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NATIONAL NCHRP REPORT 549 COOPERATIVE HIGHWAY RESEARCH PROGRAM Simplified Shear Design of Structural Concrete Members

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TRANSPORTATION RESEARCH BOARD EXECUTIVE COMMITTEE 2005 (Membership as of October 2005) OFFICERS Chair: John R. Njord, Executive Director, Utah DOT Vice Chair: Michael D. Meyer, Professor, School of Civil and Environmental Engineering, Georgia Institute of Technology Executive Director: Robert E. Skinner, Jr., Transportation Research Board MEMBERS MICHAEL W. BEHRENS, Executive Director, Texas DOT ALLEN D. BIEHLER, Secretary, Pennsylvania DOT LARRY L. BROWN, SR., Executive Director, Mississippi DOT DEBORAH H. BUTLER, Vice President, Customer Service, Norfolk Southern Corporation and Subsidiaries, Atlanta, GA ANNE P. CANBY, President, Surface Transportation Policy Project, Washington, DC JOHN L. CRAIG, Director, Nebraska Department of Roads DOUGLAS G. DUNCAN, President and CEO, FedEx Freight, Memphis, TN NICHOLAS J. GARBER, Professor of Civil Engineering, University of Virginia, Charlottesville ANGELA GITTENS, Vice President, Airport Business Services, HNTB Corporation, Miami, FL GENEVIEVE GIULIANO, Director, Metrans Transportation Center, and Professor, School of Policy, Planning, and Development, USC, Los Angeles BERNARD S. GROSECLOSE, JR., President and CEO, South Carolina State Ports Authority SUSAN HANSON, Landry University Professor of Geography, Graduate School of Geography, Clark University JAMES R. HERTWIG, President, CSX Intermodal, Jacksonville, FL GLORIA JEAN JEFF, Director, Michigan DOT ADIB K. KANAFANI, Cahill Professor of Civil Engineering, University of California, Berkeley HERBERT S. LEVINSON, Principal, Herbert S. Levinson Transportation Consultant, New Haven, CT SUE MCNEIL, Professor, Department of Civil and Environmental Engineering, University of Delaware, Newark MICHAEL R. MORRIS, Director of Transportation, North Central Texas Council of Governments CAROL A. MURRAY, Commissioner, New Hampshire DOT MICHAEL S. TOWNES, President and CEO, Hampton Roads Transit, Hampton, VA C. MICHAEL WALTON, Ernest H. Cockrell Centennial Chair in Engineering, University of Texas, Austin LINDA S. WATSON, Executive Director, LYNX--Central Florida Regional Transportation Authority MARION C. BLAKEY, Federal Aviation Administrator, U.S.DOT (ex officio) JOSEPH H. BOARDMAN, Federal Railroad Administrator, U.S.DOT (ex officio) REBECCA M. BREWSTER, President and COO, American Transportation Research Institute, Smyrna, GA (ex officio) GEORGE BUGLIARELLO, Chancellor, Polytechnic University, and Foreign Secretary, National Academy of Engineering (ex officio) J. RICHARD CAPKA, Acting Administrator, Federal Highway Administration, U.S.DOT (ex officio) THOMAS H. COLLINS (Adm., U.S. Coast Guard), Commandant, U.S. Coast Guard (ex officio) JENNIFER L. DORN, Federal Transit Administrator, U.S.DOT (ex officio) JAMES J. EBERHARDT, Chief Scientist, Office of FreedomCAR and Vehicle Technologies, U.S. Department of Energy (ex officio) JACQUELINE GLASSMAN, Deputy Administrator, National Highway Traffic Safety Administration, U.S.DOT (ex officio) EDWARD R. HAMBERGER, President and CEO, Association of American Railroads (ex officio) JOHN C. HORSLEY, Executive Director, American Association of State Highway and Transportation Officials (ex officio) JOHN E. JAMIAN, Acting Administrator, Maritime Administration, U.S.DOT (ex officio) EDWARD JOHNSON, Director, Applied Science Directorate, National Aeronautics and Space Administration (ex officio) ASHOK G. KAVEESHWAR, Research and Innovative Technology Administrator, U.S.DOT (ex officio) BRIGHAM MCCOWN, Deputy Administrator, Pipeline and Hazardous Materials Safety Administration, U.S.DOT (ex officio) WILLIAM W. MILLAR, President, American Public Transportation Association (ex officio) SUZANNE RUDZINSKI, Director, Transportation and Regional Programs, U.S. Environmental Protection Agency (ex officio) ANNETTE M. SANDBERG, Federal Motor Carrier Safety Administrator, U.S.DOT (ex officio) JEFFREY N. SHANE, Under Secretary for Policy, U.S.DOT (ex officio) CARL A. STROCK (Maj. Gen., U.S. Army), Chief of Engineers and Commanding General, U.S. Army Corps of Engineers (ex officio) NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM Transportation Research Board Executive Committee Subcommittee for NCHRP JOHN R. NJORD, Utah DOT (Chair) MICHAEL D. MEYER, Georgia Institute of Technology J. RICHARD CAPKA, Federal Highway Administration ROBERT E. SKINNER, JR., Transportation Research Board JOHN C. HORSLEY, American Association of State Highway MICHAEL S. TOWNES, Hampton Roads Transit, Hampton, VA and Transportation Officials C. MICHAEL WALTON, University of Texas, Austin

