• Steel and Composite Structures
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• 제37권2호
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• pp.117-136
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• 2020

Curved steel-concrete composite box girder has been widely adopted in urban overpasses and ramp bridges. In order to investigate its mechanical behavior under complicated and combined bending, shear and torsion load, two large-curvature composite box girders with interior angles of 25° and 45° were tested under static hogging moment. Based on the strain and deflection measurement on critical cross-sections during the static loading test, the failure mode, cracking behavior, load-displacement relationship, and strain distribution in the steel plate and rebar were investigated in detail. The test result showed the large-curvature composite box girders exhibited notable shear lag in the concrete slab and steel girder. Also, the constraint torsion and distortion effect caused the stress measured at the inner side of the composite beam to be notably higher than that of the outer side. The strain distribution in the steel web was approximately linear; therefore, the assumption that the plane section remains plane was approximately validated based on strain measurement at steel web. Furthermore, the full-process non-linear elaborate finite element (FE) models of the two specimens were developed based on commercial FE software MSC.MARC. The modeling scheme and constitutive model were illustrated in detail. Based on the comparison between the FE model and test results, the FE model effectively simulated the failure mode, the load-displacement curve, and the strain development of longitudinal rebar and steel girder with sufficient accuracy. The comparison between the FE model and the test result validated the accuracy of the developed FE model.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.1039-1044
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• 2008

By the result of efforts for the technology development of G7 trainset, the technology of domestic high-speed train KTX-II has lately been put to practical use while a forward countries of railway, which have their own developing ability of high-speed train, are competing against each other for the development of faster high-speed train system. Japan has been commissioning of FASTECH 360 which was developed in June 2005. Also France and Germany have been commissioning of next generation high-speed train such as AGV and ICE-3, developed basing on technology of their existing high-speed train system(TGV and ICE), its maximum commercial running speed is 360kph, and adopted multiple unit system. For the development of technology of domestic high-speed train and enhancement of national technology competitive power, HEMU (High-speed Electrical Multiple Unit) development project has been carried out as a national R&D project from last August. For the executing of HEMU's maximum speed test, we have investigated the high speed line characteristics (i.e. radius of curvature, gradient, cant etc.) of Seoul-Pusan line and Honam line which is under construction. We'd like to examine a study of condition for the best HEMU T&C line considering HEMU's characteristics (i.e. acceleration, deceleration etc.) and its interface with infrastructure in this paper.

• 한국측량학회지
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• 제13권2호
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• pp.209-218
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• 1995

철도속도향상 계획은 미래에 있어 풍요로운 사회를 실현시키는데 중요한 역할을 담당하게 될 것이다. 열차 운행속도에 매우 큰 영향을 주는 선형 요소는 곡선구간으로서 이 구간에서는 열차의 주행성과 승객의 승차기분을 저해하는 요인을 줄이기 위해 완화곡선구간을 포함한 곡선부에 캔트 및 슬랙을 설치하게 되는데 이러한 값들은 열차의 종류가 다르기 때문에 균형적인 값을 사용하지 못하고 어느 정도 부족한 상태로서 유지되고 있다. 본 연구에서는 곡선반경별로 설정캔트량을 조사하여 부족캔트량에 대한 횡가속도를 산출하여 곡선부에서의 주행성을 검토하여 효과적인 곡선관리 방법을 제시하였으며 선형개량요소를 적용하여 속도향상 효과를 얻었다.

• Structural Engineering and Mechanics
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• 제83권3호
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• pp.363-375
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• 2022

Flexural capacity prediction is a challenging problem for externally prestressed concrete beams (EPCBs) due to the unbonded phenomenon between the concrete beam and external tendons. Many prediction equations have been provided in previous research but typically ignored the differences in deformation mode between internal and external unbonded tendons. The availability of these equations for EPCBs is controversial due to the inconsistent deformation modes and ignored second-order effects. In this study, the deformation characteristics and collapse mechanism of EPCB are carefully considered, and the ultimate deflected shape curves are derived based on the simplified curvature distribution. With the compatible relation between external tendons and the concrete beam, the equations of tendon elongation and eccentricity loss at ultimate states are derived, and the geometric interpretation is clearly presented. Combined with the sectional equilibrium equations, a rational and simplified flexural capacity prediction method for EPCBs is proposed. The key parameter, plastic hinge length, is emphatically discussed and determined by the sensitivity analysis of 324 FE analysis results. With 94 collected laboratory-tested results, the effectiveness of the proposed method is confirmed, and comparisons with the previous formulas are made. The results show the better prediction accuracy of the proposed method for both stress increments and flexural capacity of EPCBs and the main reasons are discussed.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.805-814
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• 2008

