• Title, Summary, Keyword: CWR

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Parametric Study on Properties of bridge by CWR(Continuous Welded Rail) and Bridge Interaction Analysis (장대레일과 교량의 상호작용 해석을 통한 교량제원 매개변수 분석)

  • Kim, Jong-Min;Han, Sang-Yun;Lim, Nam-Hyoung;Kang, Young-Jong
    • Proceedings of the KSR Conference
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    • pp.1460-1465
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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.

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Review of effects of friction coefficient of moving bearing on Stability of CWR (가동단 마찰계수가 장대레일 축력 안정성에 미치는 영향 검토)

  • Ryu Jae-Nam;Choi Young-Joon;Yang Sin-Chu
    • Proceedings of the KSR Conference
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    • pp.812-817
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    • 2004
  • Recently drastic improvement of railway technology has been accompanied by the construction of very high-speed tracks. It should be noticed that Continuously Welded Rail(CWR) has played significant role in technical development of railway and that installation of CWR is now being scheduled on existing lines as well as newly-built lines. In general, interaction between CWR and bridge deck takes place on bridge section and additional axial force and displacement is to be developed owing to temperature and braking/acceleration forces. This interaction is known to be mainly governed by span organizations and arrangements of foot bearings. In common practice, movable bearing is stationed and designed on the assumption that it is not able to transfer the horizontal force of upper decks. However, it is well known that horizontal resistance is developed in movable bearings due to friction and that friction coefficient of movable bearing is ranged from 0.03 to 0.20 depending on the material of bearings and magnitude of reactions. Therefore, it is easily reasoned out that friction of movable bearing can influence the mutual behavior of CWR and bridge decks. Suggested in this study is to investigate the validity and efficiency of friction effect of movable bearings in controlling the axial force and displacement of CWR on continuous railway bridges.

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A Study on the axial force in CWR with Turnout according to Distance between Bridge Expansion Joint and Turnout (교량신축과 분기기의 이격거리에 따른 교량상 분기기 축력특성 연구)

  • Choi, Jin-Yu;Lee, Hyun-Jeong;Yang, Shin-Chu;Jeong, Jang-Yong;Yu, Jin-Young
    • Proceedings of the KSR Conference
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    • pp.1050-1055
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    • 2008
  • The demand on a turnout layed on a bridge is rising owing to the increasing number of stations on the viaduct. And also the demand on a turnout with CWR is rising to upgrade running speed of the passing train. A CWR with turnout is subjected to additional axial force induced by the thermal expansion of bridge as well as lead rail of turnout. The additional axial force is closely related with the distance between bridge expansion joint and turnout when it is located near the movable bearing of bridge, and it is required to keep some distance to prevent excessive axial stress in CWR. But, there is no guideline in specification for the proper distance from E.J. to turnout, and it caused problem in planning turnout or bridge. So, it this study, the parametric study to investigate the effect on axial stress in CWR with turnout according to span length and distance between bridge expansion joint and turnout was performed. From the results of numerical analysis, it was found out that $5{\sim}30m$ distance is required to prevent excessive axial in CWR for span length less 90m.

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An Experimental Study of Fastening System on CWR(Continuous Welded Rail) Track Stability (장대레일 궤도의 안정성에 미치는 체결장치의 실험적 연구)

  • Kim, Jung-Hun;Han, Sang-Yun;Lim, Nam-Hyoung;Kang, Young-Jong
    • Proceedings of the KSR Conference
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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.

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Investigation of Antioxidant Activity of Cynanchi Wilfordii Radix and Inhibitory Effect of 5α-reductase mRNA in Human Dermal Papilla Cells (백수오(白首烏)의 항산화 효능 및 모유두 세포의 5α-reductase mRNA 발현 억제 효능)

