• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.163-163
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• 2011

풍력타워 기둥구조물에는 유지관리 등의 이유로 출입구 역할을 하는 개구부가 존재하게 된다. 다각형 타워구조물에 개구부형상이 존재하게 되면 압축좌굴 강도에 영향이 있을 것으로 예상되지만, 이를 정량적으로 평가하거나 예측하기는 용이하지 않고 간접적으로 판단할 만한 관련 기준이나 지침도 부족한 상태이다. 이에 최병호 등(2011)에서 다룬 다각형 단면 기둥구조물의 하단에 개구부를 형상화한 수치해석 모델을 수립하고 축방향 압축하중을 재하하는 탄성좌굴 해석 및 비선형비탄성해석을 수행하였다. 본 논문에서는 기존 다각형 단면 기둥모델 중에서 6각형 단면모델에 관해 중점적으로 다루고 있다. 다각형 단면 기둥 해석모델은 단순한 다각형 단면 타워구조에 대해서 뿐 만 아니라, 각 subpanel에 종방향 보강재를 둔 모델에 대해서도 추가적으로 검토하였다. 개구부의 형상은 높이 2000mm, 폭 800mm이며 상하부에 만곡부를 둔 형태이다. 수치해석은 3차원 유한요소해석프로그램인 ABAQUS를 이용하여 수행하였으며, 보강방안으로는 일정범위까지의 모듈 subpanel의 판두께를 보강하는 방안과 edge stiffener를 적용하는 방안에 대해서 검토하였다. 각각의 보강방식에 따른 효과를 비교해 보기 위해 개구부가 없는 모델, 단순히 개구부만 설정한 모델, 판두께를 보강한 모델, edge stiffener로 보강한 모델에 대해 비교해석을 수행하였다. 보강재 없는 단순 다각형 타워구조 모델에 대한 해석결과로부터 개구부로 인한 강도저하는 미미한 수준인 것으로 나타났다. 반면, 종방향 보강재가 적용된 6각형 단면 타워구조 모델에서는 개구부로 인한 강도저감이 22.9%로 높게 나타났으며 상당한 영향이 있는 것으로 분석되었다. 또한 개구부 주변의 판두께 보강이나 edge stiffener보강 등으로 상당한 강도향상 효과가 확인되었으나, 개구부로 인해 손실된 강도 수준을 완전히 회복하는 수준에 미치지 못하는 것으로 나타났다. 따라서, 향후 다양한 보강방식에 대한 보다 포괄적인 변수연구를 통해 개구부의 영향 없이 온전한 다각형 단면 타워 구조의 극한강도에 도달되기 위한 보강 조건에 대해 검토될 필요가 있을 것으로 사료된다.

• Journal of Korean Society of Steel Construction
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• v.20 no.1
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• pp.81-92
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• 2008

Generally the connection of members is defined as hinge or rigid. But, real joints on structure have to be considered semi-rigid connections because this permits relative rotation for members on joints. The purpose of this study is to derive a generalized tangential stiffness matrix of frames with semi-rigid connections and to develop a buckling analysis program. For the exact stiffness matrix, an accurate displacement field is introduced using an equilibrium equation for beam-columns under the bending and axial forces. Also, stability functions that consider sway deformation and force-displacement relations with rotational spring on ends were defined. In order to illustrate the accuracy of this study and the characteristics of semi-rigid for system buckling load, samples of angle-, portal- and 3-story frames with semi-rigid connections are presented, where the proposed approach is found to be in excellent agreement with other research results. Meanwhile, the application of codes such as Eurocode 3 and LRFD led to significant inaccuracies.

• Journal of Korean Association for Spatial Structures
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• v.7 no.3 s.25
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• pp.79-86
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• 2007

Recently, as steel structures become higher and more long-spanned, construction of high-strength steels is increasing gradually. Application of high-strength steel can be possible to make a more light and economic steel structures by reducing thickness and space. To apply a high-strength steel to structure, criteria of high-strength steel for buckling is required. However, current specification is not sufficient for criteria of high-strength steels. In this paper, buckling behavior of high-strength steel truss columns with box sections is investigated by using three-dimensional elastic-plastic finite deformation analysis program. The criteria equation for allowable compressive stress of high-strength steel truss columns with box sections is proposed and confirmed the applicability. It is reasonable form analytical results that formulated equations after finding the upper limit of allowable axial direction compression stresses of high-strength steel truss columns. And new equation is suitable to buckling design of high-strength steel truss columns.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.1
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• pp.1-11
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• 2013

In this study, in order to increase the span length, the temporary bridge which the center part of span is strengthened by small H-beam and the end part of span is strengthened by steel plate is designed and constructed. Real behavior of proposed temporary bridge is analyzed by field loading test. Analyzed shear buckling strengths and nonlinear behavior of suggested temporary bridge are compared with the those of general temporary bridge. From the field loading test results, it is analyzed that real static behavior of suggested temporary bridge is agree with the analyzed behavior which is considered in design process. Under the proposed design condition, it is investigated that the shear buckling strength of suggested temporary bridge is about 40% higher than that of general temporary bridge, and the ultimate strength of suggested temporary bridge is about higher than that of general temporary bridge. From the study results, it is concluded that the proposed temporary bridge can be applied by the needs of field condition.

