• Journal of Korean Society of Steel Construction
• /
• v.20 no.5
• /
• pp.645-653
• /
• 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
• /
• 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 Society of Steel Construction
• /
• v.27 no.3
• /
• pp.289-298
• /
• 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 the Korea Academia-Industrial cooperation Society
• /
• v.22 no.2
• /
• pp.617-624
• /
• 2021

Concrete-filled steel tubular columns can improve the strength and deformation capacity of structures, thereby enabling the development of efficient structures. The Korean design standard (KDS41) regarding concrete-filled steel tubular structures, established by the architectural institute of Korea in 2005, was revised in 2009 and 2016. The objective was to understand the compressive strengths and deformation capacity of stub columns for concrete-filled square steel tubes under uniaxial compression and validate the KDS41's standard code for necessary corrections. Experiments were conducted on 26 specimens with parameters, such as the width-thickness ratio of cold-formed square tubes. The following values of the stub columns for concrete-filled square steel tubes were obtained: compressive strengths, relationship between the axial load and axial displacement, and failure modes. An analysis of these results enabled an understanding of the concrete-filled effect and the influence of the wide-thickness ratio. The compressive strengths of filled concrete saw a 9% increase compared to a state of uniaxial stress, which must be noted in a future edition of KDS41. After benchmarking the results regarding square steel tubes generated by cold forming to the guidelines provided by the KDS41, the KDS41's value of 2.26 for the limiting width-to-thickness ratio for the compact section was found to be inflated. With a safety concern, this paper proposes a more conservative value of 1.35.

• Journal of Korean Society of Steel Construction
• /
• v.12 no.4 s.47
• /
• pp.387-395
• /
• 2000

The purpose of this research is to evaluate the capacity of strength and plastic deformation of those members, and provide experimental data on the seismic behavior of these members as a basis for developing guidelines for designing seismically resistant concrete-filled steel tubular columns. Eighteen cantilever-type specimens were tested under constant axial load and cyclically lateral load as models of bottom columns in high-rise building. The parameters studied in the test program included, are width-thickness ratio of steel tube, slenderness ratio (Lo/D) and axial force ratio. From the test results, the effects of parameters on the strength, the deformation capacity, energy absorption capacity are discussed. The specimen flexural capacity under combined axial and lateral loading was found to be almost accurately predicted by criteria AIJ and AISC-LRFD providing conservative results. Therefore KSSC for encased composite column can be applied to the concrete filled column if composite section and elastic modulus are modified according to AIJ and AISC-LRFD. Finally, the proposed flexural capacity considering confinement effects is a food agreement on the tests results.

• Journal of Korean Society of Steel Construction
• /
• v.11 no.2 s.39
• /
• pp.191-199
• /
• 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
• /
• v.22 no.6
• /
• pp.523-532
• /
• 2010

Concrete-filled square steel tube (CFT) columns have inherently high fire resistance and load-bearing capacity. Nevertheless, it is sometimes necessary to improve their fire resistance using external fire protection. This paper presents the experimental results of the temperature distribution of CFT columns with fire protection. A fire load test was carried out by exposing small-scale specimens to heat in an electric furnace that was especially built for testing loaded columns. The temperature distribution of CFT columns under constant axial loads was determined, as were its significant parameters, such as the types of fire protection and thickness, the thickness of the square CFT, and the fire duration times. The results of this study showed the temperature distribution of each specimen of the electric furnace and the temperature distribution properties of concrete and steel. In addition, the axial displacement and local buckling behavior of CFT columns based on temperature changes was observed.

• Journal of Korean Society of Steel Construction
• /
• v.28 no.2
• /
• pp.75-83
• /
• 2016

Existing tubes for concrete filled tubular structure are made through welding of four plates irrespective, but the production performance is poor and special welding technique is needed to weld the internal or through diaphragm. Accordingly, We developed a welded built-up square steel tube having a welding lines and a stiffeners at location out of stress concentration. The welded built-up square steel tube occurred a interference with stiffeners at the internal or through diaphragm, therefore researches of a external diaphragm for welded built-up square CFT column connections are needed for the purpose of avoidance of a interfere with stiffeners. In this study we suggest a design formulation for external diaphragm of the welded built-up square CFT external diaphragm connections. Four specimens were manufactured for a experimental test, then we analyzed the behaviors of the specimens.

• Journal of Korean Society of Steel Construction
• /
• v.23 no.3
• /
• pp.317-326
• /
• 2011

Today there is a growing range of applications for Concrete-Filled Steel Tube (CFT) member because of its superior performance. Ductility estimation test of concrete-filled seismic resistant steel tubular columns, subjected to axial and cyclic lateral load, was carried out in this study. Seismic resistant steel tubes are manufactured using SN400B plates by a two-seam welding at center of the column width for cold press-formed shape plates of two pieces. A total of eight specimens were manufactured and tested with the parameters of width-thickness ratio of steel tubular column, axial load ratio, and loading conditions to act axial and cyclic lateral load two dynamic actuators were used. From test results, flexural strength, deformation capacity, energy dissipation capacity, and ductility behavior of columns were analyzed.

• 건축구조
• /
• v.8 no.4
• /
• pp.45-47
• /
• 2001