• Structural Engineering and Mechanics
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• v.42 no.6
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• pp.799-813
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• 2012

Five two-span reinforced concrete (RC) slabs and seven two-span RC beams were tested under the ISO 834 standard fire with different durations. CFRP strengthening was then applied to some of the specimens after the damaged concrete was removed from the specimens and replaced with polymer mortar. All the specimens were loaded to failure to investigate the influence of fire-damage and the effectiveness of strengthening methods. Test results indicated that the flexural capacities of specimens decrease with the fire duration increases. Moreover, fire exposure had more significant effect on the flexural rigidity than on the bearing capacity of the specimens. After rehabilitation, the bearing capacities of specimens reached or even exceeded that of the reference RC specimen, and the strengthening methods seemed to have limited effect on flexural rigidity recovery. From the analysis of moment redistribution of tested beams, elevated temperature is found having different impacts on sagging moment region and hogging moment region. The damage of RC continuous member is definitely a comprehensive response of different regions.

• Fire Science and Engineering
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• v.33 no.4
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• pp.140-151
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• 2019

It is to assess the indoor air quality of the chemical hazardous materials exposed to the fire after firefighters returned to the fire scene. The research subject randomly selected four fire stations located in Seoul, Korea. Two fire stations were set up as control groups after the return of the firefighting activities at the actual fire scene, and two other fire stations were set up as control groups to measure the air quality of the room at normal levels regardless of the action. We conducted 24-hour monitoring for all fire accidents that occurred in Seoul Metropolitan using fire safety map computer system. Also, indoor air quality was measured immediately after homecoming if the experiment group was to be dispatched due to an accident of intermediate or larger scale. 11 hazardous substance items such as fine dust, formaldehyde, volatile organic compounds, PAH, VCM, acidity, asbestos, CO₂, NO₂, O₃ were measured according to the process test method. Three of 11 types of harmful substances exceeded domestic and foreign standards, and one of them was found to be close to foreign standards. In particular, total volatile organic compounds, carbon dioxide and sulfuric acids were 2.5 times, 2.2 times and 1.1 times higher than the standard. Also, for formaldehyde and sulfuric acid, it was measured higher in the control group than in the case group. This findings could be used in policies to improve indoor air quality in the fire station of the Seoul Metropolitan Government.

• Applied Chemistry for Engineering
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• v.31 no.3
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• pp.277-283
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• 2020

The smoke hazard assessment of building materials focusing on smoke performance index-II (SPI-II) and smoke growth index-II (SGI-II) was investigated. The test species used were Japanese cedar, spruce, lauan, and red pine. The smoke characteristics of wood specimen were investigated using a cone calorimeter (ISO 5660-1). SPI-II was measured after the combustion reaction increased by 1.31~2.15 times based on red pine. The fire risk by SPI-II increased in the order of spruce, lauan, Japanese ceda, and red pine. SGI-II increased by 1.18~2.55 times compared to that of Japnese ceda. The fire risk caused by SGI-II increased in the order of Japanese ceda, spruce, lauan, and red pine. CO_mean concentrations were ranged from 58 to 133 ppm, which was higher than permissible exposure limits of the occupational safety and health administration (OSHA), 50 ppm. Therefore, woods such as red pine containing various volatile organic substances, were considered to be highly smoke hazardous due to low SPI-II and high SGI-II.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.257-260
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• 2008

The heat resistance of steel materials tends to weaken due to its high heat transfer properties, which might result in deteriorated strength because of rapidly rising temperature on surface in a fire. Particularly in case of CFT column that bears tensile stress of the structure on its external steel members, a numerical analysis on deterioration of strength and variation of stress shall be first carried out to ensure the structure will have sufficient fire resistance. In the study, based on values obtained from the high temperature material property test of steel materials and concrete, the test to forecast the fire behavior of CFT column was conducted using a finite element analysis method (ABAQUS). An Analysis in a bid to predict the heat transfer and the behavior characteristics by varying the strength of the concrete filled to the range of 40MPA and 50MPA was carried out. As a result of analysis of CFT column on condition of 180-minute exposure under the standard fire condition, 123mm of strain appeared with 40MPA model, while 91mm contraction with 50MPA model.

• Journal of the Korea Concrete Institute
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• v.21 no.4
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• pp.465-471
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• 2009

To prevent the explosive spalling of the high strength concrete and control the rise of temperature in the steel rebar during fire, a fiber cocktail method has been proposed simultaneously with the use of polypropylene and steel fiber. After applying the fiber cocktail (polypropylene and steel fibers) into the mixture of high strength concrete with a compressive strength of between 40 and 100 MPa and evaluating the thermal properties at elevated temperatures, the fire test was carried out on structural members in order to evaluate the fire resistance performance. Two column specimens were exposed to the fire without loading for 180 minutes based on the standard curve of ISO-834. No explosive spalling has been observed and the original color of specimen surface was changed to light pinkish grey. The inner temperature of concrete dropped rapidly starting from 60mm deep. After 60 minutes of exposure to the fire, the temperature gradient of fiber cocktail reinforced high strength concrete was measured as 2.2oC/mm, which is approximately 5 times less than that of normal concrete. The final temperatures of steel rebar after 180 minutes of fire test resulted in 488.0oC for corner rebar, 350.9oC for center rebar, and 419.5oC for total mean of steel rebar. The difference of mean temperature between corner and center rebar was 137.1oC The tendency of temperature rise in concrete and steel rebar changed between 100oC and 150oC The cause of decrease in temperature rise was due to the water vaporization in concrete, the lower temperature gradient of the concrete with steel and polypropylene fiber cocktails, the moisture movement toward steel rebars and the moisture clogging.

