SEISMIC ANALYSIS OF LIQUID STORAGE TANK (original) (raw)
Related papers
Seismic Analysis of Cylindrical Liquid Storage Tank
Liquid storage tanks are used in industries for storing chemicals, petroleum products, and for storing water in public water distribution systems. Behaviour of Cylindrical liquid storage tanks under earthquake loads has been studied as per Draft code Part II of IS 1893:2002. A FEM based computer software (STAAD-PRO) used for seismic analysis of tanks which gives the earthquake induced forces on tank systems. Draft code Part II of IS 1893:2002 which will contain provisions for all types of liquid storage tanks. Under earthquake loads, a complicated pattern of stresses is generated in the tanks. Poorly designed tanks have leaked, buckled or even collapsed during earthquakes. Common modes of failure are wall buckling, sloshing damage to roof, inlet/outlet pipe breaks and implosion due to rapid loss of contents. In this research, a circular cylindrical elevated water tank, with 500 cubic meters capacity is analysed by using finite modelling techniques. This paper presents the study of seismic performance of the elevated water tanks for various heights and various seismic zones of India. The effect of height of water tank, earthquake zones on earthquake forces have been presented in this paper with the help of analysis of 20 models for same parameters. Analysis is carried out by using finite element software STAAD-PRO.
The International Journal of Acoustics and Vibration, 2020
A seismic analysis of ground-supported, three-dimensional (3-D) rigid-base steel cylindrical liquid storage tank is investigated, using a coupled acoustic-structural finite element (FE) method for fluid-structure interaction (FSI). In this method, the contained liquid in the tank is modelled using acoustic elements and the cylindrical tank is modelled using shell elements. The impulsive and convective terms are estimated separately by using the appropriate boundary conditions on the free surface of the liquid. The convergence and validation studies of the proposed FE model are conducted by comparing the results reported in the literature. The parametric studies are performed for rigid and flexible tanks for the varying slenderness of the open roof tanks. The sloshing displacement and base shear time history responses are evaluated for the 3-D tanks subjected to harmonic unidirectional ground motions. Further, the results are compared with the commonly used two and three lumped-mass ...
Seismic Analysis of Liquid Storage Tanks
— Liquid storage tanks are used in industries for storing chemicals, petroleum products, and for storing water in public water distribution systems. Behavior of liquid storage tanks under earthquake loads has been studied as per Draft code Part II of IS 1893:2002. A FEM based computer software used (SAP 2000) for seismic analysis of tanks which gives the earthquake induced forces on tank systems. Indian seismic code IS 1893:1984 had some very limited provisions on seismic design of elevated tanks. This code did not cover ground-supported tanks. Draft code Part II of IS 1893:2002 which will contain provisions for all types of liquid storage tanks. Dynamic analysis of liquid containing tank is a complex problem involving fluid-structure interaction. Under earthquake loads, a complicated pattern of stresses is generated in the tanks. Poorly designed tanks have leaked, buckled or even collapsed during earthquakes. Common modes of failure are wall buckling, sloshing damage to roof, inlet/outlet pipe breaks and implosion due to rapid loss of contents. An example intz shape tank is analyzed as per the Draft code Part II of IS 1893:2002. This thesis consists of two different parts. In a first part, a theoretical point of view & formulations for analysis. The second part focuses on the model example to determine the seismic forces on tank.
Discrete Models for Seismic Analysis of Liquid Storage Tanks of Arbitrary Shape and Fill Height
Journal of Pressure Vessel Technology, 2008
A finite element method (FEM)-based formulation is developed for an effective computation of the eigenmode frequencies, the decomposition of total liquid mass into impulsive and convective parts, and the distribution of wall pressures due to sloshing in liquid storage tanks of arbitrary shape and fill height. The fluid motion is considered to be inviscid (slip wall condition) and linear (small free-surface steepness). The natural modal frequencies and shapes of the sloshing modes are computed, as a function of the tank fill height, on the basis of a conventional FEM modeling. These results form the basis for a convective-impulsive decomposition of the total liquid mass, at any fill height, for the first few (two or three at most) sloshing modes, which are by far the most important ones in comparison to all other higher modes. This results into a simple yet accurate and robust model of discrete masses and springs for the sloshing behavior. The methodology is validated through compari...
