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체결장치의 종방향 저항 특성을 반영한 교량상 콘크리트궤도의 종방향 저항력 산정
민경환(Min, Kyunghwan),윤경민(Yun, Kyungmin),박종찬(Park, Jongchan),임남형(Lim, Namhyoung) 한국방재학회 2018 한국방재학회논문집 Vol.18 No.5
궤도-교량 상호작용 검토 시 궤도의 종방향 저항력은 매우 중요한 인자이다. 하지만 다양한 설계기준에서 궤도-교량 상호작용 해석을 위한 교량상 콘크리트궤도의 종방향 저항력은 하나의 선도로 제시하고 있기 때문에 실제 부설되는 체결장치의 저항력을 고려하기 어렵다. 본 연구에서는 실내 체결장치 실험을 통하여 궤도-교량 종방향 상호작용 검토시 안전측 설계가 가능한 저항력을 산정하였다. 이를 위하여 실내 저항력 실험을 수행하였으며, 실험을 통하여 수직하중 재하 시 저항력은 수직하중의 증가에 따라 선형으로 증가하는 것을 확인하였다. 그리고 수직하중에 의한 저항력 증가를 고려하기 위한 관계식을 만들어 저항력의 신뢰 범위를 산정하였다. 또한 신뢰범위내의 저항력을 고려하여 궤도-교량 상호작용 해석을 수행하고 결과를 분석하였다. 신뢰범위 내에서 상한값을 사용한 경우에 궤도-교량 종방향 상호작용 검토시 안전측 설계가 가능함을 확인하였다. The longitudinal resistance of a railway track is one of the most important factors indicating the track-bridge interaction (TBI). However, it is difficult to consider the actual resistance of an installed fastening system of a rail because the longitudinal resistance of the concrete track on the bridge for analyzing TBI is presented as a single resistance-displacement curve in design standards. In this study, the resistance that can satisfy the design requirements from the point of view of safety was calculated through experiments of the fastening system of rails. For this purpose, laboratory experiments were performed, and it was confirmed that the resisting force increases linearly with the vertical load. Further, the confidence interval of the resistance was calculated by establishing a relation that accounts for the increase in resistance due to the vertical load. Moreover, the TBI analysis was performed considering the resistance within the confidence interval, and the results were analyzed. It is thus confirmed that safe design is possible when the upper limit of the resistance value used is within the confidence interval.
전산해석을 통한 지하 공동 및 암반 조건에 따른 철도지반 안정성 평가: 마장광산 갱도를 대상으로
장경환 ( Kyunghwan Jang ),이동원 ( Dongwon Lee ),민경남 ( Kyungnam Min ),정찬묵 ( Chanmook Chung ),유재형 ( Jaehyung Yu ),이계승 ( Gyeseung Lee ) 대한지질공학회 2021 지질공학 Vol.31 No.3
본 연구는 광산활동에 따른 철도지반 안정성 평가를 위해 채굴적의 심도, 규모 및 암반상태를 다양하게 설정하고, 표준열차하중 조건 중 여객, 화물 혼용 구간과 여객전용선 용도에 따른 지반안정성 평가를 전산해석을 통해 실시하였다. 안정성 평가는 철도설계기준 노반편에 따른 허용잔류 침하량과 선로유지관리지침 뒤틀림 보수조건을 기준으로 실시되었다. 그 결과, 채굴적의 규모 및 위치가 심도 5 m 이하일 경우 침하의 발생이 암반상태에 따라 노반 침하허용 기준을 넘어서며, 뒤틀림 보수기준에는 심도 15 m 이하의 공동일 경우 암반상태를 고려하여 지반보강 설계가 이루어져야 할 것으로 보인다. 노반의 침하허용 범위만 고려할 경우 심도 5 m 이하의 공동에서 암반상태가 고려되어야 한다. 이는 공동의 규모와 암반조건에 따른 침하량이 체계적으로 변화 함을 지시하며, 이러한 연구결과는 기존에 제시된 바가 없는 자료이다. 본 연구는 추후 철도건설이 광산지역에서 이루어질 경우 중요한 참고 자료로 활용될 수 있을 것으로 기대한다. This study used numerical modeling to investigate the stability of railway roadbed in areas with various underground cavities and rock conditions associated with mining activities. It compared combined loads from both passenger and freight trains with loads from only passenger trains. Stability was assessed with reference to the Korean government standards for railway subsidence allowance and railway warping repair. Sufficient stability regarding the railway subsidence allowance standard was not achieved when cavities were at depths of <5 m. The criteria for requiring railway warping repair were met when cavities were at depths of <15 m, depending on the rock fracture condition. This study provides the first report on systematic analysis land subsidence related to cavity size and rock fracture conditions associated with mining activities. We expect that this study could serve as an important reference for railway construction in mining areas.
Dynamic measurement of stress optical behavior of three amorphous polymers
Inki Min,Kyunghwan Yoon 한국유변학회 2012 Korea-Australia rheology journal Vol.24 No.1
In the present study, rheo-optical and mechanical properties of three amorphous polymers, i.e., PS (polystyrene), PC(polycarbonate) and COC(cyclo olefin copolymer), widely used for optical products have been investigated. Accurate measurement of stress optical coefficients and elastic modulus data across the glass transition region are essential for predicting optical anisotropy in many injection molded optical products like pickup lenses and waveguide in LCD module since the final products have both flow and thermal history from the melt to glass. To obtain stress optical behavior in wide range of frequency and temperature including rubbery, glassy and glass transition regime, frequency sweep tests with extensional bar and shear sandwich tools were undertaken. As a result, glassy and melt extreme values of stress optical coefficient of PS and PC were evaluated as well as master plots in wide frequency region. The sign change of stress optical coefficient was shown clearly for PS as the frequency increased. On the other hand, the sign of stress optical coefficient over the whole frequency region is always positive for PC. For COC's of different composition, even though the glass transition temperature can vary, the stress optical coefficient of COC's with different composition stays almost constant at two extremes
Investigation on Phase-change Synapse Devices for More Gradual Switching
Minkyu Shin,Kyunghwan Min,Hayeon Shim,Yongwoo Kwon 대한전자공학회 2019 Journal of semiconductor technology and science Vol.19 No.1
The architecture of phase-change synapses that can have more intermediate states was studied by means of TCAD simulation. After thorough investigation on the cell geometry effects, it was found that the line-and-space type architecture yields more intermediate states but consumes more power than the confined architecture does. In fact, phase-change memory has evolved from the former to the latter to achieve better power efficiency and more abrupt transition. This trade-off between the cell architectures must be overcome to make a synapse with both less power and gradual transition.