• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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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.

• Journal of Korean Society of Steel Construction
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• v.13 no.1
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• pp.71-79
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• 2001

The concrete filled tubular(CFT) columns have many excellent structural properites. such as high compressive strength high ductility and high absorption capacity However the confinement effect and limiting width-thickness ratio of CFT column have not yet been clarified. Therefore. this paper aims to clarify the confinement effect of steel tubes and strength of concrete filled steel tubular columns. And this paper presents results of a probabilistic analysis based on statistical data for strength of concrete filled steel tubular columns which has been tested in Korea for recent 10 years(1991.1~2000.6).

• International Journal of High-Rise Buildings
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• v.3 no.1
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• pp.73-79
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• 2014

In recent years, the performance requested for which an ultra-high rise buildings is diversified. Large spans are designed in order to gain wide workspace. Column positions are shifted in middle stories to provide space different from neighboring floors. Moreover, in the bottom layers of the building, it is becoming more important to expand freedom to plan flexibility such as creating publically opened wide atria that gives attractive free space. Earthquake-proof criteria is also changing not only human life protection deign but also a design that allows functional continuity. In order to achieve thee needs, as one of technology, we have developed ultra-high strength concrete filled tubular (CFT) columns of the box section that combine ultra-high strength concrete with specified strength of $150N/mm^2$ and ultra-high strength steel material with tensile strength of $780N/mm^2$. In this paper, the outline of development of an ultra-high strength CFT column is reported. Also, the structural design of the ultra-high-rise building using the CFT columns is reported.

• Steel and Composite Structures
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• v.17 no.6
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• pp.891-906
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• 2014

This study aims to present a three dimensional finite element model to investigate the wave propagation in a concrete filled steel tubular column (CFSC) due to transient impact load. Both the concrete and steel are regarded as linear elastic material. The impact load is simulated by a semi sinusoidal impulse. Besides the CFSC models, a concrete column (CC) model is established for comparing under the same loading condition. The propagation characteristics of the transient waves in CFSC are analyzed in detail. The results show that at the intial stage of the wave propagation, the velocity waves in CFSC are almost the same as those in CC before they arrive at the steel tube. When the waves reach the column side, the velocity responses of CFSC are different from those of CC and the difference is more and more obvious as the waves travel down along the column shaft. The travel distance of the wave front in CFSC is farther than that in CC at the same time. For different wave speeds in steel and concrete material, the wave front in CFSC presents an arch shape, the apex of which locates at the center of the column. Differently, the wave front in CC presents a plane surface. Three dimensional effects on top of CFSC are obvious, therefore, the peak value and arrival time of incident wave crests have great difference at different locations in the radial direction. High-frequency waves on the waveforms are observed. The time difference between incident and reflected wave peaks decreases significantly with r/R when r/R < 0.6, however, it almost keeps constant when $r/R{\geq}0.6$. The time duration between incident and reflected waves calculated by 3D FEM is approximately equal to that calculated by 1D wave theory when r/R is about 2/3.

• Journal of Korean Society of Steel Construction
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• v.14 no.6
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• pp.823-834
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• 2002

Maximum-strength concrete-filled steel square tubular columns were tested under concentric and biaxial eccentric load. Buckling length-section depth ratio $L_k/D$, magnitude of eccentricity e, and angle of eccentric load ${\theta}$ were selected as experimental parameters. Strength and behavior were also examined. Test results showed that the maximum strength of columns under biaxial eccentric load could be predicted using the previously proposed strength formula of columns undr uniaxia eccentric load. Likewise, the behavior and maximum strength of columns could be predicted using the analysis.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.613-616
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• 2003

Steel-concrete composite columns are used extensively in modern buildings. Extensive research on composite columns in which structural steel are in concrete have been carried out. In-filled composite columns, however have received limited attention compared to encased columns. In this paper, interrelationship of parameters is examined into analyzing and comparing with data through ABAQUS program and experiment on concrete filled tubular column under axial load and propriety of model is checked out by FEM analysis. The main variations of this paper are width-thickness ratio of the section(B/t =33.3, 38.9, 44.4), concrete strength($f_{ck}$=240, 360kgf/$\textrm{cm}^2$), and width-length ratio($L_o$/B=8.0, 10.0, 12.0, 15.0, 20.0). The ultimate value obtained through analysis is compared with test value and calculated by design code of other countries and previous studies.

• Steel and Composite Structures
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• v.38 no.3
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• pp.305-317
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• 2021

The mechanical behavior of the outer square inner circular concrete-filled dual steel tubular (SCCFT) stub columns under axial compression is investigated by means of experimental research, numerical analysis and theoretical investigation. Parameters such as diameter ratio, concrete strength and steel ratio were discussed to identify their influence on the mechanical properties of SCCFT short columns on the basis of the experimental investigation of seven SCCFT short columns. By establishing a finite element model, nonlinear analysis was performed to discuss the longitudinal and transverse stress of the dual steel tubes. The longitudinal stress characteristics of the core and sandwich concrete were also analyzed. Furthermore, the failure sequence was illustrated and the reasonable cross-section composition of SCCFT stub column was proposed. A formula to predict the axial load capacity of SCCFT stub column was advanced and verified by the results from experiment and the finite element.

• Steel and Composite Structures
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• v.9 no.1
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• pp.19-38
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• 2009

The present paper provides test data to evaluate the seismic performance of recycled aggregate concrete (RAC) filled steel square hollow section (SHS) beam-columns. Fifteen specimens, including 12 RAC filled steel tubular (RACFST) columns and 3 reference conventional concrete filled steel tubular (CFST) columns, were tested under reversed cyclic flexural loading while subjected to constant axially compressive load. The test parameters include: (1) axial load level (n), from 0.05 to 0.47; and (2) recycled coarse aggregate replacement ratio (r), from 0 to 50%. It was found that, generally, the seismic performance of RACFST columns was similar to that of the reference conventional CFST columns, and RACFST columns exhibited high levels of bearing capacity and ductility. Comparisons are made with predicted RACFST beam-column bearing capacities and flexural stiffness using current design codes. A theoretical model for conventional CFST beam-columns is employed in this paper for square RACFST beam-columns. The predicted load versus deformation hysteretic curves are found to exhibit satisfactory agreement with test results.

• 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.

• Steel and Composite Structures
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• v.25 no.4
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• pp.443-456
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• 2017

Many authors have established the usefulness of concrete filled steel tubular (CFST) sections as compression members while few have proved their utility as flexural members. To explore their prospective as part of CFST frame structures, two types of connections using extended end plate and seat angle are proposed for exterior joints of CFST beams and CFST columns. To investigate the performance and failure modes of the proposed bolted connections subjected to static loads, an experimental program has been executed involving ten specimens of exterior beam-to-column joints subjected to monotonically increasing load applied at the tip of beam, the performance is appraised in terms of load deformation behaviour of joints. The test parameters varied are the beam section type, type and diameter of bolts. To validate the experimental behaviour of the proposed connections in CFST beam-column joints, finite element analysis for the applied load has been performed using software ATENA-3D and the results of the proposed models are compared with experimental results. The experimental results obtained agree that the proposed CFST beam-column connections perform in a semi-rigid and partial strength mode as per specification of EC3.