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N A T I O N A L C O O P E R A T I V E H I G H W A Y R E S E A R C H P R O G R A M NCHRP REPORT 721 Fatigue Evaluation of Steel Bridges Mark D. Bowman Purdue university West Lafayette, IN Gongkang Fu illinois institute of technology Chicago, IL Y. Edward Zhou urs corPoration Hunt Valley, MD Robert J. Connor Purdue university West Lafayette, IN Amol A. Godbole Purdue university West Lafayette, IN Subscriber Categories Highwaysâ â¢â BridgesâandâOtherâStructures TRANSPORTAT ION RESEARCH BOARD WASHINGTON,âD.C. 2012 www.TRB.orgâ Research sponsored by the American Association of State Highway and Transportation Officials in cooperation with the Federal Highway Administration
NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM Systematic, well-designed research provides the most effective approach to the solution of many problems facing highway administrators and engineers. Often, highway problems are of local interest and can best be studied by highway departments individually or in cooperation with their state universities and others. However, the accelerating growth of highway transportation develops increasingly complex problems of wide interest to highway authorities. These problems are best studied through a coordinated program of cooperative research. In recognition of these needs, the highway administrators of the American Association of State Highway and Transportation Officials initiated in 1962 an objective national highway research program employing modern scientific techniques. This program is supported on a continuing basis by funds from participating member states of the Association and it receives the full cooperation and support of the Federal Highway Administration, United States Department of Transportation. The Transportation Research Board of the National Academies was requested by the Association to administer the research program because of the Boardâs recognized objectivity and understanding of modern research practices. The Board is uniquely suited for this purpose as it maintains an extensive committee structure from which authorities on any highway transportation subject may be drawn; it possesses avenues of communications and cooperation with federal, state and local governmental agencies, universities, and industry; its relationship to the National Research Council is an insurance of objectivity; it maintains a full-time research correlation staff of specialists in highway transportation matters to bring the findings of research directly to those who are in a position to use them. The program is developed on the basis of research needs identified by chief administrators of the highway and transportation departments and by committees of AASHTO. Each year, specific areas of research needs to be included in the program are proposed to the National Research Council and the Board by the American Association of State Highway and Transportation Officials. Research projects to fulfill these needs are defined by the Board, and qualified research agencies are selected from those that have submitted proposals. Administration and surveillance of research contracts are the responsibilities of the National Research Council and the Transportation Research Board. The needs for highway research are many, and the National Cooperative Highway Research Program can make significant contributions to the solution of highway transportation problems of mutual concern to many responsible groups. The program, however, is intended to complement rather than to substitute for or duplicate other highway research programs. Published reports of the NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM are available from: Transportation Research Board Business Office 500 Fifth Street, NW Washington, DC 20001 and can be ordered through the Internet at: http://www.national-academies.org/trb/bookstore Printed in the United States of America NCHRP REPORT 721 Project 12-81 ISSN 0077-5614 ISBN 978-0-309-25826-5 Library of Congress Control Number 2012940789 © 2012 National Academy of Sciences. All rights reserved. COPYRIGHT INFORMATION Authors herein are responsible for the authenticity of their materials and for obtaining written permissions from publishers or persons who own the copyright to any previously published or copyrighted material used herein. Cooperative Research Programs (CRP) grants permission to reproduce material in this publication for classroom and not-for-profit purposes. Permission is given with the understanding that none of the material will be used to imply TRB, AASHTO, FAA, FHWA, FMCSA, FTA, or Transit Development Corporation endorsement of a particular product, method, or practice. It is expected that those reproducing the material in this document for educational and not-for-profit uses will give appropriate acknowledgment of the source of any reprinted or reproduced material. For other uses of the material, request permission from CRP. NOTICE The project that is the subject of this report was a part of the National Cooperative Highway Research Program, conducted by the Transportation Research Board with the approval of the Governing Board of the National Research Council. The members of the technical panel selected to monitor this project and to review this report were chosen for their special competencies and with regard for appropriate balance. The report was reviewed by the technical panel and accepted for publication according to procedures established and overseen by the Transportation Research Board and approved by the Governing Board of the National Research Council. The opinions and conclusions expressed or implied in this report are those of the researchers who performed the research and are not necessarily those of the Transportation Research Board, the National Research Council, or the program sponsors. The Transportation Research Board of the National Academies, the National Research Council, and the sponsors of the National Cooperative Highway Research Program do not endorse products or manufacturers. Trade or manufacturersâ names appear herein solely because they are considered essential to the object of the report.
