UNIVERSITY of NAPLES FEDERICO II PH.D. PROGRAMME in MATERIALS and STRUCTURES ENGINEERING XX CYCLE PH.D. THESIS RAFFAELLO FICO LIMIT STATES DESIGN of CONCRETE STRUCTURES REINFORCED with FRP BARS COORDINATOR TUTOR Prof. DOMENICO ACIERNO Dr. ANDREA PROTA UNIVERSITY OF NAPLES FEDERICO II PH.D. PROGRAMME IN MATERIALS and STRUCTURES ENGINEERING COORDINATOR PROF. DOMENICO ACIERNO XX CYCLE PH.D. THESIS RAFFAELLO FICO LIMIT STATES DESIGN of CONCRETE STRUCTURES REINFORCED with FRP BARS TUTOR Dr. ANDREA PROTA iv “Memento audere semper” G. D’annunzio v vi ACKNOWLEDGMENTS To Dr. Manfredi, my major professor, I express my sincere thanks for making this work possible. His valuable teachings will be engraved in my mind forever. I am very grateful to Dr. Prota for his assistance and devotion; his experience and observations helped me a lot to focus on my work. I have learned many things from him during the last three years. I wish to express sincere appreciation to Dr. Nanni for animating my enthusiasm each time that I met him. A special thank goes to Dr. Parretti for supporting me any time that I asked. I would like to thank my dearest parents for making me believe in my dreams and for constantly supporting me to achieve them. I would like to extend my deepest regards to my beloved brothers and sister for being there with me throughout. My deepest thank goes to the friends (they know who they are) that shared with me the most significant moments of these years. Finally, I would like to thank all friends and colleagues at the Department of Structural Engineering who have contributed in numerous ways to make this program an enjoyable one. vii viii Limit States Design of Concrete Structures Reinforced with FRP Bars INDEX ACKNOWLEDGMENTS…………………………………...vii Chapter I: INTRODUCTION………………………….......13 1.1 BACKGROUND………………………………………………………13 1.2 OBJECTIVES………………………………………………………....15 1.3 THESIS ORGANIZATION………………………………………….15 Chapter II: LITERATURE REVIEW…………………...…16 2.1 HISTORY OF FRP REINFORCEMENT…………………………....16 2.2 PROPERTIES OF FRP BARS………………………………………..17 2.3 FORMS OF FRP REINFORCEMENT………………………………20 2.4 TYPICAL APPLICATIONS………………………………………..…22 2.5 REVIEW of EXISTING GUIDELINES DESIGN PHILOSOPHY on FRP RC…………………………………………………………….…...27 2.5.1 European Design Guidelines………………………………………………………..31 2.5.2 Japanese Design Guidelines………………………………………………………...31 2.5.3 Canadian Design Guidelines………………………………………………………..31 2.5.4 American Design Guidelines………………………………………………………..32 Chapter III: ULTIMATE FLEXURAL BEHAVIOR………………………………………………...36 3.1 INTRODUCTION……………………………………………………...36 3.2 GENERAL PRINCIPLES……………………………………………..36 3.3 PARTIAL FACTORS………………………………………………….38 3.4 RELIABILITY STUDY………………………………………………..38 ix Index 3.4.1 Reliability Index……………………………………………………………………..38 3.4.2 Background…………………………………………………………………………..41 3.4.3 Provisions on Flexural Capacity Design…………………………………………....42 3.4.4 Variables Affecting the Flexural Strength of GFRP-RC Members……………...44 3.4.5 Statistical Properties………………………………………………………………...52 3.4.6 Sample Design Space………………………………………………………………...53 3.4.7 Resistance Models for Flexural Capacity of FRP-RC Members…………………54 3.4.8 Used Load Model…………………………………………………………………….59 3.4.9 Reliability Analysis……………………………………………………………….….60 3.4.10 Reliability Index of Beams…………………………………………………………..63 3.4.11 Reliability Index of Beams Depending on γf and on ML/MD………………………64 3.4.12 Reliability Index of Beams Depending on γf, Regardless of ML/MD……………....66 3.4.13 Reliability Index of Beams Accounting for P, M and F…………………………...68 3.4.14 Reliability Index of Beams Depending on γf and γc………………………………..69 3.4.15 Minimum Reliability Index of Beams………………………………………………70 3.4.16 Reliability Index of Slabs……………………………………………………………72 3.4.17 Reliability Index of Slabs Depending on γf, Regardless of ML/MD………………..73 3.4.18 Reliability Index of Slabs Accounting for P, M and F…………………………….74 3.1 CONCLUSIVE REMARKS…………………………………………...75 Chapter IV: SERVICEABILITY FLEXURAL BEHAVIOR...………………………………………………78 4.1 INTRODUCTION……………………………………………………...78 4.2 SERVICEABILITY LIMIT STATE…………….……………………78 4.3 BOND…………………………………………………………………...80 4.3.1 Bond Tests……………………………………………………………………………81 4.3.2 Types of Failure……………………………………………………………………...83 4.3.3 Factors Affecting Bond……………………………………………………………...83 x Limit States Design of Concrete Structures Reinforced with FRP Bars 4.4 CALIBRATION OF BOND COEFFICIENT “m”…………………..84 4.4.1 Test Specimens and Variables……………………………………………………...85 4.4.2 Cracking Moment…………………………………………………………………...90 4.4.3 Calibration Analysis………………………………………………………………...91 4.5 CONCLUSIVE REMARKS………………………………………….102 CHAPTER V: SHEAR ULTIMATE BEHAVIOR...