• Journal of the Korean GEO-environmental Society
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• v.12 no.7
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• pp.57-65
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• 2011

Numerical simulations by three-dimensional Particle Flow Code($PFC^{3D}$, Itasca) considering distinct element method (DEM) were carried out for prediction of triaxial compression test with sand material. The effect of scale conditions for numerical model and distinct material on final prediction results was analyzed by numerical models under various scale conditions, and following observations were made from the numerical experiments. It is very useful to model the initial material condition without any porosity conversion from 2-D to 3-D DEM. Numerical experiments have shown that in all cases considered, 3D distinct element modeling could provide good agreement on stress-strain behavior, volume change and strength properties with laboratory testing results. It was important thing to assess reasonable scale ratio of numerical model and distinct elements for saving calculation time and securing calculation efficiency under condition with accuracy and appropriateness as numerical laboratory. As results of DEM simulations under various scale conditions, most of results show that shear strength properties as cohesion and internal friction angle are similar in condition of $D_{mod}/D_{gmax}$ < 10. It shows that 3-D distinct element method could be used as efficient tool to assess strength properties by numerical laboratory technique.

• Journal of Radiation Protection and Research
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• v.27 no.1
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• pp.67-75
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• 2002

The groundwater flow and contaminant transport numerical models have been established for understanding the movement of pollutants in surface soil environment. The numerical solutions were compared with the analytic solutions for the verification and the application of the models. The numerical solutions from the groundwater and transport models agreed welt with analytic solutions. Especially, the results of groundwater flow model were validated in one- and two-dimensional heterogeneous media. Therefore, it will represent well the characteristics of the heterogeneous media in the field applications. Also, the phenomena of the pollutant dispersion represented quite well by the advection and the hydrodynamic dispersion in the results of the transport model. The important input factor is the choice of complicated boundary conditions in operating the numerical models. The numerical results are influenced by the choice of the proper boundary conditions.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.18-20
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• 2009

입자 강화 복합재료 내에서의 다양한 손상 메커니즘은 복합재료의 전체 거동을 예측에 상당한 영향을 미친다. 이에 본 연구에서는 입자 강화 복합재료 내에서의 누적 손상을 고려한 미세역학 기반 탄소성 모델(Kim and Lee, 2009)을 소개하고자 한다. Kim and Lee (2009)에 의해서 입자 강화 복합재료의 탄소성 모델을 위해 입자 강화 복합재료 내 계면에서의 누적 손상 및 기지재의 연성 거동이 고려되었다. 제안된 모델을 이용한 입자 강화 복합재료의 탄소성 거동 예측값은 관련된 실험값 (Llorca et al., 1991)과의 비교를 통해 수치해석을 수행하였다.

• Journal of the Korean GEO-environmental Society
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• v.2 no.3
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• pp.89-99
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• 2001

In this study, the numerical analysis of piezocone penetration and dissipation tests has been conducted using the Modified Cam-Clay model, which is generally used in soil mechanics. The Modified Cam-Clay model and related mathematical equations in finite element derivation have been formulated in the Updated Lagrangian reference frame to take the large displacement and finite strain nature of piezocone penetration into consideration. The cone tip resistance, the pore water pressure, and the dissipation curve obtained from the finite element analysis have been compared and investigated with the experimental results from piezocone penetration test performed in Yangsan site. The numerical results showed good agreement with the experimental results; however, the better numerical simulation of the continuous and deep penetration needs further research.

• Tunnel and Underground Space
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• v.9 no.1
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• pp.56-63
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• 1999

Rock behaves in a complex way due to the discontinuities. To describe the complicated failure and deformation behavior of rock, many researches were focused on the development of crack models. This study discusses the validity of the sliding and shear crack model to systematically fractured rock, i.e. coal. The model was also implemented into a numerical analysis. For that, a finite element program was modified in several ways. To describe the transverse isotropy in two-dimensional analysis, the stress-strain relationship was modified for the direction of the axis of symmetry. Also, the changes of the effective elastic moduli according to the crack growth were calculated. A simple example of two-dimensional laboratory uniaxial compression test was analyzed. The results coincided with the observations obtained from the laboratory tests.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.1 s.47
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• pp.1-8
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• 2006

