Safety analysis of ship rolling in rough sea

Non-linear ship rolling and capsizing in irregular waves is analysed by a single degree-of-freedom system. The random wave excitation depends on sea state, ship speed and ship direction to wave propagation. The governing differential equation of motion is integrated by applying the harmonic acceleration method. Ship response is presented in time and frequency domains. A safe basin in the initial value plane is constructed for different values of the three excitation parameters mentioned above in order to determine the probability of ship survival, which is presented in a PC radar map as a function of heading angle.