SENSITIVITY OF THE SEISMIC PERFORMANCE OF LIQUID STORAGE TANKS WITH NONLINEAR ISOLATION SYSTEMS TO DEVIATIONS IN MECHANICAL CHARACTERISTICS OF THE SEISMIC ISOLATORS

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.

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The effects of input earthquake characteristics on the nonlinear dynamic behavior of FPS isolated liquid storage tanks

Journal of Vibration and Control ◽

10.1177/1077546316655914 ◽

2016 ◽

Vol 24 (7) ◽

pp. 1264-1282 ◽

Cited By ~ 3

Author(s):

Saman Bagheri ◽

Mostafa Farajian

Keyword(s):

Passive Control ◽

Base Isolation ◽

Ground Motions ◽

Storage Tanks ◽

Ground Acceleration ◽

Pendulum System ◽

Aspect Ratios ◽

Liquid Storage ◽

Isolation Systems ◽

Friction Pendulum

There are several methods to reduce the seismic damages in liquid storage tanks. One of these methods is to use passive control devices, in particular seismic base isolators. Among the different base isolation systems, the Friction Pendulum System (FPS) whose period does not depend on the weight of the system is more appropriate for isolation of liquid storage tanks. The aim of this paper is to investigate the effects of peak ground acceleration (PGA) and pulselike characteristics of earthquakes on the seismic behavior of steel liquid storage tanks base isolated by FPS bearings. In addition, impact effects of the slider with the side retainer are investigated, as well as effects of tank aspect ratio, isolation period and friction coefficient. The obtained results of tanks with different aspect ratios indicate that the responses get more reduced due to isolation under far-field ground motions compared to near-fault ground motions. It is also seen that the response of a base isolated tank is affected when contact takes place with the side retainer of the FPS.

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