Shear Strengthening and Anchorage Effects of CFRP U-Wraps in Flexurally Strengthened Reinforced Concrete Beams

This study investigates the combined effects of shear strengthening and anchorage provided by carbon fiber–reinforced polymer (CFRP) U-wraps in reinforced concrete beams strengthened in flexure using externally bonded CFRP sheets. Eighteen large-scale T-beams, divided into three groups based on the internal steel shear reinforcement ratio, were strengthened with flexural CFRP sheets and different configurations of unanchored U-wraps and U-wraps anchored with fiber anchors. Experimental results confirmed that U-wraps can effectively serve as supplemental shear reinforcement while simultaneously providing anchorage for flexural CFRP. U-wraps anchored with fiber anchors changed the failure modes of two shear-deficient beams from shear failure to flexural failure and increased the strain in flexural CFRP to its rupture strain. In the flexure-controlled group, U-wraps shifted the failure mode from intermediate crack debonding to U-wrap rupture or debonding, or concrete crushing, with a flexural CFRP strain increase from 45% to 55% compared to the unanchored strengthened specimen. The experimental results were compared with the analytical results computed using the current design guidelines and codes, which were more conservative for flexure-controlled specimens than for shear-controlled specimens.