Effect of Wind and Seismic Forces on Intze Type Water Tank for Different Zones as per Indian Standards

Author Name(s): Dr. P. D. Hiwase, Dr. P. P. Dahale, Dr. A. A. Mehta, Er. Bhavesh Rajesh Sahni
Author Email: prashant.hiwase@gmail.com

Abstract

Water tank structures are of high importance as they act as a storage unit for basic necessity. During disasters it is very important that these do not fail and serve the purpose they are intended for. So it becomes very necessary that water tank is analyzed and designed for seismic and wind forces so that these structures do not fail under effect of Earthquake and Wind. Our study deals with seismic wind analysis w.r.t., Base shear, Seismic Zone, Response spectrum, Time Period of Intze water tank for different zones as per Indian Standards. Analysis has been carried out using Staad pro software.

Introduction

Water tanks are used to store water. All the criteria like shape and properties like slab width and stresses all depends on the capacity and shape of Water tank. If we see generally Intz shape is preferred over other shapes is because of the uniformity in stresses in all directions. INTZ type water tank is one such water tank which has circular shape with a spherical top and conical slab with spherical dome at the bottom. The specialty of Intze water tank is that, the inward forces coming from the conical slab counteract the outward forces coming from the bottom dome which result less stress on the bottom slab of the water tank. Due to lesser stresses, the pressure on the base slab decreases and thus reduces in the quantity of members.

Conclusion

 The value of Base Shear increases with increase in Seismic Zone.  Similarly the value of moments also increases as we go up the seismic zones. Apply Response spectrum gives same result as static analysis because of the circular shape.  The time period given by staad pro matches exactly with calculated by empirical formula given in IS 1893 -2016.  The Seismic forces are dominant over the wind forces because of the topography considered by while applying wind loads.  If we change the topographical conditions then wind forces can be a driving factor.  However when wind load is governing factor then the value of moment for Tank Empty condition is maximum.

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