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

<p>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.</p><p>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.</p>

Rock mass property evaluation based on the borehole wall images taken by using an ultrasonic scanner (USS)

Discontinuities, such as faults and fractures exist even in Neogene soft sedimentary rocks. These discontinuities play an important role for determination of physical, mechanical and hydraulic properties of rock mass. For geological disposal of high-level radioactive waste, these data should be obtained for designs of the layout of repository, engineered barrier system and safety assessment. Rock mass properties are important information for quantitative rock mass classification as well as for design and construction of underground facilities and assessment of safe waste disposal. Ultrasonic wave reflection intensity of the wall of the borehole drilled from bottom of East Access Shaft in Horonobe Underground Research Laboratory Center, Hokkaido, Japan, was obtained by using the ultrasonic scanner (USS). In this paper, we compared results of USS observation with core logging data including the core observation, the optical digital scanner (ODS) observation, and result of Needle Penetration Index (NPI) tests. These results indicated that ultrasonic wave reflection intensity had a good correlation with other observation results, and USS observation and NPI test are useful techniques for the determination of the detailed rock mass classification.