Fatigue performance of orthotropic steel-concrete composite deck with large-size longitudinal U-shaped ribs

Fatigue damages in orthotropic steel deck have been a thorny problem that perplexed bridge engineers worldwide for decades. Two approaches have been applied to improve the fatigue performance of orthotropic steel decks: (1) to reduce the maximum stress range of structural components by enhancing the local stiffness through use of composite structural systems; (2) to reduce the quantity of fillet welded joints by enlarging the size of longitudinal U-shaped ribs. In this study, a full-scale model test and finite element analysis were conducted to investigate the fatigue performance of an innovative orthotropic steel-concrete composite deck (OSCD) with large longitudinal U-shaped ribs, which represents a combination of the two aforementioned strategies. Orthotropic steel deck and concrete layer are integrated through shear studs that are welded on the steel deck and embedded in concrete. The fatigue failure process of the OSCD structure was investigated, and the effects of damages in concrete and shear studs on the fatigue performance of OSCD were evaluated for the first time. The initiation and development of fatigue cracks were experimentally investigated. The interaction between the mechanical performance of OSCD and the damages caused by cyclic loadings was revealed. Concrete cracks and fracture of shear studs greatly accelerated the degradation of mechanical properties and the development of fatigue failure, and deteriorations of the mechanical properties accelerated the development of damages in concrete and shear studs.