Ultrasonic Detecting Method and Repair Technology Based on Fatigue Crack Features in Steel Box Girder

The ultrasonic detecting method and repair technology based on fatigue crack features in steel box girder are addressed in this paper. Based on the fatigue crack features in steel box girder, standard specimens with different crack features which primarily include length, width, depth, angle and location, were manufactured in the laboratory. Cracks were detected using ultrasonic techniques (UT). Through the analysis of flaw echo parameters, some methods to detect crack features are proposed. The K-value method is used to distinguish crack locations, which start from the weld toe, weld root, and the invisible parts in the U-rib. A new method, namely the one-third-length measurement method concerning the crack angle and position, is proposed based on the test results. An inclined hole is applied to stop the extension of the inclined cracks according to the detection results. Its performance was analyzed using the finite-element method, which showed that the inclined hole could reduce stress concentration effectively and has better stress distribution than the normal vertical stop holes.