• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.04b
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• pp.125-132
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• 2000

하중전달의 문제는 구조체가 하중을 지지할 때 하중을 받는 부재로부터 하중을 지지하지 않는 쪽의 구조로 얼마만큼의 하중이 전달되는가를 해석하는 것이라고 간단히 정의 할 수 있다. 효율적인 Load transfer mechanism 은 구조체의 설계와 해석의 중요한 인자와 직접적으로 관련이 되어 있기 때문에 구조체의 해석시에는 이러한 하중전달의 개념이 반드시 포함되어야 한다. 그러나 일반적인 구조체의 해석시에는 하중전달의 개념은 그 해석의 어려움과 이론적인 해석해의 부재 그리고 본질적으로 존재하는 복잡성 때문에 무시되어져 왔다. 또한 이러한 하중전달의 문제가 다른 역학적인 거동과 연관되어 해석되어 질때는 그 이론적인 해는 구할 수가 없게 된다. 따라서 본 연구에서는 다층구조체에 존재하는 하중전달의 문제를 구조체 내에 존재하는 불연속면의 영향을 고려하수 있는 수치해석적인 모델의 개발을 통하여 하중전달효율의 개념으로 분석하여 각각의 불연속면의 영향에 따른 구조체내에 존재하는 하중전달의 현상을 규명하고자 한다.

• Solar Energy
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• v.10 no.1
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• pp.47-56
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• 1990

The aerodynamic performances of Darrieus wind turbine were studied through the wind tunnel model tests and its analytical aerodynamic streamtube model. Hence, analytical streamtube model which is based on momentum and blade element theory is considered and the formulated model was generalized in non-dimensional type to predict the aerodynamic characteristics of Darrieus wind turbine. The analytical model was justified through the wind tunnel model tests for several experimental conditions but in the limited rages. These satisfactory comparative studies between the wind tunnel tests and the analytical predictions can be utilized for the basic reliable design of Darrieus wind turbine.

• Journal of Korean Society of Steel Construction
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• v.19 no.3
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• pp.291-301
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• 2007

The overlay model is a certain kinds of numerical analysis method to present the material non-lineariy which is represented the baushinger effect and the strain hardening. This model simulates the complex behavior of material by controlling the properties of the layers which like the hardening ratio, the section area and the yield stress. In this paper, the constitutive equation and plastic flow rule of each layer which are laid in the plane stress field are obtained by using the thermodynamics. Two numerical examples were tested for the validity of proposed method in uniaxial stress and plane stress field with comparable experimental results. The only parameter for the test is the yield stress distribution of each layers.

• Tunnel and Underground Space
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• v.23 no.5
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• pp.372-382
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• 2013

Thermal-hydro-mechanical (THM) modeling is a critical R&D issue in the performance and safety assessment of a high-level waste repository. With an $\ddot{A}$sp$\ddot{o}$ prototype repository, its thermal behavior was analyzed and then compared with in-situ experimental data for its validation. A model simulation was used to calculate the temperature distributions in the deposition holes, deposition tunnel, and surrounding host rock. A comparison of the simulation results with the experimental data was made for deposition hole DH-6, which showed that there was a temperature difference of $2{\sim}5^{\circ}C$ depending on the location of the measuring points, but there was a similar trend in the evolution curves of temperature as a function of time. It was expected that the coupled modeling of the thermal behavior with the hydro-mechanical behavior in the buffer and backfill of the $\ddot{A}$sp$\ddot{o}$ prototype repository would give a better agreement between the experimental and model calculation results.

• Tunnel and Underground Space
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• v.30 no.4
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• pp.382-393
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• 2020

The engineered barrier system of high-level radioactive waste disposal must maintain its performance in the long term, because it must play a role in slowing the rate of leakage to the surrounding rock mass even if a radionuclide leak occurs from the canister. In particular, it is very important to clarify gas dilation flow phenomenon clearly, that occurs only in a medium containing a large amount of clay material such as a bentonite buffer, which can affect the long-term performance of the bentonite buffer. Accordingly, DECOVALEX-2019 Task A was conducted to identify the hydraulic-mechanical mechanism for the dilation flow, and to develop and verify a new numerical analysis technique for quantitative evaluation of gas migration phenomena. In this study, based on the conventional two-phase flow and mechanical behavior with effective stresses in the porous medium, the hydraulic-mechanical model was developed considering the concept of damage to simulate the formation of micro-cracks and expansion of the medium and the corresponding change in the hydraulic properties. Model verification and validation were conducted through comparison with the results of 1D and 3D gas injection tests. As a result of the numerical analysis, it was possible to model the sudden increase in pore water pressure, stress, gas inflow and outflow rate due to the dilation flow induced by gas pressure, however, the influence of the hydraulic-mechanical interaction was underestimated. Nevertheless, this study can provide a preliminary model for the dilation flow and a basis for developing an advanced model. It is believed that it can be used not only for analyzing data from laboratory and field tests, but also for long-term performance evaluation of the high-level radioactive waste disposal system.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.3 s.73
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• pp.295-302
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• 2006

