LIMIT STATE DESIGN FOR STRUCTURAL CONCRETE

INTRODUCTION

The structural analysis and design based on “Limit State Design” was developed from the traditional Elastic Design. The method improves the design to accurately reflect actual structural stress behavior and deformation characteristic with the requirements on various limit states of structures in both safety and service conditions. In the past, the Engineering Institute of Thailand under H.M. the King’s Patronage (EIT) had ever published “The Limit State Design Standard” drafted by past president, Dr.Siriluck Chandrangsu but it was based on old international standards. The drafting committee by faculty members of Chulalongkorn university therefore has revised and improved the standard to conform with current international standards. In addition, the committee has found that it is a good opportunity to provide also the English version of the Limit State Design for Structural Concrete so that Thai engineers as well as foreign engineers who work in Thailand can adopt as a standard reference for concrete structural design. Therefore the committee has translated the original Thai version of the standard into English and transfer copyright ownership to EIT for the publishing.
Any comments or suggestions, can be sent to EIT for further improvement

Drafting Committee
LIMIT STATE DESIGN FOR STRUCTURAL CONCRETE
A.D. 2016

SUBCOMMITTEE
LIMIT STATE DESIGN FOR STRUCTURAL CONCRETE
A.D. 2016

Standards Committee
1. Prof.Dr.Ekasit Limsuwan Chairperson
2. Prof.Dr.Somnuk Tangtermsirikul Committee
3. Prof.Dr.Amorn Pimanmas Committee
4. Assoc.Prof.Dr.Trakool Aramraks Committee
5. Assoc.Prof.Anek Siripanichgorn Committee
6. Mr.Anuchit Chareonsupkul Committee
7. Assoc.Prof.Dr.Withit Pansuk Secretary

Subcommittee Drafting Standards
1. Prof.Dr.Ekasit Limsuwan Advisor
2. Assoc.Prof.Dr.Tospol Pinkaew Chairperson
3. Prof.Dr.Thaksin Thepchatri Subcommittee
4. Assoc.Prof.Dr.Phoonsak Pheinsusom Subcommittee
5. Assoc.Prof.Dr.Withit Pansuk Subcommittee
6. Asst.Prof.Dr.Pitcha Jongvivatsakul Subcommittee
7. Asst.Prof.Dr.Watanachai Smittakorn Subcommittee
8. Assoc.Prof.Dr.Jaroon Rungamornrat Secretary

