• Magazine of the Korea Concrete Institute
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• v.7 no.3
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• pp.199-210
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• 1995

We could say that the concrete filled steel tube structure is superior in the vlew of various structure properties as to promote improvement of structural capacity to dtmonstrate heterogeneous material properties interdependently. The compressive strength is increased by putting to tri axial stress because lateral expansion of concrete 1s confined by the steel tube, when concrete conflned by steel tube fall under centric axial load. Also, it have an advantage that decreasr of load carrying capacity 1s small, not occuring section deficiency due to protect falling piienornonon by co~nprrssion fallurc of concrete. So this study investigated for structural behaviors yroprrtiex of concwir. confined by steel tube throughout a series of experlmerit with kcy parxncter, such as diameter-to-thickness(D / t) ratio, strength of concrete as a study on properties of structural behaviors of confined concrete confined by circular steel tube( tri axial stress). Frorn the expcrment results, the obtained results, are surnrnarised as foliow. (1) The restraint effect of concrete by steel tube was presented significantly as the D /t ratio of steel tube and the strength of filled concrete decrease, and the confined concrete by circular steel tube was increased respectively twice as much as 4-7 in deformation capacity at the ultimate strength ,compared with those of non-confined concrete, so expected to increase flexible effect of concrete. (2) The emprical formula to predict the ultimate capacity of confined concrete by steel tube and concrete filled steel tube column using restraint coefficient of concrete were proposed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.2
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• pp.355-365
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• 2014

Concrete-filled tubes (CFTs) have been used in civil engineering practices as a column of buildings and a bridge pier. CFTs have several advantages over the conventional reinforced concrete columns, such as rapid construction, enhanced buckling resistance, and inherited confinement effect. However, CFT component have not been widely used in civil engineering practice, since the design provisions among codes significantly vary each other. It leads to conservative design of CFT component. In this study, the design provisions of AISC and EC4 for CFT component were examined, based on the extensive test results conducted by previous researchers and finite element analysis results obtained in this study. Especially, the focus was made on the validation of P-M interaction curves proposed by AISC and EC4. From the results, it was found that the current design codes considerably underestimated the strength of CFT component under general combined axial load and bending. Finally, the modified P-M interaction curve was proposed and successfully verified.

• Journal of Korean Society of Steel Construction
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• v.27 no.5
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• pp.435-445
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• 2015

Concrete filled steel tube(CFT), which has superior ductility and strength, is used for building column, bridge piers of ocean structure. Shear design equations of CFT existing in structural design provisions are excessively conservative. It has an effect on constructability and the economics of CFT. However, to suggest the reasonable shear design equation, experimental studies on the shear capacity of CFT have been rarely conducted. This study is analytical research to suggest improved shear design equations of large-diameter concrete-filled steel tubes. This analytical research was conducted to apply finite element analysis model of CFT based on the prior research. It was verified by comparison with prior test results. The verified model was used for parameter studies to estimate the influence of overhang length, concrete compressive strength and diameter-thickness ratio on shear strength.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.3A
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• pp.139-148
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• 2012

Circular concrete-filled tubes (CFTs) are composite members, which consists of a steel tube and concrete infill. CFTs have been used as building columns and bridge piers due to several advantages such as their strength-to-size efficiency and facilitation of rapid construction. Extensive experimental studies about CFT have been conducted for past decades. However experimental results alone are not sufficient to support the engineering of these components. Complementary advanced numerical models are needed to simulate the behavior of CFT to extend the experimental research and develop predictive tools required for design and evaluation of structural systems. In this study, a finite element modeling technique for CFT was developed. The confinement effects, and behavior of CFT subjected various types of loading predicted by the proposed finite element model for CFT were verified by comparing with test results.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.567-572
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• 2001

A transmission of load that is transmitted by beam in steel beam-column joint depends on bond strength between concrete and steel tube. But it is different to transmit a load efficiently in the established concrete filled steel tubular column. Therefore, shear-connector is demanded for a reinforcement about a transmission of load. An ascent of bond stress and a transmission of load after debonding are expected by a reinforcement of shear-connector.

