• 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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• 제19권4호
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• pp.967-993
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• 2015

The aim of this paper is to investigate the appropriateness of current codes of practice for predicting the axial load capacity of high-strength Concrete Filled Steel Tubular Columns (CFSTCs). Australian/New Zealand standards and other international codes of practice for composite bridges and buildings are currently being revised and will allow for the use of high-strength CFSTCs. It is therefore important to assess and modify the suitability of the section and ultimate buckling capacities models. For this purpose, available experimental results on high-strength composite columns have been assessed. The collected experimental results are compared with eight current codes of practice for rectangular CFSTCs and seven current codes of practice for circular CFSTCs. Furthermore, based on the statistical studies carried out, simplified relationships are developed to predict the section and ultimate buckling capacities of normal and high-strength short and slender rectangular and circular CFSTCs subjected to concentric loading.

• Steel and Composite Structures
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• 제4권1호
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• pp.1-8
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• 2004

Tests on steel tubular columns of square, rectangular and circular section filled with normal and lightweight aggregate concrete were conducted to investigate the failure modes of such composite columns. Thirty-six full scale columns filled with lightweight and normal weight aggregate concrete, eighteen specimens for each, were tested under axial loads. Nine hollow steel sections of similar specimens were also tested and results were compared to those of filled sections. The test results were illustrated by a number of load-deflection and axial deformation curves. The results showed that both types of filled columns failed due to overall buckling, while hollow steel columns failed due to bulging at their ends (local buckling). According to the above-mentioned results, and due to low specific gravity and thermal conductivity of the lightweight concrete the further interest should be concentrated in replacing the normal concrete by the lightweight aggregate concrete.

• Structural Engineering and Mechanics
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• 제10권6호
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• pp.577-587
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• 2000

A 3D nonlinear finite element computation model is presented in order to analyze the concrete filled rectangular tubular (CFRT) composite structures. The concrete material model is based on a hypo-elastic orthotropic approach while the elasto-plastic hardening model is employed for steel element. The comparisons between experimental and analytical results show that the proposed model is a relatively simple and effective one. The analytical results show that the capacity of inner concrete of CFRT column mainly depends on the two diagonal zones, and the confining effect of CFRT section is mainly concentrated on the corner zones. At the ultimate state, the side concrete along the section cracks seriously, and the corner concrete softens with the increase of compressive strains until failure.

• Structural Engineering and Mechanics
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• 제9권4호
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• pp.365-374
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• 2000

The structural behavior of connections between concrete-filled rectangular tubular column (CFRT column) and steel beam has been studied in this paper through sub-assemblage loading tests. It is found that the sub-assemblages exhibit ductile restoring force characteristics under seismic loading. A formula for the prediction of the yield strength of each member in the connection is proposed by using the yield line theory under the assumption of a simple stress transfer mechanism. It is shown that the proposed formula can produce a reasonable prediction while providing a basis for further investigation.

• Interaction and multiscale mechanics
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• 제5권2호
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• pp.91-104
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• 2012

There is relatively little numerical study on the behavior of eccentrically loaded high strength rectangular concrete-filled steel tubular (CFST) slender beam-columns with large depth-to-thickness ratios, which may undergo local and global buckling. This paper presents a multiscale numerical model for simulating the interaction local and global buckling behavior of high strength thin-walled rectangular CFST slender beam-columns under eccentric loading. The effects of progressive local buckling are taken into account in the mesoscale model based on fiber element formulations. Computational algorithms based on the M$\ddot{u}$ller's method are developed to obtain complete load-deflection responses of CFST slender beam-columns at the macroscale level. Performance indices are proposed to quantify the performance of CFST slender beam-columns. The accuracy of the multiscale numerical model is examined by comparisons of computer solutions with existing experimental results. The numerical model is utilized to investigate the effects of concrete compressive strength, depth-to-thickness ratio, loading eccentricity ratio and column slenderness ratio on the performance indices. The multiscale numerical model is shown to be accurate and efficient for predicting the interaction buckling behavior of high strength thin-walled CFST slender beam-columns.

