• 한국화재소방학회:학술대회논문집
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• 한국화재소방학회 2010년도 춘계학술논문발표회 논문집
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• pp.371-376
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• 2010

The strength of steel material in a concrete filled steel tube (CFT) is reduced in fire, but the filled interior concrete structurally ensures the fire resistance due to its high thermal capacity. More, the contractibility of CFT is excellent since it can be constructed without form work. This research analyzed the interior concrete strength and deformation characteristics, which are the influence factors of the fire resistance of CFT, in proportion to the axial load ratio. The fire resistance performance according to changes of the axial load ratio showed great fluctuation. As $280{\times}280{\times}6$ CFT columns with the concrete strengths of 24 MPa and 40 MPa and the axial load ratios of 0.9, 0.6, and 0.2 in accordance with KS F 2257-1 and 7 were heated with loading to examine the fire resistance performance, the 24 MPa concrete exhibited the fire resistance time as 27, 113, and 180 minutes for the axial load ratios, 0.9, 0.6, and 0.2 respectively. In case of 40 MPa concrete, the fire resistance time were turned out to be 19 and 28 minutes for the axial load ratios, 0.9 and 0.6 respectively. The results of 40 MPa concrete showed the much lower fire resistance performance when comparing with those of 24 MPa concrete. The fire resistance performance was not increased significantly when the axial load ratio was reduced. Therefore, the deceased fire resistance performance of high strength concrete is assumed to be caused by the internal pressure increase upon the heat application.

• Steel and Composite Structures
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• 제23권5호
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• pp.611-621
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• 2017

This paper presents an investigation on the fire resistance of high strength fiber reinforced concrete filled box columns (CFBCs) under combined temperature and loading. Two groups of full-size specimens were fabricated. The control group was a steel box filled with high-strength concrete (HSC), while the experimental group consisted of a steel box filled with high strength fiber concrete (HFC) and two steel boxes filled with fiber reinforced concrete. Prior to fire test, a constant compressive load (i.e., load level for fire design) was applied to the column specimens. Thermal load was then applied on the column specimens in form of ISO 834 standard fire curve in a large-scale laboratory furnace until the set experiment termination condition was reached. The test results show that filling fiber concrete can improve the fire resistance of CFBC. Moreover, the configuration of longitudinal reinforcements and transverse stirrups can significantly improve the fire resistance of CFBCs.

• International Journal of Concrete Structures and Materials
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• 제3권2호
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• pp.111-117
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• 2009

Concrete columns reinforced with Fibre Reinforced Polymer (FRP) rebar have been increasingly used in civil engineering applications, while the research on fire resistance of such structural members is still very limited. In this paper, attempts are made to predict temperature distribution and mechanical performance of FRP rebar reinforced concrete columns in fire. The effect of concrete cover and section size on fire resistance time is studied by the finite element method. Based on a parametric study, a simple empirical formula to predict fire resistance time is proposed for possible adoption in fire resistance design.

• 한국화재소방학회논문지
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• 제1권1호
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• pp.19-26
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• 1987

In this study, fire resistance of steel fiber reinforced concrete was investigated Cylindrical and prismatic specimens made of Ordinary Portland Cement plain concrete and steel fiber reinforced concrete were exposed to heating in accordance with a standard time-temperature curve as specified in KS·F22 57, method of fire resistance test for structural parts of buildings, the period of heating was 1 hour and 2 hours. After the fire resistance test, mechanical properties of specimens such as compressive and bending strength, stress-strain curve, static and dynamic modulus of elasticity and bending toughness were investigated. Also the cracks and spallings of the specimens were observed. From the test results, it was confirmed that steel fiber reinforced concrete has a excellent fire resistance than plain concrete in the view of higher residual strength of concrete and smaller crackings because of steel fibers in concrete.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
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• pp.463-468
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• 2001

A lot of considerations on the spatting by fire of high performance concrete should be taken into for fire resistance of the concrete structures. In this paper, fire resistance of high performance concrete is described using polypropylene fiber, which is known to be contributed to fire resistance. Strength level and member size are varied with. According to test results, spatting by fire takes place more easily, as W/C increases and member size decreases. It shows that concrete containing polypropylene fiber has good effects on preventing spatting by fire. In case high performance concrete does not contain polypropylene fiber, residual strength shows to be decreased remarkably compared :o that of normal concrete. Whereas, in case 0.1% of polypropylene fiber contents, high performance concrete shows higher residual strength than that of normal concrete. As member size is smaller, residual strength shows to be decreased.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2002년도 학술논문발표회
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• pp.47-50
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• 2002

This paper presents the results of fire resistance properties of high performance concrete varying with fiber kinds and the size of metal lath in order to verify the validities of fiber on the spatting resistance by fire. Metal lath, glass fiber and carbon fiber are used to confine the concrete. According to test results, plain concrete without lateral confinement and confined concrete with glass fiber and carbon fiber show entire failure after exposed to fire, while confined concrete with metal lath take place in the form of slight surface spatting by fire, which has favorable spatting resistance of concrete. As for the effect of the size of metal lath, when the size of metal lath is more than 1.2mm of thickness, the residual strength of concrete exposed to fire maintains more than 80% of its original strength. However, glass fiber and carbon fiber does not perform desirable spatting resistance by fire due to loss of lateral confinement of fiber exposed to fire caused by melting of fiber and reducing bond strength between concrete and fiber.

