Abstract
The seismic response of elevated liquid storage tanks isolated by the lead-rubber bearing is investigated under real earthquake ground motion. Two types of isolated tank models are considered in which the bearings are placed at the base and top of the tower structure. The tank liquid is modelled as lumped masses referred as convective mass, impulsive mass and rigid mass. The corresponding stiffness associated with these lumped masses has been worked out using the properties of the tank wall and liquid mass based on simple single-degree-of-freedom concepts. The mass of the tower structure is lumped equally at top and bottom. The assembled equations of motion are solved by Newmark's step-by-step method with iteration. The seismic response of two types of tanks, namely slender and broad tanks is obtained and a parametric study is carried out to study the effects of important system parameters on the effectiveness of seismic isolation. The various important parameters considered are the tank aspect ratio, the time period of the tower structure, damping and the lime period of the isolation system. It has been observed that the earthquake response of the isolated tank is reduced significantly. Further, it is observed that the isolation is more effective for the tank with a stiff tower structure in comparison to flexible towers. In addition, a simplified analysis is also presented to evaluate the response of the elevated tanks using a two-degrees-of-freedom model and two single degree-of-freedom models. It is observed that the proposed methods predict accurately the seismic response of elevated liquid storage tanks with less computational efforts.
Highlights
The tanks are lifeline structures, which are connected for public use and are strategically very important structures, since they have vital uses in industry and nuclear power plants
The specific objectives of this study are: (i) to investigate the seismic response of the isolated tanks considering the influence of various tank, tower and isolation parameters and compare with the response of a non-isolated tank to identify the effectiveness of the isolation system, (ii) to study comparative performance of base-isolated tanks when isolation bearings are placed at the top and bottom of the supporting tower stmcture, (iii) to determine the contribution of various components of base shear to total base shear and the influence of isolation on sloshing displacement and deformation of tower structure, and (iv) to investigate the response of the isolated elevated liquid storage steel tanks by approximate models to minimize the computational efforts
Comparative performance of elevated liquid storage tanks isolated by placing the lead-rubber bearings at top and bottom of the tower structure was investigated under recorded earthquakes
Summary
The tanks are lifeline structures, which are connected for public use and are strategically very important structures, since they have vital uses in industry and nuclear power plants. The specific objectives of this study are: (i) to investigate the seismic response of the isolated tanks considering the influence of various tank, tower and isolation parameters and compare with the response of a non-isolated tank to identify the effectiveness of the isolation system, (ii) to study comparative performance of base-isolated tanks when isolation bearings are placed at the top and bottom of the supporting tower stmcture, (iii) to determine the contribution of various components of base shear to total base shear and the influence of isolation on sloshing displacement and deformation of tower structure (i.e. tower drift), and (iv) to investigate the response of the isolated elevated liquid storage steel tanks by approximate models to minimize the computational efforts
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