Punching shear behavior of reinforced concrete flat slabs with a varying amount of shear reinforcement

The punching shear design procedures according to current codes (e.g., Eurocode 2 or Model Code 2010) are similar. However, the predicted punching shear capacities may differ significantly depending on the background (e.g., semi-empirical or physical) of the design provisions and the considered influences. For the evaluation and improvement of the existing provisions for flat slabs without and with high amounts of shear reinforcement, a large number of punching test series on reinforced concrete flat slabs is available in the literature. Nevertheless, the evaluation of the code equations for the design of the shear reinforcement (failure inside the shear-reinforced zone) is still not possible since only few punching tests on flat slabs with low and medium amounts of shear reinforcement have been conducted. To investigate the punching shear behavior of flat slabs with a varying amount of shear reinforcement, three systematic test series without and with stirrups as shear reinforcement were conducted. The experimental program included three reference tests without and eight tests with low and medium amounts of shear reinforcement. In the tests, the amount of shear reinforcement was varied by changing the stirrup diameter only. Further investigated influences were the shear span-depth ratio and the effective depth. The results of the test series are discussed and compared to the predictions according to Eurocode 2, Model Code 2010 and the draft of the second generation of Eurocode 2.