• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.8
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• pp.44-54
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• 2018

Stress and fatigue of the distributor, an equipment of the high-pressure evaporator for the HRSG, were evaluated according to ASME Boiler & Pressure Vessel Code Section VIII Division 2. First, from the results of the piping system analysis model, reaction forces of the tubes connected to the distributor were derived and used as the nozzle load applied to the detailed analysis model of the distributor afterward. Next, the detailed model to analyze the distributor was constructed, the distributor being statically analyzed for the design condition with the steam pressure and the nozzle load. As a result, the maximum stress occurred at the bore of the horizontal nozzle, and the primary membrane stress at the shell and nozzle was found to be less than the allowable. Next, for the transient operating conditions given for the distributor, thermal analysis was performed and the structural analysis was carried out with the steam pressure, nozzle load, and thermal load. Under the transient conditions, the maximum stress occurred at the vertical downcomer nozzle, and of which fatigue life was evaluated. As a result, the cumulative usage factor was less than the allowable and hence the distributor was found to be safe from fatigue failure.

• Journal of Korean Society of Steel Construction
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• v.18 no.5
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• pp.563-574
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• 2006

The objective of this study is to determine the effect of the loading size on displacements of stiffened plates with open ribs using the orthotropic rigidity ratio as the parameter. To analyze the displacement behavior of stiffened plates according to the loading size, a concentrated load and three types of uniform distributed loads were applied on the rib at the center of some plates. The results of the analysis of various stiffened plates show that the central displacement ratio of the distributed load to the concentrated load increased according to the decrease in the loading size, and that the ratio can be expressed as a function of the rigidity ratio for each rib space. The maximum displacement of the stiffened plate subjected to the distributed load did not appear at the center of the plate due to the local behavior, and the increasing ratio of the maximum displacement to the central displacement can be expressed as a function of the rigidity ratio for each rib space. Orthotropic plate analysis can achieve more accurate results using the proposed functions, and the application of the functions to examples of a different aspect ratio and support condition shows good accuracy. Therefore, using the functions proposed in this study, the central and maximum displacements can easily be achieved in the orthotropic plate analysis of stiffened plates subjected to the distributed load.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.2
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• pp.387-393
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• 2021

In this study, finite element analysis was performed to evaluate a method of increasing the fatigue life of the pipe connection structure commonly used in the topside structure of offshore platforms. MSC Patran/Nastran, a commercial analysis program, was used, and the critical structural model was selected from the global analysis. To realize the stress concentration phenomenon according to the load, modeling using 8-node solid elements was implemented. The main loads were considered to be two lateral loads and a tensile load on a diagonal pipe. To check the hotspot stress at the main location, a 0.01 mm dummy shell element was applied. After calculating the main stress at the 0.5-t and 1.5-t locations, the stress generated in the weld was estimated through extrapolation. In some sections, this stress was observed to be below the fatigue life that should be satisfied, and reinforcement was required. For reinforcement, a bracket was added to reduce the stress concentration factor where the fatigue life was insufficient without changing the thickness or diameter of the previously designed pipe. Regarding the tensile load, the stress in the bracket toe increased by 23 %, whereas the stress inside and outside of the pipe, which was a problem, decreased by approximately 8 %. Regarding the flexural load, the stress at the bracket toe increased by 3 %, whereas the stress inside and outside of the pipe, which was also a problem, decreased by approximately 48 %. Owing to the new bracket reinforcement, the stress in the bracket toe increased, but the S-N curve itself was better than that of the pipe joint, so it was not a significant problem. The improvement method of fatigue life is expected to be useful; it can efficiently increase the fatigue life while minimizing changes to the initial design.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.1
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• pp.83-91
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• 1994

An efficient method was developed to determine the ultimate strength for the segment subjected to cross-sectional distortion. Cumulative data based on the finite element analysis were used to perform the multi-regression analysis. A moment-thrust-curvature relationship of short segment was obtained with mathematical forms in the nonlinear range. The extensive parametric study was performed to generate the ultimate strength for the various segments. The result was compared with the experimental result which was not included in the database. The proposed method gives an essential tool for the nonlinear analysis of beam-column.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.55-58
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• 2009

본 논문에서는 독립적으로 구성된 유한요소 모델을 결합하기 위하여 계면에서 불일치 격자들을 처리하는 기법을 소개하고자 한다. 불일치 격자들로 인하여 요소들의 침투와 틈이 발생할 수 있고 일반적인 유한요소를 사용하면 계면에서 변위의 연속성과 하중전달 조건들을 만족시키기가 불가능하게 되는데 계면에서 정의된 계면요소를 사용하여 결합을 위한 조건들을 만족시킬 수 있게 된다. 요소들의 침투와 틈이 없는 연속적인 계면을 정의하고 여기에 부합하는 계면요소를 구성하며 유한요소 형상함수와 다른 계면요소 형상 함수를 사용하게 되면 독립적으로 구성된 분리 영역들을 자연스럽게 결합할 수 있게 된다. 계면요소는 연속성, 적합성, 완전성 등에서 유한요소와 유사한 특성을 갖으며 추가적인 자유도 없이 불일치 격자를 결합하게 된다. 계면요소법을 사용하여 분리된 영역의 결합이나 전체-국부 해석 그리고 유체-구조물 상호작용해석 등에 적용되어 유용한 방법으로 사용될 수 있게 된다.

