, there is a possibility of aggravating delaminations, which may promote fatigue crack propagation. EYEBAR FATIGUE TEST DATA FROM 1947 REPORT Wrought Iron

Steel

Not Shortened

Flame Shortened

Not Shortened

Flame Shortened

Max. Life/Mean Life

1.195

1.643

1.134

1.058

Min. Life/Mean Life

0.720

0.358

0.866

.900

Fatigue Strength at 500,000 cycles

32.7 ksi

30.5 ksi

36.4 ksi

37.2 ksi

Fatigue Strength at 1,000,000 cycles

28.4 ksi

26.4 ksi

31.5 ksi

32.4 ksi

Since the process has many features in common with heat straightening, a similiar temperature range was considered appropriate for investigation. Experience indicated that temperatures below 1300 degrees Fahrenheit were not effective. Since temperatures in the range of interest could be determined with sufficient accurancy using inexpensive temperature sensing crayons, the recommended temperature range was changed and narrowed to reduce the risk of metallurgical damage.

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Commentary

9.8.3 ANCHORAGE OF DECKS AND RAILS ON STEEL BRIDGES 9.8.3.1 Foreword (2010) a.

Starting in 2003, as part of the Association of American Railroads’ Strategic Research Initiatives to reduce the stress state of railroad bridges, the Transportation Technology Center, Inc. (TTCI) conducted a series of bridge tests, developed an analytical model, and performed a parametric evaluation to investigate the interaction of continuous welded rail (CWR) with long open-deck steel bridges (Reference 68). The results of this investigation indicate that there are conflicting considerations regarding thermal effects of CWR on long open-deck bridges. Rail expansion joints (See Article 8.3.4) effectively accommodate rail thermal expansion and contraction; however, their use generates high impact loads and may accelerate bridge degradation (Reference 6, 7, 51 and 68). Also they are costly to install and require high maintenance. Without rail expansion joints, longitudinal rail restraint must be incorporated to reduce gap width and derailment risk due to broken rails. Rail restraint might introduce high rail longitudinal forces into the bridge in case of a broken rail. Longitudinal restraint also causes longitudinal forces to develop in the rail during span expansion and contraction. These forces add to the rail force developed from heating and cooling of the CWR. Additional compressive forces in hot weather might increase the risk of track buckling at bridge approaches, particularly at abutments that support expansion bearings. Additional tensile forces in cold weather might accelerate rail defect and crack growth rates and increase the derailment risk in the case of a rail break. An alternative to rail expansion joints in CWR is to allow the rail to be unanchored on bridges under a certain length. The philosophy behind this approach is that the risk of rail break at cold temperatures, assuming there are no serious rail flaws, should be less as there is little or no transfer of forces between rail and bridge. See Article 9.8.3.3.5.2. A drawback is that, should a rail break, there may be little to constrain the resulting rail gap. Although not specifically simulated in this investigation, damage to decks and fasteners due to large thermal displacements between rail-tie and tie-deck interfaces has been reported in the field. This will likely be more evident on riveted or bolted top surfaces or where there are other methods of holding ties longitudinally on structures where ties do not easily slide on the top surface of the span. On long riveted or similarly constrained top surfaces of spans not protected by expansion joints, fasteners should be selected that are capable of accommodating the expected rail-tie displacement without damage to ties. Due to these fundamental conflicts, it is unlikely that all of the design goals will be completely addressed. But a balance is needed between a number of important considerations. Results emphasize the need to maintain good track lateral resistance and proper rail neutral temperature on bridge approaches to minimize track buckling potential. On approaches near expansion bearings track lateral resistance is critical. Methods to provide additional lateral resistance should be considered – for example, additional width in the ballast shoulders, full height wing walls, sheet piling and use of ties with improved lateral restraint. The recommendations in Section 8.3 assume the following: (1) Maximum hot weather temperature differential values for evaluation of forces due to span expansion and track buckling risk: • A maximum rail ΔT of 45°F above the rail neutral temperature • A maximum span ΔT of 45°F above the span installation temperature (2) Cold weather values for the evaluation of rail break risk and effects as follows: • A maximum rail ΔT of 100°F below the rail neutral temperature © 2011, American Railway Engineering and Maintenance-of-Way Association

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Steel Structures • A maximum span ΔT of 70°F below the span installation temperature For more extreme temperature variations that might occur in Northern regions of the US or in Canada, site specific evaluations should be carried out. One very cold weather case was studied using the same failure criteria. For example, with rail ΔT of -130°F and span ΔT of -90°F, the thermal rail force alone would be above 300,000 pounds, which is considered a rail break risk for 136 lb. rail. Fully anchored track on riveted-top structures is likely to be at risk of rail break on all span lengths, with forces imparted into the bridge predicted to be about 120 percent of AREMA traction and braking forces for rail ΔT of -130°F. Controlling rail gap width of a broken rail at ΔT of -130°F to values equivalent to those of anchored track on ballast away from bridges is highly unlikely for longer spans. Addition of rail expansion joints would effectively eliminate any cold weather broken rail gap condition without introducing the risk of track buckling or broken rails. However, costs of installation and maintenance for rail expansion joints are high and significant bridge degradation is likely to occur due to increased impact loading for such joints placed on a bridge. For this cold weather case, reducing the maximum span length that may remain unanchored and without rail expansion joints to 200 feet in Article 8.3.4.2 would reduce the predicted broken rail gap to about 6 inches (almost equivalent to 5 1/2 inches on anchored track on ballast away from bridges). Rail gaps of this magnitude are not acceptable in open track or on bridges. Most railroads perform frequent rail flaw detection in cold weather to find rails that have a high propensity for failure.

9.8.3.2 Anchorage of Decks to Bridge Spans (2011) 9.8.3.2.1 Open Deck Bridges a.

The maximum spacing of hook bolts was changed to 4’-8” in 2010 to reflect a connection of every 4th tie assuming 10 inch wide ties and 4 inch clear distance. The previous maximum of 4’-6” assumed 9-1/2 inch wide ties.

e.

Bolted fastening systems for timber ties can loosen under train traffic in a relatively short time if loosening is not prevented. Testing at FAST [Reference 28] has shown that systems employing some method to prevent loosening can significantly extend the time between maintenance. The provisions of Article 8.3.2.1(e.) are based on the results of this testing. A variety of solutions are possible, some more permanent than others. Locking clips and locking nuts both allow for future adjustments. New timber ties on riveted girders will typically require a tightening after a settling period under train traffic. Solutions such as double nuts or thread fastening adhesive can make adjustments more difficult. More permanent solutions might include tack welding of nuts or mashing of bolt threads; such solutions might make adjustments impossible.

9.8.3.3 Anchorage of Rail (2011) 9.8.3.3.5 Anchorage Requirements for Continuous Welded Rail (CWR) without Expansion Joints on Open Deck Bridges 9.8.3.3.5.1 Continuous Welded Rail without Expansion Joints on Open Deck Bridges, Rail Not Longitudinally Anchored Some railroads deal with the conflicting problems of potential broken rails and higher forces induced in the rails and bridge by allowing the rails to be unanchored on bridges up to a certain length. The philosophy behind this approach is that the risk of

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Commentary rail break at cold temperatures, assuming there are no serious rail flaws, should be less as there is little or no transfer of forces between rail and bridge. Railroads with cold weather rail flaw detection and management programs may find this to be an acceptable option. A drawback is that, should a rail break, there may be little to constrain the resulting rail gap. 9.8.3.3.5.2 Continuous Welded Rail without Expansion Joints on Open Deck Bridges, Rail Longitudinally Anchored Testing indicates that unanchored CWR might allow excessive rail gap widths should a rail break occur due to cold-induced tension. Anchoring rail as per this Article will reduce the severity of a rail gap due to a cold-induced tension break but will not reduce the gap to a level that permits train operation at the temperature ranges studied should a rail break. The study indicated that there is an equal propensity of failure causing an unacceptable rail gap in up to 200 foot long bridges under the extreme cold scenario (ΔT = 130° F), 300 foot long bridges under the cold scenario (ΔT = 100° F), and up to 500 foot long bridges in climates that are warmer (ΔT = 70° F). Provisions of this Article recommend rail anchors at all ties anchored to bridge spans for spans 100 feet or less and at all ties anchored to bridge spans only in the first 100 feet from the fixed end for longer spans. Testing has indicated that effective longitudinal resistance is dependent upon the interface between tie and deck, and the anchoring used. On spans with a smooth interface between the bridge and deck, while the fasteners may provide a strong bond between the rail and deck ties, longitudinal restraint is weakest at the tie-to-girder interface. On spans with rivets or bolts protruding from the top of the bridge, the tie-to-girder interface is likely to be much stronger. Unless overriding circumstances exist, anchoring more ties than recommended should also generally be avoided on riveted or bolted tops or other methods of holding ties longitudinally on spans, as it might increase the risk of hot-weather-induced buckling on bridge approaches, and it might increase the risk of cold weather rail breaks.

1

9.8.3.4 Rail Expansion Joints (2011) While use of rail expansion joints introduces increased cost and bridge degradation, their use can effectively control the risk of bridge approach track buckling, excessive rail gap widths from cold weather rail breaks, and high forces due to relative displacement between bridge and track. Results of factorial testing carried out under very cold temperatures to determine actual span/rail behavior with various bearing conditions have not been reported. Theory and extrapolation from testing at smaller temperature ranges seem to indicate a need for rail expansion joints as mentioned above. There are anecdotal instances of problems where expansion rails were not placed on: • long bridges with relatively short spans, • spans over 300 feet with provision for floor system expansion (Article 1.2.13) and • bridges resulting in damage to deck timbers from standard rail anchors. But, there is also anecdotal evidence that it is possible to eliminate rail expansion joints on some long spans without serious consequences. There are several possible explanations for this: • It is possible that the bridge and rail neutral temperatures adjust somewhat with changes of season to reduce the potential severity of the broken rail gaps and the associated forces.

