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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
1
• Standard Gage Track, • 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.
3
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.
© 2015, American Railway Engineering and Maintenance-of-Way Association
8-i
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 Treatment of Concrete Surfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.23 Repairs and Anchorage Using Reactive Resins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.24 High Strength Concrete (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.25 Specialty Concretes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.26 Self-Consolidating Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-1 8-1-6 8-1-8 8-1-10 8-1-11 8-1-16 8-1-16 8-1-19 8-1-20 8-1-21 8-1-24 8-1-27 8-1-31 8-1-37 8-1-39 8-1-43 8-1-46 8-1-47 8-1-48 8-1-51 8-1-52 8-1-53 8-1-53 8-1-55 8-1-56 8-1-57 8-1-62 8-1-64
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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) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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 8-2-24 8-2-25 8-2-27 8-2-27 8-2-29 8-2-30 8-2-30 8-2-31 8-2-32 8-2-32
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TABLE OF CONTENTS (CONT) Part/Section
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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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-33 8-2-33 8-2-35 8-2-37 8-2-42 8-2-42 8-2-42 8-2-44 8-2-44 8-2-45 8-2-52 8-2-53 8-2-53 8-2-56 8-2-58 8-2-60 8-2-68 8-2-68 8-2-68 8-2-69 8-2-69 8-2-70
Spread Footing Foundations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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 8-3-3 8-3-6 8-3-7 8-3-12 8-3-14 8-3-14 8-3-15
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Pile Foundations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3 Pile Length Determination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4 Pile Structural Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5 Installation of Piles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.6 Inspection of Pile Driving. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-4-1 8-4-2 8-4-4 8-4-7 8-4-10 8-4-15 8-4-18 8-4-18
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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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-5-1 8-5-2 8-5-4 8-5-5 8-5-7 8-5-8 8-5-9
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TABLE OF CONTENTS (CONT) Part/Section 5.7 5.8
Description
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Details of Design and Construction for Abutments and Retaining Walls . . . . . . . . . . . . . . . . . . . . . . . . Details of Design and Construction for Bridge Piers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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) R(2015) . . . . . . . . . . . . . . . . . . . . . . . . 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 8-14-24
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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-16-1 8-16-2 8-16-4 8-16-6 8-16-6 8-16-13 8-16-15
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Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-16-17
17 Prestressed Concrete. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.1 General Requirements and Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.2 Notations (2014) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.3 Terms (2014) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.4 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.5 Details of Prestressing Tendons and Ducts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.6 General Analysis (2014) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.7 Expansion and Contraction (2014) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.8 Span Length (2014). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.9 Frames and Continuous Construction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.10 Effective Flange Width . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.11 Flange and Web Thickness-Box Girders (2014). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.12 Diaphragms (2014) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.13 Deflections (2014) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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 (2014) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.21 Shear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.22 Post-Tensioned Anchorage Zones. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.23 Pretensioned Anchorage Zones (2014) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.24 Concrete Strength at Stress Transfer (2014) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.25 General Detailing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.26 General Fabrication. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.27 Mortar and Grout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.28 Application of Loads (2014) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.29 Materials - Reinforcing Steel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.30 Prestressed Concrete Cap and/or Sill for Timber Pile Trestle (2014). . . . . . . . . . . . . . . . . . . . . . . . . . . . Commentary (2014) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-17-1 8-17-4 8-17-5 8-17-7 8-17-9 8-17-11 8-17-13 8-17-13 8-17-13 8-17-14 8-17-15 8-17-15 8-17-16 8-17-16 8-17-17 8-17-18 8-17-18 8-17-20 8-17-26 8-17-28 8-17-29 8-17-30 8-17-34 8-17-44 8-17-45 8-17-45 8-17-48 8-17-52 8-17-52 8-17-53 8-17-54 8-17-57
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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-19-1 8-19-2 8-19-2 8-19-4 8-19-5 8-19-8 8-19-10 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-20-1 8-20-2 8-20-3 8-20-5 8-20-9
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20.5 Design of Anchored Bulkheads. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.6 Cantilever Bulkheads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.7 Notations (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-20-10 8-20-14 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 8-21-19
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 8-22-4 8-22-6 8-22-6 8-22-7 8-22-9 8-22-9 8-22-9 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) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-24-1 8-24-2 8-24-5 8-24-5 8-24-8 8-24-9 8-24-12 8-24-12
25 Slurry Wall Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.2 Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.3 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25.4 Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Commentary (2012) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-25-1 8-25-2 8-25-3 8-25-7 8-25-9 8-25-13
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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 8-26-32 8-26-35 8-26-36 8-26-38 8-26-38 8-26-40 8-26-40 8-26-40 8-26-41
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 8-27-14 8-27-16 8-27-24
28 Temporary Structures for Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.2 Information Required . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.3 Computation of Lateral Forces (2002) R(2015) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28.4 Stability (2002) R(2015) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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 8-28-13 8-28-18
29 Waterproofing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.1 General Principles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.2 Waterproofing (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.3 Dampproofing (1994) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.4 Specific Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.5 Terms (2001) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.6 Applicable ASTM Designations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.7 General Practices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29.8 Primers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-29-1 8-29-4 8-29-4 8-29-5 8-29-5 8-29-7 8-29-8 8-29-12 8-29-13
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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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-29-13 8-29-17 8-29-20 8-29-20 8-29-20 8-29-20 8-29-27 8-29-27 8-29-29 8-29-29
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.
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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 8-1-8 8-1-8
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) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-10 8-1-10 8-1-10 8-1-10 8-1-10 8-1-11
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.
© 2015, American Railway Engineering and Maintenance-of-Way Association
8-1-1
1
3
Concrete Structures and Foundations
TABLE OF CONTENTS (CONT) Section/Article 1.4.4
Description
Page
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 (2013) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6.2 Welding (2013) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6.3 Specifications (2013) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.6.4 Bending and Straightening Reinforcing Bars (2013) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-16 8-1-16 8-1-16 8-1-16 8-1-19
1.7
Concrete Admixtures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7.1 General (2013) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7.2 Types of Admixtures and Standard Specifications (2013) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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 (2013). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-20 8-1-20 8-1-20 8-1-21
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 8-1-23 8-1-23 8-1-23
1.10 Details of Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.10.1 Surface Conditions of Reinforcement (2013). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.10.2 Fabrication (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.10.3 Provisions for Seismic Loading (2013) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.10.4 Placing of Reinforcement (2013) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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 8-1-26
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) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-31 8-1-31
© 2014, Railway Engineering and Maintenance-of-Way Association © American 2015, American Railway Engineering and Maintenance-of-Way Association
8-1-2
AREMA Manual for Railway Engineering
Materials, Tests and Construction Requirements
TABLE OF CONTENTS (CONT) Section/Article
Description
Page
1.12.2 1.12.3 1.12.4 1.12.5 1.12.6 1.12.7 1.12.8 1.12.9 1.12.10
Measurement of Materials (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Water-Cementitious Materials Ratio (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Air Content of Air-Entrained Concrete (2009). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Strength of Concrete Mixtures (2011) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Workability (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Slump (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Compression Tests (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Field Tests (2009). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Special Provisions When Using Cementitious Materials Other Than Portland Cement (2009) . . . . .
8-1-31 8-1-31 8-1-32 8-1-33 8-1-34 8-1-35 8-1-35 8-1-35 8-1-35
1.13 Mixing 1.13.1 1.13.2 1.13.3 1.13.4 1.13.5
................................................................................ General (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Site-Mixed Concrete (2009). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ready-Mixed Concrete (2009). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Delivery (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Requirements When Using Silica Fume in Concrete (2009) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-37 8-1-37 8-1-38 8-1-38 8-1-38 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 8-1-39 8-1-40 8-1-40 8-1-40 8-1-41 8-1-41 8-1-42 8-1-42 8-1-42 8-1-42 8-1-42 8-1-43 8-1-43
1.15 Depositing Concrete Under Water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.15.1 General (2014) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.15.2 Capacity of Plant (2014) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.15.3 Standard Specifications (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.15.4 Cement (2014) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.15.5 Coarse Aggregates (2014) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.15.6 Mixing (2014) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.15.7 Caissons, Cofferdams or Forms (1993) R(2014) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.15.8 Leveling and Cleaning the Bottom to Receive Concrete (2014) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.15.9 Continuous Work (2014) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.15.10 Methods of Depositing (2014) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.15.11 Soundings (2014) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.15.12 Removing Laitance (2014). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.15.13 Concrete Seals (2014) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-43 8-1-43 8-1-43 8-1-43 8-1-43 8-1-43 8-1-44 8-1-44 8-1-44 8-1-44 8-1-44 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) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-46 8-1-46 8-1-46 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) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.17.5 Concrete for Alkali Soils or Alkali Water (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.17.6 Construction Joints (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.17.7 Minimum Cover (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.17.8 Placement of Concrete (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-47 8-1-47 8-1-47 8-1-48 8-1-48 8-1-48 8-1-48 8-1-48 8-1-48
1.18 Curing 1.18.1 1.18.2 1.18.3 1.18.4 1.18.5 1.18.6 1.18.7 1.18.8
............................................................................... General (2000) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hot Weather Curing (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wet Curing (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Membrane Curing (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Steam Curing (1993) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Curing Concrete Containing Silica Fume (2003). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Curing Concrete Containing Ground Granulated Blast-Furnace Slag (2004) . . . . . . . . . . . . . . . . . . Curing Concrete Containing Fly Ash (2004) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-48 8-1-48 8-1-49 8-1-49 8-1-50 8-1-50 8-1-50 8-1-51 8-1-51
1.19 Formed Surface Finish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.19.1 General (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.19.2 Rubbed Finish (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-51 8-1-51 8-1-52
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) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-52 8-1-52 8-1-52 8-1-52 8-1-52 8-1-52
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) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-53 8-1-53 8-1-53 8-1-53 8-1-53 8-1-54 8-1-55 8-1-55
1.23 Repairs and Anchorage Using Reactive Resins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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General (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Surface Preparation (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Application (2003) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-55 8-1-56 8-1-56
1.24 High Strength Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.24.1 General (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.24.2 Materials (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.24.3 Concrete Mixture Proportions (1995) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-56 8-1-56 8-1-56 8-1-57
1.25 Specialty Concretes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.25.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.25.2 Sulfur Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.25.3 Heavyweight Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.25.4 Polymer Concrete (2013) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.25.5 Fiber-Reinforced Concrete (2014) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.25.6 High-Performance Concrete (2014). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-57 8-1-57 8-1-57 8-1-58 8-1-59 8-1-61 8-1-61
1.26 Self-Consolidating Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.26.1 General (2013) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.26.2 Mix Design and Testing (2013) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.26.3 Forms and Reinforcement (2013) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.26.4 Mixing Concrete (2013). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.26.5 Placement (2013) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.26.6 Curing (2013) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-1-62 8-1-62 8-1-63 8-1-63 8-1-64 8-1-64 8-1-64
Commentary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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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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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
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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Description
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Maximum Permissible Water-Cementitious Materials Ratio (by Weight) for Different Types of Structures and Degrees of Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1-32 Air-Entrained Concrete Volume . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1-33 Water-Cementitious Materials Ratio for Air Entrained Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1-33 Concrete Exposed to Deicing Chemicals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1-36 Concrete Temperature Limits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1-42 Recommendations For Concrete In Sulfate Exposures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1-47
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
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Materials, Tests and Construction Requirements 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 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.
1
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.
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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.
1.1.7 TEST OF MATERIALS (2004) 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.
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Concrete Structures and Foundations 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 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
1
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.
See C - Commentary
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Materials, Tests and Construction Requirements
Table 8-1-1. Portland Cement ASTM C150 Type
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.
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.
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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.
3
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.
4
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.
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.
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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.
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. 1
Pelletized silica fume -- consisting of hard pellets, not presently being used as an additive for concrete.
See C - Commentary
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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 (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.
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SECTION 1.4 AGGREGATES
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1.4.1 GENERAL (2004) 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. 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.
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Table 8-1-3. Sampling and Testing Methods in Addition to those of ASTM C33 ASTM Designation
Type 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
c.
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 Pm) sieve. 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 Pm, 300 Pm, 600 Pm, 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
b.
