A lot of fatigue cracks have been repo巾d in welded joints between steel deck plates and vertical stiffeners of orthotropic steel deck under severe traffic load. The crack occurs at the boxing weld toe and extends to deck plate. lt is difficult to detect the crack when its tip exists along the weld toe. This fact means that it is desirable to develop the applicable method for this part in spite of the presence of the crack. In this study，in order to make clear the effect of ultrasonic impact treatment (UIT) against small fatigue crack along the weld toe， fatigue tests have been performed o n sma ll size sp ecimens modeling the w eld ed joi nts between deck plates and vertical stiffeners.
