Development And Application Of Dynamic Analysis System Of Ballastless Track On Bridge Based On Explicit Finite Element

With the large-scale construction and operation of rail transit,the performance degradation of rail system has gradually become a hot issue concerned by scholars.In the process of long-term use,CA mortar layer,as the weakest part of ballastless track system,will gradually appear different degrees of damage,resulting in the gap between mortar layer and track slab,resulting in the diseases of track system.This paper studies the influence of CA mortar separation on the ballastless track system on the bridge.Because of the possible contact,the evolution of the mechanical behavior of the system is highly nonlinear.Therefore,for the consideration of computational stability and efficiency,an analysis program that can deal with such complex contact problems is independently developed based on the explicit finite element method.The main research contents and results of this paper are as follows:(1)The dynamic explicit algorithm finite element equation of contact collision process is established by using virtual power equation,and the central difference method is used for time integration to avoid the convergence problem caused by geometric and contact nonlinearity;Then the reduced hexahedral solid element theory and the method of controlling hourglass mode are introduced,and the calculation format of stress and strain of elastic material is deduced.(2)According to the analysis requirements of contact collision problem,a general solution based on penalty function method is proposed,including global search algorithm based on bucket sorting,local search algorithm based on internal and external method and contact algorithm for penetration calculation.(3)The software architecture is designed based on the design pattern.The program is mainly divided into three levels: unit information,system aggregation and solution.According to the function,it is mainly divided into three modules: pre-processing module,solver module and post-processing module.The explicit finite element analysis program is developed by using C + + language in an object-oriented manner,and then the design process of each module,the implementation of main subroutines and methods,contact search and other algorithms are introduced.(4)The finite element model of CRTs type I ballastless track on a simply supported beam bridge with gap is established by using the self-developed program and the existing mature finite element software.The accuracy of the calculation results of the self-developed program is compared,and the influence of different gap height and length on the dynamic response of the bridge ballastless track system is analyzed.The results show that the calculation accuracy of the self-developed program is high,and the maximum error is less than3%;The shorter the length of the separation joint is,the higher the height is,and the track plate is easier to be disengaged and stressed;The vertical displacement extreme value of track slab is very sensitive to the change of the length and height of the joint,while the vertical displacement extreme value of mortar layer is more sensitive to the length of the joint.It is suggested to give priority to controlling the length of the joint and pay attention to the development of the height of the joint;Both the extreme acceleration and the extreme compressive stress of the mortar layer of the track plate are related to the contact behavior,which increases with the enhancement of the supporting effect of the mortar layer on the track plate in the contact area;Under the influence of stress redistribution,the growth rate of the extreme value of transverse and longitudinal tensile stress of the track slab will decrease after the mortar layer contacts the track slab,and even decrease with the increase of the separation length,and then rise slowly.Compared with the extreme value of longitudinal tensile stress,the extreme value of transverse tensile stress is not sensitive to the change of separation height and separation length;Under the action of moving load,the separation of CA mortar layer has little effect on the bridge system.