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Steel Structures • Rails may have the capacity to resist forces considerably greater than the 300,000 pounds considered a rail break risk for 136 lb rail. Any weaknesses in rail need to be identified through more frequent rail flaw inspections, especially during cold weather periods. • There is a difference in behavior between tie-to-structure interfaces that are smooth and those that have more resistance to sliding (e.g: protruding rivet heads or ties held in place by angles, etc.). • Use of zero longitudinal restraint rail clips eliminates most of the transfer of longitudinal forces between rail and bridge structure. • There is also a difference in behavior in cases where bearings from adjacent spans are placed to allow for opposing movement (e.g.: two expansion bearings on the same pier) and those where the bearings do not allow opposing movement. • Non-functioning bearings may play a significant role. • Stress in the bridge structure may be higher than expected, but the structure may still be able to accommodate this condition without noticeable signs of deformation. Further research is needed to fully explain the conflicting issues. 9.8.3.4.4 Number and Positioning of Rail Expansion Joints on Bridges with Continuous Welded Rail e.

Expansion length of rail is limited to 1500 feet in this Manual, which is based on: • Strength • Tolerable Rail rupture gap • Differential displacement between bridge and rail • Rail stability (Buckling)

9.8.7 GUIDE TO THE PREPARATION OF A SPECIFICATION FOR THE CLEANING AND COATING OF EXISTING STEEL RAILWAY BRIDGES 9.8.7.4 Coating Systems (2009) 9.8.7.4.1 General b.

The ratio of pigment to vehicle of a coating determines the level of coating gloss, the ease of application and other properties. Coatings are most often referred to by the resin with which they are formulated. Examples of these are alkyd, epoxy and urethane. These various resins react in different ways to develop the dry coating film; for example, oxidation, solvent evaporation or chemical reaction of multiple components called polymerization. These curing mechanisms, as well as the other common coating characteristics, are discussed in the following sections. Coatings for anti-corrosion service are segregated into three distinct types: barrier coatings, inhibitive primers and sacrificial galvanic protection providers. The barrier coatings offer protection by film forming and creating a barrier to minimize ion migration and to some extent moisture penetration to the steel substrate. Inhibitive primers reduce electro-chemical corrosive action at the steel substrate by using sacrificial inhibitive pigmentation in the coating which is effective in passivating the steel surface and deterring corrosion formation. Galvanic protection prevents corrosion

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Commentary by using a material of lower electro-chemical potential such as metallic zinc or aluminum pigmentation which sacrifices itself to protect the steel. This occurs in addition to the film’s barrier protection properties. Galvanic protective coatings, specifically zinc-rich coatings, offer the highest levels of protection to properly prepared steel substrate and are resistant to problematic undercutting corrosion. It should be noted that galvanizing can cause hydrogen embrittlement. This is usually not a problem with very heavy, thick, low strength steel members. c.

Different generic coating types are often used in conjunction with each other as “systems” to provide maximum levels of protection. However, due to the coating composition, some are not compatible with others. Therefore, development of this “blend” of different coating types is critical to the long-term performance of the system. By using a systematic approach to building a coating film, coatings that offer benefits as primers may be coupled with coatings that offer other desirable characteristics such as moisture, chemical and ultraviolet resistance, plus color/gloss retention, etc. Manufacturers also formulate coatings with different vehicles or pigment combinations, along with other complex chemical modifications to maximize the protective qualities.

9.8.7.4.2 Coating Selection Primary consideration must be given to the service environment which the coating system must endure. Railway bridge structures are often found in mild exposure environments; however, chemicals used in conjunction with snow and ice removal, the proximity of structures to industrial plants or factories, and even overspray of agricultural chemicals can dramatically affect the coating system’s performance. Coating systems for railroad bridges over roadways must also resist abrasion from splash and stones thrown against coated surfaces by moving traffic and must also have the chemistry within the system to mitigate the crevice corrosion and pack rust which is usually present on these structures. Certain coating formulations may be successfully applied with lesser degrees of surface preparation, while others require very clean surfaces. This is a factor which must be given careful attention when choosing a coating system. When cleaning steel on an existing structure where total removal is required, abrasive blast cleaning to an SSPC-SP5 “White Metal Blast Cleaning”, SSPC-SP10 “Near-White Metal Blast Cleaning” or SSPC-SP6 “Commercial Blast Cleaning” are the preferred methods of surface preparation. SP5 and SP10 cleaning standards may be difficult to achieve on existing structures under field conditions, especially for open deck structures, intricate trusses and open box sections. Another consideration in selection of a coating system is the ability of the topcoat to accept additional surface preparation and touch-up or overcoating. Many topcoats cure to form smooth, dense and hard films. Hard, abrasion-resistant coatings, such as two-component urethanes, may require more rigorous surface preparation, such as abrasive blast cleaning, to superficially roughen the surface and promote adhesion of subsequently applied coatings. On the other hand, softer film topcoats, like alkyds or acrylics, often accept additional maintenance coats of paint with minimal surface preparation (such as simple solvent cleaning or high pressure water washing).

1

3

The materials and methods used to clean and coat steel bridge structures are constantly changing. The following items, as a minimum, should be considered for all coating specifications:

4

• Life expectancy and life cycle costs • Successful protection of the structure and its critical elements (joints, connections, bearings, etc.) • Compatibility with existing systems (where applicable) • Ease of application and availability of materials • Environmental conditions • Aesthetics • Overall coating strategy 9.8.7.4.3 Materials/Systems a.

Penetrants for treating crevice corrosion and pack rusted joints that cannot be cleaned are as follows: © 2011, American Railway Engineering and Maintenance-of-Way Association

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Steel Structures (1) Epoxy Penetrating Sealers – Epoxy penetrating sealers are low molecular weight epoxies based on Chelated Polymeric Oxirane technology. These high performance, two-component chemically-cured high solids epoxy penetrating sealers are recommended for rusty steel when environmental, economic or safety concerns restrict abrasive blast cleaning. The extraordinary penetrating properties of these sealers provide a means of reinforcing rusty steel substrates, insuring adhesion of subsequent coatings. They are equally effective at penetrating, reinforcing and sealing concrete and masonry surfaces in all industrial environments. They improve the effectiveness and efficiency of the maintenance coating process by penetrating and sealing crevices, joints, backto-back angles and edges of old coatings, improving the service life of the maintenance coating system. These sealers also serve to seal aged “White-Rusted” zinc galvanized surfaces for recoating. Epoxy penetrating sealers are two-component products that cure by crosslink polymerization. These coatings provide excellent adhesion to marginally prepared steel (SP2 minimum) and old coatings. Their lower viscosities allow epoxy sealers to penetrate rust and wick into surface voids and around rivet heads. In addition, this wicking action penetrates discontinuities in existing coatings which often times seals these areas and reduces undercutting and peeling. The low viscosity also allows epoxy sealers to be applied by many techniques. This includes conventional air and airless spray, brush and roller, flood or flow coating methods, and by low pressure hand pump sprayers (similar to those used to spray concrete curing compounds, form release oils, or garden chemicals). Epoxy penetrating sealers usually possess very high volume solids content typically over 80%, develop lower contractive curing stresses, and meet the most stringent VOC regulations (often zero VOC). Corrosion inhibitors are generally used in their formulations. Since epoxy penetrating sealers provide low film build (1-2 mils), the total amount of curing stress and physical coating weight that the existing coatings must bear is also reduced. The drawbacks of these coatings are that they require multiple component mixing, have short pot lives, cure hard and may crack on flexible structures, must be topcoated to achieve maximum resistance, have high material cost, do not stay active if applied to crevice corroded or pack rusted joints and connections, have critical recoat times, and have application temperature limitations. The sealers are usually used as primers to bind up surfaces to be overcoated and are then topcoated with alkyd, acrylic, epoxy, or urethane coatings. (2) Moisture Cured Urethane Penetrating Sealers – These penetrants are thin and designed to flow into the joints and connections binding them up and sealing them up. For additional information see b(4). (3) High Ratio Co-Polymerized Calcium Sulfonate Penetrant Sealers – These penetrants are active non drying chemical treatments for crevice corroded and pack rusted joints and connections designed to stop corrosion by neutralizing acid, displacing moisture and scavenging oxygen. For more information see b(8). b.

Coatings for recoating prepared steel are as follows: The premier coatings for blast cleaned steel have historically been 3 coat zinc epoxy urethane systems (which require this type of surface to perform properly). However, this does not mean that these coatings are the answer in all situations, as they have limitations as well. The following describes the various coating types which are available, gives a brief history of their development and usage, addresses surface preparation requirements, discusses touch-up capabilities, reviews costs, and in some cases provides an estimate of the service life given the assumed exposure conditions. (1) Alkyds – Alkyds are a type of synthetic resin that cures by air oxidation. They are basically formed by a reaction among an acid, an alcohol, and oil. Alkyds are formed and classified by the amount and type of oil present within the formulation. “Long oils” contain greater quantities of oil and take longer to dry, while “short oils” have less oil and shorter dry times. Medium length oil-alkyds are a good compromise of the two and are consequently the most versatile and widely used. With the reduction in the amount of natural oil and an increase in the synthetic alkyd resin, the resistive properties of the alkyds are superior to those of natural oils. The use of synthetic resin translates into improved resistance to water, but has little or no effect on the resistance to chemicals and solvents. Because of the presence of the oil in the alkyd, which aids in surface wetting, surface preparation requirements are minimal. Therefore, the removal of all loose materials by hand or power tools is usually adequate for the use in mild to moderate exposures. However, abrasive blast cleaning or water jetting to the same cleaning standard (i.e. SSPC-SP6 or SSPC-SP12-WJ3) still provides superior surface cleanliness and may increase long-term coating © 2011, American Railway Engineering and Maintenance-of-Way Association

