Contents iii Strengthening of reinforced concrete structures Using externally-bonded FRP composites in structural and civil engineering Edited by L C Hollaway and M B Leeming CRC Press Boca Raton Boston New York Washington, DC Cambridge England SORPR 3 12/19/98, 2:33 PM iv Contents Published by Woodhead Publishing Limited, Abington Hall, Abington Cambridge CB1 6AH, England Published in North and South America by CRC Press LLC, 2000 Corporate Blvd, NW Boca Raton FL 33431, USA First published 1999, Woodhead Publishing Ltd and CRC Press LLC Reprinted 2001 © 1999, Woodhead Publishing Ltd The authors have asserted their moral rights. This book contains information obtained from authentic and highly regarded sources. Reprinted material is quoted with permission, and sources are indicated. Reasonable efforts have been made to publish reliable data and information, but the authors and the publishers cannot assume responsibility for the validity of all materials. 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British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library. Library of Congress Cataloging in Publication Data A catalog record for this book is available from the Library of Congress. Woodhead Publishing ISBN 1 85573 378 1 CRC Press ISBN 0-8493-1715-0 CRC Press order number: WP1715 Cover design by The ColourStudio Typeset by Best-set Typesetter Ltd., Hong Kong Printed by TJI Digital, Padstow, Cornwall SORPR 4 12/19/98, 2:33 PM Contents v Contents Preface ix List of contributors xiii 1 Role of bonded fibre-reinforced composites in strengthening of structures 1 J J DARBY 1.1 Introduction 1 1.2 What is ‘strengthening with bonded fibre reinforced polymer composite plates’?1 1.3 The market for strengthening 2 1.4 Strengthening techniques 3 1.5 Advantages and disadvantages of FRP composite plate bonding 4 1.6 Client concerns when introducing new techniques 8 1.7 Risk to clients when adopting FRP composite plate bonding 8 1.8 Conclusions 10 2 Review of materials and techniques for plate bonding 11 L C HOLLAWAY AND M B LEEMING 2.1 Introduction 11 2.2 Structural adhesive bonding 11 2.3 External strengthening using steel plates 17 2.4 External strengthening using composite materials 21 2.5 Strengthening of reinforced concrete members in shear 34 2.6 Applications of FRP strengthening 36 2.7 Summary and conclusions of literature review 38 2.8 References 39 3 Materials 46 A R HUTCHINSON AND J QUINN v SORPR 5 12/19/98, 2:33 PM vi Contents 3.1 Adhesive bonded connections 46 3.2 Composite materials 47 3.3 Adhesive materials 57 3.4 Adhesion and surface preparation 68 3.5 The bonding operation 75 3.6 Durability and fire 80 3.7 Painting 80 3.8 Summary 80 3.9 References 81 4 Structural strengthening of concrete beams using unstressed composite plates 83 L C HOLLAWAY AND G C MAYS 4.1 Introduction 83 Part A Laboratory tests 84 4.2 General form and behaviour of loaded beams 84 4.3 Geometric parameters 91 4.4 Discussion 107 Part B Field investigation 109 4.5 Testing programme for 18m beam 109 4.6 Observations 131 4.7 Concluding remarks 132 4.8 References 132 5 Structural strengthening of concrete beams using prestressed plates 135 H N GARDEN AND G C MAYS 5.1 Introduction 135 5.2 Review of previous prestressing studies using composite plates 137 5.3 Prestressing technique employed in the laboratory 138 5.4 Results of laboratory tests for concrete beams strengthened with prestressed plates in the ROBUST programme 140 5.5 Results of field investigations of concrete beams strengthened with prestressed plates in the ROBUST programme 146 5.6 Observations 149 5.7 Concluding remarks 154 5.8 References 154 6 Environmental durability 156 A R HUTCHINSON AND L C HOLLAWAY SORPR 6 12/19/98, 2:33 PM Contents vii 6.1 Introduction 156 6.2 Environmental and service conditions 157 6.3 Factors affecting joint durability 158 6.4 Environmental durability of adhesive bonded joints 160 6.5 Procedures for assessing environmental effects on materials and on bonded joints 163 6.6 Effect of environment on the component materials used in the ROBUST system 166 6.7 Influence of surface treatment and effects of environment on joints and interfaces 173 6.8 Other factors affecting service performance 179 6.9 Summary 181 6.10 References 181 7 Time-dependent behaviour and fatigue 183 R A BARNES AND H N GARDEN 7.1 Introduction 183 PART A Time-dependent behaviour 183 7.2 Introduction 