• Wind and Structures
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• v.29 no.5
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• pp.299-312
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• 2019

Due to the rugged terrain, metro lines in mountain city across numerous wide rivers and deep valleys, resulting in instability of high-pier bridge and insecurity of metro train under crosswind. Compared with the conditions of no-wind, crosswind triggers severer vibration of the dynamic system; compared with the short-pier viaduct, the high-pier viaduct has worse stability under crosswind. For these reasons, the running safety of the metro vehicle traveling on a high-pier viaduct under crosswind is analyzed to ensure the safe operation in metro lines in mountain cities. In this paper, a dynamic model of the metro vehicle-track-bridge system under crosswind is established, in which crosswind loads model considering the condition of wind zone are built. After that, the evaluation indices and the calculation parameters have been selected, moreover, the basic characteristics of the dynamic system with high-pier under crosswind are analyzed. On this basis, the response varies with vehicle speed and wind speed are calculated, then the corresponding safety zone is determined. The results indicate that, crosswind triggers drastic vibration to the metro vehicle and high-pier viaduct, which in turn causes running instability of the vehicle. The corresponding safety zone for metro vehicle traveling on the high-pier is proposed, and the metro traffic on the high-pier bridge under crosswind should not exceed the corresponding limited vehicle speed to ensure the running safety.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.9
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• pp.759-764
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• 2014

Lateral force of wheel is important parameter when we evaluate the safety of a railway vehicle on curved track. The lateral force of wheel is influenced by the steering performance of wheelsets. Generally, in passive type vehicles, the steering performance of wheelsets is influenced by the parameters like primary spring stiffness, wheel base, conicity of the wheel profile, etc. But, the steering performance of passive type vehicle has its limit. To overcome the limit of the steering performance of passive type vehicle, active steering technology is being developed. In this paper, we analyze the lateral force of wheel and the safety of the railway vehicle on curved track by adopting the active steering technology. As results of dynamic analysis for vehicle model equipped with active steering system, the lateral force of wheel is reduced and the safety is improved remarkably.

• Proceedings of the KSR Conference
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• 2004.06a
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• pp.664-669
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• 2004

In rolling stock, wheels are one of the most important components to run on the track in safety. Especially, it is important that wheel profile cause the variation of dynamic characteristics and running safety. The purpose of this paper is to propose the wheel profile and to know the effectiveness of improved wheel profile by using microphones. We also performed analysis of running safety to know application of improved wheel profile before the test. In result, the improved wheel profile was stable in running safety and noise level was reduced.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.382-388
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• 2005

SMSC(Seoul Metropolitan Subway Corporation) is substantially taking the core role of mass transit system in Seoul Metropolitan area. When it was built, the design had challenged to sharp curved tracks less than 250m radius considering the protection of buildings and cultural properties as well as the connection to ground roads. Such circumstances have required a certain extent of slack in track geometry and therefore led to the construction of ballasted track with wooden sleepers. However, the dynamic force from running on sharp curved track has caused the misalignment and abnormal failure of track geometry, and it has resulted in a frequent maintenance and repair works which require a lot of cost and manpower. In this paper, we present the construction case of maintenance-free track system by using of concrete sleeper and elastic rail fastening system to ensure the safety of both passengers and trains, and to contribute the effective maintenance for track facilities of SMSC.

• Journal of the Korean Society for Railway
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• v.17 no.1
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• pp.19-27
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• 2014

Urban railway vehicles operate in downtown areas. Due to increases in the number of passengers and changes in the service plans, railway vehicles are expected to operate on sharp curved tracks. However, on these tracks, the running stability of the railway vehicles is significantly decreased and the creepage is increased. Creepage causes the wheel/rail to wear and vibration. Therefore, reducing the creepage helps ensure the running stability and can be beneficial for the environment and cost. In this paper, the longitudinal creepage is analyzed using a railway vehicle model on a sharp curved track. Furthermore, in order to minimize the problems when a railway vehicle runs on a sharp curved track, the characteristics of a bogie are optimized using response optimization.

