Research On Dynamic Characteristics And Parameter Optimization Of Composite Sleeper Track On Open Deck Of Steel Truss Bridge

In order to alleviate the secondary dead load and reduce the force on the bridge,open deck is mainly used on the steel bridges in our country,that is,the sleepers are directly connected with the longitudinal beam.At present,the sleepers used on open bridge deck are mainly wooden sleepers,which have small self-weight,good elasticity,good insulating and easy installation,but there are also many disadvantages,such as perishability,poor fatigue resistance,large environmental impact on material performance,short service life,high maintenance cost.Besides,a large number of wood resources are consumed in the manufacture of wooden sleepers,and the chemical preservative used for preservation also brings certain harm to the environment.In this case,it is imperative to find an alternative material for wooden sleepers.In recent years,a composite sleeper made of waste plastics,rubber,glass fiber and other chemical additives,developed by the United States,has been gradually applied to railways in various countries.The composite sleeper has good elasticity and damping properties.At present,the domestic and foreign scholars mainly focus on the composite sleeper’s material composition,material performance,processing technology and mechanical characteristics applied to ballasted track and unballasted track structure,but there is no relevant research on the dynamic characteristics of composite sleepers applied to open deck of steel truss bridges.In this paper,the vehicle-track-bridge coupling dynamic model is established to study the dynamic response of the vehicle-track-bridge coupling system under the composite sleeper open deck on the steel truss bridge.The main contents and conclusions of this paper are as follows:1.Through the review of relevant literature,the influencing factors of the sleepers type selection on the open bridge deck are summarized,the sleepers used on the open bridge deck currently are introduced in detail,and the development,characteristics and research status of composite sleepers are investigated in detail.2.By establishing the vehicle-track-bridge coupling dynamic model,the dynamic response of composite sleepers and wooden sleepers is compared.The results show:(1)There is little difference in the dynamic response of the car body.(2)In the time domain,the composite sleeper track can reduce the vibration acceleration of the rail,sleeper and longitudinal beam of the bridge by 13.2%,12.5% and 20.5% respectively,and the vertical displacement of the rail,sleeper and longitudinal beam under the composite sleeper track structure increases,while the transverse displacement of the longitudinal beam decreases.(3)In the frequency domain,compared with wooden sleeper track,the rail’s vibration of composite sleeper track decreases obviously in the range of 1-10 Hz,the maximum reduction is about 11 dB,in the other frequency bands,there is little difference;the sleeper’s vibration decreases obviously in the range of 1~400 Hz and 1000 Hz,the maximum reduction is about 32.6dB,in the range of 500-800 Hz,the vibration level of composite sleeper increases,the maximum is about 16 dB;the vertical vibration of bridge decreases obviously in the range of 1-50 Hz,the maximum is about 21 dB,the lateral vibration decreases obviously in the range of 1-125 Hz,and the maximum is about 16.3 dB,in the remaining frequency band,the vertical and transverse vibration levels of the bridge increase,and the maximum is 8dB and 7dB respectively.3.The parameter optimization of the composite sleeper track structure on open bridge deck is studied,the influence of sleeper spacing,sleeper support spacing and fastener stiffness on the dynamic response of vehicle-track-bridge coupling system is analyzed.Considering comprehensively the influence of each parameter on the dynamic response of vehicle,track and bridge,the optimum range of sleeper spacing is 0.5-0.55 m,the optimum sleeper support spacing is 2m,and the optimum stiffness range of fasteners is 57 MN/m~76 MN/m.4.The influence of the vehicle speed on the dynamic response of vehicle-track-bridge coupling system is studied.With the increase of vehicle speed,the safety and ride index of car body increases generally;the acceleration of rail and sleeper increases,and it’s obviously affected;the displacement of rail and sleeper changes little with the speed of the vehicle;the vertical,lateral acceleration and vertical displacement of longitudinal beam increase,and the lateral displacement decreases as the vehicle speed increase.