183 7.3 Time-dependent characteristics of concrete 184 7.4 Time-dependent characteristics of steel 184 7.5 Time-dependent characteristics of adhesives 184 7.6 Time-dependent characteristics of plated beams using steel plates 192 7.7 Time-dependent characteristics of FRP component materials and FRP composites 194 7.8 Time-dependent characteristics of plated beams using polymer composite plates 196 7.9 Creep tests conducted during the ROBUST project 197 PART B Fatigue behaviour 200 7.10 Introduction 200 7.11 Fatigue of unplated beams 201 7.12 Fatigue of adhesives 203 7.13 Fatigue of FRP materials 206 7.14 Fatigue of plated beams using steel plates 208 7.15 Fatigue of short span plated beams using FRP plates 211 7.16 Fatigue of long span plated 2.3 m beams using FRP plates 213 7.17 Concluding summary 217 7.18 References 218 8 Analytical and numerical solutions to structural strengthening of beams by plate bonding 222 P S LUKE SORPR 7 12/19/98, 2:33 PM viii Contents 8.1 Introduction 222 8.2 Classical analysis 223 8.3 Finite element analysis 223 8.4 Effect of adhesive material 231 8.5 Prestressed 18.0m concrete beams 231 8.6 Beams with unstressed plates 234 8.7 Beams with stressed plates 237 8.8 Concluding remarks 240 8.9 References 241 8.10 Bibliography 241 9 Design and specifications for FRP plate bonding of beams 242 M B LEEMING AND J J DARBY 9.1 Introduction 242 9.2 Practical design rules and guidelines 242 9.3 Application of the technique 257 9.4 Materials 258 9.5 Workmanship 260 9.6 Quality control 261 9.7 In-service inspection and maintenance 266 9.8 References 267 9.9 Bibliography 268 10 Site construction techniques 270 A P RIMOLDI 10.1 Introduction 270 10.2 Steel plate bonding 270 10.3 Adhesive bonding of carbon fibre composite plates – site requirements 272 10.4 Economics 286 10.5 Conclusion 287 10.6 References 287 11 Case studies of carbon fibre bonding worldwide 288 M A SHAW AND J F DREWETT 11.1 Introduction 288 11.2 System properties 289 11.3 Case histories 290 11.4 References 324 Index 325 SORPR 8 12/19/98, 2:33 PM Contents ix Preface Structures manufactured from engineering materials such as reinforced and prestressed concrete, steel and cast iron, although durable, do have a finite life. Structures with significant problems are those exposed to marine envi- ronments, de-icing salts on highways, aggressive industrial environments and to a lesser extent those which are exposed to normal weather condi- tions. From an economic point of view it is generally more realistic to repair, if possible, rather than to demolish and rebuild the structures. The in situ rehabilitation or upgrading of reinforced concrete members using bonded steel plates has been proven in the field to be an effective, convenient and economic method of improving structural performance. However, disadvantages inherent in the use of steel have stimulated re- search into the possibility of using fibre reinforced polymer (FRP) materials in its place, providing a non-corrosive, more versatile strengthening system; it can also be used for prestressed concrete. The construction industry is currently using polymer materials for the maintenance of structures and is showing great interest in the utilisation of FRP materials to maintain structural integrity or to upgrade structural systems. Advanced composite structural materials may have aligned con- tinuous fibres and/or aligned angle plies encapsulated in a polymer to form plates, rods, tubes and structural profiles; the fibres would be either carbon, aramid or glass. When used as a structural component to repair or strengthen a system the polymer composite may be either unstressed or pretensioned at the time of bonding. If two dissimilar materials which have composite action are to be used structurally, it is necessary for designers to have a thorough understanding of the mechanical and inservice material properties of the components, the methods of joining, the composite action and failure mechanisms and the overall structural analysis of these systems. The book presents a detailed study of the flexural strengthening of rein- forced and prestressed concrete members using fibre reinforced polymer composite plates encompassing both short term and long term performance ix SORPR 9 12/19/98, 2:33 PM x ContentsPreface through experimental testing at model and full scale and theoretical and numerical considerations.