Nonlinear performance of of offshore platforms in extreme storm waves

Dynamic-transient loading effects from extreme storm waves can have important influences on the nonlinear ultimate limit state performance of fixed offshore platforms. Recorded and synthetic storm wave time histories have been used to develop loading time histories acting on template-type platforms having natural periods in the range of 1-5 s. The interactions of these loading histories with the dynamic, nonlinear, hysteretic performance characteristics of idealized systems were analyzed. A modification to static pushover capacity analysis results is proposed to enable recognition of transient loading-structure performance characteristics. The results from the idealized systems were correlated with results from time domain nonlinear analyses of platform structure systems subjected to intense wave and earthquake loadings. For the global behavior of the platforms studied, the results based on the simplified systems are in good agreement with those from the complete analyses.