Performance of Punching Shear Reinforcement under Gravity Loading: Influence of Type and Detailing

The performance of 11 different shear reinforcement systems against punching of inner slab-column connections under gravity loading was compared on the basis of experiments on 12 full-scale specimens, eight of them newly reported. The slab geometry and flexural reinforcement ratio (1.5) were kept constant. The shear reinforcement systems included different layouts of double-headed studs, individual links, bent-up bars, and bonded post-installed reinforcement. All the systems were found to increase both the strength and the deformation capacity of the members but exhibited varying performances. The factors influencing the maximum punching strength of different systems, such as the layout and the anchorage conditions of the transverse reinforcement units, are described and analyzed. The mechanical model of the Critical Shear Crack Theory is used to explain the observed differences and provide design guidance. Comparisons to the codes of practice (ACI 318, Eurocode 2, and Model Code 2010) are also presented.