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In order to solve the thorny problem of maintenance and repair of cast-in-place monolithic track slab, a new type of prefabricated slab ballastless track structure is developed for ordinary sections and damping sections. This study uses dynamics software to establish a vehicle-ballastless track coupling dynamics model, to explore the dynamic properties of the new type of prefabricated ballastless track structure in ordinary and damping sections. The model is verified using field measurement to prove its reliability. Based on the results obtained in the study, the following conclusions are deduced: (1) The vertical displacement of the floating slab in the damping section is increased by 82.95 times compared with the ordinary section. However, the vertical acceleration of the tunnel wall is reduced by 90.48%, while the insertion loss of vertical vibration acceleration of the tunnel wall is 11.08 dB, which meets the requirements of the code (CJJ/T 191-2012). (2) As the stiffness of the damping cushion increases, the vertical displacements of the rail and track slab are reduced by 43.25% and 56.68%, respectively, while the insertion loss of the vertical vibration acceleration is reduced by 31.28%. (3) As the damping increases, the vertical acceleration of the tunnel wall increases by 75.96%, whereas the insertion loss of the vertical vibration decreases by 30.51%. When the damping or the stiffness of rubber cushion is greater than 0.132 MN·s/m3 or 0.0231 N/mm3, the damping does not meet requirements. (4) When the thickness of the floating slab is increased from 200 mm to 350 mm, the vertical accelerations of the floating slab and the tunnel wall are reduced by 35.79% and 41.35%, respectively, whereas the insertion loss of the vertical vibration acceleration is increased by 37.36%. [ABSTRACT FROM AUTHOR]

To study subway turnouts' adaptability to steep gradients, a finite element model of a metro No. 9 simple turnout was established. The main works include: (1) The train's most unfavourable loading condition was modelled. (2) The turnout's longitudinal displacement and stress were analysed with different gradients under the train braking load, temperature change load and a combination of the two, to determine the structure's safety and stability under the most unfavourable working conditions. (3) The turnout structure's cumulative longitudinal deformation under reciprocating load was studied. Both a fastener longitudinal resistance-displacement experiment under reciprocating load and a numerical simulation of No. 9 turnout modelled by the finite element modelling software, ANSYS, were carried out to study the gradient's influence on the turnout's longitudinal mechanical characteristics. (1) The turnout's longitudinal displacement and stress increase linearly with an increase in gradient and temperature change, both of which are unfavourable to the turnout structure. As the gradient increases from 0& to 30&, the longitudinal stress and displacement increase by more than 10%. (2) The turnout's rail strength and displacement on a 30&slope under the most unfavourable load conditions are within the specification limitations. (3) Under reciprocating load, the fastener longitudinal stiffness decreases and the maximum and residual longitudinal displacement of the switch rail increase; an increased gradient intensifies these effects on the turnout. [ABSTRACT FROM AUTHOR]

Compared with ordinary railways, the curve radius of tram lines tends to be smaller, with minimum values of only 30 m. Therefore, wheel–rail interaction is more intense and complicated in sections of small radius tram line curves. Using a stochastic variable sample set based on a generalized probability density evolution method, the stochastic variable–spectrum representation method was used to generate a time-domain sample set of stochastic track irregularities. By inputting the stochastic set of track irregularities into a tram-track coupled dynamic system model, the stochastic dynamic response of the coupled dynamic system can be obtained. Moreover, by substituting the stochastic dynamic system response into the generalized probability density evolution formula, the process of probability density evolution of each evaluation index can be obtained by the finite difference method. Finally, the dynamic response of the tram-track coupled dynamic system can be evaluated by the probability distribution of each index. By setting a series of specific groove rail wear values, a tram-track coupled dynamic analysis was carried out, and compared with the specification requirements, vehicle safety limits under different wear values were obtained. This research has great engineering value for guiding the routine maintenance of small radius curve sections of trams. [ABSTRACT FROM AUTHOR]

The key functions of the fastener system are to hold the rail against the sleepers and to restrain the rail from all forms of movements that could lead to loss of geometry and stability of the track. Thus, fastener resistance is an important parameter in the continuously welded rail technology. This study investigates the characteristics of the longitudinal resistance of WJ-8 fasteners subjected to varying torques and vertical loadings. The vertical loading was applied to the rail section through a reaction frame, while the torque was applied using a digital torque wrench. Two types of fasteners, conventional-resistance and small-resistance fasteners, were tested in this study. The study shows that: (1) The growth rate of the longitudinal resistance of the fastener is independent of the vertical loading until the fastener slips. (2) The slip resistance of fasteners increases as the torque and vertical loading are increased. (3) The relationship between the longitudinal resistance and the displacement of fasteners at varying torques and vertical loadings fits a power index function. (4) The relationship between the longitudinal resistance and the displacement of the fastener exhibits hysteresis. The study serves as a reference for verifying and improving future calculation methods for the longitudinal resistance of fasteners in continuously welded rails. [ABSTRACT FROM AUTHOR]

This study focuses on the evaluation of simple performance tests (SPTs), such as dynamic modulus, indirect tensile strength and rutting resistance tests, as it imparts on strength, service and durability requirements of high-density polypropylene polymer waste modified over conventional asphalt. The dynamic modulus test was carried out by Simple Performance Tester (SPT) or Asphalt Mixture Performance Tester (AMPT) using International Process Control (IPC) global test machine, otherwise called Universal Test Machine, with a pneumatic load of 25kN (UTM-25P) in accordance with AASHTO TP62-03 method, in order to determine modulus value, phase angle and recoverable strain. Indirect tensile strength evaluation was carried out using ASTM D4123-05a and ASTM D6931-12 recommendations. The recommendations followed for permanent deformation (rutting) were those stated in the NCHRP Report 508:2003 and AASTHO T324. The results showed that 2.0% HDPP asphalt performed optimally and gave enhanced results for dynamic modulus, ITS and rutting than conventional asphalt (control) for mitigating pavement distresses. [ABSTRACT FROM AUTHOR]