• Journal of the Korea Concrete Institute
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• v.23 no.3
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• pp.377-384
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• 2011

Although concrete is considered as fire proof materials, high strength concrete shows severe material and structural damages when exposed to fire. To understand such damages in high strength concrete structures, the effects of various design parameters and fire condition on the thermal behaviors of high strength concrete structures are investigated in this study. In order to achieve this goal, fire tests are performed on high strength concrete columns with different fire conditions and design parameters including cross sectional area, cover thickness, and reinforcement alignment. To investigate thermal behaviors, temperature distributions and amount of spalling are measured. In overall, the columns show rapidly increasing inner temperatures between 30~60 mins of the fire tests due to spalling. In detail, the higher temperature distributions are observed from the columns with the larger cross section and less cover thickness. Moreover, among the columns with same reinforcing ratio, larger number of reinforcements with the smaller diameter causes the higher temperature distribution. The findings from the experimental study allow not only understanding of thermal behaviors of high strength concrete columns under fire, but also guidance in revising fire safety design.

• Journal of the Korea Concrete Institute
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• v.26 no.5
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• pp.643-650
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• 2014

Generally, the reinforced concrete slab has great fire resistance performance because concrete has excellent thermal material properties under fire. But, in the case of hollow slab, it will be expected that hollow slabs have different temperature distribution and fire endurance performance compare to reinforced concrete slab. Because hollow slab has internal void space that occurs decreasing regenerative effect of concrete and formation of internal air layer. Evaluation method for fire resistance performance of hollow slabs was proposed using $wickstr{\ddot{o}}m^{\prime}s$ method. For the casual use of evaluation, simplified method was proposed which was limited to solid slab and donut type hollow slab which was developed by authors of this research paper. Also, verification on proposed method was performed by comparing results of fire experiment for hollow slab and evaluation results. Proposed method of the results of this study was possible to predict the residual strength and temperature distribution of slabs under fire.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2009.04a
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• pp.61-66
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• 2009

최근 초고층 건축물 등에 적용되는 고강도콘크리트의 내화성능에 대한 문제점이 제기됨에 따라 국토해양부에서는 고강도콘크리트 내화성능 관리 기준을 고시한 바 있으며, 건설업계에서도 이에 대응하기 위해 다양한 기술 검토가 이루어지고 있다. 본 연구에서는 고강도콘크리트의 취약점으로 제기되고 있는 화재시의 폭렬문제에 대한 대응방안으로서 기존 연구를 통해 내화성능이 우수한 것으로 보고되고 있는 ECC 를 영구거푸집으로 활용한 고강도콘크리트의 내화성능을 검토하였다. ECC 영구거푸집을 활용한 고강도콘크리트 기둥부재의 내화성능 검토 결과, 영구거푸집과 고강도콘크리트 계면으로의 열 침투를 제어할 수 있도록 부재 생산 및 구축 방안을 검토하고, ECC의 적정 배합 및 두께를 확보한다면 고강도콘크리트의 내화성능 확보기술로서의 활용이 가능할 것으로 판단된다. 또한, 내화성 영구거푸집으로서의 단순 활용 방안 이외에 ECC의 우수한 물리적 성능을 활용하여 구조성능을 분담할 수 있는 방안으로의 지속적 검토가 필요할 것으로 판단된다.

• Journal of Korean Society of Steel Construction
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• v.12 no.6
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• pp.759-767
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• 2000

In this study, the time dependent internal stress changes of a Concrete Filled Steel Tube(CFT) column during a fire test were quantitatively analyzed. The strain ratio of a CFT column on the different loads was measured by tensile strength tests in terms of yield strength, tensile strength average extensibility and elasticity modulus. To understand the internal material properties change of concrete in CFT column damaged due to a fire, the compressive strength and elastic modulus tests were measured on a core sample from the center of the steel tube after the fire test. The elastic modulus test measured the strain from the stress. To determine the fire temperature of the test material, a differential thermal analysis was done. From the tested result, the gained data were conducted and an analysis method was suggested. The purpose of this work is to suggest a basic data for structure regulation enactments of the internal fire design of CFT.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2012.04a
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• pp.290-293
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• 2012

화재는 콘크리트 구조물의 역학적 특성에 치명적 손상을 일으켜 건축물의 안전성을 급격하게 감소시킬 수 있다. 특히 고강도콘크리트는 폭렬이 발생하여 심각한 단면 손실과 노출된 철근으로 인하여 건축물의 안전성에 치명적인 영향을 미친다. 이러한 폭렬에 대하여 다양한 연구가 진행되고 있지만, 폭렬의 발생원인은 명백하게 밝혀지진 않았다. 이에 본 연구는 콘크리트의 함수율과 열응력이 폭렬에 미치는 영향을 분석하여 폭렬로부터 구조물의 안전성을 확보하기 위한 기초 자료를 제시하였다.

• Magazine of the Korea Concrete Institute
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• v.20 no.5
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• pp.12-21
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• 2008

• Magazine of the Korea Concrete Institute
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• v.23 no.3
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• pp.28-31
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• 2011

• Magazine of the Korea Concrete Institute
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• v.23 no.3
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• pp.44-46
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• 2011

• Journal of the Korea Institute of Building Construction
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• v.20 no.3
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• pp.235-243
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• 2020

In recent years, the use of high-strength concrete has increased with increasing height and enlarging scale of the buildings However, it has been pointed out that the use of high-strength concrete is the most serious problem compared to ordinary concrete in terms of the spalling of concrete cross sections caused by fires. For this reason, fiber cocktail methods, which are made of polypropylene fibers, nylon fibers, etc., are mainly used to improve the fire resistance performance. However, the majority of research on high-strength concrete to which the fiber cocktail method was applied is mainly focused on the effect of reducing spalling, and few studies have investigated and analyzed the effect of micropores produced by melting PP fibers on the long-term durability of high-strength concrete after a fire. Therefore, in this study, the effect of micropores on the depth of carbonation was examined through carbonation tests and microstructure analysis, assuming high-strength concrete to which fiber-mixed construction method was applied, which caused fire damage.

• Journal of the Korea Concrete Institute
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• v.19 no.3
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• pp.283-292
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• 2007

A research projects is currently being conducted to develop a nonlinear finite element analysis methods for predicting the structural behavior of reinforced concrete frame structures, exposed to fire. As part of this, reinforced concrete frames subjected to fire loads were analyzed using the nonlinear finite-element program DIANA. Two numerical steps are incorporated in this program. The first step carries out the nonlinear transient heat flow analysis associated with fire and the second step predicts the structural behavior of reinforced concrete frames subjected to the thermal histories predicted by first step. The complex features of structural behavior in fire conditions, such as thermal expansion, plasticity, cracking or crushing, and material properties changing with temperature are considered. A concrete material model based on nonlinear fracture mechanics to take cracking into account and plasticity models for concrete in compression and reinforcement steel were used. The material and analytical models developed in this paper are verified against the experimental data on simple reinforced concrete beams. The changes in thermal parameters are discussed from the point of view of changes of structure and chemical composition due to the high temperature exposure. Although, this study considers codes standard fire for reinforced concrete frame, any other time-temperature relationship can be easily incorporated.