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عنوان کتاب (ebook) :Fundamental Concepts of EARTHQUAKE ENGINEERING
Roberto Villaverde
نوع فایل ایبوک : PDF حجم فایل ایبوک : 25.7 مگابایت
شابک : ISBN 978-1-4200-6495-7
تعداد صفحه : 937 صفحه
ناشر (انتشارات) : [ CRC Press ]
تاریخ انتشار کتاب : 2009
فهرست
Contents
Preface ...........................................................................................................................................xix
Author ......................................................................................................................................... xxiii
Chapter 1 Introduction ..................................................................................................................1
1.1 Importance of Earthquake Engineering ....................................................................................1
1.2 Damaging Effects of Earthquakes ............................................................................................1
1.2.1 Ground Failures .............................................................................................................2
1.2.2 Indirect Effects ............................................................................................................ 10
1.2.3 Ground Shaking ........................................................................................................... 16
1.3 Earthquake Forces ...................................................................................................................22
1.4 Design for Earthquake Forces .................................................................................................23
1.5 Defi nition and Scope ...............................................................................................................24
1.6 Historical Background ............................................................................................................27
Further Readings.............................................................................................................................27
Chapter 2 Seismic Regions of the World ....................................................................................29
2.1 Introduction .............................................................................................................................29
2.2 World Seismicity .....................................................................................................................30
2.3 Seismicity of United States ..................................................................................................... 32
2.4 Earthquake Statistics ............................................................................................................... 32
2.4.1 Worldwide Earthquakes ............................................................................................... 33
2.4.2 U.S. Earthquakes .........................................................................................................34
2.5 On-Line Seismicity Information .............................................................................................34
Further Readings............................................................................................................................. 35
Chapter 3 Earthquake Genesis ....................................................................................................37
3.1 Introduction .............................................................................................................................37
3.2 Types of Earthquakes ..............................................................................................................38
3.3 Earth Structure ........................................................................................................................39
3.4 Plate Tectonics Theory ............................................................................................................40
3.5 Plate Interaction, Formation of Earth’s Surface Features,
and Earthquake Generation ..................................................................................................... 42
3.6 Cause of Plate Movement ........................................................................................................ 45
3.7 Intraplate Earthquakes ............................................................................................................46
3.8 Earthquake Faults ....................................................................................................................46
3.9 Earthquake-Generation Mechanism: Elastic Rebound Theory ..............................................49
3.10 Focus, Epicenter, Rupture Surface, and Fault Slip .................................................................. 53
3.11 Foreshocks and Aftershocks ...................................................................................................54
3.12 Earthquake Prediction ............................................................................................................. 55
3.12.1 Introduction .................................................................................................................. 55
3.12.2 Historical Background ................................................................................................. 55
3.12.3 Seismic Gaps and Seismic Quiescence ........................................................................59
3.12.4 Earthquake Precursors .................................................................................................60
3.12.5 Current Status of Earthquake Predictions ................................................................... 61
Further Readings............................................................................................................................. 61
Review Questions............................................................................................................................ 61
Chapter 4 Earthquake Propagation .............................................................................................63
4.1 Introduction .............................................................................................................................63
4.2 Longitudinal Waves in Long Rod ...........................................................................................63
4.2.1 Differential Equation of Motion ..................................................................................63
4.2.2 Solution of Differential Equation.................................................................................65
4.2.3 Solution in Terms of Initial Conditions .......................................................................65
4.2.4 Solution Interpretation .................................................................................................66
4.2.5 Relationship between Particle Velocity and Wave Velocity ........................................67
4.2.6 Transmitted and Refl ected Waves at Discontinuity .....................................................68
4.3 Shear Waves in Long Shear Beam .......................................................................................... 74
