Performance Assessment of Lead Rubber–Isolated Liquid Storage Tanks with Clutching Inertial Systems

Abstract

Liquid storage tanks (LSTs)—lifeline structures—must remain functional after earthquake events. Concerns regarding high sloshing and isolator displacement have led to the use of base isolation technology to mitigate seismic responses, especially in far-field (FF) earthquakes. However, near-fault (NF) earthquakes, characterized by high-frequency content and ground-shaking intensity, may aggravate sloshing and isolator displacement. The present work aims to utilize the clutching inertial system (CIS) as a supplemental damper for base-isolated liquid storage tanks (BI-LSTs) and assess its impact on the various response quantities (sloshing and isolator displacement, overall base shear of the tank, force within the isolator and CIS). A bilinear lead rubber bearing (LRB) serves as an isolation device. Since the force-deformation (f-d) behavior of LRB and CIS is inherently nonlinear, a response-independent stochastic linearization technique has been used to assess the equivalent stiffness, damping, and inertance constants. These equivalent constants are further employed to evaluate the stationary peak response of the isolated tanks subjected to the earthquake excitation modeled using the stationary power spectral density function (PSDF). This study explores how CIS inertance affects system parameters such as isolation damping, isolation period, and tank aspect ratio (both broad and slender). It is noted that an optimal inertance of CIS exists, for which the overall base shear of the tank is minimum for both broad and slender tank configurations. The research includes testing tank configurations against 11 NF and 11 FF earthquake excitations. The effectiveness of the clutching inertial system in mitigating seismic responses of isolated tanks is well established by comparing results under real and stochastic earthquake excitations.