Brittle failure and bond development length of CFRP-concrete beams

The performance of a series of 1.5 m-long reinforced concrete beams with CF RP plates bonded to the soffit is presented. Effects of the plate length, t he reinforcing steel ratio, and the thickness of the concrete cover on beha vior of the beams are discussed with particular emphasis on the brittle fai lure mode of the concrete ripping. It was found that before the brittle fai lure, the composite action of the beam could be divided into three distinct zones based on the distribution of the strains along the CFRP plate: (1) T he "destressed" zone, (2) the "bond development" zone; and (3) the "fully c omposite" zone. Concrete ripping may be prevented by limiting the strain at the transition point of the composite zone of the plate. An analytical for mulation to predict the failure load corresponding to the concrete ripping failure mode is proposed based on composite theory in combination with a st rain limiting criterion. The strain limit can be determined based on simple bond tests with various bond lengths for a given CFRP and adhesive combina tion.