船体縦強度解析における荷重の確立変数としての特性 : 第1報 : 波浪荷重に与える重量分布の影響

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Recently, a trend toward the safety analysis of ship structural design in which both the load on hull and the structural capability can in principle be treated as random variables, has been growing. The character of the strength capability as random variable taking the irregularity and variability of material strength and imperfection of workmanship into consideration, has been investigating. The stochastic nature of critical load assuming standard loading condition is studied by means of extreme theory. The still water bending moment of a actual ship has a wide distribution. This has effects on the wave load. Moreover, the distribution is affected by accuracies of supposed wave and operating condition. So it is expected that the character of demand is not equal to that of conventional one. Authors deals with study on the characteristic of the critical load. This paper is the first report and describes the long term distribution, expected extreme and distribution of critical value of wave bending moment under the influence of the variability of still water bending moment. Supposing the distribution of still water bending moment is the normal distribution, the long term distribution of wave bending moment is a group of many exponential distributions, the distribution of parameters of which are described by normal distribution. This long term distribution for a usual ship can be approximated to Weibull distribution and its parameters are linear to coefficient of variation of . By the investigation of a series of similar cargo ships it is clarified that the coefficient of variation of is usually less than 4% and the characteristic extreme of wave load increases about 4% in comparison with the value assuming standard loading. It may be concluded that the long term distribution for these ships is approximated by exponential distribution the parameter of which is the mean value of . In usual the distribution of still water bending moment is expected to be more complicated. So the character of critical value of the wave load when the parameters showing distribution of still water bending moment are also stochastic variables, is shown. In this case, coefficient of variation of critical wave load increases with the variability of that parameters.
社団法人日本船舶海洋工学会の論文

船体縦強度解析における荷重の確立変数としての特性 : 第1報 : 波浪荷重に与える重量分布の影響

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