# SEISMIC DESIGN OF REINFORCED CONCRETE AND MASONRY BUILDINGS

By T. Paulay and M. J. N. Priestley

**Contents of SEISMIC DESIGN OF REINFORCED CONCRETE AND MASONRY BUILDINGS**

Introduction: Concepts of Seismic Design 1

1.1 Seismic Design and Seismic Performance: A Rcvicw 1

1.1.1 Seismic Design Limit States 8

(a) Serviceability Limit State 9

(b) Darnagc Control Limit Slatc 9

(c) Survival Limit Slate 10

1.1.2 Structural Properties 10

(a) Stiffness 10

(b) Strength 11

(c) Ductility 12

1.2 Essentials of Structural Systems for Seismic Resistance 13

1.2.1 Structural Systems for Seismic Forces 14

(a) Structural Frame Systems 14

(b) Structural Wall Systems 14

(c) Dual Systems 15

1.2.2 Gross Seismic Response 15

(a) Response in Elevation: The Building as a

Vertical Cantilever 15

(b) Response in Plan: Centers of Mass and

Rigidity 17

1.2.3 Influence of Building Configuration on Seismic

Response 18

(a) Role of the Floor Diaphragm 19

(b) Amelioration of Torsional Effects 20

(c) Vertical Configurations 22

1.2.4 Structural Classification in Terms of Design

Ductility Level 26

(a) Elastic Response 27

(b) Ductile Response 27

1.3 Definition of Design Quantities 29

1.3.1 Design Loads and Forces 29

(a) Dead Loads (D) 29

(b) Live Loads (L) 29

(c) Earthquake Forces (El 30

(dl Wind Forces ( W) 30

(el Other Forces 31

1.3.2 Design Combinations of Load and Force Effects 31

1.3.3 Strength Definitions and Relationships 33

(a) Required Strength (SJ 34

(b) Ideal Strength (S,) 34

(c) Probable Strength (S,) 34

(dl Overstrength (So) 35

(el Relationships between Strengths 35

(f) Flexural Overstrength Factor (4,) 35

(g) System Overstrength Factor ($,,I 37

1.3.4 Strength Reduction Factors 38

1.4 Philosophy of Capacity Design 38

1.4.1 Main Features 38

1.4.2 Illustrative Analogy 40

1.4.3 Capacity Design of Structures 42

1.4.4 Illustrative Example 43

2 Causes and Effects of Earthquakes:

Seismicity -+ St~cturaRl esponse + Seismic Action

2.1 Aspects of Seismicity 47

2.1.1 Introduction: Causes and Effects 47

2.1.2 Seismic Waves 50

2.1.3 Earthquake Magnitude and Intensity 52

(a) Magnitude 52

(b) Intensity 52

2.1.4 Characteristics of Earthquake Accelerograms 54

(a) Accelerograms 54

(b) Vertical Acceleration 54

(c) Influence of Soil Stiffness 56

(dl Directionality Effects 57

(el Geographical Amplification 57

2.1.5 Attenuation Relationships 58

2.2 Choice of Design Earthquake 61

2.2.1 Intensity and Ground Acceleration

Relationships 61

2.2.2 Return Periods: Probability of Occurrence 63

2.2.3 Seismic Risk 64

2.2.4 Factors Mecting Design Intensity 65

(a) Design Limit States 65

(b) Economic Considerations 67

2.3 Dynamic Response of Structures 68

2.3.1 Response of Single-Degree-of-Freedom Systems

to Lateral Ground Acceleration 69

(a) Stiffness 70

(b) Damping 70

(c) Period 71

2.3.2 Elastic Response Spectra 72

2.3.3 Response of Inelastic Single-Degree-of-Freedom

Systems 73

2.3.4 Inelastic Response Spectra 76

2.3.5 Response of Multistory Buildings 79

2.4 Determination ‘of Design Forces 79

2.4.1 Dynamic Inelastic Time-History Analysis 80

2.4.2 Modal Superposition Techniques 80

2.4.3 Equivalent Lateral Force Procedures 83

(a) First-Mode Period 84

(b) Factors Affecting the Seismic Base Shear

Force 85

(c) Distribution of Base Shear over the Height of

a Building 89

(d) Lateral Force Analysis 91

