Structural Performance of RCC Framed Elevated Circular Shape Tank in the Indian Region

Elevated water storage tanks are pertinent structures, and therefore, ensuring their safety aftershock is vital. Post-shaking must continue to occur to ensure the availability of potable water in quake-affected areas and to meet firefighting requirements. This study focuses on the seismic analysis of RCC-framed circular tanks as per Indian standards. Tank analysis is carried out for four seismic zones with three types of ground conditions according to Indian standards. In the present study, three different water depths, full, half-full and empty tanks, are considered. Tank analysis focuses on determining the peak shear, moment and hydrodynamic pressure. The lateral hydrodynamic impulsive and convective pressure at the base of the wall, wall inertia and pressure due to excitation in a vertical direction is calculated for the tank in full, half-filled condition. The wave height is calculated using horizontal seismic coefficient design in convective mode for four seismic zones and three types of ground conditions as per Indian standards. Tank in full capacity governs the design. For a full capacity of the tank, the horizontal seismic coefficient in convective mode is higher than in impulsive mode, as the time period value is less in impulsive mode. For the same ground conditions, the peak shear and moment values at the bottom of the container are controlled under full tank conditions for seismic zones. These values are 20% greater than those under half-filled conditions and 60% greater than those under empty tank conditions. The impulsive and convective mode seismic coefficients increase with increasing zone and are maximum in the soft soil type. The values of the vertical seismic coefficient increase with increasing zone and remain the same for all three types of soil conditions. The values of hydrodynamic maximum pressure, hydrodynamic impulsive lateral pressure on the base, hydrodynamic convective pressure on the base and wall inertia pressure in tank full case are 30% greater in soft soil type, 33% greater in medium stiff soil; additionally, the values are 38% greater in rocky or hard soil than in half-filled tank.