Experimental investigation on the seismic behavior of corroded liquid-filled steel storage tanks retrofitted with friction pendulum base isolation systems

Steel storage tanks operating in corrosive environments become increasingly vulnerable to earthquake-induced damage due to corrosion-induced deterioration. This study experimentally investigates the structural and seismic behavior of hydrochloric acid-corroded liquid-filled steel storage tanks retrofitted with friction pendulum bearing isolation systems. Slender and broad tank configurations with three different liquid heights were tested under selected historical earthquake records using both fixed-base and base isolated models. The seismic responses were evaluated through acceleration time histories, displacement responses, drift ratios, Fast Fourier Transform analyses, and convective sloshing damping characteristics. The experimental results demonstrated that friction pendulum isolation reduced the peak top accelerations by 68–82% and the peak bottom accelerations by 66–83%, depending on the earthquake record, tank geometry, and liquid height. The dominant response frequencies shifted from approximately 2.36–10.10 Hz in the fixed-base tanks to 1.04–5.71 Hz in the isolated tanks, accompanied by substantially lower spectral amplitudes. Furthermore, the drift ratios decreased from approximately 0.23–0.42% to 0.12–0.26% for slender tanks and from 0.07 to 0.31% to 0.02–0.19% for broad tanks, while the average convective sloshing damping ratio increased from approximately 10% to 11–14%. These improvements indicate that base isolation effectively decouples the tanks from ground motion, reduces inertial forces and lateral deformation demands, suppresses fluid–structure interaction, and significantly enhances the overall seismic performance of corrosion-damaged liquid-filled steel storage tanks. Therefore, base isolation provides an effective seismic retrofitting strategy for existing storage tanks in earthquake-prone regions.