“…2. Another method classifies the forces applied to the railway track into two categories of static and dynamic forces [39]. Static forces are mainly due to the weight of the railway vehicles, but it should be noted that since the rolling stock is passing over the rail and due to the existence of geometric and structural defects in the rails and in the railway vehicles, the nature of the vertical and lateral forces on the rail is dynamic [8,[40][41][42][43][44][45][46][47].…”
In the modern railway superstructure construction and maintenance, particularly where higher speeds are required, the rail sections may be welded together to form Continuous Welded Rail (CWR). There are various methods for welding the rails, such as thermite welding, flash-butt welding, gas-pressure welding, enclosed-arc welding, etc. Narrow Gap Welding is another way of welding the rail joints and because of the lower implementation costs, easier, quicker process and acceptable performance, it is usually used over other methods in maintenance operations. Since this method is newer than others, there is lack of knowledge concerning the standard process of narrow gap welding and the factors that affect the final quality. In the narrow gap welding, two different welding electrodes are used for the welding process. One electrode, with higher stiffness, is used for the rail head and the other electrode, with lower stiffness, is used for the rail web and foot. In this research, the relationship between these different welding electrodes and the amount of stress in rail joint was investigated via experiments and modeling, by a finite element method. The results indicate that the number of stresses, in the junction of rail head and web, was reduced by 37%, when the electrode with higher stiffness was used for the whole rail head, plus 1 cm of rail web. Field investigations demonstrated that the performance of rail welds was acceptable.
“…2. Another method classifies the forces applied to the railway track into two categories of static and dynamic forces [39]. Static forces are mainly due to the weight of the railway vehicles, but it should be noted that since the rolling stock is passing over the rail and due to the existence of geometric and structural defects in the rails and in the railway vehicles, the nature of the vertical and lateral forces on the rail is dynamic [8,[40][41][42][43][44][45][46][47].…”
In the modern railway superstructure construction and maintenance, particularly where higher speeds are required, the rail sections may be welded together to form Continuous Welded Rail (CWR). There are various methods for welding the rails, such as thermite welding, flash-butt welding, gas-pressure welding, enclosed-arc welding, etc. Narrow Gap Welding is another way of welding the rail joints and because of the lower implementation costs, easier, quicker process and acceptable performance, it is usually used over other methods in maintenance operations. Since this method is newer than others, there is lack of knowledge concerning the standard process of narrow gap welding and the factors that affect the final quality. In the narrow gap welding, two different welding electrodes are used for the welding process. One electrode, with higher stiffness, is used for the rail head and the other electrode, with lower stiffness, is used for the rail web and foot. In this research, the relationship between these different welding electrodes and the amount of stress in rail joint was investigated via experiments and modeling, by a finite element method. The results indicate that the number of stresses, in the junction of rail head and web, was reduced by 37%, when the electrode with higher stiffness was used for the whole rail head, plus 1 cm of rail web. Field investigations demonstrated that the performance of rail welds was acceptable.
“…However, there is no research focusing on the impacts of settlement on BTCBS, and the many studies focused on the effects of traditional subgrade and ground settlement on bridges instead. 4 Many studies have focused on the track deformation and stress regarding the effects of settlement on bridges. [5][6][7] Jiang et al 8,9 respectively investigated the mapping relationship between the deformations of a continuous bridge and a simply supported bridge and track geometry with analytical method.…”
Section: Introductionmentioning
confidence: 99%
“…However, there is no research focusing on the impacts of settlement on BTCBS, and the many studies focused on the effects of traditional subgrade and ground settlement on bridges instead. 4 Figure 1.Layout of BTCBS.…”
Section: Introductionmentioning
confidence: 99%
“…In addition, the dynamic analysis of the train were studied. Zhang et al 21 analysed the effects of different pier settlements on track deformation and running safety. Cui et al 22 studied the deformation of ballastless track under differential settlement of roadbed and discussed the effects of settlement wavelength and settlement amplitude.…”
In this paper, the effects of settlement on force, track deformation, and train dynamics to determine the settlement thresholds of ballastless track-concrete box subgrade (BTCBS) are studied. Firstly, this study introduces four settlement types, namely V-shape, box rolling, box faulting, and trapezoid settlement. The nonlinear finite element model (FEM) of BTCBS and the train-ballastless track-concrete box subgrade (TBTCBS) model considering nonlinear contact between track slabs and base slabs are established. Then, the effects of settlement on fastener force, track deformation, and vehicle dynamics are studied. According to the calculated results and China’s codes, the settlement limit values of BTCBS can be obtained. The results indicate that the settlement thresholds with box rolling and faulting are controlled by vertical force of fasteners, and the settlement limit values with V-shape and trapezoid settlement are controlled by 10 m chord versine of vertical irregularity (CVVI). The suggested settlement limit values of BTCBS for box faulting, box rolling, trapezoid, and V-shape settlement are respectively 2.48 mm, 2.55 mm, 17.43 mm, and 8.79 mm.
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