• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.5
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• pp.2505-2510
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• 2013

Parametric studies on nonhomogeneous pile and homogeneous pile installed in clay were performed through the developed technique to investigate the effects of considered factors on the lateral pile behaviors. Values of the parameters with embedment depths of the two piles having different flexural rigidity show that values of the parameters for more rigid pile were greater than those for smaller one. Parameters for the case of the nonhomogeneous pile were converged to the same ones of the homogeneous pile as nodal point moves away from point of material boundary. In order to determine adequate upper length of the nonhomogeneous pile, changing patterns of the parameters, lateral displacement, member forces and so forth should be compared.

• Journal of Korean Society of Steel Construction
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• v.13 no.5
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• pp.443-455
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• 2001

An energy method has been used for an elastic formulation of bending vibration and buckling analysis of laminated composite plates on two-parameter elastic foundations. A quasi-elastic method is used for the solution of viscoelastic analysis of the laminated composite plates. The third-order shear deformation theory is applied by using the double-fourier series. To validate the derived equations the obtained displacements for simply supported orthotropic plates on elastic foundations are compared with those of LUSAS program Numerical results of the viscoelastic bending vibration and buckling analysis are presented to show the effects of layup sequence number of layers material anisotropy and shear modulus of foundations.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.6 no.2
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• pp.103-109
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• 1986

The distributions of fatigue life of concrete for various applied fatigue stress levels are investigated. The concrete beam specimens are tested in four-point flexural loading conditions. Three different levels of applied fatigue stresses are considered. They are 85%. 75%. 65%, respectively, of the static flexural strength of concrete. The present study indicates that the shapes of the probability distribution of fatigue lives are rather different for different levels of applied fatigue stress. This necessitates the consideration of the effects of applied fatigue stress levels on fatigue life distributions of concrete in order to conduct a realistic fatigue reliability analysis. The graphical method, the method of moments, and the method of maximum likelihood estimation are used to evaluate the distribution parameters of fatigue lives. It was found that the shape parameter of Weibull distribution for the fatigue life of concrete ranges from 2.0 to 4.0 according to the level of applied fatigue stress.

• The Journal of the Korea institute of electronic communication sciences
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• v.12 no.5
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• pp.783-790
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• 2017

The energy band gaps and the bowing parameters of zincblende GaP1-xNx on the variation of temperature and composition are determined by using an empirical pseudopotential method with another virtual crystal approximation, which includes the disorder effect. The bowing parameter calculated is 13.1eV and the energy band gaps are decreased rapidly for GaP1-xNx ($0{\leq}x{\leq}0.05$, 300K). A refractive index n and a function of real dielectric constant ${\varepsilon}$ are calculated by the results of energy band gaps and the calculation results of energy band gaps are consistent with experimental values.

• The Journal of the Korea institute of electronic communication sciences
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• v.11 no.12
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• pp.1165-1174
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• 2016

The energy band gaps and the bowing parameters of zincblende InAs1-xN are determined by using an empirical pseudopotential method(EPM) within the improved virtual crystal approximation(VCA), which includes the disorder effect. The direct-band-gap bowing parameter calculated by using the EPM is 4.1eV for InAs1-xNx ($0{\leq}x{\leq}0.05$). The dependences of the band gaps of N-dilute InAs1-xNx on the temperature and composition are calculated by modifying the band anti-crossing(BAC) model. The calculation results are consistent with experimental values, and the coupling parameter CMN of InAs1-xNx is found to be equal to 1.8 by fitting the EPM data.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.6
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• pp.1213-1222
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• 2018

The energy band gaps and the bowing parameters of zincblende $GaAs_{1-x}N_x$ on the variation of temperature and composition are determined by using an empirical pseudo-potential method with another virtual crystal approximation, which includes the disorder effect. The bowing parameter is calculated as 15eV and the energy band gaps are decreasing rapidly in $GaAs_{1-x}N_x$ ($0{\leq}x{\leq}0.05$, 300K). A refractive index n and a function of high-frequency dielectric constant ${\varepsilon}$ are calculated by the results of energy band gaps and the calculation results of energy band gaps are consistent with experimental values.

