Contribution of Steel Casing to Single Shaft Foundation Structural Resistance (2018)

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2018 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 RESEARCH REPORT 872 Contribution of Steel Casing to Single Shaft Foundation Structural Resistance Michel Bruneau University at BUffalo Buffalo, NY Hadi Kenarangi University at BUffalo Buffalo, NY Thomas P. Murphy Modjeski and Masters, inc. Mechanicsburg, PA Subscriber Categories Bridges and Other Structures 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 is the most effective way to solve 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 results in increasingly complex problems of wide inter- est to highway authorities. These problems are best studied through a coordinated program of cooperative research. Recognizing this need, the leadership of the American Association of State Highway and Transportation Officials (AASHTO) in 1962 ini- tiated an objective national highway research program using modern scientific techniques—the National Cooperative Highway Research Program (NCHRP). NCHRP is supported on a continuing basis by funds from participating member states of AASHTO and receives the full cooperation and support of the Federal Highway Administration, United States Department of Transportation. The Transportation Research Board (TRB) of the National Academies of Sciences, Engineering, and Medicine was requested by AASHTO to administer the research program because of TRB’s recognized objectivity and understanding of modern research practices. 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Published research 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 by going to http://www.national-academies.org and then searching for TRB Printed in the United States of America NCHRP RESEARCH REPORT 872 Project 12-93 ISSN 2572-3766 (Print) ISSN 2572-3774 (Online) ISBN 978-0-309-44682-2 Library of Congress Control Number 2018934509 © 2018 National Academy of Sciences. All rights reserved. COPYRIGHT INFORMATION 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, FRA, FTA, Office of the Assistant Secretary for Research and Technology, PHMSA, or TDC 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 research report was reviewed by the technical panel and accepted for publication according to procedures established and overseen by the Transportation Research Board and approved by the National Academies of Sciences, Engineering, and Medicine. The opinions and conclusions expressed or implied in this report are those of the researchers who performed the research and are not necessarily those of the Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; or the program sponsors. The Transportation Research Board; the National Academies of Sciences, Engineering, and Medicine; and the sponsors of 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 the report.

The National Academy of Sciences was established in 1863 by an Act of Congress, signed by President Lincoln, as a private, non- governmental institution to advise the nation on issues related to science and technology. Members are elected by their peers for outstanding contributions to research. Dr. Marcia McNutt is president. The National Academy of Engineering was established in 1964 under the charter of the National Academy of Sciences to bring the practices of engineering to advising the nation. Members are elected by their peers for extraordinary contributions to engineering. Dr. C. D. Mote, Jr., is president. The National Academy of Medicine (formerly the Institute of Medicine) was established in 1970 under the charter of the National Academy of Sciences to advise the nation on medical and health issues. Members are elected by their peers for distinguished contributions to medicine and health. Dr. Victor J. Dzau is president. The three Academies work together as the National Academies of Sciences, Engineering, and Medicine to provide independent, objective analysis and advice to the nation and conduct other activities to solve complex problems and inform public policy decisions. The National Academies also encourage education and research, recognize outstanding contributions to knowledge, and increase public understanding in matters of science, engineering, and medicine. Learn more about the National Academies of Sciences, Engineering, and Medicine at www.national-academies.org. The Transportation Research Board is one of seven major programs of the National Academies of Sciences, Engineering, and Medicine. The mission of the Transportation Research Board is to increase the benefits that transportation contributes to society by providing leadership in transportation innovation and progress through research and information exchange, conducted within a setting that is objective, interdisciplinary, and multimodal. The Board’s varied committees, task forces, and panels annually engage about 7,000 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. Learn more about the Transportation Research Board at www.TRB.org.

