Dynamic Modal Identification of a Long-Span Suspension Bridge Using Measured Acceleration Data during a Storm

This paper presents a dynamic modal identification of the Fatih Sultan Mehmet (FSM) Bridge utilizing structural health monitoring (SHM) data recorded during a recent extreme wind event (maximum wind speed: 130 km/h) that occurred on November 29-30, 2021, to provide a preliminary report for future posthazard health assessments for similar long-span suspension bridges. First, four different operational modal analysis (OMA) techniques are performed to identify the bridge's modal parameters (modal frequencies, damping ratios, and modal shapes). The analysis results are compared with each estimator and those of an experimental investigation published in the literature to verify the bridge's modal parameters. Secondly, natural frequency history and damage indicators are determined using the modal parameters and estimated standard deviations obtained from the stochastic subspace identification with extended unweighted principal component (SSI-UPCX) technique. The result of modal damage indicators reveals a healthy structure after this extreme wind event; onsite visual inspections also support this finding. In conclusion, it is believed that these significant findings will lend invaluable knowledge to stakeholders.