• Fire Science and Engineering
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• v.34 no.3
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• pp.67-75
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• 2020

In this study, the risk of heat generation due to normal and overload currents that vary with the abnormal loosening angle of wire-connecting bolts were identified. The risks were analyzed based on the thermal characteristics to minimize the carbonization accidents of terminal blocks inside distribution panels typically used in industrial sites. We applied a method for measuring the heating temperature and temperature variations in the terminal blocks in real-time by installing a resistance temperature detector sensor board in the terminal block. The experimental results showed that the terminal block model with a low-rated current exhibited a higher heating temperature, thus, confirming the need to select the terminal block capacity based on load currents. Additionally, the higher the rated current of the terminal block with a high-rated current and the higher the degree of loosening, the faster the carbonization point. Such heating temperature monitoring enabled real-time thermal temperature measurement and a step-by-step risk level setting through thermal analysis. The results of the measurement and analysis of carbonization risks can provide a theoretical basis for further research regarding the risk of fire due to carbonization. Furthermore, the deterioration measurement method using the temperature sensor board developed in this study is widely applicable to prevent fires caused by poor electrical contact as well as risk-level management.

• Fire Science and Engineering
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• v.33 no.2
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• pp.114-123
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• 2019

The paper relates to a study on the changes in performance of insulation sheath resulting from accelerated degradation of IV and HIV insulated wire. To assume insulation degradation of IV and HIV insulated wire, accelerated life tests using Arrhenius equation were conducted among accelerated life test models, and experimental samples of 0 year, 10 years, 20 years, 30 years, and 40 years in equivalent life were produced. Whereas the maximum tensile load were increased as accelerated degradation of IV and HIV insulated wire progressed, elongation percentage, rupture time, and flexibility of insulated wires were found to be gradually reduced. According to the additional surface analysis results for the insulated wires per equivalent life using a scanning electron microscope, mechanical properties of the insulator were observed to be reduced as insulation degradation resulting from aging progressed since phenomena such as formation of crystalline structures and perforation, etc. occurred on the sample surface with progression of accelerated degradation. Consequently, institutional replacement of insulated wires and preparation of repair times considering performance degradation of the insulator installed inside buildings are considered necessary in order to prevent in advance the risks of electrical fire resulting from degradation in insulation performance.

• Safety and Health at Work
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• v.14 no.4
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• pp.457-466
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• 2023

Background: During hot environment work tasks with whole-body enclosed anti-bioaerosol suit, the combined effect of heavy sweating and exhaled hot humid air may cause the N95 medical respirator to saturate with water/sweat (i.e., water-blocking). Methods: 32 young male subjects with different body mass indexes (BMI) in whole-body protection (N95 medical respirator + one-piece protective suit + head covering + protective face screen + gloves + shoe covers) were asked to simulate waste collecting from each isolated room in a seven-story building at 27-28℃, and the weight, inhalation resistance (R_f), and aerosol penetration of the respirator before worn and after water-blocking were analyzed. Results: All subjects reported water-blocking asphyxia of the N95 respirators within 36-67 min of the task. When water-blocking occurred, the R_f and 10-200 nm total aerosol penetration (P_t) of the respirators reached up to 1270-1810 Pa and 17.3-23.3%, respectively, which were 10 and 8 times of that before wearing. The most penetration particle size of the respirators increased from 49-65 nm before worn to 115-154 nm under water-blocking condition, and the corresponding maximum size-dependent aerosol penetration increased from 2.5-3.5% to 20-27%. With the increase of BMI, the water-blocking occurrence time firstly increased then reduced, while the R_f, P_t, and absorbed water all increased significantly. Conclusions: This study reveals respirator water-blocking and its serious negative impacts on respiratory protection. When performing moderate-to-high-load tasks with whole-body protection in a hot environment, it is recommended that respirator be replaced with a new one at least every hour to avoid water-blocking asphyxia.

• Journal of the Society of Disaster Information
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• v.20 no.3
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• pp.584-592
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• 2024

Purpose: The biggest concern in cold wave situations is that the fire extinguishing water initially supplied through dry pipes with empty pipes consumes enthalpy and freezes as it rapidly approaches the surface temperature of steel pipes that have been exposed to sub-zero outdoor air for a long time. It has no choice but to be. Method: Therefore, the study found that ice crystals were generated during transport, making it difficult to transport fire extinguishing water, and as a result of the review, when the heat load passed through the piping material, the heat loss per unit length from the piping to the surroundings was 0.946. Results: When calculating the volume of the main pipe, it was calculated that the fire extinguishing water supplied at a temperature of 15 degrees from the underground pipe would have a volume of 3.33m³ to reach the first branch point. If we calculate the heat required until this volume reaches below zero, we get 316.350 kcal. When the results were reviewed using the related formula, the time required for the fire extinguishing water to completely freeze up to the first branch of the steel pipe was found to be 3,412 seconds. Conclusion: Fire-fighting water, which must reach from the main pipe to the branch pipe and nozzle in good condition, must minimize heat loss through the pipe surface along the transfer path. To achieve this, it is necessary to supplement insulation of the main pipe and branch pipes. In this study, the use of inorganic perlite material or flame-retardant rubber foam insulation was proposed through analysis of insulation properties.