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 herein was performed under NCHRP Project 12-93 by the Department of Civil, Structural, and Environmental Engineering at the University at Buffalo (UB), State University of New York (SUNY), and Modjeski and Masters, Inc. UB was the contractor for this study, with the Research Foundation of SUNY serving as fiscal administrator. Modjeski and Masters, Inc. was a subcontractor. Dr. Michel Bruneau, P.Eng., professor of civil engineering at UB, was the project director and principal investigator. The other authors of this report are Mr. Hadi Kenarangi, research assistant and Ph.D. candi- date at UB, and Thomas P. Murphy, P.E., vice president of Modjeski and Masters, Inc. Mr. Muhammad Hassan, of NESPAK, Pakistan, contributed work to Appendices A, B, and C of this report while a master’s of science student at UB. All work of graduate students was done under the general supervision of Profes- sor Bruneau. CRP STAFF FOR NCHRP RESEARCH REPORT 872 Christopher J. Hedges, Director, Cooperative Research Programs Lori L. Sundstrom, Deputy Director, Cooperative Research Programs Waseem Dekelbab, Senior Program Officer Eileen P. Delaney, Director of Publications Natalie Barnes, Associate Director of Publications Heidi Willis, Editor NCHRP PROJECT 12-93 PANEL Field of Design—Area of Bridges Bijan Khaleghi, Washington State DOT, Tumwater, WA (Chair) Miguel Antonio Carbuccia, Biggs Cardosa Associates, Incorporated, Irvine, CA Peter J. Connors, Massachusetts DOT, Boston, MA Kyung Jun “K.J.” Kim, Raleigh, NC Amir Malek, California DOT, Sacramento, CA Michael Nop, Iowa DOT, Ames, IA Halil Sezen, Ohio State University, Columbus, OH Sung Min “Sean” Yoon, Texas DOT, Austin, TX Khalid Mohamed, FHWA Liaison

This report provides proposed revisions to the AASHTO LRFD Bridge Design Specifications and AASHTO Guide Specifications for LRFD Seismic Bridge Design for a single shaft founda- tion supporting a column to account for the contribution of steel casing and composite action on structural resistance with detailed examples of the application of the proposed revisions. The proposed revisions are based on comprehensive analytical and testing programs for investigating the effects of steel casing. The material in this report will be of immediate interest to highway structural engineers. Bridges are often constructed with a single enlarged shaft foundation supporting a col- umn. In many cases the shaft foundation is constructed with a permanent steel casing. The steel casing is typically ignored in design when calculating the structural resistance of the shaft; only the reinforced concrete section of the shaft is considered for structural resistance. Bridge designers would like to account for the added structural resistance of the steel casing, but there is limited research data as to when the steel casing and concrete inner core act as a composite section. The combination of the steel casing and the interior reinforced concrete is typically called Concrete-Filled Steel Tube (CFST) or Reinforced Concrete-Filled Steel Tube (RCFST). Determining the properties of the composite RCFST section and at what point along the shaft the section can be considered a composite section would be beneficial to design and could significantly reduce construction cost. Under NCHRP Project 12-93, the University at Buffalo was asked to propose revisions to the AASHTO LRFD Bridge Design Specifications and AASHTO Guide Specifications for LRFD Seismic Bridge Design for a single shaft foundation supporting a column to account for the contribution of steel casing including reinforced concrete confinement and composite action on structural resistance. The research considered axial, flexural, and shear effects under axial and lateral loading for strength and extreme event limit states for a steel cased reinforced concrete single enlarged shaft. A number of deliverables, provided as appendices, are not published but are available on the TRB project website. These appendices are titled as follows: • Appendix A – Review of Concrete-Filled Steel Tubes • Appendix B – Requirements for Design and Detailing of CFST • Appendix C – Comparison of DOTs Design Requirements • Appendix D – Review of Finite Element Modeling Methods of Reinforced Concrete Members • Appendix E – Plastic Stress Distribution Method • Appendix F – Properties of Finite Element Models Used in the Analytical Program F O R E W O R D By Waseem Dekelbab Staff Officer Transportation Research Board

