Effect of U-Wrap Anchors on Flexural Behavior of Reinforced Concrete Beams Flexurally Strengthened with Externally Bonded CFRP Sheets

Externally bonded carbon fiber–reinforced polymer (CFRP) composites have been instrumental in the flexural strengthening of concrete structures. However, intermediate crack debonding from the concrete substrate is a governing failure mode in most externally bonded CFRP applications, limiting the composite strength utilization and deformability of a strengthened member. The addition of transverse U-wrap anchorage for longitudinally oriented CFRP sheet tension reinforcement can improve performance in terms of both deformability and ultimate strength. Due to the scarcity of experimental data, design guidance for U-wrap anchorage to mitigate intermediate crack debonding is lacking. The results of flexural tests on large-scale reinforced concrete beams strengthened in flexure with externally bonded CFRP anchored with U-wraps are reported in this paper. Test results indicate that U-wraps can increase the strain utilization of longitudinal CFRP between 40% and 57%, while also mitigating the intermediate crack debonding failure mode. Varying the ratio of the area of U-wrap anchorage to area of flexural CFRP had little effect on the beams’ flexural capacity.