Ultimate Limit State Behavior of RC Members in Bending Strengthened with GFRP Rebars

In the last decades, composite retrofit technology has been introduced for structural applications in civil engineering. The advantage of reinforcing existing reinforced concrete (RC) members with glass fiber-reinforced polymer (GFRP) bars is to provide the required additional load bearing capacity, while improving maintainability and durability. Being corrosion of steel reinforcement a major cause of damage in ordinary RC structures, the retrofit of existing structures by arranging additional GFRP reinforcing bars externally to the steel ones leads the entire RC section to be less susceptible to subsequent corrosion degradation, thus limiting further repair costs. On the other hand, the use of GFRP rebars reduces the ductility of RC members in bending and, therefore, can be critical specially for structures subjected to seismic excitations. Therefore, a hybrid use of steel and GFRP reinforcement is mandatory, to keep a sufficient level of ductility. This research aims to highlight the advantages at the Ultimate Limit State (ULS) of the design of repairing/strengthening interventions, such as concrete jacketing, using the innovative retrofitting technique with hybrid steel-GFRP reinforcement. Design models are proposed, based on fundamental theories for RC beams and available literature on failure modes of GFRP reinforced sections. Different solutions are explored by cross-sectional analysis to evaluate the increase in load bearing capacity and the resulting ductility in the bending regime.