Evaluation of appropriate intensity measures for seismic performance assessment of base-isolated liquid storage tanks

Abstract

This study proposes appropriate intensity measures (IMs) for seismic performance assessment of base-isolated liquid storage tanks (BI-LSTs) through an extensive evaluation of various scalar IMs and vector-valued IMs of earthquake ground motions. Ground-supported liquid storage tanks (LSTs) with cylindrical shapes are considered for this study. The LSTs are assumed to be base-isolated using lead core rubber bearing (LCRB), and the bearing displacement is considered as the engineering demand parameter (EDP) for assessing the seismic fragility of the BI-LSTs through cloud analysis. It is shown that the average spectral acceleration, i.e., S_a,avg(0.05T_b-T_b) [where T_b is the isolation period], is an efficient, practical, proficient and sufficient IM. Therefore, S_a,avg(0.05T_b-T_b), is recommended as an appropriate IM for seismic performance assessment of ground-supported BI-LSTs. Detailed parametric studies are also performed to investigate the effect of different slenderness ratios of the LST and isolation periods on the selection of the appropriate IM. Further, the seismic risk of the considered BI-LSTs is assessed considering the seismic hazard for Shimla, which is the capital city of the Indian state Himachal Pradesh. For the considered site, the risk of the slender tanks is found to be higher than that of the broad tanks, regardless of the isolation period. It is also concluded that the peak bearing displacement demand corresponding to the maximum considered earthquake is substantially lower than that obtained as per the selected design code recommendations.