TABLE OF CONTENTS
Page
CHAPTER 1 BASIS OF DESIGN 1
1.1 General 1
1.2 Fundamental Requirements 1
1.3 Design Service Life 2
1.4 Limit State Design 2
1.5 Loads and Actions 3
1.6 Material Properties 4
1.7 Basic Design Rule 5
1.7.1 Ultimate Limit State (ULS) 5
1.7.2 Serviceability Limit State (SLS) 6
1.7.3 Durability Limit State (DLS) 6
1.7.4 Relevant Limit States 7
CHAPTER 2 MATERIAL CHARACTERISTICS 8
2.1 General 8
2.2 Concrete 8
2.2.1 Concrete strength grade 8
2.2.2 Stress-strain curve for concrete in compression 9
2.2.3 Modulus of elasticity 11
2.2.4 Concrete tensile strength 11
2.2.5 Poisson’s ratio 11
2.2.6 Thermal characteristic 11
2.2.7 Shrinkage and creep 12
2.2.8 Fatigue strength 14
2.3 Reinforcing Steel 15
2.3.1 Steel strength grade 15
2.3.2 Stress-strain curve for steel in tension 15
2.3.3 Modulus of elasticity 16
2.3.4 Poisson’s ratio 17
2.3.5 Thermal characteristic 17
2.3.6 Fatigue strength 17
2.3.7 Compressive strength 17
2.4 Prestressing steel 17
2.4.1 Prestressing steel strength grade 17
2.4.2 Stress-strain curve 17
2.4.3 Modulus of elasticity 18
2.4.4 Bond properties 19
2.4.5 Thermal characteristic 19
2.4.6 Relaxation 19
2.4.7 Fatigue strength 19
CHAPTER 3 LOADS AND ACTIONS 21
3.1 General 21
3.2 Characteristic Values 21
3.3 Permanent Loads 22
3.3.1 Dead load 22
3.3.2 Earth pressure 22
3.3.3 Hydrostatic pressure 23
3.4 Variable Loads 23
3.4.1 Live load 23
3.4.2 Wind load 24
3.4.3 Fluid dynamic force and wave action 24
3.4.4 Earthquake action 25
3.4.5 Temperature effect 25
3.4.6 Differential settlement 25
3.5 Accidental Loads 26
3.6 Construction Loads 26
3.7 Impact Loads 26
3.8 Environmental Actions 26
CHAPTER 4 STRUCTURAL RELIABILITY AND ANALYSIS 27
4.1 General 27
4.2 Statistic in Structural Concrete 27
4.2.1 Structural reliability 27
4.3 Structural Safety 29
4.4 Load Factor 30
4.4.1 General 30
4.5 Partial Safety Factor 31
4.5.1 Materials 31
4.5.2 Members 31
4.5.3 Structural Analysis 31
4.6 Structural Analyses 32
4.6.1 General 32
4.6.2 Structural response of ultimate limit state 32
4.6.3 Structural response of serviceability limit state 33
4.6.4 Structural response of durability limit state 33
4.6.5 Structural response of relevant limit states 33
CHAPTER 5 ULTIMATE LIMIT STATE 34
5.1 General 34
5.1.1 Design principle 34
5.1.2 Design strength of structural concrete 34
5.1.3 Limit states of strain gradient 37
5.2 Flexure 37
5.2.1 General 37
5.2.2 Flexural strength 39
5.2.3 Ductility and percentage of reinforcement 40
5.3 Tension and Compression 41
5.3.1 Axial tension 41
5.3.2 Axial compression 41
5.3.3 Interaction diagram 42
5.4 Shear 45
5.4.1 General 45
5.4.2 One-way shear 45
5.4.3 Punching shear 47
5.4.4 Deep beam shear 47
5.4.5 In-plane shear 49
5.5 Torsion 50
5.5.1 General 50
5.5.2 Torsional capacity for member cross-section 51
5.5.3 Torsion capacity of torsional reinforcement 51
5.6 Stability 54
5.6.1 Rigid body stability 54
5.6.2 Flexural member (lateral stability) 54
5.6.3 Thin wall structure 54
5.6.4 Slender compression member 56
CHAPTER 6 SERVICEABILITY LIMIT STATE 60
6.1 General 60
6.1.1 Principle 60
6.1.2 Actions and action effects 60
6.1.3 Material properties 61
6.2 Limit State of Stresses 62
6.2.1 General considerations 62
6.2.2 Stresses in concrete 62
6.2.3 Stresses in steel 62
6.3 Limit State of Cracking 63
6.3.1 Requirement 63
6.3.2 Limit crack width 63
6.3.3 Calculation of crack width 64
6.3.4 Flexural cracks 65
6.3.5 Shear cracks 66
6.3.6 Torsional cracks 66
6.4 Limit State of Deformation 66
6.4.1 Requirements 66
6.4.2 Instantaneous deformation 66
6.4.3 Long-term deformation 67
6.4.4 Limit state of deflection 68
6.5 Limit State of Vibration 69
6.6 Limit State of Fatigue 71
6.7 Limit State of Fire Rating 71
