• Proceedings of the KSR Conference
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• 2007.11a
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• pp.386-394
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• 2007

Due to the transportability problems, long rail shall be from base rail unit, which is normally 100m for regular rail and 300m for high speed rail. After these rail units are transported from the fabricator to the site, the field weld would be performed.axial stresses in the long rail is mainly from the temperature differences at various locations the long rail. Also the gaps between each welds cause secondary axial stresses in the rail. In addition to these, re-welds the fractured rails, rail buckling, irregular rail vibration, rail twist also result innonuniform axial stresses in the rail. To obtain the rail buckling stability, the rail stresses shall be released due to the resetting of CWR. Traditionally two resetting of CWR methods have been applied, the one is rail heater and the other is rail tenser. these methods, the latter has been recommended because it has less limitation in the rail length and it is easier to minimized the force differences. But even in this method, the calculation is cumbersome and is not easy to find out the rail stress distribution itself.refined methodsxial stress resetting in the long rail is studied and this study be easily applied in the real construction. From this approach, more rational rail maintenance system can be expected.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1362-1369
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• 2007

Seoul Metro continuously converted the standard rail into continuous welded rail since the later part of 1990's, and currently, most of the sectors of the Seoul Metro are continuous welded rails. As the continuous welded rail is inhibited by the contraction and expansion force of the rail as well as rail-bed, this force is stored as the internal stress of the rail with the exception of portion of the both ends of the continuous welded rail. If the contraction and expansion of the rail is restricted, the internal stress, that is, the force in the direction of the axis, is proportional to the cross-sectional area of the rail. Therefore, with regards to the temperature changes, the internal stress changes in accordance with the type of rail, bolting apparatus, railroad tie and rail-bed. As such, the rail temperature becomes important data in securing the gap at the adjoining section of the rail in the standard rail section, and to determine the setting temperature for the continuous welded rail. In addition, it becomes basic data for maintenance of the track. Accordingly, this thesis introduces cases of installation of rail temperature detector in order to prevent and manage track defectiveness due to increase in rail temperature, and to utilize as basic data at the time of various construction and maintenance. Furthermore, this thesis aims to assist maintenance of track through systematic temperature management in the future by looking into means of its utilization.

• Journal of the Korean Society for Railway
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• v.3 no.1
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• pp.19-26
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• 2000

The rail temperature is important to preserve the joint gap for standard length of rail and to determine the installation temperature which has direct influence on the rail buckling and failure in welded part for continuous welded rail(CWR), Therefore, we have measured and investigated various characteristics of rail temperature for each kind of rail. As the results of this, the correlation between the atmosphere temperature and the rail temperature which is commonly used by Korean Railway should be reconsidered. Also, the daily highest '||'&'||' lowest rail temperature was occurred when each temperature is higher and when it's lower. For the light rail, the rail temperature by the sun-light increases quickly and decreases late. But the time where the highest temperature is attained is same. There are some differences between the shade and sunny place about 3.0∼4.0$\^{C}$. The temperature of rail web is almost close to the conversion rail temperature for rail expansion. The wind of 1 m/s has an influence on the rail temperature around 5$\^{C}$.

• Journal of the Korean Society of Safety
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• v.31 no.5
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• pp.89-94
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• 2016

The objective of this study was to estimate the dynamic behavior of a personal rapid transit(PRT) track system using a rail of rectangular tube section and a rail joint of sliding type, and to compare the results with the normal rail and rail joint of a PRT track system by performing field measurements using actual vehicles running along the service lines. The measured vertical displacement of rail and sleeper, and vertical acceleration of rail for the normal rail and rail joint section were found to be similar, and the rail joint of sliding type satisfied the design specifications of the track impact factor for a conventional railway track. The experimental results showed that the overall dynamic response of the rail joint were found to be similar to or less than that of the normal rail, therefore the rail joint of sliding type for PRT track system was sufficient to ensure a stability and safety of PRT track system.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.255-261
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• 2008

The importance of maintenance of rail surface defects is increasing according to the KTX operation. That is because during high speed operation of rolling stocks, rail surface defects shorten fatigue life of rail, accelerate track degradation and deteriorate ride comfort. Rail grinding has been applied for effective rail maintenance in Kyeong-Bu HS line. This paper evaluates the effectiveness of rail grinding in term of rail fatigue life. To this end, the stresses of the ground rail are measured under KTX running and the equivalent stress range is calculated by RMC after the frequency analysis done with Rainflow counting method. Also, Pamglen-Miner rule is applied to predict the fatigue life of ground rail. The result of the analysis shows that the fatigue life of ground rail is increased by 15%.

