Fatigue cracks in longitudinal ribs of steel orthotropic deck

During an inspection to the south structure of Kinuura Bridge (Japan) in June 2003, a number of fatigue cracks were found in many butt welds in the longitudinal ribs of the orthotropic deck. The structure was completed and opened to traffic in 1978. Geometry of the joints and crack features are described in detail. Experimental data obtained in the past by testing the welded joints under constant stress amplitude are compared with theoretical predictions based on Linear Elastic Fracture Mechanics. It was found that lack of penetration zones of 2–3 mm resulted in low fatigue strength of the butt welded joints.