In this paper, the influence of some important parameters affecting flexural behaviour of reinforced concrete beams strengthened with one layer of CFRP laminate has been studied. For this purpose, six reinforced concrete beams were cast and tested in the laboratory. Based on the obtained data, when CFRP laminate is applied to the tension face, too close to the steel rebar, the flexural strength of the strengthened beam is reduced. In general, the performance of the beam strengthened with one wide CFRP strip is better than that strengthened with two equivalent narrow strips. Ultimate load capacity of each strengthened beam was calculated based on the method given by the ACI 440.2R and compared with the test one. It is concluded that to avoid the steel rebar-CFRP laminate interaction effect, the CFRP laminate depth to the effective depth ratio (df / d) should not be smaller than about 1.17.
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