Concrete Buildings in Seismic Regions

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Concrete Buildings in Seismic Regions

Contents 

1  Introduction  

1.1  Historical notes  1
1.2  Structure of this book  4

2  An overview of structural dynamics  

2.1  General  5
2.2  Dynamic analysis of elastic single-degree-of-freedom systems  6
2.2.1  Equations of motion  6
2.2.2  Free vibration  7
2.2.3  Forced vibration  10
2.2.4  Elastic response spectra  13
2.2.4.1  Definition: Generation   13
2.2.4.2  Acceleration response spectra  16
2.2.4.3  Displacement response spectra  19
2.2.4.4  Velocity response spectra  20
2.2.4.5  Acceleration-displacement response spectra  21
2.3  Dynamic analysis of inelastic SDOF systems  22
2.3.1  Introduction  22
2.3.2  Viscous damping  22
2.3.3  Hysteretic damping  25
2.3.4  Energy dissipation and ductility  27
2.3.5  Physical meaning of the ability for energy absorption (damping)  32
2.3.6  Inelastic response spectra  35
2.3.6.1  Inelastic acceleration response spectra  35
2.3.6.2  Inelastic displacement response spectra  36
2.4  Dynamic analysis of MDOF elastic systems  37
2.4.1  Introduction  37
2.4.2  Equations of motion of plane systems  37
2.4.3  Modal response spectrum analysis versus time–history analysis  41
2.4.3.1  General  41
2.4.3.2  Modal response spectrum analysis  42
2.4.3.3  Time-history analysis  45
2.4.4  Pseudospatial structural single-storey system  46
2.4.4.1  General  46
2.4.4.2  Static response of the single-storey 3D system  48
2.4.4.3  Dynamic response of a single-storey 3D system  54
2.4.4.4  Concluding remarks  58
2.5  Dynamic analysis of MDOF inelastic systems  62
2.5.1  Introduction  62
2.5.2  Methodology for inelastic dynamic analysis of MDOF plane systems  63
2.5.3  Concluding remarks  69
2.6  Application example  70
2.6.1  Building description  71
2.6.2  Design specifications  71
2.6.3  Modelling assumptions  72
2.6.4  Static response  72
2.6.5  Hand calculation for the centre of stiffness  72
2.6.6  Mass calculation  73
2.6.7  Base shear calculation  73
2.6.8  Computer-aided calculation for the centre of stiffness  76
2.6.9  Dynamic response  79
2.6.10  Estimation of poles of rotation for building B  79

3  Design principles, seismic actions, performance requirements,compliance criteria  

3.1  Introduction  83
3.2  Conceptual framework of seismic design: Energy balance  84
3.2.1  General  84
3.2.2  Displacement-based design  88
3.2.2.1  Inelastic dynamic analysis and design  88
3.2.2.2  Inelastic static analysis and design  88
3.2.3  Force-based design  90
3.2.4  Concluding remarks  92
3.3  Earthquake input  93
3.3.1  Definitions  93
3.3.2  Seismicity and seismic hazard  98
3.3.2.1  Seismicity  99
3.3.2.2  Seismic hazard  100
3.3.3  Concluding remarks  102
3.4  Ground conditions and design seismic actions  103
3.4.1  General  103
3.4.2  Ground conditions  105
3.4.2.1  Introduction  105
3.4.2.2  Identification of ground types  105Contents  vii
3.4.3  Seismic action in the form of response spectra  105
3.4.3.1  Seismic zones  105
3.4.3.2  Importance factor  106
3.4.3.3  Basic representation of seismic action in the form of a response spectrum  108
3.4.3.4  Horizontal elastic response spectrum  109
3.4.3.5  Vertical elastic response spectrum  111
3.4.3.6  Elastic displacement response spectrum  112
3.4.3.7  Design spectrum for elastic analysis  113
3.4.4  Alternative representation of the seismic action  115
3.4.4.1  General  115
3.4.4.2  Artificial accelerograms  115
3.4.4.3  Recorded or simulated accelerograms  116
3.4.5  Combination of seismic action with other actions  117
3.5  Performance requirements and compliance criteria  118
3.5.1  Introduction  118
3.5.2  Performance requirements according to EC 8-1/2004  120
3.5.3  Compliance criteria  122
3.5.3.1  General  122
3.5.3.2  Ultimate limit state  122
3.5.3.3  Damage limitation state  124
3.5.3.4  Specific measures  124

