Dynamic Analysis of Ocean Structures

Improvements in the design process as applied to ocean structures have received intense interest in recent years. Part of this interest stems from the growing realization that design on a purely deterministic basis is inadequate for structures sub­ ject to random loads, which are best described by statistical (or probability) methods. This book is an attempt to bridge the gap between present design practices and available analytical techni­ ques (which may be exploited to improve present procedures). The book itself is an outgrowth of a set of notes prepared for an intensive short course presented over the past three years by the Engineering Extension Division of the University of California at Los Angeles, California. The ensuing presentation is composed of four parts. The material begins with a review of the physical environment (winds, surface gravity water waves and currents) for which engineering­ type formulations are presented. Hindcasting and forecasting techniques using spectral concepts are included. Special problem areas are enumerated.

I. Environment, Considerations for Design.- I ― Wind and Wind Loadings.- 1.1 Wind Forces.- 1.2 Specific Weight of Air.- 1.3 Wind Velocity Records.- l.4 Design Wind Velocities and Recurrence Interval.- 1.5 Wind Velocity Profiles.- 1.6 Nature of Gusts.- 1.7 Effect of Gusts.- 1.8 Drag and Lift Coefficients-Single Members.- 1.9 Drag and Lift Coefficients-Trusses.- 1.10 Drag and Lift Coefficients-Three Dimensional Effects (Sheltering).- 1.11 References.- II ― Currents and Current Loadings.- 2.1 Nature of Currents.- 2.2 Interpretation of Model Test Data for Currents.- 2.3 Drag and Lift Coefficients.- 2.4 References.- III ― Surface Gravity Water Waves.- 3.1 Introduction to Surface Gravity Water Waves.- 3.2 Definitions, Notation and Nomenclature.- 3.3 Basic Concepts.- 3.4 Classification of Waves-Part I.- 3.5 Classification of Waves-Part II.- 3.6 Classification of Waves-Part III.- 3.7 Breaking Waves and Wave Theory Selection.- 3.8 Waves as Random Processes.- 3.9 Selection of Design Wave Spectra.- 3.10 References.- IV ― Wave Forecasting and Hindcasting.- 4.1 Generation of Waves by Wind in Deep Water.- 4. 2 Wind Wave Relationships.- 4.3 Transformation of Deep Water Wave Spectra.- 4.4 References.- II. Structure-Fluid Interaction Phenomenology.- V ― Basic Concepts.- 5.1 Conservation of Mass.- 5.2 Conservation of Momentum.- 5.3 Circulation and Vorticity.- 5.4 The Stream Function and Velocity Potential.- 5.5 References.- VI ― Particle-in-Cell Method.- 6.1 Introduction.- 6.2 Governing Equations of Motion and Finite Difference Equivalents.- 6.3 Boundary Equations.- 6.4 Calculation Procedure.- 6.5 References.- VII ― Fluid-Induced Forces.- 7.1 Inertial Coefficients.- 7.2 Drag Coefficients.- 7.3 Behavior of Multiple Members.- 7.4 Statistical Approach to the Evaluation of Inertial and Drag Coefficients for Single Members.- 7.5 References.- VIII ― Forces Induced by Breaking Waves.- 8.1 Vertical Plane Barriers.- 8.2 Horizontal Members.- 8.3 References.- III. Dynamic Behavior with Particular Reference to Ocean Processes.- IX ― A Review of Some Statistical Concepts.- 9.1 The Stationary and Ergodic Hypotheses.- 9.2 Measures of a Random Variable.- 9.3 Probability Distributions.- 9. 4 References.- X ― The One Degree of Freedom and Continuous Beam Models.- 10.1 Model of a Fixed Offshore Structure.- 10.2 The Complex Frequency Response.- 10.3 The Unit Impulse Response.- 10. 4 Response to a Stationary, Ergodic Force.- 10.5 Response to Ideal White Noise.- 10.6 Response to Band-Limited White Noise.- 10.7 Probability and Design Limits.- 10.8 The Continuous Beam Model.- 10.9 Beam Responses to Harmonic and Impulse Forces.- 10.10 Beam Responses to Stationary, Ergodic Forces.- 10.11 Beam Responses to White Noise.- 10.12 Design Implications for the Beam.- 10.13 References.- XI ― Dynamic Behavior of Materials in an Environment.- 11.1 Behavior of Structural Metals with Corrosion Protection.- 11.2 Behavior of Metals in a Corrosive Environment.- 11.3 Materials Resistant to Dynamic Loads and Corrosion.- 11.4 Damage Accumulation in Metals Under Random-Stationary Stress.- 11.5 Numerical Examples.- 11.6 References.- IV. Application to Ocean Systems.- XII ― Linear Moored-Ship Systems.- 12.1 Coordinate Systems.- 12.2 Evaluation of Terms Appearing in Equations of Motion.- 12.3 Dynamic Forces and Moments Due to Body Motions.- 12.4 Damping Forces and Moments.- 12.5 Hydrostatic Restoring Forces and Moments.- 12.6 Mooring Forces and Moments.- 12.7 Evaluation of Wave Exciting Forces and Moments.- 12.8 Solution of the Equations of Motion.- 12.9 References.- XIII ― Nonlinear Response of a Moored Ship to Sea Oscillations.- 13.1 The Mathematical Model.- 13.2 Undamped, Free Vibrations.- 13.3 Undamped, Forced Vibrations.- 13.4 Damped, Forced Vibrations.- 13.5 The Jump Phenomena.- 13.6 Subharmonics.- 13.7 References.- XIV ― A Specific Nonlinear Application.- 14.1 Physical Description of Nonlinear Motion.- 14.2 References.- XV ― Miscellaneous Topics of Current Interest.- 15.1 Double Catenary Problem.- 15.2 Dynamic Stresses Induced in Cables by Random End Loads.- 15.3 Bottom Breakout Forces.- 15.4 References.- Author Index.