This study focuses on simply supported railway box girder bridges with pre‐existing cracks under high‐speed train loading. A vehicle–bridge coupled vibration model is established, and three‐dimensional dynamic stress intensity factors at the crack tip under various loading conditions are obtained using the interaction integral method. The crack propagation is quantified by defining crack propagation assessment parameters. The study investigates the effects of different web damage levels and train speeds on the vertical crack propagation behavior and patterns in the mid‐span of the bridge, as well as the propagation behavior and patterns of diagonal cracks at one‐quarter span of the bridge. The results indicate that under high‐speed train loading, an increase in the degree of web damage increases the likelihood of vertical crack propagation at the mid‐span of the bridge. The maximum value of the crack propagation evaluation parameter ( ω max ) increases with the severity of web damage. The crack propagation assessment parameters at the crack tip near the top flange are consistently lower than those at the crack tip near the bottom flange across different train speeds. This suggests that the probability of diagonal cracks at 45° in the web extending toward the bottom flange is greater compared to extending towards the flange.
Zhang et al. (Thu,) studied this question.