Damage Identification Of Elastic Fastener Of Ballastless Track Based On Bayesian Method Via Vibration Measurement

With China to further accelerate the construction of high-speed rail network in recent years,high-speed railway has become a "business card" of China,by the end of 2020,China’s high-speed railway mileage reached 37900 kilometers,making China to be the No.1in the world.Fastener system is an important part to keep safety operation of high-speed railway,and the railway bears the repeated high-speed train load,whose elasticity and adjustment of geometric error is almost all provided by the fastener system.In recent years,due to the continuous increase in the volume of high-speed railway transportation in China and the frequency of use,it has become more and more common for elastic fasteners to be damaged and loosen under the long-term action of high-strength and high-frequency train loads.If the looseness of fasteners is not timely dealt with,and it will cause damage to the track structure,even cause traffic accidents.Many cities use traditional manual inspection methods for railway maintenance.This method has low efficiency and high rate of missed detection,and the working time is limited by the skylight time,which is no longer suitable for the development of railway tracks today.This thesis proposes a structural damage identification method based on the Bayesian approach via the measured vibration response,which can directly and effectively identify the damage location and extent of rail fasteners,and at the same time evaluate the uncertainty of the damage identification results.The method proposed in this thesis can provide a reference for the damage detection of similar structures,and provide the possibility for the health monitoring and early warning of the ballastless track structure fastener system.The main contents are listed as follows:(1)Firstly,the current research status of fastener damage identification and the development status of structural damage identification methods based on model updating are briefy introduced,and then a Bayesian based ballastless track fastener damage identification method via vibration measurement is proposeds.(2)Based on the initial undamaged ballastless track structure,a set of measured vibration data were used to update the model to construct a benchmark finite element model.On this basis,numerical simulation analysis is performed,and the most plausible value of the stiffness coefficient of the elastic fastener is calculated and then the damage of the fastener can be identified,the feasibility of the proposed method by setting different damage conditions is identified to study;by adding a certain level of Gaussian white noise to the acceleration response data,the robustness of the proposed method is studied,the damage recognition result of the location of the excitation point is further studied Impact.The results show that the greater the damage degree and the closer the hammering point is to the damage location,the more accurate the recognition results will be.The method has good robustness under different noise levels.(3)Based on the laboratory scale model of ballastless track structure,experimental verification work is carried out in this thesis.The damage identification parameters are analyzed for non-destructive,end damage,intermediate damage,continuous damage,interval damage and other types of working conditions,and the uncertainty analysis of the damage identification results of the model parameters is made through the posterior probability density function of the model parameters,the results show that the damage identification result under different working conditions are consistent with the predetermined damage conditions of the test,and the damage location and extent of the elastic fasteners can be identified more accurately.The probability distribution information of the model parameters provided at the same time shows that the uncertainty of the identification parameters under the test conditions is maintained at an acceptable level.