4.4 Harmonic Waves ..................................................................................................................... 78
4.4.1 Defi nition ..................................................................................................................... 78
4.4.2 Characteristics .............................................................................................................80
4.5 Waves in Long Flexural Beam: Wave Dispersion ...................................................................82
4.5.1 Differential Equation of Motion ..................................................................................82
4.5.2 Solution to Differential Equation of Motion ................................................................83
4.5.3 Apparent Waves and Group Velocity ...........................................................................84
4.6 Elastic Waves in Unbounded Three-Dimensional Medium: P and S Waves ..........................86
4.6.1 Introduction ..................................................................................................................86
4.6.2 Stresses and Strains in Three-Dimensional Solid .......................................................86
4.6.3 Differential Equations of Motion .................................................................................89
4.6.4 First Particular Solution of Differential Equations of Motion ..................................... 91
4.6.5 Interpretation of First Particular Solution of Equations of Motion .............................94
4.6.6 Second Particular Solution of Differential Equations of Motion ................................95
4.6.7 Interpretation of Second Particular Solution of Equations of Motion .........................97
4.6.8 General Solution of Differential Equations of Motion ................................................98
4.7 Elastic Waves in Elastic Half-Space: Rayleigh Waves ............................................................99
4.7.1 Introduction ..................................................................................................................99
4.7.2 Equations of Motion for Plane Waves........................................................................100
4.7.3 Solution of Decoupled Equations of Motion ............................................................. 102
4.7.4 Particle Motion Generated by Rayleigh Waves ......................................................... 105
4.8 Elastic Waves in Layered Half-Space: Love Waves .............................................................. 108
4.8.1 Introduction ................................................................................................................ 108
4.8.2 Equations of Motion for Plane Waves........................................................................ 109
4.8.3 Solution of Equations of Motion ................................................................................ 110
4.8.4 Particle Motion Generated by Love Waves................................................................ 113
4.8.5 Dispersion of Love Waves ......................................................................................... 113
4.9 Refl ection and Refraction of Body Waves ............................................................................ 115
4.9.1 Introduction ................................................................................................................ 115
4.9.2 Elements of Ray Theory ............................................................................................ 116
4.9.3 Relative Amplitudes of Incident, Refracted, and Refl ected Waves ........................... 118
4.10 Attenuation of Wave Amplitude with Distance .................................................................... 122
4.10.1 Radiation Damping .................................................................................................... 122
4.10.2 Material Damping ...................................................................................................... 123
Further Readings...........................................................................................................................125
Problems .......................................................................................................................................125
Chapter 5 Measurement of Earthquakes ................................................................................... 129
5.1 Introduction ........................................................................................................................... 129
5.2 Intensity Scales ..................................................................................................................... 129
5.3 Seismographs and Seismograms ........................................................................................... 134
5.3.1 Historical Background ............................................................................................... 134
5.3.2 Components and Design Features ............................................................................. 135
5.3.3 Seismograms .............................................................................................................. 139
5.4 Location of Earthquake Hypocenter ..................................................................................... 140
5.5 Magnitude Scales .................................................................................................................. 146
5.5.1 Richter or Local Magnitude ....................................................................................... 146
5.5.2 Surface- and Body-Wave Magnitudes ....................................................................... 148
5.6 Seismic Moment and Moment Magnitude ............................................................................ 149
5.6.1 Scale Saturation ......................................................................................................... 149
5.6.2 Seismic Moment ........................................................................................................ 151
5.6.3 Moment Magnitude .................................................................................................... 153
5.7 Accelerographs and Accelerograms...................................................................................... 154
5.7.1 Need for Strong Motion Recording Instruments ....................................................... 154
5.7.2 Accelerograph Components and Design Features ..................................................... 155
5.7.3 Accelerograms ........................................................................................................... 159
5.7.4 Accelerogram Processing .......................................................................................... 162
5.7.5 Strong Motion Instrument Arrays.............................................................................. 165
5.7.6 Accelerograms from Near-Fault Sites ........................................................................ 166
Further Readings........................................................................................................................... 177