Nonseismic designed RC frame have a possibility of shear failure because of deficiencies of reinforcing details. To model the shear failure in numerical analysis, shear strength degradation models which Include Moehle's and ATC 40 are compared and applied to push-over analysis. For numerical analysis, three storied building frame is selected and designed according to Korean Concrete Design Code(2003). As results, It is shown that Moehle's shear strength degradation model estimates the shear strength lower than NZSEE model and has less variation than ATC 40 model and all the shear strengths of models are greater than the nominal shear strength of ACI 318. Also, from the numerical analysis, it is pointed out that there may be great difference in lateral drift capacity if a different shear strength model is used. And the capacity can be severely underestimated if the restraining model of plastic rotation of ATC 40 is used, compared to the use of shear spring model for shear degradation.

• Journal of the KSME
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• v.21 no.3
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• pp.197-204
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• 1981

본 강좌에서는 수치해석 계산의 수학과 해의 정확도에 가장 큰 영향을 미치는 난류모델의 설정과 난류유동과 열전달의 기본방정식을 수치해석하기 위하여 차분형방정식 (finite difference equation)으로 전환하는데 발생하는 문제점을 검토하고자 한다.

• Computational Structural Engineering
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• v.8 no.2
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• pp.73-84
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• 1995

The study summarized in this paper is concerned with the buckling of longitudinal bars in reinforced concrete columns with numerical analysis method. The objectives of this study are (1) to investigate the stress transfer mechanism between concrete and reinforcement and (2) to propose a modeling equation. The results give an acceptable agreement between the proposed modeling equation and published computer packages as follows; (1) the proposed equation is a possible of strain softening of concrete and buckling of reinforcement. (2) the buckling of longitudinal bar is mainly influenced by spacing of hoop and location of the bar

• 한국신재생에너지학회:학술대회논문집
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• 2006.11a
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• pp.245-248
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• 2006

풍력터빈 풍동시험의 경우 모델 축소에 의한 레이놀즈 수 감소가 ?V력터빈 성능에 미치는 영향이 적절히 고려되어야 한다. 본 연구를 통해 수치해석과 축소모델 풍동시험을 통해 모델 축소효과를 파악하여 이를 적절히 보상하는 기법을 개발하고자 한다. 이를 위해 풍력터빈 형상 및 실물모델 시험데이터가 공개되어 있는 NREL Phase VI 모델을 표준모델로 선정하여 수치해석 및 풍동시험을 수행하였다. 풍동시험은 KARI LSWT에서 2006. 10에 수행되었으며, 블레이드 끝단 속도를 실물 모델과 일치시켰으며 시험부 유속은 $0{\sim}25m/s$, 블레이드 설치각은 3도 조건을 기준조건으로 사용하였다. 축소모델 시험결과 최대토크는 약 10% 정도 감소현상을 보이고 있다.

• New & Renewable Energy
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• v.2 no.4 s.8
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• pp.12-18
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• 2006

풍력터빈 풍동시험의 경우 모델 축소에 의한 레이놀즈 수 감소가 풍력터빈 성능에 미치는 영향이 적절히 고려되어야 한다. 본 연구를 통해 수치해석과 축소모델 풍동시험을 통해 모델 축소효과를 파악하여 이를 적절히 보상하는 기법을 개발하고자 한다. 이를 위해 풍력터빈 형상 및 실물모델 시험데이터가 공개되어 있는 NREL Phase VI 모델을 표준모델로 선정하여 수치해석 및 풍동시험을 수행하였다. 풍동시험은 KARI LSWT에서 2006. 10에 수행되었으며, 블레이드 끝단 속도를 실물 모델과 일치시켰으며 시험부 유속은 0$\sim$25m/s, 블레이드 설치각은 3도 조건을 기준조건으로 사용하였다. 축소모델 시험결과 최대토크는 약 10% 정도 감소현상을 보이고 있다.