Economical design of rectangular footing subjected to uplift due to biaxial moments

Abstract

The superstructural load of the building is transferred to the ground through footing. The Footings are typically subjected to axial loads and biaxial moments. When moments are large it is uneconomical to design footings for full contact area of footing. Therefore, various codes permit uplifting of foundations. Solutions of footings subjected to biaxial moments during uplift are complex and time-consuming. Also, several algorithms are needed to achieve the desired results. This paper proposes a simplified solution to optimize footings under uplift subjected to biaxial moments. The footing with biaxial moments is categorised into different zones based on the location of neutral axis and position of eccentricity of the load. The approach described in this study utilizes the functions of the Excel solver while adding the necessary constraints to determine the minimal size of the rectangular footing. Further, the maximum pressures for different zones were estimated, and optimisation was carried out with the appropriate constraints for each zone separately. The values obtained by this approach were compared with those in the literature, and percentage decrease in the footing area was observed from 1.1 to 15.7%.