• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
• /
• pp.428-435
• /
• 2011

In general, thickness of the sublayers under track is designed based on concept of vertical soil reaction value or vertical stiffness. However, this design method cannot take consideration into soil-track interaction under repetitive load, traffic condition and velocity of the train. Furthermore, the reinforced roadbed soils experience complex behavior that cannot be explained by conventional stress-strain relation expressed as soil reaction value k. The reinforced roadbed soils also can produce cumulative permanent deformation under repetitive load caused by train. Therefore new design method for the sublayers under track must be developed that can consider both elastic modulus and permanent deformation. In this study, a new design concept, a rule-of-thumb, is proposed as the form of design monograph that is developed using elastic multi-layer and finite element programs by analyzing stress and deformation in the sublayers with changing the thickness and elastic modulus of the sublayers and also using data obtained from repetitive triaxial test. This new design concept can be applied to design of the reinforced roadbed before developing full version of design methodology that can consider MGT, axial load and the material properties of the layers. The new design monograph allows the user to design the thickness of the reinforced roadbed based on permanent deformation, elastic modulus and MGT.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
• /
• pp.1123-1128
• /
• 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.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
• /
• pp.3160-3165
• /
• 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.

• 한국철도학회논문집
• /
• 제9권3호
• /
• pp.305-312
• /
• 2006

Gravel ballasted tracks are used as a basic structure for the domestic railway tracks. However, such kind of tracks has few disadvantages with service life of the structure, such as rapid deterioration of the tracks. Due to this reason, there is a need to develop low maintenance track to improve the service life of the conventional line tracks. CMP paved tacks are one of the kind of concrete tracks those were manufactured by using the prepacked concrete techniques. The purpose to develop paved tracks is to reduce the maintenance cost. The most important controlling factors to design the paved tracks are surrounding environmental condition and repeated train loading. In this study, in order to investigate the deformation characteristics such as displacement, earth pressure, strain ratio, and crack along the repeated loading cycle, cyclic loading test through real scale model was carried out.

• Journal of Mechanical Science and Technology
• /
• 제19권spc1호
• /
• pp.411-421
• /
• 2005

The development and implementation of an appropriate methodology for the accurate geometric description of track models is proposed in the framework of multibody dynamics and it includes the representation of the track spatial geometry and its irregularities. The wheel and rail surfaces are parameterized to represent any wheel and rail profiles obtained from direct measurements or design requirements. A fully generic methodology to determine, online during the dynamic simulation, the coordinates of the contact points, even when the most general three dimensional motion of the wheelset with respect to the rails is proposed. This methodology is applied to study specific issues in railway dynamics such as the flange contact problem and lead and lag contact configurations. A formulation for the description of the normal contact forces, which result from the wheel-rail interaction, is also presented. The tangential creep forces and moments that develop in the wheel-rail contact area are evaluated using : Kalker linear theory ; Heuristic force method ; Polach formulation. The methodology is implemented in a general multibody code. The discussion is supported through the application of the methodology to the railway vehicle ML95, used by the Lisbon metro company.

• Multiscale and Multiphysics Mechanics
• /
• 제1권3호
• /
• pp.261-270
• /
• 2016

The longitudinal velocity (forward speed) having significant importance in proper running of railway wheelset on track, depends greatly upon the adhesion ratio and creep analysis by implementation of suitable dynamic system on contamination. The wet track condition causes slip and slide of vehicle on railway tracking, whereas high speed may also increase slip and skidding to severe wear and deterioration of mechanical parts. The basic aim of this research is to design appropriate model aimed estimator that can be used to control railway vehicle forward velocity to avoid slip. For the filtration of disturbance procured during running of vehicle, the kalman filter is applied to estimate the actual signal on preferered samples of creep co-efficient for observing the applied attitude of noise. Thus error level is detected on higher and lower co-efficient of creep to analyze adhesion to avoid slip and sliding. The skidding is usually occurred due to higher forward speed owing to procured disturbance. This paper guides to minimize the noise and error based upon creep coefficient.

