• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.162-166
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• 2011

In railway, Tie supports rail and plays a role that distribute train load to the ballast. Also, Tie and ballast resist against external force and fix the track position. But, weakening resistance of ballast and tie cause vertical displacement of tie and track irregularity. For reinforcement of track stiffness and reduction of track irregularity, KORAIL has developed Multi Branch type tie(GLORY Tie) that reinforced resistance than general PCT and installed in order to test in the field. This study measured and analyzed lateral resistance of ballast, wheel load of rail, bending strain of rail foot, vertical displacement and vibration acceleration of tie in order to evaluate performance of Multi Branch type tie in the field. According to the results of test, Multi Branch tie is excellent than general tie about lateral resistance of ballast and vertical displacement of tie. And, gap of measurement value between Multi Branch type tie and general tie about wheel load of rail, bending strain of rail foot were very small.

• Structural Engineering and Mechanics
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• 제48권4호
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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.

• 건축역사연구
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• 제32권5호
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• pp.31-42
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• 2023

This study examined the structural characteristics of the royal tomb equipped with only rail stones in the early Joseon Dynasty. Bongneung(封陵: the burial mound of royal tomb) equipped with only rail stones was constructed from 1468 to 1632. During this period, Hyeongung(玄宮: the underground chamber for the coffin of the king or queen) was constructed with lime. When the Hyeongung is completed, the soil is covered with a thickness of 1 foot parallel to the ground surface. On top of that, as the base of the Bongneung, the rail ground stone is constructed with a height of about 1.5 to 2 feet. The inside of the rail ground stone is also firmly filled with soil. On top of this, semicircular lime is installed with a convex center. Lastly the soil is divided and compacted several times to form a hill, and then covered with grass to complete the Bongneung. The notable feature is that between the Hyeongung made of lime and the Bongneung made of soil, the rail ground stone serves as a stylobate with the inside compacted by the soil.

• 대한의용생체공학회:의공학회지
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• 제10권3호
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• pp.269-278
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• 1989

The initial impact at foot strike is produced by a slider type mechanical model, which can be measured using a force platform to evaluate various shoes. The lower extremity and foot motion was filmed by a 16mm high speed movie camera and several points on the rear half of the shoe and those near the trochanter and the lateral epicondyle were digitized to provide the linear and angular positions and velocities during impact. With these observed kinematics, a slider type foot strike simulator composed of guide rail and sliding dummy is designed. The simulator system makes the artificial foot of the dummy with running shoe on it to follow the foot strike motion. The dummy has the relevant mass-spring-damper system modeled after McMahon's. The motion of the model is drived by the gravity force and the generated motion alone with the ground reaction forces are monitored by the same procedures afore mentioned producing the initial foot strike impact similar to the onto observed in human gait.

• Smart Structures and Systems
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• 제21권5호
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• pp.687-694
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• 2018

The problem of wheel tread defects has become a major challenge for the health management of high-speed rail as a wheel defect with small radius deviation may suffice to give rise to severe damage on both the train bogie components and the track structure when a train runs at high speeds. It is thus highly desirable to detect the defects soon after their occurrences and then conduct wheel turning for the defective wheelsets. Online wheel condition monitoring using wheel impact load detector (WILD) can be an effective solution, since it can assess the wheel condition and detect potential defects during train passage. This study aims to develop an FBG-based track-side wheel condition monitoring method for the detection of wheel tread defects. The track-side sensing system uses two FBG strain gauge arrays mounted on the rail foot, measuring the dynamic strains of the paired rails excited by passing wheelsets. Each FBG array has a length of about 3 m, slightly longer than the wheel circumference to ensure a full coverage for the detection of any potential defect on the tread. A defect detection algorithm is developed for using the online-monitored rail responses to identify the potential wheel tread defects. This algorithm consists of three steps: 1) strain data pre-processing by using a data smoothing technique to remove the trends; 2) diagnosis of novel responses by outlier analysis for the normalized data; and 3) local defect identification by a refined analysis on the novel responses extracted in Step 2. To verify the proposed method, a field test was conducted using a test train incorporating defective wheels. The train ran at different speeds on an instrumented track with the purpose of wheel condition monitoring. By using the proposed method to process the monitoring data, all the defects were identified and the results agreed well with those from the static inspection of the wheelsets in the depot. A comparison is also drawn for the detection accuracy under different running speeds of the test train, and the results show that the proposed method can achieve a satisfactory accuracy in wheel defect detection when the train runs at a speed higher than 30 kph. Some minor defects with a depth of 0.05 mm~0.06 mm are also successfully detected.

