Ahmed Godat

Bond Behavior of the ETS FRP Bar Shear-Strengthening Method

The embedded through-section (ETS) technique was recently developed to avoid the debonding failure that occurs with other fiber-reinforced polymer (FRP) strengthening techniques, such as the externally bonded (EB) and near-surface-mounted (NSM) methods. The method offers greater confinement and leads, therefore, to a substantial improvement in bond performance. In addition, it requires less concrete preparation than the EB strengthening technique. In this study, experimental results from 13 direct-shear test specimens are reported. The influence of the following major parameters on the bond behavior of FRP-strengthened reinforced concrete beams is examined: concrete strength, hole diameter, bar diameter, bar surface area, and bar bond length. The experimental results show that debonding can be avoided by providing a sufficient bar length and high concrete strength. Among the analytical models suggested in the literature for the bond behavior of FRP reinforced concrete, the Eligehausen, Popov, and Bertero (BPE) modified model and the Cosenza, Manfredi, and Realfonzo (CMR) model are compared with the experimental results obtained here. The CMR model with new fitting parameters is found to be an accurate way of simulating the experimental results. A new equation that accounts for concrete compressive strength and bar diameter is provided to estimate the development length.

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

Carbon fiber-reinforced polymer (CFRP) rope was recently developed to anchor fiber-reinforced polymers (FRP) shear-strengthened 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.