• Journal of Korean Society of Steel Construction
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• v.9 no.3 s.32
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• pp.391-400
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• 1997

The objective of this paper is to suggest formula of Concrete Filled Tube Beam-Column members maximum strength by using of numerical analysis and tests. The numerical analysis results are compared with test results for evaluating numerical analysis method. The formula of Limit State Design of Architectural Institute of KOREA is used for basic form of suggestion formula. In order to suggest formula, two methods are used. One is to use the coefficient, and the other is to use the amplified factor of material strength. The formula by two methods are compared with numerical analysis results.

• Journal of Korean Society of Steel Construction
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• v.25 no.6
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• pp.587-599
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• 2013

A simple but accurate analytical method to evaluate the fire resistance of unprotected concrete filled tubular (CFT) columns under standard fire condition is proposed based on the fire design framework of EC4. To this end, the accuracy of the current tabulation method for the temperature prediction proposed by Lawson et al. was first critically evaluated, and a new prediction equation for the temperature gradient across the CFT section was then proposed based on available test and finite element analysis results. Overall, the axial strength predicted by using the proposed equation under the general fire design framework of EC4 was more accurate than that based on existing methods and appeared reasonable for design purposes. The results of this study are directly usable for the more rational fire analysis and design of unprotected CFT columns.

• Journal of Korean Society of Steel Construction
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• v.10 no.4 s.37
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• pp.641-655
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• 1998

It researched several jointing-methods of frame consisting of a concrete-filled steel tubular column and H-shaped beam. These beam-to-column connections is parameters to following: columns of square shape pipe infilled with or without concrete, joints assembled two types of diaphragm, outside-type and through-type. And it is testing that cyclically lateral loadings used hydraulic ram. In testing. we'll be on purposed to estimate the hysteretic behavior, strength and stiffness, energy absorption capacity, deformation capacity and failure configuration of each specimen. It is concluded that the frame specimens with outside-type are more stable and exhibit more energy absorption capacity compared with the through-type, in column of filled with concrete.

• Journal of Korean Society of Steel Construction
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• v.9 no.4 s.33
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• pp.649-658
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• 1997

When steel tube as a column is filled with concrete, it is common that the load-bearing capacities of CFST(Concrete Filled Steel Tube) column are increased substantially, And the CFST column can obtain a capacity of fire resistance without any additional detail on the surface of the steel tube for fire protection. In order to clarify the behavior of CFST column during fire occurrence, a theoretical study is performed, that is, a thermal analysis is used to find temperature gradient dependent on the time on the steel tube and the infilled concrete. N-M (axial force-moment) interaction curves are summarized under the consideration for time dependent variation. The material properties of concrete and steel in accordance with a temperature variation are referred to the existing general data. Thermal transient analyses are performed by finite element method through ANSYS and then these results are verified by comparing with the existing test results. On the basis of analytical results, load-carrying capacities (N-M interaction curves) are calculated by numerical analysis method.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.1
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• pp.95-102
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• 2011

The CFT columns used in thin-walled steel tubes can be more economical, because it was expected the increase of strength by restriction for the local buckling of steel tubes. The purpose of this paper is to review feasibility of existing design formula and verify the applicability limit of width-to-thickness ratio for increasing the strength of rectangular CFT columns. As the main parameters of experiments, width-to-thickness ratios of steel tube, height of rectangular concrete columns, and concrete filled or not. The strength of concrete are selected to 90MPa. From the test results, the confinement effect of steel tube on the compressive strength of infilled concrete is remarkably appeared in the thin-walled rectangular steel tube columns infilled wih high strength concrete. By the non-linear analysis, the axial strength from experiment result was given higher than analysis result for all CFT stub columns.

