Dynamic response of ground supported rectangular water tanks to earthquake excitation (original) (raw)

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 Behaviour and Seismic Response of Ground Supported Cylindrical Water Tanks

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

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 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 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

A STUDY ON THE SEISMIC RESPONSE OF ELEVATED WATER TANK

IRJET, 2022

Water tanks have been the most vital lifeline structures. They serve as an essential component for most water supply schemes in urban and rural areas. Water storage is generally based on overhead water tanks since the required pressure in the water delivery process is achieved by gravity in elevated tanks rather than the need for large pumping systems. These elevated tanks consist of a large water mass at the top supported by a tall staging which is extremely weak against horizontal forces caused due to earthquakes. The selection of a suitable staging system plays a major role in the behaviour of elevated water tanks during earthquakes since these tanks are often utilized in seismically active regions. The ductility and energy absorbing capacity of such elevated tanks are less compared to conventional building and hence seismic safety of such structures are very important. Soil-structure interaction (SSI) is one of the most essential components of structural analysis. This interaction can change the Dynamic characteristics of a structure, which can be advantageous or detrimental to its performance. Conventional fixed base analysis disregards the effect of soil flexibility, resulting in an unsafe design. The present work is focused on the study of seismic response of elevated water tank considering the sloshing effect and to evaluate the behaviour considering Soil-Structure Interaction (SSI) effect in seismic Zone (II and III). Different soil conditions are also adopted as per IS1893(Part 2):2014. Modelling and analysis has been carried out using FEM based software SAP2000.

Seismic Performance of Circular Elevated Water Tank

International Journal of Science and Research (IJSR), 2015

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. Elevated water tanks should be competent of keeping the expected performance during and after earthquake. It has large mass concentrated at the top of slender supporting structure hence extremely vulnerable against horizontal forces due to earthquake. Staging is formed by a group of columns and horizontal braces provided at intermediate levels to reduce the effective length of the column. In this research, a circular cylindrical elevated water tank 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 Nodal displacement 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 of Circular Water Tanks under Different Seismic Conditions For Two Different Conditions

IRJET, 2022

Water tanks are very important components of lifeline. They are grave elements in municipal water supply, fire fighting systems and in many industrial amenities for storage of water. In the seismic analysis of ground supported water tanks ,the total mass subjected to the seismic forces is divided into two parts that is impulsive and convective. Impulsive mass is subjected to the impulsive pressure whereas convective mass is subjected to the convective pressure. The impulsive pressures are associated with the inertial forces produced by the accelerations of the walls of the container and are directly proportional to these accelerations. The convective pressures are those produced by the oscillations of the fluid and are therefore the consequences of the impulsive pressures. Corresponding to the impulsive and convective pressure various design parameters like time period, sloshing height, design horizontal seismic coefficient in both impulsive and convective modes is calculated.

SEISMIC BEHAVIOR OF ELEVATED WATER TANK

Hydrodynamic analysis of elevated water tank is a complex procedure involving fluid structure interaction. The elevated tank supports large water mass at the top of slender staging. In case of elevated tank the resistance against lateral forces exerted by earthquake is largely dependent of supporting system. Staging is considered to be a critical element as far as lateral resistance is concern. Satisfactory performance of staging during strong ground shaking is crucial. In this paper seismic behavior of elevated water tank in view point of their supporting system is evaluated using finite element software ETABS. The main objective is to evaluate a performance of different staging system for elevated water tank using finite element software ETABS. The spring mass model consisting of impulsive and convective masses as per IS 1893:2002 Part 2 has been used for the analysis. The parametric study is performed on mathematical model with different staging system to evaluate their performance with regard to lateral stiffness, displacement, time period, seismic base shear, overturning moment, flexure etc.

REVIEW ON SEISMIC ANALYSIS OF ELEVATED WATER TANK-2

Elevated Water Tanks are one of the most important lifeline structures in the earthquake regions. In major cities and also in rural areas elevated water tanks forms an integral part of water supply scheme. The elevated water tanks must remain functional even after the earthquakes as water tanks are required to provide water for drinking and firefighting purpose. These structures has large mass concentrated at the top of slender supporting structure hence these structure are especially vulnerable to horizontal forces due to earthquakes. All over the word, the elevated water tanks were collapsed or heavily damaged during the earthquakes because of unsuitable design of supporting system or wrong selection of supporting system and underestimated demand or overestimated strength. So, it is very important to select proper supporting system and also need to study the response of Elevated Water Tanks to dynamic forces by both equivalent Static method as well as Dynamic method and to find out the design parameters for seismic analysis. It is also necessary to consider the sloshing effect on container roof slab. This sloshing of water considerably differ the parametric values used in design and economy of construction. The effect of hydrodynamic pressure must be considered in the seismic analysis of Elevated Water Tank.