Study On Hybrid Prediction Model Of Train-Induced Environmental Vibration Considering Random Characteristics Of Vibration Source

The objective contradiction between the huge urban traffic demand and the noteworthy environmental vibration impact has become a bottleneck factor restricting the development of urban rail transit.In order to minimize the risk of environmental vibration impact of new lines,it is necessary to provide accurate and reliable vibration prediction results for different sensitive targets,and design reasonable and effective comprehensive vibration reduction and isolation technical proposal based on these results.As a technical means suitable for accurate prediction,the hybrid prediction model based on"FDL&LSTML"can take the advantages of state-of-the-art numerical/analytical method and field measurements,and has shown good application effect in environmental vibration prediction of ground lines.However,this prediction model has not yet been mature in the environmental vibration impact evaluation of underground metro lines.In addition,what is more worthy of attention is that most of the predictions of the environmental impact induced by metro trains are fixed-value predictions for the initial stage of line opening.However,due to the significant differences of vehicle parameters(such as suspension parameters,number of passengers,etc.),wheel-rail wear status and maintenance quality,the vibration source presents obvious uncertainty.With the support of National Natural Science Foundation of China,"Study on the parameter uncertainty of metro train-induced environmental vibrations based on hybrid prediction method(No.51978043)"and"Study of prediction accuracy and reliability of train-induced vibration and its environmental influence(No.51778049)",based on the study of the uncertainty of metro train vibration source,this paper proposes a hybrid prediction model suitable for the analysis of the environmental impact of train vibration on underground lines,and develops the existing fixed-value prediction model to a probability prediction model.The main research contents and results and the main innovations include:1.In this paper,selecting an operation metro line and attached depot,a systematic testing including the wheel roughness of the operating trains,the rails roughness of the of the selected section and the tunnel wall vibration was fully carried out.The complete test data of“rail surface roughness/wheel tread roughness/vibration source intensity”during the wheel/rail maintenance cycle on this operating line has been obtained.The development law and statistical distribution characteristics of vibration source intensity during the maintenance period of wheel and rail were revealed.And the technical elements of wheel repair and rail grinding in reducing the impact of subway train environmental vibration have been explored.2.Based on the mathematical theory of input and response spectrum of multi input linear time invariant system,the mathematical model of wheel-rail joint excitation input of random coupled track irregularity PSD and wheel irregularity PSD was constructed.According to this mathematical model,the frequency responses of the vibration source can be more close to the measured results.In addition,it is found that if the influence of wheel irregularity is ignored,the maximum error between the calculated and measured rail vibration acceleration level in the frequency bands corresponding to the wheel polygon wear can reach 15d B.3.According to the test samples obtained in this article and accumulated by the research group over the years,a random rail roughness PSD reflecting the"time-space randomness"of ballastless track with regular directly fixed DT?₂fasteners and Random wheel out-of-roundness PSD of typical Metro 6-car B-type train in complete maintenance cycle were constructed.Based on the frequency domain“train-track”coupled analytical model,Monte Carlo method was used to analyse the random characteristics of the responses of train vibration source under the combined action of multiple factors in frequency domain,taking random wheel-rail irregularity PSD as input excitation and considering the random characteristics of vehicle parameters.4.The vibration transmission characteristics of line-source excitation equivalent train load of underground lines under various conditions were analyzed.And the influence of equivalent line-source length,excitation spacing and excitation location on line-source transfer mobility level(LSTML)is analyzed.On this basis,the numerical method and analytical method are further used to explore the calculation method of the force density level(FDL)for underground lines.Based on the"FDL&LSTML"model,three hybrid prediction models are developed,which are suitable for the prediction of metro train induced environmental vibration impact of underground lines.5.The operation process of probabilistic prediction method for metro train induced vibration considering the random vibration source was proposed.And the effect of a planned metro line in a city on precision instruments in an existing research institute nearby was predicted in this thesis.According to the prediction results,it is found that,compared with the prediction results determined by the random vibration source measurecd at reference site of the initial operation stage,after considering the random wheel-rail irregularity induced by the continuous development of wheel-rail wear,the predicted vibration responses and exceedance probability of the sensitive location above10Hz are significantly increased.Therefore,in the process of train induced environmental vibration prediction,the random wheel-rail irregularity excitation should be reasonably selected according to the design track type and train dynamic characteristics,in order to make medium-term or long-term prediction of the random vibration response caused by the continuous development of wheel-rail wear.