Aggregate
Sodium Sulfate
Magnesium Sulfate
Fine
10
15
Coarse
12
18
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 8-15.
See C - Commentary
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Table 8-1-5. Fine Aggregate Grading
Sieve Size
b.
Total Passing Percentage by Weight
3/8 inch (9.5 mm)
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 Pm)
25-60
No. 50 (300 Pm)
10-30
No. 100 (150 Pm)
2-10
No. 200 (75 Pm)
zero
The minimum percentages shown above for material passing the No. 50 (300 Pm) and No. 100 (150 Pm) 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 Pm) sieve and not less than 3% shall pass the No. 100 (150 Pm) 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 8-1-6.
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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 Pm): 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 Pm) sieve consists of the dust of fracture, essentially free from clay or shale, these limits do not apply. 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 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)
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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 WATER1 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 GENERAL2 (2013) 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 (2013) a.
Welding of reinforcing bars shall conform to “Structural Welding Code–Reinforcing Steel” (AWS D1.4/D1.4M) 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/A706M, shall be supplemented to require a report of the chemical composition necessary to conform to welding procedures specified in AWS D1.4/D1.4M.
b.
If welding of wire to wire, and of wire or welded wire reinforcement 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 (2013) 1.6.3.1 Reinforcement Bars, wire, welded wire reinforcement, prestressing tendons, structural steel, steel pipe and tubing shall conform to one of the ASTM specifications listed in Table 8-1-7.
1 2
See C - Commentary See C - Commentary
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Table 8-1-7. ASTM Specifications for Reinforcement Type
Specifications Bars, Wire and Welded Wire
Deformed and Plain Carbon-Steel Bars Deformed and Plain Low-Alloy Steel Bars Deformed Rail-Steel and Axle-Steel Bars Deformed and Plain Stainless Steel Bars Headed Steel Bars Deformed and Plain Low-Carbon, Chromium Steel Bars Steel Wire, Plain (wire shall not be smaller than size W4 (0.226 inch (5.74 mm) dia.)) Steel Welded Wire Reinforcement, Plain Steel Wire, Deformed (wire shall not be smaller than size D4 (0.225 inch (5.72 mm) dia.)) Steel Welded Wire Reinforcement, Deformed (welded intersections shall not be spaced farther apart than 16 inches (400 mm) in direction of primary flexural reinforcement) Stainless Steel Wire and Welded Wire Reinforcement, Deformed and Plain
A615/A615M A706/A706M A996/A996M A955/A955M A970/A970M A1035/A1035M A1064/A1064M A1064/A1064M A1064/A1064M
1
A1064/A1064M
A1022/A1022M
Prestressing Tendons Uncoated Seven-Wire Steel Strand Uncoated Stress-Relieved Steel Wire Uncoated High-Strength Steel Bar
3
A416/A416M A421/A421M A722/A722M Structural Steel, Steel Pipe and Tubing
Structural-Steel
A36/A36M, A242/A242M, A529/A529M, A572/A572M, A588/A588M or A709/A709M (Grade 36, 50 or 50W) A53/A53M (Grade B) A500/A500M, A501/A501M or A618/A618M
Steel Pipe Steel Tubing
1.6.3.2 Coated Reinforcement a.
Coated reinforcement, when specified or shown on the plans as a corrosion-protection system, shall conform to one of the ASTM specifications listed in Table 8-1-8.
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Table 8-1-8. ASTM Specifications for Coated Reinforcement Type
Specification
Epoxy-Coated Steel Reinforcing Bars
A775/A775M
Epoxy-Coated Prefabricated Steel Reinforcing Bars
A934/A934M
Epoxy-Coated Steel Wire and Welded Wire Reinforcement
A884/A884M
Epoxy-Coated Seven-Wire Prestressing Steel Strand
A882/A882M
Zinc-Coated (Galvanized) Steel Reinforcing Bars
A767/A767M
Zinc and Epoxy Dual-Coated Steel Reinforcing Bars
A1055/A1055M
Zinc-Coated (Galvanized) Steel Welded Wire Reinforcement
A1060/A1060M
b.
Repair all damaged epoxy coating on reinforcing bars with patching material conforming to ASTM A775/A775M, A934/A934M or A1055/A1055M. Repair shall be done in accordance with the material manufacturer’s recommendations.
c.
Repair all damaged epoxy coating on wire or welded wire reinforcement with patching material conforming to ASTM A884/A844M. Repair shall be done in accordance with the material manufacturer’s recommendations.
d.
Repair all damaged zinc coating on reinforcing bars in accordance with ASTM A780/A780M. The maximum amount of damaged areas shall not exceed 2% of the total surface area in 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.
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 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, zinc-coated (galvanized), or zinc and epoxy dual-coated reinforcing bars, all 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 2 inches (50 mm) back from the mechanical splice to bright metal before repair.
g. After completion of welding for welded splices on epoxy-coated, zinc-coated (galvanized), zinc and epoxy dual-coated reinforcing bars, all damaged coating 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 6 inches (150 mm) back from the welded splice to bright metal before repair. h.
Repair all damaged zinc coating on welded wire reinforcement in accordance with ASTM A780/A780M.
i.
Plants applying fusion-bonded epoxy coatings to reinforcing bars shall maintain certification by the Concrete Reinforcing Steel Institute.
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1.6.4 BENDING AND STRAIGHTENING REINFORCING BARS1 (2013) 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, zinc and epoxy dual-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 or 1.6.3.2d. Field bending and/or straightening of epoxy-coated reinforcing bars conforming to ASTM A934/A934M shall be prohibited.
SECTION 1.7 CONCRETE ADMIXTURES 1.7.1 GENERAL (2013) a.
The selection of admixtures to be used in concrete, if any, shall be subject to the prior approval of the Engineer.
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.
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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. 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 from a certified third party agency.
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1.7.2 TYPES OF ADMIXTURES AND STANDARD SPECIFICATIONS (2013) The specifications listed in Paragraphs 1.7.2(a) and 1.7.2(b) apply in the use of admixtures. a.
ASTM C260 Standard Specification for Air-Entraining Admixtures for Concrete.
b.
ASTM C494 Standard Specification for Chemical Admixtures for Concrete:
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(1) Type A--Water-reducing admixtures (2) Type B--Retarding admixtures (3) Type C--Accelerating admixtures (4) Type D--Water-reducing and retarding admixtures (5) Type E--Water-reducing and accelerating admixtures (6) Type F--Water-reducing, high range admixtures (7) Type G--Water-reducing, high range, and retarding admixtures 1
See C - Commentary
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Concrete Structures and Foundations (8) Type S--Specific performance admixtures
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.
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.
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Materials, Tests and Construction Requirements
1.8.3 REINFORCEMENT (2013) 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 a month, it shall be covered to protect it from the weather. If reinforcement accumulates 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. Coated reinforcement shall be handled in accordance with Section 1.6.
b.
Epoxy-coated reinforcing bars, epoxy-coated wire and welded wire reinforcement, and zinc and/or epoxy dual-coated reinforcing bars shall be covered by 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 for air circulation around the coated reinforcement to minimize condensation under the covering. Epoxy-coated reinforcing bars, epoxy-coated wire and welded wire reinforcement, and zinc and epoxy dual-coated reinforcing bars 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.
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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.
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Concrete Structures and Foundations 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.
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.
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.
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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.
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.
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(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. 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 (2013) a.
Reinforcement at the time concrete is placed shall be free from mud, oil, or other coatings that adversely affect bond strength. Epoxy coating on bars, wire, and welded wire reinforcement conforming to standards referenced in Table 8-18 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 (2013) For structures located in earthquake-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 (2013) 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. 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 and zinc-coated and epoxy dual-coated reinforcing bars shall not be permitted.
c.
When epoxy-coated, zinc and epoxy dual-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.
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Materials, Tests and Construction Requirements 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: (1) When member size is 12 inches (300 mm) or less . . . . . . . . . . . . . . . . . . . . . . .
±3/8 inch (10 mm)
(2) When member size is over 12 inches (300 mm) but not over 2 feet (600 mm). . .
±1/2 inch (13 mm)
(3) When member size is over 2 feet (600 mm) . . . . . . . . . . . . . . . . . . . . . . . . . . . .
±1 inch (25 mm)
(4) Reduction in concrete cover shall not exceed one-third specified concrete cover. (5) 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. 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 mm to 36 mm) and minus 2 inches (50 mm) for #14 and #18 bars (43 mm and 57 mm).
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 (4.6 m) of strand length.
j.
Tolerance in the vertical and horizontal location of unbonded post-tensioning tendons and ducts in bonded posttensioning 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 (4.6 m) of strand length.
k.
In precast concrete members the bearing plates shall be concentric with the tendons and tolerance for the perpendicularity with tendons in concrete shall be ±1 degree.
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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. © 2015,©American RailwayRailway Engineering and Maintenance-of-Way Association 2014, American Engineering and Maintenance-of-Way Association
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Concrete Structures and Foundations 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 4 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 and zinc and epoxy dual-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 epoxycoated or zinc and epoxy dual-coated reinforcing bars. Reinforcing bars used as support bars shall be epoxy-coated. In walls reinforced with epoxy-coated or zinc and epoxy dual-coated reinforcing bars, spreader bars shall be epoxycoated where specified. Proprietary combination bar clips and spreaders used in walls with epoxy-coated or zinc and epoxy dual-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 and zinc and epoxy dual-coated reinforcing bars shall be fastened (tied) with plastic-coated or epoxycoated 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 non-metallic-coated tie wire, or other materials authorized by the Engineer.
1.10.4.4 Draped Welded Wire Reinforcement When welded wire reinforcement 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.
1.10.7 FUTURE BONDING (2003) Exposed reinforcement intended for bonding with future extensions shall be protected from corrosion in an approved manner.
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Materials, Tests and Construction Requirements
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.
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.
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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Concrete Structures and Foundations
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.
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. © 2014, Railway Engineering and Maintenance-of-Way Association © American 2015, American Railway Engineering and Maintenance-of-Way Association
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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.
1.11.7 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).
3
d.
Keyed joints shall not be used in slabs less than 6 inches (150 mm) thick.
4
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Concrete Structures and Foundations
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 per bag = 1/4 barrel = 1 cubic foot (1.5 kg of cement shall be assumed to be 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.
b.
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.
3
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.
4
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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 Water With 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)
–
–
(Note 4)
–
–
(Note 4)
–
–
0.53
–
–
(Note 4)
–
–
Concrete slabs laid on the ground Concrete protected from weather, interiors of buildings, concrete below ground 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
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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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
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 ratio shall not be greater than that required by Article 1.12.4.
4
Table 8-1-11. Water-Cementitious Materials Ratio for Air Entrained Concrete Specified 28 Day Compressive Strength of Concrete, fc 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:
b.
Not applicable for concrete containing lightweight aggregates or admixtures other than for entraining air.
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
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Concrete Structures and Foundations 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.
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.
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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.
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.
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.
1.12.10 SPECIAL PROVISIONS WHEN USING CEMENTITIOUS MATERIALS OTHER THAN PORTLAND CEMENT (2009)1 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.
1
See C - Commentary
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3
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Concrete Structures and Foundations
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. 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.
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Materials, Tests and Construction Requirements 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 air-entraining 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. 1.12.10.3.4 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. 1.12.10.4 Requirements When Using Ground Granulated Blast-Furnace Slag in Concrete 1.12.10.4.1 General Mix proportions, including the proportion of ground granulated blast-furnace slag, shall be determined by tests. 1.12.10.4.2 Water-Reducing Admixtures
1
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.
3
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.
4
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.
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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.
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.
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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. 1.13.5.2 Workability of Delivered Concrete1 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.
SECTION 1.14 DEPOSITING CONCRETE 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.
1
3
1.14.2 HANDLING AND PLACING (1993)
1
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.
See C - Commentary
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Concrete Structures and Foundations 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.
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 © 2014, Railway Engineering and Maintenance-of-Way Association © American 2015, American Railway Engineering and Maintenance-of-Way Association
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Materials, Tests and Construction Requirements 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.
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.
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.
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.
b.
