Reinforced Concrete Structures with Hybrid Technology of Pre-Stressed CFRP Sheets and Pre-Screwed Bolts

The carbon fiber reinforced composite polymer (CFRP) reinforcement is currently one of the most popular and effective methods for retrofitting and strengthening concrete structures. However, the nonprestressed CFRP reinforcement cannot make full use of the tensile strength of CFRP, the crack development of the stiffening beam cracks cannot restrain actively either. The failure of a strengthened or retrofitted structure with the nonprestressed CFRP is usually caused by the breakdown of the bond at the CFRP-epoxy interface or at the concrete-epoxy interface which is weaker than other places. Much effort has been made in the research community to improve the bond strength and restrain the crack development of the strengthening beam cracks. The full CFRP strength can usually be achieved in the strengthened or retrofitted structure with the prestressed CFRP. The prescrewed bolts fastening is another new mechanical fastening technique that is used to bond one material to another to improve the bond interface strength. Therefore, this paper introduces a new hybrid bonding prestressed technique that combines prestressed CFRP reinforcement and prescrewed bolts fastening. New tensioning equipment was developed to prestress CFRP. The strengthened reinforced concrete (RC) beam experiments have been finished to check the strengthening effect. Experimental tests have demonstrated that the new hybrid technology of prestressed CFRP sheets and prescrewed bolts can make full use of the tensile strength of CFRP and actively restrain the crack development of the strengthening beam cracks.