Design Tables for Cylindrical Concrete Water Tank with Annular Footing

Abstract

Water storage and wastewater treatment tanks are usually cylindrical in shape and made of reinforced cement concrete. These tanks are founded at the lowest hydraulic level to facilitate the treatment and storage process. For the designing of such tanks, the governing design forces in the cylindrical wall should be accurately assessed so that the tank satisfies the economic feasibility and serviceability requirements. For transmitting hydrostatic pressure acting on the tank wall into corresponding hoop tension and bending moment, designers make use of design tables offered by the Portland Cement Association (PCA). PCA assumes ideal conditions at wall bottom joints, such as pinned or rigid, but neither considers the effects of annular footing nor soil-structure interaction. At present, there are no design tables available for cylindrical tanks with annular footing. In this paper, using finite element analysis (FEA), the influence of the soil-structure interaction on design forces in the tank wall and the annular footing is discussed. Further, design tables are developed for hoop tension and bending moment for tank wall with annular footing on firm strata.