Monitoring of Crack Flank Movement in a Steel Orthotropic Deck

Abstract Fatigue cracking is a common issue in steel orthotropic bridge decks subjected to long-term dynamic loading. When repairs are required, especially by welding, it is typically necessary to close the bridge to traffic to ensure proper weld quality. However, bridge closures can lead to significant societal and economic impacts, including traffic congestion, long detours, increased emissions, and loss of time. Therefore, the ability to carry out repair welding without full traffic closure is of considerable interest for infrastructure operators and public authorities. The first essential step in enabling such in-service repair is to assess the dynamic behaviour of existing fatigue cracks under traffic loads. Specifically, it is crucial to monitor the crack flank movements to determine whether they remain within acceptable limits during ongoing traffic, thereby permitting welding without compromising the repair quality. This paper presents the development and deployment of a specialized monitoring system designed to measure crack flank displacements in real time. Crack flank movement amplitudes and frequency responses were recorded and analysed. Measured data were compared with results from similar monitoring campaigns conducted in other countries.