Seismic Analysis of Perfect and Imperfect Cylindrical Liquid Storage Tanks (original) (raw)
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Seismic Design Evaluation of Liquid-Filled Stiffened Steel Cylindrical Tanks
Proceedings of International Structural Engineering and Construction, 2019
This paper aims to estimate dynamic buckling loads of cylindrical liquid storage tanks. Finite element analysis is performed using ANSYS computer program. Twelve different geometries of the cylindrical tanks are analyzed with height to diameter (H/D) ratios of 0.5, 1.0, 1.5, and 2.0 and the diameter to thickness (D/t) ratios of 1000, 1500, and 2000 to cover tall and short cylindrical tanks. The dynamic buckling capacities of cylindrical tanks filled with water up to 90% of their height are investigated in this study. The transient dynamic analysis is performed to find the dynamic buckling loads. Applied dynamic loads in this study are horizontal earthquake excitations in terms of acceleration (g) due to gravity. The transient dynamic analysis results indicate that the dynamic buckling loads decrease when the H/D ratios increase, and the dynamic buckling loads decrease when the D/t ratios increase. Design curves for the cylindrical tanks of various geometries subjected to earthquake ...
Buckling Of Liquid-Filled Steel Storage Tanks Under Earthquake Loading
2017
The static and dynamic buckling loads of cylindrical liquid storage tanks were studied in this thesis. Finite element analysis was performed using ANSYS computer program. Twelve different geometries of the cylindrical tanks were analyzed with height to diameter (H/D) ratios of 0.5, 1.0, 1.5, and 2.0 and the diameter to thickness (D/t) ratios of 1000, 1500, and 2000 to cover tall and short cylindrical tanks. The transient dynamic analysis was performed to find the dynamic buckling loads. Applied dynamic loads in this study are horizontal earthquake excitations in terms of acceleration (g) due to gravity. Budiansky and Roth procedure was used to find the dynamic buckling load for both empty and tanks filled with water up to 90% of their height. Analysis results show that the dynamic buckling loads in terms of peak ground accelerations (PGA) are very high which are unrealistic for any recorded earthquake. For the cylindrical tanks filled with water up to 90% of their height; on the oth...
Buckling Strength of Liquid-Filled Steel Cylindrical Tanks Under Seismic Load
2018
This paper aims to develop practical design equations to estimate the buckling strength of the liquid-filled cylindrical tanks subjected to seismic load. Pseudo-Equilibrium path and phase plane criterion are used to evaluate buckling strength. Finite element analysis is performed using ANSYS computer program. Both geometrically perfect and imperfect tanks are studied. The modeling method, appropriate element type and necessary number of elements to use in numerical analysis are recommended. According to the results of the parametric study of the perfect tanks, the buckling strength decreases significantly as the diameter-to-thickness (D/t) ratio increases, while it decreases slightly as the height-to-diameter (H/D) ratio increases. The buckling strength of the tanks decreases significantly as the amplitudes of initial geometric imperfection are included. Based on the extensive parametric study, design equations and design curves representing the interaction of D/t and H/D ratios for...
Global Buckling Analsysis of Cylindrical Liquid Storage Tanks Under Earthquake Loading
2014
Cylindrical steel tanks are a rather economical supporting structure for the storing of liquids. However, because of their thin-walled and slender structure, they are highly vulnerable to shell buckling. Especially in case of an earthquake, structural safety is highly endangered due to additional axial and shear forces in the tank wall caused by the movement of the contained liquid. At the same time secondary damages as a result of a possible collapse are disastrous. The European code DIN EN 1993-1-6 permits three different approaches for the buckling strength verification of shell structures, which differ according to their numerical effort. The wellknown stress based verification is the traditional concept, which, however, reaches its limits for the special case of seismically loaded tank structures. Here the numerical concepts represent a very promising alternative, although their application is connected with several questionable points. Within this paper the numerical based buc...
Elephant's Foot Buckling of Cylindrical Steel Storage Tanks Subjected to Earthquake Excitation
Thin metal cylindrical shell structures such as silos and tanks are susceptible to an elastic-plastic instability failure at the base boundary known as elephant's foot buckling, due to its characteristic deformed shape. This form of buckling occurs under high internal pressure accompanied by axial compression in the shell structure. This work concerns with Theoretical studies on elephant's foot buckle failure of ground-supported, cylindrical liquid storage tanks under horizontal excitation. The buckling loads are obtained from finite elements models and codes and are compared. Theoretical nonlinear seismic analyses are carried out using ANSYS package. Studies are conducted on 13 models of cone roof tanks with height to diameter ratios (H/D) between 1 and 2, and a liquid level of 85% of the height of the cylinder with and without axial constraint at the point diametrically opposite the loading. The results are compared to which of the codes API 650, NZSEE guidelines and Eurocode 8. The comparisons of analytical buckling loads and those obtained by the codes reveal the following. Tanks designed by the codes API650 and Eurocode 8 tend to be unsafe due to elastic-plastic buckling occurrence of the shell. However, NZSEE guidelines have a near coherence to the analysis results. It is also obtained from the results that constraints at the base of the tank reduces sloshing height While cause the buckling capacity to rise up.
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.
DYNAMIC BUCKLING OF CYLINDRICAL STORAGE TANKS DURING EARTHQUAKE EXCITATIONS
The behavior of storage tanks' analysis in seismic areas is of major importance because of the strategic nature of these works. The steel cylindrical tanks are the most susceptible to damage due to dynamic buckling during earthquakes. In this study, three criteria are used to estimate the critical peak ground acceleration caused the tank instability. The liquid inside the tank was modeled using specific Ansys's finite elements and fluid-structure interaction. The calculation includes modal and time history analysis, including material and geometric non-linearity. The result values are compared with standard code previsions as well as the results of previous numerical research, and show the need to improve code provisions.
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.
Analysis and structural behavior of cylindrical steel tanks under seismic effects
International Conference of Metal Structures 2011 (Poland), 2011
"The use of large steel oil storage tanks that provide adequate safety and reasonable economy has always been an issue of major concern for the petroleum industry. To this end, efficient design and comprehensive analysis of such structures is important. This paper addresses specific issues regarding the analysis and behavior of cylindrical self supported tanks under earthquake loading and more importantly their seismic design, by comparing current codes used in practice with the finite element method (FEM). The results refer to two large cylindrical tanks and they show that even though the current design methods fail to describe their exact behavior, they do not violate fundamental safety considerations."
This research has focused on the behavior, under seismic conditions, of already existing steel storage tanks of large capacity, located in high risk zones. From the revision of analysis and design criteria concerned with thin walls structures, it has been prepared a procedure based on a numeric modeling where the mechanic characteristics of the materials and the real geometrical measures have been considered. Numeric analysis by FEM have been used in different conditions: empty tanks vibration, full tanks where fluid-structure interaction is considered to the case of flexible walls, in order to take into account the pressure distribution of the liquid. To estimate the response, real seismic records originated in the Mexican Region, have been used. Finally the numerical results obtained of the empty tanks with those calculated analytically are compared and it is observed that a good correlation between both approaches. For the results obtained of the fluid-structure interaction models with the selected seismic registry is observed that given its great dimensions and the rigidity that provides the ring to them in the top part of the tanks, the effect of the surge is not very significant due to the fluid system -structure is excited in the first seconds, reason why the action of the hydrostatic pressure on the walls of these is sample to be dominant.