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Commentary system performance. In most cases the high cost of such surface preparation would indicate the use of higher performance coatings which would increase long term performance. Touch-up may be performed with a similar material, or an oil-based coating if necessary. They can be easily applied by maintenance personnel. (2) Modified Alkyds – The versatility of alkyds is further enhanced by combining them with any number of natural and synthetic resins. By modifying the basic alkyd, additional corrosion protection may be gained while the ease of application and surface tolerance is maintained. While the basic alkyd resins have been modified by combining them with other materials, the modified product does not develop all of the characteristics of these materials. They offer increased performance to the oil-based resins alone, but do not match the performance of the more advanced coatings. These materials offer a potential solution for mild to moderate environments where additional protection is necessary, but a cost-effective coating is desired. While there are many types of modified alkyds that have been developed for specific uses, this discussion will include only three that have significance to steel from which all coatings have been removed: vinyl alkyds, calcium sulfonate modified alkyds and silicone alkyds. (a) Vinyl Alkyds – The Vinyl Alkyds offer decreased drying times, better adhesion and water resistance, and improved exterior durability compared to the basic alkyd formulation. Because of the vinyl modification, some formulations are also capable of being topcoated with high performance, stronger-solvent topcoats such as epoxy or urethane. Vinyl alkyd modifications are generally used in readily recognized products referred to as “universal metal primers”. (b) Silicone Alkyds – Similar to the vinyl alkyd, the silicone alkyds as compared to unmodified alkyds offer an increase in corrosion protection. The silicones also offer the capability of resisting somewhat higher temperatures while also improving gloss retention, color retention, and abrasion resistance. The increase in resistance qualities appears to be directly related to the quantity of silicone used in the modification. As such, the amount of silicone should be selected and specified. A 30% silicone content is a minimum amount of silicone commonly specified to ensure superior performance. (c) Calcium Sulfonate Modified Alkyds – similar to the silicone modified alkyd in that a small percentage of calcium sulfonate is used to enhance the properties of the base alkyd resin. The calcium sulfonate is added to the formula to give the alkyd better corrosion resistance, wetting properties, thixotroscopy (ability to resist runs or sags) and as a pigment suspension agent. The amount of calcium sulfonate in modified alkyds may range from 2 to 15 percent by weight with an improvement in performance with increasing calcium sulfonate content. For best performance a percentage by weight of 14% to 15 % is recommended. It is also important to insure that the ratio of calcium carbonate to active sulfonate is approximately 10 to 1. This ratio is required for a balanced formula and is the ratio that has been used in the field proven materials. To reduce costs some suppliers may supply what they call a calcium sulfonate alkyd but the formula is basically low cost, low quality calcium carbonate filler with only a small percentage of active sulfonate added. Specifications should clearly define the percentage of active sulfonate and quality control procedures should be put in place to enforce the specification. (3) Zinc-Rich Coatings – Zinc-rich coatings provide a high level of protection for blast cleaned steel, but are expensive relative to other coatings. Zinc-rich coatings provide a combination of barrier and galvanic protection. Zinc dust dispersed through various resins provides the galvanic and barrier protection as well as improved abrasion resistance. Zinc-rich coatings offer significantly better performance than other types, through galvanic action described earlier. This protection greatly reduces sub-film corrosion and cancerous undercutting corrosion. Their limitations include somewhat higher cost, reliance on a high degree of surface preparation, skilled applicators, and careful selection of intermediate and/or topcoats. Zinc-rich primers require the surface to be free of flash rust for good performance. The industry standard is for surface temperature to be several degrees above the dew point for zinc primer application. Zinc-rich coatings used alone also offer reliable one-coat protection in normal weather conditions. Zinc-rich coatings are available in organic and inorganic formulations. Inorganics are considered to provide superior protection, but they are more sensitive to the surface preparation and applicator skills. Inorganic zinc-rich

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Steel Structures coatings require surface preparation to Near-White Metal (SSPC-SP10) at a minimum, with White Metal (SSPCSP5) preferred. Field touch-up is performed with an organic material, such as a surface-tolerant epoxy, primarily because inorganic zinc-rich coatings require spray application and are less user friendly. They can be used very effectively in maintenance applications, but should be substituted with organic zinc on complex surfaces, e.g. steel lacing, corroded crevices, pack rusted joints and connections. Inorganic zinc primers may be used in one, two or three-coat systems. Usually, epoxies are used as intermediate coats and acrylic aliphatic urethanes as finish coats; however, waterborne acrylic coatings have also been successfully used as topcoats for zinc-rich coatings. Inorganic zinc or galvanizing are the preferred shop primers for replacement steel used to repair existing structures. Care must be taken to ensure that all shop and field coatings specified are compatible. Organic zinc coatings can be made from many different generic coating types, but the most prominent are epoxy and moisture-cured urethanes. Epoxy zinc-rich coatings have primarily the same characteristics as epoxies; excellent adhesion, abrasion resistance, good water resistance, and if modified increased flexibility. The zinc dust dispersed in the coating gives galvanic (sacrificial) protection against corrosion and improves abrasion resistance. Moisture-cured organic zinc-rich primers have the advantage of galvanic protection coupled with good adhesion, abrasion resistance, and sunlight resistance when topcoated with a moisture-cured aliphatic topcoat. In addition moisture-cured urethane organic zinc-rich primers have the ability to be applied in high humidity and colder temperatures. Field application must be monitored carefully as too much moisture will cause carbon dioxide gassing or poor adhesion. Coating manufacturers often tout the ability of their moisture-cured primer to adhere to damp steel. Organic zinc coatings are generally topcoated with epoxies, acrylic urethanes, 100% acrylics, or moisture-cured urethanes. (4) Moisture-Cured Urethanes – Moisture-cured urethane coatings react with atmospheric moisture (humidity) which initiates the cure, creates carbon dioxide gas and provides a protective coating film. These single-component products have excellent performance characteristics, including abrasion resistance, durability, and appearance. Zinc-rich primer formulations made from moisture-cured resins give excellent protection against corrosion of steel. Many moisture-cured urethane intermediate and finish coat formulations use micaceous iron oxide to provide corrosion resistance. Moisture-cured urethane coatings are ideal for field application, since they may be applied in periods of high humidity and moderate cold temperatures. Moisture-cured urethane coatings have several unique disadvantages. They are moisture sensitive in the container, which can lead to gelling. If too much moisture is present they will produce excessive carbon dioxide gas that could damage the film. When properly cured they provide a hard and smooth coating film that may be difficult to overcoat in the future. Recoat windows, the time during which an additional coat can be applied without additional surface preparation such as sanding or light abrasive blasting, are narrow. They are more costly to purchase than other high-performance coatings but may be more cost effective if conditions for application are right. Moisture-cured urethanes have only fair flexibility, limited resistance to acid and chemicals, and notable yellowing when exposed to the ultraviolet rays of sunlight. Moisture-cured urethanes require careful control of application thickness, particularly in windy, humid conditions. (5) Epoxy Coatings – Epoxy coatings have excellent adhesion to steel, excellent abrasion resistance, good water resistance, and when modified relatively good flexibility. For bridge coatings, epoxy resins are used primarily for zinc-rich primers, and for intermediate coats over inorganic or organic zinc-rich primers. Since epoxies are twocomponent materials, they must be mixed in proper proportions to cure correctly. Other disadvantages of epoxy coatings are that most materials have limited pot lives, specific recoat time intervals, and application temperature and humidity restrictions. Epoxies are not usually used as finish coats because UV light attacks the structure and they break down causing chalking. (6) Epoxy Mastic Coatings – Epoxy mastic coatings cure by chemical reaction when a hardener is added to the resin. Since the percentage of solids by volume is higher than that of regular epoxies, the amount of solvent used in the coating formulation is low. Therefore, most epoxy mastics are VOC compliant and are less likely to overly soften, wrinkle, or lift old coatings. They also may offer a higher film build per coat, which serves to improve on already good abrasion and environmental resistance. Additionally, many formulas have low temperature catalysts or additives which may extend the coating season into periods of cooler weather. Epoxy mastic coatings also readily lend themselves to modifications which enhance their corrosion resistance and film strength. One such

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Commentary modification is the addition of leafing or non-leafing aluminum into the coating, which serves to lower the epoxy resin’s susceptibility to degradation by ultraviolet light and decreases moisture permeability of the film. For new construction or exposed surfaces, aluminum flake pigmented epoxy mastic systems are the industry standard when epoxy mastics are used. This addition increases the corrosion protection of the system and the mechanical strength of the coating film. Disadvantages of epoxy mastics are their higher cost and the epoxy resins’ inherent degradation by ultraviolet light. Sunlight and weathering exposure commonly result in chalking and/or color fading of the exposed film. As a result, if chalking and discoloration cannot be tolerated, they must be topcoated with better gloss and color retentive finish coats, such as polyurethanes or acrylics. However, it is important to note that any chalking which takes place has been found to have little or no effect on coating performance other than life expectancy due to the film eroding away. Other disadvantages include slower drying time and strong odors. Other limitations of epoxy mastics are that many have limited recoat times and multiple components which require mixing, include toxic solvents and have limited pot life. These coatings are toxic and require special handling in the field. A large variety of epoxy mastic formulations exist, with dramatic differences in performance between the best and the worst. Proper specification is needed to achieve the desired results from this coating. (7) Waterborne Acrylic Coatings – Waterborne acrylics are single-component coatings which cure by coalescence of the resin particles that are dispersed in water. Variations of waterborne acrylics are used in both protective and architectural coatings in the form of primers, intermediate coats, and finish coats. These materials have higher moisture vapor transmission rates which allow moisture to readily pass through the coating film. Therefore, in coatings for use on steel, anti-corrosive pigments are added to inhibit rust formation. Acrylics offer excellent exterior durability along with gloss and color retention similar to that achieved by urethane coatings. Waterborne acrylics also have excellent flexibility, good drying times under low humidity conditions, relatively low odor, are easy to apply, and readily accept future overcoats. Lower abrasion resistance properties, along with relatively higher costs, are some of the disadvantages of waterborne acrylic coating materials. Limitations of acrylic coatings are their fair corrosion resistance, application temperature limitations above 50°F, and relatively poor chemical resistance compared to a two-component high performance coating system such as an epoxy. Waterborne acrylic coatings are not resistant to high levels of moisture or prolonged condensation. (8) High Ratio Co-Polymerized Calcium Sulfonates – High Ratio Co-Polymerized Calcium Sulfonate coatings are different from Calcium Sulfonate Modified Alkyds. High Ratio Co-Polymerized Calcium Sulfonates are made up of a co-polymerized reacted synthetic resin with a unique patented crystalline modification that cures by air oxidation. These coatings provide protection by a combination of chemical and physical properties. The coatings are excellent chemical treatments and film formers, and in both field and laboratory tests have demonstrated that they are at the top of the performance envelope, when compared to traditional multi-coat high performance coatings. The High Ratio Co-Polymerized Calcium Sulfonate coatings' major advantage is the active Penetrant/Sealer and Primer/Topcoat, which have a fifteen-year history on structures in the field, and that stop the progression of crevice corrosion and pack rust specifically in joints and connections. This activity, in the joints and connections, is unique to the High Ratio Co-Polymerized Calcium Sulfonate chemistry and supplies the engineer with a valuable tool for the preservation of aging complex structures, where crevice corrosion and pack rust are present. In addition the coatings are very environmentally friendly with the system having a LC50 at 96 Hrs fish kill at 41007 ppm (note typical epoxies and urethanes are 2-4 ppm). This test is used to assess the toxicity of coatings if they are introduced into the fish habitat. The performance of the High Ratio Co-Polymerized Calcium Sulfonate coatings is related directly to the percentage amount of synthetic crystalline based material and of active sulfonate in the formulation. The ratio should be a minimum 90 to maximum 105 TBN (Total Base Number) and a minimum 9.5 to 11% active sulfonate. There must be a minimum 9 to a maximum 11 to 1 ratio total base number to active sulfonate. Calcium sulfonate coatings with lower active numbers will not perform as well and are not equal to the High Ratio Co-Polymerized Calcium sulfonate type products, and should not be included in the same specification. The formulation should contain no fillers or extenders. Some manufacturers fill their coatings with low cost calcium carbonate fillers to lower the price with a negative impact on long term performance. Unlike calcium sulfonate alkyds the alkyd or co-polymer used in conjunction with the High Ratio Co-Polymerized Calcium Sulfonate should not comprise more than 25 to 27 % of the formulation. Formulations with more than

