Abstract
Over the last decade, fatigue cracks have been observed at welded joints between trapezoidal ribs and deck plates in many orthotropic steel deck bridges in Japan. Considering a fatigue crack at rib-to-deck welded joints can cause pavement damage and thus compromise transportation safety, it is necessary to detect and repair it at the early stage of its development.
This paper presents the accuracy of crack sizing with an electrically driven phased array ultrasonic scanner (PAUT scanner) developed for inspection of rib-to-deck welded joints in orthotropic steel decks. The PAUT scanner simultaneously examines a deck plate and a weld bead into either of which cracks propagate from a weld root. Moreover, it can detect the cracks as remained in the steel members.
In this research, firstly an internal crack is induced at rib-to-deck welded joints by using a plate bending fatigue testing machine where crack sizes are controlled by monitoring stresses at regions closed to weld beads. Subsequently, the joints are inspected with the PAUT scanner. Appropriate sizing methods are determined for the crack going through a deck plate and a weld bead, respectively, and the accuracy of crack sizing is evaluated by comparing with real cracks on the joints. In addition, the influence of paint coatings on the accuracy in crack sizing is examined. As a result of these investigation, it is demonstrated that the PAUT scanner has enough crack sizing performance.
