Abstract
Seismic response of liquid storage tanks isolated by elastomeric bearings and sliding system is investigated under real earthquake ground motions. The continuous liquid mass of the tank is modeled as lumped masses known as sloshing mass, impulsive mass and rigid mass. The coupled differential equations of motion of the system are derived and solved in the incremental form using Newmark's step-by-step method with iterations. The seismic response of isolated tank is studied to investigate the comparative effectiveness of various isolation systems. A parametric study is also carried out to study the effect of important system parameters on the effectiveness of seismic isolation for liquid storage tanks. The various important parameters considered are: (i) aspect ratio of the tank and (ii) the time period of the isolation systems. It was observed that both elastomeric and sliding systems are found to be effective in reducing the earthquake forces of the liquid storage tanks. However, the elastomeric bearing with lead core is found to perform better in comparison to other systems. Further, an approximate model is proposed for evaluation of seismic response of base-isolated liquid storage tanks. A comparison of the seismic response evaluated by the proposed approximate method and an exact approach is made under different isolation systems and system parameters. It was observed that the proposed approximate analysis provides satisfactory response estimates of the base-isolated liquid storage tanks under earthquake excitation.
Highlights
Liquid storage tanks are strategically very important structures, since they have vital use in industries, nuclear power plants and other activities connected to the public life
The seismic response of liquid storage tanks isolated by laminated rubber bearings (LRB), N-Z and friction pendulum system (FPS) systems is investigated under real earthquake ground motion
In order to investigate the effectiveness of base isolation, the response of the isolated tank is compared with the corresponding response of tank without isolation system
Summary
Liquid storage tanks are strategically very important structures, since they have vital use in industries, nuclear power plants and other activities connected to the public life. Kim and Lee [7] experimentally investigated the seismic performance of liquid storage tanks isolated by laminated rubber bearings under uni-directional excitation and showed that the isolation was effective in reducing the daynamic response. Malhotra [8] studied the seismic response of cylindrical liquid storage tanks, under uni-directional ground motion, in which the wall of the tank was isolated from the base plate by horizontal flexible rubber bearings. The numerical results indicated that the sloshing displacement of base-isolated liquid storage tank was increased but the decrease in axial stresses in the cylindrical shell was significant to avoid the buckling of the shell. Shrimali and Jangid [10] investigated the earthquake response of slender and broad liquid storage tanks isolated by sliding bearings and found that the response of the isolated tanks was reduced significantly. The specific objectives of this study are: (i) To investigate the comparative effectiveness of various base isolation systems for aseismic design of liquid storage tanks; (ii) to study the influence of important system parameters on the effectiveness of base isolation for liquid storage tanks; and (iii) to propose a simplified approximate analysis for evaluation of the seismic response of base-isolated liquid storage tanks and study its feasibility considering different parameters of the tank
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