Performance and failure analysis of carbon fiber-reinforced polymer (CFRP) strengthened reinforced concrete (RC) beams

At present, the strengthening and retrofitting of reinforced concrete (RC) beams using carbon fiber-reinforced polymer (CFRP) are receiving extensive attention. The use of strengthening technique for RC beams vary according to purpose. In general, this technique aims to increase load-carrying capacity, either through flexural or shear strengthening. The present study aims to investigate the load-deflection response of CFRP-strengthened RC beams through experimentation with five various strengthening configurations and two different types of surface treatment. The RC beams that were tested in this work were small scale. Results indicate that compared with control beams, CFRP-strengthened beams notably reinforced ultimate load and deflection, as well as ductility, because of the stiffness and grip provided by CFRP. Among the five configurations, the continuous U-wrapping and strip wrapping systems were proven effective for strengthening. A close interaction between internal stirrups and external CFRP strips, which will negatively affect the overall strength of the beams if the reinforcements were placed simultaneously along a similar section of the beam. The failure pattern of the strengthened beams considerably depends on strengthening configuration and internal steel reinforcement, which control the ultimate effectiveness of strengthening. In addition, the ultimate capacity of the beams was predicted in accordance with the ACI 440.2R-17 guidelines and was finally compared with the experimental ultimate loads of the CFRP-strengthened beams. Experimental results show that the predicted values were extremely conservative.