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Reinforced concrete design to Eurocode 2 Other bestselling titles from Palgrave Macmillan Reinforced Concrete Design to Eurocode 2 seventh edition Bill Mosley Formerly Senior Teaching Fellow, Nanyang Technological Institute, Singapore John Bungey Emeritus Professor of Civil Engineering, University of Liverpool, UK Ray Hulse Formerly Associate Dean, Faculty of Engineering and Computing, Coventry University, UK # W. H. Mosley and J. H. Bungey 1976, 1982, 1987, 1990 # W. H. Mosley, J. H. Bungey and R. Hulse 1999, 2007, 2012 All rights reserved. No reproduction, copy or transmission of this publication may be made without written permission. No portion of this publication may be reproduced, copied or transmitted save with written permission or in accordance with the provisions of the Copyright, Designs and Patents Act 1988, or under the terms of any licence permitting limited copying issued by the Copyright Licensing Agency, Saffron House, 6-10 Kirby Street, London EC1N 8TS. Any person who does any unauthorised act in relation to this publication may be liable to criminal prosecution and civil claims for damages. The authors have asserted their rights to be identified as the authors of this work in accordance with the Copyright, Designs and Patents Act 1988. First published 2012 by PALGRAVE MACMILLAN Palgrave Macmillan in the UK is an imprint of Macmillan Publishers Limited, registered in England, company number 785998, of Houndmills, Basingstoke, Hampshire RG21 6XS. Palgrave Macmillan in the US is a division of St Martin’s Press LLC, 175 Fifth Avenue, New York, NY 10010. Palgrave Macmillan is the global academic imprint of the above companies and has companies and representatives throughout the world. Palgrave1 and Macmillan1 are registered trademarks in the United States, United Kingdom, Europe and other countries ISBN-13: 978–0–230–30285–3 paperback This book is printed on paper suitable for recycling and made from fully managed and sustained forest sources. Logging, pulping and manufacturing processes are expected to conform to the environmental regulations of the country of origin. A catalogue record for this book is available from the British Library. A catalog record for this book is available from the Library of Congress. 10 9 8 7 6 5 4 3 2 1 21 20 19 18 17 16 15 14 13 12 Printed in China Dedicated to all our families for their encouragement and patience whilst writing this text This page intentionally left blank vii Contents Preface page x Acknowledgements xii Notation xiii 1 Introduction to design and properties of reinforced concrete 1 1.1 Design processes 2 1.2 Composite action 6 1.3 Stress–strain relations 8 1.4 Shrinkage and thermal movement 11 1.5 Creep 15 1.6 Durability 16 1.7 Specification of materials 16 2 Limit state design 20 2.1 Limit states 21 2.2 Characteristic material strengths and characteristic loads 22 2.3 Partial factors of safety 23 2.4 Combination of actions 28 2.5 Global factor of safety 32 3 Analysis of the structure at the ultimate limit state 33 3.1 Actions 34 3.2 Load combinations and patterns 35 3.3 Analysis of beams 36 3.4 Analysis of frames 43 3.5 Shear wall structures resisting horizontal loads 53 3.6 Redistribution of moments 58 4 Analysis of the section 63 4.1 Stress–strain relations 64 4.2 Distribution of strains and stresses across a section in bending 65 4.3 Bending and the equivalent rectangular stress block 67 4.4 Singly reinforced rectangular section in bending at the ultimate limit state 68 viii Contents 4.5 Rectangular section with compression reinforcement at the ultimate limit state 72 4.6 Flanged section in bending at the ultimate limit state 77 4.7 Moment redistribution and the design equations 84 4.8 Bending plus axial load at the ultimate limit state 88 4.9 Rectangular–parabolic stress block 96 4.10 Triangular stress block 98 5 Shear, bond and torsion 104 5.1 Shear 105 5.2 Anchorage bond 117 5.3 Laps in reinforcement 121 5.4 Analysis of section subject to torsional moments 123 6 Serviceability, durability and stability requirements 129 6.1 Detailing requirements 130 6.2 Span–effective depth ratios 140 6.3 Calculation of deflection 142 6.4 Flexural cracking 154 6.5 Thermal and shrinkage cracking 159 6.6 Other serviceability requirements 163 6.7 Limitation of damage caused by accidental loads 166 6.8 Design and detailing for seismic forces 171 7 Design of reinforced concrete beams 176 7.1 Preliminary analysis and member sizing 178 7.2 Design for bending of a rectangular section with no moment redistribution 180 7.3 Design for bending of a rectangular section with moment redistribution 185 7.4 Flanged beams 189 7.5 One-span beams 193 7.6 Design for shear 194 7.7 Continuous beams 198 7.8 Cantilever beams, corbels and deep beams 204 7.9 Curtailment and anchorage of reinforcing bars 210 7.10 Design for torsion 212 7.11 Serviceability and durability requirements 216 8 Design of reinforced concrete slabs 217 8.1 Shear in slabs 218 8.2 Span–effective depth ratios 224 8.3 Reinforcement details 225 8.4 Solid slabs spanning in one direction 226 8.5 Solid slabs spanning in two directions 231 8.6 Flat slab floors 236 8.7 Ribbed and hollow block floors 244 8.8 Stair slabs 250 8.9 Yield line and strip methods 253 Contents ix 9 Column design 261 9.1 Loading and moments 262 9.2 Column classification and failure modes 263 9.3 Reinforcement details 267 9.4 Short columns resisting moments and axial forces 269 9.5 Non-rectangular sections 279 9.6 Biaxial bending of short columns 282 9.7 Design of slender columns 285 9.8 Walls 289 10 Foundations and retaining walls 292 10.1 Pad footings 296 10.2 Combined footings 303 10.3 Strap footings 307 10.4 Strip footings 308 10.5 Raft foundations 311 10.6 Piled foundations 312 10.7 Design of pile caps 316 10.8 Retaining walls 320 11 Prestressed concrete 331 11.1 Principles of prestressing 333 11.2 Methods of prestressing 334 11.3 Analysis of concrete section under working loads 336 11.4 Design for the serviceability limit state 341 11.5 Analysis and design at the ultimate limit state 365 12 Water-retaining structures 381 12.1 Scope and principles 382 12.2 Joints in water-retaining structures 385 12.3 Reinforcement details 388 12.4 Basements and underground tanks 389 12.5 Design methods 390 13 Composite construction 407 13.1 The design procedure 410 13.2 Design of the steel beam for conditions during construction 411 13.3 The composite section at the ultimate limit state 