Flexure strengthening of concrete bridge girders with concavely curved soffit using near-surface-mounted CFRP bars

The experimental research focuses on the performance of concavely curved soffit reinforced girders strengthened in flexure by near-surface-mounted (NSM) carbon fiber reinforced polymer (CFRP) bars. The test program was organized in such a way to highlight the benefits of this technique for flexural strengthening of concavely curved soffit RC girders at the serviceability and ultimate limit state conditions. NSM CFRP bars used to strengthen reinforced concrete members with curved soffits generally try to straighten under load, resulting in normal tensile stress at the interface between the adhesive and the concrete substrate. Therefore, these structural members may experience premature CFRP de-bonding due to the high concentration of tensile stresses generated by the induced curvature. The interfacial cracking followed by de-bonding is the prevailing failure mode. The objective of this research is to evaluate experimentally the effect of concavity and soffit curvature on the cracking, deformability, load capacity, and the de-bonding failure mode of reinforced concrete girders strengthened with NSM CFRP bars. For this purpose, five simply supported RC beams 2.7 m length were fabricated and tested under monotonic static three-point loading up to failure.