PSI - Issue 57

Qingyang Wei et al. / Procedia Structural Integrity 57 (2024) 262–270 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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1. Introduction The in-service steel bridges with orthotropic deck systems bear a large number of alternating loads during long term traffic pressure (Dudás et al (2015)). Accordingly, steel bridges are prone to occur fatigue cracks that reduce normal function and threaten the safety of the bridges. Timely and accurate detection of fatigue cracks is meaningful for taking maintenance and repairments in steel bridges. Among many detection methods of fatigue cracks, visual inspection, carried out by experienced engineers and inspectors, is the original and most common way (Turksezer et al (2021)). Then some non-destructive testing techniques, including acoustic emission testing, ultrasonic testing, and infrared thermal imaging, are employed for assisting the visual inspection (Nemati et al (2015), Sakagami et al (2017)). Recently, the combination of unmanned aerial vehicles and image-recognizing techniques are introduced to improve convenience and overcome the limitation of subjective judgment (Fu et al (2020), Dorafshan et al (2021)). The application of these new technologies makes the original visual inspection more efficient and objective, but specific tools and complex procedures are necessary. Damage detection method based on dynamic information, appealing with nondestructive and no requirement of redundant equipment, is also an important means for detecting fatigue cracks in structures (Xu et al (2016)). Dynamic detection methods have been developed from linear problems to nonlinear problems (Landauskas et al (2020)), and have been applied to different fields such as small mechanical rotors and large hydraulic dams (Wei et al (2023)). However, the application of dynamic detection methods on the fatigue cracks of steel bridges is seldom realized because typically fatigue cracks in steel bridges are small over the entire bridge, resulting in the dynamic parameters being insensitive to the fatigue cracks. Therefore, this study tries to develop sensitive features to minor fatigue cracks from the dynamic responses of steel bridges. This study is carried out on the numerical model of an existing steel bridge over the Danube River in Hungary. 2. The Türr Istvan Danube bridge

2.1. On-site inspection

The Türr Istvan bridge had been found with a totalof 19 fatigue cracks in an on-site inspection in 2018. The cracks were searched by close visual inspection assisted by a basket-type trolley. As shown in Fig. 1 (a), all the cracks appeared in the welding zones between the longitudinal flanges and vertical ribs of cross girders.

Fig. 1. (a) Distant view of crack location; (b) local view of a typical crack; (c) crack penetration test.