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Steel Structures 27% alkyd or co-polymer would not be considered equal to the High Ratio Co-Polymerized Calcium Sulfonate formulations which have set the high performance standard since 1991. Increasing the amount of alkyd or copolymer is a way to reduce the cost, with the net effect of reducing the long term performance. (9) Galvanizing – Hot-dip galvanized steel has been effectively used for more than 150 years. The value of hot-dip galvanizing stems from the relative corrosion resistance of zinc, which, under most service conditions, is considerably better than iron and steel. In addition to forming a physical barrier against corrosion, zinc, applied as a hot-dip galvanized coating, cathodically protects exposed steel. Furthermore, galvanizing for protection of iron and steel is favored because of its low cost, the ease of application, and the extended maintenance-free service that it provides. Though the process may vary slightly from plant to plant, the fundamental steps in the galvanizing process are: Soil and grease removal – A hot alkaline solution removes dirt, oil, grease, shop oil, and soluble markings. Pickling – Dilute solutions of either hydrochloric or sulfuric acid remove surface rust and mill scale to provide a chemically clean metallic surface. Fluxing – Steel is immersed in liquid flux (usually a zinc ammonium chloride solution) to remove oxides and to prevent oxidation prior to dipping into the molten zinc bath. In the dry galvanizing process, the item is separately dipped in a liquid flux bath, removed, allowed to dry, and then galvanized. In the wet galvanizing process, the flux floats atop the molten zinc and the item passes through the flux immediately prior to galvanizing. Galvanizing – The article is immersed in a bath of molten zinc at between 815º-850º F (435º-455º C). During galvanizing, the zinc metallurgically bonds to the steel, creating a series of highly abrasion-resistant zinc-iron alloy layers, commonly topped by a layer of impact-resistant pure zinc. Finishing – After the steel is withdrawn from the galvanizing bath, excess zinc is removed by draining, vibrating or for small items - centrifuging. The galvanized item is then air-cooled or quenched in liquid. Galvanized steel that is to be topcoated for cosmetic considerations must be air-cooled without quenching to avoid adherence problems. Inspection – Coating-thickness and surface-condition inspections complete the process. (10) Metalizing – Metalizing is a thermal spray process that requires surface preparation by abrasive blasting followed by metal spraying which can then be sealed and thereafter topcoated. There is a higher initial cost for metalizing but new application technologies and life cycle costing show that it is about half the cost of coating with high performance three coat systems. The three spray wires used for atmospheric or immersion service are pure aluminum, pure zinc or an 85/15 alloy of these two metals. (The alloy is approximately 85% zinc and 15% aluminum by weight.) A metalized coating may be bare sprayed metal, sprayed-metal-plus-sealer or sprayedmetal-plus-sealer-plus-topcoat. Coating thickness may vary according to application from .004" to thicker coats of zinc in the range of .012" - .014" for seawater splash zones. Metalizing is considered a cold process in that the aluminum or zinc is deposited onto steel by spraying rather than by dipping the steel into a bath of molten zinc as with galvanizing. The steel remains relatively cool at about 250º-300ºF. There is virtually no risk of heat distortion or weld damage by metalizing. There are no VOC's (volatile organic compounds) in the metalized coating. There is no cure time or temperature limit for metalizing, so metalizing may be applied throughout the year. The sealedsprayed-metallic coating is often the most economical and is the preferred system of the three metalized coating options as it offers the longest service life. The use of a coating directly over an unsealed sprayed-metal coating should be avoided. The disadvantage to the system is that the blast profile is very specific. The profile must be a minimum of 4 to 4.5 mils and angular in nature. Careful inspection is required to insure it is achieved. (11) Polyurea Coatings – Polyurea-based thick film coatings encompass a diverse group of products. A pure polyurea is the combination of isocyanates with a long chain amine, excluding the hydroxyl reactive sites. For reference, pure polyurethane coatings are formulated using an isocyanate combined with hydroxyl-containing polyols. Polyurea coatings can be formulated as hybrids by combining isocyanates with a mixture of polyols and long chain amines, resulting in a coating that bears the performance characteristics of a polyurethane and a polyurea coating. Polyurea

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Commentary coatings can be either aromatic or aliphatic, and can be formulated with catalysts, pigments, fillers and other performance-enhancing additives. Pure polyurea coatings offer the highest degree of chemical resistance, but hybrids offer improved wetting (the cure time is retarded) and other desirable performance characteristics. The relative production cost is lowest for a polyurethane, increases for polyurea hybrids, and is the highest for pure polyurea coatings. These new technology polyurea coatings and their hybrids offer the industry an environmentally compliant, high performance option (with very attractive film forming properties) for corrosion prevention and asset protection. However, like all industrial protective coatings they have performance limitations and minimum surface preparation requirements. Use of these materials outside of the recommended service environments or over marginally prepared surfaces can result in catastrophic failure and costly rework. c.

Coatings for Overcoating Existing Coatings and Stable Substrates Many coating types are reformulated specifically for use as overcoating materials. At a minimum, the following generic coating types would usually be recommended for over coating the existing coatings on railway structures. Compatibility testing should be done between the coating to be overcoated and the coating to be applied to insure it will not delaminate or otherwise adversely affect the adhesion properties of the existing coating. (1) Alkyds – See b(1). (2) Modified Alkyds – See b(2). (3) Epoxy Mastic Coatings – Epoxy mastic coatings offer many advantages as overcoats and are widely specified for use as an overcoating material. Because epoxy mastics are formulated to have good wetting properties, they possess excellent adhesion to marginally prepared contaminant free surfaces (SSPC-SP2 minimum). Testing should always be done to insure compatibility with the existing coating. When properly formulated, the coatings will maintain very low stress, making them good overcoat candidates for aged alkyds. For additional information see b(6).

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(4) Moisture-Cured Urethane Coatings – See b(4) (5) Low Molecular Weight Epoxy Penetrants – See a(1)

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(6) Waterborne Acrylic Coatings – Waterborne Acrylic Coatings are good overcoating materials because they have lower shrinkage stresses as they cure and therefore apply little contractive stress on existing coatings. Since these coatings use water as a solvent, they are VOC compliant and do not over-soften or lift existing films. They are typically used in overcoating as finish coats over epoxy mastics or epoxy penetrant sealers. For additional information refer to b(7) (7) High Ratio Co-Polymerized Calcium Sulfonates – See b(8) (8) Urethane Systems – Chemically cured acrylic urethane coatings are not typically used as overcoating primers, but do offer excellent characteristics as finish coats with superior gloss and color retention, and UV resistance over some of the materials previously discussed (Zinc primers, epoxy mid coats, epoxy mastics, epoxy penetrating sealers, and moisture cured urethanes). These coatings offer excellent water and corrosion resistance. They also allow lower application temperatures, and can be modified to be high solids, high build, or 100% solids coatings, thus VOC compliant. Disadvantages with urethane coatings are that they have limited flexibility and are twocomponent materials with a limited pot life. They are also moisture sensitive during application and may haze or blush (develop a cloudy milky looking appearance) if applied during periods of high relative humidity. Another disadvantage is that the coating film produced is slick and hard, which may necessitate substantial surface preparation prior to future overcoating operations. This disadvantage may also prove to be advantageous in that graffiti can easily be removed from high gloss urethane coated bridges by wiping with solvent.

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Steel Structures

PART 10 BEARING DESIGN 9.10.1 INTRODUCTION 9.10.1.2 GENERAL REQUIREMENTS (2010) b.

Each bridge and span configuration induces unique loads and movements into the bearings and, in turn, each type of bearing with their varying restraint characteristics return unique forces back into the span and/or into the substructure. Movements include both translations and rotations. The sources of these movements include bridge skew and curvature effects, initial camber or curvature, construction loads, misalignment or construction tolerances, settelement of supports, thermal effects, and displacements due to live load deflections. Skewed bridges can have movements both longitudinally and transversely. Curved bridges can have movements both radially and tangentially which could be at differing angles at each substructure unit. A practical form for tabulating bearing load resistance and movement requirements is presented in Section 14 of Reference 119 or in Appendix H of Reference 122.

