• 한국방재학회 논문집
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• 제9권6호
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• pp.1-9
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• 2009

콘크리트의 구속효과 및 재료 비선형성, 강재의 변형 경화, 초기작용 축력을 고려하여 원형 콘크리트 충전 강관(Concrete Filled Steel Tube : CFT) 기둥의 해석을 위한 프로그램을 작성하고 검증 및 해석을 수행하였다. 축력-모멘트 상관관계 해석, 모멘트-곡률 해석, 모멘트-횡변위에 대한 해석을 수행하고, 선행연구자의 실험결과와 비교하여 검증하였다. 검증결과, 작성된 프로그램은 실제 CFT 기둥의 거동에 근접하였으며, 콘크리트의 구속효과를 고려한 경우 그렇지 않은 경우보다 더 큰 강도와 연성능력을 나타내었다. 콘크리트의 강도와 강관의 두께 변화에 따른 간단한 매개변수 해석을 수행하였으며, 콘크리트의 강도 증가 시 CFT 기둥의 강도는 증가하나 연성은 저하되는 결과를 보여주었다. 반면에 강관 두께를 증가시키는 경우에는, CFT 기둥의 강도와 연성 모두 증가하는 결과를 보여주었다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.405-410
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• 2000

Multi-level (macro-level, meso-level, and micro-level) mechanism of prefinitely strained concrete materials os studied The multi-level analysis explains the additional quasibrittle concrete material ductility that comes from lateral confinement and their multi-level interaction mechanisms. The so-called "upgraded tube-squash test" is used to achieve 50% axial strain and over 70 degree of deviatoric strain of quasibrittle concrete materials under extremely high pressure without producing visible cracks. In the micro-level analysis, the variations of hydration rte, micropores, and hydrate phased are analyzed. In the meso-level analysis, mesocracks (the initial invisible cracks) at the interfaces between aggregates and cement paste matrices are studied. The high confining effect in the specimen on the meso-level cracks is also studied. In the macro-level analysis, the physical behavior of prefinitely strained concrete materials is studied. The co-relationships of the results from the three distinct levels of analyses based in various prestraining (0%, 15%, 35%, and 50%) are studied. For the extremely deformed or strained concrete problems, multi-level analysis will be used to explain the unclear and unstudied mechanism of concrete materials, The multi-level analysis can provide us with valuable insights that can explain the additional ductility and confining effect in concrete. concrete.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.133-140
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• 2006

When concrete is confined triaxially, its strength and toughness are enhanced. Hoop reinforcements or transverse reinforcements laterally confine concrete in the case of a RC member and an outer tube confines concrete in a CFT(Concrete Filled Tube) member. But biaxially confined concrete. such as concrete in a hollow R.C member, does not have much enhanced strength and toughness. In this study, a new-type member. which is a hollow CFT member named as an ICH(Internally Confined Hollow) CFT member, was developed to overcome the low ductility of the hollow member and the high cost of the CFT member. A material nonlinear model for the concrete in an CFT member or an ICH CFT member was developed and coded as a computer program based on Mander's concrete model. Analysis results were verified with experimental results and the developed analysis model showed reasonable and accurate results.

• 복합신소재구조학회 논문집
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• 제4권3호
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• pp.13-21
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• 2013

In this study, uniaxial compression tests were performed to investigates the stress-strain relations of Double Skinned Composite Tubular Columns reinforced with steel tube. The confined concrete has been known as the strength of concrete increases significantly. Specimens reinforced with outer and inner steel tube were tested by uniaxial compression test. To investigate the influence of concrete strength increase by confining conditions in steel tubes, 8 specimens with different thickness of tube, hollowness ratio and concrete strength were tested and compared with other researcher's concrete material model.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.431-436
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• 2001

Lateral confining effect due to the existence of the shear reinforcements in R.C. beam is investigate in a numerical way. For the purpose, a three dimensional constitutive model of concrete is developed based on the elasto-plasticity using non-associated plastic flow rule to control the excessive inelastic dilatancy. The plastic flow direction is determined based on the associated plastic flow direction in a way to adjust the directional angle between the two normal vector components along the hydrostatic and deviatoric axis in a meridian plane in which the loading function prescribed. The current formulation is combined with the four parameter elasto-plastic triaxial concrete model recently developed. The resulting elasto-plastic triaxial concrete model predicts the fundamental behaviors of concrete under different confining levels and the 4-points flexural test of a beam with shear reinforcements, compares with the experimental results.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.705-708
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• 1999

