• Title, Summary, Keyword: track irregularity

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Estimation of rail irregularity using wavelet transfer function (웨이브렛 전달함수를 이용한 궤도틀림 추정)

  • Yoon, Seok-Jun;Choi, Bai-Sung;Lee, Hyeung-Jin;Kim, Man-Cheol;Choi, Sung-Hoon;Shin, Soo-Bong
    • Proceedings of the KSR Conference
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    • pp.330-337
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    • 2010
  • This paper shows an algorithm for identifying track irregularities using wavelet transfer function along the railway. An equivalent SISO wavelet transfer function is defined using continuous wavelet transform by the measured track geometry and acceleration at a bogie of a train. The estimated track geometry is made by inverse continuous wavelet transform from the regressed signals of measured acceleration signal and the pre-defined wavelet transfer function. The estimated rail irregularity geometry is evaluated by the coherence function and comparison of FRF(Frequency Response Function). As a result of evaluated outcome, This algorithm is regarded as appropriate for estimation of rail irregularity.

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Analysis of CWR Track Considering Wheel Loads (열차하중을 고려한 장대레일 궤도 해석)

  • Han, Sang-Yun;Kang, Young-Jong;Han, Teak-Hee;Lim, Nam-Hyoung;Kim, Jung-Hun
    • Proceedings of the KSR Conference
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    • pp.2487-2492
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    • 2011
  • At high rail temperature above the neutral temperature, high compressive axial stresses will occur in the rails. High thermal axial force and vehicle loads cause the track to shift in a lateral direction and the formation of track geometry imperfections (track irregularity). When the thermal stress level and track irregularity with vehicle load reach a critical value, the track loses stability. In many studies, the stability of CWR tracks is analyzed. However these studies are only considered in temperature load. The main objective of this investigation was to estimate a new, comprehensive, realistic, the stability of CWR tracks considering wheel load. The ballast resistance is changed by wheel load. When the wheel load is applied, rails and ties are moved upward or downward. In this case the friction between ties and ballasts is decreased or increased. In this study the change of the ballast resistance of each tie was applied to the nonlinear analysis of CWR tracks.

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Parametric analysis on Deformation of Sharp Curved Ballasted Track (급곡선 자갈궤도의 궤도변형에 관한 매개변수 해석)

  • Choi, Jung-Youl;Kim, Jun-Hyung;Son, Gab-Soo;Kim, Sang-Jin
    • Journal of the Korean Society of Safety
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    • v.32 no.4
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    • pp.28-33
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    • 2017
  • A sharp curved ballasted track on earthwork that was connected with a direct fixation slab track on steel box railway bridges have been deformed and damaged despite the frequently maintenance by a restoring force of sharp curved rail and track-bridge interaction forces such as axial forces and longitudinal displacement of continuous welded rail(CWR) owing to their structural characteristics, calling for alternatives to improve the structural safety and track irregularity. In this study, the authors aim to prove a cause of deformation for the sharp curved ballasted tracks to enhance the structural safety and track irregularity of ballasted track in service. A track-bridge interaction analysis and a finite-element method analysis for the sharp curved ballasted track were performed to consider the axial force and longitudinal displacement of CWR, the temperature and the effect of restoring force of sharp curved rail. From the results, the deformation of the sharp curved ballasted track with adjusted sleeper spacing from 833mm to 590mm were significantly reduced.

Track Wear and Irregularity Data Processing and Analysis for Life Cycle Performance (생애주기분석을 위한 궤도 마모 및 틀림 데이터 처리 및 분석)

  • Kong, Jung-Sik;Jeong, Min-Chul;Kim, Jung-Hoon;Kim, Gun-Woo
    • Proceedings of the KSR Conference
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    • pp.1123-1128
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    • 2011
  • Generally, there are many types of data, such as wear data or irregularity data, are detected for analyzing railway performance. The analysis of railroad wear or irregularity data is most effective method for the efficient railway maintenance. Especially, the track damaged directly by train, have as important position with the inspection data. This study suggest the Life-Cycle performance analysis method and process of railroad by analyzing two types of data, wear data and irregularity data. This analysis methods can be applied to suggest the Life-Cycle performance of railroad based on environmental factors or design factors, such as sleeper type, roadbed type, cant, the radius of curvature, speed, maintenance history and so on.

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The Prediction Equation for Bending Stress of Rail in Concrete Track by the Linear Multiple Regression Analysis (중회귀분석을 통한 콘크리트궤도 레일 휨응력 예측식)

  • Sung, Deok-Yong;Lim, Hyoung-Jun;Lee, Dong-Wook;Kim, Bag-Jin;Park, Yong-Gul
    • Proceedings of the KSR Conference
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    • pp.315-323
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    • 2010
  • It is suggested that the service life of the continuous welded rail(CWR) is estimated by the relationship between the rail surface irregularity according to the accumulated passing tonnage and bending fatigue of welded part in CWR. In this study, it measured bending stress of rail according to the rail surface irregularity in the concrete track on the Seoul Metro. In addition, the relationship between rail surface irregularity and bending stress in concrete track is analyzed by results of the field test. Finally, this study clarified the relationship among bending stress(Y) of rail, train speed(U), rail surface irregularity(v, w) in concrete track. The result of this study is able to use the basis data to establishing the periodic replacements criterion of CWR.

