Repair timing criteria for rib-to-deck weld-root cracks considering local stress redistribution and field-observed cracking characteristics

Rib-to-deck weld-root cracks in orthotropic steel decks are challenging to repair, and selecting appropriate repair timing criteria is particularly crucial. Existing repair timing criteria are established based on either crack propagation behavior or local stress redistribution. However, crack propagation and stress redistribution are not independent processes, and considering only one of these factors may lead to misjudgment of the optimal repair timing criteria. In this study, numerical simulations were conducted to investigate the redistribution of local stresses following weld-root cracking in rib-to-deck welded joints. The effects of crack length and depth on local stress states were analyzed, and, combined with the cracking characteristics observed in a kilometer-scale cable-stayed bridge in China, the repair timing criteria for rib-to-deck weld-root cracks were proposed. The results indicate that once the crack depth reaches 70% of the deck thickness, propagation in the depth direction becomes inhibited and subsequent crack growth is dominated by the length direction. At this stage, the load-carrying capacity of the deck within the cracked region enters a phase of rapid degradation, and stresses are redistributed to the uncracked deck and the U-rib web within the cracked region. In particular, after the crack penetrates the deck and its length exceeds 200 mm, the stress amplification in the uncracked deck on the weld-toe side enters a stage of rapid increase, while the stress amplification in the U-rib web exceeds 60%, leading to the formation of potential fatigue-prone locations. Therefore, a crack depth greater than 70% of the deck thickness or a crack length exceeding 200 mm can be adopted as repair timing criteria for rib-to-deck weld-root cracks.