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Standard Specifications for Highway Bridges 17th Edition - 2002 Adopted and Published by the American Association of S
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Standard Specifications for Highway Bridges 17th Edition - 2002
Adopted and Published by the
American Association of State Highway and Transportation Officials 444 North Capitol Street, N.W., Suite 249 Washington, D.C. 20001 © Copyright 2002 by the American Association of State Highway and Transportation Officials. All Rights Reserved. Printed in the United States of America. This book, or parts thereof, may not be reproduced in any form without permission of the publishers. Code: HB-17
ISBN: 156051-171-Q
AMERICAN ASSOCIATION OF STATE illGHWAY AND TRANSPORTATION OFFICIALS EXECUTIVE COMMITTEE
2001-2002 VOTING MEMBERS
Officers: President: Brad Mallory, Pennsylvania Vice President: James Codell, Kentucky Secretary/Treasurer: Larry King, Pennsylvania
Regional Represematives: Region /: Joseph Boardman, New York, One-Year Term James Weinstein, New Jersey, Two-Year Term Region II: Bruce Saltsman, Tennessee, One-Year Term Fred Van Kirk, West Virginia, Two-Year Term Region III: Kirk Brown, Illinois, One-Year Term Henry Hungerbeeler, Missouri, Two-Year Term Region IV: Joseph Perkins, Alaska, One-Year Term Tom Stephens, Nevada, Two-Year Term NON-VOTING MEMBERS
Immediate Past President: E. Dean Carlson, Kansas Executive Director: John Horsley, Washington, D.C.
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IDGHWAY SUBCOMMITTEE ON BRIDGES AND STRUCTURES
2002
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TOM LULAY, Oregon, Chairman SANDRA LARSON, Vice Chairman JAMES D. COOPER, Federal Highway Administration, Secretary ALABAMA, William F. Conway, George H. Connor ALASKA, Richard A. Pratt ARIZONA, F. Daniel Davis ARKANSAS, Phil Brand CALIFORNIA, Richard Land COLORADO, Mark A. Leonard CONNECTICUT, Gordon Barton DELAWARE, Doug Finney, Dennis O'Shea D.C., Donald Cooney FLORIDA, William N. Nickas GEORGIA. Paul Liles, Brian Summers HAWAII. Paul Santo IDAHO, Matthew M. Farrar ILLINOIS, Ralph E. Anderson INDIANA, Mary Jo Hamman IOWA, Norman L. McDonald KANSAS, Kenneth F. Hurst, Loren R. Risch KENTUCKY, Stephen E. Goodpaster LOUISIANA, Hossein Ghara, Mark J. Morvant MAINE, James E. Tukey MARYLAND, Earle S. Freedman MASSACHUSETTS, Alexander K. Bardow MICHIGAN, Steve Beck MINNESOTA, Dan Dorgan, Kevin Western MISSISSIPPI, Harry Lee James MISSOURI, Shyam Gupta MONTANA, William S. Fullerton NEBRASKA, Lyman D. Freemon NEVADA, William C. Crawford, Jr. NEW HAMPSHIRE, Mark Richardson NEW JERSEY, Harry A. Capers, Jr., Richard W. Dunne NEW MEXICO, Jimmy D. Camp NEW YORK, James O'Connell, George Christian NORTH CAROLINA, Gregory R. Perfettie NORTH DAKOTA, Terry Udland OHIO, Timothy Keller OKLAHOMA, Robert J. Rusch, Veldo Goins OREGON, Mark E. Hirota PENNSYLVANIA, R. Scott Christie PUERTO RICO, Jaime Cabre RHODE ISLAND, Kazem Farhoumand
SOUTH CAROLINA, Randy R. Cannon, Jeff Sizemore SOUTH DAKOTA, John C. Cole TENNESSEE, Edward P. Wasserman TEXAS, Mary Lou Ralls U.S. DOT, Nick E. Mpras UTAH, David Nazare VERMONT. James McCarthy VIRGINIA, Malcolm T. Kerley WASHINGTON, Jerry Weigel, Tony M. Allen WEST VIRGINIA, James Sothen WISCONSIN, Stanley W. Woods WYOMING, Gregg C. Fredrick, Keith R. Fulton ALBERTA, Dilip K. Dasmohapatra MANITOBA, Ismail Elkholy NORTHERN MARIANA ISLANDS, John C. Pangalinan NEW BRUNSWICK, David Cogswell NORTHAMPTON, R. T. Hughes NORTHWEST TERRITORIES, John Bowen NOVA SCOTIA, Alan MacRae, Mark Pertus ONTARIO, Vacant SASKATCHEWAN, Herve Bachelu FHWA, Shoukry Elnahal MASS. METRO. DIST. COMM., David Lenhardt N.J. TURNPIKE AUTHORITY, Richard Raczynski NY STATE BRIDGE AUTHORITY, William Moreau PORT AUTH. OF NY AND NJ, Joseph J. Kelly, Joseph Zitelli BUREAU OF INDIAN AFFAIRS, Wade Casey MILITARY TRAFFIC MANAGEMENT COMMAND, Robert D. Franz U.S. ARMY CORPS OF ENGINEERS-DEPT. OF THE ARMY, Paul Tan U.S. COAST GUARD, Jacob Patnaik U.S. DEPARTMENT OF AGRICULTUREFOREST SERVICE, Nelson Hernandez
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PREFACE to Seventeenth Edition Major changes and revisions to this edition are as follows: I. The Interim Specifications of 1997, 1998, 1999,2000,2001,2002 and 2003 have been adopted and are included. 2. The commentaries from 1996 through 2000 are provided and have been cross-referenced with each other. where appropriate. 3. In 1997. Section 15, ..TFE Bearing Surface," Division I, was replaced by Section 14, "Bearings.'' 4. In 1997, Section 19, "Pot Bearings," Division I, was replaced by Section 14...Bearings." 5. In 1997, Section 20, "Disc Bearings," Division I, was replaced by Section 14, "Bearings." 6. In 2002, Section 16, "Steel Tunnel Liner Plates," Division I, became Section 15. 7. In 2002, Section 17, "Soil-Reinforced Concrete Structure Interaction Systems," Division I, became Section 16. 8. In 2002, Section 18, "Soil-Thermoplastic Pipe Interaction Systems," Division I, became Section 17. 9. A new companion CD-ROM with advance search features is included with each book. 10. The Federal Highway Administration and the States have established a goal that the LRFD standards be used on all new bridge designs after 2007; only edits related to technical errors in the seventeenth edition will be made hereafter. These Standard Specifications are applicable to new structure designs prior to 2007 and for the maintenance and rehabilitation of existing structures.
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INTRODUCTION
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The compilation of these specifications began in 1921 with the organization of the Committee on Bridges and Structures of the American Association of State Highway Officials. During the period from 1921, until printed in 1931, the specifications were gradually developed, and as the several divisions were approved from time to time, they were made available in mimeographed form for use of the State Highway Departments and other organizations. A complete specification was available in 1926 and it was revised in 1928. Though not in printed form, the specifications were valuable to the bridge engineering profession during the period of development. The first edition of the Standard Specifications was published in 1931, and it was followed by the 1935, 1941, 1944, 1949, 1953, 1957, 1961, 1965, 1969, 1973. 1977, 1983, 1989, 1992, and 1996 revised editions. The present seventeenth edition constitutes a revision of the 1996 specifications, including those changes adopted since the publication of the sixteenth edition and those through 2002. In the past, Interim Specifications were usually published in the middle of the calendar year, and a revised edition of this book was generally published every 4 years. However, since the Federal Highway Administration and the States have established a goal that the LRFD standards be used on all new bridge designs after 2007, only edits related to technical errors in the seventeenth edition will be made hereafter. These Standard Specifications are applicable to new structure designs prior to 2007 and for the maintenance and rehabilitation of existing structures. Future revisions will have the same status as standards of the American Association of State Highway and Transportation Officials (AASHTO) and are approved by at least two-thirds of the Subcommittee on Bridges and Structures. These revisions are voted on by the Association Member Departments prior to the publication of a new edition of this book, and if approved by at least two-thirds of the members, they are included in a new edition as standards of the Association. Members of the Association are the 50 State Highway or Transportation Departments. the District of Columbia, and Puerto Rico. Each member has one vote. The U.S. Department of Transportation is a nonvoting member. Future revisions will be displayed on AASHTO's website via a link from the title's book code listing, HB-17, in the Bookstore of www.transportation.org. An e-mail notification will also be sent to previous purchasers notifying them that a revision is available for download. Please check the site periodically to ensure that you have the most up-to-date and accurate information. The Standard Specifications for Highway Bridges are intended to serve as a standard or guide for the preparation of State specifications and for reference by bridge engineers. Primarily, the specifications set forth minimum requirements which are consistent with current practice, and certain modifications may be necessary to suit local conditions. They apply to ordinary highway bridges and supplemental specifications may be required for unusual types and for bridges with spans longer than 500 feet. Specifications of the American Society for Testing and Materials (ASTM), the American Welding Society, the American Wood Preservers Association, and the National Forest Products Association are referred to, or are recognized. Numerous research bulletins are noted for references. The American Association of State Highway and Transportation Officials wishes to express its sincere appreciation to the above organizations, as well as to those universities and representatives of industry whose research efforts and consultations have been most helpful in continual improvement of these specifications. Extensive references have been made to the Standard Specifications for Transportation Materials and Methods of Sampling and Testing also published by AASHTO, including equivalent ASTM specifications which have been reproduced in the Association's Standard Specifications by permission of the American Society for Testing and Materials.
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Attention is also directed to the following publications prepared and published by the Bridge Subcommittee:
AASHTO Guide for Commonly Recognized (CoRe) Structural Elements-I998 Edition AASHTO Guide Specifications for Horizontally Curved Steel Girder Highway Bridges witlz Design Examples for /-Girder and Box-Girder Bridges-2002 Edition AASHTO Guide Specifications-Thermal Effects in Concrete Bridge Superstructures- I 989 Edition AASHTO LRFD Bridge Construction Specifications-1998 Edition AASHTO LRFD Bridge Design Specifications. 2nd Edition. Sf- I 998 Edition AASHTO LRFD Bridge Design Specifications. 2nd Edition. US-1998 Edition AASHTO LRFD Movable Highway Bridge Design Specifications, 1st Edition200 I Edition AASHTO/AWS-DJ.5MID1.5:2001 An American National Standard: Bridge Welding Code and its Commentary-2002 Edition Bridge Data Exchange (BDX) Technical Data Guide-1995 Edition Construction Handbook/or Bridge Temporary Works-1995 Edition Guide Design Specifications for Bridge Temporary Works-1995 Edition Guide for Painting Steel Structures-1991 Edition Guide Specifications and Commentary for Vessel Collision Design of Highway Bridges-1991 Edition Guide Specifications for Alternative Load Factor Design Procedures for Steel Beam Bridges Using Braced Compact Sections-1991 Edition Guide Specifications for Aluminum Highway Bridges-1991 Edition Guide Specifications for Design and Construction of Segmental Concrete Bridges, 2nd Edition-1999 Edition Guide Specifications for Design of Pedestrian Bridges, 1997 Edition Guide Specifications for Distribution of Loads for Highway Bridges-1994 Edition Guide Specifications for Fatigue Evaluation of Existing Steel Bridges-1990 Edition Guide Specifications for Highway Bridge Fabrication with HPS070W Steel2000 Edition Guide Specifications for Seismic Isolation Design, 2nd Edition-1999 Edition Guide Specifications for Strength Design of Truss Bridges (Load Factor Design)-1985 Edition Guide Specifications for Strength Evaluation of Existing Steel and Concrete Bridges-1989 Edition Guide Specifications for Structural Design of Sound Barriers- I 989 Edition Guide Specification for the Design of Stress-Laminated Wood Decks-1991 Edition Guidelines for Bridge Management Systems-1993 Edition Manual for Condition Evaluation of Bridges-2000 Edition
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Movable Bridge Inspection, Evaluation and Maintenance Manual-1998 Edition Standard Specifications for Movable Highway Bridges-1988 Edition
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Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals, 4th Edition-2001 Edition Additional bridges and structures publications prepared and published by other AASHTO committees and task forces are as follows:
Guide Specifications for Cathodic Protection of Concrete Bridge Decks-1994 Edition Guide Specifications for Polymer Concrete Bridge Deck Overlays-1995 Edition Guide Specifications for Shot crete Repair of Highway Bridges-1998 Edition Inspectors' Guide for Shotcrete Repair of Bridges-1999 Edition Manual for Corrosion Protection of Concrete Components in Bridges-1992 Edition 1\vo Parts: Guide Specifications for Concrete Overlay Pavements and Bridge Decks-1990 Edition AASHTO Mailltenance Manual: The Maintenance and Management of Roadways and Bridges-1999 Edition
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The following have served as chairmen of the Committee since its inception in 1921: Messrs, E.R Kelley, who pioneered the work of the Committee, Albin L. Gemeny, R. B. McMinn, Raymond Archiband, G. S. Paxson, E. M. Johnson, Ward Goodman, Charles Matlock, Joseph S. Jones, Sidney Poleynard, Jack Freidenrich, Henry W. Derthick, Robert C. Cassano, Clellon Loveall. James E. Siebels, David Pope, and Tom Lulay. The Committee expresses its sincere appreciation of the work of these men and of those active members of the past, whose names, because of retirement, are no longer on the roll. Suggestions for the improvement of the specifications are welcomed. They should be sent to the Chairman, Subcommittee on Bridges and Structures, AASHTO, 444 North Capitol Street, N.W., Suite 249, Washington, D.C. 20001. Inquiries as to the intent or application of the specifications should be sent to the same address. ABBREVIATIONS AASHTO ACI AISC AITC ASCE ASME ASTM ANSI AWS AWPA CRSI
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NOS NFPA RMA SAE SSPC WPA
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WRI WWPA
-American Association of State Highway and Transportation Officials -American Concrete Institute -American Institute of Steel Construction -American Institute of Timber Construction -American Society of Civil Engineers -American Society of Mechanical Engineers -American Society for Testing and Materials -American National Standards Institute -American Welding Society -American Wood Preservers Association -Concrete Reinforcing Steel Institute -Commercial Standards -National Design Specifications for Stress Grade Lumber and Its Fastenings -National Forest Products Association -Rubber Manufacturers Association -Society of Automotive Engineers -Steel Structures Painting Council -Western Pine Association -Wire Reinforcement Institute -Western Wood Products Association
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1997 Interim Specifications Table of Contents The 1997 Interim Specifications include the following revisions and additions to articles of the 16th edition of the Standard Specifications for Highway Bridges, 1996. DMSION I-DESIGN PAGE
ARTICLE
SECTION 5 ........................................................... 111 SECTION 7 ........................................................... 155 8.16.4.4 .............................................................. 177 8.16.8.3 .............................................................. 183 8.17.4 .............................................................. 184.2 8.32.2.2 and 8.32.2.5 ...... ·............................................. 193 9.16.1 ............................................................... 203 9.17.4.1 .............................................................. 207 10.2 ................................................................. 223 10.32 ....... ; ........................................................ 254 10.34.3.2.1, 10.34.3.2.2 and Figure 10.34.3.1A ...... ·.· ...................... 258 10.34.5.1 and 10.34.5.2 ................................................. 260 10.38.1.7 ............................................................. 265 10.48.4.1 ............................................................. 280 10.48.6.1 ........................................................... 281.1 10.49.3.1, 10.49.3.2 and 10.50 ........................................ 283-284 10.61 ................................................................ 295 12.4.1.4 .............................................................. 303 12.6.I.4 .............................................................. 307 12.7 ................................................................. 308 12.8 ................................................................. 313 SECTION 14 ......................................................... 343 17.I.2 ............................................................... 355 17.4.6 ............................................................... 363 17.4.7 .............................................................. 370.I I 7.6.4.7 .............................................................. 372 I 8.4.3. I .............................................................. 38 I
DIVISION II-CONSTRUCTION 3.1.3 ................................................................ 433 SECTION 5 .......................................................... 449 SECTION 7 .......................................................... 463 SECTION 18 ......................................................... 563 COMMENTARIES: DIVISION I: SECTIONS 8, 10, 12, 14, I7 AND 18 ....... : . ............C-11-C-30 DIVISION II: SECTIONS 3 AND I 8 ... ·............................. C-31-C-35
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AASHTO STANDARD SPECIFICATIONS TABLE OF CONTENTS DIVISION I DESIGN SECTION 1-GENERAL PROVISIONS
1.1 1.1.1 1.1.2 1.2 1.3 1.3.1 1.3.2 1.3.2.1 1.3.2.2 1.3.2.3
1.4 1.5 1.6 1.6.1 1.6.2 1.7
1.8 1.9
DESIGN ANALYSIS AND GENERAL STRUCTURAL INTEGRITY FOR BRIDGES ........................... 3 Design Analysis .............................................3 Structural Integrity .......................................... 3 BRIDGE LOCATIONS ........................................ 3 WATERWAYS ................................................ 3 General .................................................... 3 Hydraulic Studies .......................................... .4 Site Data .................................................4 Hydrologic Analysis ....................................... .4 Hydraulic Analysis ........................................ .4
CULVERT LOCATION, LENGTH, AND WATERWAY OPENINGS . .4 ROADWAY DRAINAGE .......................................4 RAILROAD OVERPASSES ................................... .4 Clearances ................................................. 4 Blast Protection ............................................. 4 SUPERELEVATION .......................................... 5 FLOOR SURFACES ........................................... 5 UTILITIES ..................................................5
SECTION 2-GENERAL FEATURES OF DESIGN 2.1 2.1.1 2.1.2 2.2 2.2.1 2.2.2 2.2.3 2.2.4 2.2.5 2.3 2.3.1 2.3.2 2.4 2.4.1 2.4.2 2.4.3 2.5 2.5.1 2.5.2 2.5.3 2.5.4 2.6
GENERAL ...................................................7 Notations ..................................................7 Width of Roadway and Sidewalk ..............................7 STANDARD HIGHWAY CLEARANCES-GENERAL ............. 7 Navigational ................................................7 Roadway Width .............................................7 Vertical Clearance ...........................................7 Other ..................................................... 7 Curbs and Sidewalks ........................................ 8 IDGHWAY CLEARANCES FOR BRIDGES ...................... 8 Width ..................................................... 8 Vertical Clearance ........................................... 8 IDGHWAY CLEARANCES FOR UNDERPASSES ................. 8 Width ..................................................... 8 Vertical Clearance ........................................... 8 Curbs ..................................................... 8 HIGHWAY CLEARANCES FOR TUNNELS ......................8 Roadway Width .............................................8 Clearance between Walls .................................... l 0 Vertical Clearance .......................................... I 0 Curbs .................................................... 10 IDGHWAY CLEARANCES FOR DEPRESSED ROADWAYS ....... I 0 ix
CONTENTS
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2.6.1 2.6.2 2.6.3 2.7 2.7.1 2.7.1.1 2.7.1.2 2.7.1.3 2.7.2 2.7.2.1 2.7.2.2 2.7.3 2.7.3.1 2.7.3.2 2.7.4
Roadway Width ............................................ I 0 Clearance between Walls .................................... 10 Curbs .................................................... IO RAILINGS ................................ · . · .. · · · .. · · · . · · · .1 0 Vehicular Railing ........................................... I 0 General ................................................. IO Geometry ................................................ I 0 Loads ................................................... I I Bicycle Railing ............................................. 11 General ................................................. I 1 Geometry and Loads ....................................... I I Pedestrian Railing .......................................... 12 General ................................................. I2 Geometry and Loads ....................................... 13 Structural Specifications and Guidelines ....................... 13
SECTION 3-LOADS PART A-TYPES OF LOADS 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.7.1 3.7.2 3.7.3 3.7.4 3.7.5 3.7.6 3.8 3.8.1 3.8.1.1 3.8.1.2 3.8.2
3.9 3.10
3.11 3.11. I 3.11.2 3.11.3 3.11.4 3.12 3.13 3.14 3.14.1 3.14.2 3.I4.3 3.15
NOTATIONS ................................................ 17 GENERAL .................................................. 19 DEAD LOAD ................................................ 19 LIVE LOAD ................................................ 20 OVERLOAD PROVISIONS ...................................20 TRAFFIC LANES ...........................................20 HIGHWAY LOADS .......................................... 20 Standard Truck and Lane Loads .............................. 20 Classes of Loading .......................................... 21 Designation of Loadings ..................................... 21 Minimum Loading ......................................... 21 H Loading ................................................ 21 HS Loading ............................................... 21 IMPACT .................................................... 21 Application ................................................ 21 Group A-Impact shall be included ........................... 2I Group B-Impact shall not be included ........................2I Impact Formula ...........................................21 LONGITUDINAL FORCES ...................................23 CENTRIFUGAL FORCES .................................... 25 APPLICATION OF LIVE LOAD ............................... 25 'I'raffic Lane Units .......................................... 25 Number and Position of'I'raffic Lane Units ..................... 25 Lane Loads on Continuous Spans ............................. 25 Loading for Maximum Stress ................................ 25 REDUCTION IN LOAD INTENSITY ........................... 25 ELECTRIC RAILWAY LOADS ................................26 SIDEWALK, CURB, AND RAILING LOADING .................. 26 Sidewalk Loading ..........................................26 Curb Loading ............................................. 26 Railing Loading ............................................ 26 WIND LOADS ............................................... 26
Division I
CONTENTS
Division I 3.15.1 3.15.1.1 3.15.1.2 3.15.2 3.15.2.1 3.15.2.2 3.15.3 3.16 3.17 3.18 3.18.1 3.18.1.1 3.18.1.2 3.18.1.3 3.18.2 3.18.2.1 3.18.2.2 3.18.2.3 3.19 3.20 3.21
Superstructure Design ......................................26 Group II and Group V Loadings .............................. 26 Group III and Group VI Loadings ............................26 Substructure Design ........................................27 Forces from Superstructure ..................................27 Forces Applied Directly to the Substructure ..................... 27 Overturning Forces .........................................27 THERMAL FORCES ......................................... 28 UPLIFT ....................................................28 FORCES FROM STREAM CURRENT AND FLOATING ICE, AND DRIFT CONDITIONS ...........................28 Force of Stream Current on Piers .............................28 Stream Pressure ...........................................28 Pressure Components ...................................... 28 Drift Lodged Against Pier ................................... 28 Force of Ice on Piers ........................................29 General ................................................. 29 Dynamic Ice Force ........................................ 29 Static Ice Pressure .........................................30 BUOYANCY ................................................ 30 EARTH PRESSURE ..........................................30 EARTHQUAKES ............................................30 PART B-COMBINATIONS OF LOADS
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COMBINATIONS OF LOADS ................................. 30 PART C-DISTRIBUTION OF LOADS
DISTRIBUTION OF LOADS TO STRINGERS, LONGITUDINAL BEAMS, AND FLOOR BEAMS ........................32 Position of Loads for Shear .................................. 32 3.23.1 Bending Moments in Stringers and Longitudinal Beams ......... .32 3.23.2 General ................................................. 32 3.23.2.1 Interior Stringers and Beams ................................ 32 3.23.2.2 Outside Roadway Stringers and Beams ........................ 32 3.23.2.3 Steel-Timber-Concrete T-Beams ............................ 32 3.23.2.3.1 Concrete Box Girders .................................... 33 3.23.2.3.2 Total Capacity of Stringers and Beams .......................33 3.23.2.3.3 Bending Moments in Floor Beams (Transverse) .................34 3.23.3 Precast Concrete Beams Used in Multi-Beam Decks ............. 34 3.23.4 DISTRIBUTION OF LOADS AND DESIGN OF CONCRETE 3.24 SLABS .............................................35 Span Lengths .............................................. 35 3.24.1 Edge Distance of Wheel Loads ................................35 3.24.2 Bending Moment ........................................... 35 3.24.3 Case A-Main Reinforcement Perpendicular to Traffic 3.24.3.1 (Spans 2 to 24 Feet Inclusive) ............................ 36 Case B-Main Reinforcement Parallel to Traffic .................36 3.24.3.2 Shear and Bond ............................................ 36 3.24.4 Cantilever Slabs ........................................... 36 3.24.5 Truck Loads .............................................36 3.24.5.1 Case A-Reinforcement Perpendicular to Traffic .............. 36 3.24.5.1.1 Case B-Reinforcement Parallel to Traffic ................... 36 3.24.5.1.2
3.23
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CONTENTS
xii 3.24.5.2 3.24.6 3.24.7 3.24.8 3.24.9 3.24.10 3.25 3.25.1 3.25.2 3.25.3 3.25.3.1 3.25.3.2 3.25.3.3 3.25.3.4 3.25.4 3.26 3.26.1 3.26.2 3.26.3 3.27 3.27.1 3.27.2 3.27.3 3.28 3.28.1 3.28.2 3.29 3.30
Railing Loads ............................................36 Slabs Supported on Four Sides ............................... 37 Median Slabs ..............................................37 Longitudinal Edge Beams ................................... 37 Unsupported Transverse Edges ...............................37 Distribution Reinforcement ..................................37 DISTRIBUTION OF WHEEL LOADS ON TIMBER FLOORING ...38 'Iransverse Flooring ........................................38 Plank and Nail Laminated Longitudinal Flooring ...............39 Longitudinal Glued Laminated Timber Decks .................. 39 Bending Moment ......................................... 39 Shear ...................................................40 Deflections ..............................................40 Stiffener Arrangement ..................................... .40 Continuous Flooring ....................................... .40 DISTRIBUTION OF WHEEL LOADS AND DESIGN OF COMPOSITE WOOD-CONCRETE MEMBERS ........ .40 Distribution of Concentrated Loads for Bending Moment and Shear ...........................................40 Distribution of Bending Moments in Continuous Spans .......... .40 Design ....................................................40 DISTRffiUTION OF WHEEL LOADS ON STEEL GRID FLOORS ...................................... 41 General ...................................................41 Floors Filled with Concrete ................................. .41 Open Floors ...............................................41 DISTRIBUTION OF LOADS FOR BENDING MOMENT IN SPREAD BOX GIRDERS ......................... .41 Interior Beams .............................................41 Exterior Beams ............................................41 MOMENTS, SHEARS, AND REACTIONS ......................41 TIRE CONTACT AREA ..................................... .42
SECTION 4-FOUNDATIONS
PART A-GENERAL REQUIREMENTS AND MATERIALS 4.1 4.2 4.2.1 4.2.2 4.2.2.1 4.2.2.2 4.2.2.3 4.2.3 4.3 4.3.1 4.3.2 4.3.3 4.3.4 4.3.5
GENERAL ..................................................43 FOUNDATION TYPE AND CAPACITY ........................ .43 Selection of Foundation Type .................................43 Foundation Capacity ...................................... .43 Bearing Capacity ..........................................43 Settlement ...............................................43 Overall Stability ......................................... .43 Soil, Rock, and Other Problem Conditions .................... .43 SUBSURFACE EXPLORATION AND TESTING PROGRAMS ........................................43 General Requirements ..................................... .43 Minimum Depth ...........................................44 Minimum Coverage ........................................45 Laboratory Thsting .........................................45 Scour ....................................................45
Division I
Division I
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CONTENTS PART B-SERVICE LOAD DESIGN METHOD ALLOWABLE STRESS DESIGN SPREAD FOOTINGS .........................................45 4.4 General ...................................................45 4.4.1 Applicability .............................................45 4.4.1.1 Footings Supporting Non-Rectangular Columns or Piers ..........45 4.4.1.2 Footings in Fill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........45 4.4.1.3 Footings in Sloped Portions of Embankments .................. .45 4.4.1.4 Distribution of Bearing Pressure ............................. .45 4.4.1.5 Notations .................................................45 4.4.2 Design Terminology ........................................ 48 4.4.3 Soil and Rock Property Selection ............................ .48 4.4.4 Depth ....................................................48 4.4.5 Minimum Embedment and Bench Width .......................48 4.4.5.1 Scour Protection ..........................................49 4.4.5.2 Footing Excavations .......................................49 4.4.5.3 Piping ..................................................49 4.4.5.4 Anchorage ................................................49 4.4.6 Geotechnical Design on Soil ................................. .49 4.4.7 Bearing Capacity ..........................................49 4.4.7.1 Factors Affecting Bearing Capacity .........................50 4.4.7.1.1 Eccentric Loading .....................................50 4.4.7.1.1.1 Footing Shape ........................................ 51 4.4.7.1.1.2 Inclined Loading ...................................... 51 4.4.7 .1.1.3 Ground Surface Slope .................................. 51 4.4.7 .1.1.4 Embedment Depth ....................................51 4.4.7.1.1.5 Ground Water ........................................55 4.4.7.1.1.6 Layered Soils ........................................55 4.4.7.1.1.7 Inclined Base .........................................57 4.4. 7.1.1.8 Factors of Safety ........................................ 57 4.4.7.1.2 Settlement ............................................... 57 4.4.7.2 Stress Distribution .......................................57 4.4.7.2.1 Elastic Settlement .......................................58 4.4.7.2.2 Consolidation Settlement .................................58 4.4.7.2.3 Secondary Settlement ....................................61 4.4.7.2.4 Tolerable Movement .....................................61 4.4.7.2.5 Dynamic Ground Stability .................................. 61 4.4.7.3 Geotechnical Design on Rock .................................61 4.4.8 Bearing Capacity ..........................................62 4.4.8.1 Footings on Competent Rock ..............................62 4.4.8.1.! Footings on Broken or Jointe~ Rock ........................62 4.4.8.1.2 Factors of Safety ........................................63 4.4.8.1.3 Settlement ...............................................63 4.4.8.2 Footings on Competent Rock ..............................63 4.4.8.2.1 Footings on Broken or Jointed Rock ........................63 4.4.8.2.2 Tolerable Movement .....................................64 4.4.8.2.3 Overall Stability ...........................................64 4.4.9 Dynamic/Seismic Design .....................................66 4.4.10 Structural Design ..........................................66 4.4.11 Loads and Reactions .......................................66 4.4.11.1 Action of Loads and Reactions .............................66 4.4.11.1.1 Isolated and Multiple Footing Reactions .....................67 4.4.11.1.2
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Division I
CONTENTS
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4.4.11.2 4.4.11.2.1 4.4.11.2.2 4.4.11.3 4.4.11.3.1 4.4.11.3.2 4.4.11.4 4.4.11.4.1 4.4.11.4.2 4.4.11.5 4.4.11.5.1 4.4.11.5.2 4.4.11.5.3 4.4.11.5.4 4.4.11.5.5 4.4.11.5.6 4.4.11.5.7 4.4.11.6 4.4.11.6.1 4.4.1 1.6.2 4.5 4.5.1 4.5.1.1 4.5.1.2 4.5.1.3 4.5.1.4 4.5.1.5 4.5.1.6 4.5.1.7 4.5.1.8 4.5.2 4.5.2.1 4.5.2.2 4.5.2.3 4.5.2.4 4.5.3 4.5.4 4.5.5 4.5.6 4.5.6.1 4.5.6.1.1 4.5.6.1.2 4.5.6.1.3 4.5.6.1.4 4.5.6.2 4.5.6.3 4.5.6.4 4.5.6.5 4.5.6.6 4.5.6.6.1 4.5.6.6.2 4.5.6.7 4.5.6.7.1
Moments ................................................67 Critical Section .........................................67 Distribution of Reinforcement .............................67 Shear ...................................................67 Critical Section .........................................67 Footings on Piles or Drilled Shafts ..........................67 Development of Reinforcement ..............................67 Development Length .....................................67 Critical Section .........................................67 Transfer of Force at Base of Column ..........................67 Transfer of Force ........................................67 Lateral Forces ..........................................67 Bearing ...............................................68 Reinforcement ..........................................68 Dowel Size ............................................68 Development Length .....................................68 Splicing ..................... ·..........................68 Unreinforced Concrete Footings ..............................68 Design Stress ...........................................68 Pedestals ..............................................68 DRIVEN PILES .............................................68 General ...................................................68 Application ..............................................68 Materials ................................................68 Penetration ..............................................68 Lateral Tip Restraint .......................................69 Estimated Lengths .........................................69 Estimated and Minimum Tip Elevation ........................69 Piles Through Embankment Fill ..............................69 Test Piles ................................................69 Pile 'I'ypes .................................................69 Friction Piles .............................................69 End Bearing Piles .........................................69 Combination Friction and End Bearing Piles ....................69 Batter Piles . . ............................................69 Notations .................................................69 Design Terminology ........................................70 Selection of Soil and Rock Properties ..........................70 Selection of Design Pile Capacity ............... 70 Ultimate Geotechnical Capacity ..... 70 Factors Affecting Axial Capacity .. 70 Axial Capacity in Cohesive Soils .. 70 Axial Capacity in Cohesionless Soils ........................70 Axial Capacity on Rock .................................. 70 Factor of Safety Selection . . . . . . . . . . . . . . . . . . . . . . ............. 71 Settlement ............................................... 71 Group Pile Loading ........................................71 Lateral Loads on Piles ............................. 72 Uplift Loads on Piles .......... 72 Single Pile ...... 72 72 Pile Group ............. 72 Vertical Ground Movement ..... Negative Skin Friction .......... 72 0
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Division I
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CONTENTS 4.5.6.7.2 4.5.6.8 4.5.7 4.5.7.1 4.5.7.2 4.5.7.3 4.5.7.4 4.5.7.5 4.5.8 4.5.9 4.5.10 4.5.11 4.5.12 4.5.13 4.5.14 4.5.14.1 4.5.14.2 4.5.14.3 4.5.15 4.5.15.1 4.5.15.1.1 4.5.15.1.2 4.5.15.2 4.5.16 4.5.16.1 4.5.16.2 4.5.16.3 4.5.16.4 4.5.16.5 4.5.16.6 4.5.16.7 4.5.16.8 4.5.16.9 4.5.17 4.5.17.1 4.5.17.2 4.5.17.3 4.5.17.4 4.5.17.5 4.5.17.6 4.5.17.7 4.5.17.8 4.5.18 4.5.18.1 4.5.18.2 4.5.18.3 4.5.18.4 4.5.18.5 4.5.19 4.5.19.1 4.5.19.2 4.5.19.3 4.5.19.4
Expansive Soil .........................................72 Dynamic/Seismic Design ...................................73 Structural Capacity of Pile Section ............................ 73 Load Capacity Requirements ................................73 Piles Extending Above Ground Surface ........................73 Allowable Stress in Piles ...................................73 Cross-Section Adjustment for Corrosion .......................73 Scour ................................................... 74 Protection Against Corrosion and Abrasion .....................74 Wave Equation Analysis .....................................74 Dynamic Monitoring ........................................ 74 Maximum Allowable Driving Stresses .........................74 Tolerable Movement ........................................74 Buoyancy .................................................74 Protection Against Deterioration ..............................74 Steel Piles ............................................... 74 Concrete Piles ............................................ 75 Timber Piles ............................................. 75 Spacing, Clearances, and Embedment .........................75 Pile Footings .............................................75 Pile Spacing ...........................................75 Minimum Projection into Cap ............................. 75 Bent Caps ...............................................75
Precast Concrete Piles ......................................75 Size and Shape ........................................... 75 Minimum Area ...........................................75 Minimum Diameter of Tapered Piles ..........................75 Driving Points ............................................75 Vertical Reinforcement .....................................75 Spiral Reinforcement ......................................75 Reinforcement Cover ......................................76 Splices ..................................................76 Handling Stresses .........................................76 Cast-in-Place Concrete Piles ................................. 76 Materials ................................................ 76 Shape ...................................................76 Minimum Area ...........................................76 General Reinforcement Requirements .........................76 Reinforcement into Superstructure ............................76 Shell Requirements ........................................76 Splices ..................................................76 Reinforcement Cover ...................................... 76 Steel H-Piles ............................................... 76 Metal Thickness ..........................................76 Splices .................................................. 76 Caps ....................................................77 Lugs, Scabs, and Core-Stoppers .............................. 77 Point Attachments .........................................77 Unfilled Thbular Steel Piles .................................. 77 Metal Thickness ..........................................77 Splices ..................................................77 Driving ................................................. 77 Column Action ...........................................77
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CONTENTS Prestressed Concrete Piles ...................................77 4.5.20 Size and Shape ...........................................77 4.5.20.1 Main Reinforcement .......................................77 4.5.20.2 Vertical Reinforcement .....................................77 4.5.20.3 Hollow Cylinder Piles ......................................78 4.5.20.4 Splices ..................................................78 4.5.20.5 4.5.21 Timber Piles ...............................................78 4.5.21.1 Materials ................................................78 4.5.21.2 Limitations on Untreated Timber Pile Use ......................78 4.5.21.3 Limitations on Treated Timber Pile Use ........................78 4.6 DRILLED SHAFTS ..........................................78 4.6.1 General ................................................... 78 4.6.1.1 Application ..............................................78 4.6.1.2 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... 78 4.6.1.3 Construction ............................................. 78 4.6.1.4 Embedment ..............................................78 4.6.1.5 Shaft Diameter ...........................................78 4.6.1.6 Batter Shafts .............................................78 4.6.1.7 Shafts Through Embankment Fill .............................79 4.6.2 Notations .................................................79 4.6.3 Design Terminology ............ ·............................ 80 4.6.4 Selection of Soil and Rock Properties .......................... 80 4.6.4.1 Presumptive Values ........................................80 4.6.4.2 Measured Values .......................................... 80 4.6.5 Geotechnical Design ........................................80 4.6.5.1 Axial Capacity in Soil ...................................... 80 4.6.5.1.1 Side Resistance in Cohesive Soil ........................... 8 1 4.6.5.1.2 Side Resistance in Cohesionless Soil ........................81 4.6.5.1.3 Tip Resistance in Cohesive Soil ............................82 4.6.5.1.4 Tip Resistance in Cohesionless Soil .........................83 4.6.5.2 Factors Affecting Axial Capacity in Soil ....................... 83 4.6.5.2.1 Soil Layering and Variable Soil Strength with Depth ............83 4.6.5.2.2 Ground Water .......................................... 83 4.6.5.2.3 Enlarged Bases .........................................83 4.6.5.2.4 Group Action ........................................... 83 4.6.5.2.4.1 Cohesive Soil ........................................ 83 4.6.5.2.4.2 Cohesionless Soil .....................................84 4.6.5.2.4.3 Group in Strong Soil Overlying Weaker Soil ................ 84 4.6.5.2.5 Vertical Ground Movement ................................84 4.6.5.2.6 Method of Construction ..................................84 4.6.5.3 Axial Capacity in Rock .....................................84 4.6.5.3.1 Side Resistance .........................................85 4.6.5.3.2 Tip Resistance .......................................... 85 4.6.5.3.3 Factors Affecting Axial Capacity in Rock .................... 85 4.6.5.3.3.1 Rock Stratification .................................... 85 4.6.5.3.3.2 Rock Mass Discontinuities ..............................86 4.6.5.3.3.3 Method of Construction ................................ 86 4.6.5.4 Factors of Safety ............. :............................. 86 4.6.5.5 Deformation of Axially Loaded Shafts ......................... 86 4.6.5.5.1 Shafts in Soil ........................................... 86 4.6.5.5.1.1 Cohesive Soil ........................................86 4.6.5.5.1.2 Cohesionless Soil ..................................... 86 4.6.5.5.1.3 Mixed Soil Profile .....................................87 4.6.5.5.2 Shafts Socketed into Rock ................................87
Division I
Division I
0
CONTENTS 4.6.5.5.3 Tolerable Movement ..................................... 87 Lateral Loading ........................................... 88 4.6.5.6 Factors Affecting Laterally Loaded Shafts ....................88 4.6.5.6.1 Soil Layering ......................................... 88 4.6.5.6.1.1 Ground Water ........................................ 88 4.6.5.6.1.2 Scour ............................................... 88 4.6.5.6.1.3 Group Action ......................................... 88 4.6.5.6.1.4 Cyclic Loading ....................................... 89 4.6.5.6.1.5 Combined Axial and Lateral Loading ...................... 89 4.6.5.6.1.6 Sloping Ground ....................................... 89 4.6.5.6.1.7 Tolerable Lateral Movements .............................. 89 4.6.5.6.2 Dynamic/Seismic Design ................................... 90 4.6.5.7 Structural Design and General Shaft Dimensions ................90 4.6.6 General .................................................90 4.6.6.1 Reinforcement ............................................90 4.6.6.2 Longitudinal Bar Spacing .................................90 4.6.6.2.1 Splices ................................................90 4.6.6.2.2 Transverse Reinforcement ................................90 4.6.6.2.3 Handling Stresses .......................................90 4.6.6.2.4 Reinforcement Cover ....................................90 4.6.6.2.5 Reinforcement into Superstructure .......................... 90 4.6.6.2.6 Enlarged Bases ........................................... 90 4.6.6.3 Center-to-Center Shaft Spacing .............................. 91 4.6.6.4 Load Testing .............................................. 91 4.6.7 General ................................................. 91 4.6.7.1 Load Testing Procedures .................................... 91 4.6.7.2 Load Test Method Selection ................................. 91 4.6.7.3 NOTE: Article Number Intentionally Not Used 4.7 PART C-STRENGTH DESIGN METHOD LOAD FACTOR DESIGN 4.8 4.9 4.10 4.10.1 4.10.2 4.10.3 4.10.4 4.10.5 4.10.6 4.11 4.11.1 4.11.1.1 4.11.1.2 4.11.1.3 4.11.1.4 4.11.1.5 4.11.1.6 4.11.1.7 4.11.1.8 4.11.1.9 4.11.2
SCOPE .....................................................91 DEFINITIONS ..............................................92 LIMIT STATES, LOAD FACTORS, AND RESISTANCE FACTORS ........................92 General ...................................................92 Serviceability Limit States ...................................92 Strength Limit States .......................................92 Strength Requirement ......................................93 Load Combinations and Load Factors .........................93 Performance Factors ........................................93 SPREAD FOOfiNGS .........................................93 General Considerations .....................................93 General .................................................93 Depth ...................................................93 Scour Protection ..........................................93 Frost Action .............................................. 93 Anchorage ...............................................93 Groundwater .............................................94 Uplift ...................................................94 Deterioration .............................................94 Nearby Structures .........................................95 Notations ..... : ....................................... · · · .95
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xviii
CONTENTS Movement Under Serviceability Limit States ...................97 4.11.3 General .................................................97 4.11.3.1 Loads ...................................................97 4.11.3.2 Movement Criteria ........................................97 4.11.3.3 Settlement Analyses .......................................97 4.11.3.4 4.11.3.4.1 Settlement of Footings on Cohesionless Soils .................97 4.11.3.4.2 Settlement of Footings on Cohesive Soils ....................97 4.11.3.4.3 Settlement of Footings on Rock ............................97 4.11.4 Safety Against Soil Failure ...................................97 4.11.4.1 Bearing Capacity of Foundation Soils .........................97 4.11.4.1.1 Theoretical Estimation ...................................98 4.11.4.1.2 Semi-empirical Procedures ................................98 4.11.4.1.3 Plate Loading Test .......................................98 4.11.4.1.4 Presumptive Values ......................................98 4.11.4.1.5 Effect of Load Eccentricity ................................98 4.11.4.1.6 Effect of Groundwater Table ...............................98 4.11.4.2 Bearing Capacity of Foundations on Rock ......................98 4.11.4.2.1 Semi-empirical Procedures ................................ 98 4.11.4.2.2 Analytic Method ....................................... 100 4.11.4.2.3 Load Test ............................................. 100 4.11.4.2.4 Presumptive Bearing Values .............................. 100 4.11.4.2.5 Effect of Load Eccentricity ............................... I00 4.11.4.3 Failure by Sliding ........................................ 100 4.11.4.4 Loss of Overall Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... I 00 4.11.5 Structural Capacity ....................................... 100 4.11.6 Construction Considerations for Shallow Foundations ........... 100 4.11.6.1 General ................................................ 100 4.11.6.2 Excavation Monitoring .................................... 100 4.11.6.3 Compaction Monitoring ................................... 100 4.12 DRIVEN PILES ............................................ 100 4.12.1 General .................................................. 100 4.12.2 Notations ................................................ 10 I 4.12.3 Selection of Design Pile Capacity ............................. 102 4.12.3.1 Factors Affecting Axial Capacity ............................ 102 4.12.3.1.1 Pile Penetration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... I02 4.12.3.1.2 Groundwater Table and Buoyancy ......................... 102 4.12.3.1.3 Effect of Settling Ground and Downdrag Forces .............. I02 4.12.3.1.4 Uplift ................................................ 103 4.12.3.2 Movement Under Serviceability Limit State ................... 103 4.12.3.2.1 General .............................................. 103 4.12.3.2.2 Tolerable Movement .................................... 103 4.12.3.2.3 Settlement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... I03 4.12.3.2.3a Cohesive Soil ....................................... I03 4.12.3.2.3b Cohesionless Soil .................................... 103 4.12.3.2.4 Lateral Displacement ................................... I03 4.12.3.3 Resistance at Strength Limit States ........................... I03 4.12.3.3.1 Axial Loading of Piles .................................. 103 4.12.3.3.2 Analytic Estimates of Pile Capacity ....................... .1 04 4.12.3.3.3 Pile of Capacity Estimates Based on In Situ Tests ............. 104 4.12.3.3.4 Piles Bearing on Rock ................................... I04 4.12.3.3.5 Pile Load Test ......................................... I04 4.12.3.3.6 Presumptive End Bearing Capacities ....................... 104 4.12.3.3.7 Uplift ................................................ 104
Division I
Division I
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CONTENTS 4.12.3.3.7a 4.12.3.3.7b 4.12.3.3.8 4.12.3.3.9 4.12.3.3.10 4.12.3.3.1 Oa 4.12.3.3.1 Ob 4.12.3.3.10c 4.12.3.3.11 4.12.4 4.12.4.1 4.12.5 4.13 4.13.1 4.13.2 4.13.3 4.13.3.1 4.13.3.1.1 4.13.3.1.2 4.13.3.2 4.13.3.2.1 4.13.3.2.2 4.13.3.2.3 4.13.3.2.3a 4.13.3.2.3b 4.13.3.2.4 4.13.3.3 4.13.3.3.1 4.13.3.3.2 4.13.3.3.3 4.13.3.3.4 4.13.3.3.5 4.13.3.3.6 4.13.3.3.6a 4.13.3.3.6b 4.13.3.3.7 4.13.3.3.8 4.13.3.3.8a 4.13.3.3.8b 4.13.3.3.8c 4.13.3.3.9 4.13.4 4.13.4.1
Single Pile Uplift Capacity ............................. 104 Pile Group Uplift Capacity ............................. 104 Lateral Load .......................................... 104 Batter Pile ............................................ 104 Group Capacity ........................................ 104 Cohesive Soil ......................... ~ ............. 104 Cohesionless Soil . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....... 105 Pile Group in Strong Soil Overlying a Weak or Compressible Soil .................................. 105 Dynamic/Seismic Design ................................ 105 Structural Design ......................................... 105 Buckling of Piles ......................................... I 05 Construction Considerations ................................ 105 DRILLED SHAFTS ......................................... 105 General .................................................. 105 Notations ................................................ 105 Geotechnical Design ....................................... 106 Factors Affecting Axial Capacity ............................ 107 Downdrag Loads ....................................... 107 Uplift ................................................ 107 Movement Under Serviceability Limit State ................... 107 General .............................................. I 07 Tolerable Movement .................................... I 07 Settlement ............................................ I 07 Settlement of Single Drilled Shafts ....................... 107 Group Settlement .................................... 107 Lateral Displacement ................................... 107 Resistance at Strength Limit States ........................... 107 Axial Loading of Drilled Shafts ........................... 107 Analytic Estimates of Drilled Shaft Capacity in Cohesive Soils ..................................... 107 Estimation of Drilled-Shaft Capacity in Cohesionless Soils ..... 107 Axial Capacity in Rock .................................. 107 Load Test ............................................. 108 Uplift Capacity ........................................ 108 Uplift Capacity of a Single Drilled Shaft .................. 108 Group Uplift Capacity ................................. 108 Lateral Load .......................................... 108 Group Capacity ........................................ 108 Cohesive Soil ....................................... 108 Cohesion less Soil .................................... 108 Group in Strong Soil Overlying Weaker Compressible Soil ... 108 Dynamic/Seismic Design ................................ 108 Structural Design ......................................... I08 Buckling of Drilled Shafts ................................. 109
SECTION 5-RETAINING WALLS
PART A-GENERAL REQUIREMENTS AND MATERIALS 5.1 5.2 5.2.1 5.2.1.1
GENERAL ................................................. 111 WALLTYPEANDBEHAVIOR ............................... Ill Selection of Wall Type ...................................... Ill Rigid Gravity and Semi-Gravity Walls ........................ Ill
xix
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5.2.1.2 5.2.1.3 5.2.1.4 5.2.1.5 5.2.2 5.2.2.1 5.2.2.2 5.2.2.3 5.2.2.4 5.2.3 5.3 5.3.1 5.3.2 5.3.3 5.3.4 5.3.5 5.4
Nongravity Cantilevered Walls .............................. 112 Anchored Walls .......................................... 113 Mechanically Stabilized Earth Walls ......................... 114 Prefabricated Modular Walls ................................ 115 Wall Capacity ........................................... . 115 Bearing Capacity ......................................... 115 Settlement ............................................. . 115 Overall Stability ........................................ . 115 Tolerable Deformations .................................... 116 SoU, Rock, and Other Problem Conditions .................... 116 SUBSURFACE EXPLORATION AND TESTING PROGRAMS .... 116 General Requirements ..................................... 117 Minimum Depth .......................................... 117 Minimum Coverage ....................................... 117 Laboratory Testing ........................................ 117 Scour .................................................... 117 NOfATIONS ............................................... 117
PART B-SERVICE LOAD DESIGN METHOD ALLOWABLE STRESS DESIGN 5.5 5.5.1 5.5.2 5.5.3 5.5.4 5.5.5 5.5.6 5.5.6.1 5.5.6.2 5.5.6.3 5.5.6.4 5.5.6.5 5.5.7 5.5.8 5.6 5.6.1 5.6.2 5.6.3 5.6.4 5.6.5 5.6.6 5.6.7 5.6.8 5.7 5.7.1 5.7.2 5.7.3 5. 7.4 5.7.5 5.7.6 5.7 .6.1 5.7 .6.2 5.7.7 5. 7.8 5.7.9
RIGID GRAVITY AND SEMI-GRAVITY WALL DESIGN ........ 121 Design Terminology ....................................... 121 Earth Pressure and Surcharge Loadings ..................... .121 Water Pressure and Drainage .· .............................. 126 Seismic Pressure .......................................... 126 Structure Dimensions and External Stability ................... 126 Structure Design ...... ~ .................................. .126 Base or Footing Slabs ..................................... 126 Wall Stems ............................................. 126 Counterforts and Buttresses ................................ 128 Reinforcement ........................................... 128 Expansion and Contraction Joints ............................ 129 Backfill .................................................. 129 Overall Stability .......................................... 129 NONGRAVITY CANTILEVERED WALL DESIGN .............. 129 Design Terminology ....................................... 129 Earth Pressure and Surcharge Loadings ...................... 129 Water Pressure and Drainage ............................... 132 Seismic Pressure .......................................... 132 Structure Dimensions and External Stability ................... 132 Structure Design .......................................... 132 Overall Stability .......................................... 133 Corrosion Protection ....................................... 133 ANCHORED WALL DESIGN ................................ 133 Design Terminology ....................................... 133 Earth Pressure and Surcharge Loadings ....................... 133 Water Pressure and Drainage ............................... 136 Seismic Pressure .......................................... 136 Structure Dimensions and External Stability ................... 136 Structure Design .......................................... 136 General ................................................ 136 Anchor Design .......................................... 136 Overall Stability .......................................... 138 Corrosion Protection ...................................... .138 Anchor Load Testing and Stressing ........................... 138
Division I
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CONTENTS 5.8 5.8.1 5.8.2 5.8.3 5.8.4 5.8.4.1 5.8.4.2 5.8.5 5.8.5.1 5.8.5.2 5.8.6 5.8.6.1 5.8.6.1.1 5.8.6.1.2 5.8.6.2 5.8.6.2.1 5.8.6.2.2 5.8.7 5.8.7.1 5.8.7.2 5.8.8 5.8.8.1 5.8.8.2 5.8.8.3 5.8.9 5.8.9.1 5.8.9.2 5.8.9.3 5.8.10 5.8.11 5.8.12 5.8.12.1 5.8.12.2 5.8.12.3 5.8.12.4 5.9 5.9.1 5.9.2 5.9.3 5.9.4 5.9.5
