Experimental study on the shear reinforcement contribution to punching shear resistance in flat slabs

Abstract With the growth of the adoption of flat slabs as a structural system in the usual reinforced concrete projects and the need for openings in slabs for the passage of electrical and hydraulic installations, it is necessary to thoroughly study the influence of such openings on the punching strength of slabs. In this paper, the influence of openings in punching shear resistance was investigated by testing five interior slab‐column connections 2400 mm square and 160 mm thick, with rectangular columns and with and without shear reinforcement. The openings were adjacent to the sides of rectangular supports and had a diameter of 100 mm. The results of cracking and ultimate loads, vertical displacements, and flexural reinforcement strains were analyzed, and the test results were compared with responses predicted from the normative instructions. All slabs with shear reinforcement, with or without openings, failed by crossing the shear reinforcement (Internal Punching Shear). The use of shear reinforcement in slabs with openings showed that the ultimate punching load increased by 25% when compared to the slab without openings and shear reinforcement.