Innovative warp and woof strap (WWS) method to anchor the FRP sheets in strengthened concrete beams

Abstract

U-shaped straps are an effective means to postpone premature debonding failure when fiber-reinforced polymer (FRP) composites are applied in structures. However, the U-wrap anchors are not cost-effective and in many cases cannot completely prevent the debonding phenomenon. In the current study, an innovative technique named “warp and woof strap” (WWS) is introduced for anchoring longitudinal FRP sheets, in which some parts of FRP fibers are manually made bi-directionally. Unlike the conventional U-shaped anchors, the anchorage system in this method is in direct contact with the tension side of the beam. Totally, 20 reinforced concrete (RC) beams, 120 × 160 × 1400 mm in size, were subjected to the four-point loading to evaluate the efficiency of the introduced anchorage system in comparison to the U-shaped anchorage. The effect of different parameters including the method employed for anchoring the longitudinal carbon fiber reinforced polymer (CFRP) sheet, anchorage height and width, location of FRP anchorage application, use of the corner strip and rounding corner method, and configuration of WWS anchorage were investigated. The experimental results indicated that the efficiency of the WWS method in preventing undesired debonding mode of failure is much better than that of conventional U-shaped anchor. It was also observed that using WWS method can improve the load carrying capacity and ductility up to 32% and 80%, respectively, compared to U-shaped anchors.