(e) Estimate of Deflection and Drift 92

(f) PA Effects in Frame Structures 92

(g) Torsion Effects 94

3 Principles of Member Design

3.1 Introduction 95

3.2 Materials 95

3.2.1 Unconfined Concrete 95

(a) Stress-Strain Curves for Unconfined

Concrete 95

(b) Compression Stress Block Design Parameters

for Unconfined Concrete 97

(c) Tension Strength of Concrete 98

3.2.2 Confined Concrete 98

(a) Confining Effect of Transverse

Reinforcement 98

(b) Compression Stress-Strain Relationships for

Conlined Concrete 101

(c) Influence of Cyclic Loading on Concrete

Stress-Strain Relationship 103

(d) Effect of Strain Rate on Concrete

Stress-Strain Relationship 103

(e) Compression Stress Block Design Parameters

for Confined Concrete 104

3.2.3 Masonry 106

(a) Compression Strength of the Composite

Material 108

(b) Ungrouted Masonry 109

(c) Grouted Concrete Masonry 111

(d) Grouted Brick Masonry 112

(e) Modulus of Elasticity 113

(f) Compression Stress-Strain Relationships for

Unconfined and Confined Masonry 113

(g) Compressions Stress Block Design

Parameters for Masonry 114

3.2.4 Reinforcing Steel 115

(a) Monotonic Characteristics 115

(b) Inelastic Cyclic Response 115

(c) Strain Rate Effects 117

(d) Temperature and Strain Aging Effects 117

(el Overstrength Factor (A,) 118

3.3 Analysis of Member Sections 118

3.3.1 Flexural Strength Equations for Concrete and

Concrete Sections 118

(a) Assumptions 119

(b) Flexural Strength of Beam Sections 119

(c) Flexural Strength of Column and Wall

Sections 121

3.3.2 Shear Strength 124

(a) Control of Diagonal Tension and

Compression Failures 124

(b) Sliding Shear 129

(c) Shear in Beam-Column Joints 132

3.3.3 Torsion 132

3.4 Section Design 132

3.4.1 Strength Reduction Factors 133

3.4.2 Reinforcement Limits 134

3.4.3 Member Proportions 135

3.5 Ductility Relationships 135

3.5.1 Strain Ductility 136

3.5.2 Curvature Ductility 136

(a) Yield Curvature 136

(b) Maximum Curvature 138

3.5.3 Displacement Ductility 139

3.5.4 Relationship between Curvature and

Displacement Ductilities 140

(a) Yield Displacement 140

(b) Maximum Displacement 140

(c) Plastic Hinge Length 141

3.5.5 Member and System Ductilities 142

(a) Simultaneity in the Formation of Several

Plastic Hinges 143

(b) Kinematic Relationships 144

(c) Sources of Yield Displacements and Plastic

Displacements 144

3.5.6 Confirmation of Ductility Capacity by Testing 145

3.6 Aspects of Detailing 146

3.6.1 Detailing of Columns for Ductility 147

(a) Transverse Reinforcement for Confinement 147

(b) Spacing of Column Vertical Rcinforccmcnt 148

3.6.2 Bond and Anchorage 149

(a) Development of Bar Strength 149

(b) Lapped Splices 151

(c) Additional Considerations for Anchorages 153

3.4.3 Curtailment of Flexural Reinforcement 155

3.6.4 Transverse Reinforcement 156

4 Reinforced Concrete Ductile Frames

4.1 Structural Modeling 158

4.1.1 General Assumptions 158

4.1.2 Geometric Idealizations 160

4.1.3 Stiffness Modeling 162

4.2 Methods of Analysis 165

4.2.1 “Exact” Elastic Analyses 165

4.2.2 Nonlinear Analyses 165

4.2.3 Modified Elastic Analyses 165

4.2.4 Approximate Elastic Analyses for Gravity Loads 146

4.2.5 Elastic Analysis for Lateral Forces 168

(a) Planar Analysis 168

(b) Distribution of Lateral Forces between

Frames 168

(c) Corrected Computer Analyscs 170

