Tensile behavior of FRP anchors made from CFRP ropes epoxy-bonded to uncracked concrete for flexural strengthening of RC columns

One of the major problems with using fiber reinforced polymer (FRP) in strengthening reinforced concrete (RC) structures is FRP premature debonding. Anchoring FRP materials to concrete has become associated with most of the strengthening techniques. One of the anchoring techniques is using handmade anchors made from FRP materials. In previous studies, most FRP anchors were made from rolling pre-cut FRP sheets and had short embedment (<100 mm) as they were used for flexural or shear strengthening of RC beams. In the present study, FRP anchors were made from carbon fiber reinforced polymer (CFRP) ropes and had long embedment to be used for flexural strengthening of RC columns. A total of twenty-one pullout tests were conducted on CFRP rope anchors bonded to concrete using chemical epoxy. The test parameters were embedment length (45, 90, 135, 180, 270, and 315 mm), anchor hole diameter (12.7, 19.1, and 25.4 mm), and epoxy type (Hilti 500 vs. MasterBrace SAT 4500). Test results showed that the pullout strength of CFRP anchors increased with the increase of embedment length, and no significant effect of the hole diameter on the pullout strength was observed. However, the bond strength increased with decreasing embedment length and hole diameter. The observed pullout results and failure modes were compared to the predictions of the available models. Finally, a modified model was proposed to be used to predict the pullout strength of CFRP rope anchors until more tests become available to develop a more realistic model.