Integrating CFRP U-Wrapping and Spike Anchors in the Applications of Flexural Strengthening of RC Beams

Abstract This research examines the dual role of Carbon Fiber Reinforced Polymer (CFRP) U-shaped wrapping and spike anchors (SA), installed laterally or vertically, in enhancing stress transfer at the concrete-laminate interface and mitigating premature debonding. In addition to the RC control beam, eight beams organized into three groups were investigated. Group 1 evaluated the strength gain provided by Externally Bonded Reinforcement (EBR) alone or EBR supplemented with a single anchorage system, either a U-wrap or spike anchor, to secure the CFRP laminate. Group 2 investigated EBR with a single end U-wrap paired with either double lateral or single vertical bottom SAs. Group 3 employed double end U-wraps alone or in combination with single or double lateral SAs per sheet. The results revealed that incorporating spike anchors alone was more effective than U-wrapping. Flexural capacity increased by over 81% compared to the control beam and by 50% relative to the beam strengthened solely with EBR. On the other hand, hybrid configurations of spike anchors and U-wraps showed limited additional benefit, except for the case of double U-wraps combined with double lateral SAs, which achieved flexural strength gains of over 96% and 62% compared to the control and EBR-only beams, respectively. Anchoring also resulted in an enhanced flexural behaviour where most of the anchored specimens failed by CFRP rupture rather than CFRP debonding, indicating a better utilization of CFRP material.