Impulse Response Techniques for Floating Bridges and Breakwaters Subject to Short-Crested Seas

Abstract

A frequency domain technique is presented which permits the determination of the complete covariance matrix for the six degree-of-freedom motions, and the nodal shears and bending moments, for floating bridges and breakwaters. The structures are modeled as a series of interacting modules subject to stochastic excitation from directional short-crested seas. The two principal methods of analyzing such problems— linear superposition of responses to long-crested components of the directional spectrum, and beam sea responses modified by a scalar coherency function—are carefully examined. It is shown that, under proper interpretation, the two methods are logically consistent. The paper concludes by examining two types of coherency processes in directional wave fields.