• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.297-300
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• 2010

본 논문에서는 일반적인 해석, 시공단계를 고려한 해석, 시공단계와 장기거동을 고려한 해석의 3가지 해석방법을 사용하여 수평부재의 설계에 적합한 해석방법을 제안하였다. 80층의 2D 구조모델에 3가지 해석방법을 적용하여 각 해석방법에 따라 부등축소량, 수직부재에 작용하는 축력, 수평부재의 단부에 작용하는 내력의 해석결과를 얻어 비교하였다. 또한 부재의 내부에서 철근과 콘크리트의 하중분담율의 시간에 따른 변화양상을 알아보았다. 해석결과 시공단계에 의한 영향은 수평부재에 작용하는 축력과 부등축소량 예측, 부재 내력 해석에 있어서 반드시 고려되어야 함을 알 수 있었다. 장기거동의 효과는 기둥축소에는 크게 영향을 미치지만 수직부재의 축력, 수평부재의 내력에는 변형만큼의 영향은 보이지 않는다. 시공시의 보정량을 결정하기 위해서는 장기거동이 반드시 고려되어야 하지만 부재의 단면설계의 목적으로는 제외되어도 무방할 것으로 판단된다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.542-545
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• 2010

재료의 마이크로 스케일 해석에서 결정의 geometrically necessary dislocation (GND) 효과에 의한 소성구배(plastic gradient)를 고려하는 것은 재료의 소성 거동을 분석하는데 영향을 미친다. 본 연구에서는 먼거리(long range)에서 전위(dislocation)의 영향을 고려하는 GND의 효과를 적용하여 소성 구배의 영향을 받는 다결정(polycrystal) 고체의 거동을 유한요소해석을 이용하여 살펴보았다. 재료의 거동을 분석하기 위해 탄성(elastic)과 소성(plastic) 변형에 먼 거리 변형률(long range strain)을 고려한 항(term)이 포함된 변형 구배(deformation gradient)의 multiplicative decomposition 모델을 사용하였다. 먼 거리 변형률에 의한 영향을 고려하기 위해 구배 경화 계수(gradient hardness coefficient)와 먼 거리 변형률 길이에 대한 재료변수(parameter)가 사용되었다. 각각의 계수들이 다결정 고체의 거동에 미치는 영향을 확인하기 위해 두 변수의 적용에 따른 다결정 고체의 거동을 분석하였다. 다결정 재료의 GND 효과에 의한 소성 구배 효과를 고려해서, 고려하지 않은 경우와 비교하여 발생하는 경화(hardening)의 차이를 분석함으로서 GND에 의한 다결정 고체 거동의 영향을 확인하였다.

• Structural Engineering and Mechanics
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• v.55 no.4
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• pp.703-717
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• 2015

In this paper, a simple n-order refined theory based on neutral surface position is developed for bending and frees vibration analyses of functionally graded beams. The present theory is variationally consistent, uses the n-order polynomial term to represent the displacement field, does not require shear correction factor, and gives rise to transverse shear stress variation such that the transverse shear stresses vary parabolically across the thickness satisfying shear stress free surface conditions. The governing equations are derived by employing the Hamilton's principle and the physical neutral surface concept. The accuracy of the present solutions is verified by comparing the obtained results with available published ones.

• Geomechanics and Engineering
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• v.4 no.1
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• pp.67-78
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• 2012

Soil foundations exhibit significant creeping deformation, which may result in excessive settlement and failure of superstructures. Based on the theory of viscoelasticity and fractional calculus, a fractional Kelvin-Voigt model is proposed to account for the time-dependent behavior of soil foundation under vertical line load. Analytical solution of settlements in the foundation was derived using Laplace transforms. The influence of the model parameters on the time-dependent settlement is studied through a parametric study. Results indicate that the settlement-time relationship can be accurately captured by varying values of the fractional order of differential operator and the coefficient of viscosity. In comparison with the classical Kelvin-Voigt model, the fractional model can provide a more accurate prediction of long-term settlements of soil foundation. The determination of influential distance also affects the calculation of settlements.

• Proceedings of the KIEE Conference
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• 2002.11a
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• pp.74-76
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• 2002

The suspension insulators are subjected to harsh environment in service for a long time. Long term reliability of the insulators is required for both mechanical and electrical performances. We studied an analysing method to find out a deformation of brittle porcelain with a thermal expansion of cement for suspension insulator. These simulation analysis and experimental results show that cement volume growths affect severely to be mechanical failure ageing.

