• Journal of the Korean Society for Railway
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• v.18 no.3
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• pp.232-240
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• 2015

Two types of track circuits are used in high speed railway car depots: one is High Voltage Impulse Track Circuit(HVITC); the other is AF track circuit. HVITC detects train occupation of blocks and broken rail; the AF track circuit is used for train onboard control system pretesting before departure. This testing is used to transmit train control information through the AF track circuit. The two systems are switched in turns for testing. We propose a system in which the AF track circuit is replaced by a loop cable that is installed on the inside rail; as such, engineers do not need to switch the systems. In cases in which the two systems run simultaneously, mutual interference may occur. In this paper, we identified this mutual interference by modeling of the two circuits.

• Journal of the Korean Society for Railway
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• v.7 no.3
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• pp.283-289
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• 2004

According to continuos welded rails on a bridge, temperature changes bring about the expansion of the bridge deck adding axil forces on the track. Moreover, the ballast on the bridge deck expansion joint is moved due to the bridge deck. If bridge decks are longer, the influence is greater, loosening ballast, causing track irregularities, and deteriorating passengers' comfort. Considering structure of bridge itself and tolerance of track irregularities caused by the loosened ballast on bridges, the maximum length of a deck should be less than 80m, which is the same as the standard of the French railway. In this study, an interaction between the expansion related to the bridge length and irregularity in longitudinal level referring to measurements and maintenance works performed in the high-speed railways was analyzed. This research shows that installation of sliding plate or vertical ballast stopper is not a good option since it is difficult to install. On the other hand, installation of movable fastener or gluing is easy but its influence is insignificant. To conclude, switch tie tamping or manual tamping is more effective than others.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.10a
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• pp.816-816
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• 2009

In order to attenuate structural waves in railway track, damped mass-spring absorber system and spring supported system are considered that are attached continuously along the beam length. A mathematical model is presented for the propagation of structural waves on a finitely long, periodically supported classical beam. The model in this paper could represent a railway track where the beam represents the rail and an appropriately chosen support type represents the pad/sleeper/ballast system of a railway track. And in this study, it is presented that the measurement method of health monitoring of railway track.

• Journal of Sensor Science and Technology
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• v.25 no.2
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• pp.91-102
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• 2016

The objective of this paper is to propose a heuristic algorithm to optimize the railway track maintenance scheduling, a NP-hard problem, by reflecting conditions of the actual field more quickly and easily. We develop the mechanism based on Binary Artificial Bee Colony (BABC) and Binary Harmony Search (BHS), and verify their performance through simulation experiments. Our proposed BABC and BHS mechanisms were applied to problems composed of 30, 60, 100, and 200 operations for railway track maintenance scheduling to carry out experiments and analysis. On comparing it with the results solved by CPLEX, it is found that the mechanism could present an optimal solution within limited time by user.

• International Journal of Railway
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• v.6 no.2
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• pp.59-63
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• 2013

The purpose of this paper was to evaluate the effectiveness of geogrid for conventional ballasted track and asphalt concrete underlayment track using PLAXIS finite element program. Geogrid element was modeled at various locations that include subballast/subgrade, subballast/ballast interfaces, middle of the ballast, and one-third depth of the ballast. The results revealed that the effectiveness of geogrid reinforcement appeared to be larger for ballasted track structure compared to asphalt concrete underlayment track. Particularly, in case of installing geogrid at one-third depth of ballast layer in a conventional ballasted track, the most effectiveness of geogrid reinforcement was achieved. The influence of geogrid axial stiffness on track substructure response was not clear to conclude. Further validations using a discrete element method along with experimental investigation are considered as a future study. The effect of asphalt concrete layer modulus was evaluated. The results exhibited that higher layer modulus seems to be effective in controlling displacement and strain of track substructure. However it also yields slightly higher stresses within track substructure. It infers that further validations are required to come up with optimum asphalt concrete mixture design to meet economical and functional criteria.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.1090-1095
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• 2008

