Flexural strengthening of concrete beams using externally bonded composite materials

In this study, a series of reinforced concrete beams were tested in four-point bending to determine the ability of externally bonded composite fabrics to improve the beams' flexural capacity. The fabrics used were made of aramid, E-glass and graphite fibres, and were bonded to the beams using a two-part epoxy. The different fabrics were chosen to allow a variety of fabric stiffnesses and strengths to be studied. The external composite fabric reinforcement led to a 36 to 57% increase in flexural capacity and a 45 to 53% increase in flexural stiffness. For the beams reinforced with E-glass and graphite fibre fabrics, failures were a result of fabric tensile failure in the maximum moment region. The beams reinforced with aramid fabric failed due to the crushing of the compression concrete. In addition to the test results, an analytical model based on the stress-strain relationships of the concrete, steel and composite fabrics is presented. Using the model, beam response is computed and compared with the experimental results. The comparisons indicate that the flexural behaviour of composite-fabric-reinforced concrete beams can be accurately predicted using the described method.