Seismic evaluation of frequency influence and resonant behavior for lead rubber bearing isolated rigid rectangular liquid tanks

The seismic behavior of a partially filled rigid rectangular liquid tank is investigated under short- and long-duration ground motions. A finite element model is developed to analyze the liquid domain by using four-noded quadrilateral elements. The competency of the model is verified with the available results. Parametric studies are conducted for the dynamic parameters of the base-isolated tank, using a lead rubber bearing to evaluate the optimum damping and time period of the isolator. The application of base isolation has reduced the total and impulsive hydrodynamic components of pressure by 80 to 90 percent, and base shear by 15 to 95 percent, depending upon the frequency content and duration of the considered earthquakes. The sloshing amplitude of the base-isolated tank is reduced by 18 to 94 percent for most of the short-duration earthquakes, while it is increased by 17 to 60 percent for the majority of the long-duration earthquakes. Furthermore, resonance studies are carried out through a long-duration harmonic excitation to obtain the dynamic behavior of non-isolated and isolated tanks, using a nonlinear sloshing model. The seismic responses of the base-isolated tank are obtained as higher when the excitation frequency matches the fundamental sloshing frequency rather than the isolator frequency.