Punching Shear of Two-way Slabs Retrofitted with Prestressed or

ABSTRACT: 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 2360 150mm3) 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. KEY WORDS: fiber-reinforced polymer (FRP) composite, prestress, strengthening, two-way slab