Comparision of the behavior of LNG tanks with seismic isolators under earthquake loads with nonlinear analysises

Damages in liquid storage tanks in past earthquakes; This necessitated the experimental and analytical investigation of the seismic behavior of the tanks. This study investigates the effect of different types of base isolator systems on the seismic performance of Liquefied Natural Gas storage tanks. Nonlinear time history analyses of fixed support and three different seismic isolated tanks were performed for the average acceleration of 7 different ground motions scaled according to Earthquake Ground Motion-1 (DD-1). High damping rubber, lead core rubber and friction pendulum systems are considered as insulator types. These insulators are modeled as nonlinear springs with force-displacement relationships based on experimental data. ANSYS Workbench program in modeling studies of LNG liquid, inner steel tank, outer shell, reinforced concrete ring beam, roof, foundation concrete, bottom and side wall insulations; LS-DYNA program was used for non-linear analysis of LNG liquid, inner steel tank and foundation concrete. Total bottom shear force, sloshing height, steel tank stresses, steel tank shell plate lateral deformation, steel tank bottom and wall displacements, insulator horizontal force-displacements, and vertical forces on the insulator of tanks with fixed support and three different seismic insulation were compared. The results show that there is no difference between modes in fixed and isolator systems. It was concluded that the wave motion of the liquid acts differently from the oscillation of the structure and does not affect the agitation motion of the insulators. It has been observed that the bottom shear forces and steel tank stresses of the seismic insulated tanks are reduced by 50-70% and 85-95%, respectively, compared to the fixed supports. However, there is no change in agitation heights. Horizontal displacement of isolator systems up to 400mm poses a danger to the mechanical equipment and pipes connected to the tank.