Many steel structural members have been corroded and thinned with aging lately. Hence, the structural performance has been deteriorated. This is one of the problems the Japanese construction industry has, and various countermeasures are being researched and developed continuously. Among them, the repair and reinforcement method using a CFRP attracts attention because repair and reinforcement effect can be obtained with little weight increase of the structure after construction. Repair and reinforcement by CFRP is mainly performed by adhesive bonding; however, instability due to debonding at the adhesive layer interface is concerned. Therefore, in this study, the relationship between fracture modes and strength was analyzed and evaluated by changing the number of laminated CFRPs and the bonding length for the purpose of increasing the bending stiffness of steel plate. In the test, a three-point bending test was conducted on a specimen which was molded and bonded at the same time by VaRTM technology.
