Premature Failure of Externally Plated Reinforced Concrete Beams

Abstract

Reinforced concrete beams can be strengthened and stiffened by gluing mild steel plates to the tension face of the beam. However, experimental tests show that these externally bonded plates have a tendency to peel away after the formation of shear diagonal cracks or when the curvature in the beam is increased. Fifty‐seven plated reinforced concrete beams are tested to study peeling induced by increasing curvature; in these tests, the geometry and material properties of the beams are varied, and the reinforced concrete beams are subjected to pre‐cracking and pre‐cambering, as might occur in an existing structure. A method is derived for determining the moment at which peeling starts (serviceability limit) and the moment that causes complete separation of the plate (ultimate limit). This method, which depends on the flexural rigidity of the plated beam, the thickness of the plate, and the tensile strength of the concrete, can be used to adjust the size and extent of plating so that flexural peeling does not occur under the design load.