Detection of Through-Deck Type Fatigue Cracks in Steel Bridges by Self-Reference Lock-in Thermography

Abstract

Abstract.A new remote nondestructive inspection technique, based on thermoelastic temperature measurement by infrared thermography, is developed for detection and evaluation of fatigue cracks propagating from welded joints in steel bridges. Fatigue cracks are detected from localized high thermoelastic temperature change at crack tips due to stress singularity under variable loading from traffics on the bridge. Selfreference lock-in data processing technique is developed for the improvement of signal/noise ratio in the crack detection process. The technique makes it possible to perform correlation processing without an external reference signal. It is very difficult to detect through-deck type fatigue cracks in steel decks by the conventional NDT technique, since they are not open to the inspection. In this paper, self-reference lock-in thermography is applied for detection of through-deck type fatigue cracks. Experiments are carried out to steel deck sample, which simulates an actual steel bridge, during crack propagation test. It is found that significant stress concentration zone can be observed near the crack front, which enabled us to detect through-deck type fatigue cracks and to estimate its size.

Remote nondestructive evaluation technique using infrared thermography for fatigue cracks in steel bridges

“…Another experiment was conducted to test the effectiveness of through‐deck fatigue crack detection in a steel deck specimen subjected to a travelling wheel load, as shown in Fig. .…”

“…Results of detection of through‐deck fatigue cracks using self‐reference lock‐in thermography in travelling wheel load test …”

“…23 Illustration of the travelling wheel load test and the configurations of employed specimen. 76 12 mm. The dimensions of the trough rib cross sections were indicated as U320 × 240 × 6; that is, the top width, height and thickness were 320, 240 and 6 mm, respectively.…”

“…Moreover, it was confirmed that the significant stress concentration zone that appeared on the deck-torib weld line indicates a possibility for the estimation of the location of the crack front and the half crack length of the semi-elliptical crack. Another experiment 76 was conducted to test the effectiveness of through-deck fatigue crack detection in a steel deck specimen subjected to a travelling wheel load, as shown in Fig. 23.…”

Applicability analysis of active IR thermography and selected signal processing methods for technical conditions assessment of bridge elements

“…An investigation procedure to study masonry arch bridges, including two in-situ NDT methods and numerical analysis, is presented in [1]. Advanced experiments in detection of through-deck type fatigue cracks in a steel deck, using lock-in thermography, under point load and traveling wheel load is shown in [4]. The use, comparison and combination of two NDT methods (impact-echo and IRT) to detection of simulated delaminations and cracking defects in full-scale reinforced concrete bridge deck model are described in [5].…”