Analysis of reinforced concrete beams strengthened in flexure with composite laminates

The structural behaviour of reinforced concrete beams strengthened in flexu re by means of externally bonded fibre reinforced composite laminates is si mulated numerically using a nonlinear finite element layered model. The ful l-bond assumption between the composite laminate, steel reinforcement, and the concrete is assumed, and shear deformations are neglected. Interlayer c ompatibility is achieved by imposing the same displacements at the interfac es of adjacent layers. The concrete is assumed to be nonlinear in compressi on and to exhibit a post-cracking tension-stiffening behaviour in tension. The behaviour of the steel reinforcement is modelled as elastic-plastic, wh ile that for the composite laminate is linear elastic using an equivalent e lastic modulus obtained from the so-called "classical lamination theory" of composite structures. An incremental, iterative displacement-control numer ical analysis is developed. The finite element code is validated using publ ished test results for conventional reinforced concrete beams, as well as f or beams strengthened with composite laminates. A comparison of the numeric al and experimental curves shows very good agreement. The effects of variou s parameters on the behaviour of composite-strengthened concrete beams are examined.