• Journal of the Korea Concrete Institute
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• v.17 no.1 s.85
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• pp.113-120
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• 2005

The purpose of this study is to investigate the strength and ductility improvement of columns retrofitted by steel-fiber composite plate. Test specimens strengthened by three different materials - steel plate(SP), carbon fiber sheet(CF) and fiber-steel composite plate(CP) - were tested under cyclic lateral load with a constant axial load equal to $20\%$ of the axial compression capacity. The structural capacity of composite plate was good or better than that of other retrofitting materials. Test results from all retrofitted specimens showed that considerably higher retrofitting amount was required for strength enhancement. The ductility of retrofitted columns by composite plate was fairly improved. Also, energy ductility ratio was more effective than displacement ductility ratio for ductility estimation of retrofitted column.

• Fire Science and Engineering
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• v.31 no.2
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• pp.9-16
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• 2017

In this study, fire resistance tests were conducted to evaluate the fire resistance performance of unprotected and non-welded CFT columns in relation to the shape and size of cross-sections. Unprotected slot-type CFT columns which were ${\square}300$ and ${\square}500$ in dimensions resisted fire for 125 minutes and more than 180 minutes, respectively. Strain analysis showed that slot-type CFT columns were more ductile than welded CFT columns. The temperatures of central parts measured when welded CFT columns and slot-type CFT columns had lost fire resistance performance were higher in the former than the latter. Therefore, slot connection does not a great influence on the temperatures inside the concrete.

• Fire Science and Engineering
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• v.26 no.6
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• pp.64-71
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• 2012

The fire resistance test has been conducted under the standard fire & loading conditions to evaluate fire resistance performance, according to applying to methods of the lateral confinement reinforcement by prestressed Wire Rope and fire resistance reinforcement by Fiber-Cocktail and load ratio for high strength concrete column. The test result, for 60 MPa high-strength concrete column, It was indicated that applying to the wire rope has improved axial ductility in the fire condition, and fire resistance performance has been enhanced by more than 23 %. In addition to this, in case of applying the wire rope to 60 MPa high-strength concrete column, load can be judged that about 70 % of designed load is appropriate. If the Wire Rope and Fiber-Cocktail is applied to 100 MPa high-strength concrete column, It was shown that the fire resistance performance was enhanced by 4 times as much as applying only hoops.

• Journal of Korean Society of Steel Construction
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• v.19 no.6
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• pp.575-585
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• 2007

In this study, a new design equation was presented for square CFTs with high-strength concrete subjected to axial compression and bending. In a previous study, a design equation for square CFTs with normal strength concrete was proposed. A parametric study by fiber analysis was performed taking the width-to-thickness ratio (b/t) and the relative concrete strength to the yield strength of the steel tube (fck/Fy) as the main parameters of this study to determine the maximum moment and the axial load at the maximum moment. A new constitutive model for concrete was adopted for fiber analysis in order to take into account the effect of high-strength concrete. The results of the parametric study were embedded into the method which was presented in the previous study to formulate a new design equation that can be easily used for estimating the strength of square CFTs with high-strength concrete.

• Journal of Korean Society of Steel Construction
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• v.9 no.2 s.31
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• pp.221-228
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• 1997

The main purpose of this paper is to determine the dynamic optimal shapes of simple beam-columns with the constant volume. The parabolic function is chosen as the variable equation for the depth of regular polygon cross-section. The ordinary differential equation including the effect of axial load is applied to calculate the natural frequencies. The Runge-Kutta and Regula-Falsi methods are used to integrate the differential equation and compute the frequencies, respectively. Then the dynamic optimal shape whose lowest natural frequency is highest is determined by reading the critical value of the frequency versus section ratio curve plotted by the frequency data. In the numerical examples, the simple beam-columns are analysed and the numerical results of this study are shown in tables and figures.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.457-460
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• 2008

This study evaluated fire resistance performance for polypropylene/steel fiber reinforced high strength concrete column. Full-size columns were constructed and tested with or without fibers using ISO-834 fire curve. As the result of test, non-fiber high strength concrete column specimen occurred serious spalling and indicated rapidly internal temperature increase. Specimen with polypropylene fiber occurred not spalling. Specimen with hybrid fiber occurred not spalling as well as does not propagated temperature propagation. Therefore, hybrid fiber reinforced column specimen indicated a good fire resistance performance than other cases.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.2
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• pp.189-197
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• 2008

This study presents optimal compensation algorithm of differential column shortening for more than two column groups. The proposed algorithm produces the minimum story groups and their compensation thicknesses which satisfy constraint conditions on performance and construction and enables not only the relative compensation but also the mixed compensation considering absolute shortening. The simulated annealing algorithm is used as the main optimization technique. The applicability of the proposed algorithm was verified by applying it to the 61-storey building where compensation of differential column shortening had already been performed. Using, the proposed algorithm compensation was performed easily and the number of compensation was less than the field method.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.5
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• pp.558-565
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• 2017

Accurate prediction of wave-structure interactions is important in the safety and design cost effectiveness of fixed and floating offshore structures exposed to extreme environmental conditions. In this study, regular waves and circular column structure interactions for four circular columns in regular waves are analyzed. To simulate 3D two-phase flow, open source computational fluid dynamics libraries, called OpenFOAM, were used. When the four circular columns are arranged in a square array, the interactions according to the incident slopes of the regular waves are analyzed. The wave run-up in the circular column surface was compared according to the slope of the incident wave. It was confirmed that high amplitude waves are generated between the circular columns due to the interaction between the circular column and the incident wave. It is expected that this analytical result will be used as the basic data of the study on the air gap due to the interaction between the structure and incident wave.

• Journal of Korean Society of Steel Construction
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• v.20 no.6
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• pp.793-805
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• 2008

Recently, steel modular systems are developed and have been applied to the projects requiring fast construction such as military barracks and vertical expansion of school buildings. The existing modular system with standard module of ${6m\times3m}$ has a problem that many columns are duplicated in the module connection and the wall thickness increases. In this study, $12m{\times}3m$ module is proposed to solve this problem. Various types of beam-middle column connection which are essential for realizing the $12m{\times}3m$ module are proposed and their maximum load capacity and failure mode are analytically and experimentally evaluated. The comparison between analytical and experimental results shows that the maximum axial load and failure mode can be accurately estimated by finite element analysis. Some connection types which have higher failure load than the design load of the column, can be used as the beam-middle column connection detail of the $12m{\times}3m$ module.

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.5
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• pp.101-109
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• 2018

Modular structural systems have been used increasingly for low- and mid-rise structures such as school and apartment buildings. Studies have recently been conducted on the application of the modular structural system to high-rise buildings. To provide sufficient resistances and economical construction for the high-rise modular structural system, a composite unit modular structure was proposed. In this study, the strength of the non-symmetric composite column for the proposed composite unit modular structure was investigated through a series of tests. The experimental study focused on the effect of the slenderness of the column, eccentricity, and through bars on the strength of such a column. Design equations for the non-symmetric column for a modular unit structure were also proposed. From the results, it was found that the proposed design equations provide reasonable strength prediction of the non-symmetric composite column for the modular unit structure.