Investigation and Diagnosis of Fatigue Cracks of Rib-to-Deck Welded Joints in Orthotropic Decks by the Phased Array Ultrasonic Scanner

Over the last decade, fatigue cracks have been observed at the rib-to-deck welded joints in many orthotropic decks in Japan. Considering the fatigue cracks can cause pavement damage and thus compromise transportation safety, it is necessary to detect and repair it at the early stage of its development. But the cracks occur from the weld route, it cannot be detected in early stage by visual check. Therefore, the phased array ultrasonic scanner (PAUS) has been developed as the method which can detect and measure the cracks with small size. And, it can simultaneously investigates the deck propagation type cracks and the weld bead propagation type cracks.

In this study, we propose a diagnosis method which considered the relation with selected countermeasures based on technological knowledge. And we propose an investigation area selecting method based on investigation speed of the PAUS which is confirmed by trial on the real bridge. In addition, the cost advantage by using the PAUS is estimated.