• Steel and Composite Structures
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• v.34 no.3
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• pp.441-452
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• 2020

Within the French CIFRE research project COMINO, an innovative type of composite beam was developed for buildings that need fire resistance with no additional supports in construction stage. The developed solution is composed of a steel U-shaped beam acting as a formwork in construction stage for a reinforced concrete part that provides the fire resistance. In the exploitation stage, the steel and the reinforced concrete are acting together as a composite beam. This paper presents the investigation made on the load bearing capacity of this new developed steel-concrete composite section. A full-scale test has been carried out at the Laboratory of Structural Engineering of the University of Luxembourg. The paper presents the configuration of the specimen, the fabrication process and the obtained test results. The beam behaved compositely and exhibited high ductility and bending resistance. The shear connection in the tension zone was effective. The beam failed by a separation between the slab and the beam at high deformations, excessive shear forces conducted to a failure of the stirrups in this zone. The test results are then compared with good agreement to analytical methods of design based on EN 1994 and design guidelines are given.

• Journal of the Korean Institute of Gas
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• v.4 no.2 s.10
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• pp.20-26
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• 2000

In this experimental study, we examined gas engine characteristics of a small high-speed engine in various ways. And we studied performance of natural gas, hydrogen gas and gasoline fuel engines, as emission characteristics and process of combustion. For the purpose of preventing back-fire occurred in case of high-speed and high load in hydrogen engine, we controlled air quantity by installing throttle valve in gas fuel engine. We performed experiment by mixing nitrogen to hydrogen fuel. As a result, we could find out characteristics which of a high speed small engine by applying gas fuels.

• Journal of Korean Association for Spatial Structures
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• v.20 no.3
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• pp.81-89
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• 2020

As the damage caused by earthquakes gradually increases, seismic retrofitting for existing public facilities has been implemented in Korea. Several types of structural analysis methods can be used to evaluate the seismic performance of structures. Among them, for nonlinear dynamic analysis, the hysteresis model must be carefully applied because it can significantly affect the behavior. In order to find a hysteresis model that predicts rational behavior, this study compared the experimental results and analysis results of the existing non-seismic reinforced concrete frames. For energy dissipation, the results were close to the experimental values in the order of Pivot, Concrete, Degrading, and Takeda models. The Concrete model underestimated the energy dissipation due to excessive pinching. In contrast, the other ones except the Pivot model showed the opposite results with relatively little pinching. In the load-displacement curves, the experimental and analysis results tended to be more similar when the column axial force was applied to columns.

• Steel and Composite Structures
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• v.8 no.2
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• pp.159-178
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• 2008

An analytical procedure is presented for the determination of the buckling load and the buckling temperature of a straight, slender, geometrically perfect, axially loaded, translationally and rotationally restrained steel column exposed to fire. The exact kinematical equations of the column are considered, but the shear strain is neglected. The linearized stability theory is employed in the buckling analysis. Behaviour of steel at the elevated temperature is assumed in accordance with the European standard EC 3. Theoretical findings are applied in the parametric analysis of restrained columns. It is found that the buckling length factor decreases with temperature and depends both on the material model and stiffnesses of rotational and translational restraints. This is in disagreement with the buckling length for intermediate storeys of braced frames proposed by EC 3, where it is assumed to be temperature independent. The present analysis indicates that this is a reasonable approximation only for rather stiff rotational springs.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2010.04a
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• pp.284-288
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• 2010

Length of staircase get longer and evacuation load get heavier in proportion to the building height. Therefore evacuation time could be considered proportional to square of building height. While smoke spreads vertically so rapidly, evacuation speed is too slow, therefore the reasonable measure for the safe of egress route is urgent. Existing pressurizing smoke control system of vertical exit route is seriously limited in function under the stack effect in winter. Stack effect in winter could be overcome with the methods of opening the staircase outward or letting airflow be free between staircase and outside.

• Journal of the Korean Solar Energy Society
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• v.27 no.2
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• pp.61-69
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• 2007

The final energy consumption in the building sector in Korea represents almost 20% of the total energy consumption. Besides, Space heating and hot water generation in Korea are based on fossil fuels, with a serious environmental impact. Despite the popularity of simple solar domestic hot water systems, active solar space heating remains, for various reasons, marginal. And thus, the aim of this paper is to demonstrate potentialities of solar assisted space heating systems, both technically and economically. From this study found that the solar heating system with CPC solar collectors integrated the roof of a single-story residential building shares $50{\sim}55%$ of the annual heating load.