Experimental Study on Improving Punching Shear Strength of Flat Slabs

Abstract

Punching shear failure in reinforced concrete flat slabs is a sudden and brittle mode that can govern slab design and compromise structural safety. This study provides a direct experimental comparison of three punching shear enhancement techniques under identical conditions, focusing on techniques used to enhance punching shear resistance and performance within a distance of 2d from the loading area. Seven square slab specimens (1100 × 1100 × 150 mm) were tested under concentric monotonic loading through a 100 × 100 × 25 mm steel plate: one control specimen, two specimens reinforced with closed stirrups, two reinforced with mid-depth welded mesh, and two made using Steel Fiber Concrete (SFC). All specimens had identical flexural reinforcement (Ø10 @ 100 mm in tension and Ø6 @ 100 mm in compression). Load-deflection response, strains in the reinforcing steel, cracking development, and failure characteristics were recorded up to punching failure. The test results show that all techniques increased punching shear capacity relative to the control slab. The SFC specimens provided the best overall behavior, including higher ultimate load, improved post-cracking response, and greater deformation capacity compared with the other methods. The experimental capacities were also evaluated against the predictions of ACI 318, Eurocode 2, fib Model Code 2010, and ECP 203. The comparison indicated that the ACI 318 and ECP 203 provisions provided conservative predictions, whereas the Eurocode 2 and fib Model Code showed closer agreement with the experimental results. The results provide valuable insight into the punching shear behavior of flat slabs with different techniques.