Effect of UHPFRC Overlay on Fatigue Cracks Propagating from U-rib Welds of Orthotropic Steel Decks

Over the last decade, fatigue cracks have been observed at welded joints between U-ribs and deck plates in many orthotropic steel deck bridges in Japan. This paper focuses on fatigue cracks that initiate from a weld root of rib-to-deck welded joints and propagate to a deck plate. This study examines the effect of a countermeasure that uses overlaying Ultra-High Performance Fiber Reinforced cement-based Composites (UHPFRCs) on steel decks with cracks from U-rib welds, and confirms the fatigue durability of this method. Specifically, the retardation of crack propagation and the fatigue durability of the UHPFRC itself as well as the interface between the UHPFRC and the deck plate were confirmed by a wheel running test and finite element analysis. Based on the results, it was clarified that this countermeasure has a positive effect on retarding further crack propagation compared with the method of overlaying steel fiber reinforced concrete, which is generally adopted. In addition, it was revealed that the studied countermeasure has sufficient fatigue durability.