CHAPTER 7 DURABILITY LIMIT STATE 73
7.1 General 73
7.1.1 Principle 73
7.1.2 Exposure classes 73
7.1.3 Durability criteria 74
7.2 Durability Requirement 74
7.2.1 Deterioration mechanism 74
7.2.2 Chemical actions 74
7.2.3 Physical actions 75
7.2.4 Mechanical action 75
7.3 Durability Limit State 75
7.3.1 General impact 75
7.3.2 Chemical impact 75
7.3.3 Physical impact 76
7.3.4 Mechanical impact 76
CHAPTER 8 DESIGN OF STRUCTURAL MEMBERS 80
8.1 General 80
8.2 Slabs 80
8.2.1 General requirement 80
8.2.2 Cantilever slabs 81
8.2.3 One-way slabs 82
8.2.4 Two-way slabs 85
8.2.5 Flat slabs 86
8.3 Beams 92
8.3.1 General requirement 92
8.3.2 Isolated beam 96
8.3.3 Continuous beams 96
8.3.4 Deep beam 99
8.3.5 Corbels 100
8.4 Column 102
8.4.1 General requirements 102
8.4.2 Short column 102
8.4.3 Long column 105
8.4.4 Shear in column 105
8.5 Rigid Frame 105
8.5.1 General requirements 105
8.5.2 Non-sway frame 107
8.5.3 Sway frames 109
8.6 Walls 110
8.6.1 General requirements 110
8.6.2 Isolated wall 112
8.6.3 Core wall 113
8.7 Footing 113
8.7.1 General requirement 113
8.7.2 Spread footing 114
8.7.3 Pile footing and pile caps 117
8.7.4 Combined footing and mat foundation 117
CHAPTER 9 PRESTRESSED CONCRETE 120
9.1 General 120
9.1.1 Definition 120
9.1.2 Prestressing concept 120
9.1.3 Prestressing stages 120
9.1.4 Conformance standards 120
9.2 Types of Prestressing 121
9.2.1 Prestressing system 121
9.2.2 Prestressing structure 121
9.3 Initial Prestress 121
9.3.1 Prestressing steel 121
9.3.2 Time of prestressing 122
9.4 Losses of Prestress 122
9.4.1 Immediate losses 122
9.4.2 Time-dependent losses 124
9.5 Design Consideration 125
9.5.1 Design criteria for prestress 125
9.5.2 Design requirements 126
9.5.3 Design of prestress 127
CHAPTER 10 COMPOSITE STEEL AND
CONCRETE STRUCTURE 128
10.1 General 128
10.1.1 General provision 128
10.1.2 General requirements 128
10.2 Design Method 128
10.2.1 Selection of steel 128
10.2.2 Shear connector 128
10.2.3 Effect of shrinkage and creep of in-filled concrete 129
10.2.4 Limit states during erection 129
10.2.5 Structural performance 129
10.3 Composite Decks and Girders 129
10.3.1 Structural composite types 129
10.3.2 Ultimate limit state 130
10.3.3 Serviceability limit state 132
10.3.4 Structural details 132
10.4 Composite Columns 133
10.4.1 Types of composite columns 133
10.4.2 Ultimate limit state 133
10.4.3 Serviceability limit state 133
10.4.4 Structural details 133
CHAPTER 11 STRUT-TIE MODELS 135
11.1 General 135
11.2 Strength of Struts 136
11.2.1 Concrete struts 136
11.2.2 Reinforced concrete struts 138
11.2.3 Confined concrete struts 138
11.3 Strength of Ties 139
11.3.1 Steel ties 139
11.3.2 Concrete ties 140
11.4 Strength of Nodes 140
11.4.1 General 140
11.4.2 Compression nodes 140
11.4.3 Anchorage of reinforcing bars 140
CHAPTER 12 STRUCTURAL DETAILS 142
12.1 General 142
12.1.1 Structural members 142
12.1.2 Concrete cover 142
12.1.3 Clear distance 143
12.2 Bar Bending and Development of Reinforcement 144
12.2.1 Standard hooks 144
12.2.2 Longitudinal reinforcement 145
12.2.3 Stirrup, tie and hoop 145
12.2.4 Other reinforcement 145
12.3 Development of Reinforcement 149
12.3.1 General requirements 149
12.3.2 Critical sections for development of reinforcement 149
12.3.3 Development length 151
12.3.4 Anchorage, lap splice and termination of bars 152
12.3.5 Mechanical anchorage 153
12.4 Structural Details 153
12.4.1 Slabs 153
12.4.2 Beams 156
12.4.3 Columns 158
12.4.4 Rigid frame 160
12.4.5 Wall 162
12.4.6 Footing 163
12.5 Special Details 166
12.5.1 Corner 166
12.5.2 Edge 166
12.5.3 Opening 169
12.5.4 Supports 169
12.5.5 Joints 170
Appendix
Appendix A. 173
Appendix B. 174
Appendix C. 178