• Journal of the Korean Society for Railway
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• v.7 no.4
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• pp.374-390
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• 2004

In this paper, I illustrate the situations and problems rail industry is faced with. The rail industry has been suffering deficiency in investment with low technical level. Lacks of strategic marketing plans and low competitiveness in the industry led to a small portion of modal share, estimated at 12.6% in 2001(person base). Recently, rail industry has caught up with the current flow of changes. For example, a prototype of Korea high speed train had been manufactured to be successfully tested on commercial track. And the amount of rail investment increased gradually. The rail industry of EU nations, America, Japan reveals good outcomes, which keeps the balance in the black thanks to growth of investment in rail and high technical level. I have come up with some ideas for improvement, which I believe will be helpful to lead the rail industry. First, I suggest the upbringing of rail industry and technology on a national level. Second, expanding the rail network with the rail modernization. Lastly, I think it is crucial to establish a law and institution before we advance into overseas markets.

• Structural Engineering and Mechanics
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• v.48 no.4
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• pp.455-466
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• 2013

In recent years, many countries have added railway noise to the issues covered by noise regulations. It is known that the rail is the dominant source of rolling noise at frequency range of 500Hz-2000Hz for the conventional speeds (<160km/h). One of the effective ways to reduce noise from railway track is using a rail vibration absorber. To study the acoustic performance of rail absorber, the decay rates of vibration have long been used by researcher. In this paper, A FE model of a periodic supported rail with infinite element in ABAQUS is developed to study the acoustic performance of the rail absorber. To compute the decay rates, acceleration responses along the rail transferred to MATLAB to obtain response levels in frequency domain and then by processing the response levels, the decay rates obtained for each1/3octav band. Continous rail absorber is represented by a steel layer and an elastomer layer. The decay rates for conventional rail and rail with one-side absorber and also, the rail with two side absorber are obtained and compared. Then, to improve the system of rail absorber, a steel plate with elastomer layer is added to bottom of the rail foot. The vertical decay rate results show that the decay rate of rail vibration along the track is significantly increased around the tuned frequency of the absorber and thus the rail vibration energy is substantially reduced in the corresponding frequency region and also effective in rail noise reduction.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.516-528
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• 2009

Form the application of long rail system the non-ballast steel plate bridges, fatigue strength increase and rail noise reduction can be expected. This is mainly form the reduction of the rail impact at the rail joint locations which already made to behave together from welds. In the high speed rail, application of long rail system is essential because without long rail system, the required serviceability level can not be achieved. But even with this long rail systems, the thermal expansion from the girder can not be absorbed in the normal bearing systems, and these expansion cause between girder and rail. Also unexpected rail buckling and fracture through rail thermal tension may happen. It was found through numerical analysis and field measurement that these problems can be avoided by semi-fixed bearing system. In this study, the benefits of non-ballast plate bridge through long rail system, especially at the point of girder stability, girder stiffness increase and bearing maintenance will be reviewed.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.201-207
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• 2007

At an early design stage of rail track, dynamic analyses using a standard vehicle model of ADAMS/Rail are employed. In the real field, it is very difficult to find an optimal solution on the designing of rail track considering future operating vehicles because the construction of rail track should be done in the advance of vehicle selection and operation. Using a standard vehicle model of ADAMS/Rail, however the better selection among designed rail tracks is possible by comparing the dynamic analysis.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.783-792
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• 2011

The control of rail surface irregularity is very important for the high speed train service in the high speed rail. In order to manage it, initial, preventative, and maintainable rail grinding have been performed and among them, preventative rail grinding conducts in every each year. This study carried out the field test for dynamic track response according to rail surface irregularity comparing before and after rail grinding. In addition, the change of dynamic track responses according to rail grinding was analyzed and the fatigue life was estimated though Rainflow Counting Method and RMC Equivalence Stress. Therefore, it suggested that rail fatigue life should be increased by rail grinding, because amount of impact occurred on track is decreased by getting rid of rail surface irregularity.