Distortion-induced fatigue behavior of vertical stiffener web gaps in steel girder bridges

This paper reports full-scale fatigue tests, conducted to explore the distortion-induced fatigue behavior of vertical stiffener web gaps in steel girder bridges, considering parameters such as web gap size, nominal stress ratio and distortion ratio (a newly proposed physical parameter). The results show that the fatigue strength of weathering steel web gaps improves with the increase of the web gap size, but worsens with the increase of the stress ratio and the distortion ratio. It was found that the fatigue strength for 20 mm, 40 mm and 60 mm weathering steel web gaps corresponds to categories 36, 71 and 100 in Eurocode 3, when the nominal stress ratio and the distortion ratio are less than 0.3. However, when the nominal stress ratio and distortion ratio are between 0.3 and 0.5, the fatigue strength for 20 mm is below category 36, while for 40 mm and 60 mm, it corresponds to categories 45 and 80, proving the stress and distortion ratio dependency.