• 한국강구조학회 논문집
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• 제16권1호통권68호
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• pp.155-167
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• 2004

각각 집중하중과 등분포하중을 받는 단순보의 비탄성 횡-비틀림 좌굴에 대하여 연구하였다. 잔류응력을 단순형과 다항식형으로 하여 line-type 유한요소법으로 해석하였다. 잔류응력의 형태는 플랜지에서는 4차 곡선으로 웨브에서는 2차 곡선으로 가정하였다. 우리나라에서 생산되는 4종류의 I형강에 대하여 비탄성 횡-비틀림 좌굴에 대하여 해석한 후 결과를 강구조편람의 내용과 비교하였다. 해석결과로부터 강구조 편람에 의한 설계는 주보에 보조보가 있는 경우나 없는 경우 모두 전반적으로 과설계임을 알 수 있었다.

• Steel and Composite Structures
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• 제34권4호
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• pp.511-524
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• 2020

In this research, a simple four-variable trigonometric integral shear deformation model is proposed for the static behavior of advanced functionally graded (AFG) ceramic-metal plates supported by a two-parameter elastic foundation and subjected to a nonlinear hygro-thermo-mechanical load. The elastic properties, including both the thermal expansion and moisture coefficients of the plate, are also supposed to be varied within thickness direction by following a power law distribution in terms of volume fractions of the components of the material. The interest of the current theory is seen in its kinematics that use only four independent unknowns, while first-order plate theory and other higher-order plate theories require at least five unknowns. The "in-plane displacement field" of the proposed theory utilizes cosine functions in terms of thickness coordinates to calculate out-of-plane shear deformations. The vertical displacement includes flexural and shear components. The elastic foundation is introduced in mathematical modeling as a two-parameter Winkler-Pasternak foundation. The virtual displacement principle is applied to obtain the basic equations and a Navier solution technique is used to determine an analytical solution. The numerical results predicted by the proposed formulation are compared with results already published in the literature to demonstrate the accuracy and efficiency of the proposed theory. The influences of "moisture concentration", temperature, stiffness of foundation, shear deformation, geometric ratios and volume fraction variation on the mechanical behavior of AFG plates are examined and discussed in detail.

• 대한조선학회논문집
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• 제53권3호
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• pp.237-248
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• 2016

As OPB and IPB moment-induced fatigue damage on mooring chain links were reported for a offloading buoy, verification of OPB and IPB fatigue has been a key engineering item in offshore structure mooring design. Mathematical and physical features of the conventional approach which was mainly explained in BV guideline are reviewed and disadvantages of the conventional approach are addressed in terms of stress proportionality and nonlinearity of OPB and IPB moments. In order to eradicate these disadvantages, a novel approach is newly proposed which is able to dispel apprehension on stress proportionality and is not dependent of nonlinearities of OPB and IPB moments. Significant differences between two approaches are suggested by comparing relations of OPB moment versus OPB interlink angle and IPB moment versus IPB interlink angle. For periodic OPB tension angle processes having three different OPB angle ranges with a simple irregular tension process, fatigue damage calculation reveals that OPB moment-induced fatigue damage has dominant portion to total fatigue damage. Comparative studies between two approaches also show that the conventional approach based on BV guideline predicts fatigue damage far conservatively since it assume unrealistic high stress concentration factor for tension load. Meanwhile IPB moment-induced fatigue damage is negligible compared to tension-induced fatigue damage.

• Steel and Composite Structures
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• 제6권6호
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• pp.459-477
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• 2006

A theoretical research project is undertaken to develop integrated analysis and design tools for long span composite beams in modern high-rise buildings, and it aims to develop non-linear finite element models for practical design of composite beams. As the first paper in the series, this paper presents the development study as well as the calibration exercise of the proposed finite element models for simply supported composite beams. Other practical issues such as continuous composite beams, the provision of web openings for passage of building services, the partial continuity offered by the connections to columns as well as the behaviour of both unprotected and protected composite beams under fires will be reported separately. In this paper, details of the finite elements and the material models for both steel and reinforced concrete are first described, and finite element studies of composite beams with full details of test data are then presented. It should be noted that in the proposed finite element models, both steel beams and concrete slabs are modelled with two dimensional plane stress elements whose widths are assigned to be equal to the widths of concrete flanges, and the flange widths and the web thicknesses of steel beams as appropriate. Moreover, each shear connector is modelled with one horizontal spring and one vertical spring to simulate its longitudinal shear and pull-out actions based on measured load-slippage curves of push-out tests of shear connectors. The numerical results are then carefully analyzed and compared with the corresponding test results in terms of load mid-span deflection curves as well as load end-slippage curves. Other deformation characteristics of the composite beams such as stress and strain distributions across the composite cross-sections as well as distributions of shear forces and slippages in shear connectors along the beam spans are also examined in details. It is shown that the numerical results of the composite beams compare well with the test data in terms of various load-deformation characteristics along the entire deformation ranges. Hence, the proposed analysis and design tools are considered to be simple and yet effective for composite beams with practical geometrical dimensions and arrangements. Structural engineers are strongly encouraged to employ the models in their practical work to exploit the full advantages offered by composite construction.

• 대한기계학회논문집A
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• 제36권5호
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• pp.487-495
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• 2012

요 제어는 풍력 터빈의 전력 생산과 구조물의 기계적인 하중 발생에 밀접한 관계를 갖고 있다. 풍력 터빈으로 불어오는 바람의 방향과 나셀(nacelle)의 방향이 일치하지 않을 경우 발생하는 요 오차에 의하여, 풍력 터빈의 에너지 회수 효율이 감소하고, 블레이드(blade)에는 비대칭/불평형 하중이 증가하게 된다. 따라서, 요 오차를 감소시키기 위한 요 제어 시스템은 풍력 터빈의 중요한 서브 시스템 중에 하나이다. 그러나, 요 운동은 요 축 주위에 발생하는 여러 하중들에 의하여, 그 운동의 빠르기가 제약을 받게 된다. 본 논문에서는 기본적인 요 시스템의 원리에 대하여 간략히 살펴보고, 요 운동에 의하여 회전 날개에 발생된 기계적 하중이 어떻게 요 축 주위의 하중들로 전파되는 지, 또한 이러한 하중들의 특성은 무엇인 지에 대하여 살펴보았다.