4  Configuration of earthquake-resistant R/C structural systems:Structural behaviour  

4.1  General  125
4.2  Basic principles of conceptual design  126
4.2.1  Structural simplicity  126
4.2.2  Structural regularity in plan and elevation  126
4.2.3  Form of structural walls  127
4.2.4  Structural redundancy  129
4.2.5  Avoidance of short columns  129
4.2.6  Avoidance of using flat slab frames as main structural systems  130
4.2.7  Avoidance of a soft storey  131
4.2.8  Diaphragmatic behaviour  131
4.2.9  Bi-directional resistance and stiffness  131
4.2.10  Strong columns–weak beams  132
4.2.11  Provision of a second line of defense  132
4.2.12  Adequate foundation system  134
4.3  Primary and secondary seismic members  136
4.4  Structural R/C types covered by seismic codes  137
4.5  Response of structural systems to lateral loading  139
4.5.1  General  139
4.5.2  Plane structural systems  139
4.5.2.1  Moment-resisting frames  140viii  Contents
4.5.2.2  Wall systems or flexural systems  141
4.5.2.3  Coupled shear walls  142
4.5.2.4  Dual systems  143
4.5.3  Pseudospatial multistorey structural system  144
4.6  Structural configuration of multi-storey R/C buildings  150
4.6.1  General  150
4.6.2  Historical overview of the development of R/C multi-storey buildings  152
4.6.3  Structural system and its main characteristics  156
4.6.3.1  General  156
4.6.3.2  Buildings with moment-resisting frames  156
4.6.3.3  Buildings with wall systems  157
4.6.3.4  Buildings with dual systems  160
4.6.3.5  Buildings with flat slab frames, shear walls and moment-resisting frames  161
4.6.3.6  Buildings with tube systems  162

5  Analysis of the structural system  

5.1  General  163
5.2  Structural regularity  163
5.2.1  Introduction  163
5.2.2  Criteria for regularity in plan  164
5.2.3  Criteria for regularity in elevation  166
5.2.4  Conclusions  166
5.3  Torsional flexibility   167
5.4  Ductility classes and behaviour factors  170
5.4.1  General  170
5.4.2  Ductility classes  171
5.4.3  Behaviour factors for horizontal seismic actions  172
5.4.4  Quantitative relations between the Q-factor and ductility  176
5.4.4.1  General  176
5.4.4.2  M–relation for R/C members under plain bending  177
5.4.4.3  Moment–curvature–displacement diagrams of R/C cantilever beams  180
5.4.4.4  Moment–curvature–displacement diagrams of R/C frames  182
5.4.4.5  Conclusions  183
5.4.5  Critical regions  185
5.5  Analysis methods  187
5.5.1  Available methods of analysis for R/C buildings  187
5.6  Elastic analysis methods  190
5.6.1  General  190
5.6.2  Modelling of buildings for elastic analysis and BIM concepts  190
5.6.3  Specific modelling issues  191
5.6.3.1  Walls and cores modelling  192
5.6.3.2  T-shaped beams  192Contents  ix
5.6.3.3  Diaphragm constraint  193
5.6.3.4  Eccentricity  194
5.6.3.5  Stiffness  195
5.6.4  Lateral force method of analysis  195
5.6.4.1  Base shear forces  196
5.6.4.2  Distribution along the height  196
5.6.4.3  Estimation of the fundamental period  197
5.6.4.4  Torsional effects  198
5.6.5  Modal response spectrum analysis  199
5.6.5.1  Modal participation  200
5.6.5.2  Storey and wall shears  200
5.6.5.3  Ritz vector analysis  201
5.6.6  Time–history elastic analysis  201
5.7  Inelastic analysis methods  201
5.7.1  General  201
5.7.2  Modelling in nonlinear analysis  202
5.7.2.1  Slab modelling and transfer of loads  202
5.7.2.2  Diaphragm constraint  203
5.7.2.3  R/C walls and cores  203
5.7.2.4  Foundation  205
5.7.2.5  Point hinge versus fibre modelling   205
5.7.2.6  Safety factors  207
5.7.3  Pushover analysis  209
5.7.4  Pros and cons of pushover analysis  210
5.7.5  Equivalent SDOF systems  212
5.7.5.1  Equivalent SDOF for torsionally restrained buildings  212
5.7.5.2  Equivalent SDOF for torsionally unrestrained buildings  216
5.7.6  Time–history nonlinear analysis  224
5.7.6.1  Input motion-scaling of accelerograms  224
5.7.6.2  Incremental dynamic analysis IDA  226
5.8  Combination of the components of gravity loads and seismic action  229
5.8.1  General  229
5.8.2  Theoretical background  232
5.8.3  Simplified procedures  234
5.8.3.1  Combination of the extreme values of the interacting load effects  235
5.8.3.2  Combination of each extreme load effect with the corresponding values of the interacting 
5.8.3.3  Gupta–Singh procedure  236
5.8.3.4  Rosenblueth and Contreras procedure  237
5.8.3.5  Extreme stress procedure  238
5.8.4  Code provisions  239
5.8.4.1  Suggested procedure for the analysis  239
5.8.4.2  Implementation of the reference method in case of horizontal seismic actions  240x  Contents
5.8.4.3  Implementation of the alternative method in the case of horizontal seismic actions  241
5.8.4.4  Implementation of the alternative method for horizontal and vertical seismic action  245
5.9  Example: Modelling and elastic analysis of an eight-storey RC building  245
5.9.1  Building description  245
5.9.2  Material properties  247
5.9.3  Design specifications  247
5.9.4  Definition of the design spectrum   247
5.9.4.1  Elastic response spectrum (5% damping)  247
5.9.4.2  Design response spectrum  247
5.9.5  Estimation of mass and mass moment of inertia  248
5.9.6  Structural regularity in plan and elevation  248
5.9.6.1  Criteria for regularity in plan  248
5.9.6.2  Criteria for regularity in elevation  250
5.9.7  Determination of the behaviour factor q (Subsection 5.4.3)  251
5.9.8  Description of the structural model  252
5.9.9  Modal response spectrum analysis  254
5.9.9.1  Accidental torsional effects  254
5.9.9.2  Periods, effective masses and modes of vibration  255
5.9.9.3  Shear forces per storey  255
5.9.9.4  Displacements of the centres of masses  255
5.9.9.5  Damage limitations  256
5.9.9.6  Second-order effects  258
5.9.9.7  Internal forces  259
5.10  Examples: Applications using inelastic analysis  259
5.10.1  Cantilever beam  259
5.10.1.1  Modelling approaches  259
5.10.1.2  Results  260
5.10.2  2-D MRF  261
5.10.2.1  Modelling approaches  261
5.10.2.2  Results  263
5.10.3  Sixteen-storey R/C building  264
5.10.3.1  Modelling approaches  264
5.10.3.2  Nonlinear dynamic analysis  271
5.10.3.3  Nonlinear static analysis  271
5.10.3.4  Results: Global response  272
5.10.3.5  Results: Local response  274

