• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.91-92
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• 2010

This paper is experimental study on the confinement effect of concrete using recycled coarse aggregates confined by steel spirals. The experimental results indicated that confinement effect of recycled aggregate concrete was similar to that of natural aggregate concrete ones.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.77-78
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• 2010

This study investigated the influence of concrete compressive strength for the lateral confinement of high-strength spiral reinforcement. The main test parameters were the compressive strength of concrete, the yield strength of spiral reinforcement, and cross sectional shape. A total of 48 cylindrical test specimens with circularand rectangular sections were cast and tested under monotonic concentric compression.

• 기술세미나
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• s.3
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• pp.149-177
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• 2006

• Journal of the Korea Concrete Institute
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• v.16 no.2 s.80
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• pp.175-184
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• 2004

When the columns of existing RC structures are repaired with FRP composites, the core concrete of the columns is confined by both materials of steel spirals (or steel hoops) and FRP composites because the FRP composites wrap the existing columns which have been already confined with steel spirals or hoops. As the stress-strain curves of steel and fiber are different to each other, the behavior of concrete columns confined with both steel spiral and FRP composites is also different to that of concrete columns confined with only steel spiral or FRP composites. Twenty four RC cylinders were tested in order to observe the behavior of RC cylinders confined with both materials. The observed results of the test showed that the behavior of the test cylinders confined with both materials was quite different to that of cylinders confined with only one material.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2009.11a
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• pp.265-268
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• 2009

전기로 산화 슬래그 골재는 철강산업의 부산물을 재활용한다는 측면에서 친환경적일 뿐만 아니라 고갈되고 있는 골재자원을 대체할 수 있다는 측면에서 중요한 가치를 지닌다. 본 연구에서는 다량의 철성분을 함유하고 있어 높은 밀도를 나타내는 전기로 산화슬래그 골재를 사용한 친환경 콘크리트의 횡구속 성능에 관하여 검토하였다. 이 실험에서는 전기로 산화슬래그 굵은 골재 및 잔골재를 적용한 콘크리트 공시체를 제작하여 천연 굵은 골재와 잔골재를 적용한 콘크리트의 횡구속 거동을 파악하였다. 실험변수는 콘크리트 제작에 사용한 골재의 종류, 횡보강에 사용한 나선 철근의 항복강도로 하였다. 실험결과 전기로 산화슬래그 골재를 사용하였을 경우 천연골재를 사용한 실험체와 유사한 횡구속 효과를 보였다.

• Journal of the Korea Concrete Institute
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• v.15 no.5
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• pp.715-725
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• 2003

This paper is a part of a research program to develop a new design method for reinforced concrete bridge columns under seismic loading. The objectives of this paper are to investigate the relationship between ductility and confinement steel amount and to propose a design equation for reinforced concrete bridge columns. Computer program NARCC was used for parametric study, which was proved to provide good and conservative analytical result especially for deformation capacity and ductility factor compared with test result. A total of 7,200 reinforced concrete columns confined with spirals or perfect circular hoops were selected by combination of variables such as section diameter, aspect ratio, concrete compressive strength, yielding strength of longitudinal and confinement steel, longitudinal steel ratio, axial load ratio, and confinement steel ratio. Based on the parametric study a new design equation for confinement steel amount considering ductility demand was proposed, which can be used in the new seismic design method, i.e. ductility-based seismic design, for RC bridge columns.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.4
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• pp.51-61
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• 2003

This research is a park of a research program to develope a new design method for reinforced concrete bridge columns under axial load and cyclic lateral load. The objectives of this paper are to investigate the relationship between curvature ductility and displacement ductility and to propose a correlation equation for designing of reinforced concrete bridge columns under axial load and cyclic lateral load. Computer program NARCC was used for parametric study, which was proved to provide good and conservative analytical result especially for deformation capacity and ductility factor compared with test result. A total of 7,200 spirally reinforced concrete columns were selected considering the main variables such as section diameter, aspect ratio, concrete strength, yielding strength of longitudinal and confinement steel, longitudinal steel ratio, axial load ratio, and confinement steel ratio. A new equation between curvature ductility factor displacement ductility factor with the aspect ratio was proposed by investigation of 21,600 data produced from the selected column models by applying 3 different definitions of yield displacement.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.4
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• pp.39-49
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• 2003

This research is a part of a research program to develope a new design method for reinforced concrete bridge columns under axial load and cyclic lateral load. A nonlinear analytical method is proposed to obtain moment-curvature relationship and lateral load-displacement relationship. Various analytical models that contribute seismic behavior of reinforced concrete bridge columns are adopted and modified by comparing quasi-static test results of reinforced concrete columns with spirals of circular hoops. The analysis adopts confined concrete model, longitudinal reinforcement test result of reinforced concrete columns with spirals or circular hoops. The analysis adopts confined concrete model, etc. The results obtained using the propose analytical method agree well with test results and give conservative estimations particularly for deformation capacity and ductility.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.2
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• pp.125-133
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• 2007

External confinement by CFS (Carbon Fiber Sheet) is a very effective retrofit method for the reinforced concrete columns subject to either static or seismic loads. For the reliable and cost-effective design of CFS, an accurate stress-strain curve is required for CFS-confined concrete. In this paper, uniaxial compression test on short RC column with circular section was performed. To evaluate the effect of confinement on the stress-strain relationship of CFS-confined concrete, CFS area ratio, spiral area ratio, and concrete compressive strength are considered as the test variables. Experiment results indicate that CFS jacketing significantly enhances strength and ductility of concrete. In addition, the CFS-jacketed specimens with the spiral steel show the lower load increasement ratio than those without the spiral steel.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.1
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• pp.131-139
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• 2012

The lateral reinforcements of concrete such as hoops and spiral bars are known to confine concrete to compensate the strength loss due to fire by reducing explosive spalling and improving the capacity of ductility. In this context, a study was conducted to investigate the residual mechanical properties of confined and unconfined concrete($f_{ck}$=60MPa) after a single thermal cycle at 300, 600, $800^{\circ}C$. The main parameters required to establish the stress-strain relationship are the peak stress, the elastic modulus, and the strain at peak stress. The knowledge of the residual mechanical properties of concrete is necessary whenever the thermally damaged structure is required to bear a significant share of the loads, even after a severe thermal accident. Based on the results obtained in this study, the residual stress of confined concrete under thermal damage is higher according to the level of confinement and the larger strain made it to have better ductility. The decreasing ratio of elastic modulus from the relationship of stress and strain was also smaller than that of unconfined concrete.