• Steel and Composite Structures
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• 제22권6호
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• pp.1487-1505
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• 2016

This paper presents the results of an experimental study on the behavior of a new type of composite FRP-concrete-steel member subjected to bi-axial eccentric loading. This new type of composite member is in the form of concrete-filled square steel tube slender columns with inner CFRP (carbon fiber-reinforced polymer) circular tube, composed of an inner CFRP tube and an outer steel tube with concrete filled in the two tubes. Tests on twenty-six specimens of high strength concrete-filled square steel tube columns with inner CFRP circular tube columns (HCFST-CFRP) were carried out. The parameters changed in the experiments include the slenderness ratio, eccentric ratio, concrete strength, steel ratio and CFRP ratio. The experimental results showed that the failure mode of HCFST-CFRP was similar to that of HCFST, and the specimens failed by local buckling because of the increase of lateral deflection. The steel tube and the CFRP worked together well before failure under bi-axial eccentric loading. Ductility of HCFST-CFRP was better than that of HCFST. The ultimate bearing capacity of test specimen was calculated with simplified formula, which agreed well with test results, and the simplified formula can be used to calculate the bearing capacity of HCFSTF within the parameters of this test.

• Steel and Composite Structures
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• 제15권6호
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• pp.645-658
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• 2013

The objective of the study is to predict the moment anchorage capacity of the concrete filled steel box (CFSB) as footing by using the 3D finite element program CAMUI developed by authors' laboratory. The steel box is filled with concrete and concrete filled steel tube (CFT) column is inserted in the box. Numerical simulation of the experimental specimens was carried out after introducing the new constitutive model for post peak behavior of concrete in compression under confinement. The experimental program was conducted to verify the reliability of the simulation results by the FE program. The simulated peak loads agree reasonably with the experimental ones and was controlled by concrete crushing near the column. After confirming the reliability of the FEM simulation, effects of different parameters on the moment anchorage capacity of concrete filled steel box footing were clarified by conducting numerically parametric study.

• Steel and Composite Structures
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• 제45권1호
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• pp.23-38
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• 2022

This paper presents experimental and analytical studies of eccentrically loaded concrete-filled double steel (CFDST) and concrete-filled double skin tube (DCFST) columns having outer stainless steel tube. Eighteen CFDST and DCFST column specimens were manufactured and tested to examine the strength and load-deflection responses. In the study, the main parameters were concrete strength, load eccentricity, cross section and slenderness. The strengths, load-deflection diagrams and failure patterns of the columns were observed. In addition, the tested CFDST and DCFST columns were analyzed to attain the capacity and load versus lateral deflection responses. The obtained theoretical results were compared with the test results. A parametric study was also performed to research the effects of the ratio of eccentricity (e/H_o) slenderness ratio (L/r), H_o/t_o ratio, H_i/t_i ratio and the concrete compressive strength on the behavior of columns. In this work, the obtained results indicated that the ductility and capacity of columns were affected by cross section, concrete strength, steel strength, loading eccentricity and slenderness.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.561-566
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• 2001

Load at steel beam column joints transfered by beam depend on bond strength between concrete and steel tube. But it is different to transmit a load efficiently in the established concrete filled steel tubular column. Therefore, shear-connector is demanded for transfering loads efficiently. An ascent of bond stress and a transmission of load after debonding are expected by a reinforcement of shear-connector

• Steel and Composite Structures
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• 제4권1호
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• pp.37-48
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• 2004

This paper deals with the strength and deformation of both short and slender concrete filled steel tubular columns under the combined actions of axial compression and bending moment. Sixteen specimens were tested to investigate the effect of fiber reinforced concrete on the ultimate strength and behavior of the composite column. The primary test parameters were load eccentricity and column slenderness. Companion tests were also undertaken on eight numbers of similar empty steel tubes to highlight the synergistic effects of composite column. The test results demonstrate the influence of fiber reinforced concrete on the strength and behavior of concrete filled steel tubular columns.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2008년도 춘계 학술논문 발표대회
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• pp.31-34
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• 2008

Construction of buildings downtown is increasing as much as ever with a strong demand. A Top-Down Method is suitable for its advantage in minimizing its disturbance to the neighborhood. In general, the Pre-founded Column, one of the most important aspects of the Top-Down Method, has been made with an H-Shape Steel Column. However, due to its structural and economical benefits, the usage of CFT(Concrete Filled Tube) columns in the place of Pre-founded Columns is increasing. To promote their applications, we analyze the merits of CFT columns by comparing them with I-Shape columns and propose further research.

