Flexural Performance of RC Beams Strengthened with Prestressed CFRP Sheets

Piyong Yu
Pedro Franco Silva, Missouri University of Science and Technology
Antonio Nanni, Missouri University of Science and Technology


A mechanical device for prestressing carbon fiber reinforced polymers (CFRP) sheets and its application for the flexural strengthening of reinforced concrete (RC) beams are discussed in this paper. Significant features of this mechanical device are that the CFRP sheets can be anchored directly to the mechanical device, and prestressing forces can be applied manually without the need for hydraulic jacks. the physical principle behind this mechanical device relies on: (1) prestressing a CFRP sheet that is initially straight and anchored between two points; and (2) applying a small uplift displacement at two other points that are located at a small distance away from the anchoring points. in this manner, the force necessary to create the uplift displacement can be much smaller than the force required to impose the initial prestressing on the CFRP sheets, and the uplift force may be imposed without the need for hydraulic jacks. Test results showed that the manual mechanical device proved to be practical and safe for prestressing CFRP sheets. Moreover, there is no limit for its application to other types of FRP systems. in this research program, three reinforced concrete (RC) beams were tested to investigate the feasibility of this concept for flexural strengthening. One of the beams was retrofitted with one prestressed CFRP sheet, another was also retrofitted with a CFRP sheet but it was left unprestressed. the third beam was used as the control beam. the three RC beams were then tested to ultimate condition under a four-point loading test setup. Test results showed that after strengthening with the prestressed CFRP sheet, flexural strength and serviceability of the retrofitted RC beam was increased significantly.