• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.567-572
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• 2001

A transmission of load that is transmitted by beam in steel beam-column joint depends 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 a reinforcement about a transmission of load. An ascent of bond stress and a transmission of load after debonding are expected by a reinforcement of shear-connector.

• 한국공간구조학회논문집
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• 제3권3호
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• pp.105-110
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• 2003

This paper is presented an experimental studies on bond stress between steel and concrete in concrete filled Rectangular steel tubes. In the actual building frames, vertical dead and live loads on beams are usually transferred to columns by beam-to-column connections. In case when concrete filled steel tubes are used as columns of an actual building frame which has a simple connection, shear forces in the beam ends are not directly transferred to the concrete core but directly to the steel tube. Provided that the bond effect between steel tube and concrete core should not be expected, none of the end shear in the beams would be transferred to the concrete core but only to the steel tube. Therefore, it is important to investigate the bond strength between steel tube and concrete core in the absence of shear connectors.

• Steel and Composite Structures
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• 제25권3호
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• pp.375-388
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• 2017

This paper presents a combined experimental, numerical, and analytical study on elliptical concrete-filled steel tubular (E-CFT) and rebar-stiffened elliptical concrete-filled steel tubular (RE-CFT) subjected to axial loading. ABAQUS was used to establish 3D finite element (FE) models for the composite columns and the FE results agreed well with the experimental results. It was found that the ultimate load-bearing capacity of RE-CFT stub columns was 20% higher than that of the E-CFT stub columns. Such improvement was attributed to the reinforcement effects from the internal rebar-stiffeners, which effectively enhanced the confinement effect on the core concrete, thereby significantly improved both the ultimate bearing capacity and the ductility of the E-CFT columns. Based on the results, equations were also established in this paper to predict the bearing capacities of E-CFT and RE-CFT stub columns under axial loading. The predicted results agreed well with both experimental and numerical results, and had much higher accuracy than other available methods.

• Structural Engineering and Mechanics
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• 제56권5호
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• pp.727-743
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• 2015

According to former studies, the mechanical properties of reinforced concrete filled tubular steel (RCFT) columns differed greatly from that of concrete filled steel tubular (CFT) columns because of interaction of inserted reinforcement in RCFT. Employing an experiment-based verification policy, a general FE nonlinear analysis model was developed to analyze the mechanical behavior and failure mechanism of RCFT columns under uniaxial compression. The reasonable stress-strain relationships were suggested for confined concrete, reinforcements and steel tube in the model. The mechanism for shear failure of concrete core was found out in the numerical simulation, and a none-conventional method and equation for evaluating the confinement effect of RCFT were proposed.

• 한국구조물진단유지관리공학회 논문집
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• 제9권3호
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• pp.195-202
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• 2005

본 연구에서는 순수 휨을 받는 중공 원형강관, 내부에 경량기포콘크리트 및 보통콘크리트를 충전한 원형강관 부재에 대하여 강재의 압축부에 대한 좌굴특성을 고려하고, 충전된 콘크리트의 삼축압축응력 발생에 따른 강도증가 현상을 고려하여 모멘트-곡률 관계를 계산하였다. 경량기포콘크리트를 충전하더라도 해석적으로 간편하게 모멘트-곡률 관계를 계산할 수 있다는 것을 확인하였으며, 보통콘크리트를 충전한 경우에는 해석값이 실험값에 근접한 결과를 추정함을 알 수 있었다. 또한 기존의 실험결과를 이용하여 본 연구에서 개발된 모멘트-곡률 관계 해석방법의 유효성을 검증하였다.

• Steel and Composite Structures
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• 제42권5호
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• pp.617-631
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• 2022

To study the eccentric compressive performance of the basalt-fiber reinforced recycled aggregate concrete (BFRRAC)-filled circular steel tubular stub column, 8 specimens with different replacement ratios of recycled coarse aggregate (RCA), basalt fiber (BF) dosage, strength grade of recycled aggregate concrete (RAC) and eccentricity were tested under eccentric static loading. The failure mode of the specimens was observed, and the relationship curves during the entire loading process were obtained. Further, the load-lateral displacement curve was simulated and verified. The influence of the different parameters on the peak bearing capacity of the specimens was analyzed, and the finite element analysis model was established under eccentric compression. Further, the design-calculation method of the eccentric bearing capacity for the specimens was suggested. It was observed that the strength failure is the ultimate point during the eccentric compression of the BFRRAC-filled circular steel tubular stub column. The shape of the load-lateral deflection curves of all specimens was similar. After the peak load was reached, the lateral deflection in the column was rapidly increased. The peak bearing capacity decreased on enhancing the replacement ratio or eccentric distance, while the core RAC strength exhibited the opposite behavior. The ultimate bearing capacity of the BFRRAC-filled circular steel tubular stub column under eccentric compression calculated based on the limit analysis theory was in good agreement with the experimental values. Further, the finite element model of the eccentric compression of the BFRRAC-filled circular steel tubular stub column could effectively analyze the eccentric mechanical properties.

• 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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• 제18권1호
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• pp.71-90
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• 2015

Axial compression tests have been carried out on 18 rectangular concrete-filled cold-formed steel tubular (CFST) columns with the aim of investigating the axial behaviour of rectangular CFST columns under different loading methods (steel loaded-first and full-section loaded methods). The influence of different loading methods on the ultimate strength of the specimens was compared and the development of Poisson's Ratio as it responds to an increasing load was reported and analysed. Then, the relationship between the constraining factor and the strength index, and the relationship between the constraining factor and ductility index of the specimens, were both discussed. Furthermore, the test results of the full-section loaded specimens were compared with five international code predicted values, and an equation was derived to predict the axial carrying capacity for rectangular CFST columns with a steel loaded-first loading method.

• Steel and Composite Structures
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• 제16권6호
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• pp.639-655
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• 2014

The mechanical characteristic of reinforced concrete filled steel tubular (RCFT) structures are differed from that of concrete filled tubular steel (CFT) structures because the reinforcement in RCFT largely affects the performance of core concrete such as ductility, strength and toughness, and hence the performance of RCFT should be evaluated differently from CFT. To examine the effect axial reinforcement on bending performance, an investigation on RCFT beams with varying levels of axial reinforcement is performed by the means of numerical parametric study. According to the numerical simulation results with 13 different ratios of axial reinforcement, it is concluded that the reinforcement has obvious effect on bending capacity, and the neutral axis of RCFT is different from CFT, and an evaluation equation in which the effect of axial reinforcement is considered for ultimate bending strength of RCFT is proposed.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1996년도 봄 학술발표회 논문집
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• pp.382-387
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• 1996

Three concrete filled steel tubular columns with six inner diaphrams are constructed and tested under field conditions. The size and shape of three columns are exactly same. The cross section is $40\times40cm$, and the height is 9m. Each column is constructed with normal concrete, CFST concrete, and high flowing concrete, respectively. Concrete is pumped into bottom parts of steel tubular columns from a concrete pump on the ground. Test data indicate that the slump flow of the concrete place in the top of the column is lower than that of the concrete before pumping by about 10~20cm. Slump flow loss of high flowing concrete caused by pumping is high compared to the other concretes. Concrete pump pressure of high flowing concrete is somewhat higher than that of CFST concrete.