Prestressed Concrete

916 Pages·2018·23.018 MB·English

by  Krishna Raju

Prestressed Concrete
Sixth Edition
IS: 1343-2012
BS EN: 1992-1-1-2004
ACI: 318M-2011
About the Author
N. Krishna Raju, Emeritus Professor of Civil
Engineering, M S Ramaiah Institute of Technology,
Bangalore, earned his PhD degree from the
University of Leeds, UK. He has taught at the
College of Engineering, Guindy, Chennai; Regional
Engineering College, Calicut; Lanchester College
of Technology, Coventry, UK; Indian Institute of
Science, Bangalore; and the Karnataka Regional
Engineering College, Surathkal. He was also a
visiting professor at the University of Basrah, Iraq, during 1979–82.
Dr Raju is the recipient of several awards, prominent among them being
The Sir Bowen Memorial Prize, Garudacharya and Krishna Iyengar Gold
Medals, UP Government National Award, Birla Super Endowment Award,
Eminent Civil Engineers Award, George Oomen Memorial Prize, Institution
of Engineers Prize, Naghadi Award and the ICI Silver Jubilee Award.
Dr Raju has published over 60 research papers in reputed journals and is
the author of several engineering monographs like Design of Concrete Mixes,
Prestressed Concrete, Design of Reinforced Concrete Structures, Advanced
Reinforced Concrete Design, Design of Bridges, Design and Drawing of
Reinforced Concrete and Steel Structures, Numerical Methods for Engineering
Problems, Structural Design and Drawing, Prestressed Concrete (Problems &
Solutions), Reinforced Concrete Structural Elements, Advanced Mechanics of
Solids and Structures, and Prestressed Concrete Bridges.
Dr Raju's textbooks have also been published in Indonesian and Arabic
languages. He is also a member of the Institution of Structural Engineers,
London, UK, the Institution of Engineers, India, and the Indian Concrete
Institute. He is socially active serving as the President of the Vijayanagar
Senior Citizen’s Forum and as an active anchor of Jai Maruthi Laughter Yoga
Club at Vijayanagar, Bangalore.
Prestressed Concrete
Sixth Edition
IS: 1343-2012
BS EN: 1992-1-1-2004
ACI: 318M-2011
N. Krishna Raju
B.E., M.Sc (Engg), Ph.D., M.I.E., M.I. Struct.E
Emeritus Professor of Civil Engineering
M S Ramaiah Institute of Technology, Bangalore
McGraw Hill Education (India) Private Limited
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Prestressed Concrete, 6e
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Eugene Freyssinet
(Father of Prestressing)
The book is dedicated to the pioneers and research workers
Eugene Freyssinet, Yves Guyon, Gustav Magnel,
Paul W. Abeles, M. Birkenmaier, F. Dischinger, Finister Walder,
T.Y. Lin, Fritz Leonhardt, Ben C. Gerwick Jr, R.H. Evans, E.W. Bennett,
P.E. Regan, J.J. Mc Namee, Y. Guyon, D.J. Dowrick, T.N. Subba Rao,
V.V. Mikhailov, V.K. Raina, Brandestini, Ros, Vogt, J.R. Libby, J. Muller,
R.E. Rowe, O.C. Zienkienwicz, W. Rockenhouser, P.B. Morice, A.R. Anderson,
W. Podolony, J.M. Crom, A.H. Mattock, Lee McCall, Shu-Tien-Li, G.S. Rama Swamy
and a host of others who toiled incessantly for the development and widespread use of
Prestressed Concrete

