Punching shear strength of reinforced concrete slabs with plastic void formers

In order to reduce the amount of concrete and self-weight of flat slabs, plastic void formers are used in slabs. The most critical areas of flat slabs are slab-column junctions and the zones where huge concentrated loads act. This area is more prone to punching shear failure. The cross section of concrete in reinforced concrete slabs with plastic void formers is significantly smaller, and hence the punching shear capacity of such junctions is insufficient. This article discusses the results of an experimental and theoretical study that investigated the punching shear capacity of reinforced concrete biaxial voided slabs. In order to increase the punching shear capacity of flat slabs, shear reinforcement is provided between voids in the concrete ribs. Slabs with void-forming inserts placed in the entire slab area, voided slabs with solid cross shapes and voided slabs with solid heads were analysed in this study. A method to calculate punching shear capacity based on EC2 methodology has been proposed. The results obtained for the punching shear capacity of the experimental slabs were verified with the EC2 methodology, and a method to calculate the length of the punching shear perimeter has been proposed.