4.2.6 Regularity in the Framing System 171

4.3 Derivation of Design Actions for Beams 172

4.3.1 Redistribution of Design Actions 172

4.3.2 Aims of Moment Redistribution 175

4.3.3 Equilibrium Requirements for Moment

Redistribution 175

4.3.4 Guidelines for Redistribution 178

4.3.5 Examples of Moment Redistribution 180

4.3.6 Moment Redistribution in Inelastic Columns 182

4.3.7 Graphical Approach to the Determination of Beam

Design Moments 183

4.4 Design Process 185

4.4.1 Capacity Design Sequence 185

(a) Beam Flexural Design 185

(b) Beam Shcar Design 186

(c) Column Flexural Strength 186

(d) Transverse Reinforcement for Columns 186

(el Beam-Column Joint Design 186

4.4.2 Design of Floor Slabs 186

4.5 Design of Beams 187

4.5.1 Flexural Strength of Beams 187

(a) Design for Flexural Strength 187

(b) Effective Tension Reinforcement 189

(c) Limitations to the Amounts of Flexural

Tension Reinforcement 193

(d) Potential Plastic Hinge Zones 194

(el Flexural Overstrength of Plastic Hinges 199

(f) Beam Overstrength Factors (4,) 199

(g) System Overstrength Factor ($,) 200

(h) Illustration of the Derivation of Overstrength

Factors 200

4.5.2 Development and Curtailment of the Flexural

Reinforcement 204

4.5.3 Shear Strength of Beams 205

(a) Determination of Design Shear Forces 205

(b) Provisions for Design Shear Strength 207

4.5.4 Detailing Requirements 207

4.6 Design of Columns 210

4.6.1 Limitations of Existing Procedures 210

4.6.2 Deterministic Capacity Design Approach 211

4.6.3 Magnification of Column Moments Due to

Flexural Overstrength of Plastic Hinges in

Beams 212

(a) Columns above Lcvel 2 212

(b) Columns of the First Story 214

(c) Columns in the Top Story 214

(dl Columns Dominated by Cantilever Action 215

4.6.4 Dynamic Magnification of Column Moments 215

(a) Columns of One-way Frames 217

(b) Columns of Two-way Frames 218

(c) Required Flexural Strength at the Column

Base and in the Top Story 219

(dl Higher-Mode Effects of Dynamic Response 219

(el Columns with Dominant Cantilever Action 220

4.6.5 Column Design Moments 221

(a) Column Design Moments at Node Points 221

(b) Critical Column Section 222

(c) Reduction in Design Moments 223

4.6.6 Estimation of Design Axial Forces 225

4.6.7 Design Column Shear Forces 226

(a) Typical Column Shear Forces 226

(b) Design Shear in First-Story Columns 227

(c) Shear in Columns of Two-way Frames 227

(d) Shear in Top-Story Columns 228

4.6.8 Design Steps to Determine Column Design

Actions: A Summary 228

4.6.9 Choice of Vertical Reinforcement in Columns 230

4.6.10 Location of Column Splices 232

4.6.11 Design of Transverse Reinforccmcnt 233

(a) General Considerations 233

(b) Configurations and Shapes of Transverse

Reinforcement 234

(c) Shear Resistance 237

(d) Lateral Support for Compression

Reinforcement 237

(e) Confinement of the Concrete 237

(f) Transverse Reinforcement at Lapped

Splices 239

4.7 Frame Instability 240

4.7.1 P-A Phenomena 240

4,7.2 Current Approaches 240

4.7.3 Stability Index 241

4.7.4 Influence of PA Effects on Inelastic Dynamic

Response 243

(a) Energy Dissipation 243

(b) Stiffness of Elastic Frames 244

(c) Maximum Story Drift 245

(dl Ductility Demand 245

4.7.5 Strength Compensation 246

(a) Compensation for Losses in Energy

Absorption 246

(b) Estimate of Story Drift 246

(c) Necessary Story Moment Capacity 247

