DIRECTIONAL SPECTRA DENSITY OF FORCES ON A FIXED PLATFORM

The purpose of the work described in this paper is to develop transfer functions for estimating the spectral density of the total horizontal force on a fixed-leg structure from the sea surface spectral density. The platform is represented by a geometric assemblage of vertical cylinders extending from the sea floor up through the sea surface. Equations are derived in terms of elliptical integrals for the spectra and cross-spectra of the horizontal components of total force. Exact results are presented where possible, otherwise results based on linear wave theory are developed. The theoretical results are compared with field measurement data.