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Spans, of any length, with similar live load deflection to span length ratios will experience similar angular rotations at the bearings. Short spans see many times more rotation cycles than longer spans (once per axle, truck, or car vs. once per train). Many, but not all, short spans (50 feet or less) have historically performed well using simple flat plate on flat plate bearings. The practice has succeeded because: • Short spans, particularly deck girder spans, often have small span to depth ratios, and are much stiffer than required to meet deflection criteria contained in Article 1.2.5.b., reducing rotations at the bearings. • Flat plate on flat plate bearings often permit adequate rotation to occur, usually through a combination of edge bearing of the sole plate on the bed plate, use of elastomeric or malleable pads between the bed plate and the bearing seat, and sometimes soft bearing seats absorb rotations of the bed plate (for example timber caps and/or blocking beneath the bearings). Unless extensive experience in similar circumstances has proven the success of flat plate on flat plate bearings in a particular design, the designer should verify that rotation is adequately accommodated. Best practices for using flat plate on flat plate bearings include: • Keeping sole plates as small as possible, and setting them on larger bed plates so that edge bearing stresses from the sole plate are reduced and are ideally applied within the middle third of the bed plate. • Installation of elastomeric or malleable pads between the bed plate and the bridge seats. • Flexible connection of the sole plate to the span (bolted rather than welded).

9.10.1.5 BEARING SELECTION CRITERIA (2010) a.

Table 15-10-1, Bearing Suitability, the bearing selection criteria, and insights into typical movement accommodation characteristics of each bearing type delineated herein are a composite of that presented in Reference 101; Reference 119, Section 14; and Reference 122, Appendix H; with appropriate adjustments made for usual railroad bridge bearing practice. Specific bearing type suitability characteristics listed in the table and their application to railroad bridges are based on the following: (1) Resistance to Vertical Loads: All bearing types listed in Table 15-10-1 were chosen for their suitable resistance to downward vertical loads, except Plain Elastomeric Pad Bearings which have limited application as discussed © 2011, American Railway Engineering and Maintenance-of-Way Association

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Commentary below. However, since uplift can occur at the bearings of railroad bridges due to the highly dynamic effect of railroad live loading, Article 10.1.2.b requires that hold-down devices be provided at all bearings unless waived by the Engineer. When calculated uplifts occur, additional, more substantial elements, such as link bars or other heavy hold-down devices are to be designed and incorporated into the bridge bearings. (2) Fixed Bearings: Fixed Bearings are intended to restrain translations in all directions while allowing rotation on at least one axis. Since the primary movements in the typical railroad bridge are generally in the longitudinal direction, all Fixed Bearings are indicated to be suitable for rotations about a transverse axis. Fixed Bearings that restrain rotations in all directions are generally not practical for railroad bridge applications, thus are not included in Table 15-10-1. (3) Flat Steel Plate on Flat Steel Plate Bearings: Steel-on-steel sliding bearings are common in historical railroad bridge practice for spans less than 50 feet (15 000 mm) in length particularly when utilizing rolled beams. Thus, because of the span length limits, the usual limit on longitudinal translation is 0.5 inches (12 mm) and the usual limit on rotation about the transverse axis is 0.01 radians. Steel-on-steel sliding surfaces develop a higher frictional force than Bronze or Copper Alloy and PTFE sliding surfaces. This friction force acts on the superstructure, substructure, and bearing and is an important design consideration. Steel-on-steel sliding bearings are still used in modern railroad bridge practice when an economical bearing type is desired and the span and substructure can accommodate the loads induced by the higher coefficient of friction between the steel plates. Beam span lengths of 70 feet (21 000 mm) have been used with steel-on-steel sliding bearings and with a plain elastomeric pad placed under the masonry plate to accommodate rotations. (4) Rocker and Roller Bearings: Rocker Plate, Pin and Rocker, and Roller Bearings utilize a cylindrical surface which is generally aligned on a transverse axis to the bridge to accommodate the primary longitudinal movements found in most railroad bridges. Because of this, all bearings of these types are listed as suitable for rotations about a transverse bridge axis and unsuitable for rotations about a longitudinal bridge axis.

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To maintain stability of the rocker (prevent rocker tip-over), a 4 inch (100 mm) longitudinal translation limit is commonly considered appropriate for Pin and Rocker Bearings in the typical railroad bridge designed in accordance with AREMA Manual for Railway Engineering, Chapter 15 which has a limit of applicability to spans of 400 feet or less. Larger bearings can be designed to accommodate larger translations from longer spans or long continuous multi-span units, but the rocker becomes very tall so rocker stability must be specifically addressed in the bearing design. Special restrainers may be required, particularly in high seismic zones.

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(5) Bronze or Copper Alloy and PTFE Sliding Surfaces: Bronze or Copper Alloy and PTFE sliding surfaces are commonly used as components of bridge bearings to accommodate the sliding and/or rotating movements. Sliding surfaces develop a frictional force that acts on the superstructure, substructure, and the bearing. Friction, thus, is an important design consideration. PTFE Sliding Surfaces generally will have the lowest friction coefficient resulting in the transfer of the lowest friction forces into the bridge or its supports.

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Flat Bronze or Copper Alloy or PTFE Sliding Surfaces can be designed to accommodate very large translations, but cannot accommodate rotations by themselves. Other elements, such as pins, rocker plates, curved sliding surfaces, elastomeric pads, etc. must be added to the complete bearing assembly if rotations are to be accommodated. Restrainers, such as guide bars or other devices are frequently added to limit translations in certain directions and to provide resistance to loads in those directions. Cylindrical Bronze or Copper Alloy or PTFE Sliding Surfaces can be designed to accommodate very large rotations, but only in one direction. Thus, as described above in Item 4 for Rocker Plate and Roller Bearings, the cylindrical surface is generally aligned with the transverse axis of the bridge, which provides suitable accommodation of the primary longitudinal rotations while preventing transverse rotations about a longitudinal bridge axis. A cylindrical surface alone thus aligned cannot accommodate longitudinal translations and can only accommodate limited transverse translations.

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Steel Structures Spherical Bronze or Copper Alloy or PTFE Sliding Surfaces can be designed to accommodate large rotations in any direction; thus, they are classified as Multi-rotational Bearings. A spherical surface alone cannot accommodate translations in any direction. Combined flat and curved Bronze or Copper Alloy or PTFE Sliding Surfaces can be utilized to accommodate both large translations and rotations. When this is required the flat surface should be placed at the bottom of the Bronze or Copper Alloy or PTFE element with the curved surface at the top. Double Cylindrical (Bi-radial) Bronze or Copper Alloy or PTFE Sliding Surfaces can, in general, be designed to accommodate large rotations about any horizontal axis and limited translations in any horizontal direction. Even though rotation about a vertical axis cannot be accommodated, this type of bearing is still classified as a Multirotational Bearing. A 1 inch (25 mm) limit on translations should be used in the typical railroad bridge bearing since this type of bearing can become unstable with larger translations in one or more directions, particularly when combined with larger rotations. While adding a separate flat sliding surface would accommodate larger translations, the complex configuration of having three sliding surfaces combined with the restrainers required to prevent or limit translations along the axis of the cylindrical surfaces renders a very difficult and costly design. Spherical Bearings combined with a flat sliding surface should be used to accommodate large translations and rotations in multiple directions. (6) Plain Elastomeric Pads: The three most important properties of Elastomeric Bearings that distinguish them from other construction materials are: 1) flexibility in shear relative to their thickness; 2) stiffness in bulk or direct compression relative to their shear flexibility; and 3) ability to undergo very large shear deformations without damage relative to their thickness. However, a simple block of elastomer subjected to compression expands laterally due to the Poisson effect and is much softer than other typical railroad bridge construction materials. If the lateral expansion occurs freely, the resulting compressive deflection is unacceptable. For railroad bridges, the total compressive deflection is limited by Article 10.6.3.5.e to 0.125 inches (3 mm) to provide acceptable ride quality. Plain Elastomeric Pads rely on friction at their top and bottom surfaces to restrain compressive bulging. Friction is unreliable, however, and local slip results in a larger elastomer strain. The increased elastomer strain limits the load capacity of the Plain Elastomeric Pad. The allowable stress depends upon the shape factor of the elastomeric bearing pad. Plain Elastomeric Pads, therefore, must be relatively thin, which leads to the thickness limits of Article 10.6.3.8 and Article 11.5.1.c. Thin elastomeric bearing pads can tolerate only small translations; thus, a small 0.25 inch (6 mm) maximum translation limit is recommended for Plain Elastomeric Pads used in the typical railroad bridge application. Since rotation is accommodated in Elastomeric Bearings by an increase in compression on one side of the pad and a reduction on the other side, thin elastomeric bearing pads can tolerate only small rotations also. This leads to the recommendation that a small 0.01 radian maximum rotation limit be considered in the design of Plain Elastomeric Pad bearings for railroad bridges. (7) Steel Reinforced Elastomeric Bearings: Many of the issues with total elastomer thickness, load capacity, translation and rotation limits of Plain Elastomeric Pads can be addressed by increasing the number of elastomer layers by adding thin steel reinforcing plates between the layers. The steel reinforcing plates prevent outward movement of the elastomer at the interface between the two materials so that lateral expansion can take place only by bulging. Thinner elastomer layers thus lead to less bulging and higher compression strength and stiffness, which is desirable, but this also results in high rotational stiffness. Larger rotations can be accommodated by adding more layers. A bearing that is too stiff in rotation leads to lift-off and high local stresses that could cause damage. Thus, selection of the number and thickness of the elastomer layers is a compromise between the needs for compressive stiffness and rotational flexibility. For railroad bridges, the total thickness of the bearing or thickness and number of individual layers is limited by the total compressive deflection limit of 0.125 inches (3 mm) as defined in Article 10.6.3.5.e. Since accommodating rotation is an important part of railroad bridge bearing design, being able to utilize the full

