The punching shear strength of laterally restrained concrete slabs is significantly enhanced by the effect of compressive membrane action. Details and results of tests on laterally restrained square slabs subjected to concentrated loading are presented, which substantiate the concept of compressive membrane action in restrained specimens.
By adopting a parabolic failure criterion for concrete, an upper-bound rigid-plastic solution for predicting the punching shear strength of concrete slabs is derived. The method is less empirical and the predictions show good agreement with a wide range of test results from various sources. Moreover, the proposed theoretical model is extended to cover laterally restrained slabs to allow for the effect of compressive membrane action, in which a flow-theory approach of plasticity has been used to determined the compressive membrane forces. The proposed method for predicting the punching shear strength of laterally restrained slabs is shown to give good correlation with experimental test results.
The proposed plastic method of analysis is considered as a step in the development of a less empirical, consistent and physically meaningful theoretical approach for punching shear failure of concrete slabs with compressive membrane action.