• Journal of the Korea Concrete Institute
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• v.13 no.4
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• pp.371-378
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• 2001

Recently, the parameters, models, and experimentations, which evaluate the fracture properties of concrete, have been proposed by many researchers, and their developments allow us to analyze the non-linear and quasi-brittle fracture mechanisms. In this paper, a brief treatment of the fracture parameters was presented and the experiments of 3-point bending tests were conducted to compare J-integral($J_{Ic}$ /) with other parameters($K_{Ic}$ , $G_{v}$ , and $G_{F}$ ). The change of parameter values according to the width and notch length of concrete beam specimens was also considered. The load-displacement curves are used to experimentally measure concrete fracture toughness. From the results of experiment, it is noted that the value of $GF$ and tic decreases as the notch depth increases and $G_{F}$ is less sensitive than $J_{Ic}$ . Therefore, the former is more appropriate to use as the concrete fracture toughness parameter. The values of $v_{v}$ and $J_{Ic}$ increase when the width of concrete specimens increase from 75 mm to 150 mm. Therefore, the effects of specimen width need to be considered in determining the concrete fracture toughness.

• Journal of Korean Society of Steel Construction
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• v.29 no.1
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• pp.1-12
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• 2017

This paper proposes nominal flexural strength considering strain-hardening effect of HSB600 high performance steel for compact composite I-girders in positive bending. Unlike conventional steels, HSB600 undergoes strain-hardening just after yielding without going through yield plateau. However, because the nominal flexural strength specified in domestic and foreign bridge design specifications has been developed for the conventional steel composite girders, the nominal flexural strength does not appropriately consider the strain-hardening of HSB600. Therefore, plastic moment considering a strain-hardening is proposed so as to consider effect of the strain-hardening of HSB600 on flexural strength and then moment-curvature analysis is performed to a wide range of cross-sections. From results of the analysis, a parameter representing the effect of the strain-hardening on the flexural strength of HSB600 composite girders is proposed. Furthermore, by using this parameter, the nominal flexural strength considering the strain-hardening effect for HSB600 composite I-girders in positive bending is proposed and then evaluated by comparing with the current AASHTO LRFD bridge design specifications.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.14 no.1
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• pp.43-55
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• 2001

본 논문에서는 현행 표준적인 P.S.C거더 교량의 적정 가로보 수를 위한 매개변수 연구를 수행하였다. 교량의 길이는 P.S.C거더교로서 국내에서 가장 흔히 사용되는 30m의 단순교를 채택하였다. 교량의 해석방법으로는 상부의 슬래브와 거더를 효율적으로 모델링하기 위하여 정밀해석법인 유한요소법을 사용하였다. 본 연구에서 사용된 매개변수로는 크게 두 가지로 분류되는데, 하나는 사용된 가로보의 개수이고 다른 하나는 교량의 사각(Skew)이다. 상부 슬래브는 쉘 요소와 빔 요소를 연결하는데 효율적인 회전자유도를 가지는 쉘 요소로 모델링 하였다. 슬래브와 거더의 중심축이 이격되어 있는 문제를 정확히 고려하기 위하여 편심보 요소를 사용하였다. 해석 모델은 가로보가 각각 7,5,3개 있는 경우를 선정하였다. 이러한 조건하에서 정적 해석을 수행하여 최대 휨모멘트, 전단력, 비틀림 모멘트값을 구하여 현행 시방서에서 규정된 극한치를 만족하는지 검토하였다. 검토결과 현재 사용되고 있는 P.S.C거더 교량에서의 가로보 개수는 과다한 것으로 판단되며 경제적인 설계를 위하여 가로보의 개수를 줄일 수 있을 것으로 제안하였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.6
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• pp.659-666
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• 2015

In this paper, various influence factors on the impact-echo test which is an effective method in characterizing defects such as such as the delamination in the concrete structures were studied. The side to thickness ratio(a/h), the relative position of impacting and sensing points over the delamination that have great effects on the flexural and impact-echo(thickness) modes were investigated and examined by the parametric finite element analysis. As a result, the flexural modes dominate in the case of a/h > 2 and the thickness mode was more evident when a/h < 2. With regard to the relative position of impact source and sensing point to the defect, the flexural modes dominate even when either the loading or sensing point was over the delamination defect. However, the thickness mode prevails when both the impacting and sensing points are over the solid region beyond the delamination area.