6  Capacity design – design action effects – safety verifications  

6.1  Impact of capacity design on design action effects  277
6.1.1  General  277
6.1.2  Design criteria influencing the design action effects  278
6.1.3  Capacity design procedure for beams  279
6.1.4  Capacity design of columns  281Contents  xi
6.1.4.1  General  281
6.1.4.2  Bending  282
6.1.4.3  Shear  285
6.1.5  Capacity design procedure for slender ductile walls  287
6.1.5.1  General  287
6.1.5.2  Bending  287
6.1.5.3  Shear  289
6.1.6  Capacity design procedure for squat walls  290
6.1.6.1  DCH buildings  291
6.1.6.2  DCM buildings  291
6.1.7  Capacity design of large lightly reinforced walls  291
6.1.8  Capacity design of foundation  292
6.2  Safety verifications  294
6.2.1  General  294
6.2.2  Ultimate limit state  294
6.2.2.1  Resistance condition  295
6.2.2.2  Second-order effects  295
6.2.2.3  Global and local ductility condition  297
6.2.2.4  Equilibrium condition  298
6.2.2.5  Resistance of horizontal diaphragms  298
6.2.2.6  Resistance of foundations  299
6.2.2.7  Seismic joint condition  299
6.2.3  Damage limitation  299
6.2.4  Specific measures  302
6.2.4.1  Design  302
6.2.4.2  Foundations  302
6.2.4.3  Quality system plan  302
6.2.4.4  Resistance uncertainties  303
6.2.4.5  Ductility uncertainties  303
6.2.5  Concluding remarks  303

7  Reinforced concrete materials under seismic actions  

7.1  Introduction  305
7.2  Plain (unconfined) concrete   307
7.2.1  General  307
7.2.2  Monotonic compressive stress–strain diagrams  307
7.2.3  Cyclic compressive stress–strain diagram  308
7.2.4  Provisions of Eurocodes for plain (not confined) concrete   311
7.3  Steel  314
7.3.1  General  314
7.3.2  Monotonic stress–strain diagrams  314
7.3.3  Stress–strain diagram for repeated tensile loading  314
7.3.4  Stress–strain diagram for reversed cyclic loading  316
7.3.5  Provisions of codes for reinforcement steel  317
7.3.6  Concluding remarks  318xii  Contents
7.4  Confined concrete   321
7.4.1  General  321
7.4.2  Factors influencing confinement   322
7.4.3  Provisions of Eurocodes for confined concrete   323
7.4.3.1  Form of the diagram 
7.4.3.2  Influence of confinement   325
7.5  Bonding between steel and concrete  329
7.5.1  General  329
7.5.2  Bond–slip diagram under monotonic loading  332
7.5.3  Bond–slip diagram under cyclic loading  334
7.5.4  Provisions of Eurocodes for bond of steel to concrete  335
7.5.4.1  Static loading  335
7.5.4.2  Seismic loading  337
7.6  Basic conclusions for materials and their synergy  337

