Seismic Responses Analysis Of Large-scale LNG Tanks With Seismic Isolation System

There are varieties of mega LNG tanks, the full containment tank are widelyused in China. The safety of LNG tanks during construction and operation is highlyimportant. If destroy, leakage, fire or explosion occur during the operation of LNGtank, it may cause extremely bad influence and damage in society. The safety of thetanks in the earthquake can be guaranteed by using the seismic isolation technique,which usually applies rubber bearings at the top of the pile foundations. The rubberbearing has many advantages and its mechanical parameters can be obtained from thecompany, and they are usually got through experiment or approximate formulas.In this research, the safety analysis of the LNG tank with seismic isolation iscarried out. Based on the classic theory of shell, ansys modals of LNG tanks withseismic isolation and without seismic isolation are established respectively. Uponthese two modals three different earthquake waves (Tianjin wave, EI-Centro wave andartificial wave) are exerted to calculate their seismic response in two differentconditions, meaning OBE(operating base earthquake) and SSE(safe shutdownearthquake). Comparing the acceleration, displacement and Overturning moment ofthe two modals, isolation efficiency of the rubber bearings and the scale of dampingrate are achieved.Then, the economic efficiency of the LNG tank with seismic isolation is carriedout. The thickness of the LNG tank with seismic isolation in the ansys modal will bereduced based on the scale of damping rate and its seismic response is re-analyzed.And the cost of LNG tank without seismic isolation and the cost of thin-tank withseismic isolation will be compared to analyze the economic efficiency.According to the analysis result, the rubber bearings can greatly reduce theacceleration and the stress of the upper construction, at the same time they increasethe displacement. Basically the rubber bearings improve the safety of the LNG tank.The rubber bearings also decrease the cost of LNG tank construction, compared withsafety of the LNG tank, the rubber bearings are necessary in the construction of theLNG tank construction. So using seismic isolation in the LNG tank construction willbe a trend.The results obtained in this research provide the reference for design andconstruction of seismic isolated LNG storage tanks.