Research On Dynamic Properties And Early Warning Of Long Span High Speed Railway Bridges

During the operation period of high-speed railway bridge,it has been affected by various environmental factors and operation factors for a long time.The safety and durability of bridge structure have been widely concerned at home and abroad.For the long-span steel truss bridge,when the high-speed train is the main load,the static and dynamic performance of the bridge structure is different from that of the ordinary simply supported railway bridge.The specific research contents of this paper are as follows:Time domain analysis of acceleration response.For the acceleration peak value and root mean square value index,the correlation of adjacent sensor signals is analyzed.For different working conditions,the statistical characteristics of acceleration response are determined,and the influences of train route,train formation,temperature and train speed on vibration response are analyzed.The peak acceleration velocity amplitude curve is studied when the train length is close to the bridge length,and the resonance characteristics of Long-span Railway Bridge are analyzed.Time frequency domain analysis of acceleration response.The loading frequency of train passing bridge is studied;The time-frequency analysis method and frequency-domain analysis method are compared and analyzed.The wavelet ridge algorithm is used to obtain the ridge line with the maximum energy in frequency domain when the train crosses the bridge,and the change trend of loaded frequency in the forced vibration stage is obtained.The time-frequency diagram of Hilbert normalized signal can further reflect the variation trend of on load frequency with time.Long term safety warning based on acceleration response.Comparing the probability estimation threshold calculation method with interval estimation threshold calculation method,the interval estimation method is selected to establish the long-term safety early warning model.The time series analysis and multivariate statistical technology are combined to establish the damage eigenvalue index,and the Mahalanobis distance is used for multi-sensor information fusion to establish the benchmark model of damage identification.Through this study,the characteristics of acceleration vibration response in time domain and time-frequency domain can be obtained,and the structural safety early warning model and benchmark model in the long-term operation process can be established,which provides a reference for structural safety assessment.