Experimental and numerical analysis of the strengthening of slab-column connection against punching shear using strain-hardening cementitious composite

Abstract

This study presents an innovative hybrid strengthening technique aimed at improving the punching shear resistance and ductility of flat slab–column connections by implanting Strain-Hardening Cementitious Composite (SHCC) beams within the critical punching region and mechanically confined using U-shaped galvanized steel rods (UGSRs). The UGSRs were anchored through a demountable steel–rubber strip system designed to improve confinement efficiency and promote ductile load transfer. An experimental program involving seven full-scale slabs investigated the effects of UGSR location, rubber interlayers, and SHCC beam thickness on structural performance. The results demonstrated that closer UGSR placement enhanced confinement and load-carrying capacity, while rubber layers significantly improved ductility and energy dissipation. The proposed system effectively transformed brittle punching failure into a stable ductile mechanism. The best performance was achieved using a 70 mm thick SHCC beam positioned at 3d from the column face, resulting in an 89% increase in punching capacity along with substantial gains in stiffness and energy dissipation. A validated three-dimensional linear and nonlinear finite element model, showing less than 5% deviation from experimental results, was further employed for parametric analysis. Based on the experimental and numerical findings, an analytical equation was developed to predict the ultimate punching shear capacity of slab–column connections strengthened using implanted SHCC beams with confined UGSR anchorage.