Research On Fatigue Performance Of CRTS Ⅲ Ballastless Track Slab Based On Concrete Fatigue Damage Constitutive Model

As an under-track stress structure with reinforced concrete as the main body,the high-speed railway ballastless track will inevitably experience fatigue damage accumulation under the action of long-term train cyclic loads,which will affect the integrity,stability,durability,reliability and driving safety of the track structure.Therefore,it has important theoretical significance and engineering practical value to study the life cycle fatigue damage behavior of CRTS III ballastless track slab.In this paper,CRTS III ordinary reinforced concrete ballastless track plate is taken as the research object.Based on the elastic-plastic fatigue damage constitutive model of concrete and its supporting structural fatigue analysis and accelerated calculation method,the flexural fatigue performance,main influencing factors and laws of the track plate are studied in depth.The main research work is as follows:(1)Based on irreversible thermodynamics and continuum damage mechanics,the adaptability of the static damage constitutive relation of concrete under fatigue loading conditions was studied,and the preconditions and deficiencies of using conventional methods to extend the static constitutive model to fatigue loading conditions are analyzed.On this basis,the fatigue loading and unloading criterion and the fatigue damage healing-expansion effect theory are introduced,and the concrete constitutive relation which can reflect the damage accumulation phenomenon in the fatigue loading process is established;(2)According to the characteristics of static and fatigue elastic-plastic damage constitutive models,the numerical algorithms of material constitutive relation adapted to incremental iteration method were established respectively.The corresponding material constitutive subroutines were written by using ABAQUS secondary development platform,and verified at the material level and structure level.On the basis of the existing cyclic jumping fatigue acceleration algorithm,the forward Euler integral method of material constitutive display is adopted to further optimize it,and the accelerated solution of high cycle fatigue problem is realized;(3)Based on the aforementioned elastoplastic fatigue damage constitutive model of concrete and its supporting high-cycle fatigue analysis acceleration algorithm,a simulation method of CRTS III ordinary reinforced concrete ballastless track slab life cycle fatigue degradation behavior under typical loading conditions is proposed.The damage distribution and evolution characteristics of the plate structure during the service period are summarized,and the influence law of the relevant variables in the track plate on its fatigue damage deterioration is summarized.There are 78 figures,24 tables,107 references in the thesis.