Seismic analysis of liquid storage tank using oblate spheroid base isolation system based on rolling friction

Abstract

The seismic isolation of ground-supported cylindrical liquid storage tank using the newly developed oblate spheroid base isolation (OSBI) system is investigated. The OSBI is an ellipsoidal-shaped isolator in both of its horizontal axes and dissipates seismic input energy in rolling friction apart from period lengthening achieved through the oblateness. The detailed mathematical formulation and governing dynamical equations of motion for a tank mounted on the non-linear OSBI are derived and analyzed using the numerical integration technique to unravel the underlying mechanics behind its dynamic behavior. An idealized mechanical model of the tank consists of three-lumped masses: convective, impulsive, and rigid. The dynamic responses are investigated for the tank subjected to uni-directional sinusoidal harmonic motion as well as to five time-varying, bi-directional horizontal components of earthquakes. The seismic response of the liquid storage tanks with the OSBI system is compared with that of the same tank either isolated using pure-friction (P-F) system or kept non-isolated. In order to understand the dynamic behavior of the tank mounted on the OSBI system, the influence of different isolator parameters such as eccentricity, coefficient of rolling friction, and aspect ratio of the tank are studied. The energy responses are also evaluated to assess the performance of the OSBI system. From the present study, it is found that the OSBI system is effective in mitigating the seismic response in the liquid storage tanks.