Problems ....................................................................................................................................... 177
Chapter 6 Characterization of Strong Ground Motions ............................................................ 181
6.1 Introduction ........................................................................................................................... 181
6.2 Peak Ground Acceleration .................................................................................................... 181
6.3 Strong-Motion Duration ........................................................................................................ 182
6.4 Response Spectrum ............................................................................................................... 182
6.4.1 Background ................................................................................................................ 182
6.4.2 Defi nition ................................................................................................................... 183
6.4.3 Importance of Response Spectrum ............................................................................ 186
6.4.4 Tripartite Representation ........................................................................................... 189
6.4.5 Computation of Response Spectra ............................................................................. 193
6.5 Nonlinear Response Spectrum.............................................................................................. 196
6.5.1 Background ................................................................................................................ 196
6.5.2 Load-Deformation Curves under Severe Cyclic Loading ......................................... 197
6.5.3 Defi nition ................................................................................................................... 199
6.5.4 Graphical Representation........................................................................................... 199
6.5.5 Computation of Nonlinear Response Spectrum ........................................................202
6.6 Fourier Spectrum ..................................................................................................................207
6.6.1 Theoretical Background.............................................................................................207
6.6.1.1 Fourier Series ..............................................................................................207
6.6.1.2 Exponential Fourier Series ..........................................................................208
6.6.1.3 Fourier Transform ....................................................................................... 210
6.6.2 Defi nition ................................................................................................................... 210
6.6.3 Total Energy and Fourier Spectrum .......................................................................... 212
6.6.4 Relationship between Fourier and Undamped Velocity Response Spectra ............... 214
6.6.5 Computation of Fourier Spectrum ............................................................................. 216
6.6.6 Fast Fourier Transform .............................................................................................. 218
6.7 Power Spectral Density .........................................................................................................222
6.8 Single-Parameter Measures of Ground Motion Intensity .....................................................225
6.8.1 Introductory Remarks ................................................................................................225
6.8.2 Root Mean Square Acceleration ................................................................................225
6.8.3 Housner Spectral Intensity .........................................................................................225
6.8.4 Arias Intensity ............................................................................................................226
6.8.5 Araya–Saragoni Intensity ..........................................................................................228
6.9 Design-Spectrum-Compatible Time Histories .....................................................................228
Further Readings...........................................................................................................................230
Problems .......................................................................................................................................230
Chapter 7 Seismic Hazard Assessment .....................................................................................237
7.1 Introduction ...........................................................................................................................237
7.2 Identifi cation of Seismic Sources .......................................................................................... 239
7.3 Factors Affecting Ground Motion Characteristics at Site ....................................................244
7.4 Ground Motion Intensity at Given Site: Attenuation Laws ...................................................246
7.4.1 Background ................................................................................................................246
7.4.2 Boore, Joyner, and Fumal Equations for Shallow Crustal
Earthquakes in Active Regions ..................................................................................247
7.4.3 Campbell Equations for Shallow Crustal Earthquakes
in Active Regions ....................................................................................................... 253
7.4.4 Youngs, Chiou, Silva, and Humphrey Equations
for Subduction-Zone Earthquakes ............................................................................. 257
7.5 Magnitude-Recurrence Relationships ................................................................................... 261
7.5.1 Introduction ................................................................................................................ 261
7.5.2 Gutenberg–Richter Recurrence Law ......................................................................... 261
7.5.3 Bounded Gutenberg–Richter Recurrence Law ..........................................................262
7.5.4 Characteristic Earthquake Recurrence Law ..............................................................263
7.6 Ground Motion Intensity in Given Time Interval .................................................................264
7.6.1 Introduction ................................................................................................................264
7.6.2 Poisson Probabilistic Model ......................................................................................265
7.6.3 Probability of Exceeding Given Ground Motion Intensity
in Given Time Interval ...............................................................................................267
7.6.4 Exceedance Probability Curves ................................................................................267
7.6.5 Frequency-Intensity Curves .......................................................................................268
