Fatigue Performance Analysis of Welded T-Joints in Orthotropic Steel Bridge Decks with Ultrasonic Impact Treatment

This study aims to assess the effect of ultrasonic impact treatment (UIT) on the exterior weld seam of S355J2 T-joints used in orthotropic steel bridge decks. The microstructure and mechanical behavior of T-joints after UIT was investigated in this study. Fatigue tests of T-joints before and after UIT were performed. The stress concentration at the interior and exterior weld toe of T-joints was considered using the traction structural stress method. The results showed that hardness increases by 10% due to the localized grain refinement caused by UIT. UIT significantly improves the fatigue life of T-joint specimens by 350% and 150% at stress ratios of 0.1 and 0.3, respectively. As the transition angle between the weld profile and the base metal profile increases, the stress concentration factor decreases.