Study of Improvement of Fatigue Strength on Connection of Stiffening Members Considering Automatic Welding

In recent years, the orthotropic steel deck bridges have been constructed at many places due to numerous merits. And the automatic fabrication of them have been forwarded. However, a noticeable increase in recent heavy through traffic has accelerated the fatigue damages at the connections between longitudinal and crossing member due to the existense of slits. In order to improve the fatigue strength of them considering automatic welding, F.E.M. analysis and large scale fatigue testing were carried out. As the results of this study shows, the details of the slit can be improved considering automatic welding and improvement of fatigue strength. (1) The upper width of slit is narrower than ordinary shape. (2) The upper scallop can be removed. (3) Boxing weld between upper flange and web can be removed. (4) The fillet weld between longitudinal rib and web plate is stopped about 20 mm before the web edge. (5) The fillet welds between longitudinal rib and upper flange should precede the other welds.