• Appendix G – Design of Flexural Specimens • Appendix H – Construction and Preparation of the Test Specimens • Appendix I – Test Results • Appendix J – Finite Element Modeling of the Test Specimens • Appendix K – Design Examples • Appendix L – Quantifying the Economic Impact • Appendix M – CAD Drawings

1 Summary 5 Chapter 1 Background 5 1.1. Introduction 5 1.2. Objectives and Scope of Work 6 1.3. Review of Current Practice on the Design of Concrete-Filled Steel Tube (CFST) Drilled Shafts 8 1.3.1. Requirements for Specific Design Parameters 11 1.3.2. Type I and Type II Shafts 12 1.3.3. Standard Details 12 1.3.4. Review of the Other Countries’ Design Codes Requirements 14 1.4. Review of Design and Detailing Requirements for CFSTs 15 1.4.1. Requirement of Maximum Permitted D/t Ratio 17 1.4.2. Effective Flexural Stiffness 18 1.4.3. Strength of the CFST Shafts 19 1.5. Review of Finite Element Modeling Methods of Reinforced Concrete Shafts 20 Chapter 2 Research Approach 20 2.1. Introduction 20 2.2. Analytical Program 22 2.2.1. Enlarged Pile Shaft Simulation 24 2.2.2. Finite Element Modeling of RCFST Shaft 30 2.2.3. Analytical Program Matrix 34 2.2.4. Finite Element Models Used in This Study 35 2.2.5. Contribution of Casing and Reinforced Concrete Core 38 2.2.6. Effect of Friction Coefficient (Friction Force) 40 2.2.7. Non-Composite Behavior of RCFST 42 2.2.8. Non-Composite Behavior of CFST 45 2.2.9. Effect of Reinforcement in Composite RCFST and CFST 47 2.2.10. Effect of Shaft Height 57 2.2.11. Effect of Shaft Diameter 59 2.2.12. Effect of Attached Column 64 2.2.13. Effect of Axial Load 67 2.2.14. Effect of Steel Tube Thickness (Effect of D/t) 72 2.2.15. Cyclic Response of RCFST Shaft 79 2.2.16. Effect of Surrounding Soil 84 2.3. Testing Program 84 2.3.1. Test Specimens 87 2.3.2. Flexural Specimen Design Procedure 89 2.3.3. Loading Protocol 91 2.3.4. Test Setup Details 96 2.3.5. Construction and Preparation of the Specimens C O N T E N T S

100 Chapter 3 Findings and Applications 100 3.1. Introduction 100 3.2. Flexural Test Results and Findings 100 3.2.1. Force-Displacement Relationships of the Flexural Specimens 101 3.2.2. Comparison of the Flexural Specimens’ Strengths 107 3.2.3. Finite Element Modeling of the Flexural Tests 107 3.2.4. Finite Element Analyses of RCFST Shafts Embedded in the Soil 108 3.2.5. Moment–Curvature Relationships for the Flexural Test Specimens 113 3.2.6. Proposed Limit States for Displacement-Based Design 118 3.2.7. Effective Flexural Stiffness Equations for Force-Based Design 130 3.3. Shear Test Results and Findings 130 3.3.1. Force-Displacement Relationships of Shear Specimens 136 3.3.2. Comparison of the Shear Specimens’ Shear Strengths 140 3.3.3. Finite Element Modeling of the Shear Tests 141 3.3.4. Discussion of Finite Element Analyses Results of the Shear Tests 144 3.3.5. Proposed Shear Strength for RCFST Shafts 153 3.3.6. Comparison of the Proposed Shear Strength with the Experimental Data 157 3.4. Economic Impact 158 3.5. Design Examples for the Proposed Revisions 158 3.5.1. Example 1: Force-Based Design of RCFST 158 3.5.2. Example 2: Displacement-Based Design of RCFST 159 Chapter 4 Conclusions 159 4.1. Conclusions from the Analytical Program 160 4.2. Conclusions from Flexural and Shear Tests 163 4.3. Other Conclusions 164 References Note: Photographs, figures, and tables in this report may 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.