Structural Behavior of Composite RC Beams with Externally Bonded CFRP

The overall objective of this paper is to establish the structural behavior of reinforced concrete (RC) beams strengthened with externally bonded carbon-fiber-reinforced plastic (CFRP) sheets. Four beams, three with bonded CFRP plates on the tension face, and two of which were provided with carefully designed external anchorages at the ends of the plates and along the span, were tested under four-point bending over a span of 4.8 m. The tests were carried out under displacement control. The beams were extensively instrumented to monitor strains, deflection, and curvature over the entire spectrum of loading to total failure, and to determine the structural response to load of the composite beams. The results show that bonding a CFRP plate on the tension face of a RC beam, without consideration of the end-anchorage stresses and the bond slip between the plate and the concrete substrate, can lead to significant degradation in the structural response of the plated beam. Carefully designed external anchorages, on the other hand, can lead to preservation of composite action to almost the failure load, increases in load capacity of up to 70%, substantial regain of structural ductility, and the transformation of a brittle failure to a more ductile failure.