Seismic Fragility of Aging Elevated Water Tank with Smooth Bars Considering Soil Structure Interaction

Abstract

The functionality of elevated water tanks is pivotal to assure after an earthquake as water supply is expected to be uninterrupted. Although elevated water tanks with deformed bars are widely studied, limited works exist for water tanks with smooth bars, although such tanks comprise a considerable fraction, even in the high seismic regions. To quantify the seismic vulnerability of aging elevated water tanks with smooth bars, we created analytical fragility functions for full, half, and empty reservoir conditions, considering fluid–structure and soil–structure interactions. The sum of findings reflects that soil flexibility and the amount of water present in the tank have a significant effect on overall seismic fragility, especially at higher damage states. The tanks are found to be most vulnerable when they are fully filled with water. The effect of soil flexibility is more pronounced at higher damage states. The difference between the fragility of flexible base and fixed base structures is found to increase with increasing ground motion intensity and it is the highest for the empty tank condition.

System identification based appraisal of soil structure interaction in elevated water tank for various reservoir conditions

“…Damage mechanisms due to earthquakes to various components of elevated water tanks are reported by Soroushnia et al [5]. Similarly, seismic performance and vulnerability of elevated water tanks is reported by several researchers (see e. g. [2,[6][7][8][9][10][11][12][13][14][15][16]). Although numerical assessments have incorporated both fixed base as well as flexible base analyses, existing studies report the results probabilistically without discerning the exacting behavior of elevated reinforced concrete (RC) water tanks.…”

“…Reportedly, the effect of soil structure interaction is found to be less profound in the case of low-rise special moment resisting frame buildings constructed in different locations within the valley [18]. Contrary to the results reported by Adhikari et al [18], Rimal et al [10] highlighted that the higher damage states in water tanks are significantly affected by soil structure interaction, leading to an increased vulnerability. These contrasting numerical results and field observations laid the ground for this study to assess whether soil structure interaction matters in elevated water tanks.…”

“…The finite element model of the case study tank was prepared using the material characteristics as reported by Rimal et al [10]. For the 20 MPa concrete, which is estimated using rebound hammer testing in situ, the elastic modulus was empirically estimated as 22360.68 MPa, and the unit weight of the concrete was adopted as 25 KN/m 3 .…”

“…Since the shear wave velocity profile for the site was not available, we used the empirical relations developed by Gautam [35] to estimate shear wave velocity from the standard penetration resistance values. Further details regarding the estimation of link properties can be found in [10]. A threedimensional finite element model is shown in Fig.…”