Fragility Analysis of Base-Isolated Liquid Storage Tanks under Random Sinusoidal Base Excitation Using Generalized Polynomial Chaos Expansion-Based Simulation

Generalized polynomial chaos (gPC) expansion-based simulation technique is used to investigate the influence of input parameter uncertainty, on peak response quantities and fragility curves of base-isolated liquid storage tanks. Unidirectional horizontal sinusoidal base excitation is considered to develop the fragility curves for the base-isolated liquid storage tanks. Extensively used laminated rubber bearing (LRB), with linear force-deformation behavior, is considered as the isolation system. The liquid storage tank is modeled using a widely accepted lumped mass model. The failure of the liquid storage tank is defined corresponding to the elastic buckling of the tank wall. The uncertainties are considered in the isolator parameters and in the base excitation. Considerable difference in the peak response estimation is observed when the input parameters are represented using different probability distributions, especially when the uncertainties are higher. It is also observed that when the uncertainties in the input parameters increase, probability of failure at given amplitude of the excitation increases. It is demonstrated that the probability of failure estimated using gPC expansion-based simulations closely matches the same obtained through the direct Monte Carlo (MC) simulations. Significant influence of the time period of the isolation system is observed on the fragility curves of the base-isolated liquid storage tanks. However, isolation damping has a marginal effect on the fragility curves of the base-isolated liquid storage tanks.