Survival analysis of fishing vessels rolling in rough seas

A new approach to the problem of predicting the safety of vessels rolling in rough seas is described. It is based on the state of the art in nonlinear dynamics of a, single-degree-of-freedom system. The random wave excitation depends on sea state, vessel speed and direction of wave propagation. The differential equation of rolling motion is integrated by the harmonic acceleration method. The procedure is illustrated for the case of a typical fishing vessel. The roll response of an intact and damaged vessel is presented in the time and frequency domain. The fractal erosion of the safe basin in the initial-value plane is analysed. Finally, these results are used to determine the probability of a vessel's survival as a function of sea state, vessel speed and heading angle.