Structural behaviour of RC beams externally strengthened with FRP sheets under fatigue and monotonic loading

This paper presents experimental research on the fatigue and post-fatigue static behaviour of reinforced concrete beams strengthened with glass or carbon fibre reinforced polymer (FRP) sheets placed either vertically or obliquely. All beams for fatigue tests were subjected to four-point bending for one million cycles with a frequency of 5 Hz. The results show that the FRP sheets can be used to significantly enhance the fatigue resistance of the beams strengthened. Also the results from the post-fatigue monotonous tests indicate that FRP sheets contribute the significant increase of the ultimate strength and ductility of the beams tested. The diagonal GFRP reinforcing arrangement is more effective than the vertical one in enhancing shear strength and stiffness. Finally, some moment deflection models were adapted to predict the ultimate loads of the beams tested, which give very good correlation to the experimental results.