In order to investigate the vibration characteristics of a composite sleeper-ballasted track and provide a basis for further popularization, a vehicle–track dynamic coupling model is established and the viscoelastic properties of the composite sleeper are considered. The power flow method is employed to reveal the power flow distribution characteristics of the composite sleeper. The results show that the viscoelastic properties of the composite sleeper have little influence on the rail power and have a greater influence on the power flow of the sleeper and ballast bed in some frequency ranges. The viscoelastic properties of the composite sleeper can effectively improve the calculation accuracy of the track structure’s power flow. Compared with the type-III pre-stressed concrete sleepers widely used in China, composite sleepers consume more energy in the vibration process due to their own physical characteristics, which reduces the power flow transmitted downward and relieves vibration on the ballast bed, especially in the ranges of 80–125 Hz and 250–400 Hz. The temperature change mainly affects the power flow of the composite sleeper in the frequency range above 50 Hz. As the temperature increases, the modulus of the composite sleeper decreases and the vibration reduction effect of the ballast bed is improved.

As a symmetrical structure in track system, the dynamic properties of recycled composite sleepers are important factors affecting the vibration characteristics of track structure. To study the viscoelastic dynamic properties of the composite sleeper, dynamic mechanical analysis (DMA) tests of a composite sleeper at −5 to 30 °C and 1–60 Hz were first carried out, and then the time-temperature superposition (TTS) and the Williams–Landel–Ferry (WLF) formula were used to predict the dynamic properties of a composite sleeper at a wider frequency range. Finally, the generalized Maxwell model was adopted to characterize the dynamic properties of the composite sleeper, which provides parameters and theoretical models for dynamic analysis. The research results show that the composite sleeper has obvious viscoelasticity. Its modulus is large at low temperature or high frequency. On the contrary, the modulus is small at high temperature or low frequency. Under the test conditions, its complex modulus ranges from 1500 to 2700 MPa. The loss factor is in the range of 0.08–0.13. Using the generalized Maxwell model (n = 4), which can better reflect the dynamic properties of the composite sleeper.

Due to the discrete deterioration characteristics of timber sleepers on open bridge deck, continuous replacement is difficult. New bamboo-based composite sleepers (BCSs) offer excellent performance at a low price, making them an ideal alternative to timber sleepers. Therefore, this study focuses on the mechanical properties and safety of the interspersed replacement of timber Sleepers with BCSs. A static model of the open deck track and a vehicle-track coupling dynamic model were established to precisely analyze the influence of 1 in 2, 1 in 3, and 1 in 4 interspersed replacement, as well as full replacement with BCSs on the force and deformation of the track structure and the dynamic characteristics of the vehicle-track system. After the interspersed replacement of timber sleepers with BCSs, the sleeper compression, sleeper vertical displacement, and gauge reduction were decreased; however, the sleeper bending moment, vehicle acceleration, wheel-rail force, and bridge deck acceleration were slightly increased. At the longitudinal beam support, the BCSs showed a negative bending moment, with compression at the bottom and tension at the top. The maximum tensile and compressive stresses were 4.87 MPa and 7.97 MPa, respectively, which are both below the allowable stress of the material—meeting the strength requirements for BCSs. Although the interspersed replacement of timber sleepers with BCSs leads to uneven track stiffness, the track deformation, stress distribution and dynamic response remain within acceptable limits. This research provides new ideas for track structure upgrades and maintenance strategies.