Dynamic amplification of offshore steel platform responses due to non-Gaussian wave loads

Abstract

The dynamic response of offshore steel platforms subjected to random non-normal wave loads is considered. Two procedures are described. The first is a simplified quasi-static approach based on the classical one degree-of-freedom dynamic amplification factor. In the second procedure the statistical moments of the non-normal dynamic response are calculated without approximations using the theory of diffusion processes and moment closure techniques. An example jack-up platform is considered. It is found that the quasi-static approach is rather accurate for extreme value predictions, but not applicable for fatigue analysis where the second procedure should be applied. It is also observed that the dynamic amplification changes the statistical behaviour of the response significantly towards a Gaussian process.