• 복합신소재구조학회 논문집
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• 제6권2호
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• pp.32-39
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• 2015

So far, square concrete filled tubular(CFT) columns have been used in a limited width thickness ratio. The reason is that local buckling occurs in steel tube easily. Once the local buckling occurs, the confinement effect of steel tube on concrete disappears. In this study, we developed welded built-up square steel tube with reinforcement which are placed at the center of the tube width acts as an anchor. 3 specimens of slender welded built-up square CFT columns and 3 specimens of slender welded built-up square steel tube columns were manufactured with parameters of width(B) of steel tube, width thickness ratio(B/t). we conducted a experimental test on the 6 specimens under eccentric load, and evaluated the structural resistance and behavior of 6 specimens.

• 한국디지털건축인테리어학회논문집
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• 제11권2호
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• pp.31-39
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• 2011

Concrete-filled steel tube(CFT) columns have become popular for building construction due to not only composite effect of steel tube and infilled concrete, but also more economical. The purpose of this paper is to propose the applicable boundary formula of width-to-thickness ratio for rectangular steel tube as using CFT column. A parametric study was performed taking width-to-thickness ratio of rectangular steel tube and compressive strength of concrete as the main parameter. The strength of concrete are selected to 30, 60, 90MPa. The non-linear analysis was adopted in order to take into account the effect of concrete strength. Finally, from the test and analysis results, the effect of increasing strength according to concrete strength and width-to-thickness of steel tube and plastic behavior of specimens were verified distinctly.

• 한국강구조학회 논문집
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• 제20권5호
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• pp.645-653
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• 2008

용접조립 각형강관은 얇은 강판을 L형으로 절곡한 4개의 단위 부재를 플레어 용접으로 용접한 강관으로 용접조립 각형강관이 CFT 기둥으로 사용될 경우 콘크리트와 강관 폭의 중앙에 설치된 리브가 국부좌굴을 방지하는 역할을 하며 강관은 내부의 콘크리트의 구속하여 콘크리트의 구조내력을 향상시키는 역할을 한다. 본 연구에서는 용접조립 각형강관기둥의 제작방법을 소개하고 용접조립 각형강관과 용접조립 각형CFT 기둥 의 구조성능을 평가하기 위해 강관의 형상(용접조립 각형강관, 일반강관)과 폭두께비(B/t=50, 58, 67), 콘크리트의 강도(f'c=, 10MPa, 40MPa) 를 변수로 총 15개의 실대형 실험체를 제작하여 구조실험을 수행하였으며 용접조립 각형강관의 단면효율과 구조내력의 우수성을 확인하였다.

• 한국강구조학회 논문집
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• 제21권5호
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• pp.515-526
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• 2009

콘크리트 충전강관에 사용되는 강관의 제작법은 재단된 4장의 플레이트를 모서리에서 용접하는 일반강관 제작법과, ㄷ형으로 절곡성형과정을 거쳐 2-Seam으로 용접하는 제작방법, 그리고 원형강관을 압축하여 4각형태로 만드는 방법등이 일반적으로 사용되며, 강관제작에 사용되는 용접방법과 용접량의 선택은 강관 제작비용에 큰 부분을 차지하고 있다. 새로운 제작형식으로 개발된 각형강관은 4장의 플레이트를 ㄱ형으로 절곡성형한 후 강관 폭의 중앙에서 4-Seam Flare 용접하는 방식이다. 본 연구에서는 새로운 제작형식의 CFT 각형 기둥에 대하여 용접량 평가를 위한 실험방법을 제시하고, 강관 제작법, 강관두께 및 용접량을 변수로 총 6개의 실험체를 제작하여 구조실험 및 해석을 수행하여 강관내부의 수압에 따른 강관의 거동을 평가하였다.