A Comparative Study on Seismic Analysis of Elevated Water Tanks with Different Staging Arrangements as per IS 1893 (Part-2): 2014

Abstract

An earthquake is a natural phenomenon caused by the sudden release of stored energy within the Earth’s crust, which propagates as seismic waves on the surface. Earthquakes typically manifest through ground shaking, displacement, and, in certain cases, the generation of tsunamis, often resulting in significant loss of life and damage to infrastructure. Ensuring the seismic safety of civil engineering structures is therefore of utmost importance. Among these, liquid storage tanks (both ground-supported and elevated) play a vital role in water supply, firefighting systems, and industrial use. Elevated liquid storage tanks, however, are particularly critical because a large lumped mass of liquid is supported at a considerable height on staging systems that are often vulnerable during seismic events. Consequently, the seismic analysis of such tanks requires special considerations to account for the hydrodynamic forces generated by the sloshing action of liquid on the tank walls during an earthquake.

This study presents a comparative seismic analysis of four different staging systems for rectangular elevated liquid storage tanks with a capacity of 250 m³. The analysis is carried out in accordance with IS 1893 (Part-2): 2014. To study the influence of staging configuration on seismic performance, four structural models (Model-I, Model-II, Model-III, and Model-IV) are developed, incorporating different arrangements of frames, shear walls, and bracings. The seismic behaviour is assessed for Zone IV conditions on hard soil, considering two tank-fill scenarios: full tank and empty tank. The study highlights the effect of staging patterns on the seismic response and structural performance of elevated liquid storage tanks.

 A program has been developed in Microsoft Excel for the seismic analysis of elevated liquid storage tanks, based on the GSDMA guidelines provided by NICEE, IIT Kanpur. The study focuses on comparing key structural parameters such as lateral stiffness, displacement, fundamental time period, seismic base shear, and overturning moment at the base of staging and hydrodynamic pressure.

 The present study will be helpful to Civil Engineers enabling a better understanding of the influence of staging system configurations on the seismic performance of elevated liquid storage tanks.