Retrofitting of Interior Slab-to-Column Connections for Punching Shear Using Different Techniques

This paper presents different strengthening techniques to eliminate some drawbacks associated with the available techniques. The considered strengthening techniques for the punching shear of RC slabs use the combined effect of internal single-leg stirrups and a double-skin steel assembly and properly anchored externally bonded glass fiber–reinforced polymer (EB-GFRP) sheets. Nine slab specimens divided into four groups are prepared and configured. It is found that the slab provided with properly anchored single-leg stirrups with a double-skin orthogonal steel assembly exhibits the most efficient technique among all considered techniques. This technique enables the slab to sustain a punching load about 1.69 times greater than that of the control unstrengthened slab. In addition, it triggers the slab to provide ductile punching failure showing strain hardening and softening plateaus. The experimental shear resistance of all strengthened slabs are compared with the design resistance stipulated by different design standards. It is concluded that the failure characteristics stipulated by German codes have the most rational results compared with those of the experimental findings.