The method of controlling the temperature of the concrete shall be approved by the Engineer.
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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
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 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. 1.14.12.2 Consolidation Careful attention to effective vibration is required for concrete containing silica fume.
1
See C - Commentary
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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.
SECTION 1.15 DEPOSITING CONCRETE UNDER WATER 1.15.1 GENERAL (2014) a.
b.
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.
1
The methods, equipment and materials proposed to be used, shall be submitted first to the Engineer for review before the work is started. The methods used shall 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 (2 degrees C).
3
1.15.2 CAPACITY OF PLANT (2014) Sufficient mixing, transporting and placing equipment will be provided to ensure 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 GENERAL GUIDELINES (2014)
4
The materials, preparations and methods to be used in making concrete to be deposited under water shall conform to the requirements of these guidelines except as modified or supplemented by the following Articles.
1.15.4 CEMENT (2014) Not less than 610 lb per cubic yard (362 kg per cubic meter) of cement in concrete shall be used.
1.15.5 COARSE AGGREGATES (2014) Coarse aggregate for this work shall be of good quality, strong and durable as specified in Section 1.4. The maximum size of aggregate preferably shall be 2 inches (51 mm) and shall not exceed 3 inches (76 mm). 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. Maximum size of coarse aggregate shall be adjusted when depositing concrete by tremie pipe or pump.
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1.15.6 MIXING (2014) 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 (152 mm) nor more than 8 inches (203 mm) for concrete placed by tremies, and not less than 3 inches (76 mm) nor more than 6 inches (152 mm) for concrete placed by bottom dump buckets or for concrete placed in sacks.
1.15.7 CAISSONS, COFFERDAMS OR FORMS (1993) R(2014) 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.
1.15.8 LEVELING AND CLEANING THE BOTTOM TO RECEIVE CONCRETE (2014) a.
Before starting to deposit concrete under water, the condition of the bottom surface receiving concrete shall be examined by an approved method and reported to the Engineer for review.
b.
The bottom surface receiving concrete, whether of clay, rock, or other material, shall be leveled as directed by the Engineer, before depositing concrete.
c.
Where the bottom surface on which concrete is to be deposited under water is likely to be covered with silt or unwanted material, such material shall be removed down to solid surface before any concrete is placed. The method to be used to clean the bottom of silt or unwanted material shall be subject to the review of the Engineer.
1.15.9 CONTINUOUS WORK (2014) Concrete shall be deposited continuously until it reaches the required elevation. While depositing concrete, the top surface shall be kept as nearly level as possible, and the formation of laitance planes avoided.
1.15.10 METHODS OF DEPOSITING (2014)1 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. (1) The tremie pipe shall be not less than 8 inches (203 mm) 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. (2) 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 out of the bottom end of the pipe by filling the pipe with concrete. (3) It will be necessary to slowly raise the tremie in order to allow a uniform flow of the concrete, but the tremie pipe shall not be emptied so that water enters above the concrete in the pipe. (4) 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 in order to avoid formation of laitance layers.
1
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Materials, Tests and Construction Requirements (5) 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. b.
Pumping. When concrete is to be deposited by pump, the methods, equipment and properties of coarse and fine aggregates suitable for pumping shall be submitted to the Engineer for review. Maximum coarse aggregate size shall be limited to one-third the smallest inside diameter of the pump or pipe. Fineness modulus of sand meeting the requirements of ASTM C33/C33M shall fall between 2.40 and 3.00 with the median being 2.70.
c.
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. (1) 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. (2) 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. (3) The bucket shall be submerged slowly until it is completely under water. The normal line speed after that shall not exceed 200 feet (61 m) 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 feet (1.83 m) or 8 feet (2.44 m) while the concrete is being deposited.
d.
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 fabric free from deleterious materials, and shall be filled about two-thirds full of concrete with the sack openings securely tied.
e.
Grouted Aggregate. Coarse aggregate shall be installed by placing in the forms followed by injecting cement grout through pipes that extend to the bottom of the forms. The pipes shall be withdrawn as grouting proceeds. The grout shall force the water up in the forms and fill interstices in the aggregate. (1) The grout injecton 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 or an approved alternate method shall 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 that 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 that will ensure complete filling of voids, and the grout injection 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 work shall necessitate 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 and cleaned of all grout after every shift or work stoppage.
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1.15.11 SOUNDINGS (2014) During the time that concrete is being deposited under water, soundings shall be taken to the surface of the deposited concrete and recorded at regular intervals as directed by the Engineer. The surface of the deposited concrete shall be maintained relatively level over the area being covered.
1.15.12 REMOVING LAITANCE (2014) 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. The laitance removal process shall be reviewed by the Engineer. Following removal and cleaning, the final upper surface shall be examined and reported to the Engineer for review prior to additional concrete being deposited.
1.15.13 CONCRETE SEALS (2014) 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. 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.
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 air-entrained 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.
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.
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1.16.4 MINIMUM COVER (1993) Reinforcing steel or other corrodible metal shall have a cover of not less than 4 inches of concrete.
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.
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.
1 Table 8-1-14. Recommendations For Concrete In Sulfate Exposures
Sulfate Concentration as SO4
Sulfate Exposure
Normal Weight Aggregate Concrete
Lightweight Aggregate Concrete
Maximum Tricalcium Aluminate in Maximum WaterMinimum Cement, Percent Cementitious In Soil, Percent In Solution, PPM Compression (Note 1) by Weight Material Ratio, Strength, fc c, psi by Weight
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
4
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 air-entrained in accordance with Section 1.12, Proportioning, Article 1.12.4.
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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. NOTE:
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.
1.17.8 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.
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.
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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.
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 temperature-change 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 sulfatebearing 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.
1.18.5 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 (25 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 (25 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:
1 2
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.
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.
1.20.2 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.
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.
1 2
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
1.22.3 ENVIRONMENTAL REQUIREMENTS (2003) a.
3
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).
4
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.
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.
1.22.4 APPLICATION (2003) a.
1
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
See C - Commentary
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Concrete Structures and Foundations 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 isooctytrialkoxy 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) 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. (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.
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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.
1
3 SECTION 1.23 REPAIRS AND ANCHORAGE USING REACTIVE RESINS1 1.23.1 GENERAL (2003)
1
4
a.
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.
b.
The material shall be a non-metallic, non-shrinking polymer resin supplied in prepackaged and/or pre-measured 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.
See C - Commentary
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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.
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.
b.
1
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) . . . . . . . . . . . . . . . . . . . . . . . . . .
4%
Ignition Loss . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
0.5%
Fineness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
375 cm2/g (Blaine)
Sulfate (SO3) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
0.20% of optimum
Mortar cube tests shall be performed in accordance with ASTM C109.
See C - Commentary
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Materials, Tests and Construction Requirements 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
1.24.3 CONCRETE MIXTURE PROPORTIONS (1995) Trial batches shall be performed to generate sufficient data to obtain optimum mixture proportions.
3 SECTION 1.25 SPECIALTY CONCRETES 1.25.1 GENERAL
4
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.
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
See C - Commentary
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Concrete Structures and Foundations 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. 1.25.2.4 Placing Sulfur concrete can be placed in either wooden or metal forms.
1.25.3 HEAVYWEIGHT CONCRETE 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.
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. 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.
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1.25.4 POLYMER CONCRETE (2013) 1.25.4.1 General1 This section covers polymer concrete that is to be used for repair of bridges and other structures. The section describes the selection, sampling and testing of materials, material properties and construction requirements under specific conditions. 1.25.4.2 Selection of Materials2 The materials shall meet the project requirements and be approved by the Engineer. 1.25.4.3 Submittals a.
Submittals shall be reviewed and approved by the Engineer.
b.
Contractor shall have a copy of all approved submittals at work site during construction.
c.
Manufacturer(s) Submittals: (1) Material descriptions, brochures and technical data sheets including general chemical composition and physical properties, pertinent test data, and specific recommendations for surface preparation, testing, mixing, application, fillers (e.g. aggregates, sands) and curing. (2) Manufacturer’s Material Safety Data Sheets (MSDS) for all materials to be used including instructions for storing and handling.
d.
1
Contractor’s Submittals: (1) Details of proposed storage methods. (2) Form(s): drawings, prepared by a licensed engineer, including fabrication, assembly, and support of forms per Section 1.9.
3
(3) Detailed installation procedures: (a) Surface preparation including testing.
4
(b) Mixing, including detailed mixing and application instructions. (c) Installation. (d) Quality assurance. (4) Concrete design mixture including procedures for ensuring quality of polymer concrete and repair materials. 1.25.4.4 Surface Preparation3 a.
The substrate to which the polymer concrete is to be applied must be sound, clean, dry and properly prepared.
1
See C - Commentary See C - Commentary 3 See C - Commentary 2
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Concrete Structures and Foundations b.
Sufficient surface preparation shall be demonstrated, when specified, by use of a tensile adhesion test in accordance with ASTM D4541.
c.
Defective areas and honeycombed areas shall not be patched until examined and approved by the Engineer. When such approval is received by the Contractor, areas involved shall be repaired in accordance with the applicable manufacturers written instructions.
1.25.4.5 Installation1 Installation shall be in accordance with the Manufacturer’s recommendations as approved by the Engineer. 1.25.4.6 Quality Assurance2 a.
Applicator: Personnel using the product must have previous experience using similar products.
b.
Manufacturer(s): (1) Submit a listing of representative projects installed in similar climates and for similar substrate conditions, in the last 5 years. (2) Manufacturer must employ trained technical representatives who will be available for consultation and project site inspection.
c.
Contractor: Contractor shall confirm in writing that substrates have been inspected, are adequately prepared and represent a suitable substrate for the application of the materials.
d.
Testing and inspection services shall be approved by the Engineer.
e.
Pre-installation Conference: Engineer may conduct conference at Project site with Contractor and/or Manufacturer.
1.25.4.7 Delivery, Storage and Handling a.
Materials delivered to the project site shall be in sealed in, undamaged containers with labels intact and legible, indicating the material name and lot number.
b.
Comply with manufacturer’s written instructions for minimum and maximum temperature requirements and other conditions for storage. Store materials in a dry location, at temperatures not exceeding 90ºF (32ºC) or as otherwise permitted by the manufacturer.
1.25.4.8 Removal of Forms Contractor shall be responsible for proper removal of forms in accordance with Article 1.9.8.
1 2
See C - Commentary See C - Commentary
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1.25.5 FIBER-REINFORCED CONCRETE (2014) 1.25.5.1 General1 Fiber-Reinforced Concrete (FRC) is concrete made primarily of hydraulic cements and aggregates where discrete fibers of various types are added to the concrete mix to inhibit cracking and improve resistance to deterioration due to fatigue, impact, shrinkage and/or thermal stresses. Fibers added to the concrete mix shall not be used as a replacement for steel reinforcement, where steel reinforcement is required in accordance with Part 2, Reinforced Concrete Design. FRC shall conform to ASTM C1116/C116M. 1.25.5.2 Design a.
Types of fibers used in the concrete mix shall be the following: (1) Steel fibers: Fibers manufactured from carbon or stainless steel shall be shaped into various geometric shapes such as crimped, hooked-end or other mechanical deformations for anchorage in the concrete. Steel fibers shall conform to ASTM A820/A820M. (2) Glass fibers: Fibers shall be alkali resistant and manufactured by processes intended for use in FRC. Glass fibers shall conform to ASTM C1666/C1666M. (3) Synthetic fibers: Fibers shall be made from materials such as polypropylene, polyethylene, polyester, nylon and other synthetic materials such as carbon, aramid and other acrylics. Fibers shall be manufactured by processes intended for use in FRC and meet the requirements for ASTM C1116/C1116M, Type III, synthetic fiber-reinforced concrete.
1
(4) Cellulose fibers: Fibers manufactured from processed wood pulp or other plant-based material and intended for use in fiber-reinforced concrete. Fibers shall meet the requirements of ASTM D7357. b.
Concrete mix design and concrete mixing process shall be approved by the Engineer. Dosage of fibers shall be in accordance with the fiber manufacturer’s recommendations. Mixing shall be sufficient to prevent formation of fiber balls.
