Abstract：The fatigue problem of orthotropic steel bridge deck can be viewed as the fatigue problem with multiple fatigue failure modes of structure system. In view of the intrinsic characteristics, with the typical structural system of orthotropic steel bridge deck taken as the research subject, a new evaluation method of the fatigue resistance of orthotropic steel bridge deck was proposed based on the dominant fatigue failure modes of structural system. Furthermore, with the rib-to-deck welded joints and the longitudinal rib-to-diaphragm welded joints taken as the main research subject, eight full-scale girder segment models, including traditional rib-to-deck welded joints, new upsetting edge rib-to deck welded joints and longitudinal rib-to-diaphragm welded joints, were designed, the dominant fatigue failure modes and the actual fatigue resistance for the two types of structural details were investigated by the fatigue test, and then the key issues such as the notch stress S-N curve equation of structural details and the dominant fatigue failure modes of orthotropic steel bridge deck structural system were discussed based on the notch stress method. The results showed that the fatigue cracks of traditional rib-to-deck welded joints and the new upsetting edge rib-to-deck welded joints initiated from weld root and propagated along the deck thickness direction, the actual fatigue resistances of two welded joints were basically the same; As for the rib-to-diaphragm welded joints, its fatigue failure mode that the fatigue cracks initiated from the weld toe and propagated along the web of rib. The mode with fatigue cracks initiating from weld root of rib-to-deck welded joints and propagating along deck thickness was the dominant fatigue failure mode of orthotropic steel bridge deck structural system.
