Results are reported for four tests on reinforced concrete beams having steel plates bonded to their tension flanges with structural epoxy resin. The four tests covered the effects of changes in plate thickness, type of adhesive, inclusion of a joint in the plate, and a limited study of the effects of cyclic loading on the structural performance. There was a significant stiffening effect of between 72 and 105 per cent using one type of adhesive; the higher value includes the effect of a joint in the plate. For the other type of adhesive the increase in stiffness was 35 per cent. There was a corresponding effect on the development of cracks; the load to produce a 0.1 mm crack width in a plated beam was approximately double the load to produce the same size crack in the unplated beam. There was a much smaller increase in load carrying capacity, between 12 and 24 per cent, when the loads to cause separation of the plates are compared with the ultimate loads of the respective beams with plates removed. In all cases, failure of the plated beam occurred by horizontal shear in the concrete adjacent to the steel plate, the calculated shear stress at failure being rather less than the nominal shear strength of the concrete used.

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