Structural analysis and design of irregular shaped footings subjected to eccentric loading

Abstract

This article presents a simplified analytical model for designing irregular shaped reinforced concrete (RC) footings supporting square column and subjected to eccentric loading, that is, axial load P and biaxial moments, Mx in (x-x) axis and My in (y-y) axis, respectively. In this study, four design variations of footing sections are considered, namely, square, triangular, circular, and trapezoidal. Seven different footings (F-1 to F-7), each with a different loading condition, are used to analyze and design each of the selected irregular footings with the goal of getting the optimum footing section. The required reinforcing area of steel (As) is obtained using the SDM method in each selected footing which is then compared using finite element software (SAFE). The percentage difference of area of steel (As) for simplified method with the finite element software ranges within 1% to 13%. Moreover, the concrete volume results show that the circular and triangular footings prove to be the most economical footings followed by square and trapezoidal shaped footing sections. However, the results show that triangular shaped footings under heavy loads require a larger steel area (As) as in footing F-7, which is not economical for heavy loads.