Static and dynamic fiber optic strain monitoring of ferry quays

In many coastal areas, ferry terminals serve as essential links where fixed crossings like bridges or subsea tunnels are impractical. Exposed to saltwater, waves, and constant berthing operations, these structures can experience rapid degradation. Hence, from a health monitoring perspective, it is desirable to estimate the ferry impact loading and detect occurring damage in early stages. Typical damage mechanisms include overloading events that may cause sudden local damage, as well as fatigue and corrosion that lead to gradual deterioration. To this end, a permanent structural-health-monitoring system was installed in September 2025 on the Magerholm ferry quay in Norway, comprising 37 distributed Fiber Bragg Grating (FBG) strain sensors. This system complements an existing acceleration-based monitoring setup, providing additional insight into the local structural behavior and load transfer mechanisms. Operational strains are recorded before, during, and after every ferry passage. The strain signals are processed in two different ways. First, the quasi-static strain signals are used, combined with a finite element model, to improve the estimation of the berthing location and impact load. The monitoring data is used to calibrate this model, thereby reducing uncertainties, particularly those related to the boundary conditions. Second, an automated operational modal analysis process infers natural frequencies and strain mode shapes from the dynamic strain measurements. It is investigated whether these modal characteristics allow for the detection and localization of potential damage. This paper introduces the monitoring concept, sensor layout, and data-processing workflow, and reports initial findings from the ongoing campaign.