Numerical Assessment of Flat Slabs with Openings Strengthened Using Shear Bolts

Abstract Openings near column regions significantly reduce the punching shear capacity of flat slabs, while existing strengthening methods are primarily developed for solid flat slabs. The interaction of slab openings with post-installed shear reinforcement has not been systematically studied. This study numerically investigates the behaviour of reinforced concrete flat slabs with openings strengthened using post-installed shear bolts with small and large end anchorages. A nonlinear finite element model, previously validated against experimental results, is adopted to simulate slab-column connections with different opening sizes, locations, and strengthening layouts. A parametric study of eighteen slab models evaluates the effects of opening size, location, and bolt arrangement. Results indicate that openings considerably reduce punching resistance; however, appropriate strengthening can increase capacity by up to 91%, with notable improvements in ductility, stiffness, and energy absorption. Radial bolt arrangements with large end anchorages provide the most effective performance. This study presents a comprehensive and systematic evaluation of shear bolt efficiency in perforated flat slabs. Strengthened slabs exhibit a flexural response with distinct crack patterns. Current design codes ACI 318-25 and Eurocode 2 (EC2-2004) are shown to provide conservative pre-dictions.