Fatigue strength analysis of a large membrane LNG carrier
For the structural design of a 175 000 m3 LNG carrier,the fatigue strength of typical details is analyzed through spectral method.For two most frequently used seagoing loading conditions,the finite model of global ship and hy-drodynamic model are built.The wave loads are calculated for a series of wave directions and frequencies,the Response Amplitude Operators(RAO)between the waves and the stresses,for each operating condition are obtained later.According to Miner's rule,calculated the fatigue damage with North Atlantic scatter diagram and suitable S-N curves.In addition to the high-cycle wave induced fatigue damage,the low-cycle fatigue damage due to loading/unloading sequences is also calcu-lated.The results show that some structural details can meet the requirement of NA40 years by increasing the size and optim-izing the type,thus little ones need to be grinded.Based on a project,has a good understanding of construction demands and rules by close communications with the owner and the class society,can provide valuable references for the design of large LNG carriers.
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