• Journal of the Korean Society for Nondestructive Testing
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• v.35 no.2
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• pp.150-156
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• 2015

In this study, the effects of different mix proportions and fire scenarios (exposure temperatures and post-fire-curing periods) on fire-damaged concrete were analyzed using a nonlinear resonance vibration method based on nonlinear acoustics. The hysteretic nonlinearity parameter was obtained, which can sensitively reflect the damage level of fire-damaged concrete. In addition, a splitting tensile strength test was performed on each fire-damaged specimen to evaluate the residual property. Using the results, a prediction model for estimating the residual strength of fire-damaged concrete was proposed on the basis of the correlation between the hysteretic nonlinearity parameter and the ratio of splitting tensile strength.

• Journal of Korean Society of Steel Construction
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• v.27 no.2
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• pp.143-153
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• 2015

In this paper, the standard fire resistance test under load and associated numerical study were carried out to evaluate the fire resistance of unprotected partially encased beams and slimfloor beams. The temperature evolution and the deflection increase of the composite beam specimens were investigated and the effects of the key behavioral parameters including the load ratio, the reinforcement, and the fire exposure were analyzed. The test results showed that the temperature rise of the partially encased beams and slimfloor beams is considerably slow compared to the conventional H-shape composite beams. Up to at least 90 minutes, the reinforcements in the partially encased composite beams maintained below the temperature at which the cold steel strength is sustained. Unprotected partially encased beams and slimfloor beams in the experimental program achieved the fire resistance more than 2 hours according to the limiting deflection criteria. This implies that unprotected partially encased beams and slimfloor beams can be very promising alternatives to enhancing the fire resistance of steel beams. This study also conducted the fully coupled thermal-stress analysis by using the commercial code ABAQUS to the thermal and structural behaviour of composite beams in fire. The numerical predictions provide acceptable correlations with the experimental results.

• Fire Science and Engineering
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• v.33 no.4
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• pp.28-34
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• 2019

Regardless of the ignition source, the main factors affecting the spread of flames to the human body are combustibles. The sound absorption material, which is the finishing material used in music institutes and karaoke rooms, consists of polyurethane that generates a large amount of toxic gas with a high amount of combustion gases during a fire. Still, the current law does not require the use of impregnated finishing materials for tutoring services with less than 100 users. In this study, the rate of flame diffusion was measured using the MultiRaelite composite gas measuring instrument (target substance VOC, HCHO, SO₂, CO₂, CO, HCN, and NO₂) for the collection of sound-absorbing materials installed in the actual music academy. The results showed that the toxic gas found in this experiment exceeded the allowable concentration of TWA (Time Weighted Average) and STEL (Short Term Exposure Limit). In addition, a comparative combustion test of the general sound absorber and non-combustion sound absorbing materials on the market showed wide differences in ignition and diffusion. Therefore, based on the results of the experiment, private institutes with less than 100 users should be mandated to use non-combustion sound absorbing materials.

• Fire Science and Engineering
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• v.28 no.2
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• pp.1-8
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• 2014

Despite advancements in the development of synthetic fibers and materials that provide better insulation, fire burn injuries remain a significant issue. To ensure adequate protection, clothing and equipment must be selected on the basis of performance. There are different standards like ISO standards applicable to each of the various types of clothing used by fire fighters. But, in most cases, the tests are performed in the conditions of high heat flux exposure, the clothing material can be destroyed easily. Thus the effective way to investigate the protective performance for the low (radiant) heat flux conditions should be needed. Therefore improved RPP (Radiant Protective Performance) test method based on the onset of pain burn injury was suggested. Experiments were performed to verify the proposed method with current protective clothing for fire fighters and the transient heat transfer characteristics were identified, also. Moreover, several protective performance indices were acquired from experimental results to analyze their relations.

• Fire Science and Engineering
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• v.26 no.6
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• pp.45-50
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• 2012

The spalling causes the sever reduction of the cross sectional area with the exposure of the reinforcing steel, which originates a problem in the structural behaviour. By coating surface of high strength concrete with fireproof mortar, the high strength concrete is protected from the spalling in fire and the method to constrain the temperature increase of steel bar within the concrete. The purpose of this study is to investigate the temperature history properties of lightweight mortar using perlite and polypropylene fiber for fire protection covering material. For this purpose, selected test variables were the contents and length of polypropylene fiber. As a result of this study, it has been found that addition of polypropylene fiber to mortar modifies its pore structure and this causes the internal temperature to rise. And it has been found that a new lightweight mortar can be used in the fire protection covering material.