Stochastic Combination of Ship Hull Primary Load Effects

On the basis of the time variation of still water load effects, a new method is developed for the combination of still water and wave induced load effects. Compared to the combination format based on Ferry Borges Castenheta model or on the up crossing rate of a stochastic process, the new method is easy to be conceptually understood and to be computationally performed. Accounting for the gene rally accepted probability level of exceeding the codified maximum allowable still water bending moment of the still water load process and the upper bound feature of the probability of the still water load process exceeding a given fixed level, the probability of its exceeding the codified maximum allowable moment for 20 years is prescribed as the probability level by which load effect characteristic extreme values are determined. By doing so, the overestimates of load effect characteristic extreme values are avoided. The numerical analysis is conducted to examine the validity of the method. It is shown by numerical results that the comsistent estimates of the characteristic extreme values of the combined load effect can be obtained by the method.