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NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM NCHRP REPORT 549 Simplified Shear Design of Structural Concrete Members NEIL M. HAWKINS DANIEL A. KUCHMA University of Illinois at Urbana-Champaign Urbana, IL ROBERT F. MAST M. LEE MARSH Berger/ABAM Engineers, Inc. Federal Way, WA AND KARL-HEINZ REINECK University of Stuttgart Stuttgart, Germany S UBJECT A REAS Bridges, Other Structures, and Hydraulics and Hydrology Research Sponsored by the American Association of State Highway and Transportation Officials in Cooperation with the Federal Highway Administration TRANSPORTATION RESEARCH BOARD WASHINGTON, D.C. 2005 www.TRB.org

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NATIONAL COOPERATIVE HIGHWAY RESEARCH NCHRP REPORT 549 PROGRAM Systematic, well-designed research provides the most effective Project 12-61 approach to the solution of many problems facing highway administrators and engineers. Often, highway problems are of local ISSN 0077-5614 interest and can best be studied by highway departments ISBN 0-309-08844-5 individually or in cooperation with their state universities and Library of Congress Control Number 2005935299 others. However, the accelerating growth of highway transportation develops increasingly complex problems of wide interest to 2005 Transportation Research Board highway authorities. These problems are best studied through a coordinated program of cooperative research. Price $20.00 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 NOTICE Department of Transportation. The project that is the subject of this report was a part of the National Cooperative The Transportation Research Board of the National Academies Highway Research Program conducted by the Transportation Research Board with the was requested by the Association to administer the research approval of the Governing Board of the National Research Council. Such approval program because of the Board's recognized objectivity and reflects the Governing Board's judgment that the program concerned is of national understanding of modern research practices. The Board is uniquely importance and appropriate with respect to both the purposes and resources of the suited for this purpose as it maintains an extensive committee National Research Council. structure from which authorities on any highway transportation The members of the technical committee selected to monitor this project and to review subject may be drawn; it possesses avenues of communications and this report were chosen for recognized scholarly competence and with due cooperation with federal, state and local governmental agencies, consideration for the balance of disciplines appropriate to the project. The opinions and universities, and industry; its relationship to the National Research conclusions expressed or implied are those of the research agency that performed the Council is an insurance of objectivity; it maintains a full-time research, and, while they have been accepted as appropriate by the technical committee, research correlation staff of specialists in highway transportation they are not necessarily those of the Transportation Research Board, the National matters to bring the findings of research directly to those who are in Research Council, the American Association of State Highway and Transportation a position to use them. Officials, or the Federal Highway Administration, U.S. Department of Transportation. The program is developed on the basis of research needs Each report is reviewed and accepted for publication by the technical committee identified by chief administrators of the highway and transportation according to procedures established and monitored by the Transportation Research departments and by committees of AASHTO. Each year, specific Board Executive Committee and the Governing Board of the National Research areas of research needs to be included in the program are proposed Council. 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. Published reports of the The needs for highway research are many, and the National NATIONAL COOPERATIVE HIGHWAY RESEARCH PROGRAM Cooperative Highway Research Program can make significant contributions to the solution of highway transportation problems of are available from: mutual concern to many responsible groups. The program, however, is intended to complement rather than to substitute for or Transportation Research Board duplicate other highway research programs. Business Office 500 Fifth Street, NW Washington, DC 20001 and can be ordered through the Internet at: Note: 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 http://www.national-academies.org/trb/bookstore 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. Printed in the United States of America