• 한국화재소방학회논문지
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• 제25권1호
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• pp.78-84
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• 2011

최근 콘크리트 내화 연구는 대부분 고강도 콘크리트의 내화성능 확보에 많은 초점이 맞추어져 있다. 그러나 국내의 콘크리트 수요를 살펴보면 40MPa 이하의 일반강도 콘크리트의 수요가 전체 콘크리트 수요량의 대부분을 차지한다. 따라서 고강도 콘크리트의 내화성능에 대한 연구뿐만 아니라 일반콘크리트의 내화성능에 관한 연구도 필요하다. 본 연구에서는 40MPa 콘크리트 기둥을 대상으로 콘크리트 피복 두께와 단면크기를 변수로하여 내화성능을 평가하였으며, 연구 결과 단면크기가 커질수록, 피복두께가 두꺼워질수록 내화성능은 향상되는 것으로 나타났다.

• 한국화재소방학회논문지
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• 제24권6호
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• pp.104-111
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• 2010

CFT기둥은 강관내부에 콘크리트를 채워 넣은 구조로서, 화재 시 강관의 강도는 저하되나 내부 콘크리트의 높은 열용량 효과로 내화성능을 확보할 수 있는 구조이다. 본 연구에서는 강관내부의 충전된 콘크리트의 압축강도 및 축력비 변화에 따른 CFT기둥의 내화성능을 평가하였다. 내화성능의 평가는 KS F 2257-1 및 KS F 2257-7에 따라 수행되었으며, 적용 부재 단면은 $280{\times}280{\times}6$, 콘크리트 압축강도 24MPa, 40MPa 및 축력비 0.9, 0.6, 0.2를 실험변수로 설정하였다. 재하가열시험을 통한 내화성능평가 결과, 콘크리트 압축강도 24Mpa의 경우 축력비 0.9, 0.6, 0.2에서는 각각 27분, 113분, 3시간 이상으로 나타나 축력비 변화에 따른 내화성능이 크게 변화하는 것으로 나타났다. 콘크리트 압축강도 40MPa의 경우, 축력비 0.9, 0.6에서는 각각 19분, 28분으로 나타났다. 40MPa는 24MPa에 비해서 축력비 변화에 따른 내화성능 향상 효과는 크지 않은 것으로 나타났다. 이는 고강도의 경우 가열시 발생되는 내부 압력의 상승로 성능저하가 크게 발생되는 것으로 판단되었다.

• 한국건축시공학회지
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• 제13권3호
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• pp.272-281
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• 2013

Concrete filled tube (CFT) columns, which consist of a steel tube filled with concrete, combine the benefits of the two materials. The steel tube provides a confining pressure to the concrete, while the local buckling of steel plate can be prevented by the concrete core. CFT columns also have a high fire resistance due to the heat storage effect of concrete under fire. For this reason, it is possible to develop CFT columns without fire protection measures. CFT columns without fire protection have many advantages, including quality control, cost reduction, better space efficiency and a shorter construction period. Due to these advantages, studies on the development of CFT columns without fire protection measures have been performed. However, CFT columns lose their bearing capacity under fire because the steel tube is exposed to the outside. As a result, the structure is collapsed, causing significant damage. In this research, we made a CFT column using high strength concrete (100 MPa) and high strength steel (800 MPa). We use steel fiber and nylon fiber with concrete to provide fire resistance. We perform the fresh concrete experiment and investigate the fire resistance of the CFT column (${\Box}400{\times}400{\times}15{\times}3000mm$) under loading. To investigate the effect of steel fiber on increasing fire resistance, we compare the fire resistance time according to the steel fiber. Through the test, it was found that the CFT specimen with steel fiber had better fire resistance performance than other cases.

• 대한건축학회논문집:구조계
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• 제36권5호
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• pp.147-154
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• 2020

Currently, there are no specific repair methods for RC structures damaged by fire, and repair methods are applied when durability deteriorates due to aging. In addition, a number of recent studies have been reported that have conducted fire resistance assessment of the repair materials themselves, assuming exposure to high-temperature environments such as fires. However, researches that evaluate the fire resistance performance of the repair materials by applying existing repair materials to the actual fire damaged reinforced concrete structures are very rare. Therefore, in this study, a number of existing repair materials were applied to fire-damaged concrete column to compare and evaluate the fire resistance performance with the original cover concrete.