Probabilistic study on the bearing capacity of strip footing subjected to combined effect of inclined and eccentric loads

This paper investigates the importance of inherent variability of soil under strip footing subjected to combined effect of inclined and eccentric loads using probabilistic analysis. Plastic analysis is performed using lower bound formulation of finite element limit analysis. Soil is considered as cohesionless, and modelled as a random field. The random field is discretized using Karhunen-Loéve expansion method. Stochastic results of the collapse load for various conditions of internal friction angle, load inclination angle, eccentricity, vertical correlation distance and coefficient of variation of the tangent of internal friction angle are determined using Monte Carlo Simulation technique. Failure probability results are plotted as contour charts to show the effect of combined loading as well as the spatial variability of soil on the bearing capacity of strip footing. For all the cases of higher vertical correlation distances, the mean bearing capacity factor is found to be higher than the deterministic value. However, the probability of failure of the footing is reported to be more than 50% for the same case, addressing the need for probabilistic analysis. Failure contours are presented for some representative cases to display the behavior of footing due to different loading and spatial variability conditions.