No abstract

A probabilistic method based on FEMA P695 is employed for validating the response modification factor of reinforced concrete pedestals in elevated water tanks. In the current codes and standards, the response modification factor of elevated water tanks is mainly based on engineering judgement. Ten models of elevated water tanks with different tank sizes and pedestal heights are selected for the investigation. Initially, the prototypes are designed based on the current codes and standards. Next, the finite element models of the prototypes are developed. By performing incremental dynamic analysis, the probability of collapse for each prototype is calculated under different seismic loading conditions and system uncertainties. The results of the study validate and confirm the current response modification factor values and show that the tank size has a significant effect on the nonlinear seismic response behaviour of elevated water tanks. In addition, it is revealed that heavy tank sizes that are designed in accordance with codes and guidelines are more vulnerable under seismic loading compared with light and medium tank sizes.

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.

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.