Abstract
In this study, we studied the fatigue strength of sleeper supports, which are attached to upper flange of open floor type steel railway bridges with uneven leg length type fillet welding and receives direct vertical load. We used the method of crack investigation on actual bridges and fatigue test. Results tell us that fatigue cracks always propagate from weld root area at transverse fillet weld and the main cause will be bending stress on the girder. Also, the result of fatigue tests clarified that fatigue strength without direct vertical load will be level F, but with direct vertical load, or without sufficient leg length, it doesn't reach the level F, and the fatigue strength of actual bridges can be even below this level.
