Bond mechanism of a new anchorage technique for FRP shear-strengthened T-beams using CFRP rope

Abstract

Carbon fiber-reinforced polymer (CFRP) rope was recently developed to anchor fiber-reinforced polymers (FRP) shearstrengthened beams that conventionally uses U-wrap scheme. The rope is a bundle of flexible CFRP strands held together by a thin tissue net. In this technique, holes are drilled through the web at the web-flange intersection, and CFRP ropes are inserted through the holes and flared onto the two free ends of the U-wrap scheme. The technique offers substantial improvements in bond strength and ductility because it converts the U-wrap scheme similar to a full-wrap scheme. The objective of this paper was to investigate the bond behavior of CFRP L-strip plates anchored with CFRP ropes. The experimental program consisted of 16 tests on FRP-to-concrete joints, of which six were unanchored (control specimens) and 10 were anchored by CFRP ropes. The influence of concrete strength, rope length, and plate width on bond behavior was examined. Experimental results showed that the bond performance greatly improved with increasing FRP plate width and rope length, but concrete strength had a negligible effect, which is attributed to high thickness and narrow width of CFRP L-strips used. Theoretical formulations provided to account for the ultimate bond load were compared with the experimental results, and a modification factor to estimate the effect of the presence of CFRP rope was suggested.