• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
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• pp.434-437
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• 2006

Structures tend to become high-rise, large and specialized due to the urban concentration. Technology related to the structure and construction is required to improve, for which the use of high strength concrete(HSC) with better material property, and composite member with the combined advantage of both concrete and steel for better performance, is suggested. Over a half of fires, which increase by over 10% every year recently, come from the architectural structure, causing a loss at national level. However, little study has been conducted on the member at high temperature despite the increase in the use of HSC composite members. In this study, the techniques of modeling for analysing by DIANA (Displacement Analyzer) the fire damaged HSC composite compressive members are researched. We can review the effect of change in the steel ratio, section size and the steel ratio on the residual strength of structural members by parameter analysis study.

• 한국응용과학기술학회지
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• 제18권4호
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• pp.316-324
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• 2001

To prepare an acrylic type pressure-sensitive adhesive, quarternary polymers were synthesized from butyl acrylate (BA), 2-ethyl hexyl acrylate (2-EHA), methyl methacrylate (MMA), and 2-hydroxy ethyl methacrylate (2-HEMA). The quarternary polymers were identified by FT-IR and Molecular weight was measured by Gel Pearmeation Chromatography. Also, viscosity, solid content and peel strength were examined. The peel strength was 160 $g_{f}/25$ mm when the volume ratio of feed monomer to solvent was 1.3:1, and the ratio was relevant to commercial usage. The pot life of adhesive was 30 sec at the 50 m/min of heat treatment rate at, and it indicated that the minimum drying time was 30 sec. In weathering resistance test, peel strength of $160{\sim}180$ $g_{f}/25$ mm after 1000 h, with no residual remains on the adhesive surface.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 추계학술대회 논문집
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• pp.138-144
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• 2003

Rencentely, the request for the light weight is more incresed in the area of industrial environment and machinery and consistent effort is needed to accomplish high strength of material for the direction of light weight. we got the following characteristic from crack growth test carried out in the range of stress ration of 0.1, 0.3 and 0.6 by means of opening mode displacement. At the content stress ratio, the threshold stress intensity factor crack range ${\Delta}K_{th}$in the early stage of fatigue crack growth (Region I) and dtress intensity factor range ${\Delta}K$ in the stable of fatigue crack growth (Region II) with an increase in ${\Delta}K$. Fatigue life shows more improvement in the Shot-peened material than in the Un-peening material. And compressive residual stress of surface on the Shot peening processed operate resistance force of fatigue. So we can obtain fallowings. (1) The fatigue crack growth rate on stage II is conspicuous with the size of compressive residual stress and is depend on Paris equation. (2) Although the maxium compressive residual stress is deeply and widely formed from surface, fatigue life does not improve than when maxium compressive residual stress is formed in surface. (3) The threshold stress intensity factor range is increased with increasing compressive residual stress.

• Advances in concrete construction
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• 제8권4호
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• pp.311-320
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• 2019

In this study, the effect of cellulose nanocrystals (CNCs) on the fire resistance properties of fiber-reinforced cement composites was investigated. The main variables were CNCs content (0.4, 0.8 and 1.2vol.% compared with cement), steel fiber ratio, and exposure temperature (100, 200, 400, 600 and 800℃). The fire resistance properties, i.e., residual compressive strength, flexural strength, and porosity, were evaluated in relation with the exposure temperature of the specimens. The CNCs suspensions were prepared to composited dispersion method of magnetic stirring and ultra-sonication. CNCs are effective for increasing the compressive strength at high temperatures but CNCs do not seem to have a significant effect on flexural reinforcement. Porosity test result showed CNCs reduce the non-hydration area inside the cement and promote hydration.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2006년도 추계 학술논문 발표대회 논문집
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• pp.95-98
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• 2006

This study investigates spalling properties of high performance concrete, 60MPa clan, made with the various types of coarse aggregate and adding ratio of polypropylene(PP) fiber. As experimental parameters, totally sixteen specimens of ${\phi}100{\times}200mm$ in size are prepared: one specimen for control without fiber, ten specimens with different coarse aggregate types, along with 0.05, 0.1, 0.15 percent of PP fiber in each. 1 hour fire test is conducted and then spalling appearance, spalling degree and residual compressive strength are examined. In addition, sit specimens made with two types of coarse aggregate site, along with same adding ratio of fiber are supplementally done, and only spalling properties is examined. Test results showed that control concrete and most specimens containing 0.05% of PP fiber exhibited 4 to 3 level of spalling degree, resulting severe explosive spalling, except for the specimen using basalt aggregate(Bc) showing 2 to 3 level of that. Especially, the Bc specimen containing 0.1% of the fiber exhibited that residual compressive strength value was 32%, which is 10% higher than other specimens using limestone or granite. Spalling resistance performance was also effective as aggregate size increase.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 추계학술발표대회 논문집
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• pp.60-63
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• 2002

