Heat-Straightening Repair of Damaged Steel Bridge Girders: Fatigue and Fracture Performance (2008)

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TRANSPORTAT ION RESEARCH BOARD WASHINGTON, D.C. 2008 www.TRB.org 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 604 Subject Areas Bridges, Other Structures, and Hydraulics and Hydrology • Maintenance Heat-Straightening Repair of Damaged Steel Bridge Girders: Fatigue and Fracture Performance R.J. Connor PURDUE UNIVERSITY West Lafayette, IN M.J. Urban HNTB CORPORATION Philadelphia, PA E.J. Kaufmann LEHIGH UNIVERSITY Bethlehem, PA 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 Board’s 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 604 Project 10-63 ISSN 0077-5614 ISBN: 978-0-309-099370 Library of Congress Control Number 2008928066 © 2008 Transportation Research Board COPYRIGHT PERMISSION 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. Such approval reflects the Governing Board’s judgment that the program concerned is of national importance and appropriate with respect to both the purposes and resources of the National Research Council. The members of the technical committee selected to monitor this project and to review this report were chosen for recognized scholarly competence and with due consideration for the balance of disciplines appropriate to the project. The opinions and conclusions expressed or implied are those of the research agency that performed the research, and, while they have been accepted as appropriate by the technical committee, they are not necessarily those of the Transportation Research Board, the National Research Council, the American Association of State Highway and Transportation Officials, or the Federal Highway Administration, U.S. Department of Transportation. Each report is reviewed and accepted for publication by the technical committee according to procedures established and monitored by the Transportation Research Board Executive Committee and the Governing Board of the National Research Council. The Transportation Research Board of the National Academies, the National Research Council, the Federal Highway Administration, the American Association of State Highway and Transportation Officials, and the individual states participating in the National Cooperative Highway Research Program do not endorse products or manufacturers. Trade or manufacturers’ names appear herein solely because they are considered essential to the object of this report.

CRP STAFF FOR NCHRP REPORT 604 Christopher W. Jenks, Director, Cooperative Research Programs Crawford F. Jencks, Deputy Director, Cooperative Research Programs Edward T. Harrigan, Senior Program Officer Eileen P. Delaney, Director of Publications Margaret B. Hagood, Editor Andrea Briere, Editor NCHRP PROJECT 10-63 PANEL Field of Materials and Construction—Area of Specifications, Procedures, and Practices Harold R. “Skip” Paul, Louisiana DOTD, Baton Rouge, LA (Chair) Scot Becker, Wisconsin DOT, Madison, WI David R. Bruce, Washington State DOT, Olympia, WA Jon J. Edwards, Springfield, IL John P. Weisner, Maryland State Highway Administration, Greenbelt, MD Dingyi Yang, Texas DOT, Austin, TX Ellen Zinni, New York State DOT, Poughkeepsie, NY William Wright, FHWA Liaison Krishna K. Verma, Other Liaison Frederick Hejl, TRB Liaison AUTHOR ACKNOWLEDGMENTS The research reported herein was performed under NCHRP Project 10-63 by the ATLSS Engineering Research Center at Lehigh University. Robert J. Connor, Assistant Professor at Purdue University and Eric J. Kaufmann, Senior Research Engineer at the ATLSS Center, are the principal investigators. The other author of this report is Michael J. Urban, a bridge design engineer with HNTB Corporation, formerly a Graduate Research Assistant at Lehigh University during the time of the research. Professor Emeritus, Dr. John W. Fisher, of Lehigh University, also provided valuable input throughout the research. The authors appreciate the support of NCHRP, the direction of Edward Harrigan, and the planning, review, and sug- gestions of the project panel. 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

