Experimental study on repair method of cracked steel members with pre-tensioned CFRP strips

In this study, the repair method of cracked steel members with pre-tensioned CFRP strips was investigated experimentally. Since the compressive force is introduced into the steel member by releasing the pre-tension of CFRP strips after bonding, this technique has attracted attention as an effective way for fatigue crack repair. Aiming to apply to real structure, the prototype of the simple and compact pre-tensioning device has been developed, and the repair effect by introducing the compressive force to the steel member were verified experimentally. The fundamental experimental programs were conducted using the flat steel plates and varying the pre-tension of CFRP strips. As the result of tensile test and creep test, it was found that it is possible to introduce the compressive force of approx. 17 kN, which is equivalent to approx. 70 MPa of the pre-stress, to the steel plate rationally. Moreover, the strains in the steel plate were measured for approx. 900 days after introducing the compressive force. Approx. 10% of losses of pre-stress due to the creep of adhesive joint were observed under room temperature. As the result of fatigue test, the application to fatigue crack repair has been confirmed feasible.