In this paper, a numerical simulation method of mixed-mode fatigue crack propagation was explored using the extended finite element method (XFEM) and the Virtual Crack Closure Technique (VCCT). Both 2D and 3D numerical models were selected to simulate the fatigue crack propagation of steel specimens. Two coefficients were proposed to calculate the equivalent energy release rate (Geq) for a better simulation of the mixed-mode fatigue crack propagation of S355 steel. The Walker equation and the calculation formula of Geq were realized by a user-defined subroutine. A set of optimal correction coefficients of mode II energy release rate (GII) and mode III energy release rate (GIII) were quantitatively comparing the simulation results and test data. The results will contribute to fatigue crack propagation prediction of steel structures in the civil engineering field.@en

Strengthening fatigue damage of orthotropic steel decks (OSDs) needs to comprehensively consider the strengthening effect and the dead weight introduced during the strengthening process, especially for OSDs in super large-span bridges or old renovated bridges, where the dead weight cannot be significantly increased during repair and maintenance. This paper proposed a new CFRP prestressed reinforcement method, that does not significantly increase dead weight while effectively inhibiting fatigue crack growth. The strengthening effects of various strengthening methods on the fatigue crack propagation of rib to deck joint in OSDs were compared. Besides, the strengthening effects of different crack sizes were also analyzed. The results showed that the proposed method is effective in reducing fatigue damage at the rib to deck joint in OSDs.@en