Punching strength of concrete footings based on the compression zone failure mechanism

Abstract

A strength model based on the compression zone failure mechanism was developed to predict the punching shear strength of concrete footings without transverse reinforcement. The proposed model assumes that the punching shear at a critical section is primarily counteracted by the compression zone of intact concrete at the footing. According to the material failure criteria of concrete, part of the compression zone failed by concrete crushing and the remaining part failed by inclined tensile cracking. In addition, the shear capacity of the concrete in the compression zone was evaluated considering the compressive normal stress developed by the flexural action of the footing. The strength model can be used for squat concrete footings with a low shear span to depth ratio as well as slender footings. The proposed model was verified by applying it to existing test specimens. The predictions of the proposed model demonstrated very good agreement with the test results and the model was found to be a better predictor than current design codes, specifically ACI 318-14 and KCI 2012.