• 대한건축학회논문집:구조계
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• 제34권4호
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• pp.35-42
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• 2018

This study evaluated the fire resisting capacity and post-fire serviceability of the concrete beams retrofitted by near surface mounted method(NSM) using GFRP plates. Main parameters in the test are grout materials and fire exposure. For the test, two types of grout materials between concrete substrate and GFRP plate were used; flame resisting epoxy and filling mortar. Four RC beam specimens were made and two of them were exposed to fire according to real scale fire curve proposed KS F 2257. After the fire exposure test, flexural test were performed to investigate the flexural performance of concrete beams including strength and deformation. From the test results, it was found that the beam retrofitted by NSM-GFRP presented higher flexural strength than that of the beam without retrofit, which indicates NSM-GFRP retrofit technologies is effective to maintain flexural strength even after fire exposure. In addition, the specimens grouted by epoxy showed good performance in strength but bad performance in ductility.

• Computers and Concrete
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• 제26권2호
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• pp.115-125
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• 2020

To reduce the damage of concrete in fire, a new type of lightweight cinder aggregate concrete was developed due to the excellent fire resistance of cinder. To further enhance its fire resistance, Polypropylene (PP) Fibers which can enhance the fire resistance of concrete were also used in this type of concrete. However, the bond behavior of this new type of concrete after fire exposure is still unknown. To investigate its bond behavior, 185 specimens were heated up to 22, 200, 400, 600 or 800℃ for 2 h duration respectively, which is followed by subsequent compressive and tensile tests at room temperature. The concrete-rebar bond strength of C30 PP fiber-reinforced cinder concrete was subsequently investigated through pull-out tests after fire exposure. The microstructures of the PP fiber-reinforced cinder concrete and the status of the PP fibre at different temperature were inspected using an advanced scanning electron microscopy, aiming to understand the mechanism of the bonding deterioration under high temperature. The effects of rebar diameter and bond length on the bond strength of PP fiber-reinforced cinder concrete were investigated based on the test results. The bond-slip relation of PP fiber-reinforced cinder concrete after exposure at different temperature was derived based on the test results.

• Steel and Composite Structures
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• 제38권1호
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• pp.87-102
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• 2021

To investigate the failure form, bending stiffness, and residual bearing capacity of monolithic composite beams with laminated slab throughout the fire process, fire tests of four monolithic composite beams with laminated slab were performed under constant load and temperature increase. Different factors such as post-pouring layer thickness, lap length of the prefabricated bottom slab, and stud spacing were considered in the fire test. The test results demonstrate that, under the same fire time and external load, the post-pouring layer thickness and stud spacing are important parameters that affect the fire resistance of monolithic composite beams with laminated slab. Similarly, the post-pouring layer thickness and stud spacing are the predominant factors affecting the bending stiffness of monolithic composite beams with laminated slab after fire exposure. The failure forms of monolithic composite beams with laminated slab after the fire are approximately the same as those at room temperature. In both cases, the beams underwent bending failure. However, after exposure to the high-temperature fire, cracks appeared earlier in the monolithic composite beams with laminated slab, and both the residual bearing capacity and bending stiffness were reduced by varying degrees. In this test, the bending bearing capacity and ductility of monolithic composite beams with laminated slab after fire exposure were reduced by 23.3% and 55.4%, respectively, compared with those tested at room temperature. Calculation methods for the residual bearing capacity and bending stiffness of monolithic composite beams with laminated slab in and after the fire are proposed, which demonstrated good accuracy.

• Structural Engineering and Mechanics
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• 제69권2호
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• pp.193-204
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• 2019

This paper presents results from experimental and numerical studies on the response of steel-concrete composite box bridge girders under certain localized fire exposure conditions. Two composite box bridge girders, a simply supported girder and a continuous girder respectively, were tested under simultaneous loading and fire exposure. The simply supported girder was exposed to fire over 40% of its span length in the middle zone, and the two-span continuous girder was exposed to fire over 38% of its length of the first span and full length of the second span. A measurement method based on comparative rate of deflection was provided to predict the failure time in the hogging moment zone of continuous composite box bridge girders under certain localized fire exposure condition. Parameters including transverse and longitudinal stiffeners and fire scenarios were introduced to investigate fire resistance of the composite box bridge girders. Test results show that failure of the simply supported girder is governed by the deflection limit state, whereas failure of the continuous girder occurs through bending buckling of the web and bottom slab in the hogging moment zone. Deflection based criterion may not be reliable in evaluating failure of continuous composite box bridge girder under certain fire exposure condition. The fire resistance (failure time) of the continuous girder is higher than that of the simply supported girder. Data from fire tests is successfully utilized to validate a finite element based numerical model for further investigating the response of composite box bridge girders exposed to localized fire. Results from numerical analysis show that fire resistance of composite box bridge girders can be highly influenced by the spacing of longitudinal stiffeners and fire severity. The continuous composite box bridge girder with closer longitudinal stiffeners has better fire resistance than the simply composite box bridge girder. It is concluded that the fire resistance of continuous composite box bridge girders can be significantly enhanced by preventing the hogging moment zone from exposure to fire. Longitudinal stiffeners with closer spacing can enhance fire resistance of composite box bridge girders. The increase of transverse stiffeners has no significant effect on fire resistance of composite box bridge girders.

• Steel and Composite Structures
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• 제46권3호
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• pp.345-352
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• 2023

A thermal-mechanical coupling finite element model of the steel-plate concrete composite (SC) wall is established, taking into account the strain rate effect and variation in mechanical and thermal properties under different temperatures. Verifications of the model against previous fire test and impact test results are carried out. The impact response of the SC wall under elevated temperatures is further investigated. The influences of the fire exposure time on the impact force and displacement histories are discussed. The results show that as the fire exposure time increases, the deflection increases and the impact resistance decreases. A formula is proposed to calculate the reduction of the allowable impact energy considering the fire exposure time.

