Strain Mode Of Long-span Suspension Bridge Considering Temperature Effect Parameter Identification

With the rapid development of China’s transportation network,bridges have become an indispensable link in the construction of highways and railways.However,due to the longterm exposure of the bridge structure to the complex natural environment,the data collected by the sensor is affected by various environmental factors,of which the temperature factor has the most significant impact on the vibration characteristics of the bridge structure.At the same time,the identification of strain modal parameters that are more sensitive to structural state changes has also been gradually paid attention.However,the existing research on temperature effects and strain modal parameter identification still has certain limitations,so the identification of strain modal parameters considering temperature effects is carried out Research,the main work of the paper includes:1)Summarize the related research and existing research limitations of modal parameter identification,strain modal analysis methods and the effect of temperature on the dynamic characteristics of the structure,and use this to determine the research objectives and main research content.2)Briefly introduced the composition of the strain and temperature monitoring system of a long-span suspension bridge,and comparatively analyzed the change law of environmental temperature,structural temperature and strain data in a long period of time.It is found that the measured strain data of the bridge is very susceptible to changes in temperature and has a significant positive correlation with the temperature data.The slope of the fitted linear equation changes with the change of seasonal temperature.3)Separate the temperature effect of the simulated data and the measured strain data by the frequency domain separation method of Hilbert marginal spectrum and Fre ?chet distance and the time domain separation method based on linear regression equation,and use the exploratory data analysis method for the processed data To judge and filter effective data.The results show that the separation method in the frequency domain can more thoroughly separate the temperature effect components in the strain data.4)The theory of strain mode response,strain mode of truss structure,random subspace of strain mode,etc.are derived in detail.It is proved that the axial strain of the element represented by the node displacement can be orthogonally decomposed into any two vertical strain components,and the covariance random subspace modal identification method of the strain mode is verified by the simple supported truss beam finite element model The effectiveness of the method is summarized to summarize the modal identification method of the axial strain data of the truss members.5)The covariance random subspace method is used to identify the strain modal parameters of the strain data of a long-span suspension bridge to separate the temperature effect,and the frequency and corresponding vibration mode are obtained.The results show that the effective dynamic strain data modal obtained by the temperature effect method in the frequency domain The parameter identification result is better.The study of the relationship between the frequency and temperature of the temperature data without separation at different time scales shows that there is no significant correlation between the frequency change of the main beam of the bridge and the temperature fluctuation,but the temperature fluctuation has a greater impact on the frequency change of each order of the main beam,and the lower order The higher-order frequency of frequency change amplitude is more sensitive to temperature,so it is necessary to separate the temperature effect on the original strain data.