Load-Displacement and Stiffness Characteristics of Carbon-Fiber Reinforced Polymer (CFRP) Strengthened Reinforced Concrete Beams

In the current study, the efficiency of the carbon-fiber reinforced polymer (CFRP) strengthening technique is experimentally applied to reinforced concrete (RC) beams. In total, four types of test beam specimens are fabricated and tested, labeled as B-1, B-2, B-3, and B-4 for controlled specimens; the beams strengthened at high-level bending-moment regions, beams strengthened at bending-moment regions with enhanced development length, and U-wrapped shear plus flexural strengthened beams, respectively. The control specimens were fabricated under-reinforced in order to exhibit ductile failure according to ACI 318-08. The variation in the CFRP external configuration included a change in the bond length and use of U-shaped strips to limit the CFRP debonding. For strengthening the beams, Sika group CFRP was used in this study. The test specimens were subjected to three-point loading following seven days of strengthening. The test result includes failure modes, load displacement curves, and stiffness degradation. The proposed CFRP strengthening configuration of the RC beams (B-2, B-3, and B-4) demonstrated improved behavior of their load response as compared to that of control beam (B-1). The CFRP configuration used of RC beam B-4 exhibited almost double flexural strength to that of control beam B-1. Moreover, the deformability of the CFRP strengthened RC beams was also increased.