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Identification of Track Irregularity by Frequency-Domain Transfer Function (주파수영역 전달함수를 이용한 궤도틀림 식별)

  • Kim, Jae-Cheon;Kwon, Soon-Jung;Yin, Jing-Lin;Lee, Hyeung-Jin;Kim, Man-Cheol;Shin, Soo-Bong
    • Journal of the Korean Society for Railway
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    • v.12 no.4
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    • pp.506-511
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    • 2009
  • An algorithm for identifying track irregularities along the railway is presented. A baseline frequency-domain transfer function based on the equivalent SlSO(Single Input Single Output) model is defined at the intact condition between the measured track geometry of the ground displacement and the acceleration measured at a location in a train. The pre-defined transfer function at the intact condition is used inversely to predict track geometry in time with the currently measured acceleration at the same location in a train. The predicted track geometry is compared in time with that of the baseline values at the intact condition. The difference between them is calculated as an error in time and used to identify the track irregularities. An irregularity index is proposed as the ratio between the moving variance of the error at the current inspection and that at the intact condition. A 3D numerical simulation study has been carried out with a train model to verify the validity of the presented algorithm. In the analysis for the simulation, the track geometry has been considered as the displacement boundary condition varying in time.

Development of a Numerical Method of Vertical Train/Track Interaction in the Track Section with Hanging Sleepers (뜬침목구간에서 차량/궤도 상호작용 수치해석기법 개발)

  • Yang, Sin-Chu;Lee, Jee-Ha
    • Journal of the Korean Society for Railway
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    • v.15 no.3
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    • pp.251-256
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    • 2012
  • Hanging sleepers are frequently observed in the ballasted track with the rail of high rigidity. These hanging sleepers at the high speed line could cause such large dynamic force compared to those at the conventional line. This dynamic force would, in turn, deteriorate train running stability as well as riding comfort, and accelerate irregularity of track and failure of track materials, leading to a sharp increase in track maintenance cost. When the wheel-rail contact spring exhibits nonlinear behavior and some components of the system like hanging sleeper exhibit bi-linear behaviors, an effective analytical method is proposed for train-track interactions. The verification of the present method is carried out comparing numerical results by the present method and those by Ono's method of RTRI.

Study for The Lateral Displacement of Railway Vehicle (철도차량의 횡 변위에 대한 연구)

  • 양희주;오택열
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.535-538
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    • 1997
  • Studied in this paper was the lateral displacement of railway vehicle using the multi-body dynamic simulation program (VAMPIRE) and the BASS 501. The lateral displacement of railway vehicle is occurred by thc clearance between wheel flange and rail, the track irregularity, the property of each suspension of vehicle and the cant etc. The results of analysis shown that Vehicle is not interfere with subway platform in any conditions namely the tare and full load condition, the wheel. wear condition and the stationary and running of vehicle.

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Determination of Upper Limit of Rail Pad Stiffness for Ballasted and Concrete Track of High-Speed Railway Considering Running Safety (주행 안전을 고려한 고속철도 자갈궤도 및 콘크리트궤도 레일패드의 강성 상한 결정)

  • Yang, Sin-Chu;Jang, Seung-Yup;Kim, Eun
    • Journal of the Korean Society for Railway
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    • v.14 no.6
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    • pp.526-534
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    • 2011
  • In this study, proposed is the methodology to determine the upper limit for stiffness of rail pad for the ballasted and concrete track in high-speed railway in the viewpoint of running safety, considering the dynamic characteristics of train and track and the operation environment. For the track irregularity, one of the most important input parameters for traintrack interaction analysis, the reference vertical track irregularity PSDs(power spectral densities) for the ballasted and concrete track in a wide range of frequencies were proposed based on those presented in France and Germany and that obtained from the measured data at Kyeong-Bu 1st phase high-speed railway line. Using these reference PSD models, the input data for the vertical track irregularity data were regenerated by random generation process, and then, the wheel load reduction rates according to the stiffness of the rail pads have been calculated by the train-track interaction analysis technique. Finally, by comparing the wheel load reduction rates calculated with the derailment criteria prescribed in the Korean standards for railway vehicle safety criteria, the upper limits for the stiffness of rail pad have been proposed.

An Identification of Track Irregularity by Analyzing Dynamic Characteristics of a Train (차량의 동적 특성 분석을 통한 궤도틀림 식별)

  • Kim, Sung-Yong;Park, Eun-Churn
    • Proceedings of the KSR Conference
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    • pp.2095-2106
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    • 2010
  • In this study, to grasp the stability of train and to identify the track irregularity, the algorithm was proposed. As the track deformation occur due to running train, the dynamic characteristics of train show non-linearity. The representative transfer functions of wheel to car response were calculated from the frequency response functions which were estimated from measured triaxial accelerations. The measured acceleration responses were compared with the estimated responses from filtered acceleration outputs. This result could show the non-linearity of train system at the location of track deformed. The proposed algorithm was verified by matching with the site investigation.

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