Evaluation of Seismic Performance Factors for Elevated Reinforced Concrete Tanks (original) (raw)
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Seismic Behavior Assessment of Concrete Elevated Water Tanks
Journal of Rehabilitation in Civil Engineering, 2013
Elevated tanks are very important structures and consist of various types. Water supply is vital to control fires during earthquakes. Also they are utilized to store different products, like petroleum supplies in cities and industrial zones. Damage to these structures during strong ground motions may lead to fire or other hazardous events. Elevated tanks should stay functional after and before earthquakes. However their dynamic behavior differs greatly in comparison with other structures. In this research, a sample of reinforced concrete elevated water tank, with 900 cubic meters capacity, exposed to three pair of earthquake records have been studied and analyzed in time history using mechanical and finite-element modeling technique. The liquid mass of tank is modeled as lumped masses known as sloshing mass, or impulsive mass. The corresponding stiffness constants associated with these lumped masses have been worked out depending upon the properties of the tank wall and liquid mass....
Seismic Behavior Evaluation of Concrete Elevated Water Tanks
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.
Seismic Evaluation of Elevated Water Tank Models under Different Earthquake Characteristics
—Seismic analysis of hydrodynamic structure such as elevated concrete water tank is somewhat complex when compared with other structures. Also, dynamic fluid-structure interaction (FSI) plays an important effect in this complexity. The main objective of this study is the analytical evaluation of seismic response of elevated water tanks under different earthquake time history records with SAP2000 structural software. Two models were simulated in empty, Half-full and full condition. For later conditions water mass has been considered in two parts as impulsive and convective suggested by GSDMA guidelines. In addition to that impulsive mass of water has been added to the container wall using Westergaard's added mass approach. Tank responses including base shear, overturning moment and roof displacement have been observed, and then the results have been compared and contrasted. The result shows that the structure responses are exceedingly influenced by the presence of water and the earthquake characteristics.
DYNAMIC ANALYSIS OF WATER TANKS WITH INTERACTION BETWEEN FLUID AND STRUCTURE
Due to growing population and expansion of cities, the number of elevated water tanks supplying the demand urban water system is on the rise. As it has been mentioned in the Iranian code of practice for Earthquake /2800 because of the importance of sanitation and hygiene water tanks have been considered as important structures during the unexpected events such as earthquake. There is a great expectation not to see any phase out for their serviceability after the earthquake. Because of the presence of fluid with different behavioral properties of structures containing it and the most part of mass of tanks are located in a considerable distance from its foundation, the behavior of these types of structures in compare with conventional structures are more complicated. In this research, cylindrical concrete water tanks, which have a central shaft, have been evaluated with considering the effect of the structure's interaction with water through precise implementation of boundary conditions on the interface between fluid and structure. Also considering the level of water in the tank and their behavior under recorded acceleration of different earthquakes using finite element method. The results were then compared with suggested methods by Iranian code /2800, which the results show a relatively considerable difference between mentioned methods.
Seismic Vulnerability of Elevated Water Tanks Using Performance Based-Design
dist.unina.it
Liquid tanks and especially the elevated tanks are structures of high importance which are considered as the main lifeline elements that should be capable of keeping the expected performance. i.e. operation during and after earthquakes. Thus, researchers, in recent years, have focused on studying the seismic behavior of these tanks. Many researches have been done on the behavior, analysis, and design of seismic tanks, particularly ground tanks, while only a few of these researches have concerned with the elevated tanks and even less with the reinforced concrete elevated tanks. In this research, a sample of a reinforced concrete elevated water tank, with 900 cube meters under seven earthquake records have been studied and analyzed in dynamic time history and the tank's responses including base shear, overturning moment, tank displacement, and sloshing displacement under these seven record have been calculated, and then the results have been compared and contrasted.
FLUID-STRUCTURE INTERACTION APPROACHES FOR SEISMIC BEHAVIOR OF ELEVATED WATER TANK
In the 21st Century, with the expansion of cities, it is required to store and distribute water to areas far away from water reservoirs. RC elevated water tank is a feasible alternate for distributing water under natural head to the maximum possible area. It is very important for water tank to remain in function later to any natural calamity like earthquake. Seismic behaviour of them has to be investigated in depth. It can be seen from the literature that fluid-structure interaction plays an important role on seismic behaviour of elevated tanks. The main aim of this study is to analyse water tank in SAP 2000 considering fluid-structure interaction and compute structural response such as base shear, overturning moment, top displacement and sloshing displacement under response spectrum seismic analysis. Result shows dynamic response of SAP 2000 can be used for further analysis and fluid-structure interaction can be assigned using alternate approach.
