• Structural Engineering and Mechanics
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• 제64권3호
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• pp.339-346
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• 2017

Slabs prevent harmful effects of fire that may occur in any floor. However, it is necessary to protect the slabs from fire. Insulation materials may be appropriate to protect reinforced concrete (RC) slab from elevated temperature. In the present study, a model has been developed in artificial neural network (ANN) to predict the moment capacity ($M_r$) of RC slabs exposed to fire with insulation material. 672 data were obtained for ANN model through author's prepared program. Input layer in model consisted of seven input parameters; such as effective depth (d), ratio of d'/d, thermal conductivity coefficient ($k_{insulation}$), insulation materials thickness ($L_{insulation}$), reinforcement area ($A_{st}$), fire exposure time ($t_{\exp}$), and concrete compressive strength ($f_c$). The predicted $M_r$ by ANN was consistent with the obtained $M_r$ by author. It is proposed to ease computational complexity in determining $M_r$ using ANN. The effects of using insulation material on the moment capacity in RC slabs were also investigated. Insulating material with low thermal conductivity has been found to be more effective for durability to high temperature.

• Structural Engineering and Mechanics
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• 제77권5호
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• pp.673-689
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• 2021

This paper addresses the efficiency of thermal insulation layers applied to protect structural elements strengthened by fiber-reinforced polymers (FRP) in the case of fire event. The paper presents numerical modeling and nonlinear analysis of reinforced concrete (RC) columns externally strengthened by FRP and protected by thermal insulation layers when subjected to elevated temperature specified by standard fire tests, in order to predict their residual capacity and fire endurance. The adopted numerical approach uses commercial software includes heat transfer, variation of thermal and mechanical properties of concrete, steel reinforcement, FRP and insulation material with elevated temperature. The numerical results show good agreement with published results of full-scale fire tests. A parametric study was conducted to investigate the influence of several variables on the structural response and residual capacity of insulated FRP-confined columns loaded by service loads when exposed to fire. The residual capacity of FRP-confined RC column was affected by concrete grade and insulation material and was shown to improve substantially by increasing the concrete cover and insulation layer thickness. By increasing the VG insulation layer thickness 15, 32, 44, 57 mm, the loss in column capacity after 5 hours of fire was 30%, 13%, 7% and 5%, respectively. The obtained results demonstrate the validity of the presented approach for estimation of fire endurance and residual strength, as an alternative for fire testing, and for design of fire protection layers for FRP-confined RC columns.

• 한국소음진동공학회논문집
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• 제22권9호
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• pp.837-844
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• 2012

We considered an approach in terms of materials for improvement of insulation performance of vehicle rubber hoses. Ethylene propylene rubber(EPDM) for heater hoses in cooling system and acrylic rubber(AR) for intercooler hose in intake system were chosen for mixing for the vibration and noise performance. We modified EPDM and AR through changing compound of base polymer, reinforcement fillers and additives. Dynamic mechanical analysis(DMA) was used to measure viscoelastic properties such as shear modulus and loss factor($tan{\delta}$). Vehicle acceleration test was also conducted to observe indoor changes in insulation performance of hoses.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2013년도 춘계 학술논문 발표대회
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• pp.71-72
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• 2013

This study investigates the effect of the diameters of reinforcement bars located in an euro-form before placing concrete in a cold weather condition. The diameters of reinforcement bars with 13 mm, 19 mm, 25 mm and 32 mm were prepared for the experimental tests. Results showed that the larger the size of the diameter of the bars, the higher were the temperature drop. However, this study found that its effect on the temperature drop of the bars was insignificant.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 A
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• pp.569-571
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• 2005

In case of dead-tank circuit breaker with the earthed enclosure, the dielectric performance for phase to ground should be verified under the hot-gas condition produced by the current interruption. This test condition is required in breaking test duties with the rated short-circuit current and rated voltage. And, KERI has completed the reinforcement of the synthetic testing facilities and these facilities have the testing capacity which enables the full-pole testing for 800kV circuit breaker by adopting the series voltage injection method. So, this paper introduced the test circuit and procedures about the full-pole and the multi-part testing method which was devised to estimate the full -insulation of phase-to-ground for the multi-pole and dead-tank circuit breaker.