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The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished schol- ars 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 techni- cal 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 Acad- emy 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 achieve- ments of engineers. Dr. William A. Wulf 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 Academy's purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Acad- emy, 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 the Academies and the Institute of Medicine. Dr. Ralph J. Cicerone and Dr. William A. Wulf are chair and vice chair, respectively, of the National Research Council. The Transportation Research Board is a division of the National Research Council, which serves the National Academy of Sciences and the National Academy of Engineering. The Board's mission is to promote innovation and progress in transportation through research. In an objective and interdisciplinary setting, the Board facilitates the sharing of information on transportation practice and policy by researchers and practitioners; stimulates research and offers research management services that promote technical excellence; provides expert advice on transportation policy and programs; and disseminates research results broadly and encourages their implementation. The Board's varied activities annually engage more than 5,000 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 individuals interested in the development of transportation. www.TRB.org www.national-academies.org

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COOPERATIVE RESEARCH PROGRAMS STAFF FOR NCHRP REPORT 549 ROBERT J. REILLY, Director, Cooperative Research Programs CRAWFORD F. JENCKS, Manager, NCHRP DAVID B. BEAL, Senior Program Officer EILEEN P. DELANEY, Director of Publications HILARY FREER, Senior Editor NCHRP PROJECT 12-61 PANEL Field of Design--Area of Bridges EDWARD P. WASSERMAN, Tennessee DOT (Chair) MARCUS H. ANSLEY, Florida DOT TIMOTHY BRADBERRY, Texas DOT VIJAY CHANDRA, Parsons Brinckerhoff, New York, NY SUSAN E. HIDA, California DOT PETER C. MCCOWAN, New York State DOT DENNIS R. MERTZ, University of Delaware, Newark, DE LOREN RISCH, Kansas DOT HALA ELGAALY, FHWA Liaison STEPHEN F. MAHER, TRB Liaison AUTHOR ACKNOWLEDGMENTS The research reported herein was performed under NCHRP Proj- of Illinois at Urbana-Champaign. The other Co-PIs and authors on ect 12-61 by the Department of Civil and Environmental Engineer- this report were Robert F. Mast, M. Lee Marsh, and Karl-Heinz ing at the University of Illinois at Urbana-Champaign, with subcon- Reineck. tracting services being provided by Berger/ABAM Engineers, Inc., The work was done under the general supervision of Neil M. and Karl-Heinz Reineck from the University of Stuttgart. Hawkins. The work at the University of Illinois was done under the The Principal Investigators on this project were Neil M. supervision of both Neil M. Hawkins and Daniel A. Kuchma, with Hawkins (PI) and Daniel A. Kuchma (Co-PI) from the University the assistance of Kang Su Kim, Sang-Ho Kim, and Shaoyun Sun.

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This report contains the findings of research performed to develop practical equa- FOREWORD tions for design of shear reinforcement in reinforced and prestressed concrete bridge By David B. Beal girders. Recommended specifications, commentary, and examples illustrating applica- Staff Officer tion of the specifications were also developed. The material in this report will be of Transportation Research immediate interest to bridge designers. Board Applying the LRFD shear provisions is difficult for designers. The sectional design model is not intuitively related to physical behavior, and the strut-and-tie model requires several trials to produce an efficient model and does not provide a unique solu- tion. Mechanistic models that can be applied to shear design of conventional structures and to estimate shear reinforcement requirements in more complex structural configu- rations are needed. Such tools would permit designers to develop a more intuitive feel for shear reinforcement needs and permit verification of solutions developed from auto- mated design software. The objective of this research was to supplement the LRFD methods for shear design with procedures providing a direct solution for transverse and longitudinal rein- forcement of concrete structures of common proportions. This work focused on development of resistance equations that yield unique solutions with defined limits of applicability. The recommended equations are similar in format and application to the resistance equations currently found in the AASHTO Standard Specifications. The equations apply to conventional structure types such as reinforced concrete T-beams, prestressed concrete I girders continuous for live load, prestressed concrete box beams, cast-in-place post-tensioned box girders, hammerhead piers and footings, and multi- post reinforced concrete bents and footings. The recommendations for additions to the LRFD specifications apply to precast concrete strengths up to 18 ksi and cast-in-place concrete strengths up to 10 ksi. This research was performed by the University of Illinois at Urbana-Champaign. The report fully documents the research leading to the recommended shear design pro- cedures and includes design examples. NCHRP Web-Only Document 78 contains extensive supporting information, including a database that can be used to compare the predictions from the recommended procedures to existing design procedures. AASHTO is expected to consider these recommendations for adoption in 2007.

