Dynamic analysis of high-level waste 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

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.

2017

A three-dimensional surrogate model is presented for the seismic performance assessment of cylindrical atmospheric liquid storage tanks. The proposed model consists of a concentrated fluid mass attached to a single vertical beam-column element, that rests on rigid beam-spokes with edge springs. The model is suitable for rapid static and dynamic seismic performance assessment. Contrary to other simplified models for tanks, its properties are determined through simple structural analysis that can be performed in any nonlinear analysis software, without the need for complex finite element models. The results compare favorably to those of three-dimensional finite element models on three tanks of varying aspect ratios. A step-by-step example of the modelling procedure is presented for a squat unanchored tank, and a sensitivity analysis is conducted in order to investigate the effect of various modelling parameters on the seismic response of the proposed tank model. CE Database subject he...

Journal of The Institution of Engineers (India): Series A, 2018

Liquid storage tank such as in water distribution systems, petroleum plants etc., constitute a vital component of life line systems. Reducing earthquake effects on liquid storage tanks, to minimize the environmental and economic impact of these effects, have always been an important engineering concern. In this paper, the dynamic behavior of cylindrical ground supported concrete water tanks with different aspect ratios is investigated using finite element software ANSYS. The natural frequencies and modal responses are obtained for impulsive and convective modes of vibration. The natural frequency of vibration of the tank is observed to be the lowest at maximum water depth. The fundamental impulsive frequency increases as water level reduces and for water level less than 1/3 of tank height, there is significantly no change in impulsive frequency. The effect of wall flexibility on dynamic behavior of the tank is investigated by performing the modal analysis of flexible and rigid tanks. For a partially filled tank, the results of the present study are of significant relevance. The response of the tank to the transient loading as horizontal ground motion of El Centro earthquake is studied for various water heights. As the height of water on the tank increases, the ultimate maximum seismic response parameters are also observed to be increased. The location of maximum hoop stress varies in accordance with the variations in input ground motion and water fill condition whereas shear and bending moment are maximum at the base. Keywords Liquid storage tank Á Ground supported circular tank Á Modal analysis Á Time history analysis Á Tank wall flexibility

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.

2011

The paper examines some special issues on the structural behaviour of uprightcylindrical liquid storage tanks, which are widely used in industrial facilities and for water storage. Two main design standards are considered: EN 1998-4, a relatively new standard, and Appendix E of API 650, which has been through substantial amendments and revisions in its new version (11 th edition, 2007). There are significant differences between the two specifications, which are due to the fact that there exist several controversial issues on this subject, open to further research. These issues are (a) the number of modes necessary to estimate accurately the convective seismic force due to the hydrodynamic behaviour of the liquid containment; (b) the appropriate combination of the impulsive and the convective component of seismic force; (c) the uplifting behaviour of unanchored tanks, with emphasis on the base plate behaviour and the increase of meridional compression; (d) the choice of an appropriat...

Proceedings of the 13th …, 2004

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 ...

Elevated tanks are important structures in storing vital products, such as petroleum products for cities and industrial facilities, as well as water storage. These structures have various types and are constructed in a way that a greater portion of their weight is concentrated at an elevation much about the base. Damage to these structures during strong ground motions may lead to fire or other hazardous events. In this research, a reinforced concrete elevated water tank, with 900 cubic meters capacity, exposed to three pairs of earthquake records was analyzed in time history using mechanical and finite-element modeling techniques. The liquid mass of the tank was modeled as lumped mass known as sloshing mass, or impulsive mass. The corresponding stiffness constants associated with the lumped mass were determined depending upon the properties of the tank wall and liquid mass. Tank responses including base shear, overturning moment, tank displacement, and sloshing displacement were also calculated. Obtained results revealed that the system responses are highly influenced by the structural parameters and the earthquake characteristics such as frequency content.