4.7.6 Summary and Design Rccommcndations 248

4.8 Beam-Column Joints 250

4.8.1 General Design Criteria 250

4.8.2 Performance Criteria 252

4.8.3 Features of Joint Behavior 252

(a) Equilibrium Criteria 252

(b) Shear Strength 254

(c) Bond Strength 256

4.8.4 Joint Types Used in Frames 256

(a) Joints Affected by the Configuration of

Adjacent Members 256

(b) Elastic and Inelastic Joints 257

4.8.5 Shear Mechanisms in Interior Joints 258

(a) Actions and Disposition of Internal Forces at

a Joint 259

(b) Development of Joint Shear Forces 260

(c) Contribution to Joint Shear Strength of the

Concrete Alone 261

(d) Contribution to’Joint Shear Strength of the

Joint Shear Reinforcement 262

4.8.6 Role of Bar Anchorages in Developing Joint

Strength 263

(a) Factors Affecting Bond Strength 263

(b) Required Average Bond Strength 265

(c) Distribution of Bond Forces within an

Interior Joint 271

(d) Anchorages Requirements for Column Bars 273

4.8.7 Joint Shear Requirements 273

(a) Contributions of the Strut Mechanism

(V,, and V,,) 273

(b) Contributions of the Truss Mechanism

(V,, and 5,) 277

(c) Joint Shear Stress and Joint Dimensions 280

(d) Limitations of Joint Shear 281

(e) Elastic Joints 282

4.8.9 Special Features of Interior Joints 285

(a) ContributiGn of Floor Slabs 285

(b) Joints with Unusual Dimensions 288

(c) Eccentric Joints 290

(d) Joints with Inelastic Columns 291

4.8.10 Alternative Detailing of Interior Joints 292

(a) Beam Bar Anchorage with Welded

Anchorage Plates 292

(b) Diagonal Joint Shear Reinforcement 292

(c) Horizontally Haunched Joints 294

4.8.11 Mechanisms in Exterior Joints 294

(a) Actions at Exterior Joints 294

(b) Contributions of Joint Shear Mechanisms 295

(c) Joint Shear Reinforcement 297

(d) Anchorage in Exterior Joints 297

(e) Elastic Exterior Joints 301

4.8.12 Design Steps: A Summary 302

4.9 Gravity-Load-Dominated Frames 303

4.9.1 Potential Seismic Strength in Excess of That

Required 303

4.9.2 Evaluation of the Potential Strength of Story Sway

Mechanisms 305

4.9.3 Deliberate Reduction of Lateral Force

Resistance 308

(a) Minimum Level of Lateral Force

Resistance 308

(b) Beam Sway Mechanisms 310

(c) Introduction of Plastic Hinges in Columns 311

(d) Optimum Location of Plastic Hinges

in Beams 312

4.9.4 Design for Shear 314

4.10 Earthquake-Dominated Tube Frames 314

4.10.1 Critical Design Qualities 314

4.10.2 Diagonally Reinforced Spandrel Beams 315

4.10.3 Special Detailing Requirements 316

4.10.4 Observed Beam Performance 318

4.11 Examples in the Design of an Eight-Story Frame 319

4.11.1 General Description of the Project 319

4.11.2 Material Properties 319

4.11.3 Specified Loading and Design Forces 319

(a) Gravity Loads 319

(b) Earthquake Forces 321

(a) Members of East-West Frames 321

(b) Members of North-South Frames 323

4.11.5 Gravity Load Analysis of Subframes 324

4.11.6 Lateral Force Analysis 331

(a) Total Base Shear 331

(b) Distribution of Lateral Forces over the Height

of the Structure 332

(c) Torsional Effects and Irregularities 333

(d) Distribution of Lateral Forces among All

Columns of the Building 335

(el Actions in Frame 5-6-7-8 Due to Lateral

Forces 336

(f) Actions for Beam 1-2-C-3-4 Due to Lateral

Forces 339

4.1 1.7 Design of Beams at Level 3 340

(a) Exterior Beams 340

(b) Interior Beams 343

