The aim of the study is to investigate the influence of an external CFRP reinforcement on the time dependent behaviour of flexural members. Four reinforced concrete beams are tested in relaxation under three-point bending: three of them have a composite plate bonded to their tensile soffit; the last one is not strengthened. The test results show a positive influence of the composite reinforcement on the long term behaviour of the beams. Moreover, a difference is observed, depending if the beam has been pre-cracked or not before being strengthened. The test results are analyzed in two ways: an incremental method specially adapted for this purpose shows that the difference above may be explained by a coefficient of contribution applied to the composite reinforcement; a detailed analysis of the internal equilibrium of the beam in the course of time leads to the conclusion that the existence of a period of loading before strengthening has a positive influence on the long term behaviour of the beam.
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