New Hybrid Bonding Technique Of CFRP To Reinforced Concrete Beams

CFRP materials have many advantages, such as light weight, convenience in construction, high tensile strength, good corrosion resistance and durability. Therefore it is widely applied to strengthening of reinforced concrete structures. However, the reinforced concrete beams strengthened with traditional methods usually fail by CFRP debonding. Consequently, the tensile strength of the CFRP materials cant be fully utilized and the number of CFRP layers is limited. Therefore, it is important to improve the bond strength between CFRP and reinforced concrete structure, which is helpful in avoiding the premature CFRP debonding failure and fully utilizing tensile strength of CFRP. A new hybrid bonding technique is proposed in this paper to solve this problem. This technique combines externally bonded FRP (EB-FRP) with mechanically fastened FRP (MF-FRP). This new technique is validated by experiments to be effective in improving the ultimate bearing capacity and avoiding premature debonding of CFRP. Furthermore, comparative studies were carried out, with these parameters considered:the steel reinforcement ratio, the number of CFRP layers and anchor distance. The study is the foundation of project application and the follow-up research. The major conclusions are summarized as follow:1. The strengthening procedure and the related notice are introduced, including the treatment of concrete surface, the paste program of CFRP sheets and the maintenance methods of the strengthened beams. They provide the guidance for practical applications.2. The comparison of the failure modes between the reference beams and the strengthened beams proves that the new hybrid bonding technique can avoid the premature CFRP debonding failure, ensure the fully utilization of CFRP tensile strength and improve the ductility of beams.3. The new hybrid bonding technique can increase the ultimate bearing capacity and the stiffness of the beams significantly.4. The effects of reinforcement ratio, the number of paste layers of CFRP sheet and anchor distance are discussed. Furthermore, experimental results indicate that CFRP sheets can be multi-layer pasted with the new hybrid bonding technique and that the maximum number of CFRP layers is seven.