Non-Symmetrical Limit Loads on Strip Footings

Abstract

Limit loads on footings (bearing capacity) can be conveniently analyzed using the kinematic approach of limit analysis. Nonsymmetrical loads on strip footings include the horizontal component of the load and the moment. They can be also represented as load inclination and eccentricity. For the analysis to be sensitive to nonsymmetrical loads, the collapse mechanisms also need to be nonsymmetrical, i. e., they need to allow for footing rotation and horizontal component of displacement. Based on such mechanisms, inclination coefficients for surface strip footings are derived. These coefficients fit the numerical limit analysis results better than the coefficients suggested earlier in the literature. It is also shown that for cohesive-frictional soils the method often used to account for the load eccentricity (where the footing width is reduced by twice-the-eccentricity) yields a bearing capacity lower than that obtained from the kinematic limit analysis. However, this method overestimates the bearing capacity for purely frictional soils, particularly when the surcharge load is small.