MECHANICALLY STABILIZED EARTH WALL DESIGN ....... 138 Structure Dimensions ...................................... 138 External Stability ......................................... 138 Bearing Capacity and Foundation Stability .................... 143 Calculation of Loads for Internal Stability Design .............. 144 Calculation of Maximum Reinforcement Loads ................. 146 Determination of Reinforcement Tensile Load at the Connection to the Wall Face ...................................... 147 Determination of Reinforcement Length Required for Internal Stability .................................... 147 Location of Zone of Maximum Stress ....................... .147 Soil Reinforcement Pullout Design ......................... .148 Reinforcement Strength Design ............................. .149 Design Life Requirements ................................. 152 Steel Reinforcement .................................... 152 Geosynthetic Reinforcement .............................. 155 Al1owable Stresses ....................................... 157 Steel Reinforcements ................................... 157 Geosynthetic Reinforcements ............................. 157 Soil Reinforcement/Facing Connection Strength Design ......... 158 Connection Strength for Steel Soil Reinforcements ............. 158 Connection Strength for Geosynthetic Reinforcements . . . . . . . . . . 158 Design of Facing Elements ................................. 160 Design of Stiff or Rigid Concrete, Steel, and Timber Facings ...... 160 Design of Flexible Wall Facings ............................. 160 Corrosion Issues for MSE Facing Design ...................... 161 Seismic Design ............................................ 161 External Stability ........................................ 161 Internal Stability ......................................... 163 Facing/Soil Reinforcement Connection Design for Seismic Loads ....................................... 164 Determination of Lateral Wall Displacements .................. 164 Drainage ................................................. 164 Special Loading Conditions ................................. 165 Concentrated Dead Loads .................................. 165 Traffic Loads and Barriers ................................. 169 Hydrostatic Pressures ..................................... 170 Design for Presence of Obstructions in the Reinforced Soil Zone ........................................... 171 PREFABRICATED MODULAR WALL DESIGN ................ 171 Structure Dimensions ...................................... 171 External Stabllity ......................................... 171 Bearing Capacity and Foundation Stabllity .................... 173 Allowable Stresses ......................................... 174 Drainage ................................................. 174
PART C-STRENGTH DESIGN METHOD LOAD FACTOR DESIGN 5.10 5.11 5.12 5.13
SCOPE .................................................... 174 DEFINITIONS ............................................. 174 NOTATIONS ........................................... ·.· .174 LIMIT STATES, LOAD FACTORS AND RESISTANCE FACTORS ............................ 175
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CONTENTS
xxii 5.13.1 5.13.2 5.13.3 5.13.4 5.13.5 5.14 5.14.1 5.14.2 5.14.3 5.14.4 5.14.5 5.14.6 5.14.6.1 5.14.6.2 5.14.6.3 5.14.6.4 5.14.7 5.14.7.1 5.14.7.2 5.14.7.3 5.14.7.4 5.14.7.5 5.14.8
Serviceability Limit States .................................. 175 Strength Limit States ...................................... 175 Strength Requirement .................................... .175 Load Combinations and Load Factors ........................ 175 Performance Factors ....................................... 175 GRAVITY AND SEMI-GRAVITY WALL DESIGN, AND CANTILEVER WALL DESIGN ....................... 175 Earth Pressure Due to Backfill .............................. 175 Earth Pressure Due to Surcharge ........................... .176 Water Pressure and Drainage ............................... 176 Seismic Pressure .......................................... 176 Movement Under Serviceability Limit States .................. 176 Safety Against Soil Failure ................................. .176 Bearing Capacity Failure .................................. 177 Sliding ................................................. 177 Overturning ............................................. I 77 OveraU Stability (Revised Article 5.2.2.3) ..................... I 77 Safety Against Structural Failure ............................ 179 Base of Footing Slabs ..................................... 179 Wall Stems ............................................. 179 Counterforts and Buttresses ................................ I 79 Reinforcement ........................................... I 79 Expansion and Contraction Joints ........................... .179 Backfill . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... 179
SECTION 6-CULVERTS
6.1 6.2 6.2.1 6.2.2 6.3 6.4 6.5 6.6
CULVERT LOCATION, LENGTH, AND WATERWAY OPENINGS ........................................ 18I DEAD LOADS .............................................. 181 Culvert in trench, or culvert untrenched on yielding foundation ... 181 Culvert untrenched on unyielding foundation .................. 181 FOOTINGS ................................................ 181 DISTRIBUTION OF WHEEL LOADS THROUGH EARTH FILLS ..................................... 181 DISTRIBUTION REINFORCEMENT ......................... 181 DESIGN ................................................... 181
SECTION 7-8UBSTRUCTURES
PART A-GENERAL REQUIREMENTS AND MATERIALS 7.1 7.1.1 7.1.2 7.1.3 7.1.4 7.2
GENERAL ................................................. 183 Definition . . . . ............................................ 183 Loads ................................................... 183 Settlement ............................................... 183 Foundation and Retaining Wall Design ....................... 183 NO'I'ATIONS ............................................... 183
PART B-sERVICE LOAD DESIGN METHOD ALLOWABLE STRESS DESIGN 7.3 7.3.1
PmRS ..................................................... 183 Pier'JYpes ................................................ 183
DiVision I
CONTENTS
Division I
0
0
7.3.1.1 7.3.1.2 7.3.1.3 7.3.1.4 7.3.2 7.3.2.1 7.3.2.2 7.3.2.3 7.3.2.4 7.4 7.4.1 7.4.2 7.5 7.5.1 7.5.1.1 7.5.1.2 7.5.1.3 7.5.1.4 7.5.2 7.5.2.1 7.5.2.2 7.5.2.3 7.5.3 7.5.4 7.5.5 7.5.6 7.5.6.1 7.5.6.2
Solid Wall Piers .......................................... 183 Double Wall Piers ........................................ 183 Bent Piers .............................................. 184 Single-Column Piers ...................................... 184 Pier Protection ............................................ 184 Collision ............................................... 184 Collision Walls .......................................... 184 Scour .................................................. 184 Facing ................................................. 184 TUBULAR PIERS ... 0....••..•.....••...... 0....... 00...•• o184 Materials ......... o...•..... 0......................... 0. 0184 Configuration ................. 0• 0..•....•..•• 0•. 000•.•.. 0.184 ABUTMENTS ........ o•.. o0.....•..••.....•.•••••..•....... 184 Abutment Types .......... 0...........•....... 0.... 0•.•... 184 Stub Abutment ................................ 0••.. 0. 0.. 184 Partial-Depth Abutment .... 00. 0... 0•• 0..•. 0.. 0.•.. 0... 0... 184 Full-Depth Abutment ............. 0•. 0.••. 00o0•.. 00•• 0... 0184 Integral Abutment ..................... 0.••.•..••......... 185 Loading .. 0...... 0...•.......•........•.... 0.•.•. 00...... 185 Stability .............. 0..........•......••. 0.... 0•..•... 185 Reinforcement for Temperature ............................. 185 Drainage and Backfilling .................... 0......• 0....• 185 Integral Abutments ..... 0.....•. 0.. 0..•.. 00• 0•.... 000• 0.. 00185 Abutments on Mechanically Stabilized Earth Walls ............. 185 Abutments on Modular Systems ............................. 186 Wingwalls ...... 0.. 0..........•. 0•...... 00....•.•. 0. 0. 000.187 Length . 0...... 0........ 0.•......•..•..... 00•.. 0•• 0....• 187 Reinforcement . 0...•. 0••.......•...•...•....•.........•.. 187 PART C-STRENGTH DESIGN METHOD LOAD FACTOR DESIGN
7.6
GENERAL . 0. o.... 0..•.•• 0....•... 0•.••.••. 0•• 0•. 0.. 0•..••. 187
SECTION 8-REINFORCED CONCRETE
PART A-GENERAL REQUIREMENTS AND MATERIALS 8.1 8.1.1 8.1.2 801.3 8.2 8.3
APPLICATION .......... 0••....• 0..••••..•.•••.•••. 0...• 0•• 189 General ................................................. 0189 Notations . 0• 0..•. 0. 0... 0. 00.....•••...... 0•. 0•• 0. 0•..•••. 189 Definitions . 0•..• 0.•.• 0. 0.....•..•.•..•.•.. 0.•.. 0......• 0.192 CONCRETE ...... 0.•...•. 0•...••• 0••...• oo•...•...••••..• 0192 REINFORCEMENT ........ o•.... 0. o• o•...•. 0o.•••.. 0.... 0. o193
PART B-ANALYSIS 8.4 8o5 8.6 8.7 8.8 8.9 8.9.1
GENERAL ... 0.......••• 0..•.•.. 0...•••..•.•••.•••.. 0. o. oo.193 EXPANSION AND CONTRACTION o. o..• ooo••• o. o••• o. o..• o.• 193 STIFFNESS 0000• 00• 0. 00.. o..• oo.• oo.•.•.••• o•••••• o0. 0.••.• 193 MODULUS OF ELASTICITY AND POISSON'S RATIO. oo•.... oo193 SPAN LENGTH . 0. 0...... 0•... 0. 0•.•..•...•. 0..•••••• 0.... 0193 CONTROL OF DEFLECTIONS ..... 0...•. 0••... o... 0••... o•• 194 General ....... 0. 0.• 0...•• 0.. 0.••.....••.•... 0..•.••.• 0• 0.194
xxiii
CONTENTS
xxiv 8.9.2 8.9.3 8.10 8.10.1 8.10.2 8.11 8.12 8.13
Superstructure Depth Limitations ......................... · .194 SuperstrUcture Deftection Limitations ...................... · .194 COMPRESSION FLANGE WIDTH ........................... 194 T-Girder .............................. · · · · · · · · · · · · · · .·. · · .194 Box Girders ................................. ·. · · · · · · · · · · .194 SLAB AND WEB THICKNESS ............................... 194 DIAPHRAGMS ........................ ···· .. ·············· .195 COMPUTATION OF DEFLECTIONS ...............•........ .195
PART C-DESIGN GENERAL ........................................ · ..... · .. 195 8.14 Design Methods ........................................... 195 8.14.1 Composite Flexural Members ............................... 196 8.14.2 Concrete Arches .......................................... 196 8.14.3 SERVICE LOAD DESIGN METHOD (Allowable Stress Design) .... 197 8.15 General Requirements ...................................... 197 8.15.1 Allowable Stresses ......................................... 197 8.15.2 Concrete ............................................... 197 8.15.2.1 Flexure .............................................. 197 8.15.2.1.1 Shear ................................................ 197 8.15.2.1.2 Bearing Stress ......................................... 197 8.15.2.1.3 Reinforcement ........................................... 197 8.15.2.2 Flexure .................................................. 197 8.15.3 Compression Members ..................................... 197 8.15.4 Shear .................................................... 198 8.15.5 Shear Stress ............................................. 198 8.15.5.1 Shear Stress Carried by Concrete ............................ 198 8.15.5.2 Shear in Beams and One-Way Slabs and Footings ... : ......... 198 8.15.5.2.1 Shear in Compression Members ........................... 198 8.15.5.2.2 Shear in Tension Members ............................... 198 8.15.5.2.3 Shear in Lightweight Concrete ............................ 198 8.15.5.2.4 Shear Stress Carried by Shear Reinforcement .................. 199 8.15.5.3 Shear Friction ........................................... 199 8.15.5.4 Shear-Friction Design Method ............................ 199 8.15.5.4.3 Horizontal Shear Design for Composite Concrete 8.15.5.5 8.15.5.5.5 8.15.5.6 8.15.5.7 8.15.5.8 8.16 8.16.1 8.16.1.1 8.16.1.2 8.16.2 8.16.3 8.16.3.1 8.16.3.2 8~ 16.3.3 8.16.3.4 8.16.3.5 8.16.4
Flexural Members ....................................200 Ties for Horizontal Shear ................................200 Special Provisions for Slabs and Footings ..................... 200 Special Provisions for Slabs of Box Culverts ...................20 I Special Provisions for Brackets and Corbels ...................201 STRENGTH DESIGN METHOD (Load Factor Design) ...........202 Strength Requirements ..................................... 202 Required Strength ........................................202 Design Strength ..........................................202 Design Assumptions ....................................... 202 Flexure ..................................................203 Maximum Reinforcement of Flexural Members ................203 Rectangular Sections with Tension Reinforcement Only ..........203 Flanged Sections with Tension Reinforcement Only ............. 203
Rectangular Sections with Compression Reinforcement ..........204 Other Cross Sections ......................................204 Compression Members .....................................204
Division I
Division I
0 '
0
CONTENTS
8.16.4.1 8.16.4.2 8.16.4.2.1 8.16.4.2.2 8.16.4.2.3 8.16.4.2.4 8.16.4.3 8.16.4.4 8.16.5 8.16.5.1 8.16.5.2 8.16.6 8.16.6.1 8.16.6.2 8.16.6.2.1 8.16.6.2.2 8.16.6.2.3 8.16.6.2.4 8.16.6.3 8.16.6.4 8.16.6.4.4 8.16.6.5 8.16.6.5.5 8.16.6.6 8.16.6.7 8.16.6.8 8.16.7 8.16.8 8.16.8.1 8.16.8.2 8.16.8.3 8.16.8.4
General Requirements ..................................... 204 Compression Member Strengths .............................204 Pure Compression ...................................... 204 Pure Flexure .......................................... 205 Balanced Strain Conditions ............................... 205 Combined Flexure and Axial Load .........................205 Biaxial Loading .......................................... 205 Hollow Rectangular Compression Members ...................205
Slenderness Effects in Compression Members .................. 206 General Requirement.c; ..................................... 206 Approximate Evaluation of Slenderness Effects ................206 Shear ....................................................207 Shear Strength ........................................... 207 Shear Strength Provided by Concrete ......................... 208 Shear in Beams and One-Way Slabs and Footings ............. 208 Shear in Compression Members ........................... 208 Shear in Tension Members ...............................208 Shear in Lightweight Concrete ............................208 Shear Strength Provided by Shear Reinforcement ............... 208 Shear Friction ...........................................209 Shear-Friction Design Method ............................209 Horizontal Shear Strength for Composite Concrete Flexural Members ....................................210 Ties for Horizontal Shear ................................ 210 Special Provisions for Slabs and Footings ..................... 2 10 Special Provisions for Slabs of Box Culverts ................... 211 Special Provisions for Brackets and Corbels ................... 211 Bearing Strength ..........................................212
Serviceability Requirements ................................ 212 Application ............................................. 212 Service Load Stresses ..................................... 212 Fatigue Stress Limits ...................................... 212 Distribution of Flexural Reinforcement ....................... 212 PART D-REINFORCEMENT
8.17 8.17.1 8.17.2 8.17.2.1 8.17.2.2 8.17.2.3 8.17.3 8.17.4 8.18 8.18.1
REINFORCEMENT OF FLEXURAL MEMBERS ............... 213 Minimum Reinforcement ................................... 213 Distribution of Reinforcement ............................... 213 Flexural Tension Reinforcement in Zones of Maximum Tension ... 213 Transverse Deck Slab Reinforcement in T-Girders and Box Girders ..................................... 213 Bottom Slab Reinforcement for Box Girders ................... 214
8.18.2
Lateral Reinforcement of Flexural Members ................... 214 Reinforcement for Hollow Rectangular Compression Members ... 214 REINFORCEMENT OF COMPRESSION MEMBERS ........... 215 Maximum and Minimum Longitudinal Reinforcement .......... 215 Lateral Reinforcement .....................................2 15
8.18.2.1 8.18.2.2 8.18.2.3 8.18.2.4 8.19
General ................................................ 215 Spirals ................................................. 215 Ties ...................................................215 Seismic Requirements ..................................... 216 LIMITS FOR SHEAR REINFORCEMENT ..................... 216
XXV
CONTENTS
xxvi 8.19.1 8.19.2 8.19.3 8.20 8.21 8.22 8.23 8.23.1 8.23.2 8.24 8.24.1 8.24.2 8.24.3 8.25 8.26 8.27
8.28 8.29 8.30 8.30.1 8.30.2 8.31 8.32 8.32.1 ~.32.2
8.32.3 8.32.4 8.32.4.1 8.32.4.2 8.32.4.3 8.32.5 8.32.6
Minimum Shear Reinforcement .............................216 Types of Shear Reinforcement ............................... 216 Spacing of Shear Reinforcement .............................216 SHRINKAGE AND TEMPERATURE REINFORCEMENT ....... 216 SPACING LIMITS FOR REINFORCEMENT ...................216 PROTECTION AGAINST CORROSION ....................... 217 HOOKS AND BENDS ....................................... 217 Standard Hooks ...........................................217 Minimum Bend Diameters .................................. 217 DEVELOPMENT OF FLEXURAL REINFORCEMENT .......... 218 General .................................................. 218 Positive Moment Reinforcement .............................2 I 8 Negative Moment Reinforcement ............................ 218 DEVELOPMENT OF DEFORMED BARS AND DEFORMED WIRE IN TENSION .................................219 DEVELOPMENT OF DEFORMED BARS IN COMPRESSION ....219 DEVELOPMENT OF SHEAR REINFORCEMENT .............. 220 DEVELOPMENT OF BUNDLED BARS ........................ 220 DEVELOPMENT OF STANDARD HOOKS IN TENSION ........220 DEVEI~OPMENT OF WELDED WIRE FABRIC IN TENSION .... 221 Deformed Wire Fabric .....................................221 Smooth Wire Fabric .......................................222 MECHANICALANCHORAGE ............................... 222 SPLICES OF REINFORCEMENT ............................222 Lap Splices ...............................................222 Welded Splices and Mechanical Connections ................... 222 Splices of Deformed Bars and Deformed Wire in Tension ........223 Splices of Bars in Compression ..............................223 Lap Splices in Compression ................................223 End-Bearing Splices ......................................223 Welded Splices or Mechanical Connections .................... 223 Splices of Welded Deformed Wire Fabric in Tension ............. 223 Splices of Welded Smooth Wire Fabric in Tension ............... 224
SECTION 9-PRESTRESSED CONCRETE PART A-GENERAL REQUIREMENTS AND MATERIALS 9.1 9 .1.1 9 .1.2 9.1.3 9.2 9.3 9.3.1 9.3.2
APPLICATION .............................................225 General ..................................................225 Notations ................................................225 Definitions ...............................................227 CONCRETE ............................................... 228 REINFORCEMENT .........................................228 Prestressing Steel .......................................... 228 Non-Prestressed Reinforcement .............................. 228 PART B-ANALYSIS
9.4 9.5 9.6 9. 7
GENERAL .................................................228 EXPANSION AND CONTRACTION ........................... 228 SPAN LENGTH ............................................228 FRAMES AND CONTINUOUS CONSTRUCTION ............... 228
Division I
CONTENTS
Division I 9.7.1 9.7.2
0
9.7.2.1 9.7.2.2 9.7.2.3 9.7.3 9.7.3.1 9.7.3.2 9.7.3.3 9.8 9.8.1 9.8.2 9.8.3 9.9 9.9.1 9.9.2 9.9.3 9.10 9.10.1 9.10.2 9.10.3 9.11 9.11.1 9.11.2 9.11.3 9.12 9.12.1 9.12.2
Cast-in-Place Post-Tensioned Bridges .........................228 Bridges Composed of Simple-Span Precast Prestressed Girders Made Continuous ...................................229 General ................................. ·............... 229 Positive Moment Connection at Piers ......................... 229 Negative Moments ....................................... 229 Segmental Box Girders .....................................229 General ................................................229 Flexure ................................................ 229 Torsion ................................................ 229 EFFECTIVE FLANGE WIDTH ...............................229 T-Beams .................................................229 Box Girders ..............................................229 Precast/Prestressed Concrete Beams with Wide Top Flanges ...... 230 FLANGE AND WEB THICKNESS-BOX GIRDERS ............ 230 Top Flange ............................................... 230 Bottom Flange ............................................ 230 Web ..................................................... 230 DIAPHRAGMS .............................................230 General ..................................................230 T-Beams ................................................. 230 Box Girders .............................................. 230 DEFLECTIONS ............................................230 General .................................................. 230 Segmental Box Girders .....................................231 Superstructure Deflection Limitations ........................231 DECK PANELS ............................................ 231 General ..................................................231 Bending Moment ..........................................231 PART C-DESIGN
9.13 9.13.1 9.13.2 9.13.3 9.14 9.15 9.15.1 9.15.2 9.15.2.1
0
GENERAL ................................................. 231 Design Theory and General Considerations ....................231 Basic Assumptions .........................................231 Composite Flexural Members ...............................231 LOAD FACTORS ...........................................232 ALLOWABLE STRESSES ...................................232 Prestressing Steel .......................................... 232 Concrete .................................................232
Temporary Stresses Before Losses Due to Creep and Shrinkage ....................................... 232 Stress at Service Load After Losses Have Occurred ............. 232 9.15.2.2 Cracking Stress .......................................... 233 9.15.2.3 Anchorage Bearing Stress .................................. 233 9.15.2.4 LOSS OF PRESTRESS ......................................233 9.16 Friction Losses ............................................ 233 9.16.1 Prestress Losses ...........................................233 9.16.2 General ................................................233 9.16.2.1 Shrinkage ............................................. 233 9.16.2.1.1 Elastic Shortening ......................................234 9.16.2.1.2 Creep of Concrete ......................................234 9.16.2.1.3 Relaxation of Prestressing Steel ........................... 234 9.16.2.1.4 Estimated Losses .........................................236 9.16.2.2
xxvii
CONTENTS
xxviii 9.17 9.17.1 9.17.2 9.17.3 9.17.4 9.18 9.18.1 9.18.2 9.19 9.20 9.20.1 9.20.2 9.20.3 9.20.4 9.20.4.5 9.21 9.21.1 9.21.2 9.21.2.1 9.21.2.2 9.21.2.3 9.21.3 9.21.3.1 9.21.3.2 9.21.3.3 9.21.3.4 9.21.3.5 9.21.3.6 9.21.3.7 9.21.4 9.21.4.1 9.21.4.2 9.21.4.3 9.21.4.4 9.21.5 9.21.6 9.21.6.1 9.21.6.2 9.21.6.3 9.21.6.4 9.21.7 9.21.7.1 9.21.7.2 9.21.7.3 9.22 9.23 9.24
FLEXURAL STRENGTH ....................................236 General ..................................................236 Rectangular Sections ......................................236 Flanged Sections ..........................................236 Steel Stress ...............................................237 DUCTaiTY LIMITS .......................................237 Maximum Prestressing Steel ................................237 Minimum Steel ........................................... 237 NON-PRESTRESSED REINFORCEMENT .....................238 SHEAR ....................................................238 General .................................................. 238 Shear Strength Provided by Concrete .........................238 Shear Strength Provided by Web Reinforcement ............... 239 Horizontal Shear Design-Composite Flexural Members ........ 239 Ties for Horizontal Shear ..................................240 POST-TENSIONED ANCHORAGE ZONES ....................240 Geometry of the Anchorage Zone ............................240 General Zone and Local Zone ...............................240 General Zone ............................................240 Local Zone .............................................240 Responsibilities ..........................................240 Design of the General Zone ................................. 241 Design Methods .........................................241 Nominal Material Strengths ................................241 Use of Special Anchorage Devices ...........................241 General Design Principles and Detailing Requirements ...........241 Intermediate Anchorages ..................................242 Diaphragms ............................................. 243 Multiple Slab Anchorages ..................................243 Application of Strut-and-Tie Models to the Design of Anchorage Zones ..................................243 General ................................................243 Nodes .................................................244 Struts ..................................................244 Ties ...................................................244 Elastic Stress Analysis ......................................244 Approximate Methods .....................................244 Limitations .............................................244 Compressive Stresses ..................................... 245 Bursting Forces ..........................................245 Edge-Tension Forces ......................................245 Design of the Local Zone ...................................246 Dimensions of the Local Zone ..............................246 Bearing Strength .........................................246 Special Anchorage Devices ................................. 247 PRETENSIONED ANCHORAGE ZONES ......................247 CONCRETE STRENGTH AT STRESS TRANSFER ............. 247 DECK PANELS ............................................247 PART D-DETAILING
9.25 9.26
FLANGE REINFORCEMENT ................................247 COVER AND SPACING OF STEEL ...........................247
Division I
Division I
0
CONTENTS 9.26.1 9.26.2 9.26.3 9.26.4 9.27 9.28 9.29
Minimum Cover ..........................................247 Minimum Spacing .........................................248 Bundling .................................................248 Size of Ducts ..............................................248 POST-TENSIONING ANCHORAGES AND COUPLERS ......... 248 EMBEDMENT OF PRESTRESSED STRAND ..................249 BEARIN'GS ................................................ 249
SECTIONl~TRUCTURALSTEEL
PART A-GENERAL REQUIREMENTS AND MATERIALS 10.1 10.1.1 10.2 10.2.1 10.2.2 10.2.3 10.2.4 10.2.5 10.2.6 10.2.6.1 10.2.6.2 10.2.6.3
0
PART B-DESIGN DETAILS 10.3 10.3.1 10.3.2 10.3.3 10.3.4 10.4 10.5 10.6 10.7 10.8 10.9 10.10 10.11 10.12 10.13 10.14 10.15
0
APPLICATION .............................................251 Notations ................................................251 MATERIALS ............................................... 257 General .................................................. 257 Structural Steels ..........................................257 Steels for Pins, Rollers, and Expansion Rockers ................257 Fasteners-Rivets and Bolts ................................ 257 Weld Metal ...............................................257 Cast Steel, Ductile Iron Castings, Malleable Castings, Cast Iron, and Bronze or Copper Alloy .......................... 257 Cast Steel and Ductile Iron .................................257 Malleable Castings .......................................257 Cast Iron ............................................... 257
10.15.1 10.15.2 10.15.3 10.16
REPETITIVE LOADING AND TOUGHNESS CONSIDERATIONS ................................259 Allowable Fatigue Stress Ranges .............................259 Load Cycles ..............................................259 Charpy V-Notcb Impact Requirements .......................259 Shear ....................................................259 EFFECTIVE LENGm OF SPAN .............................259 DEPTH RATIOS ............................................260 DEFLECTION .............................................260 LIMITING LENGTHS OF MEMBERS ........................263 MINIMUM TIDCKNESS OF METAL .........................265 EFFECTIVE AREA OF ANGLES AND TEE SECTIONS IN TENSION .......................................265 OUTSTANDING LEGS OF ANGLES .......................... 266 EXPANSION AND CONTRACTION ...........................266 FLEXURAL MEMBERS .....................................266 COVER PLATES ...........................................266 CAMBER .................................................. 267 HEAT-CURVED ROLLED BEAMS AND WELDED PLATE GIRDERS ..................................267 Scope .................................................... 267 Minimum Radius of Curvature ..............................267 Camber ..................................................267 TRUSSES ..................................................268
xxix
CONTENTS
XXX
10.16.1 10.16.2 10.16.3 10.16.4 10.16.5 10.16.6 10.16.7 10.16.8 10.16.9 10.16.10 10.16.11 10.16.12 10.16.13 10.16.14 10.17 10.17.1 10.17.2 10.17.3 10.17.4 10.17.5 10.18 10.18.1 10.18.1.1 10.18.1.2 10.18.1.3 10.18.1.4 10.18.2 10.18.2.1 10.18.2.2 10.18.2.3 10.18.3 10.18.4 10.18.5 10.19 10.19.1 10.19.2 10.19.3 10.20 10.20.1 10.20.2 10.20.2.1 10.20.2.2 10.20.3 10.21 10.22 10.23 10.23.1 10.23.2 10.23.2.1 10.23.2.2 10.23.3
General ..................................................268 'Ii'uss Members ........................................... 268 Secondary Stresses ........................................268 Diaphragms ..............................................268 Camber ..................................................269 Working Lines and Gravity Axes ............................269 Portal and Sway Bracing ................................... 269 Perforated Cover Plates .................................... 269 Stay Plates ...............................................269 Lacing Bars ..............................................270 Gusset Plates .................................... ·.........270 Half-Through Truss Spans ..................................270 Fastener Pitch in Ends of Compression Members ...............271 Net Section of Riveted or High-Strength Bolted Tension Members ................................... 271 BENTS AND TOWERS ...................................... 271 General ..................................................271 Single Bents .............................................. 271 Batter ................................................... 271 Bracing .................................................. 271 Bottom Struts ............................................272 SPLICES .................................................. 272 General .................................................. 272 Design Strength .......................................... 272 Fillers ................................................. 272 Design Force for Flange Splice Plates ........................ 272 Truss Chords and Columns .................................272 Flexural Members ......... ·................................ 273 General ................................................273 Flange Splices ...........................................273 Web Splices .............................................275 Compression Members .....................................277 Tension Members .........................................277 Welded Splices ............................................ 277 STRENGTH OF CONNECTIONS .............................278 General ..................................................278 End Connections of Floor Beams and Stringers ................279 End Connections of Diaphragms and Cross Frames ............. 279 DIAPHRAGMS AND CROSS FRAMES ........................ 279 General .................................................. 279 Stresses Due to Wind Loading When Top Flanges Are Continuously Supported ..........................279 Flanges ................................................279 Diaphragms and Cross Frames ..............................279 Stresses Due to Wind Load When Top Flanges Are Not Continuously Supported ...................... 280 LATERAL BRACING ....................................... 280 CLOSED SECTIONS AND POCKETS ......................... 280 WELDING ................................................. 280 General ..................................................280 Effective Size of Fillet Welds ................................280 Maximum Size of Fillet Welds .............................. 280 Minimum Size of Fillet Welds ..............................280 Minimum Effective Length of Fillet Welds ..................... 281
Division I
CONTENTS
Division I
0
0
Fillet Weld End Returns .................................... 281 10.23.4 Seal Welds ............................................... 281 10.23.5 FASTENERS (RIVETS AND BOLTS) ..........................281 10.24 General .................................................. 281 10.24.1 Hole 'JYpes ............................................... 282 10.24.2 Washer Requirements ...................................... 282 10.24.3 Size of Fasteners (Rivets or High-Strength Bolts) ............... 283 10.24.4 Spacing of Fasteners ....................................... 283 10.24.5 Pitch and Gage of Fasteners ................................283 10.24.5.1 Minimum Spacing of Fasteners ............................. 283 10.24.5.2 Minimum Clear Distance Between Holes ...................... 283 10.24.5.3 Maximum Spacing of Fasteners .............................283 10.24.5.4 Maximum Spacing of Sealing and Stitch Fasteners .............. 283 10.24.6 Sealing Fasteners ........................................283 10.24.6.1 Stitch Fasteners .......................................... 283 10.24.6.2 Edge Distance of Fasteners .................................. 284 10.24.7 General ................................................ 284 10.24.7.1 Long Rivets .............................................. 284 10.24.8 LINKS AND HANGERS ..................................... 284 10.25 Net Section ............................................... 284 10.25.1 Location of Pins ........................................... 284 10.25.2 Size of Pins ............................................... 284 10.25.3 Pin Plates ................................................ 284 10.25.4 Pins and Pin Nuts ......................................... 285 10.25.5 UPSET ENDS ..............................................285 10.26 EYEBARS .................................................285 10.27 Thickness and Net Section .................................. 285 10.27.1 Packing of Eyebars ........................................285 10.27.2 FORKED ENDS ............................................ 285 10.28 FIXED AND EXPANSION BEARINGS ........................ 285 10.29 General ..................................................285 10.29.1 Bronze or Copper-Alloy Sliding Expansion Bearings ............ 285 10.29.2 Rollers ..................................................285 10.29.3 Sole Plates and Masonry Plates .............................. 286 10.29.4 Masonry Bearings ......................................... 286 10.29.5 Anchor Bolts ............................................. 286 10.29.6 Pedestals and Shoes ........................................ 286 10.29.7 FLOOR SYSTEM ........................................... 286 10.30 Stringers .................................................286 10.30.1 Floor Beams .............................................. 286 10.30.2 Cross Frames ............................................. 286 10.30.3 Expansion Joints .......................................... 286 10.30.4 End Floor Beams .......................................... 287 10.30.5 End Panel of Skewed Bridges ............................... 287 10.30.6 Sidewalk Brackets ......................................... 287 10.30.7 Stay-in-Place Deck Forms .................................. 287 10.30.8 Concrete Deck Panels ..................................... 287 10.30.8.1 Metal Stay-in-Place Forms ................................. 287 10.30.8.2 PART C-SERVICE LOAD DESIGN METHOD ALLOWABLE STRESS DESIGN 10.31 10.32
SCOPE ............................................ · .. ···· .287 ALLOWABLE STRESSES ................................... 287
xxxi
CONTENTS
xxxii 10.32.1 10.32.2 10.32.3 10.32.3.1 10.32.3.3 10.32.3.4 10.32.4 10.32.5 10.32.5.1 10.32.5.2 10.32.5.3 10.32.5.4 10.32.6 10.33 10.33.1 10.33.2 10.34 10.34.1 10.34.2 10.34.2.1 10.34.2.2 10.34.3 10.34.3.1 10.34.3.2 10.34.4 10.34.5 10.34.6 10.34.6.1 10.34.6.2 10.35 10.35.1 10.35.2 10.36 10.37 10.37.1 10.37.2 10.37.3 10.38 10.38.1 10.38.2 10.38.3 10.38.4 10.38.5 10.38.5.1 10.38.5. I .1 10.38.5.1.2 I 0.38.5.1.3 10.38.5.2 10.38.6 10.39 10.39.1 10.39.2
Steel ....................................................287 Weld Metal ...............................................287 Fasteners (Rivets and Bolts) .................................290 General ................................................290 Applied Tension, Combined Tension, and Shear ................292 Fatigue .................................................292 Pins, Rollers, and Expansion Rockers .........................292 Cast Steel, Ductile Iron Castings, Malleable Castings, and Cast Iron .......................................293 Cast Steel and Ductile Iron .................................293 Malleable Castings .......................................293 Cast Iron ...............................................293 Bronze or Copper-Alloy ...................................293 Bearing on Masonry .......................................294 ROLLED BEAMS ...........................................294 General ..................................................294 Bearing Stiffeners .........................................294 PLATE GIRDERS ..........................................294 General ..................................................294 Flanges ..................................................294 Welded Girders ..........................................294 Riveted or Bolted Girders ..................................295 Thickness of Web Plates ....................................296 Girders Not Stiffened Longitudinally .........................296 Girders Stiffened Longitudinally ............................296 Transverse Intermediate Stiffeners ...........................297 Longitudinal Stiffeners .....................................298 Bearing Stiffeners .........................................299 Welded Girders ..........................................299 Riveted or Bolted Girders ..................................299 TRUSSES ..................................................300 Perforated Cover Plates and Lacing Bars .....................300 Compression Members-Thickness of Metal ..................300 COMBINED STRESSES .....................................301 SOLID RIB ARCHES ....................................... .302 Moment Amplification and Allowable Stress ................... 302 Web Plates ............................................... 303 Flange Plates .............................................303 COMPOSITE GIRDERS .....................................303 General ..................................................303 Shear Connectors .........................................304 Effective Flange Width .....................................304 Stresses .................................................. 304 Shear ...................................................305 Horizontal Shear ......................................... 305 Fatigue ...............................................305 Ultimate Strength ......................................306 Additional Connectors to Develop Slab Stresses .............. 307 Vertical Shear ...........................................307 Deflection ................................................307 COMPOSITE BOX GIRDERS ................................307 General ..................................................307 Lateral Distribution of Loads for Bending Moment .............307
Division I
Division I
CONTENTS 10.39.3 Design of Web Plates ....................................... 307 10.39.3.1 Vertical Shear ...........................................307 10.39.3.2 Secondary Bending Stresses ............................... .308 10.39.4 Design of Bottom Flange Plates ............................. .308 10.39.4.1 Tension Flanges .........................................308 10.39.4.2 Compression Flanges Unstiffened ...........................308 10.39.4.3 Compression Flanges Stiffened Longitudinally .................308 10.39.4.4 Compression Flanges Stiffened Longitudinally and Transversely ... 311 10.39.4.5 Compression Flange Stiffeners, General ..................... .312 10.39.5 Design of Flange to Web Welds ..............................312 10.39.6 Diaphragms .............................................. 312 10.39.7 Lateral Bracing ...........................................312 10.39.8 Access and Drainage .......................................312 10.40 HYBRID GIRDERS .........................................312 10.40.1 General ..................................................312 10.40.2 Allowable Stresses ........................................ .313 10.40.2.1 Bending ................................................313 10.40.2.2 Shear .................................................. 313 10.40.2.3 Fatigue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .314 10.40.3 Plate Thickness Requirements .............................. .314 10.40.4 Bearing Stiffener Requirements .............................314 10.41 ORTHOTROPIC-DECK SUPERSTRUCTURES ................. 314 10.41.1 General ..................................................314 10.41.2 Wheel Load Contact Area ..................................314 10.41.3 Effective Width of Deck Plate .............................. .314 Ribs and Beams ..........................................314 10.41.3.1 10.41.3.2 Girders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 3 14 10.41.4 Allowable Stresses ........................................ .314 Local Bending Stresses in Deck Plate ....................... .314 10.41.4.1 Bending Stresses in Longitudinal Ribs ....................... .315 10.41.4.2 Bending Stresses in Transverse Beams ........................315 10.41.4.3 Intersections of Ribs, Beams, and Girders ..................... 315 10.41.4.4 Thickness of Plate Elements ................................ 315 10.41.4.5 Longitudinal Ribs and Deck Plate ......................... 315 I 0.41.4.5.1 Girders and Transverse Beams ............................315 I 0.41.4.5.2 Maximum Slenderness of Longitudinal Ribs .................. .315 10.41.4.6 Diaphragms .............................................315 10.41.4.7 Stiffness Requirements .................................... 315 10.41.4.8 Deflections ........................................... 315 10.41.4.8.1 Vibrations ............................................ 315 10.41.4.8.2 Wearing Surface .........................................316 10.41.4.9 Closed Ribs .............................................316 10.41.4.10 PART D-STRENGTH DESIGN METHOD LOAD FACTOR DESIGN
I 0.42 10.43 10.44 10.45 10.46 10.47 10.48
SCOPE ........................................... · · · · · · · · .316 LOADS ..................................... ·············· .316 DESIGN THEORY ......................................... .316 ASSUMPTIONS ....................................... · ... .316 DESIGN STRESS FOR STRUCTURAL STEEL .................316 MAXIMUM DESIGN LOADS ................................317 FLEXURAL MEMBERS .............................. · · · ... .317
xxxiii
CONTENTS
xxxiv 10.48.1 10.48.2 10.48.3 10.48.4 10.48.5 10.48.6 10.48.7 10.48.8 10.49 10.49.1 10.49.2 10.49.3 10.49.4 10.49.5 10.50 10.50.1 10.50.1.1 10.50.1.2 10.50.2 10.50.2.1 10.50.2.2 10.51 10.51.1 10.51.2 10.51.3 10.51.4 10.51.5 10.51.6 10.51.7 10.52 10.52.1 10.52.2 10.52.3 10.53 10.53.1 10.53.1.1 10.53.1.2 10.53.1.3 10.53.2 10.53.3 10.54 10.54.1 10.54.1.1 10.54.1.2 10.54.2 10.54.2.1 10.54.2.2 10.55 10.55.1 10.55.2 10.55.3 10.56 10.56.1
Compact Sections ......................................... 317 Braced Noncompact Sections ................................318 'I'ransitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .........318 Partially Braced Members ..................................319 'I'ransversely Stiffened Girders ..............................320 Longitudinally Stiffened Girders ............................. 321 Bearing Stiffeners .........................................321 Shear ....................................................321 SINGLY SYMMETRIC SECTIONS ...........................322 General .................................................. 322 Singly Symmetric Sections with 'I'ransverse Stiffeners ...........322 Longitudinally Stiffened Singly Symmetric Sections .............322 Singly Symmetric Braced Noncompact Sections ................323 Partially Braced Members with Singly Symmetric Sections ......323 COMPOSITE SECTIONS ................................... .323 Positive Moment Sections ...................................324 Compact Sections ........................................324 Noncompact Sections .....................................325 Negative Moment Sections ..................................325 Compact Sections ........................................326 Noncompact Sections ..................................... 326 COMPOSITE BOX GIRDERS ................................326 Maximum Strength ........................................326 Lateral Distribution ...................................... .327 Web Plates ...............................................327 Thnsion Flanges ...........................................327 Compression Flanges ......................................327 Diaphragms .............................................. 328 Design of Flange to Web Welds .............................. 328 SHEAR CONNECTORS ..................................... 328 General .................................................. 328 Design of Connectors ....................... ·...............328 Maximum Spacing ........................................328 HYBRID GIRDERS .........................................328 Noncomposite Hybrid Sections ..............................329 Compact Sections ........................................329 Braced Noncompact Sections ...............................329 PartiaiJy Braced Members ..................................329 Composite Hybrid Sections ................................. 329 Shear ....................................................329 COMPRESSION MEMBERS .................................330 Axial Loading ............................................330 Maximum Capacity .......................................330 Effective Length .........................................330 Combined Axial Load and Bending ..........................330 Maximum Capacity .......................................330 Equivalent Moment Factor C ...............................331 SOLID RIB ARCHES ........................................331 Moment Amplification and Allowable Stresses ................ .331 Web Plates ...............................................331 Flange Plates .............................................331 SPLICES, CONNECTIONS, AND DETAILS ....................331 Connectors ...............................................331
Division I
CONTENTS
Division I
0
10.56.1.1 10.56.1.2 10.56.1.3 10.56.1.4 10.56.2 10.56.3 10.57 10.57.1 10.57.2 10.57.3 10.58 10.58.1 10.58.2 10.58.2.1 10.58.2.2 10.58.3 10.59 10.60 10.61 10.61.1 10.61.2 10.61.3 10.61.4
General ................................................ 331 Welds .................................................. 331 Bolts and Rivets ......................................... 331 Slip-Critical Joints ....................................... 333 Bolts Subjected to Prying Action by Connected Parts ........... 333 Rigid Connections ......................................... 333 OVERLOAD ............................................... 333 Noncomposite Sections .....................................334 Composite Sections ........................................334 Slip-Critical Joints ....................................... .334 FATIGUE ..................................................335 General .................................................. 335 Composite Construction .................................... 335 Slab Reinforcement ....................................... 335 Shear Connectors ........................................335 Hybrid Beams and Girders .................................335 DEFI.,ECTION ............................................. 335 ORTHOTROPIC SUPERSTRUCTURES ...................... .335 CONSTRUCTffiiLITY ..................................... .336 Web Bend Buckling ....................................... .336 Web Shear Buckling ....................................... 336 Lateral-Torsional Buckling of the Cross Section ................ 336 Compression Flange Local Buckling ......................... .336
SECTION 11-ALUMINUM DESIGN
0
II. I 11.2 11.3 11.4
11.5
GENERAL ................................................. 337 BRIDGES .................................................337 SOIL-METAL PLATE INTERACTION SYSTEMS .............. 337 STRUCTURAL SUPPORTS FOR mGHWAY SIGNS, LUMINAIRES, AND TRAFFIC SIGNALS ............. .337 BRIDGE RAILING .........................................337
SECTION 12-SOIL-CORRUGATED METAL STRUCTURE INTERACTION SYSTEMS 12.1 12.1.1 12.1.2 12.1.3 12.1.4
12.1.5 12.1.6 12.1.6.1 12.1.6.2 12.1.6.3 12.1.7 12.1.8 12.1.9 12.1.10
12.2 12.2.1
GENERAL .................................................339 Scope .................................................... 339 Notations ................................................339 Loads ............................. ; .....................339 Design ................................................... 340 Materials ................................................340 Soil Design ............................................... 340 Soil Parameters .......................................... 340 Pipe Arch Design ........................................ 340 Arch Design ............................................340 Abrasive or Corrosive Conditions ............................ 341 Minimum Spacing .........................................341 End 'freatment ............................................ 341 Construction and Installation ...............................341 SERVICE LOAD DESIGN ................................... 341 Wall Area ................................................ 341
XXXV
CONTENTS
xxxvi 12.2.2 12.2.3 12.2.4 12.3 12.3.1 12.3.2 12.3.3 12.3.4 12.4 12.4.1 12.4.1.2 12.4.1.3 12.4.1.4 12.4.1.5 12.4.2 12.4.3 12.4.3.1 12.4.3.2 12.4.4 12.4.5 12.5 12.5.1 12.5.2 12.5.2.3 12.5.2.4 12.5.2.5 12.5.3 12.5.3.2 12.5.3.3 12.5.4 12.5.4.1 12.5.4.2 12.5.5 12.5.5.1 12.5.5.2 12.6 12.6.1 12.6.1.2 12.6.1.3 12.6.1.4 12.6.1.5 12.6.2 12.6.3 12.6.3.1 12.6.3.2 12.6.4 12.6.4.1 12.6.4.2
Buckling .................................................341 Seam Strength ............................................341 Handling and Installation Strength ........................... 34 I LOAD FACTOR DESIGN ....................................342 Wall Area ................................................342 Buckling .................................................342 Seam Strength ............................................ 342 llandling and Installation Strength ........................... 342 CORRUGATED METAL PIPE ................................342 General ..................................................342 Service Load Design-safety factor, SF ....................... 342 Load Factor Design-capacity modification factor, ••••••••••• .342 Flexibility Factor ........................................ .343 Minimum Cover ......................................... 343 Seam Strength ............................................ 343 Section Properties ......................................... 344 Steel Conduits ...........................................344 Aluminum Conduits ......................................344 Chemical and Mechanical Requirements ...................... 345 Smooth-Lined Pipe ........................................345 SPIRAL RIB METAL PIPE ................................. .345 General .................................................. 345 Soil Design ......... , ..................................... 345 Pipe-Arch Design ........................................ 345 Special Conditions .......................................345 Construction and Installation . . . . . . . . . . . . . . . . . . . . . . . ........345 Design ................................................... 345 Flexibility Factor ......................................... 346 Minimum Cover .........................................346 Section Properdes .........................................346 Steel Conduits ........................................... 346 Aluminum Conduits ......................................346 Chemical and Mechanical Requirements ...................... 346 Steel Spiral Rib Pipe and Pipe-Arch RequirementsAASHTOM218 .....................................346 Aluminum Spiral Rib Pipe and Pipe-Arch RequirementsAASHTO M 197 .....................................346 STRUCTURAL PLATE PIPE STRUCTURES ...................347 General .................................................. 347 Service Load Design-safety factor, SF ....................... 347 Load Factor Design-capacity modification factor, • • • . . • • • • • • . • • • • • • • • . • • • . . • • • . • • •••••..•...• 347 Flexibility Factor ......................................... 347 Minimum Cover .........................................347 Seam Strength ............................................ 347 Section Properties .........................................347 Steel Conduits ........................................... 347 Aluminum Conduits ......................................347 Chemical and Mechanical Properties ......................... 348 Aluminum Structural Plate Pipe, Pipe-Arch, and Arch Material Requirements-AASHTO M 219, Alloy 5052 ..............348 Steel Structural Plate Pipe, Pipe-Arch, and Arch Material Requirements-AASHTO M 167 ........................348
Division I
Division I
0
0
CONTENTS 12.6.5 Structural Plate Arches ...................... ·..............348 12.7 LONG-SPAN STRUCTURAL PLATE STRUCTURES ............348 General .................................................. 348 12.7.1 12.7.2 Structure Design ..........................................348 General ................................................348 12.7.2.1 12.7.2.2 Acceptable Special Features ................................349 Foundation Design ........................................349 12.7.3 Settlement Limits ........................................ 349 12.7.3.1 Footing Reactions (Arch Structures) .........................350 12.7.3.2 Footing Design ..........................................350 12.7.3.3 Soil Envelope Design ...................................... .350 12.7.4 Soil Requirements ........................................ 350 12.7.4.1 Construction Requirements ................................ .350 12.7.4.2 Service Requirements ..................................... 350 12.7.4.3 End Treatment Design .................................... .351 12.7.5 Standard Shell End Types ................................. .351 12.7.5.1 Balanced Support ........................................ 352 12.7.5.2 Hydraulic Protection ..................................... .352 12.7.5.3 Backfill Protection .................................... .352 12.7.5.3.1 Cut-Off (Toe) Walls ....................................352 12.7.5.3.2 Hydraulic Uplift ....................................... 354 12.7.5.3.3 Scour ................................................ 354 12.7.5.3.4 Multiple Structures ........................................ 354 12.7.6 STRUCTURAL PLATE BOX CULVERTS ..................... .354 12.8 General ..................................................354 12.8.1 Scope .................................................. 354 12.8.1.1 Structural Standards ...................................... 354 12.8.2 Structure Backfill ........................................ .354 12.8.3 Design ...................................................355 12.8.4 Analytical Basis for Design ................................ 355 12.8.4.1 Load Factor Method ......................................355 12.8.4.2 Plastic Moment Requirements ............................. .355 12.8.4.3 Footing Reactions ........................................356 12.8.4.4 Manufacturing and Installation .............................. 356 12.8.5
SECTION 13-WOOD STRUCTURES 13.1 13.1.1 13.1.2 13.1.3 13.1.4 13.2 13.2.1 13.2.1.1 13.2.1.2 13.2.2 13.2.2.1 13.2.2.2 13.2.3 13.2.3.1 13.2.3.2 13.2.3.3
GENERAL AND NOTATIONS ................................ 357 General ..................................................357 Net Section ............................................... 357 Impact ..................................................357 Notations ................................................ 357 MATERIALS ...............................................358 Sawn Lumber ............................................ 358 General ................................................ 358 Dimensions ............................................. 358 Glued Laminated Timber ................................... 358 General ................................................ 358 Dimensions ............................................. 358 Structural Composite Lumber .............................. .359 General ................................................359 Laminated Veneer Lumber .................................359 Parallel Strand Lumber .................................... 359
xxxvii
CONTENTS
xxxviii 13.2.3.4 13.2.4 13.3 13.3.1 13.3.2 13.3.3 13.3.4 13.4 13.5 13.5.1 13.5.2 13.5.2.2 13.5.3 13.5.4 13.5.5 13.5.5.1 13.5.5.2 13.5.5.3 13.6 13.6.1 13.6.2 13.6.3 13.6.4 13.6.4.1 13.6.4.2 13.6.4.3 13.6.4.4 13.6.4.5 13.6.5 13.6.5.1 13.6.5.2 13.6.5.3 13.6.6 13.6.6.1 13.6.6.2 13.6.6.3 13.6.7 13.7 13.7.1 13.7.2 13.7.3 13.7.3.1 13.7.3.2 13.7.3.3 13.7.3.4 13.7.3.5 13.7.4 13.8 13.8.1 13.8.2 13.9 13.9.1 13.9.2
Dimensions .............................................359 Piles .....................................................359 PRESERVATIVE TREATMENT ................ ~ .............359 Requirement for Treatment .................................359 'I'reatment Chemicals ...................................... 359 Field 'I'reating ............................................ 359 Fire Retardant Treatments ..................................359 DEFLECTION .............................................359 DESIGN VALUES ........................................... 360 General .........................................._........360 Thbulated Values for Sawn Lumber ..........................360 Stress Grades in Flexure ................................... 360 Tabulated Values for Glued Laminated Timber .................360 Tabulated Values for Structural Composite Lumber ............360 Adjustments to Thbulated Design Values ......................360 Wet Service Factor, CM .................................... 360 Load Duration Factor, C0 ••••••••••••••••••••••••••••••••• .369 Adjustment for Preservative Treatment .......................369 BENDING MEMBERS ......................................369 General ......................... ·.........................369 Notching .................................................377 Modulus of Elasticity ...................................... 377 Bending .................................................377 Allowable Stress ......................................... 377 Size Factor, CF ...........................................377 Volume Factor, Cv ........................................378 Beam Stability Factor, CL ..................................378 Form Factor, Cr ..........................................379 Shear Parallel to Grain .....................................379 General ................................................379 Actual Stress ............................................379 _ Allowable Stress ......................................... 379 Compression Perpendicular to Grain .........................380 General ................................................ 380 Allowable Stress .........................................380 Bearing Area Factor, Cb ....................................380 Bearing on IncUned Surfaces ................................380 COMPRESSION MEMBERS .................................380 General ..................................................380 Eccentric Loading or Combined Stresses ...................... 381 Compression .............................................381 Net Section ............................................. 381 Allowable Stress .........................................381 Column Stability Factor, Cp ................................ 381 Tapered Columns ........................................382 Round Columns .........................................382 Bearing Parallel to Grain ................................... 382 TENSION MEMBERS .......................................382 Tension Parallel to Grain ...................................382 Tension Perpendicular to Grain ............................. 383 MECHANICAL CONNECTIONS .............................383 General ..................................................383 Corrosion Protection .......................................383
Division I
. 0 .
