Page 16 - Pipelines and Risers

Contents XI11

6.5 Hydrodynamic Forces ............................................................................................................................ 91
6.5.1 Hydrodynamic Drag and Inertia Forces ......................................................................................... 91
6.5.2 Hydrodynamic Lift Forces ............................................................................................................. 94
6.6 References .............................................................................................................................................. 95
Chapter 7 Finite Element Analysis of In-situ Behavior 97
7.1 Introduction ............................................................................................................................................ 97
7.2 Description of the Finite Element Model ............................................................................................... 98
7.2.1 Static Analysis Problems ................................................................................................................ 98
7.2.2 Dynamic Analysis Problems ...............................................................
7.3 Steps in an Analysis and Choice of Analysis Procedure ............................. ................................... 101
7.3.1 The Static Analysis Procedure ..................................................................................................... 101
7.3.2 The Dynamic Analysis Procedure ................................................................................................ 101
7.4 Element Types used in the Model ........................................................................................................ 102
7.5 Non-linearity and Seabed Model ......................................................................................................... 104
7.5.1 Material Model ............................................................................................................................. 104
7.5.2 Geometrical non-linearity .................................................
7.5.3 Boundary Conditions ........................................................
7.5.4 Seabed Model ....................................................................
7.6 Validation of the Finite-Element Model ...................................
7.7 References ............................................................................................................................................ 106
Chapter 8 On-bottom Stability I09

8.1 General ................................................................................................................................................. 109
8.2 Force Balance: The Simplified Method ............................................................................................... 110
8.3 Acceptance Criteria ............................................................... .......................................................... 110
8.3.1 Allowable Lateral Displacement ................................................................................................. 110
8.3.2 Limit-state Strength Criteria .................. .................................................................................. 110
8.4 Special Purpose Program for Stability Analysis .................................................................................. 111
8.4. I General ......................................................................................................................................... 111
8.4.2 PONDUS ...................................................................................................................................... 111
8.4.3 PIPE ............................................................................................................................................. 113
8.5 Use of FE Analysis for I ntion Design .............................
8.5.1 Design Procedure .. ............................................................................................................. 114
8.5.2 Seabed Intervention ............................................................................................
8.5.3 Effect of Seabed Intervention ....................................................................................................... 115
8.6 References ................................................................................................................................
Chapter 9 Vortex-induced Vibrations (WV) and Fatigue 117
9 .I ...................................................................................................... 117
9.2 ..........................................
9.2.1 ..........................................
9.2.2 .......................................................
9.2.3 Soil Stiffness Analysis ..................................................................
9.2.4 Vibration Amplitude and Stress Range Analysis ......................................................................... 124
................................................................................................................ 124
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9.4.2 Cross-flow VIV in Combined Wave and Current ........................................................................ 128
9.5 Modal Analysis ................ ...................... .................. ......... . 129
9.5.1 Introduction .................................................................................................................................. 129