Comparative Seismic Analysis of Intz Tank with Change in Seismic Severity

Abstract

A 10lac liters of Intz type water tank is considered for this thesis work. The structural size was decided on the basis of the various literates studied and considering practical site considerations. For this purpose, types of loads and their intensities were considered as per the particular Indian code such as IS 875 part-01 and 02 for dead load and live load and IS 1893 part 01 for seismic loading on water tank. As these loading and loading combinations undergoes a tedious manual calculations structural design software Staad Pro. will be used for analysis and design. After detailed analysis it is found that Values of base reactions in horizontal direction due to seismic action increases drastically with 260 % from 53.93 in Zone II to 194.22 in Zone V, representing very high significance of change in seismic severity. Values of base reactions in vertical direction increases gradually with 52.57 % from 1957.08 Kn in Zone II to 2986.02 Kn in Zone IV, representing moderate significance of change in seismic severity. Values of base moments shows again shows drastic increase of 257.62 % from 139.74 Kn.m in Zone II to 499.74 Kn.m in Zone IVin horizontal direction. Whereas there is no such major change found in moments in vertical directions.

Introduction

1. Introduction

• Water tanks store daily water needs.

• Concrete impermeability is vital in liquid-retaining structures.

• Lower water-cement ratio reduces permeability but may hinder compaction.

• Crack prevention is crucial due to the tensile nature of concrete.

2. Literature Review

• Nupur Gautam: Highlighted the need for updating tank design to follow IS 3370-2009, considering seismic forces.

• Anurag Bajpai: Found higher lateral forces in full tanks; analyzed tanks across seismic zones using Response Spectrum Method.

• Ankita Katkar: Designed and analyzed a 250,000L tank using STAAD Pro considering wind and seismic loads. Found structural moments increase with height.

• Hemish Patel: Used optimization for cost-effective design of Intze tanks; tank capacity and floor slab thickness were key cost drivers.

3. Methodology

• Data Collection: Identified tank types, framing systems, and seismic analysis methods.

• Literature Study: Determined that tank shape and capacity significantly affect seismic behavior.

• Materials & Modeling: A 10-lakh-liter Intze tank was selected. M30 concrete and Fe-500 steel were used.

• Loading: Dead, live, and seismic loads were applied per IS 875 and IS 1893.

• Analysis Method: Used Seismic Coefficient Method (static equivalent) due to its significance in earthquake damage.

• Software: STAAD Pro was used for structural modeling and analysis.

4. Modeling Details

• Designed four models (I-01 to I-04) of the same tank under Seismic Zones II, III, IV, and V.

• Key structural specs include:

  • Cylindrical wall diameter: 12m

  • Column dia: 650 mm

  • Concrete: M30; Steel: Fe-500

  • Staging height: 4.0 m

  • Soil type: Medium stiff

  • Dome and slab thickness vary from 100mm to 300mm

5. Results and Discussion

A. Base Reactions

• Base reaction forces increase with seismic zone severity.

• Zone II (I-01): Lowest base reaction.

• Zone V (I-04): Highest base reaction.

B. Moments

• Moments in X and Z directions increase from Zone II to V.

• I-04 showed maximum moment ~500 kNm.

C. Displacement

• Displacement also increases with zone level.

• Maximum resultant displacement:

  • Zone II (I-01): ~46.73 mm

  • Zone V (I-04): ~98.50 mm

Conclusion

1) Values of base reactions in horizontal direction due to seismic action increases drastically with 260 % from 53.93 in Zone II to 194.22 in Zone V, representing very high significance of change in seismic severity. 2) Values of base reactions in vertical direction increases gradually with 52.57 % from 1957.08 Kn in Zone II to 2986.02 Kn in Zone IV, representing moderate significance of change in seismic severity. 3) Values of base moments shows again shows drastic increase of 257.62 % from 139.74 Kn.m in Zone II to 499.74 Kn.m in Zone IVin horizontal direction. Whereas there is no such major change found in moments in vertical directions. 4) As the severity of seismic zone increases the values of horizontal displacement goes on increasing order of 45.43 % from Zone II to Zone III, 41.63 % from Zone III to Zone IV, and 44.11 % from Zone IV to Zone V resulting in a drastic change of 196.85 % from Zone II to Zone IV

References

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Copyright

Copyright © 2025 Arati Ambhore, Dr. A. R. Gupta. 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.