Strength Assessment Of Independent Type B LNG Tank Under Sloshing Loads And Skeleton Optimization

With the global shortage of resources and continuous improvement of the world economic,the world begins to pay attention to the development and utilization of green energy.Natural gas has become more and more widely used due to its green and low carbon advantages.At the same time,the special ship—LNG(Liquefied Natural Gas)ship,which is used for the transport of liquefied natural gas,has been widely favored.When the LNG ship is used,it is necessary to assess the strength of the tank because of the sloshing loads bad effects on the structural safety.The sloshing assessment of the LNG ship with independent tanks is chosen as the study object and conducts local strength analysis under sloshing loads.Based on rules of classification,the target tank sloshing loads are calculated.The calculation condition of the target tank under sloshing loads is determined.A finite element model of target tank is built.The ground spring element and GAP elements are used to simulate the structure between tank and ship and the results show that the strength of target tank with two methods are similar.Spring elements and GAP elements are both effective.Then the region which exceeded the allowable stress is filtered and fine mesh analysis on the target region in danger condition is done.The result shows that the method can be used to evaluate the sloshing strength of the independent tank effectively,and the result of the fine mesh calculation can reflect the stress distribution state of the high gradient region truly.At last,the layout of the horizontal girders of the target tank is optimized and the results show that the reasonable arrangement of horizontal girders can improve the distribution of stress.The effect of the vertical girder panel on the stress of the tank is discussed.It is shown that increasing the flexural rigidity of the vertical girders is a good way to reduce the high stress of the horizontal girders.The analysis results can provide reference for the evaluation of the tank sloshing strength,optimization of the tank skeleton structure and further design of the similar LNG ships.