This study developed two-and-half dimensional (2.5-D) finite element method (FEM) to predict viscoelastic pavement responses under moving loads and nonuniform tire contact stresses. The accuracy of 2.5-D FEM was validated with two analytical solutions for elastic and viscoelastic conditions. Compared to three-dimensional (3-D) FEM, the computational efficiency of the 2.5-D method was greatly improved. The effects of loading pattern and speed on pavement surface deflection and strain responses were analyzed for asphalt pavements with four different asphalt layer thicknesses. The analyzed pavement responses included surface deflections, maximum tensile strains in the asphalt layer, and maximum compressive strains on top of subgrade. The loading patterns have influence on the mechanical responses. According to the equivalent rule, the point load, rectangle type, and sinusoid-shape contact stresses were studied. It was found that the point load caused much greater pavement responses than that of the area-based loading. When the tire loading was simplified as uniform contact stress in rectangular area, the maximum tensile strains in the asphalt layer varied with the width/length ratio of contact area. Additionally, it was shown that the dynamic responses of pavement structure induced by the sinusoid-shape contact stresses and realistic nonuniform stresses were quite similar to each other in all the cases. The pavement strain responses decreased as the speed increased due to viscoelastic behavior of asphalt layer. The study results indicate that asphalt pavement responses under moving load can be calculated using the proposed 2.5-D FEM in a fast manner for mechanistic-empirical pavement design and analysis.
A comprehensive evaluation of the current state of the railway transport system in eleven countries of the Economic Community of West African States (ECOWAS) is presented. Four themes of the railway transportation system comprise of infrastructure, rolling stock, operational performance, telecommunication and signaling are examined in the article. The transport policy regarding the railway transport system is analyzed along with the regulation and institutional framework. The findings of this study show that the railway transportation system is characterized by deteriorated infrastructure, obsolete technologies, fragmented and old databases, scarcely accessible investments, low-quality operations regarding safety and performance, and restricted connectivity and interoperability. Based on the socio-economic context in the region and review of recent railway projects, a series of strategies are proposed to meet future regional visions. These strategies are envisaged to contribute to the development of an efficient and interoperable railway transportation system in the Economic Community of the West African States which in turn will improve the interconnectivity and enhance the economic growth and trade in West Africa.
Optimizing the dynamic responses of a slab track system is a key aspect to improve the quality of a railway track structure. In this paper, numerical modelling and simulation of vertical dynamics of the railway track structure engaging the asphalt concrete in substructures were carried out. us, a 3D finite element (FE) model was developed. e developed model was validated by comparing its outputs, that is, acceleration with the measured ones from realistic experimental data. e good agreement between the simulated and measured data which resulted from the validation confirmed that the proposed model has a capability of simulating the complex dynamic performances of the train-track-ground system under different loading conditions. Analyses of the determined results from the simulation model performances revealed that three specific factors, which were the speed of the train, the temperature, and thickness of the asphalt concrete trackbed, mainly influenced the dynamic behavior of the railway structure. ereby, those factors were taken into consideration while evaluating the dynamic responses and designing the asphalt concrete trackbed in railway substructures.
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