XFEM-based Fatigue Crack Propagation Analysis on Key Welded Connections of Orthotropic Steel Bridge Deck

Orthotropic steel decks(OSD's) are prone to fatigue cracking under cyclic loads, especially for rib-to-deck welded connection and rib-to-crossbeam welded connection. To reveal fracturing behaviors of these fatigue-prone sites, a multi-scale model of OSD's specimen is established, including segmental shell-element part and local solid-element configuration. Based on the extended finite element method(XFEM), propagation analysis was carried out in this research. The analysis of stress intensity factor (SIF) shows that the crack at the weld root or weld toe of the rib-to-deck welded connection is a mixed-crack with modes I, II and III, where mode I plays a leading role. Besides, the maximum SIF K(I )of the crack at the weld toe is slightly larger than that at the weld root. For rib-to-crossbeam welded connection, the maximum SIF K-I at the weld toe of the U-rib is greater than that at the weld toe of the crossbeam. The analysis of crack propagation shows that the crack growth rate at the weld toe is faster than that at the weld root with the same initial crack size and loading conditions. Similarly, for rib-to-crossbeam welded connection, the crack propagation at the weld toe of U-rib performs faster than that at the weld toe of crossbeam.