Groove and embedding techniques using CFRP trapezoidal bars for strengthening of concrete structures

An experimental program to apply a new retrofit technology using high performance carbon fiber reinforced polymer (CFRP) bars with a trapezoidal cross section to reinforce concrete beams has been investigated. The proposed method has two important advantages in the retrofit of concrete beams: the failure mode of the beam is controlled by flexural failures before reaching local failures and the retrofitting process in the construction field is simple and easy to apply in aged reinforced concrete beams or beam–column members. The new methodology has been proposed based on a system where geometrically modulated CFRP trapezoidal bars are embedded into grooved concrete with additional assistance from externally applied U-type metal fittings. The proposed retrofit method is validated by comparing it with the experimental results of conventionally strengthened beams and showing that the proposed method gives good improvement in ductility and load-carrying capacities of concrete beams. When compared with conventional retrofit methods using steel plates or FRP sheets, the proposed method is effective in preventing local failures before reaching the flexural failure of retrofitted beams, due to the superior composite action between the concrete and embedded CFRP trapezoidal bars.