Application Of GB-InSAR Technology In Dynamic Detection Of Bridge

The change of wind,traffic load,temperature,earthquake will cause vibration and dynamic deformation of railway bridges,which seriously affect not only the passengers' comfort,but also the safe operation of the train.In recent years,with the rapid development of high-speed railways,a large number of high-speed railway bridges have been built in China.In order to guarantee the safety of the bridge operation,it is of necessity to acquire the vibration parameters of the measured bridges for the bridge operation detection work.However,It is difficult to achieve good measurement by the commonly used instrument.Ground-based InSAR(GB-InSAR),using stepped frequency-continuous wave technique,synthetic aperture radar and interferometric measurement technique,can undertake high frequency dynamic measurement,especially suitable for dynamic detection of bridge.This paper studies the application of GB-InSAR technology in dynamic detection of bridge.Compared with the common deformation detection technology,GB-InSAR has obvious technical superiority and application value.Combining of IBIS system,one of the GB-InSAR system developed in Florence University.This paper concludes the research status of GB-InSAR as well as the application examples of IBIS system at home and abroad,and summarizes three key technologies of GB-InSAR.To investigate the measurement accuracy of the microwave radar,the slow deformation accuracy test was designed and the research of the influence of angle observation error to observation accuracy was conducted.Slow deformation accuracy test,using the dynamic detection of IBIS-S system towards the combination of micrometer and corner reflector,shows that the dynamic measurement accuracy can reach to the submillimeter level and IBIS-S system can accurately detect tiny changes of the target.Aiming at the effects of angle observation error to its accuracy,this paper derives the error calculation model of RMSE in relation to horizontal displacement and vertical displacement,analyzing the influence of angle observation error to the abservation accuracy,which comes to a meaningful conclusion.Dynamic detection of high-speed railway shows that atmospheric factors has a great influence on microwave measurment.This paper deeply analyzes the meteorological parameter correction method and the selection of stable point correction method.On that basis,study the influence of atmospheric factors towards the IBIS-S system dynamic measurement accuracy by using Luneberg ball and corner reflector.The results show that the selection of stable point correction method can eliminate some influence of atmospheric factors and improve the measurment accuracy of IBIS-S system dynamic detection.The calculation model of horizontal displacement and vertical displacement are deduced because both of them are needed but only the displacement in rang direction can be obtained by IBIS-S system.The model can also be applied to analyze dynamic detection of bridge and noise barrier.This paper draws the rule of the bridges' dynamic change when the train passing by studying the dynamic detection of 1/4 beam vertical displacement of high-speed railway continuous girder and 1/2 beam horizontal displacement of simply supported box girder through IBIB-S system,which provides scientifical and reliable data to safety detection and assessment of bridges' structures.When the train passing by high speed,the change of weight,wind load and impulsive pressure will cause vibration and deformation of noise barrier.The flexibility of noise barriers' structures is an important content to the traffic safety.Therefore,this paper studies the dynamic detection of horizontal displacement of noise barrier in a high-speed railway and analyzes the results,discussing the feasibility of the application of IBIS-S system in dynamic detection of noise barrier.The traditional Fourier transform and wavelet analysis can not accurately analyze the signals in bridge detection data sequence,which shows the characteristics of nonlinear and nonstationary,but Hilbert Huang Transform(HHT)is suitable for nonlinear and nonstationary signal analysis.Therefore,this paper studies the application of the HHT in dynamic detection of bridge,analyzing the two steps of the HHT method: Empirical Mode Decomposition and Hilbert transform and briefly illustrating the advantages and disadvantages of HHT method.The bridge vibration data from IBIS-S system dynamic detection carries on HHT by using of MATLAB(a programming language).The analysis of data shows that when the train passing,the instantaneous frequency of Intrinsic Mode Function will have an obvious mutation.This results show that HHT can be applied to analyze the nonlinear and nonstationary signals of bridge.The feasibility of the application of dynamic detection data collected by GB-InSAR for bridge structure safety analysis is discussed further.