In this study, computational structural dynamic analyses of a gyrocopter have been conducted considering unsteady dynamic hub-loads due to rotating blades. 3D CATIA models with detailed mechanical parts we constructed and virtually assembled into the complete aircraft configuration. The dynamic loading generated by rotating blades in the forward flight condition are calculated by a commercial computational fluid dynamics (CFD) code such as FLUENT. Modal based transient and frequency response analyses are used to efficiently investigate vibration characteristics of the gyrocopter. Free vibration analysis results for different fuel and pilot conditions, frequency responses and transient responses for critical flight conditions are also presented in detail.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 1996.03a
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• pp.83-94
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• 1996

지하 암반구조물의 안정적 설계 및 효율적 시공을 위해서는 공동설계 및 거동예측에 필요한 지질공학적 자료의 획득이 가장 중요하다. 현재 절리 등의 불연속면을 포함한 현장암반의 역학적 특성계수 및 응력 상태에 대한 조사기법들이 다양하게 개발되어 신뢰성 있는 분석결과를 제공하고 있다. (중략)

• Journal of the Korean Geotechnical Society
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• v.31 no.9
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• pp.5-15
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• 2015

In this study, rainfall-induced slope stability and coupling effect are investigated using hydro-mechanical finite element model. This model is developed by formulating constitutive and coupled balance equations and is verified by comparing the numerical results with field matric suction. The homogeneous soil layer (soil column) and soil slope are modeled by this model, and the results of variation in matric suction, mean effective stress, porosity, displacement, factor of safety are compared with those of staggered analysis. It is found that the vertical and horizontal displacement from coupling analysis considering change in porosity is larger than that of staggered analysis. The displacement and matric suction from coupling analysis by rainfall infiltration can affect slope instability, which shows a progressive failure behavior. The lowest factor of safety is observed under short-term rainfall. This results confirm the fact that coupling analysis is needed to design soil slope under severe rain condition.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.2
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• pp.45-52
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• 2011

To improve fire-resistance of a high strength concrete against spalling under elevated temperature, fibers can be mixed to provide flow paths of evaporated water to the surface of concrete when heated. In this study, the experiment of a column under fire and mechanical loads is conducted and the material model for predicting temperature of reinforcement steel bar and mechanical behavior of fiber-mixed high strength concrete is suggested. The material model in previous studies is modified by incorporating physical behavior of internal concrete and thermal characteristics of concrete at the elevated temperature. Thermo-mechanical analysis of the fiber-mixed high strength concrete column is conducted using the calibrated material model. The performance of the proposed material model is confirmed by comparing thermo-mechanical analysis results with the experiment of a column under fire and mechanical loads.

• Magazine of the Korea Concrete Institute
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• v.9 no.4
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• pp.187-196
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• 1997

시멘트를 기초로하는 복합재료의 파괴거동은 주균열이 진행하기 이전에 파괴진행영역이라고 하는 미세균열대가 콘크리트 내부에 형성고기 때문에 선형파괴역하게 입각하여 해석하게 되면 실험치와 상당한 차이를 나타낸다. 이러한 문제점을 해결하기 위해 가상균열모델이나 균열띠 모델, 두 파라메터 파괴모델 등 비선형해석에 따른 여러 파괴역학모델들이 제안되었으나 이들 모델들은 2차원 해석에 근거를 두고 있기 때문에 구조체의 두께 방향으로 동일한 균열이 형성되며, 특히 콘크리트 실험에서 관찰되는 비연속적 균열발생에 대해서 설며이 어려웠다. 이에 본 연구는 콘크리트를하나의 다종복합체로 가정하고 연립변형모드 및 진행파괴모드 방향으로 구성재료를 배열한 상태에서 가상균열 이론에 근거한 비선형해석방법으로 모델링하였다. 진행파괴모드로 구성재료를 배열하면 강성이 높은 구성재료를 통과하여 균열이 진행될 때 균열선단으로부터 분포된 응력이 상층의 허용인장강도를 초과하게 되어 균열이 발생되며 이러한 균열은점진적인 균열진행과는 달리 비연속 동시 발생 균열ㄹ로 나타났다. 본 연구는 진행파괴모드에서의 파괴 해석 방법과연립변형모드에서의 해석 방법을 제시하였으며, 해석결과를 실험결과와 비교함으로써 검증하였다.