• Communications of the Korean Mathematical Society
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• v.37 no.4
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• pp.1269-1284
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• 2022

This paper is concerned with the following Schrödinger-Poisson system $$\{\begin{array}{lll}-{\Delta}u+V(x)u+K(x){\phi}u=a(x){\mid}u{\mid}^{p-2}u&&\text{ in }{\mathbb{R}}^3,\\-{\Delta}{\phi}=K(x)u^2&&\text{ in }{\mathbb{R}}^3,\end{array}$$ where 4 < p < 6. For the case that K is nonnegative, V and a are indefinite, we prove the above problem possesses one ground state sign-changing solution with exactly two nodal domains by constraint variational method and quantitative deformation lemma. Moreover, we show that the energy of sign-changing solutions is larger than that of the ground state solutions. The novelty of this paper is that the potential a is indefinite and allowed to vanish at infinity. In this sense, we complement the existing results obtained by Batista and Furtado [5].

• Journal of the Korea Concrete Institute
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• v.18 no.3 s.93
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• pp.339-346
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• 2006

The purpose of this study is to suggest a method to quantitatively predict long-term deformation of walls under an axial load concentrated to a part of the whole width. Four wall specimens were tested and three-dimensional finite element analyses were performed for these specimens. The finite element models established in this study were verified from the test results. On the basis of this verification, analysis parameters were selected considering various dimensions of walls and sectional area that a concentrated load is acting on, and finite element analyses for these parameters were carried out. The concept of the effective width coefficient was newly introduced as a method to predict the long-term behavior of walls, and a function that is able to optimally fit the effective width coefficients calculated from the analysis results for the selected parameters was found from regression analysis. The found function can be conveniently used in practice to predict the long-term behavior under loads concentrated to a local area of the whole width of walls.

• International Journal of Highway Engineering
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• v.4 no.3 s.13
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• pp.43-49
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• 2002

Asphalt pavements have to perform under the conditions of heavily-loaded vehicles due to the industrialization and large temperature variance between the summer and the winter. Due to these factors, a characteristics change of early permanent deformation becomes a big issue, and to remedy this problem many research to use modified asphalt are being widely conducted. However, most of the modified asphalt is being paved after milling the surface course and applying tackcoating, and it is being used mostly for the repair and maintenance purpose rather than pavement of new national road. The purpose of this investigation is to obtain some fundamental data for the evaluation of the performance and long-term performance of the construction material mixtures by the laboratory test and field experiments. For the field experiment, 200m of two-lanes national road, that is being paved for the new national road under the direction of Pusan Regional Construction Management Office, was paved with SBS PMA and PSMA asphalt mixtures, which are an modified asphalt mixtures used for the surface course, on top of the base course paved with other modified asphalt mixtures. The remaining section of the new national road was paved with dense grade mixture. The laboratory tests assessed and analyzed the mixture characteristics by Marshall's stability test, strength tests and wheel-tracking test. On the basis of the evaluation result of the temperature control and roughness of the newly constructed road at the field experiment site, it is desired to evaluate and identify the most economic modified asphalt mixtures by long-term performance evaluation and LCC(Life Cycle Cost) analysis in order to apply the test result to the design of new road construction in the future.

• Journal of the Korean GEO-environmental Society
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• v.8 no.2
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• pp.19-27
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• 2007

In this study, the centrifugal tests were performed with varying the angle of slope such as 1:3, 1:2.5, and 1:2 in order to analyze the deformation and failure type of dredged clay slope for a short term. The displacement mode, displacement vector and the variation of pore pressure with the different slope angle were measured. As a results, even though the displacement in the slope after 4 months were developed in the case of 1:3 for the dredged slope, there are little problems to obtain the stability of dredged slope because the original construction section maintains. Also, in the case of 1:2.5 after 4 months the local slope failure occurred and in the case of 1:2 after 2 months the circle failure starting from the point of the tensile crack occurred. After reviewing the results, the maximum vertical displacement occurred at the crest of slope and maximum horizontal displacement was about double of maximum vertical displacement.

• Journal of the Korean Association of Geographic Information Studies
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• v.8 no.2
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• pp.186-195
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• 2005

Topography of beach line is keeping stability for several years, their soil values have been maintained in balances. Install of coastal structures have caused deformation for beaches and acted as a function to structures. Therefore, quantitative prediction of beaches topography according to structure install is required to prevent the beaches deformation and progress proper coastal preservation work. In this study, we analyzed coastal changes caused by erosion and accretion according to development and drew up a cross-section to share 8 stations using coordinates and depth surveying in groin of Soheuksan island port. Elevation distribution and changes by observation period is calculated -0.30m~+0.20m after comparing results of five months in October 7, 2004 surveying results and fell into insignificance. We thinks periodic observation of coastal erosion and accretion take place for the season and long-term coastal changes in beaches width is analyzed.