TABLE OF CONTENTS It is shown in this chapter the complexity in performing stochastic analysis of fixed offshore structures. The frequency-domain treatment of two types of drag nonlinearities arising from wave loadings is presented. Volterra series and cumulant spectral analysis approaches for higher-order spectral analyses of Morison force, inundation force and the resultant total force are discussed. Least squares and moment-based polynomial approximations of drag nonlinearities are presented for the frequency-domain manipulations.
For the example illustrated, the response power spectra and cumulants obtained using cumulant spectral analysis are in good agreement with simulation results, but with less computational time. Inundation has the effect of increasing the response skewness and kurtosis. The need for including wave nonlinearities is confirmed by the numerical results.
