tailieuxdcd@gmail.com Page iii DESIGN OF PRESTRESSED CONCRETE tailieuxdcd@gmail.com Page ii This page intentionally left blank tailieuxdcd@gmail.com Page iii DESIGN OF PRESTRESSED CONCRETE tailieuxdcd@gmail.com Page iv TITLES OF RELATED INTEREST Analytical and computational methods in engineering rock mechanics E.T.Brown (ed.) Boundary element methods in elastodynamics G.D.Manolis & D.E.Beskos Boundary element methods in solid mechanics S.L.Crouch & A.M.Starfield Computers in construction planning and control M.J.Jackson A concise introduction to engineering economics P.Cassimatis Distribution-free tests H.R.Neave & P.B.Worthington Earth structures engineering R.J.Mitchell The finite element method in thermomechanics T.-R.Tsu Hemispherical projection methods in rock mechanics S.D.Priest Hydraulic structures P.Novak et al Hydraulics in civil engineering A.Chadwick & J.Morfett Intelligent planning R.Wyatt Marine geotechnics H.Poulos Numerical methods in engineering and science G.deV.Davis Planning and design of engineering systems R.Warner & G.Dandy tailieuxdcd@gmail.com Plastic design P.Zeman & H.M.Irvine Rock mechanics for underground mining B.H.G.Brady & E.T.Brown Structural dynamics H.M.Irvine tailieuxdcd@gmail.com Page v DESIGN OF PRESTRESSED CONCRETE R.I.Gilbert & N.C.Mickleborough School of Civil Engineering The University of New South Wales, Sydney, Australia LONDON AND NEW YORK tailieuxdcd@gmail.com Page vi First published in 1990 by Unwin Hyman Ltd Transferred to Digital Printing 2004 Spon Press is an imprint of the Taylor & Francis Group This edition published in the Taylor & Francis e-Library, 2005 To purchase your own copy of this or any of Taylor & Francis or Routledge’s collection of thousands of eBooks please go to www.eBookstore.tandf.co.uk © R.I.Gilbert & N.C.Mickleborough, 1990 This book is copyright under the Berne Convention No reproduction without permission All rights reserved British Library Cataloguing in Publication Data Gilbert, R.I Design of prestressed concrete Prestressed concrete I Title II Mickleborough, N.C 666.893 ISBN 0-203-98586-9 Master e-book ISBN ISBN 0-419-16160-0 (Print Edition) Library of Congress Cataloging-in-Publication Data Gilbert, R.I., 1950– Design of prestressed concrete/R.I.Gilbert, N.C.Mickleborough p cm Includes bibliographical references ISBN 0-04-445402-3 (alk paper) ISBN 0-04-445403-1 (pbk.: alk paper) Prestressed concrete construction Structural design I.Mickleborough, N.C (Neil C.) II Title TA683.9.G52 1990 624.1' 83412–dc20 89–77745 CIP tailieuxdcd@gmail.com Page vii Preface The design of structures in general, and prestressed concrete structures in particular, requires considerably more information than is contained in building codes A sound understanding of structural behaviour at all stages of loading is essential The aim of this book is to present a detailed description and explanation of the behaviour of prestressed concrete members and structures both at service loads and at ultimate loads and, in doing so, provide a comprehensive guide to design The design criteria and procedures contained in several major building codes, including ACI 318–83, BS 8110:1985, and AS 3600–1988, are also presented Each aspect of the analysis and design of fully prestressed and partially prestressed concrete members is approached from first principles and illustrated by numerous worked examples The text is written for senior undergraduate and postgraduate students of civil and structural engineering, and also for practising structural engineers The book began as notes for a series of lectures to structural engineers in a short course on prestressed concrete design conducted in Sydney in 1985 and has been further developed over the past years as part of the authors’ involvement in research and the teaching of prestressed concrete to graduate students at the University of New South Wales The work has also gained much from the membership of Professor Gilbert on committees of the Standards Association of Australia and his involvement in the development of the Australian Standard for Concrete Structures, AS 3600–1988 The scope of the work ranges from an introduction to the fundamentals of prestressed concrete to in-depth treatments of more advanced topics Chapter introduces the basic concepts of prestressed concrete and the limit states design philosophies used in North American, British, European, and Australian practice Material properties relevant to design are discussed in Chapter A comprehensive treatment of the design of prestressed concrete beams for serviceability is presented in Chapter The instantaneous and time-dependent behaviour of cross-sections under service loads are discussed in considerable detail Both uncracked and cracked cross-sections are considered Techniques for determining the section size, the magnitude and eccentricity of prestress, the losses of prestress and the deflection of members are outlined Each aspect of design is illustrated by numerical examples Chapters and deal with the design of members for strength in bending, shear, and torsion, and Chapter covers the design of the anchorage zones tailieuxdcd@gmail.com Page viii in both pretensioned and post-tensioned members A guide to the design of composite prestressed concrete beams is provided in Chapter 7, and includes a detailed worked example of the analysis of a composite trough girder footbridge Chapter discusses design procedures for statically determinate beams Comprehensive