Crack propagation prediction of double-edged cracked steel beams strengthened with FRP plates

Existing studies have showed that externally bonded fiber reinforced polymer (FRP) plates can significantly improve the fatigue behavior of cracked steel members. Of the existing studies, limited studies have been conducted on FRP-strengthened cracked steel beams, especially on the prediction methods for the crack propagation. In this paper, two prediction methods, named as the asymmetrical prediction method and the symmetrical prediction method, were developed to evaluate the fatigue crack propagation of FRP-strengthened double-edged cracked steel beams based on the fracture mechanics theory and finite element (FE) modeling. The asymmetrical prediction method considered the asymmetrical growth of the double-edged cracks along the tension flange of the steel beam. According to the developed prediction method, the stress intensity factors were analyzed, and the crack growth behavior was predicted for the un-strengthened and FRP-strengthened cracked steel beams. This method was verified by comparing the predicted and experimental results. Furthermore, the simplified symmetrical prediction method was also used to predict the crack growth life. The comparative results indicate that the crack growth life of the FRP-strengthened double-edged cracked steel beam can be predicted approximately by assuming that the double-edged cracks propagate symmetrically along the tension flange.