• 한국강구조학회 논문집
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• 제22권4호
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• pp.365-375
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• 2010

콘크리트 충전형 합성부재는 압축하중 상태에서 강재에 의한 콘크리트의 구속효과와 콘크리트에 의한 강재의 국부좌굴에 대한 보강효과를 기대할 수 있는 압축부재이다. 기존의 연구결과를 실험결과와 비교한 후, 구속효과가 하중-변위 관계에 미치는 영향을 평가하여 기존의 응력-변형률 관계를 수정하였다. 수정된 응력-변형률 관계를 적용한 비선형 수치해석 프로그램을 작성하여 단면특성과 재료특성에 따른 각각의 설계 변수들이 하중-변위 관계와 모멘트-곡률 관계에 미치는 영향을 평가하였다.

• 대한기계학회논문집
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• 제14권5호
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• pp.1193-1199
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• 1990

본 연구에서는 가공경화지수 (n)가 서로 다른 몇가지 재료를 선택하고 과대하 중의 비 (%PL)를 달리하는 단일 과대하중 피로 시험을 행하여 재료의 가공경화지수가 피로 균열 진파의 지연거동에 미치는 영향과 아울러 균열닫힘현상과의 관계를 구명하였다.

• 콘크리트학회논문집
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• 제15권2호
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• pp.163-172
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• 2003

최근 콘크리트 구조물이 점차 대형화, 고층화, 장대화 및 특수화 됨에 따라 강섬유 콘크리트의 적용이 요구되고 있다. 본 연구에서는 반복하중을 받는 강섬유를 혼입한 2경간 연속보에 대한 실험적 연구를 수행하여 피로하중에 의한 강섬유 혼입율(0%, 0.75%, 1.00%, 1.25%)에 따른 피로강도를 규명하고자 하였다. 정적실험을 통하여 극한하중, 초기 휨균열하중 등을 측정하였고 하중과 철근의 변형율 관계, 하중과 처짐 관계 그리고 하중증가에 따른 균열성장과 파괴양상 등을 관찰하였다. 피로실험을 통하여 반복횟수와 처짐 관계, 반복횟수와 변형율 관계 그리고 반복횟수에 따른 균열성장과 파괴양상을 관찰하였다. 피로실험 결과 강섬유를 혼입하지 않은 2경간 연속보는 정적극한강도의 60~70%에서 파괴되었고 S-N곡선으로부터 반복횟수 200만회에 대한 피로강도는 정적극한강도의 67.2% 전후임을 확인 할 수 있었다. 또한, 강섬유를 혼입한 2경간 연속보는 정적극한강도의 65∼85%에서 파괴되었고 S-N곡선으로부터 반복횟수 200만회에 대한 피로강도는 정적극한강도의 71.7%전후임을 확인할 수 있었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.739-744
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• 2001

The concrete bridge deck is quitely required to be replaced or strengthened due to decreasing load carrying capacity. In this study, to increase load capacity of the reinforced concrete slab, bridge deck is reinforced with the glass fiber sheets. they are examined on the strengthen effect and the static behavior, This paper considers relation of load-displacement and strain-distance. The static behavior of the slab strengthened is represented to maximum load. Owing to that, they are examined on increasing load carrying capacity of reinforced bridge deck and strengthen effect about on the crack.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2000년도 춘계학술대회논문집 - 한국공작기계학회
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• pp.66-72
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• 2000

Commercial eddy current dynamometers control the torque of ratating body (poer supply machine) with the field coil current being operated as a braking force. In this paper, we studied about the relation between the field coil current and the torque load of eddy current dynamometer. By the torque measuring analysis of eddy current dynamometer, it is linear relation between the brake force measured from the torque meter (e.g. load cell, strain gage or spring balance etc.) which is installed at the case of dynamometer and the multiply of shaft rpm by the square of field coil current (N$\times$Ia2). To prove the relation, it was experimented and showed that the torque operated by the rotating body can be measured with the shaft rpm and the field coil current of eddy current dynamometer. This result shows a possibility that eddy current dynamometer can measures the torque of rotating body without special torque measuring devices.

