Analysis In Dynamic Deformation Of Long Span Bridges Based On RTK-GNSS And Accelerometer Technology

Long-span bridge structure in service are highly susceptible to the influence of environmental factors such as wind load,traffic load and earthquake load,which may even damage the bridge.Thus,in order to ensure the safety and stability of bridges,it is necessary to adopt reasonable and effective monitoring technology to obtain dynamic response information of bridges under environmental load.In this paper,RTK-GNSS and accelerometer are used together to monitor the dynamic response information of the bridge.The main research work and innovation include the following points:(1)A combining filtering method based on wavelet packet decomposition(WPD)and ensemble empirical mode decomposition(EEMD)is proposed.Root mean square value(RMS)and signal to noise ratio(SNR)were used as two indicators to evaluate the signal de-noising effect.The results show that the method can effectively eliminate the noise,the root mean square planting is reduced from 1.3484 to 0.6610,and the signal-to-noise ratio is changed from 10 to 13.9756.(2)RTK-GNSS technology was used to monitor the dynamic displacement information of the Tianjin Fumin bridge.WPDEEMD method was used to process the measured data,the results show that this method can effectively suppress GNSS multipath effect error.At the same time,in order to eliminate the random errors in the monitoring process,the moving average filter method(MAF)was used to further process the measured data after noise reduction.Finally,the dynamic displacement and modal frequency of the Fumin bridge was successfully identified,which is consistent with the finite element model.(3)RTK-GNSS and accelerometer were used together to acquire the dynamic response information of the Tianjin Yonghe bridge under environmental load.The combining filtering method(WPDEEMD+MAF)was adopted to process the measured data,and the dynamic displacement and acceleration were obtained successfully.The acceleration frequency-domain integration algorithm was proposed to reconstruct the corresponding displacement signal.The results indicates that the frequency-domain integration algorithm can avoid integrating trend term.At the same time,the accelerometer monitoring technology also verified the accuracy of RTK-GNSS monitoring technology.(4)This paper adopted the fast Fourier transform and ITD algorithm to identify the modal parameters from GNSS monitoring data and accelerometer monitoring data.The natural vibration frequencies of the bridge were successfully obtained.(5)In order to compare with the measured results,the finite element model of the Yonghe bridge was established and the natural frequencies of bridge were obtained.The results showed that the results from GNSS monitoring data were basically the same as results from accelerometer monitoring data,the difference ratio between the two was less than 1%.The natural frequency obtained by the finite element model was also in good agreement with the natural frequency obtained by the accelerometer monitoring data,and the difference ratio was less than 5%.