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

The overall aim of the study reported in this paper was to examine the plat e-debonding phenomenon when carbon-fibre-reinforced polymer (CFRP) laminate s are used as externally bonded additional reinforcement to strengthen rein forced concrete beam structural elements. The main variables investigated i nclude the amount of tension reinforcement, the concrete strength, the amou nt of shear reinforcement and the location and arrangement of externally bo nded anchorages. Six strengthened reinforced concrete beams, 150 x 250 x 30 00 mm in size, with externally bonded unidirectional CFRP laminates, mere t ested under four-point bending over an effective span of 2800 mm, The disti nguishing feature in the design of the beams was the arrangement and locati on of the externally bonded anchorages. The beams were extensively instrume nted, and deflection, concrete/steel/plate strain and the plate-debonding p rocess were continuously monitored during load testing to failure. The resu lts of the tests mere then critically analysed. It is shown that plate debo nding in a sudden, brittle manner is a major problem associated with CFRP p late-bonding technology. Carefully designed external anchorages and lateral confinement of the compression zone are shown to be very effective in enha ncing the overall performance of the strengthened beams and the utilization of the CFRP sheet.