Seismic Performance of Isolated Liquid Storage Tanks Supplemented with Negative Stiffness and Inerter Based Dampers

Liquid storage tanks (LSTs) are lifeline structures that must stay operational during and after earthquakes. Their ability to withstand large earthquakes is a major worry. Although base-isolation protects LSTs from far-fault earthquakes, large-amplitude and long-period velocity pulses seen in near-fault earthquakes can generate substantial isolator and sloshing displacements, posing a problem. Supplemental damping in the isolation system may reduce isolator displacements, but the superstructure responsemay be hampered. To remove the drawback, this study presents novel combinations of negative stiffness dampers (NSDs) and inerter based dampers that utilise minimal dashpot co-efficient as supplemental dampers to base-isolated LSTs. The continuous liquid mass of the tank is modelled as lumped masses known as sloshing mass, impulsive mass and rigid mass. Based on the tank wall and liquid mass parameters, the stiffness constants associated with these lumped masses are calculated. The governing equations for isolated LSTs with proposed supplemental dampers are derived and represented in state-space form. Numerical studies show that combinations of optimally designed NSDs and inerter based dampers improve the performance of base-isolated LSTs in terms of isolator displacement, sloshing displacement and sloshing height under both near-fault and far-field ground motion.