4.11.8 Design of Columns 350

(a) Exterior Column 5 at Level 3 350

(b) Interior Column 6 at Level 3 352

(c) Interior Column 6 at Level 1 355

4.11.9 Design of Beam-Column Joints at Level 3 357

(a) Interior Joint at Column 6 357

(b) Interior Joint at Column 5 360

5 Structural Walls

5.1 Introduction 362

5.2 Structural Wall System 363

5.2.1 Strategies in the Location of Structural Walls 363

5.2.2 Sectional Shapes 368

5.2.3 Variations in Elevation 370

(a) Cantilever Walls without Openings 370

(b) Structural Walls with Openings 372

5.3 Analysis Procedures 376

5.3.1 Modeling Assumptions 376

(a) Member Stiffness 376

(b) Geometric Modeling 378

(c) Analysis of Wall Sections 379

5.3.2 Analysis for Equivalent Lateral Static Forces 381

(a) Interacting Cantilever Walls 381

(b) Coupled Walls 384

(c) Lateral Force Redistribution between Walls

387

5.4 Design of Wall Elements for Strength and Ductility 389

5.4.1 Failure Modes in Structural Walls 389

5.4.2 Flexural Strength 391

(a) Design for Flexural Strength 391

(b) Limitations on Longitudinal Reinforcement 392

(c) Curtailment of Flexural Reinforcement 393

(d) Flexural Overstrength at the Wall Base 396

5.4.3 Ductility and Instability 397

(a) Flexural Response 397

(b) Ductility Relationships in Walls 399

(c) Wall Stability 400

(dl Limitations on Curvature Ductility 405

(e) Confinement of Structural Walls 407

5.4.4 Control of Shear 411

(a) Determination of Shear Force 411

(b) Control of Diagonal Tension and

Compression 414

(c) Sliding Shear in Walls 416

5.4.5 Strength of Coupling Beams 417

(a) Failure Mechanisms and Behavior 417

(b) Design of Beam Reinforcement 418

(c) Slab Coupling of Walls 421

5.5 Capacity Design of Cantilever Wall Systems 423

5.5.1 Summary 423

5.5.2 Design Example of a Cantilever Wall System 426

(a) General Description of Example 426

(b) Design Steps 427

5.6 Capacity Design of Ductile Coupled Wall Structures .440

5.6.1 Summary 440

5.6.2 Design Example of Coupled Walls 445

(a) Design Requirements and Assumptions 445

(b) Design Steps 447

5.7 Squat Structural Walls 473

5.7.1 Role of Squat Walls 473

5.7.2 . Flexural Response and Reinforcement

Distribution 474

5.7.3 Mechanisms of Shear Resistance 474

(a) Diagonal Tension Failure 475

(b) Diagonal Compression Failure 475

(c) Phenomenon of Sliding Shear 476

5.7.4 Control of Sliding Shear 477

(a) Ductility Demand 479

(b) Sliding Shear Resistance of Vertical Wall

Reinforcement 480

(c) Relative Size of Compression Zone 480

(d) Effectiveness of Diagonal Reinforcement 482

(e) Combined Effects 483

5.7.5 Control of Diagonal Tension 483

5.7.6 Framed Squat Walls 484

5.7.7 Squat Walls with Openings 486

5.7.8 Design Examples for Squat Walls 488

(a) Squat Wall Subjected to a Large Earthquake

Force 488

(b) Alternative Solution for a Squat Wall

Subjected to a Large Earthquake Force 491

(c) Squat Wall Subjected to a Small Earthquake

Force 494

(d) Squat Wall with Openings 495

6 Dual Systems

Introduction 500

Categories, Modeling, and Behavior of Elastic Dual

Systems 501

6.2.1 Interacting Frames and Cantilever Walls 501

6.2.2 Ductile Frames and Walls Coupled by Beams 505

6.2.3 Dual Systems with Walls on Deformable

Foundations 506

6.2.4 Rocking Walls and Three-Dimensional Effects 508

6.2.5 Frames Interacting with Walls of Partial Height 510

