Rehabilitation Systems of Damaged Infrastructures by Using Carbon Fiber Sheets

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Much attention has been paid in recent years to rehabilitation of damaged infrastructures by using composite wrap such as fiber reinforced plastics (FRP) sheets as external reinforcements. The purpose of this study is to make a quantitative clarification of the reinforcing effects of carbon fiber sheets bonded on damaged infrastructures and to give a theoretical basis to establish a rehabilitation system by using composite wrap.(1) A mechanical model was proposed based on linear elastic fracture mechanics to investigate the reinforcing effect for strength reduction due to a crack, the bonding strength and the failure modes in view of the rehabilitation of cracked beams by using composite wrap. A three-point flexure test method was devised in which a single edge notched concrete beam specimen strengthened externally by bonding unidirectional FRP sheets on the bottom tensile zone to evaluate the reinforcing effects quantitatively.(2) The above test method was applied to concrete and mort … More ar beam specimens with and without a center notch with carbon fiber sheets bonded through the actual spot processing in view of evaluating rehabilitation as reinforcing and repair. The failure process as well as load, strain and crack opening displacement behavior were monitored by detecting acoustic emission (AE) activity and by AE moment tensor analysis. The relation between reinforcing effect and fracture toughness at the initiation of AE activity was discussed based on these results.(3) A new peeling test method to evaluate bonding strength between FRP sheets and concrete was proposed in which a thin FRP sheet was bonded on a concrete block and out-of-plane force was applied to FRP sheet to propagate debonding. This test method gave a good measure to characterize a peeling strength and examine the effects of different surface treatment and primer in terms of energy release rate. A simplified data reduction method was also proposed to measure the energy release rate based on the deformation of membrane. Less