• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.2125-2128
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• 2011

The continuous welded rail(CWR) track without the rail expansion joint has many advantages over the conventional track in a variety of fields including the speed-up and the ride comport. However, due to the excessive axial force in the CWR and the track-bridge interactive behavior, inevitably, the rail expansion joint must be installed at the vulnerable zone such as the bridge end zone, etc. In this rail expansion joint zone, the frequency of the maintenance work to repair the track irregularity is on the rise. This is because that the creep of the sleeper is occurred in the moveable zone of the rail expansion joint. In this study, among the several options for reducing the track irregularity on the rail expansion joint zone, the application and efficiency of the tied sleeper is investigated. Field test construction has been conducted, then the progress of the track irregularity and the frequency of the maintenance work are analyzed before and after the filed test construction.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.468-475
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• 2007

The Steel deck a structural analysis in head plate form change the objective bridge which it sells it accomplished a detailed structural analysis from the research which it sees and Bulk-head plate it accomplished. The length rib where the fatigue crack which is considerable generally occurs, width rib connection department and the length rib side, the width rib side it compares principal stress in the object and it does to sleep. It applied the grudge element model which it describes consequently after words and a load and a boundary condition and it executed it compared a static test and principal stress. It grasped the stress conduct of the The Steel deck petal which it follows in hand weaving rib affix location and the affix location to sleep in order to analyze a same location Bulk-head the head and comparison considered. From the detailed section which is reinforced with the stress investigation result hand weaving rib of the location which is weak in structural analysis result fatigue crack of form star reinforcement details basic form and Bulk-head the form which is reinforced with the head plate compared to principal stress investigation hour it is judged at the section which separates most.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.65-70
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• 2008

PC보의 솟음량은 강연선을 통한 인장력 도입에 따른 윗방향 변위량을 의미한다. 솟음량은 재료특성, 시공방식 등에 따라 많은 영향을 받기 때문에 이를 PC보의 품질을 나타내는 지표로 사용하고자 하는 노력이 있어왔다. 하지만, 현장 제작되는 PC보의 경우 재료 및 시공품질의 변동이 발생함에 따라 현장 조건을 솟음량 산정 시 반영하기가 어렵기 때문에 이를 관리지표로 적용 시 많은 제약이 있어왔다. 본 연구는 현장 타설되는 PC보 솟음량 산정의 유효성을 평가하는 것을 목적으로 실제 철도교량에 사용되는 PC보 2개에 대해 콘크리트 탄성계수, 인장력도입에 따른 단면 변형률 및 솟음량을 측정하여 이를 이론적 솟음량과 비교하여 보았다. 단순화된 해석모델을 사용하여 계산된 PC보의 솟음량은 실제 측정된 솟음량을 효과적으로 예측하였다. 위의 결과는 솟음량 추정에 대한 신뢰성을 높이기 위하여 현장 조건에 대한 적절한 고려가 수행되어야함을 의미한다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.829-834
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• 2009

Alluvial soil is one of the most difficult grounds for tunneling works due to the insufficient ground strength and excessive ground water inflow. Dduk island in Seoul has a wide alluvium developed by two rivers, Han and Jung-Ryang. Subway tunnel of $\bigcirc\bigcirc$ line planed across Dduk island has highly poor ground conditions due to small cover and deeply developed alluvium. Moreover, much part of this tunnel is located parallel to the bridge foundations of another railway with a small horizontal distance. Original design was done in 2002 and construction has been in progress. During the construction, tunnel design has been partly changed and adjusted for the complex ground condition and the demand from related organizations. This paper intend to introduce the urban tunnel design and construction in alluvial soils. This line could be divided three sections(A, B, C) according to ground and adjacent conditions. Section A is featured by mixed tunnel faces consisted with alluvial soils and weathered or weak rocks. The feature of section B is that tunnel underpasses near the bridge foundations of another subway. Lastly, section C with a very short length is the most difficult construction conditions due to the small cover, poor ground, obstacles on and underneath ground surface.

• 전력전자학회논문지
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• 제20권4호
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• pp.337-343
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• 2015

The multi-level inverters are highly efficient for high-power and medium-voltage AC driving applications, such as high-speed railway systems and renewable energy resources, because such inverters generate lower total harmonic distortion (THD) and electromagnetic interface (EMI). Lower switching stress occurs on switching devices compared with conventional two-level inverters. Depending on the multi-level inverter topology, the required components and number of switching devices are different, influencing the overall efficiency. Comparative studies of multi-level inverters based on loss analysis and output characteristic are necessary to apply multi-level inverters in high-power AC conversion systems. This paper proposes a theoretical loss analysis method based on piecewise linearization of characteristic curves of power semiconductor devices as well as loss analysis and output performance comparison of five-level neutral-point clamped, flying capacitor inverters, and high-level cascaded H-bridge multi-level inverters.