3
1.25.5.3 Placing Use of a water-reducing agent is permitted to prevent slump loss during placement. Vibration may be needed to ensure consolidation.
1.25.6 HIGH-PERFORMANCE CONCRETE
4
(2014)2
1.25.6.1 General High-Performance Concrete (HPC) is concrete made from cementitious materials, water and aggregates to which chemical admixtures and/or fibers are added to meet an array of performance requirements dictated by project needs. Specific mixing, placing and curing techniques are needed to produce the desired results. The American Concrete Institute (ACI) defines HPC as "concrete which meets special performance and uniformity requirements that cannot always be achieved routinely by using only conventional materials and normal mixing, placing, and curing practices." Extensive testing is required to ensure that the concrete meets the specific project requirements. HPC is intended to be more durable with enhanced properties compared to concrete without special additive. 1 2
See C - Commentary See C - Commentary
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Concrete Structures and Foundations Typical requirements for HPC includes some or all of the following properties: • High strength • High early strength • High modulus of elasticity • High abrasion resistance • Increased durability and additional service life in severe environments • Low permeability and diffusion • Resistance to chemical attack • High resistance to frost and deicer scaling damage • Toughness • Impact resistance • Volume stability • Ease of placement • Consolidation without segregation • Inhibition of bacterial and mold growth 1.25.6.2 Verification of property HPC requirements for each project shall be defined by the Engineer and verified prior to construction for each specific HPC property.
SECTION 1.26 SELF-CONSOLIDATING CONCRETE 1.26.1 GENERAL (2013)1
1
a.
Self-consolidating concrete (SCC) is a highly fluid yet stable concrete mix that can spread readily into place and fill the forms without mechanical consolidation or undergoing significant segregation. Concrete is not made selfconsolidating by the addition of extra water, which would increase segregation and have other undesired effects.
b.
Self-consolidating concrete shall be designed, mixed, formed, and cured in accordance with the other provisions of Part 1 except as stipulated herein.
See C - Commentary
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1.26.2 MIX DESIGN AND TESTING (2013)1 1.26.2.1 Mix Design The mix designer shall be experienced in the design and production of SCC. High-range water-reducing and viscositymodifying admixtures as well as fine limestone powder and mineral pozzolans are generally included in the design mix. The size, smoothness and gradation of the aggregates shall be selected based on the requirements of the particular project. The required slump flow to be achieved by the mix design is dependent upon the requirements for placement of the SCC. By careful selection and design of the mix, the cured SCC can have properties comparable to that of conventional concrete. 1.26.2.2 Quality Control Testing Slump flow, visual stability index, column segregation and J-Ring tests shall be performed on the as-designed mixture by the supplier at the plant. Tests of the cured concrete shall also be performed to ensure that the design mix produces the required properties. Test results shall be subject to review for approval by the Engineer. New tests will be required whenever there is a change in the source of a component material or whenever there is a change in a production procedure. 1.26.2.3 Testing Methods a.
Among the tests specifically designed for ensuring the desired flow and stability characteristics of fresh SCC are the following: (1) ASTM C1610 Test Method for Static Segregation of Self-Consolidating Concrete Using Column Technique,
1
(2) ASTM C1611 Test Method for Slump Flow of Self-Consolidating Concrete, and (3) ASTM C1621 Test Method for Passing Ability of Self-Consolidating Concrete by J-Ring. b.
c.
Other tests can also be used in addition to or in place of the tests listed above. The Engineer will direct which tests shall be employed and the frequency of testing. See Articles 1.12.8 and 1.12.9 of this Part for testing requirements for the hardened concrete. The tests shall be performed by qualified personnel.
3
Quality control personnel must understand the engineering properties, placement techniques, element characteristics, and raw materials considerations that were used to determine mixture proportions and fresh concrete properties.
1.26.3 FORMS AND REINFORCEMENT (2013)2
1 2
a.
The structural design of forms shall take into account the fluid nature of self-consolidating concrete as well as the rate of placement. Forms shall be designed to support lateral concrete pressures in accordance with the full fluid pressure provisions of ACI 347R. If the design of the forms is in accordance with ACI 347R, but to a loading less than the full fluid pressure, form pressure measuring devices shall be used to prevent rapid concrete placements from exceeding the rated capacity of the forms.
b.
Forms should be sufficiently watertight to prevent leakage of fluid from the SCC. Form release agents with a high solids content should be used.
c.
Reinforcement ties and other attachments shall be designed to account for the fluid nature of the concrete.
See C - Commentary See C - Commentary
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1.26.4 MIXING CONCRETE (2013) Mixing proportions and procedures shall be carefully controlled to achieve consistency in the stability and fluidity of SCC. SCC may require additional mixing time (30 to 90 seconds) as compared to conventional concrete. Wash water, if used, shall be completely discharged from the drum before a succeeding batch is produced.
1.26.5 PLACEMENT (2013)1 SCC should be placed continuously and in layers of such thickness that no fresh SCC is placed on concrete that has hardened enough to cause a plane of weakness. A detailed placement plan shall be submitted to the Engineer and approved prior to placing SCC.
1.26.6 CURING (2013) Curing of SCC is essential and early protection of exposed surfaces is critical to preventing plastic shrinkage cracking. Procedures for curing conventional concrete should be applied.
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. 1
See C - Commentary
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Materials, Tests and Construction Requirements Possible benefits of using fly ash in a concrete mix which is properly designed, deposited and cured include increased longterm 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 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.
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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 non-potable 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. 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. Test results for non-potable water shall be furnished to the Engineer and approved prior to use.
C - SECTION 1.6 REINFORCEMENT C - 1.6.1 GENERAL (2013) “Report on Steel Reinforcement - Material Properties and U.S. Availability (ACI 439.4R-09)” provides further guidance for steel reinforcement.
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C - 1.6.4 BENDING AND STRAIGHTENING REINFORCING BARS (2013) a.
Field bending and straightening of partially embedded reinforcing 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.
b.
Numerous technical papers published on this subject contain varying opinions on the best procedures to use. Current known factors that affect field bending and straightening of partially embedded reinforcing bars in concrete include: (1) Application of heat appears to be necessary to bend or straighten larger sized bars, but either overheating (above 1800 degrees F (980 degrees C)) or under heating between 450 degrees F (230 degrees C) and 650 degrees F (340 degrees C) can result in reduced strength or even cause failure of the bars. (2) Repeated bending and straightening weakens the steel and could result in failure even under the best controlled conditions. (3) Tight bending diameters decreases the strength of the steel.
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 low-alloy steel bars (ASTM A706/A706M) rather than carbon-steel bars (ASTM A615/A615M) in locations where field bending and/or straightening will be required.
d.
When field bending and straightening of partially embedded bars is permitted by the Engineer, the following example procedural guideline should be used: (1) Bars of size #3 (10 mm) through #7 (22 mm). (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 a uniform application of force. (e) Straightening should be accomplished by using a steel pipe pushed tightly against the bend, with application of force as follows: 1 Steel pipe should have an inside diameter 1/8 inch to 3/8 inch (3 mm to 9 mm) larger than the outside diameter of the bar to be straightened. 2 Steel pipe should be long enough to provide sufficient leverage. 3 Straightening pipe should be reset against the bar at 45 degrees for #4 (13 mm) and smaller bars and at 30 degrees and 60 degrees for #5 to #7 (16 mm to 22 mm) bars. 4 Workers should have a firm base from which to apply straightening pressure. (2) Bars of size #8 through #11 (25 mm through 36 mm). (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-indicating crayons.
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Materials, Tests and Construction Requirements (b) Concrete must be protected from exposure to excessive heat. If necessary protective insulation should be used. (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 a uniform application of force. (g) Straightening should be accomplished by using a steel pipe pushed tightly against the bend, with application of force as follows: 1 Steel pipe should have an inside diameter 1/8 inch to 3/8 inch (3 mm to 9 mm) larger than the outside diameter of the bar to be straightened. 2 Steel pipe should be long enough to provide sufficient leverage. 3 Straightening pipe should be reset progressively against the bar around the bend. 4 Workers should have a firm base from which to apply straightening pressure.
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.
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C - 1.12.10.2.2 High-Range Water Reducing Admixtures 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 cement, the characteristics of the cement, and the water to
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Materials, Tests and Construction Requirements 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 blast-furnace 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
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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 1.15 DEPOSITING CONCRETE UNDER WATER C - 1.15.10 METHODS OF DEPOSITING (2014) a.
Tremie. Preferably, flanged steel pipe of adequate strength should be used, 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. Experience has shown that temie concrete can be placed as specified, so that it will flow as much as 50 feet (15.24 m) horizontally from the discharge end of the tremie with a slope of less than 3 feet (1 m) in 50 feet (15.24 m).
b.
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Bottom Dump Bucket. The bucket should preferably be designed for hinged bottom doors to operate inside of a steel skirt. The skirt should surround the bucket while the bottom doors are shut and extend below the bucket as the bottom doors open, minimizing turbulence and motion while concrete is deposited.
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.
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 70q F (21q 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.
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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.
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.
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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.
b.
Surface preparation may be accomplished by: (1) High pressure water (hot or cold). (2) Chemical cleaners. (3) Sandblasting. (4) Shotblasting.
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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 high-pressure 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.
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 d.
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.
e.
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-in-place concrete buildings. Highstrength concrete has also been used in bridge structures. Research has been conducted on the performance of highstrength 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 high-strength concrete (ACI 363R-92) defines high-strength as having compressive strengths of 6,000 psi (41 MPa) or greater.
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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.
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.
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.
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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.
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 watercementitious 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.
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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 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 highrange 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 highstrength concretes when used in combination with conventional water reducers or retarders.
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3
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.
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 conditions. Once a desirable mixture has been formulated in the laboratory, field testing with production-sized batches should be preformed.
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Concrete Structures and Foundations
C - SECTION 1.25 SPECIALTY CONCRETES C - 1.25.2 SULFUR CONCRETE C - 1.25.2.1 General f.
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.
C - 1.25.4 POLYMER CONCRETE (2013) C - 1.25.4.1 General a.
Polymer concretes are composite materials that combine synthetic resins with blended aggregates and graded fillers to produce low permeability concretes, mortars and grouts with high resistance to water, chlorides, and freeze-thaw cycles.
b.
The resins comprise of monomers, or monomers and polymers which polymerize when mixed with cure initiators or catalysts. Graded fillers, sands and, where applicable, aggregates are then added into the polymerizing solution. The resin binds the materials tightly together to form a hard impermeable composite.
c.
The resins are formulated to provide a range of characteristics, including varying degrees of flexibility, rigidity and strength.
d.
The resins used in these products are from a wide range of generic chemical groups, most commonly epoxies, methyl methacrylates, polyesters and polyurethanes.
e.
Polymer concretes typically cure more rapidly than cement-based equivalents, while exhibiting greater flexural and tensile strengths. The rate of curing depends on the polymer resin base.
f.
As a result, polymer concretes can be used to provide effective solutions to construction conditions, particularly where rapid cure and high strength gain may be required. © 2014, Railway Engineering and Maintenance-of-Way Association © American 2015, American Railway Engineering and Maintenance-of-Way Association
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Materials, Tests and Construction Requirements g.
Common uses are keyway joint grouting, joint headers, bedding of bridge bearings, and structural repairs.
h.
The repair areas and volume of polymer concrete placements are generally small.
i.
Polymer concretes are also used as an alternative to cement-based material in locations exposed to high chloride and water ingress.
j.
The materials can generally be placed without specialized equipment and do not require a sensitive curing procedure.
C - 1.25.4.2 Selection of Materials Care must be taken to ensure that the properties of the product proposed meet the specific site requirements: a.
Some products are susceptible to outgassing when installed in humidity levels above 85%, which may lead to pinholing and/or foaming, causing a reduced impermeability to liquid water and reduced ultimate strength.
b.
Some resins have strict allowable timeframes for overcoating their primers, without which their removal or other treatment may be required.
c.
Some products, such as some epoxy-based systems, exhibit a slower rate of curing or even no curing at lower temperatures.
d.
Elevated temperatures can make certain products unsuitable.
e.
Filler aggregate - For applications greater than 1 inch of thickness, add aggregate in accordance with the Manufacturer’s recommendations.
