Low-Vibration Tracks (LVTs) are widely used in subway tunnels for their excellent performance, but the application in heavy-duty railways still requires a lot of feasibility studies. In this study, the statics performance of LVT under different axle loads, load direction, and load position is explored using the finite element software Abaqus. The Timoshenk beam element and nonlinear spring element 3D solid element are used to represent rails, fasteners, and the other track structure respectively. The paper established the finite element model of LVT to study the mechanical characteristics of low vibration track structure under varying loading condition. The applied loads are determined according to the Heavy-Haul Railway Track Structure Design Code. The results shows: (1) The deformation and stress of the LVT structure show a linear relationship with the increase of the axle load. (2) Slab end loading and lateral load are more unfavorable to the stress and deformation of the track structure. When slab end is loaded with vertical load, the vertical load is distributed on four supporting blocks along the longitudinal direction with a ratio of 1:4:4:1, and the lateral direction is mainly borne by two adjacent fastener nodes with the total load proportion of 47% and 47% respectively. (3) The LVT structure can guarantee the safety of static performance under 30 t axle load and the maximum axle load should not exceed 36 t. The paper provides a guideline for the construction and maintenance of LVT structure in heavy haul railway.
A novel frame-embedded track (NFET) with additional beams between the prefabricated rail seats before was proposed, but its geometric parameters need to be further optimized, in order to solve the problem of difficulty in adjustment, due to the independence of the two prefabricated rail seats during the construction of tram. Based on the finite element method, the geometric parameters of the NFET structure are systematically studied and optimized. The research shows: (1) As the width of the beams and the thickness of the lower slab increases, the mechanical characteristics of the NFET structure does not change significantly; therefore, the recommended design reference value for these two are 240 mm and 80 mm, respectively. (2) When considering the cable and the drainage facilities, the stress state of the NFET structure is less affected (or even improved), which proves that the layout of the cable and the drainage facilities is feasible. (3) According to the analysis during different construction stages, the stress of the NFET rail seats is generally greater than the stress of the cast-in-place concrete. It is recommended that the intensity of the cast-in-place concrete should be greater than that of the prefabricated frame structure.
In view of the problems present in the construction process of the embedded track structure of modern tram, we have designed a Novel Fastener Type Ballastless Track (NFTBT) for tram. To optimize the size of the NFTBT’s structure, the finite element model of the NFTBT’s structure in the tram running stage is built, the mechanical characteristics of the NFTBT’s structure are calculated, and the geometric parameters of the NFTBT’s structure are systematically studied. The research results are as follows: (1) As the size of the track slab increases, the displacement differences of the middle part of the NFTBT are similar, and the size of the track slab has little effect on the displacement. (2) The stress difference of the NFTBT’s structure under the different distances between the centers of the adjacent grouting holes’ conditions is small. Although a larger distance between the centers of the adjacent grouting holes can reduce the number of grouting holes in the track slab, the distance should not be too large to reduce the peak stress at the bottom of the NFTBT. (3) When the distance between the adjacent fasteners of the NFTBT changes within a certain range, the rail is greatly affected by the uneven settlement of the subgrade, and the track irregularity will be aggravated. (4) The NFTBT does not require the implementation of cable passages at intervals, which facilitates the passage and fixation of the cables in the tram operation section and can reduce the difficulty of adjusting the geometry of the track structure, thus accelerating the construction progress.
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