船体主要载荷效应的随机组合

Stochastic Combination of Ship Hull Primary Load Effects

基于静水载荷的时间变异性 ,导出了一种静水载荷效应与波浪载荷效应组合的新方法。同基于 FBC(Ferry Borges Castenhete)模型或随机过程的上跨率的组合形式相比较 ,此新方法的概念更清晰 ,计算更容易实施。考虑到规范中给定的最大允许静水载荷效应对应的普遍接受的超越概率水平 ,以及静水载荷过程跨越某一固定水平的概率的上界特性 ,规定静水载荷过程超越二十年最大允许载荷效应的概率为确定载荷效应特征值的概率水平。经过这样处理 ,避免了载荷效应特征值的过高估计。通过数值分析检验方法的有效性 ,结果表明本文的方法可以得到组合载荷效应特征极值的一致估计。

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.