• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2001년도 추계학술발표대회 논문집
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• pp.163-169
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• 2001

The solution of two-dimensional deflection of circular wavy reinforcing fiber elastics was obtained for one end clamped boundary under concentrated load condition. The fiber was regarded as a linear elastic material. Wavy shape was described as a combination of half-circular arc smoothly connected each other with constant curvature of all the same magnitude and alternative sign. Also load direction was taken into account. As a result, the solution was expressed in terms of a series of elliptic integrals. These elliptic integrals had two different transformed parameters involved with load value and initial radius of curvature. While we found the exact solutions and expressed them in terms of elliptic integrals, the recursive ignition formulae about the displacement and arc length at each segment of circular section were obtained. Algorithm of determining unknown parameters was established and the profile curve of deflected beam was shown in comparison with initial shape.

• Computers and Concrete
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• 제15권4호
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• pp.673-686
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• 2015

R-curve based on the size effect law previously developed for geometrically similar specimens (geometry type III) is extended to geometries with variable depth (geometry type I) as well as with variable notch (geometry type II), where the R-curve is defined as the envelope of the family of critical strain energy release rates from specimens of different sizes. The results show that the extended R-curve for type I tends to be the same for different specimen configurations, while it is greatly dependent on specimen geometry in terms of the initial crack length. Furthermore, the predicted load-deflection responses from the suggested R-curve are found to agree well with the testing results on concrete and rock materials. Besides, maximum loads for type II specimen are predicted well from the extended R-curve.

• 한국공작기계학회논문집
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• 제16권1호
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• pp.26-32
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• 2007

This study was carried out fusion-welded butt joints in SWS 490A high strength steel subjected to tensile test that load-deflection curve. The windowed or short-time Fourier transform(WFT or STFT) makes possible for the analysis of non-stationary or transient signals into a joint time-frequency domain and the wavelet transform(WT) is used to decompose the acoustic emission(AE) signal into various discrete series of sequences over different frequency bands. In this paper, for acoustic emission signal analysis to use a continuous wavelet transform, in which the Gabor wavelet base on a Gaussian window function is applied to the time-frequency domain. A wavelet transform is demonstrated and the plots are very powerful in the recognition of the acoustic emission features. As a result, the technique of acoustic emission is ideally suited to study variables which control time and stress dependent fracture or damage process in metallic materials.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2005년도 춘계학술대회 논문집
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• pp.342-348
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• 2005

This study was carried out fusion-welded butt joints in SWS 490A high strength steel subjected to tensile test that load-deflection curve. The windowed or short-time Fourier transform (WFT or SIFT) makes possible for the analysis of non-stationary or transient signals into a joint time-frequency domain and the wavelet transform (WT) is used to decompose the acoustic emission (AE) signal into various discrete series of sequences over different frequency bands. In this paper, for acoustic emission signal analysis to use a continuous wavelet transform, in which the Gabor wavelet base on a Gaussian window function is applied to the time-frequency domain. A wavelet transform is demonstrated and the plots are very powerful in the recognition of the acoustic emission features. As a result, the technique of acoustic emission is ideally suited to study variables which control time and stress dependent fracture or damage process in metallic materials.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회논문집(I)
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• pp.733-738
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• 2000

It is difficult to obtain accurate fracture toughness values by RILEM committees proposed three point bend test(TPB) because the shape of load-deflection curve is irregular and final crack propagation occurs after some slow stable cracking. However, for disk test, fracture toughness is easily obtained from crack initial load. We examined the cracked high strength concrete disk and the experimental results were compared with the results by finite element analysis(FEA). Also we compared experimental fracture locus with theoretical fracture locus.

• 대한토목학회논문집
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• 제30권4A호
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• pp.383-389
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• 2010

현재 우리나라의 콘크리트구조설계기준은 강도설계법에 근간하고 있다. 강도설계법에 의해 휨부재를 설계할 경우, 콘크리트 응력-변형률 관계는 사용하중 상태에서 선형으로 가정하지만 이후 극한한계 상태까지에 대해서는 규정되어 있지 않다. 이로 인해 콘크리트구조설계기준에서는 처짐 및 균열폭 등의 산정에 대해 개별적인 규정을 두고 있다. 그러나 한계상태설계법에 근거한 EC에서는 재료에 대한 응력-변형률 관계를 규정하고 있다. 따라서 재료의 응력-변형률 관계로부터 휨강도 및 처짐 등을 직접 계산할 수 있다. 본 연구에서는 휨부재에 대하여 주어진 재료 모델을 바탕으로 평형방정식과 적합조건식을 적용하여 휨모멘트-곡률 관계를 계산하였다. 이로부터 휨강도 및 처짐을 산정하여 현행 콘크리트구조설계기준에 의한 값과 비교하였다. 해석 결과 재료 모델로부터 휨모멘트-곡률 관계를 통해 산정된 처짐은 실험 결과와도 비교적 잘 일치하고, 항복 이후의 처짐 계산도 가능한 것으로 나타났다.

