Fatigue durability of proposed vertical stiffener to deck connection details in orthotropic steel decks

Many fatigue cracks were reported at welded joints between vertical stiffeners and deck plates in orthotropic steel decks (OSDs) in Japan. These fatigue cracks were caused by restraining deck's deflection by stiffeners. To prevent such cracks, reducing stiffness of stiffener top can be a solution. For newly fabricated OSDs, the Japan Road Association recommends cutting off the top of vertical stiffeners on cross beams. However, stiffeners with the gap have very little vertical load carrying capacity and it could not be applied to main girders. Half-circle notch method is retrofitting method for existing structures. For new OSD structures, it can be installed. Whereas a fillet detail is currently used for the beam-to-column connections of steel bridge frame piers to reduce stress concentration at right-angle corners of flanges. The fillet detail, which has not been considered for stiffeners, may be effective for new OSDs. In this study, fatigue durability of the half-circle notch detail and the fillet detail for new OSDs are evaluated through finite element analyses and fatigue tests using a full-scale specimen. As a result, the fillet detail showed superior fatigue durability without no fatigue cracks, while some fatigue cracks were developed in the half-circle notch detail.