• Journal of Korean Society of Steel Construction
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• v.17 no.3 s.76
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• pp.375-384
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• 2005

The goal of this paper is to understand the stress-transfer mechanism of concrete-filled tubular column to H-beam connections with external T-stiffener through the finite element method and to offer basic data for the design of T-stiffener. To identify the problems of previous test results, the same shapes of the full-scale test specimens were modeled for the finite element analysis. Results of the analysis were compared with the test results. Several stress and strain indices were used to understand the stress-transfer mechanism of connection with various T-stiffeners parameters. The models of analysis with different T-stiffener are grouped into TS, TSD, and TSH series. An alternative plan that decreases the stress concentration of beam flange to horizontal stiffener connection is proposed through the elasto-plastic finite element method. The basic design idea and minimum sizes of T-stiffener were proposed based on the various indices in relation to the connection details.

• Structural Engineering and Mechanics
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• v.73 no.6
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• pp.613-620
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• 2020

The research study is focuses on a form of all-bolted joint with the external ring stiffening plate in the prefabricated steel structure. The components are bolted at site after being fabricated in the factory. Six specimens were tested under cyclic loading, and the effects of column axial compression ratio, concrete-filled column, beam flange sub plate, beam web angle cleats, and spliced column on the failure mode, hysteretic behavior and ductility of the joints were analyzed. The results shown that the proposed all-bolted joint with external ring stiffening plate performed high bearing capability, stable inflexibility degradation, high ductility and plump hysteretic curve. The primary failure modes were bucking at beam end, cracking at the variable section of the external ring stiffening plate, and finally welds fracturing between external ring stiffening plate and column wall. The bearing capability of the joints reduced with the axial compression ratio increased. The use of concrete-filled steel tube column can increase the bearing capability of joints. The existence of the beam flange sub plate, and beam web angle cleat improves the energy dissipation, ductility, bearing capacity and original rigidity of the joint, but also increase the stress concentration at the variable section of the external reinforcing ring plate. The proposed joints with spliced column also performed desirable integrity, large bearing capacity, initial stiffness and energy dissipation capacity for engineering application by reasonable design.

• Journal of Korean Society of Steel Construction
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• v.26 no.3
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• pp.169-176
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• 2014

This paper presents the experimental results of behavior of square CFT columns with large the width-ro thickness ratio strengthened with carbon fiber reinforced polymers (CFRP) sheets subjected to concentrated axial loading. The main parameters were b/t ratio and the number of CFRP layers and 6 specimens were fabricated. The values of b/t were ranged from 60 to 100. From the tests, Maximum increase of 16% was also achieved in axial-load capacity with three transverse layered CFRP applied on four sides of steel tubes. The load capacity decreased up to 41% comparing with nominal load capacity of unstrengthened CFT column. However, for CFRP strengthened CFT, the load capacity decreased up to 32%. Finally, from the load-strain relationships, the local buckling occurred before yield point of steel tubes. Also, from the load-strain relationships, it was observed that local buckling were delayed on CFT columns by CFRP sheets retrofitting.

• Journal of Korean Society of Steel Construction
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• v.23 no.1
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• pp.51-59
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• 2011

Although an uncoated CFT column with a high axial-force ratio can be used to secure fire resistance for two hours or less in low-rise buildings, it does not satisfy the three-hour-long fire resistance required in high-rise buildings. Accordingly, so that the uncoated CFT column could be used for high-rise buildings, additional measures for the improvement of its fire resistance should be proposed. In this regard, the use of a Double CFT column as a measure for improving the fire resistance of the uncoated CFT column was proposed in this paper. A fire resistance test was conducted on an uncoated CFT column and a Double CFT column in real scale, under a load. Through such test, the effect of the Double CFT column on fire resistance was evaluated and then compared with that of a variant shape of the cross-section of a steel column.

• Journal of Korean Society of Steel Construction
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• v.26 no.4
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• pp.311-322
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• 2014

Concrete filled tubular structure should be installed diaphragms for moment connection. However internal and through diaphragm should be special welded when connected to column tube. The other hand, that has become increase of stress concentration and extend of construction error. Therefore, In this study the seismic performance of beam to column connections with External Diaphragms and implement cycle loading experiment. we had evaluated seismic performance with mentioned experiment which is concrete filled or not, variable shapes, to be welded or not of diaphragm. Also, formula of strength of external diaphragm was analyzed and looked into adequacy with regard to formula of tension strength.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.1A
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• pp.19-30
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• 2009

The primary objective of the present study was to attempt to quantify the effect of the existing codes for CFT composite section on initial section flexural stiffness, based on the measured vibration frequency of CFT truss girders. The formulae for the initial flexural stiffness of the composite sections in the different codes are compared with the free vibration test results. The results of the free vibration test on the CFT truss girders are in good agreement with the analysis results when used in ACI formulae. The free vibration analysis of CFT truss girders for different f/L ratios was conducted to determine how the natural frequency of the CFT truss girder is affected by different f/L ratios. The presence of the f/L ratios in CFT truss girders alters its frequencies of vibration because of the global stiffness of the CFT girders. The frequency in horizontal modes decreases as the f/L ratio increases. However, the frequency in vertical modes increases as the f/L ratio increases.

• Journal of Korean Association for Spatial Structures
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• v.20 no.3
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• pp.9-14
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• 2020

• International Journal of High-Rise Buildings
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• v.7 no.3
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• pp.233-242
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• 2018

Since the response reduction effect on over 200-meter-tall resulting from the seismic isolation system is smaller in general than low-rise and mid-rise buildings, mid-story isolated buildings are considered to reduce the response in the upper part above the isolation story, however, in many cases, the acceleration response just below the isolation story is likely to be the largest. This paper presents the structural design schemes, the design of the main structural frames, and the constructions of a 230-meter-tall super high-rise building with mid-story isolation mechanism integrated in Roppongi, Tokyo. Moreover, this paper shows how the architectural and structural design for integrating a mid-story isolation system in a super high-rise building has been conducted and what solutions have been derived in this project. The realization of this building indicates new possibilities for mid-story isolation design for super high-rise buildings.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.2
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• pp.209-218
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• 2003

The analytical studies included nonlinear finite element analysis of split-tee connection details subjected to axial load and lateral load. A three-dimensional model of the connections between CFT columns and H-beams has been developed. Both initial geometrical imperfections and residual stresses are taken into consideration. A geometrically nonlinear load-displacement analysis of the structure containing the imperfection is then performed, using the Riks method. Analytical results are compared with existing experimental results. Extensive parametric analyses are carried out to investigate the relation of the connections between CFT columns and H-beam to various parameters such as the axial load, column width-thickness ratio, and split-tee thickness.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.05a
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• pp.179-180
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• 2018

This study aims to provide a more comfortable environment for the external environment by designing a rotable dwelling that deviates from the conventional fixed residential concept. The round pillars, which are the center of the building, are constructed by placing the CFT (concrete Filled steel Tube) technique in place and assembling modular houses with columns. This study combines existing building techniques. Korea also needs to develop various related studies quickly.