Study On Dynamic Damage Of Ballastless Track Concrete Considering Strain-rate Effect

The concrete structure is the main component of the ballastless track.The ballastless track is in a dynamic loading process under the load of the train.Its damage mechanism and dynamic mechanical properties are different from those in the static state.At different loading rates,the stress characteristics of the concrete structure are also different,so the influence of the strain rate effect of the concrete on the ballastless track under the load of the train cannot be ignored.The design and analysis of the track structure in the static constitutive relationship will inevitably have certain differences compared with those in the actual situation.Therefore,analyzing the strain rate range of the ballastless track concrete material in the service process systematically and using the dynamic damage constitutive model within this strain rate range to analyze the ballastless track structure has important significance and reference value for studying the effect of strain rate on the damage evolution and dynamic performance of ballastless track concrete structures.Based on finite element software,this paper summarizes and analyzes the strain rate range of ballastless track under train load.Based on the existing concrete rate-related dynamic performance tests,a concrete material subprogram that can consider the strain rate effect is compiled,and the influence of the strain rate effect on the damage development and dynamic performance of the ballastless track concrete structure under moving load is studied.The main research contents are as follows:（1）The dynamic analysis model of the double-block ballastless track is established,and the influence of the strain rate of the double-block ballastless track is analyzed from four aspects:different load types,static and dynamic moving loads,different load moving speeds and the nonlinearity of concrete materials.It is concluded that the strain rate of the ballastless track concrete is generally in the range of 10^-4～10^-3 s^-1 under the action of the train load,and the strain rate of the track bed slab can reach the maximum 10^-2 s^-1,indicating that the ballastless track concrete is in the range of dynamic characteristics under the train load.（2）Based on the ABAQUS user material subroutine,the standardized uniaxial constitutive relationship of concrete is adopted,the concrete rate-related constitutive model and the concrete material failure criterion are introduced,and the subroutine that can effectively consider the rate effect of concrete and material damage and degradation behavior is compiled.（3）By establishing the dynamic damage model of ballastless track considering the effect of strain rate,the influence of strain rate effect on the damage evolution and dynamic performance of the concrete structure of ballastless track is studied.The research results show that the ballastless track concrete exhibits strong rate sensitivity under moving load.Considering the strain rate effect on the concrete of the track bed slab and supporting layer,its damage development rate and range of action are all reduced.In addition,the concrete strain of the track bed slab and the supporting layer has been reduced.It is recommended that the design and calculation of the ballastless track should consider the impact of the dynamic performance of the concrete.