8  Seismic-resistant R/C frames  

8.1  General  339
8.2  Design of beams  340
8.2.1  General  340
8.2.2  Beams under bending  343
8.2.2.1  Main assumptions  343
8.2.2.2  Characteristic levels of loading to failure (limit states)  344
8.2.2.3  Determination of the characteristic points diagram and ductility in terms of curvature for orthogonal cross section  348
8.2.2.4  Determination of the characteristic points diagram and ductility in terms of curvature for a generalised cross section  354
8.2.3  Load–deformation diagrams for bending under cyclic loading  359
8.2.3.1  General  359
8.2.3.2  Flexural behaviour of beams under cyclic loading  360
8.2.4  Strength and deformation of beams under prevailing shear  361
8.2.4.1  Static loading  361
8.2.4.2  Cyclic loading  369
8.2.4.3  Concluding remarks on shear resistance  370
8.2.5  Code provisions for beams under prevailing seismic action  371
8.2.5.1  General  371
8.2.5.2  Design of beams for DCM buildings  372
8.2.5.3  Design of beams for DCH buildings  376
8.2.5.4  Anchorage of beam reinforcement in joints  379
8.2.5.5  Splicing of bars  381
8.3  Design of columns  382
8.3.1  General  382
8.3.2  Columns under bending with axial force  383
8.3.2.1  General  383Contents  xiii
8.3.2.2  Determination of characteristic points of M–diagram and ductility in terms of curvature under axial load for an orthogonal cross-section  386
8.3.2.3  Behaviour of columns under cyclic loading  392
8.3.3  Strength and deformation of columns under prevailing shear  393
8.3.3.1  General  393
8.3.3.2  Shear design of rectangular R/C columns  395
8.3.4  Code provisions for columns under seismic action  399
8.3.4.1  General  399
8.3.4.2  Design of columns for DCM buildings  399
8.3.4.3  Design of columns for DCH buildings  407
8.3.4.4  Anchorage of column reinforcement  409
8.3.4.5  Splicing of bars  409
8.3.5  Columns under axial load and biaxial bending  410
8.3.5.1  General  410
8.3.5.2  Biaxial strength in bending and shear  410
8.3.5.3  Chord rotation at yield and failure stage: Skew ductility 
8.3.5.4  Stability of M diagrams under cyclic loading: Form of the hysteresis loops  415
8.3.5.5  Conclusions  415
8.3.6  Short columns under seismic action  415
8.3.6.1  General  415
8.3.6.2  Shear strength and failure mode of conventionally reinforced squat columns  418
8.3.6.3  Shear strength and failure mode of alternatively reinforced short columns  425
8.3.6.4  Code provisions for short columns  427
8.4  Beam–Column joints  428
8.4.1  General  428
8.4.2  Design of joints under seismic action  429
8.4.2.1  Demand for the shear design of joints  429
8.4.2.2  Joint shear strength according to the Paulay and Priestley method  431
8.4.2.3  Background for the determination of joint shear resistance according to ACI 318-2011 
8.4.2.4  Joint shear strength according to A.G. Tsonos  437
8.4.3  Code provisions for the design of joints under seismic action  440
8.4.3.1  DCM R/C buildings under seismic loading according to EC 8-1/2004  440
8.4.3.2  DCH R/C buildings under seismic loading according to EC 8-1/2004  441
8.4.4  Non-conventional reinforcing in the joint core  443
8.5  Masonry-infilled frames  444
8.5.1  General  444xiv  Contents
8.5.2  Structural behaviour of masonry infilled frames under cyclic loading reversals  446
8.5.3  Code provisions for masonry-infilled frames under seismic action   452
8.5.3.1  Requirements and criteria  452
8.5.3.2  Irregularities due to masonry infills  453
8.5.3.3  Linear modeling of masonry infills  454
8.5.3.4  Design and detailing of masonry-infilled frames  454
8.5.4  General remarks on masonry-infilled frames  456
8.6  Example: Detailed design of an internal frame  456
8.6.1  Beams: Ultimate limit state in bending  457
8.6.1.1  External supports on C2 and C28 (beam B8-left, B68-right)  457
8.6.1.2  Internal supports on C8 and on C22 
8.6.1.3  Internal supports on C14 and C18 (beam 
8.6.1.4  Mid-span (beams B8, B68)  461
8.6.1.5  Mid-span (beams B19, B37, B57)  461
8.6.2  Columns: Ultimate limit state in bending and shear  461
8.6.2.1  Column C2 (exterior column)  462
8.6.2.2  Design of exterior beam–column joint  466
8.6.2.3  Column C8 (interior column)  469
8.6.2.4  Design of interior beam–column joint  474
8.6.3  Beams: Ultimate limit state in shear  476
8.6.3.1  Design shear forces  476
8.6.3.2  Shear reinforcement  481

