• Computers and Concrete
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• 제31권4호
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• pp.307-314
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• 2023

In this paper we back-analyze a failure event of a 9 m high concrete cantilever wall subjected to earth loading. Granular soil was deposited into the space between the wall and a nearby rock slope. The wall segments were not designed to carry lateral earth loading and collapsed due to excessive bending. As many geotechnical programs rely on the Mohr-Coulomb (MC) criterion for elastoplastic analysis, it is useful to apply this failure criterion to the concrete material. Accordingly, the back-analysis is aimed to search for the suitable MC parameters of the concrete. For this study, we propose a methodology for accelerating the back-analysis task by automating the numerical modeling procedure and applying a machine-learning (ML) analysis on FE model results. Through this analysis it is found that the residual cohesion and friction angle have a highly significant impact on model results. Compared to traditional back-analysis studies where good agreement between model and reality are deemed successful based on a limited number of models, the current ML analysis demonstrate that a range of possible combinations of parameters can yield similar results. The proposed methodology can be modified for similar calibration and back-analysis tasks.

• 한국지반공학회논문집
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• 제27권9호
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• pp.25-36
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• 2011

조적식 석축옹벽의 거동 특성을 규명하기 위하여 실내 모형시험과 수치해석을 수행하였다. 실내 모형시험에서 옹벽 블록과 뒤채움재의 변위를 측정하기 위해 PIV 기법의 디지털 이미지 해석을 실시하였다. 유한요소 수치해석을 위해 상용프로그램인 ABAQUS를 사용하였다. 모형시험에서 관찰된 뒤채움재의 변위 발생 과정은 파괴면의 형성이 점진적임을 보여준다. 수치해석 결과에서 석축옹벽의 시공 과정에서 발생하는 전체적인 수평 토압 분포는 기존의 Rankine 이론과 큰 차이가 없지만, 뒤채움재의 내부 마찰각과 석축을 구성하는 석재 간의 마찰각이 작으면 토압의 분포가 불규칙해짐을 확인하였다.

• 동력기계공학회지
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• 제13권2호
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• pp.36-41
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• 2009

An experimental investigation was conducted to examine the fluid flow resistance in the rectangular channel with two inclined wire screen baffles. Two different types of wire screens; dutch weave and plain weave, were used as baffle devices in this experiment. Three kinds of baffles with different mesh specifications were made up of dutch type and four different kinds of baffles were made up of plain weave type. The stainless steel wire screen baffles were mounted on the bottom wall with varied angle inclination. Reynolds numbers were varied from 23,000 to 57,000. Results show that the mesh number of baffles plays an important role on friction factor behaviour. It is found that the baffle with the most number of meshes (type SA) has the highest fluid flow resistance.

• Journal of Advanced Marine Engineering and Technology
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• 제39권6호
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• pp.609-613
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• 2015

축방향 거리에 따라 확대되는 정사각 채널에서 발달된 난류유동의 국부 난류 열전달과 압력강하를 실험적으로 조사하였다. 정사각 확대채널에 한 면에만 높이가 10 mm인 리브를 설치하였다. 리브의 충돌 각은 $30^{\circ}$, $45^{\circ}$, $60^{\circ}$ 그리고 $90^{\circ}$로 한 벽면에 만 설치하였다. 레이놀즈수가 22,000~79,000의 범위에서 실험을 수행하였다. 연구 결과 $45^{\circ}$의 리브 충돌각이 가장 우수한 열전달 성능을 보였다.

• 한국지반신소재학회논문집
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• 제7권3호
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• pp.9-16
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• 2008

본 논문에서는 보강토 옹벽의 파괴거동을 탄소성이론에 의한 수치해석적으로 평가에 관한 연구내용을 다루었다. 우선, 보강토 옹벽의 기본적인 파괴거동에 대하여 검토하였다. 유한요소법을 사용하여 보강토 옹벽의 파괴거동에 영향을 미치는 주요 요인에 대하여 매개변수연구를 실시하였다. 주 검토목적으로는 보강토 옹벽의 파괴형상에 미치는 요인 및 영향에 대하여 분석하는 것이다. 뒤채움흙의 마찰각, 보강재 종류, 보강재 길이에 따른 파괴거동에 미치는 영향에 대하여 수치해석적 분석을 하였다.

