Much attention has recently been paid to rehabilitation such as repair and preservation of infrastructure with the use of fiber reinforced plastics (FRP) wraps or sheets. A widespread use of carbon fiber sheets has already been found in Japan with hundreds of field applications including repairs of bridge beams, retaining walls, utility poles, slabs, chimneys, tunnels and other structures requiring strengthening, stabilization or seismic upgrade. The use of externally bonded FRP sheets as reinfocement in concrete members has recently been investigated both theoretically and experimentally, showing a good promise of effective strengthening in view of the simplicity of application relative to bonding of steel plates. The strength of structural members reinforced by bonding FRP sheets depend naturally on the bonding or peeling strength between FRP sheets and structures. Evaluation of failure process and bonding strength against debonding or peeling is a matter of concern for structural reinforcement by FRP sheets. This paper describes the authors' recent fundamental study aiming at establishing some theoretical basis and guideline for such applications by examining the failure process and the increased fracture toughness of concrete beams reinforced with carbon fiber (CF) and glass fiber (GF) sheets in the following three parts.
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