• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1667-1673
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• 2011

For performance evaluation of modified wide sleepers(MF-140 PSC sleepers), design moment for urban transit was calculated and then performance evaluation criteria were set up according to EN 13230-2. Next, static bend tests, dynamic tests at rail seat section of sleeper were carried out and static bend tests at center section of sleeper were fulfilled. The test results for modified wide sleepers were in excess of performance evaluation criteria and structural safety of sleepers was able to guaranteed from the results. As modifying depth of wide sleepers, construction convenience in underground will be expected to be improved and construction costs will be expected to be decreased.

• Proceedings of the KSR Conference
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• 2002.10b
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• pp.1106-1111
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• 2002

The design of sleeper in high-speed railway turnouts is complicated and time-consuming because the length and loading position of sleepers change continuously along the turnout line. It is, therefore, necessary to develop an automated design program which can design automatically the PSC sleepers in turnout region. In this study, a computer program for automatic design of turnout sleepers was developed based on graphic user-interface(GUI) environment. The structural analysis is performed considering the varying loading position of vehicular wheels. The sleepers are treated as located on elastic supports. The user can choose the desirable shape of sleepers before starting the detail design. The present study allows more realistic and automatic design of PSC sleepers in high-speed railway turnouts.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.977-981
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• 2004

Variety of recent railroad markets arouses the need for steel sleepers. Steel sleepers have many advantages over conventional timber or PC sleepers with respect to safety, environment and economical efficiency due to less effort for maintenance. Weak points of timber sleepers are to cut trees and apply toxic creosote as well as to need frequent maintenances while it is difficult to apply PC sleepers to steel bridge or crossing and to recycle them completely. In this paper, technical trends are analyzed in order to develop suitable steel sleepers for domestic railroads.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.370-375
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• 2005

Floating sleepers in a ballasted track increase both track deterioration and track irregularities. Consequently, a considerable maintenance work is required and maintenance cycle is shortened due to the floating sleepers. This paper quantifies the degrees of void between the floating sleepers and a ballast bed. In the future, the influence of floating sleepers on the track will be investigated by an analytical method using a dynamic model.

• Structural Engineering and Mechanics
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• v.44 no.1
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• pp.51-60
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• 2012

Concrete sleepers are essential components of the conventional railway. As support elements, sleepers are always subjective to a variety of time-dependent loads attributable to the train operations, either wheel or rail abnormalities. It has been observed that the sleepers may deteriorate due to these loads, inducing the formation of hairline cracks. There are two areas along the sleepers that are more prone to crack: the central and the rail seat sections. Several non-destructive methods have been developed to identify failures in structures. Health monitoring techniques are based on vibration responses measurements, which help engineers to identify the vibration-based damage or remotely monitor the sleeper health. In the present paper, the dynamic effects of the cracks in the vibration signatures of the railway pre-stressed concrete sleepers are investigated. The experimental modal analysis has been used to evaluate the modal bending changes in the vibration characteristics of the sleepers, differentiating between the central and the rail seat locations of the cracks. Modal parameters changes of the 'healthy' and cracked sleepers have been highlighted in terms of natural frequencies and modal damping. The paper concludes with a discussion of the most suitable failure indicator and it defines the vibration signatures of intact, central cracked and rail seat cracked sleepers.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1126-1131
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• 2007

In 1st Phase Kyeong-Bu High-Speed Line, to lessen the impact in the transition zone between concrete slab track(in tunnel) and ballasted track(on embankment), the ballast bonding method has been adopted. However, in this area, in the beginning of the operation, unsupported sleepers are found, and the track deterioration and damage of concrete sleepers have occurred. In this paper, the status and causes of unsupported sleepers are discussed and several repair measures are proposed.

• Journal of the Korean Society for Railway
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• v.13 no.6
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• pp.565-569
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• 2010

Sleepers perform bearing rails and are underneath rails. Therefore, the current and voltage of rails are related to the resistance of sleepers. In case that the resistance of sleepers are low, operation problems of relays in tr ack circuits are occur because of flowing leakage current through sleepers. So the condition that the track circuit is always occupied by a train is kept. Currently, the creosote has been used in wood sleepers due to prevention against putrefaction. After a long time, the material is changeable to the chemistry material bases on carbon dioxide or carbon. So, the insulation resistance of wood sleepers is lower than the initial insulation resistance. In case of effecting wood sleepers as conductors, amplitude of the current and voltage on rails is decreased. This phenomenon causes that a train does not receive signals. In this paper, four-network model on the track circuit including the insulation resistance of sleepers is suggested. Also, the standard value of the resistance in straight section is proposed in the wood sleeper.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04b
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• pp.755-760
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• 1998

In the present, we have developed high strength concrete for the sleepers of high speed rail and verified its applicability by in-situ applications. Concrete for sleepers is manufactured by steam curing at low temperature(below 55$^{\circ}C$), and should be finished its manufacturing process such as placing, curing, demolding and prestressing in 24 hours. The sleepers need its compressive strength above 350kg/$\textrm{cm}^2$ in 15 hours, air-entrainment for durability and nominal design strength of 600kg/$\textrm{cm}^2$, considering its quality variation at factory. We performed the optimum mix design of concrete and verified the rightness of the use of TYPE III cement. Finally, we have confirmed the manufactured sleepers satisfy the required material properties through in-situ application.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.1332-1339
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• 2006

Hanging sleepers, which are not fully supported between the sleepers and the ballast, could cause large dynamic forces especially on high speed ballasted track. The dynamic forces resulting from insufficient supporting forces may badly affect the running stability and safety of train. These also accelerate track irregularities and deteriorate track components rapidly. Consequently, the hanging sleepers will lead to sharp increases in track maintenance cost. This paper introduces a rapid and easy method to detect hanging sleepers with portable light falling weight deflectometer (LFWD) and summarizes the results of experiments performed at the high speed ballasted track.

• Journal of the Korean Society for Railway
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• v.13 no.2
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• pp.214-221
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• 2010

The transitional zone between tunnel and earthwork is one of the most vulnerable areas site for railway lines and because of differential settlement due to different stiffness of each supporting layer, it has to conducted a maintenance work constantly. In this study, it is conducted to compare the effect of reinforcement by wheel load and displacement of the sleepers after existing sleepers are replaced with the large sleepers for 20m long in-field transitional zone. Also, numerical parametric study using multi-layer elastic method has been performed to compare rail force, settlement and stresses of ballast while varying size and space of the sleeper. The field test and numerical results show that replacing the large sleepers improves about 10% of total settlement and coefficient of wheel force than conventional sleepers. Effectiveness of improvement is about 9.3%, 4%, 14.5% for rail seat force, settlement of sleepers and ballast pressure respectively with size of sleepers.