Numerical investigations on punching shear behavior of eccentrically loaded reinforced concrete footings

Abstract

The undesired punching shear failure around the columns is the most critical scenario that causes a brittle failure of reinforced concrete flat plates. Matured studies and code provisions are available to assess the punching shear strength of thin flat plates. The punching shear behavior of thick plates differs from thin flat ones and produces a steeper shear crack. At the construction of thick footing plates, as some tolerances are permitted, the footing may be subjected to eccentric loading. However, there is a lack of studies on the footing performance under eccentric load. This numerical study aims to develop and validate a numerical model to examine the punching shear behavior of full-scale eccentrically loaded footings. The results have shown the accurate prediction of the developed numerical model of the reference case studies. The validated model has been utilized to examine the influence of three eccentricity ratios; 1/18, 1/9, and 1/6 of the footing length. The results demonstrated the significant influence of the load eccentricity on the punching shear strength of footings and the shear crack distribution. Moreover, parametric studies on sets of footings indicate that column perimeter to depth ratio and shear span to depth ratio play a key role in determining the footing behavior. The shear strength is found to increase with the increase of column perimeter to depth ratio and with the reduction of shear span to depth ratio. In addition, the negative effect of the eccentricity is less pronounced in the case of footings with a low shear span to depth ratio. Furthermore, the prEC2 approach for predicting the shear strength of eccentrically loaded footings has been assessed. It has been observed that the codeequation is found inaccurate with eccentric loading cases and needs some modification. The study ended with the development and verification of an equation that helps in obtaining more accurate results compared to the reference tests.