• 소성∙가공
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• 제9권1호
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• pp.59-65
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• 2000

Most studies of failure analysis in ductile metals have been based on the classical plasticity theory using the local constitutive relations. These frequently yields a physically unrealistic solution, in which a numerical prediction of the onset of a deformation localization shows an inherent mesh-size sensitivity. A one way to remedy the spurious mesh sensitivity resulted in the unreasonable results is to incorporate the non-local plasticity into the simulation model, which introduce an internal (material) length-scale parameter into the classical constitutive relations. In this paper, a non-local version of the modified Gurson constitutive relation has been introduced into the finite element formulation of the simulation for plane strain compression of the visco elastic-plastic void material. By introducing the non-local constitutive relations we could successfully removed the inherent mesh-size sensitivity for the prediction of the deformation localization. The effects of non-local constitutive relation are discussed in terms of the load-stroke curve and the strain distributions accross the shear band.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.787-790
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• 2000

This paper presents an experimental study on flexural behavior of structural member enlarged with epoxy mortar system. The main test variable is flexural tensile strength. A series of 4 test beams was tested to shoe the corresponding effect of each variables on maximum load capacity, load-deflection and moment-curvature relationship, interface behavior and failure mode. The results show that the flexural tensile strength of retrofitted materials have no relation load-deflection, but to load-strain, and failure mode.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.933-943
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• 2009

Axial loads and shaft resistances can be calculated by load transfer analysis using strain data with load level. In load transfer analysis, the elastic modulus of concrete is a one of the most important parameters to consider. The elastic modulus, $E_{50}$, suggested by ACI (American Concrete Institute), has been commonly used. However, elastic modulus of concrete shows nonlinear stress-strain characteristic, so nonlinearity should be considered in load transfer analysis. In this paper, a load transfer analysis was performed by using data obtained from bi-directional pile load tests for four cases of drilled shafts. For consideration of nonlinearity, elastic modulus was calculated by both the Fellenius method and the nonlinear method, assuming the stress-strain relation of concrete to be a quadratic function, and then, the calculated elastic modulus was applied to the estimation of shaft resistance. The calculated shaft resistances were compared with the result obtained using the constant elastic modulus of ACI code. It was found that the f-w curves are similar to each method, and elastic modulus and shaft resistances decreased as strain increased. Moreover, shaft resistances estimated from elastic modulus considering nonlinearity were 5~15% different than those obtained using the constant elastic modulus.

• Journal of Mechanical Science and Technology
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• 제20권6호
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• pp.819-827
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• 2006

The stress-strain relation of aluminum (Al) alloy foam cell wall was evaluated by the instrumented sharp indentation method. The indentation in a few micron ranges was performed on the cell wall of Al-alloy foam having a composition or Al-3wt.%Si-2wt.%Cu-2wt.%Mg as well as its precursor (material prior to foaming). To extract the stress-stram relation in terms of yield stress ${\sigma}_y$, strain hardening exponent n and elastic modulus E, the closed-form dimensionless relationships between load-indentation depth curve and elasto-plastic property were used. The tensile properties of precursor material of Al-alloy foam were also measured independently by uni-axial tensile test. In order to verify the validity of the extracted stress-strain relation, it was compared with the results of tensile test and finite element (FE) analysis. A modified cubic-spherical lattice model was proposed to analyze the compressive behavior of the Al-alloy foam. The material parameters extracted by the instrumented nanoindentation method allowed the model to predict the compressive behavior of the Al-alloy foam accurately.

• Journal of Hydrospace Technology
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• 제2권2호
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• pp.80-87
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• 1996

A creep-buckling analysis is studied for a simply-supported viscoelastic column. The fluid-type four-parameter model is employed because of its general applicability to creep materials. Using the imperfection-based incremental approach, a nonlinear load deflection equation is derived. Safe load and critical (or life) time which characterize the stability of the viscoelastic column are obtained mathematically and interpreted physically. A finite difference algorithm is applied to solve the second-order differential equation of the viscoelastic stress-strain relation. Numerical calculation has been made and discussed far a SUS316 stainless steel column.