Application of Annular Damper Reaction Wall in Seismic Isolated LNG Tank

Most of the large LNG tanks have a fundamental frequency between 2 and 10 Hz which involves range of resonance of most earthquake ground motions. It is a fact that tanks could be damaged easily in the earthquake, which had been proved in many cases in the past few decades. It is an effective way to reduce the response for an isolation system being used for large LNG storage tanks in the strong earthquake. However, the displacement of the isolation story for actual project is very large in soft site so that the design of connection components is relatively difficult. In order to solve this problem, isolation system which is composed of annular damper reaction wall, viscous dampers, and lead rubber bearings mounted on the top of the piles is presented in this paper. The annular damper reaction wall which is not connected with the piles is embedded into the ground independently. The multi-degree-of-freedom lumped mass model is used to solve the governing equations of motion in which convective, impulsive and rigid masses are included. Simplified model of an actual LNG tank which can contain 160000m³ gases is analyzed by using isolators and annular damper reaction wall. The efficiency of the isolation system is investigated by analyzing various parameters such as displacement of the isolation story, base shear and so on. The results show that isolation system is very effective to control the displacement of isolation story, and at the same time base shear and other parameters are also effectively controlled.