7.7 Semiprobabilistic Seismic Hazard Evaluation ...................................................................... 270
7.8 Probabilistic Seismic Hazard Evaluation .............................................................................. 275
7.8.1 Introduction ................................................................................................................ 275
7.8.2 Probability Distribution of Source-to-Site Distance ................................................. 275
7.8.3 Probability Distribution of Earthquake Magnitude ...................................................277
7.8.4 Probability of Exceeding Specifi ed Value of Ground
Motion Parameter ......................................................................................................277
7.8.5 Annual Probability of Exceeding Specifi ed Ground
Motion Intensity Level ............................................................................................... 278
7.9 Seismic Zonation Maps .........................................................................................................282
7.10 Microzonation Maps .............................................................................................................287
Further Readings...........................................................................................................................289
Problems .......................................................................................................................................289
Chapter 8 Infl uence of Local Site Conditions ...........................................................................295
8.1 Problem Identifi cation ...........................................................................................................295
8.2 Effect of Site Conditions on Ground Motion Characteristics ...............................................299
8.3 Evaluation of Site Effects Using Statistical Correlations......................................................304
8.4 Evaluation of Site Effects Using Analytical Techniques ......................................................306
8.4.1 Introductory Remarks ................................................................................................306
8.4.2 One-Dimensional Continuous Model ........................................................................306
8.4.3 One-Dimensional Lumped-Mass Model ................................................................... 315
8.4.4 One-Dimensional Continuous Model: Solution in Frequency Domain ..................... 319
8.4.4.1 Case I: Homogeneous, Undamped Soil on Rigid Rock .............................. 319
8.4.4.2 Case II: Homogeneous, Damped Soil on Rigid Rock ................................. 321
8.4.4.3 Case III: Homogeneous, Damped Soil on Flexible Rock ........................... 325
8.4.4.4 Case IV: Layered, Damped Soil on Flexible Rock ..................................... 327
8.4.5 Nonlinear Site Response ............................................................................................ 332
8.5 Determination of Shear Modulus and Damping Ratio ......................................................... 334
8.5.1 Shear Modulus and Damping Ratio of Sands ............................................................ 336
8.5.2 Shear Modulus and Damping Ratio of Gravels ......................................................... 338
8.5.3 Shear Modulus and Damping Ratio of Saturated Clays ............................................340
Further Readings........................................................................................................................... 347
Problems ....................................................................................................................................... 347
Chapter 9 Design Response Spectrum ...................................................................................... 353
9.1 Introduction ........................................................................................................................... 353
9.2 Peak Ground Acceleration and Response Spectrum Shape Method .................................... 354
9.2.1 Elastic Design Spectrum ............................................................................................ 354
9.2.2 Inelastic Design Spectrum ......................................................................................... 355
9.3 Newmark–Hall Approach .....................................................................................................360
9.3.1 Background ................................................................................................................360
9.3.2 Elastic Design Spectra ...............................................................................................360
9.3.3 Inelastic Design Spectra ............................................................................................364
9.4 Direct Statistical Correlations ............................................................................................... 375
Further Readings........................................................................................................................... 375
Problems ....................................................................................................................................... 376
Chapter 10 Structural Response by Response Spectrum Method ............................................. 379
10.1 Introduction ........................................................................................................................... 379
10.2 Modal Superposition Method ............................................................................................... 379
10.2.1 Discrete Model ........................................................................................................... 379
10.2.2 Equation of Motion ....................................................................................................380
10.2.3 Transformation of Equation of Motion ...................................................................... 382
10.2.4 Solution of rth Independent Equation ........................................................................386
10.2.5 Structural Response in Terms of Modal Responses ..................................................386
10.2.6 Maximum Structural Response ................................................................................. 389
10.3 Maximum Structural Response Using Response Spectra .................................................... 389
10.3.1 Maximum Modal Responses in Terms of Response Spectrum Ordinates ................ 389
10.3.2 Approximate Rules to Estimate Maximum System Response .................................. 391
10.3.2.1 Double-Sum Combination Rule .................................................................. 391
10.3.2.2 Square Root of the Sum of the Squares ....................................................... 393
10.3.2.3 Rosenblueth’s Rule ......................................................................................394
10.3.2.4 Complete Quadratic Combination ............................................................. 395
10.3.2.5 Singh and Maldonado’s Rule ..................................................................... 395
