Elevated tanks effect on transient pressures: case study

Elevated tanks are an integral part of the water supply networks. This paper highlights the effect of elevated tanks' location and size on the transient pressures resulting from the sudden failure of pumps. A comparison between the impact of elevated tanks and air vessels on the water hammer was also performed. The Bentley HAMMER model was first validated then applied to analyze the unsteady flow within an actual distribution network. The results display that the elevated tanks have a considerable effect on the surge pressures, where they improve the extreme pressures effectively at and around them, but they cannot fully protect the system from the water hammer risks, as there are still relatively large negative pressures at some distant junctions. Besides, as the tank capacity increases, the surge pressures increase slightly. In our case study, the best location of the elevated tank is at the network extremity and then at the pumping stations, since the minimum pressures improve by 67 and 54%, respectively. Although the present case study may differ from other supply systems, the obtained results can provide an indication of the elevated tanks' role in alleviating undesirable water hammer effects.

Seismic Response of Ground Cylindrical and Elevated Conical Reinforced Concrete Tanks

In this study, the seismic performance of concrete ground-supported cylindrical as well as liquid-filled elevated water tanks supported on concrete shaft is evaluated using the finite element method. The effects of a wide spectrum of parameters such as liquid sloshing, tank wall flexibility, vertical ground acceleration, tank aspect ratio, base fixity, and earthquake frequency content on dynamic behaviour of such structures are examined. Furthermore, the adequacy of current practice in seismic analysis and design of liquid containing structures is investigated. A comprehensive parametric study covering a wide range of tank capacities and aspect ratios found in practice today is also carried out on elevated tanks. Two different innovative strategies to reduce the seismic response of elevated tanks are examined, in the first strategy the inclined cone angle of the lower portion of the vessel is increased while in the second strategy the supporting shaft structure is isolated either from the ground or the vessel mounted on top. The results of this study show that capability of the proposed finite element technique. Using this method, the major aspects in the fluid-structure interaction problems including wall flexibility, sloshing motion, damping properties of fluid domain, and the individual effects of impulsive and convective terms can be considered. The effects of tank wall flexibility, vertical ground acceleration, base fixity, and earthquake frequency content are found to be significant on the dynamic behaviour of liquid tanks. The parametric study indicates that the results can be utilized with high level of accuracy in seismic design applications for conical elevated tanks. This study further shows that increasing the cone angle of the vessel can result in a significant reduction in seismically induced forces of the tank, leading to an economical design of the shaft structure and the foundation system. It is also concluded that the application of passive control devices to conical elevated tanks offers a substantial benefit for the earthquake-resistant design of such structures.

Seismic Response of Ground Cylindrical and Elevated Conical Reinforced Concrete Tanks

In this study, the seismic performance of concrete ground-supported cylindrical as well as liquid-filled elevated water tanks supported on concrete shaft is evaluated using the finite element method. The effects of a wide spectrum of parameters such as liquid sloshing, tank wall flexibility, vertical ground acceleration, tank aspect ratio, base fixity, and earthquake frequency content on dynamic behaviour of such structures are examined. Furthermore, the adequacy of current practice in seismic analysis and design of liquid containing structures is investigated. A comprehensive parametric study covering a wide range of tank capacities and aspect ratios found in practice today is also carried out on elevated tanks. Two different innovative strategies to reduce the seismic response of elevated tanks are examined, in the first strategy the inclined cone angle of the lower portion of the vessel is increased while in the second strategy the supporting shaft structure is isolated either from the ground or the vessel mounted on top. The results of this study show that capability of the proposed finite element technique. Using this method, the major aspects in the fluid-structure interaction problems including wall flexibility, sloshing motion, damping properties of fluid domain, and the individual effects of impulsive and convective terms can be considered. The effects of tank wall flexibility, vertical ground acceleration, base fixity, and earthquake frequency content are found to be significant on the dynamic behaviour of liquid tanks. The parametric study indicates that the results can be utilized with high level of accuracy in seismic design applications for conical elevated tanks. This study further shows that increasing the cone angle of the vessel can result in a significant reduction in seismically induced forces of the tank, leading to an economical design of the shaft structure and the foundation system. It is also concluded that the application of passive control devices to conical elevated tanks offers a substantial benefit for the earthquake-resistant design of such structures.

Dynamic Behavior of Elevated Water Tanks under Seismic Excitation

Elevated tanks are considered very sensitive to seismic excitations. That is why several researchers have studied the performance of these structures under seismic loading. The elevated tanks support‘s design are the most responsible reason of the damages and failures of this kind of structure . In this present paper, we are used the finite element technique to study the seismic response of them with taking into account the interaction between fluid and structure in the presence of sloshing. Modal and transient analysis are carried out on two types of the elevated tanks support, while keeping the same quantity of concrete and the same fluid volume. The displacements at the top of the tank and The fundamental period of the impulsive mode of the elevated water tank with shaft support decreased compared to the elevated water tank with frame support .The obtained results confirm the supporting system effect on dynamic behavior of elevated water tanks .