• Journal of Korean Society of Steel Construction
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• v.21 no.5
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• pp.461-470
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• 2009

A column resisting axial load and seismic load is one of the main members in a structural system. The heated column by event of a fire can lose its strength and it may damage its structural system or cause the collapse of the entire structural system. In this study, the fire resistance capacity of internally confined hollow concrete filled tube (ICH CFT) column was investigated. In an ICH CFT column, the yield strength of the external tube is important as a concrete filled tube (CFT) column because the external tube confines the filled concrete and the strength of the column depends on the confined effect. A study was performed by finite element analyses considering the confined effect and material nonlinearity as the temperature changes by the fire. The hollow ratio, the thickness of the external tube, and the strength of concrete were selected as the parameters for the analyses. The analyses were performed by using a commercial FEA program (ABAQUS) and nonlinear concrete model program. The analysis results showed that the hollow ratio and the strength of concrete mainly affect the fire resisting capacity of an ICH CFT column.

• Journal of Korean Society of Steel Construction
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• v.13 no.1
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• pp.1-8
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• 2001

The purpose of this study is to examine the utility of concretefilled steel tubular column to H-beam connections with tubular stiffener. As a preliminary step. a tensile experiment was undertaken to scrutinize characteristics of the structural behavior that take place between beam flanges and column with tubular stiffener. A total of 4 types of experimental settings were developed as tabular stiffeners are made up 9, 18, and 27 mm of thickness and 50 and 80 mm of height respetively Along with the overall load subsequently the degree of displacement and strain were recorded. Based on the yield line theory results of this of this study were evaluated and further critically reviewed the applicability of the strength formula. This study found that collapse mechanism was emerged on the beam flange as reinforcing tabular stiffeners Complementary studies of this sort, including numerical analyses should be undertaken in order to develope specific design critera.

• Journal of Korean Society of Steel Construction
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• v.9 no.2 s.31
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• pp.205-220
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• 1997

The objective of this study is to investigate the structural behavior of concrete-filled steel tubular column-H beam connections with exterior stiffeners. As a preliminary test, simple tensile test on the column to H-beam flange connections stiffened were conducted The paramaters of tensile test are the thickness(T=9, 12, 15m) and the width(W=50, 75, 100, 150mm) of exterior stiffeners. The simple tensile test were conducted to 7 kinds of specimens. Estimating the load, displacement, and strain from each kind, results of simple tensile test were compared with results of second test. On the basis of simple tensile test, test on the column to H-km connections stiffened with the sames under monotonic and cyclic load were conducted. Specimens of 5 for the second experiment were made. In analysis, comparing each strengthes and stiffnesses we estimated deformation capacity. Comparing and estimating each yielding strength ratios and maxium-strength ratios on the basis of yield line theory, new strength formula of beam-to-column connections was suggested.

• Journal of Korean Society of Steel Construction
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• v.9 no.3 s.32
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• pp.377-390
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• 1997

The objective of this study is to investigate the structural behavior of concrete-filled steel tubular column to H-beam connections with reinforced bar. As a preliminary test, simple tensile test on the column to H-beam connections stiffened were conducted. The parameters of tensile test are the diameters of each rebars. The simple tensile test were conducted to 5 kinds of specimens. Estimating the load. displacement and strain for specimens, the result of tensile test were compared with the results of main test. On the basis of simple tensile test, tests are conducted to montonic and cyclic loading column to H-beam connections with the same diameters of rebars. Specimens of 5 are made for monotonic and cyclic loading test. In analysis, estimating the yielding strength and maximum strength of specimens on the basis of yield line theory, strength formula of beam-to column connections with concrete-filled steel tubular column was suggested.

• Journal of Korean Society of Steel Construction
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• v.15 no.2
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• pp.207-217
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• 2003

The Concrete Filled Steel Tube (M) Column has excellent structural capacities that are in accordance with the interaction effect between the steel tube and concrete. CFT structure has been focussed on a struc tural system for high-rise buildings. The purpose of this study is to evaluate the strength and deformation capacities of CFT columns that are subject to constant axial and cyclic lateral load. The test parameters are diameters to the thickness ratio of the steel tube, axial load ratios, and the shapes of the tube. Total eighteen specimens were fabricated to clarify the energy absorption capacity of the CFT columns. Experimental results were summarized for their ultimate strengths and deformation capacities.