Study On The Decoupling Of Train-Track-Bridge System Vertical Vibration

The dynamic interaction between vehicle and bridge has attracted great attention in recent decades with the rapid development of high-speed railway construction worldwide.Currently,detailed vehicle-bridge interaction models considering the vibration of both the vehicle and the bridge have been developed to evaluate the bridge performance due to passing trains.But some problems remain unresolved: the traditional vehicle-bridge coupling model and the moving concentrated force model do not account the effect of the track structure.The moving concentrated force model tends to overestimate the dynamic response of bridges,and its internal mechanisms not revealed.The traditional vehicle-bridge coupling model can only be solved by numerical simulation,which is not helpful to explaining the vehicle-bridge system intrinsic mechanism of coupling effect and practical application.The research content of this thesis includes:(1)Modeling the load from moving vehicle as more reasonable distributed load,the reduction effect is investigated analytically by solving the moving load problem for both the point load and the spread load cases.The analytical solution reveals that bridge responses from the spread load model can be obtained by filtering bridge responses from the point load model.The filter function is exactly the Fourier Transform(FT)of the load spreading function.Based on this relationship,a reduction coefficient reflecting the load spreading effect on bridge responses is derived.Through numerical examples,the accuracy of this proposed reduction coefficient is validated not only for the moving load models but also for vehicle-bridge interaction(VBI)problems.(2)Based on the internal mechanism of the vehicle-bridge coupling system and the idea of equivalent viscous damping,a vehicle-bridge decoupling model is proposed.According to the vehicle-bridge decoupling model proposed in this thesis,an additional damping is added to the moving concentrated force model.It can be used to estimate the dynamic response of a bridge under the vehicle-bridge coupling model.The accuracy of the vehicle-bridge decoupling model is verified.In order to facilitate the use of actual engineering,a graph of the additional damping in the decoupling model is given.(3)Compared with the complex vehicle-track-bridge coupling model,the proposed vehicle-track-bridge vertical decoupling model,needs merely the additional damping,which is provided in this thesis.The chart given is quickly queried,which greatly simplifies the calculation and facilitates the use in practical application.The vehicle-track-bridge decoupling model is compared with the vehicle-track-bridge coupling model,and the accuracy of the decoupling model is verified.