Study and Analysis of Circular and Rectangular Water Tank in all Seismic Zones

Abstract

In the present work a comparative analysis for finding the optimized shape of water tank was performed. All models were then analyzed with action of loads and loading combinations prescribed by IS 1893 using STAAD PRO V8i SS5 series software for getting the most efficient and precise results. Total 08 models will be analyzed as per IS 1893 (part2), which are divided as 04 models of circular shape tank in all 04 seismic zones with tank empty condition and 04 models of rectangular shape tank in all 04 seismic zones with tank empty condition after detailed analysis it was found that rectangular thank shows lowest values of reactions for same gravity and seismic loading in low seismic zone circular tank shows 6.62% higher values than rectangular tank. While in Severe seismic zone circular tank shows 15 % increase in its values. As like of structural stability economy is also a perspective for major high-cost work. Above graph of reinforcement requirement shows that in zone-2, zone-3, zone-4 circular tank requires be comparatively lower values of staging reinforcement. But in severe zone this scenario goes inverse showing higher values for circular shape tank. From this it can be concluded that from zone-2 to zone-4 circular tank should be preferred but in zone-4 rectangular shape tank should be preferred.

Introduction

Water tanks play a vital role in water storage and distribution, especially in varying seismic zones. Elevated water tanks provide pressure for water distribution systems and come in various shapes like circular and rectangular, each with structural and cost implications. Different methods of liquid storage, such as underground, ground-supported, and elevated tanks, are used based on need. Municipal and industrial sectors heavily rely on these tanks for storing water and chemicals.

The literature review highlights research on structural behavior of water tanks under seismic and other loads. Studies indicate that circular tanks generally consume fewer materials and exhibit better structural efficiency compared to rectangular tanks. Various bracing patterns and staging systems impact displacement and base shear during earthquakes. The geometry and staging height significantly influence the seismic response, with elevated tanks experiencing higher base reactions than ground-supported tanks.

The methodology outlines a three-phase approach: defining objectives, studying structural and seismic effects, and analyzing models of circular, rectangular, and square tanks using STAAD Pro software per IS 1893 guidelines. Tank dimensions and water capacity are calculated based on projected population growth and water demand.

Results show that rectangular tanks tend to have lower base shear, overturning moments, and reaction forces compared to circular tanks across different seismic zones, indicating greater structural efficiency in these respects. However, circular tanks exhibit less displacement, which is a critical factor under seismic loads. Reinforcement needs vary accordingly. The study concludes that while rectangular tanks may be preferred for base shear and moment resistance, circular tanks are advantageous for minimizing displacement, especially in higher seismic zones.

Conclusion

1) The structural behavior of water tank for same capacity affects with the shape of container shape as the severity of seismic zone increases. 2) The design of the water tank must primarily be dictated by the condition of the tank when it is full. This entails that all engineering and structural considerations, such as material strength, shear forces, and overall stability, should account for the maximum load scenario, where the tank is completely filled with water, thus representing the most challenging conditions the tank must endure during its operational life. 3) Research indicates that rectangular tanks exhibit the lowest values when it comes to base shear, overturning moment, and reactions during seismic events. This suggests that rectangular configurations are inherently more stable and can effectively resist the dynamic forces generated during such occurrences without experiencing excessive stress or potential failure. 4) However, it is important to note that while rectangular tanks are advantageous in terms of shear forces, they also produce higher levels of displacements compared to other shapes. This means that to mitigate these displacements and ensure the tank remains within acceptable limits of movement, additional bracing must be integrated into the design to provide adequate support and maintain stability.

References

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Copyright

Copyright © 2025 Nivrutti V Datkar, Prof. A. R. Pohare. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.