Concrete Bridge Shear Load Rating Synthesis Report Publication No. FHWA-HIF-18-061 Federal Highway Administration Office of Infrastructure November 2018 FOREWORD Currently, evaluating shear capacity for load rating of concrete bridges is quite challenging due to the evolution of the shear design provisions over approximately 80 years in the AASHTO Standard Specifications for Highway Bridges (Standard Specifications) and the multiple procedures included in past and current editions of the AASHTO LRFD Bridge Design Specifications (LRFD Specifications). There is also a degree of uncertainty and inconsistency in the shear capacity load rating requirements of the AASHTO Manual for Bridge Evaluation (MBE) which adds to the complexity of the task. The objective of this report is to synthesize the technical aspects of shear load rating for concrete bridges and the challenges and difficulties States experience in doing so. This report summarizes the history of changes in the shear design and rating provisions in the aforementioned AASHTO publications. The report also includes survey results from nine State Departments of Transportation (States) that have large inventories of concrete highway bridges of diverse types. The survey results summarize each State’s practices and identifies the issues they face in rating existing concrete bridges using the MBE shear provisions. Finally, the report makes findings and recommendations to improve the practice and understanding of concrete bridge shear load rating. The subject matter expert technical reviewers for this report included Matt Farrar (Idaho Transportation Department) and Kevin Keady (California Department of Transportation) as well as other engineering professionals and academics from the highway bridge community. Their advice, counsel and contributions during the preparation of this synthesis report are greatly appreciated. Joseph L. Hartmann, PhD, P.E. Director, Office of Bridges and Structures Office of Infrastructure Federal Highway Administration Notice This document is disseminated under the sponsorship of the U.S. Department of Transportation in the interest of information exchange. The U.S. Government assumes no liability for the use of the information contained in this document. The U.S. Government does not endorse products or manufacturers. Trademarks or manufacturers’ names appear in this report only because they are considered essential to the objective of the document. They are included for informational purposes only and are not intended to reflect a preference, approval, or endorsement of any one product or entity. Quality Assurance Statement The Federal Highway Administration (FHWA) provides high-quality information to serve Government, industry, and the public in a manner that promotes public understanding. Standards and policies are used to ensure and maximize the quality, objectivity, utility, and integrity of its information. FHWA periodically reviews quality issues and adjusts its programs and processes to ensure continuous quality improvement. Cover Photos: Top Right: Bixby Creek Bridge, California State Route 1. Photo taken by John Baker, courtesy Caltrans. Lower Right: South Fork of the Eel River Bridge, US-101, California. Photo taken by Matt O’Leary, courtesy Caltrans. Left: North to West Direct Connector, I-35/US-183 Interchange, Texas. Photo taken by Lisa Powell, courtesy P.E. Structural Consultants, Inc. Cover logo: courtesy of FHWA. 2 TECHNICAL REPORT DOCUMENTATION PAGE 1. Report No. 2. Government Accession No. 3. Recipient’s Catalog No. FHWA-HIF-18-061 4. Title and Subtitle 5. Report Date Concrete Bridge Shear Load Rating, Synthesis Report November 2018 6. Performing Organization Code: 7. Author(s) 8. Performing Organization Report No. John Holt, Uriel Garcia, Stephen Waters, Christopher Monopolis, Andy Zhu, Oguzhan Bayrak, Lisa Powell, Kedar Halbe, Pradeep Kumar, Brandon Chavel 9. Performing Organization Name and Address 10. Work Unit No. HDR Engineering, Inc. 11. Contract or Grant No. 8404 Indian Hills Drive Omaha, NE DTFH6114D00049 12. Sponsoring Agency Name and Address 13. Type of Report and Period Covered Federal Highway Administration 1200 New Jersey Ave., SE Washington, D.C. 20590 14. Sponsoring Agency Code 15. Supplementary Notes HDR Project Manager: Brandon Chavel, Ph.D., P.E. FHWA Contracting Officer Representative (COR): William Bergeson, P.E. FHWA Task Order COR (Task Order Manager): Lubin Gao, Ph.D., P.E. 16. Abstract This report synthesizes the current state of practice in the shear load rating of concrete bridges. A brief overview of the historical approaches, encompassing the methods from the first to the latest AASHTO Specifications, to shear demand and resistance is presented. The overview includes load combinations, live load distribution, and shear strength in both reinforced and prestressed concrete. A historical overview of the bridge load rating is presented. The use of software in concrete shear load rating is also investigated. The study of current policies, practices, and challenges in concrete bridge shear load rating is conducted through a survey of nine state DOTs. An extensive literature review is performed to highlight recent and relevant research on concrete shear strength, concrete bridge behavior in shear and concrete bridge shear load rating. This synthesis report identifies recommendations on research, modifications to existing specifications and manuals, and the development of clear and concise guidance to practitioners. 17. Key Words 18. Distribution Statement Highway, Bridges, Concrete Shear, Load Rating, No restrictions. This document is available through the Design, Design Loads, Legal Loads, Permit National Technical Information Service, Springfield, VA Loads, ASR, LFR, LRFR, ASD, LFD, LRFD 22161. http://www.ntis.gov 19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No. of Pages 22. Price Unclassified Unclassified Form DOT F 1700.7 (8-72) Reproduction of completed page authorized. iii 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) °F Fahrenheit 5 (F-32)/9 or Celsius °C (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 Source: Federal Highway Administration. 2013. “SI* (Modern Metric) Conversion Factors”. https://www.fhwa.dot.gov/publications/convtabl.cfm. Note: 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 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 yard 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) °C Celsius 1.8C+32 Fahrenheit °F Illumination lx lux 0.0929 foot-candles fc cd/m2 candela/m2 0.2919 foot-Lamberts fl Force and Pressure or Stress N newtons 02.225 poundforce lbf kPa kilopascals 0.145 poundforce per square inch lbf/in2 Source: Federal Highway Administration. 2013. “SI* (Modern Metric) Conversion Factors”. https://www.fhwa.dot.gov/publications/convtabl.cfm. Note: 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) v Contents Chapter 1. Introduction ....................................................................................................................... 1 1.1. Concrete Bridge Background ................................................................................................. 2 1.1.1. United States Statistics ..................................................................................................... 2 1.1.2. Governing Entities ............................................................................................................ 3 1.1.3. Governing Publications .................................................................................................... 3 1.1.4. Shear Design ...................................................................................................................... 3 1.1.5. Load Rating ....................................................................................................................... 3 Chapter 2. Requirements for Shear Design