10.3.2.6 Comparative Studies ..................................................................................397
10.3.2.7 Final Remarks ...........................................................................................403
10.4 Properties of Modal Participation Factors ..........................................................................406
10.5 Determination of Modal Damping Ratios ...........................................................................407
10.6 Summary of Response Spectrum Method .......................................................................... 416
10.7 Response Spectrum Method Based on Modal Acceleration Method ................................. 423
10.8 Response Spectrum Method for Multicomponent Ground Motions ................................... 431
10.8.1 Introduction ............................................................................................................ 431
10.8.2 Equation of Motion ................................................................................................ 432
10.8.3 Transformation of Equation of Motion .................................................................. 434
10.8.4 Solution of rth Independent Equation .................................................................... 434
10.8.5 Structural Response in Terms of Modal Responses .............................................. 435
10.8.6 Maximum Modal Responses in Terms of Response Spectrum Ordinates ............ 436
10.8.7 Approximate Rule to Estimate Maximum System Response ................................ 437
10.9 Response Spectrum Method for Spatially Varying Ground Motions .................................449
Further Readings...........................................................................................................................462
Problems .......................................................................................................................................462
Chapter 11 Structural Response by Step-by-Step Integration Methods ...................................469
11.1 Introduction .........................................................................................................................469
11.2 General Classifi cation .......................................................................................................... 470
11.3 Central Difference Method ................................................................................................. 470
11.4 Houbolt Method ................................................................................................................... 476
11.5 Constant Average Acceleration Method ..............................................................................482
11.6 Linear Acceleration Method ................................................................................................489
11.7 Wilson-θ Method ................................................................................................................. 495
11.8 Newmark-β Method .............................................................................................................500
11.9 Stability and Accuracy Issues .............................................................................................503
11.9.1 Introductory Remarks ............................................................................................503
11.9.2 Numerical Stability ................................................................................................504
11.9.3 Accuracy ................................................................................................................ 510
11.10 Analysis of Nonlinear Systems ........................................................................................... 513
11.10.1 Introduction ............................................................................................................ 513
11.10.2 Incremental Equations of Motion .......................................................................... 513
11.10.3 Solution of Incremental Equation of Motion ......................................................... 516
11.10.3.1 Solution by Central Differences Method ............................................. 516
11.10.3.2 Solution by Newmark-β Method ......................................................... 518
11.10.4 Updating of Stiffness Matrix: Elastoplastic Case .................................................. 521
11.10.5 Sources of Error and Corrective Techniques ......................................................... 530
11.11 Final Remarks ..................................................................................................................... 537
Further Readings........................................................................................................................... 539
Problems ....................................................................................................................................... 539
Chapter 12 Structural Response by Equivalent Lateral Force Procedure................................. 541
12.1 Introduction ......................................................................................................................... 541
12.2 Derivation of Procedure ...................................................................................................... 541
12.2.1 Overview ................................................................................................................ 541
12.2.2 Maximum Modal Lateral Forces ........................................................................... 542
12.2.3 Modal Base Shear .................................................................................................. 543
12.2.4 Modal Lateral Forces in Terms of Base Shear ......................................................544
12.2.5 Basic Assumptions ................................................................................................. 545
12.2.6 Approximate Maximum Lateral Forces ................................................................ 545
12.2.7 Approximate Fundamental Natural Period ...........................................................546
12.3 Application of Procedure .................................................................................................... 547
12.4 Limitations of Procedure ....................................................................................................564
12.5 Nonlinear Static Procedure .................................................................................................565
Further Readings...........................................................................................................................568
Problems .......................................................................................................................................568
Chapter 13 Structural Response Considering Soil–Structure Interaction ................................ 571
13.1 Problem Defi nition .............................................................................................................. 571
13.2 Kinematic and Inertial Interaction ...................................................................................... 572
