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Deokyong Sung,Sukhoon Pyo,Seongkyu Chang 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.41 No.2
A railway bridge with slab track is subjected to end rotations because of the deflection of the girder during train operation. At the ends of a slab track, the end rotation of the bridge girder causes uplift deformation of the slab track, and leads to compressive stresses in the rail fasteners. In this study, a prototype bridge consisting of one span of a girder and one span of an abutment along with a slab track was constructed, and the uplift and compressive forces generated in the rail fastening system were experimentally analyzed. To effectively analyze the experimental results using a numerical method, a series of finite element analyses were performed considering the nonlinear nature of the rail fastening system. A comparison between the experimental and analytical results indicated that the higher the stiffness of the rail fastening system, the greater the uplift and compressive forces. In addition, a nonlinear model provided better correlation with the experimental results than a linear model. Therefore, when reviewing the serviceability of the rail fastening system at railway bridge ends, an adequate finite element model considering the uplift and compressive forces in the rail fastening system should be used.
Experimental study on long-term behavior of prestressed steel I-beam–concrete composite beams
Deokyong Sung,Seongwon Hong 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.42 No.5
To investigate and predict the long-term time-dependent behavior, such as creep, shrinkage, and relaxation of PS strands, and prestress loss in prestressed steel–concrete composite beams, named Precom, full-scale tests were conducted and the collected data were compared with those obtained from the two proposed analytical models. The combined effective modulus method (EMM)-empirical model proposed with a flowchart considered the creep effect to determine the prestress loss. Conversely, the age-adjusted effective modulus method (AEMM) with CEB-FIP equation was developed to account for the concrete aging. The results indicated that the AEMM with CEB-FIP model predicts the long-term behavior of Precom effectively.
Hindawi Limited 2018 Advances in civil engineering Vol.2018 No.-
<P>In this study, a nonlinear analysis method was proposed to evaluate the serviceability review of a rail fastening system on concrete slab track at railway bridge ends. The serviceability review of the end deck is time-consuming in that it is necessary to calculate the force of fasteners; also, the design is complex because of the many girders, fasteners, and loads. In addition, there is also a case in which a special, expensive fastening device is installed because the stiffness of the rail fastening device is assumed to be linear, and excessive design results are produced by the linear analysis method. In this study, a clamping force test of the fastening system was performed to confirm the real stiffness and the force versus displacement relationship. The test results were applied in the conventional linear analysis method and the proposed nonlinear analysis method to a railway bridge model specimen with concrete slab tracks. The results of the nonlinear analysis method considering the nonlinear stiffness of the rail fastening system through the clamping force test confirmed that the uplift force acting on the rail fastener was considerably reduced compared with that in the linear analysis method.</P>
오수진(Oh, Soojin),성덕룡(Sung, Deokyong),박용걸(Park, Yonggul) 한국방재학회 2017 한국방재학회논문집 Vol.17 No.3
철도 자갈궤도에서는 열차운행에 따른 반복적인 하중이 작용하여 침목저부 자갈의 파쇄를 가져오고, 침목과 자갈사이에 빈 공간이 생기는 뜬 침목 현상이 자주 발생하게 된다. 이러한 뜬 침목 현상은 선로유지보수 비용을 증가시킨다. 뜬 침목은 궤도재료의 피로 및 궤도침하와 같은 궤도열화를 유발하고, 수직방향 궤도틀림 진전을 발생시키기 때문에 이에 대한 분석은 매우 중요하다. 하지만 실제 현장에서는 뜬 침목에 대한 정량적인 검토가 매우 어렵다. 본 연구에서는 뜬 침목 개수와 뜬 침목 량을 변수로 한 뜬 침목을 모형화하여 실내시험을 수행하였다. 시험분석결과, 뜬 침목 개수가 증가함에 따라 궤도지지강성은 감소하고, 궤광의 강성이 유연해진다. 또한, 실제 열차운행 시 하중진폭은 열차운행 및 궤도 상태에 의해 결정되는 요인으로 동일한 조건에서 하중의 진폭이 증가할 경우 궤도 동적응답도 비례하여 증가하는 것으로 분석되었다. 따라서 궤도재료의 피로수명을 감소시키는 원인이 되는 뜬 침목에 대한 궤도 유지관리는 매우 중요하다. In the ballast track, a repeated load of the train leads to fracture of the bottom gravel of the sleepers, and a frequent loose sleeper occurs in which there is an empty space between the sleepers and the gravel. This loose sleeper increases the cost of track maintenance. In particular, it is very important to understand loose sleepers, which commonly appear when vertical track irregularities progress, when causing track deteriorations such as track settlement and fatigue of track materials. However, the quantitative analysis for loose sleeper is very difficult in the field. In this study, the laboratory test was performed for loose sleeper models which were distinguished by number of loose sleeper, gap of loose sleeper. The track support stiffness decreases and the stiffness of track skeleton is much more flexible according to increase the number of loose sleeper. It increases the static and dynamic responses of ballasted track. Also, the dynamic responses of track according to increasing load amplitude increase in proportion because the load amplitude depends on the conditions of track and train. Therefore, the track maintenance for loose sleeper is very important because of causing the fatigue fracture of track materials.