LIST OF ILLUSTRATIONS

Page
CHAPTER 2 MATERIAL CHARACTERISTICS 8
Fig. 2.1 Stress-strain curve for concrete in compression 10
Fig. 2.2 Shrinkage strain in concrete 13
Fig. 2.3 Creep coefficient in concrete 14
Fig. 2.4 Fatigue S-N curve for concrete 15
Fig. 2.5 Stress-strain curve for reinforcing steel in tension 16
Fig. 2.6 Stress-strain curve for prestressing steel in tension 18
CHAPTER 4 STRUCTURAL RELIABILITY AND ANALYSIS 27
Fig. 4.1 Distribution function of load or action (S) and resistance (R) 28
Fig. 4.2 Analyses for structural reliability 29
CHAPTER 5 ULTIMATE LIMIT STATE 34
Fig. 5.1 Design strength of concrete 35
Fig. 5.2 Design strength of reinforcing steel 36
Fig. 5.3 Design strength of prestressing steel 36
Fig. 5.4 Strain gradient for structural concrete member at the ultimate
limit state 37
Fig. 5.5 Stress-strain relationship of concrete in compression 38
Fig. 5.6 Stess-strain relationship of bonded reinforcing steel in tension 39
Fig. 5.7 Analysis for flexure of the cross-section 39
Fig. 5.8 Equivalent stress block for concrete in compression 40
Fig. 5.9 Axial compression of structural concrete member 43
Fig. 5.10 Interaction diagram for axial compression and bending moment 44
Fig. 5.11 Inclination angle of longitudinal reinforcement 46
Fig. 5.12 Deep beam shear 49
Fig. 5.13 Detail dimension for and for linear member 53
Fig. 5.14 Detail dimensions for and for planar members and
combination of linear and planar members 53
Fig. 5.15 Effective width of compression flange 55
Fig. 5.16 Spacing of lateral supports 55
Fig. 5.17 Buckling length for isolated columns 57
Fig. 5.18 Buckling length for actual column 59
CHAPTER 6 SERVICEABILITY LIMIT STATE 60
Fig. 6.1 Multiplier for long-term deformation 69
CHAPTER 8 DESIGN OF STRUCTURAL MEMBERS 80
Fig. 8.1 Restrained supports for cantilever slabs 81
Fig. 8.2 Effective width of cantilever slab (uniformly distributed load) 82
Fig. 8.3 Effective width of cantilever slab (concentrated load) 82
Fig. 8.4 Continuous one-way slabs 84
Fig. 8.5 Effective width of one-way slab subjected to concentrated load 84
Fig. 8.6 Minimum reinforcement for restraint and continuity in two-way slab 85
Fig. 8.7 Additional reinforcement at corners of two-way slab 86
Fig. 8.8 Flat slab systems 88
Fig. 8.9 Column strips and middle strips of flat slab system 89
Fig. 8.10 Flat slab system : column head 89
Fig. 8.11 Equivalent frame of flat slab system 90
Fig. 8.12 Distribution of moments 91
Fig. 8.13 Effective width of compression flange for flexure 94
Fig. 8.14 Load distribution on beam subjected to rectangular panel 95
Fig. 8.15 Critical loading for moments in continuous beam 97
Fig. 8.16 Critical loading for shear in continuous beam 98
Fig. 8.17 Design bending moment at intermediate support 99
Fig. 8.18 Corbel 101
Fig. 8.19 Truss model for corbel 101
Fig. 8.20 Tributary areas for axial forces in columns 103
Fig. 8.21 Effective length factors, of a column or compression member 104
Fig. 8.22 Column types 104
Fig. 8.23 Subframe for gravity loads or actions 106
Fig. 8.24 Substitute frame for lateral loads or action 107
Fig. 8.25 Bending moment of the section 107
Fig. 8.26 Non-Sway Frames 109
Fig. 8.27 Sway frames 109
Fig. 8.28 Structural system for walls 111
Fig. 8.29 Frame and wall interaction 112
Fig. 8.30 Critical cross section for flexure of spread footing 115
Fig. 8.31 Critical cross-section for shear of spread footing 116
Fig. 8.32 Pile footing and pile caps 118
Fig. 8.33 Critical cross-section for flexure of pile footing 118
Fig. 8.34 Critical cross-section for shear of pile footing 119
CHAPTER 10 COMPOSITE STEEL AND
CONCRETE STRUCTURE 128
Fig. 10.1 Shear connectors 129
Fig. 10.2 Composite decks and girders 131
Fig. 10.3 Composite columns 134
CHAPTER 11 STRUT-TIE MODELS 135
Fig. 11.1 Strut-tie model 135
Fig. 11.2 B region and D region of strut-tie model 136
Fig. 11.3 Equivalent compression block for concrete 137
Fig. 11.4 Capacity of confined concrete struts 139
Fig. 11.5 Typical nodes in strut-tie model 141
CHAPTER 12 STRUCTURAL DETAILS 142
Fig. 12.1 Bundled bars 144
Fig. 12.2 Standard hooks 144
Fig. 12.3 Inside diameter of bend for bent bar 147
Fig. 12.4 Reinforcement at a corner or a haunch 148
Fig. 12.5 Critical section for development of reinforcement 150
Fig. 12.6 Minimum reinforcement for slabs 154
Fig. 12.7 Minimum reinforcement at corner of slabs 155
Fig. 12.8 Reinforcement along a free edge of a slab 156
Fig. 12.9 Longitudinal reinforcement for beams 157
Fig. 12.10 Possible layouts of transverse reinforcement in beams 158
Fig. 12.11 Transverse reinforcement for columns 159
Fig. 12.12 Detail reinforcement of beam-column connection 159
Fig. 12.13 Typical haunch detail 160
Fig. 12.14 Embedment and development length corresponding to BMD 161
Fig. 12.15 Transverse and diagonal reinforcement 161
Fig. 12.16 Distribution of longitudinal reinforcement in a deep beam 162
Fig. 12.17 Detailed reinforcement for a deep beam with suspended loading 163
Fig. 12.18 Minimum reinforcement in footing 164
Fig. 12.19 Minimum depth of footing 165
Fig. 12.20 Shear-key and interface of reinforcement 165
Fig. 12.21 Recommended corner reinforcement 167
Fig. 12.22 Special detail for edges of slab 168
Fig. 12.23 Additional reinforcement in the vicinity of opening 169
Fig. 12.24 Addition reinforcement for supports and concentrated reaction 171
Fig. 12.25 Special provision for brackets or corbels 172

