Seismic Soil-Structure Interaction Analysis and Design of Overhead Liquid Storage Tanks in Kathmandu Valley, Nepal

Abstract

This research investigates the soil-structure interaction (SSI) effects on the analysis and design of overhead liquid storage tanks located in Kathmandu Valley, Nepal; a region characterized by deep alluvial deposits and high seismic vulnerability. Recognizing the limitations of conventional fixed-base assumptions, the research integrates dynamic SSI effects to more accurately capture the tank–foundation–soil system response under earthquake loading. The geological complexity of the valley, characterized by deep alluvial deposits and variable stiffness profiles, necessitates a site-specific approach to modeling soil flexibility and damping. To address this, the study integrates SSI into the dynamic analysis using Midas Gen and GTS Nx software platforms, modelling a reinforced concrete overhead tank with a capacity of 75,000 litres. Time history analysis under EL Centro earthquake loading reveals that SSI significantly influences structural response parameters, including displacement, shear force, bending moment, and natural period. Comparative results show increases of up to 55% in shear force, 52% in bending moment, and substantial elongation of natural periods across varying water levels. These findings underscore the necessity of SSI-inclusive design for critical infrastructure in seismic zones. The study concludes with design recommendations aligned with Indian Standards (IS 1893:2016, IS 3370:2009), advocating for performance-based seismic resilience in municipal water systems.