Fatigue Behavior of FRCM Strengthened RC Beams: State of the Art and Future Developments

Numerous reinforced concrete (RC) structures are subjected to cyclic loading that may decrease their service life due to the occurrence of fatigue issues. Externally bonded (EB) fiber-reinforced composites have proven to be an effective solution to increase the fatigue life of RC members due to the stress re-distribution from the internal reinforcing steel to the external composite material. Besides, the effectiveness of fiber-reinforced composites is related to the quality of bond between the composite and the concrete substrate. Thus, the bond fatigue response should be investigated as well as the overall fatigue response of the strengthened RC element. Within the broad family of fiber-reinforced composites, those comprised of high-strength fiber textiles embedded within an inorganic matrix, which are generally referred to as fiber- (or fabric-) reinforced cementitious matrix composites (FRCM), showed promising results as a strengthening and retrofitting solution for RC structures. However, limited research has been carried out to investigate the fatigue behavior of the bond between the composite and the substrate and therefore the overall contribution to the fatigue life of the strengthened RC member. This paper presents a state-of-the-art on the fatigue behavior of RC beams strengthened in flexure with different FRCM composites. Furthermore, preliminary results of an ongoing experimental campaign aimed at studying the bond fatigue behavior of polyparaphenylene benzo-bisoxazole (PBO) FRCMs through a modified-beam test set-up are presented and discussed.