• Structural Engineering and Mechanics
• /
• 제75권4호
• /
• pp.519-527
• /
• 2020

Dynamic analysis of a vehicle-track coupling system is important to structural design, damage detection and condition assessment of the structural system. Deterministic analysis of the vehicle-track coupling system has been extensively studied in the past, however, the structural parameters of the coupling system have uncertainties in engineering practices. It is essential to treat the parameters of the vehicle-track coupling system with consideration of uncertainties. In this paper, a method for predicting the bounds of the vehicle-track coupling system responses with uncertain parameters is presented. The uncertain system parameters are modeled as fuzzy variables instead of conventional random variables with known probability distributions. Then, the dynamic response functions of the coupling system are transformed into a component function based on the high dimensional representation approximation. The Lagrange interpolation method is used to approximate the component function. Finally, the bounds of the system's dynamic responses can be predicted by using Monte Carlo method for the interpolation polynomials of the Lagrange interpolation function. A numerical example is introduced to illustrate the ability of the proposed method to predict the bounds of the system's dynamic responses, and the results are compared with the direct Monte Carlo method. The results show that the proposed method is effective and efficient to predict the bounds of the system's dynamic responses with fuzzy variables.

• 한국철도학회논문집
• /
• 제12권4호
• /
• pp.597-603
• /
• 2009

본 연구에서는 승차감을 목적함수로 하고 궤도부담력을 경계조건으로 하는 곡선부 평면선형의 최적설계 기법을 제시하였다. 평면선형 최적화시 중요한 변수인 곡선반경-완화곡선장은 엄주환 등(2009)에서 제시한 결정방법을 적용하였으며 승차감 평가방법은 영국 BSI(2006)에서 제시하는 곡선부 전용 승차감 평가방법인 $P_{CT}$방법을 활용하였다. 또한 한국형 고속전철 G7(KTX-II)모델을 이용한 차량/궤도선형 상호작용 해석을 수행하였다. 해석결과, 최적선형조건은 교각 I(곡선부 양 끝단 직선과 직선이 만나는 교차각) 크기 및 곡선반경-완화곡선장 조합에 따라 다름을 알 수 있었다. 또한 Kufver(1997) 등에서 제시하는 간략화 해석방법과 유사한 경향이 나타남을 알 수 있었으나, 대부분의 경우 동적해석결과 값이 크게 나타났다. 따라서 곡선부 최적선형 설계시 동적해석과 간략화 해석을 병행한다면 신속하고 신뢰성 높은 최적선형을 결정할 수 있을 것으로 판단된다.

• 한국철도학회논문집
• /
• 제18권2호
• /
• pp.117-126
• /
• 2015

600km/h급 철도노반 개발은 초고속주행에 의한 동적상호작용의 예측이 어렵기 때문에 기술개발에 애로사항이 많다. 특히 교량/토공 접속부는 동적 상호작용을 포함하여 지지력, 압축, 침하, 배수, 유동 등의 영향 요소가 복합적으로 발생하는 구간으로서 접속부에서의 안정성이 확보된다면 초고속 열차용 토공노반의 안정성도 확보 가능할 것으로 예상된다. 본 논문에서는 초고속철도 접속구조개발의 기초 연구단계로서 국내 고속철도에서 적용하고 있는 접속부의 보강방안을 우선적으로 적용하여 초고속 주행시의 설계변수 영향을 해석적으로 검토하였다. 설계변수는 설계단계에서 검토 가능한 항목인 보강방안의 유무, 기하하적 형상, 재료의 강성 등이며, 분석내용은 초고속주행에 따른 궤도의 변형응답과 주행안정성을 검토하였다.

• 한국철도학회논문집
• /
• 제18권3호
• /
• pp.241-251
• /
• 2015

유도상 아스팔트 콘크리트 궤도(이하, 유도상 AC궤도)는 아스팔트 콘크리트 노반(이하, AC노반)의 존재에 의해 유도상 궤도에 비해 열차하중 분산효과에 의한 강화노반 두께 감소가 가능하며 누적 소성 변위도 작을 뿐만 아니라 유지관리 측면에서도 유리한 궤도 구조이기 때문에 국외에서 적용 사례가 증가하고 있다. 그러므로 유도상 AC궤도의 국내 도입을 검토하기 위해 선행 연구를 통해 수행한 AC노반 유무에 따른 거동 특성을 분석하여 현재 설계기준에 명시된 유도상 궤도의 단면과 유사한 성능을 보이는 유도상 AC궤도의 단면을 분석한 바 있으며, 실대형 정 동적 열차하중 재하 실험 결과와의 비교를 통해 해석 결과의 신뢰성을 검증하였다. 본 연구에서는 선행 연구를 바탕으로 AC노반의 두께를 일정하게 하고 강화노반 두께를 변화시켰을 때에 획득된 AC노반 하면에서의 변형률을 이용하여 설계 수명을 산정하였고 각각의 단면에 대한 확률론적 LCC분석을 통해 기대 설계 수명을 만족하면서 기존 유도상 궤도와 비교하여 동등 또는 동등이상의 성능을 갖는 유도상 AC궤도의 설계 단면을 제시하였다.