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Commentary available rotation limit of 0.04 radians as listed for highway bridges in Reference 101 is typically considered important. This recommended maximum rotation limit, however, when considered in relation to the compressive deflection limit for railroad bridges, dictates a reduction in the maximum translation available for railroad bridges compared to highway bridges. Thus, it is recommended that a translation limit of 2 inches (50 mm) be considered unless other accommodation, such as a separate flat sliding surface, is provided. (8) Disc Bearings: In a Disc Bearing, compressive load is carried by a hard elastomeric (polyether urethane) disc. As with all elastomeric type bearings, rotations are accommodated by an increase or decrease in compressive deformations on opposite sides of the disc. The hard elastomer used in Disc Bearings is not flexible in shear so it cannot accommodate horizontal translations without the addition of a flat sliding surface or other device. To prevent the disc being overstressed by horizontal loads, a metal pin is placed through a hole in the center of the disc. Thus, Disc Bearings by themselves are listed in Table 15-10-1 as fixed bearings with no translation allowed. Disc Bearings are classified as a multi-rotational bearing. At low loads, they work like an unreinforced plain elastomeric pad as described above. The elastomer used in Disc Bearings, however, is very much stiffer than that used in a typical elastomeric pad. Some slip and some lateral expansion occur. It has been shown that the rotation and compression stiffness are both related to the square of the shape factor. The shape factor therefore cannot be too small or the disc would deflect too much under compression, and it cannot be too big, or the bearing would be too stiff in rotation. The choice of disc dimensions is therefore a compromise between these two design goals. This need for compromise means that designing for a rotation much larger than 0.02 radians is difficult, particularly for the typical railroad bridge application. See Reference 122, Appendix H. The rotation may need to be further limited since, for high rotations under lighter loads, significant uplift can occur creating potential for damage to the Bronze or Copper Alloy or PTFE Sliding Surfaces that may be used to accommodate lateral translations. Even for fixed bearings, uplift conditions will cause abrasion of the disc and raises the possibility of ingress of dirt. See Reference 122, Appendix H. b.

Pot-type bearings are not recommended for support of railroad bridges because of concerns over reduced bearing life due to large cyclical live load deformations and rotations.

c.

As described in Article 9.10.1.5a(6) and Article 9.10.1.5a(7), design of Plain Elastomeric Pads and Steel Reinforced Elastomeric Bearings is a compromise between the need for compressive stiffness and rotational flexibility. To provide the minimum rotational flexibility required by typical railroad bridge applications and stay within the rotational limits recommended in Article 9.10.1.5a(6) and Article 9.10.1.5a(7) without lift-off, further limits on the width of elastomeric pads or bearings are required.

9.10.2 BASIC ALLOWABLE STRESSES

The allowable stress in bearing between rockers and rocker pins was adapted from editions of AREMA Manual Chapter 15, Steel Structures, Section 1.4, prior to the 1969 edition and the low value of 0.375 Fy was retained to minimize pin wear. Pin wear had historically been a cause of trouble when higher values for this condition were permitted. The allowable stress in bearing on expansion rollers and rockers was based on static and rolling tests on rollers and rockers (Reference 14). The average vertical pressures over calculated contact areas for loads substantially less than allowable design values are in excess of the yield point, causing a flow of the material. It was concluded that the resulting “spread” of the roller and base, measured parallel to the axis of the roller at points near the surfaces in contact, was the most satisfactory phenomenon to use in determining design values. Such “spreads” or deformations were measured in units of 0.001 per inch per 1,000 strokes, each stroke corresponding to a roller movement of 4 inches and an equal movement back. Design values according to the tests would give total deformations varying from about 3 units to less than 1.

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9.10.2.1 STRUCTURAL STEEL, BOLTS AND PINS (2000) R(2008) c.

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9.10.2.6 POLYETHER URETHANE DISC BEARINGS (2007) The recommended average allowable compressive stress on polyether urethane discs in Disc Bearings of 5,000 psi matched AASHTO’s average allowable compressive stress in 2005 when it was recommended by a special Subcommittee 7 Task Force on Implementation of Higher Allowable Bearing Stresses. Even though there was limited test data in 2005 for disc bearings in railroad bridges or for disc bearings subjected to high live load to dead load ratios, the Task Force believed that the existing data and current testing indicate that an allowable average bearing pressure of 5,000 psi on polyether urethane discs is conservative for the polymer compound recommended in Article 10.7.2.d.

9.10.3 STEEL BEARING COMPONENTS 9.10.3.3 SHOES AND PEDESTALS (1997) R(2008) The requirements of Article 10.3.3 provide that the load is uniformly distributed over the entire bearing surface, and that, in the case of welded bearings, the load is transmitted in bearing.

9.10.4 BRONZE OR COPPER-ALLOY SLIDING EXPANSION BEARINGS 9.10.4.3 DESIGN (2001) R(2008) b. For design, the static coefficient of friction is specified to be a minimum of 0.10 since it is to be applied when calculating loads acting on bearing components or the bridge substructure or superstructure due to friction, thermal restraints or the portion of other horizontal loads transferred through an expansion bearing with bronze or copper-alloy sliding plates. The provision in Article 11.3.1 that limits the coefficient of friction of the bronze or copper-alloy sliding expansion bearing plates to a maximum of 0.10 will theoretically assure that Article 10.4.3 produces conservative loads for designing other elements of the bearing or bridge. At the discretion of the Engineer, when calculating loads acting on other bridge elements, a higher coefficient of friction, such as 0.25 specified by some railroads, may be used to accommodate the possibility of future partially frozen bearings.

9.10.5 PTFE SLIDING BEARING SURFACES 9.10.5.3 DESIGN (2006) 9.10.5.3.1 General c.

For design, the static coefficient of friction is specified to be a minimum, over the range listed, since it is to be applied when calculating loads acting on bearing components or the bridge substructure or superstructure due to friction, thermal restraints or the portion of other horizontal loads transferred through an expansion bearing with PTFE sliding surfaces. The provison in Article 11.4.1(c) that limits the coefficient of friction of the PTFE sliding surfaces to a maximum of the listed values will theoretically assure that Article 10.5.3.1(b) produces conservative loads for designing other elements of the bearing or bridge. At the discretion of the Engineer, when calculating loads acting on other bridge elements, some railroads specify a higher coefficient of friction, such as 0.25, to accommodate future partially frozen bearings.

9.10.7 MULTI-ROTATIONAL BEARINGS 9.10.7.1 SCOPE (2007) c.

Pot type bearings are not recommended for railroad loading due to experiences with seal failures.

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Commentary

9.10.7.3 DESIGN (2007) R(2008) 9.10.7.3.1 General h.

Differing deflection and rotation characteristics of different types of multi-rotational bearings may result in damage to the bearings and/or structure.

PART 11 BEARING CONSTRUCTION 9.11.3 BRONZE OR COPPER-ALLOY SLIDING EXPANSION BEARINGS 9.11.3.1 GENERAL (2001) R(2008) b.

See Article 9.10.4.3b.

9.11.4 PTFE SLIDING BEARING SURFACES 9.11.4.1 GENERAL (2002) R(2008) c.

See Article 9.10.5.3.1c.

1

WELDING INDEX (2004) This Welding Index makes reference to some of the articles in the Manual pertaining to Welding involved in design, fabrication, repair and rating of steel structures. This index does not include every reference to welding within the Manual, but can serve as a ready guide for designers. Subject

Article Reference

3

Allowable stresses–base metal

1.3.13; 1.4.1; 9.1.4 and Tables 15-1-9, 15-1-10 and 15-7-1

Allowable stresses–weld metal

1.3.13; 1.4.2; 6.5.36.10b; 9.1.4 and Tables 15-1-9, 15-1-13 and 15-7-1

Attachments

1.10.4

Bridge types

1.2.3

Bridge welding code, AWS D1.5

1.2.2; 1.10.2; 1.10.6; 1.14.1; 3.3.1a; 3.3.5; 3.5.5b and c; 9.1.2.2; 9.1.4.2; 9.1.10.1; 9.1.14.1; 9.3.1.6

Butt joints

1.7.2.2a; 1.10.1; 7.4.4; 8.1.4.12c; 9.1.10.1

Closed boxes

1.5.15

Combination of welds with rivets and/or bolts

1.5.12b; 9.1.5.12

Compression in welded box-type flexural members

1.4.1

Compression in welded built-up flexural members 1.4.1; 1.6.1; 1.6.2; 1.6.3; 1.6.4.2g; 9.1.7.1 Connections

1.5.9

Connections, field welded

1.5.10; 1.5.12b

Cover plates, fillet welded

1.7.2.2b

Deck plate–girder flanges

1.7.4b

Drainage pockets

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Subject

Article Reference

Eccentric connections

1.5.7b

Existing bridges

7.4.1.5; 7.4.2.2; 7.4.2.3a and b; 7.4.2.4; 7.4.3.2; 7.4.4.1e

Fabrication tolerances

3.1.7.1d and e; 3.1.7.2

Fatigue

1.3.13; 7.3.3.2c and f

Field welding

1.5.10; 4.20; 9.1.5.10

Fillet welds

1.7.4b; 1.10.3; 3.3.3; 3.5.5b and c; 7.4.2.3a and b; 9.1.10.4

Fire damage

8.6.5c

Flange to web welds

1.7.4b; 3.3.3; 3.5.5c; 9.1.7.4; 9.3.3.3

Flange splices

1.7.5

Fracture critical members

Section 1.14

Full penetration groove welds

1.5.9b; 1.7.5; 1.7.6c; 3.1.10a; 3.5.5b; 6.5.36.10c; 9.1.7.4

Groove welds

1.10.1; 3.5.5b

Impact tests

1.14.5 and Table 15-1-14

Inspection

3.5.5; 7.2.7; 7.2.8; 9.3.5.5

Intermittent fillet welds

1.10.2; 7.4.2.3b

Lacing bars, fillet welded

1.6.4.2g

Lateral bracing

1.11.2c

Longitudinal load–welded rail

1.3.12

Machine welding

9.3.3.3

Materials

1.2.1 and Tables 15-1-1 and 15-1-2

Plate girder

1.2.3; 1.7.1; 1.7.2.2; 1.7.4b; 1.7.5; 1.7.6; 1.7.8a and b; 7.4.2; 9.1.7.1; 9.1.7.4