Division I
CONTENTS 13.9.3 13.9.4
Fasteners ................................................383 Washers ................................................. 383
....
SECTION 14-BEARINGS 14.1 14.2 14.3 14.4 14.4.1 14.5 14.5.1 14.5.2 14.5.3
~
\.z/
14.5.3.1 14.5.3.2 14.6 14.6.1 14.6.1.1 14.6.1.2 14.6.1.3 14.6.1.4 14.6.2 14.6.2.1 14.6.2.2 14.6.2.3 14.6.2.3.1 14.6.2.3.2 14.6.2.4 14.6.2.5 14.6.2.6 14.6.2.6.1 14.6.2.6.2 14.6.3 14.6.3.1 14.6.3.2 14.6.4 14.6.4.1 14.6.4.2 14.6.4.3 14.6.4.4 14.6.4.5 14.6.4.5.1 14.6.4.5.2 14.6.4.6 14.6.4.7 14.6.4.8 14.6.5 14.6.5.1 14.6.5.2 14.6.5.3 14.6.5.3.1
SCOPE ....................................................385 DEFINITIONS ............................................. 385 NOTATIONS ...............................................385 MOVEMENTS AND LOADS ................................. 386 Design Requirements ......................................387 GENERAL REQUIREMENTS FOR BEARINGS ................ 387 Load and Movement Capabilities ........................... .387 Characteristics ............................................ 387 Forces in the Structure Caused by Restraint of Movement at the Bearing ......................................387 Horizontal Force ......................................... 387 Bending Moment ........................................390 SPECIAL DESIGN PROVISIONS FOR BEARINGS ............. 390 Metal Rocker and Roller Bearings ........................... 390 General Design Considerations ............................. .390 Materials ...............................................390 Geometric Requirements .................................. 390 Contact Stresses .........................................390 PTFE Sliding Surfaces ..................................... 391 PTFE Surface ........................................... 391 Mating Surface ..........................................391 Minimum Thickness Requirements .......................... 391 P'fFE ................................................ 391 Stainless Steel Mating Surfaces ...........................391 Contact Pressure .........................................391 Coefficient of Friction ..................................... 391 Attachment ............................................. 392 PTFE ................................................392 Mating Surface ........................................392 Bearings with Curved Sliding Surfaces .......................392 Geometric Requirements .................................. 392 Resistance to Lateral Load .................................393 Pot Bearings ..............................................393 General ................................................ 393 Materials ...............................................394 Geometric Requirements ..................................394 Elastomeric Disc ......................................... 394 Sealing Rings ........................................... 394 Rings with rectangular cross-sections .......................394 Rings with circular cross-sections ......................... 394 Pot .................................................... 394 Piston .................................................394 Lateral Loads ...........................................395 Steel Reinforced Elastomeric Bearings-Method B ............. 395 General ................................................ 395 Material Properties ....................................... 395 Design Requirements .....................................396 Scope ................................................ 396
xxxix
CONTENTS
xi
Compressive Stress .....................................396 Compressive Deflection .................................397 Shear ................................................ 397 Combined Compression and Rotation ...................... 397 Stability ..............................................398 Reinforcement .........................................398 Elastomeric Pads and Steel Reinforced Elastomeric BearingsMethod A ..........................................398 I4.6.6.I General ................................................398 I4.6.6.2 Material Properties .......................................398 14.6.6.3 Design Requirements .....................................398 14.6.6.3.I Scope ................................................398 14.6.6.3.2 Compressive Stress ..................................... 399 14.6.6.3.3 Compressive Deflection ................................. 399 14.6.6.3.4 Shear ................................................ 399 14.6.6.3.5 Rotation .............................................. 399 14.6.6.3.5a PEP and COP .........................................399 14.6.6.3.5b FOP and Steel Reinforced Elastomeric Bearings ..............399 14.6.6.3.6 Stability ..............................................400 14.6.6.3.7 Reinforcement .........................................400 14.6.6.4 Resistance to Deformation .................................400 14.6.7 Bronze or Copper Alloy Sliding Surfaces .......................400 14.6.7.1 Materials ...............................................400 14.6.7.2 Coefficient of Friction .....................................400 14.6.7.3 Limits on Load and Geometry ............................. .400 14.6.7.4 Clearances and Mating Surface ............................ .400 14.6.8 Disc Bearings .............................................400 14.6.8.1 General ................................................400 14.6.8.2 Materials ...............................................400 14.6.8.3 Overall Geometric Requirements ..........................• .400 14.6.8.4 Elastomeric Disc ........................................ .40 I 14.6.8.5 Shear Resisting Mechanism ................................40 I 14.6.8.6 Steel Plates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ............40 I 14.6.9 Guides and Restraints ..................................... .40I 14.6.9.1 General ................................................40 I 14.6.9.2 Design Loads ...........................................401 14.6.9.3 Materials ...............................................401 14.6.9.4 Geometric Requirements ..................................40 I 14.6.9.5 Design Basis ............................................40 I 14.6.9.5.1 Load Location .........................................40 I 14.6.9.5.2 Contact Stress .........................................40 I 14.6.9.6 Attachment of Low-Friction Material ........................ .401 I4.6.IO Other Bearing Systems .................................... .402 I4.7 LOAD PLATES AND ANCHORAGE FOR BEARINGS ...........402 14.7.1 Plates for Load Distribution ................................. .402 14.7.2 Tapered Plates .............................................402 14.7.3 Anchorage ................................................402 I4.8 CORROSION PROTECTION ................................402 I4.6.5.3.2 I4.6.5.3.3 I4.6.5.3.4 I4.6.5.3.5 14.6.5.3.6 I4.6.5.3.7 I4.6.6
SECTION 15-STEEL TUNNEL LINER PLATES 15.1 15.1.1
GENERALANDNOTATIONS ................................403 General ..................................................403
Division I
CONTENTS
Division I 15.1.2 15.2 15.3 15.3.1 15.3.2 15.3.3 15.3.4 15.3.5 15.4 15.4.1 15.4.2 15.4.3 15.5 15.6 15.7 15.8
Notations ................................................403 LOADS ...................................................403 DESIGN ...................................................404 Criteria ..................................................404 Joint Strength ............................................404 Minimum Stiffness for Installation .......................... .405 Critical Buckling of Liner Plate Wall ........................ .405 Deflection or Flattening ................................... .405 CHEMICAL AND MECHANICAL REQUIREMENTS ...........406 Chemical Composition .................................... .406 Minimum Mechanical Properties of Flat Pipe Before Cold Forming ............................... .406 Dimensions and Tolerances ................................ .406 SECTION PROPERTIES ................................... .406 COATINGS ................................................ 406 BOLTS ................................................... 406 SAFETY FACTORS ........................................ .406
SECTION 16--SOIL-REINFORCED CONCRJi~TE STRUCTURE INTERACTION SYSTEMS GENERAL .................................................407 16.1 Scope ...................................................407 16.1.1 Notations ................................................407 16.1.2 Loads ...................................................409 16.1.3 Design ................................................... 409 16.1.4 Materials ................................................409 16.1.5 Soil .....................................................409 16.1.6 Abrasive or Corrosive Conditions ........................... .409 16.1.7 End Structures ...........................................409 16.1.8 Construction and Installation ...............................409 16.1.9 SERVICE LOAD DESIGN .................................. .409 16.2 FACTOR DESIGN .................................... 409 LOAD 16.3 REINFORCED CONCRETE PIPE ........................... .409 16.4 Application ...............................................409 16.4.1 Materials ................................................409 16.4.2 Concrete ...............................................409 16.4.2.1 Reinforcement ...........................................409 16.4.2.2 Concrete Cover for Reinforcement ...........................410 16.4.2.3 Installations ..............................................41 0 16.4.3 Standard Installations .................................... .410 16.4.3.1 Soils .................................................. 410 16.4.3.2 Design ................................................... 410 16.4.4 General Requirements ..................................... 410 16.4.4.1 Loads ............................................. · .... 411 16.4.4.2 Earth Loads and Pressure Distribution ..................... .411 16.4.4.2.1 Standard Installations ................................ .411 16.4.4.2.1.1 Nonstandard Installations ..............................411 16.4.4.2.1.2 Pipe Fluid Weight ..................................... .411 16.4.4.2.2 Live Loads ...........................................412 16.4.4.2.3 Minimum Fill ...........................................412 16.4.4.3 Design Methods .........................................412 16.4.4.4 Indirect Design Method Based on Pipe Strength 16.4.5 and Load-Carrying Capacity ......................... .412
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CONTENTS
xliv 17.1.4 17.1.5 17.1.6 17.1.6.1 17.1.7 17.1.8 17.1.9 17.1.10 17.2 17.2.1 17.2.2 17.2.3 17.3 17.3.1 17.3.2 17.3.3 17.4 17.4.1 17.4.1.2 17.4.1.3 17.4.1.4 17.4.1.5 17.4.1.6 17.4.1.7 17.4.2 17.4.2.1 17.4.2.2 17.4.2.3 17.4.3 17.4.3.1 17.4.3.1.1 17.4.3.1.2 17.4.3.1.3 17.4.3.2 17.4.3.2.1 17.4.3.2.2
Design ...................................................431 Materials ......................... · .. · · · · · · · · · · · · · · · · · · · .431 Soil Design ...............................................431 Soil Parameters ..........................................431 Abrasive or Corrosive Conditions ............................432 Minimum Spacing .........................................432 End 'I'reatment ............................................432 Construction and Installation ...............................432 SERVICE LOAD DESIGN ...................................432 Wall Area ................................................432 Buckling .................................................432 Handling and Installation Strength .......................... .433 LOAD FACTOR DESIGN ....................................433 Wall Area ................................................433 Buckling .................................................433 Handling and Installation Strength .......................... .433 PLASTIC PIPE .............................................433 General ..................................................433 Service Load Design-safety factor, SF .......................434 Load Factor Design-capacity modification factor, •••••••••••• 434 Flexibility Factor ......................................... 434 Minimum Cover .........................................434 Maximum Strain .........................................434 Local Buckling ..........................................434 Section Properties ........................................ .434 PE Corrugated Pipes ......................................434 PE Ribbed Pipes ......................................... 434 Profile Wa11 PVC Pipes ....................................434 Chemical and Mechanical Requirements ......................435 Polyethylene ............................................435 Smooth wall PE pipe requirements ........................ .435 Corrugated PE pipe requirements ......................... .435 Ribbed PE pipe requirements .............................435 Poly (Vinyl Chloride) (PVC) .............................. .435 Smooth wall PVC pipe requirements .......................435 Ribbed PVC pipe requirements ...........................436
DIVISION I-A SEISMIC DESIGN SECTION I-INTRODUCTION 1.1 1.2 1.3 1.4 1.5 1.6
PURPOSE AND PHILOSOPHY ...............................439 BACKGROUND ............................................439 BASIC CONCEPTS .........................................440 PROJECT ORGANIZATION .................................440 QUALITY ASSURANCE REQUIREMENTS ....................440 FLOW CHARTS ............................................441
SECTION 2-SYMBOLS AND DEFINITIONS 2.1
NOTATIONS ...............................................445
Division 1-A .~
1
~
J
Division I-A
CONTENTS
SECTION 3-GENERAL REQUIREMENTS
0
3.1 3.2 3.3 3.4 3.5 3.5.1 3.6 3.6.1 3.6.2 3.7 3.8
3.9 3.10 3.11 3.12
APPLICABILITY OF SPECIFICATIONS ......................447 ACCELERATION COEFFICIENT ............................447 IMPORTANCE CLASSIFICATJON ...........................449 SEISMIC PERFORMANCE CATEGORIES ....................449 SITE EFFECTS ............................................449 Site Coefficient ............................................449 ELASTIC SEISMIC RESPONSE COEFFICIENT ...............450 Elastic Seismic Response Coefficient for Single Mode Analysis ... .450 Elastic Seismic Response Coefficient for Multimodal Analysis ... .450 RESPONSE MODIFICATION FACTORS ......................450 DETERMINATION OF ELASTIC FORCES AND DISPLACEMENTS .............................450 COMBINATION OF ORTHOGONAL SEISMIC FORCES ....... .450 MINIMUM SEAT·WIDTH REQUIREMENTS ..................451 DESIGN REQUIREMENTS FOR SINGLE SPAN BRIDGES ..... .451 REQUIREMENTS FOR TEMPORARY BRIDGES AND STAGED CONSTRUCTION ................................. .452
SECTION 4-ANALYSIS REQUIREMENTS 4.1 4.2 4.2.1 4.2.2 4.2.3 4.3 4.4 4.5 4.5.1 4.5.2 4.5.2(A) 4.5.2(B) 4.5.3 4.5.4 4.5.5 4.6
GENERAL .................................................453 SELECTION OF ANALYSIS METHOD ........................453 Special Requirements for Single-Span Bridges and Bridges in SPC A ................................453 Special Requirements for Curved Bridges ~ ................... .453 Special Requirements for Critical Bridges .....................454 UNIFORM LOAD MEmOD-PROCEDURE 1 ................ .454 SINGLE MODE SPECTRAL ANALYSIS METHODPROCEDURE 2 ....................................454 MULTIMODE SPECTRAL ANALYSis METHODPROCEDURE 3 ....................................455 General ..................................................455 Mathematical Model .......................................456 Superstructure ...........................................456 Substructure ............................................456 Mode Shapes and Periods ..................................456 Multimode Spectral Analysis ............................... .456 Combination of Mode Forces and Displacements ...............456 TIME HISTORY METHOD-PROCEDURE 4 ................. .456
SECTION S-DESIGN REQUIREMENTS FOR BRIDGES IN SEISMIC PERFORMANCE CATEGORY A 5.1 5.2 5.3 5.4
5.5
GENERAL .................................................457 DESIGN FORCES FOR SEISMIC PERFORMANCE CATEGORY A .....................................457 DESIGN DISPLACEMENTS FOR SEISMIC PERFORMANCE CATEGORY A .....................................457 FOUNDATION AND ABUTMENT DESIGN REQUIREMENTS FOR SEISMIC PERFORMANCE CATEGORY A .......457 STRUCTURAL STEEL DESIGN REQUIREMENTS FOR SEISMIC PERFORMANCE CATEGORY A .......458
xlv
CONTENTS
xlvi 5.6
REINFORCED CONCRETE DESIGN REQUIREMENTS FOR SEISMIC PERFORMANCE CATEGORY A .......458
SECTION 6-DESIGN REQUIREMENTS FOR BRIDGES IN SEISMIC PERFORMANCE CATEGORY B 6.1 6.2 6.2.1 6.2.2 6.2.3 6.3 6.3.1 6.4 6.4.1 6.4.2 6.4.2(A} 6.4.2(B} 6.4.2(C} 6.4.3 6.4.3(A} 6.4.3(B} 6.5 6.5.1 6.5.2 6.6 6.6.1 6.6.2 6.6.2(A} 6.6.2(B}
GENERAL .................................................459 DESIGN FORCES FOR SEISMIC PERFORMANCE CATEGORY B ............................. ·........459 Design Forces for Structural Members and Connections ........ .459 Design Forces for Foundations ...............................459 Design Forces for Abutments and Retaining Walls ............. .460 DESIGN DISPLACEMENTS FOR SEISMIC PERFORMANCE CATEGORY B .....................................460 Minimum Support Length Requirements for Seismic Performance Category B .............................460 FOUNDATION AND ABUTMENT DESIGN REQUIREMENTS FOR SEISMIC PERFORMANCE CATEGORY B ...... .460 General ..................................................460 Foundations ..............................................460 Investigation ........................................... .460 Foundation Design ...................................... .461 Special Pile Requirements ................................ .461 Abutments ............................................... 461 Free-Standing Abutments ..................................461 Monolithic Abutments ....................................462 STRUCTURAL STEEL DESIGN REQUIREMENTS FOR SEISMIC PERFORMANCE CATEGORY B ...... .462 General ..................................................462 P-delta Effects ............................................462 REINFORCED CONCRETE DESIGN REQUIREMENTS FOR SEISMIC PERFORMANCE CATEGORY B ...... .462 General ..................................................462 Minimum Transverse Reinforcement Requirements for Seismic Performance Category B ...................462 Transverse Reinforcement for Confinement ................... .462 Spacing of Transverse Reinforcement for Confinement .......... .463
SECTION 7-DESIGN REQUIREMENTS FOR BRIDGES IN SEISMIC PERFORMANCE CATEGORIES C AND D 7.1 7.2
7.2.1 7.2.l(A} 7.2.l(B} 7.2.2
GENERAL .......-..........................................465 DESIGN FORCES FOR SEISMIC PERFORMANCE CATEGORIES C AND D ............................ .465 Modified Design Forces ................................... .465 Modified Design Forces for Structural Members and Connections .....................................465 Modified Design Forces for Foundations ..................... .465 Forces Resulting from Plastic mnging in the Columns, Piers, or Bents ......................................466
Division 1-:'A
Division 1-A
0
CONTENTS 7.2.2(A) 7.2.2(B) 7.2.3 7.2.4 7.2.5 7.2.5(A) 7.2.5(B) 7.2.5(C) 7.2.6 7.2.7 7.3
7 .3.1 7.4
7.4.1 7.4.2 7.4.2(A) 7.4.2(B) 7.4.2(C) 7.4.3
0 '
7.4.3(A) 7.4.3(B) 7.4.4 7.4.4(A) 7.4.4(B) 7.4.5 7.5 7.5.1 7.5.2 7.6
7.6.1 7.6.2 7.6.2(A) 7.6.2(B) 7.6.2(C) 7.6.2(D) 7.6.2(E) 7.6.2(F) 7.6.3 7.6.4 7.6.5
Single Columns and Piers ................................. .466 Bents with Two or More Columns .......................... .466 Column and Pile Bent Design Forces ........................ .467 Pier Design Forces .........................................467 Connection Design Forces ................................. .467 Longitudinal Linkage Forces .............................. .467 Hold-Down Devices ......................................467 Column and Pier Connections to Cap Beams and Footings ....... .467 Foundation Design Forces ................................. .467 Abutment and Retaining Wall Design Forces .................. .468
DESIGN DISPLACEMENT FOR SEISMIC PERFORMANCE CATEGORIES C AND D ............................ .468 Minimum Support Length Requirements for Seismic Performance Categories C and D ................................. .468 FOUNDATION AND ABUTMENT DESIGN REQUIREMENTS FOR SEISMIC PERFORMANCE CATEGORIES CANDD ..........................................468 General ..................................................468 Foundation Requirements for Seismic Performance Category C .........................................469 Investigation ............................................469 Foundation Design ...................................... .469 Special Pile Requirements ................................ .469
Abutment Requirements for Seismic Performance Category C .........................................470 Free-Standing Abutments ................................. .470 Monolithic Abutments ................................... .470
Additional Requirements for Foundations for Seismic Performance Category D .................. .470 Investigation ............................................470 Foundation Design ...................................... .471
Additional Requirements for Abutments for Seismic Performance Category D ...................471 STRUCTURAL STEEL DESIGN REQUIREMENTS FOR SEISMIC PERFORMANCE CATEGORIES C AND D ........ : . ..471 General ..................................................471 P-delta Effects ............................................471 REINFORCED CONCRETE DESIGN REQUIREMENTS FOR SEISMIC PERFORMANCE CATEGORIES CANDD ..........................................471 General ..................................................471 Column Requirements .................................... .471 Vertical Reinforcement ....................................471 Flexural Strength ........................................ .471 Column Shear and Transverse Reinforcement ................. .472 Transverse Reinforcement for Confinement at Plastic Hinges ......472 Spacing of Transverse Reinforcement for Confinement .......... .473 Splices .................................................473 Pier Requirements ........................................473 Column Connections .......................................474 Construction Joints in Piers and Columns .................... .474
xlvii
CONTENTS
xlviii
DIVISIONU CONSTRUCTION INTRODUCTION .....................................................476 SECTION I-STRUCTURE EXCAVATION AND BACKFILL 1.1 1.2 1.3 1.4 1.4.1 1.4.2 1.4.2.1 1.4.2.2 1.4.2.3 1.4.2.4 1.4.2.5 1.4.3 1.5 1.5.1 1.5.2
GENERAL .................................................477 WORKING DRAWINGS .....................................477 MATERIALS ...............................................477 CONSTRUCTION ......................................... .477 Depth of Footings .........................................477 Foundation Preparation and Control of Water ................ .478 General ................................................478 Excavations Within Channels ...............................478 Foundations on Rock .....................................478 Other Foundations ....................................... .478 Approval of Foundation ...................................478 Backfill ..................................................478 MEASUREMENT AND PAYMENT ............................479 Measurement .............................................479 Payment .................................................479
SECTION 2-REMOVAL OF EXISTING STRUCTURES 2.1 2.2 2.3 2.3.1 2.3.2 2.3.3 2.3.4 2.4
DESCRIPTION .............................................481 WORKING DRAWINGS .....................................481 CONSTRUCTION ..........................................481 General ..................................................481 Salvage ..................................................481 Partial Removal of Structures .............................. .481 Disposal .................................................482 MEASUREMENT AND PAYMENT ............................482
SECTION 3-TEMPORARY WORKS 3.1 3.1.1 3.1.2 3.1.3 3.1.4 3.1.5 3.2 3.2.1 3.2.2 3.2.2.1 3.2.2.2 3.2.2.3 3.2.2.4 3.2.2.5 3.2.3 3.2.3.1
GENERAL .................................................483 Description ...............................................483 Working Drawings ....................................... .483 Design ...................................................483 Construction .............................................483 Removal .................................................483 FALSEWORK AND FORMS ................................ .484 General ..................................................484 Falsework Design and Construction ..........................484 Loads ..................................................484 Foundations .............................................484 Deflections ............................. '................484 Clearances ..............................................484 Construction ............................................484 Formwork Design and Construction ..........................485 General ................................................485
Division ll
Division II
CONTENTS
3.2.3.2
0 .
3.2.3.3 3.2.3.4 3.2.3.5 3.2.4 3.2.4.1 3.2.4.2 3.2.4.3 3.3 3.3.1
3.3.2 3.3.3 3.4 3.4.1
3.4.2 3.4.3 3.5 3.5.1
3.5.2 3.5.3
3.5.4 3.6
Design .................................................485 Construction ............................................485 Thbe Forms .............................................485 Stay-in-Place Forms ......................................486 Removal of Falsework and Forms ........................... .486 General ................................................486 Time of Removal ........................................486 Extent of Removal .......................................486 COFFERDAMS AND SHORING ..............................487 General ..................................................487 Protection of Concrete .................................... .487 Removal .................................................487 TEMPORARY WATER CONTROL SYSTEMS ................. .487 General ..................................................487 Drawings ................................................ 487 Operations ...............................................487 TEMPORARY BRIDGES ................................... .488 General ..................................................488 Detour Bridges ...........................................488 Haul Bridges .............................................488 Maintenance .............................................488 MEASUREMENT AND PAYMENT ........................... .488
SECTION 4-DRIVEN FOUNDATION PILES
0
4.1 4.2 4.2.1 4.2.1.1 4.2.2 4.2.3 4.3 4.3.1 4.3.1.1 4.3.1.2 4.3.1.3 4.3.1.4 4.3.1.5 4.3.1.5.1 4.3.1.6 4.3.2 4.3.2.1 4.3.2.2 4.4 4.4.1 4.4.1.1 4.4.1.1.1 4.4.1.1.2 4.4.1.1.3 4.4.1.1.4 4.4.1.1.5 4.4.1.1.6
DESCRIP'fiON .............................................489 MATERIALS ...............................................489 Steel Piles ................................................489 Painting ................................................489 Timber Piles ..............................................489 Concrete Piles ............................................489 MANUFACTURE OF PILES .................................490 Precast Concrete Piles .....................................490 Forms ..•..............................................490 Casting ................................................490 Finish .................................................490 Curing and Protection .................................... .490 Prestressing .............................................490 Working Drawings .....................................490 Storage and Handling .....................................490 Cast-in-Place Concrete Piles ............................... .490 Inspection of Metal Shells ................................ .490 Placing Concrete .........................................490 DRIVING PILES ...........................................491 Pile Driving Equipment ................................... .491 Hammers ...............................................491 General ..............................................491 Drop Hammers ........................................491 Air Steam Hammers ................................... .491 Diesel Hammers .......................................491 Vibratory Hammers .....................................492 Additional Equipment or Methods ........................ .492
xlix
CONTENTS 4.4.1.2 4.4.1.2.1 4.4.1.2.2 4.4.1.2.3 4.4.1.2.4 4.4.1.2.5 4.4.1.2.6 4.4.2 4.4.2.1 4.4.2.1.1 4.4.2.1.2 4.4.2.1.3 4.4.2.2 4.4.2.2.1 4.4.2.2.2 4.4.2.2.3 4.4.3 4.4.3.1 4.4.3.2 4.4.4 4.4.4.1 4.4.4.2 4.4.4.3 4.4.4.4 4.4.4.5 4.4.5 4.4.5.1 4.4.5.2 4.4.5.3 4.4.6 4.4.7 4.4.7.1 4.4.7.2 4.5 4.5.1 4.5.1.1 4.5.1.1.1 4.5.1.1.2 4.5.1.2 4.5.1.3 4.5.2
Driving Appurtenances ....................................492 Hammer Cushion ......................................492 Pile Drive Head ........................................492 Pile Cushion ..........................................492 Leads ................................................492 Followers .............................................492 Jets ..................................................493 Preparation for Driving ....................................493 Site Work ...............................................493 Excavation ............................................493 Preboring to Facilitate Driving ........................... .493 Predrilled Holes in Embankments .........................493 Preparation of Piling ......................................493 Collars ...............................................493 Pointing .............................................. 493 Pile Shoes and Lugs ....................................493 Driving ..................................................493 Driving of Test Piles ..................................... .493 Accuracy of Driving ..................................... .494 Determination of Bearing Capacity ..........................494 General ................................................494 Method A-Empirical Pile Formulas ........................ .494 Method B-Wave Equation Analysis .........................494 Method C-Dynamic Load Tests ........................... .495 Method D-Static Load Tests ...............................495 Splicing of Piles .......................................... .496 Steel Piles ..............................................496 Concrete Piles ...........................................496 Timber Piles ............................................496 Defective Piles ............................................496 Pile Cut-otT ...............................................496 General ................................................496 Timber Piles ............................................496 MEASUREMENT AND PAYMENT ........................... .497 Method of Measurement .................................. .497 Timber, Steel, and Concrete Piles ............................497 Piles Furnished ....................................... .497 Piles Driven ...........................................497 Pile Splices, Pile Shoes, and Pile Lugs ....................... .497 Load Tests ..............................................497 Basis of Payment ..........................................497
SECTION 5-DRILLED PILES AND SHAFfS 5.1 5.2 5.2.1 5.2.2 5.3 5.3.1 5.3.2 5.3.3 5.4
DESCRIPTION .............................................499 SUBMITTALS ..............................................499 Contractor Qualifications .................................. .499 Working Drawings ........................................499 MATERIALS ...............................................500 Concrete .................................................500 Reinforcing Steel ..........................................500 Casings .................................................. 500 CONSTRUCTION ..........................................500
Division ll
Division ll
0
0
CONTENTS 5.4.1 5.4.2 5.4.3 5.4.4 5.4.5 5.4.6 5.4.7 5.4.8 5.4.9 5.4.10 5.4.11 5.4.12 5.4.13 5.4.14 5.4.15 5.4.16 5.4.17 5.5 5.6 5.6.1 5.6.1.1 5.6.1.2 5.6.1.3 5.6.1.4 5.6.1.5 5.6.1.6 5.6.1.7 5.6.2 5.6.2.1 5.6.2.2 5.6.2.3 5.6.2.4 5.6.2.5 5.6.2.6 5.6.2.7 5.6.2.8
Protection of Existing Structures .............................500 Construction Sequence .....................................500 General Methods and Equipment ............................ 500 Dry Construction Method ..................................500 Wet Construction Method ..................................500 Temporary Casing Construction Method ......................501 Permanent Casing Construction Method ......................50 I Alternative Construction Methods ...........................50 I Excavations ..............................................501 Casings ..................................................501 Slurry ...................................................502 Excavation Inspection ......................................502 Reinforcing Steel Cage Construction and Placement ............502 Concrete Placement, Curing, and Protection ...................503 Test Shafts and Bells .......................................503 Construction Tolerances ....................................503 Integrity Testing .......................................... 504 DRILLED SHAFT LOAD TESTS .............................504 MEASUREMENT AND PAYMENT ............................504 Measurement .............................................504 Drilled Shaft ............................................ 504 Bell Footings ............................................504 Test Shafts ..............................................505 Test Bells ...............................................505 Exploration Holes ........................................505 Permanent Casing ........................................505 Load Tests ..............................................505 Payment ................................................. 505 Drilled Shaft ............................................505 Bell Footings ............................................505 Test Shafts ..............................................505 Test Bells ...............................................505 Exploration Holes ........................................505 Permanent Casing ........................................505 Load Tests ..............................................505 Unexpected Obstructions .................................. 505
SECTION 6-GROUND ANCHORS
0
6.1 6.2 6.3 6.3.1 6.3.2 6.3.3 6.3.4 6.3.5 6.4 6.4.1 6.4.1.1 6.4.1.2 6.4.2 6.4.3 6.4.4 6.5
DESCRIPTION ............................................. 507 WORKING DRAWINGS .....................................507 MATERIALS ...............................................507 Prestressing Steel .......................................... 507 Grout ...................................................507 Steel Elements ............................................508 Corrosion Protection Elements ..............................508 Miscellaneous Elements ....................................508 FABRICATION .............................................508 Bond Length and Tendon Bond Length .......................508 Grout Protected Ground Anchor Tendon ......................508 Encapsulation Protected Ground Anchor Tendon ................509 Unbonded Length .........................................509 Anchorage and Trumpet ...................................509 Tendon Storage and Handling ...............................509 INSTALLATION ............................................509
1i
Iii
CONTENTS 6.5.1 6.5.2 6.5.3 6.5.4 6.5.5 6.5.5.1 6.5.5.2 6.5.5.3 6.5.5.4 6.5.5.5 6.5.5.6 6.6
Drilling ..................................................509 Tendon Insertion ..........................................510 Grouting .................................................510 Trumpet and Anchorage ....................................510 Testing and Stressing .......................................510 Testing Equipment .......................................510 Performance Test .........................................511 Proof Test ..............................................511 Creep Test .............................................. 512 Ground Anchor Load Test Acceptance Criteria .................512 Lock Off ............................................... 513 MEASUREMENT AND PAYMENT ............................ 513
SECTION 7-EARTH RETAINING SYSTEMS
7.1 7.2 7.3 7.3.1 7.3.1.1 7.3.1.2 7.3.1.3 7.3.1.4 7.3.2 7.3.3 7.3.4 7.3.5 7.3.5.1 7.3.5.2 7.3.5.3 7.3.5.4 7.3.6 7.3.6.1 7.3.6.2 7.3.6.3 7.4 7.4.1 7.4.2 7.4.3 7.5 7.5.1 7.5.2 7.5.3 7.5.4 7.6 7.6.1 7.6.2 7.6.2.1 7.6.2.2 7.6.2.3 7.6.2.3.1 7.6.2.3.2
DESCRIP'fiON .............................................515 WORKING DRAWINGS .....................................515 MATERIALS ...............................................515 Concrete ................................................. 515 Cast-in-Place ............................................515 Pneumatically Applied Mortar ..............................515 Precast Elements .........................................515 Segmental Concrete Facing Blocks ..........................515 Reinforcing Steel ..........................................516 Structural Steel ...........................................516 Timber ..................................................516 Drainage Elements ........................................516 Pipe and Perforated Pipe ...................................516 Geotextile .............................................. 516 Permeable Material .......................................516 Geocomposite Drainage Systems ............................516 Structure Backfill Material ; ................................516 General ................................................516 Crib and Cellular Walls ....................................516 Mechanically Stabilized Earth Walls .........................516 EARTHWORK .............................................517 Structure Excavation ......................................517 Foundation Treatment .....................................517 Structure Backfill .........................................517 DRAINAGE ................................................517 Concrete Gutters ..........................................517 Weep Holes ..............................................517 Drainage Blankets .........................................518 Geocomposite Drainage Systems .............................518 CONSTRUCTION ..........................................518 Concrete and Masonry Gravity Walls, Reinforced Concrete Retaining Walls ...................518 Sheet Pile and Soldier Pile Walls .............................518 Sheet Pile Walls .........................................518 Soldier Pile Walls ........................................519 Anchored Sheet Pile and Soldier Pile Walls ....................519 General ..............................................519 Wales ................................................520
Division II
Division ll
CONTENTS 7.6.2.3.3 7.6.2.3.4 7.6.2.3.5 7.6.2.3.6 7.6.3 7.6.3.1 7.6.3.2 7.6.3.3 7.6.3.4 7.6.3.5 7.6.4 7.6.4.1 7.6.4.2 7.6.4.3 7.7
Concrete Anchor Systems ................................520 Tie-rods ..............................................520 Ground Anchors .......................................520 Earthwork ............................................520 Crib Walls and Cellular Walls ...............................520 Foundation .............................................520 Crib Members ...........................................520 Concrete Monolithic Cell Members ..........................521 Member Placement ....................................... 521 Backfilling ..............................................521 Mechanically Stabilized Earth Walls .........................521 Facing .................................................521 Soil Reinforcement ....................................... 522 Construction ............................................522 MEASUREMENT AND PAYMENT ............................522
SECTION 8-CONCRETE STRUCTURES 8.1 8.1.1 8.1.2 8.1.3 8.2 8.2.1 8.2.2 8.2.3 8.3 8.3.1 8.3.2 8.3.3 8.3.4 8.3.5 8.3.6 8.3.7 8.3.8 8.4 8.4.1 8.4.1.1 8.4.1.2 8.4.1.3 8.4.2 8.4.3 8.4.4 8.4.5 8.5 8.5.1 8.5.2 8.5.3 8.5.4 8.5.4.1 8.5.4.2 8.5.5 8.5.6
GENERAL .................................................525 Description ...............................................525 Related Work .............................................525 Construction Methods .....................................525 CLASSES OF CONCRETE ..................................525 General ..................................................525 Normal Weight Concrete ...................................525 Lightweight Concrete ...................................... 525 MATERIALS ...............................................525 Cements .................................................525 Water ...................................................526 Fine Aggregate ............................................526 Coarse Aggregate .........................................526 Lightweight Aggregate .....................................526 Air-Entraining and Chemical Admixtures .....................526 Mineral Admixtures .......................................527 Steel .....................................................527 PROPORTIONING OF CONCRETE ..........................527 Mix Design ...............................................527 Responsibility and Criteria .................................527 Trial Batch Tests ..........................................527 Approval ............................................... 527 Water Content ............................................527 Cement Content ..........................................528 Mineral Admixtures .......................................528 Air-Entraining and Chemical Admixtures ......... : ...........528 MANUFACTURE OF CONCRETE ............................528 Storage of Aggregates ......................................528 Storage of Cement .........................................528 Measurement of Materials ..................................529 Hatching and Mixing Concrete ..............................529 Batching ............................................... 529 Mixing .................................................529 Delivery .................................................529 Sampling and Testing ...................................... 529
Iiii
CONTENTS
liv 8.5.7 8.5.7.1 8.5.7.2 8.5.7.3 8.5.7.4 8.5.7.5 8.6 8.6.1 8.6.2 8.6.3 8.6.4 8.6.4.1 8.6.4.2 8.6.4.3 8.6.5 8.6.6 8.6.7 8.7 8.7.1 8.7.2 8.7.2.1 8.7.2.2 8.7.2.3 8.7.2.4 8.7.2.5 8.7.3 8.7.3.1 8.7.3.2 8.7.4 8.7.5 8.7.5.1 8.7.5.2 8.7.5.3 8.8 8.8.1 8.8.2 8.8.3 8.8.4 8.9 8.9.1 8.9.2 8.9.2.1 8.9.2.2 8.9.2.3 8.9.2.4 8.9.2.5 8.9.2.6 8.9.2.6.1 8.9.2.6.2 8.9.2.6.3 8.9.2.6.4 8.9.3 8.9.3.1
Evaluation of Concrete Strength .............................530 Tests ..................................................530 For Controlling Construction Operations ......................530 For Acceptance of Concrete ................................530 For Control of Mix Design .................................530 Steam and Radiant Heat-Cured Concrete ......................530 PROTECTION OF CONCRETE FROM ENVIRONMENTAL CONDITIONS ......................................531 General ..................................................531 Rain Protection ........................................... 531 Hot Weather Protection ....................................531 Cold Weather Protection ................................... 531 Protection During Cure ....................................531 Mixing and Placing ....................................... 531 Heating of Mix ..........................................531 Special Requirements for Bridge Decks .......................532 Concrete Exposed to Salt Water .............................532 Concrete Exposed to Sulfate Soils or Water ....................532 HANDLING AND PLACING CONCRETE .....................532 General ..................................................532 Sequence of Placement .....................................532 Vertical Members ........................................532 Superstructures ..........................................533 Arches .................................................533 Box Culverts ............................................533 Precast Elements .........................................533 Placing Methods ..........................................533 General ................................................533 Equipment ..............................................533 Consolidation .............................................534 Underwater Placement .....................................534 General ................................................534 Equipment ..............................................534 Cleanup ................................................535 CONSTRUCTION JOINTS ...................................535 General ..................................................535 Bonding .................................................535 Bonding and Doweling to Existing Structures ..................535 Forms at Construction Joints ................................535 EXPANSION AND CONTRACTION JOINTS ...................535 General ..................................................535 Materials ................................................536 Premo1ded Expansion Joint Fillers ...........................536 Polystyrene Board Fillers ..................................536 Contraction Joint Material ................................. 536 Pourable Joint Sealants ....................................536 Metal Armor ............................................536 Waterstops ..............................................536 Rubber Waterstops .....................................536 Polyvinylchloride Waterstops .............................536 Copper Waterstops .....................................537 Testing of Waterstop Material .............................537 Installation ...............................................537 Open Joints .............................................537
Division II
Divisionll
0 '
CONTENTS Filled Joints .............................................537 Sealed Joints ...................... ·......................537 Waterstops .............................................. 537 Expansion Joint Armor Assemblies ..........................537 FINISHING PLASTIC CONCRETE ........................... 537 General ..................................................537 Roadway Surface Finish ....................................538 Striking Off and Floating ..................................538 Straightedging ...........................................538 Texturing ...............................................538 Dragged .............................................. 539 Broomed .............................................539 Tined ................................................ 539 Surface Testing and Correction .............................. 539 Pedestrian Walkway Surface Finish .......................... 539 Troweled and Brushed Finish ...............................539 Surface Under Bearings ....................................539 CURING CONCRETE .......................................539 General .................................................. 539 Materials ................................................540 Water ..................................................540 Liquid Membranes .......................................540 Waterproof Sheet Materials ................................540 Methods .................................................540 Forms-In-Place Method ................................... 540 Water Method ...........................................540 Liquid Membrane Curing Compound Method ..................540 Waterproof Cover Method .................................540 Steam or Radiant Heat CuringMethod ........................541 Bridge Decks .............................................541 FINISHING FORMED CONCRETE SURFACES ................541 General ..................................................541 Class !-Ordinary Surface Finish ...........................541 Class 2-Rubbed Finish .................................... 542 Class 3-Tooled Finish .....................................542 Class 4-Sandblasted Finish ................................542 Class 5-Wire Brushed or Scrubbed Finish .................... 542 PRECAST CONCRETE MEMBERS ...........................543 General ..................................................543 Working Drawings ........................................ 543 Materials and Manufacture ..... ·............................543 Curing ..................................................543 Storage and Handling ......................................543 Erection .................................................544 Epoxy Bonding Agents for Precast Segmental Box Girders .......544 Materials ...............................................544 Test 1-Sag Flow of Mixed Epoxy Bonding Agent ............544 Test 2-Gel Time of Mixed Epoxy Bonding Agent ............ 544 Test 3-0pen Time of Bonding Agent ......................544 Test 4-Three-Point Tensile Bending Test ...................545 Test 5-Compression Strength of Cured Epoxy Bonding Agent ...................................... 545 Test 6-Temperature Deflection of Epoxy Bonding Agent ...... 545 8.13.7.1.6
8.9.3.2 8.9.3.3 8.9.3.4 8.9.3.5 8.10 8.10.1 8.10.2 8.10.2.1 8.10.2.2 8.10.2.3 8.10.2.3.1 8.10.2.3.2 8.10.2.3.3 8.10.2.4 8.10.3 8.10.4 8.10.5 8.11 8.11.1 8.11.2 8.11.2.1 8.11.2.2 8.11.2.3 8.11.3 8.11.3.1 8.11.3.2 8.11.3.3 8.11.3.4 8.11.3.5 8.11.4 8.12 8.12.1 8.12.2 8.12.3 8.12.4 8.12.5 8.12.6 8.13 8.13.1 8.13.2 8.13.3 8.13.4 8.13.5 8.13.6 8.13.7 8.13.7.1 8.13.7.1.1 8.13.7.1.2 8.13.7.1.3 8.13.7.1.4 8.13.7.1.5
8.13.7.1.7
Test ?-Compression and Shear Strength of Cured Epoxy
1v
CONTENTS
Ivi 8.13.7.2 8.14 8.14.1 8.14.2 8.14.3 8.15 8.15.1 8.15.2 8.15.3 8.15.4 8.16 8.16.1 8.16.2
Bonding Agent ............................ · · · .. · · · · .545 Mixing and Installation of Epoxy ............................546 MORTAR AND GROUT .....................................546 General ...................................... · . · · · · · · · · · .546 Materials and Mixing ................................. · . · · .546 Placing and Ctlring ........................................547 APPLICATION OF LOADS ..................................547 General ..................................................547 Earth Loads ..............................................547 Construction Loads ........................................547 'Iraffic Loads .............................................547 MEASUREMENT AND PAYMENT ............................547 Measurement .............................................547 Payment .................................................548
SECTION 9-REINFORCING STEEL 9.1 9.2 9.2.1 9.2.2 9.2.3 9.2.4 9.3 9.4 9.4.1 9.4.2 9.4.3 9.5 9.6 9.6.1 9.6.2 9.6.3 9.6.4 9.6.5 9.6.6 9.7 9.7.1 9.7.2 9.7.3 9.7.4 9.8 9.9 9.10 9.11
DESCRIPTION .............................................549 MATERIAL ................................................ 549 Uncoated Reinforcing Steel .................................549 Epoxy-Coated Reinforcing Steel .............................549 Stainless Steel Reinforcing Bars .............................549 Mill'l'est Reports· ..........................................549 BAR LISTS AND BENDING DIAGRAMS ......................549 FABRICATION .............................................550 Bending .................................................550 Hooks and Bend Dimensions ................................550 Identification .............................................550 HANDLING, STORING, AND SURFACE CONDmON OF REINFORCEMENT .............................550 PLACING AND FASTENING .................................550 General ..................................................550 Support Systems ..........................................550 Precast Concrete Blocks .................................... 550 Wire Bar Supports ........................................550 Adjusbnents ..............................................551 Repair of Damaged Epoxy Coating ...........................551 SPLICING OF BARS ........................................551 General ..................................................551 Lap Splices ............................................... 551 Welded Splices ............................................551 Mechanical Splices ........................................551 SPLICING OF WELDED WIRE FABRIC ......................552 SUBSTITUTIONS ..........................................552 MEASUREMENT ...........................................552 PAYMENT .................................................552
SECTION tO-PRESTRESSING I 0.1 10.1.'1 10.1.2 10.2 10.2.1
GENERAL .................................................553 Description ...............................................553 Details of Design ...........................................553 SUPPLEMENTARY DRAWINGS .............................553 Working Drawings ........................................553
Division ll
Division ll
c ~
0
.