13.3 Vibration of Foundations on Elastic Halfspace .................................................................. 574
13.3.1 Introductory Remarks ............................................................................................ 574
13.3.2 Displacements under Static Point Loads ............................................................... 574
13.3.3 Displacements and Rotations under Static Distributed Loads .............................. 575
13.3.4 Soil Spring Constants ............................................................................................ 582
13.3.5 Displacements and Rotations under Dynamic Loads ............................................ 583
13.3.6 Vibrations of Rectangular Foundations .................................................................590
13.4 Lumped-Parameter Models ................................................................................................. 591
13.4.1 Hsieh’s Equations ................................................................................................... 591
13.4.2 Lysmer and Hall Analogs ...................................................................................... 593
13.5 Coupled Rocking and Horizontal Vibrations of Rigid Circular Foundations .................... 598
13.6 Vibration of Rigid Circular Foundations Supported by Elastic Layer ................................603
13.7 Vibration of Embedded Foundations ..................................................................................605
13.8 Foundation Vibrations by Method of Impedances .............................................................. 610
13.9 Material or Internal Damping in Soils ................................................................................ 621
13.10 Vibrations of Foundations on Viscoelastic Halfspace ........................................................624
13.11 Simplifi ed Equivalent Single-Degree-of-Freedom System Method ................................... 627
13.12 Advanced Methods of Analysis .......................................................................................... 637
13.12.1 Introduction ............................................................................................................ 637
13.12.2 Direct Method ........................................................................................................ 638
13.12.3 Substructure Method ..............................................................................................642
13.12.4 Computer Programs ...............................................................................................645
13.13 Experimental Verifi cation ...................................................................................................645
Further Readings ...........................................................................................................................646
Problems .......................................................................................................................................647
Chapter 14 Seismic Response of Nonstructural Elements ........................................................649
14.1 Introduction .........................................................................................................................649
14.2 Importance of Nonstructural Elements ...............................................................................649
14.3 General Physical Characteristics ........................................................................................ 653
14.4 General Response Characteristics.......................................................................................654
14.5 Modeling of Nonstructural Elements ..................................................................................654
14.6 Methods of Analysis ........................................................................................................... 655
14.7 Floor Response Spectrum Method ......................................................................................656
14.8 Modal Synthesis Method ....................................................................................................663
14.8.1 Introduction ............................................................................................................663
14.8.2 Mode Shapes and Natural Frequencies of Combined System ...............................663
14.8.2.1 Primary System .....................................................................................664
14.8.2.2 Secondary System .................................................................................665
14.8.2.3 Compatibility Requirements .................................................................668
14.8.2.4 Eigenvalue Problem ...............................................................................668
14.8.2.5 Mode Shapes of Combined System in Terms of Modal
Coordinates ........................................................................................... 670
14.8.3 Approximate Natural Frequencies and Mode Shapes of
Combined System .................................................................................................. 674
14.8.4 Damping Ratios of Combined System ...................................................................680
14.8.5 Maximum Elastic Response of Nonstructural Element ........................................ 681
14.8.6 Effect of Structural and Nonstructural Nonlinear Behavior .................................683
Further Readings...........................................................................................................................685
Problems .......................................................................................................................................686
Chapter 15 Seismic Protection with Base Isolation ..................................................................689
15.1 Introduction .........................................................................................................................689
15.2 Basic Concept ......................................................................................................................689
15.3 Historical Perspective ......................................................................................................... 691
15.4 Isolation Bearings ...............................................................................................................695
15.4.1 Introduction ............................................................................................................695
15.4.2 Laminated Rubber Bearings ..................................................................................695
15.4.2.1 Low-Damping Rubber Bearings............................................................696
15.4.2.2 Lead–Rubber Bearings ..........................................................................697
15.4.2.3 High-Damping Rubber Bearings ...........................................................698
15.4.3 Sliding Bearings.....................................................................................................700
15.4.3.1 Electricité-de-France Bearing ...............................................................700
