Influence of Slab Thickness on Punching Shear Strength

Tests to study the influence of slab thickness on the punching shear strength of flat slabs clearly demonstrate the significant effect of size on the shear stress resistance, particularly for tests without shear reinforcement. New tests in which the slab thickness varied between 160 and 300 mm (6.3 and 11.8 in.) and tests by others with slabs up to 500 mm (19.7 in.) thick indicate that slabs without shear reinforcement thicker than approximately 260 mm (10.2 in.) may not have a high factor of safety if designed according to ACI 318-05. For thick slabs with shear reinforcement, the shear stress resistance provided by concrete is also reduced but to a lesser degree. [PUBLICATION ABSTRACT]