• 기술사
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• 제44권4호
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• pp.44-49
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• 2011

For the pleasant dwelling place, the most of apartments are designed with the increased green area ratio in ground space and the underground parking lot. However, the condensation in underground space has occasionally occurred due to the insufficient ventilation and insulation treatment. Despite reinforcement of the insulation treatment and mechanical ventilation for the preventing method of condensation. It seems difficult to expect preventing effects for the condensation without consideration of the thermal characteristic of structures. Furthermore, no fundamental measure has been established because maintenance work for these defects incurs a lot of costs and these defects could be occurred again. This study suggests a new method for preventing floor surface condensation through analyzing the reasons of condensation which occurred in the underground floor.

• 한국세라믹학회지
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• 제55권6호
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• pp.527-555
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• 2018

High-temperature thermal insulation materials challenge extensive oxide candidates such as porus $SiO_2$, $Al_2O_3$, yttria-stabilized zirconia, and mullite, due to the needs of good mechanical, thermal, and chemical reliabilities at high temperatures simultaneously. Recently, porous rare earth (RE) silicates have been revealed to be excellent thermal insulators in harsh environments. These materials display attractive properties, including high porosity, moderately high compressive strength, low processing shrinkage (near-net-shaping), and very low thermal conductivity. The current critical challenge is to balance the excellent thermal insulation property (extremely high porosity) with their good mechanical properties, especially at high temperatures. Herein, we review the recent developments in processing techniques to achieve extremely high porosity and multiscale strengthening strategy, including solid solution strengthening and fiber reinforcement methods, for enhancing the mechanical properties of porous RE silicate ceramics. Highly porous RE silicates are highlighted as emerging high-temperature thermal insulators for extreme environments.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2018년도 춘계 학술논문 발표대회
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• pp.149-150
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• 2018

Recently, a large fire has occurred through a dry bit, which is a flammable exterior material, in Daebong Green Apartment Fire in Uijeongbu in 2015 and Jecheon Sports Center Fire in 2017. In this study, KS F ISO 5660-1 Cone calorimeter experiment was used to examine the fire risk of dry bit. Also, the performance of the repair and reinforcement materials to prevent fire expansion was examined. As a result, the dry bit is likely to be ignited by internal and external flower gardens, and its combustion rate and calorific value are very high. In addition, the performance of heat resistance such as ALC panel and ceramic board as a repair and reinforcement material has been proved. However, the insulation is expected to require further consideration.

• Structural Engineering and Mechanics
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• 제5권4호
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• pp.339-353
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• 1997

Fiber reinforced plastic (FRP) rods provide certain benefits over steel as concrete reinforcement, such as corrosion resistance, magnetic and electrical insulation, light weight, and high strength. FRP composites can be combined with a steel core to form hybrid reinforcing rods that take advantage of properties of both materials. The objective of this study was to characterize the bond behavior of hybrid FRP rods made with braided epoxy-impregnated aramid or poly-vinyl alcohol FRP skins. Eleven rod types were tested using two concrete strengths. Specific topics examined were bond strength, slip, and type of failure in concentric pull-out tests from concrete cubes. From analysis of identical pull-out tests on both hybrid and steel rods, information on relative bond strength and behavior were obtained. It is concluded that strength is similar but slip in hybrid rods is much higher. Hybrid rods failed either by pull-out or splitting the concrete block (with or without yielding of the steel core). Experimental data showed consistency with similar test results presented in the literature.

• Architectural research
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• 제20권3호
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• pp.83-92
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• 2018

Recently, there has been inter-Korean exchanges are active, in company with an assertive international activity with North Korea and inter-Korean Summits. Thus, there is a growing possibility of Korean reunification. However, when the unification situation occurs, population inflow by North Korean residents will be expected, and it will be necessary to prepare a housing supply strategy. In addition, even if North Koreans are prevented from entering, a plan is necessary to ensure structural safety since most buildings in North Korea are aging and a recent natural disaster occurs frequently. In this research, we will try to present a temporary housing supply strategy and a short-term structural reinforcement plan based on analysis of the standard housing conditions in North Korea. In this research, we represent the analysis result of the existing construction level, supply status and structural performance of North Korea. When we consider the reinforcement period and social costs, a short-term reinforcement plan is recommended rather than the full reinforcement of the aged housing in North Korea. Furthermore, we examine the ways to secure the residential safety of North Koreans through a case study of domestic and overseas temporary residential facilities, until the permanent residential facilities were supplied. According to the analysis, the tent houses were used as a form of relief housing in overseas frequently. However, the tent house is difficult to apply for domestic country with clear seasons due to insulation and heating problems. Therefore, it is appropriate to develop a residential supply strategy as focusing on the temporary housing facilities in assembled or container from, in preparation for the future population inflow.