• Structural Engineering and Mechanics
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• 제68권4호
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• pp.399-408
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• 2018

Cable supported structures have been widely used in civil engineering. Cable tension estimation has great importance in cable supported structures' analysis, ranging from design to construction and from inspection to maintenance. Even though the Bernoulli-Euler beam element is commonly used in the traditional finite element method for calculation of frequency and cable tension estimation, many elements must be meshed to achieve accurate results, leading to expensive computation. To improve the accuracy and efficiency, a dynamic finite element method for estimation of cable tension is proposed. In this method, following the dynamic stiffness matrix method, frequency-dependent shape functions are adopted to derive the stiffness and mass matrices of an exact beam element that can be used for natural frequency calculation and cable tension estimation. An iterative algorithm is used for the exact beam element to determine both the exact natural frequencies and the cable tension. Illustrative examples show that, compared with the cable tension estimation method using the conventional beam element, the proposed method has a distinct advantage regarding the accuracy and the computational time.

• 한국산학기술학회논문지
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• 제13권7호
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• pp.2858-2864
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• 2012

곡선보 (curved beam)의 내평면 모멘트 및 등분포하중 하에서 평면내 (in-plane) 좌굴 (buckling)을 미분구적법(DQM)을 이용하여 해석하였다. 다양한 경계조건 (boundary conditions)과 굽힘각 (opening angles)에 따른 임계모멘트 및 임계하중을 계산하였다. DQM의 해석결과는 해석적 해답 (exact solution) 결과와 비교하였으며, DQM은 적은 요소 (grid points)를 사용하여 정확한 해석결과를 보여주었다. 두 경계조건(고정-고정, 단순지지-고정)하에서 새 결과를 또한 제시하였다.

• Structural Engineering and Mechanics
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• 제19권5호
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• pp.551-566
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• 2005

Using two different, but related approaches, an exact dynamic stiffness matrix for a two-part beam-mass system is developed from the free vibration theory of a Bernoulli-Euler beam. The first approach is based on matrix transformation while the second one is a direct approach in which the kinematical conditions at the interfaces of the two-part beam-mass system are satisfied. Both procedures allow an exact free vibration analysis of structures such as a plane or a space frame, consisting of one or more two-part beam-mass systems. The two-part beam-mass system described in this paper is essentially a structural member consisting of two different beam segments between which there is a rigid mass element that may have rotatory inertia. Numerical checks to show that the two methods generate identical dynamic stiffness matrices were performed for a wide range of frequency values. Once the dynamic stiffness matrix is obtained using any of the two methods, the Wittrick-Williams algorithm is applied to compute the natural frequencies of some frameworks consisting of two-part beam-mass systems. Numerical results are discussed and the paper concludes with some remarks.

• 대한기계학회논문집
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• 제12권6호
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• pp.1428-1437
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• 1988

본 연구에서는 흡수, 방사 및 비등방성 산란을 하는 축대칭 유한원통형매질에 서의 형식해로부터 Gaussian Quadrature를 이용하여 수치적으로 엄밀해를 구하고 P-1 과 P-3근사해법을 통하여 얻어진 해와 비교하여 P-1과 P-3근사해법의 타당성을 검토하 였다.또한 매질의 광학두께, 산란알베도, 벽면방사율, 형상계수 등을 주요 파라미 터로 하여 이들의 영향에 대하여 고찰하였다.

• 한국안전학회지
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• 제17권4호
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• pp.189-195
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• 2002

I-단면 곡선보 (curved beam)의 모멘트 하중 하에서 비틀림(warping)을 포함한 평면외 (out-of-plane)의 좌굴을 미분구적법 (DQM)을 이용하여 해석하였다. 다양한 경계조건(boundary conditions) 및 굽힘각(opening angles)에 따른 임계모멘트 (critical moments)를 계산하고, DQM의 해석결과는 해석적 해답 (exact solution) 과 비교 분석하였다. DQM은 적은 요소(grid points)를 사용하여 정확한 해석결과를 보여주었고, 두 경계조건 (고정-고정, 고정-단순지지)하에서 새로운 결과 또한 제시하였다.