Advanced composite materials such as carbon fiber, aramid, and glass fiber sheet, are widely used recently to strengthening existing reinforced concrete structures. The purpose of this paper was to investigate the mechanical characteristics of concrete compressive members confined with carbon fiber sheet and evaluate the efficiency of the strengthening under load actions. Uniaxal compression tests of concrete compressive members confined with carbon fiber sheet were experimentally used to develop a relationship between the axial stresses and the lateral stresses. The resulting axial and lateral strains were used to determine the confinement effect of concrete compressive members.

• Steel and Composite Structures
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• 제13권3호
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• pp.259-275
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• 2012

Concrete filled steel tubular (CFST) member has been widely used in the construction of high-rise buildings for its high axial bearing capacity. It can also be applied on long-span structures such as spatial structures or bridges not only for its high bearing capacity but also for its construction convenience. Concrete casting effect of CFST member is considered in the study of its bearing capacity in this paper. Firstly, in order to authenticate the applicability of constitutive relationship and yield criterion of steel and concrete based on FEM, two ANSYS models are built to simulate and compared with other's test. Secondly, in order to find the huge difference in bearing capacity due to different construction processes, two full-size CFST models are studied when they are horizontally cast and axially compressed. Finally, the effects of slenderness ratio (L/D) and confining parameter (D/t) of CFST members are studied to reveal the intrinsic links between bearing capacity and slenderness ratio or confining parameter.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
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• pp.353-356
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• 2004

Nonlinear numerical analysis was performed to investigate the behavioral characteristics and failure mechanism of flexure -dominated structural walls with partially confined boundary elements. Based on the results, deformability of walls with partially confined boundary elements was evaluated, and a design method which can determine depth of confined boundary element according to given ductility demand, was developed. Also, effective details of laterally confining re-bars were proposed for boundary elements with rectangular cross-section. The design method can be used to choose the spacing of confining re-bars assuring the confining effect and constructability.

• 한국강구조학회 논문집
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• 제23권4호
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• pp.439-454
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• 2011

내부구속 중공 콘크리트 충전 강관(ICH CFT: Internally Confined Hollow Concrete Filled Tube) 기둥의 비선형 해석모델을 제안하고 기존 연구자의 실험 결과를 이용하여 검증하였다. 제안된 모델은 콘크리트의 구속효과와 재료비선형성을 고려하였다. 검증결과, 제안된 해석 모델은 ICH CFT 기둥의 거동을 예측하는데 합리적이고 신뢰할 수 있는 결과를 보여주었다. 제안된 모델을 이용하여 매개변수 연구를 수행하였으며, 기둥의 거동에 영향을 미치는 주요인자로서 콘크리트의 강도, 중공비, 내부강관의 두께를 매개변수로 선택하였다. 해석결과, 콘크리트 강도와 내부강관의 두께는 기둥의 축강도와 모멘트 저항능력에 큰 영향을 주었으나, 중공비의 변화는 축강도에만 영향을 미치는 결과를 보여주었다.

• 콘크리트학회논문집
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• 제21권5호
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• pp.649-660
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• 2009

내부 구속 중공 철근콘크리트(ICH RC, internally confined hollow reinforced concrete) 기둥의 비선형해석 모델을 제시하고 매개변수 연구를 수행하였다. 제안된 기둥 해석 모델은 콘크리트의 구속효과와 재료비선형을 고려하였으며, 해석 결과와 이 연구에서 수행된 ICH RC 기둥 실험 결과 및 선행 연구자들의 실험 결과를 비교하여, 해석 모델을 검증하였다. 검증 결과 제안된 기둥 해석 모델은 만족할 만한 결과를 보여주었으며, 매개변수 연구를 통하여 내부강관의 두께, 콘크리트의 강도와 중공비에 따른 ICH RC 기둥의 거동 특성을 나타내었다.