Analysis and Design Of Circular Prestressed Concrete Tank

Abstract

This report presents a comprehensive analytical investigation concerning behavior and design of ground supported closed cylindrical prestressed circular concrete tank subjected to static and dynamic loading conditions with special emphasis on IS: 3370 , IITK draft code, SAP2000 and STAAD.Pro. The method used in this report is based in the classical shell and plate theories for the elastic analysis of cylindrical water tank. Spherical dome roof, cylindrical container, top and bottom ring beams together with base slab are considered. The effect of the tank aspect ratio, foundation interaction and soil characteristics are reviewed and considered in the Analysis and Design. Both completely full with liquid and empty condition and for two cases with and without prestressing have been considered. Detailed process of Dynamic analysis of circular prestressed concrete tank is carried out by IITK draft code for the tank calculating time period, base shear, moments at the base of wall, overturning moment and Hydrodynamic pressure on walls considering the soil structure interaction. Separate models for impulsive and convective, with spring supports at the base giving respective spring stiffness of the soil, were developed on SAP2000 with the same parameter (spring mass model) calculated by the draft-code. Linear and dynamic methods including spread sheet program based on IS: 3370 and IS: 1893 (part-2) with IITK draft code have been incorporated. Components in Circular Prestressed Concrete tank such as loss calculations, top dome, ring beam, vertical walls and end zone. As the tank is ground supported, considering certain type of soil such as soft, elastic foundation concept was used for the designing of base slab and bottom ring beam foundation. An important aim of this report is to determine the area where the current codes are lagging and needs further refinement and improvement. IV Modeling assumption along with process of models for different components in Pushover and Time-History analysis are presented. Process of modeling includes proper formulae used generation of the curve for the respective components in analysis. An attempt is made, with the help of different parametric study, to clearly understand the complication and hindrance generated in the different situation of Circular Prestressed Concrete Tanks. Parametric study are carried out for different zones, different subgrade soil condition, optimization of tank by variation in D/h ratio, Different (ground) support condition. Conclusions and recommendations are given by illustrating application of the above procedure.