Dynamics of Offshore Structures

Dynamics of Offshore Structures......Page 3
Contents......Page 7
Preface......Page 13
Contributors......Page 15
Acknowledgments......Page 17
1 Structures in the Offshore Environment......Page 19
1.1 Historical Perspective......Page 20
Fixed-Bottom Platforms......Page 22
Buoyant Platforms......Page 25
Temporary Anchor Moorings......Page 27
Platform Pile and Single-Point Moorings......Page 28
Sea Floor Pipelines......Page 29
Vertical Pipelines......Page 30
Structural Materials......Page 32
References......Page 33
2.1 Single Degree of Freedom Structures......Page 35
Classical Inviscid Fluid Flow......Page 39
Real Viscous Fluid Flow......Page 41
Conservation of Linear Momentum and Flow Superposition......Page 43
Buoyancy and Gravity......Page 46
Winds and Currents......Page 51
Earthquake Forces......Page 54
Ice Impact Forces......Page 56
Wave Slamming Forces......Page 57
Structural Mass and Stiffness......Page 58
Cable Restraints......Page 61
Soil Foundation Restraints......Page 70
Problems......Page 72
References......Page 74
3 Deterministic Descriptions of Offshore Waves......Page 79
3.1 Description of Plane Waves......Page 80
3.2 Linear Plane Waves......Page 83
3.3 Nonlinear Waves......Page 86
Stokes Theory......Page 87
Solitary Theory......Page 90
Numerical Theory......Page 91
3.4 Domains of Validity for Wave Theories......Page 93
Problems......Page 98
References......Page 99
4.1 Wave Loading of Flexible Cylinders......Page 102
4.2 Classification of Fluid Load Regimes......Page 105
4.3 Flow Regimes for Offshore Structures......Page 109
4.4 Summary of Flow Coefficients C(D) and C(M)......Page 111
4.5 Transfer Functions for Wave Loading......Page 112
Problems......Page 114
References......Page 116
5 Deterministic Responses for Single Degree of Freedom Structures......Page 118
Direct Method......Page 119
The Rayleigh Method......Page 123
5.2 Frequencies for Nonlinear Structures......Page 129
5.3 Response Functions for Linear Structures......Page 133
Harmonic Response Function......Page 134
Impulse Response Function......Page 136
Convolution Integral......Page 137
5.4 Response of Linear Structures to Earthquake Loading......Page 138
Responses to Harmonic Excitation......Page 141
Jumps......Page 144
Subharmonics......Page 147
5.6 Nonlinear Responses for a SALM Buoy......Page 149
Physical Description and Dynamic Model......Page 150
Numerical Results and Conclusions......Page 154
Problems......Page 156
References......Page 160
6.1 Introduction to Wave Spectra......Page 162
6.2 Concept of the Significant Wave......Page 165
Wave Height Distributions......Page 166
Wave Height-Wave Spectrum Relationships......Page 168
Alternative Definitions......Page 170
Empirical Forms......Page 172
6.4 Selection of Design Wave Spectra......Page 174
6.5 Synthesis of Time Histories from Spectra......Page 177
References......Page 180
7 Statistical Responses for Single Degree of Freedom Linear Structures......Page 183
7.1 Averages and Probabilities......Page 184
7.2 Stationary and Ergodic Hypotheses......Page 187
7.3 Autocorrelation and Spectral Density......Page 190
7.4 Structural Response Statistics: Part I......Page 191
The Fourier Transform......Page 192
The Autocorrelation Functions......Page 193
Response Parameters......Page 194
Approximate Responses......Page 198
Extensions......Page 200
7.5 Structural Response Statistics: Part II......Page 201
State Variable Form......Page 202
Covariance Propagation Equation: Derivation......Page 203
Steady State Solutions......Page 205
A Closed Form Solution......Page 206
Problems......Page 208
References......Page 211
8 Multi-Degree of Freedom Linear Structures......Page 213
The Coordinate Vector, x......Page 214
The Loading Vector, p......Page 216
The Mass Matrix, M......Page 217
The Stiffness Matrix, K......Page 219
The Damping Matrix, C......Page 221
8.2 Equations of Motion: Newton\'s Method......Page 222
System Energies......Page 226
Derivation for a Simple System......Page 227
Comments......Page 230
Modal Vectors and Normalization......Page 232
Orthogonality of the Modal Vectors......Page 233
8.5 Forced, Damped Motion......Page 234
Modal Damping Matrix, C......Page 235
Uncoupling the Equations of Motion......Page 236
8.6 Summary of the Normal Mode Method......Page 237
Problems......Page 238
References......Page 239
9 Applications of Multi-Degree of Freedom Analysis......Page 241
Mathematical Model......Page 242
Frequencies......Page 243
Modal Vectors and Normalization......Page 244
Response to a Harmonic Wave......Page 245
Response to Earthquake Excitation......Page 249
Mathematical Model......Page 251
Frequencies and Mode Shapes......Page 254
Dynamic Stability......Page 256
9.3 Structural Response Statistics for Wave Loading......Page 257
9.4 A Fixed Leg Platform: Statistical Responses......Page 260
References......Page 264
10 Continuous Systems......Page 266
Governing Equations......Page 268
Cable Frequencies and Mode Shapes......Page 270
Beam Frequencies and Mode Shapes......Page 272
Transverse End Excitation......Page 277
Parametric Excitation......Page 279
10.3 Beam Responses......Page 283
Transverse Excitation......Page 284
Parametric Excitation......Page 287
Statistical Wave Excitation......Page 290
10.4 Deployment of an OTEC Pipeline......Page 293
Mathematical Model......Page 294
Pipe Excitations by Barge and Waves......Page 295
Numerical Results......Page 298
Problems......Page 302
References......Page 305
11 Behavior of Piles Supporting Offshore Structures......Page 307
11.1 Characteristics of Soil and Response to External Loading......Page 308
11.2 Design of Single Piles under Axial Loading......Page 309
11.3 Design of Single Piles under Lateral Loading......Page 314
Pile Model and Method of Solution......Page 315
Response of Soil......Page 316
Cyclic Loading......Page 317
Scour......Page 318
Solutions Using Nondimensional Parameters......Page 319
Computer-Aided Solutions......Page 324
11.4 An Example: Lateral Pile Loading......Page 325
Problem Description......Page 326
Solutions Using Nondimensional Parameters......Page 328
Computer-Aided Solutions......Page 331
Earthquakes......Page 334
Time-Dependent Loading Above the Mudline......Page 335
Problems......Page 336
References......Page 337
Conversion Table......Page 339
Index......Page 341