• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.605-608
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• 2008

This study investigated fundamental properties corresponding to mixtures for the high strength, and their properties of spalling prevention after a fire test. The results were summarized as following. For the flowability of using mixtures for the high strength, the target flow was satisfied with a small quantity of high performance reducing water agent to compare with silica fume. For the compressive strength in the case of using mixtures for the high strength, it was higher to compare with silica fume at 7 days, so it was proved that using mixtures for the high strength was profitable to prevent early frost damage. The compressive strength at the 28 days of silica fume and mixtures for the high strength were similar. There was no reduced tendency at the compressive strength according fiber contents, so it found out that the bonding strength between the fiber and concrete was hardly effective. For the spalling properties, the specimens without fibers were destroyed, however using over 0.05% of NY and PP fibers was effective to prevent spalling on the high strength concrete.

• Advances in concrete construction
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• v.9 no.4
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• pp.355-365
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• 2020

The influence of temperature on the material of concrete filled columns (CFCs) under axial loading has been quantitatively studied in this research. CFCs have many various advantages and disadvantages. One of the important inefficiency of classic CFCs design is the practical lack of hooped compression under the operational loads because of the fewer variables of Poisson's rate of concrete compared to steel. This is the reason why the holder tends to break away from the concrete core in elastic stage. It is also suggested to produce concrete filled steel tube columns with an initial compressed concrete core to surpass their design. Elevated temperatures have essentially reduced the strengths of steel tubes and the final capacity of CFCs exposed to fire. Thus, the computation of bearing capacity of concrete filled steel tube columns is studied here. Sometimes, the structures of concrete could be exposed to the high temperatures during altered times, accordingly, outcomes have shown a decrement in compressive-strength, then an increase with the reduction of this content. In addition, the moisture content at the minimal strength is declined with temperature rising. According to Finite Element (FE), the column performance assessment is carried out according to the axial load carrying capacities and the improvement of ductility and strength because of limitations. Self-stress could significantly develop the ultimate stiffness and capacity of concrete columns. In addition, the design equations for the ultimate capacity of concrete columns have been offered and the predictions satisfactorily agree with the numerical results. The proposed based model (FE model of PEC column) 65% aligns with the concrete exposed to high temperature. Therefore, computed solutions have represented a better perception of structural and thermal responses of CFC in fire.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.10
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• pp.6816-6822
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• 2015

In this study, silica aerogel-glass wool composites were developed for improvement of thermal conductivity and overcoming the water adsorption of glass wool boards. Silica aerogel-glass wool composites were prepared by glass wool and silica aerogel with liquid binder. Mixtures with binder were composed of CMC (carboxymethyl cellulose) and silica aerogel for glass wool board. Silica aerogel-glass wool composite boards were had $0.065g/cm^3$ density by impregnation silica aerogel where from origin glass wool board at $0.048g/cm^3$ density. Thermal conductivity of silica aerogel-glass wool composites were 0.0315 W/mK (up to 7.4% thermal resistance) and fire penetration time came to 362 seconds (up to 2.7 times stronger than origin glass wool board). In addition, hydrophobic aerogel characteristics prevented the adsorption of water onto silica aerogel-glass wool composite boards that was good for lightweight.

• Fire Science and Engineering
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• v.19 no.1 s.57
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• pp.93-98
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• 2005

The purpose of this paper is to judge the damage cause of instrument transformer(MOF; Metering Out Fit) installed in 22.9kV power receiving system. In the three-dimensional analysis of the restored MOF, the damage pattern progressed from inside to outside, there was no damaged part in the upside. The resistance of the carbonized middle part is roughly $100\kappa\Omega$ and the exothermic temperature at inside is presumed as about $300\~800^{\circ}C$ in the result of metallurgical structure analysis. The structure and the composition rate on metal surface by SEM is similar. In the result of FT-IR analysis, we can observe the absorbtion peak at $1500cm^{-1}\;and\;1730 cm^{-1}$ is small. The high exothermic peak showed at the center part of the coil in the result of DTA.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.3
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• pp.1-9
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• 2008

Fiber Reinforced Polymer (FRP) composites are used extensively in aerospace, marine, automotive, infrastructure, chemical processing and sporting good applications. A concern with using FRP composites in some engineering structures is their high flammability and poor fire resistance In this research, material properties of FRP composites at increasingly high temperatures was measured and verified. The obtained mechanical properties of FRP composites were performed according to ASTM D3039/D3039M and tested to a wide range of heat conditions with temperatures from Room-temp. to 300 for times up to 30 min. It is found that the mechanical properties of FRP composites dropped with increasing heat or temperature. The reduction to the properties was due mainly to thermal degradation and combustion of the polymer matrix.

