Performance Study On Temperature Behavior Of CRTSⅡ Slab Ballastless Track-bridge Structure

At present,CRTS II slab ballastless track bridge structure has been widely used in the field of high-speed railways in China because of its high driving comfort and economic safety.In the actual operation and maintenance process,due to the complex and long-term temperature load,CRTS II slab ballastless track,as a multi-layer composite structure shows different degrees of deterioration,affecting the normal operation of the train.In this thesis,combined with the theoretical knowledge of Meteorology and heat transfer using the experimental test and finite element analysis,CRTS Ⅱ slab ballastless track structure on the box girder bridge systematically has been explored.The temperature of each structural layer under daily temperature load,time-varying laws of the temperature of different structural layers,and further expounds the occurrence conditions of the most unfavorable temperature field.The specific research contents are as follows:(1)Based on the basic theories of heat transfer and meteorology,this thesis expounds the mechanism of heat exchange between the outer surface of the structure and the environment,the heat conduction process inside the structure,analyzes and determines the relevant parameters of structural thermodynamics,the specific heat and thermal expansion coefficient can be taken empirical values.The thermal conductivity can be calculated from the measured data.Furthermore,this thesis Provides the theoretical basis for boundary treatment and parameter selection for the following test and simulation analysis;(2)The model of the ballastless track bridge structure system was established.By adopting the method of layered embedding,the temperature measuring points are scientifically arranged in each structural layer,and the daily temperature cyclic load tests in summer and winter were carried out.The spatial and time-varying laws of temperature field and temperature gradient of each structural layer of the ballastless track under the action of daily temperature load are analyzed.The results show that the temperature response of CA mortar layer is more significant than that of the other two structural layers;(3)Based on the thermal analysis module of ANSYS,the temperature field of ballastless track is analyzed,and the feasibility of the simulation method is compared and verified.Furthermore,the refined research of structural temperature response is carried out.The effects of different meteorological parameters,thermal parameters and structural dimensions on structural temperature field are discussed,and the occurrence conditions of the most unfavorable temperature field are pointed out.Compared with the current design value of temperature load,it is suggested that the temperature gradient should be 1.0 ～ 1.5 times the existing code value in the design process.The qualitative reference suggestions are given from the aspects of thermal parameter selection and structural size.