Abstract

In this study, a method to predict the extreme value distribution of the vertical bending moment (VBM) of a ship in the nonlinear wave field is proposed. The method is based on a combination of the Higher Order Spectrum Method (HOSM) and First Order Reliability Method (FORM), by which the most probable wave episodes (MPWEs) associated with extreme waves and responses can be efficiently calculated. A probabilistic aspect of the nonlinear wave crests is first discussed, by comparing to the Monte Carlo Simulation (MCS) results using HOSM. Following this, to estimate the wave-induced VBM in the nonlinear waves, the HOSM-based wave profiles are approximated by the linear combination of sinusoidal waves in a short-time window, and then the wave-induced VBM time histories are generated by introducing the transfer function of VBM. An effect of the nonlinearity in waves on the profiles of MPWEs and reliability indices for extreme wave-induced VBMs is discussed. It turned out that if the transfer function of VBM is sensitive to high frequency waves, the effect of the nonlinearity in waves is found to be significant in the reliability index distribution.

This content is only available via PDF.
You do not currently have access to this content.