Random Extreme Wave Analysis of Deepwater Structures

Abstract

This paper reviews various wave analysis procedures for designing deepwater structures under an extreme seastate. The random wave analysis procedures suitable for fixed stiff platforms and compliant towers are discussed. The random wave analysis procedures are then applied to a 1350-ft water depth fixed platform. The reduction in design force levels due to random waves is indicated by comparing with the conventional regular wave analysis approach. The second harmonic effects due to waves can be easily identified through the dynamic response spectrum which has two peaks occurring at the peak frequency of the input wave spectrum and the natural frequency of the structure. The study also shows that the expected extreme value estimated based on the upcrossing approach agrees well with the snapshot peak response derived from a wave record containing an extreme wave height.