CONTENTS 10.2.2 10.3 10.3.1 10.3.1.1 10.3.1.2 10.3.1.3 10.3.2 10.3.2.1 10.3.2.2 10.3.2.3 10.3.2.3.7 10.3.2.3.8 10.3.2.3.9 10.4 10.4.1 10.4.1.1 10.4.2 10.4.2.1 10.4.2.2 10.4.2.2.1 10.4.3 10.5 10.5.1 10.5.2 10.5.3 10.6 10.7 10.8 10.8.1 10.8.2 10.8.3 10.8.4 10.9 10.9.1 10.9.2 10.9.3 10.10 10.10.1 10.10.1.1 10.10.1.2 10.10.1.3 10.10.1.4 10.10.2 10.10.3 10.11 10.11.1 10.11.2 10.11.3 10.11.4 10.11.5 10.11.6 10.12
Composite Placing Drawings ................................ 554 MATERIALS ............................................... 554 Prestressing Steel and Anchorages ........................... 554 Strand ................................................. 554 Wrre ................................................... 554 Bars ...................................................554 Post-Tensioning Anchorages and Couplers ....................554 Bonded Systems .........................................554 Unbonded Systems ....................................... 554 Special Anchorage Device Acceptance Test ....................555 Cyclic Loading Test ....................................555 Sustained Loading Test .................................. 555 Monotonic Loading Test .................................555 PLACEMENT OF DUCTS, STEEL, AND ANCHORAGE HARDWARE .......................................556 Placement of Ducts ........................................ 556 Vents and Drains .........................................556 Placement of Prestressing Steel .............................. 556 Placement for Pretensioning ................................ 556 Placement for Post-Tensioning .............................. 557 Protection of Steel After Installation ........................557 Placement of Anchorage Hardware ...........................557 IDENTIFICATION AND TESTING ............................557 Pretensioning Method Tendons ..............................558 Post-Tensioning Method Tendons ............................558 Anchorage Assemblies and Couplers .........................558 PROTECTION OF PRESTRESSING STEEL ...................558 CORROSION INHIBITOR .................................. .558 DUCTS ....................................................558 Metal Ducts ..............................................559 Polyethylene Duct ......................................... 559 Duct Area ................................................559 Duct Fittings ............................................. 559 GROUT ................................................... 559 Portland Cement .......................................... 559 Water ...................................................559 Admixtures .............................................. 560 TENSIONING ..............................................560 General Tensioning Requirements ........................... 560 Concrete Strength ........................................560 Prestressing Equipment .................................... 560 Sequence of Stressing .....................................561 Measurement of Stress ....................................561 Pretensioning Method Requirements .........................561 Post-Tensioning Method Requirements .......................562 GROUTING ...............................................562 General .................................................. 562 Preparation of Ducts .......................................562 Equipment ............................................... 562 Mixing of Grout ..... : .....................................562 Injection of Grout .........................................563 Temperature Considerations ................................563 MEASUREMENT AND PAYMENT ............................563
I vii
CONTENTS
Iviii
10.12.1 10.12.2
Measurement .............................................563 Payment ................................................. 563
SECTION II-STEEL STRUCTURES
11.1 11.1.1 11.1.2 11.1.3 11.1.4 11.2 11.2.1 11.2.2 11.2.3 1.1.3 11.3.1 I 1.3.1.1 11.3.1.2 11.3.1.3 I 1.3.1.4 11.3.1.5 11.3.1.6 11.3.1.7 11.3.2 11.3.2.1 11.3.2.2 11.3.2.3 11.3.2.4 11.3.2.5 11.3.2.6 11.3.3 11.3.3.1 11.3.3.2 11.3.3.3 11.3.3.4 11.3.3.5 11.3.4 11.3.4.1 11.3.4.2 11.3.5 11.3.5.1 11.3.5.2 11.3.6 11.3.6.1 11.3.6.2 11.3.6.3 11.3.7 11.4 11.4.1 11.4.2 11.4.3
GENERAL .................................................565 Description ...............................................565 Notice of Beginning of Work ................................565 Inspection ................................................565 Inspector's Authority ......................................565 WORKING DRAWINGS .....................................566 Shop Drawings ...........................................566 Erection Drawings ........................................ 566 Camber Diagram .........................................566 MATERIALS ...............................................566 Structural Steel ...........................................566 General ................................................566 Carbon Steel ............................................566 High-Strength Low-Alloy Structural Steel ..................... 566 High-Strength Low-Alloy, Quenched and Tempered Structural Steel Plate ..........................................566 High-Yield Strength, Quenched and Tempered Alloy Steel Plate ... 566 Eyebars ................................................567 Structural Thbing ........................................567 High-Strength Fasteners ....................................567 Material ................................................567 Identifying Marks ........................................567 Dimensions .............................................567 Galvanized High-Strength Fasteners .........................568 Alternative Fasteners .....................................568 Load Indicator Devices ....................................568 Welded Stud Shear Connectors ..............................568 Materials ...............................................568 Test Methods ............................................568 Finish .................................................568 Certification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .569 Check Samples ..........................................569 Steel Forgings and Steel Shafting ............................569 Steel Forgings ...........................................569 Cold Finished Carbon Steel Shafting .........................569 Steel Castings .............................................569 Mild Steel Castings .......................................569 Chromium Alloy-Steel Castings .............................569 Iron Castings .............................................569 Materials ...............................................569 Workmanship and Finish ..................................569 Cleaning ............................................... 569 Galvanizing ..............................................569 FABRICATION .............................................570 Identification of Steels During Fabrication ....................570 Storage of Materials .......................................570 Plates ...................................................570
Division II
CONTENTS
Division II
0
11.4.3.1 11.4.3.2 11.4.3.2.1 11.4.3.2.2 11.4.3.2.3 11.4.3.3 11.4.3.3.1 11.4.3.3.2 11.4.3.3.3 11.4.4 11.4.5 11.4.6 11.4.7 11.4.8 11.4.8.1 11.4.8.1.1 11.4.8.1.2 11.4.8.1.3 11.4.8.1.4 11.4.8.2 11.4.8.2.1 11.4.8.2.2 11.4.8.3 11.4.8.4 11.4.8.5 11.4.9 11.4.9.1 11.4.9.2 11.4.9.3 11.4.10 11.4.11 11.4.12 11.4.12.1 11.4.12.2 11.4.12.2.1 11.4.12.2.2 11.4.12.2.3 11.4.12.2.4 11.4.12.2.5 11.4.12.2.6 11.4.12.2. 7 11.4.13 11.4.13.1 11.4.13.2 11.4.13.3 11.4.13.4 11.4.14 11.4.15 11.5
Direction of Rolling ...................................... 570 Plate Cut Edges .......................................... 570 Edge Planing ..........................................570 Oxygen Cutting ........................................570 Visual Inspection and Repair of Plate Cut Edges .............. 570 Bent Plates .............................................570 General .............................................. 570 Cold Bending ......................................... 570 Hot Bending .......................................... 571 Fit of Stiffeners ...........................................571 Abutting Joints ...........................................571 Facing of Bearing Surfaces .................................. 571 Straightening Material .....................................571 Bolt Holes ................................................ 571 Holes for High-Strength Bolts and Unfinished Bolts ..............................................571 General .............................................. 571 Punched Holes ........................................ 572 Reamed or Drilled Holes ................................572 Accuracy of Holes ......................................572 Accuracy of Hole Group ...................................572 Accuracy Before Reaming ...............................572 Accuracy After Reaming ................................. 572 Numerically Controlled Drilled Field Connections ..............572 Holes for Ribbed Bolts, Turned Bolts, or Other Approved Bearing Type Bolts ................... 572 Preparation of Field Connections ............................573 Pins and Rollers ........................................... 573 General ................................................ 573 Boring Pin Holes .........................................573 Threads for Bolts and Pins .................................573 Eyebars ..................................................573 Annealing and Stress Relieving ..............................573 Curved Girders ...........................................574 General ................................................574 Heat Curving Rolled Beams and Welded Girders ...............574 Materials .............................................574 Type of Heating ........................................574 Temperature ..........................................57 4 Position for Heating ....................................574 Sequence of Operations .................................575 Camber ..............................................575 Measurement of Curvature and Camber ..................... 575 Orthotropic-Deck Superstructures ...........................575 General ................................................57 5 Flatness of Panels ........................................575 Straightness of Longitudinal Stiffeners Subject to Calculated Compressive Stress, Including Orthotropic-Deck Ribs .......576 Straightness of Transverse Web Stiffeners and Other Stiffeners Not Subject to Calculated Compressive Stress ..............576 Full-Sized 'I'ests ...........................................576 Marking and Shipping .....................................576 ASSEMBLY ................................................576
lix
CONTENTS
lx
Bolting ..................................................576 11.5.1 11.5.2 Welded Connections .......................................576 11.5.3 Preassembly of Field Connections ............................576 11.5.3.1 General ................................................576 11.5.3.2 Bolted Connections .......................................577 11.5.3.3 Check Assembly-Numerically Controlled Drilling .............577 11.5.3.4 Field Welded Connections .................................577 11.5.4 Match Marking ...........................................577 11.5.5 Connections Using Unfinished, 'fumed, or Ribbed Bolts .........577 11.5.5.1 General ................................................577 I 1.5.5.2 Turned Bolts ............................................577 11.5.5.3 Ribbed Bolts ............................................577 11.5.6 Connections Using High-Strength Bolts .......................578 11.5.6.1 General ................................................578 11.5.6.2 Bolted Parts ............................................. 578 11.5.6.3 Surface Conditions .......................................578 11.5.6.4 Installation ..............................................578 11.5.6.4.1 General ..............................................578 11.5.6.4.2 Rotational-Capacity Tests ................................579 11.5.6.4.3 Requirement for Washers .................................580 11.5.6.4.4 Tum-of-Nut Installation Method ..........................580 11.5.6.4.5 Calibrated Wrench Installation Method ..................... 580 11.5.6.4.6 Alternative Design Bolts Installation Method ................581 11.5.6.4.7 Direct Tension Indicator Installation Method .................581 11.5.6.4.7a Verification .......................................... 581 11.5.6.4.7b Installation ...........................................582 11.5.6.4.8 Lock-Pin and Collar Fasteners ............................ 582 11.5.6.4.9 Inspection ............................................582 11.5.7 Welding .................................................583 11.6 ERECTION ................................................583 11.6.1 General ..................................................583 11.6.2 Handling and Storing Materials .............................583 1I.6.3 Bearings and Anchorages ...................................583 11.6.4 Erection Procedure ........................................583 11.6.4. I Conformance to Drawings ................................. 583 11.6.4.2 Erection Stresses .........................................584 11.6.4.3 Maintaining Alignment and Camber ..........................584 11.6.5 Field Assembly ............................................584 I1.6.6 Pin Connections ...........................................584 11.6.7 Misfits ...................................................584 11.7 MEASUREMENT AND PAYMENT ............................584 I 1.7.1 Method of Measurement ...................................584 11.7.2 Basis of Payment ..........................................585 SECTION 12-STEEL GRID FLOORING
12.1 12.1.1 12. I .2 12.2 12.2.1 12.2.2
GENERAL .................................................587 Description ...............................................587 Working Drawings ........................................587 MATERIA~ ...............................................587 Steel ....................................................587 Protective Theatment .......................................587
Division ll
Division ll
0
CONTENTS 12.2.3 12.2.4 12.3 12.4 12.5 12.6 12.7 12.8 12.9 12.9.1 12.9.2 12.10
Concrete ................................................. 587 Skid Resistance ...........................................587 ARRANGEMENT OF SECTIONS ............................. 587 PROVISION FOR CAMBER .................................588 FIELD ASSEMBLY .........................................588 CONNECTION TO SUPPORTS ...............................588 WELDING ................................................. 588 REPAIRING DAMAGED GALVANIZED COATINGS ............588 PLACEMENT OF CONCRETE FILLER ....................... 588 Forms ................................................... 588 Placement ................................................ 589 MEASUREMENT AND PAYMENT ........... ·................. 589
SECTION 13-PAINTING
0
13.1 13.1.1 13.1.2 13.1.3 13.1.4 13.2 13.2.1 13.2.2 13.2.3 13.2.3.1 13.2.3.2 13.2.3.3 13.2.3.4 13.2.4 13.2.4.1 13.2.5 13.3 13.4 13.4.1 13.4.2 13.4.3 13.4.4 13.4.5 13.4.6 13.5 13.5.1 13.5.2 13.5.3 13.5.4
GENERAL .................................................591 Description ...............................................591 Protection of Public and Property ............................ 591 Protection of the Work .....................................591 Color ....................................................591 PAINTING METAL STRUCTURES ...........................591 Coating Systems and Paints ................................. 591 Weather Conditions ....................................... 591 Surface Preparation .......................................592 Blast Cleaning ...........................................592 Steam Cleaning .......................................... 593 Solvent Cleaning ......................................... 593 Hand Cleaning .......................................... 593 Application of Paints ....................................... 593 Application of Zinc-Rich Primers ............................594 Measurement and Payment ................................. 594 PAINTING GALVANIZED SURFACES ........................594 PAINTING TIMBER ........................................595 General .................................................. 595 Preparation of Surfaces ....................................595 Paint .................................................... 595 Application .............................................. .595 Painting Treated Timber ...................................595 Payment ................................................. 595 PAINTING CONCRETE .....................................595 Surface Preparation .......................................595 Paint ....................................................595 Application ...............................................595 Measurement and Payment ................................. 596
SECTION 14-STONE MASONRY
0
14.1 14.1.1 14.1.2 14.2
DESCRIP'fiON ............................................. 597 Rubble Masonry ..........................................597 Ashlar Masonry ....................................... · ...597 MATERIALS ........................................ · · · · . · .597
Ixi
CONTENTS
lxii 14.2.1.1 14.2.1.2 14.2.2 14.2.3 14.3 14.3.1 14.3.2 14.3.3 14.3.3.1 14.3.3.2 14.3.3.3 14.3.4 14.3.4.1 14.3.4.2 14.3.4.3 14.3.5 14.4 14.4.1 14.4.2 14.4.3 14.4.3.1 14.4.3.2 14.4.3.3 14.4.4 14.4.5 14.4.6 14.4.6.1 14.4.6.2 14.4.6.3 14.4.6.4 14.4.7 14.4.8 14.4.8.1 14.4.8.2 14.4.9 14.4.10 14.4.11 14.4.12 14.5
Rubble Stone ............................................597 Ashlar Stone ............................................597 Shipment and Storage of Stone .............................. 597 Mortar .................................................. 597 MANUFACTURE OF STONE FOR MASONRY ................. 598 General .................................................. 598 Surface Finishes of Stone ...................................598 Rubble Masonry ..........................................598 Size ...................................................598 Shape ..................................................598 Dressing ...............................................598 Ashlar Masonry ........................ , ..................598 Size ...................................................598 Dressing ............................................... 598 Stretchers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...599 Arch Ring Stones .......................................... 599 CONSTRUCTION .......................................... 599 Weather Conditions .......................................599 Mixing Mortar ............................................599 Selection and Placing of Stone ...............................599 General ................................................ 599 Rubble Masonry ......................................... 599 Ashlar Masonry .......................................... 600 Beds and Joints ...........................................600 Headers .................................................600 Cores and Backing ........................................600 General ................................................600 Stone ..................................................600 Concrete ...............................................600 Leveling Courses ........................................600 Facing for Concrete ........................................601 Copings .................................................601 Stone ..................................................601 Concrete ...............................................601 Dowels and Cramps .......................................601 Weep Holes ..............................................601 Pointing ..................................................601 Arches ...................................................602 MEASUREMENT AND PAYMENT ............................602
SECTION IS-CONCRETE BLOCK AND BRICK MASONRY
15.1 15.2 15.2.1 15.2.2 15.2.3 15.2.4 15.2.5 15.2.6 15.2.6.1 15.2.6.2
DESCRIPTION .............................................603 MATERIALS ...............................................603 Concrete Block ........................................... 603 Brick ....................................................603 Reinforcing Steel ..........................................603 Mortar ..................................................603 Grout ...................................................603 Sampling and Testing ......................................603 Mortar .................................................603 Grout ..................................................604
Division ll
Division II
c .
.
CONTENTS 15.3 15.3.1 15.3.2 15.3.3 15.3.4 15.3.5 15.4
CONSTRUCTION ..........................................604 Weather Conditions .......................................604 Laying Block and Brick ....................................604 Placement of Reinforcement ................................604 Grouting of Voids .........................................604 Copings, Bridge Seats, and Backwalls ........................605 MEASUREMENT AND PAYMENT ............................606
SECTION 16-TIMBER STRUCTURES
0
16.1 16.1.1 16.2 16.2.1 16.2.2 16.2.3 16.2.4 16.2.5 16.2.6 16.2.6.1 16.2.6.2 16.2.6.3 16.2.6.4 16.3 16.3.1 16.3.2 16.3.3 16.3.3.1 16.3.3.2 16.3.3.3 16.3.3.4 16.3.3.5 16.3.4 16.3.5 16.3.6 16.3.7 16.3.8 16.3.9 16.3.9.1 16.3.9.2 16.3.9.3 16.3.9.4 16.3.9.5 16.3.9.6 16.3.10 16.3.11 16.3.12 16.3.13 16.3.14 16.3.15 16.3.16 16.4
GENERAL .................................................607 Related Work .............................................607 MATERIALS ............................................... 607 Lumber and Timber (Solid Sawn or Glued Laminated) ..........607 Steel Components ......................................... 607 Castings .................................................608 Hardware ................................................608 Galvanizing .............................................. 608 Timber Connectors ........................................608 Dimensions .............................................608 Split Ring Connectors .....................................608 Shear-Plate Connectors ....................................608 Spike-Grid Connectors ....................................608 FABRICATION AND CONSTRUCTION ....................... 609 Workmanship ............................................609 Storage of Material ........................................609 1'reated Timber ........................................... 609 Handling ...............................................609 Framing and Boring ......................................609 Cuts and Abrasions .......................................610 Bored Holes ............................................610 Temporary Attachment ....................................61 0 Installation of Connectors .................................. 610 Holes for Bolts, Dowels, Rods, and Lag Screws .................610 Bolts and Washers .........................................610 Countersinking ........................................... 611 Framing .................................................611 Framed Bents .............................................611 Mud Sills ...............................................611 Concrete Pedestals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ......611 Sills ...................................................611 Posts ..................................................611 Caps ...................................................611 Bracing ................................................611 Stringers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .611 Plank Floors ..............................................612 Nail Laminated or Strip Floors ..............................612 Glue Laminated Panel Decks ................................ 612 Composite Wood-Concrete Decks ............................612 Wheel Guards and Railing ..................................612 1'russes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .... 613 PAINTING .................................................613
lxiii
CONTENTS
lxiv 16.5 16.6
MEASUREMENT ...........................................613 PAYMENT .................................................613
SECTION 17-PRESERVATIVE TREATMENT OF WOOD 17.1 17.2 17.2.1 17.2.2 17.2.3 17.3 17.3.1 17.3.2 17.3.3 17.4
GENERAL .................................................615 MATERIALS ...............................................615 Wood ....................................................615 Preservatives and Treatments ...............................615 Coal-tar Roofing Cement ...................................615 IDENTIFICATION AND INSPECTION ........................615 Branding and Job Site Inspection ............................615 Inspection at Treatment Plant ...............................616 Certificate of Compliance ...................................616 MEASUREMENT AND PAYMENT ............................ 616
SECTION 18-BEARINGS SCOPE ....................................................617 APPLICABLE DOCUMENTS ................................617 AASHTO Standards .......................................617 ASTM Standards .........................................617 Other Standards ..........................................618 GENERAL REQUIREMENTS ................................618 MATERIALS ...............................................618 General ..................................................618 Steel ................................................... 618 Special Material Requirements for Metal Rocker and Roller Bearings .....................................618 18.4.3 Special Material Requirements for PTFE Sliding Surfaces .....•.619 18.4.3.1 PTFE .................................................•619 18.4.3.2 Adhesives ..............................................619 18.4.3.3 Lubricants .......................................... , ...619 18.4.3.4 Interlocked Bronze and Filled PTFE Structures .................619 18.4.4 Special Material Requirements for Pot Bearings ................619 18.4.5 Special Material Requirements for Steel Reinforced Elastomeric Bearings and Elastomeric Pads .............620 18.4.5.1 Elastomer ..............................................620 18.4.5.2 Fabric Reinforcement .....................................620 18.4.5.3 Bond ..................................................620 18.4.6 Special Material Requirements for Bronze or Copper Alloy Sliding Surfaces .........................620 18.4.6.1 Bronze and Copper Alloys .................................620 18.4.6.1.1 Bronze ................................ ; ..............620 18.4.6.1.2 Rolled Copper-Alloy ....................................620 18.4.6.2 Oil Impregnated Metal Powder Sintered Material ...............620 18.4.7 Special Material Requirements for Disc Bearings ...............620 18.4.7.1 EJastomeric Rotational Element .............................620 18.4.8 Special Material Requirements for Guides ....................620 18.4.8.1 Low-friction Material .....................................620 18.4.8.2 Adhesive ...............................................623 18.4.9 Speclal Requirements for Bedding Materials ................... 623 18.1 18.2 18.2.1 18.2.2 18.2.3 18.3 18.4 18.4.1 18.4.1. I 18.4.2
Division ll
CONTENTS
Division II
0
18.4.9.1 18.4.9.2 18.4.9.3 18.4.9.4 18.5 18.5.1 18.5.2 18.5.2.1 18.5.2.2 18.5.3 18.5.3.1 18.5.3.2 18.5.3.2.1 18.5.3.2.2 18.5.3.2.3 18.5.3.3 18.5.3.4 18.5.4 18.5.5 18.5.5.1 18.5.5.2 18.5.5.3 18.5.6 18.5.6.1 18.5.6.2 18.5.6.3 18.5.6.4 18.5.7
0
18.5.7.1 18.5.7.2 18.5.8 18.5.8.1 18.5.8.2 18.5.9 18.5.10 18.5.11 18.6 18.7 18.7.1 18.7.1.1 18.7.1.2 18.7.1.3 18.7.1.4 18.7.2 18.7.2.1 18.7.2.2 18.7.2.3 18.7.2.4 18.7.2.5 18.7.2.6
Fabric-Reinforced Elastomeric Bedding Pads ..................623 Sheet Lead ..............................................623 Caulk ..................................................623 Grout and Mortar ........................................623 FABRICATION .............................................623 General .................................................. 623
Special Fabrication Requirements for Metal Rocker and Roller Bearings .....................................623 Steel ...................................................623 Lubricant ...............................................623 Special Fabrication Requirements for PI'FE Sliding Bearings ....625 Fabrication of PTFE ......................................625 Attachment of PTFE ......................................625 Flat Sheet PTFE .......................................625 Curved Sheet P'fFE .....................................625 Woven PTFE Fabric .................................... 625 Stainless Steel Mating Surface ..............................625 Lubrication .............................................625 Special Fabrication Requirements for Curved Sliding Bearings ...625
Special Fabrication Requirements for Pot Bearings ............. 625 Pot ................................................... 625 Sealing Rings ...........................................625 Elastomeric Rotational Element .............................626
Special Fabrication Requirements for Steel Reinforced Elastomeric Bearings and Elastomeric Pads ............. 626 Requirements for All Elastomeric Bearings .................... 626 Steel Laminated Elastomeric Bearings ........................626 Fabric Reinforced Elastomeric Pads ..........................626 Plain Ela~tomeric Pads ....................................626
Special Fabrication Requirements for Bronze and Copper Alloy Bearings ...............................626 Bronze Sliding Surfaces ...................................626 Copper Alloy Plates ...................................... 626 Special Fabrication Requirements for Disc Bearings ............626 Steel Housing ...........................................626 Elastomeric Rotational Element .............................626 Special Fabrication Requirements for Guides ..................626 Special Requirements for Load Plates ........................627 Special Requirements for Anchor Bolts .......................627 CORROSION PROTECTION ................................627 TESTING AND ACCEPTANCE ...............................627 General ..................................................627 Scope ..................................................627 Definitions ..............................................627 Test Pieces to be Supplied to the Engineer .....................627 Tapered Sole Plates .......................................627 Tests ...................................................627 Material Certification Tests ................................. 627 Material Friction Test (Sliding Surfaces Only) .................. 628 Dimensional Check .......................................628 Clearance Test ...........................................628 Short-term Compression Proof Load Test .....................628 Long-term Compression Proof Load Test ......................628
lxv
CONTENTS
Ixvi 18.7.2.7 18.7.2.8 18.7.2.9 18.7.3 18.7.4 18.7.4.1 18.7.4.2 18.7.4.3 18.7.4.4 18.7.4.4.1 18.7.4.4.2 18.7.4.4.3 18.7.4.5 18.7.4.5.1 18.7.4.5.2 18.7.4.5.3 18.7.4.5.4 18.7.4.5.5 18.7.4.5.6 18.7.4.5.7 18.7.4.5.8 18.7.4.7 18.7.4.8 18.7.4.8.1 18.7.4.802 18.7.4.8.3 18.7.5 18.7.6 1808 18o9 18.9.1 18.9.2 18.9.2.1 l8o9.2.2 18.9.2.3 18.9.2.4 18.10 18.10.1 18.10.2 18.1003 18.11 18.12
Bearing Friction Test {for sliding surfaces only) .... 0...........628 Long-term Deterioration Test . 0.... oo.. o.. o............ oo...629 Bearing Horizontal Force Capacity {Fixed or Guided Bearings Only) .................. 0.............629 Performance Criteria .. o...................................629 Special Testing Requirements ................ o..............629 Special Test Requirements for Rocker and Roller Bearings .... 0...629 Special Test Requirements for PTFE Sliding Bearings ...... 0....629 Special Test Requirements for Curved Sliding Bearings .. ooo.....630 Special Test Requirements for Pot Bearings ....................630 Material Certification Tests .. 0. o.... 0..... o.. 0.. 0.. 00.... o630 Testing by the Engineer . o. 00. ooooooooo. o..... 0.... o.. 00o630 Bearing Tests 0.... 0.... 00..................... 000......630 Test Requirements for Elastomeric Bearings ..... 0.............630 Scope. 0. 0. ooo00..... ooo000.... 0. 0. 00.... 00. 0. 000.. 0..630 Frequency of Testing .. 0.... 0. o.. 00. 0.. 0.. 0000... 0.... 00o630 Ambient Temperature Tests on the Elastomer .... 0.. 0. oo.... o631 Low Temperature Tests on the Elastomer 0... oo........ 0. 0. 0.631 Visual Inspection of the Finished Bearing . 0.... 000...... 0.. o631 Short-Duration Compression Tests on Bearings . 0. 00.. 0. 0000. o631 Long~Duration Compression Tests on Bearings 000.... 0. 00. 00o631 Shear Modulus Tests on Materials from Bearings 000. 0... 0000.631 Test Requirements for Bronze and Copper Alloy Bearings ...... 0.631 Test Requirements for Disc Bearings .........................632 Material Certification Tests ..................... 0.........632 Testing by the Engineer ........ o. 0......................632 Bearing Tests ....... 0.... 0. 0o............ 0o0. 0.. o......632 Cost of Transporting ... o...... o............... o...... o.....632 Use of Tested Bearings in the Structure .......................632 PACKING, SHIPPING AND STORING ............... o.... o...632 INSTALLATION .. o.... o.. o.. o............ o.... oo...... o.. o.632 General Installation Requirements . 0o... 0...... o.............632 Special Installation Requirements ............................633 Installation of Rocker and Roller Bearings .....................633 Installation of Elastomeric Bearings ..........................633 Installation of Guideways and Restraints ......................633 Installation of Anchorages ..... 0...........•...............633 DOCUMENTATION ........................................633 Working Drawings ........................................633 Marking 0............................... o................633 Certification .......... o...................................633 MEASUREMENT .............. o... o. oooo.. 0. oo.... o.... o...634 PAYMENT .. o.. ooo.. o. oo. o.... oo. oo. o.... o............ o... o634
SECTION 19-BRIDGE DECK JOINT SEALS
19.1 19.2 19o3 19.4 19.4.1 19.4.2
GENERAL .. oo....... o. o. oooo. o. o................. 0. o......635 WORKING DRAWINGS .. o.. oo. o..... o.... o........ 0...... 0.635 MATERIALS .. ooo... o. o0. o. oo. o.. 0o. 0. o...... 0... 0.... 0....635 MANUFACTURE AND FABRICATION ..... o. ooo. o..... 0.. 00..635 Compression Seal Joints ...... 0.. 0. 00.... 0.. 0........... 00.. 635 Joint Seal Assemblies 0..•...... 0........ 0......... 0. 0......635
Division ll
Division ll
0
CONTENTS 19.5 19.5.1 19.5.2 19.5.3 19.6
INSTALLATION ............................................635 General ..................................................635 Compression Seal Joints .................................... 636 Joint Seal Assemblies ...................................... 636 MEASUREMENT AND PAYMENT ............................636
SECTION 20-RAILINGS
0
20.1 20.1.1 20.1.2 20.1.3 20.1.4 20.2 20.2.1 20.2.1.1 20.2.1.2 20.2.1.3 20.2.1.4 20.2.2 20.2.3 20.3 20.3.1 20.4 20.5 20.6 20.7 20.7.1 20.7.2
GENERAL ................................................. 637 Description ............................................... 637 Materials ................................................ 637 Construction ............................................. 637 Line and Grade ...........................................637 METAL RAILING ..........................................637 Materials and Fabrication ..................................637 Steel Railing ............................................ 637 Aluminum Railing .......................................637 Metal Beam Railing ......................................637 Welding ................................................ 637 Installation ...............................................637 Finish ...................................................638 CONCRETE RAILING ......................................638 Materials and Construction ................................. 638 TIMBER RAILING .........................................638 STONE AND BRICK RAILINGS ..............................638 TEMPORARY RAILING ....................................638 MEASUREMENT AND PAYMENT ............................ 638 Measurement .............................................638 Payment .................................................638
SECTION 21-WATERPROOFING
21.1 21.1.1 21.1.2 21.2 21.2.1 21.2.1.1 21.2.1.2 21.2.1.3 21.2.2 21.2.2.1 21.2.2.2 21.2.2.3 21.2.3 21.2.4 21.2.5 21.3 21.4 21.4.1
GENERAL .................................................639 Waterproofing ............................................639 Dampproofing ............................................639 MATERIALS ..........................................· ..... 639 Asphalt Membrane Waterproofing System ....................639 Asphalt ................................................639 Primer .................................................639 Fabric ................................................. 639 Preformed Membrane Waterproofing Systems .................639 Primer .................................................639 Preformed Membrane Sheet ................................ 639 Mastic .................................................640 Protective Covers .........................................640 Dampproofing ............................................640 Inspection and Delivery ....................................640 SURFACE PREPARATION ...................................640 APPLICATION ....................... ~ .....................640 Asphalt Membrane Waterproofing ...........................641
lxvii
CONTENTS
lxviii 21.4.1.1 21.4.1.2 21.4.1.3 21.4.1.4 21.4.2 21.4.2.1 21.4.2.2 21.4.2.3 21.4.3 21.4.4 21.5
General ................................................641 Installation ..............................................641 Special Details ..........................................641 Damage Patching ........................................641 Preformed Membrane Waterproofing Systems .................642 General ................................................642 Installation on Bridge Decks ................................642 Installation on Other Surfaces ...............................642 Protective Cover ..........................................642 Dampproofing ............................................643 MEASUREMENT AND PAYMENT ............................643
SECTION 22-SLOPE PROTECTION
22.1 22.1.1 22.1.2 22'.2 22.3 22.3.1 22.3.2 22.3.3 22.3.4 22.3.5 22.3.6 22.3.7 22.3.8 22.3.9 22.3.10 22.4 22.4.1 22.4.2 22.4.3 22.4.4 22.4.5 22.4.6 22.4.6.1 22.4.6.2 22.4.7 22.4.7.1 22.4.7.2 22.4.8 22.4.9 22.4.10 22.4.10.1 22.4.10.2 22.4.10.3 22.5 22.5.1 22.5.1.1 22.5.1.2 22.5.1.3
GENERAL .................................................645 Description ...............................................645 'IYpes ....................................................645 WORKING DRAWINGS ..................................... 645 MATERIALS ...............................................645 Aggregate ................................................645 Wire-Enclosed Riprap (Gabions) ............................645 Filter Fabric ..............................................645 Grout ....... ·............................................646 Sacked Concrete Riprap ....................................646 Portland Cement Concrete ..................................646 Pneumatically Applied Mortar ..............................646 Precast Portland Cement Concrete Blocks and Shapes .........................................646 Reinforcing Steel ..........................................646 Geocomposite Drain .......................................646 CONSTRUCTION ..........................................646 Preparation of Slopes ......................................646 Bedding .................................................646 Filter Fabric ..............................................646 Geocomposite Drain .......................................647 Hand Placing Stones .......................................647 Machine-Placed Stones .....................................647 Dry Placement ...........................................647 Underwater Placement ....................................647 Wire-Enclosed Riprap (Gabions) ............................647 Fabrication .............................................647 Installation ....................................... ', ......648 Grouted Riprap ...........................................648 Sacked Concrete Riprap ....................................648 Concrete Slope Paving .....................................648 General ................................................648 Cast-in-Place Slope Paving .................................649 Precast Slope Paving ......................................649 MEASUREMENT AND PAYMENT ............................649 Method of Measurement ...................................649 Stone Riprap and Filter Blanket .............. .' ..............649 Sacked Concrete Riprap ...................................649 Wire-Enclosed Riprap (Gabions) ............................649
Division IT
CONTENTS
Division II
0
22.5.1.4 22.5.1.5 22.5.1.6 22.5.2 22.5.2.1 22.5.2.2 22.5.2.3 22.5.2.4 22.5.2.5 22.5.2.6 22.5.2.7 22.5.2.8 22.5.2.9
Cast-in-Place Concrete Slope Paving .........................650 Precast Concrete Slope Paving ..............................650 Filter Fabric ............................................. 650 Payment .................................................650 General ................................................650 Stone Riprap ............................................650 Sacked Concrete Riprap ...................................650 Wrre-Enclosed Riprap (Gabions) ............................650 Cast-in-Place Concrete Slope Paving ..........................650 Precast Concrete Slope Paving ..............................650 Filter Blanket ........................................... 650 Filter Fabric ............................................. 650 Geocomposite Drain System ................................650
SECTION 23-MISCELLANEOUS METAL
23.1 23.2 23.3 23.4 23.5 23.6
0
DESCRIPTION .............................................651 MATERIALS ...............................................651 FABRICATION ............................................. 651 GALVANIZING ............................................651 MEASUREMENT ...........................................651 PAYMENT ................................................. 651
SECTION 24-PNEUMATICALLY APPLIED MORTAR
24.1 24.2 24.2.1 24.2.2 24.2.3 24.3 24.3.1 24.3.2 24.4 24.4.1 24.4.2 24.4.3 24.5 24.5.1 24.5.2 24.5.2.1 24.5.2.2 24.5.3 24.5.4 24.6
DESCRIPTION .............................................653 MATERIALS ...............................................653 Cement, Aggregate, Water, and Admixtures ...................653 Reinforcing Steel .......................................... 653 Anchor Bolts or Studs ......................................653 PROPORTIONING AND MIXING ............................653 Proportioning ............................................653 Mixing ..................................................653 SURFACE PREPARATION ...................................654 Earth ....................................................654 Fonns ...................................................654 Concrete or Rock .........................................654 INSTALLATION ............................................654 Placement of Reinforcing ...................................654 Placement of Mortar .......................................654 Weather Limitations ......................................655 Protection of Adjacent Work ................................655 Finishing ................................................655 Curing and Protecting .....................................655 MEASUREMENT AND PAYMENT ............................655
SECTION 25-STEEL AND CONCRETE TUNNEL LINERS
0
25.1 25.2
SCOPE ....................................................657 DESCRIPTION ............................................. 657
lxix
CONTENTS
lxx 25.3 25.3.1 25.3.2 25.4 25.4.1 25.4.2 25.4.3 25.5 25.6
MATERIALS AND FABRICATION ............................657 General ..................................................657 Forming and Punching of Steel Liner Plates ...................657 INSTALLATION ............................................658 Steel Liner Plates ..........................................658 Precast Concrete Liner Plates ...............................658 Grouting .................................................658 MEASUREMENT ...........................................658 PAYMENT .............. ·...................................658
SECTION 26-METAL CULVERTS 26.1 26.1.1 26.2 26.3 26.3.1 26.3.2 26.3.3 26.3.4 26.3.5 26.3.6 26.3.7 26.3.8 26.3.8.1 26.3.8.2 26.3.8.3 26.4 26.4.1 26.4.2 26.4.2.1 26.4.2.2 26.4.2.3 26.4.2.4 26.4.3 26.5 26.5.1 26.5.2 26.5.3 26.5.4 26.5.4.1 26.5.4.2 26.5.4.3 26.5.4.4 26.5.4.5 26.5.5 26.5.6 26.6 26.7 26.8
GENERAL .................................................659 Description ...............................................659 WORKING DRAWINGS .....................................659 MATERIALS ...............................................659 Corrugated Metal Pipe .....................................659 Structural Plate ............................................659 Nuts and Bolts ............................................ 659 Mixing of Materials ........................................659 Fabrication ...............................................659 Welding .................................................660 Protective Coatings ........................................660 Bedding and Backfill Materials ................... ·...........660 General ................................................660 Long-Span Structures .....................................660 Box Culverts ............................................660 ASSEMBLY ................................................660 General ..................................................660 Joints ......... ·..........................................660 Field Joints .............................................661 Joint l'ypes .............................................661 Soil Conditions ..........................................661 Joint Properties ..........................................661 Assembly of Long-Span Structures ...........................662 INSTALLATION ................................. ·...........662 Placing Culverts-General .................................662 Foundation ............................................... 662 Bedding .................................................664 Structural Backfill .........................................665 General ................................................665 Arches .................................................665 Long-Span Structures .....................................665 Box Culverts ............................................666 Bracing ................................................666 Arch Substructures and Headwalls ...........................666 Inspection Requirements for CMP ........................... 667 CONSTRUCTION PRECAUTIONS ...........................667 MEASUREMENT ...........................................667 PAYMENT .................................................667
SECTION 27-CONCRETE CULVERTS 27.1
GENERAL .................................................669
Division ll
Division II
CONTENTS WORKING DRAWINGS .....................................669 27.2 MATERIALS ...............................................669 27.3 Concrete Culverts ...............................669 Reinforced 27.3.1 Joint Sealants .............................................669 27.3.2 Cement Mortar ..........................................669 27.3.2.1 Aexible Watertight Gaskets ................................669 27.3.2.2 Other Joint Sealant Materials ...............................670 27.3.2.3 Bedding, Haunch, Lower Side and Backfill or Overfill Material ... 670 27.3.3 Precast Reinforced Concrete Circular, Arch, and Elliptical Pipe ....670 27.3.3.1 Precast Reinforced Concrete Box Sections .....................670 27.3.3.2 ASSEMBLY ................................................670 27.4 General ..................................................670 27.4.1 Joints ...................................................670 27.4.2 INSTALLATION ............................................670 27.5 General ..................................................670 27.5.1 Bedding .................................................670 27.5.2 General ................................................670 27.5.2.1 Precast Reinforced Concrete Circular Arch and Elliptical Pipe .....673 27.5.2.2 Precast Reinforced Concrete Box Sections ..................... 673 27.5.2.3 Placing Culvert Sections .................................... 673 27.5.3 Haunch, Lower Side and Backfill or Overfill ...................674 27.5.4 Precast Reinforced Concrete Circular Arch and Elliptical Pipe .....674 27.5.4.1 Haunch Material ....................................... 674 27.5.4.1.1 Lower Side Material .................................... 677 27.5.4.1.2 Overfill ..............................................677 27.5.4.1.3 Precast Reinforced Concrete Box Sections .....................677 27.5.4.2 Backfill ..............................................677 27.5.4.2.1 Placing of Haunch, Lower Side and Backfill or Overfill ..........677 27.5.4.3 Cover Over Culvert During Construction ......................678 27.5.4.4 MEASUREMENT ...........................................678 27.6 PAYMENT .................................................678 27.7 SECTION 28-WEARING SURFACES DESCRIPTION .............................................679 28.1 LATEX MODIFIED CONCRETE TYPE WEARING SURFACE ...679 28.2 General ..................................................679 28.2.1 Materials ................................................679 28.2.2 Portland Cement .........................................679 28.2.2.1 Aggregate ..............................................679 28.2.2.2 Water ..................................................679 28.2.2.3 ..........................................679 Latex Emulsion 28.2.2.4 Latex Modified Concrete ..................................680 28.2.2.5 Surface Preparation ....................................... 680 28.2.3 New Decks ............................................. 680 28.2.3.1 Existing Decks .......................................... 680 28.2.3.2 Proportioning and Mixing .................................. 681 28.2.4 Installation ............................................... 681 28.2.5 Weather Restrictions ...................................... 681 28.2.5.1 Equipment ............................................ · .681 28.2.5.2 Placing and Finishing .....................................682 28.2.5.3 Construction Joints .....................................682 28.2.5.3.1 Placing ..................................... · ... · · · · · .682 28.2.5.3.2
bod
CONTENTS
lxxii
Finishing .............................................682 Curing ..................................................682 Acceptance Testing ........................................682 Measurement and Payment .................................683
28.2.5.3.3 28.2.6 28.2.7 28.2.8
SECTION 29-EMBEDMENT ANCHORS 29.1 29.2 29.3 29.4 29.5 29.6 29.7
DESCRIPTION .............................................685 PREQUALIFICATION ......................................685 MATERIALS ...............................................685 CONSTRUCTION METHODS ................................685 INSPECTION AND TESTING ................................685 MEASUREMENT ...........................................686 PAYMENT .................................................686
SECTION 30-THERMOPLASTIC PIPE 30.1 30.1.1 30.1.2 30.2 30.3 30.3.1 30.3.2 30.4 30.4.1 30.4.2 30.4.2.1 30.5 30.5.1 30.5.2 30.5.3 30.5.4 30.5.5 30.5.6 30.6 30.7
GENERAL ................................................. 687 Description ...............................................687 Workmanship and Inspection ...............................687 WORKING DRAWINGS .....................................687 MATERIALS ...............................................687 Thermoplastic Pipe ........................................687 Bedding Material and Structural Backfill .....................687 ASSEMBLY ................................................688 General .................................................. 688 Joints ...................................................688 Field Joints .............................................688 INSTALLATION ............................................688 General Installation Requirements ...........................688 'I'rench Widths ............................................688 Foundation and Bedding ...................................689 Structural Backfill .........................................689 Minimum Cover ..........................................689 Installation Deftection ......................................689 MEASUREMENT ...........................................689 PAYMENT .................................................689 LIST OF FIGURES DIVISION I DESIGN
SECTION 2-GENERAL FEATURES OF DESIGN Figure 2.3.1
Figure 2.4A Figure 2.5
Figure 2.7.4A Figure 2.7.4B
Clearance Diagram for Bridges .........................8 Clearance Diagrams for Underpasses .....................9 Clearance Diagram for Thnnels-Two-Lane Highway Traffic ..9 Pedestrian Railing, Bicycle Railing ...................... 12 Traffic Railing ....................................... 13
SECTION 3-LOADS Figure 3.7.6A
Standard H 'I'rucks ...................................22
Figures
Figures
CONTENTS
Figure 3.7.6B Figure 3.7.7A
Lane Loading .......................................23 Standard HS Trucks ..................................24
SECTION 4--FOUNDATIONS
Figure 4.4.3A Figure 4.4.7.1.1.1A
Figure 4.4.7.1.1.1 B Figure 4.4.7.1.1.1C Figure 4.4. 7 .1.1.4A Figure 4.4.7 .1.1.4B Figure 4.4.7 .1.1.6A Figure 4.4.7.1.1.7A Figure 4.4.7.1.1.7B Figure 4.4. 7.1.1.8A Figure 4.4. 7.2.1 A Figure 4.4.7.2.3A
~I Figure 4.4.7.2.3B
Figure 4.4.7.2.3C Figure 4.4.7.2.30 Figure 4.4.8.1.1 A Figure 4.4.8.2.2A
Figure 4.5.4A Figure 4.6.3A Figure 4.6.5.1.1 A
Figure 4.6.5.3.1A Figure 4.6.5.5.1.1 A Figure 4.6.5.5.1.1 B Figure 4.6.5.5.1.2A
Design Terminology for Spread Footing Foundations .......48 Definition Sketch for Loading and Dimensions for Footings Subjected to Eccentric or Inclined Loads, Modified after EPRI (1983) ..........................52 Contact Pressure for Footing Loaded Eccentrically About One Axis .................................... 52 Contact Pressure for Footing Loaded Eccentrically About Two Axes, Modified after AREA (1980) ..........53 Modified Bearing Capacity Factors for Footings on Sloping Ground, Modified after Meyerhof (1957) .....54 Modified Bearing Capacity Factors for Footing Adjacent Sloping Ground, Modified after Meyerhof (1957) .........54 Definition Sketch for Influence of Ground Water Table on Bearing Capacity ................................55 Typical Two-Layer Soil Profiles .........................56 Modified Bearing Capacity Factor for Two-Layer Cohesive Soil with Softer Soil Overlying Stiffer Soil, EPRi (1983) .. 56 Definition Sketch for Footing Base Inclination ............57 Boussinesg Vertical Stress Contours for Continuous and Square Footings, Modified after Sowers (1979) ...... 58 Typical Consolidation Compression Curve for Overconsolidated Soil-Void Ratio Versus Vertical Effective Stress, EPRI (1983) ...........60 Typical Consolidation Compression Curve for Overconsolidated Soil-Void Strain Versus Vertical Effective Stress .......................60 Reduction Factor to Account for Effects of ThreeDimensional Consolidation Settlement, EPRI (1983) .....60 Percentage of Consolidation as a Function of Time Factor, T, EPRI (1983) ..............................61 Allowable Contact Stress for Footings on Rock with Tight Discontinuities, Peck, et al. (1974) .....................62 Relationship Between Elastic Modulus and Uniaxial Compressive Strength for Intact Rock, Modified after Deere (1968) ..................................66 Design Terminology for Driven Pile Foundations ..........71 Design Terminology for Drilled Shaft Foundations ......... 81 Identification of Portions of Drilled Shafts Neglected for Estimation of Drilled Shaft Side Resistance in Cohesive Soil, Reese and O'Neill (1988) .............. 82 Procedure for Estimating Average Unit Shear for Smooth Wall Rock-Socketed Shafts, Horvath et al. (1983) ........ 85 Load Transfer in Side Resistance Versus Settlement Drilled Shafts in Cohesive Soil, after Reese and O'Neill (1988) ... 87 Load Transfer in Tip Bearing Settlement Drilled Shafts in Cohesive Soil, after Reese and O'Neill (1988) .........87 Load Transfer in Side Resistance Versus Settlement Drilled Shafts in Cohesionless Soil, after Reese and O'Neill (1988) ......88
lxxiii
CONTENTS
lxx.vi
SECTION 8-REINFORCED CONCRETE Figure 8.15.5.8 Figure 8.16.4.4.1 Figure 8.16.6.8 Figure 8.29 .1 Figure 8.29.4
Untitled ...........................................202 Definition of Wall Slenderness Ratio ...................206 Untitled ........................................... 211 Hooked-Bar Details for Development of Standard Hooks .. 221 Hooked-Bar Tie Requirements ........................ 221
SECTION 9-PRESTRESSED CONCRETE Figure 9.16.2.1.1
Mean Annual Relative Humidity ......................235
SECTIONl~TRUCTURALSTEEL
Figure 10.3.1C Figure CI0.18.2.3.4 Figure CI0.18.2.3.4 Figure I 0.18.5A Figure I 0.34.3.1 A Figure I0.39.4.3A Figure 10.39.4.3B Figure Figure Figure Figure
10.40.2.1 A 10.40.2.I B 10.50A 1
Ulustrative Examples ................................ 264 Positive Flexure Case ..............................C-101 Negative Flexure Curve ............................C-101 Splice Details ....................................... 278 Web Thickness Versus Girder Depth for Noncomposite Symmetrical Sections .............................. 296 Longitudinal Stiffeners-Box Girder Compression Flange .......................................... 309 Spacing and Size of Transverse Stiffeners (for Flange Stiffened Longitudinally and Transversely) ............ 310 Untitled ........................................... 3I3 Untitled ........................................... 313 Plastic Stress Distribution ............................323 Article ClO.S0.1.2.1 ...............................C-130
SECTION 12-SOIL-CORRUGATED METAL STRUCTURE INTERACTION SYSTEMS Figure 12.7.1A Figure 12.7.4A Figure 12.7.4B Figure 12.7.5A Figure 12.8.2A
Standard Terminology of Structural Plate Shapes Including Long-Span Structures .....................349 'l)'pical Structural Backfill Envelope and Zone of Structure Influence .............................351 Assumed Pressure Distribution ........................352 Standard Structure End Types ........................353 Standard Terminology of Structural Plate Box Culvert Shapes ..........................................355
SECTION 13--WOOD STRUCTURES Figure 13.7.1A
Untitled ...........................................381
SECTION 14--BEARINGS Figure 14.4 Figure 14.5.2-1 Figure 14.6.3.2-1 Figure Cl4.6.4.3-l
Untitled ........................................... 388 Typical Bearing Components ........................ .389 Untitled ...........................................393 Pot Bearing-Critical Dimensions for Clearances .......C- J7
Figures
CONTENTS
Figures
.
