GNSS dynamic monitoring and time-frequency feature analysis in structural seismic response assessment

This study investigates GNSS (Global Navigation Satellite System) dynamic monitoring for assessing structural seismic damage. Initially, vibration table experiments were designed to simulate structural seismic response, in which structural response signals were collected by GNSS. The FFT+NTFT (Fast Fourier Transform and Normal Time-Frequency Transform) method was utilised to extract the signal’s time-frequency features and the maximum relative errors of calculation results are 4.90%, verifying the GNSS dynamic monitoring accuracy. Subsequently, the study utilised the GNSS dynamic monitoring data from the Su-Tong Bridge during the Hengchun earthquake. The response of the structural vibration with an amplitude of approximately 5 mm was extracted by comparing the spectral variation characteristics of the monitoring data before and after two consecutive earthquake excitations. The vibration response signal frequencies for the two earthquake excitations were found to be 0.1564 Hz and 0.1553 Hz, respectively. The structural vibration response time was found to be 8.0 minutes and 9.5 minutes, respectively. The research results demonstrate that leveraging the advantages of GNSS dynamic monitoring for rapid acquisition of structural seismic response signals, combined with time-frequency characteristic analysis of the signals, enables prompt assessment of structural damage and determination of remaining load-bearing capacity, thereby providing crucial reference bases for emergency decision-making.