• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.10a
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• pp.83-84
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• 2016

Surplus water inside a concrete other than moisture that is used for hydration of the cement affects the physical properties of the concrete (modulus of elasticity, compressive strength, drying shrinkage, and creep) by drying. Changes in temperature and humidity inside a concrete has correlation with the movement speed and reaction rate of deterioration factors such as carbon dioxide and chloride ions. In this study, comparison was performed between temperature and relative humidity inside the concrete and meteorological data for exposure environment through measurement at the site for two years. Surface temperature of the concrete (depth 1cm) was measured higher by 6℃ during the summers, while it was measured lower by 2℃ during the winters due to solar radiation, wind, and radiation cooling. As for relative humidity, change was large in the depth of 1cm, while more than 85% was maintained in the depth of 10cm.

• Geotechnical Engineering
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• v.7 no.4
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• pp.15-24
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• 1991

This paper reports the application study of the concrete bedding reinforcement under a buried conduit with flexible joints subjected to differential settlement via a finite elemen modeling. The reinforcement of concrete bedding helps to minimize the differential settlement between the adjoining conduit segments. Three different field conditions have been considered. The settlement pattern and deformation slope have been evaluated for each boundary condition. The analysis results are compared for both non-reinforced and reinforced cases to measure the effectiveness of concrete bedding reinforcement for restraining deformation of a conduit with flexible joints.

• Geotechnical Engineering
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• v.7 no.4
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• pp.5-14
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• 1991

This paper reports the application study of the ground reinforcement under a buried conduit subjected to differential settlement via a finite element modeling. The soil-reinforcement inter- action helps to minimize the differential settlement between the adjoining conduit segments. Three different field conditions have been considered. The settlement pattern and deformation slope have been evaluated for each boundary condition. The analysis results are compared for both non-reinforced and reinforced case to measure the effectiveness of the soil reinforcement for restraining deformation of the conduit.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.3
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• pp.385-396
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• 1989

In this paper, using by the orthogonalities of modes for trainwheel (as Mindlin's annular plate and rail (as Timoshenko beam), the frequency equation of the coupled system are induced. It is convinced that the natural frequencies of coupled system are distributed to be about quadratic order function examined through the experimental and numerical analysis. The natural frequencies of the system coupled by both creep force and creep moment are composed of the natural frequencies of the system coupled by creep force and the natural frequencies of the system coupled by creep moment . And it is shown that the coupled natural frequencies up to 3rd do not make much difference from the values of the system coupled by individual creep force of creep moment. But the coupled natural frequencies higher than the 3rd are quite different from those of individual case.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.3
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• pp.248-257
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• 2011

In the present study, we proposed a new numerical wave tank model to analyze the vertical tension-leg circular floating bodies, using a 2-D Navier-Stokes solver. An IBM(Immersed Boundary Method) capable of handling interactions between waves and moving structures with complex geometry on a standard regular Cartesian grid system is coupled to the VOF(Volume of Fluid) method for tracking the free surface. Present numerical results for the motions of the floating body were compared with existing experimental data as well as numerical results based on FAVOR(Fractional Area Volume Obstacle Representation) algorithm. For detailed examinations of the present model, the additional hydraulic experiments for floating motions and free surface transformations were conducted. Further, the versatility of the proposed numerical model was verified via the numerical and physical experiments for the general rectangular floating bodies. Numerical results were compared with experiments and good agreement was archived.

• Journal of Ocean Engineering and Technology
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• v.10 no.3
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• pp.44-49
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• 1996

후방계단(backward facting step) 주위의 난류 유동 특성을 수치 해석을 통해 파악하고자 하였다. 지배방정식은 2차 정도의 유한 차분 기법으로 이산화하였으며 비교차격자계를 사용하여 양해법으로 계산하였다. 난류 모형으로는 이층 모형(two-layer)을 사용하였고 압력 Poisson 방정식을 이용하여 압력과 속도를 연성 시켰다. Re=44,000인 경우에 대해 계산 결과로 부터 후방 계단 뒤의 속도 벡터, 유선, 압력 및 속도 분포, 재부착 길이(reattachment length)등의 실험치와 비교하였다. 본 계산에 사용한 수치 해석 기법은 박리등이 포함된 복잡한 난류 유동 현상을 잘 재현할 수 있음을 확인할 수 있었다.

• Composites Research
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• v.28 no.4
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• pp.204-211
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• 2015

This paper presents a theory related to a two-dimensional linear cross-sectional analysis, recovery relationship and a one-dimensional nonlinear beam analysis for composite wing structure with initial twist. Using VABS including a related theory, the design process of the composite rotor blade has been described. Cross-sectional analysis was performed at cutting point including all the details of geometry and material. Stiffness matrix and mass matrix were linked to each section to make 1D beam model. The 3D strain distributions within the structure were recovered based on the global behavior of the 1D beam analysis and visualize numerical results.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.12 no.4
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• pp.537-549
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• 1999

선형탄성 파괴해석은 균열을 갖는 변형률 경화재료의 파괴거동을 예측하는데 불충분하기 때문에 최근에는 균열 선단 부에서 대규모 소성 역을 갖는 균열 체에 적용할 수 있는 많은 파괴역학개념이 제안되고 있다. 따라서, 본 연구에서는 대규모항복 조건하의 연성파괴를 보이는 평판을 정확하게 해석할 수 있는 새로운 유한요소모델을 제시하고자 한다. 균열 선단 부의 응력 장을 정의하는데 가장 지배적인 파괴매개변수인 J-적분 값과 소성 역의 크기 및 형상을 J-적분법과 등가영역적분법을 통해 파괴거동을 설명할 수 있도록 증분소성이론에 기초를 둔 p-version 유한요소해석이 채택되었다. 제안된 유한요소모델에 의한 수치해석결과는 이론 해와 h-version 유한요소해석과 비교되었다.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.201-207
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• 2010

In this study, we calculated arc discharges happened in high-voltage circuit breakers for understanding the complex physics and the probability of thermal breakdown. The four main parts of arc model for this virtual-reality are radiation, PTFE abaltion, Cu evaporation and turbulence. Among these important parts the turbulence model can be critical to the reliability of computation results during high-current period because the plasma flow is affected by high eat energy and mass momentum. Two kinds of turbulence model, zero-equation model and two-equation model, are applied for these calculations and are compared with the measured pressure data inside a chamber.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.7
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• pp.727-734
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• 2014

This paper describes multi-scale based ductile fracture simulation using finite element (FE) damage analysis. The maximum and crack initiation loads of cracked components were predicted using proposed virtual testing method. To apply the local approach criteria for ductile fracture, stress-modified fracture strain model was adopted as the damage criteria with modified calibration technique that only requires tensile and fracture toughness test data. Element-size-dependent critical damage model is also introduced to apply the proposed ductile fracture simulation to large-scale components. The results of the simulation were compared with those of the tests on SA333 Gr. 6 full-scale pipes at $288^{\circ}C$, performed by the Battelle Memorial Institute.