G
Figure 14.6.5.2-1 Figure 14.6.5.3.3-1 Figure CI4.6.5.3.3-1 Figure C14.6.5.3.6-1
Map of Low Temperature Zones .......................396 Load Deflection Behavior of Elastomeric Bearings ....... .396 Load Deflection Behavior of Elastomeric Bearings .......C-21 Elastomeric Bearing-Interaction Between Compressive Stress and Rotation Angle .........................C-22
SECTION 15-STEEL TUNNEL LINER PLATES Figure 15.2.3A
Diagram for Coefficient Cd for 'funnels in Soil (cp =Friction Angle) ...............................404
SECTION 16-SOIL-REINFORCED CONCRETE STRUCTURE INTERACTION SYSTEMS Figure 16.4A Figure 16.48 Figure 16.4C Figure 16.40 Figure 16.4E Figure 16.4F Figure 16.40 Figure 16.4H Figure 16.6A
0
Heger Pressure Distribution and Arching Factors ........413 Standard Embankment Installations ...................414 Standard Trench Installations ........................ .414 Trench Beddings, Miscellaneous Shapes ................416 Embankment Beddings, Miscellaneous Shapes ...........417 Suggested Design Pressure Distribution Around a Buried Concrete Pipe for Analysis by Direct Design ...........420 Essential Features of Types of Installation ...............420 General Relationship of Vertical Earth Load and Lateral Pressure ..............................421 Concrete Box Sections ...............................424 DIVISION 1-A SEISMIC DESIGN
SECTION I-INTRODUCTION Figure 1.6A Figure 1.6B
Design Procedure Flow Chart .........................442 Sub Flow Chart for Seismic Performance Categories B, C,and D .........................................443
SECTION 3-GENERAL REQUIREMENTS Figure C3.2
Figure 3.2A Figure 3.2B Figure C3.5A Figure C3.5B Figure C3.5C Figure C3.5D Figure C3.5E
0
Figure 3.10
Schematic Representation Showing How Effective Peak Acceleration and Effective Peak Velocity Are Obtained from a Response Spectrum ............C-42 Acceleration Coefficient-Continental United States ......447 Acceleration Coefficient-Alaska, Hawaii and Puerto Rico ..................................448 Average Acceleration Spectra for Different Site Conditions (after Seed, et al., 1976) ...........................C-44 Normalized Response Spectra ........................C-45 Ground Motion Spectra for A = 0.4 ...................C-46 Ground Motion Spectra for A = 0.4 ...................C-46 Comparison of Free Field Ground Motion Spectra and Lateral Design Force Coefficients ...................C-47 Dimensions for Minimum Support Length Requirements ....................................452
lxxvii
CONTENTS
lxxviii
SECTION 4-ANALYSIS REQUIREMENTS Figure 4.4A Figure C4.4A Figure 4.4B Figure C4.4B Figure C4.4C Figure C4.4D Figure C4.4E Figure C4.5.2
Bridge Deck Subjected to Assumed Transverse and Longitudinal Loading ......................... .455 Plan View of a Bridge Subjected to a Transverse Earthquake Motion ..............................C-54 Bridge Deck Subjected to Equivalent Transverse and Longitudinal Seismic Loading ...................455 Displacement Function Describing the Transverse Position of the Bridge Deck ........................C-54 Deflected Shape Due to Uniform Static Loading .........C-55 Transverse Free Vibration of the Bridge in Assumed Mode Shape ............................C-55 Characteristic Static Loading Applied to the Bridge System ...................................C-56 Iterative Procedure for Including Abutment Soil Effects in the Seismic Analysis of Bridges ............C-57
SECTION 7-DESIGN REQUIREMENTS FOR BRIDGES IN SEISMIC PERFORMANCE CATEGORIES C AND D Figure C7.2.2A
Figure C7.6.2A Figure C7.6.2B Figure C7.6.2C Figure C7.6.2D
Development of Approximate Overstrength Interaction Curves from Nominal Strength Curves (after Gajer and Wagh) .....................C-65 Confining Pressure Provided by a Spirally Reinforced Column ............................... C-69 Confining Pressure Provided by a Rectangular Reinforced Column ...............................C-70 Tie Details in a Rectangular Column ..................C-71 Tie Details in a Square Column ......................C-71 DIVISION II CONSTRUCTION
SECTIONl&-~BERSTRUCTURES
Figure 16.3
Nail Placement Pattern ..............................613
SECTION 2&-METAL CULVERTS Figure 26.5 Figure 26.5.2 Figure 26.5.3 Figure 26.5.4
Typical Cross-Section Showing Materials Around the Pipe .................................. 663 A-D: Foundation Improvement Methods When Required ..664 "V" Shaped Bed (Foundation) for Larger Pipe Arch, Horizontal Ellipse and Underpass Structures ..........665 End Treatment of Skewed Flexible Culvert ..............666
SECTION 27-CONCRETE CULVERTS Figure 27.5A Figure 27.58 Figure 27.5C
Standard Embankment Installations ...................671 Standard Trench Installations .........................672 Trench Beddings, Miscellaneous Shapes ................673
Figures
CONTENTS
Tables
0
Figure 27.50 Figure 27 .5E
Embankment Beddings, Miscellaneous Shapes ...........674 Box Sections, Embankmentl'lnmch Bedding .............678
SECTION 30--THERMOPLASTIC PIPE
Figure 30.5.1
Untitled ........................................... 688 LIST OF TABLES DIVISION I DESIGN
SECTION 3-LOADS
Table 3.22.1A Table 3.23.1 Table 3.23.3.1
Table of Coefficients 'Y and p ...........................31 Distribution of Wheel Loads in Longitudinal Beams ....... 33 Distribution of Wheel Loads in Transverse Beams ......... 34
SECTION 4-FOUNDATIONS
Table 4.2.3A Table 4.4.7.1A Table 4.4.7.2.2A Table 4.4.7.2.28 Table 4.4.8.1.2A
0 .
Table 4.4.8.1.28 Table 4.4.8.2.2A Table 4.4.8.2.28 Table 4.5.6.2A Table 4.5. 7.3A Table 4.6.5.1.1 A
Table 4.6.5.1.4A
Table 4.10.6-1 Table 4.10.6-2 Table 4.10.6-3 Table 4.11.4.1.4-1
0 '
Table 4.11.4.2.4-1
Problem Conditions Requiring Special Consideration ..... 44 Bearing Capacity Factors ............................. 50 Elastic Constants of Various Soils, Modified after U.S. Department of Navy (1982) and Bowles (1982) ..........59 Elastic Shape and Rigidity Factor, EPRI (1983) ...........59 Values of Coefficient Nms for Estimation of the Ultimate Bearing Capacity of Footings on Broken or Jointed Rock (Modified after Hoek (1983)) .........................63 Typical Range of Uniaxial Compressive Strength (C0 ) as a Function of Rock Category and Rock Type .............64 Summary of Poisson's Ration for Intact Rock, Modified after Kulhawy (1978) ...............................65 Summary of Elastic Moduli for Intact Rock, Modified after Kulhawy (1978) ....................................65 Recommended Factor of Safety on Ultimate Geotechnical Capacity Based on Specified Construction Control ......72 Allowable Working Stress for Round Timber Piles ......... 73 Recommended Values of a and f, 1 for Estimation of Drilled Shaft Side Resistance in Cohesive Soil, Reese and O'Neill (1988) ............................82 Recommended Values of qT* for Estimation of Drilled Shaft Tip Resistance in Cohesionless Soil, after Reese and O'Neill (1988) ............................................83 Performance Factors for Strength Limit States for Shallow Foundations .......................................94 Performance Factors for Geotechnical Strength Limit States in Axially Loaded Piles ..............................95 Performance Factors for Geotechnical Strength Limit States in Axially Loaded Drilled Shafts ................96 Presumptive Allowable Bearing Pressures for Spread Footing Foundations, Modified after U.S. Department of the Navy, 1982 ...................................99 Presumptive Bearing Pressures (tsO for Foundations on Rock (after Putnam, 1981) .......................... 101
lxxix
CONTENTS
lxxx
Tables
SECTIONS-RETAINING WALLS
Table 5.5.2A
Relationship Between Soil Backfill Type and Wall Rotation to Mobilize Active and Passive Earth Pressures Behind Rigid Retaining Walls . 122 ffitimate Friction Factors and Friction Angles for Dissimilar Materials, after U.S. Department of the Navy (1982) ..................... o ol28 General Notes and Legend Simplified Earth Pressure Distributions for Permanent and Temporary Flexible Cantilevered Walls with Discrete Vertical Wall Elements . ol31 Presumptive Ultimate Values of Load Transfer for Preliminary Design of Anchors in Soil, Modified after Cheney (1982) .. o.. oo o o. o.. o. o ooo.... 137 Presumptive ffitimate Values of Load Transfer for Preliminary Design of Anchors in Rock, Modified after Cheney (1982) .. .137 Default Values for the Scale Effect Correction Factor, (infinity sign*) o. o 151 Minimum Requirements for Geosynthetic Products to Allow Use of Defaulted Reduction Factor for Long-Term Degradation . .156 Default of Minimum Values for the Total Geosynthetic Ultimate Limit State Strength Reduction Factor, RF .... 157 Default and Minimum Values for the Total Geosyntbetic Ultimate Limit State Strength Reduction Factor at the Facing Connection, RFc o. o.... 158 0
Table 5.5.2B
Table 5.6.2A
Table5.7.6.2A
Table 5.7 .6.28
Table5.8.5.2A
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Table 5.8.6.1.2A
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SECTION 8--REINFORCED CONCRETE
Table 8o9.2
Recommended Minimum Depths for Constant Depth Members ..... o..... 194 Effective Length Factors, k ........................... 196 Minimum Diameters of Bend ............... 217 Tension Lap Splices ...... 223 0
Table 8.14.3 Table 8.23.2.1 Table 8o32.3.2
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SECTION 9-PRESTRESSED CONCRETE
Table 9.16.2.2
Estimate of Prestress Losses ................
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236
SECTIONl~TRUCTURALSTEEL
Table 10.2A Table 10.2B Table 10.3.IA Table 10.3.IB Table 10.3.2A Table 10.3.3A
Untitled ... 258 Untitled 258 Allowable Fatigue Stress Range 260 Untitled . 261 Stress Cycles .......... 265 Temperature Zone Designations for Charpy V-Notch Impact Requirements ........ 265 Nominal Hole Dimension .......... .282 Allowable Stresses-Structural Steel (In pounds per square inch) . o...... o.... 288 Allowable Stresses for Low-Carbon Steel Bolts and Power Driven Rivets (in psi) .............................. 290 0
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Table 10.32.3A
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Tables
CONTENTS Table 10.32.3B
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Table 10.32.3C Table Table Table Table Table Table Table
10.32.4.3A 10.32.5.1A 10.36A 10.48.l.2A 10.48.2.1 A 10.56A I0.57 A
lxxxi
Allowable Stresses on High-Strength Bolts or Connected Material (ksi) .....................................290 Nominal Slip Resistance for Slip-Critical Connections (Slip Resistance per Unit of Bolt Area, F5 , ksi) .......... 291 Allowable Stresses-Steel Bars and Steel Forgings ........ 293 Allowable Stresses-Cast Steel and Ductile Iron ......... 294 Bending-Compression Interaction Coefficients ...........302 Limitations for Compact Sections ..................... .318 Limitations for Braced Noncompact Sections ............318 Design Strength of Connectors ........................332 Design Slip Resistance for Slip-Critical Connections (Slip Resistance per Unit of Bolt Area,
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10
HIGHWAY BRIDGES
The clearances and width of roadway for two-lane traffic shall be not less than those shown in Figure 2.5. The roadway width shall be increased at least 10 feet and preferably 12 feet for each additional traffic lane.
2.5.1
railing or barrier with a pedestrian railing along the edge of the structure. On urban expressways, the separation shall be made by a combination railing. 2.7.1 Vehicular Railing
2.5.2 Clearance between Walls 2.7.1.1 General
The minimum width between walls of two-lane tunnels shall be 30 feet. 2.5.3 Vertical Clearance
The vertical clearance between curbs shall be not less than 14 feet. 2.5.4 Curbs
The width of curbs shall be not less than 18 inches. The height of curbs shall be as specified for bridges. For heavy traffic roads, roadway widths greater than the above minima are recommended. If traffic lane widths exceed 12 feet the roadway width may be reduced 2 feet 0 inches from that calculated from Figure 2.5. 2.6 HIGHWAY CLEARANCES FOR DEPRESSED ROADWAYS 2.6.1 Roadway Width The clear width between curbs shall be not less than that specified for tunnels. 2.6.2 Clearance between Walls The minimum width between walls for depressed roadways carrying two lanes of traffic shall be 30 feet. 2.6.3 Curbs The width of curbs shall be not less than 18 inches. The height of curbs shall be as specified for bridges.
2. 7.1.1.1 Although the primary purpose of traffic railing is to contain the average vehicle using the structure, consideration should also be given to (a) protection of the occupants of a vehicle in collision with the railing, (b) protection of other vehicles near the collision, (c) protection of vehicles or pedestrians on roadways underneath the structure, and (d) appearance and freedom of view from passing vehicles. 2. 7.1.1.2 Materials for traffic railings shall be concrete, metal, timber, or a combination thereof. Metal materials with less than l 0-percent tested elongation shall not be used.
2. 7.1 .1.3 Traffic railings should provide a smooth, continuous face of rail on the traffic side with the posts set back from the face of rail. Structural continuity in the rail members, including anchorage of ends, is essential. The railing system shall be able to resist the applied loads at all locations. 2. 7.1.1.4 Protrusions or depressions at rail joints shall be acceptable provided their thickness or depth is no greater than the wall thickness of the rail member or 3/s inch, whichever is less. 2.7.1.1.5 Careful attention shall be given to the treatment of railings at the bridge ends. Exposed rail ends, posts, and sharp changes in the geometry of the railing shall be avoided. A smooth transition by means of a continuation of the bridge barrier, guardrail anchored to the bridge end, or other effective means shall be provided to protect the traffic from direct collision with the bridge rail ends.
2.7.1.2 Geometry 2.7 RAILINGS
Railings shall be provided along the edges of structures for protection of traffic and pedestrians. Other suitable applications may be warranted on bridge-length culverts as addressed in the AASHTO Roadside Design Guide. Except on urban expressways, a pedestrian walkway may be separated from an adjacent roadway by a traffic
2. 7.1.2.1 The heights of rails shall be measured relative to the reference surface which shall be the top of the roadway, the top of the future overlay if resurfacing is anticipated, or the top of curb when the curb projection is greater than 9 inches from the traffic face of the railing. 2.7.1.2.2 Traffic railings and traffic portions of combination railings shall not be less than 2 feet 3 inches
2.7.1.2.2
0 .
DIVISION I-DESIGN
from the top of the reference surface. Parapets designed with sloping traffic faces intended to allow vehicles to ride up them under low angle contacts shall be at least 2 feet 8 inches in height.
load of the rail. The vertical load shall be applied alternately upward or downward. The attachment shall also be designed to resist an inward transverse load equal to onefourth the transverse rail design load.
2.7.1.2.3 The lower element of a traffic or combination railing should consist of either a parapet projecting at least 18 inches above the reference surface or a rail centered between 15 and 20 inches above the reference surface.
2. 7.1.3.5 Rail members shall be designed for a moment, due to concentrated loads, at the center of the panel and at the posts of P'U6 where L is the post spacing and P' is equal to P, P/2, or P/3, as modified by the factor C where required. The handrail members of combination railings shall be designed for a moment at the center of the panel and at the posts of 0.1 wL2•
2.7.1.2.4 For traffic railings, the maximum clear opening below the bottom rail shall not exceed 17 inches and the maximum opening between succeeding rails shall not exceed 15 inches. For combination railings, accommodating pedestrian or bicycle traffic, the maximum opening between railing members shall be governed by Articles 2.7.2.2.2 and 2.7.3.2.1, respectively. 2. 7.1.2.5 The traffic faces of all traffic rails must be within 1 inch of a vertical plane through the traffic face of the rail closest to traffic. 2.7.1.3
0
Loads
2. 7. 1.3. 1 When the height of the top of the top traffic rail exceeds 2 feet 9 inches, the total transverse load distributed to the traffic rails and posts shall be increased by the factor C. However, the maximum load applied to any one element need not exceed P, the transverse design load.
2. 7.1 .3.2 Rails whose traffic face is more than I inch behind a vertical plane through the face of the traffic rail closest to traffic or centered less than 15 inches above the reference surface shall not be considered to be traffic rails for the purpose of distributing P or CP, but may be considered in determining the maximum clear vertical opening, provided they are designed for a transverse loading equal to that applied to an adjacent traffic rail or P/2, whichever is less. 2. 7. 1.3.3 Transverse loads on posts, equal toP, or CP, shall be distributed as shown in Figure 2.7.4B. A load equal to one-half the transverse load on a post shall simultaneously be applied longitudinally, divided among not more than four posts in a continuous rail length. Each traffic post shall also be designed to resist an independently applied inward load equal to one-fourth the outward transverse load.
0
11
2. 7. 1.3.4 The attachment of each rail required in a traffic or combination railing shall be designed to resist a vertical load equal to one-fourth of the transverse design
2.7.1.3.6 The transverse force on concrete parapet and barrier walls shall be spread over a longitudinal length of 5 feet. 2.7.1.3.7 Railings other than those shown in Figure 2.7.4B are permissible provided they meet the requirements of this Article. Railing configurations that have been successfully tested by full-scale impact tests are exempt from the provisions of this Article. 2.7.2 Bicycle RaJ ling 2.7.2.1
General
2. 7.2.1.1 Bicycle railing shall be used on bridges specifically designed to carry bicycle traffic, and on bridges where specific protection of bicyclists is deemed necessary. 2.7.2.1.2 Railing components shall be designed with consideration to safety, appearance, and when the bridge carries mixed traffic freedom of view from passing vehicles. 2.7.2.2 Geometry and Loads
2.7.2.2.1 The minimum height of a railing used to protect a bicyclist shall be 54 inches, measured from the top of the surface on which the bicycle rides to the top of the top rail. 2. 7.2.2.2 Within a band bordered by the bikeway surface and a line 27 inches above it, all elements of the railing assembly shall be spaced such that a 6-inch sphere will not pass through any opening. Within a band bordered by lines 27 and 54 inches, elements shall be spaced such that an 8-inch sphere will not pass through any opening. If a railing assembly employs both horizontal and vertical elements, the spacing requirements shall apply to one or the other, but not to both. Chain link fence
HIGHWAY BRIDGES
12
2.7.2.2.2
is exempt from the rail spacing requirements listed above. In general, rails should project beyond the face of posts and/or pickets.
ter of gravity of the upper rail, but at a height not greater than 54 inches.
2. 7.2.2.3 The minimum design loadings for bicycle railing shall be w = 50 pounds per linear foot transversely and vertically, acting simultaneously on each rail.
2.7.2.2.6 Refer to Figures 2.7.4A and 2.7.48 for more information concerning the application of loads.
2. 7.2.2.4 Design loads for rails located more than 54 inches above the riding surface shall be determined by the designer.
2.7.3 Pedestrian Railing
2.7.2.2.5 Posts shall be designed for a transverse load of wL (where Lis the post spacing) acting at the cen-
2.7.3.1.1 Railing components shall be proportioned commensurate with the type and volume of anticipated
2.7.3.1 General
(To be used adjacent to a sidewalk when highway traffic is separated from pedestrian
traffic by a traffic railing.) PEDESTRIAN RAILING
BICYCLE RAJLING NOTE: If screening or solid face is presented, number of rails may be reduced; wind loads must be added if solid face is utilized.
NOTES: 1. Loadings on left are applied to rails. 2. Loads on right are applied to posts. 3. The shapes of rail members are illustrative only. Any material or combination of materials listed in Article 2.7 may be used in any configuration.
4. The spacing illustrated are maximum values. Rail elements spacings shall conform to Articles 2. 7 .2.2.2 and 2.7.3.2.1.
NOMENCLATURE: w = Pedestrian or bicycle loading per unit length of rail L = Post spacing
FIGURE 2.7.4A Pedestrian Railing, Bicycle Railing
2.7.3.1.1
0 '
'
'
DIVISION I-DESIGN
pedestrian traffic. Consideration should be given to appearance, safety and freedom of view from passing vehicles.
2. 7.3.2.2 The minimum design loading for pedestrian railing shall be w = 50 pounds per linear foot, transversely and vertically, acting simultaneously on each longitudinal member. Rail members located more than 5 feet 0 inches above the walkway are excluded from these requirements.
2.7.3.1.2 Materials for pedestrian railing may be concrete, metal, timber, or a combination thereof. 2.7.3.2
2. 7.3.2.3 Posts shall be designed for a transverse load of wL (where Lis the post spacing) acting at the center of gravity of the upper rail or, for high rails, at 5 feet 0 inches maximum above the walkway.
Geometry and Loads
2. 7.3.2.1 The minimum height of a pedestrian railing shall be 42 inches measured from the top of the walkway to the top of the upper rail member. Within a band bordered by the walkway surface and a line 27 inches above it, all elements of the railing assembly shall be spaced such that a 6-inch sphere will not pass through any opening. For elements between 27 and 42 inches above the walking surface, elements shall be spaced such that an eight-inch sphere will not pass through any opening.
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Structural Specifications and Guidelines
2.7.4.1 Railings shall be designed by the ela()tic method to the allowable stresses for the appropriate material.
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(1b be used when curb projects more than 9" from the traffic face of railing.)
COMBINATION TRAFFIC AND PEDESTRIAN RAIUNG
(To be used where there is no curb or curb projects 9" or less from traffic face of railing.)
TRAFFIC RAILING
0 "
FIGURE 2.7.48 Traffic Railing
HIGHWAY BRIDGES
14
2.7.4.1
~
e
·r:
·e ~~·:~ ·'
...
.. .
~
c
• e :,
~ l
N
' :·..
~
•
' '
·.)
COMBINATION TRAFFIC AND BICYCLE RAILING NOTES: 1. Loadings on left are applied to raiJs. 2. Loadings on right are applied to posts. 3. The shapes of rail members are illustrative only. Any material or combination of materials listed in Article 2.7 may be used in any configuration. 4. The spacings illustrated are maximum values. Rail element spacings shall conform to Article 2. 7.1.2.4. NOMENCLATURE: P = Highway design loading = 10 kips. h = Height of top of top rail above reference surface (in.). L = Post spacing (ft). w = Pedestrian loading per unit length of rail. C
= 1 + b- 33 i:!:: I 18
FIGURE 2.7.48 (Continued)
For aluminum alloys the design stresses given in the Specifications for Aluminum Structures Fifth Edition, December 1986, for Bridge and Similar 'JYpe Structures published by the Aluminum Association, Inc. for alloys 6061T6 (Table A.6), 6351-T5 (Table A.6) and 6063-T6 (Table A.6) shall apply, and for cast aluminum alloys the design stresses given for alloys A444.0-T4 (Table A.9), A356.0T61 (Table A.9) and A356.0-T6 (Table A.9) shall apply. For fabrication and welding of aluminum railing, see Article 11.5. 2.7.4.2 The allowable unit stresses for steel shall be as given in Article I 0.32, except as modified below. For steels not generally covered by these Specifications, but having a guaranteed yield strength, Fy. the allowable unit stress, shall be derived by applying the general formulas as given in these Specifications under "Unit Stresses" except as indicated below. The allowable unit stress for shear shall be Fv = 0.33Fy. Round or oval steel tubes may be proportioned using an allowable bending stress, Fb = 0.66Fy. provided the Rlt ratio (radius/thickness) is less than or equal to 40.
Square and rectangular steel tubes and steel W and I sections in bending with tension and compression on extreme fibers of laterally supported compact sections having an axis of symmetry in the plane of loading may be designed for an allowable stress Fb = 0.60Fy.
2.7.4.3 The requirements for a compact section are as follows: (a) The width to thickness ratio of projecting elements of the compression flange of W and I sections shall not exceed (2-1)
(b) The width to thickness ratio of the compression flange of square or rectangular tubes shall not exceed (2-2)
DIVISION I-DESIGN
2.7.4.3
(e) the distance between lateral supports in inches of W or I sections shall not exceed
(c) The D/t ratio of webs shall not exceed
0
15
.
(2- 3)
(d) If subject to combined axial force and bending, the D/t ratio of webs shall not exceed
13,3~1-1.43
D (;. )] - < ---=--==-----=
~
t
(2-4)
but need not be less than D
7,000
- 5B. For intermediate footing lengths, the minimum depth of exploration may be estimated by linear interpolation as a function of L between depths of 2B and 5B below the bearing level. Greater depths may be required where warranted by local conditions.
4.3.2
DIVISION I-DESIGN
Where substructure units will be supported on deep foundations, the depth of the subsurface exploration shall extend a minimum of 20 feet below the anticipated pile or shaft tip elevation. Where pile or shaft groups will be used, the subsurface exploration shall extend at least two times the maximum pile group dimension below the anticipated tip elevation, unless the foundations will be end bearing on or in rock. For piles bearing on rock, a minimum of 10 feet of rock core shall be obtained at each exploration location to insure the exploration has not been terminated on a boulder. For shafts supported on or extending into rock, a minimum of 10 feet of rock core, or a length of rock core equal to at least three times the shaft diameter for isolated shafts or two times the maximum shaft group dimension for a shaft group, whichever is greater, shall be obtained to insure the exploration has not terminated in a boulder and to determine the physical characteristics of rock within the zone of foundation influence for design.
4.3.3 Minimum Coverage A minimum of one soil boring shaiJ be made for each substructure unit. (See Article 7 .1.1 for definition of substructure unit.) For substructure units over I 00 feet in width, a minimum of two borings shall be required.
4.3.4 Laboratory Testing Laboratory testing shalJ be performed as necessary to determine engineering properties including unit weight, shear strength, compressive strength and compressibility. In the absence of laboratory testing, engineering properties may be estimated based on published test results or local experience.
4.3.5 Scour The probable depth of scour shall be determined by subsurface exploration and hydraulic studies. Refer to Article 1.3.2 and FHWA (1988) for general guidance regarding hydraulic studies and design.
PartB SERVICE LOAD DESIGN METHOD ALLOWABLE STRESS DESIGN
45
4.4.1.2 Footings Supporting Non-Rectangular Columns or Piers Footings supporting circular or regular polygonshaped concrete columns or piers may be designed assuming that the columns or piers act as square members with the same area for location of critical sections for moment, shear, and development of reinforcement.
4.4.1.3 Footings in Fill Footings located in fill are subject to the same bearing capacity, settlement, and dynamic ground stability considerations as footings in natural soil in accordance with Articles 4.4.7.1 through 4.4.7.3. The behavior of both the fill and underlying natural soil shall be considered.
4.4.1.4 Footings in Sloped Portions of Embankments The earth pressure against the back of footings and columns within the sloped portion of an embankment shall be equal to the at-rest earth pressure in accordance with Article 5.5.2. The resistance due to the passive earth pressure of the embankment in front of the footing shall be neglected to a depth equal to a minimum depth of 3 feet, the depth of anticipated scour, freeze thaw action, and/or trench excavation in front of the footing, whichever is greater.
4.4.1.5 Distribution of Bearing Pressure Footings shall be designed to keep the maximum soil and rock pressures within safe bearing values. To prevent unequal settlement, footings shall be designed to keep the bearing pressure as nearly uniform as practical. For footings supported on piles or drilled shafts, the spacing between piles and drilled shafts shall be designed to ensure nearly equal loads on deep foundation elements as may be practical. When footings support more than one column, pier, or wall, distribution of soil pressure shall be consistent with properties of the foundation materials and the structure, and with the principles of geotechnical engineering.
4.4.2 Notations 4.4 SPREAD FOOTINGS 4.4.1 General 4.4.1.1 Applicability
0
Provisions of this Article shall apply for design of isolated footings, and to combined footings and mats (footings supporting more than one column, pier, or wall).
The foJiowing notations shall apply for the design of spread footings on soil and rock:
A
A'
= Contact area of footing (ft2) =Effective footing area for computation of bearing capacity of a footing subjected to eccentric load (ft2); (See Article 4.4. 7 .1.1.1)
46 be, b-y, bq B B' c c' c* Ca Cv
c1
c2
Ce Ccr Cee Co
Crt Cae
D Dr e
er eo
t;, e8
eL
Eo
Em
HIGHWAY BRIDGES =Base inclination factors (dim); (See Article 4.4.7.1.1.8) = Width of footing (ft); (Minimum plan dimension of footing unless otherwise noted) =Effective width for load eccentric in direction of short side, L unchanged (ft) = Soil cohesion (ksf) =Effective stress soil cohesion (ksf) = Reduced effective stress soil cohesion for punching shear (ksf); (See Article 4.4. 7 .I) = Adhesion between footing and foundation soil or rock (ksf); (See Article 4.4.7.1.1.3) = Coefficient of consolidation (ft2/yr); (See Article4.4.7.2.3) = Shear strength of upper cohesive soil layer below footing (ksf); (See Article 4.4.7.1.1.7) = Shear strength of lower cohesive soil layer below footing (ksf); (See Article 4.4.7.1.1.7) =Compression index (dim); (See Article 4.4.7.2.3) =Recompression index (dim); (See Article 4.4.7.2.3) == Compression ratio (dim); (See Article 4.4.7.2.3) = Uniaxial compressive strength of intact rock (ksf) =Recompression ratio (dim); (See Article 4.4.7.2.3) = Coefficient of secondary compression defined as change in height per log cycle of time (dim); (See Article 4.4.7.2.4) = Influence depth for water below footing (ft); (See Article 4.4. 7 .1.1.6) = Depth to base of footing (ft) = Void ratio (dim); (See Article 4.4. 7.2.3) = Void ratio at final vertical effective stress (dim); (See Article 4.4.7.2.3) = Void ratio at initial vertical effective stress (dim); (See Article 4.4.7.2.3) = Void ratio at maximum pac;t vertical effective stress (dim); (See Article 4.4.7.2.3) = Eccentricity of load in the B direction measured from centroid of footing (ft); (See Article 4.4.7.1.1.1) = Eccentricity of load in the L direction measured from centroid of footing {ft); (See Article4.4.7.1.1.1) = Modulus of intact rock (ksf) = Rock mass modulus (ksf); (See Article 4.4.8.2.2)
~
4.4.2
= Soil modulus (ksf) = Total force on footing subjected to an inclined load (k); (See Article 4.4. 7 .1.1.1) f~ =Unconfined compressive strength of concrete (ksf) FS = Factor of safety against bearing capacity, overturning or sliding shear failure (dim) H = Depth from footing base to top of second cohesive soil layer for two-layer cohesive soil profile below footing (ft); (See Article 4.4.7.1.1.7) He · = Height of compressible soil layer (ft) Herit = Critical thickness of the upper layer of a two-layer system beyond which the underlying layer will have little effect on the bearing capacity of footings bearing in the upper layer (ft); (See Article 4.4.7 .1.1.7) Hd = Height of longest drainage path in compressible soil layer (ft) Hs = Height of slope (ft); (See Article 4.4.7.1.1.4) = Slope angle from horizontal of ground surface below footing (deg) ie, i..,, iq =Load inclination factors (dim); (See Article 4.4.7.1.1.3) IP = Influence coefficient to account for rigidity and dimensions of footing (dim); (See Article4.4.8.2.2) t = Center-to-center spacing between adjacent footings (ft) L = Length of footing (ft) L' =Effective footing length for load eccentric in direction of long side, B unchanged (ft) Lt = Length (or width) of footing having positive contact pressure (compression) for footing loaded eccentrically about one axis (ft) n = Exponential factor relating BIL or UB ratios for inclined loading (dim); (See Article 4.4.7.1.1.3) N = Standard penetration resistance (blows/ft) N1 = Standard penetration resistance corrected for effects of overburden pressure (blows/ ft); (See Article 4.4.7.2.2) Nc, Nl, Nq = Bearing capacity factors based on the value of internal friction of the foundation soil (dim); (See Article 4.4.7.1) Nm = Modified bearing capacity factor to account for layered cohesive soils below footing (dim); (See Article 4.4.7.1.1.7) Nms = Coefficient factor to estimate qu11 for rock (dim); (See Article 4.4.8.1.2) Ns =Stability number (dim); (See Article 4.4.7.1.1.4) F
4.4.2 Nc:q, N-,q
0
P
DIVISION I-DESIGN =Modified bearing capacity factors for effects of footing on or adjacent sloping ground (dim); (See Article 4.4.7.1.1.4) = Tangential component of force on footing (k)
Pmax
q Q qui qc qmax Q11111x
qmin qo qurt q1
q2
R r RQD Sc, s1 , Sq Su Sc Se S5 S, t
t., t2
= Maximum resisting force between footing base and foundation soil or rock for sliding failure (k) = Effective overburden pressure at base of footing (kst) = Normal component of force on footing (k) = Allowable uniform bearing pressure or contact stress (ksf) = Cone penetration resistance (ksf) = Maximum footing contact pressure (kst) = Maximum normal component of load supported by foundation soil or rock at ultimate bearing capacity (k) = Minimum magnitude of footing contact pressure (kst) =Vertical stress at base of loaded area (ksf); (See Article 4.4. 7 .2.1) = Ultimate bearing capacity for uniform bearing pressure (ksf) =Ultimate bearing capacity of footing supported in the upper layer of a two-layer system assuming the upper layer is infinitely thick (kst); (See Article 4.4.7.1.1.7) = Ultimate bearing capacity of a fictitious footing of the same size and shape as the actual footing, but supported on surface of the second (lower) layer of a two-layer system (kst); (See Article 4.4. 7 .1.1. 7) = Resultant of pressure on base of footing (k) = Radius of circular footing or B/2 for square footing (ft); (See Article 4.4.8.2.2) = Rock Quality Designation (dim) =Footing shape factors (dim); (See Article 4.4.7.1.1.2) = Undrained shear strength of soil (kst) =Consolidation settlement (ft); (See Article 4.4.7.2.3) =Elastic or immediate settlement (ft); (See Article4.4.7.2.2) = Secondary settlement (ft); (See Article 4.4.7.2.4) =Total settlement (ft); (See Article 4.4.7.2) = Time to reach specified average degree of consolidation (yr); (See Article 4.4.7.2.3) = Arbitrary time intervals for determination of S5 (yr); (See Article 4.4. 7 .2.4)
a
'Y
-y' 'Ym 8
8'
e K
v cr(
cr'p
SB): quit= cNc
+ 0.5'YBN'Y + qNq
(4.4.7.1-1)
The a11owable bearing capacity shall be determined as: (4.4.7.1-2) Refer to Table 4.4. 7.1 A for values of Nc, N-y. and Nq. If local or punching shear failure is possible. the value of qu 11 may be estimated using reduced shear strength parameters c* and~* in Equation (4.4.7.1-1) as follows: c* ~*
= 0.67c
= tan- 1 (0.67tan
(4.4.7.1-3) ~)
(4.4.7.1-4)
Effective stress methods of analysis and drained shear strength parameters shall be used to determine bearing capacity factors for drained loading conditions in all soils. Additiona11y, the bearing capacity of cohesive soils shall
HIGHWAY BRIDGES
50
TABLE 4.4.7.1A
4.4.7.1
Bearing Capacity Factors
~
Nc
Nq
N.,
~
Nc
Nq
0 1 2 3 4
5.14 5.38 5.63 5.90 6.19 6.49 6.81 7.16 7.53 7.92 8.35 8.80 9.28 9.81 10.37 10.98 11.63 12.34 13.10 13.93 14.83 15.82 16.88 18.05 19.32 20.72
1.00 1.09 1.20 1.31 1.43 1.57 1.72 1.88 2.06 2.25 2.47 2.71 2.97 3.26 3.59 3.94 4.34 4.77 5.26 5.80 6.40 7.07 7.82 8.66 9.60 10.66
0.00 0.07 0.15 0.24 0.34 0.45 0.57 0.71 0.86 1.03 1.22 1.44 1.69 1.97 2.29 2.65 3.06 3.53 4.07 4.68 5.39 6.20 7.13 8.20 9.44 10.88
26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
22.25 23.94 25.80 27.86 30.14 32.67 35.49 38.64 42.16 46.12 50.59 55.63 61.35 67.87 75.31 83.86 93.71 105.11 118.37 133.88 152.10 173.64 199.26 229.93 266.89
11.85 13.20 14.72 16.44 18.40 20.63 23.18 26.09 29.44 33.30 37.75 42.92 48.93 55.96 64.20 73.90 85.38 99.02 115.31 134.88 158.51 187.21 222.31 265.51 319.07
5
6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
be checked for undrained loading conditions using bearing capacity factors based on undrained s.hear strength parameters. 4.4. 7.1.1
Factors Affecting Bearing Capacity
N" 12.54 14.47 16.72 19.34 22.40 25.99 30.22 35.19 41.06 48.03 56.31 66.19 78.03 92.25 109.41 130.22 155.55 186.54 224.64 271.76 330.35 403.67 496.01 613.16 762.89
calculate the ultimate load capacity of the footing. The reduced footing dimensions shall be determined as follows: B'
= B- 2es
(4.4.7.1.1.1-1)
L'
= L- 2eL
(4.4.7.1.1.1-2)
A modified form of the general bearing capacity equation may be used to account for the effects of footing shape, ground surface slope, base inclination, and inclined loading as follows:
The effective footing area shall be determined as follows:
qu11 = cNcscbcic + 0.5-yBN.ys..,b'Yi.v + qNqsqbqiq
A'=B'L'
(4.4.7.1.1-1) Reduced footing dimensions shall be used to account for the effects of eccentric loading. 4.4. 7.1.1.1
Eccentric Loading
For loads eccentric relative to the centroid of the footing, reduced footing dimensions (B' and L') shall be used to determine bearing capacity factors and modifiers (i.e., slope, footing shape, and load inclination factors), and to
(4.4.7.1.1.1-3)
Refer to Figure 4.4.7. I .1. I A for loading definitions and footing dimensions. The value of qu11 obtained using the reduced footing dimensions represents an equivalent uniform bearing pressure and not the actual contact pressure distribution beneath the footing. This equivalent pressure may be multiplied by the reduced area to determine the ultimate load capacity of the footing from the standpoint of bearing capacity. The actual contact pressure distribution (i.e., trapezoidal for the conventional assumption of a rigid
0 .
footing and a positive pressure along each footing edge) shall be used for structural design of the footing. The actual distribution of contact pressure for a rigid footing with eccentric loading about one axis is shown in Figure 4.4. 7.1.1.1 B. For an eccentricity (ed in the L direction, the actual maximum and minimum contact pressures may be determined as follows:
ic:
=l
iq
= [I
- (nP/BLcNc:) (for - P/(Q
= Q[ I + (6eLIL)l/BL
(4.4.7.1.1.1-4)
qmi11 = Q[I - (6etfL)]/BL
(4.4.7.1.1.1-5)
qllUL\
for U6 < eL < U2: q~
= 2Q/(3B[U2)- cd)
L 1 = 3[(L/2) - ed
(4.4.7.1.1.1-6)
n
Footing Shape
For footing shapes other than continuous footings (i.e., L < 5B ), the following shape factors shall be applied to Equation 4.4.7.1.1-1:
(4.4.7.1.1.3-3)
11
(4.4.7.1.1.3-4)
(4.4.7.1.1.3-5)
Refer to Figure 4.4. 7 .1.1.1 A for loading definitions and footing dimensions. For cases in which the loading is eccentric, the terms L and B shall be replaced by L 1 and B1 , respectively, in the above equations. Failure by sliding shall be considered by comparing the tangential component of force on the footing (P) to the maximum resisting force (Pmax) by the following: Pmax = Qtan8
+ BLcn
FS = Pmn.,.IP;::: 1.5
(4.4.7.1.1.3-6) (4.4.7.1.1.3-7)
In determining Pmnx• the effect of passive resistance provided by footing embedment shall be ignored, and BL shall represent the actual footing area in compression as shown in Figure 4.4.7.1.1.18 or Figure 4.4.7.1.1.1C. 4.4. 7.1.1.4
Ground Suiface Slope
For footings located on slopes or within 3B of a slope crest, quit may be determined using the following revised version of Equation 4.4. 7.1.1-1 :
Sc = 1 + (B/L) (Nc/Nc)
{4.4.7.1.1.2-1)
Sq = 1 + (B/L) tan
(4.4. 7.1.1.2-2)
Refer to Figure 4.4.7.1.1.4A for values ofNc:q and N-yq for footings on slopes and Figures 4.4. 7 .1.1.4B for values of Nc:q and Nyq for footings at the top of slopes. For footings in or above cohesive soil slopes, the stability number in the figures, N5 , is defined as follows:
Sy = 1 - 0.4 (BIL)
(4.4.7.1.1.2-3)
(4.4.7 .1.1.4-2)
For circular footings, B equals L. For cases in which the loading is eccentric, the terms L and B shall be replaced by L' and B', respectively, in the above equations.
