Dynamic Amplification of Jack-Up Platforms Subjected to Non-Gaussian Wave Loads

Jack-up platforms are sensitive to dynamic amplification in waves because their fundamental period can be as high as 7 s-8 s. Where as the dynamic motion of the platforms is rather well described by linear theory the excitation depends nonlinearly on the wave height. The stochastic wave loading is thus far from being normally distributed. In this paper dynamic amplifications obtained by the diffusion theory extended to cover nonnormal excitations are compared with available time simulation results in irregular seaways. Generally, the time simulations seem to yield responses less nonlinear in the wave heights than the responses estimated from the diffusion theory. Explanations for these discrepancies are discussed and mainly attributed to a proper choice of total damping.