• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.379-382
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• 2009

횡방향으로 구속된 콘크리트의 응력-변형률 거동은 구속되지 않은 콘크리트와는 다른 거동을 한다. 보통강도 콘크리트에서 구속효과를 고려한 콘크리트 재료모델로는 Mander 모델이 대표적이며 고강도 콘크리트의 구속효과의 경우 여러 연구자들에 의하여 제안된 모델 중 공시체 수준의 실험결과와 잘 일치하는 Sakino-Sun 모델을 사용하였다. 보통강도에서는 Mander모델을 고강도 콘크리트에서는 Sakino-Sun 모델을 사용하였으나 중간 강도인 30-40MPa의 강도에서 Mander 모델과 Sakino-Sun 모델의 적용시 실험결과와 해석결과가 다소 차이를 보이며 또한 두 모델은 적용할 수 있는 최대 또는 최소 콘크리트 압축강도의 한계범위가 명확하지 않다. 따라서 이 연구에서는 30-40MPa의 강도의 횡방향으로 구속된 콘크리트의 비선형 재료모델을 제안하고 실제 30-40MPa의 압축강도를 갖는 콘크리트 공시체의 일축압축시험 결과와의 비교를 통해 그 적용성을 검토하였다.

• Journal of Korean Society of Steel Construction
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• v.19 no.1
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• pp.43-52
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• 2007

There is a growing range of applications for concrete-filled steel tube (CFT) member because of its superior performance. But a CFT member may be uneconomical or has weight problems because it is fully filled with concrete. In this study, a new type of member, called internally confined hollow (ICH) CFT member, was developed to solve the high cost and weight problems of the CFT member. To determine stress-strain model of the concrete in an ICH CFT column, possible failure modes of an ICH CFT column were suggested and confining pressure was derived from equilibriums for each failure mode. From the derived equations, a computer program was coded and parametric studies were performed for some examples. Analytical results showed that internally confined concrete has enhanced strength and ductility compared with those of unconfined or biaxially confined concrete.

• Journal of Korean Society of Steel Construction
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• v.23 no.4
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• pp.439-454
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• 2011

A nonlinear analysis model for internally confined hollow concrete-filled tube (ICH CFT) columns was suggested and was verified by the test results obtained by the previous researchers. The suggested model considered the confining effect and nonlinearity of concrete. The verified results showed that the suggested model was reasonable and reliable for predicting the behavior of an ICH CFT column. Additionally, a simple parametric study was carried out. The strength of concrete, the hollow ratio of a column, and the thickness of an inner tube were selected as parameters affecting the behavior of an ICH CFT column. The analysis results showed that the concrete strength and the thickness of the inner tube affect the axial strength and moment capacity of the column while the hollow ratio affects only its axial strength.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.6
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• pp.1-9
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• 2009

An analysis program to predict the behavior of a concrete filled steel tube column (CFT) was developed. It considered confining effect, material nonlinearity, strain hardening of steel, and initial axial load. With the developed program, axial load-bending moment interaction analyses, moment-lateral displacement relation analyses, and lateral load-lateral displacement relation analyses were performed. For the verification of the developed program, analysis results were compared with the test results from the other researches. The verified results showed that the developed program predicted the behavior of the CFT column with agreeable accuracy. And they showed that it is necessary to consider the confining effect for the reasonable analysis of the CFT column. A simple parametric study was performed and it chose the strength of unconfined concrete and the thickness of a steel tube as the major parameters affecting the behavior of the CFT column. The parametric analysis results showed that the CFT column had higher strength and smaller ductility by increasing the strength of concrete. But the CFT column showed higher strength and larger ductility by increasing the thickness of the steel tube.

• Journal of the Korean Geotechnical Society
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• v.17 no.4
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• pp.107-115
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• 2001

해성토층 위에 준설매립된 수도권 해안매립지역에서 원형의 대심도 굴착공사로 인하여 발생하는 지중연속벽의 수평변위를 예측하기 위하여 수치해석을 수행하였고, 이러한 수치해석결과와 현장측정값을 비교하여 각각의 수치해석방법의 적용성을 평가하였다. 수치해석법으로는 지반반력해석, 선형 유한요소법 그리고 비선형 유한요소법이 수행되었다. 각각의 방법들에서는 미소변형률에서의 지반거동특성인 비선형성과 굴착으로 인한 구속압감소효과를 고려한 경우와 고려하지 않은 경우에 대하여 수치해석을 수행하여 각각 그 결과들을 비교.분석하였다. 이러한 분석결과 미소변형률에서의 비선형성과 굴착으로 인한 구속압감소 효과를 고려한 비선형 유한요소해석법이 가장 정확하게 수평변위를 예측할 수 있는 방법임을 알 수 있었다.

• Journal of the Korea Concrete Institute
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• v.21 no.5
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• pp.649-660
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• 2009

A nonlinear column model of an internally confined hollow (ICH) reinforced concrete (RC) column was suggested and a parametric study was performed. The suggested column model considered the confining effect and the material nonlinearity of concrete. To verify the suggested column model, its analysis results were compared with the test results from previous researchers and a quasi static test performed in this study. They showed that the suggested column model was reasonable and had acceptable accuracy. The results from parametric studies showed that the thickness of the internal tube, concrete strength, and the hollow ratio of the ICH RC column affected its behavior.

• Proceedings of the KSR Conference
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• 2006.05b
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• pp.565-574
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• 2006

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.4A
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• pp.227-235
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• 2012

Recently, study of confining effect in column members is progressed. But these studies are limited to about RC column and external confining effect in hollow columns. Internal confining effect in hollow columns has not researched. Internal confining stress is assumed the same external confining stress in hollow columns. In this study, there are to investigate the internal direction confining effect in ICH CFT column by FEA analysis. FEA analysis methods have verified by experimental values. Parametric study has performed as thickness of internal tube, hollow ratio, diameter of column and bending stiffness between concrete and external tube. Modified equations have suggested to estimating economic and reasonable thickness of internal tube.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.305-308
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• 2008

The purpose of this study is to propose the confinement effectiveness of precast segmental concrete that binding by lateral confining steel in the method of precast segmental concrete pridge piers construction. Generally, the confinement effect of concrete that binding by lateral confining steel is defined by the confinement effectiveness coefficient and the confinement effectiveness coefficient is defined as the ratio of area of effectively confined concrete core to area of confined concrete core. The area of effectively confined concrete core is defined by Arching action occurred on a space of lateral confinement steel and The area of confined concrete core is defined by the ratio of area of longitudinal reinforcement to area of core of section. But in case of precast segmental concrete, concrete cover that exist on top and bottom of concrete segment should be considered.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.261-264
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• 2008

When the concrete is confined to width direction, stress-strain curve of concrete are different from the uniaxial behavior. In case of normal strength concrete, Mander model are used with concrete material model which considers confining effect. Sakino-Sun model showed experimental result of specimen-level and the highest accuracy. Therefore, Normal strength concrete used Mander model. and High strength concrete used Sakino-Sun model. But there are significant differences from actual data when medium strength concrete used Mander or Sakino-Sun model. and Limit scope of maximum or minimum compressive strength of concrete is not clear when applied to two models. Therefore, In this research, material nonlinear model of confined concrete is suggested when concrete which has 30-40MPa's strength is confined to width direction.