1
C - 1.25.4.4 Surface Preparation a.
b.
A suitably level area on the prepared substrate should be identified and primed. Using the proposed polymer concrete material as the adhesive, the primed area should be tensile tested per ASTM D4541. After sufficient curing of the polymer concrete the adhesion should be tested, and the mode of failure must be in the concrete substrate. Failure at the bond line indicates insufficient surface preparation, and further removal of additional weak or unsound material is required. The surface should be prepared by shotblasting or other mechanical means to remove all laitance, weak, damaged, contaminated and friable material. Saw cut repair boundaries along straight edge and chip edge down a minimum of 1 inch (25 mm) to sound concrete by means of cold chisels or pneumatic chipping hammers. Where honeycombing exists around reinforcing, chip concrete to provide a minimum space of ¾ inch (19 mm) around the reinforcing to afford sufficient bond.
C - 1.25.4.5 Installation Installation should be in accordance with the Manufacturer’s recommendations, however, but the minimum guidelines below should be followed: a.
Surfaces to be treated should be primed as required.
b.
Do not apply materials if rain is anticipated within three hours of application without approved protective measures in place.
c.
Ensure that the product’s maximum humidity limit and over-coating window are adhered to.
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Concrete Structures and Foundations d.
Mix and place polymer concrete used for structural concrete slabs and full depth overlays in accordance with manufacturer's printed instructions.
e.
Provide control joints as recommended by Manufacturer, or as indicated on drawings.
f.
Repair placement cavities in accordance with repair procedures outlined below. (1) Place patching mortar by trowelling toward edges of patch to force intimate contact with edge surfaces. For large patches, fill edges first and then work toward center, always troweling toward edges of patch. At fully exposed reinforcing bars, force patching mortar to fill space behind bars by compacting with trowel from sides of bars. (2) For vertical patching, place material in lifts of not more than 2 inch (50 mm) nor less than 1/8 inch (3 mm). Do not feather edge. (3) For overhead patching, place material in lifts of not more than 1½ inch (38 mm) nor less than 1/8 inch (3 mm). Do not feather edge. (4) Where multiple lifts are used, score surface of lifts to provide a rough surface for application of subsequent lifts. Allow each lift to reach final set before placing subsequent lifts.
g. Allow surfaces of lifts that are to remain exposed to become firm and then finish to a smooth surface with a trowel. h.
Floated finish: Provide where concrete flatwork is to receive waterproofing membranes or setting beds for finished materials.
i.
Contractor, at his own expense, shall level depressed spots and grind high spots in concrete surfaces which are in excess of specified tolerances. Leveling materials proposed for providing proper surface shall be approved by Engineer.
j.
Some Manufacturers recommend using lifts no greater than 2 inch (50 mm) in thickness for polymer concrete, but some specific products are designed for lifts greater than 2 inch (50 mm) thickness.
C - 1.25.4.6 Quality Assurance a.
Applicator Documentation of experience shall be provided in a listing of representative projects completed by personnel using the proposed materials in the last 5 years. Provide Owner contact information for each representative project.
d.
Testing Services and Inspection Services: (1) The Contractor should accept as indicative, the results of tests, including results involving mix designs and field quality control of materials. If, as a result of these tests, it is determined that the specified material properties are not being obtained, the Engineer may order such changes in proportions or materials, or both, as may be necessary to secure the specified properties, at no additional expense to the Company. (2) The use of testing and inspection services should not relieve the Contractor of his/her responsibility to furnish materials and construction in compliance with the Contract. (3) Failure to detect any defective work or material should not in any way prevent later rejection when such defect is discovered, nor should it obligate the Engineer for final acceptance.
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Materials, Tests and Construction Requirements (4) Additional testing and inspection services requested by the Contractor because of changes in materials, sources, or proportions, or occasioned by failure of tests and inspection to meet specification requirements, should be paid for by the Contractor. (5) The minimum number of test cylinders to be made for each type of polymer concrete and for each placement should be as specified by the Engineer or as recommended by the Manufacturer.
C - 1.25.5 FIBER-REINFORCED CONCRETE (2014) C - 1.25.5.1 General Fibers should be used only to inhibit cracking and improve resistance to material deterioration as a result of fatigue, impact, shrinkage, and/or thermal stresses. All flexural and tensile stresses must be resisted by steel reinforcement. Where the use of steel reinforcement is not essential by design such as concrete pavement, concrete overlays and shotcrete linings, the Engineer may use fibers. Testing data provided by the manufacturer of fibers intended for use in fiber-reinforced can be used to evaluate its performance. Such data shall be from testing meeting the requirements of ASTM C1399/C1399M-10. Detailed information for Fiber-Reinforced Concrete can be obtained from publications by ACI Committee 544.
C - 1.25.6 HIGH-PERFORMANCE CONCRETE (2014) Detailed information on High-Performance Concrete can be obtained from the Portland Cement Association publication, “Design and Control of Concrete Mixtures”, 15th edition, 2011.
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C - SECTION 1.26 SELF-CONSOLIDATING CONCRETE C - 1.26.1 GENERAL (2013) a.
SCC may be used to reduce labor during placement, to more completely fill around and between congested reinforcement, and to reduce or eliminate honeycombing and bug holes. It may also be used in such structural elements as drilled shafts, where the difficulty of inspecting the placement for air pockets is a concern.
b.
SCC normally contains a greater percentage of fine materials making up the paste and of fine aggregates, and a lesser percentage of coarse aggregates than conventional concrete.
3
C - 1.26.2 MIX DESIGN AND TESTING (2013)
4
C - 1.26.2.1 Mix Design As with conventional concrete, the water-cement ratio, quality and gradation of aggregates, and the inclusion of mineral admixtures such as fly ash and silica fume affect the strength, modulus of elasticity and creep and shrinkage properties of the hardened concrete. For structural elements such as columns, cantilevers and prestressed concrete beams where those properties are important, relevant tests should be performed unless information from other completed projects can confirm that the mix design will produce the required properties despite the high fines content and reduced maximum aggregate size typical of SCC. C - 1.26.2.2 Quality Control Testing a.
The supplier should have a full range of test results for the mix that is proposed. The purpose of the plant testing is to ensure that the concrete can flow into and completely fill forms under its own weight, that it will flow around and bond to reinforcing steel under its own weight, and that it will have a high resistance to segregation.
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Concrete Structures and Foundations (1) ASTM C1610 is used to evaluate the stability of a concrete mixture. A column is filled with concrete and given time to segregate. The column is then separated into sections and each section is washed over a sieve and the retained aggregate is weighed. The degree of segregation is measured by the difference in the results for the various sections. This is a laboratory test and is normally not practical to be performed in the field. (2) ASTM C1611 is used to evaluate the filling ability (deformability) of a concrete mixture and its stability. The test is performed similar to a standard slump cone test. However, instead of measuring the slump vertically, the mean spread of the resulting concrete is recorded as the slump flow with results ranging between 22 to 28 inches (560 to 710 mm) being typical, depending on project requirements. The standard slump cone is inverted for this test, which is suitable for laboratory and field use. (3) ASTM C1621 is used to evaluate the passing ability of a concrete mixture. The test consists of a ring of reinforcing bars that fits around the base of a standard test cone. The slump flow is measured with and without the J-Ring and the difference is noted. A difference of less than 1 inch (25 mm) indicates good passing ability, whereas a difference of more than 2 inches (50 mm) indicates poor passing ability. This test can be used in the laboratory and in the field.
C - 1.26.3 FORMS AND REINFORCEMENT (2013) a.
Rapid placement into the forms is desirable in order to achieve the economies that can result from the use of selfconsolidating concrete. Maintaining the flowability of a concrete pour even after it is placed in order to improve the bond to subsequent pours also implies rapid placement. Rapid placement can reduce the thixotrophic properties of the concrete mass to act as a semi-solid or gel and this has the potential to increase form pressures beyond those which would normally be expected. Stronger form systems allow faster placement since the labor involved with normal consolidation techniques is not required when using SCC.
b.
Form release agents with a high-solids content will better resist abrasion from the movement of the concrete. Light application of form release agents, or wiping off after application is also recommended to avoid staining of architectural finishes.
C - 1.26.5 PLACEMENT (2013) a.
SCC is commonly placed by discharging the material into the forms at a single location, depending on the fluidity of the SCC to fill the forms within a distance of about 33 feet (10 m). Considerations with respect to placement that determine the required slump flow include the intricacy of the form, depth, length and size of form, surface finish, and amount of reinforcement. A high rate of placement can be desirable to achieve flow momentum, which is also helpful in filling the forms. Overfilling of forms should be avoided due to the difficulty of screeding the fluid material.
b.
Specific placement techniques may be required for various types of structural elements, such as beams, double-tees, slabs, modules and walls, columns and drilled shafts. Free falling placement should be avoided.
c.
The field inspector should expect to see a sheen but no sign of free water on the top of the concrete as it is being placed. The coarse aggregates should also remain prominent on top of the concrete as a sign that segregation is not taking place. Concrete should not be allowed to set up before subsequent lifts are placed, and production rates and delivery schedules should be arranged accordingly. The previous lift should be able to flow under the weight of the subsequent lift. If the previous lift has begun to gel but has not hardened significantly, it may be rodded to restore its flowability.
d.
Dropping concrete during placement will increase turbulence and could result in entrapped air and segregation. Any anomaly on the surface of the forms, such as that resulting from splashed concrete is also likely to be visible on the face of the completed work. A tremie tube may be used to avoid dropping the concrete. SCC should not splatter.
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Part 2 Reinforced Concrete Design1 — 2014 — TABLE OF CONTENTS
Section/Article 2.1
2.2
2.3
Description
Page
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
Notations, Definitions and Design Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.1 Notations (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.2 De f i ni t i o n s (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.3 Design Loads (2012) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2.4 Loading Combinations (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-8 8-2-8 8-2-11 8-2-11 8-2-19
Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.1 Concrete (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3.2 Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-20 8-2-20 8-2-20
Details of Reinforcement 2.4
Hooks and Bends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4.1 Standard Hooks (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4.2 Minimum Bend Diameter (2005). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-21 8-2-21 8-2-21
2.5
Spacing of Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-22
2.6
Concrete Protection for Reinforcement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6.1 Minimum Concrete Cover (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.6.2 Concrete Cover for Bar Bundles (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-22 8-2-22 8-2-22
1
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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3
Concrete Structures and Foundations
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) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-23 8-2-23
2.7
Minimum Reinforcement of Flexural Members (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-23
2.8
Distribution of Reinforcement in Flexural Members (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-23
2.9
Lateral Reinforcement of Flexural Members (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-24
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) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-24 8-2-24 8-2-24 8-2-25
2.11 Limits for Reinforcement of Compression Members . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.11.1 Longitudinal Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.11.2 Lateral Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-25 8-2-25 8-2-25
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). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-27 8-2-27 8-2-28 8-2-28 8-2-29
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) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-30
2.16 Development Length of Bundled Bars (1990) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-30
2.17 Development of Standard Hooks in Tension (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-31
2.18 Combination Development Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-32
2.19 Development of Welded Wire Fabric in Tension . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.19.1 Deformed Wire Fabric (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.19.2 Smooth Wire Fabric (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-32 8-2-32 8-2-33
2.20 Mechanical Anchorage (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-33
2.21 Anchorage of Shear Reinforcement (2005). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-33
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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 8-2-35 8-2-36 8-2-36 8-2-36 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) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-37 8-2-37 8-2-37 8-2-37 8-2-38 8-2-38 8-2-38 8-2-38 8-2-39 8-2-39 8-2-40 8-2-40
2.24 Design Methods (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Service Load Design 2.25 General Requirements (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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2.26 Allowable Service Load Stresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.26.1 Concrete (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.26.2 Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-42 8-2-42 8-2-43
2.27 Flexure (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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2.28 Compression Members with or without Flexure (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-44
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 8-2-45 8-2-47 8-2-47 8-2-49 8-2-50 8-2-51
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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). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-52 8-2-52 8-2-52
2.31 Design Assumptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.31.1 Strength Design (2005). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-53 8-2-53
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). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-53 8-2-53 8-2-54 8-2-54 8-2-55 8-2-56
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). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-56 8-2-56 8-2-57 8-2-58
2.34 Slenderness Effects in Compression Members. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.34.1 General Requirements (2005). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.34.2 Approximate Evaluation of Slenderness Effects (2005). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-58 8-2-58 8-2-58
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) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-60 8-2-60 8-2-61 8-2-62 8-2-63 8-2-65 8-2-66 8-2-67
2.36 Permissible Bearing Stress (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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2.37 Serviceability Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.37.1 Application (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.37.2 Service Load Stresses (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-68 8-2-68 8-2-68
2.38 Fatigue Stress Limit for Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-68
2.39 Distribution of Flexural Reinforcement (2005) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8-2-69
2.40 Control of Deflections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.40.1 General (1992) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.40.2 Superstructure Depth Limitations (1992). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Commentary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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Reinforced Concrete Design
LIST OF FIGURES Figure 8-2-1 8-2-2 8-2-3 8-2-4 C-8-2-1 C-8-2-2
Description Cooper E 80 (EM 360) Axle Load Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reinforcement Spacing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Standard Hook Bars. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . #6, #7, or #8 Stirrups (fy > 40,000 psi) (#19, #22, or #25) (fy > 280 MPa) . . . . . . . . . . . . . . . . . . . . . . . . . Pier Protection: Minimum Crash Wall Requirements (Not To Scale) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Comparison of Impact Formulas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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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
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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 2c-6s (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.
