Three-dimensional seismic isolation analysis of LNG storage tanks incorporating vertical isolation devices and friction pendulum bearings

In this paper, three-dimensional (3D) seismic isolation analysis was performed on a liquefied natural gas (LNG) storage tank incorporating friction pendulum bearings (FPBs) and vertical isolation devices. Cyclic loading tests and numerical simulations were first conducted to investigate the mechanical behavior of the proposed vertical isolation device. Subsequently, a numerical model of a representative LNG tank was established to explore the seismic performance of the 3D isolation system under multidirectional near-fault earthquakes. Parametric analyses were further performed to investigate the effects of vertical isolation period T v and yield-weight ratio Q / W on seismic responses of the isolated LNG tank. Results showed that the 3D isolation system effectively reduced the seismic responses of the LNG tank in comparison with the structure using the FPB-only system. The maximum average reduction ratios of horizontal acceleration for the outer and inner tanks reached 77.0% and 72.3%, respectively, whereas the maximum reduction ratios of tank-wall stress and hydrodynamic pressure reached 40.6% and 25.9%, respectively. Increasing the vertical isolation period effectively improved the seismic mitigation performance by filtering high-frequency vertical vibration components, whereas increasing the yield-weight ratio reduced the deformation response but weakened the hysteretic energy dissipation capability.