Punching Shear of Two-way Slabs Retrofitted with Prestressed or Non-prestressed CFRP Sheets

This study presents punching shear behavior of two-way slabs strengthened with prestressed or non-prestressed carbon fiber reinforced polymer (CFRP) sheets. Four two-way slabs (2360 x 2360 x 150 mm(3)) with a steel reinforcement ratio of 1.44% are tested under concentric load. All slabs exhibit a punching shear failure mode. The strengthened slabs show an increase of up to approximately 20% in load-carrying capacity and an increase of up to 25% in cracking load with respect to the unstrengthened control slab. A detailed stress analysis in reinforcement is conducted along the loading span of the slabs, including the critical shear perimeter surrounding the column stub. The effective strain zone near the slab-column connection, where a sudden increase of strains in the reinforcement is observed, is also studied. The development of shear stresses in the vicinity of the slab-column connection is examined. A non-linear 3D finite element analysis is conducted and analytical predictive models for the punching shear failure are evaluated as well.