9  Seismic-resistant R/C walls and diaphragms  

9.1  General  485
9.2  Slender ductile walls  486
9.2.1  A summary on structural behaviour of slender ductile walls  486
9.2.2  Behaviour of slender ductile walls under bending with axial load  488
9.2.2.1  General  488
9.2.2.2  Dimensioning of slender ductile walls with orthogonal cross-section under bending with axial
9.2.2.3  Dimensioning of slender ductile walls with a composite cross-section under bending with 
9.2.2.4  Determination of M–diagram and ductility in terms of curvature under axial load for orthogonal cross-sections  493
9.2.3  Behaviour of slender ductile walls under prevailing shear  494
9.2.4  Code provisions for slender ductile walls  495
9.2.4.1  General  495
9.2.4.2  Design of slender ductile walls for DCM buildings  495
9.2.4.3  Design of slender ductile walls for DCH buildings  503Contents  xv
9.3  Ductile coupled walls  509
9.3.1  General  509
9.3.2  Inelastic behaviour of coupled walls  510
9.3.3  Code provisions for coupled slender ductile walls  512
9.4  Squat ductile walls  513
9.4.1  General  513
9.4.2  Flexural response and reinforcement distribution  514
9.4.3  Shear resistance  515
9.4.4  Code provisions for squat ductile walls  515
9.5  Large lightly reinforced walls  517
9.5.1  General  517
9.5.2  Design to bending with axial force  518
9.5.3  Design to shear  519
9.5.4  Detailing for local ductility  519
9.6  Special issues in the design of walls  520
9.6.1  Analysis and design using FEM procedure  520
9.6.2  Warping of open composite wall sections  523
9.6.2.1  General  523
9.6.2.2  Saint-Venant uniform torsion  524
9.6.2.3  Concept of warping behaviour  526
9.6.2.4  Geometrical parameters for warping bending  534
9.6.2.5  Implications of warping torsion in analysis and design to seismic action of R/C buildings  
9.7  Seismic design of diaphragms  541
9.7.1  General  541
9.7.2  Analysis of diaphragms  542
9.7.2.1  Rigid diaphragms  542
9.7.2.2  Flexible diaphragms  543
9.7.3  Design of diaphragms  544
9.7.4  Code provisions for seismic design of diaphragms  544
9.8  Example: Dimensioning of a slender ductile wall with a composite cross-section  544
9.8.1  Ultimate limit state in bending and shear  545
9.8.2  Estimation of axial stresses due to warping torsion  548
9.8.2.1  Estimation of the geometrical parameters for warping bending of an open composite C-shaped wall section  548
9.8.2.2  Implementation of the proposed methodology for deriving the normal stresses due to warping  550