Overall stability shall be evaluated for footings on or adjacent to sloping ground surfaces as described in Article 4.4.9.
4.4.7.1.1.3
4.4.7.1.1.5
Inclined Loading
For inclined loads, the following inclination factors shall be applied in Equation 4.4. 7.1.1-1:
0
(4.4.7.1.1.3-2)
= [(2 + UB)/(1 + UB)]cos29
(4.4.7.1.1.1-8)
For an eccentricity (ep) in the B direction, the maximum and minimum contact pressures may be determined using Equations 4.4. 7.1 .1.1-4 through 4.4. 7. 1.1.1-8 by replacing terms labeled L by B, and terms labeled B by L. Footings on soil shall be designed so that the eccentricity of loading is less than X, of the footing dimension in any direction. 4.4.7.1.1.2
+ BLc cot)]
iy = [1 - P/(Q + BLc cot)]l" + H
(4.4.7.1.1.1-7)
.
= 0)
+ [(2 + B/L)/(1 + BIL)]sin28
foreL < U6:
0
51
DIVISION I-DESIGN
4.4.7 .1.1.1
ic:
= iq- [(1
- iq)!Nc tan 1 (for > 0)
(4.4.7.1.1.3-1)
Embedment Depth
The shear strength of soil above the base of footings is neglected in determining qu11 using Equation 4.4.7.1.1-l. If other procedures are used, the effect of embedment shall be consistent with the requirements of the procedure followed.
HIGHWAY BRIDGES
52
F" _____
4.4.7.1.1.5
Q
I
I I I
I I
8
FIGURE 4.4.7.1.1.1A Definition Sketch for Loading and Dimensions for Footings Subjected to Eccentric or Inclined Loads Modified after EPRI (1983)
-----· - .. < 37°, the following equations may be used to determine the weighted average unit weight: for
Zw 2:
B: use -y = 'Ym (no effect)
= -y' + (z"/B)('Ym -
for Zw < B: use -y
(4.4.7.1.1.6-1)
-y')
55
= {20- Zw){Zw-yn/1)2) + (-y'/D2){D -
Zw) 2
(4.4.7.1.1.6-4) D
= 0.5Btan(45° + 4>/2) (4.4.7.1.1.6-5)
4.4.7.1.1. 7 Layered Soils If the soil profile is layered, the general bearing capacity equation shall be modified to account for differences in failure modes between the layered case and the homogeneous soil case assumed in Equation 4.4. 7 .1.1-1.
(4.4.7.1.1.6-2) Undrained Loading for Zw
:s;
0: use -y
= -y'
(4.4.7.1.1.6-3)
Refer to Figure 4.4.7.1.1.6A for definition of terms used in these equations. If ~ 37°, the following equations may be used to determine the weighted average unit weight:
0
For undrained loading of a footing supported on the upper layer of a two-layer cohesive soil system, q 1111 may be determined by the following: (4.4.7.1.1.7-1)
'
.
y,
z.
+
~., Q '
.
W.T.
sz
-
'-
•
FIGURE 4.4.7.1.1.6A Definition Sketch for Inftuence of Ground Water Table on Bearing Capacity
HIGHWAY BRIDGES
56
Refer to Figure4.4.7.1 .1.7A for the definition of c 1• For undrained loading, c 1 equals the undrained soil shear strength Suh and 1 = 0. If the bearing stratum is a cohesive soil which overlies a stiffer cohesive soil, refer to Figure 4.4.7. 1.1.78 to determine Nm. If the bearing stratum overlies a softer layer, punching shear should be assumed and Nmmay be calculated by the following:
The subscripts l and 2 refer to the upper and lower layers, respectively. K = (1 - sin2 1')/( l + sin2 1') and q2 equals qu11 of a fictitious footing of the same size and shape as the actual footing but supported on the second (or lower) layer. Reduced shear strength values shall be used to detennine q2 in accordance with Article 4.4.7.1. lf the upper layer is a cohesion less soil and ' equals 25° to 50°, Equation 4.4.7.1.1.7-3 reduces to qull
Drained Loading
Hen,= [3B 1n(ql/q2)1/[2(1 + BIL)l
= lq2 + (I/K)c 1'cot 1' l exp{2[1 +
= q2exp(0.67[1 + (BIL))H/B }
(B/L)IKtanI'(H/8 )} - ( I/K)c1' cot(l>1'
100 90
aob 70
i
..
~
QuJI
t
.~l~
60
HI -s- c: •0
50
C2 ·2·0
.!!
,. ,. "
!: :50 u
0
/
Q,
/
0
u
."'
.~
.,.
40
u
(a)
(4.4.7.1.1.7-5)
In the equation, q 1 equals the bearing capacity of the upper layer assuming the upper layer is of infinite extent.
(4.4.7. 1.1.7-3)
z
(4.4.7. 1. 1.7-4)
The critical depth of the upper layer beyond which the bearing capacity will generally be unaffected by the presence of the lower layer is given by the following:
For drained loading of a footing supported on a strong layer overlying a weak layer in a two-layer system, qu11 may be determined using the following: qull
4.4.7.1.1.7
/
/
20
,. " " "'
"'"'
" "'
"
"CXI
0
•
- LI B • I (square or cir cle)
.0 'Q
.!
15
'Q
0
2
10 9
2 3
4
5
6
1
8
9
10
(b)
FIGURE 4.4.7.1.1.7A Typical Two-Layer Soil Profiles
FIGURE 4.4.7.1.1.7B Modified Bearing Capacity Factor for 1\vo-Layer Cohesive Soil with Softer Soil Overlying Stiffer Soil EPRI (1983)
4.4.7.1.1.8
DIVISION I-DESIGN
57
4.4.7.1.1.8 Inclined Base
(4.4.7.2-1)
Footings with inclined bases are generally not recommended. Where footings with inclined bases are necessary, the following factors shall be applied in Equation 4.4.7.1.1-1: bq =by= (1 - atan) 2 (4.4.7.1.1.8-1) be= by- (1 - b'Y)/(Netan
> 0)
(4.4.7.1.1.8-2) be = I - [2al('lT
+ 2)] (for 4>
= 0) (4.4.7.1.1.8-3)
Refer to Figure 4.4. 7 .1.1.8A for definition sketch. Where footings must be placed on sloping surfaces, refer to Article 4.4.6 for anchorage requirements.
4.4. 7.1.2
Factors of Safety
Spread footings on soil shall be designed for Group 1 loadings using a minimum factor of safety (FS) of 3.0 against a bearing capacity failure.
4.4.7.2 Settlement
0
.
.
The total settlement includes elastic, consolidation, and secondary components and may be determined using the following:
Elastic settlement shall be determined using the unfactored dead load, plus the unfactored component of live and impact loads assumed to extend to the footing level. Consolidation and secondary settlement may be determined using the full unfactored dead load only. O.ther factors which can affect settlement (e.g., embankment loading, lateral and/or eccentric loading, and for footings on granular soils. vibration loading from dynamic live loads or earthquake loads) should also be considered, where appropriate. Refer to Gifford, et al., ( 1987) for general guidance regarding static loading conditions and Lam and Martin (1986) for guidance regarding dynamic/seismic loading conditions.
4.4. 7.2.1
Stress Distribution
Figure 4.4.7.2.1A may be used to estimate the distribution of vertical stress increase below circular (or square) and long rectangular footings (i.e., where L > 5B). For other footing geometries, refer to Poulos and Davis (1974). Some methods used for estimating settlement of footings on sand include an integral method to account for the effects of vertical stress increase variations. Refer to Gifford, et al., ( 1987) for guidance regarding application of these procedures.
GROUND SURFACE
FIGURE 4.4.7.1.1.8A Definition Sketch for Footing Base Inclination
HIGHWAY BRIDGES
58 4.4.7.2.2
termined at a depth of about Y2 to % of B below the footing. If the soil modulus varies significantly with depth, a weighted average value of Es may be used. Refer to Gifford, et al., ( 1987) for general guidance regarding the estimation of elastic settlement of footings on sand.
Elastic Settlement
The elastic settlement of footings on cohesionless soils and stiff cohesive soils may be estimated using the following:
Refer to Table 4.4.7.2.2A for approximate values of Es and v for various soil types, and Table 4.4.7.2.2B for values of ~z for various shapes of flexible and rigid footings. Unless Es varies significantly with depth, Es should be de-
48
:!8
a
28
4.4.7.2.2
4.4. 7.2.3
Consolidation Settlement
The consolidation settlement of footings on saturated or nearly saturated cohesive soils may be estimated using
U11J! ~~,,
~--'-
48
31
211
~ ~ ~ ~~ fMI ' ... ' ,~~ ~~ '~o.l..-1 I ' rtIf/ ~1.t"" _) _ Vi ~\ I , "I I' • , ·' .... '\ ' ,-'lj ... "' .,.~· ..I 1/ v L ,.. lL \, ~.. 1/ 1 ~ " t.. ·-~ .ft!.. .. ~ ' lj / ' ·' -- j_ v II / --........ v 'l ·I J \ sa·- I -·-v : \ :: v 1\ ~ ...···v I ' I -v ~ \ ... ·- 171 1\ "~
I
8
~~./
~
z~~
~.
,~
~
f/1
\~
I
~
;
L
o-i# '_(
I
~-
1!!1.
~,
~":":!·-~
If
_)_
1....
~
J
'\
\
~
0.~....
'I
j
- ....
j
~
I
[/'
~
I••
J
\
4 ...
t..•
1-..
~
f"-..
r--
,,
~0.1 .....
~
118
--...
...........
t--
.......
\
-~·
~
~
j
,_ 1'-
r--......
......... -,., ~
~I
_;_
\
\
98
Ia•
--
l' ~,
~
"
oa ·-
r....
~
-
~-~
~~
--
lcaa
_,, ·' ~
.... 10I
....
·-
Ill
Ill
48
!I lnfinatelr
za (a)
FIGURE 4.4.7.2.1A
a
Lane Foundation
o
0
a
ZB
!I
48
Sqawe F'aunattGn
(/,J
Boussinesg Vertical Stress Contours for Continuous and Square Footings Modified after Sowers (1979)
-~
4.4.7.2.3
59
TABLE 4.4.7.2.2A Elastic Constants of Various Soils Modified after U.S. Department of the Navy (1982) and Bowles (1982)
0
Estimating E,. From N< n
'I}'pical Range of Values
Soil1}tpe Clay: Soft sensitive Medium stiff to stiff Very stiff
Loess Silt
0
DIVISION I-DESIGN
Fine sand: Loose Medium dense Dense Sand: Loose Medium dense Dense Gravel: Loose Medium dense Dense
Young's Modulus, E,. (ksf)
50-300 300-1,000 1,000·2,000
Poisson's Ratio,v (dim)
0.4-0.5 (undrained)
300-1 ,200 40-400
0.1-0.3 0.3-0.35
Es Soil1}tpe
{ksf)
Silts, sandy silts, slightly cohesive mixtures Clean fine to medium sands and slightly silty sands Coarse sands and sands with little gravel
8Nt< 2>
Sandy gravel and gravels
24Nt
20Nt
Estimating E8 From Su
160-240 240-400 400-600
0.25
0.2-0.35
200-600 600-1,000 1,000-1 ,600
Soft sensitive clay Medium stiff to stiff clay Very stiff clay
0.2-0.35
60()..1,600
1,600-2,000 2,000-4,000
Sandy soils
0.3-0.4
= Standard Penetration 'lest (SPT) resistance. = SPT corrected for depth. (3>Su = Undrained shear strength (ksO. qc = Cone penetration resistance (ks0. "'N 1
TABLE 4.4.7.2.28 Elastic Shape and Rigidity Factors EPRI (1983)
Pz
lJB
Circular 1 2 3
5 10
Flexible (average) 1.04 1.06 1.09 1.13 1.22
1.41
400Su·l ,OOOsu 1,500Su·2,400su 3,CKMlsu--4,Osu
Estimating E5 From qc
0.3-0.4
(I>N 2 C
14N 1
Pz
Rigid
1.13 1.08 1.10 1.15 1.24 1.41
4qc
HIGHWAY BRIDGES
60
4.4.7.2.3
the following when laboratory test results are expressed in terms of void ratio (e): • For initial overconsolidated soils (i.e., up' Sc = [lic/(1 + eo)][(Ccr log{up'luo'} + Cc log{ar'/up'})]
> uo'):
(4.4.7.2.3-1)
• For initial normally consolidated soils (i.e., up' 6.25 feet (75 inches) and shaft settlements will not be evaluated, the value of qT should be reduced to qTR as follows: qTR =FAT= (2.5/[aBl12
+ 2.5b])qT
+ 0.0021(DIB 1); as 0.015
a= 0.0071
0 1)
b = 0.45(Su .5; 0.5 S b S 1.5
(4.6.5.1.3-3) (4.6.5.1.3-4) (4.6.5.1.3-5)
The limiting value of qTR is 80 ksf. For shafts in cohesive soil under drained loading conditions, QT may be estimated using the procedure described in Article 4.6.5.1.4.
4.6.5.1.4
Tip Resistance in Cohesionless Soil
For axially loaded drilled shafts in cohesionless soils or for effective stress analysis of axially loaded drilled shafts in cohesive soil, the ultimate tip resistance may be estimated using the following: (4.6.5.1.4-1)
0
The value of qT may be determined from the results of standard penetration testing using uncorrected blow count readings within a depth of 2B below the tip of the shaft. Refer to Table 4.6.5.1.4A for recommended values of qT. If B1 > 4.2 feet (50 inches) and shaft settlements will not be evaluated, the value of qT should be reduced to qTR as follows: (4.6.5.1.4-2) 4.6.5.2
4.6.5.2./
Factors Affecting Axial Capacity in Soil
Soil Layering and Variable Soil Strength with Depth
The design of shafts in layered soil deposits or soil deposits having variable strength with depth requires evaluation of soil parameters characteristic of the respective layers or depths. Qs in such soil deposits may be estimated by dividing the shaft into layers according to soil type and properties. determining Qs for each layer. and summing values for each layer to obtain the total Q 8 • If the soil below the shaft tip is of variable consistency, Qr may be estimated using the predominant soil strata within 2B below the shaft tip. For shafts extending through soft compressible layers to tip bearing on firm soil or rock, consideration shall be
83
TABLE 4.6.5.1.4A Recommended Values of qT• for Estimation of Drilled Shaft Tip Resistance in Cohesionless Soil after Reese and O'Neill (1988) Standard Penetration Resistance N (Blows/Foot) (uncorrected) Oto75 Above 75
ValueofqT (kst)
1.20N
90
*Ultimate value or value at settlement of 5 percent of base diameter.
given to the effects of negative skin friction (Article 4.6.5.2.5) due to the consolidation settlement of soils surrounding the shaft. Where the shaft tip would bear on a thin firm soil layer underlain by a softer soil unit, the shaft shall be extended through the softer soil unit to eliminate the potential for a punching shear failure into the softer deposit.
4.6.5.2.2
Ground Water
The highest anticipated water level shall be used for design.
4.6.5.2.3
Enlarged Bases
An enlarged base (bell or underream) may be used at the shaft tip in stiff cohesive soil to increase the tip bearing area and reduce the unit end bearing pressure, or to provide additional resistance to uplift loads. The tip capacity of an enlarged base shall be determined assuming that the entire base area is effective in transferring load. Allowance of full effectiveness of the enlarged base shall be permitted only when cleaning of the bottom of the drilled hole is specified and can be acceptably completed before concrete placement.
4.6.5.2.4
Group Action
Evaluation of group shaft capacity assumes the effects of negative skin friction (if any) are negligible.
4.6.5.2.4./
Cohesive Soil
Evaluation of group capacity of shafts in cohesive soil shall consider the presence and contact of a cap with the ground surface and the spacing between adjacent shafts. For a shaft group with a cap in firm contact with the ground, Qu11 may be computed as the lesser of (I) the sum of the individual capacities of each shaft in the group or (2) the capacity of an equivalent pier defined in the perimeter area of the group. For the equivalent pier, the
HIGHWAY BRIDGES
84
shear strength of soil shall not be reduced by any factor (e.g., a 1) to determine the Qs component of Qu1tt the total base area of the equivalent pier shall be used to determine the Qr component of Qu~., and the additional capacity of the cap shall be ignored. If the cap is not in firm contact with the ground, or if the soil at the surface is loose or soft, the individual capacity of each shaft should be reduced to t times Qr for an isolated shaft, where t = 0.67 for a center-to-center (CTC) spacing of 38 and t = 1.0 for a CTC spacing of 68. For intermediate spacings, the value oft may be determined by linear interpolation. The group capacity may then be computed as the lesser of ( 1) the sum of the modified individual capacities of each shaft in the group, or (2) the capacity of an equivalent pier as described above.
4.6.5.2.4.2
Cohesionless Soil
Evaluation of group capacity of shafts in cohesionless soil shall consider the spacing between adjacent shafts. Regardless of cap contact with the ground, the individual capacity of each shaft should be reduced to t times Qr for an isolated shaft, where t = 0.67 for a center-to-center (CTC) spacing of 3B and t = 1.0 for a CTC spacing of 88. For intermediate spacings. the value oft may be determined by linear interpolation. The group capacity may be computed as the lesser of (I) the sum of the modified individual capacities of each shaft in the group or (2) the capacity of an equivalent pier circumscribing the group, including resistance over the entire perimeter and base areas.
4.6.5.2.4.3
Group in Strong Soil Overlying Weaker Soil
If a group of shafts is embedded in a strong soil deposit which overlies a weaker deposit (cohesionless and cohesive soil), consideration shall be given to the potential for a punching failure of the tip into the weaker soil strata. For this case, the unit tip capacity of the equivalent shaft (qE) may be determined using the following:
If the underlying soil unit is a weaker cohesive soil strata, careful consideration shall be given to the potential for large settlements in the weaker layer.
4.6.5.2.5
Vertical Ground Movement
The potential for external loading on a shaft by vertical ground movement (i.e., negative skin friction/downdrag due to settlement of compressible soil or uplift due to heave of expansive soil) shall be considered as a part of
4.6.5.2.4.1
design. For design purposes, it shall be assumed that the full magnitude of maximum potential vertical ground movement occurs. Evaluation of negative skin friction shall include a load-transfer method of analysis to determine the neutral point (i.e., point of zero relative displacement) and load distribution along shaft (e.g., Reese and O'Neill, 1988). Due to the possible time dependence associated with vertical ground movement, the analysis shall consider the effect of time on load transfer between the ground and shaft and the analysis shall be performed for the time period relating to the maximum axial load transfer to the shaft. Shafts designed for and constructed in expansive soil shall extend to a sufficient depth into moisture-stable soils to provide adequate anchorage to resist uplift movement. In addition, sufficient clearance shall be provided between the ground surface and underside of caps or beams connecting shafts to preclude the application of uplift loads at the shaft/cap connection from swelling ground conditions. Uplift capacity shall rely only on side resistance in conformance with Article 4.6.5.1. If the shaft has an enlarged base, Qs shall be determined in conformance with Article 4.6.5.2.3.
4.6.5.2.6 Method of Constntction The load capacity and deformation behavior of drilled shafts can be greatly affected by the quality and method(s) of construction. The effects of construction methods are incorporated in design by application of a factor of safety consistent with the expected construction method(s) and level of field quality control measures (Article 4.6.5.4). Where the spacing between shafts in a group is restricted, consideration shall be given to the sequence of construction to minimize the effect of adjacent shaft construction operations on recently constructed shafts.
4.6.5.3 Axial Capacity in Rock Drilled shafts are socketed into rock to limit axial displacements, increase load capacity and/or provide fixity for resistance to lateral loading. In determining the axial capacity of drilled shafts with rock sockets, the side resistance from overlying soil deposits may be ignored. '!Ypically, axial compression load is carried solely by the side resistance on a shaft socketed into rock until a total shaft settlement (p5 ) on the order of 0.4 inches occurs. At this displacement, the ultimate side resistance, QsR, is mobilized and slip occurs between the concrete and rock. As a result of this slip, any additional load is transferred to the tip. The design procedures assume the socket is constructed in reasonably sound rock that is little affected by
4.6.5.3
c
DIVISION I-DESIGN
construction (i.e., does not rapidly degrade upon excavation and/or exposure to air or water) and which is cleaned prior to concrete placement (i.e., free of soil and other debris). If the rock is degradable, consideration of special construction procedures, larger socket dimensions, or reduced socket capacities should be considered.
4.6.5.3.1
85
4.6.5.3.2
Tip Resistance
Evaluation of ultimate tip resistance (Qn) for rocksocketed drilled shafts shall consider the influence of rock discontinuities. QTR for rock-socketed drilled shafts may be determined using the following: (4.6.5.3.2-1)
Side Resistance
Preferably, values of Co should be determined from the results of laboratory testing of rock cores obtained within 2B of the base of the footing. Where rock strata within this interval are variable in strength, the rock with the lowest capacity should be used to determine QTR· Alternatively, Table 4.4.8.1.2B may be used as a guide to estimate C 0 • For rocks defined by very poor quality, the value of Qn cannot be less than the value of QT for an equivalent soil mass.
The ultimate side resistance (QsR) for shafts socketed into rock may be determined using the following:
Refer to Figure 4.6.5.3.1A for values of qsR- For uplift loading Qu11 of a rock socket shall be limited to 0.7QsR· The design of rock sockets shall be based on the unconfined compressive strength of the rock mass (Cm) or concrete, whichever is weaker (ac)- C 111 may be estimated using the following relationship: (4.6.5.3.1-2)
4.6.5.3.3.1
-
400 _,_
r-
LJ 200 0
------ - - --
~
--
z
II)
l&J
100
l&J
0
t::::>
ti ~
0
en ~
...... v
7-·
,
v / ~ ,. ··/
-- ·- - -
----50
--
-f--
~: ~---
iii
z
-· -·
--
./
iii ~
Rock Stratification
Rock stratification shall be considered in the design of rock sockets as follows:
Refer to Article 4.4.8.2.2 for the procedure to determine aE as a function of RQD.
'i' a.
Factors Affecting Axial Capaci~v in Rock
4.6.5.3.3
v
!.""'
-/ / -.--
...,.Iii"
_/
.
/
/ 7
v
vv
~
~
~
1-
y
,
,"'
/ r---
v --
--
-
~ ~~
/
-
-
,
__ -f--
-
0
~ 20
200 500 1000 2000 5000 10,000 20,000 UNCONnNED COMPRESSIVE STRENGTH OF ROCK OR CONCRElE. WHia-tEVER IS WEAKER,ac(psi)
0
FIGURE 4.6.5.3.1A Procedure for Estimating Average Unit Shear for Smooth Wall Rock-Socketed Shafts Horvath, et al. (1983)
HIGHWAY BRIDGES
86
• Sockets embedded in alternating layers of weak and strong rock shall be designed using the strength of the weaker rock. • The side resistance provided by soft or weathered rock should be neglected in determining the required socket length where a socket extends into more competent underlying rock. Rock is defined as soft when the uniaxial compressive strength of the weaker rock is less than 20% of that of the stronger rock, or weathered when the RQD is less than 20%. • Where the tip of a shaft would bear on thin rigid rock strata underlain by a weaker unit, the shaft shall be extended into or through the weaker unit (depending on load capacity or deformation requirements) to eliminate the potential for failure due to flexural tension or punching failure of the thin rigid stratum. • Shafts designed to bear on strata in which the rock surface is inclined should extend to a sufficient depth to ensure that the shaft tip is fully bearing on the rock. • Shafts designed to bear on rock strata. in which bedding planes are not perpendicular to the shaft axis shall extend a minimum depth of2B into the dipping strata to minimize the potential for shear failure along natural bedding planes and other slippage surfaces associated with stratification.
4.6.5.3.3.2
Rock Mass Discontinuities
The strength and compressibility of rock will be affected by the presence of discontinuities (joints and fractures). The influence of discontinuities on shaft behavior will be dependent on their attitude, frequency and condition, and shall be evaluated on a case-by-case basis as necessary.
4.6.5.3.3.3
Method of Construction
The effect of the method of construction on the engineering properties of the rock and the contact between the rock and shaft shall be considered as a part of the design process.
4.6.5.4 Factors of Safety Drilled shafts in soil or socketed in rock shall be designed for a minimum factor of safety of 2.0 against bearing capacity f()ilure (end bearing, side resistance or combined) when the design is based on the results of a load test conducted at. the site. Otherwise. shafts shall be designed for a minimum factor of safety 2.5. The minimum recommended factors of safety are based on an assumed normal level of field quality control during shaft construction. If a normal level of field quality control cannot be assured, higher minimum factors of safety shall be used.
4.6.5.3.3.1
4.6.5.5 Deformation of Axially Loaded Shafts The settlement of axially loaded shafts at working or allowable loads shall be estimated using elastic or load transfer analysis methods. For most cases. elastic analysis will be applicable for design provided the stress levels in the shaft are moderate relative to Qu11 • Where stress levels are high, consideration should be given to methods of load transfer analysis.
4.6.5.5.1
Shafts in Soil
Settlements should be estimated for the design or working load.
4.6.5.5.1.1
Cohesive Soil
The short-term settlement of shafts in cohesive soil may be estimated using Figures 4.6.5.5.1.1 A and 4.6.5.5.1.18. The curves presented indicate the proportions of the ultimate side resistance (Qs) and ultimate tip resistance (Qr) mobilized at various magnitudes of settlement. The total axial load on the shaft (Q) is equal to the sum of the mobilized side resistance (Qs) and mobilized tip resistance (Q1). The settlement in Figure 4.6.5.5.1.JA incorpomtes the effects of elastic shortening of the shaft provided the shaft is oftypicallength (i.e., D < 100ft). For longer shafts, the effects of elastic shortening may be estimated using the following:
Pe
= PD/AEc
(4.6.5.5.1.1-1)
For a shaft with an enlarged base in cohesive soil, the diameter of the shaft at the base (8b) should be used in Figure 4.6.5.5.1.18 to estimate shaft settlement at the tip. Refer to Article 4.4. 7 .2.3 for procedures to estimate the consolidation settlement component for shafts extending into cohesive soil deposits.
4.6.5.5.1.2
Cohesionless Soil
The short-term settlement of shafts in cohesionless soil may be estimated using Figures 4.6.5.5. I .2A and 4.6.5.5. I .28. The curves presented indicate the proportions of the ultimate side resistance (Qs) and ultimate tip resistance (Qr) mobilized at various magnitudes of settlement. The total axial load on the shaft (Q) is equal to the sum of the mobilized side resistance (Qs) and mobilized tip resistance (Q1). Elastic shortening of the shaft shall be estimated using the following relationship:
Pe = PD/AEc
(4.6.5.5.1.2-1)
4.6.5.5.1.2
DIVISION I-DESIGN
87
0
Range of Res&llts - - Trend Une
-
Range of Results
· - - - Trend Une
0.2
o.o ~~---_...._.......__,j..._......._"'----'--_,_--.1 0.0 0.2 0.4
0.8
0.8
1.0
1.2
1.4
1.8
1.8
0.1
2.0
Settlement ------,% Diameter of Shaft
0
2
FIGURE 4.6.5.5.1.1A Load Transfer in Side Resistance Versus Settlement Drilled Shafts in Cohesive Soil After Reese and O'Neill (1988)
4.6.5.5./.3
Shafts Socketed into Rock
In estimating the displacement of rock-socketed drilled shafts, the resistance to deformation provided by overlying soil deposits may be ignored. Otherwise, the load transfer to soil as a function of displacement may be estimated in accordance with Article 4.6.5.5.1. The butt settlement (p5 ) of drilled shafts fully socketed into rock may be determined using the following which is modified to include elastic shortening of the shaft:
0
ro
FIGURE 4.6.5.5.1.18 Load Transfer in Tip Bearing Settlement Drilled Shafts in Cohesive Soil After Reese and O'Neill (1988)
Pu = Qu[(I.JB,Em>
= Q[(lp!>IB,Em) + (D,/AE.J]
(4.6.5.5.2-1)
Refer to Figure 4.6.5.5.2A to determine 1~. The uplift displacement (pu) at the butt of drilled shafts fully socketed into rock may be determined using the following which is modified to include elastic shortening of the shaft:
+ (D/AEc)]
(4.6.5.5.2-2)
Refer to Figure 4.6.5.5.2B to determine Ipu. The rock mass modulus (Em) should be determined based on the results of in-situ testing (e.g., pressure-meter) or estimated from the results of laboratory tests in which Em is the modulus of intact rock specimens, and (E0 ) is estimated in accordance with Article 4.4.8.2.2. For preliminary design or when site-specific test data cannot be obtained, guidelines for estimating values of Eo. such as presented in Table 4.4.8.2.2B or Figure 4.4.8.2.2A, may be used. For preliminary analyses or for final design when in-situ test results are not available, a value of aE = 0.15 should be used to estimate Em.
4.6.5.5.3 p11
s
Mixed Soil Profile
The short-term settlement of shafts in a mixed soil profile may be estimated by summing the proportional settlement components from layers of cohesive and cohesionless soil comprising the subsurface profile.
4.6.5.5.2
3 4 s a 1 a Settlement of Base , % Diameter of Base
Tolerable Movemellt
Tolerable axial displacement criteria for drilled shaft foundations shall be developed by the structural designer consistent with the function and type of structure, fixity of bearings, antiCipated service life, and consequences of unacceptable displacements on the structure performance. Drilled shaft displacement analyses shall be based on the results of in-situ and/or laboratory testing to characterize
4.6.5.5.3
HIGHWAY BRIDGES
88
l8 tO
-
Ran;• o1 ReiUita fer C.flec1lon-Softlflfng ReiCIOf'lt
-
- - - Aln;t of RIIUita for Defttcdon-Harc:ttmlg RIIPOftll
Ran;e of Results
· - - · Trend Une
- - - Trend Unt
0.00.0
o.2
0.4
0.6
o.8
lO
1.2
Settlement
1.4
1.6
1.8
2.0
, %
Diameter of Shaft
FIGURE 4.6.5.5.1.2A Load Transfer in Side Resistance Versus Settlement Drilled Shafts in
Cobesionless SoU After Reese and O'Neill (1988)
the load-deformation behavior of the foundation materials. Refer to Article 4.4.7.2.5 for additional guidance regarding tolerable vertical and horizontal movement criteria.
4.6.5.6 Lateral Loading The design of laterally loaded drilled shafts shall account for the effects of soil/rock-structure interaction between the shaft and ground (e.g., Reese, 1984; Borden and Gabr, 1987). Methods of analysis evaluating the ultimate capacity or deflection of laterally loaded shafts (e.g., Broms, 1964a,b; Singh, et al., 1971) may be used for preliminary design only as a means to determine approximate shaft dimensions. 4.6.5.6.1 4.6.5.6.1.1
Factors Affecting Laterally Loaded Shafts Soil Layering
The design of laterally loaded drilled shafts in layered soils shall be based on evaluation of the soil parameters characteristic of the respective layers. 4.6.5.6.1.2
Ground Water
The highest anticipated water level shall be used for design.
2
3
4
5
8
7
8
9
w "
~
Settlement of Base , " Diameter of ease
FIGURE 4.6.5.5.1.28 Load Transfer in Tip Bearing Versus SeUlement Drilled Shafts in
Cohesionless Son After Reese and O'Nelll (1988)
4.6.5.6.1.3 Scour
The potential for loss of lateral capacity due to scour shall be considered in the design. Refer to Article 1.3.2 and FHWA (1988) for general guidance regarding hydraulic studies and design. If heavy scour is expected, consideration shall be given to designing the portion of the shaft that would be exposed as a column. In all cases, the shaft length shall be determined such that the design structural load can be safely supported entirely below the probable scour depth. 4.6.5.6.1.4 Group Action
There is no reliable rational method for evaluating the group action for closely spaced, laterally loaded shafts. Therefore, as a general guide, drilled shafts in a group may be considered to act individually when the center-to-center (CTC) spacing is greater than 2.5B in the direction normal to loading, and CTC > 8B in the direction parallel to loading. For shaft layouts not conforming to these criteria, the effects of shaft interaction shall be considered in the design. As a general guide, the effects of group action for in-line CTC < 8B may be considered using the ratios (COS, 1985) appearing on page 89.
4.6.5.6.1.4
DMSION I-DESIGN
89
0 '
-· Ec
Em
, ·0
0·2 0·5 0·6
l,os
0·~
11
0·1 0·01 0·08 0·07
0·4 0·3
m•0·2~
O·Oe ~-~-~-~-~-~--+--:--:-~
0
0•2
FIGURE 4.6.5.5.28 Influence Coefficient for Elastic Uplift Displacement of Rock-Socketed Drilled Shafts Modified after Pells and Thrner (1979)
0 1 ' 0
4.6.5.6.1. 7 Sloping Ground
0
FIGURE 4.6.5.5.2A Influence Coefficient for Elastic Settlement of Rock-Socketed Drilled Shafts Modified after Pells and Thmer (1979)
CTC Shaft Spacing for In-line Loading
8B
Ratio of Lateral Resistance of Shaft in Group to Single Shaft
6B 4B
1.00 0.70 0.40
3B
0.25
4.6.5.6.1.5
Cyclic Loading
The effects of traffic, wind, and other nonseismic cyclic loading on the load-deformation behavior of laterally loaded drilled shafts shall be considered during design. Analysis of drilled shafts subjected to cyclic loading may be considered in the COM624 analysis (Reese, 1984).
4.6.5.6.1.6
Combined Axial and Lateral Loading
The effects of lateral loading in combination with axial loading shall be considered in the design. Analysis of drilled shafts subjected to combined loading may be considered in the COM624 analysis (Reese, 1984).
~
\~
For drilled shafts which extend through or below sloping ground, the potential for additional lateral loading shall be considered in the design. The general method of analysis developed by Borden and Gabr ( 1987) may be used for the analysis of shafts in stable slopes. For shafts in marginally stable slopes, additional consideration should be given for ' low factors of safety against slope failure or slopes showing ground creep, or when shafts extend through fills overlying soft foundation soils and bear into more competent underlying soil or rock formations. For unstable ground, detailed explorations, testing and analysis are required to evaluate potential additional lateral loads due to slope movements.
4.6.5.6.2
Tolerable Lateral Movements
Tolerable lateral displacement criteria for drilled shaft foundations shall be developed by the structural designer consistent with the function and type of structure, fixity of bearings, anticipated service life, and consequences of unacceptable displacements on the structure performance. Drilled shaft lateral displacement analysis shall be based on the results of in-situ and/or laboratory testing to characterize the load-deformation behavior of the foundation materials.
4.6.5.6.7
HIGHWAY BRIDGES
90
4.6.5.7 Dynamic/Seismic Design Refer to Division 1-A and Lam and Martin (1986a; J986b) for guidance regarding the design of drilled shafts subjected to dynamic and seismic loads.
4.6.6 Structural Design and General Shaft Dimensions 4.6.6.1
General
Drilled shafts shall be designed to insure that the shaft will not collapse or suffer loss of serviceability due to excessive stress and/or deformation. Shafts shall be designed to resist failure following applicable procedures presented in Section 8. All shafts should be sized in 6-inch increments with a minimum shaft diameter of I 8 inches. The diameter of shafts with rock sockets should be sized a minimum of 6 inches larger than the diameter of the socket. The diameter of columns supported by shafts shall be less than or equal to B.
4.6.6.2 Reinforcement Where the potential for lateral loading is insignificant, driJied shafts need to be reinforced for axial loads only. Those portions of drilled shafts that are not supported laterally shall be designed as reinforced concrete columns in accordance with Articles 8.15.4 and 8.16.4, and the reinforcing steel shall extend a minimum of 10 feet below the plane where the soil provides adequate lateral restraint. Where permanent steel casing is used and the shell is smooth pipe and more than 0.12 inch in thickness, it may be considered as load carrying in the absence of corrosion. The design of longitudinal and spiral reinforcement shaH be in conformance with the requirements of Articles 8.18. I and 8.18.2.2, respectively. Development of deformed reinforcement shall be in conformance with the requirements of Articles 8.24. 8.26, and 8.27.
4.6.6.2.1
Longitudinal Bar Spacing
The minimum clear distance between longitudinal reinforcement shall not be less than 3 times the bar diameter nor 3 times the maximum aggregate size. If bars are bundled in forming the reinforcing cage, the minimum clear distance between longitudinal reinforcement shall
not be less than 3 times the diameter of the bundled bars. Where heavy reinforcement is required, consideration may be given to an inner and outer reinforcing cage.
4.6.6.2.2
Splices
Splices shall develop the full capacity of the bar in tension and compression. The location of splices shall be staggered around the perimeter of the reinforcing cage so as not to occur at the same horizontal plane. Splices may be developed by lapping, welding, and special approved connectors. Splices shall be in conformance with the requirements of Article 8.32.
4.6.6.2.3
Transverse Reinforcement
Transverse reinforcement shall be designed to resist stresses caused by fresh concrete flowing from inside the cage to the side of the excavated hole. Transverse reinforcement may be constructed of hoops or spiral steel.
4.6.6.2.4
Handling Stresses
Reinforcement cages shall be designed to resist handling and placement stresses.
4.6.6.2.5 Reinforcement Cover The reinforcement shall be placed a clear distance of not less than 2 inches from the permanently cased or 3 inches from the uncased sides. When shafts are constructed in corrosive or marine environments, or when concrete is placed by the water or slurry displacement methods, the clear distance shall not be less than 4 inches for uncased shafts and shafts with permanent casings not sufficiently corrosion resistant. The reinforcement cage shall be centered in the hole using centering devices. All steel centering devices shall be epoxy coated.
4.6.6.2.6 Reinforcement into Superstructure Sufficient reinforcement shall be provided at the junction of the shaft with the superstructure to make a suitable connection. The embedment of the reinforcement into the cap shall be in conformance with Articles 8.24 and 8.25.
4.6.6.3 Enlarged Bases Enlarged bases shall be designed to insure that plain concrete is not overstressed. The enlarged base shall slope at a side angle not less than 30 degrees from the vertical and have a bottom diameter not greater than 3 times the
4.6.6.3
c '
DIVISION I-DESIGN
diameter of the shaft. The thickness of the bottom edge of the enlarged base shall not be less than 6 inches.
'
'
4.6.6.4
Center-to-Center Shaft Spacing
The center-to-center spacing of drilled shafts should be 38 or greater to avoid interference between adjacent shafts during construction. If closer spacing is required, the sequence of construction shall be specified and the interaction effects between adjacent shafts shall be evaluated by the designer. 4.6. 7
Load Testing
4.6.7.1
General
Where necessary. a full scale load test (or tests) should be conducted on a drilled shaft foundation(s) to confirm response to load. Load tests shaH be conducted using a test shaft(s) constructed in a manner and of dimensions and materials identical to those planned for the production shafts into the materials planned for support. Load testing should be conducted whenever special site conditions or combinations of load are encountered, or when structures of special design or sensitivity (e.g .• large bridges) are to be supported on drilled shaft foundations.
0 ~
4.6.7.2
Load Testing Procedures
'
Load tests shall be conducted following prescribed written procedures which have been developed from accepted standards (e.g .• ASTM, 1989; Crowther, 1988) and modified, as appropriate, for the conditions at the site. Standard pile load testing procedures developed by ASTM which may be modified for testing drilled shafts include:
• Apparatus for measuring movements. • Apparatus for measuring loads. • Procedures for loading including rates of load application, load cycling and maximum load. • Procedures for measuring movements. • Safety requirements. • Data presentation requirements and methods of data analysis. • Drawings showing the procedures and materials to be used to construct the load test apparatus. As a minimum, the results of the load test(s) shall provide the load-deformation response at the butt of the shaft. When appropriate, information concerning ultimate load capacity, load transfer, lateral load-displacement with depth, the effects of shaft group interaction, the degree of fixity provided by caps and footings, and other data pertinent to the anticipated loading conditions on the production shafts shall be obtained. 4.6.7.3
0
• Apparatus for applying loads including reaction system and loading system.
Load Test Method Selection
Selection of an appropriate load test method shall be based on an evaluation of the anticipated types and duration of loads during service, and shall include consideration of the following: • The immediate goals of the load test (i.e., to proof load the foundation and verify design capacity). • The loads expected to act on the production foundation (compressive and/or uplift, dead and/orlive), and the soil conditions predominant in the region of concern. • The local practice or traditional method used in similar soiVrock deposits. • Time and budget constraints.
• ASTM D 1143. Standard Method of Testing Piles Under Static Axial Compressive Load; • ASTM D 3689, Standard Method of Testing Individual Piles Under Static Axial Tensile Load; and • ASTM D 3966, Standard Method for Testing Piles Under Lateral Loads. A simplified procedure for testing drilled shafts permitting determination of the relative contribution of side resistance and tip resistance to overall shaft capacity is also available (Osterberg, 1984). As a minimum, the written test procedures should include the following:
91
Parte STRENGTH DESIGN METHOD LOAD FACTOR DESIGN Note to User: Article Number 4. 7 has beell omitted illtemionally.
4.8
SCOPE
Provisions of this section shall apply for the design of spread footings, driven piles, and drilled shaft foundations.
4.9
4.9
HIGHWAY BRIDGES
92 DEFINITIONS
Batter Pile-A pile driven at an angle inclined to the vertical to provide higher resistance to lateral loads. Combination End-Bearing and Friction Pile-Pile that derives its capacity from the contributions of both end bearing developed at the pile tip and resistance mobilized along the embedded shaft. Deep Foundation-A foundation which derives its support by transferring loads to soil or rock at some depth below the structure by end bearing, by adhesion or friction or both. Design Load-All applicable loads and forces or their related internal moments and forces used to proportion a foundation. In load factor design, design load refers to nominal loads multiplied by appropriate load factors. Design Strength-The maximum load-carrying capacity of the foundation, as defined by a particular limit state. In load factor design, design strength is computed as the product of the nominal resistance and the appropriate performance factor. Drilled Shaft-A deep foundation unit, wholly or partly embedded in the ground, constructed by placing fresh concrete in a drilled hole with or without steel reinforcement. Drilled shafts derive their capacities from the surrounding soil and/or from the soil or rock strata below their tips. Drilled shafts are also commonly referred to as caissons, drilled caissons, bored piles or drilled piers. End-Bearing Pile-A pile whose support capacity is derived principally from the resistance of the foundation material on which the pile tip rests. Factored Load-Load, multiplied by appropriate load factors, used to proportion a foundation in load factor design. Friction Pile-A pile whose support capacity is derived principally from soil resistance mobilized along the side of the embedded pile. Limit State-A limiting condition in which the foundation and/or the structure it supports are deemed to be unsafe (i.e., strength limit state), or to be no longer fully useful for their intended function (i.e., serviceability limit state). Load Effect-The force in a foundation system (e.g., axial force, sliding force, bending moment, etc.) due to the applied loads. Load Factor-A factor used to modify a nominal load effect, which accounts for the uncertainties associated with the determination and variability of the load effect. Load Factor Design-A design method in which safety provisions are incorporated by separately accounting for uncertainties relative to load and resistance. Nominal Load-A typical value or a code-specified value for a load.
