GNSS-based Real-time Vibration Monitoring and Dynamic Response Analysis of a Long-span Suspension Bridge During an Extreme Typhoon Event
The structural health monitoring system for long-span bridges provides important parameter information and a decision basis for bridge modal identification,damage detection,and safety assessments.Traditional methods such as accelerometers,computer vision,and fiber-optic sensors suffer from various issues such as inaccurate displacement measurements,susceptibility to external conditions,and limited capture of local variables.To address these challenges,the authors constructed a new method for monitoring the real-time vibration of large suspension bridges using the Global Navigation Satellite System(GNSS)and improving the empirical wavelet transform(EWT)for structural dynamic response analyses.The application of the deformation monitoring system GeoSHM for the Forth Road Bridge in Scotland based on the use of GNSS receivers,accelerometers,and wind speed sensors since 2014,realized high-precision,fully automatic,all-weather,and three-dimensional real-time monitoring of the bridge towers and main beams.The frequency band division method-based on the improved covariance autoregressive power spectrum-and the effective intrinsic mode function screening criterion of the Pearson correlation coefficient were established,and the improved EWT algorithm was proposed to perform noise reduction filtering and displacement decomposition to realize dynamic response analyses of the vibration responses of wind-induced bridges.Analysis of GNSS monitoring data during storm Ciara in February 2020 revealed that the maximum amplitude of the longitudinal vibration displacement of the cable tower was 7.91 cm,and the dynamic displacement was 2.84 cm.The modal frequencies identified by GNSS receivers on the two bridge towers were in good agreement,and there was a positive correlation between wind speed and the tower's horizontal displacement.The horizontal displacement of the cable tower increased considerably along the wind direction.The maximum amplitudes of the three-dimensional(longitudinal,lateral,and vertical)vibration displacement of the main beam were 5.51 cm,152.47 cm,and 68.17 cm,respectively.The maximum amplitudes of the dynamic displacement were 3.73 cm,31.93 cm,and 54.22 cm;these values are consistent with the dynamic displacement and vibration frequency results identified by the accelerometer.The wind speed is also positively correlated with the three-dimensional displacement of the main beam.The lateral,typhoon-induced vibration was the largest and the trend of lateral displacement increased as a function of wind speed.The research results demonstrate that the constructed GNSS monitoring technology and improved EWT data processing method can achieve real-time monitoring and dynamic response analysis of wind-induced vibrations in super-large bridge structures with significant scientific and engineering im-plications.