Design Considerations for Shear Bolts in Punching Shear Retrofit of Reinforced Concrete Slabs

This study addresses design aspects for the punching shear bolt retrofitting system for reinforced concrete flat slabs supported on columns. Shear bolts are an external type of reinforcement installed in existing slabs by first drilling small holes through the slab thickness, installing the bolts into them, and tightening the bolt nuts. Previous experimental research at the University of Waterloo showed the effectiveness of this system in increasing strength and ductility of existing slabs, with little changes in the slab's appearance. The procedures for the design of the shear bolts and their installation in slabs are proposed in the paper. Recommendations are provided regarding the stem diameter, the head area and thickness, and the spacing and the layout of the bolts in a plane of a slab.