Strength of RC Cantilever Slabs Bonded with GFRP Strips

Strengthening of RC cantilever slabs using bonded glass-fiber-reinforced plastic (GFRP) strips has recently been explored. That work led to the proposal that the GFRP strips should be anchored to the supporting wall using epoxy-mortar-filled horizontal slots and to the slab using fiber anchors, to prevent or limit debonding. This paper focuses on the strength of RC cantilever slabs strengthened using this method. Experimental work on model cantilever slabs with steel reinforcement of different amounts and different positions is presented. Because of the presence of fiber anchors, all strengthened slabs failed by tensile rupture of the fiber-reinforced plastic (FRP), although in some of the slabs partial debonding had appeared before the FRP rupture took place. Flexural strength equations based on the conventional plane section assumption are next described and shown to predict the test results well, even for slabs with partially debonded FRP strips. Finally, the effect of preloading on the strength of strengthened slabs is discussed.