Seismic Retrofitting Manual for Highway Structures: Part 1 – Bridges PUBLICATION NO. FHWA-HRT-06-032 JANUARY 2006 Research, Development, and Technology Turner-Fairbank Highway Research Center 6300 Georgetown Pike McLean, VA 22101-2296 Technical Report Documentation Page 1. Report No. 2. Government Accession No. 3. Recipient’s Catalog No. FHWA-HRT-06-032 N/A N/A 4. Title and Subtitle 5. Report Date SEISMIC RETROFITTING MANUAL FOR HIGHWAY January 2006 STRUCTURES: PART 1 – BRIDGES 6. Performing Organization Code N/A 7. Author(s) 8. Performing Organization Report No. Ian Buckle, Ian Friedland, John Mander, Geoffrey Martin, Richard Nutt and Maurice Power 9. Performing Organization Name and Address 10. Work Unit No. Multidisciplinary Center for Earthquake Engineering Research N/A University at Buffalo, State University of New York 11. Contract or Grant No. Red Jacket Quadrangle DTFH61-92-C-00106 Buffalo, NY 14261 12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered Office of Infrastructure Research and Development Final Report Federal Highway Administration 14. Sponsoring Agency Code 6300 Georgetown Pike McLean, VA 22101-2296 15. Supplementary Notes: Contracting Officer’s Technical Representatives: James Cooper, P.E., HRDI-03, Wen-huei (Phillip) Yen, Ph.D., P.E., HRDI-07, John D. O’Fallon, P.E., HRDI-07 16. Abstract This report is the first of a two-part publication entitled: Seismic Retrofitting Manual for Highway Structures: Part 1: Bridges Part 2: Retaining Structures, Slopes, Tunnels, Culverts and Roadways. Part 1 of this manual is based on previous Federal Highway Administration (FHWA) publications on this subject including Seismic Retrofitting Manual for Highway Bridges, published in 1995 as report FHWA-RD-94-052. Revisions have been made to include current advances in earthquake engineering, field experience with retrofitting highway bridges, and the performance of bridges in recent earthquakes. It is the result of several years of research with contributions from a multidisciplinary team of researchers and practitioners. In particular, a performance-based retrofit philosophy is introduced similar to that used for the performance-based design of new buildings and bridges. Performance criteria are given for two earthquake ground motions with different return periods, 100 and 1000 years. A higher level of performance is required for the event with the shorter return period (the lower level earthquake ground motion) than for the longer return period (the upper level earthquake ground motion). Criteria are recommended according to bridge importance and anticipated service life, with more rigorous performance being required for important, relatively new bridges, and a lesser level for standard bridges nearing the end of their useful life. Minimum recommendations are made for screening, evaluation and retrofitting according to an assigned Seismic Retrofit Category. Bridges in Category A need not be retrofitted whereas those in Categories B, C and D require successively more rigorous consideration and retrofitting as required. Various retrofit strategies are described and a range of related retrofit measures explained in detail, including restrainers, seat extensions, column jackets, footing overlays, and soil remediation. 17. Key Words 18. Distribution Statement Bridges, earthquakes, performance-based retrofitting, No restrictions. This document is available to the public through seismic retrofit categories, screening, prioritization, the National Technical Information Service, Springfield, VA evaluation, retrofit strategies, measures, guidelines 22161. 19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No of Pages 22. Price Unclassified Unclassified 656 Form DOT F 1700.7 (8-72) Reproduction of completed pages authorized PREFACE This report is a major revision of the Federal Highway Administration publication Seismic Retrofitting Manual for Highway Bridges, which was published in 1995 as report FHWA-RD- 94-052. This edition expands the coverage of the previous publication by including procedures for evaluating and retrofitting retaining structures, slopes, tunnels, culverts, and pavements, in addition to bridges. It is published in two parts as follows: Part 1: Bridges Part 2: Retaining Structures, Slopes, Tunnels, Culverts, and Pavements Whereas Part 1 maintains the basic format of the retrofitting process described in the 1995 report, major changes have been made in this revision to include current advances in earthquake engineering, field experience with retrofitting highway bridges, and the performance of bridges in recent earthquakes in California and elsewhere. It is the result of several years of research with contributions from a multidisciplinary team of researchers and practitioners. In particular, a performance-based retrofit philosophy is introduced similar to that used for the performance-based design of new buildings and bridges. Performance criteria are given for two earthquake ground motions with different return periods, 100 and 1000 years. A higher level of performance is required for the event with the shorter