Structural behavior of orthotropic steel decks with artificial cracks in longitudinal ribs

The butt welds at U-rib connections of orthotropic steel deck are usually connected by field welding. In recent years, long fatigue cracks have been observed in the field welds of U-ribs within the decks. In this study, to investigate the effect of rib fractures on structural response, the field tests were carried out at an actual bridge with artificial cracks by gas-cut. Moreover, FE models with the combination of artificial rib crack and rib-to-deck cracks were established. Based on the field measurement and FE analysis results, the deformation and stress fluctuation of structure details were investigated via quantitative analysis. The results show that once the fatigue cracks occurred at butt weld of ribs, the longitudinal stress withstood by the stiffener would be transferred to the localized deck plate and adjacent ribs. Besides, the butt weld crack of ribs would result two consequences: one is the effect of rib rotation on out-of-bending at crossbeams, another is the interaction between adjacent ribs. The fatigue strength recommended by the specifications might not applicable for the evaluation of butt welds when adjacent rib cracks occurred. In addition, for the combination of multiple cracks propagating to different directions, the strength reduction of structure could seriously compromise the bridge safety. Finally, the asphalt pavement variation caused by seasonal temperature has similar influence on the stress responses for cracked or no-cracked structures.