  • Cho, Nam Joon;Choi, Young Ho;Jeon, Hai Li;Lee, Woong Hee;Kim, Kee Kwang;Han, Hyo Sang
    • Journal of Physiology & Pathology in Korean Medicine
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    • v.31 no.6
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    • pp.374-379
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    • 2017
  • Hair loss affects interpersonal relationships and causes psychological stress. In this study, we investigated the antioxidant activity of Cynanchi Wilfordii Radix (CWR) and its effects on dermal papilla (DP) cells. Antioxidant efficacy was examined by ABTS assay. To confirm the effect on cell activity, MTS assay was performed and cell count was directly measured by hemocytometer. The mRNA expression of genes involved in hair formation and hair loss formation was confirmed by quantitative RT-PCR. CWR has a strong antioxidant activity. Cell viability of DP cells was increased to 118.5% by treatment of 0.5 mg/ml CWR for 24 hours, but the effect on the cell number was insignificant. These results suggest that CWR increases mitochondrial activity without promoting cell proliferation. Treatment of DP cells with 0.5 mg/ml CWR resulted in 48.5% reduction of mRNA expression of type 2 $5{\alpha}$-reductase, a major cause of male hair loss. In addition, mRNA expression of bone morphogenetic pretein (BMP), fibroblast growth factor (FGF)7, and FGF10, which are closely related to hair growth, was also decreased. Reactive oxygen species (ROS) acts as a cause of hair loss. The excellent antioxidant efficacy of CWR is thought to be able to effectively remove ROS. The dihydrotestosterone produced by type 2 $5{\alpha}$-reductase in DP cells is a potent inducer of male pattern hair loss. The inhibitory effect of type 2 $5{\alpha}$-reductase mRNA on DP cells induced by CWR may induce a positive therapeutic effect of male pattern hair loss.

Stability of Continuous Welded Rail Track under Thermal Load (온도하중을 고려한 장대레일 궤도의 안정성 해석)

  • Kang, Young Jong;Lim, Nam Hyoung;Shin, Jeong Ryol;Yang, Jae Seong
    • Journal of Korean Society of Steel Construction
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    • v.11 no.3
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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.

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Effect of Track Resistance on Linear Thermal Buckling Characteristics of CWR (도상이 장대 레일의 선형 온도 좌굴에 미치는 영향)

  • 강영종;임남형;신정렬;양재성
    • Proceedings of the KSR Conference
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    • pp.580-587
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    • 1998
  • 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 and 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 and vehicle loads. Thermal loads are caused by an increase in the temperature of railway track. In this paper, CWR track model and CWRB program are developed for linear buckling analysis using finite element method(FEM). The finite element discretization is used with a total of 14 degrees of freedom for each rail element. 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 in the paper.

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Sensitivity of the Continuous Welded Rail and the Fastener on the Track Stability (궤도 안정성에 대한 장대레일과 체결구의 민감도)

  • Han, Sang Yun;Park, Nam Hoi;Lim, Nam Hyoung;Kang, Young Jong
    • Journal of The Korean Society of Civil Engineers
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    • v.26 no.4A
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    • pp.719-726
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    • 2006
  • The use of CWR track not only reduces the track maintenance cost, but increase the life cycle of track components. Therefore, the use of the CWR track has increased consistently in the worldwide. As the use of CWR increases in track structures, derailing disasters associating with track buckling also increase in great numbers due to high compressive thermal stress in the summer. Among many CWR parameters, the influence of the sectional properties of the rail was investigated on the stability of CWR track in this study. Also, the sensitivity of the broken fastener and the stiffness of the fastener system such as the translational and rotational stiffness was investigated.

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Parametric Study on Thermal Buckling of CWR Tracks (장대레일궤도의 온도좌굴에 영향을 미치는 매개변수 연구)

  • 최동호;김호배
    • Proceedings of the KSR Conference
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    • pp.295-302
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    • 2001
  • The lateral stability of curved continuous welded rail (CWR) is studied fur buckling prevention. This study includes the influences of vehicle induced loads on the thermal buckling behavior of straight and curved CWR tracks. quasi-static loads model is assumed to determine the uplift region, which occurs due to the vertical track deformation induced by wheel loads of vehicle. Parametric numerical analyses are performed to calculate the upper and lower critical buckling temperatures of CWR tracks. The parameters include track lateral resistance, track curvature, longitudinal stiffness, tie-ballast friction coefficient, axle load, truck center spacing, and the ratio of lateral to vertical vehicle load. This study provides a guideline for the improvement or stability for dynamic buckling in on tracks.

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The characteristics of buckling of the CWR with respect to the ballast behaviour (도상 저항력 거동을 고려한 장대레일의 좌굴 특성)

  • Kim Hyun-June;Lee Bang-Woo;Sim Hyun-Woo
    • Proceedings of the KSR Conference
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    • pp.82-90
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    • 2003
  • The advance in technology of the CWR in Korea has led the establishment of the CWR on the sharp curve (i.e. less than R=600m). As thermit welding used in the sharp-curved construction site is carried out on the curve track, it is difficult to adjust a curve shape accurately and these difficulties have occurred in a number of cases. Therefore, in this study, the lateral buckling analysis of CWR track was carried out considering the actual ballast resistance force. In addition, the cant and vertical resistance force in ballast was considered in order to predict the initial behaviour of bucking in track under the more accurate method.

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