Stochastic Response of Offshore Structures Excited by Drag Forces

Abstract

This paper describes a new method for representing hydrodynamic drag forces on a marine structure subjected to random waves. It is shown that the obtained force representation has the correct statistical properties to good approximation. A fair agreement can also be obtained between the spectral density of the force representation and that of the original drag force. The distinct advantage of the proposed representation is that it becomes possible to carry out a dynamic analysis of a linear structure in the frequency domain using available techniques, which are part of a larger packet that includes efficient tools for providing detailed statistical information about the response process. This has implications toward more efficient analyses of, for example, long-term fatigue of offshore structures.