ABSTRACT
The fatigue crack on the rib-to-deck welded joint is the most harmful crack type on orthotropic steel decks (OSDs). It will lead to the loss of local stiffness, which is closely related to the pavement damage and consequently leads to the reduction of bridge serviceability. In order to assess the fatigue performance of OSD, attentions should be paid to the fatigue process instead of the fatigue life only, and in the meantime, the scattered results of the fatigue tests imply the necessity to use a probabilistic way. This study is therefore conducted using the probabilistic fracture mechanics (PFM), with several key factors addressed in the application of PFM on the fatigue of rib-to-deck welded joint. Based on the fatigue test results, the effect of the early-stage crack behavior in the heat-affected zone is illustrated. The two-stage model that considers both the Paris region and the near-threshold region is then compared with the conventional one that focus on the Paris region only. The results indicate that the overlook of the near-threshold region will lead to an exaggeration of the fatigue crack growth rate. Accordingly, the PFM model that is feasible on this issue is determined, by which the Monte-Carlo simulation on the crack growth under the realistic traffic flow is carried out, though the computational efficiency is unfavorable due to the large amount of vehicles. The histogram of the crack growth life is demonstrated together with the cumulative probability. The results will help to improve the fatigue reliability evaluation of OSDs, and eventually benefit the inspection work and the decision making in the bridge maintenance and management.
