• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2891-2894
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• 2011

Recently, the rise of the rail temperature is accelerating further due to the global warming, and the track stability(buckling) problem result from the axial force in the continuous welded rail(CWR) have become the most important issue. This track stability threatens the security of running trains in the hot summer. In order to prevent the track buckling in the hot summer and ensure the safety of the running train, as a part of the safety control plan for KORAIL high-speed railway, the train speed restriction according to the rail temperature was introduced in 2004. However, the conceptual and theoretical background of train-speed restriction is uncertain. In this paper, the theoretical study about the reasonable train-speed restriction is performed. For this purpose, the risk-based probabilistic stability evaluation of the track buckling is applied.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.3160-3165
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• 2011

The track and bridge interaction should be considered for the safety check of railway bridge design as the longitudinal forces transmitted to rail and bridge are changed by longitudinal stiffness of bridge system. The longitudinal stiffness of bridge structures is determined by the magnitude of the ballast resistance, the expansion length of superstructure, and longitudinal stiffness of substructure including pier and foundations. In this study, the main factors affect on the longitudinal rail forces are discussed and the computational parametric analysis of rail forces considering rail-bridge interactions. And the required range of stiffness of sub-structures and span length for the assurance of safety of CWR(continuous welded rail) track is suggested.

• Interaction and multiscale mechanics
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• v.5 no.1
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• pp.1-12
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• 2012

Considerable longitudinal rail forces and displacements may develop in continuous welded rail (CWR) track on long-span bridges due to temperature variations. The track stability may be disturbed due to excessive relative displacements between the sleepers and ballast bed and the accompanied reduction in frictional resistance. For high-speed tracks, however, solving these problems by installing rail expansion devices in the track is not an attractive solution as these devices may cause a local disturbance of the vertical track stiffness and track geometry which will require intensive maintenance. With reference to temperature, two actions are considered by the bridge loading standards, the uniform variation in the rail and deck temperature and the temperature gradient in deck. Generally, the effect of temperature gradient has been disregarded in the interaction analysis. This paper mainly deals with the effect of temperature gradient on the track-bridge interaction with respect to the support reaction, rail stresses and stability. The study presented in this paper was not mentioned in the related codes so far.

• Journal of the Korean Society for Railway
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• v.9 no.6 s.37
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• pp.689-694
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• 2006

Most of design parameters of Railway Structures are determined by the serviceability requirements, rather than the structural safety requirements. The serviceability requirements come from Ensuring of running safety and ride comfort of train, reduction of track maintenance working Track-Bridge interaction should be considered in the design of railway structures. In this study, a numerical method which precisely evaluate an axial force of rail and a rail expansion and contraction when turnout exist in succession on a CWR of bridge is developed.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.684-691
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• 2010

Rail is one of major track components for train service, it should be provided in the condition of flat and smooth driving aspect. Therefore, it is inevitable that there would be the field welding to integrate on CWR(Continuous Welded Rail) removing rail joint in these days. It is high chance to be some rail surface irregularity due to the limitation on the status of work condition If a high speed train runs on the rail surface irregularity in the welding part, big impact load comes to pass on that, so track irregularity cycle is reduced, therefore track maintenance cost can be increased. this paper has analyzed wheel load variation according to removing the rail surface irregularity using portable grinding machine in the high speed line. The result measured before and after in the field is decreased about 9.26% on the wheel load variation.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.505-515
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• 2009

In railway bridges, various loads including train load, transverse load and braking force are applied to continuous CWR or semi-continuous longer rail located on non-continuous bridge superstructures. The rail-girder interaction due to thermal expansion is also very complex in railway bridges because the thermal characteristics for each of the rails and girder are quite different. Recently, the bridge retrofits for seismic loads were performed on bridges not designed for these loads. These retrofits may however have limitations with respect to rail-girder interactions because, in general these retrofits address issues related only to seismic loads. In this study of seismic evaluations for railway bridges, the load effects on the bridge rails from the road beds through the continuous rails shall be considered. Practical methods will be proposed which will increase the railway stability. For this, rail-girder interaction analyses due to train loads, temperature changes and seismic loads were performed and the results reviewed from a practical point of view.

• Journal of the Korean Society for Railway
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• v.6 no.4
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• pp.239-245
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• 2003

In this paper, the track impact factor of conventional line was evaluated using the data for wheel load measured in field and the properties of current operating trains. The equation for track impact factor was presented through the statistical analysis of variational ratio in wheel load and compared with other design equations in domestic and foreign countries. A review on the safety of track system in conventional line was made from the relationship between the velocity and the corresponding impact factor. It was found that the impact factor from the proposed equation is a little less than the values from the equations adopted in both AREA and domestic railway, while it is same as the equation for continuous welded rail(CWR) in Japan. Therefore it could be said that the track satisfies a criteria for dynamic load caused by the train and the corresponding level of safety is guaranteed for dynamic load of the train

• Proceedings of the KSR Conference
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• 2001.05a
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• pp.369-374
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• 2001

It was estimated that the anti-vibration measures at the source location of railroad are the most active and effective ones. Among CWR(Continuously Welded Rail), elastic rail fastener, floating slab, ballast mat, under sleeper pad, etc. like these various kinds of measures in the source, under sleeper pad as an anti-vibration measure was constructed at the railroad track supporting structures in the Jeon-la Line. In this study, through the field measurement of vibration at the railroad track supporting structures and nearby the ground, the vibration reduction effect of under sleeper pad were evaluated by insertion loss. As a result, vibration reduction effects were 5.0∼12.5㏈ on the concrete slab of the bridge, 3.9∼7.5㏈ on the ground nearby the bridge respectively.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.793-799
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• 2004

In track a third weakness point is joint part, turnout part, curve part. One of them joint part of rail have been known to the most weak point by loosen of joint bar and fish bolt due to impulse and vibration by wheel contact at times. In addition happen to deformation and failure at end of rail, failure and miniature of ballast gravel. Finally impact between wheel and rail become origin cause of a welded rail, noise and vibration. riding condition deterioration, besides track failure. In the present domestic, Thermite and Gas pressure weldings have been used to continuous welded rail(CWR), however stiffness and confidence in quality is lower than Flash butt welding method. FRW have the excellent capacity, however have a shortcoming large scale of machine and power equipment. Therefore we will introduce Mobile Flash Butt Welder can weld in track.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.806-811
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• 2004

Currently, in the design criteria for the high speed railway bridges, the maximum distance between bridge expansion joint is limited to 80m using a continuous welded mil, in order to limit the additional stress in the rail due to the rail-bridge interaction. In the past study on the resonance effect of HSR train, it is known that the reduction of resonance and dynamic responses of bridge deck occurs at the specific expansion length of 28.05m and 46.75m. In this study, the stability of track structure on the HSR bridges with expansion length of 90m has checked by finite element method. And the track behavior including mil stresses and relative displacements are compared to the current state of track structures on the bridge system with 80m long expansion length.