A Comparative Study on the Seismic Behaviour of Square and Circular Water Tank Considering Soil-Structure Interaction
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K S Jayadeep*
M S Ramya
The seismic performance of elevated water tanks is a major concern due to the large mass of stored water at an elevated level and the flexibility of the supporting staging system. Unlike conventional buildings, the dynamic response of elevated water tanks under seismic loading is complex, depending on tank geometry, staging characteristics, fluid-structure interaction, and soil-structure interaction (SSI). The traditional fixed-base approach assumes a rigid foundation and ignores soil flexibility, potentially leading to inaccurate seismic response predictions, particularly for structures on soft or layered soil. Additionally, water sloshing introduces a dynamic component that further affects tank behaviour. This study presents a comparative numerical investigation of the seismic behaviour of square and circular elevated water tanks, explicitly incorporating SSI. Both tank configurations were analysed under identical geometric, material, loading, and staging conditions to isolate the effect of tank geometry on seismic response. The influence of soil flexibility and water sloshing was considered, and structural responses were compared using natural period, base shear, and displacement. Results show that circular tanks exhibit lower seismic responses than square tanks under both fixed-base and SSI conditions. The influence of SSI becomes more pronounced as soil stiffness decreases, with the fundamental time period increasing by approximately three times under soft-soil conditions relative to the fixed-base case. These findings offer insight into the combined effect of tank geometry and soil–structure interaction on seismic performance, supporting the selection of more suitable and resilient tank configurations for seismic regions.
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