Metal/intermetallic laminated composites have been manufactured by SHS reactions between Ni and Al elemental metal foils. Microstructure showed that the intermetallic volume fraction was 55%, 45%, 35% in the 1:1, 2:1, 4:1 thickness ratio(Ni:Al) specimen and the main phases of the intermetallic were transformed from $Ni_2Al_3$ to NiAl when the thickness ratio was increased. Tensile strength and elongation were increased when the volume fraction of Ni metallic phase was increased. Under assumptions of isostrain condition, the tensile strength of metal/intermetallic laminated composites didn't obey the ROM due to the thermal residual stress and this was confirmed by X-ray residual stress analysis. Fracture toughness results by the SENB test showed R-curves with upward curvature based on LSB condition. Bridging stress based on LSB condition was determined by the curve fitting analysis, In-situ observed microstructure during fracture test showed that the various bridging mechanism such as crack bridging, crack branching and ductile failure of metallic layer were occurred

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2016년도 춘계 학술논문 발표대회
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• pp.53-54
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• 2016

In this study, the effect of high temperature on the compressive strength and elastic modulus of ultra high strength concrete with PP fiber were experimentally investigated. As the result, the compressive strength and elastic modulus of ultra high strength concrete were irrespectively evaluated mixed ratio of PP fiber at high temperature.

• 한국터널지하공간학회 논문집
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• 제15권3호
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• pp.175-186
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• 2013

본 연구에서는 Model Code 2010에 제시된 실험방법에 근거하여 설계강도 60MPa의 강섬유보강 콘크리트의 휨강도와 잔존강도, 휨인성을 평가하였다. 비교를 위하여 설계강도 40MP의 강섬유보강 콘크리트도 실험하였다. 또한, 배합의 평가를 위하여 파괴된 시험체의 파괴면을 육안으로 관찰하여 강섬유의 분산도를 평가하였다. 본 실험에서 사용된 강섬유는 형상비 64, 67 및 80의 국내산 후크 강섬유이다. 강섬유 혼입률은 체적에 대하여 0.5%로 동일하다. 실험결과, 설계강도 60MPa에서는 형상비가 큰 강섬유가 혼입된 강섬유보강 콘크리트만이 Model Code 2010에서 제시된 요구성능을 만족하는 것으로 나타났다. 고강도 콘크리트에서는 큰 형상비의 강섬유가 심대한 균열에서 충분한 인성을 확보하는데 기여할 수 있는 것으로 판단된다. 또한, 섬유의 고른 분산도 확보를 위해서는 낮은 슬럼프가 유리한 것으로 나타났다.

• Steel and Composite Structures
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• 제33권1호
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• pp.111-122
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• 2019

This paper presents an experimental work on the post-fire behavior of two kinds of innovative composite stub columns under eccentric compression. The partially precast steel reinforced concrete (PPSRC) column is composed of a precast outer-part cast using steel fiber reinforced reactive powder concrete (RPC) and a cast-in-place inner-part cast using conventional concrete. Based on the PPSRC column, the hollow precast steel reinforced concrete (HPSRC) column has a hollow column core. With the aim to investigate the post-fire performance of these composite columns, six stub column specimens, including three HPSRC stub columns and three PPSRC stub columns, were exposed to the ISO834 standard fire. Then, the cooling specimens and a control specimen unexposed to fire were eccentrically loaded to explore the residual capacity. The test parameters include the section shape, concrete strength of inner-part, eccentricity ratio and heating time. The test results indicated that the precast RPC shell could effectively confine the steel shape and longitudinal reinforcements after fire, and the PPSRC stub columns experienced lower core temperature in fire and exhibited higher post-fire residual strength as compared with the HPSRC stub columns due to the insulating effect of core concrete. The residual capacity increased with the increasing of inner concrete strength and with the decreasing of heating time and load eccentricity. Based on the test results, a FEA model was established to simulate the temperature field of test specimens, and the predicted results agreed well with the test results.

• 한국강구조학회 논문집
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• 제19권6호
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• pp.725-735
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• 2007

이 연구에서는 두께가 얇은 강판을 가진 철골-콘크리트 합성기둥에서 강판의 국부 좌굴 강도 및 국부 좌굴 후 강도에 대한 해석적인 연구를 수행하였다. 콘크리트 충전에 의하여 합성기둥에서 판의 국부 좌굴 성능이 향상되는 것을 경계 조건을 조정하여 해석에 반영하였고, 탄성 좌굴 해석을 통해 한계 폭-두께비를 제안하였다. 또한 초기 처짐 및 잔류 응력을 해석에 반영하여, 다양한 폭-두께비에 해당하는 평판의 비선형 유한 요소 해석을 통해 초기 국부 좌굴 강도 및 좌굴 후 강도를 산정하였다. 이러한 비선형 해석 결과를 이용하여 판의 유효 폭을 산정하였고, 유효 폭을 이용한 철골-콘크리트 합성기둥의 최대 압축 내력식을 제안하였다. 제안식에 의한 계산된 값과 기존의 실험결과를 비교함으로서 제안식의 타당성을 검증하였다.