• Structural Engineering and Mechanics
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• 제65권4호
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• pp.491-504
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• 2018

Because of sandwich structures with low weight and high stiffness have much usage in various industries such as civil and aerospace engineering, in this article, buckling and free vibration analyses of coupled micro composite sandwich plates are investigated based on sinusoidal shear deformation (SSDT) and most general strain gradient theories (MGSGT). It is assumed that the sandwich structure rested on an orthotropic elastic foundation and make of four composite face sheets with temperature-dependent material properties that they reinforced by carbon and boron nitride nanotubes and two flexible transversely orthotropic cores. Mathematical formulation is presented using Hamilton's principle and governing equations of motions are derived based on energy approach and applying variation method for simply supported edges under electro-magneto-thermo-mechanical, axial buckling and pre-stresses loadings. In order to predict the effects of various parameters such as material length scale parameter, length to width ratio, length to thickness ratio, thickness of face sheets to core thickness ratio, nanotubes volume fraction, pre-stress load and orthotropic elastic medium on the natural frequencies and critical buckling load of double-bonded micro composite sandwich plates. It is found that orthotropic elastic medium has a special role on the system stability and increasing Winkler and Pasternak constants lead to enhance the natural frequency and critical buckling load of micro plates, while decrease natural frequency and critical buckling load with increasing temperature changes. Also, it is showed that pre-stresses due to help the axial buckling load causes that delay the buckling phenomenon. Moreover, it is concluded that the sandwich structures with orthotropic cores have high stiffness, but because they are not economical, thus it is necessary the sandwich plates reinforce by carbon or boron nitride nanotubes specially, because these nanotubes have important thermal and mechanical properties in comparison of the other reinforcement.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 가을 학술발표회 논문집
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• pp.333-339
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• 2003

Recently, the bridges become greater according to development of a construction technology. This phenomenon requires long span bridge, so that increases the dead weight. The orthotropic steel deck bridges have much advantages such as the light dead weight and the reduction of construction period. And almost whole process of carried out is manufactured at factory, so it can cause the increase of quality authoritativeness. But orthotropic steel deck bridge is consist of structure by welding, it can not avoid a lot of welding jobs, defects and transformation by welding are becoming problem accordingly. Specially, topical stress concentration phenomenon in cross connection area of longitudinal and transverse rib causes fatigue failure. The Bulkhead Plate for prevention of this stress concentration phenomenon was applied by changing the orthotropic steel deck of Williamsburg bridge in USA. But, it is principle that a Bulkhead Plate is not established in the domestic design standard. Therefore, it is estimated that the study for installation of Bulkhead Plate is needed. This treatise with considering these circumstances proves efficiency of Bulkhead Plate and will be presented optimal design details through finite element analysis according to change the geometrical of Bulkhead Plate and tile cross-connection area of longitudinal and transverse rib.

• Journal of Ship and Ocean Technology
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• 제4권2호
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• pp.38-57
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• 2000

This paper deals with reliability analysis of specially orthotropic plates subjected to transverse lateral pressure loads by using Monte Carlo simulation method. The plates are simply supported around their all edges and have a low short span to plate depth ratio with rectangular plate shapes. Various levels of reliability analyses of the plates are performed within the context of First-Ply-Failure(FPF) analysis such as ply-/laminate-level reliability analyse, failure tree analysis and sensitivity analysis of basic design variables to estimated plate reliabilities. In performing all these levels of reliability analyses, the followings are considered within the Monte Carlo simulation method: (1) input parameters to the strengths of the plates such as applied transverse lateral pressure loads, elastic moduli, geometric including plate thickness and ultimate strength values of the plates are treated as basic design variables following a normal probability distribution; (2) the mechanical responses of the plates are calculated by using simplified higher-order shear deformation theory which can predict the mechanical responses of thick laminated plates accurately; and (3) the limit state equations are derived from polynomial failure criteria for composite materials such as maximum stress, maximum strain, Tsai-Hill, Tsai-Wu and Hoffman.

• 복합신소재구조학회 논문집
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• 제2권3호
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• pp.42-47
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• 2011

임의의 단면과 지점을 갖고 임의의 하중을 받는 보나 탑의 진동해석 방법이 발표된 바가 있다. 이러한 진동해석을 위하여 처짐의 영향을 고려한 다양한 방법이 검토되었다. 본 연구에서 얻은 결과를 보 이론과 비교하였다. 이러한 목적으로 본 논문에서는 유한차분법을 사용하였다. 고유진동수에 대한 $D_{22}$ 탄성계수의 영향을 철저히 검토하였다. 본 논문에서는 구조부재의 고유진동수와 적용 하중의 크기에 대한 관련성을 연구하였으며 그 결과를 제시하였다. 본 논문에서는 특별직교이방성 판이론 이용하여 강교량과 철근콘크리트 슬래브 교량에 적용하여 을 해석하였으며 그 결과를 제시하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제7권4호
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• pp.81-89
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• 2003

본 논문에서는 단순지지된 철근콘크리트 슬래브 교량을 특별직교이방성 복합적층판 이론으로 해석하였다. 이 방법은 실무에 있는 엔지니어들에게는 너무나 어려운 방법이다. 본 논문에서는 교량 상판을 이미 저자에 의해 발표된 단위 폭을 가진 보 이론을 사용하여 해석하였다. 판에 대한 정확한 해로부터 얻은 수정계수를 사용하면 보 이론으로도 쉽게 얻을 수 있다. 본 연구의 결과로 머지않은 장래에 학부정도의 수준인 엔지니어들에게도 철근콘크리트 슬래브 교량을 복합적층판 이론으로 해석할 수 있으리라 기대된다.

