• Journal of Korean Society of Steel Construction
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• v.25 no.4
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• pp.347-357
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• 2013

Recently, In recognition of outstanding structural performance the use of Concrete Filled steel Tube(CFT) columns has been increased. Research is ongoing that effective use of cross-sectional because steel strength development and rising prices. In this Lab, suggests new shape by Thin steel plates bent to be L-channel welded to form square steel tube to maximize efficiency of the cross section. In addition, since the rib placed at the center of the tube width acts as an anchor; higher load capacity of buckling is acceptable. we have developed New shape welded built-up square tube for broader usability which were bent to be L-shaped and thin Plate each unit member were welded. In order to apply the new shape built-up square columns, we predicted structure behavior, stress distribution with parameter Width thickness ratio. The experimental results presented in standards and even exceed the b/t of the rib anchors installed in the role due to exert enough strength and deformation to improve performance was favorable.

• Journal of Korean Society of Steel Construction
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• v.27 no.3
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• pp.289-298
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• 2015

The steel tube of Concrete-Filled Tube(CFT) confines the concrete and the concrete restrains the buckling of the tube, The objective of this study is to investigate the influences of the opening shape of the through diaphragm in case of the rectangular CFT column-to-beam connection through the structural experiment. The experiment results are compared with analysis results obtained by using the FEM program. These results are shown that strength of the rectangular CFT column-to-beam connection have similar structural performance regardless of the opening shape if opening areas of the through diaphragm are same. Also in case the connection area/shape of the through diaphragm and the flange of H-beam are similar, it was ascertained that the bending stress occurred at the beam can be transferred to the column through the diaphragm.

• Journal of Korean Society of Steel Construction
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• v.27 no.6
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• pp.525-536
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• 2015

An experimental study was performed to investigate the axial-flexural load-carrying capacity of concrete-encased and-filled steel tube (CEFT) columns. To restrain local buckling of longitudinal bars and to prevent premature failure of the thin concrete encasement, the use of U-cross ties was proposed. Five eccentrically loaded columns were tested by monotonic compression. The test parameters were axial-load eccentricity, spacing of ties, and the use of concrete encasement. Although early cracking occurred in the thin concrete encasement, the maximum axial loads of the CEFT specimens generally agreed with the strengths predicted considering the full contribution of the concrete encasement. Further, due to the effect of the circular steel tube, the CEFT columns exhibited significant ductility. The applicability of current design codes to the CEFT columns was evaluated in terms of axial-flexural strength and flexural stiffness.

• Journal of Korean Society of Steel Construction
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• v.11 no.2 s.39
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• pp.191-199
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• 1999

This paper is the first step on the study of the industrialization of the mid-story steel building structures. The purpose of this study is to investigate the structural behavior of concrete-filled square steel tubular column to H-beam connections using angles and high tension bolts. The tests are carried out with five types of specimens under static loading and the main parameter is the thickness of angles. Yield-line theory which obtains connection strength by way of the lowest value based on upper-limit theory is applied to predict strength formulas.

• Journal of Korean Society of Steel Construction
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• v.16 no.5 s.72
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• pp.529-541
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• 2004

Concrete filled steel tube structures were recently used in constructing high-rise buildings due to their effectiveness. Studies on concrete filled steel tubes have been focused on the experiments of uni-axial compression and bending and eccentric compression. There were also a few studies that investigated CFT member behavior under combined compression and torsion. The behavior of a circular CFT column under combined torsion and compression was theoretically investigated, considering the confinement of steel tubes on the concrete, the softening of the concrete, and the spiral effect, which were the dominant factors that influenced compression and torsion strength. The biaxial stress effects due to diagonal cracking were also taken into account. By applying those factors to compatibility and equilibrium conditions, the basic equation was derived, and the equation could be used to incorporate the torsional behavior of the entire loading history of the CFT member.

• Journal of the Korea Concrete Institute
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• v.14 no.6
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• pp.864-873
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• 2002

Recently, CFT Column has reported a lot of study result, because a CFT column has certain superior structural properties as well as good productivity, execution efficiency, and improved rigidity over existing column. However, CFT column still has problems clearing the capacity evaluation between its steel tube member and high-strength concrete materials. Also, high-strength concrete filled steel square tube column(HCFT) examined numerical value explanatorily about transformation performance(M-ø) of when short-column receives equal flexure-moment from axial stress on research for concrete. hnd, with basis assumption, executed development of analysis program of moment-curvature relation for analytic analysis of transformation performance of HCFT section that get by an experiment. This study investigated to properties of structural(capacity, curvature), through a series of experiments for HCFT with key parameters, such as strength of concrete(600kgf/$\textrm{cm}^2$), D/t ratio, slenderness ratio(λ) and concrete kinds under eccentric load. And, I executed comparative analysis with AISC-LRFD, AIJ and Takanori Sato etc. and experiment result that is capacity design formula.

• Journal of Korean Society of Steel Construction
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• v.20 no.1
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• pp.205-213
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• 2008

The objective of this study is to evaluate the yield stress of SM570TMC CFT column subject to axial force. These columns were evaluated and compared by statistical tests, during which the displacements and axial loads of column specimens were measured. Test results showed that the yield stress of CFT columns under axial load could be predicted using the previously proposed the yield stress of steel columns.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.7
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• pp.9-16
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• 2017

To improve concrete-filled tube (CFT) columns, an octagonal concrete-filled tube (OCFT) column was developed. Because the OCFT column requires a small boring diameter, the OCFT column is suitable for Top-Down construction method. In this study, the compression performance of OCFT column to be used as Top-Down pile foundation was verified using centrifuge equipment. Under 12 g centrifugal acceleration, the bearing capacities of the pile foundations of OCFT and H-shaped sections were tested. When the pile foundations were embedded in soil of full depth, 45 % of the design strength, which was assumed to be the construction load, was supported by the OCFT and H-shaped sections in the elastic states. When the pile foundations were embedded in soil of half depth, the buckling of the pile foundations was not investigated. After the loading test, the rock at the bottom of pile foundation, which had a strength of 3.5 MPa, was not damaged due to 45 % of the design strength.

• Journal of Korean Society of Steel Construction
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• v.20 no.5
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• pp.645-653
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• 2008

Welded built-up square tubes are manufactured by flare welding at the center of the column width for cold-formed L-shaped four-piece plates and improved composite effect of concrete and steel by vertical inner anchor. Also, the axial resistance of concrete is increased by the thinness of the steel column, and the composite effect of concrete and steel prevents the steel column from local buckling. In this study, we introduced a manufacturing method of built-up square column steel square concrete-filled tubular column with vertical inner anchor and superior structural performance of the square stub column verified by the structural test for 15 specimens with parameters of shape of tube (built-up square tube, general steel tube), width over thickness of the steel tube (B/t=50, 58, 67) and the strength of concrete (f'c=10MPa, 50MPa).

• Journal of Korean Society of Steel Construction
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• v.23 no.4
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• pp.439-454
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• 2011

A nonlinear analysis model for internally confined hollow concrete-filled tube (ICH CFT) columns was suggested and was verified by the test results obtained by the previous researchers. The suggested model considered the confining effect and nonlinearity of concrete. The verified results showed that the suggested model was reasonable and reliable for predicting the behavior of an ICH CFT column. Additionally, a simple parametric study was carried out. The strength of concrete, the hollow ratio of a column, and the thickness of an inner tube were selected as parameters affecting the behavior of an ICH CFT column. The analysis results showed that the concrete strength and the thickness of the inner tube affect the axial strength and moment capacity of the column while the hollow ratio affects only its axial strength.