Dynamic Response of Dual Systems 513

Capacity Design Procedure for Dual Systems 516

Issues of Modeling and Design Requiring Engineering

Judgment 526

6.5.1 Gross ~rre~ularitiiens the Lateral-Force-Resisting

System 527

6.5.2 Torsional Effects 527

6.5.3 Diaphragm Flexibility 528

6.5.4 Prediction of Shear Demand in Walls 529

6.5.5 Variations in the Contributions of Walls to

Earthquake Resistance 531

7 Masonry Structures

7.1 Introduction 532

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CONTENTS xix

7.2.1 Categories of Walls for Seismic Resistance 535

(a) Cantilever wills 535

(b) Coupled Walls with Pier Hinging 536

(c) Coupled Walls with Spandrel Hinging 538

(d) Selection of Primary and Secondary

Lateral-Load-Resisting Systems 538

(e) Face-Loaded Walls 539

7.2.2 Analysis Procedure 540

7.2.3 Design for Flexure 540

(a) Out-of-Plane Loading and Interaction with

In-Plane Loading 540

(b) Section Analysis for Out-of-Plane Flexure 543

(c) Design for Out-of-Plane Bending 545

(d) Analysis for In-Plane Bending 547

(e) Design for In-Plane Bending 551

(f) Dcsign of a Confined Iicctangular

Masonry Wall 552

(g) Flanged Walls 555

7.2.4 Ductility Considerations 555

(a) Walls with Rectangular Section 556

(b) Walls with Nonrectangular Scction 561

7.2.5 Design for Shear 563

(a) Design Shear Force 563

(b) Shear Strength of Masonry Walls

Unreinforced for Shear 564

(c) Design Recommendations for Shear

Strength 565

(d) Effective Shear Area 567

(e) Maximum Total Shear Stress 568

7.2.6 Bond and Anchorage 569

7.2.7 Limitation on Wall Thickness 571

7.2.8 Limitations on Reinforcement 571

(a) Minimum Reinforcement 571

(b) Maximum Rcinforccment 572

(c) Maximum Bar Diameter 573

(d) Bar Spacing Limitations 573

(e) Confining Plates 573

7.3 Masonry Moment-Resisting Wall Frames 574

7.3.1 Caiacity Design Approach 575

7.3.2 Beam Flexure 576

7.3.3 Beam Shear 577

7.3.4 Column Flexure and Shear 577

7.3.5 Joint Design 578

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(b) Joint Shear Forces 579

(c) Maximum Joint Shear Stress 581

7.3.6 Ductility 581

7.3.7 Dimensional Limitations 583

7.3.8 Behavior of a Masonry Wall-Beam Test Unit 583

7.4 Masonry-Infilled Frames 584

7.4.1 Influence of Masonry Infill on Seismic Behavior

of Frames 584

7.4.2 Design of Infilled Frames 587

(a) In-Plane Stiffness 587

(b) In-Plane Strength 588

(c) Ductility 592

(d) Out-of-Plane Strength 593

7.5 Minor Masonry Buildings 595

7.5.1 hw-Rise Walls with Openings 595

7.5.2 Stiffness of Walls with Openings 595

7.5.3 Design Level of Lateral Force 597

7.5.4 Design for Flexure 597

(a) Piers 597

(b) Spandrels 600

7.5.5 Design for Shear 600

7.5.6 Ductility 600

7.5.7 Design of the Wall Base and Foundation 601

7.5.8 Ductile Single-Story Columns 602

7.6 Design Example of a Slender Masonry Cantilever Wall . 604

7.6.1 Design of Base Section for Flexure and’Axia1

Load 604

7.6.2 Check of Ductility Capacity 605

7.6.3 Redesign for Flexure with f; = 24 MP~ 605

7.6.4 Recheck of Ductility Capacity 606

7.6.5 Flexural Reinforcement 606

7.6.6 Wall Instability 606

7.6.7 Design for Shear Strength 607

(a) Determination of Design Shear Force 607

(b) Shear Stresses 608

(c) Shear Reinforcement 608

7.7 Design Example of a Three-Story Masonry Wall

with Openings 609

7.7.1 Determination of Member Forces 40

(a) Pier Stiffnesses 610 .

