Fatigue Evaluation of Steel Bridges (2012)

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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 Highways  •  Bridges and Other Structures TRANSPORTAT ION RESEARCH BOARD WASHINGTON, D.C. 2012 www.TRB.org  Research sponsored by the American Association of State Highway and Transportation Officials in cooperation with the Federal Highway Administration

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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, “Evaluation of Fatigue on the Serviceability of Highway Bridges” 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 Leader—Bridge 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 Design—Area 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. “Sam” 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 By Waseem DeKelbab Staff Officer Transportation Research Board The report provides proposed revisions to Section 7—Fatigue 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 7—Fatigue 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, “Evaluation of Fatigue on the Serviceability of Highway Bridges”, 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 7—Fatigue 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 E—Proposed Sec- tion 7 of MBE and Appendix F—Fatigue 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 A— Survey Interview Forms • APPENDIX B— AASHTO Fatigue Truck Validation Analysis Results • APPENDIX C— Tack Weld Tests • APPENDIX D— Distortion Induced Fatigue Tests

C O N T E N T S 1  Summary 5 Chapter 1  Background 7 Chapter 2  Research Approach 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 3  Findings and Applications 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 4  Conclusions 62 Proposed Revisions to MBE Section 7 62 Options for Design Consideration 64  References 65 Appendices A–D E-1 Appendix E Proposed Section 7 of MBE F-1 Appendix F Fatigue Examples 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.