…………………………………………......105 5.1 INTRODUCTION…………………………………………………105 5.2 LITERATURE REVIEW…………………………………………105 5.3 REVIEW OF CURRENT DESIGN PROVISIONS……………..109 5.3.1 ACI 440.1R-06 Design Guidelines…………………………………………………109 5.3.2 CAN/CSA-S806_02 Design Guidelines……………………………………………111 5.3.3 JSCE Design Guidelines…………………………………………………………...113 5.3.4 Italian Guidelines…………………………………………………………………..114 5.4 COMPARISON BETWEEN EXPERIMENTAL RESULTS AND CODES PREDICTIONS………………………………………………...116 5.4.1 Members Without Shear Reinforcement…………………………………………116 5.4.2 Members With Shear Reinforcement…………………………………………….119 5.4.3 Influence of Bent Strength of Stirrups and Shear Reinforcement Ratio……….123 5.5 CONCLUSIVE REMARKS………………………………………127 Chapter VI: TEST METHODS FOR THE CHARACTERIZATION OF FRP BARS………………………………………………............128 xi Index 6.1 INTRODUCTION…………………………………………………….128 6.2 MECHANICAL CHARACTERIZATION OF LARGE-DIAMETER GFRP BARS……………………………………………….............................129 6.2.1 Overview of the Existing Standard Test Methods………………………………..129 6.2.2 Experimental Program…………………………………………………………….130 6.2.3 Test Results…………………………………………………………………………135 6.3. CONCLUSIVE REMARKS……………………………………………137 Chapter VII: CONCLUSIONS……………………………138 7.1 ULTIMATE FLEXURAL BEHAVIOR….…………………………138 7.2 SERVICEABILITY FLEXURAL BEHAVIOR……………………140 7.3 SHEAR ULTIMATE BEHAVIOR…………......……………………141 7.4 TEST METHODS FOR THE CHARACTERIZATION OF FRP BARS………………………………………………………………………....142 7.5 RECOMMENDATIONS……………………………………………..143 REFERENCES……………………………………………143 Appendix A: DESIGN CASES……………………………158 VITA………………………………………………………………………………………..167 xii Limit States Design of Concrete Structures Reinforced with FRP Bars Chapter I: INTRODUCTION 1.1 BACKGROUND Design Guidelines CNR-DT 203/2006, “Guide for the Design and Construction of Concrete Structures Reinforced with Fiber-Reinforced Polymer Bars”, have been lately developed under the auspices of the National Research Council (CNR). The new document (see front page in Figure 1) adds to the series of documents recently issued by the CNR on the structural use of fiber reinforced polymer (FRP) composites, started with the publication of CNR-DT 200/2004, pertaining to the use of externally bonded systems for strengthening concrete and masonry structures. The approach followed is that of the limit states semi-probabilistic method, like all the main current guidelines, while the format adopted is that of ‘principles’ and ‘practical rules’, in compliance with the classical style of Eurocodes. It is also conceived with an informative and educational spirit, which is crucial for the dissemination, in the professional sphere, of the mechanical and technological knowledge needed for an aware and competent use of such materials. A guideline, by its nature, is not a binding regulation, but merely represents an aid for practitioners interested in the field of composites. Nevertheless, the responsibility of the operated choices remains with the designer. The document is the result of a remarkable joint effort of researchers from 7 Italian universities and practitioners involved in this emerging and promising field, of the technical managers of major production and application companies, and of the representatives of public and private companies that use FRP as reinforced concrete (RC) reinforcement (see Figure 2). Thus, the resulting FRP code naturally encompasses all the experience and knowledge gained in ten years of countless studies, researches and applications of FRP in Italy, joined to the learning gathered from the available international codes on the design of FRP RC structures. After its publication, the document n. 203/2006 was subject to a public hearing between February and May 2006. Following the public hearing, some modifications and/or integrations have been made to the document including corrections of typos, 13 Chapter I additions of subjects that had not been dealt with in the original version, and elimination of others deemed not to be relevant. The updated document has been approved as a final version on 18/06/2007 by the “Advisory Committee on Technical Recommendation for Construction”. Figure 1 - Front Page of CNR-DT 203/2006 Task Group Contents University of Bologna Materials Polytechnic of Milan Basis of Design Appendix A University of Naples “Federico II” (manufacturing techniques of FRP bars) University of Rome “La Sapienza” Appendix B University of Rome “Tor Vergata” (test methods for characterizing FRP bars) University of Salerno Appendix C University of Sannio - Benevento (technical data sheet for FRP bars) ATP Pultrusion - Angri (SA) Appendix D Hughes Brothers - Nebraska, U.S.A. (tasks and responsibilities of professionals) Interbau S.r.l.- Milan Appendix E Sireg - Arcore (MI) (deflections and crack widths) Figure 2 - Task Group and Contents of CNR-DT 203/2006 14 Limit States Design of Concrete Structures Reinforced with