15.4.3.2 TASS Bearing ........................................................................................ 701
15.4.3.3 Friction Pendulum Bearing ...................................................................702
15.4.4 Helical Steel Springs .............................................................................................. 705
15.5 Methods of Analysis ...........................................................................................................706
15.5.1 Linear Two-Degree-of-Freedom Model ................................................................706
15.5.1.1 Equations of Motion ..............................................................................706
15.5.1.2 Natural Frequencies ...............................................................................709
15.5.1.3 Mode Shapes ......................................................................................... 712
15.5.1.4 Modal Participation Factors .................................................................. 713
15.5.1.5 Uncoupled Equations of Motion ............................................................ 715
15.5.1.6 Damping Ratios ..................................................................................... 716
15.5.1.7 Maximum Response .............................................................................. 717
15.5.2 Rigid Structure Single-Degree-of-Freedom Model ............................................... 721
15.5.3 Linear Multi-Degree-of-Freedom Model .............................................................. 721
15.5.3.1 Equations of Motion .............................................................................. 721
15.5.3.2 Natural Frequencies and Mode Shapes .................................................724
15.5.3.3 Approximate Maximum Response ........................................................ 727
15.5.4 Linear Multi-Degree-of-Freedom Model with
Nonclassical Damping ........................................................................................... 732
15.5.5 Equivalent Linear Model ....................................................................................... 746
15.5.5.1 Effective Stiffness ................................................................................. 746
15.5.5.2 Effective Damping Ratio ....................................................................... 746
15.6 Implementation Issues ......................................................................................................... 747
Further Readings ........................................................................................................................... 748
Problems ....................................................................................................................................... 749
Chapter 16 Seismic Protection with Energy Dissipating Devices ............................................ 753
16.1 Introduction ......................................................................................................................... 753
16.2 Basic Concepts .................................................................................................................... 754
16.3 Energy Dissipating Devices ................................................................................................760
16.3.1 Introduction ............................................................................................................760
16.3.2 Friction Dampers ...................................................................................................760
16.3.3 Viscoelastic Dampers ............................................................................................764
16.3.4 Fluid Dampers ....................................................................................................... 771
16.3.5 Yielding Metallic Dampers ................................................................................... 776
16.4 Analysis of Structures with Added Dampers...................................................................... 785
16.4.1 Overview ................................................................................................................ 785
16.4.2 Seismic Response of Simple Structure with Added Dampers ............................... 786
16.4.2.1 Viscoelastic Damper .............................................................................. 787
16.4.2.2 Fluid Damper ......................................................................................... 787
16.4.2.3 Friction or Yielding Steel Damper ........................................................ 788
16.4.3 Seismic Response of Multistory Structures with Added Dampers .......................800
16.4.3.1 Viscoelastic Dampers ............................................................................ 801
16.4.3.2 Fluid Dampers .......................................................................................802
16.4.3.3 Friction or Yielding Steel Dampers .......................................................804
16.5 Implementation Issues ......................................................................................................... 810
Further Readings........................................................................................................................... 812
Problems ....................................................................................................................................... 812
Chapter 17 Seismic Code Provisions .......................................................................................... 815
17.1 Introduction ......................................................................................................................... 815
17.2 General Requirements......................................................................................................... 816
17.2.1 Allowable Seismic-Force-Resisting Systems......................................................... 816
17.2.2 Load Combinations ................................................................................................ 819
17.2.3 Story Drift Limits .................................................................................................. 821
17.2.4 Direction of Earthquake Loads ............................................................................. 821
17.3 Design Ground Motion ....................................................................................................... 821
17.3.1 Overview ................................................................................................................ 821
17.3.2 Ground Motion Intensity Maps ..............................................................................822
17.3.3 Site-Specifi c Response Spectra ..............................................................................822
17.3.4 Site Classes and Site Coeffi cients ..........................................................................822
17.3.5 Design Spectral Accelerations ............................................................................... 831
17.3.6 Design Response Spectrum ................................................................................... 831
