Research Of Condition Assessment Of High Speed Railway Bridge Based On Dynamic Interaction Of The Coupled Train And Bridge

High speed Railway Bridge is an important part of high speed railway, with theconstant rising of speed and loads, its operation state attracts much attention duringlong-term serving. In normal operation of high speed railway bridge structure, it iseasy to cause the stiffness degradation of beam by multi-stage variable amplitudefatigue loads, reinforcement corrosion, concrete carbonation, chloride ion erosion,prestressed reinforcement stress corrosion and other reasons. These factors cannotsignificantly damage the strength of the bridge structure, but for the long-termperformance, especially for the operation safety of high speed trains, it has vitaleffects. On account of the above consideration, according to the characteristics ofhigh speed railway bridge structure, this paper analyzes of the dynamic responsedata of bridge and put forward a condition assessment method for small and mediumspan high-speed railway bridge based on bridge health monitoring system.Firstly, this paper sets forth and analyzes the train-track-bridge dynamics theory,and establishes the train-track-bridge simulation model using its mechanicalinteraction relations. Through the design of bridge health monitoring system and thearrangements of sensors on bridge span, when the trains are driving on the bridge, itcan obtain the original strain response data which is used for the conditionassessment of bridge.Next, after obtaining the bridge strain response data, bridge conditionassessment indicators of bridge can be detected. In this paper, two indicators aredetermined, which are respectively natural frequency and vertical deflection. Naturefrequency can be obtained by analyzing the strain response data in somemathematical methods, such as Fourier transform. Vertical deflection can be got byconversion using the relationship between strain and displacement derived in thispaper. If the indicators of bridge are bigger than the specifications stipulated value,the bridge maybe damaged, it needs immediately further analyze the collected dataand undertake artificial bridge detection. If the indicators of bridge are smaller thanthe specifications stipulated value, it still needs to do routine analysis of theresponse data.Last, for the routine analysis of bridge in a safe state, its nature is to analyze thestiffness degradation of bridge. According to the analysis, this paper presents astrain difference method to locate the position of stiffness degradation, and definesthe identified fingerprint by combined Frequency Domain Decomposition with Freemodel of the strain modal identification method to identify the degree of stiffnessdegradation. In order to verify the locate method and identified method are useful, this paper simulates twelve different working conditions to analyze, the analysisresults mainly agree with the simulated situation, which prove the effectiveness ofthis method.The condition assessment of high speed railway bridge which is based on thebridge health monitoring system put forward by this paper has the features of simple,economic, rapid, accurate and effective. If wanted to apply the method in practicalengineering, it should note that different bridges need specific analysis according tothe actual situation.