• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.05a
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• pp.21-22
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• 2015

The CFT(Concrete Filled Tube) system has been developed to behave well in a structural performance such as stiffness, stress, ductility, fire resistance that is derived from its mechanical advantages of composite structure. There were number of studies about unprotected CFT columns for improving their fire resistance through reinforcing bars or plates being placed inside the steel tube. It was also known that reinforcing plates of flat type need stiffeners in a certain distance to avoid their buckling failure so it cost as much as their using consequentially. This paper is planned to test the work of beam elements attached inner side of CFT depending on its shape. More discussions on beam's design could be followed after some fire tests accordingly conducted within this project.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.5-8
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• 2004

In order to investigate the effect of the height of application point of lateral loads and reinforcing steel bars in walls and columns in improving the seismic behavior of confined concrete block masonry walls, an experimental research program is conducted. A total of four one-half scale specimens are tested under repeated lateral loads. Specimens are tested to failure with increasing maximum lateral drifts while a vertical axial load was applied and maintained constant. The constant vertical axial stresses applied are 0, 0.84 and 1.80MPa, while the amount of reinforcements in horizontal and vertical directions are $0\%,\;0.08\%\;and\;0.18\%$ respectively. Test results obtained for each specimen include cracking patterns, load-deflection data, and strains in reinforcement and walls in critical locations. Analysis of test data showed that above parameters generate a considerable effect on the seismic performance of confined concrete block masonry walls.

• Earthquakes and Structures
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• v.22 no.1
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• pp.39-51
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• 2022

The axial compression behavior of nine self-compacting concrete columns confined with CFRP-PVC spirals was studied. Three parameters of spiral reinforcement spacing, spiral reinforcement diameter and height diameter ratio were studied. The test results show that the CFRP strip and PVC tube are destroyed first, and the spiral reinforcement and longitudinal reinforcement yield. The results show that with the increase of spiral reinforcement spacing, the peak bearing capacity decreases, but the ductility increases; with the increase of spiral reinforcement diameter, the peak bearing capacity increases, but has little effect on ductility, and the specimen with the ratio of height to diameter of 7.5 has the best mechanical properties. According to the reasonable constitutive relation of material, the finite element model of axial compression is established. Based on the verified finite element model, the stress mechanism is revealed. Finally, the composite constraint model and bearing capacity calculation method are proposed.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.10a
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• pp.151-158
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• 2000

In this paper, It is presented that concrete-filled composite piers have large energy-absorption capacity and high strength and stiffness on account of mutual confinement between the steel plate and filled-in concrete. Concrete-filled composite columns were tested to failure under axial compression and cyclic lateral loading. Displacement ductility index obtained by using the load-displacement relation has been increased with the increment of filled-in concrete length, while it has been decreased according to the incrementation of width-thickness ratio, slenderness ratio and the number of loading cycles. Structural behavior and ductility index estimated for the seismic design showed that composite piers could be used as a very efficient earthquake-resistant structural member. The response modification factor could be re-evaluated for concrete-filled composite piers.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2008.04a
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• pp.319-324
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• 2008

In this study the progressive collapse potential of special concentrically braced frames were investigated using the nonlinear static. All of seven different brace types were considered. According to the pushdown analysis results, most braced frames designed according to current design codes satisfied the design guidelines for progressive collapse initiated by loss of a first story mid-column; however most model structures showed brittle failure mode. This was caused by buckling of columns after compressive braces buckled. Among the braced frames considered, the inverted-V type braced frames showed superior ductile behavior during progressive collapse.

• Steel and Composite Structures
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• v.8 no.4
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• pp.297-312
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• 2008

A concrete filled double skin tubular (called CFDST in abbreviation) member consists of two concentric circular steel tubes and filled concrete between them. Purpose of this study is to investigate their bending characteristics experimentally. The two test parameters of the tubes considered were an inner-to-outer diameter ratio and a thickness-diameter ratio. As a result, their observed failure modes were controlled by tensile cracking or local buckling of the outer tube. Discussion is focused on the confinement effect on the filled concrete due to the both tubes and also the influence of the inner-to-outer diameter ratios on their deformability and load carrying capacity.

• Structural Engineering and Mechanics
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• v.10 no.6
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• pp.577-587
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• 2000

A 3D nonlinear finite element computation model is presented in order to analyze the concrete filled rectangular tubular (CFRT) composite structures. The concrete material model is based on a hypo-elastic orthotropic approach while the elasto-plastic hardening model is employed for steel element. The comparisons between experimental and analytical results show that the proposed model is a relatively simple and effective one. The analytical results show that the capacity of inner concrete of CFRT column mainly depends on the two diagonal zones, and the confining effect of CFRT section is mainly concentrated on the corner zones. At the ultimate state, the side concrete along the section cracks seriously, and the corner concrete softens with the increase of compressive strains until failure.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.757-762
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• 2000

The purpose of this study is to investigate the performance of slab-beam-column subassemblage in the Ordinary Moment Frame(OMF). For this purpose, 3-story building was designed according to UBC and ACI building code(ACI 318-99) and the subassemblages of in the first story were constructed. The subassemblages were classified into interior and exterior. Each interior and exterior subassemblage is modeled by the 2/3 scale experimental specimens. All the specimens have the transverse beam and the columns on the slab have the lap splice as the typical exterior and interior slab-beam-column subassemblage. The interior subassemblage was tested under the constant axial force, while the exterior subassemblage was tested under the fluctuating axial force. Based on the results of the experiments, the performance of each subassemblage is evaluated and the failure mode is investigated.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.466-472
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• 1996

The nonlinear analysis was perforned for a 2-bay 2-story moment-resisting reinforced concrete plane frame with seismic detail using KDARC 2D program. The analytical models consist of the material model, the member model, the hysteretic model, and the damage model etc. The conclusion based on the results of analysis is as following. : (1) Story shear-displacement relationship is similar to the experiment result but from the energy point of view, the analysis relationship is similar to the experiment result but from the energy point of view, the analysis result was different from the experiment result. (2) Plastic hinges were found to occur mainly in beams at first story while all the columns had plastic hinges throughout the structure. (3) Failure mode is a little different from experiment result in the yielding mechanism. (4) Damage index isabout 0.25. This means that the degree of damage is moderate and can be repairable.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.7
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• pp.4930-4935
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• 2015

In the actual research fields, the studies for applications of 180 MPa ultra high performance concrete (UHFRCC) to compressive members are limited due to its very high compressive strength. In this study, in order to find its practical use, UHPC was producted by using twin-shaft mixer batch plant. Also, to get basic research data for the design specification of UHPC compressive members, a series of draft experiments, including short columns with square and circular sections, were performed and its failure modes and behaviors were assessed.