On the nonlinear seismic response of liquid filled thin-walled steel elevated containers isolated by bearings to earthquake ground motions

Abstract

In the present study two base isolation systems, i.e. lead-rubber and elastomeric bearings are analyzed and their seismic applicability is compared with reference to a liquid-filled conical elevated container undergoing different ground motions. The drilled shaft system is unlinked either from the base or from the top-mounted bowl by means of damping devices and the impact of such amendment on seismic performance of elevated liquid tank is examined by carrying out time-dependent finite element (FE) analyses on several pedestal-container systems. The developed FE procedure is competent in assaying the precise three-dimensional performance of the isolated elevated containers including the hysteretic performance of bi-linear isolation devices. For the input ground motions, the impacts of various parameters on the efficiency of the seismic bilinear hysteretic members are inspected. The results obtained from the FE analysis are validated against available numerical predictions in the time domain, and a good agreement is found between two methods. The sensitivity of induced forces, the internal hydrodynamic pressure, base moments and displacements in regard to some system parameters comprising lateral versus vertical isolation and locations of isolation devices, have been highlighted. Finally the numerical procedure suggests that earthquake response spectrum in various intensity levels has an influential role in the performance of elevated containers and special attention should be given to the dynamic analysis of such structures.