Consideration of Wave-Induced Loads for Direct Strength Calculation Under Extreme Waves

Relationship between extreme values in long-term distribution and the short-term values under each sea-state in which ships may encounter through their lifetime is discussed regarding wave-induced loads such as ship motions, hull girder moments and hydrodynamic pressures. Based on the discussion, a simplified formula of the wave-induced loads equivalent to the extreme value in the long-term distribution at the exceedance probability of 10−8 is proposed together with the corresponding sea-states by a series of direct load analyses of the tankers and bulk carriers. Furthermore, nonlinear characteristics with respect to waveheight on wave-induced loads are discussed based on the comprehensive experiment results of a blunt ship model in regular/irregular extreme waves. Finally, a correction method of the observed nonlinear phenomenon is proposed.© 2002 ASME