Elevated water tanks are employed in water distribution facilities in order to provide storage
and necessary pressure in water network systems. These structures have demonstrated poor
seismic performance in the past earthquakes. In this study, a finite element method is employed
for investigating the nonlinear seismic response of reinforced concrete (RC) pedestal in elevated
water tanks. A combination of the most commonly constructed tank sizes and pedestal heights in
industry are developed and investigated. Pushover analysis is performed in order to construct the
pushover curves, establish the overstrength and ductility factor, and evaluate the effect of various
parameters such as fundamental period and tank size on the seismic response factors of elevated
water tanks. Furthermore, a probabilistic method is implemented to verify the seismic
performance and response modification factor of elevated water tanks. The effect of wall openings in the seismic response characteristics of elevated water tanks is investigated as well. Finally, the effect of axial compression on
shear strength of RC pedestals is evaluated and compared to nominal shear strength from current guideline and standards.
The results of the study show that the tank size, pedestal height, fundamental period, and pedestal height to
diameter ratio, could significantly affect the overstrength and ductility factor of RC pedestals. The nonlinear
dynamic analysis results reveal that under the maximum considered earthquake (MCE) intensity, light and medium size tank models do not experience significant damages. However, heavy tank size models experience more damage in comparison with light and medium tank sizes. This study shows that the current code response modification factor values are appropriate for light and medium tank sizes; however they need to be modified
for heavy tank sizes. The results of this study also reveal that if the pedestal wall openings are designed based on
current design guidelines, then nearly identical nonlinear seismic response behaviour is expected from the pedestals with and without openings. Finally, it is shown that the pedestal maximum shear strength calculated by finite element method for the full tank state is higher than the nominal shear strength determined based on the current design guidelines compared to the nominal shear strength from current guideline and standards.
Nonlinear seismic response of reinforced concrete pedestals in elevated water tanks