• 한국농촌건축학회논문집
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• 제15권1호
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• pp.29-36
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• 2013

This study is to diagnose causes of damage and defects on external walls of brick structures, focused on "Naju Noahn" Catholic Church of Modern Architectural Properties. The causes of crack and deflection are overloading, shortage strength of arch. Among those, main cause is cauesd by shortage strength of arch because center of arch is dislocated and skew back of arch is small angle. The causes of damage and elimination are weathering, plants of friction, freezing and thawing, durability decrement of material and attach defection. This defects and damage is caused by high-moisture that occurs in soil. The causes of discoloration are change of soil moisture and flimsy brickwork. These defects and damage are mainly occurred in coping of cornice, weathering of window sill.

• 한국지반공학회지:지반
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• 제7권3호
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• pp.43-50
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• 1991

굴착 중 slurry로 지대되고 있는 상태에서 지하수와 상재하중의 영향을 고려한 diaphragm wall 의 안정도를 해석하기 위하여 Belt Piaskowski/kowalewski, Washbourne의 모델을 확장하고, 확장된 이론으로 프로그램 SL3D를 개발하였다. Washbourne의 모델에서는 Bell, Piaskowski / Kowalewski의 모델에 비해, 굴착깊이가 증가함에 따라 안정도가 매우 큰 폭으로 증가하고, 비교적 초기굴착단계에서 부터 안전측에 속한다. 또한 slurry의 밀도, 지하수위, 흙의 내부마찰각, trench의 길이,상재단위하중등이 안정도에 미치는 영향을 분석하였고, 이것을 근거로 nomogram을 작성하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 춘계 학술발표회
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• pp.419-433
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• 2009

Pressure grouting is a common technique in geotechnical engineering to increase the stiffness and strength of the ground mass and to fill boreholes or void space in a tunnel lining and so on. Recently, the pressure grouting has been applied to a soil-nailing system which is widely used to improve slope stability. The soil-nailing design has been empirically performed in most geotechnical applications because the interaction between pressurized grouting paste and the adjacent ground mass is complicated and difficult to analyze. The purpose of this study is to analyze the increase of pullout resistance induced by pressurized grouting with the aid of performing laboratory model tests and field tests. In this paper, two main causes of pullout resistance increases induced by pressurized grouting were verified: the increase of residual stress; and the increase of coefficient of pullout friction. From the laboratory tests, it was found that residual stress in borehole increases by pressurized grouting and dilatancy angle could be estimated by cavity expansion theory using the measured wall displacements. From the field test results, the pullout resistance of soil-nailing with pressurized grouting was found to be 10% larger than that of soil-nailing with gravitational grouting, mainly caused by mean normal stress increase and dilatancy effect. So, the pullout resistance could be estimated by considering these two effects. The radial displacement increases with dilatancy angle increase and the dilatancy angle decreases with injection pressure increase. The measured pullout resistance obtained from field tests is in good agreement with the estimated one from the cavity expansion theory.

• 설비공학논문집
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• 제14권7호
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• pp.567-574
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• 2002

In the present study, ventilation flow rates and pressure rises through a road tunnel are simulated numerically using CFD with the various conditions such as roughness height, swirl angle of jet fan, entrance and exit effect and hub to tip ratio. By using a modified wall function, friction factor can be predicted under 10％ of error with respect to the Moody chart for the circular pipe flow and 15％, for the present tunnel. For more precise design, the effects of the swirl angle and hub to tip ratio of jet fan, which is not included in the theoretical equation of pressure rise by jet fan are necessary to be considered.

• Journal of Advanced Marine Engineering and Technology
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• 제29권3호
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• pp.260-274
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• 2005

An experimental investigation was performed to study the characteristics of turbulent swirling flow in the cylindrical annuli. The swirl angle measurements were performed by flow visualization technique using smoke and dye liquid. By using the particle image velocimetry method. this study has found the time-mean velocity distribution and turbulent intensity with swirl for Re=20,000. 30.000. 50.000. and 70,000 along longitudinal sections. The results appear to be physically reasonable. Other experimental study was performed to investigate heat transfer characteristics of turbulent swirling air flow in axisymmetric annuli. The static pressure. the local air flow temperature, and the wall temperature with decaying swirl were measured by using thermocouples and the friction factor and the local Nusselt number were calculated for Re=30,000. 50,000 and 70000. The local Nusselt number was compared with that obtained from the Dittus-Boelter equation with swirl and without swirl, respectively. The results showed that the swirl enhances the heat transfer at the inlet and the outlet of the test tube.