• Steel and Composite Structures
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• 제13권6호
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• pp.521-537
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• 2012

In this study, an experimental study is performed to understand the effect of spalling on the structural behavior of fire damaged steel reinforced high strength concrete (SRHSC) columns, and the test results of temperature distributions and the displacements at elevated temperature are analyzed. Toward this goal, three long columns are tested to investigate the effect of various test parameters on structural behavior during the fire, and twelve short columns are tested to investigate residual strength and stiffness after the fire. The test parameters are mixture ratios of polypropylene fiber (0 and 0.1 vol.%), magnitudes of applied loads (concentric loads and eccentric loads), and the time period of exposure to fire (0, 30, 60 and 90 minutes). The experimental results show that there is significant effect of loading on the structural behaviors of columns under fire. The loaded concrete columns result more explosive spalling than the unloaded columns under fire. In particular, eccentrically loaded columns are severely spalled. The temperature distributions of the concrete are not affected by the loading state if there is no spalling. However, the loading state affects the temperature distributions when there is spalling occurred. In addition, it is found that polypropylene fiber prevents spalling of both loaded and unloaded columns under fire. From these experimental findings, an equation of predicting residual load capacity of the fire damaged column is proposed.

• Advances in concrete construction
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• 제6권5호
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• pp.485-507
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• 2018

Concrete-Filled Steel Tube (CFST) columns are an increasingly popular means to support great compressive loads in buildings. The residual strength capacity of CFST stub columns may be utilized to assess the potential damage caused by fire and calculate the structural fire protection for least post-fire repair. Ten specimens under room conditions and 10 specimens under fire exposure to the Eurocode smouldering slow-growth fire were tested to examine the effects of diameter to thickness D/t ratio and reinforcing bars on residual strength capacity, ductility and stiffness of CFST stub columns. On the other hand, in sixteen among the twenty specimens, three or six reinforcing bars were welded inside the steel tube. The longitudinal strains in the steel tube and load-displacement relationships were recorded throughout the subsequent compressive tests. Corresponding values of residual strength capacity calculated using AISC 360-10 and EC4 standards are presented for comparison purposes with the experimental results of this study. The test results showed that after exposure to $750^{\circ}C$, the residual strength capacity increased for all specimens, while the ductility and stiffness were slightly decreased. The comparison results showed that the predicted residual strength using EC4 were close to those obtained experimentally in this research.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.32-35
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• 2004

In recent years a number of catastrophic tunnel fires, the Euro tunnel, the Mont Blanc tunnel, the Tauem tunnel and the Gotthard tunnel, have occurred and inflicted serious damages to European countries. If a fire occurs in shield tunnels, the reinforced concrete segment linings playing as an important structural member is expected to damage severely and finally can be caused the collapse of tunnel. The purpose of this study is to evaluate the performance of concrete segment lining under heat exposure and to obtain information to assist a new technical approach to fighting fires in tunnels. In order to evaluate the fire-resistance performance of concrete segment by adding Polypropylene fibers, fire tests using the RABT heat-load curve is carried out. The temperature rise of this curve is very rapid up to $1200^{\circ}C$ within 5 minutes, and duration time of the $1200^{\circ}C$ exposure is 55 minutes. From the fire test, it was found that the explosive spalling was rapidly reduced by adding polypropylene fibers and this method is considered as an effective fireproof material to upgrade fire safety in tunnels economically.

• 국제초고층학회논문집
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• 제7권4호
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• pp.299-311
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• 2018

As engineered timber such as Glulam is seeing increasing use in tall timber buildings, building codes are adapting to allow for this. In order for this material to be used confidently and safely in one of these applications, there is a need to understand the effects that fire can have on an engineered timber structural member. The post-fire resilience aspect of glulam is studied herein. Two sets of experiments are performed to consider the validity of zero strength guidance with respect to short duration fire exposure on thin glulam members. Small scale samples were heated in a cone calorimeter to different fire severities. These samples illustrated significant strength loss but high variability despite controlled quantification of char layers. Large scale samples were heated locally using a controlled fuel fire in shear and moment locations along the length of the beam respectively. Additionally, reduced cross section samples were created by mechanically carving a way an area of cross section equal to the area lost to char on the heated beams. All of the samples were then loaded to failure in four-point (laterally restrained) bending tests. The beams that have been burnt in the shear region were observed as having a reduction in strength of up to 34.5% from the control beams. These test samples displayed relatively little variability, apart from beams that displayed material defects. The suite of testing indicated that zero strength guidance may be under conservative and may require increasing from 7 mm up to as much as 23 mm.

• 한국화재소방학회논문지
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• 제23권4호
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• pp.59-66
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• 2009

본 연구는 합성구조에 사용되는 스터드커넥터의 화재시 성능에 대한 연구이다. 스터드커넥터는 전단연결재로 가장 폭넓게 사용되고 있으며, 콘크리트와 강재를 일체화시켜 합성 성능을 확보한다. 스터드커넥터에 대한 상세 내화성능은 아직 명확한 자료가 없으며, 향후 성능설계에서 무피복 합성보 등에 대한 설계 자료로 요구 된다. 본 실험의 스터드커넥터 성능시험은 푸시 아웃 실험을 변형하여 특수 전기로와 결합 ISO 표준온도곡선을 기본으로 거동 성능실험을 수행하였으며, 화재 조건의 파괴 형상을 기반으로 성능 분석 방법을 제안하였다.