Seismic analysis of cylindrical liquid storage tanks
Computers & Structures, 1989
This paper summarizes the results of a comprehensive analytical investigation concerning the seismic analysis of ground supported, circular cylindrical liquid storage tanks subject to a horizontal component of earthquake ground motion. A procedure to evahrate the dynamic seismic response of a wide range of cylindrical liquid storage tanks is developed. The procedure, which is applicable to tanks both completely full and partially full with liquid, has been incorporated into a BASIC computer program. Several numerical examples are presented which illustrate application of the procedure and verify its NOTATION frequency constant (5252 ft/sec) diameter of a cylindrical tank Young's modulus Young's modulus for steel (34000 ksi) height of a cylindrical tank equivalent stiffness of flexible shell and stationary fluid mass spring stiffness of liquid mass participating in first sloshing mode shell membrane stress resultants convective hydrodynamic base shear impulsive hydropic base shear maximum pseudo spectral acceleration spectral acceleration of fundamental sloshing fluid mass maximum spectral displacement spectra1 displa~ent of fund~en~l s~o~in3 fluid mass radius of cylindrical shell rn~irn~ water surface displa~ment natural frequency, cycles/set nondimensional frequency function acceleration of gravity shell wall thickness height of liquid in tank height to stationary fluid mass, q,, measured from the base of the tank height to fundamental sloshing fluid mass, m,, measured from the base of the tank distance measured from the free surface of the liquid to the location of the stationary fluid mass, m, distance measured from the free surface of the liquid to the location of the sloshing fluid mass ~~ci~ting in the first mode of vibration, m, axial wave number total mass of fluid in tank stationary liquid mass mass of liquid participating in the first sloshing
Looking back to past earthquakes shows seismic performance, destruction of liquid storage tanks regarding flat floor. Failure of these tanks causes human dire consequences, environmental and economical problems. Therefore, considering these destructions is of priorities. Since dynamic operation of tanks and researchers modelling in the past is the base of regulation design, so due to low thickness to the radius and length of cylindrical shells is prone to buckling. In this survey, with dynamic analysing of steel tanks we investigated the vibration behaviour of water and structure in an uninhibited manner regarding different water height ratios. To do this, a cylindrical tank is modelling using finite element analysis with ANSYS software. To model liquidshell system in shell part we use finite element analysis and liquid surrounding by added mass analysis. Comparing with regulations, the findings will be investigated with static analysis and the most critical result for tension and movement will be presented in dynamic analysis. In the following compare seismic performance of uninhibited tanks using added mass analysis and the results present in diagrams and tables.
Non linear vibration analysis of liquid storage tank
This study presents an idealization scheme for the analysis of rectangular storage tanks acted upon by earthquake excitations. Above and below ground tank, are considered. A linear three-dimensional finite element analysis is adopted to predict the natural frequencies. The analysis parameters are the ratio of height to length of the tank, the type of soil, level of water in the tank, and also the wall thickness. Tanks made from steel as well as from concrete are investigated. A general purpose finite element program (ANSYS 12.0) used to model the analysed system. The tank base and wall are modelled by plane strain shell elements. The contained liquid is represented by a special solid element. Finally, the soil is modelled by simple spring-damper elements. The soil medium is idealized by the elastic half space model, that is, linear springs are assumed to represent the structure-soil interface. Which is then modelled by two-node spring dashpot elements. Forced vibration analysis is conducted on above ground and buried concrete tank. This analysis is carried out by applying the records of the North-South component of the 1940 El Centro earthquake with peak acceleration of 0.32g. It is found that the bending stresses in above ground concrete tank is (74.167) % greater than the stresses in buried tank with the same dimensions.
Simple Procedure for Seismic Analysis of Liquid-Storage Tanks
Structural Engineering International, 2000
This paper provides the theoretical background of a simplified seismic design procedure for cylindrical ground-supported tanks. The procedure takes into account impulsive and convective (sloshing) actions of the liquid in flexible steel or concrete tanks fixed to rigid foundations. Seismic responses-base shear, overturning moment, and sloshing wave height-are calculated by using the site response spectra and performing a few simple calculations. An example is presented to illustrate the procedure, and a comparison is made with the detailed modal analysis procedure. The simplified procedure has been adopted in Eurocode 8. Fig. 1: Elephant-foot buckling of a tank wall (courtesy
Liquid storage tanks constitute an important component of life line systems such as water distribution system, petroleum plants etc. Seismic design of liquid storage tanks requires knowledge of sloshing frequency of liquid and hydrodynamic pressure on the wall. This in turn, requires proper analysis of fluid-tank interaction under seismic excitation. In the design codes, mechanical analogs of tank-fluid system are commonly used to obtain the sloshing frequency, hydrodynamic pressure and design seismic forces. Such mechanical analogs are and developed for simple geometries, like circular and rectangular tanks. However, for tanks of other shapes and for tanks with internal obstructions, there are a very few studies on the mechanical analogs. In the present paper, experimental and numerical study is taken up to obtain the sloshing frequency of liquid contained in tanks of other shapes and tanks with internal obstructions. The experimental study is done on laboratory models of tanks, which are excited using an Electro-Magnetic Shake The numerical study is done with the help of finite element model of tank-fluid system using ANSYS software. A comparison of experimental and numerical results is given.
Finite element procedures for fluid-structure interactions and application to liquid storage tanks
Nuclear Engineering and Design, 1981
Most of the failures of large tanks after severe earthquakes are suspected to have resulted from the dynamic buckling caused by overturning moments of seismically induced liquid inertia and surface slosh waves. In this paper, a nonlinear finite element method is presented which can treated the structural behavior of the tanks in conjunction with fluid, including the dynamics and buckling. Both the formulation and computer implementation aspects are presented. The areas upon which attention is focused are: the mixed Lagrangian-Eulerian kinematical description for modeling fluid subdomains in fluid-structure interaction problems, the finite rotation effects in numerical integration of rate constitutive equations arising in largedeformation analysis and the implicit-explicit finite element techniques for transient analysis. All these nonlinear methodologies have been integrated into a finite element computer code . A number of physically important buckling and dynamic analyses of tanks are being investigated. Various other fluid structure phenomena such as the stability of off-shore structures can be analyzed with this computer program. The proposed nonlinear finite-element procedures can serve as a basis for future developments of various other fluid-structure phenomena such as the transient motion of submerged or partially submerged structures. T = 1.2 sec T --1.4 sec T = 1.6 sec T = 1.8 sec Fig. 12. Tank response (with the input translational motion subtracted), magnified by a factor of 76.31. J J J J X J / J T : I.O sec T = 2.0 sec