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CONTENTS 1 SUMMARY 5 CHAPTER 1 Introduction and Research Approach 1.1 The AASHTO LRFD Shear Design Specifications, 5 1.1.1 Summary of the LRFD Sectional Design Model (S5.8.3), 5 1.1.2 Basis of the LRFD Sectional Design Model, 10 1.1.3 Comparison of AASHTO LRFD and AASHTO Standard Specifications, 11 1.2 Introduction to Shear Behavior and Design Practices, 12 1.2.1 Development of Traditional U.S. Code Provisions for Shear, 12 1.2.2 Compression Field Approaches for Modeling Shear Behavior, 14 1.2.3 Other Approaches and Design Provisions, 14 1.2.4 Factors Influencing Shear Resistance, 15 1.2.5 Experimental Test Data, 16 1.2.6 Analysis Tools, 16 1.2.7 Design Cases, 17 1.3 Project Objectives and Tasks, 18 1.3.1 Project Motivation and Objectives, 18 1.3.2 Research Approach and Project Tasks, 18 20 CHAPTER 2 Findings 2.1 Differences in Underlying Bases of Code Provisions, 20 2.1.1 Type 1: Empirical Relationships Designed to Fit Test Data, 20 2.1.2 Type 2: Relationships Based on Specific Condition of Member in Its Ultimate Limit State, 21 2.1.3 Type 3: Relationships Derived from Comprehensive Behavioral Model, 21 2.2 Comparison of Shear Design Methods, 23 2.3 Evaluation of Shear Design Methods Using Test Database, 26 2.4 Results of Survey of Practice, 28 2.5 Criteria for Proposed Simplified Provisions, 30 31 CHAPTER 3 Proposed Changes to LRFD Bridge Design Specifications 3.1 Change Proposal 1: Proposed Simplified Approach (Modified VCW and VCI or Modified Standard), 31 3.1.1 Basis of Proposed Simplified Provisions, 31 3.1.2 Proposed Simplified Provisions, 32 3.2 Change Proposal 2: Modification of LRFD Sectional Design Model (S5.8.3), 33 3.3 Discussion of Design Examples, 33 3.4 Evaluation of Simplified Provisions with Selected Test Data, 36 3.5 Comparison of Required Strength of Shear Reinforcement in Design Database, 37 3.6 Effect of Change Proposals on Design Process, 41 3.6.1 AASHTO-Standard Specifications LRFD Modified Sectional Design Method (CSA Method), 41 3.6.2 AASHTO-Standard Specifications LRFD Proposed Simplified Provisions (Modified Standard), 41 3.6.3 LRFD Sectional Design Model LRFD Modified Sectional Design Model (CSA Method), 42 3.6.4 LRFD Sectional Design Model LRFD Proposed Simplified Provisions (Modified Standard), 42 3.7 Safety and Economy of Structures Designed by Simplified Provisions, 42 3.7.1 Minimum Shear Reinforcement Requirements, 42 3.7.2 Maximum Shear Design Stress Limit, 42 3.7.3 Evaluation of Change Proposals Using Experimental Test Results, 43 3.7.4 Evaluation of Change Proposals using Design Cases Examples, 43 3.8 Utilization of NCHRP Process 12-50, 45 47 CHAPTER 4 Conclusions and Suggested Research 4.1 Conclusions, 47 4.1.1 Basis of Design Provisions, 47

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4.1.2 Role of Experimental Research and Field Experience, 47 4.1.3 Role of Design Database and Numerical Tools, 48 4.1.4 Differences in Shear Design Provisions, 48 4.2 Recommended Research, 49 50 NOTATION 53 REFERENCES