Debonding of carbon-fibre-reinforced polymer plate from concrete beams

The overall aim of the study reported in this paper was to examine the plate-debonding phenomenon when carbon-fibre-reinforced polymer (CFRP) laminates are used as externally bonded additional reinforcement to strengthen reinforced concrete beam structural elements. The main variables investigated include the amount of tension reinforcement, the concrete strength, the amount of shear reinforcement and the location and arrangement of externally bonded anchorages. Six strengthened reinforced concrete beams, 150 x 250 x 3000 mm in size, with externally bonded unidirectional CFRP laminates, mere tested under four-point bending over an effective span of 2800 mm, The distinguishing feature in the design of the beams was the arrangement and location of the externally bonded anchorages. The beams were extensively instrumented, and deflection, concrete/steel/plate strain and the plate-debonding process were continuously monitored during load testing to failure. The results of the tests mere then critically analysed. It is shown that plate debonding in a sudden, brittle manner is a major problem associated with CFRP plate-bonding technology. Carefully designed external anchorages and lateral confinement of the compression zone are shown to be very effective in enhancing the overall performance of the strengthened beams and the utilization of the CFRP sheet.