• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.991-996
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• 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 investigate the concrete property under diaphragm, concrete packing ability tests is peformed. High fluidity and strength concrete which satisfied with mix criteria could apply to building construction field. It it is quality managed with use of packing ability analysis.

• Journal of Korean Society of Steel Construction
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• v.10 no.2 s.35
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• pp.177-186
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• 1998

The concrete filled steel tubular column have to superior in compressive load carrying capacity, compared with same section typed hollow steel tube column, and have many excellent structural properties, such as stiffness improvement by filled concrete, improvement of ductility by reinforced effect of local buckling, and the like. However, it has not clear the effect of interaction between steel tube and filled concrete, stress portion ratio and fracture mechanism of concrete. This study investigated to structural properties for high strength concrete filled steel tube column by loading conditions through a series of experiments. Especially, this study investigated the properties of structural behaviors for concrete filled steel tube column stress ratio by loading conditions and failure mechanism of filled concrete.

• Journal of the Korea Institute of Building Construction
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• v.11 no.4
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• pp.353-362
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• 2011

High Strength Concrete (HSC) has weakness that in a fire, it is spalled and brittles. The phenomenon of spalling is made by water vapor's being confined in watertight concrete. This study is aimed to evaluate explosive spalling properties of high strength concrete with ${\square}100{\times}100{\times}200$ mm specimen and ${\square}400{\times}400{\times}1500$ mm column. To prevent spalling of concrete, fireproof coating and PP fiber are used. As a result, ${\square}400{\times}400{\times}1500$ mm column was prevented spalling likes ${\times}100{\times}100{\times}200$ mm specimen. When concrete protected failure to explosive spalling, quantity heat ratio (which fireproof coating specimen to pp fiber mixed specimen) between ${\square}100{\times}100{\times}200$ mm and ${\square}400{\times}400{\times}1500$ mm was maximum value at 20 minute, but difference of quantity heat ratio decreased and quantity heat ratio of each specimen is almost same at 30 minute.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.21-24
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• 2005

A computational analysis of hygro-thermal and mechanical behaviour of concrete column at high temperature is presented. The objective of this study is to develop a finite difference model that simulates coupled heat and transport phenomena in reinforced concrete structures exposed to rapid heating conditions such as fires. The theoretical basis for the integrated finite difference method is presented to describe a powerful numerical technique for solving of fluid flow in porous media. The numerical results predict the phenomena of 'moisture clog' and the explosive spalling of concrete under fire. The investigations show that high-strength concrete(HSC) and normal-strength concrete(NSC) exposed to high temperature have different pore pressure buildup dependent on porosity, permeability and moisture contents. HSC has more possibility than NSC on spalling.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.454-457
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• 2004

Due to social problems such as the increasing of land price and the expanding of city, buildings require more complex and bigger components and structure. However, the complex and massive building projects need new technology to solve effect of local buckling and the needs for more space. Hence, Concrete Filled Tube Steel (CFT), the tube steel to hold concrete during pouring and curing of concrete procedure, which helps to reduce local buckling and space, was developed. Most researches on CFT might not be focused on the characteristic of concrete 'filled in tube but structural analysis. However, it is the essential factor to increase the strength of concrete on CFT for having efficient results. Therefore, this paper will describe how to apply CFT into the construction site through examining High Strength Concrete $(800kg/cm^2)$, the strength of core, and bleeding during pouring strategy.

• 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).

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.3
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• pp.205-213
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• 2003

The primary purpose of this study is to investigate punching shear capacity of flat plate slab using high strength concrete in column. It may be much contributed to economy efficiency and structural advantages that High Strength Concrete(HSC) used for vertical member and Normal Strength Concrete(NSC) for horizontal member. Therefore, six plate flat slab specimens with HSC column and NSC slab had been made and tested with real scale. The major variables were compressive strength of concrete(fck=285, $460kgf/cm^2$), extended length of HSC from column face and amount of shear reinforcements. As the result of this test, the maximum load and punching shear capacity of specimens is affected by extended length and shear reinforcements.

• Earthquakes and Structures
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• v.19 no.5
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• pp.361-377
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• 2020

In the present research work, the effectiveness and the efficiency of a retrofitting approach using a layer of ultra-high performance fiber reinforced concrete (UHPFRC) jacket for damaged substandard exterior beam-column joints (BCJs) is experimentally investigated. The main objective of this study is to rehabilitate the already damaged BCJs to meet the serviceability requirements without compromising safety. According to the proposed strengthening technique, a chipped surface, lightly brushed with a dry condition was selected for making a successful bond between normal concrete substrate surface (NCSS) and UHPFRC. Then a fresh UHPFRC jacket with a thickness of 30 mm was cast around the damaged specimens. The entire test matrix was comprised of three 1/3 scale damaged exterior BCJs with a different column axial load (CAL). These specimens were repaired with UHPFRC and retested under monotonic loading. Based on the experimental results, repaired specimens showed an excellent performance in terms of their load-displacement response, maximum strength, displacement ductility, initial stiffness, secant stiffness and energy dissipation capacity when compared with the corresponding values registered when these specimens were tested in their virgin state. This rehabilitative intervention not only restored the strength, stiffness, ductility and energy dissipation capacity of severely damaged specimens but also improved their performance.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.10a
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• pp.284-292
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• 1995

This paper is on experimental study on the behavior of reinforced concrete columns subjected to longitudinal steel ratio To investigate the effects of concrete strength and longitedinal steel ratio on the behavior of reinforced concrete columns. a series of tests were carried out for thirty-six tied reinforced concrete columns with a 100mm square cross section and three slendemess ratio of 15, 30 and 50. And To study and illustrate the change of the ultimate loads and that of displacements, two different concrete strength of 180,26kfg/$\textrm{cm}^2$, 819,36kfg/$\textrm{cm}^2$ and five different longitudinal steel ratio of 0.5, 1.0, 4.0, 5.7 and 10.3% were used. The boundary conditions at the ends were both hinged and the end eccentricities (17mm) were equal and of the same sign. While the ultimate load capacity of high-strength concrete column was much increased when the columns were short, that was not when the columns were slender. The effect of longitudinal steel ratio on the increased of ultimate load of column was more evident for slender columns than for short ones and the ultimate of longitudinal steel ratio were more pronounced with increasing concrete strength. The more inserted the longitudinal steel, the more increased the ultimate load, but the superabundance of longitudinal steel ratio over the limitation of maximum steel ratio in ACI code was used, it was showed that the ultimate load was rather decreased.

• Steel and Composite Structures
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• v.32 no.5
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• pp.583-594
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• 2019

In recent years, composite concrete-filled steel tubular (CFST) members have been widely utilized in framed building structures like beams, columns, and beam-columns since they have significant advantages such as reducing construction time, improving the seismic performance, and possessing high ductility, strength, and energy absorbing capacity. This paper presents a new composite joint - the composite CFST beam-column joint in which the CFST member is used as the beam. The main components of the proposed composite joint are steel H-beams, CFST beams welded with the steel H-column, and a reinforced concrete slab. The steel H-beams and CFST beams are connected with the concrete slab using shear connectors to ensure composite action between them. The structural performance of the proposed composite joint was evaluated through an experimental investigation. A three-dimensional (3D) finite element (FE) model was developed to simulate this composite joint using the ABAQUS/Explicit software, and the accuracy of the FE model was verified with the relevant experimental results. In addition, a number of parametric studies were made to examine the effects of the steel box beam thickness, concrete compressive strength, steel yield strength, and reinforcement ratio in the concrete slab on the proposed joint performance.