17.4 Analysis Procedures ............................................................................................................ 835
17.4.1 Overview ................................................................................................................ 835
17.4.2 Occupancy Categories and Importance Factors .................................................... 835
17.4.3 Seismic Design Category ....................................................................................... 835
17.4.4 Structural Irregularities ......................................................................................... 836
17.4.5 Allowable Analysis Procedures ............................................................................. 837
17.4.6 Mathematical Model ..............................................................................................840
17.5 Simplifi ed Method...............................................................................................................840
17.6 Equivalent Lateral Force Procedure ................................................................................... 841
17.6.1 Overview ................................................................................................................ 841
17.6.2 Base Shear .............................................................................................................. 841
17.6.3 Natural Period ........................................................................................................842
17.6.4 Equivalent Lateral Forces ......................................................................................844
17.6.5 Horizontal Shear Distribution ................................................................................844
17.6.6 Overturning Moment .............................................................................................845
17.6.7 Story Drift Determination .....................................................................................846
17.6.8 P-Delta Effects .......................................................................................................846
17.7 Modal Response Spectrum Analysis ..................................................................................850
17.7.1 Modal Properties ...................................................................................................850
17.7.2 Modal Base Shears ................................................................................................ 851
17.7.3 Modal Lateral Forces and Drifts ........................................................................... 851
17.7.4 Design Values ........................................................................................................ 852
17.8 Linear Response Time-History Analysis ............................................................................ 852
17.9 Nonlinear Response Time-History Analysis ......................................................................854
17.10 Soil–Structure Interaction Effects ...................................................................................... 862
17.10.1 Introduction ............................................................................................................ 862
17.10.2 Modifi cations to Equivalent Lateral Force Procedure ...........................................863
17.10.2.1 Base Shear ............................................................................................863
17.10.2.2 Effective Building Period .....................................................................864
17.10.2.3 Effective Damping Ratio .....................................................................866
17.10.2.4 Vertical Distribution of Base Shear ..................................................... 867
17.10.2.5 Story Shears, Overturning Moments, and Torsional Moments ........... 867
17.10.2.6 Lateral Displacements ..........................................................................868
17.10.3 Modifi cations to Modal Analysis Procedure ......................................................... 871
17.10.3.1 Modal Base Shears ............................................................................... 871
17.10.3.2 Modal Lateral Forces, Story Shears, and Overturning Moments ........ 872
17.10.3.3 Modal Lateral Displacements .............................................................. 872
17.10.3.4 Design Values ....................................................................................... 872
17.11 Nonstructural Components ................................................................................................. 872
17.12 Base-Isolated Structures .....................................................................................................880
17.12.1 Overview ................................................................................................................880
17.12.2 General Requirements ...........................................................................................880
17.12.3 Effective Natural Periods and Minimum Displacements ...................................... 881
17.12.4 Equivalent Lateral Force Procedure ......................................................................883
17.12.4.1 Conditions for Use................................................................................883
17.12.4.2 Minimum Displacements .....................................................................883
17.12.4.3 Minimum Lateral Forces .....................................................................884
17.12.4.4 Drift Limits ..........................................................................................884
17.12.5 Dynamic Analysis ..................................................................................................885
17.12.5.1 Choice of Procedure .............................................................................885
17.12.5.2 Input Earthquake ..................................................................................885
17.12.5.3 Response Spectrum Analysis ...............................................................885
17.12.5.4 Time-History Analysis .........................................................................885
17.12.5.5 Minimum Displacements .....................................................................886
17.12.5.6 Minimum Lateral Forces .....................................................................886
17.12.5.7 Drift Limits ..........................................................................................887
17.12.6 Required Testing of Isolation System Components ...............................................887
17.12.7 Effective Stiffness and Effective Damping of Isolating System ...........................887
17.12.8 Peer Review ...........................................................................................................888
17.13 Structures with Added Damping Devices ........................................................................... 891
17.13.1 Overview ................................................................................................................ 891
17.13.2 General Requirements ........................................................................................... 891
