Numerical simulation of fatigue crack propagation of typical welded structural details in steel bridge decks

In order to investigate the fatigue cracking of typical structural details of steel bridge decks under the coupling of welding residual stress and vehicle loads, a numerical simulation of the welding process was carried out for the U-rib double-sided welded joints and U-rib–diaphragm joints, and a shell-solid coupled segmented finite element model for steel bridge decks was established to carry out the calculation of the static stress intensity factor and the analysis of the dynamic crack propagation behavior based on the extended finite element method (XFEM). The results show that high welding residual tensile stresses can be observed in the weld area of the U-rib double-sided welded joints and the U-rib–diaphragm joints, with maximum values close to the yield strength of the steel. By considering only the vehicle load, fatigue cracks in the roof and the weld toe of the U-rib double-sided welded joints will not propagate, as well as those in the arc-shaped openings on the diaphragm of the U-rib structure. However, fatigue cracks in the weld toe of the U-rib web and the diaphragm will propagate, but do not consistent with actual bridge observations. After introducing welding residual stress, the crack at the inner weld toe of the roof propagates faster than at the outer weld toe, and it becomes mixed cracks of ModeⅠ–Ⅲ, led by Mode Ⅰ; the crack in U-rib web weld toe is mixed cracks of Mode Ⅰ–Ⅱ–Ⅲ, led by Mode Ⅰ; the fatigue crack in diaphragm weld toe is mixed cracks of Mode Ⅰ–Ⅱ, led by Mode Ⅰ. The fatigue crack in the arc-shaped openings on the diaphragm is Mode Ⅰ.