Summary Prestressed Concrete Design

Preface xi Symbols xii 1 Basic principles 1 1.1 Introduction 1 1.2 Methods of prestressing 6 1.3 Structural behaviour 9 1.4 Internal equilibrium 12 1.5 Deflected tendons 16 1.6 Integral behaviour 18 1.7 Forces exerted by tendons 19 1.8 Loss of prestress force 23 1.9 Degrees of prestressing 24 1.10 Safety 25 Problems 25 2 Properties of materials 29 2.1 Strength of concrete 29 2.2 Modulus of elasticity of concrete 30 2.3 Creep of concrete 32 2.4 Shrinkage of concrete 32 2.5 Lightweight concrete 34 2.6 Steel for prestressing 34 2.7 Relaxation of steel 36 2.8 Stress-strain curves for steel 37 2.9 Corrosion of steel 40 3 Limit state design 42 3.1 Introduction 42 3.2 Limit states 42 3.3 Characteristic loads and strengths 44 Page viii 3.4 Partial factors of safety 46 3.5 Stress-strain curves 48 3.6 Loading cases 49 3.7 Allowable stresses 51 3.8 Fire resistance 51 3.9 Fatigue 53 3.10 Durability 54 3.11 Vibration 55 4 Loss of prestress force 57 4.1 Introduction 57 4.2 Elastic shortening 58 4.3 Friction 61 4.4 Anchorage draw-in 67 4.5 Variation of initial prestress force along a member 67 4.6 Long-term losses 70 4.7 Total prestress losses 73 4.8 Measurement of prestress force 73 4.9 Initial overtensioning 76 Problems 76 5 Analysis of sections 79 5.1 Introduction 79 5.2 Serviceability limit state 80 5.3 Additional steel stress due to bending 83 5.4 Post-cracking behaviour 84 5.5 Ultimate load behaviour 86 5.6 Variation of steel stress 90 5.7 Design ultimate strength 91 5.8 Simplified concrete stress block 94 5.9 Design charts 94 5.10 Untensioned reinforcement 96 5.11 Cracked members 97 5.12 Members with unbonded tendons 100 Problems 103 6 Deflections 107 6.1 Limits to deflection 107 6.2 Short-term deflections of uncracked members 108 6.3 Long-term deflections 112 6.4 Deflections of cracked members 113 6.5 Load balancing 117 6.6 Load-deflection curves 118 Problems