Non Linear Time History Analysis of Elevated Water Tank

Elevated water tank is a water storage facility supported by a tower and constructed at an elevation to provide useful storage and pressure for a water distribution system. Due to post earthquake functional needs, seismic safety of water tanks is of most important. These structures have large mass concentrated at the top with a supporting structure of beams and columns (staging).The present study focuses on the response of the elevated circular water tanks to dynamic forces. Tanks of various capacities viz. 1000 m3, 1500 m3 and 2000 m3 having different staging heights such as 16 m, 20 m, 25 m, and 30 m are considered. The present study is an effort to identify the behaviour of RCC Elevated water tank, by varying the volume of water in the tank viz. tank empty, tank 25% filled, tank 50% filled tank 75% filled and tank full condition to determine the effect on staging height under five different earthquake ground motion viz. EI-Centro (1979), Bhuj (1993), Uttarkashi (1993), Koyna (1993) and Chamoli (1992). Non linear time history analysis has been carried out. The simulation of water tank is done in SAP2000 v18. For modelling of water in SAP2000 v18, water mass is divided into two main components namely impulsive and convective. These impulsive and convective masses are obtained from IS1893 (Part 1):2002. Various response quantities such as base shear, time period, displacements, acceleration are obtained. A circular acrylic elevated water tank of 0.0044 m3 capacity having internal diameter 0.266 m and height of 0.058 m is considered for the study. For validation the results obtained from experiment and analysis, of scaled down model same steel model is used. A comparison of experimental and numerical results is also carried out for validation purpose.