Fatigue performance of U-rib butt welds in orthotropic steel decks

This study focuses on the orthotropic steel deck (OSD) of a cable-stayed bridge with a plate-truss composite structure. Fatigue tests and numerical simulations were conducted to investigate fatigue features in an OSD with a broad U-rib and embedded sections, considering the assembly tolerance. For the purpose of this study, the pre-stressing force method was adopted to simulate the initial axial pressure in the deck. Fatigue tests were done on three full-scale segment specimens (a total of 6.5 million variable amplitude fatigue cycles). Initial long macro cracks are observed in the arc segment of butt welds. The length of these initial cracks is proportional to the stress amplitude. Fatigue crack propagation stages in the broad U-rib can be divided into four parts with clear demarcation points. The crack growth rate is proportional to the crack length; this increases as a result of the axial force. The initial axial pressure accelerated the crack propagation rate of fatigue details of butt welds. It is recommended that the butt welds of the broad U-rib embedded section can be designed using the fatigue strength of category FAT112 in Eurocode 3. In addition, empirical correction formulas for fatigue strength correction for assembly tolerance of the embedded section are proposed.