• 산업기술연구
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• 제17권
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• pp.199-204
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• 1997

In this paper, the result of application of vibration method to the orthotropic plates with free edges supported on elastic foundation and with a pair of opposite edges under axial forces is presented. Such plates represent the concrete highway slab and hybrid composite pavement of bridges. The reinforced concrete slab can be assumed as a special orthotropic plate, as a close approximation. The highway slab is supported on elastic foundation, with free boundaries. Sometimes, the pair of edges perpendicular to the traffic direction may be subject to the axial forces. The plate is subject to the concentrated load/loads, in the form of traffic loads, or the test equipments. Finite difference method is used to obtain the deflection influence surfaces needed for vibration analysis. The influence of the modulus of the foundation, the aspect ratio of the plate, and the magnitudes of the axial forces and the concentrated attached mass on the plate, under the natural frequency is thoroughly studied.

• 산업기술연구
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• 제19권
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• pp.227-233
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• 1999

Simple equations which can predict "exact" values of the natural frequency of vibration for the special orthotropic laminates are presented. Many laminates with certain orientations have decreasing values of $B_{16}$ and $B_{26}$ as the number of plies increases. Such laminates, with $D_{16}=D_{26}{\rightarrow}0$, including the laminates with anti-symmetric configurations can be solved by the same equation for the special orthotropic laminates. If the quasi-isotropic constants are used, the equations for the isotropic plates can be used. Use of some coefficients cab produce "exact" value for laminates with such configurations. Natural frequencies of the plate with varying aspect ratios is presented.

• 산업기술연구
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• 제18권
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• pp.97-105
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• 1998

The most of the design engineers for construction has academic background of bachelors degree. Theories for advanced composite structures are too difficult for such engineers and some simple but accurate enough methods are necessary. The senior author has reported that some laminate orientations have decreasing values of $D_{16}$, $B_{16}$, $D_{26}$ and $B_{26}$ stiffnesses as the ply number increases. Such plates behave as special orthotropic plates and simple formulas developed by the author can be used. Most of the bridge and building slabs on girders have large aspect ratios. For such cases further simplification is possible by neglecting the effect of the longitudinal moment terms($M_x$) on the relevant partial differential equations of equilibrium. In this paper, the result of the study on the subject problem is presented.

• 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.

• Composites Research
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• 제12권4호
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• pp.25-32
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• 1999

불규칙단면과 다양한 경계조건을 갖는 보와 타워구조물의 1모드 하에서 고유진동수를 계산하는 방법은 1974년 Kim, D.H에 의해 개발되었다. 이 논문에서는 자유경계를 갖고 탄성지지된 특별직교 이방성 적층복합판에 대한 이 방법의 응용결과가 주어진다. 이러한 판들은 고속도로 콘크리트 슬래브와 교량 혼성 복합 포장에서 볼 수 있다. 이 진동해석을 위해 어떤 방법이라도 처짐에 대한 영향면을 구하는데 사용될 수 있다. 이 논문에서는 유한차분법이 사용되었다. 고유진동수에 대한 기초 탄성계수의 영향과 판의 형상비의 영향이 연구되었다. 고유진동수에 대한 판 자중의 무시효과가 또한 심도있게 연구되었다.

• 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.

• Coupled systems mechanics
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• 제11권5호
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• pp.459-483
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• 2022

In the present work, a new photothermoelastic model based on Moore-Gibson-Thompson theory has been constructed. The governing equationsfor orthotropic photothermoelastic plate are simplified for two-dimension model. Laplace and Fourier transforms are employed after converting the system of equations into dimensionless form. The problem is examined due to various specified sources. Moving normal force, ramp type thermal source and carrier density periodic loading are taken to explore the application of the assumed model. Various field quantities like displacements, stresses, temperature distribution and carrier density distribution are obtained in the transformed domain. The problem is validated by numerical computation for a given material and numerical obtained results are depicted in form of graphs to show the impact of varioustheories of thermoelasticity along with impact of moving velocity, ramp type and periodic loading parameters. Some special cases are also explored. The results obtained in this paper can be used to design various semiconductor elements during the coupled thermal, plasma and elastic wave and otherfieldsin thematerialscience, physical engineering.

• 대한기계학회논문집
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• 제16권8호
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• pp.1485-1492
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• 1992

본 연구에서는 Rayleigh-Ritz method를 사용하여 타원형(원형 포함) 평판의 자유 진동 문제를 해석한다. admissible함수로서는 단순 다항식의 곱(products of simple polynomials)을 사용한다. 이 함수는 다항식의 첫 항의 차수를 0,1 또는 2로 함으로써 각각 자유, 단순 지지 또는 고정인 경계 조건을 간편히 처리할 수 있게 하며, 에너지식에 포함된 적분값을 계산함에 있어서 점화식을 유도하여 사용함으로써 계산을 매우 간편히 수행할 수 있게 한다. 본문의 이론 해석은 직교 이방성 타원형 평판에 대해서 제시된다. 그러나 수치 결과는, 이방성의 다양한 조합에 대한 많은 결과를 제시하는 것은 그다지 의미가 없는 관계로, 등방성 평판에 대해서 주어진다. 등방성 평판의 여러 가지 세장비에 대한 결과는 설계 데이터로써 활용될 수 있을 것이다. 덧붙여 대표적으로 세장비가 0.5인 평판에 대해서 nodal pattern이 그림으로 제시된다.

• 산업기술연구
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• 제17권
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• pp.191-197
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• 1997

For each construction material used, there is certain theoretical limit in sizes. For tall building construction, the reduction in slab weight is the first step to take in order to break such size limits. In this paper, the feasibility of such objective is proven and given by numerical analysis result. For a typical building slab, both concrete and advanced composite sandwich panels are considered. The concrete slab is treated as a special orthotropic plate to obtain more accurate result. Any method may be used to obtain the deflection influence surfaces needed for this vibration analysis. Finite difference method is used for this purpose, in this paper. The influence of the modulus of the foundation on the natural frequency is thoroughly studied.

• Structural Engineering and Mechanics
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• 제67권3호
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• pp.219-232
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• 2018

This paper deals with the static bending of various types of FGM sandwich plates resting on two-parameter elastic foundations in hygrothermal environment. The elastic foundation is modeled as Pasternak's type, which can be either isotropic or orthotropic and as a special case, it converges to Winkler's foundation if the shear layer is neglected. The present FGM sandwich plate is assumed to be made of a fully ceramic core layer sandwiched by metal/ceramic FGM coats. The governing equations are derived from principle of virtual displacements based on a shear and normal deformations plate theory. The present theory takes into account both shear and normal strains effects, thus it predicts results more accurate than the shear deformation plate theories. The results obtained by the shear and normal deformation theory are compared with those available in the literature and also with those obtained by other shear deformation theories. It is concluded that the present results are slightly deviated from other results because the normal deformation effect is taken into account. Numerical results are presented to show the effects of the different parameters, such as side-to-thickness ratio, foundation parameters, aspect ratio, temperature, moisture, power law index and core thickness on the stresses and displacements of the FG sandwich plates.