Abstarct: A 3D nonlinear finite element analysis modelling frxamework was developed for simulating the behaviour of beams retrofitted with fibre reinforced polymer (FRP). The ABAQUS program was used for this purpose. Concrete was modelled using a plastic damage model. Steel bars were modelled as an elastic perfectly plastic material, with perfect bond between concrete and steel. A cohesive model was used for modelling the FRP-concrete interface. Bond properties needed as input to the cohesive model, such as initial stiffness, shear strength and fracture energy were proposed baxsed on fitting FEM results to experimental results from literature. Initial stiffness was related to the adhesive properties. Shear strength and fracture energy were expressed as functions of tensile strength of concrete and of adhesive properties. The model was verified through comparison with the experimental data regarding failure mode and load-displacement behaviour. The influence of several parameters such as elastic modulus, thickness, length and width of FRP were investigated. The result showed that when the length of FRP increases, the load capacity of the beam increases for flexural strengthening. The result also showed that the FRP to concrete width ratio and the stiffness of FRP affect the failure mode of retrofitted beams. The maximum load increases with increased width ratio. Increased FRP stiffness increases the maximum load only up to a certain value of the stiffness, and thereafter the maximum load decreases.