Analytical study of a 2-span reinforced concrete beam strengthened with fibre reinforced polymer Lander VASSEUR Civil Engineer Magnel Laboratory for Concrete Research, Ghent University, Ghent, BELGIUM lander.vasseur@ugent.be Stijn MATTHYS Prof. Dr. Engineer Magnel Laboratory for Concrete Research, Ghent University, Ghent, BELGIUM stijn.matthys@ugent.be Luc TAERWE Prof. Dr. Engineer Magnel Laboratory for Concrete Research, Ghent University, Ghent, BELGIUM Luc.taerwe@ugent.be Summary The structural behaviour of reinforced concrete beams strengthened in flexure with externally bonded FRP (Fibre Reinforced Polymer) reinforcement has been extensively investigated with respect to isostatic beams. However, limited information is available on the behaviour of continuous beams, strengthened with composite reinforcement [1]. For flexural strengthening of a 2-span continuous beam the FRP can be applied above the middle support, at the two field spans or at both locations. Through an analytical study the non-linear behaviour of the beam is investigated. It is verified in which degree moment redistribution still is present when applying this strengthening technique. Keywords: Continuous concrete beam; flexural strengthening; FRP (Fibre Reinforced Polymer), EBR (Externally Bonded Reinforcement); non-linear behaviour; moment redistribution. 1. Introduction Structures may need to be strengthened for different reasons, among which a change in function, implementation of additional services or to repair damage. Different strengthening techniques exist. Often applied is externally bonded reinforcement (EBR), based on fibre reinforced polymer (FRP), the so-called FRP EBR. FRP EBR can be applied for the strengthening of existing structures, enhancing the flexural and shear capacity, or to strengthen by means of confinement. This paper discusses flexural strengthening of a 2 span reinforced concrete beam. Herewith, CFRP (Carbon FRP) laminates are glued on the bottom or on the top or on both sides of a concrete beam. The efficiency of the FRP EBR strengthening technique is often limited by the capability to transfer stresses in the bond interface. Hereby bond failure between the laminate and the concrete may occur. The aim of this study is to have a better insight in the behaviour of reinforced concrete structures strengthened in flexure in a multi-span situation. 2. Analytical study of continuous beams 2.1 Non-linear moment-curvature diagram Performing an analysis of a construction according to the linear elasticity theory, a linear relationship between the moment and the curvature is obtained, namely EI M r = 1 (1) with 1/r the curvature, M the bending moment and K = EI the bending stiffness. This stiffness is assumed to be constant and therefore independent of the value of the bending moment. However,