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2 2020

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Numerical investigation on train-induced environmental vibration in floating ladder tracks

Zakeri Jabbar Ali, Ebrahimi-Gholami Omid, Liravi Hassan, Satar-Boroujen Golshan

Journal of Theoretical and Applied Mechanics

2020

Vol. 58 nr 4

871--883

A floating ladder track is established in the present paper as a next-generation non-ballasted track system. The three-dimensional model consists of a track (mass-spring-damping system) and the underlying soil. Rectangular pulse loading with an amplitude of 60 kN is considered as the wheel loading system. A time domain coupled finite element with a semi-infinite absorbing boundary condition is employed using FEM software. Due to axial symmetry of the model instead of the track axle, only half of the model is simulated. It is observed that the performance of the floating ladder track is better in mitigating measured vibration than that of the traditional ballasted track. Numerical results of the floating ladder track reveal that the increase of damping and stiffness yields more vibration responses, which is a straight nonlinear relationship. Although increasing density of the protective layer decreases vibrations on the ground, it has no effect on structural components of the track except for the protective layer. Furthermore, this kind of track is more effective at a closer distance to the source of vibrations.

Effective time interval for railway track geometry inspection

Kasraei Ahmad, Zakeri Jabbar Ali

Archives of Transport

2020

Vol. 53, iss. 1

53--65

A proper decision-making scheme for track geometry maintenance requires a knowledge of the real condition of track geometry. Therefore, the track must be inspected by measurement cars at different time intervals. The frequency of track geometry inspection plays a crucial role in decision-making and has always been a big concern for infrastructure managers. The inspection interval should be chosen properly, it means that the small period can decrease the capacity of line and affect the operation of network and the big period can result in low quality of track and in some cases derailments and possible loss of human lives. The aim of this paper is to determine the effective inspection interval such that the total maintenance cost is minimized. In the proposed cost model, the costs of inspection, preventive maintenance, corrective maintenance and the penalty for exceeding the corrective maintenance level are considered. A case study is performed on a real dataset collected from a railway line in Iran. The standard deviation of longitudinal level is considered to measure track geometry degradation. A widely applied linear model is used to model track geometry degradation over time. Monte Carlo technique is used to simulate the track geometry behavior under various track geometry inspection intervals. In addition, a set of sensitivity analyses are carried out to assess the effect of various inspection intervals on different terms of maintenance cost. The results indicate that not only can substantial costs be saved by setting effective inspection intervals, but also the time during which the track suffers from bad conditions is dramatically reduced. The result of this study has shown the appropriate inspection interval for the studied case can result in 13.6 percent decrease in maintenance cost in comparison with the current maintenance policy. Besides, it would lead to more reliable railway track by preventing the system exceed the corrective threshold.