• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.717-720
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• 1999

Recently, the fiber composite materials such as carbon fiber, glass fiber, or aramid, have been frequently used in strengthening reinforced concrete structures. The fiber composite materials typically have orthotropic characteristic and the strength changes significantly acording to the direction of fibers and the method of the lamination. In this study, an algorithm to estimate the stress-strain relationship of the composite materials which have different fiber directions and symmetric or non-symmetric lamination has been developed by using Tsai-Hill and Tsai-Wu failure criteria and progressive laminate failure theory. This algorithm has been implemented to several stress-strain models for the laterally confined concrete compression members such as Mander, Hosotani, and Nakatsuka. The evaluated stress-strain behaviors by the different models are discussed.

• 복합신소재구조학회 논문집
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• 제6권3호
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• pp.1-7
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• 2015

Compared with conventional construction materials such as steel and concrete, the advanced composite materials are corrosion-free, light-weight, and when used as construction materials, the construction period can be made less than one-tenth needed for conventional materials. However, because of the difficult theories and formulas, the ordinary construction engineers have difficulties in understanding and calculating formulas needed in construction. In this paper, calculation of the stiffnesses of the advanced composite laminated plates and compared with the result of stiffnesses.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2004년도 추계학술발표대회 논문집
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• pp.147-150
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• 2004

In order to describe the mechanical behavior of highly anisotropic and asymmetric materials such as fiber­reinforced composites, the elastic-plastic constitutive equations were used here based on the recently developed yield criterion and hardening laws. As for the yield criterion, modified Drucker-Prager yield surface was used to represent the orthotropic and asymetric properties of composite materials, while the anisotropic evolution of back­stress was accounted for the hardening behavior. Experimental procedures to obtain the material parameters of the hardening laws and yield surface are presented for 3D Circular Braided Glass Fiber Reinforced Composites. For verification purpose, comparisons of finite element simulations using the elastic-plastic constitutive equations, anisotropic elastic constitutive equations and experiments were performed for the three point bending tests. The results of finite element simulations showed good agreements with experiments, especially for the elastic-plastic constitutive equations with yield criterion considering anisotropy as well as asymmetry and anisotropic back stress evolution rule.

• 대한기계학회논문집A
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• 제25권11호
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• pp.1835-1843
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• 2001

The energy release rate for an interface crack in anisotropic dissimilar materials was obtained by the eigenfunction expansion method and also was analyzed numerically by the reciprocal work contour integral method. It was shown that the results for orthotropic dissimilar materials are consistent with the other worker's results.

• Composites Research
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• 제14권4호
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• pp.1-7
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• 2001

본 연구는 등분포 압축을 받는 비대칭 연단보강된 직교이방성 개방단면 구조용 부재의 탄성국부좌괄에 대한 이론적 연구의 결과이다. 비대칭 연단보강재는 비틀림강성을 무시한 보요소로 간주하였다. 플랜지판의 일부와 플랜지의 연단에 부착된 판으로 구성된 비대칭 연단보강재에 대한 이론적 해석 모델을 제시하였으며, 이 결과로부터 얻어지는 비대칭 연단보강재 단면의 도심을 지나는 축에 대한 단면2차모멘트를 계산하였다. 유도된 식을 사용하여 비대칭 연단보강된 직교이방성 I형 압축재의 국부좌굴계수를 구하였으며 그 결과를 그래프로 제시하였다.

• 대한기계학회논문집A
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• 제21권3호
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• pp.447-456
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• 1997

Stress intensity factor of semi-infinite parallel crack propagation with constant velocity in dissimilar orthotropic strip under out-of-plane clamped desplacement is investigated. Using Fourier integral transforms the boundary value problem is derived by a pair of dual integral equation and finally reduced to a single Wiener-Hopf equation. By applying Wiener-Hopf technique the equation is solved. Applying this result the asymptotic stress fields near the crack tip are determined, from which the stress intensity factor is obtained in closed form. The more the ratio of anisotropy or the ratio of bi-material shear modulus increase in the main material including the crack, the more the stress intensity factor increases. Discontinuity in the stress intensity factor is found as the parallel crack approaches the interface. In special case, the results of isotropic materials agree well with those by the previous researchers.

• 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.

• Composites Research
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• 제29권6호
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• pp.347-352
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• 2016

적층 복합재료 주름판에 대한 진동특성을 이론적 방법을 이용하여 분석하였다. 고려된 주름 형상은 사다리꼴을 기본으로 삼각형, 사각형 및 요각 사다리꼴형이다. 3차원 주름 구조물을 해석적으로 기계적 거동을 표현하는 것이 매우 어렵기 때문에 본 해석에서는 주름판의 진동특성을 분석하기 위해 등가균질모델을 적용하였다. 이를 위해 단위 주름을 직교이방성재료로 등가시켰으며, 해석에서 등가 신장 강성 및 굽힘 강성이 모두 고려되었다. 이론해석 결과의 타당성을 검증하기 위해 셸요소를 적용한 3차원 유한요소해석을 수행하였으며, 두 방법을 이용해 얻은 고유진동수 및 진동형상을 비교하였다. 주름판의 기하형상에 따른 영향을 분석하기 위해 다양한 수치예가 제시되었다.

• Structural Engineering and Mechanics
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• 제44권1호
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• pp.15-34
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• 2012

In the present paper, an improved high-order theory is used for bending analysis of soft-core sandwich plates. Third-order plate assumptions are used for face sheets and quadratic and cubic functions are assumed for transverse and in-plane displacements of the orthotropic soft core. Continuity conditions for transverse shear stresses at the interfaces as well as the conditions of zero transverse shear stresses on the upper and lower surfaces of the plate are satisfied. Also, transverse flexibility and transverse normal strain and stress of the orthotropic core are considered. The equations of motion and boundary conditions are derived by principle of minimum potential energy. Analytical solution for bending analysis of simply supported sandwich plates under various transverse loads are presented using Navier's solution. Comparison of the present results with those of the three-dimensional theory of elasticity and some plate theories in the literature confirms the accuracy of the proposed theory.

• 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.