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3
4
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See Commentary
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SECTION 2.2 NOTATIONS, DEFINITIONS AND DESIGN LOADS 2.2.1 NOTATIONS (2005) a ab av A
Ab Ac Af Ag Ah An As Acs Asf Ask Ast Av Avf Aw b bo bv bw c Cm d dc ds db
= depth of equivalent rectangular stress block, inches (mm). See Article 2.31.1f = depth of equivalent rectangular stress block for balanced strain conditions, inches (mm). See Article 2.33.2 = shear span, distance between concentrated load and face of support, inches (mm). See Article 2.29.7 and Article 2.35.7 = 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 = area of an individual bar, square inches (mm2). See Section 2.14 = 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 = area of reinforcement in bracket or corbel resisting moment, square inches (mm2). See Article 2.29.7 and Article 2.35.7 = gross area of section, square inches (mm2). = area of shear reinforcement parallel to flexural tension reinforcement, square inches (mm2). See Article 2.29.7 and Article 2.35.7 = 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 = area of tension reinforcement, square inches (mm2) = area of compression reinforcement, square inches (mm2) = area of reinforcement to develop compression strength of overhanging flanges of I- and T-sections, square inches (mm2). See Article 2.32.3 = area of skin reinforcement per unit height in one side face, square inches/foot (mm2/m). See Section 2.8 = total area of longitudinal reinforcement, square inches (mm2). See Article 2.33.1 and 2.33.2 = area of shear reinforcement within a distance s, square inches (mm2) = area of shear-friction reinforcement, square inches (mm2). See Article 2.29.4 and Article 2.35.4 = area of individual wire to be developed or spliced, square inches (mm2) = width of compression face of member, inches (mm) = perimeter of critical section for slabs and footings, inches (mm). See Article 2.29.6 and Article 2.35.6 = width of cross section being investigated for horizontal shear, inches (mm). See Article 2.29.6 and Article 2.35.5 = 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 = distance from extreme compression fiber to neutral axis, inches (mm). See Article 2.31.1 = a factor relating the actual moment diagram to an equivalent uniform moment diagram. See Article 2.34.2 = distance from extreme compression fiber to centroid of tension reinforcement, inches (mm) = distance from extreme compression fiber to centroid of compression reinforcement, inches (mm) = distance from centroid of gross section neglecting the reinforcement, to centroid of tension reinforcement, inches (mm) = diameter of bar or wire, inches (mm)
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Reinforced Concrete Design
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 cc = specified compressive strength of concrete, psi (MPa) fc 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 = stress range in steel reinforcement, ksi (MPa). See Section 2.38 and Article 2.26.2 ff fs = tensile stress in reinforcement at service loads, psi (MPa). See Article 2.26.2 f csb = 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) 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 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 Mu = factored moment at section d)Mn Mux = factored moment component in direction of x axis. See Article 2.33.3 © 2015,©American RailwayRailway Engineering and Maintenance-of-Way Association 2014, American Engineering and Maintenance-of-Way Association
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Concrete Structures and Foundations
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 d)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) 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 D = angle between inclined shear reinforcement and longitudinal axis of member Df = angle between shear-friction reinforcement shear plane. See Article 2.29.4 and Article 2.35.4 © 2014, Railway Engineering and Maintenance-of-Way Association © American 2015, American Railway Engineering and Maintenance-of-Way Association
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Reinforced Concrete Design
Eb Ec Ed E1 Gb Gs O P U Uc Ub Us Uv Uw )
= ratio of area of bars cut off to total area of bars at the section. See Article 2.13.1 = ratio of long side to short side of concentrated load or reaction area. See Article 2.29.6 and Article 2.35.6 = 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 = a factor defined in Article 2.31.1 = Moment magnification factor for members braced against sidesway to reflect effects of member curvature between ends of compression member. = Moment magnification factor for members not braced against sidesway to reflect lateral drift resulting from lateral and gravity loads. = correction factor related to unit weight of concrete. See Article 2.29.4 and Article 2.35.4 = coefficient of friction. See Article 2.29.4 and Article 2.35.4 = tension reinforcement ratio = As/bd = compression reinforcement ratio = Acs/bd = reinforcement ratio producing balanced strain conditions. See Article 2.32.1 = 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 = ratio of tie reinforcement area to area of contact surface = reinforcement ratio (As/bwd) used in EQ 2-15 and EQ 2-46. See Article 2.29.2 and Article 2.35.2 = strength reduction factor. See Article 2.30.2
1
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.
3 Compressive Strength of Concrete (f cc)
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
4
Factored Load
2.2.3 DESIGN LOADS (2012) a.
General.
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Concrete Structures and Foundations (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. (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.
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Reinforced Concrete Design
Figure 8-2-1. Cooper E 80 (EM 360) Axle Load Diagram (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. (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:
1
• For two tracks – full live load, • 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: (U.S. Customary)
1
3
For L d 14 feet
I = 60
For 14 feet < L d 127 feet
I = 225 e L
For L > 127 feet
I = 20
See Commentary
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Concrete Structures and Foundations (Metric) For L d 4 meters
I = 60
For 4 meters < L d 39 meters
I = 125 e 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
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)
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Reinforced Concrete Design
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. 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.
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
(1) The longitudinal force for E-80 (EM-360) loading shall be taken as the larger of: – 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
3
(Longitudinal braking force (kN) = 200 + 17.5L) – 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 )
4
For design of superstructure elements, L shall be taken as the length in feet (meters) of the span under consideration. For design of substructure elements, L shall be as follows: – Where rail is continuous across the bridge, or where load transfer devices that are approved by the Engineer are employed at discontinuities in the rail, L shall be the total bridge length in feet (meters). Longitudinal force shall be distributed to individual substructure units as described in Article 2.2.3(j)(2) below. – Where rail is not continuous across the bridge, and approved load transfer devices are not employed, L shall be taken as the length in feet (meters) of each bridge segment with rail continuity. The substructure units for each segment shall be evaluated and the longitudinal force computed for that segment shall be distributed to individual substructure units as described in Article 2.2.3(j)(2) below. 1
See Commentary
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Concrete Structures and Foundations – 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 be investigated. The stream flow pressure acting on the superstructure may be taken as Pmax with a uniform distribution. (3) Pressure Components
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Reinforced Concrete Design 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; (b) static ice pressure due to thermal movements of continuous stationary ice sheets onlarge bodies of water; (c) static pressure resulting from ice jams;
1
(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:
3
EQ 2-5
F = Cnptw where:
4 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) 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
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Concrete Structures and Foundations (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. (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.
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AREMA Manual for Railway Engineering
Reinforced Concrete Design (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. 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)
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
(1) The group loading combinations for SERVICE LOAD DESIGN are as shown in Table 8-2-4.
3
Table 8-2-4. Group Loading Combinations – Service Load Design Group
Item
Allowable Percentage of Basic Unit Stress
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
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.
c.
Load Factor Design.
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Concrete Structures and Foundations (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
Item
I IA II III IV V VI VII VIII
1.4 (D + 5/3 (L + I) + CF + E + B + SF) 1.8 (D + L + I + CF + E + B + SF) 1.4 (D + E + B + SF + W) 1.4 (D + L + I + CF + E + B + SF + 0.5W + WL + LF + F) 1.4 (D + L + I + CF + E + B + SF + OF) Group II + 1.4 (OF) Group III + 1.4 (OF) 1.0 (D + E + B + EQ) 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 cc for which each part of the structure is designed, shall be shown on the plans.
b.
Specified compressive strength of concrete f cc shall be the basis for acceptance. Requirements for f cc 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.
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AREMA Manual for Railway Engineering
Reinforced Concrete Design 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.
DETAILS OF REINFORCEMENT
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.
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
1
(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.
3
Table 8-2-6. Minimum Diameter of Bend Bar Size
Minimum Diameter
#3 through #8 (#10 through #25)
6 bar diameters
#9, #10 and #11 (#29, #32 and #36)
8 bar diameters
#14 and #18 (#43 and #57)
10 bar diameters
4
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.
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Concrete Structures and Foundations
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 1-1/2 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. Table 8-2-7. Minimum Concrete Cover Condition of Concrete Concrete cast against and permanently exposed to earth Concrete exposed to earth or weather Principal reinforcement Stirrups, ties and spirals Concrete bridge slabs Top reinforcement Bottom reinforcement Concrete not exposed to weather or in contact with ground Principal reinforcement Stirrups, ties and spirals
Minimum Cover (Inches)
Minimum Cover (mm)
3
75
2 1-1/2
50 40
2 1-1/2
50 40
1-1/2 1
40 25
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.
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Reinforced Concrete Design
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.
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.
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 )Mn 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.
1 SECTION 2.8 DISTRIBUTION OF REINFORCEMENT IN FLEXURAL MEMBERS (2005) a.
Flexural tension reinforcement shall be well distributed in the zones of maximum tension. (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 t0.012(d-30) (or Ask t 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.
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4
Concrete Structures and Foundations
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.
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.
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. (2) Welded wire fabric with wires located perpendicular to axis of member.
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Reinforced Concrete Design (3) Longitudinal bars with a bent portion making an angle of 30 degrees or more with the longitudinal tension bars. (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.
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.
3
2.11.2 LATERAL REINFORCEMENT (2005) a.
1
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).
4
(2) Ratio of spiral reinforcement Us shall not be less than the value given by: A fc U s = 0.45 § ------g – 1· -----c©A ¹f c y
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.
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Concrete Structures and Foundations (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 (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 two or more bars larger than #10 (#32) are bundled, 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.
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.
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AREMA Manual for Railway Engineering
Reinforced Concrete Design 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).
DEVELOPMENT AND SPLICES OF REINFORCEMENT
SECTION 2.13 DEVELOPMENT REQUIREMENTS
1
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 8d 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, )Vn, 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
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4
Concrete Structures and Foundations proportioned such that their (Av/bws)fy is not less than 60 psi (0.42 MPa). The resulting spacings shall not exceed d/(8Eb) where Eb 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, )Vn.
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.
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 ldd ----- la V
EQ 2-8
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.
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.
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.
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Reinforced Concrete Design
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. 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 (in) 0.04A b f y ----------------------fc c
(Note 1)
but not less than: 0.0004dbfy (Note 2) For #14 bars
0.085f y ------------------fc c
For #18 bars
0.11f y ---------------fc c
For deformed wire
0.03d b f y ---------------------fc c
(Note 3)
3
(Note 3)
4
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 fc c e f ct
(or 0.56 fc c e 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.
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Concrete Structures and Foundations 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.
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 e f cc
(or f y d b e 4 f cc 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.
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.
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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 100d b e f cc in metric).
c.
