Fatigue evaluation and structural optimization of rib-to-diaphragm connection in orthotropic steel decks

Abstract

The fatigue cracking at transverse diaphragm cutouts and rib-to-diaphragm connections is one of the primary ways in which orthotropic steel decks (OSDs) are damaged. In this study, the fatigue damage mechanism of the cutouts and rib-to-diaphragm connections was investigated through a full-scale model experiment and numerical simulations. The applicability and accuracy of different fatigue evaluation methods for the cutouts and rib-to-diaphragm connections were compared. Furthermore, the fatigue behavior of the novel rib-to-diaphragm connection was evaluated, and its optimized structure was suggested based on parametric analysis. The results show that a complex stress distribution dominated by in-plane stresses was observed at the rib-to-diaphragm connection under wheel loading. The cracking of the weld toe at the transverse diaphragm side was found to be the dominant failure mode. The hot spot stress method has a higher prediction accuracy than the critical distance theory for predicting the fatigue life of the cutouts. For the longitudinal rib-to-transverse diaphragm connection, the hot spot stress method could be used to predict the fatigue life of U-rib side weld toes based on fatigue grade FAT 90, and the equivalent structural stress method provided a reasonable prediction of the fatigue life for all fatigue failure modes. Last but not least, a novel rib-to-diaphragm connection structure that can effectively improve fatigue performance was suggested, and its fatigue life was evidenced to be greater than 50 million cycles after geometrical parameter optimization.