• Journal of Korean Society of Steel Construction
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• v.20 no.4
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• pp.549-559
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• 2008

The objective of this paper is to identify the compression forces and inelastic failure mode using stiffened steel plate-concrete structures. The compression tests were carried out for the three types of B/t ratios by 25, 33 and 50. The test results proved that the compressive strength of the stiffened SC structures can be estimated by the summation of the strengths both stiffened steel plate and concrete. The buckling of the steel plates had been occurred at the plates between studs. The empirical estimation of compressive strength for the stiffened SC structures under compressive loadings was suggested. The buckling behavior also compared with the results of the finite element analysis. The good agreement has been achieved between the experimental results and finite element results.

• Magazine of the Korea Concrete Institute
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• v.5 no.2
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• pp.129-139
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• 1993

본 연구에서는 철근콘크리트 기둥의 거동을 예측하기 위하여 층상화 방법을 이용한 유한요소 해석방법이 제안되었다. 콘크리트의 강도와 철근비가 기둥의 극한강도와 거동에 미치는 영향을 규명하기 위하여 세장비가 10, 60, 100인 정방형 단면(80$\times$80mm)을 갖는 30개의 기둥에 대하여 실험을 수행하였다. 이때, 콘크리트의 강도는 25.5, 63.5, 86.2MPa로, 철근비는 1.98, 3.95%로 변화시켰다. 또한, 단부조건은 양단힌지로 하고, 편심량은 기둥은 양단에서 같은 방향으로 24mm로 동일하게 하였다. 본 연구에서 제안된 해석방법은 철근콘크리트 기둥의 거동을 잘 예측하며, ACI의 모멘트 확대계수법은 고강도 콘크리트 장주에 대해서는 안전측이 아닌 것으로 나타났다. 콘크리트의 강도가 기둥의 극한강도에 미치는 영향은 기둥의 세장비가 증가할수록 감소하였으며, 콘크리트의 강도가 커질수록 세장기둥의 좌굴파괴 가능성은 증가하였다. 또한, 철근비를 증가시킬 경우, 기둥의 축력이 최대가 될 때의 모멘트가 증가되었으며, 기둥의 극한강도 증가량은 단주보다는 장주에서 더 크게 나타났다. 철근비 증가에 의해 나타나는 이러한 기둥의 극한강도 증가량과 모멘트 증가량은 콘크리트의 강도가 커질수록 증대되었다.

• Journal of Korean Society of Steel Construction
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• v.17 no.1 s.74
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• pp.53-62
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• 2005

The purpose of this study is to improve the seismic behavior of the bracing members. Lee and Goel's (1987) concrete filling in the hollow structural section (HSS) reduced the severity of local buckling and increased the fracture life. However, concrete filling in the HSS did not prevent the occurrence of local buckling in the midsection of the bracing member, which resulted in continuous strength degradation. This study investigated the seismic behavior of the concrete-filled HSS bracing member, which is reinforced by ribs in the midsection of the bracing member. The main variable of the specimens is rib length. The test results showed that buckling mode, cyclic compression strength, and energy dissipation capacity of the bracing members were affected by rib length. Specimen reinforced with ribs with a length of 63% had better structural performance.

• Journal of Korean Society of Steel Construction
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• v.25 no.2
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• pp.115-130
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• 2013

In this study, lateral-torsional buckling (LTB) strength of high-strength H-beams built up from 800MPa tensile-strength steel was experimentally and analytically evaluated according to current lateral stability provisions (KBC 2009, AISC-LRFD 2010). The motivation was to evaluate whether or not current LTB provisions, which were originally developed for ordinary steel with different stress-strain characteristics, are still applicable to high-strength steel. Two sets of compact-section specimens with relatively low (Set A) or high (Set B) warping stiffness were prepared and tested under uniform moment loading. Laterally unbraced lengths of the test specimens were controlled such that inelastic LTB could be induced. All specimens exhibited LTB strength exceeding the minimum limit required by current provisions by a sufficient margin. Moreover, some specimen in Set A reached a rotation capacity required for plastic design, although its laterally unbraced length belonged to the inelastic LTB range. All the test results indicated that extrapolation of current provisions to high-strength steel is conservative. In order to further analyze the test results, the relationship between inelastic moment and laterally unbraced length was also derived in explicit form for both ordinary- and high-strength steel based on the effective tangent modulus of inelastic section. The analytical relationship derived again showed that extrapolation of current laterally unbraced length limit leads to a conservative design in the case of high-strength steel and that the laterally unbraced length to control the inelastic LTB behavior of high-strength steel beam should be specified by including its unique post-yield strain-hardening characteristics.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.1A
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• pp.9-18
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• 2011

Generally the connection of structural members is assumed as hinge, rigid and semi-rigid connections. The exact tangent stiffness matrix of a semi-rigid frame element is newly derived using the stability functions considering shear deformations. Also, linearized elastic- and geometric-stiffness matrices of shear deformable semi-rigid frame are newly proposed. For the exact stiffness matrix, an accurate displacement field is introduced by equilibrium equation for beam-column under the bending and the axial forces. Also, stability functions considering sway deformation and force-displacement relations with elastic rotational spring on ends are defined. In order to illustrate the accuracy of this study, various numerical examples are presented and compared with other researcher's results. Lastly, shear deformation and semi-rigid effects on buckling behaviors of structure are parametrically investigated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.1
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• pp.106-114
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• 2001

In this study, a shape optimization of stiffener was conducted to increase buckling load or failure load in each case with a different design value and a different objective function for stiffened laminated composite panel of I-type under compression loading. Regarding each of buckling load or failure load as objective function, optimum design was carried out. In respect of optimum design, the effects of relative length of web and cab of stiffener on buckling load or failure load of postbuckling were investigated.