• Journal of Korean Society of Steel Construction
• /
• v.9 no.4 s.33
• /
• pp.611-623
• /
• 1997

This paper provides the results of an experimental and analytical study performed on the beam to Concrete Filled Circular Steel Column connections with the external stiffener rings under the gravity loads. Specimens are modeled as a 1/4 scale of the beam-columns as gravity loads are applied to a multi-story frame. Important parameters in this study are the width of the external rings, the diameter-thickness ratios of column and whether or not the external rings are welded to the circular column. A total of 20 specimens are tested to clarify the structural behavior of the CFT column connections with the external stiffener rings. The test results are summarized for the yield and maximum strength and stiffness. The existing design equations for the allowable and yield load capacities are referred to verify the structural characteristics for the connections.

• Journal of Korean Society of Steel Construction
• /
• v.12 no.4 s.47
• /
• pp.437-443
• /
• 2000

In order to clarify the behavior of beam-to-concrete filled steel tube column under cyclic loading condition, experimental studies were carried out on shear connections. Test parameters of this study are the width-to-thickness ratio and the effect on beams with or without slab and diaphragm. Test results show that the moment-rotation relationships of connections without slab are in the range of AISC regulation of pinned connections and the rotation capacity of connection is dependent upon the width-to-thickness ratio of the column.

• Journal of Korean Association for Spatial Structures
• /
• v.6 no.3 s.21
• /
• pp.69-76
• /
• 2006

Concrete Filled Steel Tube (CFT) system is advantageous because it increases the load-carrying capacity without increasing the size of column. However CFT system has many benefits, it is not applied to field generally because of its heavyweight and difficulty of concrete filling method. As a solution to these problems, we proposed concrete filled steel tube column with hollow made by factory-manufactured PC method. The hollow concrete filled steel tube system is expected to obtain the high strength and high capacity of deformation despite it is a lightweight. This study deals with mechanical properties, strength and deformation, of hollow concrete filled steel tube subjected to axial load. 9 specimens were tested to examine mechanical properties closely, and the following results were obtained: All specimens basically showed higher initial rigidity and maximum strength with increased concrete filling rate. And most specimens showed almost linear behavior until around 80% of maximum strength regardless of filling rate, it is estimated that the elastic range is up to a half of the maximum strength which is the yield strength level.

• Journal of Korean Society of Steel Construction
• /
• v.11 no.4 s.41
• /
• pp.385-395
• /
• 1999

Square hollow section columns and H-section beams have recently been increasing1y used. Rigid column-beam connections cannot be made for the structural system and thus some measures to improve the rotational stiffness of connections should be developed. For this purpose, several types of connections. such as H-section beams connected to concrete-filled square hollow section columns, have been contrived and put to experiment. Since the experimental works are usually difficult and expensive. Particularly test of all the types of connections with similar behavior may not be feasible. Instead, the numerical analysis will be adopted predict the flexural stiffness of connections. In this work, FEM modeling techniques are examined and parametric analysis study has been carried out. The major parameters considered are concrete strength, thickness of steel column, magnitude and eccentricity of axial forces.

• Journal of Korean Society of Steel Construction
• /
• v.20 no.5
• /
• pp.655-663
• /
• 2008

In this research, the fire resistance of Concrete-Filled Circular Steel Tube Columns (CFT) was evaluated by numerical analysis. As the materials of CFT columns, the steel of SPSR 400 grade and the concrete of 27.5MPa, 37.8MPa strengths were used. Significant parameters,such as concrete strength, axial load, and cross-sectional dimensions were determined. To verify the accuracy of the numerical analysis,the analysis results were compared with the former experiment results. The effect of the fire resistance time, axial load ratio, cross-sectional dimensions and concrete strength was evaluated by comparison with the fire resistance of the square CFT columns. This research showed that the structural behavior and fire resistance from the findings of numerical parametric studies showed a similarity to that of the experimental results. Therefore, this numerical analysis is reasonable in estimating the fire resistance of the circular CFT column.

• Journal of Korean Society of Steel Construction
• /
• v.19 no.6
• /
• pp.703-714
• /
• 2007

The aim of this research is to evaluate the fire resistance of concrete-filled steel square tube columns (square CFT columns) under constant axial loads by numerical analysis. The authors examined the experimental results on the fire resistance of concrete-filled steel square tube columns without fire protection. As the materials of CFT columns, steel of SPSR 400 grade and concrete of 27.5MPa and 37.8MPa strengths were used. The significant parameters were determined, such as load ratio, cross-sectional dimensions, and concrete strength. Detailed analytical simulations of fire resistance and axial deformation showed good agreement with the experimental observations. Therefore, this numerical analysis exhibited a reasonable estimation of fire resistance of the square CFT column. Results of the numerical parametric studies showed that the fire resistance of the CFT columns increased with the decrease of the concrete strength and the increase of the cross-sectional dimensions about the constant axial load ratio ($N/N_c$).

• Magazine of the Korea Concrete Institute
• /
• v.13 no.3
• /
• pp.61-68
• /
• 2001

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.217-220
• /
• 2008

Recently, many studies about a high-strength concrete and composite structures are being progressed to get the more economic and stable result in the construction of structure all over the world. One of those studies is about CFTA(Concrete Filled and Tied Steel Tubular Arch) girder that applies an arch structure and a pre-stressed structure to CFT(Concrete Filled Steel Tubular) Structure which is filled with a concrete and improve the stiffness and strength of the structure by the confinement effect of fillers to maximize the efficiency of structure and economic. In this study, non-linear behavior of CFTA girders filled with a general concrete and the high-strength concrete respectively were analyzed by using ABAQUS 6.5-1 and results were compared.

• Journal of the Korea Institute of Building Construction
• /
• v.2 no.1
• /
• pp.163-169
• /
• 2002

In this study, there are kind of property experiments like fluidity, compressive strength, bleeding measurement, concrete sink for CFT use high fluidity concrete. The property difference between before transmit and after transmit concrete in the mock up test with ready mixed concrete equipment is examined. The variable factors in mock up are diaphragm existence and nonexistence, diaphragm placing hole sizes. To investing the concrete Property under diaphragm, concrete packing ability, hydration heat, core specimen strength tests are performed.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
• /
• 2010.10a
• /
• pp.29-32
• /
• 2010

콘크리트 충전 강관기둥부재(이하 CFST)는 대칭성을 유지하는 기하학적 특성과 내부에 충전된 콘크리트의 구조 및 내화성능의 향상으로 최근 초고층 건축물의 주요 요소로 활용되는 추세에 있다. 반면 CFST는 실험적 결과에 의존하는 경향을 보이고 있으나 이는 많은 비용과 시간이 소요되는 단점이 있으므로 강재의 고온특성을 적용한 해석적 결과와의 상관성은 매우 중요한 의미가 있다. 따라서 본 연구의 목적은 CFST 내화성능을 해석 및 실험결과를 활용하여 상호 관계를 파악하고자 한다.