| Summary: | Due to the affects of working conditions, ship and offshore structures are suffered from various loadings. For the fatigue loadings, it comes from the waves and the sea salty environmental condition primarily. The number of loadings working on the marine structures in this environment is millions times per year. Usually, The S-N curve is used to predict the fatigue life of the structures, While the fracture mechanics approach is used when an initial crack is emerged, then to research the crack extend under cyclic loading. Hull girder structures are subjected to aggressive environmental conditions. To conduct the evaluation of the ship hull girder reliability, the ultimate bending strength and the environmental condition are the two main factors. lACS recommendation is used for the still water and wave-induced bending moment analysis, while dynamic bending moments were computed by Sikora's research (1983). Taking the fatigue cracking formulating as the time-variant random functions, the ultimate bending moment can be estimated. After the system analysis, welded details analysis is necessary. This report makes the hull girder of 57000T Bulk Carrier as the example. Through analyzing and computing, checking the structural fatigue. And by researching the welded detail of the hull girder, the fatigue maximum allowable stress is obtained. Finally, the fatigue lifetime is determined.
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