Simple beam-stick models are widely used for seismic analysis or design of structures. For the liquid storage tank, the tank structure and the liquid are modeled as lumped parameters, such as springs and masses. However, response spectrum analysis with these simple models, it would be possible that the results might give somewhat differences in section forces of shell structures such as the LNG (Liquid Natural Gas) storage tank, where especially the roof structure exists. Also the sloshing height could be underestimated when it is considered only one sloshing mode. Therefore, axisymmetric finite elements were employed to model the LNG storage tank in present study. The general purpose FE analysis program, ANSYS was utilized to model the LNG liquid, the inner steel tank and the outer concrete tank consisting of LNG storage tank. Modal analysis result shows that the axisymmetric finite element model of LNG tank considering FSI (fluid-structure interaction) effect is quite adequate. The response spectrum analysis was conducted on axisymmetric finite element model of LNG storage tank. And the results were discussed comparing with simple model. Finally full dynamic analyses in time domain were performed to examine the validity of the results. It is concluded that the response spectrum analysis of axisymmetric finite element considering FSI would result in more accurate seismic design of LNG storage tank than the simple model and be more practical than the full dynamic analysis.
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