COMPARATIVE ANALYSIS AND DESIGN OF CIRCULAR WATER TANK AS PER IS 3370 (1967) AND IS 3370 (2009)

Abstract

The code of practice for the design of reinforced concrete structures for the storage of liquids has been revised recently in 2009. The revision incorporates the Limit States Design philosophy. Until

recently, liquid retaining structures, such as water tanks, were designed using working stress design method, prescribed

in IS 3370 (part 2):1965. This had necessitated thicker concrete sections to limit the tensile stresses in concrete. In the

revised code, the old working stress design provisions are retained as an alternative to limit states design. It would be

interesting to study the relative economics of using these two different design philosophies prescribed in the revised

code. This is explored in the present study, with reference to intze tank supported on circular shaft.The Indian Standards code for the design of  RCC liquid retaining structures has been recently revised. The pre-revised version included the provisions of design of water retaining structures by Working Stress Method only, but in the revised version of the code incorporates the Working stress design method as well as Limit State design method for designing RCC water tanks. The major amendments in the revised version is the introduction of Limit State Design Method for water tanks, which was not recommended by BIS earlier and slight changes in the Working Stress Method. This includes the permissible stresses in steel were reduced to 130 Mpa for deformed bars and the clause for minimum steel has also been modified.

In this paper, circular type tank with top and bottom dome was designed by adopting both Working Stress Method IS 3370 (1967) and IS 3370 (2009), and Limit State Design Method as per IS 3370 (2009) and the results are discussed in the end of this paper. It was observed that the steel requirements increased, for permissible stress in steel less than or equals to 130 MPa, is same for both the cases.