The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. On the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Ralph J. Cicerone is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. Charles M. Vest is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, on its own initiative, to identify issues of medical care, research, and education. Dr. Harvey V. Fineberg is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academyâs purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Ralph J. Cicerone and Dr. Charles M. Vest are chair and vice chair, respectively, of the National Research Council. The Transportation Research Board is one of six major divisions of the National Research Council. The mission of the Transporta- tion Research Board is to provide leadership in transportation innovation and progress through research and information exchange, conducted within a setting that is objective, interdisciplinary, and multimodal. The Boardâs varied activities annually engage about 7,000 engineers, scientists, and other transportation researchers and practitioners from the public and private sectors and academia, all of whom contribute their expertise in the public interest. The program is supported by state transportation departments, federal agencies including the component administrations of the U.S. Department of Transportation, and other organizations and individu- als interested in the development of transportation. www.TRB.org www.national-academies.org
C O O P E R A T I V E R E S E A R C H P R O G R A M S AUTHOR ACKNOWLEDGMENTS The research reported in this Final Report was performed under NCHRP Project 12-81, âEvaluation of Fatigue on the Serviceability of Highway Bridgesâ by the School of Civil Engineering at Purdue Uni- versity in West Lafayette, IN. Purdue University is the prime contractor for this study, with Dr. Fu as a private consultant to Purdue, and URS Corporation serving as a sub-contractor to Purdue. Dr. Mark D. Bowman, Professor of Civil Engineering at Purdue, is the Project Director and Principal Investigator. The other authors of this report are: Dr. Gongkang Fu, Professor of Civil Engineering at Illinois Institute of Technology; Dr. Y. Edward Zhou, National Practice LeaderâBridge Instrumentation and Evaluation at URS Corporation; Dr. Robert J. Connor, Associate Professor of Civil Engineering at Purdue; and Amol A. Godbole, Research Assistant and Ph.D. Candidate at Purdue University. CRP STAFF FOR NCHRP REPORT 721 Christopher W. Jenks, Director, Cooperative Research Programs Crawford F. Jencks, Deputy Director, Cooperative Research Programs Waseem DeKelbab, Senior Program Officer Danna Powell, Senior Program Assistant Eileen P. Delaney, Director of Publications Maria Sabin Crawford, Assistant Editor NCHRP PROJECT 12-81 PANEL Field of DesignâArea of Bridges Barton J. Newton, California DOT, Sacramento, CA (Chair) Sreenivas Alampalli, New York State DOT, Albany, NY Laura M. Amundson, Parsons Brinckerhoff, Minneapolis, MN Lian Duan, California DOT, Sacramento, CA Hussam Z. âSamâ Fallaha, Florida DOT, Tallahassee, FL Thomas K. Koch, North Carolina DOT, Raleigh, NC Keith L. Ramsey, Texas DOT, Austin, TX Joey Hartmann, FHWA Liaison Stephen F. Maher, TRB Liaison
F O R E W O R D ByâWaseemâDeKelbab StaffâOfficer TransportationâResearchâBoard The report provides proposed revisions to Section 7âFatigue Evaluation of Steel Bridges of the AASHTO Manual for Bridge Evaluation with detailed examples of the application of the proposed revisions. The proposed revisions and examples were developed based on analytical and experimental research conducted to improve existing methods to evaluate and assess the serviceability of bridge structures for the fatigue limit state. The material in this report will be of immediate interest to highway design engineers. The AASHTO Guide Specifications for Fatigue Evaluation of