EFFECT OF STAGGING HEIGHT ON THE SEISMIC PERFORMANCE OF RC ELEVATED WATER TANK

Elevated water tanks are i ntegral part of lifeline facilities in any town/city. They are used to store water for various purposes like drinking, fire fighting, etc and are vulnerable in resisting earthquake forces due to presence of large mass on a slender staging.. Further, the su pporting structures i.e. the staggings have been found to be extremely susceptible to earthquake forces, sometimes leading to collapse of water tanks. Bhuj earthquake is an epitome of this hazard. Further, in view of the limitations of IS 1893 - part2 with r espect to the international practice for seismic resistant design of water tanks, IITK - GSDMA has presented certain additional guidelines. This study is mainly focused in understanding the seismic behaviour and vulnerability of elevated reinforced concrete water tanks and supporting structures for various seismic intensities, soil conditions, staging heights etc. with respect to the provisions of IS1893 Part2 and guidelines proposed by IITK - GSDMA. Finite element modelling and dynamic analysis of elevated water tanks has been performed using SAP2000. Since available earthquake data is not adequate, response spectrum analysis has been carried out to understand the seismic behaviour of water tanks. Fu rther, Nonlinear static analysis has been performed to assess the ductility characteristics of the water tank for varying staging heights, for a given capacity of water tank (Empty and Full water level conditions). In this study Circular water tank has bee n chosen as a case study and analysed for staging heights 5, 8,11,14,17,20,23 & 26, for an interval of 3 meters.