• 한국구조물진단유지관리공학회 논문집
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• 제20권3호
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• pp.33-41
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• 2016

콘크리트는 내화재료로서 우수한 성능을 발휘하지만 화재가 지속됨에 따른 재료특성 변화 또는 성능저하의 위험을 갖는다. 이 연구는 실물모형 철근 콘크리트 (RC) 보를 활용하여 비재하 화재 실험을 수행하여 화재노출 전후의 콘크리트 및 보강철근의 재료특성을 실험적으로 분석한 연구이다. 화재실험에 사용된 보는 길이 4 m의 RC 보로서 KS F 2257 화재실험 규격에 따라 시험 체를 제작 및 화재실험을 수행하였다. 화원의 가력은 ISO 834의 표준화재 곡선을 사용하였으며 보 가열부에서의 온도를 계측하고자 하면 및 측면에 열전대를 설치하였다. 실험결과, 화재에 노출된 화재 코어 공시체의 경우 약 11 MPa로 약 66%의 강도저하가 발생하였다. 화재에 직접 노출된 철근의 경우 노출되지 않은 철근에 비해 약 17%에 해당하는 75 MPa의 항복강도 저하를 나타낸 것으로 분석되었다. 철근의 경우 콘크리트라는 내화피복에 의하여 보호되어 약 4시간의 화재 실험에서도 온도는 한계온도의 최댓값인 $649^{\circ}C$를 크게 상회하지 않는 것으로 나타났다.

• 대한건축학회논문집:구조계
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• 제33권12호
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• pp.19-27
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• 2017

This paper is a study to improve the fire-resistance capacity of reinforced concrete (RC) members strengthened by fiber-reinforced-polymer (FRP). The fire resistance of the RC members strengthened by FRP was evaluated through high temperature exposure test. In order to improve the fire resistance of the FRP reinforcing method, a fire-proof board was attached to the reinforced FRP surface and then the high temperature exposure test was carried out to evaluate the improvement of the fire resistance performance. It was confirmed that the resistance to high temperature of NSMR could be improved somewhat compared with that of EBR from the experiment that exposed to high temperature under the load corresponding to 40% of nominal strength. When 30 mm thick fire-resistance (FR) board is attached to the FRP surface, the surface of the reinforced FRP does not reach $65^{\circ}C$, which is the glass transition temperature (GTT) of the epoxy until the external temperature reaches $480^{\circ}C$. In particular, when a high performance fire-proof mortar was first applied prior to FR board attachment, the FRP portion did not reach the epoxy glass transition temperature until the external temperature reached $600^{\circ}C$.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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• pp.57-60
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• 2005

This study discusses spalling and fire enduring performance of high performance concrete (HPC) RC column subjected to loading under heating for 3 hours. According to the test, both the plain concrete and the concrete attached with fire enduring PC panel exceed allowable temperature after 60 minutes due to the exposure of steel bar and falling off of concrete resulting from severe spalling failure. It leads to buckling of main bar and at the same time, occurrence of collapse of plain HPC column member is observed after 2 hours and 1 hour 40 minutes's exposure to fire, respectively. On the other hand, HPC applying both PP fiber of 0.1$\%$ by mass of concrete and PP fiber+lateral confinement by metal lath maintains their original cross section, which is satisfied with the 3 hours fire endurance criteria, by discharging internal vapour pressure and enhanced lateral confinement force.

• Safety and Health at Work
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• 제15권1호
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• pp.114-117
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• 2024

A lithium-ion battery is a rechargeable battery that uses the reversible reduction of lithium ions to store energy and is the predominant battery type in many industrial and consumer electronics. The lithium-ion batteries are essential to ensure they operate safely. We conducted an exposure assessment five days after a fire in a battery-testing facility. We assessed some of the potentially hazardous materials after a lithium-ion battery fire.We sampled total suspended particles, hydrogen fluoride, and lithium with real-time monitoring of particulate matter (PM) 1, 2.5, and 10 micrometers (㎛). The area sampling results indicated that primary potential hazardous materials such as dust, hydrogen fluoride, and lithium were below the recommended limits suggested by the Korean Ministry of Labor and the American Conference of Governmental Industrial Hygienists Threshold Limit Values. Based on our assessment, workers were allowed to return to work.

• 한국산업보건학회지
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• 제34권1호
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• pp.14-17
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• 2024

Objectives: This is a case of air exposure assessment conducted after researchers complained of headaches and odor due to residual substances from fire extinguishing agents spread throughout the laboratory due to a malfunction of the fire extinguishing facility. Methods: A component analysis was conducted on the residual substances of a fire extinguishing agent spread in a laboratory using Py-GC-MS (pyrolysis gas chromatography mass spectrometry) at the research institute's own central equipment research center. As a result of the component analysis, several types of substances were detected. Among these, five types of substances subject to work environment measurement in the aromatic hydrocarbon series, which can affect headaches and odor, were selected as substances subject to exposure assessment in the air, and the measurement and analysis methods of the target substances were conducted in accordance with the KOSHA Guide for each substance. Conclusions: The measurement results showed that all 5 types of substances were not detected at locations A, B, and C. This is believed to be the result of the residual substances in the fire extinguishing agent being measured when approximately two months had elapsed after being exposed to the test bench, and the substances already exposed had volatilized and disappeared. In this survey, it is believed that the measurement process is more important than the measurement results.