• Journal of the Korean Society for Railway
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• v.17 no.3
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• pp.193-200
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• 2014

In this study, fatigue tests on existing continuous welded rail (CWR) on a concrete track were carried out. Based on the test results, a S-N curve expressing the remaining life of the CWR at a fracture probability of 50% was obtained using weighted probit analysis suitable for small-sample fatigue data sets. As rails had different histories in terms of accumulated passing tonnage, the test data were corrected to average out the accumulated passing tonnage. The remaining service life for the CWR on the concrete track in an urban railway was estimated using the prediction equation for the bending stress of rail developed in the past to estimate rail base bending stress and taking the surface irregularities into consideration. Estimating the remaining service life of the CWR in an urban railway showed that the rail replacement period could be extended over 200MGT. In addition, comparing the concrete track to the ballast track, the fatigue life of rail was analyzed as approximately 300MGT higher than. Therefore, the rail replacement criteria needs to distinguish between the ballast track and the concrete track, and not the criteria needs to be changed as a target for the maintenance, although it is necessary to remove longitudinal rail surface irregularities at welds by grinding.

• Structural Engineering and Mechanics
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• v.63 no.6
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• pp.713-723
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• 2017

As a new type of ballastless track, longitudinal continuous slab track (CST) has been widely used in China. It can partly isolate the interaction between the ballastless track and the bridge and thus the rail expansion device would be unnecessary. Compared with the traditional track, CST is composed of multi layers of continuous structures and various connecting components. In order to investigate the performance of CST on a long-span bridge, the spatial finite element model considering each layer of the CST structure, connecting components, bridge, and subgrade is established and verified according to the theory of beam-rail interaction. The nonlinear resistance of materials between multilayer track structures is measured by experiments, while the temperature gradients of the bridge and CST are based on the long-term measured data. This study compares the force distribution rules of ballasted track and CST as respectively applied to a long span bridge. The effects of different damage conditions on CST structures are also discussed. The results show that the additional rail stress is small and the CST structure has a high safety factor under the measured temperature load. The rail expansion device can be cancelled when CST is adopted on the long span bridge. Beam end rotation caused by temperature gradient and vertical load will have a significant effect on the rail stress of CST. The additional flexure stress should be considered with the additional expansion stress simultaneously when the rail stress of CST requires to be checked. Both the maximum sliding friction coefficient of sliding layer and cracking condition of concrete plate should be considered to decide the arrangement of connecting components and the ultimate expansion span of the bridge when adopting CST.

• Journal of the Korean Society for Railway
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• v.13 no.2
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• pp.179-185
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• 2010

In order to secure safety for the buckling and fracture of continuous welded rail and improve the efficiency of maintenance work, it is very important that grasp the characteristics of rail temperature. Recently, the maximum air temperature in summer season rises gradually and the minimum air temperature in winter season is decreasing gradually due to the climate change. Therefore, these phenomenon influences in the change amount of yearly rail temperature and can cause change of laying and maintenance temperature. In this study, actual measurement of rail temperature including climatic factors is carried out by constructing the temperature and climate measurement system as realistic as possible. Through the intensive investigation of actual data, it is founded that the existing prediction formulas for rail temperature may be used only in certain climatic conditions (certain combination of climatic factors). It may be more reasonable that the rail temperature considering actual climatic factors in site is predicted on probabilistic approach.

• Proceedings of the KSR Conference
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• 2002.10a
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• pp.654-659
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• 2002

Continuous Welded rail(C.W.R.) tracks has many advantages over the conventional jointed rail track. Due to the elimination of rail joints for thermal expantion, however it many cause the track to be suddenly bucklled by thermal loads. The present study investigates the influences of Pad-fastner on the Thermal buckling behavior of C.W.R. Parametric studies are performed to evaluate the effects of the individual parameters on the upper and lower critical bucklig temperature.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6D
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• pp.895-904
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• 2008

CWR (Continuous Welded Rail) may be broken when a temperature drop below the neutral temperature changes in axial force, causing tensile fracture and rail gap, in winter. Rail-breaks may lead to the damage of the rail and wheel by dynamic load, and the reduction of running safety if not detected before the passage of a train. In this study, the track and train coupled model with open gap for dynamic interaction analysis, is proposed. Linear track and train systems is coupled by the nonlinear Herzian contact spring and the complete system matrices of total track-train system is constructed. And the interaction phenomenon considering open gap, was defined by assigning the irregularity functions between the two sides of a gap. Time history analysis, which have an iteration scheme such as $Newmark-{\beta}$ method based on Modified Newton-Raphson methods, was performed to solve the nonlinear equation. Finally, numerical studies are performed to assess the effect of various parameters of system, apply to various speeds, open gap size and the support stiffness of rail.

• Journal of Korean Society of Steel Construction
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• v.17 no.5 s.78
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• pp.519-526
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• 2005

During summer, very high compressive force occurs on the continuous welded rail (CWR) track because of the increase of rail temperature (max. $60^{\circ}C$). This extreme temperature stress can cause the CWR track to buckle. Among many CWR parameters affecting the track buckling, the influence of the lateral and longitudinal ballast resistance was investigated on the stability of the CWR track in this study. Also, the sensitivity of the track irregularity such as the alignment defect and the gauge irregularity was investigated.

• 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.

• Journal of Korean Society of Steel Construction
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• v.11 no.3 s.40
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• pp.281-290
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• 1999

For many decades, the railway was constructed using tracks with jointed rails of relatively short lengths in accordance with rolling and handling technology. The joints cause many drawbacks in the track and lead to significant maintenance cost. So, railroad engineers became interested in eliminating joints to increase service loads ana speeds by improving rolling, welding, and fastening technology. Continuous welded rail(CWR) track has many advantages over the conventional jointed-rail track. But, in the case of the elimination of rail joints, it may cause the track to be suddenly buckled laterally by thermal loads. In this paper, CWR track model and CWRB program are developed for linear buckling analysis using finite element method. Rail element with a total of 14 degrees of freedom is used. The stiffness of the fastener, tie, and ballast bed are included by a set of spring elements. The investigation on the buckling modes and temperature of CWR track is presented.

• 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.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.445-450
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• 2007

CWR(Continuous Welded Rail) and bridge interaction produce rail force, bridge displacement and rail/bridge relative displacement. Each of these has limitation by many codes. In this paper, analysis of interaction has been carried out by using foreign codes(UIC 774-3 R code of Europe etc.) because there is no code about interaction between rail and bridge in Korea. Recently, railway bridges with CWR has been constructed for structural and economical reasons. When designer plans railway bridges, design a bridge model first and then investigate railway forces and displacement by interaction analysis. If these results go out bounds from limitation, designer plans railway bridges again and again. In this paper, using the parametric study on CWR and railway bridge interaction, railway bridge parameters such as length of bridge span, area of bridge, moment of inertia, stiffness of pier, etc. are presented. It helps preliminary design of railway bridges.