Repairing half-loaded flat slabs against punching shear using steel stiffeners

In this paper, a repairing system was implemented on flat slabs that have been suffered from punching shear stresses due to loading to half their capacities. The repairing system primarily relies on retrofitting the damaged concrete by adding steel stiffeners of different dimensions and numbers. The experimental procedure included casting four flat slabs of identical flexural reinforcement and dimensions of (1.5 × 1.5 × 0.1) m. The efficiency of the proposed repairing system was evaluated experimentally in terms of shear capacity, deformation properties and crack behavior. The experimental results were utilized to calibrate a nonlinear finite element model which was constructed using (ABAQUS). The finite element model was then used to conduct a parametric study to check the influence of changing the compressive strength and flexural reinforcement on the shear capacity. Test results showed that the proposed system was effective in repairing the damaged flat slabs in terms of punching shear, in which enhancements in both the strength and deformation capacities were recorded by about 74.2% and 66.4%, respectively. Furthermore, the numerical investigation revealed that increasing the concrete compressive strength and flexural reinforcement ratios has a considerable positive effect on the punching shear capacity of the slab.