(b) Shear Forces and Moments for Members 611

7.7.2 Design of First-Story Piers 612

(a) Flexural Strength 612

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CONTENTS xxi

7.7.3 Design of Spandrels at Level 2 616

(a) Flexural Strength 616

(b) Shear Strength 617

7.7.4 Design of Wall Base and Foundation 617

(a) Load Effects 617

(b) Flexural Strength 619

(c) Shear Strength 620

(dl Transverse Bending of Footing Strip 620

7.7.5 Lapped Splices in Masonry 621

7.8 Assessment of Unreinforced Masonry Structures 621

7.8.1 Strength Design for Unreinforced Masonry 621

7.8.2 Unreinforced Walls Subjected to Out-of-Plane

Excitation 623

(a) Response Accelerations 623

(b) Conditions at Failure and Equivalent Elastic

Response 627

(c) Load Deffcction Rclation for Wall 628

(d) Example of Unreinforced Masonry Building

Response 631

7.8.3 Unreinforced Walls Subjected to In-Plane

Excitation 636

8 Reinforced Concrete Buildings with Restricted Ductility

8.1 Introduction 639

8.2 Design Strategy 641

8.3 Frames of Restricted Ductility 643

8.3.1 Design of Beams 643

(a) Ductile Beams 643

(b) Elastic Beams 644

8.3.2 Design of Columns Relying on Beam

Mechanisms 645

(a) Derivation of Design Actions 645

(b) Detailing Requirements for Columns 646

8.3.3 Columns of Soft-Story Mechanisms 647

8.3.4 Design of Joints 649

(a) Derivation of Internal Forces 649

(b) Joint Shear Stresses 650

(c) Usable Bar Diameters at Interior Joints 650

(dl Contribution of the Concrete to Joint Shear

Resistance 651

(el Joint Shear Reinforcement 652

(f) Exterior Joints 652

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XXu CONTENTS

8.4 Walls of Restricted Ductility 653

8.4.1 Walls Dominated by Flexure 653

(a) Instability of Wall Sections 653

(b) Confinement of Walls 654

(c) Prevention of Buckling of the Vertical Wall

Reinforcement 654

(d) Curtailment of the Vertical Wall

Reinforcement 654

(el Shear Resistance of Walls 654

(f) Coupling Beams 655

8.4.2 ‘ Walls Dominated by Shear 656

(a) Considerations for Developing a Design

Procedure 656

(b) Application of the Design Procedure 659

(c) Consideration of Damage 660

8.5 Dual Systems of Restricted Ductility 661

9 Foundation Structures

9.1 Introduction 662

9.2 Classification of Intended Foundation Response 663

9.2.1 Ductile Superstructures 663

9.2.2 Elastic Superstructures 663

(a) Elastic Foundation Systems 663

(b) Ductile Foundation Systems 664

(c) Rocking Structural Systems 664

9.3 Foundation Structures for Frames 664

9.3.1 Isolated Footings 664

9.3.2 Combined Footings 665

9.3.3 Basements 668

9.4 Foundations for Structural Wall Systems 668

9.4.1 Elastic Foundations for Walls 668

9.4.2 Ductile Foundations for Walls 669

9.4.3 Rocking Wall Systems 671

9.4.4 Pile Foundations 672

(a) Mechanisms of Earthquake Resistance 672

(b) Effects of Lateral Forces on Piles 674

(c) Detailing of Piles 677

9.4.5 Example Foundation Structures 679

9.4.6 Effects of Soil Deformations 686

9.5 Design Example for a Foundation Structure 686

9.5.1 Specifications 686

9.5.2 Load Combinations for Foundation Walls 688

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CONTENTS xxiii

9.5.3 Reinforcement of the Foundation Wall 690

(a) Footings 690

(b) Flexural Reinforcement 690

(c) Shear Reinforcement 691

(d) Shear Reinforcement in the Tension Flange 692

(e) Joint Shear Reinforcement 692

9.5.4 Detailing 694

(a) Anchorage and Curtailment 694

(b) Detailing of Wall Corners 694

APPENDIX A Approximate Elastic Analysis of Franics Subjected

to Lateral Forces 696

APPENDIX B Modificd Mcrcalli Intensity Scale 706

SYMBOLS

REFERENCES 719

INDEX 735

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