International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 11 Issue: 06 | Jun 2024
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p-ISSN: 2395-0072
EFFECT OF STRATIFIED SOIL DEPOSIT ON SEISMIC BEHAVIOUR OF ELEVATED WATER TANK Nayana N1, L.Govindaraju2 1P.GStudent, Department of Civil Engineering ,U.V.C.E, Bangalore University,Bengaluru 2Professor,Department of Civil Engineering,U.V.C.E,Bangalore University,Bengaluru
---------------------------------------------------------------------***--------------------------------------------------------------------1. INTRODUCTION Abstract -.As a vital infrastructure, elevated water
tanksneed to be built to withstand all the forces expected to act during their life time. An elevated water tank attracts high lateral loads due to the huge mass concentrated at high elevation. The dynamic interaction between an elevated water tank and the underlying soil, especially in earthquake- prone regions, is a major factor that significantly influences the seismic performance of the water tank. In earthquake- resistant building designs, the inclusion of Soil-Structure Interaction (SSI) effects in the analysis is crucial for obtaining realistic performance of water tank during seismic events. Water tanks situated on sloping ground face heightened vulnerability to earthquakes, primarily due to irregularities in both plan and elevation. But many water tanks are routinely analyzed under earthquake loadings without accounting for Soil-Structure Interaction (SSI). From a practical standpoint, this approach is strongly discouraged, emphasizing the necessity of considering Soil-Structure Interaction (SSI) for a comprehensive and accurate seismic assessment of water tanks
In the present study, the seismic behavior of an elevated water tank positioned at leveled and sloping ground has been studied, considering flexible base (Soil-Structure Interaction) using Time History Method (THM)for seismic zone II . The numerical analysis is carried out using the Finite Element Analysis (FEA) softwareSAP2000 v22, and it evaluates the effects of Stratified Soil-Structure Interaction (SSI) using combination of soil profile –Soft clay and loose sand, considering one with a full tank and one with an empty tank condition. The study reveals the structural response of the elevated water tank under seismic loading, and the variation in ground sloping exposes the structural vulnerabilities associated with different sloping ground, and consequently highlights the significance of incorporating the effects of stratification in seismic analysis. Key Words: Soil-Structure Interaction (SSI), Underlying soil, Time History Method (THM), Elevated water tank, Seismic Analysis, Finite Element Analysis (FEA).
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The allocation of water in a particular area relies heavily on the configuration of its water reservoir. Typically, overhead water tanks are favored as they capitalize on gravitational force to generate the necessary pressure for water distribution, eliminating the necessity for extensive pumping infrastructure. The Indian subcontinent frequently faces natural disasters like earthquakes, droughts, floods, and cyclones. With over 60% of India susceptible to earthquakes, as per the seismic code IS: 1893(Part- 1):2016, the stability of elevated water tanks becomes paramount. The substantial water mass atop slender supports poses a significant risk for tank failure in seismic events. Given their frequent use in seismic regions, the seismic performance of elevated tanks warrants meticulous examination. Instances of tank collapses or severe damage often stem from inadequate understanding of support systems and erroneous selection of staging designs. Liquid storage encompasses various forms such as underground, ground-supported, and elevated tanks. Municipalities and industries rely on these tanks to store water, flammable substances, and more. Consequently, uninterrupted water supply is vital for firefighting amid earthquakes, mitigating property damage and potential casualties. Therefore, ensuring the continued functionality of water tanks in the aftermath of seismic events is imperative. Dynamic analysis of these tanks must encompass both the water's movement relative to the tank and the tank's motion relative to the ground. A closed tank behaves as a one-mass structure, regardless of its water content, while a tank with a free water surface transforms into a two-mass structure due to water sloshing during earthquakes. Hence, thorough seismic analysis is imperative, as poorly designed structures, not earthquakes, pose the primary threat to lives.Designing elevated water tanks on sloped ground demands a deep understanding of geotechnical and structural engineering principles. Evaluation of soil conditions, slope stability, and seismic factors is crucial for determining an appropriate foundation design. Moreover, considerations like tank capacity, material strength, and environmental factors significantly
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