• 콘크리트학회논문집
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• 제17권2호
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• pp.281-290
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• 2005

이 연구에서 중심축 하중을 받는 각형 CFT 기둥의 장기거동에 관한 실험과 해석을 수행하였으며, 이를 통해 각형 CFT 기둥의 장기거동을 예측할 수 있는 방법을 모색하고 그 거동 특성을 파악해 보고자 하였다. 중심축 하중에 대해 두 가지 가압 방법이 고려되었다. 첫째는 콘크리트에만 하중이 가해지는 경우이고, 둘째는 콘크리트와 강관에 동시에 하중이 가해지는 경우이다. 각형 CFT 기둥 실험체에 대한 삼차원 유한요소 모델로 해석을 수행하였으며, 해석결과는 실험결과를 매우 정확히 모사하였다. 따라서 강관과 콘크리트의 부착거동을 고려한 3차원 유한요소 모델링으로부터 실제 각형 CFT 기둥에 대한 장기거동 예측이 가능할 것으로 판단된다. 또한 실험과 해석결과로부터 다음의 거동 특성을 파악하였다. 콘크리트에만 하중이 가해지는 경우 구속압에 의해 유발되는 부착응력은 시간에 따라 증가하며, 강관과 콘크리트 사이의 미끄럼 또한 시간에 따라 증가한다. 강관에 의한 구속압은 시간에 따라 증가하는 반면. 가압판에 의한 구속압은 시간에 따라 감소한다. 강관과 콘크리트에 동시에 하중이 가해지는 경우 강관에 의한 콘크리트의 구속 효과와 미끄럼은 발생하지 않는다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
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• pp.427-430
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• 2005

The study for seismic characteristics of square concrete-filled steel tubular (CFT) columns is analytically conducted. For predicting the strength and ductility of CFT columns, fiber analysis technique is used. The analytical results show reasonable agreement with experiment results. The influence of the steel tube on the lateral response of CFT columns is studied for the evaluation of seismic performance.

• Steel and Composite Structures
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• 제8권6호
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• pp.491-510
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• 2008

This paper presents a plan and guidelines that were drawn for Korean based research carried out on the fire-resistance of CFT columns. This research was carried out by reviewing the Korean regulations related to the fire-resistance of CFT columns and examining studies which had been made in Korea as well as overseas. The first phase of the study plan was to compare the fire-resistance of square CFT columns without fire protection (obtained through fire-resistance tests and numerical analyses) with estimated values (obtained through fire-resistance design formulas proposed in Korea and overseas). This comparison provided conclusions as outlined below. Fire-resistance tests conducted in this study proved that, when the actual design load is taken into consideration, square CFT columns without fire protection are able to resist a fire for more than one hour. A comparison was made of test and analysis results with the fire-resistance time based on the AIJ code, the AISC design formula and the estimation formula suggested for Korea. The results of this comparison showed that the test and analysis results for specimens SAH1, SAH2-1, SAH2-2 and SAH3 were almost identical with the AIJ code, the AISC design formula and estimation formula. For specimens SAH4 and SAH5, the estimation formula was more conservative than the AIJ code and the AISC design formula. It was necessary to identify the factors that have an influence on the fire-resistance of CFT columns without fire protection and to draw fire-resistance design formulas for these columns. To achieve this, it is proposed that numerical analyses and tests be conducted in order to evaluate the fire-resistance of circular CFT columns, the influence of eccentricity existing as an additional factor and the influence of the slenderness ratio of the columns. It is also suggested that the overall behavior of CFT structures without fire protection within a fire be evaluated through analysis simulation.

• Steel and Composite Structures
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• 제33권2호
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• pp.181-194
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• 2019

This paper presents an efficient approach to generate a new empirical formula to predict the axial compression capacity (ACC) of circular concrete-filled tube (CCFT) columns using the artificial neural network (ANN). A total of 258 test results extracted from the literature were used to develop the ANN models. The ANN model having the highest correlation coefficient (R) and the lowest mean square error (MSE) was determined as the best model. Stability analysis, sensitivity analysis, and a parametric study were carried out to estimate the stability of the ANN model and to investigate the main contributing factors on the ACC of CCFT columns. Stability analysis revealed that the ANN model was more stable than several existing formulae. Whereas, the sensitivity analysis and parametric study showed that the outer diameter of the steel tube was the most sensitive parameter. Additionally, using the validated ANN model, a new empirical formula was derived for predicting the ACC of CCFT columns. Obviously, a higher accuracy of the proposed empirical formula was achieved compared to the existing formulae.

• 한국기계가공학회지
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• 제10권6호
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• pp.56-62
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• 2011

In this study, a method for the press forming of rectangular aluminium tube has been proposed. Rectangular aluminium tube has high stiff as the cold steel which can be lighter over 30% weight. It is increased every year by being recycled over 80%. Press die consists of punch, wing-die and holder for aluminium tube bending. When punch is applied with aluminium tube, holder is operated as same punch and wing-die is rotated through hinge. Stress-strain relations and springback are considered by bending angle of aluminium tube. In this study, the behaviors on tubes of square aluminium and rectangular aluminium with different thickness and area are established by the analysis of $DEFORM^{TM}$-3D program. Reducing fuel consumption is expected by using the aluminium tube deformation and it becomes the lightweight through recycling.