Plug welds

1.10.2

Prohibited welds

1.10.2

Sealing welds

1.5.5; 1.5.13c

Seam welding

6.7.5.35c

Sheaves

6.5.36.10

Shop painting joints

3.4.1b

Slot welds

1.10.2

Splices

1.5.9b; 1.7.5c and d; 6.6.6

Spot welding

6.7.5.35c

Stay plates

1.6.3d

Stiffener plate

1.7.7a and d; 1.7.8b; 1.10.4; 3.1.10; 7.4.2.2

Tack welding

3.3.4; 3.3.5; 9.3.3.4

Welded construction

1.7.2.2; Section 1.10; Section 3.3; 6.2.11.9; 7.4.1.5

Welder and welding operator qualifications

3.3.5

Welding: connection angle flexing (O.S.L.) leg

1.8.3a

Welding: electrodes

1.2.1

Welding: machinery weldments

6.2.11.9; 6.5.36.10

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Commentary

Subject

Article Reference

Welding: preparation of material

3.3.2

Welding: repair of flame cut edges

3.1.6

Welding rope splices

6.6.6

Welding: requirements

1.2.2; 1.14.4; 3.3.1; 7.4.1.5

REFERENCES (2005) References includes only the specific material used in developing or explaining recommended practice requirements. In most cases, these requirements are supported by studies and tests reported in other engineering literature. References is located at the end of this chapter.

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Part 10 Bearing Design1 — 2011 — Current until revision of next edition

FOREWORD The purpose of this part is to formulate specific and detailed recommendations for the design of bearings for nonmovable railway bridges. Recommendations for the design of special bearings for movable railway bridges are included in Part 6, Movable Bridges.

1

TABLE OF CONTENTS Section/Article

Description

Page

10.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.1.1 Definition of Terms (2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.1.2 General Requirements (2010). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.1.3 Expansion Bearings (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.1.4 Fixed Bearings (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.1.5 Bearing Selection Criteria (2010) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-10-3 15-10-3 15-10-6 15-10-8 15-10-8 15-10-8

10.2 Basic Allowable Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.1 Structural Steel, Bolts and Pins (2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.2 Cast Steel (1997) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.3 Bronze or Copper-Alloy Plates (2001) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.4 PTFE Sliding Bearing Surfaces (2002) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.5 Elastomeric Bearings (2001) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.6 Polyether Urethane Disc Bearings (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.7 Masonry (2001) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.8 Timber (1997) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-10-10 15-10-10 15-10-10 15-10-10 15-10-11 15-10-11 15-10-11 15-10-11 15-10-11

10.3 Steel Bearing Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3.1 Scope (1997) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3.2 Materials (2007). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3.3 Shoes and Pedestals (2001) R(2008). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3.4 Rocker Plates, Rockers and Rollers (2001) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3.5 Sole, Base and Masonry Plates (2001) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-10-11 15-10-11 15-10-12 15-10-13 15-10-13 15-10-14

1

References, Vol. 96, p.92.

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TABLE OF CONTENTS (CONT) Section/Article

Description

Page

10.3.6 Inclined Bearings (1997) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-10-15 10.3.7 Anchor Bolts and Rods (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-10-15 10.3.8 Central Guide Keys and Guide Bars (2001) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-10-16 10.4 Bronze or Copper-Alloy Sliding Expansion Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4.1 Scope (2000) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4.2 Materials (2000) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4.3 Design (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-10-17 15-10-17 15-10-17 15-10-17

10.5 PTFE Sliding Bearing Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.5.1 Scope (2002) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.5.2 Materials (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.5.3 Design (2006) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-10-18 15-10-18 15-10-18 15-10-19

10.6 Elastomeric Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.6.1 Scope (1999) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.6.2 Materials (2001) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.6.3 Design (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-10-21 15-10-21 15-10-21 15-10-22

10.7 Multi-Rotational Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.7.1 Scope (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.7.2 Materials (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.7.3 Design (2007) R(2008) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.7.4 Disc Bearings (2007). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.7.5 Spherical Bearings (2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-10-32 15-10-32 15-10-32 15-10-33 15-10-35 15-10-36

LIST OF FIGURES Figure

Description

Page

15-10-1 Stress to Strain and Shear Modulus to Hardness Relationship of Neoprene Compounds . . . . 15-10-29 15-10-2 Stress to Strain and Shear Modulus to Hardness Relationship of Polyurethane Compounds . 15-10-30

LIST OF TABLES Table

Description

Page

15-10-1 Bearing Suitability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15-10-2 Classes of Steel Forgings Acceptable for Pins, Rollers, and Rockers . . . . . . . . . . . . . . . . . . . . . 15-10-3 Elastomeric Material Property Test Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

15-10-9 15-10-12 15-10-23

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Bearing Design

SECTION 10.1 INTRODUCTION 10.1.1 DEFINITION OF TERMS (2011) 10.1.1.1 Contractual Terms a.

The term “Company” means the railway company party to the contract. The term “Engineer” means the chief engineering officer of the Company or his authorized representatives. The term “Inspector” means the inspector representing the Company. The term “Contractor” means the manufacturing, fabricating or erecting contractor party to the contract.

b. See Section 1.1, Proposals and Drawings, for other contractual terms and/or requirements for “Proposals,” “Shop Drawings,” “Drawings to Govern,” “Patented Technologies” and “Notice to Engineer.” 10.1.1.2 Bearing Component Terms Anchor Bolt: A mechanical device, such as a threaded rod or headed bolt with one or more nuts or other locking mechanism, that is embedded in concrete or grouted, chemically adhered, or wedged into concrete or masonry for the purpose of transferring horizontal and uplift forces from the superstructure or bridge bearings to the substructure or bridge seat. Anchor Rod: A plain or deformed bar or rod that is embedded in concrete or grouted, chemically adhered, or wedged into concrete or masonry for the purpose of transferring horizontal forces from the superstructure or bridge bearings to the substructure or bridge seat. Deformed bars may also be designed to transfer uplift forces.

1

Base Plate: A steel plate, whether cast, rolled or forged, usually used to uniformly distribute line bearing loads from a rocker, rocker plate, roller, or roller nest to other bridge bearing components. Bed Plate: See Masonry Plate or Base Plate.

3

Bronze or Copper-Alloy Sliding Expansion Bearing: A sliding expansion bearing device consisting of a bronze or copper-alloy plate assembled between upper and lower steel plates and having finished surfaces to accomodate heavy loads undergoing slow rotational and/or translational movements. The bronze or copper-alloy plate is frequently fabricated with a lubricating material compressed into trepanned recesses in the upper and/or lower surfaces of the plate. The lubricating material is intended to provide permanent lubrication to the sliding contact surfaces with the steel plates.

4

Bolster: A block-like member composed of wood, metal, or concrete used to transmit and distribute a bridge bearing load to the top of a pier cap or abutment bridge seat; or to raise a bridge bearing above moisture or debris that may collect on a bridge seat. Metal bolsters frequently consist of voided iron or steel castings, or built up steel weldments. Disc Bearing: A type of multi-rotational bearing which provides for end rotation of bridge spans by means of a flat, circular shaped, elastomeric disc. Elastomeric Bearing: A device constructed partially or wholly from elastomer for the purpose of transmitting loads and accommodating movement between a bridge span and its supporting structure. External Steel Load Plate: A steel plate bonded to the upper and/or lower surfaces of an elastomeric bearing.

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15-10-3

Steel Structures

Guide Bar: An element of an expansion bearing which is usually a steel bar of rectangular or square cross section fastened to or machined from a sole plate, base plate, or masonry plate and protrudes beyond the sliding surface of the bearing assembly. The guide bar’s long dimension is parallel to the direction of movement and limits the lateral movement of the bearing or span. Guide Key: An element of a steel expansion bearing consisting of a projecting bar fitted into a keyway in the opposing bearing element. Keyways are machined into the upper and/or lower bearing elements. The key is of rectangular or square cross section. The fit between the key and keyway is such as to limit lateral movement of the bearing or span, while allowing longitudinal movement. The long dimension of the guide key is parallel to the direction of movement. Hold Down Device: An assembly which prevents upward vertical movement of the bridge superstructure with respect to the substructure that is added to a bearing with no inherent resistance to vertical uplift. Lateral Restraint Device: An assembly which prevents lateral movement of the bridge superstructure with respect to the substructure at an expansion bearing with no inherent resistance to lateral movement. Masonry Plate: A steel plate or plate-shaped member, whether cast, rolled or forged, usually placed upon a masonry pier, abutment or other substructure unit and used to distribute loads from upper components of a bridge bearing uniformly over the masonry bridge seat below. Multi-Rotational Bearing: A type of bearing or bearing device which has the capability of allowing rotation in any of several directions, typically both transverse and longitudinal directions. Multirotational bearings frequently include a circular elastomeric disc or pad, or spherical sliding surface. Pedestal: A block-like member or assemblage composed of wood, metal, or concrete used to transmit and distribute a load from a bridge bearing or other member or part of a structure to another member or part. Metal pedestals frequently consist of voided iron or steel castings, or built up steel weldments. Pin: A cylindrical bar, usually steel, used to connect, hold in position, and/or transmit loads from one bridge bearing component to another, while allowing for the rotation of those bridge bearing components relative to each other. Pintle: A machined steel pin press fit, machined or fastened into an upper or lower element, frequently a base plate, of a bearing assembly. One or more pintles are usually used with bearings utilizing a rocker, rocker plate or roller element. The pintle provides a positive horizontal shear connection between the upper or lower element, or base plate, and the rocker or roller elements of the bearing while allowing for rotation.The head of the pintle is shaped and sized to fit into a hole machined into the mating element of the bearing assembly. Plain Elastomeric Bearing: An elastomeric bearing that consists of elastomer only. Pot Bearing: A type of bearing which usually consists of an elastomeric disc confined in a steel cylinder, or pot, with a ring sealed steel piston which transmits bridge bearing loads to the elastomeric disc. PTFE Bearing Surface: A low-friction sliding surface which utilizes a polytetrafluoroethylene (PTFE) sheet or woven fiber fabric manufactured from pure virgin unfilled PTFE resin, which is bonded to a steel backing substrate and usually slides against a polished stainless steel sheet. Reinforced Elastomeric Bearing: An elastomeric bearing that consists of layers of elastomer restrained at their interfaces by integrally bonded steel reinforcement.

