Experimental study of flexural fatigue performance of reinforced concrete beams strengthened with prestressed CFRP plates

Fiber reinforced polymers (FRPs) have commonly been used for the retrofitting and strengthening of bridges, especially in the strengthening flexural members. Considerable research has been conducted to investigate the static behavior of reinforced concrete (RC) beams strengthened with externally bonded FRP laminates, initially using non-prestressed FRPs and more recently using prestressed FRPs. However, the research examining the flexural fatigue behavior of beams with either non-prestressed or prestressed FRPs is not adequate. In this paper, seven RC beams (two regular and five beams strengthened with externally bonded non-prestressed and prestressed CFRP plates) were studied to examine the effects of the different strengthening methods on the flexural fatigue performance of the beams. Furthermore, the effect of debonding on the fatigue behavior of the strengthened beams was investigated. It is evident from the experimental results that strengthening with prestressed CFRP plates significantly enhanced the monotonic and fatigue performances of reinforced concrete beams. The prestressed CFRP plates significantly reduced the deflection and reinforcing bar stress of the beams. The test results also indicated that under similar loads, the strain range and maximum strain of the reinforcing bars of beams with prestressed CFRP plates were significantly less than those of beams with non-prestressed CFRP plates. Moreover, the debonding, observed between the CFRP plate and the concrete during the fatigue test resulted in stress redistributions between the CFRP plate and the reinforcing bars.