Experimental studies of concrete beams strengthened with prestressed CFRP laminates

摘要

Several conclusions were drawn from the experimental results in this study. 1. The modified anchorage system that was developed for prestressing high-strength CFRP laminates is an improvement over its predecessor because it allowed a greater level of prestress to be achieved. 2. Prestressing the CFRP laminate prior to bonding it to the concrete beam provides the possibility of laminate failure by fracture. Nonprestressed CFRP laminates failed by debonding between the CFRP laminates and the concrete, whereas the prestressed laminates had different failure modes, including debonding followed by crushing of the concrete, debonding followed by laminate rupture during the crushing of the concrete, and CFRP laminate rupture accompanied with crushing of the concrete. 3. Bonding CFRP laminates to a concrete beam increases the beam's flexural capacity. Prestressing the CFRP laminate prior to bonding provides additional flexural capacity, which increases as the prestress level and laminate width increase. 4. Bonding CFRP laminates to a concrete beam restricts the cracking propagation. The CFRP laminates had a compressive effect on the base of the beam, which tended to confine the concrete. The confinement effect on the crack development increased with greater prestress levels and wider laminates. 5. Reinforcing concrete beams with CFRP laminate lowers the ductility coefficient of the beams, and prestressing the laminates lowers the coefficient more. The ductility of beams with prestressed laminates was better in the ones that failed without debonding of the laminate than in those that failed with debonding. 6. Steel laminates were used to fabricate the anchorage system in this study for the convenience of manufacturing. In practice, anticorrosive measures should be taken to protect the anchorage system because it remains with the CFRP laminate after releasing the prestress. A completely non-corrosive strengthening system should be developed for the CFRP endplates and bolts in a future study. 7. The long-term behavior of the beams strengthened with prestressed CFRP laminates needs further investigation.