414 13.4 Design of shear connectors 419 13.5 Transverse reinforcement in the concrete flange 423 13.6 Deflection checks at the serviceability limit state 426 Appendix 431 Further reading 442 Index 444 x Preface The purpose of this book is to provide a straightforward introduction to the principles and methods of design for concrete structures. It is directed primarily at students and young engineers who require an understanding of the basic theory and a concise guide to design procedures. Although the detailed design methods are generally according to European Standards (Eurocodes), much of the theory and practice is of a fundamental nature and should, therefore, be useful to engineers in countries outside Europe. The search for harmonisation of Technical Standards across the European Community (EC) has led to the development of a series of these Structural Eurocodes which are the technical documents intended for adoption throughout all the member states. The use of these common standards is intended to lower trade barriers and enable companies to compete on a more equitable basis throughout the EC. Eurocode 2 (EC2) deals with the design of concrete structures and, in the UK, has replaced BS8110. Eurocode 2 consist of 4 parts and adopts the limit state principles established in British Standards. This book refers primarily to part 1, dealing with general rules for buildings. Eurocode 2 must be used in conjunction with other European Standards including Eurocode 0 (Basis of Design) that deals with analysis and Eurocode 1 (Actions) that covers loadings on structures. Other relevant Standards are Eurocode 7 (Geotechnical Design) and Eurocode 8 (Seismic Design). Several UK bodies have also produced a range of supporting documents giving commentary and background explanation. Further supporting documentation includes, for each separate country, the National Annex which includes information specific to the individual member states and is supported in the UK by the British Standards publication PD 6687:2006 which provides background information. Additionally, the Concrete Centre has produced The Concise Eurocode for the Design of Concrete Buildings which contains material that has been distilled from EC2 but is presented in a way that makes it more user-friendly than the main Eurocode and contains only that information which is essential for the design of more everyday concrete structures. The Institution of Structural Engineers has also produced a new edition of their Design Manual. These latter two documents also contain information not included in EC2 such as design charts and design methods drawn from previous British Standards. The presentation of EC2 is oriented towards computer solution of equations, encompasses higher concrete strengths and is quite different from that of BS8110. xi Preface However the essential feature of EC2 is that the principles of design embodied in the document are almost identical to the principles inherent in BS8110. Hence, although there are some differences in details, engineers who are used to designing to the previous British Standard should have no difficulty in grasping the essential features of EC2. New grades of reinforcing steel are used and design is now based on concrete cylinder strength, with both of these features incorporated in this edition. Changes in terminology, arising partly from language differences, have resulted in the introduction of a few terms that may be unfamiliar to UK engineers. The most obvious of these is the use of actions to describe the loading on structures and the use of the terms permanent and variable actions to describe dead and imposed loads. Throughout this text, terminology has been kept as consistently as possible in line with accepted UK practice and hence, for example, loads have commonly, but not exclusively, been used instead of actions. Other ‘new’ terminology is identified at appropriate points in the text. The subject matter in this book has been arranged so that chapters 1 to 5 deal mostly with theory and analysis while the subsequent chapters cover the design and detailing of various types of member and structure. In order to include topics that are usually in an undergraduate course, there are sections on seismic design, earth-retaining structures as well as chapters on prestressed concrete and composite construction. A new chapter on water retaining structures has been added together with other new sections including the design of deep beams. Additions and modifications have also been made to reflect UK interpretation and practice in the use of EC2 since its introduction. Additional figures and examples have been added to assist understanding and a new section has been added to Chapter 1 to provide an introduction to design processes. This includes consideration of conceptual design, Sustainability and Health & Safety as well as the role of computer software in design. Important equations that have been derived within the text are highlighted by an asterisk adjacent to the equation number and in the Appendix a summary of key equations is given. Where it has been necessary to include material that is not directly provided by the Eurocodes, this has been based on currently accepted UK good practice. In preparing this new edition one aim has been to retain the structure and features of the earlier 5th edition of the well-established book Reinforced Concrete Design by Mosley, Bungey and Hulse (Palgrave) which is based on British Standards. By comparing both books it is possible to compare the essential differences between Eurocode 2 and previous British Standards and to contrast the different outcomes when structures are designed to either codes. It should be emphasised that Codes of Practice are always liable to be revised, and readers should ensure that they are using the latest edition of any relevant standard. Finally, the authors would like to thank Mr Charles Goodchild (The Concrete Centre) and Dr Steve Jones (Liverpool University) for their helpful comments and suggestions during the writing of this edition. xii Acknowledgements Permission to reproduce extracts from BS EN 1992-1-1: 2004 and BS EN 1990: 2002 is granted by British Standards Institution (BSI). No other use of this material is permitted. British Standards can be obtained in pdf or hard copy formats from the BSI online shop: http://shop.bsigroup.com or by contacting BSI Customer Services for hard copies only: Tel. +44 (0)20 8996 9001, Email: