Earthquake Engineering for Concrete Dams - Analysis, Design, and Evaluation

Preface xiii Acknowledgments xv 1 Introduction 1 1.1 Earthquake Experience: Cases with Strongest Shaking 1 1.2 Complexity of the Problem 6 1.3 Traditional Design Procedures: Gravity Dams 8 1.3.1 Traditional Analysis and Design 8 1.3.2 Earthquake Performance of Koyna Dam 9 1.3.3 Limitations of Traditional Procedures 9 1.4 Traditional Design Procedures: Arch Dams 11 1.4.1 Traditional Analysis and Design 11 1.4.2 Limitations of Traditional Procedures 12 1.5 Unrealistic Estimation of Seismic Demand and Structural Capacity 13 1.6 Reasons Why Standard Finite-Element Method is Inadequate 13 1.7 Rigorous Methods 14 1.8 Scope and Organization 16 Part I: Gravity Dams 2 Fundamental Mode Response of Dams Including Dam-Water Interaction 21 2.1 System and Ground Motion 21 2.2 Dam Response Analysis 22 2.2.1 Frequency Response Function 22 2.2.2 Earthquake Response: Horizontal Ground Motion 23 2.3 Hydrodynamic Pressures 24 2.3.1 Governing Equation and Boundary Conditions 24 2.3.2 Solutions to Boundary Value Problems 26 2.3.3 Hydrodynamic Forces on Rigid Dams 28 2.3.4 Westergaard's Results and Added Mass Analogy 30 2.4 Dam Response Analysis Including Dam-Water Interaction 32 2.5 Dam Response 33 2.5.1 System Parameters 33 2.5.2 System and Cases Analyzed 34 2.5.3 Dam-Water Interaction Effects 34 2.5.4 Implications of Ignoring Water Compressibility 37 2.5.5 Comparison of Responses to Horizontal and Vertical Ground Motions 39 2.6 Equivalent SDF System: Horizontal Ground Motion 40 2.6.1 Modified Natural Frequency and Damping Ratio 40 2.6.2 Evaluation of Equivalent SDF System 42 2.6.3 Hydrodynamic Effects on Natural Frequency and Damping Ratio 43 2.6.4 Peak Response 45 Appendix 2: Wave-Absorptive Reservoir Bottom 46 3 Fundamental Mode Response of Dams Including Dam-Water-Foundation Interaction 49 3.1 System and Ground Motion 50 3.2 Dam Response Analysis Including Dam-Foundation Interaction 51 3.2.1 Governing Equations: Dam Substructure 51 3.2.2 Governing Equations: Foundation Substructure 52 3.2.3 Governing Equations: Dam-Foundation System 53 3.2.4 Dam Response Analysis 54 3.3 Dam-Foundation Interaction 54 3.3.1 Interaction Effects 54 3.3.2 Implications of Ignoring Foundation Mass 55 3.4 Equivalent SDF System: Dam-Foundation System 56 3.4.1 Modified Natural Frequency and Damping Ratio 56 3.4.2 Evaluation of Equivalent SDF System 57 3.4.3 Peak Response 59 3.5 Equivalent SDF System: Dam-Water-Foundation System 60 3.5.1 Modified Natural Frequency and Damping Ratio 60 3.5.2 Evaluation of Equivalent SDF System 61 3.5.3 Peak Response 62 Appendix 3: Equivalent SDF System 63 4 Response Spectrum Analysis of Dams Including Dam-Water-Foundation Interaction 65 4.1 Equivalent Static Lateral Forces: Fundamental Mode 66 4.1.1 One-Dimensional Representation 66 4.1.2 Approximation of Hydrodynamic Pressure 67 4.2 Equivalent Static Lateral Forces: Higher Modes 68 4.3 Response Analysis 70 4.3.1 Dynamic Response 70 4.3.2 Total Response 70 4.4 Standard Properties for Fundamental Mode Response 71 4.4.1 Vibration Period and Mode Shape 71 4.4.2 Modification of Period and Damping: Dam-Water Interaction 72 4.4.3 Modification of Period and Damping: Dam-Foundation Interaction 72 4.4.5 Generalized Mass and Earthquake Force Coefficient 74 4.5 Computational Steps 74 4.6 CADAM Computer Program 76 4.7 Accuracy of Response Spectrum Analysis Procedure 77 4.7.1 System Considered 77 4.7.2 Ground Motions 77 4.7.3 Response Spectrum Analysis 78 4.7.4 Comparison with Response History Analysis 79 5 Response History Analysis of Dams Including Dam-Water-Foundation Interaction 83 5.1 Dam-Water-Foundation System 83 5.1.1 Two-Dimensional Idealization 83 5.1.2 System Considered 84 5.1.3 Ground Motion 85 5.2 Frequency-Domain Equations: Dam Substructure 86 5.3 Frequency-Domain Equations: Foundation Substructure 87 5.4 Dam-Foundation System 88 5.4.1 Frequency-Domain Equations 88 5.4.2 Reduction of Degrees of Freedom 89 5.5 Frequency-Domain Equations: Fluid Domain Substructure 90 5.5.1 Boundary Value Problems 90 5.5.2 Solutions for Hydrodynamic Pressure Terms 91 5.5.3 Hydrodynamic Force Vectors 92 5.6 Frequency-Domain Equations: Dam-Water-Foundation System 93 5.7 Response History Analysis 94 5.8 EAGD-84 Computer Program 95 Appendix 5: Water-Foundation Interaction 96 6 Dam-Water-Foundation Interaction Effects in Earthquake Response 101 6.1 System, Ground Motion, Cases Analyzed, and Spectral Ordinates 101 6.1.1 Pine Flat Dam 101 6.1.2 Ground Motion 103 6.1.3 Cases Analyzed and Response Results 103 6.2 Dam-Water Interaction 105 6.2.1 Hydrodynamic Effects 105 6.2.2 Reservoir Bottom Absorption Effects 107 6.2.3 Implications of Ignoring Water Compressibility 108 6.3 Dam-Foundation Interaction 112 6.3.1 Dam-Foundation Interaction Effects 112 6.3.2 Implications of Ignoring Foundation Mass 112 6.4 Dam-Water-Foundation Interaction Effects 115 7 Comparison of Computed and Recorded Earthquake Responses of Dams 117 7.1 Comparison of Computed and Recorded Motions 117 7.1.1 Choice of Example 117 7.1.2 Tsuruda Dam and Earthquake Records 118 7.1.3 System Analyzed 119 7.1.4 Comparison of Computed and Recorded Responses 120 7.2 Koyna Dam Case History 122 7.2.1 Koyna Dam and Earthquake Damage 122 7.2.2 Computed Response of Koyna Dam 123 7.2.3 Response of Typical Gravity Dam Sections 126 7.2.4 Response of Dams with Modified Profiles 127 Appendix 7: System Properties 129 Part II: Arch Dams 8 Response History Analysis of Arch Dams Including Dam-Water-Foundation Interaction 133 8.1 System and Ground Motion 133 8.2 Frequency-Domain Equations: Dam Substructure 136 8.3 Frequency-Domain Equations: Foundation Substructure 137 8.4 Dam-Foundation System 138 8.4.1 Frequency-Domain Equations 138 8.4.2 Reduction of Degrees of Freedom 139 8.5 Frequency-Domain Equations: Fluid Domain Substructure 140 8.6 Frequency-Domain Equations: Dam-Water-Foundation System 142 8.7 Response History Analysis 143 8.8 Extension to Spatially Varying Ground Motion 144 8.9 EACD-3D-2008 Computer Program 146 9 Earthquake Analysis of Arch Dams: Factors to Be Included 149 9.1 Dam-Water-Foundation Interaction Effects 149 9.1.1 Dam-Water Interaction 150 9.1.2 Dam-Foundation Interaction 151 9.1.3 Dam-Water-Foundation Interaction 153 9.1.4 Earthquake Responses 153 9.2 Bureau of Reclamation Analyses 153 9.2.1 Implications of Ignoring Foundation Mass 156 9.2.2 Implications of Ignoring Water Compressibility 157 9.3 Influence of Spatial Variations in Ground Motions 158 9.3.1 January 13, 2001 Earthquake 159 9.3.2 January 17, 1994 Northridge Earthquake 160 10 Comparison of Computed and Recorded Motions 163 10.1 Earthquake Response of Mauvoisin Dam 163 10.1.1 Mauvoisin Dam and Earthquake Records 163 10.1.2 System Analyzed 165 10.1.3 Spatially Varying Ground Motion 166 10.1.4 Comparison of Computed and Recorded Responses 166 10.2 Earthquake Response of Pacoima Dam 168 10.2.1 Pacoima Dam and Earthquake Records 168 10.2.2 System Analyzed 171 10.2.3 Comparison of Computed and Recorded Responses: January 13, 2001 Earthquake 172 10.2.4 Comparison of Computed Responses and Observed Damage: Northridge Earthquake 172 10.3 Calibration of Numerical Model: Damping 174 11 Nonlinear Response History Analysis of Dams 177 Part A: Nonlinear Mechanisms and Modeling 178 11.1 Limitations of Linear Dynamic Analyses 178 11.2 Nonlinear Mechanisms 178 11.2.1 Concrete Dams 178 11.2.2 Foundation Rock 181 11.2.3 Impounded Water 181 11.2.4 Pre-Earthquake Static Analysis 181 11.3 Nonlinear Material Models 182 11.3.1 Concrete Cracking 182 11.3.2 Contraction Joints: Opening, Closing, and Sliding 183 11.3.3 Lift Joints and Concrete-Rock Interfaces: Sliding and Separation 184 11.3.4 Discontinuities in Foundation Rock 185 11.4 Material Models in Commercial Finite-Element Codes 185 Part B: Direct Finite-Element Method 186 11.5 Concepts and Requirements 186 11.6 System and Ground Motion 187 11.6.1 Semi-Unbounded Dam-Water-Foundation System 187 11.6.2 Earthquake Excitation 189 11.7 Equations of Motion 191 11.8 Effective Earthquake Forces 193 11.8.1 Forces at Bottom Boundary of Foundation Domain 193 11.8.2 Forces at Side Boundaries of Foundation Domain 194 11.8.3 Forces at Upstream Boundary of Fluid Domain 195 11.9 Numerical Validation of the Direct Finite Element Method 196 11.9.1 System Considered and Validation Methodology 196 11.9.2 Frequency Response Functions 199 11.9.3 Earthquake Response History 200 11.10 Simplifications of Analysis Procedure 201 11.10.1 Using 1D Analysis to Compute Effective Earthquake Forces 201 11.10.2 Ignoring Effective Earthquake Forces at Side Boundaries 203 11.10.3 Avoiding Deconvolution of the Surface Free-Field Motion 203 11.10.4 Ignoring Effective Earthquake Forces at Upstream Boundary of Fluid Domain 206 11.10.5 Ignoring Sediments at the Reservoir Boundary 207 11.11 Example Nonlinear Response History Analysis 211 11.11.1 System and Ground Motion 211 11.11.2 Computer Implementation 212 11.11.3 Earthquake Response Results 213 11.12 Challenges in Predicting Nonlinear Response of Dams 215 Part III: Design and Evaluation 12 Design and Evaluation Methodology 219 12.1 Design Earthquakes and Ground Motions 219 12.1.1 ICOLD and FEMA 220 12.1.2 U.S. Army Corps of Engineers (USACE) 221 12.1.3 Division of Safety of Dams (DSOD), State of California 221 12.1.4 U.S. Federal Energy Regulatory Commission (FERC) 221 12.1.5 Comments and Observations 221 12.2 Progressive Seismic Demand Analyses 224 12.3 Progressive Capacity Evaluation 226 12.4 Evaluating Seismic Performance 227 12.5 Potential Failure Mode Analysis 228 13 Ground-Motion Selection and Modification 231 Part A: Single Horizontal Component of Ground Motion 232 13.1 Target Spectrum 232 13.1.1 Uniform Hazard Spectrum 232 13.1.2 Uniform Hazard Spectrum Versus Recorded Ground Motions 232 13.1.3 Conditional Mean Spectrum 234 13.1.4 CMS-UHS Composite Spectrum 235 13.2 Ground-Motion Selection and Amplitude Scaling 239 13.3 Ground-Motion Selection to Match Target Spectrum Mean and Variance 241 13.4 Ground-Motion Selection and Spectral Matching 243 13.5 Amplitude Scaling Versus Spectral Matching of Ground Motions 247 Part B: Two Horizontal Components of Ground Motion 247 13.6 Target Spectra 247 13.7 Selection, Scaling, and Orientation of Ground-Motion Components 250 Part C: Three Components of Ground Motion 252 13.8 Target Spectra and Ground-Motion Selection 252 14 Application of Dynamic Analysis to Evaluate Existing Dams and Design New Dams 253 14.1 Seismic Evaluation of Folsom Dam 253 14.2 Seismic Design of Olivenhain Dam 257 14.3 Seismic Evaluation of Hoover Dam 261 14.4 Seismic Design of Dagangshan Dam 265 References 271 Notation 281 Index 291