• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.1
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• pp.101-113
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• 2015

This paper introduces a numerical analysis method for reinforced-concrete(RC) members exposed to fire and proposes considerations in designing RC structures on the basis of the comparison between numerical results and design codes. The proposed analysis method consists of two procedures of the transient heat transfer analysis and the non-linear structural analysis. To exactly evaluate the structural behavior under fire, two material models are considered in this paper. One is "Under-Fire" condition for the material properties at the high temperature and the other one is "After-Cooling" condition for the material properties after cooling down to air temperature. The proposed method is validated through the correlation study between experimental data and numerical results. In advance, the obtained results show that the material properties which are fittable to the corresponding temperature must be taken into account for an accurate prediction of the ultimate resisting capacity of RC members. Finally, comparison of the numerical results with the design code of EN1992-1-2 also shows that the design code needs to be revised to reserve the safety of the fire-damaged structural member.

• Journal of the Korea Concrete Institute
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• v.13 no.3
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• pp.195-205
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• 2001

This Paper describes a numerical method to evaluate the flexural strength of reinforced concrete members exposed to fire. An analytical method is developed for the moment-curvature relationship for the cross section which is subjected to high temperature. The method performs heat-transfer analysis for the cross sections and subsequently performs numerical analysis using the stress-strain relationships of concrete and reinforcing steel in various heat conditions. The results of the numerical studies are ; 1) the residual flexural strength exposing at high temperature is affected by the heating time, the depth of concrete cover and reinforcement ratio, 2) the residual flexural strength after exposed at high temperature is recovered of its original strength at minimum ratio of reinforcement, while members having half of maximum ratio and maximum ratio of reinforcement do not recover its original strength, 3) furthermore, the concrete may reach its maximum capacity before reinforcement yields in reinforced concrete members having maximum ratio of reinforcement.

• Fire Science and Engineering
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• v.13 no.3
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• pp.19-26
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• 1999

$CO_2$ extinguishing system is the most $\phi$pular among the gas extinguishing system. $CO_2$ is usually stored with liquified state. But, it gasifies at the tip of nozzle when $CO_2$ was released through the pipe and head. A ro$\alpha$n temperature is very low when $CO_2$ was released. So electrical instrument, magnetic storage equipment and memory semiconductor are electrically or physically injured by cooling effect in a few minutes. So, we intend to find out temperature profile and electrical damage in compartment area, and supply basic d data for research and making standards and code through the full scale experiment. As result of experiment on the damage due to cooling effect from $CO_2$ extinguishing system, i instantaneous discharging temperature. was $-82.5^{\circ}C$ in average. An average temp. in the compartment after discharging $CO_2$ was $-40^{\circ}C$.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.4A
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• pp.391-398
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• 2010

The fire performance of RC slabs with half-depth precast panel after exposure to the ISO-834 fire standard without loading has been experimentally investigated. During heating, according to the ISO 834 fire curve, concrete spalling was observed for concrete without PP(polypropylene) fibers. No spalling occurred when heating concrete containing PP fibers. The maximum temperature of RC slabs with PP fibers with half-depth precast panel was lower than that of concrete without PP fibers. The ultimate load after cooling of the RC slabs that were not loaded during the furnace tests was evaluated by means of 3 points bending tests. The ultimate load of the RC slabs without PP fibers showed a considerable reduction (around 32.5%) of the ultimate load after cooling if compared with of RC slabs with PP fibers. The ultimate load of the RC slabs with half-depth precast panel with PP fibers is higher than that of a full-depth RC slabs with PP fibers. Also, the addition of PP fibers and the use of half-depth precast panel improve fire resistance.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.415-415
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• 2011

국제핵융합실험로(ITER)에 장착되는 한국형 헬륨 냉각 고체형 증식(Helium Cooled Solid Breeder : HCSB) 시험 블랑켓(Test Blanket Module : TBM)은 ITER 참여국 중 유일하게 중성자 반사 재료를 채택한 것이 특징이다. 중성자 반사재료로는 지름 1 mm 내외의 흑연 페블을 사용 할 예정이다. 흑연은 중성자 반사특성은 우수하지만 기계적 특성이 비교적 좋지 않다는 단점이있다. 뿐만 아니라, 산화나 화재 등에 대해서도 취약하기 때문에 흑연이 노출된 상태로 사용하는 것은 위험부담이 클 수밖에 없다. 따라서 흑연을 코팅해서 사용하기 위한 연구개발이 진행 중이며, 코팅 후보물질로는 저방사화 및 고경도의 특성을 갖는 SiC가 유력시 되고 있다. 흑연위에 SiC를 코팅하는 방법은 여러 가지가 있으며, 그 중에서 비교적 간단한 RF Sputtering, PECVD를 이용해서 SiC를 코팅하고 그 특성을 평가했다. RF Sputtering에서 흑연의 온도를 상온으로 두었을 때는 SiC가 결정으로 성장되지 않는 것을 확인할 수 있었으며, $900^{\circ}C$ 이상의 온도에서 열처리과정을 거친 후 결정이 형성되는 것을 확인할 수 있었다. 그리고 열처리 온도가 $1200^{\circ}C$ 부근에서는 SiC nano-wire가 형성되는 것을 확인할 수 있었다. PECVD의 경우 전구체 물질로 사용된 $SiH_4$와 $CH_4$의 비율에 따라서 SiC의 형성비율이 다른 것을 알 수 있었으며, 결정 상태는 성장시 기판온도에 크게 의존하는 것을 확인할 수 있었다. 최근에는 보다 효율적으로 SiC를 코팅하기 위하여 흑연페블을 spouting시키면서 코팅할 수 있는 CVD 장치를 설계-제작했으며, 전구체 물질로는 $SiH_4$, $Si(CH_3)_4$, $CH_3$ $SiCl_3$ 등이 사용될 예정이다.