• Steel and Composite Structures
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• 제18권4호
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• pp.833-852
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• 2015

Self-compacting Concrete Filled steel Tubes (SCFT), which combines the advantages of steel and concrete materials, can be applied to strengthen the RC columns. In order to investigate the eccentric loading behavior of the strengthened columns, this paper presents an experimental and numerical investigation on them. The experimental results showed that the use of SCFT is interesting since the ductility and the bearing capacity of the RC columns are greatly improved. And the performance of strengthened columns is significantly affected by four parameters: column section type (circular and square), wall thickness of the steel tube, designed strength grade of strengthening concrete and initial eccentricity. In the numerical program, a generic fiber element model which takes in account the effect of confinement is developed to predict the behavior of the strengthened columns subjected to eccentric loading. After the fiber element analysis was verified against experimental results, a simple design formula based on the model is proposed to calculate the ultimate eccentric strength. Calibration of the calculated results against the test results shows that the design formula closely estimates the ultimate capacities of the eccentrically compressed strengthened columns by 5%.

• Steel and Composite Structures
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• 제30권2호
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• pp.171-183
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• 2019

As China's infrastructure continues to grow, concrete filled steel tubular (CFST) structures are attracting increasing interest for use in engineering applications in earthquake prone regions owing to their high section modulus, high strength, and good seismic performance. However, in a corrosive environment, the seismic resistance of the CFST columns may be affected to a certain extent. This study attempts to investigate the mechanical behaviours of square CFST members under both a cyclic load and an acid rain attack. First, the tensile mechanical properties of steel plates with various corrosion rates were tested. Second, a total of 12 columns with different corrosion rates were subjected to a reversed cyclic load and tested. Third, comparisons between the test results and the predicted ultimate strength by using four existing codes were carried out. It was found that the corrosion leads to an evident decrease in yield strength, elastic modulus, and tensile strain capacity of steel plates, and also to a noticeable deterioration in the ultimate strength, ductility, and energy dissipation of the CFST members. A larger axial force ratio leads to a more significant resulting deterioration of the seismic behaviour of the columns. In addition, the losses of both thickness and yield strength of an outer steel tube caused by corrosion should be taken into account when predicting the ultimate strength of corroded CFST columns.

• 한국공간구조학회논문집
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• 제8권5호
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• pp.83-93
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• 2008

국민소득수준의 향상에 따라 국내 건축물의 디자인 및 사용목적의 대한 다양성이 요구되고 있다. 대공간 구조물은 이러한 시대적 요구에 적합한 구조물로서 최근 대공간 구조물에 대한 설계 및 시공법에 관한 관심이 꾸준히 증가하고 있다. 트러스구조는 대공간 구조에 보편적으로 사용되는 구조시스템으로 트러스의 부재는 단면의 효율이 높은 강관을 사용하는 것이 일반적이다. 현재 국내에 유통되고 있는 강관은 생산처에 따라 다양한 제품이 생산되고 있으나 강관 소재의 출처 및 강관 자체의 실제 성능에 관한 연구는 미비한 실정이다. 이 연구는 국내에 유통되고 있는 일반구조용 각형강관, 원형강관 및 비계용 강관에 대하여 소재의 인장시험과 Stub-column 압축시험 및 기둥의 좌굴실험을 통해 강관의 소재성능 및 구조부재로서의 압축성능을 파악하는 것을 목적으로 한다. 소재시험결과, 구입처 구분 및 단면형상에 따른 강관 소재성능의 편차가 확인되었다. 기둥좌굴 실험결과, 각 실험체의 압축내력은 LSD 기준곡선에 만족하는 결과를 나타내었으며, SSRC 곡선1, ECCS-a곡선에 상회하는 결과를 나타내었다.

• 한국강구조학회 논문집
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• 제26권6호
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• pp.499-509
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• 2014

본 연구에서는 해결방안으로 내부 콘크리트를 강섬유와 혼입하여 기둥자체의 연성과 인성을 증대시키는 것에 중점을 맞추고 있다. 즉, 강섬유 혼입량과 하중조건에 따른 내력 및 변형능력을 종합적으로 파악하여 강섬유 콘크리트와 용접조립각형 강관기둥의 상호작용을 구조, 내화측면에서 분석해 보고자 한다. 동일한 형상과 경계조건(하중비)에서 강섬유 혼입(0.375%)으로 내화성능은 약 1.1~1.3배 향상된 실험결과를 얻을 수 있었다. 강섬유 콘크리트의 균열 억제 특성은 열 하중에 의한 콘크리트의 변형저항 성능을 증가 시키면서 내화성능의 향상을 가져온 것으로 판단된다. 또한, 내부 리브의 열 변형에도 내부 콘크리트 단면은 건전한 상태로 남아있어 하중 분담능력이 증폭된 결과로 분석됐다.

• Steel and Composite Structures
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• 제3권3호
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• pp.199-212
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• 2003

An experimental investigation of lightweight aggregate and foamed concrete contribution to the ultimate strength capacity of square and rectangular steel tube sections is presented in this study. Thirty-four simply supported beam specimens, 1000-mm long, filled with lightweight aggregate and foamed concretes were tested in pure flexural bending to calculate the ultimate moment capacity. Normal concrete-filled steel tubular and bare steel sections of identical dimensions were also tested and compared to the filled steel sections. Theoretical values of ultimate moment capacity of the beam specimens were also calculated in this study for comparison purposes. The test results showed that lightweight aggregate and foamed concrete significantly enhance the load carrying capacity of steel tubular sections. Furthermore, it can be concluded from this study that lightweight aggregate and foamed concretes can be used in composite construction to increase the flexural capacity of the steel tubular sections.