• 한국강구조학회 논문집
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• 제9권4호통권33호
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• pp.543-555
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• 1997

일반적으로 합성형 교량에 있어서 강판형과 콘크리트 슬래브 사이의 일체성은 강재와 콘크리트라는 이질재료의 접합부 사이에 위치한 전단연결재의 강성과 배치간격에 의해 영향을 받게 된다. 따라서 전단연결재는 두 재료가 일체로 거동할 수 있도록 충분한 강성을 가져야만 하며, 강성이 부족하게 되면 접촉면에서 미끄러짐이 발생한다. 이때, 미끄러짐의 발생을 고려한 것을 불완전합성형이라 한다. 본 논문에서는 불완전합성형의 해석에서 복잡한 계산과정을 거치지 않고 불완전율에 따라서 전단연결재의 강성과 간격을 산정하는 간이추정법에 대하여 연구하였으며, 단면과 지간에 따른 형특성, 불완전율, 하중작용점에 따라서 전단연결재에 작용하는 수평전단력, 축력 등의 변화양상을 간단한 영향선으로 나타내었다. 또한, 해석 예로서 Newmark의 partial interaction theory이론을 기초로 한 블완전합성형의 기초미분방정식을 적용하여 불완전율에 따라서 1) 스프링상수와의 관계 2) 축력 및 수평전단력과의 관계 3) 응력 및 중립축과의 관계를 고찰하였다.

• Smart Structures and Systems
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• 제19권2호
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• pp.163-179
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• 2017

The axisymmetric buckling delamination of the Piezoelectric/Metal/Piezoelectric (PZT/Metal/PZT) sandwich circular plate with interface penny-shaped cracks is investigated. The case is considered where open-circuit conditions with respect to the electrical displacement on the upper and lower surfaces, and short-circuit conditions with respect to the electrical potential on the lateral surface of the face layers are satisfied. It is assumed that the edge surfaces of the cracks have an infinitesimal rotationally symmetric initial imperfection and the development of this imperfection with rotationally symmetric compressive forces acting on the lateral surface of the plate is studied by employing the exact geometrically non-linear field equations and relations of electro-elasticity for piezoelectric materials. The sought values are presented in the power series form with respect to the small parameter which characterizes the degree of the initial imperfection. The zeroth and first approximations are used for investigation of stability loss and buckling delamination problems. It is established that the equations and relations related to the first approximation coincide with the corresponding ones of the three-dimensional linearized theory of stability of electro-elasticity for piezoelectric materials. The quantities related to the zeroth approximation are determined analytically, however the quantities related to the first approximation are determined numerically by employing Finite Element Method (FEM). Numerical results on the critical radial stresses acting in the layers of the plate are presented and discussed. In particular, it is established that the piezoelectricity of the face layer material causes an increase (a decrease) in the values of the critical compressive stress acting in the face (core) layer.

• Structural Engineering and Mechanics
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• 제62권1호
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• pp.113-123
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• 2017

The bi-material elastic system consisting of the circular hollow cylinder and the infinite elastic medium surrounding this cylinder is considered and it is assumed that on the inner free face of the cylinder a point-located axisymmetric time harmonic force, with respect to the cylinder's axis and which is uniformly distributed in the circumferential direction, acts. The shear-spring type imperfect contact conditions on the interface between the constituents are satisfied. The mathematical formulation of the problem is made within the scope of the exact equations of linear elastodynamics. The focus is on the frequency-response of the interface normal and shear stresses and the influence of the problem parameters, such as the ratio of modulus of elasticity, the ratio of the cylinder thickness to the cylinder radius, and the shear-spring type parameter which characterizes the degree of the contact imperfectness, on these responses. Corresponding numerical results are presented and discussed. In particular, it is established that the character of the influence of the contact imperfection on the frequency response of the interface stresses depends on the values of the vibration frequency of the external forces.

• 한국강구조학회 논문집
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• 제10권3호통권36호
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• pp.437-449
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• 1998

합성형구조에서 콘크리트와 강재가 일체로 거동하기 위해서 전단연결재는 충분한 강성과 강도를 지니고 있어야 한다. 만약 콘크리트와 판형의 경계면에서 수직 또는, 수평방향으로 미끄러짐이 발생하지 않는다면 전단연결재는 무한강성으로 표현되어지고, 이상적으로 완전합성거동을 하게 된다. 그러나, 모든 전단연결재는 어느 정도의 범위내에서 유연성을 가지게 되며, 항상 불완전합성작용을 하게 된다. 본 논문에서는 3가지 방법에 의해서 불완전합성작용을 하는 합성형을 해석하는 실용적인 방법에 대하여 연구하였다. 미분방정식의 일반해로부터 유도된 강도매트릭스법과 경계부분의 스프링상수를 뼈대구조로 대체한 유한요소법, 가상일의 원리를 이용한 유한요소법의 3가지 방법에 의하여 합성형의 처짐특성을 고찰하였다. 또한, 불완전합성형에서 단면특성과 전단연결재의 스프링상수를 이용하여 합성형의 합성정도를 추정할수 있는 간이법을 제시하였다.

• Structural Engineering and Mechanics
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• 제4권5호
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• pp.529-540
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• 1996

The dynamic buckling mechanism of a single-degree-of-freedom dissipative/nondissipative gradient system is thoroughly studied, employing energy criteria. The model is chosen in such a manner, that its corresponding static response is associated with all types of distinct critical points. Under a suddenly applied load of infinite duration, it is found that dynamic buckling, occurring always through a saddle, leads to an escaped motion, which is finally attracted by remote stable equilibrium positions, belonging sometimes also to complementary paths. Moreover, although the existence of initial imperfection changes the static behaviour of the system from limit point instability to bifurcation, it is established that the proposed model is dynamically stable in the large, regardless of the values of all other parameters involved.

