Key Influencing Factors of Fatigue Crack Propagation in Rib-to-deck Welded Joints of Orthotropic Steel Bridge Deck

Orthotropic steel bridge decks generally suffer severe fatigue problems. Rib-to-deck welded joints are typical parts of the orthotropic steel bridge deck that are vulnerable to fatigue. Studying the fatigue crack propagation in rib-to-deck welded joints and identifying the key influencing factors that affect crack propagation are helpful for understanding the mechanisms of fatigue damage. A finite element model was established for an orthotropic steel bridge deck fatigue experiment model. The fatigue cracks at the weld root of the rib-to-deck welded joints were simplified to a semi-elliptical crack to enable continuous 3D simulations of the propagation process based on fracture mechanics. On this basis, the influences of the initial crack location and initial crack shape on the fatigue crack propagation process were studied. Further, the fatigue crack shape change during propagation and stress intensity factor range variations of the relevant points of the fatigue crack were explored. The research shows that for typical rib-to-deck welded joints of orthotropic steel bridge decks, the longitudinal location of the initial crack has little effect on the crack propagation within a certain distance. The effect of initial crack shape on the crack propagation is mainly reflected in the initial stage of crack propagation. The shapes of different initial cracks stabilize after a finite period of propagation. Once the shape is maintained for a certain period of time, the crack will gradually flatten. When the depth of the fatigue crack is more than approximately half the thickness of the deck, the propagation rate of the deepest point decreases. When the depth is in the same value, more flat crack tend to propagate in the depth direction, while less flat crack tend to propagate in the length direction. © 2019, Editorial Department of China Journal of Highway and Transport. All right reserved.