Time Synchronization And Modal Identification Of Civil Engineering Structural Health Monitoring Data

The application of structural health monitoring(SHM)systems in long-span bridges and super-tall buildings is increasingly valued by civil engineering circles at home and abroad.Among them,the synchronicity of the measurement data at different locations of a structure is essential to structural health monitoring.Sometimes,however,non-synchronicity may occur in them.The structural health monitoring system evaluates the performance and state of the structure based on the actual measured data.The asynchronization of the measured data will lead to the misidentification of modal parameters,and eventually lead to false damage alarm.In this thesis,the time synchronization and structural modal identification algorithm of measured data are studied by using the asynchronous acceleration data during ship collision of Jiangyin Bridge and the synchronous acceleration data of Canton Tower under ambient excitation.The contents and progress are as follows:1.In terms of the asynchronicity issue of the multiple sensor data,a new time synchronization algorithm of the extended frequency domain method is studied and thereby proposed to identify the time delay of the measured asynchronous data.Making use of the mapping between a relative time lag in the time domain and a phase angle shift in the frequency domain,the relative time lag between either two outputs of a structure is determined by finding a mode where the actual phase angle between them is ideally zero and then calculating the perturbed phase angle that corresponds to the modal frequency of the selected mode.2.Making use of the mapping between a relative time lag in the time domain and a phase angle shift in the frequency domain,the relative time lag between either two outputs of a structure is determined by finding a mode where the actual phase angle between them is ideally zero and then calculating the perturbed phase angle that corresponds to the modal frequency of the selected mode.3.The recognition performance of two time domain time synchronization algorithms(difference sum of squares algorithm and correlation coefficient algorithm)and extended frequency domain algorithm are systematically compared.A stationarity test was performed on the measured time series.Among them,the feasibility and effectiveness of the three time synchronization algorithms in the case of known measured data as stationary data and non-stationary data are discussed in detail.