Punching shear strength of RC column footings considering soil–footing friction

Abstract

It is well recognized that various design codes and models have been developed to predict the punching shear strength of reinforced concrete column footings. Generally, the strength predictions by using current design codes and existing models are conservative, and inaccurately match the experimental results. This is because although a column footing and a flat plate (or slab) have different geometries and mechanisms, the same design method is used for them. Thus, to accurately assess and evaluate the punching shear strength of column footings, their design method should be improved. The present study paper proposes a strength model based on the compression zone failure mechanism to predict the punching shear strength of concrete footings without shear reinforcement. The punching shear at the critical section was assumed to be mainly counteracted by the intact concrete in the compression zone of the footing. In the model, the effect of the friction force between the bottom surfaces of the footings and the soil was considered. The proposed model was applied to the existing test results for verification. The predictions by the proposed model were also compared with those by current design codes and existing models. Based on the proposed model, the effects of various design parameters on the punching shear strength of the column footings were analyzed and investigated in detail.