Analysis of Fragility of Elevated Water Tanks with Base Uplift Foundations

• Main Authors: Yun-Lon Chen, 陳雲龍
• Other Authors: Kuan-Hsoung Chen
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/31854364126213764902

碩士 === 中華技術學院 === 土木防災工程研究所 === 95 === The objective of this research is to develop the fragility curves of elevated water tanks with base-lifting foundations. Previous researchers mostly have an extensive study on the free-standing, unanchored liquid-storage tanks, but none of them include elevated water tanks with base-lifting foundations. In reality, the consideration in design of an elevated water tank with spread footing on the stiff site is added concrete at the bottom of column to avoid overturning of tanks. However, the risk of overturning of tanks is increased with the increase of intensity of lateral seismic ground accelerations- particularly, near fault earthquakes. A case study of a three thousand tones of an elevated water tank situated at the industrial park is performed a nonlinear time history analysis. For comparison, the foundation of tanks is classified into one with the base fixed on the ground and the other base-uplifting allowed. Reinforced concrete walls are simulated as shell elements, a circular foundation modeled as solid elements, the gap between foundation and soil represented with nonlinear interface elements, and Housner’s equivalent liquid mechanism adopted to reflect the impulsive and sloshing masses. Empty and full-liquid tanks are accounted for upper and lower bounds of liquid depths in the tanks. Hanging walls and footwalls of near fault earthquakes in the 1999 Chi-Chi earthquakes served as an input ground excitation. The vulnerability of the tank is identified with the fragility curves to correlated PGA and the damage states of tanks. The fragility curves of an elevated tank with base-uplifting can provide an design reference for tanks on the area prone to earthquake attack.