• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4A
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• pp.565-575
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• 2006

When concrete is confined, its strength is enhanced by confining stress. Thus, increasing confining stress makes concrete strength higher. But a brittle failure may occur in hollow RC(Reinforced Concrete) column although its concrete is confined by transverse reinforcements. This brittle failure results from the absence of internal confinement and it decreases the strength and the ductility of a hollow RC column. To overcome this brittle failure problem, a hollow RC column which has a internal steel tube was developed. In this study, an experiment was performed to investigate the existence of to internal confinement by a settled steel tube. Thirty six specimens were tested and test results show the existence of internal confinement by the increase of concrete strength.

• Journal of the Korea Concrete Institute
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• v.27 no.5
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• pp.569-577
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• 2015

The aim of this study is to qualitatively evaluate the cracking control effects of expansive concrete used in reinforced concrete building. The result of experiments in laboratory shows that autogenous shrinkage and drying shrinkage are suppressed by using expansive additive. The tensile stress-strength ratio is lower in expansive concrete than normal concrete under fully restrained condition. Compression stress could be effectively generated in early age in the walls in buildings by the use of expansive additive, and tensile stress due to drying shrinkage at later age eventually decreased. Additionally, visual observation at long-term ages shows that the cracking area of expansive concrete was approximately 35% of normal concrete, which confirms that the use of expansive additive reduces concrete cracking in reinforced concrete buildings.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.3
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• pp.110-118
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• 2008

The use of FRP bar as reinforced concrete beams is considered as one of the most prominent solution that may overcome the corrosion of reinforcing steel bars. However, in the case of FRP reinforced concrete, both the reinforcing and the reinforced materials are brittle. For this reason, ductility of structures with FRP reinforcement is much less than that of structures with steel reinforcements. In this study, a method has been suggested to provide a meaningful quantification of ductility for concrete beams reinforced with FRP bars. This paper shows which the confinement to the compression concrete by the spiral can increase the ductility of FRP over-reinforced concrete beams.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.4
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• pp.11-24
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• 1990

The effect of end restraints for adjoining members is the different variables influencing the column ultimate strength and the behavior. The propose of this study is to analyze eccentrically loaded reinforced concrete columns with the end restraind effect having rectangular cross-section and general boundary conditions. Accordingly, this investigation are to construct a typical analytical model of the reinforced concrete columns with general end boundary conditions. The mechanical components of the analytical model are to be rationally defined the actual behavior as possible, and the different variables influencing the behavior and the ultimate strength of the reinforced concrete columns are investigated by using a parametric study.

• Computational Structural Engineering
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• v.4 no.1
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• pp.121-132
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• 1991

The purpose of this study is to analyze concentrically loaded reinforced concrete columns with the restrained effect having rectangular cross-section and general boundary conditions. Accordingly, this investigation is to construct a typical analytical model of the reinforced concrete columns with general boundary conditions. The mechanical components of the analytical model are to be rationally defined so as to model the actual behavior as closely as possible, and the ultimate strength of the reinforced concrete columns are investigated by end restrained effect.

• Journal of the Korea Concrete Institute
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• v.27 no.1
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• pp.45-53
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• 2015

In general, RC columns are reinforced by spiral or tied steel and a strength of confined concrete is more increased than this of unconfined concrete. And strength and ductility of column are increased by a confinement effect. A confinement effect is affected by concrete strength, spacing, volume and strength of confinement steel. Many researchers suggested various confinement models which reflected these parameters by many experimental results. In this study, a load-strain relationship is evaluated by a confinement model in EC2, and it is compared with Mander model, Saatchioglu-Razvi model and Cusson et al. model. As results, it is appeared that a confinement model in EC2 is able to apply all kinds of concrete strength and a consistency in sectional analysis can be secured using material models in EC2. In parameter studies using material models in EC2, a confinement effect is more affected by a confinement steel than a concrete strength.

• Journal of Korean Society of Steel Construction
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• v.15 no.2
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• pp.159-165
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• 2003

A tubular member with through-gusset plate is often used to transmit axial compression in an electric transmission towers. In current code, the strength of tubular member is evaluated with an effective length factor k=0.9 without considering the deformation of boundary element. A buckling strength of member with end gusset plate is affected by stiffness ratio($\beta$) and the length ratio(G) between main tubular member and end gusset plate. In this study theoretical mechanism based on the elastic buckling behavior was investigated, and finite element analysis was performed to propose a formula for the buckling strength and effective length factor of tubular member in elsatic and inelastic ranges.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.7
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• pp.3562-3569
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• 2013

The performance of concrete structure decreases with change in time and the external environment. In order to reinforce the structure, the research about new material development and application of newly developed materials are widely conducted. In the case of composite FRP, it received good attention in the academia due to its high intensity-weight ratio, excellent corrosion resistency as well as good workability. When applying at the construction field, however, the utilization of FRP did not increase as much due to lack of reliability and design standard. Current study investigated the material characteristics during the temperature change at high temperature and the structural behavior from restraint effect for GFRP reinforcing materials. Two experimental variables were set in this study: GFRP reinforcements due to tensile properties of temperature and restraint compression effects. Three concrete specimen were selected for each set temperatures. For this reason, as a variable to experiment with the effects confined compression concrete members value and tensile properties with temperature reinforcement GFRP, experiment produced three pieces each for each set temperature, the concrete specimen, which is confined in the GFRP was selected each I did. For the temperature change during the experiment, the concrete specimen were mounted in order to expose to experimental high temperature for certain period of time. For compression performance evaluation, reinforcement effect from horizontal constraint of the fiber were measured using an Universal Material Testing Machine (UTM). Finally, this study revealed that the binding characteristics of GFRP materials from temperature change decreased. Also, this study showed that the maximum compression intensity decreased as the temperature increased up to $150^{\circ}C$ in the constraints ability of the GFRP reinforcements during the horizontal constraint of concrete.

• Journal of Korean Society of Steel Construction
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• v.25 no.1
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• pp.1-13
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• 2013

Most rahmen-type temporary bridges are constructed with limited bridge length to prevent excessive horizontal forces due to the thermal expansion of main girder. To achieve a long length temporary bridge several independent bridges are required and they can not share the bents, at the rahmen-type ends, with the adjacent ones. The additional bents require more cost and reduce the section space under bridges. In order to remove extra bents with keeping the rahmen effect at the bridge ends, this study proposes a new rahmen-type movable joint system for temporary bridges.

• Journal of the Korean Society for Advanced Composite Structures
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• v.2 no.2
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• pp.7-12
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• 2011

Presently, composite method for steel and concrete is often used the stud. Steel properties of composite column could be changed by increasing of welding. The changed properties is possibly to cause local-buckling. Composite column had a large effect by slip instead of pull-out force in comparison composite girder. Improvement of adhesive force had effect by contact area rather than height of stud in composite column. This paper proposed new type of stud and analyzed performance through experimental study. This method would be effect steel structure with curvature.