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유민택,백민철,이일화,이진선,Yoo, Mintaek,Back, Mincheol,Lee, Ilhwa,Lee, Jinsun 한국지진공학회 2017 한국지진공학회논문집 Vol.21 No.5
Dynamic numerical simulation of pile-supported slab track system embedded in a soft soil and embankment was performed. 3D model was formulated in a time domain to consider the non-linearity of soil by utilizing FLAC 3D, which is a finite difference method program. Soil non-linearity was simulated by adopting the hysteric damping model and liner elements, which could consider soil-pile interface. The long period seismic loads, Hachinohe type strong motions, were applied for estimating seismic respose of the system, Parametric study was carried out by changing subsoil layer profile, embankment height and seismic loading conditions. The most of horizontal permanent displacement was initiated by slope failure. Increase of the embedded height and thickness of the soft soil layer leads increase of member forces of PHC piles; bending moment, and axial force. Finally, basic guidelines for designing pile-supported slab track system under seismic loading are recommended based on the analysis results.
연약지반 침하 억제를 위한 성토지지 말뚝 공법 적용성 평가
유민택(Mintaek, Yoo),이성지(Sungji Lee),이수형(Suhyung Lee),백민철(Mincheol Baek),최규문(Gyumoon Choi),이일화(Ilhwa Lee) 한국철도학회 2017 한국철도학회 학술발표대회논문집 Vol.2017 No.05
연약지반에 철도 구조물을 건설하는 경우, 궤도구조물에 의해 발생하는 정적 사하중(Dead load) 및 열차 하중에 의한 활하중 (Live load)에 의한 장기 침하는 구조물의 안전성 및 승차감 측면에서 문제를 야기하게 된다. 이러한 문제를 해결하기 위해, 연약지반 상부에 건설되는 성토구조물의 잔류침하를 억제하고, 공사기간을 단축할 수 있는 방법으로 토목섬유를 보강한 성토지지말뚝(GRPS) 공법의 적용이 확대되고 있다. 토목섬유를 보강한 성토지지말뚝 공법의 경우 성토체 내 지반의 아칭형상과 토목섬유의 인장력을 이용하여 상부로부터 전달되는 하중을 말뚝으로 전이 시키게 된다. 본 연구에서는 이러한 섬유보강 성토지지말뚝 공법에 대한 성토하중 및 열차하중 재하실험을 수행하였고, 이를 바탕으로 하중전이 매커니즘 분석 및 공법의 효율성에 대해 규명하였다 When railroad structure is constructed on soft ground, long-term settlement due to static dead load and dynamic train load could cause a number of problems, such as reduction of safety and ride quality. In order to resolve this problem, Geosynthetic-reinforced and Pile-supported(GRPS) embankment method is widely used to construct structures on the soft soil due to restraining residual settlement and their rapid construction. The load transfer mechanism of GRPS system is that almost external load is transferred on the pile by arching effect and tensile strength of geogrid. In this paper, static and cyclic loading tests were conducted to investigate load transfer characteristics of pile-supported embankment under additional loading. Based on test results, the load transfer mechanism is analyzed and verify the efficiency of GRPS method.
철도교량 교각 안전성 평가를 위한 현장 충격 진동하중 실험
유민택 ( Yoo Mintaek ),이명재 ( Lee Myoung-jae ),정현석 ( Jung Hyun-seok ),이일화 ( Lee Il-wha ) 한국구조물진단유지관리공학회 2020 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.24 No.1
The current stability assessment criteria for railway bridge pier depends on only macroscopy visual examination, therefore, it is needs to systematic and quantitative method for evaluating the stability of railway bridge pier system. In this research, the impact load tests were performed to measure natural frequency of railway bridge pier, the results of tests were analyzed to evaluate bridge pier stability quantitatively. The targer bridge pier is located in Donghae-Nambu line which has plan to be removed. In order to measure dynamic behavior of bridge pier, three accelerometers were installed model pier, which are attached from 50 cm of upper and lower side and center of pier. As the results, the bridge pier is generally stable in case of rock condition, and is not stable in case of sand condition. In addition, scour effect could be evaluate by analyzing torsional dynamic behavior of bridge pier.
원심모형 실험을 이용한 반복하중을 받는 모노파일 거동 평가
이명재,유민택,박정준,민경찬,Lee, Myungjae,Yoo, Mintaek,Park, Jeongjun,Min, Kyungchan 한국지반공학회 2019 한국지반공학회논문집 Vol.35 No.6
본 연구는 원심모형실험을 이용해 건조 사질토 지반에 근입된 모노파일의 수평 반복하중에 대한 거동을 연구하였다. 실험에 사용된 지반 시료는 상대밀도 80%에서 마찰각이 $38^{\circ}$인 건조 주문진 표준사를 사용했다. 실험 과정은 우선 반복하중의 크기를 결정하기 위해 정적 하중 실험을 수행하여 극한하중을 결정하였다. 이를 통해 도출된 극한 하중 값의 30%, 50%, 80%, 120%을 반복하중의 값으로 결정하였고, 반복횟수는 100회로 수행되었다. 이 결과를 통해 실험 반복하중 p-y 곡선을 산정하였고 도출된 하중 별 최대 지반반력점들을 이용하여 깊이 별 반복하중 p-y 중추곡선을 도출하였다. 이를 기존 p-y 곡선과 비교 결과, 동일 깊이에서 초기기울기가 API(1987) p-y 곡선보다 과소평가 되었으며, 극한지반반력은 과대평가되었다. 또한, 동적 p-y 곡선과 비교하였을 때, 동일 깊이에서의 반복하중 p-y 중추곡선의 초기기울기와 지반반력이 작게 평가되었다. 이는 말뚝이 받는 하중 조건에 따라 p-y 곡선을 다르게 적용해야 할 것으로 판단된다. This study investigated the lateral behavior of monopile embedded in the dry sand through cyclic lateral loading test using a centrifuge test. The sand sample for the experiment was the dry Jumunjin standard sand at 80% relative density and the friction angle of $38^{\circ}$. In the experimental procedure, firstly, it was determined the static lateral bearing capacity by performing the static lateral loading test to decide the cyclic load. This derived static lateral bearing capacity values of 30%, 50%, 80%, 120% were determined as the cyclic lateral load, and the number of cycle was performed 100 times. Through the results, the experiment cyclic p-y curve was calculated, and the cyclic p-y backbone curve by depth was derived using the derived maximum soil resistance point by the load. The initial slope at the same depth was underestimated than API (1987) p-y curves, and the ultimate soil resistance was overestimated than API (1987) p-y curves. In addition, the result of the comparison with the suggested dynamic p-y curve was that the suggested dynamic p-y curve was overestimated than the cyclic p-y backbone curve on the initial slope and soil resistance at the same depth. It is considered that the p-y curve should be applied differently depending on the loading conditions of the pile.