Nominal Resistance-The analytically estimated loadcarrying capacity of a foundation calculated using nominal dimensions and material properties, and established soil mechanics principles. Performance Factor-A factor used to modify a nominal resistance, which accounts for the uncertainties associated with the determination of the nominal resistance and the variability of the actual capacity. Pile-A relatively slender deep foundation unit, wholly or partly embedded in the ground, installed by driving, drilling, augering, jetting, or otherwise, and which derives its capacity from the surrounding soil and/or from the soil or rock strata below its tip. Piping-Progressive erosion of soil by seeping water, producing an open pipe through the soil, through which water flows in an uncontrolled and dangerous manner. Shallow Foundation-A foundation which derives its support by transferring load directly to the soil or rock at shallow depth. If a single slab covers the supporting stratum beneath the entire area of the superstructure, the foundation is known as a combined footing. If various parts of the structure are supported individually, the individual supports are known as spread footings, and the foundation is called a footing foundation. 4.10
4.10.1
LIMIT STATES, LOAD FACTORS, AND RESISTANCE FACTORS
General
All relevant limit states shall be considered in the design to ensure an adequate degree of safety and serviceability. 4.10.2 Serviceability Limit States Service limit states for foundation design shall include: -settlements, and -lateral displacements. The limit state for settlement shall be based upon rideability and economy. The cost of limiting foundation movements shall be compared to the cost of designing the superstructure so that it can tolerate larger movements, or of correcting the consequences of movement~ through maintenance, to determine minimum lifetime cost. More stringent criteria may be established by the owner. 4.10.3
Strength Limit States
Strength Jimit states for foundation design shall include:
4.10.3
DIVISION I-DESIGN
-bearing resistance failure, -excessive loss of contact, -sliding at the base of footing, -loss of overall stability, and -structural capacity. Foundations shall be proportioned such that the factored resistance is not less than the effects of factored loads specified in Section 3.
4.10.4 Strength Requirement Foundations shall be proportioned by the methods specified in Articles 4.11 through 4.13 so that their design strengths are at least equal to the required strengths. The required strength is the combined effect of the factored loads for each applicable load combination stipulated in Article 3.22. The design strength is calculated for each applicable limit state as the nominal resistance, Rm multiplied by an appropriate performance (or resistance) factor, . Methods for calculating nominal resistance are provided in Articles 4.11 through 4.13, and values of performance factors are given in Article 4.1 0.6.
0
4.10.5 Load Combinations and Load Factors .
Foundations shall be proportioned to withstand safely all load combinations stipulated in Article 3.22 which are applicable to the particular site or foundation type. With the exception of the portions of concrete or steel piles that are above the ground line and are rigidly connected to the superstructure as in rigid frame or continuous structures, impact forces shall not be considered in foundation design. (See Article 3.8.1.) Values of -y and ~ coefficients for load factor design, as given in Table 3.22.1A, shall apply to strength limit state considerations; while those for service load design (also given in Table 3.22.1A) shall apply to serviceability considerations.
93
4.11 SPREAD FOOTINGS 4.11.1 General Considerations 4.11.1.1 General Provisions of this article shall apply to design of isolated footings, and where applicable, to combined footings. Special attention shall be given to footings on fill. Footings shall be designed to keep the soil pressure as nearly uniform as practicable. The distribution of soil pressure shall be consistent with properties of the soil and the structure, and with established principles of soil mechanics.
4.11.1.2 Depth The depth of footings shall be determined with respect to the character of the foundation materials and the possibility of undermining. Footings at stream crossings shall be founded at depth below the maximum anticipated depth of scour as specified in Article 4.11.1.3. Footings not exposed to the action of stream current shall be founded on a firm foundation and below frost level. Consideration shall be given to the use of either a geotextile or graded granular filter layer to reduce susceptibility to piping in rip rap or abutment backfill .
4.11.1.3 Scour Protection Footings supported on soil or degradable rock strata shall be embedded below the maximum computed scour depth or protected with a scour counter-measure. Footings supported on massive, competent rock formations which are highly resistant to scour shall be placed directly on the cleaned rock surface. Where required, additional lateral resistance shall be provided by drilling and grouting steel dowels i1_1to the rock surface rather than blasting to embed the footing below the rock surface.
4.11.1.4 Frost Action 4.10.6 Performance Factors Values of performance factors for different types of foundation systems at strength limit states shall be as specified in Tables 4.1 0.6-1, 4.1 0.6-2, and 4.1 0.6-3, unless regionally specific values are available. If methods other than those given in Tables 4.1 0.6-1, 4.10.6-2, and 4.10.6-3 are used to estimate the soil capacity, the performance factors chosen shall provide the same reliability as those given in these tables.
In regions where freezing of the ground occurs during the winter months, footings shall be founded below the maximum depth of frost penetration in order to prevent damage from frost heave.
4.11.1.5 Anchorage Footings which are founded on inclined smooth solid rock surfaces and which are not restrained by an overburden of resistant material shall be effectively anchored by
4. I 1.1.5
HIGHWAY BRIDGES
94 TABLE 4.10.6-1
Perfonnance Factors for Strength Limit States for Shallow Foundations
Performance Factor (~)
1}rpe of Limit State
1. Bearing capacity a. Sand -Semi-empirical procedure using SPT data -Semi-empirical procedure using CPT data -Rational methodusing ~r estimated from SPT data using ~' estimated from CPf data b. Clay -Semi-empirical procedure using CPT data -Rational method using shear strength measured in lab tests using shear strength measured in field vane tests using shear strength estimated from CPf data c. Rock -Semi-empirical procedure (Carter and Kulhawy) 2. Sliding Sliding on clay is controlled by the strength of the clay when the clay shear strength is less than 0.5 times the normal stress, and is controlled by the normal stress when the clay shear strength is greater than 0.5 times the normal stress. a. Precast concrete placed on sand using 4»t estimated from SPT data using 4»t estimated from CPT data b. Concrete cast in place on sand using 4»f estimated from SPT data using 4»f estimated from CPT data c. aay (where shear strength is less than 0.5 times normal pressure) using shear strength measured in lab tests using shear strength measured in field tests using shear strength estimated from CPT data d. aay (where the strength is greater than 0.5 times normal pressure)
0.45 0.55 0.35 0.45 0.50 0.60 0.60 0.50
0.60
0.90 0.90 0.80 0.80 0.85 0.85 0.80 0.85
where «1»1 = frictional angle of sand, SPT = Standard Penetration Test, CPT = Cone Penetration Test.
means of rock anchors, rock bolts, dowels, keys or other suitable means. Shallow keying of large footing areas shan be avoided where blasting is required for rock removal.
4.11.1.7 Uplift Where foundations may be subjected to uplift forces, they shall be investigated both for resistance to pullout and for their structural strength.
4.11.1.6 Groundwater 4.11.1.8 Deterioration Footings shan be designed for the highest anticipated position of the groundwater table. The influence of the groundwater table on bearing capacity of soils or rocks, and settlements of the structure shall be considered. In cases where seepage forces are present, they should also be included in the analyses.
Deterioration of the concrete in a foundation by sulfate, chloride, and acid attack should be investigated. Laboratory testing of soil and groundwater samples for sulfates, chloride and pH should be sufficient to assess deterioration potential. When chemical wastes are suspected, a more thorough chemical anal-
4.11.1.8
c
DIVISION I-DESIGN TABLE 4.10.6-2
Performance Factors for Geotechnical Strength Limit States in Axially Loaded Piles
Performance Factor
Method/Soil/Condition Ultimate bearing capacity of single piles
Skin friction
a-method P-method A-method
0.70 0.50 0.55
End bearing
Oay (Skempton, 1951) Sand (Kulhawy, 1983) ct»r from CPT ct»r from SPT Rock (Canadian Geotech. Society, 1985)
0.70 0.45 0.35 0.50
SPT-method CPf-method Load test Pile driving analyzer
0.45 0.55 0.80 0.70
Skin friction and end bearing
Clay
0.65
Uplift capacity of single piles
a-method p-method A-method SPT-method CPT-method Load Test
0.60 0.40 0.45 0.35 0.45 0.80
Group uplift capacity
Sand Clay
0.55 0.55
Block failure
0
95
ysis of soil and groundwater samples should be considered.
4.11.1.9 Nearby Structures In cases where foundations are placed adjacent to existing structures, the inft uence of the existing structures on the behavior of the foundation, and the effect of the foundation on the existing structures, shall be investigated.
4.11.2 Notations B
B'
= footing width (in length units) =reduced effective footing width (see Article 4.11.4.1.5) (in length units) = soil cohesion (in units of force/length 2) = correction factors for groundwater effect (dimensionless) =depth to footing base (in length units) = depth to groundwater table (in length units) = elastic modulus of rock masses (in units of force/length 2)
i L'
= type of load effective length (see Article 4.11.4.1.5) (in length units) = load type i Li N = average value of standard penetration test blow count (dimensionless) N111 , Ncnu Nqnl = modified bearing capacity factors used in analytic theory (dimensionless) qc = cone resistance (in units of force/length 2) qu11 = ultimate bearing capacity (in units of force/length 2 ) R1 = reduction factor due to the effect of load inclination (dimensionless) = nominal resistance Rn = rock quality designation RQD = span length (in length units) s = undrained shear strength of soil (in units of force/length 2) = load factor coefficient for load type i (see Article 4.1 0.4) = load factor (see Article 4.1 0.4) 'Y = total (moist) unit weight of soil (see Arti'Y cle 4.11.4.1.1)
= reduced
4.1 1.2
HIGHWAY BRIDGES
96 TABLE 4.10.6-3
Performance Factors for Geotechnical Strength Limit States in Axially Loaded Drilled Shafts
Performance Factor
Method/Soil/Condition Ultimate bearing capacity of single drilled shafts
Side resistance in clay
a-method (Reese & O'Neill)
0.65
Base resistance in clay
Total Stress (Reese & O'Neill)
0.55
Side resistance in sand
1) Touma & Reese 2) Meyerhof 3) Quiros & Reese 4) Reese & Wright 5) Reese & O'Neill
See discussion in article 4.13.3.3.3
Base resistance in sand
1) Touma & Reese 2) Meyerhof 3) Quiros & Reese 4) Reese & Wright 5) Reese & O'Neill
See discussion in article 4.13.3.3.3
Side resistance in rock
Carter & Kulhawy Horvath and Kenney
0.55 0.65
Base resistance in rock
Canadian Geotechnical Society Pressuremeter Method (Canadian Geotechnical Society)
0.50
Load test
0.80
Cay
0.65
a-method (Reese & O'Neill) Belled Shafts (Reese & O'Neill)
0.55
Side resistance and end bearing Block failure Uplift capacity of single drilled shafts
Group uplift capacity
Clay
0.50
0.50
Sand
1) Touma & Reese 2) Meyerhof 3) Quiros & Reese 4) Reese & Wright 5) Reese & O'Neill
Rock
Carter & Kulhawy Horvath & Kenney
0.45 0.55
Load test
0.80
Sand Cay
0.55 0.55
See discussion in section 4.13.3.3.3
4.11.2
DIVISION I-DESIGN
= differential settlement between adjacent
0
footings = performance factor = friction angle of soil
4.11.3 Movement Under Serviceability Limit States 4.11.3.1
General
Movement of foundations in both vertical settlement and lateral displacement directions shall be investigated at service limit states. Lateral displacement of a structure shall be evaluated when: -horizontal or inclined loads are present, -the foundation is placed on an embankment slope, -possibility of loss of foundation support through erosion or scour exists, or -bearing strata are significantly inclined.
4.11.3.2 Loads Immediate settlement shall be determined using the service load combinations given in Table 3.22.1 A. Timedependent settlement shall be determined using only the permanent loads. Settlement and horizontal movements caused by embankment loadings behind bridge abutments should be investigated. In seismically active areas, consideration shall be given to the potential settlement of footings on sand resulting from ground motions induced by earthquake loadings. For guidance in design, refer to Division 1-A of these Specifications.
0
4.11.3.3 Movement Criteria
0
.
Vertical and horizontal movement criteria for footings shall be developed consistent with the function and type of structure, anticipated service life, and consequences of unacceptable movements on structure performance. The tolerable movement criteria shall be established by empirical procedures or structural analyses. The maximum angular distortion (8/s) between adjacent foundations shall be limited to 0.008 for simple span bridges and 0.004 for continuous span bridges. These 8/s limits shall not be applicable to rigid frame structures. Rigid frames shall be designed for anticipated differential settlements based on the results of special analyses .
97
4.11.3.4 Settlement Analyses Foundation settlements shall be estimated using deformation analyses based on the results of laboratory or in situ testing. The soil parameters used in the analyses shall be chosen to reflect the loading history of the ground, the construction sequence and the effect of soil layering. Both total and differential settlements, including time effects, shall be considered.
4.1 1.3.4.1
Settlement of Footings on Cohesionless Soils
Estimates of settlement of cohesionless soils shall make allowance for the fact that settlements in these soils can be highly erratic. No method should be considered capable of predicting settlements of footings on sand with precision. Settlement'i of footings on cohesionless soils may be estimated using empirical procedures or elastic theory.
4.1 1.3.4.2
Settlement of Footings on Cohesive Soils
For foundations on cohesive soils, both immediate and consolidation settlements shall be investigated. If the footing width is small relative to the thickness of a compressible soil, the effect of three-dimensional loading shall be considered. In highly plastic and organic clay, secondary settlements are significant and shall be included in the analysis.
4.11.3.4.3
Settlements of Footings on Rock
The magnitude of consolidation and secondary settlements in rock masses containing soft seams shall be estimated by applying procedures discussed in Article 4.11.3.4.2.
4.11.4 Safety Against Soll Fallure 4.11.4.1
Bearing Capacity of Foundation Solls
Several methods may be used to calculate ultimate bearing capacity of foundation soils. The calculated value of ultimate bearing capacity shall be multiplied by an appropriate performance factor, as given in Article 4.1 0.6, to determine the factored bearing capacity. Footings are considered to be adequate against soil failure if the factored bearing capacity exceeds the effect of design loads.
98
HIGHWAY BRIDGES
4.11.4.1.1
Theoretical Estimation
The bearing capacity should be estimated using accepted soil mechanics theories based on measured soil parameters. The soil parameter used in the analysis shall be representative of the soil shear strength under the considered loading and subsurface conditions.
4.11.4.1.2
Semi-empirical Procedures
The bearing capacity of foundation soils may be estimated from the results of in situ tests or by observing foundations on similar soils. The use of a particular in situ test and the interpretation of the results shall take local experience into consideration. The following in situ tests may be used: -Standard penetration test (SPT), -Cone penetration test (CPT), and -Pressuremeter test.
4. I 1.4.1.3
Plate Loading Test
Bearing capacity may be determined by load tests providing that adequate subsurface explorations have been made to determine the soil profile below the foundation. The bearing capacity determined from a load test may be extrapolated to adjacent footings where the subsurface profile is similar. Plate load test shall be performed in accordance with the procedures specified in ASTM Standard D 1194-87 or AASHTO Standard T 235.
4.11.4.1.4
Presumptive Values
Presumptive values for allowable bearing pressures on soil and rock, given in Table 4.11.4.1.4-1, shall be used only for guidance, preliminary design or design of temporary structures. The use of presumptive values shall be based on the results of subsurface exploration to identify soil and rock conditions. All values used for design shall be confirmed by field and/or laboratory testing. The values given in Table 4.11.4.1.4-l are applicable directly for working stress procedures. When these values are used for preliminary design, all load factors shall be taken as unity.
sure that: (l) the product of the bearing capacity and an appropriate performance factor exceeds the effect of vertical design loads, and (2) eccentricity of loading, evaluated based on factored loads, is less than ~ of the footing dimension in any direction for footings on soils. For structural design of an eccentrically loaded foundation, a triangular or trapezoidal contact pressure distribution based on factored loads shall be used.
4.11.4.1.6
Effect of Load Eccentricity
For loads eccentric to the centroid of the footing, a reduced effective footing area (B' XL') shall be used in design. The reduced effective area is always concentrically loaded, so that the design bearing pressure on the reduced effective area is always uniform. Footings under eccentric loads shall be designed to en-
Effect of Groundwater Table
Ultimate bearing capacity shall be determined based on the highest anticipated position of groundwater level at the footing location. In cases where the groundwater table is at a depth less than 1.5 times the footing width below the bottom of the footing, reduction of bearing capacity, as a result of submergence effects, shall be considered.
4.11.4.2 Bearing Capacity of Foundations on Rock The bearing capacity of footings on rock shall consider the presence, orientation and condition of discontinuities, weathering profiles and other similar profiles as they apply at a particular site, and the degree to which they shall be incorporated in the design. For footings on competent rock, reliance on simple and direct analyses based on uniaxial compressive rock strengths and RQD may be applicable. Competent rock shall be defined as a rock mass with discontinuities that are tight or open not wider than ~ inch. For footings on less competent rock, more detailed investigations and analyses shall be performed to account for the effects of weathering, and the presence and condition of discontinuities. Footings on rocks are considered to be adequate against bearing capacity failure if the product of the ultimate bearing capacity determined using procedures described in Articles 4.11.4.2.1 through 4.11.4.2.3 and an appropriate performance factor exceeds the effect of design loads.
4.11.4.2.1 4.11.4.1.5
4.11.4.1.1
Semi-empirical Procedures
Bearing capacity of foundations on rock may be determined using empirical correlation with RQD, or other systems for evaluating rock mass quality, such as the Geomechanic Rock Mass Rating (RMR) syste~ or Norwegian Geotechnical Institute (NGI) Rock Mass Classification System. The use of these semi-empirical procedures shall. take local experience into consideration.
4.11.4.2.1 TABLE 4.11.4.1.4-1
0
Presumptive Allowable Bearing Pressures for Spread Footing Foundations Modified after U.S. Department of the Navy, 1982
Allowable Bearing Pressure (tst) Type of Bearing Material
Massive crystalline igneous and metamorphic rock: graphite, diorite, basalt, gneiss, thoroughly cemented conglomerate (sound condition allows minor cracks) Foliated metamorphic rock: slate, schist (sound condition allows minor cracks) Sedimentary rock: hard cemented shales, siltstone, sandstone, limestone without cavities Weathered or broken bedrock of any kind except highly argillacous rock (shale) Compaction shale or other highly argillacous rock in sound condition Well-graded mixture of fine- and coarse-grained soil: glacial till, hardpan, boulder clay (GW-GC, GC, SC) Gravel, gravel-sand mixtures, boulder-gravel mixtures (GW, GP, SW, SP) Coarse to medium sand, sand with little gravel (SW, SP)
0
Fine to medium sand, silty or clayey medium to coarse sand (SW, SM, SC) Find sand, silty or clayey medium to fine sand (SP, SM, SC) Homogeneous inorganic clay, sandy or silty clay (CL, CH) Inorganic silt, sandy or clayey silt, varved silt-clay-fine sand (ML, MH)
0
99
DIVISION I-DESIGN
.
Ordinary Range
Recommended Value for Use
Very hard, sound rock
60 to 100
80
Hard sound rock
30 to 40
35
Hard sound rock
15 to 25
20
Medium hard rock
8 to 12
10
Medium hard rock
8 to 12
10
Very dense
8 to 12
10
Very dense Medium dense to dense Loose Very dense Medium dense to dense Loose Very dense Medium dense to dense Loose Very dense Medium dense to dense Loose Very stiff to hard Medium stiff to stiff Soft Very stiff to hard Medium stiff to stiff Soft
6 to 10 4 to 7 2 to 6 4 to 6 2 to 4
7 5 3 4 3 1.5 3
Consistency in Place
1 to 3 3 to 5 2 to 4 1 to 2 3 to 5 2 to 4 1 to 2 3 to 6 1 to 3 0.5 to 1 2 to 4 1 to 3 0.5 to 1
2.5 1.5
3
2.5 1.5 4 2 0.5 3 1.5 0.5
4.11.4.2.2
HIGHWAY BRIDGES
100 4.11.4.2.2 Analytic Method
The ultimate bearing capacity of foundations on rock shall be determined using established rock mechanics principles based on the rock mass strength parameters. The influence of discontinuities on the failure mode shall also be considered. 4.11.4.2.3 Load Test
Where appropriate, load tests may be performed to determine the bearing capacity of foundations on rock. 4.11.4.2.4
Presumptive Bearing Values
For simple structures on good quality rock masses, values of presumptive bearing pressure given in Table 4.11.4.2.4-1 may be used for preliminary design. The use of presumptive values shall be based on the results of subsurface exploration to identify rock conditions. All values used in design shaH be confirmed by field and/or laboratory testing. The values given in Table 4.11.4.2.4-1 are directly applicable to working stress procedure, i.e., all the load factors shall be taken as unity. 4.11.4.2.5 Effect of Load Eccentricity
If the eccentricity of loading on a footing is less than Y6 of the footing width, a trapezoidal bearing pressure shall be used in evaluating the bearing capacity. If the eccentricity is between Y6 and Y.a of the footing width, a triangular bearing pressure shall be used. The maximum bearing pressure shall not exceed the product of the ultimate bearing capacity multiplied by a suitable performance factor. The eccentricity of loading evaluated using factored loads shall not exceed Ys (37.5%) of the footing dimensions in any direction.
4.11.4.3 Failure by Sliding
Failure by sliding shall be investigated for footings that support inclined loads and/or are founded on slopes. For foundations on clay soils, possible presence of a shrinkage gap between the soil and the foundation shall be considered. If passive resistance is included as part of the shear resistance required for resisting sliding, consideration shall also be given to possible future removal of the soil in front of the foundation. 4.11.4.4 Loss of Overall Stability
The overall stability of footings, slopes and foundation soil or roc~ shall be evaluated for footings located on or near a slope using applicable factored load combinations in Article 3.22 and a performance factor of0.75.
4.11.5 Structural Capacity
The structural design of footings shall comply to the provisions given in Articles 4.4.11 and 8.16. 4.11.6 Construction Considerations for Shallow Foundations 4.11.6.1
General
The ground conditions should be monitored closely during construction to determine whether or not the ground conditions are as foreseen and to enable prompt intervention, if necessary. The control investigation should be performed and interpreted by experienced and qualified engineers. Records of the control investigations should be kept as part of the final project data, among other things, to permit a later assessment of the foundation in connection with rehabilitation, change of neighboring structures, etc. 4.11.6.2 Excavation Monitoring
Prior to concreting footings or placing backfill, an excavation shall be free of debris and excessive water. Monitoring by an experienced and trained person should always include a thorough examination of the sides and bottom of the excavation, with the possible addition of pits or borings to evaluate the geological conditions. The assumptions made during the design of the foundations regarding strength, density, and groundwater conditions should be verified during construction, by visual inspection. 4.11.6.3 Compaction Monitoring
Compaction shall be carried out in a manner so that the fill material within the section under inspection is as close as practicable to uniform. The layering and compaction of the fill material should be systematic everywhere, with the same thickness of layer and number of passes with the compaction equipment used as for the inspected fill. The control measurements should be undertaken in the form of random samples. 4.12 DRIVEN PILES 4.12.1
General
The provisions of the specifications in Articles 4.5.1 through 4.5.21 with the exception of Article 4.5.6, shall apply to strength design (load factor design) of driven piles. Article 4.5.6 covers the allowable stress design of
4.12.1 TABLE 4.11.4.2.4-1
0
0
Presumptive Bearing Pressures (tsf) for Foundations on Rock (After Putnam, 1981~
Sound Foliated Rock
Sound Sedimentary Rock
Code
Year 1
Bedrock2
Baltimore BOCA Boston Chicago Cleveland Dallas Detroit Indiana Kansas City Los Angeles New York City New York State Ohio Philadelphia Pittsburgh Richmond St. Louis San Francisco Uniform Building Code NBC Canada New South Wales, Australia
1962 1970 1970 1970 1951/1969 1968 1956 1967 1961/1969 1970 1970
100 100 100 100
40
25
50 100
10
.2qus 100 .2qu .2qu 10
.2qu 100 .2qu .2qu 4
60
60 40 40
1970 1969 1959/1969 1968 1960/1970 1969 1970
100 100 50 25 100 100 3-5 .2qu
35
25 .2qu 9,600 .2qu .2qu 3 60
15 15 10-15 25
15 25 3-5 .2qu
Soft Roctl
Soft Shale
10 10 10
Broken Shale (4)
4
1.5
.2qu 12 .2qu .2qu 1 8
.2qu 12 .2qu .2qu 1
10 8
4
(4)
.2qu .2qu .2qu 1
8
8
25 3-5 .2qu
10 10
4 1.5
1.5 1.5
.2qu
.2qu
.2qu
100 33
13
4.5
25
40 40
1970 1974
Note: 1-Year of code or original year and date of revision. 2-Massive crystalline bedrock. 3--Soft and broken rock, not including shale. 4-Allowable bearing pressure to be determined by appropriate city official. 5--qu = unconfined compressive strength. piles and shall be replaced by the articles in this section for load factor design of driven piles, unless otherwise stated.
4.12.2 Notations
as Ap As
0
101
DIVISION I-DESIGN
= pile perimeter
= area of pile tip = surface area of shaft of pile
CPT = cone penetration test = dimensionless depth factor for estimating tip cad pacity of piles in rock D = pile width or diameter D' = effective depth of pile group Db = depth of embedment of pile into a bearing stratum D~ = diameter of socket ex =eccentricity of load in the x-direction ey = eccentricity of load in the y-direction Ep = Young's modulus of a pile
Es
f\ H H5 I
Ip K
Kc Kr. K~11
Lr nh N
N
= soil modulus = sleeve friction measured from a CPT at point considered =distance between pile tip and a weaker underlying soil layer = depth of embedment of pile socketed into rock =influence factor for the effective group embedment = moment of inertia of a pile = coefficient of lateral earth pressure = correction factor for sleeve friction in clay = correction factor for sleeve friction in sand = dimensionless bearing capacity coefficient = depth to point considered when measuring sleeve friction = rate of increase of soil modulus with depth = Standard Penetration Test (SPT) blow count = average uncorrected SPT blow count along pile shaft
102
HIGHWAY BRIDGES
NCOIT =average SPT-N value corrected for effect of overburden Npne = number of piles in a pile group OCR = overconsolidation ratio P0 = unfactored dead load P8 = factored total axial load acting on a pile group Px.y = factored axial load acting on a pile in a pile group; the pile has coordinates (X,Y) with respect to the centroidal origin in the pile group PI = plasticity index q = net foundation pressure Qc = static cone resistance q1 = limiting tip resistance qo = limiting tip resistance in lower stratum qp = ultimate unit tip resistance q!) = ultimate unit side resistance qu = average uniaxial compressive strength of rock cores qu11 = ultimate bearing capacity QP = ultimate load carried by tip of pile Q~ = ultimate load carried by shaft of pile Qug = ultimate uplift resistance of a pile group or a group of drilled shafts Qu11 = ultimate bearing capacity R = characteristic length of soil-pile system in cohesive soils sd = spacing of discontinuities S = average spacing of piles Su = undrained shear strength SPT = Standard Penetration Test Su = average undrained shear strength along pile shaft ftt = width of discontinuities T = characteristic length of soil-pile system in cohesionless soils W8 = weight of block of soil, piles and pile cap x = distance of the centroid of the pile from the centroid of the pile cap in the x-direction X = width of smallest dimension of pile group y = distance of the centroid of the pile from the centroid of the pile cap in the y-direction Y = length of pile group or group of drilled shafts = total embedded pile length Z a = adhesion factor applied to Su ~ =coefficient relating the vertical effective stress and the unit skin friction of a pile or drilled shaft -y' =effective unit weight of soil 8 = angle of shearing resistance between soil and pile ~ = empirical coefficient relating the passive lateral earth pressure and the unit skin friction of a pile T) = pile group efficiency factor p = settlement Pcol = tolerable settlement a~ = horizontal effective stress
a~
~8
= = = =
~q
=
~qs
=
~qp
=
~u
=
fiSug
=
U8 v
~
4.12.3
4.12.2
vertical effective stress average shear stress along side of pile performance factor performance factor for the bearing capacity of a pile group failing as a unit consisting of the piles and the block of soil contained within the piles performance factor for the total ultimate bearing capacity of a pile performance factor for the ultimate shaft capacity of a pile performance factor for the ultimate tip capacity of a pile Performance factor for the uplift capacity of a single pile performance factor for the uplift capacity of pile groups Selection of Design Pile Capacity
Piles shall be designed to have adequate bearing and structural capacity, under tolerable settlements and tolerable lateral displacements. The supporting capacity of piles shall be determined by static analysis methods based on soil-structure interaction. Capacity may be verified with pile load test results, use of wave equation analysis, use of the dynamic pile analyzer or, less preferably, use of dynamic formulas. 4.12.3.1
Factors Affecting Axial Capacity
See ArticJe 4.5.6. I .1. The following sub-articles shall supplement Article 4.5.6.1.1.
4.12.3. 1.1
Pile Penetration
Piling ~sed to penetrate a soft or loose upper stratum overlying a hard or firm stratum, shall penetrate the hard or firm stratum by a sufficient distance to limit lateral and vertical movement of the piles, as well as to attain sufficient vertical bearing capacity.
4.12.3.1.2
Groundwater Table and Buoyancy
Ultimate bearing capacity shall be determined using the groundwater level consistent with that used to calculate load effects. For drained loading, the effect of hydrostatic pressure shall be considered in the design.
4.12.3.1.3
Effect Of Settling Ground and Downdrag Forces
Possible development of downdrag loads on piles shall be considered where sites are underlain by compressible clays, silts or peats, especially where fill has recently been
4.12.3.1.3
0
DIVISION I-DESIGN
placed on the earlier surface, or where the groundwater is substantially lowered. Downdrag loads shall be considered as a load when the bearing capacity and settlement of pile foundations are investigated. Downdrag loads shall not be combined with transient loads. The downdrag loads may be calculated, as specified in Article 4.12.3.3.2 with the direction of the skin friction forces reversed. The factored downdrag loads shall be added to the factored vertical dead load applied to the deep foundation in the assessment of bearing capacity. The effect of reduced overburden pressure caused by the downdrag shall be considered in calculating the bearing capacity of the foundation. The downdrag loads shall be added to the vertical dead load applied to the deep foundation in the assessment of settlement at service limit states.
4.12.3.1.4
llplij1
Pile foundations designed to resist uplift forces should be checked both for resistance to pullout and for structural capacity to carry tensile stresses. Uplift forces can be caused by lateral loads, buoyancy effects, and expansive soils.
0 '
4.12.3.2 Movement Under Serviceability Limit State 4.12.3.2.1
General
For purposes of calculating the settlements of pile groups, loads shall be assumed to act on an equivalent footing located at two-thirds of the depth of embedment of the piles into the layer which provide support as shown in Figure 4.12.3.2.1- 1. Service loads for evaluating foundation settlement shall include both the unfactored dead and live loads for piles in cohesionless soils and only the unfactored dead load for piles in cohesive soils. Service loads for evaluating lateral displacement of foundations shall include all lateral loads in each of the load combinations as given in Article 3.22.
4.12.3.2.2
0
Tolerable Movement
Tolerable axial and lateral movements for driven pile foundations shall be developed consistent with the function and type of structure, fixity of bearings. anticipated service life and consequences of unacceptable displacements on performance of the structure. Tolerable settlement criteria for foundations shall be developed considering the maximum angular distortion according to Article 4.1 1.3.3. Tolerable horizontal displacement criteria shall be de-
103
veloped considering the potential effects of combined vertical and horizontal movement. Where combined horizontal and vertical displacements are possible, horizontal movement shall be limited to 1.0 inch or less. Where vertical displacements are small, horizontal displacements shall be limited to 2.0 inches or less (Moulton. et al., 1985). If estimated or actual movements exceed these levels, special analysis and/or measures shall be considered.
4.12.3.2.3 Settlement The settlement of a pile foundation shall not exceed the tolerable settlement, as selected according to Article 4.12.3.2.2. 4.12.3.2.3a
Cohesive Soil
Procedures used for shallow foundations shaH be used to estimate the settlement of a pile group, using the equivalent footing location shown in Figure 4.12.3.2.1-1.
4. 12.3.2.3b
Cohesionless Soil
The settlement of pile groups in cohesion less soils can be estimated using results of in situ tests, and the equivalent footing location shown in Figure 4.12.3.2.1-1.
4.12.3.2.4
Lateral Displacement
The lateral displacement of a pile foundation shall not exceed the tolerable lateral displacement, as selected according to Article 4.12.3.2.2. The lateral displacement of pile groups shall be estimated using procedures that consider soil-structure interaction.
4.12.3.3 Resistance at Strength Limit States The strength limit states that shaU be considered include: -bearing capacity of piles, -uplift capacity of piles, -punching of piles in strong soil into a weaker layer, and -structural capacity of the piles.
4.1 2.3.3. 1 Axial Loading of Piles Preference shall be given to a design process based upon static analyses in combination with either field monitoring during driving or load tests. Load test results may be extrapolated to adjacent substructures with similar subsurface conditions. The ultimate bearing capacity of piles may be estimated using analytic methods or in situ test methods.
4.12.3.3.2
Analytic Estimates of Pile Capacity
Analytic methods may be used to estimate the ultimate bearing capacity of piles in cohesive and cohesionless soils. Both total and effective stress methods may be used provided the appropriate soil strength parameters are evaluated. The performance factors for skin friction and tip resistance, estimated using three analytic methods, shall be as provided in Table 4.10.6-2. If another analytic method is used, application of performance factors presented in Table 4.10.6-2 may not be appropriate. 4.12.3.3.3
Pile of Capacity Estimates Based on In Situ Tests
In situ test methods may be used to estimate the ultimate axial capacity of piles. The performance factors for the ultimate skin friction and ultimate tip resistance, estimated using in situ methods, shall be as provided in Table 4.10.6-2. 4.12.3.3.4
4.12.3.3.2
HIGHWAY BRIDGES
104
Piles Bearing on Rock
For piles driven to weak rock such as shales and mudstones or poor quality weathered rock, the ultimate tip capacity shall be estimated using semi-empirical methods. The performance factor for the ultimate tip resistance of piles bearing on rock shall be as provided in Table 4.10.6-2. 4.12.3.3.5 Pile Load Test
The load test method specified in ASTM D 1143-81 may be used to verify the pile capacity. Tensile load testing of piles shall be done in accordance with ASTM D 3689-83 Lateral load testing of piles shall be done in accordance with ASTM D 3966-81. The performance factor for the axial compressive capacity, axial uplift capacity and lateral capacity obtained from pile load tests shall be as provided in Table 4.10.6-2. 4.12.3.3.6 Presumptive End Bearing Capacities
Presumptive values for allowable bearing pressures given in Table 4.11.4.1.4-1 on soil and rock shall be used only for guidance, preliminary design or design of temporary structures. The use of presumptive values shall be based on the results of subsurface exploration to identify soil and rock conditions. All values used for design shall be confirmed by field and/or laboratory testing.
When piles are subjected to uplift, they should be investigated for both resistance to pullout and structural ability to resist tension. 4.12.3.3.7a
Single Pile Uplift Capacity
The ultimate uplift capacity of a single pile shall be estimated in a manner similar to that for estimating the skin friction resistance of piles in compression in Article 4.12.3.3.2 for piles in cohesive soils and Article 4.12.3.3.3 for piles in cohesionless soils. Performance factors for the uplift capacity of single piles shall be as provided in Table 4.10.6-2. 4.12.3.3.7b
Pile Group Uplift Capacity
The ultimate uplift capacity of a pile group shall be estimated as the lesser of the sum of the individual pile uplift capacities, or the uplift capacity of the pile group considered as a block. The block mechanism for cohesionless soil shall be taken as provided in Figure C4.12.3.7.2-1 and for cohesive soils as given in Figure C4.12.3.7.2-2. Buoyant unit weights shall be used for soil below the groundwater level. The performance factor for the group uplift capacity calculated as the sum of the individual pile capacities shall be the same as those for the uplift capacity of single piles as given in Table 4.10.6-2. The performance factor for the uplift capacity of the pile group considered as a block shall be as provided in Table 4.10.6-2 for pile groups in clay and in sand. 4.12.3.3.8 Lateral Load
For piles subjected to lateral loads, the pile heads shall be fixed into the pile cap. Any disturbed soil or voids created from the driving of the piles shall be replaced with compacted granular material. The effects of soil-structure or rock-structure interaction between the piles and ground, including the number and spacing of the piles in the group, shall be accounted for in the design of laterally loaded piles. 4.12.3.3.9 Batter Pile
The bearing capacity of a pile group containing batter piles may be estimated by treating the batter piles as vertical piles. 4.12.3.3.10 Group Capacity
4.12.3.3. 7 Uplift
Uplift shall be considered when the force effects calculated based on the appropriate strength limit state load combinations are tensile.
4.12.3.3.10a
Cohesive Soil
If the cap is not in firm contact with the ground, and if the soil at the surface is soft, the individual capacity of
0
104.1
DIVISION I-DESIGN
4.12.3.3.10a
1/;(\\
JJ:(\\
Equivalent footing
(a) 0.4
mw Soft layer
0.3 )t.t 'a
•
0 .
/lA\
"
j
0.2
Firm layer 0.1
Equivalent footing
o--~------_.
0
(b) FIGURE C4.12.3.2.1-l Location of Equivalent Footing (After Duncan and Buchignani, 1976)
0
0.2
0.4
__________________________
0.6
0.8
1.0
1.2
1.4
1.6
1.8
AatloiJD
FIGURE C4.12.3.3.4-1 Bearing capacity coefficient, Ksp (After Canadian Foundation Engineering Manual, 1985)
2.0
HIGHWAY BRIDGES
104.2
4.12.3.3.10a
As referenced in Section 4.12.3.3.7b and 4.13.2, the following figures have been reprinted from the 1993 Commentary of the 1993 Interims to the Standard Specifications for Highway Bridges.
z
XbyY
FIGURE C4.12.3.7.2-2 Uplift of group of piles in cohesive soils (After Tomlinson, 1987)
FIGURE C4.12.3.7.2-l UpUft of group of closely-spaced piles in cohesionless soils
,._
.,.
1.1 1.0
_.
0.9
0
0.8
II.
0.7
..
uCD
0.4
ij
G
u
c:
0.6
.a
0.5
c
o.•
E
!
0.3
Cl)
'CD
0.2
CD
:5
IJ
Ha
~
\"" ~ ~
o,
t
0.3
X
-·- ~!£e, __
'8
j
r-'10-
0.2
I" ~ ~ ....... ........ r-- so. . r--... ~ ..... 1- 100-
0.1
~~
~
0.1
5000s:: ~
0
2
•
6
8
10
12
....
20
Embedment Ratio HiD, FIGURE C4.13.3.3.4-l Elastic Settlement Influence Factor as a Function of Embedment Ratio and Modulus Ratio (After Donald, Sloan and Chiu, 1980, as presented by Reese and 0 'Neill, 1988)
0~__.___.___~--~--~--._--~--~---L--~
0
0.2
0.4
0.6
0.1
1.0
1.2
1.4
1.6
1.8
RatloiJD1
FIGURE C4.13.3.3.4-4 Bearing Capacity Coefficient, Ksp (After Canadian Geotechnical Society, 1985)
2.0
4.12.3.3.1 OA
DIVISION I-DESIGN
each pile shall be multiplied by an efficiency factor 1}. where 11 = 0.7 for a center-to-center spacing of three diameters and 11 = 1.0 for a center-to-center spacing of six diameters. For intermediate spacings, the value of 11 may be determined by linear interpolation. If the cap is not in firm contact with the ground and if the soil is stiff, then no reduction in efficiency shall be required. If the cap is in firm contact with the ground, then no reduction in efficiency shall be required. The group capacity shall be the lesser of: -the sum of the modified individual capacities of each pile in the group, or -the capacity of an equivalent pier consisting of the piles and a block of soil within the area bounded by the piles.
0 .
For the equivalent pier, the full shear strength of soil shall be used to determine the skin friction resistance, the total base area of the equivalent pier shall be used to determine the end bearing resistance, and the additional capacity of the cap shall be ignored. The performance factor for the capacity of an equivalent pier or block failure shall be as provided in Table 4.10.6-2. The performance factors for the group capacity calculated using the sum of the individual pile capacities, are the same as those for the single pile capacity as given in Table 4.1 0.6-2.
4. 12.3.3.1 Ob Cohesionless Soil The ultimate bearing capacity of pile groups in cohesionless soil shall be the sum of the capacities of all the piles in the group. The efficiency factor, 1}. shall be 1.0 where the pile cap is, or is not, in contact with the ground. The performance factor is the same as those for single pile capacities as given in Table 4.1 0.6-2.
4.1 2.3.3. 1Oc Pile Group in Strollg Soil Overlyillg a Weak or Compressible Soil If a pile group is embedded in a strong soil deposit overlying a weaker deposit, consideration shall be given to the potential for a punching failure of the pile tips into the weaker soil stratum. If the underlying soil stratum consists of a weaker compressible soil, consideration shall be given to the potential for large settlements in that weaker layer.
4.12.3.3.1 1 Dynamic/Seismic: Design Refer to Division I-A of these Specifications and Lam and Martin ( 1986a, 1986b) for guidance regarding the de-
105
sign of driven piles subjected to dynamic and seismic loads.
4.12.4 Structural Design The structural design of driven piles shall be in accordance with the provisions of Articles 4.5.7, which was developed for allowable stress design procedures. To use load factor design procedures for the structural design of driven piles, the load factor design procedures for reinforced concrete, prestressed concrete and steel in Sections 8, 9, and 10, respectively, shall be used in place of the allowable stress design procedures.
4.12.4.1
Buckling of Piles
Stability of piles shall be considered when the piles extend through water or air for a portion of their lengths.
4.12.5 Construction Considerations Foundation design shall not be uncoupled from construction considerations. Factors such as pile driving, pile splicing, and pile inspection shall be done in accordance with the provisions of this specification and Division II.
4.13 DRILLED SHAFTS 4.13.1
General
The provisions of the specifications in Articles 4.6.1 through 4.6.7, with the exception of Article 4.6.5, shall apply to the strength design (load factor design) of drilled shafts. Article 4.6.5 covers the allowable stress design of drilled shafts, and shall be replaced by the articles in this section for load factor design of drilled shafts, unless otherwise stated. The provisions of Article 4.13 shall apply to the design of drilled shafts, but not drilled piles installed with continuous flight augers that are concreted as the auger is being extracted.
4.13.2 Notations a
= parameter used for calculating F,
Ap
= area of base of drilled shaft = surface area of a drilled pier = cross-sectional area of socket = annular space between bell and shaft = perimeter used for calculating F, = cone penetration test = dimensionless depth factor for estimating tip capacity of drilled shafts in rock
A~
As.oc Au b CPT d
106
D Dt,
I1r k
K
LL N
qs qsbe11 qu quit
Qp Qs Qsa
HIGHWAY BRIDGES = diattieter of drilled shaft = embedment of drilled shaft in layer that provides support = diameter of base of a drilled shaft = diameter of a drilled shaft socket in rock =Young's modulus of concrete = intact rock modulus = Young's modulus of a drilled shaft = modulus of the in situ rock mass =soil modulus = reduction factor for tip resistance of large diameter dri11ed shaft = depth of embedment of drilled shaft socketed into rock = moment of inertia of a drilled shaft = influence coefficient (see Figure C4.13.3.3.4-1) = influence coefficient for settlement of drilled shafts socketed in rock = factor that reduces the tip capacity for shafts with a base diameter larger than 20 inches so as to limit the shaft settlement to 1 inch = coefficient of lateral earth pressure or load transfer factor = dimensionless bearing capacity coefficient for drilled shafts socketed in rock using pressuremeter results = modulus modification ratio = dimensionless bearing capacity coefficient (see Figure C4.13.3.3.4-4) = liquid limit of soil = uncorrected Standard Penetration Test (SPT) blow count = bearing capacity factor =corrected SPT-N value = uplift bearing capacity factor = limit pressure determined from pressuremeter tests within 2D above and below base of shaft = at rest horizontal stress measured at the base of drilled shaft = unfactored dead load = plastic limit of soil = ultimate unit tip resistance = reduced ultimate unit tip resistance of drilled shafts = ultimate unit side resistance = unit uplift capacity of a belled drilled shaft = uniaxial compressive strength of rock core = ultimate bearing capacity = ultimate load carried by tip of drilled shaft = ultimate load carried by side of drilled shaft = ultimate side resistance of drilled shafts socketed in rock
Quit R RQD sd SPT Su ~
T z Z
4.13.2 = total ultimate bearing capacity = characteristic length of soil-drilled shaft system in cohesive soils = Rock Quality Designation = spacing of discontinuities = Standard Penetration Test = undrained shear strength = width of discontinuities = characteristic length of soil-drilled shaft system in cohesionless soils =depth below ground surface = total embedded length of drilled shaft
Greek = adhesion factor applied to Su = coefficient relating the vertical effective stress and the unit skin friction of a drilled shaft -y' = effective unit weight of soil 8 = angle of shearing resistance between soil and drilled shaft 11 = drilled shaft group efficiency factor Pba\C = settlement of the base of the drilled shaft Pe = elastic shortening of drilled shaft Ptol = tolerable settlement a~ = vertical effective stress av = total vertical stress IPi = working load at top of socket
= performance factor ' or r = angle of internal friction of soil q = performance factor for the total ultimate bearing capacity of a drilled shaft qs = performance factor for the ultimate shaft capacity of a dri11ed shaft qp = performance factor for the ultimate tip capacity of a dril1ed shaft a
jj
4.13.3 Geotechnical Design Drilled shafts shall be designed to have adequate bearing and structural capacities under tolerable settlements and tolerable lateral movements. The supporting capacity of drilled shafts shall be estimated by static analysis methods (analytical methods based on soil-structure interaction). Capacity may be verified with load test results. The method of construction may affect the drilled shaft capacity and shall be considered as part of the design process. Drilled shafts may be constructed using the dry, casing or wet method of construction, or a combination of methods. In every case, hole excavation, concrete placement, and all other aspects shall be performed in conformance with the provisions of this specification and Division II.
DIVISION I-DESIGN
4.13.3.1
c
4.13.3.1 Factors Affecting Axial Capacity See Article 4.6.5.2 for drilled shafts in soil and Article 4.6.5.3.3 for drilled shafts in rock. The following sub-articles shall supplement Articles 4.6.5.2 and 4.6.5.3.3.
4.13.3.2.3a
Downdrag Loads
Downdrag loads shall be evaluated, where appropriate, as indicated in Article 4.12.3.1.3.