• Journal of the Korean Geotechnical Society
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• v.27 no.12
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• pp.69-84
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• 2011

This paper presents the applicability of NATM Composite Lining method in domestic tunnel construction sites. Firstly, in order to produce high quality PC Panel, optimal steam curing condition is reviewed. And in preparation for fire inside the tunnel, the fire-resistance test of PC Panel is carried out. The constructability of NATM Composite Lining method and the drainage ability of light-weight foamed mortar is also evaluated through field construction test. And PC Panel combination program is developed to calculate the quantity of PC Panel efficiently. Besides, economic evaluation for NATM Composite Lining method is conducted. From this research, it is clearly found that NATM Composite Lining method is applicable to domestic tunnel construction site.

• Fire Science and Engineering
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• v.10 no.3
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• pp.3-9
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• 1996

The Polyimide thin films based on PMDA and 4,$4^{\circ}$'-DDE were fabricated by VDPM, and their heat resistance characteristics were invastigated by TGA(Thermogravimetry Analyzer). It was found that deposition rate decreased with increasing substrate temperature and the thin films were not fabricated over the substrate temperature of $70^{\circ}$. $T_{TG}$ of weight loss temperature is $565^{\circ}$, $397^{\circ}$ and $210^{\circ}$ at the substrate temperature of $20^{\circ}$, $40^{\circ}$ and $70^{\circ}$, respectively. It is realized that the endurace temperature for 20,000 hour of thin films fabricated at $20^{\circ}$ and $40^{\circ}$ is $230^{\circ}$ and $200^{\circ}$, respectively.

• Fire Science and Engineering
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• v.33 no.4
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• pp.70-76
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• 2019

This paper reports development of a low-power standalone heat detector using a Critical-Temperature Switch. The Critical-Temperature Switch, which is a thermally sensitive and passive component whose resistance decreases significantly at 70 ℃ due to a metal-insulator transition, provides reliable temperature measurements. This digital-like behavior of the Critical-Temperature Switch can detect fires without a microcontroller, meaning that it can minimize the power consumption of the standalone heat detector. The experimental results showed that the standalone heat detector using the Critical-Temperature Switch complied with the Notification of the National Emergency Management Agency. Compared to conventional standalone heat detectors, only 70% of the power was consumed monitoring the fires.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.2
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• pp.155-163
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• 2007

High Strength Concrete (HSC) has weakness that in a fire, it is spalled and brittles. The phenomenon of spalling is made by water vapor's (resulting from evaporation in the material at over $100{^{\circ}C}$)' being confined in watertight concrete. As the concrete strength increases, the degree of damage caused by the spalling becomes more serious because of the permeability. It is reported that the polypropylene(PP) fiber has an important role in protecting concrete from spalling and the optimum dosage of PP fiber is 0.2%. This study was conducted on the nonreinforced concrete specimens. The high-temperature behavior of high-strength reinforced concrete columns with various concrete strength and various dosage of PP fibers was investigated in this study. The results show that the ratio of unstressed residual strength of columns increases as the concrete strength increases and the ratio of unstressed residual strength of columns increases as the dosage of PP fiber increases from 0% to 0.2%, however, the effect of fiber dosage on residual strength of column barely changes above 0.2%.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1994.11a
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• pp.21-26
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• 1994

Conventional electroexplosive devices (EED) commonly use a very small metal bridgewire to ignite explosive materials i.e. pyrotechnics, primary and secondary explosives. The use of semiconductor devices to replace “hot-wire” resistance heating elements in automotive safety systems pyrotechnic devices has been under development for several years. In a typical 1 amp/1 watt electroexplosive devices, ignition takes place a few milliseconds after a current pulse of at least 25 mJ is applied to the bridgewire. In contrast, as for a SCB devices, ignition takes place in a few tens of microseconds and only require approximately one-tenth the input energy of a conventional electroexplosive devices. Typically, when SCB device is driven by a short (20 $\mu\textrm{s}$), low energy pulse (less than 5 mJ), the SCB produces a hot plasma that ignites explosive materials. The advantages and disadvantages of this technology are strongly dependent upon the particular technology selected. To date, three distinct technologies have evolved, each of which utilizes a hot, silicon plasma as the pyrotechnic initiation element. These technologies are 1.) Heavily doped silicon as the resistive heating initiation mechanism, 2.) Tungsten enhanced silicon which utilizes a chemically vapor deposited layer of tungsten as the initiation element, and 3.) a junction diode, fabricated with standard CMOS processes, which creates the initial thermal environment by avalanche breakdown of the diode. This paper describes the three technologies, discusses the advantages and disadvantages of each as they apply to electroexplosive devises, and recommends a methodology for selection of the best device for a particular system environment. The important parameters in this analysis are: All-Fire energy, All-Fire voltage, response time, ease of integration with other semiconductor devices, cost (overall system cost), and reliability. The potential for significant cost savings by integrating several safety functions into the initiator makes this technology worthy of attention by the safety system designer.