Shear strengthening of reinforced concrete beams with CFRP

The current paper reviews existing design guidelines for strengthening beams in shear with carbon fibre reinforced polymer (CFRP) sheets and proposes a modification to Concrete Society Technical Report TR55. It goes on to present the results of an experimental programme which evaluated the contribution of CFRP sheets towards the shear strength of continuous reinforced concrete (RC) beams. A total of seven, two-span concrete continuous beams with rectangular cross-sections were tested. The control beam was not strengthened, and the remaining six were strengthened with different arrangements of CFRP sheets. The experimental results show that the shear strength of the beams was significantly increased by the CFRP sheet and that it is beneficial to orientate the FRP at 458 to the axis of the beam. The shear strength of FRP strengthened beams is usually calculated by adding individual components of shear resistance from the concrete, steel stirrups and FRP. The superposition method of design is replaced in Eurocode 2 by the variable angle truss model in which all the shear is assumed to be resisted by the truss mechanism. The current paper proposes a methodology for strengthening beams with FRP that is consistent with Eurocode 2.