Dynamic analysis and seismic performance evaluation of above-ground liquid-containing tanks
Engineering Structures, 2008
A large number of industrial facilities were damaged during the 1999 M w 7.4 Kocaeli, Turkey earthquake. One of those industrial facilities, Habas plant located within 10 km of the fault trace, provides liquefied gases to commercial plants and medical facilities. Two of the three tanks at the Habas facility collapsed during the earthquake. The main objectives of this paper were to evaluate the seismic performance of tanks and investigate the parameters influencing the dynamic behaviour. Simplified and finite element dynamic analyses of the tanks are carried out including the effect of liquefied gas-structure interaction using a ground motion recorded at a nearby site. The vulnerabilities of the structural system, the observed performance, and damage pattern are discussed by comparing the dynamic analysis results with the strength and deformation capacity of the support columns. The dynamic analysis results from a simplified three-mass model and a finite element model confirmed that the axial and lateral strength of the columns supporting the two nearly full tanks were not sufficient to resist the demand imposed during the earthquake. Consistent with the observed structural performance, an elastic response is predicted for the columns supporting the undamaged 25% full identical tank.
Seismic Assessment of Elevated Circular Water Tank
The present study reports the analysis and design (Response Spectrum Analysis, Frequency Analysis and Time History Analysis) of an elevated circular water tank using STAAD.Pro V8i. The design involves load calculations manually and analysing the whole structure by STAAD.Pro V8i. The design method used in STAAD.Pro analysis is Limit State Design and the water tank is subjected to live load, dead load, self – weight and seismic loads. Seismic load calculations are done as per IS 1893-2000. Response Spectrum Analysis gives displacement, bending moment, shear force, axial force, and torsion values. Eigen solution so obtained helps in determining the base shear and various peak story shear values of the structure. Frequency analysis gives the natural frequency of the structure and time history, which defines the behaviour of the structure in certain interval of time against various functions like velocity, displacement and acceleration and hence the graphical solutions has been drawn for each analysis. Notations: 1. CPS = Cycles per second 2. D.L. = Dead Load 3. E.L. = Earthquake Load 4. f ck = Compressive Strength of Concrete (Mpa) 5. f y = Yield Stress of Steel (Mpa) 6. L.L. = Live Load 7. STAAD.Pro = Structural Analysis and Design for Professionals 1. Introduction and Background Storage tanks are built for storing water, liquid petroleum, petroleum products and similar liquids. Analysis and design of such tanks is independent of chemical nature of product. They are designed as crack free structures to eliminate any leakage. Adequate cover to reinforcement is necessary to prevent corrosion. In order to avoid leakage and to provide higher strength, concrete of grade M30 and above is recommended for liquid retaining structures. A new procedure to determine hydrodynamic pressures for rectangular tanks was discussed by Chen J.Z & Kianoush M.R [1] in which the effect of wall flexibility on impulsive pressures is considered and the behaviour of three types of open type tanks namely " shallow " , " medium " and " tall " , under seismic ground motions has been studied. For dynamic time history analysis Chen J.Z & Kianoush M.R [1] uses three suites of time history representing low, medium and high earthquake zones and while calculating the hydraulic pressure they assumed that the liquid storage tank is fixed to the rigid foundation and a Cartesian coordinate system has been used with origin located at the centre of the tank base. The motion of water relative to tank and motion of tank relative to ground was accounted by Housner G.W[2] which indicates a simplified dynamic analysis for the response of elevated water tanks to earthquake ground motion and it has also been pointed out that if a closed tank is completely full of water or completely empty, it is essentially a one-mass structure and if the tank has a freewater surface, there will be slashing of the water during an earthquake and this makes the tank essentially a two-mass structure. The earthquake performance of storage tanks in terms of earthquake resistance in Turkish industrial facilities was evaluated by Korkmaz K.A Et.Al [4] who believed that modelling a typical storage tank of an industrial
KSCE Journal of Civil Engineering, 2012
In this paper, a reinforced concrete elevated water tank, with a capacity of 900 cubic meters and height of 32 meters, has been utilized and subjected to an ensemble of earthquake records. Finite element model has been employed to model elevated water tank system. Fluid-structure interaction for modeling is considered by Eulerian method. Also the behaviors of concrete and steel material were considered to be nonlinear. Seismic responses of the elevated water tank such as base shear force, overturning moment, displacement and hydrodynamic pressure have been assessed for ensemble earthquake records. The obtained result revealed that scattering of responses in range of the mean minus standard deviation and mean plus standard deviation are approximately 60 to 70 percents. Also, responses of elevated water tank are dependent with earthquake characteristics and frequency of elevated water tank. The maximum response of base shear force, overturning moment, displacement and hydrodynamic pressure occurred in different case of vessel filling.
Study The Fluid Structure Interaction Due to Dynamic Response of Elevated Concrete Water Tank
2011
Fluid structure interaction (FSI) is complicated phenomena in which researches trying to suggest new techniques to account its effects in elevated concrete water tanks. Rectangular and circular shapes of elevated tanks have been chosen to conduct this study. In this paper the adding of impulsive mass to elevated tank has been modified instead to Westergaard approach, by examined six rectangular and six circular models of elevated tanks that suggested by authors through three dimensional finite elements method (FEM), using LUSAS FEA 14.1, based on vibration dynamic analysis to obtain the time of impulsive mass at every case. The results shows a small deviations obtained in both shapes (rectangular and circular) between Westergaard approach and approaches suggested