• Nuclear Engineering and Technology
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• 제44권2호
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• pp.151-160
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• 2012

The advantages for using Monte Carlo methods to analyze full-core reactor configurations include essentially exact representation of geometry and physical phenomena that are important for reactor analysis. But this substantial advantage comes at a substantial cost because of the computational burden, both in terms of memory demand and computational time. This paper focuses on the challenges facing full-core Monte Carlo for keff calculations and the prospects for Monte Carlo becoming a routine tool for reactor analysis.

• 건축사
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• 11호통권82호
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• pp.22-25
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• 1975

The aim of this study is the introduction of simplified method for the design stress analysis of multi-span gable frame structures with crane supports. Under the author's assumptions made previously for the same structures of single span, simplified stress analysis and exact computer analysis are excuted for some multi-span sample structures. Comparing the results of both stress analysis and with some modifications, a feasible simplified method for the design stress analysis of multi-span gable frame structures with crane supports is established.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.216-221
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• 2008

Shape design optimization for linear elasticity problem is performed using isogeometric analysis method. In many design optimization problems for real engineering models, initial raw data usually comes from CAD modeler. Then designer should convert this CAD data into finite element mesh data because conventional design optimization tools are generally based on finite element analysis. During this conversion there is some numerical error due to a geometry approximation, which causes accuracy problems in not only response analysis but also design sensitivity analysis. As a remedy of this phenomenon, the isogeometric analysis method is one of the promising approaches of shape design optimization. The main idea of isogeometric analysis is that the basis functions used in analysis is exactly same as ones which represent the geometry, and this geometrically exact model can be used shape sensitivity analysis and design optimization as well. In shape design sensitivity point of view, precise shape sensitivity is very essential for gradient-based optimization. In conventional finite element based optimization, higher order information such as normal vector and curvature term is inaccurate or even missing due to the use of linear interpolation functions. On the other hands, B-spline basis functions have sufficient continuity and their derivatives are smooth enough. Therefore normal vector and curvature terms can be exactly evaluated, which eventually yields precise optimal shapes. In this article, isogeometric analysis method is utilized for the shape design optimization. By virtue of B-spline basis function, an exact geometry can be handled without finite element meshes. Moreover, initial CAD data are used throughout the optimization process, including response analysis, shape sensitivity analysis, design parameterization and shape optimization, without subsequent communication with CAD description.

• Structural Engineering and Mechanics
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• 제7권5호
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• pp.513-525
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• 1999

This paper presents exact close form solutions of plastic limit loads of a clamped circular plate under uniformly distributed load with different loading radii. A unified yield criterion, which includes a family of piecewise linear yield criteria and the commonly adopted yield criteria such as the Tresca criterion and the maximum principal deviatoric stress criterion or the twin shear stress criterion that are its special cases, and the Mises criterion can be approximated by it, is employed in the analysis. The plastic limit loads, moment fields and velocity fields of the clamped circular plate are calculated based on the unified yield criterion. The influences of the yield criteria, the edge effects and the loading radius on the plastic limits of the clamped circular plate are investigated. Analytical results are calculated and compared. The exact close form solutions presented in this paper provide efficient approaches for obtaining plastic limit loads and the corresponding moments and velocities of the clamped circular plates. The previously derived solutions based on the Tresca and the Mises criteria are its special cases.

• Nuclear Engineering and Technology
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• 제22권2호
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• pp.95-100
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• 1990

유체 유동상의 인자로 구성된 핵연료집합체에 걸리는 수력적 양력의 정확한 표현식은 핵연료의 건전성 설계 및 해석에 중요한 인자이다. 그러나 현재까지 이 양력에 대한 이론적인 해석이 제대로 이루어지고 있지 않아 이 분야에 혼란이 빚어지고 있다. 본 논문에서는 핵연료 집합체에 걸리는 수력적 양력에 대한 정확한 표현식을 이론적인 고찰을 통하여 유도하였으며 또한 양력에 관련된 제반 힘 요소들 즉, 압력강하, 부력, 전단응력, 집합체하중, 상호간의 관계를 검토하였다. 유도된 정확한 이론식을 이용하여 양력에 관한 간이식 오차의 특성을 분석한 결과 오차는 4가지 항으로 구성됨과 총 오차의 크기는 노심 유량의 변화 방향에 따라 달라짐을 알 수 있었다. 정량적인 분석을 COBRAIV-I를 이용하여 수행한 결과 총 오차의 크기는 약 1% 정도임이 밝혀졌다.