• Magazine of the Korea Concrete Institute
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• v.9 no.5
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• pp.115-125
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• 1997

콘크리트의 변형률국소화는 콘크리트의연화거동에 수반되어 변형이 국부적으로 집중되는 현상이다. 본 연구의 목적은 인장과 압축하중상태에서 콘크리트 부재에 발생하는 콘크리트 변형률 국소화 거동을 해석적으로 재현할 수 있는 통일된 모형을 제안하는 것이다. 본 논문에서는 인장과 압축에 대하여 변형률국소화가 일어나는 콘크리트 부재를 변형률 연화가 일어나는 국소화영역과 탄성제하가 발생하는 비국소화영역으로 구분하여 모델링하는 통일된 모형을 제안하였다. 또한 제안된 모형에서 미시역학적 평균화기법을 이용해 평균등가탄성계수와 수정된 평균등가탄성계수를 구하여 시편의 크기와 국소화영역의 크기에 따는 해석을 수행하였으며 기존의 실험값과 비교하였다. 연구결과, 본 연구에서의 변형률국소화모형이 크기효과를 포함한 콘크리트의 변형률국소화거동 해석에 타당하게 적용될 수 있음을 보여주었다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.5 no.2
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• pp.131-138
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• 1981

The effect of axial stress on the plastic deformation of rigid-perfectly plastic cylindrical tube under the impulsive band pressure is investigated. It is assumed that the tube is constructed with the material of Tresca's yield criterion. A closed from sloution is obtained for a rectangular pulse shape of uniform band pressure by using the circumscribed yield surface. The analysis shows that the effect ot exial stress is negligible when the dimensionless axial stress(n$\sub$x/= N$\sub$x/.delta.$\sub$y/H) is less than 0.2 or the dimensionless whdth of band pressure(.xi.=C/.root.RH) is greater than 2, but the effect of axial stress is of considerable importance when the axial stress is greater than 0.3 and the width of band pressure is less than 1.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.5
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• pp.170-177
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• 1997

In this study, an analysis technique using simple beam model for predicting structure crashworthiness of the passenger car side impacted with an angle by another passenger car was investigated. The simple model was composed of major beam-like side structure which carry almost all side impact load. A procedure of component collapse test, calculation of load carrying capability and dynamic simulation was carryed out sequentially. Transient dynamic algorithms and a computer program to simulate deformations and motions of the impacted car was developed. The developed procedure was applied to a 3 door passenger car side impacted with an angle of 75 degree and the analysis results show good agreements with the actual test results.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 1995.04a
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• pp.529-533
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• 1995

안장은 인체하중이 집중되고, 자전거의 충격과 진동이 직접 전달되는 부위로서 주행 안락도를 높이고 buttock의 discomfort를 감소시킬 수 있도록 설계되어야 한다. 본 연구의 목적은 인체곡면을 본뜬 안장형상 설계를 통하여 buttock의 국부적 discomfort를 감소시키고자 하는 것이다. 인간의 앉은자세에 대한 해부학적 고찰을 통해 좌골결절(Ischial Tuberosity)과 치골결합면(Symphyseal Surface)이 안장과 직접 맞닿는 면으로 파악되었으며, 이들 부위에 대한 집중적 개선이 이루어져야 할 것으로 제안되었다. 문헌조사를 통해 의자설계시 고려해야 할 인체치수 및 지침을 파악하였으며, 안장과 의자의 기능비교를 통해 이를 선별적으로 적용하였다. 인체곡면 측정을 위해 Rod Matrix(3cm 간격, 13*20)방법을 이용하여 10명의 buttock contour를 측정하였으며, 측정된 자료를 분석하여 안장의 곡면형상을 결정하였다. General Comfort Rating, Body Part Discomfort 등의 주관적 안락도 평가방법을 통하여 기존 자전거 안장과 본 연구를 통해 개발된 안장을 비교 평가한 결과, 전반적인 안락도의 향상과 좌골결절 및 치골 결합부의 discomfort 감소효과를 가져온 것으로 파악되었다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.10a
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• pp.203-209
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• 2004

Recently, various and new special methods of construction about steel bridges have been tried, and the study about local buckling under this methods have been performed too. But because of various cases, structural analysis is performed to check safety for each step of construction, and this is not efficient and economical method for time and manpower. So, for solution of this problems, general method about checking safety needs to he developed. In this study, local buckiling of web of girder due to various load cases under construction by ILM(Incremental Launching Method) will be studio considering various parameters such as forces, aspect ratio, boundary condition and so on. Also interaction curve will he plotted for each case.