Reviewing dynamic analysis of base-isolated cylindrical liquid storage tanks under near-fault earthquakes

摘要

Base-isolated structures are susceptible to more damage under near-fault earthquakes, due to its long fundamental time period, than under far-fault earthquakes. A brief review of the literature, related to the response of base-isolated structures under near-fault earthquake and representation of near-fault earthquake motion using equivalent pulses, is presented herein. Dynamic analyses are carried out to investigate the response of cylindrical liquid storage tanks under near-fault earthquakes. The studies are carried out for ground supported, anchored without isolation and base-isolated anchored tanks, where the isolator considered is lead-rubber bearing. Two types of configurations of the cylindrical liquid storage tanks, i.e. broad and slender, are considered in the present study. Equivalent pulse type acceleration inputs are used to study their effectiveness to predict the seismic response of base-isolated liquid storage tanks. The response under equivalent pulse type acceleration inputs are compared with the response under recorded near-fault earthquake ground accelerations. The response under the residual motion is also investigated to study their influence on the different response time histories. The cylindrical liquid storage tanks are subjected to bi-directional earthquake excitation to examine the effect of the interaction between two mutually perpendicular displacement components of the isolator. Parametric studies were conducted to investigate the variation of the peak response with important isolator parameters such as isolation time period, characteristic strength and isolation damping. It is observed that equivalent pulses are suitable for predicting the unidirectional response for slender liquid storage tanks; however, under the bi-directional excitation, prediction of the response is less accurate. The effect of the interaction is observed more crucial for lower isolation time periods under bidirectional excitation. The base shear, base displacement and overturning moment of the tanks decrease with increasing isolation damping; however, the sloshing displacement is found to be less sensitive to the change in the isolation damping.