Multi-scale deformation monitoring and characterization of large-span railway bridge by joint satellite/ground-based InSAR and BDS

Combining various monitoring technologies for deformation monitoring of large-span railway bridge helps to gain a comprehensive understanding of the bridge’s dynamic characteristics and deformation characteristics. This paper proposes a joint satellite/ground-based InSAR (Interferometric Synthetic Aperture Radar) and BDS (Beidou Navigation Satellite System) method for the deformation monitoring and analysis of large-span railway bridges. Initially, the satellite-based InSAR is employed to conduct large-scale and long-term deformation monitoring of the Ganjiang Super Bridge. Time series deformation is then analyzed using ESMD (extreme-point symmetric mode decomposition). Following that, ground-based radar interferometry and BDS are employed for small-scale and high-frequency deformation monitoring of critical structural points on the bridge. Lastly, time series deformation and spectral analysis are used to summarize the dynamic characteristics of the bridge. The following conclusions are obtained based on the study: (1) From June 2021 to August 2023, InSAR monitoring results indicated relatively substantial subsidence on the bridge east side, likely due to sediment accumulation; ESMD deformation decomposition revealed a 160-day deformation periodicity and multiple mutations. (2) By comparing the deformation of adjacent points using ground radar interferometry and BDS, it is found that the deformation trends in their monitoring results are relatively similar; both methods excellently capture significant deformation data. (3) BDS monitoring results are related to bridge structural components and force transmission direction; ground-based radar interferometry results are influenced by the bridge structure and external forces; the natural frequency of the Ganjiang Super Bridge is 0.54 Hz.