Basic development length lhb shall be multiplied by applicable modification factor or factors for:
1200d b e f cc (or
(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
1
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, reinforcement in excess of that required by analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
A s required -------------------------------- A s provided
3
(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.
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Concrete Structures and Foundations
Figure 8-2-3. Standard Hook Bars
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 e 0.36d b f y – 140 e
f cc
f cc
NOTE: The 20,000 has units of psi. NOTE: The 140 has units of MPa.
EQ 2-9 EQ 2-9M
but not less than
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0.20A w § f y · ------------------ ¨ ----------¸ s w © fc ¹ c c.
EQ 2-10
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 § f y · ------------------ ¨ ----------¸ s w © fc ¹ c
EQ 2-11
3.3A w § f y · --------------- ¨ ----------¸ s w © fc ¹ 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.
1
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.
3
4 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.
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Concrete Structures and Foundations (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 e
f cc ( 0.17d b f y e
f cc 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 U-stirrup 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 252.
Figure 8-2-4. #6, #7, or #8 Stirrups (fy > 40,000 psi) (#19, #22, or #25) (fy > 280 MPa)
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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.
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.
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.
1
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),
3
where: Class A splice = 1.0ld
4
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.
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:
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Concrete Structures and Foundations
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. (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).
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 cc 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.
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.
b.
Lap splices of welded deformed wire fabric, with no cross wires within the lap splice length, shall be determined as for deformed wire.
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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.
ANALYSIS AND DESIGN – GENERAL CONSIDERATIONS
1 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)
4
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.
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2.23.4 MODULUS OF ELASTICITY (2005) a.
Modulus of elasticity Ec for concrete may be taken as w c
1.5
33 f cc , in psi (or w c
1.5
0.043 f cc 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 b.
57 000 f cc (or 4700 f cc in metric).
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.
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.
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
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Reinforced Concrete Design 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 = § -------- I g + 1 – § -------- I ©M ¹ © M ¹ cr a a
EQ 2-12
where: f r Ig Mcr= -------yt
EQ 2-13
fr = modulus of rupture of concrete specified in Article 2.26.1a (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
1
§ 2 – 1.2 Ac --------s· t 0.6 © A ¹ 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.
3
2.23.9 COMPOSITE CONCRETE FLEXURAL MEMBERS (1992) a. b.
Application. Composite flexural members consist of concrete elements constructed in separate placements but so interconnected that the elements respond to loads as a unit. 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.
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Concrete Structures and Foundations 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.
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.
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.
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Reinforced Concrete Design (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.
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
Superstructure Type Bridge slabs with main reinforcement parallel or perpendicular to traffic
1
S+3 -----------17 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.
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4
Concrete Structures and Foundations (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.
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.
SECTION 2.26 ALLOWABLE SERVICE LOAD STRESSES 2.26.1 CONCRETE (2005) For service load design, stresses in concrete shall not exceed the following: a.
Flexure: Extreme fiber stress in compression fc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.40 f cc Extreme fiber stress in tension for plain concrete, ft . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.21 fr Modulus of rupture f r , from tests, or if data are not available: Normal weight concrete. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.5 f cc 0.62 f cc (metric)
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6.3 f cc
Lightweight concrete. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
0.52 f cc (metric) 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 cc 0.079 f cc (metric)
Maximum shear carried by concrete plus shear reinforcement
v c + 4 f cc v c + 0.33 f cc (metric)
Two-way slabs and footings: (If shear reinforcement is provided see Article 2.29.6d) Shear carried by concrete vc
2· § 0.8 + ---- f cc © E¹
1
c
§ 0.066 + 0.17 ----------· f cc (metric) © E ¹ c
1.8 f cc
but not greater than
3
0.15 f cc (metric) c.
Bearing on loaded area fb, but not to exceed 1050 psi (7.2 MPa) . . . . . . . . . . . . . . . . . . . . . .0.30 f cc Minimum distance from edge of bearing to edge of supporting concrete shall be 6 inches (150 mm).
4
2.26.2 REINFORCEMENT (2005) a.
b.
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)
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)
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Concrete Structures and Foundations where: ff = stress range in steel reinforcement, ksi (MPa). 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.
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, ) shall be taken as 1.0.
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SECTION 2.29 SHEAR 2.29.1 SHEAR STRESS (2005) a.
Design shear stress v shall be computed by: Vv = --------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
1
3
f cc 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 cc (or 0.079 f cc 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 cc + 1100U w ------M Vd v c = 0.075 f cc + 7.58U w ------M
EQ 2-15
EQ 2-15M
Vd but vc shall not exceed 1.6 f cc (or 0.13 f cc in metric). The quantity ------- shall not be taken greater than 1.0, where M M is the design moment occurring simultaneously with V at the section considered.
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Concrete Structures and Foundations c.
For members subject to axial compression, vc may be computed by: v c = 0.9 § 1 + 0.0006N ---------------------· f cc © Ag ¹
EQ 2-16
0.0006N v c = 10.8 § 0.0069 + ---------------------· f cc © Ag ¹
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 § 1 + ------------------· fcc © Ag ¹
EQ 2-17
0.004N v c = 10.8 § 0.0069 + ------------------· fcc © Ag ¹
EQ 2-17M
where: N is 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 fc c + 2200U ------M
EQ 2-18
v c = 0.083 fc c + 15.2U Vd ------M
EQ 2-18M
but vc shall not exceed 1.8 fc c (or 0.15 fc c in metric). For single cell box culverts only, vc need not be taken less than 1.4 fc c (or 0.12 fc c in metric) for slabs monolithic with walls or 1.2 fc c (or 0.10 fc c in metric) for slabs simply supported. The quantity of Vd ------- shall not be taken greater than 1.0, where M is moment occurring M simultaneously with V 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 1.8 fct in metric) for value of fct/6.7 (or 1.8 fct in metric) used shall not exceed
fc c but the
fc c .
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Reinforced Concrete Design (2) When fct is not specified, shear stress vc shall be multiplied by 0.85.
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
b.
EQ 2-19
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 D + cos D
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 D in which (v – vc) shall not exceed 1.5 fc c (or
EQ 2-21
0.12 fc c
1
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).
3
(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.
d.
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. When (v – vc) exceed 2 fc c (or 0.17 fc 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 fc c (or 0.33 fc 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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Concrete Structures and Foundations 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: VA vf = ------f sP
EQ 2-22
where: P = 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 shearfriction reinforcement, area of shear-friction reinforcement Avf shall be computed by: V A vf = ------------------------------------------------f s P sin D f + cos D f
EQ 2-23
where: Df = angle between shear-friction reinforcement and shear plane. (3) Coefficient of friction P in EQ 2-22 and EQ 2-23 shall be concrete placed monolithically . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4O concrete placed against hardened concrete with surface intentionally roughened as specified in Article 2.29.4g. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.0O concrete placed against hardened concrete not intentionally roughened . . . . . . . . . . . . 0.6O concrete anchored to as-rolled structural steel by headed studs or by reinforcing bars (see Article 2.29.4h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.7O where: O= 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 cc 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 Av f f s , when calculating required A vf .
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.
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Reinforced Concrete Design 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 P is assumed equal to 1.0O, 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: Vv dh = --------bw d
EQ 2-24
1
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).
3
(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. (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). © 2015,©American RailwayRailway Engineering and Maintenance-of-Way Association 2014, American Engineering and Maintenance-of-Way Association
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Concrete Structures and Foundations (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. (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. (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: Vv = -------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. 2 v c = § 0.8 + -----· fc c ; f’c in psi © E¹
EQ 2-26
c
v c = § 0.066 + 0.17 ----------· fc c ; f’c in MPa © E ¹
EQ 2-26M
c
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Reinforced Concrete Design or D s d· v c = § 0.8 + -------- fc c ; f’c in psi © b ¹
EQ 2-27
o
D s d· fc c v c = § 0.8 + -------- ---------- ; f’c in MPa © b ¹ 12
EQ 2-27M
o
but not greater than 1.8 fc (or 0.15 fc in metric). Ec is the ratio of long side to short side of concentrated load or c c reaction area. Ds 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 fc c (or 0.075 fc c in metric) and v shall not exceed 3 fc c (or 0.25 fc 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
3
(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 cc nor 360 psi (2.5 MPa). For “sand-lightweight” concrete, shear stress v shall not exceed (0.09 – 0.03av/d)f cc 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). 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 U = As/bd shall not be taken less than 0.04 (f cc /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;
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Concrete Structures and Foundations (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 (APPLICABLE TO Section 2.30 THROUGH Section 2.39) SECTION 2.30 STRENGTH REQUIREMENTS 2.30.1 REQUIRED STRENGTH (2005) 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 I.
b.
Strength reduction factor I shall be taken as follows: For flexure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I = 0.90 For shear. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I = 0.85 For spirally reinforced compression members, with or without flexure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I = 0.75 For tied reinforced compression members with or without flexure. . . . . . . . . . . I = 0.70
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Reinforced Concrete Design
NOTE:
The value of I 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I = 0.70 NOTE:
Development and splices of reinforcement specified in Section 2.13 through Section 2.22 do not require a I 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.
3
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 fcc 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 = E1c) 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 E1 shall be taken as 0.85 for concrete strength fcc up to and including 4000 psi (28 MPa). For strengths above 4000 psi (28 MPa) E1 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 E1 shall not be taken less than 0.65.
4
SECTION 2.32 FLEXURE 2.32.1 MAXIMUM REINFORCEMENT OF FLEXURAL MEMBERS (1992) a.
For flexural members, the reinforcement U provided shall not exceed 0.75 of that ratio Ub which would produce balanced strain conditions for the section under flexure.
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Concrete Structures and Foundations For flexural members with compression reinforcement, the portion of Ub 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 U d 0.75 Ub the design moment strength )Mn may be computed by: 0.6Uf )M n = ) A s f y d § 1 – ---------------y-· © fc c ¹
EQ 2-28
a = ) A s f y § d – ---· © 2¹
EQ 2-29
where: As f y a = -------------------0.85fc c b b.
The balanced reinforcement ratio Ub for rectangular sections with tension reinforcement only is given by: 0.85E 1 fc c § 87 000 · U b = ---------------------- ----------------------------© 87 000 + f ¹ fy y
EQ 2-30
0.85E 1 fc c § 600 · U b = ---------------------- -------------------© 600 + f ¹ fy y
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 U d 0.75 Ub, the design moment strength )Mn 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 )Mn may be computed by: )M n = ) A s – A sf f y § d – --a-· + A sf f y d – 0.5h f © 2¹
EQ 2-31
where:
Asf =
h 0.85fc c b – b w ----ffy
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Reinforced Concrete Design
A s – A sf f y a = ------------------------------0.85fc c b w c.
The balanced reinforcement ratio Ub for I- and T-sections with tension reinforcement only is given by: b 0.85E 1 fc c § 87 000 · U b = -----w- ---------------------- ----------------------------- + U f © 87 000 + f ¹ b fy y b 0.85E 1 fc c § 600 · U b = -----w- ---------------------- -------------------- + U f © 600 + f ¹ b fy y
EQ 2-32
EQ 2-32M
where: A sf U f = --------bw d d.
When the compression flange thickness is greater than a, the design moment strength, )Mn, 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.
1
2.32.4 RECTANGULAR SECTIONS WITH COMPRESSION REINFORCEMENT (2005) a.
For rectangular sections when U d 0.75 Ub, the design moment strength )Mn may be computed by: )M n = ) A s – Ac s f y § d – --a-· + Ac s f y d – dc © 2¹
3 EQ 2-33
where:
4
A s – Ac s f y a = -----------------------------0.85fc c b and the following condition shall be satisfied: A s – Ac s 0.85E 1 fc c d c § 87 000 · -------------------- t ---------------------------- ----------------------------© 87 000 – f ¹ bd f yd y A s – Ac s 0.85E 1 fc c d c § 600 · -------------------- t ---------------------------- -------------------© 600 – f ¹ bd f yd y b.