• Coupled systems mechanics
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• 제3권3호
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• pp.247-265
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• 2014

This article discusses the dynamic response of Bernoulli-Euler straight beam with angular elastic supports subjected to moving load with variable velocity. A new engineering approach for determination of the dynamic effect from the moving load on the stressed and strained state of the beam has been developed. A dynamic coefficient, a ratio of the dynamic to the static deflection of the beam, has been defined on the base of an infinite geometrical absolutely summable series. Generalization of the R. Willis' equation has been carried out: generalized boundary conditions have been introduced; the generalized elastic curve's equation on the base of infinite trigonometric series method has been obtained; the forces of inertia from normal and Coriolis accelerations and reduced beam mass have been taken into account. The influence of the boundary conditions and kinematic characteristics of the moving load on the dynamic coefficient has been investigated. As a result, the dynamic stressed and strained state has been obtained as a multiplication of the static one with the dynamic coefficient. The developed approach has been compared with a finite element one for a concrete engineering case and thus its authenticity has been proved.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제20권1호
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• pp.17-35
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• 2016

In this study, the dynamic behaviour of a rotating Timoshenko beam when under the actions of a variable magnitude load moving at non-uniform speed is carried out. The effect of cross-sectional dimension and damping on the flexural motions of the elastic beam was neglected. The coupled second order partial differential equations incorporating the effects of rotary and gyroscopic moment describing the motions of the beam was scrutinized in order to obtain the expression for the dynamic deflection and rotation of the vibrating system using an elegant technique called Galerkin's Method. Analyses of the solutions obtained were carried out and various results were displayed in plotted curve. It was found that the response amplitude of the simply supported beam increases with an increase in the value of the foundation reaction modulus. Effects of other vital structural parameters were also established.

• 한국안전학회지
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• 제37권4호
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• pp.101-112
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• 2022

Expanding urbanization practices result in high numbers of buildings being developed in city centers. This high building concentration leads to an increased fire risk, resulting in higher casualty rates and increased economic damages compared to fires in the past. The purpose of this study was to analyze the structural behavior of fire-damaged reinforced concrete buildings using analytical methods and to suggest methods of improving fire resistance in the event of a fire. Damage levels were measured using commercial software to apply the finite element method, ABAQUS, and MIDAS GEN to the dataset. Load-deflection curves were calculated using the effective area and moment of inertia of the fire-damaged columns provided by ABAQUS. The results of this analysis indicate that fire-damaged beams with experience greater deflection from indoor fires than they will from outdoor fires. Fires that occurred on the middle floors were more dangerous than those occurring on higher floors, and eccentrically loaded columns experienced more damage than axially loaded columns. The results indicate that these methods accurately predict structural behaviors of fire damaged concrete columns by considering fire exposure area and eccentric loading.

• 한국풍공학회지
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• 제22권4호
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• pp.155-161
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• 2018

현대 사회에서 도시화와 온난화로 인한 태풍 등 강풍에 의한 피해는 증가될 것으로 예상된다. 본 연구에서는 기 개발된 창호보호장치의 보강성능을 시험하기 위해 비 보강된 판유리와 보강된 판유리의 2점 가력실험과 등분포하중 실험을 수행하였다. 창호보호장치의 보강성능은 휨 성능평가를 토대로 평가하였다. 창호보호장치의 이론적 성능 산정은 탄성하중법과 처짐 곡선의 미분방정식을 이용한 수식해석과 Midas-Gen을 이용한 전산해석을 통해 수행하였다. 실험값과 이론 산정 값의 최대하중 가력시의 판유리 중앙부 최대 처짐 비교를 통해 산정방법의 유효성을 검토하였다. 창호보호장치 부착 시 실험조건하에서 40%까지의 응력감소효과와 동일 하중하에서 71.4%까지의 처짐 감소 효과가 있었다. 판유리를 보요소로 해석한 결과보다 판유리를 판 요소로 해석한 결과가 오차가 적으므로 성능 판단 시 가능하면 판 요소로 해석을 수행하는 것이 유리하다.