Train-Track-Bridge System And Train-Bridge Stochastic Vibration

From the point of view of system dynamics, the train-track-bridge dynamics analysis theory and computing programs are established. Computing results and in site testing results are compared to validate the train-track-bridge analysis theory. A covariance method for time-variant system is proposed to analyze the vehicle-bridge random vibration excited by random rail irregularities. Finally, a perturbation method is derived to analyze the train-bridge transient stochastic responses due to the randomness of bridge parameters. The proposed covariance method and the perturbation method are validated by comparing with Monte Carlo simulation method. The main research work is as follows:1. Dynamic analysis models for the train, bridge and track are established. And their dynamic equilibrium equations are derived. The train is treated as multi-body system, and its dynamic equations are derived using the D'Alembert principle. The rail structure is modeled as discrete-supported three-layer system considering the degrees of rail, sleeper and ballast. The bridge dynamic model is derived using the finite element method.2. The wheel/rail contact geometry and rolling contact theories are discussed. A new type wheel/rail relationship is applied, which takes the difference of wheel/rail compression between right and left rail and wheel/rail separation into accounts. The trace line method is introduced to solve the wheel/rail space contact geometry. The Hertz non-linear contact theory is used to calculate the wheel/rail normal forces. Wheel/rail creepage formulas are derived, and several important creep theory are discussed.3. An explicit-implicit hybrid dynamic integration method is introduced to calculate the train-track-bridge responses; and a computing program based on this method is developed. Great difference exists between the dynamic characteristics of the train-track and bridge systems; and this hybrid integration method can improve the calculation efficiency while retaining considerable accuracy. Base on the train-track-bridge dynamic equations, wheel/rail relationship and hybrid integration method, analysis program to calculate the train-track-bridge dynamic responses is developed on the Visual C++ platform.4. Dynamic responses of a continuous beam bridge passed by loaded-empty mixed arranged train and a continuous beam bridge on QinShen Passenger Line passed by high speed train are calculated. The calculation results of train-track-bridge system are compared with in site testing results separately, and the correctness of the train-track-bridge analysis theory is partially validated.5. A time domain method is proposed for analyzing the vehicle-bridge stochastic vibration. The rail irregularity under a single wheelset is produced by the white noise filtration method. The parameters of the shape filter are identified in a wide frequency range; and train speed transformation formula of the shape filter is derived. The Pade approximation of time-delay system is introduced to reflect time-delays among irregularities under different wheelsets. Then, a covariance recursive method for the stochastic vibration analysis of time-variant system is proposed. Results of the covariance method are compared with the Monte Carlo method, which indicates the high accuracy of the proposed method6. A time domain method is proposed for analyzing the train-bridge stochastic vibration. A stepwise time-delay system based on the high order Pade approximation is proposed to simulate large time-delay excitations under all wheelsets. The train-bridge vertical stochastic vibration model is established. Covariance method to calculate both the displacement and acceleration stochastic responses of train-bridge system is given. Numerical results of the recursive covariance method are compared with those of Monte Carlo simulation to examine the correctness of the proposed method.7. Extending the improved perturbation method to train-bridge time-variant system, a method to calculate the transient stochastic responses of train-bridge system with uncertain parameters is proposed. An improved perturbation algorithm is derived to evaluate the transient stochastic response of the train-bridge time-variant system. The correctness of the method is verified by comparing with Monte Carlo method. Finally, the effects of randomness of bridge parameters on the stochastic dynamic responses of train and bridge are discussed.