• Smart Structures and Systems
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• v.21 no.5
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• pp.677-686
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• 2018

The structural responses are often used to identify the structural local damages. However, it is usually difficult to gain the responses of the track, as the sensors cannot be installed on the track directly. The vehicles running on a track excite track vibration and can also serve as response receivers because the vehicle dynamic response contains the vibration information of the track. A damage identification method using the vehicle responses and sensitivity analysis is proposed for the vehicle-track coupling system in this paper. Different from most damage identification methods of vehicle-track coupling system, which require the structural responses, only the vehicle responses are required in the proposed method. The local damages are identified by a sensitivity-based model updating process. In the vehicle-track coupling system, the track is modeled as a discrete point supported Euler-Bernoulli beam, and two vehicle models are proposed to investigate the accuracy and efficiency of damage identification. The measured track irregularity is considered in the calculation of vehicle dynamic responses. The measurement noises are also considered to study their effects to the damage identification results. The identified results demonstrate that the proposed method is capable to identify the local damages of the track accurately in different noise levels with only the vehicle responses.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.317-324
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• 2007

Until now, the railway has been constructed using track with jointed rails of relatively short lengths to allow thermal expansion in hot summer months. These joints weaken the track structurally and increase track maintenance cost and power consumption of the running train. The CWR(Continuous Welded Rail) Track is the solution of these drawbacks. Although the CWR track not only reduces the track maintenance cost but also increases the life cycle of track components, the stability of the track is highly affected by change of temperatures and vehicle load. A three dimensional nonlinear analysis which considers rail, fastening system and tie has been performed to understand structural behavior of the CWR track. In this case, the translational and rotational stiffness values of fastening system have not been studied. The fastening system makes ties and rails connect. In this study, the stiffness values of various types of fastening systems which consist of clips, rail-pads and insulators are determined by the experiment. The experimental results of the fastening system are compared with the results of parametric study that is performed to investigate the sensitivity of fastening system on stability of CWR track.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.1359-1370
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• 2008

In the track geometry such as rails, sleepers, ballasts and fastener, track deterioration occurs by repetitive train weight and the high-speed railway takes a trend faster than normal. Track deterioration of over threshold value harms ride comfort and furthermore affect in trains safety seriously. An organic and systematic track maintenance system is very important because a trend of the track deterioration effects on track life-cycle and running safety. Also costs of the railway track permanent way and its maintenance are extremely large, forming a significant part of the total infrastructure expenditure. Therefor reasonable and efficient track maintenance has to be planed on a budget. It is required to carry out not only corrective maintenance but preventive maintenance for the track maintenance. In order to perform maintenance jobs in the boundary of the machines and resources given regarding the type and amount jobs, it is necessary to determine feasible or optimal scheduling considering the priority. In this study, the system organization and required functions for the development of track maintenance system supported track deterioration prediction and optimal scheduling are proposed.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2838-2843
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• 2011

Recently, the floating slab track that can effectively mitigate the vibration and structure-borne noise is being discussed to be adopted. The floating slab track which is a track system isolated from the sub-structure by vibration isolators. Unsimilarly to conventional track and the slab deflection is large. Therefore, the running safety and ride comfort should be investigated. Especially at slab joint since the load cannot be transferred, the possibility that the dynamic behavior of track and train became unstable is high. Thus, in general dowel bar are often installed at slab joints. To determine the appropriate dowel ratio the load transfer characteristics should be investigated. In this study, dowel bar joint is modeled by equivalent shear spring and this model is verified by comparison with experimental results. Using the proven model, the load transfer efficiency and deflection at slab joint according to dowel ratio, and stiffness and spacing of vibration isolator were examined.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.722-728
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• 2012

In railway vehicle, riding comfort depends mainly on the secondary lateral damper and track condition. When the damping force of lateral damper becomes abnormal condition or the track condition is worse, the running stability and ride comfort of the railway vehicles go down. In addition, the lateral motion of carbody is increased. Therefore, the lateral motion of carbody is reviewed carefully by considering lateral damping force and track condition of the railway line in design stage. In this study, the lateral displacement of carbody was studied in accordance with lateral damping force and track condition. The target vehicle is EMU for subway line.