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15-10-4

AREMA Manual for Railway Engineering

Bearing Design

Rocker: A cylindrical sector shaped member attached, frequently by a pin at its axis location, to the expansion end of a girder or truss that will transmit bridge bearing loads in line bearing contact upon its perimetrical surface with a base plate, bolster, pedestal or masonry plate and thus provide for longitudinal movements by a wheel-like translation. Rocker Plate: A steel plate with one cylindrical surface that will transmit bridge bearing loads in line bearing contact upon its perimetrical surface to other bearing components and allow for longitudinal rotation of the span ends due to span deflection. Roller: A steel, cylindrical shaped member, frequently forming an element of a roller nest or any other bearing device intended to provide longitudinal movements by rolling contact and that will transmit bridge bearing loads in line bearing contact with both a top plate or sole plate above, and a base plate, bolster, pedestal or masonry plate below. Roller Nest: A group of two or more steel cylinders forming a part of an expansion bearing at the movable end of a girder or truss intended to provide longitudinal movements by rolling contact and that will transmit bridge bearing loads in line bearing contact with both a top plate or sole plate above, and a base plate, bolster, pedestal or masonry plate below. Commonly, the rollers of a roller nest are assembled in a frame or box. Seismic Isolation Bearing: A type of bridge bearing which is intended to reduce the dynamic response of a bridge superstructure and thus minimize seismic loads acting on, and damage to, the bridge by providing a compliant connection between the superstructure and substructure through viscous damping, friction or metallic yielding. Seismic Isolation Device: A device which is intended to reduce the dynamic response of a bridge superstructure and thus minimize seismic loads acting on, and damage to, the bridge by providing a compliant connection between the superstructure and substructure through viscous damping, friction or metallic yielding. A seismic isolation device may be a component of a seismic isolation bearing or may be a device, or one of several devices, independently connected between the bridge superstructure or substructure.

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Shoe: A bolster-like or pedestal-like member or plate, typically placed under the end of a plate girder or truss, to transmit and distribute bridge bearing loads to the masonry bridge seat, other bearing components or other substructure members. Sole Plate: A steel plate bolted, riveted, or welded directly under the bottom flange of a rolled beam or plate girder, bottom chord of a truss, or cast into the bottom of a concrete girder, to uniformly distribute the bridge bearing loads into other bridge bearing components below, such as a roller nest, rocker plate, base plate, pedestal, multi-rotational bearing or masonry plate. Spherical Bearing: A type of multi-rotational bearing which provides for end rotation of bridge spans by means of a convex spherical surface hinging, rocking or sliding in a mating concave spherical surface. Lubrication of the mating surfaces is usually required and is frequently accomplished by providing a PTFE Bearing Surface or a Bronze or Copper-Alloy Sliding Surface. Trepanned Recess: A disk or ring shaped void machined into a metal plate or bushing. The disk or ring shaped void usually has a rectangular or square cross section. Trepanned recesses are generally machined into bronze or copper-alloy bearing elements and are filled with a lubricating material. The lubricating material is intended to provide permanent lubrication to the sliding interface between the bronze or copper-alloy bearing element and the opposing steel bearing elements.

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AREMA Manual for Railway Engineering

15-10-5

4

Steel Structures 10.1.1.3 Common Bearing Type and Component Illustrations

10.1.2 GENERAL REQUIREMENTS (2010)1 a.

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Bearings may be fixed or expansion as required by the bridge configuration and design. Expansion bearings may include guides or other means to control the direction of translation. Fixed and guided bearings shall have lateral strength adequate to resist all design loads and restrain unwanted translations. Combinations of different types of bearings shall not be used at the same bearing line or

See Part 9 Commentary

© 2011, American Railway Engineering and Maintenance-of-Way Association

15-10-6

AREMA Manual for Railway Engineering

Bearing Design

substructure unit unless the effects of differing deflection and rotational characteristics on the bearings and structure are accounted for in the design. b. Bearings shall be designed to resist the loads and accomodate the movements stipulated herein. The most adverse combination of movements shall be used for design. No damage to bridge span, bearings, or substructure due to joint or bearing movements shall be permitted under any appropriate combination of design load and movement. Horizontal forces and moments induced in the bridge by restraint of movement at the bearings shall be taken into account in the design of the bridge and the bearings. They should be determined using the calculated movements and the bearing characteristics given in Sections 10.2 through 10.7. It is recommended that all bearing design requirements be tabulated in a rational form to substantiate bearing type selection. c.

Design of bearings shall be such as to allow for expansion and contraction of the spans resulting from change in temperature at the rate of 1 inch (25 mm) in 100 feet (30 000 mm) for Minimum Service Temperature1 Zone 1 and 1-1/4 inch (30 mm) in 100 feet (30 000 mm) for Minimum Service Temperature Zones 2 and 3. Provisions shall also be made for change in length of the span resulting from live load. In steel spans more than 300 feet (90 000 mm) long, allowance shall be made for expansion of the floor system. Due consideration shall be given to the effects of lateral thermal movement for structures wider than 40 feet (12 000 mm).

d. Bearings and ends of spans shall be securely anchored against lateral and vertical movement as stipulated in Article 10.3.7. The Engineer may waive the requirement for vertical restraint of concrete spans. e.

Bearings for spans of less than 50 feet (15 000 mm) need not use radial/spherical surfaces or other special mechanisms to accommodate rotation due to live load deflection of the span, provided that the structural system otherwise permits adequate rotation.

f.

Bearings for spans of 50 feet (15 000 mm) or greater shall have provision to accommodate rotation due to deflection of the span. This requirement can be accommodated by use of a type of bearing employing a hinge, curved bearing plate or rocker plate, elastomeric pad, or pin arrangement.

g.

End bearings subject to both longitudinal and transverse rotation shall consist of elastomeric or multirotational bearings.

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h. Due consideration shall be given to bearing stability under seismic loading in the selection of bearing type. i.

j.

Bearings on masonry preferably shall be raised above the bridge seat by masonry plates, pedestals or bolsters. The Engineer may waive this requirement for elastomeric bearings. Provision for the replacement of bearings shall be considered in the design.

k. When directed or authorized by the Railroad, bearings may incorporate special devices to attenuate the transfer of horizontal forces such as braking, traction and seismic loads, to the substructure. These devices may transmit forces past weak or flexible substructures and through adjacent spans into stronger substructure elements. They may allow controlled differential displacements between the span and the substructure and may also include energy dissipation mechanisms. Such devices must not prevent the proper transfer of Dead, Live, Impact, Centrifugal, and Wind loadings to the substructure, nor may they appreciably restrict thermal expansion and contraction of the spans.

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See Commentary, Article 9.1.2.1d and e.

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AREMA Manual for Railway Engineering

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4

Steel Structures

10.1.3 EXPANSION BEARINGS (2007) a.

The expansion end of spans of 70 feet (21 000 mm) or less may be designed to accommodate movement through the use of low friction sliding surfaces or elastomeric pads.

b. The expansion end of spans longer than 70 feet (21 000 mm) shall be supported by bearings employing rollers, rockers, reinforced elastomeric pads, or low friction sliding surfaces designed to accommodate larger longitudinal movements. c.

Expansion bearings shall be capable of accommodating the full anticipated longitudinal movement plus an allowance for construction tolerances. The minimum construction tolerance shall be one-half inch (13 mm) for every 100 feet (30 000 mm) of span length but shall not be less than one inch (25 mm).

10.1.4 FIXED BEARINGS (2004) a.

The fixed end of spans shall be securely anchored to the substructure as stipulated in Article 10.3.7 to prevent horizontal movement.

b. Span rotation shall be accommodated as stipulated in the provisions of Article 10.1.2 e, f and g.

10.1.5 BEARING SELECTION CRITERIA (2010)1 a.

Each type of bearing system or component has differing characteristics and capacities to accommodate or restrain translational and rotational movements and to resist vertical and horizontal loads. The bearing type chosen for a particular application must have adequate load and movement capabilities. Table 1510-1 may be used as a guide for selecting appropriate bearing types for each application. Commentary Article 9.10.1.5.a provides additional insight into typical movement capabilities of the various bearing types.

b. Bearing types with an “R” listed in Table 15-10-1, may be suitable for the application but require special considerations or additional elements such as sliders or guideways to accomodate or control movements; or pintles, link bars, or other restrainers to provide load resistance. c.

Pot-type multi-rotational bearings should not be used for support of railroad bridges due to concerns over large cyclical live load deformations and rotation.

d. Due to thickness, rotation and compressive deflection limitations stipulated in Section 10.6, the size of elastomeric bearings is limited for applications with rotation. For preliminary bearing selection, unless approved by the Engineer, the width of elastomeric bearings in the direction perpendicular to the axis of rotation shall be limited to 12 inches (300 mm) for plain elastomeric pads and to 24 inches (600 mm) for reinforced elastomeric bearings.

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See Part 9 Commentary

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15-10-8

AREMA Manual for Railway Engineering

Translation2 Bearing Type

© 2011, American Railway Engineering and Maintenance-of-Way Association

AREMA Manual for Railway Engineering

Table 15-10-1. Bearing Suitability Rotation About Bridge Axis Indicated2

Resistance to Loads

Trns

Trns

Long

Vert

Vert

Long

Trns

Flat Steel Plate on Flat Steel Plate [