This report summarizes the results of a project to establish limits, based on fatigue and fracture performance, on the number of damage and repair cycles to which damaged steel bridge girders may be subjected using the heat-straightening procedure. A key product presented here are suggested revisions to the Federal Highway Administration (FHWA) manual of practice for heat straightening. The report will be of particular interest to engineers in state highway agencies and industry responsible for bridge maintenance and repair. Heat straightening refers to the in-place application of heat and jacking forces to remove bends and distortion in steel bridge girders damaged by the impact of over-height vehicles. The procedure is often described as combining art with engineering, and is principally con- ducted by specialized firms in the private sector. Since 1999, however, the FHWA has pre- sented workshops intended to acquaint state forces and consultants with the use of heat straightening. The syllabus for this workshop is based on the 1998 report FHWA-IF-99-004, “Heat-Straightening Repairs of Damaged Steel Bridges: A Manual of Practice and Techni- cal Guide,” prepared by R. Avent and D. Mukai. Key questions in heat-straightening technology are the procedure’s effect on the fatigue and fracture of repaired steel girders and the degree to which the damage and heat-straightening history of the steel influence that performance. These questions have been prompted by situ- ations in which field-repaired girders subsequently fractured. Under NCHRP Project 10-63, “Heat-Straightening Repair of Damaged Steel Bridge Gird- ers: Fatigue and Fracture Performance,” the ATLSS Engineering Research Center of Lehigh University was assigned the tasks of (1) determining the relative effects of damage and subsequent heat-straightening on the fatigue and fracture performance of steel girders; (2) identifying and quantifying the material and process parameters that may affect the fatigue and fracture performance of heat-straightened steel girders; and (3) establishing guidelines, including limits on initial damage and critical process parameters, to minimize the potential for fracture and fatigue problems in heat-straightened steel girders. The research team designed and conducted a major program of large-scale laboratory experiments to accomplish these tasks. Multiple steel girders were dynamically damaged using a large-scale, purpose-built drop-weight machine, repaired using the heat-straightening procedure, and fatigue tested. Up to three damage and repair cycles were made at the same position on a girder. Based on the results of this testing program, the report concludes that the number of repairs should be limited to two for subsequent impact damage within the geometric limits of the first impact repair (i.e., the region where the most severe initial dam- age was focused). F O R E W O R D By Edward T. Harrigan Staff Officer Transportation Research Board

The research also reviewed and developed (as needed) techniques for evaluation, repair, and inspection of damaged steel girders to assist the owner, engineer, and heat-straightening contractor during the repair process. Finally, the research team suggested changes to the FHWA manual of practice that reflect the findings and conclusions of the project. This report presents the full text of the contractor’s final report of the project and four appendices, which present (1) drawings of purpose-built test equipment and specimen gages (Appendix A), (2) fatigue test results (Appendix B), (3) material properties of the damaged and repaired steel girders (Appendix C), and (4) suggested revisions to 1998 report FHWA- IF-99-004, “Heat-Straightening Repairs of Damaged Steel Bridges: A Manual of Practice and Technical Guide,” (Appendix D).

C O N T E N T S 1 Summary 3 Chapter 1 Introduction and Research Approach 3 1.1 Background 3 1.2 Objectives and Scope 3 1.3 Research Approach 3 1.3.1 Experiment Design 4 1.3.2 Specimen Configuration and Materials 4 1.3.3 Detail Categories Investigated 7 1.3.4 Test Matrix 7 1.4 Experimental Procedures 7 1.4.1 Damaging the Specimens 11 1.4.2 Nondestructive Testing of the Specimens 12 1.4.3 Heat-Straightening the Specimens 14 1.4.4 Fatigue Testing the Specimens 15 1.4.5 Material Testing of the Specimens 16 Chapter 2 Findings 16 2.1 Literature Review 17 2.2 Questionnaire 17 2.3 Fatigue Performance 17 2.3.1 One Damage/Repair Cycle 22 2.3.2 Two Damage/Repair Cycles 28 2.3.3 Three Damage/Repair Cycles 31 2.4 Material Properties 32 2.4.1 Fracture Toughness 34 2.4.2 Tensile Properties 35 2.4.3 Chemical Composition 35 2.4.4 Microstructure Inspection 35 2.5 Restraining Force Evaluation 36 2.5.1 Laboratory Instrumentation of Localized Damage 38 2.5.2 Finite Element Modeling 40 2.6 Residual Damage Evaluation 41 2.6.1 Finite Element Studies 41 2.6.2 Shell Element Models 50 2.6.3 Solid Element Models 55 Chapter 3 Interpretation, Appraisal, and Applications 55 3.1 Fatigue and Fracture Performance 55 3.1.1 Recommended Number of Repairs 55 3.1.2 NDT Inspection 55 3.1.3 Treatment of an Impact Area Prior to Heat-Straightening 56 3.1.4 Restraining Force Evaluation

57 3.1.5 Repair of Transverse Stiffeners 57 3.1.6 Residual Damage Evaluation 59 Chapter 4 Conclusions and Suggested Research 59 4.1 Fatigue and Fracture Performance 59 4.2 Restraining Force Evaluation 60 4.3 Residual Damage Evaluation 60 4.4 Suggested Research 61 References 62 Appendix A Drawings 89 Appendix B Fatigue Test Results 92 Appendix C Material Properties 108 Appendix D Proposed Revisions to FHWA Manual