Contents
Preface to the Sixth Edition xvii
Preface to the First Edition xxi
List of Symbols xxiii
1. Introduction 1
1.1 Basic Concepts of Prestressing 1
1.2 Historical Development 1
1.3 Need for High-Strength Steel and Concrete 2
1.4 Terminology 3
1.5 Advantages of Prestressed Concrete 5
1.6 Applications of Prestressed Concrete 6
References 17
Review Questions 18
Objective-type Questions 19
Answers to Objective-type Questions 19
2. Materials for Prestressed Concrete 20
2.1 High-Strength Concrete 20
2.2 High-Tensile Steel 42
References 50
Review Questions 52
Objective-type Questions 53
Answers to Objective-type Questions 53
3. Prestressing Systems 54
3.1 Introduction 54
3.2 Tensioning Devices 54
3.3 Pretensioning Systems 55
3.4 Post-Tensioning Systems 57
3.5 Thermo-Electric Prestressing 67
3.6 Chemical Prestressing 68
References 68
Review Questions 69
Objective-type Questions 70
Answers to Objective-type Questions 71
viii Contents
4. Analysis of Prestress and Bending Stresses 72
4.1 Basic Assumptions 72
4.2 Analysis of Prestress 72
4.3 Resultant Stresses at a Section 74
4.4 Pressure Line or Thrust Line and Internal Resisting Couple 79
4.5 Concept of Load Balancing 88
4.6 Stresses in Tendons 94
4.7 Cracking Moment 99
References 101
Review Questions 101
Exercises 101
Objective-type Questions 104
Answers to Objective-type Questions 105
5. Losses of Prestress 106
5.1 Nature of Losses of Prestress 106
5.2 Loss Due to Elastic Deformation of Concrete 107
5.3 Loss of Prestress due to Shrinkage of Concrete 112
5.4 Loss of Prestress due to Creep of Concrete 115
5.5 Loss of Prestress due to Relaxation of Stress in Steel 117
5.6 Loss of Prestress due to Friction 118
5.7 Loss due to Anchorage Slip 122
5.8 Total Losses Allowed for in Design 124
References 130
Review Questions 130
Exercises 131
Objective-type Questions 133
Answers to Objective-type Questions 134
6. Deflections of Prestressed Concrete Members 135
6.1 Importance of Control of Deflections 135
6.2 Factors Influencing Deflections 135
6.3 Short-term Deflections of Uncracked Members 136
6.4 Prediction of Long-time Deflections 144
6.5 Deflections of Cracked Members 147
6.6 Requirements of Various Codes of Practise 163
References 170
Review Questions 171
Exercises 172
Objective-type Questions 173
Answers to Objective-type Questions 174
7. Flexural Strength of Prestressed Concrete Sections 175
7.1 Types of Flexural Failure 175
7.2 Strain Compatibility Method 177
7.3 Simplified Code Procedures 183
7.4 Comparative Analysis of Code Procedures 204
Contents ix
7.5 Sections with Steel in Compression Zone 207
References 214
Review Questions 214
Exercises 215
Objective-type Questions 216
Answers to Objective-type Questions 217
8. Shear and Torsional Resistance of Prestressed
Concrete Members 218
8.1 Shear and Principal Stresses 218
8.2 Ultimate Shear Resistance of Prestressed Concrete
Members 224
8.3 Design of Shear Reinforcements 231
8.4 Prestressed Concrete Members in Torsion 233
8.5 Design of Reinforcements for Torsion Shear and
Bending 239
References 250
Review Questions 252
Exercises 253
Objective-type Questions 255
Answers to Objective-type Questions 256
9. Transfer of Prestress in Pretensioned Members 257
9.1 Transmission of Prestressing Force by Bond 257
9.2 Transmission Length 257
9.3 Bond Stresses 261
9.4 Transverse Tensile Stresses 263
9.5 End-Zone Reinforcement 264
9.6 Flexural-Bond Stresses 266
9.7 Code Provisions for Bond and Transmission Length 268
References 270
Review Questions 271
Exercises 272
Objective-type Questions 273
Answers to Objective-type Questions 274
10. Anchorage Zone Stresses in Post-tensioned Members 275
10.1 Introduction 275
10.2 Stress Distribution in End Block 275
10.3 Investigations on Anchorage Zone Stresses 277
10.4 Comparative Analysis 293
10.5 Anchorage Zone Reinforcement 294
References 302
Review Questions 303
Exercises 303
Objective-type Questions 305
Answers to Objective-type Questions 306
x Contents
11. Limit-state Design Criteria for Prestressed Concrete Members 307
11.1 Introduction 307
11.2 Inadequacies of the Elastic and Ultimate Load Methods 307
11.3 Philosophy of Limit-state Design 308
11.4 Criteria for Limit States 309
11.5 Design Loads and Strengths 310
11.6 Strength and Serviceability Limit States 313
11.7 Crack Widths in Prestressed Members 316
11.8 Principles of Dimensioning Prestressed Concrete Members 327
References 328
Review Questions 330
Exercises 330
Objective-type Questions 331
Answers to Objective-type Questions 332
12. Design of Prestressed Concrete Sections 333
12.1 Design of Sections for Flexure 333
12.2 Design of Sections for Axial Tension 350
12.3 Design of Sections for Compression and Bending 353
12.4 Design of Prestressed Sections for Shear and Torsion 370
12.5 Design of Prestressed Members for Bond 370
12.6 Design of Prestressed Members for Bearing 371
References 372
Review Questions 373
Exercises 373
Objective-type Questions 375
Answers to Objective-type Questions 376
13. Design of Pretensioned and Post-tensioned Flexural Members 377
13.1 Dimensioning of Flexural Members 377
13.2 Estimation of Self-Weight of Beams 379
13.3 Design of Pretensioned Beams 379
13.4 Design of Post-tensioned Beams 385
13.5 Design of Partially Prestressed Members 392
References 405
Review Questions 406
Exercises 407
Objective-type Questions 409
Answers to Objective-type Questions 410
14. Composite Construction of Prestressed and in situ Concrete 411
14.1 Composite Structural Members 411
14.2 Types of Composite Construction 412
14.3 Analysis of Stresses 414
14.4 Differential Shrinkage 418
14.5 Deflection of Composite Members 422
14.6 Stresses at Serviceability Limit State 424