• Structural Engineering and Mechanics
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• 제55권2호
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• pp.335-348
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• 2015

The influence of the interface imperfect bonding on the flexural wave dispersion in the bilayered hollow circular cylinder is studied with utilizing three-dimensional linear theory of elastodynamics. The shear-spring type model is used for describing the imperfect bonding on the interface between the layers and the degree of the imperfectness is estimated through the dimensionless shear-spring parameters which enter the mentioned model. The method for finding the analytical expressions for the sought values and dispersion equation are discussed and detailed. Numerical results on the lowest first and second modes are presented and analyzed. These results are obtained for various values of the shear-spring parameters. According to these results, in particular, it is established that as a results of the imperfection of the bonding between the layers the new branches of the dispersion related the first fundamental mode arise and the character of the dispersion curve related to the second mode becomes more complicated.

• 한국농공학회지
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• 제43권3호
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• pp.85-93
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• 2001

In this study, a computer program considering shape imperfections of arch under dynamic loading was developed. The shape imperfection of arch was assumed as higher degree polynomial expressed as $\omega$$_{i}$ = $\omega$$_{o}$ (1-(2$\chi$/L)$^{m}$ )$^n$and sinusoidal curve such as $\omega$$_{i}$ = $\omega$$_{o}$ sin(η$\pi$$\chi$/L). In finite element formulation, the material nonlinear behavior was assumed the elasto-viscoplastic model highly corresponding to the real behavior of the material and the geometrically nonlinear behavior was modeled using Lagrangian description of motion. Also, the behavior of steel was modeled by applying yield criteria of Von Mises. The developed program was applied to the analysis of the dynamic behavior for the clamped beam subjected to the concentrated load at midspan and the results were compared with those from other research to investigate accuracy of the presented finite element program. In numerical examples, the shape imperfections of L/500, L/1,000 and L/2,000 were considered and the modes of shape imperfections of the symmetric and antisymmetric were adopted. The effects of the shape imperfections on the dynamic behavior of arch were conspicuous and results of analysis indicate that the reasonable values of arch rise to arch span ratio ranged between 0.1 and 0.3.

• Structural Engineering and Mechanics
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• 제2권4호
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• pp.359-367
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• 1994

The stability behaviour of symmetrically laminated rectangular composite plates with loaded ends clamped and unloaded edges simply-supported, and subjected to uniform in-plane compression is investigated. A numerical and experimental investigation is presented in this contribution. The stacking sequence of the laminated glass/epoxy composite plates is symmetric about the middle surface and consists of 8-ply [0, 90, +45, -45]s lamination. Numerical predictions were obtained through the use of the finite element method. The above plates were modelled with 8-noded isoparametric layered shell elements. The effect of the input parameters such as the degree and forms of prescribed initial imperfection and the incremental step size required for incremental loading, on the convergence of the solution is thoroughly examined. Experimental results are presented for 10 test panels. All test panels were made from glass/epoxy unidirectional prepregs and have aspect ratio of 5.088. The laminate thicknesses were found to vary from 1.054 mm to 1.066 mm. Comparison of experimental data with predicted results show good correlation and give confidence in the finite element model.

• 디자인학연구
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• 제20권2호
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• pp.17-28
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• 2007

Despite a current fascination with East Asian iconography such as Zen Style among contemporary designers, there is a lack of genuine cross-cultural discourse that could enable us to share essential design experiences. To bring the discussion a deeper level, traditional Japanese tea-house in its design philosophy of body-mind interplay is explored. Tea-house is a superb manifestation to reveal a holistic understanding of the world. Nondualistic realization is generally associated with the dominant tendency of traditional East Asian philosophy, namely the view that the self and environment, and that the mind and the body exist in unity. The essence of tea-house is not in its poetic style or meticulous details, but in its unmistakably monistic approach of creating inseparable form, function and meaning. Tea-house bestows dignity upon restraint, imperfection, discomfort, poverty, and even humility. This concept offers a tremendous insight since it implies that the rational and effective design solution to the greatest degree is not sufficient. Perhaps the most challenging question about tea-house is: How does our experience with human-made 'design' in the broadest sense help both our body and mind attain a full harmony of being? It is the heading which this research inquires.

• 대한전자공학회논문지
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• 제5권1호
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• pp.1-5
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• 1968

GaAs의 단결정은 Ga의 용액으로부터 epitaxial 방법으로 성장시키는데 300°K에서는 carrier concentration 10 /㎤에서 electron-mobility 7,500∼9,300㎠/V-sec. 정도의 것이 얻어지며 77°K에서는 electron-mobility 50,000∼95,000㎠/V-sec.의 것이 얻어진다. mobility-온도 관계곡선의 이론적인 것과 실험적인 것을 비교해 보면 77°K에서 430°K의 온도범위내에서 ion화한 불순물과 phonon이 주요한 scattering mechanism이라는 것을 나타낸다. 이것은 epitaxial층이 mobility를 제한하는 다른 결함을 별로 내포하지 않는다는 것을 의미한다. epitaxial층의 photoluminescence spectra는 심부에 존재하는 결함의 준위에 의한 방출을 나타내지 않는다.