Slightly nonlinear extreme loads and load combinations

A simple approach for the preliminary estimate of characteristic extreme values of a slightly nonlinear load is presented. A newly defined nonlinearity parameter is introduced which depends on the skewness and kurtosis of the underlying process from which the extreme value is estimated, and on the number of peaks. The skewness and kurtosis are shown to depend on the sea state and the physical properties of the system. This simple approach may be particularly useful in the preliminary estimates of hogging and sagging bending moments acting on ships. The paper presents also an approximate method for combining slightly nonlinear loads and concludes with application examples.