Dynamic Response of the Magerholm Ferry Quay During Storm Ingunn

Ferry quays are essential maritime structures in coastal transport networks, yet full-scale measurements of their behaviour during extreme environmental events remain rare. This paper presents the dynamic response of the linkspan of the Magerholm ferry quay during Storm Ingunn on 31 January 2024, when the structure became submerged, and ferry operations were interrupted. The quay had been instrumented as part of an ongoing structural health monitoring programme, enabling acceleration responses to be recorded before, during, and after the event. The recorded data are analysed using temporal moment analysis, time--frequency analysis, and operational modal analysis to investigate changes in signal energy, excitation characteristics, and modal properties. The results show that, before submergence, the horizontal response is correlated with wind gusts and influenced by ferry docking events, whereas after submergence, the response becomes dominated by sustained wave excitation. The spectrograms clearly capture the transition from an intermittent, broadband, impact-driven response to persistent, low-frequency, wave-driven loading. Modal identification indicates that the first global modes remain broadly unchanged after the event, suggesting that the observed damage is not primarily global in nature. The study demonstrates the value of continuous monitoring in detecting serviceability-level failure and improving understanding of structural response during extreme coastal storms.