• Steel and Composite Structures
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• 제22권5호
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• pp.937-974
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• 2016

While extensive efforts have been made in the past to develop finite element models (FEMs) for concrete-filled steel tubular columns (CFSTCs), these models may not be suitable to be used in some cases, especially in view of the utilisation of high strength steel and high strength concrete. A method is presented herein to predict the complete stress-strain curve of concrete subjected to tri-axial compressive stresses caused by axial load coupled with lateral pressure due to the confinement action in square and rectangular CFSTCs with normal and high strength materials. To evaluate the lateral pressure exerted on the concrete in square and rectangular shaped columns, an accurately developed FEM which incorporates the effects of initial local imperfections and residual stresses using the commercial program ABAQUS is adopted. Subsequently, an extensive parametric study is conducted herein to propose an empirical equation for the maximum average lateral pressure, which depends on the material and geometric properties of the columns. The analysis parameters include the concrete compressive strength ($f^{\prime}_c=20-110N/mm^2$), steel yield strength ($f_y=220-850N/mm^2$), width-to-thickness (B/t) ratios in the range of 15-52, as well as the length-to-width (L/B) ratios in the range of 2-4. The predictions of the behaviour, ultimate axial strengths, and failure modes are compared with the available experimental results to verify the accuracy of the models developed. Furthermore, a design model is proposed for short square and rectangular CFSTCs. Additionally, comparisons with the prediction of axial load capacity by using the proposed design model, Australian Standard and Eurocode 4 code provisions for box composite columns are carried out.

• 한국강구조학회 논문집
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• 제27권2호
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• pp.219-229
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• 2015

각형 CFT 기둥에 대한 실험 연구를 수행하였다. 본 연구는 세장 단면의 고강도 강관을 적용한 CFT 기둥의 압축성능 평가하는 것이 주요 목적이다. 실험 변수는 강관의 판폭두께비, 콘크리트 강도, 강관 항복강도, 그리고 스티프너의 사용여부이다. 총 5개의 기둥 실험체에 대하여 중심압축 실험을 수행하였다. 고강도 강관을 적용한 실험체는 탄성국부좌굴이 발생하였지만, 높은 항복강도로 인하여 상당한 후좌굴강도를 발휘하였다. 또한, 실험결과는 현행 설계기준에 의한 예상강도를 대체로 만족하였다. 세장 단면의 고강도 강관에 스티프너를 보강할 경우 강도와 변형능력 면에서 우수한 구조성능을 발휘하였다.

• 한국공간구조학회논문집
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• 제6권1호
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• pp.55-63
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• 2006

본 논문은 콘크리트 충전 원형 및 각형 합성 강관을 기둥부재로서의 적합성 및 적용성을 위한 연구로 두개의 강관을 합성한 콘크리트 충전 강관 기둥의 축압축 좌굴내력 및 변형형상에 대한 실험적 연구이다. 강관 기둥에 대한 연구는 콘크리트 충전 원형 강관 기둥, 콘크리트 충전 각형 강관 기둥, 콘크리트 충전 합성 강관 기둥으로 분류하여 실험을 수행하였다.

• Computers and Concrete
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• 제25권1호
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• pp.1-14
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• 2020

This study presents applications of the multivariate adaptive regression splines (MARS) method for predicting the ultimate loading carrying capacity (N_u) of rectangular concrete-filled steel tubular (CFST) columns subjected to eccentric loading. A database containing 141 experimental data was collected from available literature to develop the MARS model with a total of seven variables that covered various geometrical and material properties including the width of rectangular steel tube (B), the depth of rectangular steel tube (H), the wall thickness of steel tube (t), the length of column (L), cylinder compressive strength of concrete (f'_c), yield strength of steel (f_y), and the load eccentricity (e). The proposed model is a combination of the MARS algorithm and the grid search cross-validation technique (abbreviated here as GS-MARS) in order to determine MARS' parameters. A new explicit formulation was derived from MARS for the mentioned input variables. The GS-MARS estimation accuracy was compared with four available mathematical methods presented in the current design codes, including AISC, ACI-318, AS, and Eurocode 4. The results in terms of criteria indices indicated that the MARS model was much better than the available formulae.