Punching of Reinforced Concrete Flat Slabs with Double- Headed Shear Reinforcement

Twelve slabs, 11 of which contained double-headed studs, as shear reinforcement were tested, supported by central column and loaded concentrically. Their behavior is described in terms of deflections, rotations, strains of the concrete close to the column, strains of the flexural reinforcement across the slab width, and strains of the studs. All failures were by punching, in most cases within the shear reinforced region. The treatments of punching resistance in ACI 318, Eurocode 2 (EC2), and the critical shear crack theory (CSCT) are described, and their predictions are compared with the results of the present tests and 39 others from the literature. The accuracy of predictions improves from ACI 318 to EC2 to CSCT -- that is, with increasing complexity. However, the CSCT assumptions about behavior are not well supported by the experimental observations.