Punching Tests of Slabs with Low Reinforcement Ratios

The results of a test series on the punching behavior of slabs with varying flexural reinforcement ratios and without transverse reinforcement are presented. The aim of the tests was to investigate the behavior of slabs failing in punching shear with low reinforcement ratios. The size of the specimens and of the aggregate was also varied to investigate its effect on punching shear. Measurements at the concrete surface as well as through the thickness of the specimens allowed the observation of phenomena related to the development of the internal critical shear crack prior to punching. The results are compared with design codes and to the critical shear crack theory. From that comparison, it is shown that the formulation of ACI 318-08 can lead to less conservative estimates of the punching strength for thick slabs and for lower reinforcement ratios than in the test results. Satisfactory results are, on the other hand, obtained using Eurocode 2 and the critical shear crack theory.