• Structural Engineering and Mechanics
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• 제55권5호
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• pp.1015-1035
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• 2015

A three-dimensional (3D) numerical analysis for the train-bridge interaction (TBI) system is actively developed in this study in order to investigate the vibration characteristics of rigid-frame reinforced concrete (RC) viaducts in both vertical and lateral directions respectively induced by running high-speed trains. An analytical model of the TBI system is established, in which the high-speed train is described by multi-DOFs vibration system and the rigid-frame RC viaduct is modeled with 3D beam elements. The simulated track irregularities are taken as system excitations. The numerical analytical algorithm is established based on the coupled vibration equations of the TBI system and verified through the detailed comparative study between the computation and testing. The vibration responses of the viaducts such as accelerations, displacements, reaction forces of pier bottoms as well as their amplitudes with train speeds are calculated in detail for both vertical and lateral directions, respectively. The frequency characteristics are further clarified through Fourier spectral analysis and 1/3 octave band spectral analysis. This study is intended to provide not only a simulation approach and evaluation tool for the train-induced vibrations upon the rigid-frame RC viaducts, but also instructive information on the vibration mitigation of the high-speed railway.

• 한국정밀공학회지
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• 제17권11호
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• pp.176-184
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• 2000

Recently, it becomes a very important issue to consider the mechanical systems such as high-speed vehicle and railway train moving on a flexible beam structure. Using general approach proposed in the first part of this paper, it tis possible to predict planar motion of constrained mechanical system and elastic structure with various kinds of foundation supporting condition. Combined differential-algebraic equations of motion derived from both multibody dynamics theory and Finite Element Method can be analyzed numerically using generalized coordinate partitioning algorithm. To verify the validity of this approach, results from simply supported elastic beam subjected to a moving load are compared with exact solution from a reference. Finally, parameter study is conducted for a moving vehicle model on a simply supported 3-span bridge.

• Structural Engineering and Mechanics
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• 제56권2호
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• pp.241-256
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• 2015

Channel girder bridges that consist of a deck slab and two side beams are good choices for railway bridges and urban rail transit bridges when the vertical clearance beneath the bridge is restricted. In this study, the behavior of simply supported channel girder bridges was theoretical studied based on the theory of elasticity. The accuracy of the theoretical solutions was verified by the finite element analysis. The global bending of the channel girder and the local bending of the deck slab are two contributors to the deformations and stresses of the channel girder. Because of the shear lag effect, the maximum deflection due to the global bending could be amplified by 1.0 to 1.2 times, and the effective width of the deck slab for determining the global bending stresses can be as small as 0.7 of the actual width depending on the width-to-span ratio of the channel girder. The maximum deflection and transversal stress due to the local bending are obtained at the girder ends. For the channel girders with open section side beams, the side beam twist has a negligible effect on the deflections and stresses of the channel girder. Simplified equations were also developed for calculating the maximum deformations and stresses.

• Structural Engineering and Mechanics
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• 제69권4호
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• pp.399-405
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• 2019

The present study assessed the reliability-based reinforcement ratio of FRP reinforced concrete structure applying recycled coarse aggregate (RCA) concrete. The statistical characteristics of FRP bars and RCA concrete were investigated from the previous literatures and the mean value and standard deviation were employed for the reliability analysis. The statistics can be regarded as the material uncertainty for configuring the probability distribution model. The target bridge structure is the railway bridge with double T-beam section. The replacement ratios of RCA were 0%, 30%, 50%, and 100%. From the probability distribution analysis, the reliability-based reinforcement ratios of FRP bars were assessed with four cases according to the replacement ratio of RCA. The reinforcement ratio of FRP bars at RCA 100% showed about 17.3% higher than the RCA 0%, where the compressive strength at RCA 100% decreased up to 27.5% than RCA 0%. It was found that the decreased effect of the compressive strength of RCA concrete could be compensated with increase of the reinforcement ratio of FRP bars. This relationship obtained by the reliability analysis can be utilized as a useful information in structural design for FRP bar reinforced concrete structures applying RCA concrete.

• Geomechanics and Engineering
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• 제30권1호
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• pp.27-44
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• 2022

Gravelly soil is a kind of special geotechnical material, which is widely used in the subgrade engineering of railway, highway and airport. Its mechanical properties are very complex, and will greatly influence the stability of subgrade engineering. To investigate the mechanical properties and failure mechanism of gravelly soils, this paper introduced and verified a new discrete element method (DEM) of gravelly soils in large scale direct shear test, which considers the actual shape and broken characteristics of gravels. Then, the stress and strain characteristics, particle interaction, particle contact force, crack development and energy conversion in gravelly soils during the shear process were analyzed using this method. Moreover, the effects of gravel content (GC) on the mechanical properties and failure characteristics were discussed. The results reveal that as GC increases, the shear stress becomes more fluctuating, the peak shear stress increases, the volumetric strain tends to dilate, the average particle contact force increases, the cumulative number of cracks increases, and the shear failure plane becomes coarser. Higher GC will change the friction angle with a trend of "stability", "increase", and "stability". Differently, it affects the cohesion with a law of "increase", "stability" and "increase".