4.13.3.1.2
Uplift
The provisions of Article 4.12.3.1.4 shall apply a~ applicable. Shafts designed for and constructed in expansive soil shall extend for a sufficient depth into moisture-stable soils to provide adequate anchorage to resist uplift. Sufficient clearance shall be provided between the ground surface and underside of caps or beams connecting shafts to preclude the application of uplift loads at the shaft/cap connection due to swelling ground conditions. Uplift capacity of straight-sided drilled shafts shall rely only on side resistance in conformance with Article 4.13.3.3.2 for drilled shafts in cohesive soils, and Article 4.13.3.3.3 for drilled shafts in cohesionless soils. If the shaft has an enlarged base, Qs shall be determined in conformance with Article4.13.3.3.6.
4.13.3.2 Movement Under Serviceability Limit State 4.1 3.3.2. 1 General The provisions of Article 4.12.3.2.1 shall apply as applicable. In estimating settlements of drilled shafts in clay, only unfactored permanent loads shall be considered. However unfactored live loads must be added to the permanent loads when estimating settlement of shafts in granular soil.
4.13.3.2.2
Tolerable Movement
The provisions of Article 4.12.3.2.2 shall apply as applicable.
4.13.3.2.3
0
Settlement
The settlement of a drilled shaft foundation involving either single drilled shafts or groups of drilled shafts shall not exceed the tolerable settlement as selected according to Article 4.13.3.2.2
Settlement of Single Drilled Shafts
The settlement of single drilled shafts shall be estimated considering short-term settlement, consolidation settlement (if constructed in cohesive soils), and axial compression of the drilled shaft.
4.1 3.3.2.3b 4.13.3.1.1
107
Group Settlement
The settlement of groups of drilled shafts shall be estimated using the same procedures as described for pile groups, Article 4.12.3.2.3. -Cohesive Soil, See Article 4.12.3.2.3a -Cohesionless Soil, See Article 4.12.3.2.3b
4.1 3.3.2.4
Ltzteral Displacement
The provisions of Article 4.12.3.2.4 shall apply as applicable.
4.13.3.3 Resistance at Strength Limit States The strength limit states that must be considered include: ( 1) bearing capacity of drilled shafts, (2) uplift capacity of drilled shafts, and (3) punching of drilled shafts bearing in strong soil into a weaker layer below.
4.13.3.3. I
Axial Loading of Drilled Shafts
The provisions of Article 4.12.3.3.1 shall apply as applicable.
4.13.3.3.2
Analytic Estimates of Drilled Shaft Capacity ill Cohesive Soils
Analytic (rational) methods may be used to estimate the ultimate bearing capacity of drilled shafts in cohesive soils. The performance factors for side resistance and tip resistance for three analytic methods shall be as provided in Table 4.10.6-3. If another analytic method is used, application of the performance factors in Table 4.10.6-3 may not be appropriate.
4. I 3.3.3.3
Estimation of Drilled-Shaft Capacity in Cohesionless Soils
The ultimate bearing capacity of drilled shafts in cohesionless soils shall be estimated using applicable methods. and the factored capacity selected using judgment, and any available experience with similar conditions.
4. 13.3.3.4 Axial Capacity in Rock In determining the axial capacity of drilled shafts with rock sockets, the side resistance from overlying soil deposits shall be ignored.
HIGHWAY BRIDGES
108
If the rock is degradable, consideration of special construction procedures, larger socket dimensions, or reduced socket capacities shall be considered. The performance factors for drilled shafts socketed in rock shall be as provided in Table 4.1 0.6-3. 4.13.3.3.5 Load Test
Where necessary, a full scale load test or tests shall be conducted on a drilled shaft or shafts to confirm response to load. Load tests shall be conducted using shafts constructed in a manner and of dimensions and materials identical to those planned for the production shafts. Load tests shall be conducted following prescribed written procedures which have been developed from accepted standards and modified, as appropriate, for the conditions at the site. Standard pile load testing procedures developed by ASTM as specified in Article 4.12.3.3.5 may be modified for testing drilled shafts. The performance factor for axial compressive capacity, axial uplift capacity, and lateral capacity obtained from load tests shall be as provided in Table 4.1 0.6-3. 4.13.3.3.6
Uplift Capacity
Uplift shall be considered when (i} upward loads act on the dri1led shafts and (ii) swelling or expansive soils act on the drilled shafts. Drilled shafts subjected to uplift forces shall be investigated, both for resistance to pullout and for their structural strength. 4.13.3.3.6a
Uplift Capacity of a Single Drilled Shaft
The uplift capacity of a single straight-sided drilled shaft shall be estimated in a manner similar to that for estimating the ultimate side resistance for drilled shafts in compression (Articles 4.13.3.3.2, 4.13.3.3.3, and 4.13.3.3.4). The uplift capacity of a belled shaft shall be estimated neglecting the side resistance above the bell, and assuming that the bell behaves as an anchor. The performance factor for the uplift capacity of drilled shafts shall be as provided in Table 4.1 0.6-3.
4.13.3.3.4
or structural failure of the drilled shaft. The design oflaterally loaded drilled shafts shall account for the effects of interaction between the shaft and ground, including the number of piers in the group. 4.13.3.3.8 Group Capacity
Possible reduction in capacity from group effects shall be considered. 4.13.3.3.8a
Cohesive Soil
The provisions of Article 4.12.3.3.1 Oa shall apply. The performance factor for the group capacity of an equivalent pier or block failure shall be as provided in Table 4.10.62 for both cases of the cap being in contact, and not in contact with the ground. The performance factors for the group capacity calculated using the sum of the individual drilled shaft capacities are the same. as those for the single drilled shaft capacities. 4.13.3.3.8b
Cohesionless Soil
Evaluation of group capacity of shafts in cohesionless soil shall consider the spacing between adjacent shafts. Regardless of cap contact with the ground, the individual capacity of each shaft shall be reduced by a factor 11 for an isolated shaft, where 11 = 0.67 for a center-to-center (CTC) spacing of three diameters and 11 = 1.0 for a center-to-center spacing of eight diameters. For intermediate spacings, the value of 11 may be determined by linear interpolation. See Article 4.13.3.3.3 for a discussion on the selection of performance factors for drilled shaft capacities in cohesionless soils. 4.13.3.3.8c
Group in Strong Soil Overlying Weaker Compressible Soil
The provisions of Article 4.12.3.3.10c shall apply as applicable. 4.13.3.3.9 Dynamic/Seismic Design
4.13.3.3.6b
Group Uplift Capacity
See Article 4.12.3.3. 7b. The performance factors for uplift capacity of groups of drilled shafts shall be the same as those for pile groups as given in Table 4.10.6-3. 4.13.3.3. 7 Lateral Load
The design of laterally loaded drilled shafts is usually governed by lateml movement criteria (Article 4.13.3.2)
Refer to Division I-A for guidance regarding the design of drilled shafts subjected to dynamic and seismic loads.
4.13.4 Structural Design The structural design of drilled shafts shall be in accordance with the provisions of Article 4.6.6, which was developed for allowable stress design proce-
4.13.4
c .
.
0
DIVISION I-DESIGN
dures. In order to use load factor design procedures for the structural design of drilled shafts, the load factor design procedures in Section 8 for reinforced concrete shall be used in place of the allowable stress design procedures.
4.13.4.1
109
Buckling of Drilled Shafts
Stability of drilled shafts shall be considered when the shafts extend through water or air for a portion of their length.
0 Section 5 RETAINING WALLS Part A GENERAL REQUIREMENTS AND MATERIALS
5.1
0
'
cept they rely more on structural resistance through cantilevering action, with this cantilevering action providing the means to mobilize dead weight for resistance. Nongravity cantilever walls rely strictly on the structural resistance of the wall and the passive resistance of the soiVrock, in which vertical wall elements are partially embedded in the soiVrock to provide fixity. Anchored walls derive their capacity through cantilevering action of the vertical wall elements (similar to a non-gravity cantilever wall) and tensile capacity of anchors embedded in stable soil or rock below or behind potential soiVrock failure surfaces.
Retaining walls shall be designed to withstand lateral earth and water pressures, including any live and dead load surcharge, the self weight of the wall, temperature and shrinkage effects, and earthquake loads in accordance with the general principles specified in this section. Retaining walls shall be designed for a service life based on consideration of the potential long-term effects of material deterioration, seepage, stray currents and other potentially deleterious environmental factors on each of the material components comprising the wall. For most applications, permanent retaining walls should be designed for a minimum service life of 75 years. Retaining walls for temporary applications are typically designed for a service life of 36 months or less. A greater level of safety and/or longer service life (i.e., 100 years) may be appropriate for walls which support bridge abutments, buildings, critical utilities, or other facilities for which the consequences of poor performance or failure would be severe. The quality of in-service performance is an important consideration in the design of permanent retaining walls. Permanent walls shall be designed to retain an aesthetically pleasing appearance, and be essentially maintenance free throughout their design service life.
5.2
0
GENERAL
5.2.1
Selection of Wall Type
Selection of wall type is based on an assessment of the magnitude and direction of loading, depth to suitable foundation support, potential for earthquake loading, presence of deleterious environmental factors, proximity of physical constraints, wall site cross-sectional geometry, tolerable and differential settlement, facing appearance, and ease and cost of construction.
5.2.1.1
Rigid Gravity and Semi-Gravity Walls
Rigid gravity walls use the dead weight of the structure itself and may be constructed of stone masonry, unreinforced concrete, or reinforced concrete. Semi-gravity cantilever, counterfort, and buttress walls are constructed of reinforced concrete. Rigid gravity and semi-gravity retaining walls may be used for bridge substructures or grade separation. Rigid gravity and semi-gravity walls are generally used for permanent wall applications. These types of walls can be effective for both cut and fill wall applications due to their relatively narrow base widths which allows excavation laterally to be kept to a minimum. Gravity and semi-gravity walls may be used without deep foundation support only where the bearing soiVrock is not prone to excessive or differential settlement. Due to their rigidity, excessive differential settlement can cause
WALL TYPE AND BEHAVIOR
Retaining walls are generally classified as gravity, semigravity, non-gravity cantilever, and anchored. Examples of various types of walls are provided in Figures 5.2A. 5.2B, and 5.2C. Gravity walls derive their capacity to resist lateral loads through a combination of dead weight and lateral resistance. Gravity walls can be further subdivided by type into rigid gravity walls, mechanically stabilized earth (MSE) walls, and prefabricated modular gravity walls. Semi-gravity walls are similar to gravity walls, exIll
5.2.1.1
HIGHWAY BRIDGES
112
.........,. CIP CCIHCRETE CIA SHO TCAETE f='ACI
r""' !""""'"
~
NG---...
CEOSYNTHETIC R£1 WCJRCI NG
cRANULAR
MSE WALL W1 TH f4JOULAR PRECAST CONCRETE FACING PANELS
F'l LL
MSE WALL WITH GEOSYNTHETIC REINFORCEMENT AND CIP CONCRETE OR SHOTCRETE FACING
MSE VALL VI TH SEGIENTAL CONCRETE BLOCK FACING FIGURE 5.2A
Typical Mechanically Stabilized Earth Gravity Walls
cracking, excessive bending or shear stresses in the wall, or rotation of the overall wall structure. 5.2.1.2 Nongravity Cantllevered Walls
Nongravity cantilevered walls derive lateral resistance through embedment of vertical wall elements and support retained soil with facing elements. Vertical wall elements may consist of discrete vertical elements (e.g., soldier or sheet piles, caissons, or drilled shafts) spanned by a structural facing (e.g., wood or reinforced concrete lagging, precast or cast-in-place concrete panels, wire or fiber reinforced shotcrete, or metal elements such as sheet piles). The discrete vertical elements typically extend deeper into the ground than the facing to provide vertical and lateral support. Alternately, the vertical wall elements and facing are continuous and, therefore, also form the structural facing. Typical continuous vertical wall elements include piles, precast or cast-in-place concrete diaphragm wall panels, tangent piles, and tangent caissons.
Permanent nongravity cantilevered walls may be constructed of reinforced concrete, timber, and/or metals. Temporary nongravity cantilevered walls may be constructed of reinforced concrete, metal and/or timber. Suitable metals generally include steel for components such as piles, brackets and plates, lagging and concrete reinforcement. Nongravity cantilevered walls may be used for the same applications as rigid gravity and semi-gravity walls, as well as temporary or permanent support of earth slopes, excavations, or unstable soil and rock masses. This type of wall requires little excavation behind the wall and is most effective in cut applications. They are also effective where deep foundation embedment is required for stability. Nongravity cantilevered walls are generally limited to a maximum height of approximately 5 meters (15 feet), unless they are provided with additional support by means of anchors. They generally cannot be used effectively where deep soft soils are present, as these walls depend on the passive resistance of the soil in front of the wall.
,·I~
~
·;'
5.2.1.3
DIVISION I- DESIGN
I'ETAL BIN WALL
PRECAST CONCRETE BIN WALL
11 3
PRECAST CONCRETE CRIB WALL
CiABION WALL
FIGURE 5.2B Typical Prefabricated Modular Gravity Walls
5.2.1.3 Anchored Walls Anchored walls are typically composed of the same elements as nongravity cantilevered walls (Article 5.2. 1.2), but derive additional lateral resistance from one or more tiers of anchors. Anchors may be prestressed or deadman type elements composed of strand tendons or bars (with corrosion protection as necessary) extending from the wall face to a ground zone or mechanical anchorage located beyond the zone of soil applying load to the wall. Bearing elements on the vertical support elements or facing of the wall transfer wall loads to the anchors. In some cases, a spread footing is used at the base of the anchored wall facing in lieu of vertical element embedment to provide vertical support. Due to their fl exibility and method of support, the distribution of lateral pressure on anchored walls is influenced by the method and sequence of wall construction and anchor prestressing. Anchored walls are applicable for temporary and permanent support of stable and unstable soi I and rock masses.
Anchors are usually required for supp01t of both temporary and permanent nongravity cantilevered walls higher than about 5 meters ( 15 feet), depending on soil conditions. Anchored walls are typically constructed in cut situations, in which construction occurs from the top down to the base of the wall. Anchored walls have been successfully used to support fi lls; however, certain difficulties arising in fill wall applications require special consideration during design and construction. In particular, there is a potential for anchor damage due to settlement of backfill and underlying soil s or due to improperly controlled backfilling procedures. Also, there is a potential for undesirable wall deflection if anchors are too highly stressed when the backfi ll is only partially complete and provides li mited passive resistance. The base of the vertical wall elements should be located below any soft soils which are prone to settlement, as settlement of the vertical wall elements can cause destressing of the anchors. Also, anchors should not be located within soft clays and silts, as it is difficult to obtain
114
HIGHWAY BRIDGES
Mort.ar Rubble Ma•onrJ' Rl&ld GraYlt.J' Wall
Reinforced Concrete Counlerfor\ Seml·Gra•ltJ' Wall
5.2.1.3
Reinforced Concrete Can Ule•er Semi•GraYl\7 Wall
Sharr7 or C7Under Pile Non·araYI\J' Can\Ue•er Wall
Soldier Plle Tl•baclc Wall
FIGURE 5.2C Typical Rigid Gravity, Semi-Gravity Cantilever, Nongravity Cantilever, and Anchored Walls
adequate long-term capacity in such materials due to creep.
5.2.1.4 Mechanically Stabilized Earth Walls MSE systems, whose elements may be proprietary, employ either metallic (strip or grid type) or geosynthetic (geotextile, strip, or geogrid) tensile reinforcements in the soil mass, and a facing element which is vertical or near vertical. MSE walls behave as a gravity wall, deriving their lateral resistance through the dead weight of the re-
inforced soil mass behind the facing. For relatively thick facings, such as segmental concrete block facings, the dead weight of the facing may also provide a significant contribution to the capacity of the wall system. MSE walls are typically used where conventional gravity, cantilever, or counterforted concrete retaining walls are considered, and are particularly well suited where substantial total and differential settlements are anticipated. The allowable settlement of MSE walls is limited by the longitudinal defonnability of the facing and the performance requirements of the structure. MSE walls
5.2.1.4
0 .
DIVISION I-DESIGN
have been successfully used in both fill and cut wall applications. However, they are most effective in fill wall applications. MSE walls shall not be used under the following conditions.
115
lutants, other environmental conditions which are defined as aggressive as described in Division II, Article 7 .3.6.3, or where deicing spray is anticipated .
5.2.2 Wall Capacity • When utilities other than highway drainage must be constructed within the reinforced zone if future access to the utilities would require that the reinforcement layers be cut, or if there is potential for material which can cause degradation of the soil reinforcement to leak out of the utilities into the wall backfill. • With soil reinforcements exposed to surface or ground water contaminated by acid mine drainage, other industrial pollutants, or other environmental conditions which are defined as aggressive as de- . scribed in Division II, Article 7.3.6.3, unless environment specific long-term corrosion or degradation studies are conducted. • When floodplain erosion may undermine the reinforced fill zone or facing column, or where the depth of scour cannot be reliably determined.
Retaining walls shall be designed to provide adequate structural capacity with acceptable movements, adequate foundation bearing capacity with acceptable settlements, and acceptable overall stability of slopes adjacent to walls. The tolerable level of wall lateral and vertical deformations is controlled by the type and location of the wall structure and surrounding facilities.
5.2.2.1
Bearing Capacity
The bearing capacity of wall foundation support systems shall be estimated using procedures described in Articles 4.4, 4.5, or 4.6, or other generally accepted theories. Such theories are based on soil and rock parameters measured by in situ and/or laboratory tests.
5.2.2.2 Settlement MSE walls may be considered for use under the following special conditions:
0
• When two intersecting walls form an enclosed angle of 70° or less, the affected portion of the wall is designed as an internally tied bin structure with at-rest earth pressure coefficients. • Where metallic reinforcements are used in areas of anticipated stray currents within 60 meters (200 feet) of the structure, a corrosion expert should evaluate the potential need for corrosion control requirements.
5.2.1.5 Prefabricated Modular Walls
0
Prefabricated modular wall systems, whose elements may be proprietary, generally employ interlocking soilfilled reinforced concrete or steel modules or bins, rock filled gabion baskets, precast concrete units, or dry cast segmental masonry concrete units (without soil reinforcement) which resist earth pressures by acting as gravity retaining walls. Prefabricated modular walls may also use their structural elements to mobilize the dead weight of a portion of the wall backfill through soil arching to provide resistance to lateral loads. Prefabricated modular systems may be used where conventional gravity, cantilever or counterfort concrete retaining walls are considered. Steel modular systems shall not be used where the steel will be exposed to surface or subsurface water which is contaminated by acid mine drainage, other industrial pol-
The settlement of wall foundation support systems shall be estimated using procedures described in Articles 4.4, 4.5, or 4.6, or other generally accepted methods. Such methods are based on soil and rock parruneters measured directly or inferred from the results of in situ and/or laboratory test.
5.2.2.3 Overall Stability The overall stability of slopes in the vicinity of walls shall be considered as part of the design of retaining walls. The overall stability of the retaining wall, retained slope, and foundation soil or rock shall be evaluated for all walls using limiting equilibrium methods of analysis such as the Modified Bishop, simplified Janbu or Spencer methods of analysis. A minimum factor of safety of 1.3 shall be used for walls designed for static loads, except the factor of safety shall be 1.5 for walls that support abutments, buildings, critical utilities, or for other installations with a low tolerance for failure. A minimum factor of safety of 1.1 shall be used when designing walls for seismic loads. In all cases, the subsurface conditions and soil/rock properties of the wall site shall be adequately characterized through in-situ exploration and testing and/or laboratory testing as described in Article 5.3. Seismic forces applied to the mass of the slope shall be based on a horizontal seismic coefficient kh equal to onehalf the ground acceleration coefficient A, with the vertical seismic coefficient kv equal to zero.
116
HIGHWAY BRIDGES
It must be noted that, even if overall stability is satisfactory, special exploration, testing and analyses may be required for bridge abutments or retaining walls constructed over soft subsoils where consolidation and/or lateral flow of the soft soil could result in unacceptable longterm settlements or horizontal movements. Stability of temporary construction slopes needed to construct the wall shall also be evaluated. 5.2.2.4 Tolerable Deformations
Tolerable vertical and lateral deformation criteria for retaining walls shall be developed based on the function and type of wall, unanticipated service life, and consequences of unacceptable movements (i.e., both structural and aesthetic). Allowable total and differential vertical deformations for a particular retaining wall are dependent on the ability of the wall to deflect without causing damage to the wall elements or exhibiting unsightly deformations. The total and differential vertical deformation of a retaining wall should be small for rigid gravity and semi-gravity retaining walls, and for soldier pile walls with a cast-in-place facing. For walls with anchors, any downward movement can cause significant destressing of the anchors. MSE walls can tolerate larger total and differential vertical deflections than rigid walls. The amount of total and differential vertical deflection that can be tolerated depends on the wall facing material, configuration, and timing of facing construction. A cast-in-place facing has the same vertical deformation limitations as the more rigid retaining wall systems. However, an MSE wall with a castin-place facing can be specified with a waiting period before the cast-in-place facing is constructed so that vertical (as well as horizontal) deformations have time to occur. An MSE wall with welded wire or geosynthetic facing can tolerate the most deformation. An MSE wall with multiple precast concrete panels cannot tolerate as much vertical deformation as flexible welded wire or geosynthetic facings because of potential damage to the precast panels and unsightly panel separation. Horizontal movements resulting from outward rotation of the wall or resulting from the development of internal equilibrium between the loads applied to the wall and the internal structure of the wall must be limited to prevent overstress of the structural wall facing and to prevent the wall face batter from becoming negative. In general, if vertical deformations are properly controlled, horizontal deformations will likely be within acceptable limits. For MSE walls with extensible reinforcements, reinforcement serviceability criteria, the wall face batter, and the facing type selected (i.e., the flexibility of the facing) will influence the horizontal deformation criteria required. · Vertical wall movements shall be estimated using conventional settlement computational methods (see Articles
5.2.2.3
4.4, 4.5, and 4.6. For gravity and semi-gravity walls, lateral movement results from a combination of differential vertical settlement between the heel and the toe of the wall and the rotation necessary to develop active earth pressure conditions (see Table 5.5.2A). If the wall is designed for at-rest earth pressure conditions, the deflections in Table 5.5.2A do not need to be considered. For anchored walls, deflections shall be estimated in accordance with Article 5.7.2. For MSE walls, deflections may be estimated in accordance with Article 5.8.10. Where a wall is used to support a structure, tolerable movement criteria shall be established in accordance with Articles 4.4.7.2.5, 4.5 and 4.6. Where a wall supports soil on which an adjacent structure is founded, the effects of wall movements and associated backfill settlement on the adjacent structure shall be evaluated. For seismic design, seismic loads may be reduced, as result of lateral wall movement due to sliding, for what is calculated based on Division 1A using the MononobeOkabe method if both of the following conditions are met: • the wall system and any structures supported by the wall can tolerate lateral movement resulting from sliding of the structure, • the wall base is unrestrained regarding its ability to slide, other than soil friction along its base and minimal soil passive resistance. Procedures for accomplishing this reduction in seismic load are provided in the AASHTO LRFD Bridge Design Specifications, 2nd Edition. In general, this only applies to gravity and semi-gravity walls. Though the specifications in Division 1A regarding this issue are directed at structural gravity and semi-gravity walls, these specifications may also be applicable to other types of gravity walls regarding this issue provided the two conditions listed above are met. 5.2.3 SoU, Rock, and Other Problem Conditions
Geologic and environmental conditions can influence the performance of retaining walls and their foundations, and may require special· consideration during design. To the extent possible, the presence and influence of such conditions shall be evaluated as part of the subsurface exploration program. A representative, but not exclusive, listing of problem conditions requiring special consideration is presented in Table 4.2.3A for general guidance. 5.3 SUBSURFACE EXPLORATION AND
TESTING PROGRAMS
The elements of the subsurface exploration and testing programs shall be the responsibility of the Designer, based
·~.
. J
5.3
~l ~
DIVISION I-DESIGN
on the specific requirements of the project and his or her experience with local geological conditions.
5.3.1 General Requirements As a minimum, the subsurface exploration and testing programs shall define the following, where applicable:
0
• Soil strata: -Depth, thickness, and variability -Identification and classification -Relevant engineering properties (i.e., natural moisture content, Atterberg limits, shear strength, compressibility, stiffness, permeability, expansion or collapse potential, and frost susceptibility) -Relevant soil chemistry, including pH, resistivity, and sulfide content • Rock strata: -Depth to rock -Identification and classification -Quality (i.e., soundness, hardness, jointing and presence of joint filling, resistance to weathering, if exposed, and solutioning) -Compressive strength (e.g., uniaxial compression, point load index) -Expansion potential • Ground water elevation, including seasonal variations, chemical composition, and pH (especially important for anchored, non-gravity cantilevered, modular, and MSE walls) where corrosion potential is an important consideration • Ground surface topography • Local conditions requiring special consideration (e.g., presence of stray electrical currents). Exploration logs shall include soil and rock strata descriptions, penetration resistance for soils (e.g., SPT or qc), and sample recovery and RQD for rock strata. The drilling equipment and method, use of drilling mud, type of SPT hammer (i.e., safety, donut, hydraulic) or cone penetrometer (i.e., mechanical or electrical), and any unusual subsurface conditions such as artesian pressures, boulders or other obstructions, or voids shall also be noted on the exploration logs.
117
local conditions. Where the wall is supported on deep foundations and for all non-gravity walls, the depth of the subsurface explorations shall extend a minimum of 6 meters (20 feet) below the anticipated pile, shaft, or slurry wall tip elevation. For piles or shafts end bearing on rock. or shafts extending into rock, a minimum of 3 meters (10 feet) of rock core, or a length of rock core equal to at least three times the shaft diameter, which ever is greater, shall be obtained to insure that the exploration has not been tenninated on a boulder and to determine the physical characteristics of the rock within the zone of foundation influence for design.
5.3.3 Minimum Coverage A minimum of one soil boring shall be made for each retaining wall. For retaining walls over 30 meters ( 100 feet) in length, the spacing between borings should be 30 meters ( l 00 feet). The number and spacing of the bore holes may be increased or decreased from 30 meters ( l 00 feet), depending upon the anticipated geological conditions within the project area. In planning the exploration program, consideration should be given to placing borings inboard and outboard of the wall line to define conditions in the scour zone at the toe of the wall and in the zone behind the wall to estimate lateral loads and anchorage or reinforcement capacities.
5.3.4 Laboratory Testing Laboratory testing shall be performed as necessary to determine engineering characteristics including unit weight, natural moisture content, Atterberg limits, gradation, shear strength, compressive strength and compressibility. In the absence of laboratory testing, engineering characteristics may be estimated based on field tests and/or published property correlations. Local experience should be applied when establishing project design values based on laboratory and field tests.
5.3.5 Scour The probable depth of scour shall be determined by subsurface exploration and hydraulic studies. Refer to Article 1.3.2 and FHWA (1991) for general guidance regarding hydraulic studies and design.
5.3.2 Minimum Depth
5.4 NOTATIONS
Regardless of the wall foundation type, borings shall extend into a bearing layer adequate to support the anticipated foundation loads, defined as dense or hard soils, or bedrock. In general, for walls which do not utilize deep foundation support, subsurface explorations shall extend below the anticipated bearing level a minimum of twice the total wall height. Greater depths may be required where warranted by
The following notations apply for design of retaining walls: A
Ac
=Acceleration coefficient (dim); (See Article 5.8.9.1) = Reinforcement area corrected for corrosion losses (mm2); (See Article 5.8.6)
118 Am
HIGHWAY BRIDGES
= Maximum wall acceleration coefficient at the centroid (dim); (See Article 5.8.9.1) b = Width of discrete wall backfill element (m); (See Article 5.8.6) br = Width of vertical or horizontal concentrated dead load (m); (See Article 5.8.12.1) B = Total base width of wall, including facing elements (m); (See Article 5.5.5) B' = Effective base width of retaining wall foundation (m); (See Article 5.8.3) C = Overall reinforcement surface area geometry factor (dim); (See Article 5.8.5.2) Cr = Distance from back of wall facing to front edge of footing or other concentrated surcharge load (m); (See Article 5.8.12.1) CRr. = A reduction factor to account for reduced connection strength resulting from pullout of the connection (dim); (See Article 5.8.7.2) CRu = A reduction factor to account for reduced ultimate strength resulting from rupture of the connection (dim); (See Article 5.8.7.2) Cu = Soil coefficient of uniformity (dim); (See Article 5.8.5.2) d = Distance from back of wall face to center of concentrated dead load (m); (See Article 5.8.12.1); also, the effective depth relative to stem of concrete semi-gravity walls for locating critical section for shear (m); (See Article 5.5.6.1) Di = Effective width of applied load at depth within or behind wall due to surcharge (m); (See Article 5.8.12.1) D* = Reinforcement bar diameter corrected for corrosion losses (mm); (See Article 5.8.6) e, e' = Eccentricity of forces contributing to bearing pressure (m); (See Articles 5.8.3 and 5.8.12.1) Ec = Thickness of metal reinforcement at end of service life (mm); (See Article 5.8.6) En = Nominal thickness of steel reinforcement at construction (mm); (See Article 5.8.6.1.1) ~ = Equivalent sacrificed thickness of metal expected to be lost by uniform corrosion to produce expected loss of tensile strength during service life of structure (nun); (See Article 5.8.6.1.1) f = Friction factor (dim); (See Article 5.5.2) F* = Pullout resistance factor (dim); (See Article 5.8.5.2) FP = Lateral force resulting from KruilCTv (kN/m); (See Article 5.8.12.1) Fy = Yield strength of the steel (kN/mm2); (See Article 5.8.6.1.1) F, =Active lateral earth pressure force for level backfill conditions (k.N/m); (See Article 5.8.2) F2 = Lateral earth pressure force due to traffic or other continuous surcharge (kN/m); (See Article 5.8.2)
FH FT FS FSOT FSro FSsL
Fv Gu
h
hp H H1
H2 Hh Hs Hu Hw I ib kh kv
K Kae 4Kae Knr
Kr
Ka
Ko
5.4
= Horizontal component of active lateral earth pressure force (kN/m); (See Article 5.8.2) =Resultant active lateral earth pressure force (kN/m); (See Article 5.8.2) = Factor of safety (dim); (See Article 5.5.5) =Factor of safety against overturning (dim); (See Article 5.8.2) =Safety factor against pullout (dim); (See Article 5.8.5.2) =Factor of safety against sliding (dim); (See Article 5.8.2) = Vertical component of active lateral earth pressure force (kN/m); (See Article 5.8.2) = Distance to center of gravity of a modular block facing unit, including aggregate fill, measured from the front of the unit (m); (See Article 5.8.7 .2) = Equivalent height of soil representing surcharge pressure or effective total height of soil at back of reinforced soil mass (m); (See Article 5.8.2) = Vertical distance Fp is located from bottom of wall (m); (See Article 5.8.12.1) = Design wall height (m); (See Article 5.8.1) = Equivalent wall height (m); (See Article 5.8.5.1) = Effective wall height (m); (See Article 5.8.9.1) = Hinge height for block facings (m); (See Article 5.8.7.2) = Surcharge height (m of soil); (See Article 5.5.2) = Facing unit height (m); (See Article 5.8.7.2) = Height of water in backfill above base of wall (m) = Average slope of broken back soil surcharge above wall (deg); (See Article 5.8.2) = Inclination of wall base from horizontal (deg); (See Article 5.8.7.2) = Horizontal seismic coefficient (dim); (See Article 5.8.9.1) = Vertical seismic coefficient (dim); (See Article 5.8.9.1) = Earth pressure coefficient (dim); (See Article 5.5.2) = Total Mononobe-Okabe seismic lateral earth pressure coefficient (dim); (See Article 5.8.9.1) = Dynamic increment of the Mononobe-Okabe seismic lateral earth pressure coefficient (dim); (See Article 5.8.9.1) = Active earth pressure coefficient for the soil behind the MSE wall reinforcements (dim); (See Article 5.8.2) = Lateral earth pressure coefficient for the soil within the MSE wall reinforced soil zone (dim); (See Article 5.8.4.1) =Active earth pressure coefficient (dim); (See Article 5.5.2) =At-rest earth pressure coefficient (dim); (See Article 5.5.2)
5.4
0
K,
K'p 1., h
L
Lu Le
Lei m
MA
Ma n
0
N Pa Pir pi!>
Po PR PAE Pu Pt PIR
PN Pv
0
Pv'
DIVISION I-DESIGN
119
= Passive earth pressure coefficient for curved fail-
Pw
ure surface (dim); (See Article 5.5.2) = Passive earth pressure coefficient for planar faiJure surface (dim); (See Article 5.5.2) = Depth from concentrated horizontal dead load 1ocation that force is distributed (m); (See Article 5.8.12.1) = Length of soil reinforcing elements (m); (See Article 5.8.2); length of structural footings (m); (See ArticJe 5.8.12.1) =Length of reinfor~ement in the active zone (m); (See Article 5.8.5.2) = Length of reinforcement in the resistant zone (m); (See Article 5.8.5.2) =Effective reinforcement length for layer i (m); (See ArticJe 5.8.9.2) = Relative horizontal distance of point load from back of wall face (dim); (See Article 5.5.2) = The moment about point z at base of segmental concrete facing blocks due to force W A (mkN/m); (See Article 5.8.7.2) = The moment about point z at base of segmental concrete facing blocks due to force W 8 (mkN/m); (See Article 5.8.7.2) =Relative depth below top of wall when calculating lateral pressure due to point load above wall (dim); (See Article 5.5.2) = Number of reinforcement layers vertically within MSE wall (dim); (See Article 5.8.9.2) =Active earth pressure force (kN/m); (See Article 5.5.2) = Inertial force caused by seismic acceleration of the reinforced soil mass (kN/m); (See Artide 5.8.9.1) = Inertial force caused by seismic acceleration of the sloping soil surcharge above the reinforced soil mass (kN/m); (See ArticJe 5.8.9.1) = At-rest earth pressure force (kN/m); (See ArticJe 5.5.2) = Earth pressure force resulting from uniform surcharge behind wall (kN/m); (See ArticJe 5.5.2) = Dynamic horizontal thrust due to seismic loading (kN/m); (See Article 5.8.9.1) = Concentrated horizontal dead load force (kN/m); (See Articles 5.5.2 and 5.8.12.1) = Inertial force of ma"s within active zone due to seismic loading (kN/m); (See Article 5.8.9.2) = Reinforced wall mass inertial force due to seismic loading (kN/m); (See ArticJe 5.8.9.1) = Resultant horizontal load on wall due to point load (kN/m), (See ArticJe 5.5.2) = Concentrated vertical dead load force for strip load (kN/m); (See Article 5.8.12.1) = Concentrated vertical dead load force for isolated footing or point load (kN/m); (See Article 5.8. 12. I)
wall (kN/m); (See Article 5.5.3) =Traffic live load pressure (kN/m2 ); (See Article 5.8.2) qc = Cone end bearing resistance (kN/m2). (See Article 5.3.1) QL =Line load force (kN/m); (See ArticJe 5.5.2} Qp = Point load force (kN); (See Article 5.5.2) R = Resultant of foundation bearing pressure (kN or kN/m); (See ArticJe 5.8.3) R' = Distance above walJ base to resultant of lateral pressure due to surcharge (m); (See Article 5.5.2) Rc = Soil reinforcement coverage ratio (dim); (See Artide 5.8.6) RF = Reduction factor applied to the ultimate tensile strength to account for short and long-term degradation factors such as instalJation damage, creep, and chemical aging (dim); (See ArticJe 5.8.6.1.2) RFc: = Reduction factor applied to the ultimate tensile reinforcement-facing connection strength to account for long-term degradation factors such as creep and chemical aging (dim); (See ArticJe 5.8.7.2) RF10 = Reinforcement strength reduction factor to account for installation damage (dim); (See ArticJe 5.8.6.1.2) RFcR = Reinforcement strength reduction factor to account for creep rupture (dim); (See Article 5.8.6.1.2) RFo = Reinforcement strength reduction factor to account for rupture due to chemical/biological degradation (dim); (See Artide 5.8.6. I .2) s = Equivalent soil surcharge height above wall (m); (See Article 5.8.4.1) sh = Horizontal reinforcement spacing of discrete reinforcements (mm); (See Article 5.8.6) sr!o = The reinforcement strength needed to resist the static component of load (kN/m); (See Artide 5.8.9.2) srt = The reinforcement strength needed to resist the dynamic or transient component of load (kN/m); (See Artide 5.8.9.2) = Transverse grid element spacing (mm); (See Ars. ticle 5.8.5.2) = Vertical spacing of soil reinforcement (mm); (See Sv Article 5.8.4.1) =Transverse grid or bar mat element thickness (mm); (See ArticJe 5.8.5.2) = Total load applied to structural frame around obT struction (kN); (See Article 5.8.12.4) = The allowable load which can be applied to each Ta soil reinforcement layer per unit width of reinforcement (kN/m); (See Article 5.8.6) Tac = The allowable load which can be applied to each soil reinforcement layer per unit width of rein-
q
= Force due to hydrostatic water pressure behind
Tmu
T111
T1ot
Tmd
To
T~
T,ota~
Tuh
Tulle:
v. V2
w WA Wa
Ww Wu
x.
z Zp
5.4
HIGHWAY BRIDGES
120
forcement at the connection with the wall face (kN/m); (See Article 5.8.7 .2) = Maximum load applied to each soil reinforcement layer per unit width of wall (kN/m); (See Article 5.8.4.1) =Allowable long-term reinforcement tension per unit reinforcement width for ultimate limit state (kN/m); (See Article 5.8.6.1.2) = The ultimate wide width tensile strength for the reinforcement material lot used for connection strength testing (kN/m); (See Article 5.8.7.2) = Incremental dynamic inertia force at level i (kN/m of structure); (See Article 5.8.9.2) = Applied reinforcement load per unit width of wall at the connection with the facing (kN/m); (See Article 5.8.4.2) The peak load per unit reinforcement width in the connection test at a specified confining pressure where reinforcement pullout is known to be the mode of failure (kN/m); (See Article 5.8.7.2) = The total static plus seismic load applied to each reinforcement layer per unit width of wall (KN/m); (See Article 5.8.9.2) = Ultimate tensile strength of geosynthetic reinforcement per unit reinforcement width (kN/m); (See Article 5.8.6.1.2.) The peak load per unit reinforcement width in the connection test at a specified confining pressure where reinforcement rupture is known to be the mode of failure (kN/m); (See Article 5.8.7.2) = Weight of reinforced soil mass (kN/m); (See Article 5.8.2) = Weight of sloping soil surcharge on top of reinforced soil mass (kN/m); (See Article 5.8.2) = Weight of reinforced wall mass (kN/m); (See Article 5.8.9.1) = Weight of facing blocks outside the heel of the base unit (kN/m); (See Article 5.8.7.2) = Weight of facing blocks inside the heel of the base unit within hinge height {kN/m); (See Article 5.8.7.2) = Weight of facing blocks over the base unit (kN/m); (See Article 5.8.7.2) = Width of wall facing or facing blocks (mm); (See Article5.8.7.2) = Horizontal distance of concentrated dead load from Point 0 toe of wall {m); (See Article 5.8.12.1) = Depth below effective top of wall or to reinforcement (m); (See Article 5.8.4.1 or 5.8.12.1) = Depth to reinforcement at beginning of resistant zone for pullout computations (m); (See Article 5.8.4.1)
=
=
~
= Depth where effective surcharge width Di inter-
a
= Scale effect correction factor (dim); (See Article
~
= Inclination of ground slope behind wall measured
sects back of wall face (m); (See Article 5.8.12.1) 5.8.5.2)
counterclockwise from horizontal plane (deg); (See Article 5.5.2) 8 = Friction angle between two dissimilar materials (deg); (See Article 5.5.2) 8mu = Maximum lateral wall displacement occurring during wall construction (mm); (See Article 5.8.1 0) 8R = Relative lateral wall displacement coefficient (dim); (See Article 5.8.10) d = Lateral Rotation at top of wall (mm); (See Article 5.5.2) dah = Horizontal stress at the soil reinforcement location resulting from a concentrated horizontal load (kN/m2); (See Article 5.8.12.1) Aav 1 = Vertical stress at the soil reinforcement location resulting from a concentrated vertical load (kNfm2); (See Article 5.8.12.1) = Soil unit weight (kN/ml) 'Y = Soil unit weight for random backfill behind and 'Yr above reinforced backfill (kN/m3); (See Article 5.8.1) = Soil unit weight for reinforced wall backfill 'Yr (kN/m3); (See Article 5.8.4.1) 'Y' = Effective unit weight of soil or rock (kN/ml) 'Yw = Unit weight of water (kNfml) =Friction angle of the soil (deg); (See Article
5.5.2) = Effective stress angle of internal friction (deg); ' (See Article 5.5.2) = Friction angle of the soil behind the MSE wall rer inforcements (deg); (See Article 5.8.1 or 5.8.4.1) , = Friction angle of the soil within the MSE wall reinforcement zone (deg); (See Article 5.8.1 or 5.8.4.1) e = Inclination of back of wall measured clock-wise from horizontal plane (deg); (See Article 5.5.2) p = SoiVreinforcement interface friction angle (deg); (See Article 5.8.2) 0'2 = Vertical stress due to equivalent horizontal soil surcharge above wall when sloping ground present (kN/m2); (See Article 5.8.4.1) O'g = Active pressure on the back of a wall (kN/m2); (See Article 5.5.2) O'h = Horizontal soil stress at the soil reinforcement (kN/m2); (See Article 5.8.4.1) O'v = Vertical stress on the soil reinforcement (kN/mZ); (See Articles 5.8.4.1 and 5.8.5.2) O'H = Horizontal stress due to point load above wall (kN/m2); (See Article 5.5.2)
5.4
r. ~
w
'IF
DIVISION I-DESIGN
=Wall face batter due to setback per course (deg); (See Article 5.8.5. I) = Inclination of internal failure surface from horizontal (deg); (See Article 5.8.5.1)
The notations for dimension units include the following: deg = degree; dim = dimensionless; m = meter; mm = millimeter; kN = kilonewton; and kg = kilogram. The dimensional units provided with each notation are presented for illustration only to demonstrate a dimensionally correct combination of units for the wall design procedures presented herein. If other units are used, the dimensional correctness of the equations should be confirmed.
PartB SERVICE LOAD DESIGN METHOD ALLOWABLE STRESS DESIGN 5.5
RIGID GRAVITY AND SEMI-GRAVITY WALL DESIGN
5.5.1 Design Terminology
5.5.2 Earth Pressure and Surcharge Loadings Earth pressute loading on rigid gravity and semi-gravity walls is a function of the type and condition of soil backfill, the slope of the ground surface behind the wall, the rrlction between the wall and soil, and the ability of the wall to translate or rotate about their base. Restrained walls are fixed or partially restrained against translation and/or rotation. For yielding walls, lateral earth pressures shall be computed assuming active stress conditions and wedge theory using a planar surface of sliding defined by Coulomb Theory. Development of an active state of stress in the soil behind a rigid wall requires an outward rotation of the wall about its toe. The magnitude of rotation required to develop active pressure is a function of the soil type and conditions behind the wall, as defined in Table 5.5.2A. Refer to Figure 5.5.2A for procedures to determine the magnitude and location of the earth pressure resultant for gravity and semigravity retaining walls subjected to active earth pressures. For restrained or yielding walls for which the tilting or deflection required to develop active earth pressure is not tolerable (i.e., yielding walls located adjacent to structures sensitive to settlement), lateral earth pressures shall be computed assuming at-rest conditions using the relationships
Refer to Figure 5.5.1A for terminology used in the design of rigid gravity and semi-gravity retaining walls.
0 .
STRUCTURAL KEY BETWEEN CONCRETE POURS
FRONT FACE
I BUTTRESS
1'I
STRUCTURAL KEY
BASE SHEAR KEY
r'h
~
121
FIGURE S.S.tA Terms Used in Design of Rigid Gravity and Semi-Gravity Retaining WaDs
(5.5.2-1)
HIGHWAY BRIDGES
122
5.5.2
TABLE S.S.2A Relationship Between Soil Backfill Type and Wall Rotation to Mobilize Active and Passive Earth
Pressures Behind Rigid Retaining Walls Wall Rotation, 4/H Active Passive
Soil1)rpe and Condition Dense Cohesionless Loose Cohesionless Stiff Cohesive Soft Cohesive
Ko =
0.001
0.020
0.004
0.060
0.010 0.020
0.040
I - sin'
0.020
(5.5.2-2)
When traffic loads are applied within a horizontal distance from the top of the wall equal to one-half the wall height, the· lateral earth pressure for design shall be increased by a minimum surcharge acting on the backslope equivalent to that applied by 0.6 meters· (2 feet) of soil as described in Article 3.20.3. The surcharge will result in the application of an additional uniform pressure on the back of the wall having a resultant magnitude
sin• 8 sin(8-8 >
E·
(5.5.2-3) acting at the mid-height of the wall where K is equal to K11 or Ko depending on wall restraint. If the surcharge is greater than that applied by 0.6 meters (2 feet) of soil, the design earth pressures shall be increased by the actual amount of the surcharge. Unless actual data regarding the magnitude of the anticipated surcharge loads is available, assume. a minimum soil unit weight of 19.6 kN/m3 (0.125 kcO in determining the surcharge load. The effects of permanent point or line surcharge loads (other than normal traffic live loads) on backslopes shall also be considered in developing the design earth pressures. See Figure 5.5.2B to estimate the effects of permanent point and line surcharge loads. The effect of compacting backfill in confined areas behind retaining walls may result in development of earth pressures greater than those represented by active or atrest conditions. Where use of heavy static or vibratory compaction equipment within a distance of about 0.5H behind the wall is anticipated, the effects of backfill com-
sin(c#»'• 8) sin(4»'-S> sintB- 8) sln(8 • B>
J•
Y'= EFFECTIVE UNIT WEIGHT ~·=EFFECTIVE ANGLE OF INTERNAL FRICTION 8 = ANGLE OF WALL FRICTION CSEE TABLE 5.5.28> S = SLOPE ANGLE B = WALL FACE BATTER ALL ANGLES ARE POSITIVE(+) AS SHOWN FIGURE 5.5.2A
Computational Procedures for Active Earth Pressures (Coulomb Analysis)
0
123
DIVISION I-DESIGN
5.5.2
Point. Load
Line LoadQL
Qp
.
~-m~
"
f.+-..,_ _ _, .L. H
i.~........__._ PLAN
SECTION
SE~TION
POINT LOAD
LINE LOAD
0
'• 0.4~--~-----.----~--~~~~ N
0
c .
0. 6
t----+--....;,j~,......---+-~R-.--t
l
0.60K 0.60H 0.&6H 0.48H
I
1.0 .._.........._.........._ _ _ _ _ ___, 0
0.8
Value of CTH
0.8
(.Ji) QL
LINE LOAD FIGURE 5.5.2B
0
1.0
0
0.5
1.0
Value of CTH
1.5