Strain measurements of orthotropic steel deck in steel box girder, Yahagigawa Bridge, were carried out in May and August 2011. The thickness of deck plate is mainly 12mm. However, partially deck plate of 16mm thickness is used near the end of bridge because of the reinforcement against the impact loads. Furthermore, ICR treatment for improving the fatigue strength of welded joint between vertical stiffener end in diaphragm and deck plate was carried out in this bridge. Therefore, strain measurements focused on the welded joints between vertical stiffener and deck plate and between deck plates of 12mm and 16mm in thickness and trapezoidal ribs. Equivalent stresses of deck plate near the vertical stiffener end and deck plate of 12mm thickness measured in August were higher than that measured in May. Equivalent stress of 12mm deck plate was higher than that of 16mm deck plate in both seasons.
