Experimental investigation of punching resistance for flat slabs with various shear reinforcement

Abstract Punching can trigger catastrophic failures in reinforced concrete (RC) flat slabs due to its sudden nature resulting from exceeding the slab's shear capacity. The effect of using stirrups with various yield strengths and steel bands on the punching behavior of these slabs was not sufficiently investigated in the literature. Hence, this paper aims to experimentally study the effect of using vertical/inclined stirrups as well as steel bands on the punching shear capacity (PSC) of RC flat slabs. Moreover, the effect of welding stirrups on PSC was studied. Nine slab‐column specimens with a slab thickness of 150 mm and different stirrup types and steel yield strengths of 326, 537, and 592 MPa were prepared and tested under a central point load. Increasing the yield strength of the stirrups from 326 to 537 MPa led to improving the PSC by 21.7%–27.2%. Using combined steel bands as punching shear reinforcement resulted in reducing the PSC by 6.5%–10.6% compared to the slabs with traditional stirrups having a yield strength of 326 MPa. Welding of stirrups to top and bottom longitudinal bars or using inclined stirrups did not have a noticeable effect on the PSC of the test slabs compared to those with traditional stirrups. Compared to the experimental PSC of the test slabs with stirrups having a yield strength of 537 and 592 MPa, the American Concrete Institute (ACI) 318, Eurocode 2, Egyptian Code of Practice (ECP) 203, and International Federation for Structural Concrete ( FIB ) MC codes overestimated the PSC by 38.1%–45.9%, 103.2%–136.3%, 29.6%–37.8%, and 33.1%–38.1%, respectively. Using stirrups with a yield strength of 326, the Eurocode 2 and FIB MC overestimated the PSC by 36.9%–87.7% and 21.9%–60.2%, respectively, while the ACI 318 and ECP 203 codes underestimated the PSC by 2.8%–24.2% and 13.5%–32.9%, respectively.