 10  Seismic design of foundations  

10.1  General  553
10.2  Ground properties  554
10.2.1  Strength properties  554
10.2.1.1  Clays  554
10.2.1.2  Granular soils (sands and gravels)  555xvi  Contents
10.2.1.3  Partial safety factors for soil  555
10.2.2  Stiffness and damping properties  555
10.2.3  Soil liquefaction  557
10.2.4  Excessive settlements of sands under cyclic loading  558
10.2.5  Conclusions  558
10.3  General considerations for foundation analysis and design  558
10.3.1  General requirements and design rules  558
10.3.2  Design action effects on foundations in relation to ductility and capacity design  559
10.3.2.1  General  559
10.3.2.2  Design action effects for various types of R/C foundation members  560
10.4  Analysis and design of foundation ground under the design action effects  563
10.4.1  General requirements  563
10.4.2  Transfer of action effects to the ground  563
10.4.2.1  Horizontal forces  563
10.4.2.2  Normal force and bending moment  564
10.4.3  Verification and dimensioning of foundation ground at ULS of shallow or embedded foundations  564
10.4.3.1  Footings  564
10.4.3.2  Design effects on foundation horizontal connections between vertical structural elements  
10.4.3.3  Raft foundations  566
10.4.3.4  Box-type foundations  566
10.4.4  Settlements of foundation ground of shallow or embedded foundations at SLS  567
10.4.4.1  General  567
10.4.4.2  Footings  567
10.4.4.3  Foundation beams and rafts  568
10.4.5  Bearing capacity and deformations of foundation ground in the case of a pile foundation  570
10.4.5.1  General  570
10.4.5.2  Vertical load resistance and stiffness  570
10.4.5.3  Transverse load resistance and stiffness  572
10.5  Analysis and design of foundation members under the design action effects  575
10.5.1  Analysis  575
10.5.1.1  Separated analysis of superstructure and foundation  575
10.5.1.2  Integrated analysis of superstructure and foundation (soil–structure interaction)  576
10.5.1.3  Integrated analysis of superstructure foundation and foundation soil  577
10.5.2  Design of foundation members  578
10.5.2.1  Dissipative superstructure – non-dissipative foundation elements and foundation ground  
10.5.2.2  Dissipative superstructure – dissipative foundation elements – elastic foundation ground  
10.5.2.3  Non-dissipative superstructure – non-dissipative foundation elements and foundation ground  582
10.5.2.4  Concluding remarks  582
10.6  Example: Dimensioning of foundation beams  582
10.6.1  Ultimate limit state in bending  583
10.6.2  Ultimate limit state in shear  586

11  Seismic pathology  

11.1  Classification of damage to R/C structural members  589
11.1.1  Introduction  589
11.1.2  Damage to columns  590
11.1.3  Damage to R/C walls  596
11.1.4  Damage to beams  600
11.1.5  Damage to beam–column joints  602
11.1.6  Damage to slabs  603
11.1.7  Damage to infill walls  605
11.1.8  Spatial distribution of damage in buildings  607
11.1.9  Stiffness degradation  609
11.2  Factors affecting the degree of damage to buildings  610
11.2.1  Introduction  610
11.2.2  Deviations between design and actual response spectrum  611
11.2.3  Brittle columns  611
11.2.4  Asymmetric arrangement of stiffness elements in plan  613
11.2.5  Flexible ground floor  613
11.2.6  Short columns  616
11.2.7  Shape of the floor plan   616
11.2.8  Shape of the building in elevation  617
11.2.9  Slabs supported by columns without beams (flat slab systems)  617
11.2.10 Damage from previous earthquakes  617
11.2.11 R/C buildings with a frame structural system  618
11.2.12 Number of storeys  619
11.2.13 Type of foundations  619
11.2.14 Location of adjacent buildings in the block  621
11.2.15 Slab levels of adjacent structures  622
11.2.16 Poor structural layout  623
11.2.17 Main types of damage in buildings designed on the basis of modern codes  624

12  Emergency post-earthquake damage inspection, assessment and human life protection measures  

12.1  General  625
12.2  Inspections and damage assessment  625
12.2.1  Introductory remarks  625
12.2.2  Purpose of the inspections  626
12.2.3  Damage assessment  627xviii  Contents
12.2.3.1  Introduction  627
12.2.3.2  General principles of damage assessment  628
12.3  Organisational scheme for inspections  629
12.3.1  Introduction  629
12.3.2  Usability classification–inspection forms  629
12.3.3  Inspection levels  630
12.4  Action plan  633
12.4.1  Introduction  633
12.4.2  State agency responsible for the operation  633
12.4.3  Inspection personnel  633
12.4.4  Pre-earthquake organising procedures  634
12.4.5  Post-earthquake organising procedures  634
12.5  Emergency measures for temporary propping  636
12.5.1  General  636
12.5.2  Techniques for propping vertical loads  637
12.5.2.1  Industrial-type metal scaffolds  637
12.5.2.2  Timber  638
12.5.2.3  Steel profiles  638
12.5.3  Techniques for resisting lateral forces  638
12.5.3.1  Bracing with buttresses  638
12.5.3.2  Bracing with diagonal X-braces  641
12.5.3.3  Bracing with interior anchoring  641
12.5.3.4  Bracing with tension rods or rings  641
12.5.4  Wedging techniques  642
12.5.5  Case studies  642
12.6  Final remarks  643