Track geometry changes by traffic loads. The bigger the changes are, the worse the riding comfort and running stability of train. This is so-called track irregularity and is the most important quality parameters of ballasted track. To objectively assess track irregularity, track geometry should be able to be measured. Practically, railway companies use moving chord method, which determine versine values via a chord. The versine is the vertical distance to curve measured in the middle of the chord. This type of method measures only versine of track irregularity curve by transfer function from the characteristics of measuring device. In this report, review the characteristics of two types of measuring tools by comparing the measurements. The one is GRP-1000 system, optical surveying system with Total station and lazar prism trolley. This calculates track geometry by surveying absolute coordinates of two points each on both rail heads. The other is EM-120, measures versine with 10m of symmetrical chord length.

• Journal of the Korean Society for Railway
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• v.20 no.5
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• pp.649-657
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• 2017

In this study, fatigue testing was carried out for long-term use of rail according to track type. From S-N curves for 50%~0.01% failure probability, the fatigue life of the long-term use rail for each track type was derived using the weight probability analysis technique on the experimental data. Because the rails used in the fatigue test have different cumulative tonnages, the number of repetitions was modified by averaging the cumulative tonnage. In addition, the bending stresses of rail bottoms, considering rail surface irregularities, track support stiffnesses and train speeds, were evaluated using the predicted rail bending stresses derived from existing studies. As a result, for rail fatigue life evaluation, the fatigue life of rail on the ballast track was found to be more than 200 million tons higher than the standard value for rail replacement. Also, the fatigue life of rail on concrete track is more than 300 million tons higher than that on ballast track. The Haibach rule is adaptable for the fatigue life evaluation of rail for stress range under fatigue limit.

• Journal of the Society of Disaster Information
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• v.14 no.4
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• pp.458-465
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• 2018

Purpose: Concrete track that affects on railway safety can detect cracks using image processing technique. However, since a condition of concrete track and surface noisy are obstructed to detect cracks, there is a need for a way to remove them effectively. Method: In this study, we proposed an image processing to detect cracks effectively for Korean railway and verified its performance through experiment. We developed image acquisition system for capture a railway concrete track and acquired railway concrete track images, randomly selected 2000 images and detected cracks in the image process using proposed Gabor Filter Bank methods. Results: As a result, 94% of detection rate are matched to the actual cracks in same quality and format railway concrete track image. Conclution: The crack detection method using Garbor Filter Bank was confirmed to be effective for crack image including noise in the Korean railway concrete track. This system is expected to become an automated maintenance system in the existing human-centered railway industry.

• Journal of the Korean Society for Railway
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• v.20 no.5
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• pp.658-667
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• 2017

Rail is the main track component, playing the most important role in safe railways. For the sake of safety, it is strictly required to secure reliability against fatigue and destruction of rail. In this paper, by field measurement on concrete track, it is confirmed that the rail surface roughness and rail bending stress are linearly correlated with each other; the bending stress of rail can be presented as a function of train speed, track support stiffness, and rail surface roughness. The fatigue life of rail can be estimated by deriving the S-N curve through the fatigue test.

• Journal of the Korean Society for Railway
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• v.14 no.6
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• pp.526-534
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• 2011

In this study, proposed is the methodology to determine the upper limit for stiffness of rail pad for the ballasted and concrete track in high-speed railway in the viewpoint of running safety, considering the dynamic characteristics of train and track and the operation environment. For the track irregularity, one of the most important input parameters for traintrack interaction analysis, the reference vertical track irregularity PSDs(power spectral densities) for the ballasted and concrete track in a wide range of frequencies were proposed based on those presented in France and Germany and that obtained from the measured data at Kyeong-Bu 1st phase high-speed railway line. Using these reference PSD models, the input data for the vertical track irregularity data were regenerated by random generation process, and then, the wheel load reduction rates according to the stiffness of the rail pads have been calculated by the train-track interaction analysis technique. Finally, by comparing the wheel load reduction rates calculated with the derailment criteria prescribed in the Korean standards for railway vehicle safety criteria, the upper limits for the stiffness of rail pad have been proposed.