Probabilistic study on the macro-crack initiation of the rib-to-deck welded joint on orthotropic steel deck

摘要

The inherent randomness of the fatigue issues on the orthotropic steel deck (OSD) requires a probabilistic investigation. With respect to the unfavorable crack on the rib-to-deck welded joint of OSD, the macro-crack initiation, namely the process of the crack growth until it is detected, is studied using the probabilistic fracture mechanics (PFM). The PFM model is established based on the two-stage crack growth model and validated by test results. It is applied in the Monte-Carlo simulation (MCS) to reproduce the crack growth under the realistic traffic load obtained by the WIM data on an OSD for one year, suggesting that a lognormal function can be used in fitting the distribution of the life till the crack grows to half of the deck plate thickness. Based on the MCS results, further analysis is carried out on the macro-crack initiation by considering the probability of detection (PoD) of two different ways of non-destructive evaluation (NDE) method. Due to the lack of ability in detecting tiny cracks, it is stated that the endeavors in finding cracks in the early years could be inefficient, especially for the first 10 years. Fortunately, it is highly possible to detect the crack when it grows to a larger size by applying multiple times of inspections. With consideration of the repairs works for detected cracks, the probability that the crack grows to the critical size, e.g. half of the deck plate thickness, can be calculated. Accordingly, the inspections for the fatigue-prone sites can be optimized in a probabilistic way for the maintenance and management of the bridge.