Seismic Vulnerability Assessment of Baffled Elevated Water Tank with Fluid–Structure–Soil Interaction Having Variable Staging Pattern

The damages found in the elevated water tank from previous earthquake events confirm that the failures occur mainly in the staging of the water tank. It is essential to quantify these damages to investigate its performance. Fluid–structure–soil interaction plays an important role in the investigation of structural performance of baffled elevated water tank. With the use of performance-based earthquake engineering, in this study the performance level is investigated by utilizing spectral acceleration as intensity measure and the engineering demand parameter is the top drift of staging. With the use of SAP2000 software various models were developed by considering variations in water level and staging configuration of baffled elevated water tank by considering fluid–structure–soil interactions. Non-linear dynamic analysis were conducted following FEMA P695 guidelines by considering five ground motions with gradually increasing intensities in increments of 0.1 g up to failure and IDA curves were obtained. Fragility curves were made from the IDA curves according to three performance limit states for assessing seismic risk. For evaluating safety margin against collapse, collapse margin ratios were obtained. It shows that cross staging is having a safety margin of 32.5% higher than radial and basic staging. From the result it shows that hard soil is having a safety margin of 99% higher than soft soil and medium soil has 25% higher safety than soft soil. The seismic fragility analysis by considering variation in water level shows that half-filled water level shows more critical condition than Full and Empty condition.