Model testing and response surface investigation of eccentric loading on closely spaced strip footings

This study analyzes the impact of eccentric loads on the ultimate bearing capacity, failure mechanisms and the settlement of two strip footings placed on sand. In the first section, Laboratory tests were conducted using an experimental model to assess the influence of different parameters, such as spacing between footings to-width footing ratio (S/B), the load eccentricity ratio (e/B), and the resulting failure mechanisms. The results show that the bearing capacity decreases with increasing eccentricity. Additionally, the interference effect between footings becomes negligible for eccentricity ratio e/B > 0.1. Analyzing of efficiency factors highlights a maximum interference effect at S/B = 0.5. In the second section, the response surface methodology (RSM) successfully modelled the nonlinear influence of spacing ratio (S/B) and load eccentricity ratio (e/B) on the bearing efficiency factor, achieving a high coefficient of determination (R² = 0.958). The developed quadratic model demonstrated excellent predictive performance with low error metrics featuring a Root Mean Square Error (RMSE) of 0.063 and a Mean Absolute Error (MAE) of 0.0231. Validation of the results through comparison with theoretical and numerical data shows a good concordance with the experimental model.