||Carlos Guedes Soares, Josko Parunov
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The design of ship structures follows several steps and one of them consists on the determination of the design wave induced bending moment. This reference value, weighted by an appropriate safety factor, is added to the still water bending moment and the result is used to verify the structure ultimate strength. The design wave bending moment represents the maximum expected moment that the hull will be subjected during the operational lifetime. There are different methods to calculate this moment, while the simplest is given by the Classification Societies as an empirical formula. Over the last years efforts have been made to develop methods based on first principles so that they can be incorporated in structural reliability formulations. A review of such methods is presented by Guedes Soares et al. (1996), Guedes Soares (1998) and Parunov and Senjanovic (2003). The trend to rely on more direct methods of load assessment implies that the non-linear effects associated with large amplitude motions need to be properly accounted for. This has been achieved by methods such as the one of Fonseca and Guedes Soares (1998a, b) and few others of similar nature as reported in Watanabe and Guedes Soares (1999). This nonlinearity of the response needs to be reflected on the long term distributions and an approach to achieve that has been proposed by Guedes Soares and Schellin (1996).