• Journal of Advanced Marine Engineering and Technology
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• v.35 no.1
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• pp.32-39
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• 2011

The purpose of VDR capsule is to maintain a stored information securely and retrievably in the extreme environment like voyage incident. This study shows the modellings, the analyses and the experiments of the survivability test of penetration, high and low temperature fire. The capsule housing is used to protect capsule against penetration and the influences of its thickness are studied by the modelling and analysis of penetration using LS-DYNA. The phase change material and thermal insulation material are used to protect capsule against high and low temperature fire test. The thermal characteristics of various volume ratios of phase change material to thermal insulation material were conducted. Also the tests were conducted to confirm the structural and thermal reliability.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.1
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• pp.61-68
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• 2012

The purpose of Crash Protected Module in Black Box used at aircraft is to protect a stored information(Flight data & Cockpit Voice) safely even after extreme environment like a plane crash. This study shows the structure & thermal analyses and the comparisons of predictions and results of tests about CPM for Crash Survival through extreme environment such as Penetration Resistance, High Temperature Fire, Low Temperature Fire. Specially, the Effect of housing thickness change was studied through the Penetration Resistance analysis using LS-DYNA, and the influence of volume ratio change between phase change material and thermal insulation material was studied through the High Temperature & Low Temperature analysis using Icepak. Also, structural and thermal reliability of CPM was validated through the tests.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.3
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• pp.33-41
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• 2016

Concrete is inherently a good fire-resistance material among all other constrcution materials and protects the reinforcing steel inside. This study investigates the material characteristics of concrete and steel bar inside the full scale reinforced concrete(RC) beam exposed to fire test. The fire test specimen was 4 m long and the test was conducted under no loading condition following KS F 2257. Fire source is simulated by ISO 834 and number of thermocouples were installed to measure temperature variation of surfaces and inside of the beam. The measured compressive strength of cored specimen, which was exposed to fire test, was 11 MPa, about 66% lower than the strength before exposure. The yielding strength of steel bar also decreased about 75 MPa, about 17% lower. The measured temperature of protected steel bar was around $649^{\circ}C$, the critical limit, after 4 hour exposure.

• 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 Computational Structural Engineering Institute Conference
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• 2005.04a
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• pp.283-290
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• 2005

제철용 고로구조물의 안전성 위협 요인으로는, 고로자중이나 철광석 낙하 둥과 같은 기계하중 외에도 구조물 내부 온도가 최대 $1700^{\circ}C$에 이르는 고온 환경을 들 수 있다. 이러한 고온의 작업 환경은 고로 구성부재들의 크립손상, 열피로 문제 등을 야기시키기 때문에 이들 고열에 의한 영향평가는 고로의 안전성 평가에 있어 필수요소로 거론되고 있다. 일반적으로 고로의 단면을 구성하고 있는 내화재, 냉각판, 철피 등의 냉각시스템을 거치면서 내부의 고온 환경은 고로 외피에 이르는 동안 온도강하가 이루어진다. 급격한 온도강하는 나타나지 않지만 장기간 고로 가동에 있어 상시하중으로 작용하는 이 열원에 의해 고로 각 구부위에는 열응력이 발생하고 이 열응력과 나머지 기계적 하중의 조합에 의해 크립이나 열피로 등과 같이 고로 구조물 안전성 위해요인들이 발생한다고 분석되어 진다. 따라서 본 연구에서는, 고로 안전성 평가를 위한 첫 번째 단계로서 범용유한요소해석 프로그램인 ANSYS를 이용한 열응력 해석을 수행하여 잠재적인 안전성 위해요인으로 알려진 열응력 발생 특성을 분석하고, 고로 건전설계 및 보수 유지 관리지침으로 활용할 수 있는 기반기술을 개발한다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.48-48
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• 2018

습도는 대기중에 분포되어있는 물 분자의 양으로 사람이 살아가는데 있어 막대한 영향을 주는 환경적 요소중 하나이다. 산업적 가스의 순도에 막대한 영향을 끼치기도 하고, 반도체 산업에서 불량률과도 밀접한 관련이 있다. 또한, 식품학이나 기상학, 농사와도 밀접한 관련이 있어서 습도를 측정하는 것은 중요시 되고 있다. 이를 위해서 많은 물질들이 사용되고, 연구되었다. 산화 구리, 산화 아연, 산화 납 등의 산화금속 물질들이나 전도성 고분자, 실리콘 기반의 물질들이 주로 사용되고 있는데, 그 중 산화 금속이 쉬운 합성 방법과 낮은 단가, 명확한 작동 원리로 인해 널리 사용되고 있다. 산화 아연의 경우 넓은 direct band gap energy와 우수한 내화학성으로 인해 주로 사용되는데 그 중 1차원 물질인 nanowire의 경우 비등성 구조와 높은 비표면적을 갖는 특성으로 인해 산화 아연의 nanowire 구조가 많이 사용된다. 본 연구에서는 열처리 공정을 이용하여 산화아연의 nanowire 구조를 합성하였고, 합성된 nanowire는 양쪽의 미세전극을 직접적으로 연결하여 간편한 방식으로 소형 소자를 만들 수 있다는 장점이 있다. 열처리 공정 이전에 전기도금 방식을 이용하여 아연층을 증착 하였다. 전기도금 조건은 0.1 M의 염화 아연과 1 M의 염화 칼륨으로 구성된 용액에 -1.1 V를 인가하였다. 합성된 아연층은 열처리 공정에 의해 산화아연의 nanowire 구조체로 변환되고, SEM (scanning electron microscope)를 통해 표면 형상을 관찰 하였고, XRD (X-ray diffraction)을 통해 미세구조를 확인하였다. -1 V부터 1 V 범위의 전압을 흘려주어 형성된 소자의 전기적 특성을 확인하였고, 1 V를 인가하였을 때, 습도 변화에 따른 센서 소자의 저항변화를 통해 습도 센서로서의 특성을 확인 하였다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.5
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• pp.313-322
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• 2019

