Abstract: At present, the reinforcement specification of China adopts the design method based on the ultimate state of the bearing capacity when externally sticking FRP to strength the concrete beam. In the design stage, only the bearing capacity of the strengthened beam is designed, and there is a lack of controlling checking for the deformation of the reinforced beam. The process cannot guarantee that the strengthened beam meets the requirements of the normal service limit state during long-term use. However, the methods used to calculate the long-term deflection of the strengthened beam in the existing studies mostly require complicated programming and cumbersome iterative calculation processes and are not applicable to the reinforcement design phase. Therefore, there is still a need of a simple, relatively accurate and safe analytical method to calculate the deflection of the reinforcement beam, so as to meet the requirements for a wide range of designs used in actual engineering for structural reinforcement. In this paper, creep tests of concrete beams (RC beams) reinforced with CFRP plates are carried out under sustaining-load. The short-term stiffness B_s of reinforcement beams and the deflection increase coefficient λ caused by concrete creep and shrinkage are deduced. A method for checking the deflection of strengthened beams at the design stage was proposed and compared with the test data. The results show that the method proposed in this paper can be used to check the deformation of the reinforced beam during the reinforcement design process, which can ensure the safe use of the strengthened beam.

Key words: CFRP plates, long-term deformation, creep, shrinkage