Fatigue assessment in FPSO mooring design using moment based Hermit Approximation

Hermite models are verified to describe analytically the statistics of nonlinear responses based on the response mean, standard deviation, skewness and kurtosis. Comparison are made between the numerical fittings and data obtained from a nonlinear mooring simulation programme obtained for moored 250 Kdwt FPSO. Good agreements are obtained down to the lowest levels of probability in the simulations.

This investigation is an intermediate step in the development of a complete method to calculate the statistics of nonlinear mooring loads loads in arbitrary wave spectra. Since the Hermite models turn out to give very accurate results, the main attention should be addressed to the calculation of the statistical response moments in nonlinear conditions.