• 한국강구조학회 논문집
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• 제14권1호
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• pp.23-29
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• 2002

거더와 가로보를 포함하는 많은 교량시스템과 콘크리트 상판은 특별직교이방성 판처럼 거동한다. 그런데 Navier나 Levy의 해로 해결할 수 없는 경계조건을 가졌거나, 불규칙 단면을 가진 경에에 해석해를 얻기 것이 매우 어렵다. 더구나 이러한 경우, 고유치 문제에 대한 수치해법은 너무 복잡하다. 그러나 불규칙 단면을 갖는 보와 탑에 대해, 첫 번째 진동모드에 해당하는 고유진동수를 계산하는 방법이 1974년 '김'에 의해 개발되어 발표되었다. 최근에 이 방법은 2차원 문제로 확장되었고 전단변형이 고려된 복합판에 적용되어 왔다. 본 연구에서는 이 방법을 다양한 경계조건을 갖는 특별직교이방성 복합적층판에 적용하여 타당성을 검토하고 그 해석결과를 제시한다.

• 한국도로학회논문집
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• 제16권3호
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• pp.1-8
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• 2014

PURPOSES : The purpose of this paper is to demonstrate to the practicing engineers, how to apply the advanced composite materials theory to the road structures. For general construction material used, there is certain theoretical limit in sizes. For super road structure construction, the reduction in panel weight is the first step to take in order to break such size limits. METHODS : For a typical road structures panel, both concrete and advanced composite sandwich panels are considered. The concrete panel is treated as a special orthotropic plate. RESULTS : All types of advanced composite sandwich panels are considered as a self-weights less than one tenth of that of concrete panel. The concrete panel is treated as a special orthotropic plate to obtain more accurate result. CONCLUSIONS : Advanced composite sandwich panels are considered as a self-weights less than one tenth (10%) of that of concrete panel, with deflections less than that of the concrete panel. This conclusion gives good guide line for design of the light weight of road structures.

• 오토저널
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• 제8권2호
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• pp.51-64
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• 1986

There has been considerable interest over the last twenty years in the subject of the elastic properties of the cord-rubber laminate. This has been due to the rather intensive study of the composites materials characteristics brought about by the increased use of rigid composites materials characteristics brought about by the increased use of rigid composites in many structural applications. The object of this study is to obtain the natural frequencies and modes of the simply supported cord-rubber laminate plates prior to the study on the analysis of the dynamic properties of the pneumatic tire. To obtain these natural frequencies and modes, the 12 degrees of freedom orthotropic rectangular plate finite elements are developed. By using classical lamination theory, the stress-strain relations are represented. The governing equation for the finite element is derived by energy method. To find the natural frequencies and modes, he eigenvalues and corresponding eigenvectors are computed by the well known Jacobi power method. In order to verify the capability of this present finite element, the results of the specially orthotropic plate and the angle-ply laminate plate are compared with the analytical solution. The analytical and numberical results are in good agreement. The following problems of the simply supported plate are analyzed by the present finite element. a) the natural frequencies and mode shapes of the cord-rubber laminate plate for various aspect ratio. b) The natural frequencies and mode shapes of the orthotropic plate with the rectangular hole in its center.

• 한국강구조학회 논문집
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• 제13권1호
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• pp.53-60
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• 2001

건설관련 설계기술자들에게는 첨단 복합재료구조에 대한 이론이 너무 어려워서 간단하면서도 쉽게 적용할 수 있는 정확한 방법을 필요로 하고 있다. 몇 가지 섬유 배향각을 가진 적층판은 층수가 증가하면 D16, B16, D26 및 B26 강성이 감소하게 되어 특별직교이방성 판처럼 거동함을 밝히고, 간단한 공식들을 개발하여 발표한 바 있다. 대부분의 교량이나 건물의 상판은 형상비가 큰 경우가 많은데, 이런 구조물의 평형방정시에 대한 종방향 모멘트항(Mx)의 영향은 매우 작아서, 더욱 간단한 해석이 가능하다. 본 논문에는 이러한 문제들에 대한 연구 결과를 제시하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제14권3호
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• pp.83-90
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• 2010

구조물의 해석, 설계, 시공, 품질관리 등을 수립할 때 토목기술자는 경제적이며 효율적인 복합재료를 사용할 수 있다. 거더, 가로보, 콘크리트 상판으로 이루어진 교량시스템은 특별직교이방성 판으로 거동한다. 이러한 경계조건을 갖는 단면을 Navier 해 형태의 해석적 해를 구하기가 매우 어렵다. 복합재료로 이루어진 교량을 설계하기위하여, 단면은 가장 경제적이면서 응력에 유리한 폼코어 형태를 채택하였고, 응력을 산출함에 있어서는 유한차분법 프로그램을 사용하였다. 응력영역은 Tasi-Wu 파괴영역 기준을 이용하였다. 본 논문에서는 치수가 증가됨에 따른 인장강도 감소율을 고려하였다. 또한 이러한 경우에 대한 수치해석을 수행하였다.