return period (the lower level earthquake ground motion) than for the longer return period (the upper level earthquake ground motion). Criteria are recommended according to bridge importance and anticipated service life, with more rigorous performance being required for important, relatively new bridges, and a lesser level for standard bridges nearing the end of their useful life. Minimum recommendations are made for screening, evaluation, and retrofitting according to an assigned Seismic Retrofit Category. Bridges in Category A need not be retrofitted, whereas those in Category B may be assessed without a detailed evaluation, provided certain requirements are satisfied. Bridges in Categories C and D require more rigorous evaluation and retrofitting, as required. Various retrofit strategies are described and a range of related retrofit measures explained in detail, including restrainers, seat extensions, column jackets, footing overlays, and soil remediation. This manual comprises 11 chapters and six appendices as follows: Chapter 1 gives a complete overview of the retrofitting process including the philosophy of performance-based retrofitting, the characterization of the seismic and geotechnical hazards, the assignment of the Seismic Retrofit Category, and summaries of recommended screening methods, evaluation tools, and retrofit strategies. Topics in this chapter are described in greater detail in the following 10 chapters. Chapters 2 and 3 describe the characterization of the seismic and geotechnical hazards. ii Chapter 4 presents two screening and prioritization methods, with examples of each method. Chapters 5, 6, and 7 describe six evaluation methods, of increasing rigor, for the detailed assessment of demand and capacity, using either a component-by-component approach or a system approach for a complete bridge. Chapters 8, 9, 10, and 11 describe retrofitting measures for bearings, seats, columns, piers, cap beams, column-to-cap joints, abutments, and foundations. Remedial techniques for hazardous sites are also addressed. Appendices A through D provide supplementary material on conducting site-specific geotechnical investigations, the evaluation of geotechnical hazards, fragility curve theory, and the calculation of capacity/demand ratios for bridge components. Appendices E and F present two examples illustrating the application of the component capacity/demand method (Method C) to multi-span concrete and steel highway bridges, respectively. A glossary and lists of abbreviations, symbols, and references are also included. It is noted that this manual was developed while the U.S. Department of Transportation was transitioning to metric units. As a consequence, example problems are presented in SI units. Future editions may however use Customary U.S. units to reflect the current movement in many State DOTs back to customary units. iii SI* (MODERN METRIC) CONVERSION FACTORS APPROXIMATE CONVERSIONS TO SI UNITS Symbol When You Know Multiply By To Find Symbol LENGTH in inches 25.4 millimeters mm ft feet 0.305 meters m yd yards 0.914 meters m mi miles 1.61 kilometers km AREA in2 square inches 645.2 square millimeters mm2 ft2 square feet 0.093 square meters m2 yd2 square yard 0.836 square meters m2 ac acres 0.405 hectares ha mi2 square miles 2.59 square kilometers km2 VOLUME fl oz fluid ounces 29.57 milliliters mL gal gallons 3.785 liters L ft3 cubic feet 0.028 cubic meters m3 yd3 cubic yards 0.765 cubic meters m3 NOTE: volumes greater than 1000 L shall be shown in m3 MASS oz ounces 28.35 grams g lb pounds 0.454 kilograms kg T short tons (2000 lb) 0.907 megagrams (or "metric ton") Mg (or "t") TEMPERATURE (exact degrees) oF Fahrenheit 5 (F-32)/9 Celsius oC or (F-32)/1.8 ILLUMINATION fc foot-candles 10.76 lux lx fl foot-Lamberts 3.426 candela/m2 cd/m2 FORCE and PRESSURE or STRESS lbf poundforce 4.45 newtons N lbf/in2 poundforce per square inch 6.89 kilopascals kPa APPROXIMATE CONVERSIONS FROM SI UNITS Symbol When You Know Multiply By To Find Symbol LENGTH mm millimeters 0.039 inches in m meters 3.28 feet ft m meters 1.09 yards yd km kilometers 0.621 miles mi AREA mm2 square millimeters 0.0016 square inches in2 m2 square meters 10.764 square feet ft2 m2 square meters 1.195 square yards yd2 ha hectares 2.47 acres ac km2 square kilometers 0.386 square miles mi2 VOLUME mL milliliters 0.034 fluid ounces fl oz L liters 0.264 gallons gal m3 cubic meters 35.314 cubic feet ft3 m3 cubic meters 1.307 cubic yards yd3 MASS g grams 0.035 ounces oz kg kilograms 2.202 pounds lb Mg (or "t") megagrams (or "metric ton") 1.103 short tons (2000 lb) T TEMPERATURE (exact degrees) oC Celsius 1.8C+32 Fahrenheit oF ILLUMINATION lx lux 0.0929 foot-candles fc cd/m2 candela/m2 0.2919 foot-Lamberts fl FORCE and PRESSURE or STRESS N newtons 0.225 poundforce lbf kPa kilopascals 0.145 poundforce per square inch lbf/in2 *SI is the symbol for the International System of Units. Appropriate rounding should be made to comply with Section 4 of ASTM E380. (Revised March 2003) iv TABLE OF CONTENTS PAGE CHAPTER 1: SEISMIC RETROFITTING OF HIGHWAY BRIDGES ...........................