Existing Steel Bridges (Guide) and the 2003 AASHTO Guide Manual for Condition Evaluation and Load and Resistance Fac- tor Rating (LRFR) of Highway Bridges (Manual) provide guidance on fatigue evaluation of steel bridges. The Guide is more than 17 years old, and the material in the Manual is derived from the Guide. Section 7âFatigue Evaluation of Steel Bridges of the AASHTO Manual for Bridge Evaluation (MBE), First Edition/2008, incorporates the material in the Manual. In recent years, more information on steel bridges has been developed that provides a founda- tion upon which to update the procedures for fatigue evaluation of steel bridges. Areas in need of improvement include: (a) methods of estimating total and remaining fatigue life as the current methods can result in unrealistic and inaccurate predictions, (b) guidance on the evaluation of retrofit and repair details used to address fatigue cracks, and (c) guidance for the evaluation of distortion-induced fatigue cracks. The research was performed under NCHRP Project 12-81, âEvaluation of Fatigue on the Serviceability of Highway Bridgesâ, by a team led by Dr. Mark D. Bowman, the School of Civil Engineering at Purdue University in West Lafayette, IN. The objectives of NCHRP Project 12-81 were to (1) propose updates to Section 7âFatigue Evaluation of Steel Bridges of the AASHTO Manual for Bridge Evaluation and (2) provide detailed examples of the application of the proposed revisions. A number of deliverables are provided as appendices. Only Appendix EâProposed Sec- tion 7 of MBE and Appendix FâFatigue Examples are published herein. Other appendi- ces are not published but are available on the TRB website at http://www.trb.org/Main/ Blurbs/167233.aspx. These appendices are titled as follows: ⢠APPENDIX Aâ Survey Interview Forms ⢠APPENDIX Bâ AASHTO Fatigue Truck Validation Analysis Results ⢠APPENDIX Câ Tack Weld Tests ⢠APPENDIX Dâ Distortion Induced Fatigue Tests
C O N T E N T S 1â Summary 5 Chapter 1â Background 7 Chapter 2â ResearchâApproach 7 History of AASHO/AASHTO Provisions for Fatigue Design and Evaluation of Bridges 8 Review of Fatigue Specifications in Other Countries 9 Eurocode Specification 9 Australian Specification 9 Survey 9 Summary of DOT Survey Results 10 Summary of Identified Fatigue Expert Survey Results 10 Identify Critical Issues and Needed Research 10 The S-N Curve 10 Unnecessary Approximation Leading to Unreliable Estimates 11 Negative Remaining Fatigue Life 12 Multiple Presence Factor 12 Lack of Detailed Guidance for Field Measurement as an Option 12 Lack of Guidance on Tack Welds and Riveted Members 14 Lack of Guidance for the Evaluation of Distortion-Induced Fatigue Cracks 16 Fatigue Serviceability Index 16 Additional Factors 16 Experimental Setup and Test Procedures 16 Tack Weld Tests 18 Distortion-Induced Fatigue Tests 24 Chapter 3â FindingsâandâApplications 24 S-N Curve 24 Validation of AASHTO Fatigue Truck 25 Multiple Presence Factor 26 Concept of Multiple Presence Factor 27 Analysis Overview and WIM Data Used 27 Sensitivity Analysis 27 Negative Remaining Life 30 RR Factor 32 Fatigue Serviceability Index 36 More Accurate Estimation for Truck Traffic 36 Example 1 37 Example 2 39 Tack Weld Tests 40 Bolt Tightening Procedure
42 Finite Element Analysis of Tack Weld Specimen 44 Test Results 45 Comparison of Test Results 46 Distortion-Induced Fatigue Tests 46 Finite Element Analysis for Distortion-Induced Fatigue Tests 57 Test Results 61 Chapter 4â Conclusions 62 Proposed Revisions to MBE Section 7 62 Options for Design Consideration 64â References 65 Appendices AâD E-1 Appendix E ProposedâSectionâ7âofâMBE F-1 Appendix F FatigueâExamples Note: Many of the photographs, figures, and tables in this report have been converted from color to grayscale for printing. The electronic version of the report (posted on the Web at www.trb.org) retains the color versions.