Dynamic Reliability Analysis And Design Optimization Of The Train-bridge Vibration System

With the rapid development of the modern rail transit,the vehicle weight,carrying density and running speed are greatly improved,which makes the service environment of vehicle,track,bridge and other structures worse.Therefore,it is very important to carry out the dynamic and reliability analysis of train bridge coupling system.The parameters of the trainbridge coupled vibration system have random uncertainty,and the random excitation such as track irregularity further aggravates the randomness of the vibration response of the system.Therefore,considering the randomness of train-bridge coupled system model parameters and the load excitation,this paper carries out the dynamic modeling and analysis of the system coupling uncertainty,obtains the probability characteristic description method of train safety and stability indexes under different service conditions,and studies the influence of rail load spectrum model,train running speed and other factors on system safety and stability.Under the condition of parameter uncertainty,the robust optimization design of dynamic parameters for the train-bridge coupled vibration system is carried out,and the results are verified by literature and numerical simulation.The main contents of this paper include:(1)Modeling and simulation analysis of the train-bridge coupling dynamicsFirstly,a four-axle bus model including the car body,front and rear bogies and four wheelsets is selected,and a multi-body dynamic model of the train with 27 degrees of freedom including the yaw,roll,shake,sink and float motions of the car body and bogie as well as the yaw,roll and sink and float motions of the wheelsets is established;secondly,the generalized coordinate method is used to approximate the bridge as a simply supported beam with constant cross-section,and the train-bridge coupled dynamic model is established considering the torsional and vertical modes of the bridge;several track irregularity load models,such as German spectrum,American spectrum and China trunk spectrum,are introduced to simulate and verify the track spectrum in time domain;finally,the train stability and safety indexes are obtained by Newmark-? step-by-step integration method,and the numerical simulation results of the train-bridge coupling dynamic model are compared and analyzed according to relevant specifications and literature results,which verifies the correctness and effectiveness of the train-bridge spatial coupling dynamic model.(2)Dynamic reliability analysis of the train-bridge coupled vibration systemBased on the train-bridge coupled random vibration model,the fractional moments of train operation safety and stability indexes are obtained by combining the experimental design and Latin hypercube sampling technology;with this constraint and the maximum entropy optimization method,the probability distribution characteristics of performance indexes such as train safety and stability are reconstructed;according to the national standard GB5599-85,the dynamic reliability of the train under the excitation of random parameters and track irregularity load is studied,and the accuracy of the calculation results is verified by Monte Carlo method;and the influence of the operation speed and load spectrum type on the dynamic reliability of the system is studied in the end.(3)Global sensitivity analysis of the train-bridge coupled vibration system parametersBased on the multiplicative reduced dimension expansion model for the calculation of train stability and safety indexes,combined with the variance orthogonal decomposition model for the global sensitivity analysis of complex system parameters,the influence of suspension parameters,model structural parameters and geometric parameters on the dispersion of vehicle stability and safety indexes is calculated,and the importance ranking of each parameter is given,which provides the basis for simplifying dimension reduction and the optimization design of the system uncertainty.(4)Parameter optimal design of the train-bridge coupling vibration dynamic systemAccording to the global sensitivity analysis results of the train-bridge coupled vibration system parameters,the important system dynamic parameters are selected,and the Kriging agent models for the derailment coefficient,wheel unloading rate and horizontal and vertical comfort indexes are established respectively.The accuracy of the alternative models is verified by the experimental design and random simulation method;on this basis,with the goal of minimizing the dispersion of the safety and stability indexes and the mean value of the performance indexes,the single objective and the comprehensive robustness optimization design scheme of the dynamic performance for the train-bridge coupling vibration system are obtained through the global optimization of the genetic optimization algorithm.The numerical simulation shows that the performance improvement effect of the comprehensive robustness optimization scheme is more obvious.