Abstract
In the previous paper, authors have proposed a new fatigue design method based on storm model in the North Pacific using crack growth analysis. Following results were obtained: fatigue strength of ship structural members is strongly influenced by the number, the order, and the size of sea state. In order to develop the storm model for ocean route, many data are needed such as wave scatter diagram, a number of storm, a duration of storm and relative angle in storms. When we can obtain these data, we can make storm model according to our proposed procedure. However, in general, there are few data in ocean route.
In this paper, authors propose a procedure to develop storm model in any ocean route where there is only wave scatter diagram. Fatigue crack growth life is analyzed under following three different cases of relative angle and duration of storm: 1) relative angle is kept constant during a sea state, 2) relative angle is kept constant until reaching maximum wave height and then is reversed by 180 degree, 3) relative angle is changed every wave, and for duration of storms, 2 days, 3.5 days, and 4.7 days. Referring to the results of crack growth simulation, authors propose a procedure to develop storm model in any ocean route.