self-contained design examples are provided for fully prestressed and partially prestressed, post-tensioned, and pretensioned concrete members The analysis and design of statically indeterminate beams and frames is covered in Chapter 9, and provides guidance on the treatment of secondary effects at all stages of loading Chapters 10 and 11 provide a detailed discussion of the analysis and design of two-way slab systems Chapter 10 is concerned with the behaviour and strength of slabs, whilst Chapter 11 deals with serviceability Complete design examples are provided for panels of an edgesupported slab and a flat slab The behaviour of axially loaded members is dealt with in Chapter 12 Compression members, members subjected to combined bending and compression, and prestressed concrete tension members are discussed and design aspects are illustrated by examples A special feature of the book is the treatment of serviceability aspects of design Concrete structures are prestressed to improve behaviour at service loads and thereby increase the economical range of concrete as a construction material In conventional prestressed structures, the level of prestress and the position of the tendons are usually based on considerations of serviceability Practical methods for accounting for the non-linear and timedependent effects of cracking, creep, shrinkage, and relaxation are presented in a clear and easy-to-follow format The authors hope that Design of Prestressed Concrete will be a valuable source of information and a useful guide to design R.I.Gilbert & N.C.Mickleborough Sydney, 1990 tailieuxdcd@gmail.com Page ix Contents Preface vii Notation xiii Basic concepts 1.1 Introduction 1.2 Methods of prestressing 1.3 Introductory example 1.4 Transverse forces caused by draped tendons 1.5 Calculation of elastic stresses 1.6 Flexural behaviour—from initial to ultimate loads 15 1.7 Design procedures 17 1.8 References 28 Design properties of materials 29 2.1 Introduction 29 CONCRETE 2.2 Composition of concrete 30 2.3 Strength of concrete 30 2.4 Deformation of concrete 34 2.5 Predictions of the creep coefficient and shrinkage 42 2.6 Thermal expansion 47 STEEL 2.7 Steel used for prestressing 48 2.8 Steel relaxation 52 2.9 Non-prestressed reinforcement 54 2.10 References 58 tailieuxdcd@gmail.com Page x Design for serviceability 60 3.1 Introduction 60 3.2 Stress limits 61 3.3 Determination of prestress and eccentricity in flexural members 64 3.4 Cable profiles 75 3.5 Short-term analysis of cross-sections 77 3.6 Time-dependent analysis of cross-sections 89 3.7 Losses of prestress 102 3.8 Deflection calculations 108 3.9 References 120 Ultimate flexural strength 121 4.1 Introduction 121 4.2 Flexural behaviour at overloads 122 4.3 Flexural strength theory 124 4.4 Approximate code-oriented procedures 140 4.5 Design calculations 147 4.6 Flanged sections 153 4.7 References 159 Design for shear and torsional strength 5.1 Introduction 160 160 SHEAR IN BEAMS 5.2 Inclined cracking 161 5.3 Effect of prestress 162 5.4 Web reinforcement 163 5.5 Shear strength 165 TORSION IN BEAMS 5.6 Compatibility torsion and equilibrium torsion 182 5.7 Effects of torsion 183 5.8 Design provisions for torsion in AS 3600–1988 185 tailieuxdcd@gmail.com Page xi SHEAR IN SLABS AND FOOTINGS 5.9 Punching shear 195 5.10 Design procedures for punching shear in AS 3600–1988 198 5.11 References 208 Anchorage zones 209 6.1 Introduction 209 6.2 Pretensioned concrete—force transfer by bond 210 6.3 Post-tensioned concrete anchorage zones 214 6.4 References 238 Composite members 240 7.1 Types and advantages of composite construction 240 7.2 Behaviour of composite members 242 7.3 Stages of loading 243 7.4 Determination of prestress 246 7.5 Methods of analysis at service loads 249 7.6 Ultimate flexural strength 265 7.7 Horizontal shear transfer 265 7.8 Ultimate shear strength 275 7.9 References 280 Design procedures for determinate beams 281 8.1 Introduction 281 8.2 Types of section 281 8.3 Initial trial section 283 8.4 Design procedures—fully prestressed beams 286 8.5 Design procedures—partially prestressed beams 312 Statically indeterminate members 319 9.1 Introduction 319 9.2 Tendon profiles 321 9.3 Continuous beams 323 9.4 Staticaily indeterminate frames 350 9.5 Design of continuous beams 354 9.6 References 375 tailieuxdcd@gmail.com Page xii 10 Two-way slabs—behaviour and design 376 10.1 Introduction 376 10.2 Effects of prestress 378 10.3 Design approach—general 381 10.4 One-way slabs 382 10.5 Two-way edge-supported slabs 382 10.6 Flat plate slabs 394 10.7 Flat slabs with drop panels 415 10.8 Band-beam and slab systems 416 10.9 References 417 11 Two-way slabs—serviceability 418 11.1 Introduction 418 11.2 The balanced load stage 419 11.3 Initial sizing of slabs 421 11.4 A review of simplified slab deflection models 429 11.5 Cracking in prestressed slabs 438 11.6 Long-term deflections 442 11.7 Worked examples 443 11.8 References 452 12 Compression and tension members 454 12.1 Types of compression members 454 12.2 Classification and behaviour of compression members 455 12.3 Cross-sectional analysis—compression and bending 457 12.4 Slenderness effects 471 12.5 Reinforcement requirements in compression members 481 12.6 Tension members 483 12.7 References 489 Appendix I Alternative models for creep and shrinkage 490 A.1 Introduction 490 A.2 The ACI Committee 209 Method (1978) 490 A.3 The CEB–FIP Method (1978) 493 A.4 References 497 Index 498 tailieuxdcd@gmail.com tailieuxdcd@gmail.com