LIST OF TABLES

Page
CHAPTER 1 BASIS OF DESIGN 1
Table 1.1 Indicative design service life 2
CHAPTER 2 MATERIAL CHARACTERISTICS 8
Table 2.1 Concrete strength class (TIS 213 – 2552**) 9
Table 2.2 Final shrinkage strain in concrete (micro-strain, ) 12
Table 2.3 Final creep coefficient in concrete [ / (kg/cm2)] 13
Table 2.4 Fatigue strength for steel embedded in concrete (kg/cm2) 20
CHAPTER 3 LOADS AND ACTIONS 21
Table 3.1 Combination of design loads 21
Table 3.2 Unit Weights of Materials 23
CHAPTER 4 STRUCTURAL RELIABILITY AND ANALYSIS 27
Table 4.1 Recommended safety factor 29
Table 4.2 Load Factors 31
Table 4.3 Partial Safety Factor of Materials 31
Table 4.4 Partial Safety Factor of Members 32
CHAPTER 6 SERVICEABILITY LIMIT STATE 60
Table 6.1 Combination of actions for SLS 61
Table 6.2 Limits for the characteristic crack width 64
Table 6.3 Minimum thickness of non-prestressed beams and slabs 68
Table 6.4 Maximum permissible computed deflections 70
Table 6.5 Critical frequency in structures subject to vibrations caused
by movements of people 70
Table 6.6 Fire endurance of concrete structure 72
Table 6.7 Minimum concrete cover for fire protection 72
CHAPTER 7 DURABILITY LIMIT STATE 73
Table 7.1 Exposure classes related to environmental conditions 73
Table 7.2 General specification for exposure conditions 77
Table 7.3 Concrete cover subjected to exposure class and environment conditions 77
Table 7.4 Requirement for concrete exposed to air pollutants 78
Table 7.5 Durability limit state by cement type for concrete exposed to sulphate
(SO4) 78
Table 7.6 Maximum chloride content for corrosive protection 78
Table 7.7 Durability limit state of alkality by percentage of Calcium Hydroxide
[Ca(OH)2] (% by wt. of cement) 79
Table 7.8 Durability limit state for abrasive resistance (% by volume) 79
Table 7.9 Durability limit state by air content of permeable concrete 79
CHAPTER 9 PRESTRESSED CONCRETE 120
Table 9.1 and for calculation of friction losses 123
Table 9.2 Loss of prestress in the tendon due to shrinkage 125
Table 9.3 Practical values for the amount of prestress 126
CHAPTER 10 COMPOSITE STEEL AND
CONCRETE STRUCTURE 128
Table 10.1 Upper limits of tensile stress in steel 132
CHAPTER 12 STRUCTURAL DETAILS 142
Table 12.1 Concrete cover due to strength 143
Table 12.2 Inside diameter of bar bending 145
Table 12.3 Lap splice class and lap splice coefficient 153