Nonlinear Static Analysis Of Elevated Rcc Water Tank

Abstract

Elevated water tank is storage system of huge mass of water at certain height. Be- cause of large mass, especially when tank is full lateral forces are more or less govern by tank. So due to earthquake damage or collapse of elevated tank is at risk. Ele- vated tank should be safe and functional during and after earthquake for providing necessary water supply for drinking and for fire fighting. However some repairable damage may be acceptable during sever earthquake not afecting the functionality of tank. Whatever may be the cause of distress but water tanks should fulfil the purpose for which it has been designed and constructed with minimum maintenance throughout its intended life. It is necessary to understand the seismic behaviour of elevated tank. As codal based design of structure is limited up to elastic behaviour of structure. Nonlinear static analysis is useful to understand post elastic behaviour of structure. Achievement of good performance and less damage with less loss of lives, it is necessary to understand nonlinear behaviour of structure. Pushover analysis is a method to perform nonlinear static analysis. In this study, elevated tank is design with limit state method as per IS:3370 (part 1 and 4) -2009. Water tank container should free from cracks so it can avoid leakage problem. Water generates hydrostatic pressure on tank walls. Due to seismic forces hydrodynamic forces also exerted on the walls in addition to hydrostatic forces. These hydrodynamic forces are evaluated with the help of spring mass model of tanks as per IS: 1893:2002 (part-2). Finite element model is generated in SAP2000 as per design of tank. Pushover analysis is performed to obtain pushover curve i.e. base shear v/s roof displacement. Concluded the capacity to resist earthquake by tank.