13  Seismic assessment and retrofitting of R/C buildings  

13.1  General  647
13.2  Pre-earthquake seismic evaluation of R/C buildings  648
13.2.1  Introduction  648
13.2.2  Rapid visual screening procedure  650
13.2.3  Seismic evaluation of buildings according to ASCE 31-02/FEMA 310/1998  653
13.2.4  Concluding remarks  655
13.3  Post-earthquake seismic evaluation of R/C buildings  656
13.3.1  Introduction  656
13.3.2  Terms and definitions related to post-earthquake evaluation   657
13.3.2.1  Seismic demand  657
13.3.2.2  Seismic capacity  658
13.3.2.3  Residual seismic resistance  658
13.3.2.4  Loss of seismic resistance  659
13.3.2.5  Repair  659
13.3.2.6  Strengthening  659
13.3.2.7  Strength index  659Contents  xix
13.3.3  Objectives and principles of retrofitting   660
13.3.4  Criteria for repair or strengthening  661
13.3.5  UNIDO/UNDP procedure  662
13.3.5.1  Arrangement of the structural elements  662
13.3.5.2  Strength of the structure  662
13.3.5.3  Flexibility of the structure  664
13.3.5.4  Ductility of the structure  664
13.3.5.5  Decision for the degree and type of intervention  664
13.3.5.6  Concluding remarks  666
13.4  Design of repair of R/C buildings (local intervention)  667
13.4.1  Repair of the structural system  667
13.4.1.1  Information necessary for the final structural assessment  667
13.4.1.2  Analysis and design in case of repair  667
13.4.2  Repair of the masonry infills  667

14  Detailed seismic assessment and rehabilitation of R/C buildings  

14.1  General  669
14.2  Overview of displacement-based design for seismic actions  669
14.2.1  Introduction  669
14.2.2  Displacement-based design methods  670
14.2.2.1  N2 method (EC8-1/2004)  670
14.2.2.2  Capacity-spectrum method ATC 40-1996  677
14.2.2.3  Coefficient method/ASCE/SEI 41-06 (FEMA 356/2000)  679
14.2.2.4  Direct displacement-based design  681
14.2.2.5  Concluding remarks  683
14.3  Scope of the detailed seismic assessment and rehabilitation of R/C buildings  684
14.4  Performance requirements and compliance criteria  685
14.4.1  Performance requirements  685
14.4.2  Compliance criteria  686
14.4.2.1  Seismic actions  686
14.4.2.2  Safety verification of structural members  687
14.4.2.3  ‘Primary’ and ‘secondary’ seismic elements  687
14.4.2.4  Limit state of NC  687
14.4.2.5  Limit state of SD  687
14.4.2.6  Limit state of DL  688
14.5  Information for structural assessment  688
14.5.1  General  688
14.5.2  Required input data  688
14.5.2.1  Geometry of the structural system  688
14.5.2.2  Detailing  689
14.5.2.3  Materials  689
14.5.2.4  Other input data not related to the structural system  692
14.5.3  Knowledge levels and confidence factors  692
14.6  Quantitative assessment of seismic capacity  693xx  Contents
14.6.1  General  693
14.6.2  Seismic actions  694
14.6.3  Structural modelling  694
14.6.4  Methods of analysis  694
14.6.4.1  General  694
14.6.4.2  Lateral force elastic analysis  695
14.6.4.3  Multi-modal response spectrum analysis  697
14.6.4.4  Non-linear static analysis  697
14.6.4.5  Non-linear time–history analysis  698
14.6.4.6  The q-factor approach  698
14.6.4.7  Additional issues common to all methods of analysis  699
14.6.5  Safety verifications  699
14.6.5.1  General  699
14.6.5.2  Linear methods of analysis  700
14.6.5.3  Non-linear methods of analysis (static or dynamic)  701
14.6.5.4  The q-factor approach  702
14.6.5.5  Acceptance criteria  702
14.7  Decisions for structural retrofitting of R/C buildings  704
14.7.1  General  704
14.7.2  Criteria governing structural interventions  705
14.7.2.1  General criteria  705
14.7.2.2  Technical criteria  706
14.7.2.3  Types of intervention  706
14.7.2.4  Examples of repair and strengthening techniques  706
14.8  Design of structural rehabilitation  708
14.8.1  General  708
14.8.2  Conceptual design  708
14.8.3  Analysis  708
14.8.4  Safety verifications  709
14.8.4.1  Verifications for non-linear static analysis method   709
14.8.4.2  Verifications for the q-factor approach   711
14.8.5  Drawings  712
14.9  Final Remarks  713

