Practical Model for Load-Carrying Capacity of Eccentrically Loaded Square Column Footings

In this paper, a practical calculus model based on the strut-and-tie approach for prediction of the load-carrying capacity of eccentrically loaded RC column footings with square cross sections is presented. Existing models based on beam or slab models with flexural and two-way slab punching shear failure are presented and discussed. Several subgrade contact pressure distributions for column footings are considered. A parametric analysis of the effects of footing and column dimensions (depth, width), longitudinal ratio of longitudinal steel, and strength of concrete and steel is made for all models examined. Available experimental data are utilized to verify the model in comparison with existing models. The comparison between analytical and experimental results allows one to validate the proposed model in comparison with others. Results obtained showed that by increasing the eccentricity, the load-carrying capacity decreases significantly, up to 40% for e:B = 1:6. For ratio between the compressive strength of concrete and the allowable stress on the soil between 10 and 50, the ratio B:b is between 3 and 7. Finally, simple analytical expressions are derived for a preliminary design of column footings.