Effectiveness of Externally Applied CFRP Stirrups for Rehabilitation of Slab-Column Connections

Abstract

The application of externally bonded carbon fiber-reinforced polymer (CFRP) stirrups is by now proven as an effective technique to strengthen slab-column connections for punching shear. However, there has not been adequate study into its effectiveness for repair and rehabilitation of existing slab-column connections with different levels of prior damage. The punching performance of predamaged slab-column connections rehabilitated with CFRP stirrups was investigated for the first time in this study. Two series of 2/3 scale slab-column connections with two different concrete compressive strengths (low and normal) were rehabilitated using CFRP stirrups at different damage levels. The specimens were all tested under a concentric punching load. Test results showed that externally applied CFRP stirrups could restore the punching shear capacity of fully damaged slabs to levels above their undamaged conditions. The lower concrete strength proved to have no detrimental effect on the effectiveness of the CFRP rehabilitation. This study also showed that American Concrete Institute ACI 318 provisions could be safely used for the design of CFRP rehabilitation of damaged slab-column connections.