ANALYSIS OF ANNULAR FOUNDATION

Abstract

Annular R. C. foundations are commonly used for circular overhead R.C. tanks, which are generally supported on columns, spaced uniformly on a circle. This type of foundation comprises an annular slab with a circular ring beam to take the load of the columns. The annular foundation is preferred because a circular foundation without a central opening would have large moments. This study covers three types of analysis: Conventional analysis, F.E.M analysis assuming uniform soil pressure, and F.E.M soil structure interaction analysis treating soil as an elastic medium. In soil structure interaction three values of elastic moduli of soil were considered. Detailed moment, torsion, shear, deformation and soil pressure results have been obtained by this study. A detailed comparison between the three types of analysis has been made. It is concluded that conventional analysis is extremely conservative and F.E.M. analysis assuming uniform soil pressure is less conservative but both will result in an uneconomical design. Only the soil structure interaction analysis is able to give accurate result and so is recommended.