EQ 2-34
EQ 2-34M
When the value of (As – Acs)/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
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Concrete Structures and Foundations 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 Ub for rectangular section with compression reinforcement is given by: 0.85E 1 fc c § 87 000 · Ucfc sb U b = ---------------------- ----------------------------- + -------------© 87 000 + f ¹ fy fy y
EQ 2-35
0.85E 1 fc c § 600 · Ucfc sb U b = ---------------------- -------------------- + -------------© 600 + f ¹ fy fy y
EQ 2-35M
where: f csb is stress in compression reinforcement at balanced strain conditions f csb = f csb =
dc 87 000 – ---- 87 000 + f y d f y d dc 600 – ---- 600 + f y d f y d
(metric)
2.32.5 OTHER CROSS SECTIONS (1992) For other cross sections the design moment strength )Mn 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.
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 )Pa of compression members shall not be taken greater than the following: (1) For members with spiral reinforcement conforming to Article 2.11.2a: )P a (max) = 0.85) > 0.85fc c A g – A st + f y A st @
EQ 2-36
(2) For members with tie reinforcement conforming to Article 2.11.2b:
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)P a (max) = 0.80) > 0.85fc c A g – A st + f y A st @
EQ 2-37
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 )Po may be computed by: )P o = ) > 0.85fc c A g – A st + A st f y @
EQ 2-38
(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 )Mn 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 )Pb and balanced moment strength )Mb may be computed by: )P b = ) > 0.85fc c ba b + Ac s fc sb – A s f y @
EQ 2-39
1
and a )M b = ) 0.85fc c ba b § d – ds – ----b-· + Ac s fc sb d – dc – ds + A s f y ds © 2¹
EQ 2-40
3
where: 87 000 -· E d ab = §© ---------------------------1 87 000 + f y¹ 600 ab = §© --------------------·¹ E 1 d 600 + f y
d.
f csb =
dc 87 000 – ---- 87 000 + f y d f y d
f csb =
600 – dc ---- 600 + f y d f y d
4 (metric)
(metric)
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.
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Concrete Structures and Foundations (2) The nominal values of axial load strength Pn and moment strength Mn must both be multiplied by the appropriate strength reduction factor ) for spirally reinforced or tied compression members as given in Article 2.30.2. The value of ) may be increased linearly from the value for compression members to the value for flexure as the design axial load strength )Pn decreases from 0.10f cc A g or )Pb whichever is smaller, to zero.
2.33.3 BIAXIAL LOADING (1992) 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 -· + § ------1 -· – § ----1· § ------©P ¹ ©P ¹ ©P ¹ nx ny o
EQ 2-41
where the factored axial load, P u t 0.1fc c A g or M ux M uy -------------- + --------------d1 )M nx )M ny
EQ 2-42
when the factored axial load, P u 0.1fc c A g
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.
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Reinforced Concrete Design 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, Gs shall be taken as 1.0. For members not braced against sidesway, Gb shall be evaluated as for a braced member and Gs as for an unbraced member. M c = G b M 2b + G s M 2s
EQ 2-43
1
where:
Gb =
Cm ----------------- t 1.0 Pu 1 – --------IP c
Gs =
1 - t 1.0 --------------------6P u 1 – -----------I6P c
3
and
4 Pc =
2
S EI-------------2 kl u
In lieu of a more precise calculation, EI may be taken either as Ec Ig ----------- + E s I s 5 EI = --------------------------1 + Ed or conservatively
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Ec Ig ----------2.5 EI = -------------1 + Ed For members braced against sidesway and without transverse loads between supports, Cm may be taken as: M 1b C m = 0.6 + 0.4 --------M 2b
EQ 2-44
but not less than 0.4.
For all other cases Cm shall be taken as 1.0. f.
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 Gs shall be computed for the member group with 6Pu and 6Pc equal to the summations for all compression members in the group.
g.
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 G 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.
SECTION 2.35 SHEAR 2.35.1 SHEAR STRENGTH (2005) a.
Factored shear stress vu shall be computed by: Vu v u = -------------)b 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.
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Reinforced Concrete Design 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:
d.
The design criteria for combined shear and torsion given in “Building Code Requirements for Reinforced Concrete – ACI318-02” may be used.
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:
The value f’c used in computing vc shall not be taken greater than 10,000 psi (69 MPa).
a.
Shear stress carried by concrete vc shall not exceed 2 fc c (or 0.17 fc 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:
1
Vu d v c = 1.9 fc c + 2500U w --------Mu
EQ 2-46
Vu d v c = 0.16 fc c + 17U w --------Mu
EQ 2-46M
3
Vu d - shall not be taken greater than 1.0, where but vc shall not exceed 3.5 fc c (or 0.29 fc c in metric). The quantity --------Mu Mu is the factored moment occurring simultaneously with Vu at the section considered. c.
4
For members subject to axial compression, vc may be computed by: N v c = 2 § 1 + 0.0005 ------u-· fc c © A g¹ N v c = 0.17 § 1 + 0.072 ------u-· fc c © A g¹
EQ 2-47
EQ 2-47M
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
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N v c = 2 § 1 + 0.002 ------u-· fc c © A g¹
EQ 2-48
N v c = 0.17 § 1 + 0.29 ------u-· fc c © A g¹
EQ 2-48M
where: Nu is negative for tension 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 fc c + 4600U --------Mu
EQ 2-49
Vu d v c = 0.18 fc c + 32U --------Mu
EQ 2-49M
but vc shall not exceed 4 fc c (or 1--- fc c in metric). For single cell box culverts only, vc need not be taken less than 3 fc 5 3 fc c (or ----------c in metric) for slabs monolithic with walls or 2.5 fc c (or ------ fc c in metric) for slabs simply 24 4 Vu d supported. The quantity --------- shall not be taken greater than 1.0, where Mu is factored moment occurring Mu 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 value of fct/6.7 (or 1.8fct in metric) used shall not exceed
fc c , but the
fc 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:
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v u – v c b w s A v = -----------------------------fy b.
EQ 2-50
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 D + cos D
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 D
EQ 2-52
fc in which (vu – vc) shall not exceed 3 fc c (or ---------c- 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.
d.
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 more than 2/3 of the total shear resisted by reinforcement. In such computations, vc shall be included only once. When (vu – vc) exceeds 4 fc c
1
3
fc (or ----------c in metric), maximum spacings given in Article 2.10.3 shall be reduced by 3
one-half. 2 fc 8 fc c (or -------------c in metric). 3
e.
The value of (vu – vc) shall not exceed
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.
4
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.
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Concrete Structures and Foundations c.
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 = ----------If y P
EQ 2-53
where: P = 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 shearfriction reinforcement, area of shear friction reinforcement Avf shall be computed by: Vu A vf = ---------------------------------------------------If y P sin D f + cos D f
EQ 2-54
where: Df = angle between shear-friction reinforcement and shear plane (3) Coefficient of friction P in EQ 2-53 and EQ 2-54 shall be: concrete placed monolithically. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.4O concrete placed against hardened concrete with surface intentionally roughened as specified in Article 2.35.4g. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.0O concrete placed against hardened concrete not intentionally roughened . . . . . . . . . . . . . . . . . . . . . . . 0.6O concrete anchored to as-rolled structural steel by headed studs or by reinforcing bars (see Article 2.35.4h) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.7O where O = 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 cc 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 Av f f y, when calculating required A vf .
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 P is assumed equal to 1.0O, 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.
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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 = ----------Ib 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: (1) When contact surface is clean, free of laitance, and intentionally roughened, shear stress vh shall not exceed 80 psi (0.55 MPa).
1
(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 + 0.6Uvfy O in psi [(1.8 + 0.6Uvfy O in MPa]; but not greater than 500 psi (3.5 MPa).
3
(4) When factored shear stress, vu, at section considered exceeds I 500 psi (I 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). (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. © 2015,©American RailwayRailway Engineering and Maintenance-of-Way Association 2014, American Engineering and Maintenance-of-Way Association
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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. (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 = ------------)b 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. Ds d v c = § -------- + 2· fc c ©b ¹ o
EQ 2-57
fc Ds d v c = § -------- + 2· ----------c ©b ¹ 12 o
EQ 2-57M
4-· fc v c = § 2 + ---c © E¹
EQ 2-58
fc 2 v c = § 1 + -----· ----------c © ¹ 6 E
EQ 2-58M
c
c
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EQ 2-59
v c = 4 fc c 1 v c = --- fc c 3
EQ 2-59M
Ec is the ratio of long side to short side of concentrated load or reaction area. Ds 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 section shall 1 1 not exceed 2 fc c (or --- fc c in metric) and vu shall not exceed 6 fc c (or --- fc c in metric). Shear stresses shall be 6 2 investigated at the critical section defined in Article 2.35.6a(2) and at successive sections more distant from the support.
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
(1) In all design calculations in accordance with this paragraph, strength reduction factor I 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 cc nor 800 psi (5.5 MPa). For “sand-lightweight” concrete, shear stress vu shall not exceed (0.2 – 0.07a v /d) f cc nor (800 – 280a v /d) psi (5.5 – 1.9a v /d MPa).
3
(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/Ify. Tensile force Nuc shall not be taken less than 0.2Vu unless special provisions are made to avoid tensile forces. (5) Area of primary tension reinforcement As shall be made equal to the greater of (Af + An), or (2A 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 U = As/bd shall not be taken less than 0.04 (f cc /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
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Concrete Structures and Foundations (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).
SECTION 2.36 PERMISSIBLE BEARING STRESS (2005) Design bearing stress shall not exceed I(0.85f cc), 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 e 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)
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Reinforced Concrete Design where: ff = stress range in steel reinforcement, ksi (MPa) 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 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 f s = -------------but fs shall not be greater than 0.5 fy 3 d A c
EQ 2-60
1
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
3
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.
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.
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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.
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:
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AREMA Manual for Railway Engineering
Reinforced Concrete Design (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 (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.
1
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.
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.
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 (2014) 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 (Reference 132). In order to resolve this discrepancy, a new impact formula was developed based on work in Europe (Reference 132) and Canada (References 137, 138). 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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3
4
Figure C-8-2-1. Pier Protection: Minimum Crash Wall Requirements (Not To Scale)
Concrete Structures and Foundations
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AREMA Manual for Railway Engineering
Figure C-8-2-2. Comparison of Impact Formulas
Reinforced Concrete Design
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AREMA Manual for Railway Engineering
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Concrete Structures and Foundations According to the ORE report (Reference 132) 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 Reference 136) as: f = 3.5 e G where G is the deflection due to dead and live load in inches or; f = 5.6 e G where Gis 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. When the substructure and superstructure are rigidly connected together, the superstructure will undergo additional 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. © 2014, Railway Engineering and Maintenance-of-Way Association © American 2015, American Railway Engineering and Maintenance-of-Way Association
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AREMA Manual for Railway Engineering
Reinforced Concrete Design 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 all had impacts less than 30 percent. The AAR performed further testing on three prestressed concrete bridges in the early 1990s [References 134 & 135]. 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. Testing on the concrete bridges at the Facility for Accelerated Service Testing (FAST) (References 139-146) and complementary testing in revenue service (Reference 147) have shown: • Impacts measured in a prestressed concrete span with concrete ties and a bolted rail joint were approximately twice as high as those measured with continuous welded rail.
1
• Maximum impacts measured in prestressed concrete spans of various lengths generally follow the design impact formula for wood ties with 8 inches of ballast or concrete ties with 12 inches of ballast with continuous welded rail. • Use of wood ties, concrete ties with under-tie pads, plastic composite ties, or ballast mat each helped to reduce impact compared to that measured under conventional concrete ties on a concrete span. The use of a resilient layer in the track structure reduces the track stiffness to better match the stiffness of approach track. A resilient layer also results in better retention of track geometry requiring less frequent track surfacing maintenance.
3
• Reducing ballast depth from 12 inches (300 mm) below wood ties to 8 inches (200 mm) below wood ties resulted in an increase of approximately 30 percent in measured impacts and an increase in track maintenance demand. • As ballast degraded and became increasingly fouled, measured impacts increased.
4
C - 2.2.3 (j.) LONGITUDINAL LOAD. (2008) (References 34, 35, 36, 46, 52, 55, 66, 67, 68, 69, and 105) 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 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.
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AREMA Manual for Railway Engineering
8-2-75
Concrete Structures and Foundations 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 E60 (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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8-2-76
AREMA Manual for Railway Engineering
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