• Fire Science and Engineering
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• v.30 no.3
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• pp.7-15
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• 2016

The cross-sectional shape factor is used worldwide to evaluate the scientific performance of fire-resistant structures. In South Korea, however, a system for applying a cross-sectional shape factor has not been arranged and circular or rectangular steel pipes are commonly used for large-scale steel frame buildings. On the other hand, coating material-spray steel beams and pillars that have received the certification of a fire-resistant structure from recognized organizations are mostly limited to a H-beam. A H-beam is granted a wide range of certifications without size limitations from a non-loading performance test with test standards based on the relevant provisions. Other types of steel pipe are to be certified for fireresistance according to shape. In this study, a cross-sectional shape factor was used to propose standard testing specifications for the application of coating material-sprayed circular and rectangular steel pipes, eventually to set the scope of certification for reasonable fire-resistant structures.

• Journal of Korean Association for Spatial Structures
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• v.12 no.3
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• pp.63-70
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• 2012

In this study, the displacement-based design concept, the performance by the existing reinforced concerte column and steel reinforced concrete composite column for SRC purchased the maximum design ground acceleration improvement compared to the performance design. SRC have several advantages such as strength enhancement and high ductility. H-beam or steel tubes were used for embedded elements of the SRC composite columns. SRC cross-section for the P-M diagram and analysis on the nominal bending monent SRC designed for composite columns for disparity estimation is presented to the displacement-based seismic design. Performance improvement of the performance-based design performance targets for the design seismic displacement and design criteria for the direct displacement-based design methods and to improve the seismic performance due to the displacement coefficient method is proposed to design. SRC compared with the RC column designed to improve the performance and displacement ductility ratio displacement results in the performance design results showed significantly improved performance.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.10a
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• pp.215-218
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• 1995

This paper presents an experimental study on the strength and deformation of concrete-filled circular steel short columns. Six specimens of concrete-filled circular short columns were tested under concentric compressive load. For comparsion, three specimens of circular steel short columns were also loaded to failure. The ultimate strength, ductility, and confinement mechanism of columns were compared. In the comparison, the effect of witch-thickness ratio and concrete compressive strength on the behavior of colimns were examed. As a result, the axial load verse axial average strain relationship of concrete-filled circular steel columns was very stable, because of interactions between the concrete and steel, the strength are 13% and 30% larger than the strength extimated by simply superimposed method of the concrete and steel. The ratio of the circumferential to longitudinal strain increment, both measured on the steel suface, was 0.28 up to the longitudinal strain of 0.1%, increases from 0.3 to 0.8 between the strain of 0.1% to 0.3%, and 0.8 beyond the strain of 0.3%

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.2
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• pp.213-220
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• 2015

CFT column has a lot of structural advantages due to the composite behavior between in-filled concrete and steel tube. This paper deals with the development of an effective numerical model which can consider the bond-slip behavior between both components of concrete matrix and steel tube without taking double nodes. Since the applied axial load to in-filled concrete matrix is delivered to steel tube by the confinement effect and the friction, the governing equation related to the slip behavior can be constructed on the basis of the force equilibrium and the compatability conditions. In advance, the force and displacement relations between adjacent two nodes make it possible to express the slip behavior with the concrete nodes only. This model results in significant savings in the numerical modeling of CFT columns to take into account the effect of bond-slip. Finally, correlation studies between numerical results and experimental data are conducted to verifying the efficiency of the introduced numerical model.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.121-124
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• 2008

Fast construction of bridge substructures is a new trend of bridge design. A precast pier system with bonded prestressing bars was proposed. In this paper, quasi-static tests on precast prestressed piers were conducted to evaluate the seismic behavior of the precast piers with bonded prestressing bars. In order to strengthen the shear strength of the joints between column segments, steel tubes filled with mortar were used. Displacement ductility and energy dissipation capacity of the precast piers were evaluated. The suggested precast pier system showed better seismic performance than the required ductility. Based on the research results, an example bridge pier for light-railway lines was designed and design considerations were discussed.