This study focused on the resilient modulus prediction model, which is the functions of mean effective principal stress and axial strain, for three types of railroad trackbed materials such as crushed stone, weathered soil, and crushed-rock soil mixture. The model is composed with the maximum Young's modulus and nonlinear values for higher strain in parallel with dynamic shear modulus. The maximum values is modeled by model parameters, $A_E$ and the power of mean effective principal stress, $n_E$. The nonlinear portion is represented by modified hyperbolic model, with the model parameters of reference strain, ${\varepsilon}_r$ and curvature coefficient, a. To assess the performance of the prediction models proposed herein, the elastic response of a test trackbed near PyeongTaek, Korea was evaluated using a 3-D nonlinear elastic computer program (GEOTRACK) and compared with measured elastic vertical displacement during the passages of freight and passenger trains. The material types of sub-ballasts are crushed stone and weathered granite soil, respectively. The calculated vertical displacements within the sub-ballasts are within the order of 0.6mm, and agree well with measured values with the reasonable margin. The prediction models are thus concluded to work properly in the preliminary investigation.

• 한국철도학회논문집
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• 제13권5호
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• pp.509-515
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• 2010

곡선부에서 도입되는 완화곡선은 곡률을 점진적으로 변화시킴으로써 곡선부에서의 차량의 주행안전성 및 승차감을 향상시킨다. 이러한 완화곡선은 클로소이드, 3차포물선 및 사인반파장 등 여러 종류가 있다. 본 논문에서는 차량의 주행해석을 통하여 3차 포물선과 사인반파장 완화곡선의 주행거동 특성을 분석하였다. 각 완화곡선별로 승차감 평가와 주행안전성 평가를 통하여 각 완화곡선의 성능을 정량적으로 비교하였다.

• 한국철도학회논문집
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• 제16권4호
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• pp.311-317
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• 2013

철도선형에서 종곡선과 평면선형의 경합은 차량의 주행안정성 뿐만 아니라 건설비에도 많은 영향을 끼칠 수 있다. 본 연구에서는 종곡선과 평면곡선의 다양한 경합조건별 차량의 주행안전성 및 승차감에 미치는 영향을 분석하였다. 그 결과 종곡선과 평면원곡선의 경합 뿐만 아니라 종곡선의 완화곡선상 경합, 그리고 완화곡선-원곡선 연결부상의 경합에서도 차량의 주행안전, 승차감 및 궤도작용력 기준을 모두 만족하는 것으로 나타남을 알 수 있었다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2005년도 춘계학술대회 논문집
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• pp.459-466
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• 2005

In this paper, we have systematically formulated the equations concerned to the in-plane and out-of-plane motions and deformations of a thick circular beam by using the kinetic and strain energies in order to analyse natural frequencies of a thick ring. The effects of variation of radius of curvature across the cross-section and also the effects of bending shear, extension and twist are considered. The equations of motion for natural vibration analysis of a ring are obtained utilizing the cyclic symmetry of vibration modes of the ring. The frequencies calculated using thick ring model and thin ring model are compared and discussed with the ones obtained from finite element analysis using the method of cyclic symmetry with 20-node hexahedral solid elements for rings with the different ratio of radial thickness to mean radius.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.1861-1867
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• 2010

This paper described the positioning algorithm of partial discharge in insulation oil by acoustic method for the application of an on-line diagnosis in oil-immersed transformers. In the experiment, five AE sensors having the resonant frequency of 150 kHz were used, and a signal conditioner was fabricated. A needle-plane electrode system which is composed of a needle with a curvature radius of $10{\mu}m$ and a plane electrode with a diameter of 60 mm was installed to simulate partial discharges in insulation oil. From the time difference of arrival (TOA) of acoustic signal, we calculated the location of partial discharge in insulation oil. In the experiment, an algorithm of positioning of PD occurrence by the time difference of arrival was proposed. From the experimental results, the positioning error of PD calculated by three AE sensors was within 4%.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2002년도 추계학술대회 논문집(I)
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• pp.709-714
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• 2002

Recently, the applications of corrugated plates(or folded plates) are increasing due to economic and structural advantages in certain situations. And, because of the higher strength of corrugated plates than flat plates, the usage of the corrugated plates is increasing. So there are many necessities for specifications of corrugated plates. For flat plates, there are many design details in almost specifications. However, there are no detail design guides such as shear strength except the bending strength and the normal strength. So, it is difficult for engineers to design structures consist of corrugated plates. Therefore, a provision is necessary for engineers to refer for designing corrugated plates. The conclusion of this study shows a formula that helps to determine the shear strength of corrugated plates under various geometric conditions ; the size of corrugation ; the curvature of corrugation and ; the thickness of the corrugated plate. Also, it shows that corrugated plates have higher shear buckling strength than flat plates.