摘要：Accurate estimation of the wave load acting on a ship hull structure is one of the most important factors in ship structural design. The present authors reported in the previous report about the sea condition which actual ship encountered using AIS (Automatic Identification System) data and Hindcast wave data. However, the quantitative evaluation regarding to the maximum wave load considering with operational conditions could not be carried out. In this research, for container ships with the length 280 m to 400 m, the vertical bending moment (VBM) were estimated utilizing the joint probability consisting of ship operational conditions and its sea states. Joint probability density function p ( Hs,Tz, X ,V ),which consists of the significant wave height Hs , the zero-crossing wave period Tz , the encounter wave direction X and the ship speed V , were obtained from the AIS data and the Hindcast wave data. We developed a method to obtain the maximum load corresponding to the exceedance probability Q = 10 -8 , which is required for ultimate strength evaluation, considering with the effect of the conditional probability of operations given sea states. Using the developed method, it was found that the maximum load is reduced by about 10% by applying the joint probability density function p(Hs,Tz, X ,V) compared with the conventional method based on independent probability density functions p(X) and p(V) . In addition, it was found that the worst sea state in which the maximum load acts, does not coincide with the sea condition and operation condition in the class rules specified for strength evaluation. Container ships with the length 280 m to 310 m tend to avoid head seas under rough seas, and it was indicated that the maximum load acted in following seas condition. And it was indicated that the maximum load acts on container ships with the length 310 m to 340 m in the head seas condition as assumed in the class rules, but the ship speed slightly higher than those assumed in the class rules..
