Stochastic And Extreme Value Analysis For The Coupling Vibration And Wind Loads Responses Of Train-bridge System(U1334201)

With the rapid development of high-speed railway system,the train speed and the proportion of railway bridge are increasing as well.The researches on dynamic interactions between trains and bridges have become extremely crucial.When the railway vehicles are passing through the bridges,the interactions between two subsystems perform strong stochastic characteristics.Wind loads not only increase the vibration of vehicles and bridges,but also its strong randomness make the vehicle-bridge coupling system vibrate randomly.Based on the coupling vibration theory of vehicle-bridge system,this paper focuses on the stochastic responses and extreme value analysis of vehicle-bridge system with or without the wind loads.Main research works are as follows:(1)Firstly,combining the pseudo excitation method with the self-adaptive gauss integral method to calculate the stochastic response of vehicle-bridge coupling system.This combination increases the computational efficiency of stochastic vibration of time-dependent system further and makes the coupling system distinguish the important and unimportant frequency regions of the external excitation autonomously.The hybrid method automatically subdivides the important frequency regions to pinpoint the effects of the loads on the vibration of system and guarantees that every effective frequency is put into calculation.Rough decomposition or elimination of the unimportant regions reduces the calculation cost.Secondly,based on the theory of pseudo excitation method,a so-called stochastic pseudo excitation method(SPEM),which acquires the sampling results of structural response directly,is presented.This method can investigate the effect of structure uncertainties and variation coefficient of external excitation on the stochastic responses.Finally,the high slender bridge tower subjected to the Davenport fluctuating wind loads is selected to prove the efficiency and the accuracy of the hybrid method,thus to verify the stochastic pseudo excitation method.The research case is also applied to study the effect of the structure uncertainties and wind loads on the structural random vibration.(2)Based on the structural characteristics and mechanical properties of railway vehicles and bridges,finite element method is applied to build the vehicle bridge model which avoid the complexity of deriving the matrix of vehicle.It also obtains the structural damping ratio for the every natural modal according to the structural dynamics theory.In order to calculate the dynamic responses of vehicles and bridges,the author establishes the motion equations of the vehicle subsystem and the bridge subsystem separately.Besides the Duhammel integral is used to solve the equations and obtains accurate results.An analysis program of vehicle-bridge coupling system is compiled and verified which achieves the diversity of the software analyses and the variability of the targets.This program provides technical supports for the refined modeling and universality of software.(3)The hybrid method,which combines the pseudo excitation method and the self-adaptive Gauss integral method,is applied to calculate the stochastic responses of vehicle-bridge coupling system.And the calculations are verified by the Monte Carlo method.On account of the stochastic results,the cumulative distribution function curve of the coupling system responses is plotted and the extreme value and the probability of the system are discussed.The research studies the effect of the different vehicle speed,the type of rail irregularity and the organization of vehicles on the stochastic responses.(4)Non-dimensional time is used to evaluate the steady-state characteristics of the vehicle stochastic responses,which presents the internal connections between the vehicle steady-state responses and the coupling system.The study analyzes the effects of vehicle running speed on the stochastic responses and carries out the extreme value of vehicle-bridge coupling system under different running speed.Vehicle-bridge coupling system,therefore studying the extreme value of the whole running period of vehicle is more scientific and practical.When the variation of the different power spectrum of rail irregularity in certain section is the same,the curve of calculated stochastic responses stays the same.The calculations get the peak factor of the vehicle-bridge coupling system which mainly influenced by the structural characteristics.Where as the impacts of the speed and the types of track irregularity are not sensitive.(5)The stochastic responses of vehicle-bridge coupling system which subject to the wind loads is calculated by using multi-sample and it shows the independent features between the track irregularity and the wind loads.The variance results of the stochastic responses of vehicle-bridge coupling system which under the action of wind loads and rail irregularity together are equivalent to the sum of the variance of the responses subject to each excitation.The mean squared deviation meets the principle of the equivalence of quadratic sum,which satisfies the superposition principle of statistics.The stochastic responses and the extreme value distributions of the coupling system under different wind velocity,vehicle speed and vehicle formation are studied likewise.