• Advances in concrete construction
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• 제11권1호
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• pp.11-18
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• 2021

The present study fabricated polyvinyl alcohol (PVA) fiber-reinforced alkali-activated slag/fly ash (AASF) composites with varying mixture ratios of slag and fly ash. The thermomechanical behaviors of the AASF composites exposed to 200, 400, 600, or 800℃ were evaluated by means of compressive strength test, visual observation, and fire resistance tests. X-ray diffractometry, mercury intrusion porosimetry, and thermogravimetry tests were performed to analyze the microstructure change of the AASF composites upon exposure to high temperatures. Specimens exhibited a gradual strength loss up to 600℃, while also showing a significant decrease in the strength above 600℃. The fire resistance test revealed the occurrence of an inflection point as indicated by an increase in the internal temperature at around 200℃. In addition, specimens showed the dehydration of C-S-H gel, the presence of åkermanite, gehlenite, and anorthite upon exposure to 800℃, which is associated with the formation of macropore population with pores having diameters of 1-3 ㎛ and 20-40 ㎛. Visual observation indicated that the PVA fibers mitigated the cracking and/or spalling of the specimens upon exposure to 800℃.

• Advances in materials Research
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• 제5권1호
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• pp.21-34
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• 2016

Fire is one of the most destructive powers to which a building structure can be subjected, often exposing concrete elements to elevated temperatures. The relative properties of concrete after such an exposure are of significant importance in terms of the serviceability of buildings. Unraveling the heating history of concrete and different cooling regimes is important for forensic research or to determine whether a fire-exposed concrete structure and its components are still structurally sound or not. Assessment of fire-damaged concrete structures usually starts with visual observation of colour change, cracking and spalling. Thus, it is important to know the effect of elevated temperatures on strength retention properties of concrete. This study reports the effect of elevated temperature on the mechanical properties of the concrete specimen with polypropylene fibres and cooled differently under various regimes. In the heating cycle, the specimen were subjected to elevated temperatures ranging from $200^{\circ}C$ to $800^{\circ}C$, in steps of $200^{\circ}C$ with a retention period of 1 hour. Then they were cooled to room temperature differently. The cooling regimes studied include, furnace cooling, air cooling and sudden cooling. After exposure to elevated temperatures and cooled differently, the weight loss, residual compressive and split tensile strengths retention characteristics were studied. Test results indicated that weight and both compressive and tensile strengths significantly reduce, with an increase in temperature and are strongly dependent on cooling regimes adopted.

• 대한안전경영과학회지
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• 제24권4호
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• pp.117-124
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• 2022

This study collected powder extinguishers with 6-10 years of elapsed life from January 2012 to January 2017 in market, factory, and apartment areas to experiment with changes in fineness and to examine the characteristics of extinguishing power. First, in the case of ABC powder, 98.3 wt% of the 8-year market area and 98.6 wt% of the 10-year apartment complex were found to be inappropriate in the first, second, and third arithmetic average analysis of the powder extinguisher from 6 to 10 years. That is, the fine distribution and size of the powder extinguishing agent particles should be managed within an appropriate range. It is analyzed that the powder fire extinguisher may experience a change in the fineness of the powder depending on the external environment exposure, placement, management status, and age of use, resulting in a decrease in digestive power or inability to radiate. Second, the fire extinguisher cannot be used in the initial fire suppression depending on the place of deployment, the environment of deployment, the progress of the number of years of use, and maintenance, so it is necessary to strengthen the device that enables fire extinguisher maintenance and inspection. Third, in the manufacturing process, the charging method should also be reviewed in consideration of the conditions of the workplace, the humid season, and the rainy environment.

• 한국화재소방학회논문지
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• 제26권1호
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• pp.102-112
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• 2012

본 연구에서는 건축물 외장재 화재 시 수직화재에 대해 화염의 수직확산 방지 및 지연을 위한 외벽방호 스프링클러 설비 구성에 관하여 연구하였다. 본 연구에 앞서 관련 수직확산 방지용 스프링클러 헤드의 개발이 이루어졌으며, 적용된 스프링클러시스템은 NFPA13의 연소확대방지시스템에 명기된 방사압 0.05 MPa와 유량 60 l/min를 도입하여 적용하였다. 시스템 설계를 통하여 소방대상물에 적용하였으며 본 시스템은 감지시스템과 연동하여 자동과 수동으로 작동하도록 하였다. 또한 외벽방호 스프링클러 설비의 유용성 평가를 위해 실물실험을 실시하여 외벽의 냉각효과와 화재의 지연을 확인할 수 있었다.

• Advances in concrete construction
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• 제8권4호
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• pp.311-320
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• 2019

In this study, the effect of cellulose nanocrystals (CNCs) on the fire resistance properties of fiber-reinforced cement composites was investigated. The main variables were CNCs content (0.4, 0.8 and 1.2vol.% compared with cement), steel fiber ratio, and exposure temperature (100, 200, 400, 600 and 800℃). The fire resistance properties, i.e., residual compressive strength, flexural strength, and porosity, were evaluated in relation with the exposure temperature of the specimens. The CNCs suspensions were prepared to composited dispersion method of magnetic stirring and ultra-sonication. CNCs are effective for increasing the compressive strength at high temperatures but CNCs do not seem to have a significant effect on flexural reinforcement. Porosity test result showed CNCs reduce the non-hydration area inside the cement and promote hydration.