Equivalent capacity and efficiency of reinforced concrete beams strengthened with carbon fibre reinforced plastic sheets

Fibre reinforced plastic sheets have recently been used in Switzerland and Japan as an alternative to steel plates for the external strengthening of structural components. This paper presents the results of an experimental program that examines the behaviour of reinforced concrete beams strengthened using carbon fibre reinforced plastic (CFRP) sheets. The concept of equivalent strength is introduced for comparative purposes, and its applicability to design is discussed. The results and analysis of three 2 m reinforced concrete beams and two 5 m reinforced concrete beams of various tensile reinforcement configurations are presented. The CFRP sheets are shown to enhance the stiffness of the beams, the load at which the tensile steel yields, the stiffness of the beams after yielding of the tensile steel, and the maximum load of the beam. The behaviour of the rehabilitated beam is compared to the understrength beam and the equivalent all steel reinforced beam. An equivalent capacity based on the load at which the tensile steel yields is proposed to ensure adequate stiffness within the working stress range. The concept is equally applicable to strengthening as it is to rehabilitation.