• 대한토목학회논문집
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• 제36권6호
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• pp.1161-1167
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• 2016

본 연구에서는 대단면 고속철도 시공중 단층파쇄대 구간과 조우시 터널의 안정성 확보를 위해 보조 및 보강공법을 적용했음에도 불구하고 추가적인 지반이완과 원지반 지지력 부족에 따른 터널 전체의 안정성 저감 및 과다변위가 발생한 시공사례를 분석하였다. 그리고, 이러한 터널굴착 중 단층파쇄대 구간 통과시 현장계측분석을 통하여 터널지보패턴의 적정성 및 우각부 보강(레그파일) 효과를 현장계측결과와 비교분석하여 평가하였다. 또한, 우각부보강 시공조건(레그파일 각도 및 길이에 대한 영향)에 따른 보강효과를 수치해석적으로 검토하여 현장적용시 최적의 보강조건을 분석한 결과 단층대 구간에서의 우각부 적용조건은 상반바닥면 수직에 가까운 방향으로 설치할 경우 변위제어에 가장 효과적이고, 시공성 및 경제성 고려 레그파일의 적용조건은 45도 각도 이내로 설치하고 하반굴착 바닥면 까지인 6m의 길이를 적용하는 것이 터널주변지반 이완하중의 분산 전달 및 측방변형 억제에 가장 효과적인 유리한 조건으로 확인되었다.

• Structural Engineering and Mechanics
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• 제83권6호
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• pp.709-727
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• 2022

Fastening systems have a significant role in the response of railway slab track systems. Although experimental tests indicate nonlinear behavior of fastening systems, they have been simulated as a linear spring-dashpot element in the available literature. In this paper, the influence of the nonlinear behavior of fastening systems on the slab track response was investigated. In this regard, a nonlinear model of vehicle/slab track interaction, including two commonly used fastening systems (i.e., RFFS and RWFS), was developed. The time history of excitation frequency of the fastening system was derived using the short time Fourier transform. The model was validated, using the results of a comprehensive field test carried out in this study. The frequency response of the track was studied to evaluate the effect of excitation frequency on the railway track response. The results obtained from the model were compared with those of the conventional linear model of vehicle/slab track interaction. The effects of vehicle speed, axle load, pad stiffness, fastening preload on the difference between the outputs obtained from the linear and nonlinear models were investigated through a parametric study. It was shown that the difference between the results obtained from linear and nonlinear models is up to 38 and 18 percent for RWFS and RFFS, respectively. Based on the outcomes obtained, a nonlinear to linear correction factor as a function of vehicle speed, vehicle axle load, pad stiffness and preload was derived. It was shown that consideration of the correction factor compensates the errors caused by the assumption of linear behavior for the fastening systems in the currently used vehicle track interaction models.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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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.

• 한국철도학회논문집
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• 제13권2호
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• pp.236-243
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• 2010

본 연구는 2004년 KTX 도입 이후 암환자의 의료이용 패턴 변화에 대한 조사연구이다. 2004년과 2005년 전체 의료이용에 있어 서울지역 상급종합병원에서의 의료이용량 비중은 급격히 증가하였는데 이는 KTX 영향권 내 지역 상급종합병원에서의 의료이용량 비중 감소 현상과 맞물려 발생했다. 이와 달리 KTX 영향권 외 지역 상급종합병원에서의 의료이용량 비중은 큰 변화 없이 완만한 추세를 보였다. 따라서 의료소비자의 선택이 "foot voting"의 특성을 보이는 한국의 의료서비스 시장에서 KTX 도입은 장거리 교통 관련 비용을 감소시킴으로써 암환자의 지역 간 의료이용 패턴에 큰 영향을 주었음을 시사한다. 따라서 KTX가 암환자의 의료접근성 제고에 기여할 수 있는 측면을 고려할 경우 지방 거주 저소득 암환자에 대한 요금할인정책 등을 고려할 필요가 있다. 특히 적절히 설계된 요금할인정책은 저소득층 암환자의 KTX 이용 증가를 통해 추가적인 비용 유발 없이도 가능할 수 있을 것으로 보인다.

• 한국지반공학회논문집
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• 제29권11호
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• pp.129-138
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• 2013

산업화의 발달과 더불어, 도로 등 교통시설과 건설 장비의 발달로 공장 제작하여 운반 설치하는 프리캐스트 구조물이 급속히 확장되는 추세이며, 2000년 대 부터는 철근콘크리트 옹벽도 프리캐스트 공법이 개발되고 현장에서 적용이 확대되고 있는 추세이다. 본 연구에서는 기존에 항타하여 설치해 온 앵커 파일 옹벽에서 기초에 설치되는 앵커파일을 일반돌기에서 나선형 플렌지 타입으로 설치하여 유압모터를 이용한 압입, 회전 방식으로 설치하고 앵커파일의 형태를 개선하고 이에 따른 기술적 검증과 최적의 적용형태를 도출하였다. 이를 위하여 현장 실규모 시험 및 수치해석적 검증을 수행하였으며, 인발실험 결과 앵커파일은 나선형 플렌지를 설치하는 것이 돌기가 없거나 다른 형상의 돌기가 설치된 파일에 비해 1.5~8배의 높은 인발 저항력을 보였으며, 나선형 플렌지가 설치된 APC옹벽에서 인발 저항력의 증대로 기초와 벽체의 변위도 25% 이상 감소됨을 보였다.