Recently, there have been frequent occurrences of bridge fires. Fires in cable-supported bridges can damage and brake cables due to high temperatures. In this study, fire scenarios that can occur on cable-supported bridges were set up. In addition, based on the results of vehicle fire tests, a fire intensity model was proposed and cable heat transfer analyses were performed on a target bridge. The analyses results demonstrated that temperature rises were identified on cables with a smaller cross-sectional area. Furthermore, vehicles other than tankers did not exceed the fire resistance criteria. When the tanker fire occurred on a bridge shoulder, the minimum diameter cable exceeded the fire resistance criteria; the height of the cable exceeding the fire resistance criteria was approximately 14 m from the surface. Therefore, the necessity of countermeasures and reinforcements of fire resistance was established. The results of this study confirmed that indirect evaluation of the temperature changes of bridge cables under fire is possible, and it was deemed necessary to further study the heat transfer analysis considering wind effects and the serviceability of the bridge when the cable temperature rises due to fire.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.1
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• pp.23-29
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• 2022

This study was conducted to confirm the applicability of recycled aggregates as aggregates for structural concrete as a way to respond to the shortage of natural aggregates. The two-stage mixing approach developed by Tam et al. is known to be a method that can improve the mechanical performance of recycled aggregate concrete without the installation of new additional facilities. In this work, modified version of two stage mixing approach, which was used in our earlier work, was introduced to prepare mortar specimens with recycled fine aggregate, and the compressive strength and fire resistance were compared to mortar mixed with normal mixing approach. According to the experimental results from mortar with recycled fine aggregate, the use of two-stage mixing approach was found to be more effective than normal mixing approach for compressive strength development. In addition, the residual strengths of the mortar with two-stage mixing approach was higher than mortar made of normal mixing approach after exposure to 600 and 900 ℃. It is possible to manufacture high-performance cement composites with recycled fine aggregates through the active use of the two-stage mixing approach.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.5
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• pp.23-29
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• 2023

The goal of this study is to evaluate the bursting characteristics and fire resistance performance of mixed cement concrete containing fibers at very high temperatures. For this purpose, FA-based, Slag-based, and each mix according to the amount of fiber mixed were heated to room temperature, 150℃, 300℃, 600℃, and 900℃, and then the burst shape, compressive strength, and elastic modulus were measured and evaluated. As a result of the experiment, it was found that relatively more surface damage occurred in FA-based specimens when heated at ultra-high temperatures than in slag-based specimens, and there was a difference between the mix without fibers and the mix with fibers when heated at ultra-high temperatures, that is, at 900℃. In the mix without fibers, a decrease in strength of more than 5% occurred. In addition, the elastic modulus also showed the same phenomenon as the compressive strength, and in particular, the decrease in elastic modulus was found to be greater than the amount of decrease in compressive strength. Meanwhile, estimation equations for compressive strength and elastic modulus according to heating temperature were statistically proposed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.3 s.55
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• pp.127-134
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• 2009

This study investigated their properties of spalling resistance and residual compressive strength after fire test corresponding to various ISO, RABT heating curves, and contents of hybrid organic fiber of high strength concrete. The results were summarized as following. As fundamental characters of concrete with hybrid organic fiber, the flowability was directly declined as the increase of fiber contents, and air contents were decreased or increased a little bit, but there was not big difference. The compressive strength was gradually declined sluggishly at 28 days. As properties of fire resistance, in case of RABT heating curves, compare with ISO heating curves a spalling aspect showed till range that has much contents of hybrid organic fiber, but they are mostly peeling spalling, which means spalling aspect didn't happen to inside. In conclusion, in case of W/B 25% high strength concrete, the spalling was prevented over 0.04% of contents of fiber at ISO heating curve and over 0.10% of contents of fiber at the RABT heating curve. In case of spalling was prevented, mass reduction rate according to the change of heating temperature curves showed around 7% at ISO heating curves and around 9% at RABT heating curves. The residual compressive strength rate corresponding to the change of heating temperature curves showed 50%~60% at ISO heating temperature curves and 30%~35% at RABT heating temperature curves in case of spalling was prevented.