Research On Vibration Reduction Characteristics And Application Of Composite Sleeper

As a new type of sleeper,the composite sleeper has the properties of excellent elasticity and large damping.It can increase the track elasticity from the sleeper itself,ans has the effect of vibration reduction on the substructure.In addition,the composite sleeper is energy-saving and environmental protection,which is in line with the concept of green development in China,and has good economic and social benefits.At present,composite sleepers are rarely used in China,and the researches on the performance of composite sleepers and their track structures are insufficient.Therefore,it is necessary to fully study the characteristics of composite sleepers and their track structures to provide theoretical guidance for their further promotion and application.Based on the summary of the research status of composite sleepers and the characteristics of composite sleepers,this dissertation studies the vibration reduction characteristics and application of two composite sleepers(recycled composite sleepers and bamboo-based composite sleepers).The details are as follows:(1)Research on the deformation composition of sleepers and the parameters of composite sleepersBased on the working state and structural characteristics of the sleeper,it is proposed that the deformation of the sleeper is composed of the flexural deformation and the compression deformation.The elastic modulus is an important parameter of the elastic sleeper,especially the composite sleeper with good elasticity.Based on the basic theory of viscoelastic properties,dynamic mechanical analysis(DMA)method was used to test the complex modulus,storage modulus,loss factor and other mechanical parameters of composite sleepers.The modulus of the two kinds of composite sleepers is much smaller than that of concrete sleepers,and the modulus increases with the increase of loading frequency.Through theoretical analysis,the deformation characteristics of the composite sleeper was verified.(2)Prediction and theoretical characterization of the dynamic properties master curve of composite sleepersSince the test frequency range of DMA cannot cover the load frequency range of composite sleepers in service,in order to accurately obtain the dynamic properties of composite sleepers,combined with the existing test data,the time-temperature superposition(TTS)and the Williams–Landel–Ferry(WLF)formula were used to predict the dynamic properties of composite sleepers at a wider frequency range under different reference temperatures.Based on the viscoelastic properties of composite sleepers and the theoretical model,the generalized Maxwell model was adopted to characterize the dynamic properties of composite sleepers.The analysis results show that the generalized Maxwell model can better reflect the frequency-dependent properties of composite sleepers,and provides a more accurate theoretical model for the analysis of the vibration characteristics of composite sleepers.(3)Research on vibration reduction characteristics of composite sleepers ballasted trackThe vehicle-track dynamic coupling model was established.In order to improve the calculation accuracy,the viscoelastic properties of composite sleepers were considered in the model.Compared with type-III pre-stressed concrete sleepers,the power flow method was used to analyze the vibration energy transfer and internal consumption characteristics of two kinds of composite sleepers under the action of passenger cars and freight cars.The distribution characteristics of vibration energy along the longitudinal direction of sleepers,the transmission characteristics of power flow inside sleepers,the vibration reduction effect of the track bed and the influence of temperature changes on power flow transmission of composite sleeper track were obtained.The vibration reduction characteristics of composite sleepers are revealed from the perspective of vibration energy.The results show that in the process of power flow transmission,the internal consumption of composite sleepers are significantly larger than that of concrete sleepers,which reduces the downward transmission of power flow and reduces vibration of the substructure.(4)Research on composite sleepers vibration reduction effect on environmental sensitive areasIn order to study the vibration reduction effect of composite sleepers ballasted track on environmental sensitive areas,a case in which the Chenglan Railway passes through environmental sensitive area was taken.The vibration model of the environmental sensitive area of the Chenglan Railway was established.The vibration reduction effect of composite sleepers ballasted track under the operation of the passenger car and the freight car were analyzed from the aspects of track structure vibration,tunnel vibration,and fault zone vibration.Based on the premise of driving safety and reasonable stress and deformation of each track structure,and for the purpose of reducing the vibration of the track bed,tunnel,and fault zone,the recommended values of the relevant parameters of composite sleepers were proposed.