Research On The Evaluation Method Of The Safe State For The Steel-truss Arch High-speed Railway Bridge

The long-span high-speed railway bridges are the control nodes of the China railway network.The steel-truss arch bridge has become a generally-used structural type for long-span multitrack high-speed railway bridges due to its large stiffness,smooth and beautiful lines of arch,and good capability in span.The long-term behavior and service state of the bridge structure during operation not only reflect the safety of the bridge itself,but also the safety and stability of the trains running on bridges.This doctoral dissertation takes a typical bridge on the BeijingShanghai high-speed railway which crosses the Changjiang River,the Nanjing Dashengguan Yangtze River Bridge,as the engineering background.The whole dissertation integrates various technologies in signal processing,probability and statistics,finite element numerical simulation,machine learning,and operational research.The real-time/long-term behaviors of bridge members under the effects of in-service loads(temperature,vehicle)are analyzed,the early warning method of vehicle–bridge system is developed,and the evaluation method of the service state of bridge structure is established.The work scope and main achievements of this dissertation are as follows:(1)Based on the strain monitoring data of the bridge during operation,the feature parameters of the vehicle-induced strain of the main components such as steel trusses are analyzed and evaluated.A new adaptive finite impulse response filter was developed to obtain the strain influence line and the strain dynamic amplification factor for a various of bridge members.The correlation between the strain influence line and temperature,and correlation between the strain dynamic amplification factor and train speed are established.Using the numerical simulation method of the finite element,the transverse dynamic-static displacement and the displacement dynamic amplification factor of the hangers under the effects of high-speed trains are obtained by nonlinear dynamic analysis.The characteristics of the dynamic response of the rigid hanger under the high-speed trains are analyzed and evaluated.(2)Based on the bridge monitoring data and the numerical analysis results,the vibration performance of the vehicle–bridge system under the effects of single /multiple high-speed trains is evaluated.Via multiple sensors of the structural health monitoring system,the train loadingcases of girder vibration responses are obtained.According to the correlation between train speed and bridge acceleration under each loading-case of the single-train: the girder acceleration amplitude of the long-span multi-track railway bridge will have obvious peak value at one or more train speeds,the early-warning method of train–bridge vibration performance is developed using the wavelet packet decomposition and the interval estimation theory.Furthermore,the train–rail–bridge dynamics model is established,and the transverse and vertical vibration characteristics of the vehicle–bridge system(acceleration of the girder,train running parameters)under the multi-trains loading-cases are analyzed.The control indexes of train running parameters under multi-trains loading-cases are presented.(3)Based on the bridge monitoring system and the finite element numerical simulation,the early-warning and evaluation methods are developed for the girder displacement during the bridge operation.The temperature-induced/train-induced deflections of the bridge girder are obtained by the wavelet transform.The principal components of the bridge temperature field are obtained using the principal component analysis.The effect of the temperature-induced girder deformation on the train-induced girder deflections is analyzed using the train-bridge dynamic model.The statistical laws of the downward and upward of the train-induced girder deflections are described using the t location-scale distribution.Based on the above processes,the warning threshold of girder deflections under the coupling effects of temperature and trains can be determined finally.Driven by the longitudinal displacement monitoring data of the bridge,the longitudinal displacement behavior of the girder system of the bridge during operation is evaluated.The fatigue of expansion device and the reliability of crossing train under the effects of the relative transverse displacement are studied and analyzed using the three-dimensional finite element model of the expansion device of girder end.(4)Based on the big monitoring data from the structural health monitoring system of the steel-truss arch high-speed railway bridge,the calculation methods of the failure-risk score,the safety/availability score,and the maintenance score for each single-response monitoring item(about each corresponding member)are developed using the reliability,availability,maintainability and safety(RAMS)theory.The weights of the performance items and the single-response monitoring items in all evaluation levels are obtained using the analytic hierarchy process.Finally,the comprehensive service state of the whole structure of bridge can be evaluated.