New Trends in Foundation Design Using the Finite Element Analysis Method

This paper presents an advanced analysis of shallow foundations using both strip and isolated footings. Taylor (1948) assumed uniform distributions for the contact stresses under the concentrically loaded footings, and most references and standards have followed this assumption. They have also used this distribution in the calculation of the bending moment acting on footings that are resting on sand and clay. In the literature, many researchers have presented distributions that depart from the Taylor assumption. Approximately equal distributions of contact stress in sand and clay are presented here. The distribution is of higher stress near the edges and lower stress under the column. This paper also examines the problem of contact stress distribution under strip and isolated footings using PLAXIS 2D-AE and 3D-AE, respectively. Linear elastic and Mohr-Coulomb models are adopted to simulate the soils. The results showed that the Mohr-Coulomb soil model is more appropriate in the study of the contact stress distribution than the linear elastic model. The resulting contact stress distributions under the concentrically loaded strip and isolated footings are in good agreement with the previous research results. The contact stresses is highly concentrated near edges and lower under the column. These concentrations of stresses near edges have long arms in the calculation of the maximum bending moment under the footings. Therefore, the maximum bending moment estimated by this modern analysis is higher than the one calculated using the Taylor (1948) assumption. Accordingly, references and standards should be updated to include the real distributions of contact stress. Large scale models should be established to determine the real distributions of the contact stress under footings.