15  Technology of repair and strengthening  

15.1  General  715
15.2  Materials and intervention techniques  716
15.2.1  Conventional cast-in-place concrete  716
15.2.2  High-strength concrete using shrinkage compensating admixtures  717
15.2.3  Shotcrete (gunite)  718
15.2.3.1  Dry process  718
15.2.3.2  Wet process  719
15.2.3.3  Final remarks  719
15.2.4  Polymer concrete  720
15.2.5  Resins  721
15.2.6  Resin concretes  722Contents  xxi
15.2.7  Grouts  722
15.2.8  Epoxy resin-bonded metal sheets on concrete  723
15.2.9  Welding of new reinforcement  723
15.2.10 Fibre-reinforced plastic (FRP) laminates and sheets bonded on concrete with epoxy resin  
15.2.10.1 General  724
15.2.10.2 Technical properties of FRPs  725
15.2.10.3 Types of FRP composites  725
15.3  Redimensioning and safety verification of structural elements  728
15.3.1  General  728
15.3.2  Revised 
15.3.3  Load transfer mechanisms through interfaces  728
15.3.3.1  Compression against pre-cracked interfaces  729
15.3.3.2  Adhesion between non-metallic materials  729
15.3.3.3  Friction between non-metallic materials  729
15.3.3.4  Load transfer through resin layers  731
15.3.3.5  Clamping effect of steel across interfaces  731
15.3.3.6  Dowel action  732
15.3.3.7  Anchoring of new reinforcement  732
15.3.3.8  Welding of steel elements  732
15.3.3.9  Final remarks  733
15.3.4  Simplified estimation of the resistance of structural elements  733
15.4  Repair and strengthening of structural elements using conventional means  734
15.4.1  General  734
15.4.2  Columns  735
15.4.2.1  Local interventions  735
15.4.2.2  R/C jackets  736
15.4.2.3  Steel profile cages  738
15.4.2.4  Steel or FRP encasement  739
15.4.2.5  Redimensioning and safety verifications  740
15.4.2.6  Code (EC 8-3/2005) provisions  741
15.4.3  Beams  742
15.4.3.1  Local interventions  742
15.4.3.2  R/C jackets  742
15.4.3.3  Bonded metal sheets  742
15.4.3.4  Redimensioning and safety verification   743
15.4.4  Beam–column joints  749
15.4.4.1  Local repairs  749
15.4.4.2  X-shaped prestressed collars  749
15.4.4.3  R/C jackets  749
15.4.4.4  Bonded metal plates  749
15.4.4.5  Redimensioning and safety verification   751
15.4.5  R/C walls  751
15.4.5.1  Local repairs  752
15.4.5.2  R/C jackets  752
15.4.5.3  Redimensioning and safety verification   753xxii  Contents
15.4.6  R/C slabs  754
15.4.6.1  Local repair  754
15.4.6.2  Increase of the thickness or the reinforcement of a slab  754
15.4.6.3  Redimensioning and safety verifications  756
15.4.7  Foundations  756
15.4.7.1  Connection of column jacket to footing  756
15.4.7.2  Strengthening of footings  756
15.4.8  Infill masonry walls  757
15.4.8.1  Light damage  758
15.4.8.2  Serious damage  759
15.5  Repair and strengthening of structural elements using FRPs  760
15.5.1  General considerations  760
15.5.2  Bending  760
15.5.2.1  Intermediate flexural crack-induced debonding   761
15.5.2.2  Crushing of concrete under compression before tension zone failure  764
15.5.2.3  Plate-end debonding  765
15.5.2.4  Theoretical justification of debonding 
15.5.3  Shear  769
15.5.4  Axial compression and ductility enhancement  770
15.5.4.1  Axial compression  770
15.5.4.2  Ductility enhancement  774
15.5.4.3  Clamping of lap-splices  775
15.5.5  Strengthening of R/C beam–column joints using FRP sheets and laminates  775
15.6  Addition of new structural elements  776
15.7  Quality assurance of interventions  778
15.7.1  General  778
15.7.2  Quality plan of design  779
15.7.3  Quality plan of construction  779
15.8  Final Remarks  779

16  Seismic risk management  

16.1  General  781
16.2  Conceptual approach to the steps of seismic risk management  782
16.3  Seismic risk assessment in the United States and European Union  783
16.4  Seismic hazard  784
16.5  Seismic vulnerability  785
16.5.1  Fundamentals  785
16.5.2  Inventory of the building stock-classification   789
16.5.2.1  Inventory of the building stock  789
16.5.2.2  Building classification based on the structural system and its material  789
16.5.2.3  Classification of non-structural systems and contents  790Contents  xxiii
16.5.2.4  Damage states  792
16.5.2.5  Relation of seismic intensity and the damage index  792
16.5.2.6  Relation of structural damage to non-structural damage and contents  797
16.6  Seismic risk analysis  799
16.6.1  General  799
16.6.2  Specific seismic risk analysis  801
16.6.3  Losses for elements at risk  803
16.6.4  Casualties  803
16.6.5  Seismic risk outputs  804
16.7  Cost–benefit analysis  806
16.7.1  General  806
16.7.2  Basic seismic risk mitigation alternatives  807
16.7.3  Semi-empirical seismic risk management  808

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