• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 춘계학술대회 논문집
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• pp.967-973
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• 2004

Rock socketed drilled shafts transfer significant portion of structural loads at the socketed part. Therefore, a proper design of side and base resistances of a shaft at the socket is a major concern for the geotechnical engineers. In this study, we modified the Hoek-Brown criterion to estimate side resistance of rock socketed drilled shafts. Earlier method to compute side resistance of a shaft is linear or power functions of intact rock masses. However, side resistance is mobilized like shearing which influenced by the mechanical properties of concrete and rock masses, adhesion of rock/concrete interface, roughness of rock socket. Therefore, a single coefficient or power of uniaxial compressive strength of intact rock cannot provide accurate values of side resistance in a wide range of the uniaxial compressive strength. A new approach proposed in this study can consider in situ rock mass condition (frequency or discontinuities, weathering condition), and rock types thus, it has a wider applicability than the earlier models.

• 한국가구학회지
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• 제26권4호
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• pp.428-434
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• 2015

In this study, we received each wood plastic composites (WPC) from three manufacturers. These WPCs were evaluated regarding their physical and mechanical properties of both before and after accelerated weathering by ultraviolet (UV) irradiation. The total time of exposure of the WPCs to UV irradiation was 1800 h. The water absorption, volumetric swelling and shrinkage of WPCs did not affected by UV irradiation. Among the mechanical properties, there was no significant differences in bending strength and screw withdrawal resistance of UV treated WPCs compared with those of reference WPCs. However, surface hardness of WPCs showed decrease under UV irradiation. Stereoscopic microscopy observation revealed deterioration of the surface layer polymer in all weathered WPCs by UV. Exposure of the WPCs to UV irradiation caused decomposition and disappearance of the polymer layer. From this result, we can estimate that damage of polymer by UV led to a decrease in the surface hardness of the WPCs. The wood flours retained original shape after accelerated weathering by UV irradiation.

• Elastomers and Composites
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• 제33권3호
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• pp.193-200
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• 1998

고무소재는 다양한 종류별로 구조에 따라 다른 물성을 갖는 것으로 알려져 있다. 일반적으로 EPDM 고무는 내후성과 내오존성이 뛰어나고 열이나 냉기, 습기의 노출에도 잘 견디는 것으로 밝혀진 바 있다. 한편 crosslinked IIR은 물과 기체투과에 대한 저항성이 큰 것으로 알려져 두가지 성분의 장점을 갖도록 EPDM/crosslinked IIR의 블렌드를 새로운 형태의 소재로 추천할 수 있다. 따라서 본 실험에서는 EPDM과 crosslinked IIR의 블렌드비를 변화시키면서 가교시간과 블렌드후 물리/화학적 특성의 개선을 목표로 하였다. 결과적으로 30wt.%의 crosslinked IIR 조성을 갖는 블렌드소재가 내후성, 내오존성 및 내기체투과 특성이 뛰어나, O-링이나 전기관련 제품에 상업적으로 응용가능한 것으로 판단되었다.

• 공업화학
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• 제5권4호
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• pp.722-730
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• 1994

전기절연체로 사용되는 가교폴리에틸렌(XLPE)의 내후성에 미치는 산화방지제(Antioxidant)와 카본블랙의 효과를 살펴 보았다. 산화방지제와 카본블랙을 조합하여 16가지의 시료를 제작하고 xenon-arc lamp type의 Weather-Ometer로 500, 1000, 1500, 2000 시간 촉진열화시켰을 때 촉진열화 각 시간대별로 열화거동을 관찰하였다. 인장강도, 신장율, 절연파괴전압, tan ${\delta}$로 XLPE의 내후성을 평가한 결과, 산화방지제보다는 카본블랙이 더 효과적이었고 두 첨가제를 조합해서 사용할 때 내후성이 우수한 synergistic effect를 나타냈다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2014년도 춘계 학술논문 발표대회
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• pp.220-221
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• 2014

The various type of polymer such as silicone, modified silicone, polyurethane, etc are being used in domestic construction sealant market. Once sealant is installed in building, it should maintain their specific performances such as preventing moisture, rain, air, etc against environment conditions for several decades. In this study, weather resistance as per polymer type of sealant has been evaluated using QUV accelerated weathering tester. As a result, weather resistance of silicone is highest and modified silicone is lowest in the comparison of other type of polymer.

• 보존과학회지
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• 제25권1호
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• pp.77-86
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• 2009

석조문화재 보존처리제로 사용되는 에폭시수지의 물성변화를 충전제의 함량변화와 인공풍화를 통한 가속화시험으로 연구하였다. 충전제로서 탈크를 첨가한 에폭시수지(L-30) 시편에서 함수율이 감소하였고, 표면접촉각이 증가하여 수분에 대한 저항성이 높았다. 탈크의 첨가량을 일정량 증가시켰을 때 접착 성능에서는 문제가 발생되지 않았으나 에폭시수지 자체의 압축강도는 저하되었다. 탈크 함량에 따른 에폭시수지의 물성변화는 그 주변 환경요소에 각기 다른 경향을 보였다. 온 습도 변화에 의한 인공풍화시험 후 탈크가 첨가된 에폭시수지에서 순수한 에폭시수지에 비해 함수율의 변화가 적었으며, 색차변화가 작았고 표면접촉각이 커진 것으로 확인되었다. 자외선조사에 의한 인공풍화시험에서는 탈크함량이 증가할수록 에폭시의 물성이 악화되는 결과를 보였다. 이는 에폭시수지의 내구성을 향상시키기 위해서 첨가하는 충전제의 함량이 보존처리될 석조물의 주변환경에 따라 다르게 적용되어야 함을 의미한다.

• 한국가구학회지
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• 제13권1호
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• pp.27-37
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• 2002

This study was investigated with the surface properties such as physical and accelerated tests of wood-based floorings. In physical test, hardness and abrasion resistance values of laminate floorings were higher than those of others. The center line average surface roughness($R_a$) of imported laminate flooring was highest value($1.34{\mu}m$) and that of imported solid wood flooring was lowest value($0.62{\mu}m$). In cold resistance and moist heat resistance, no defects were found on the surface of all flooring (crack, blistering, peeling, and gloss loss etc.) after testing. Wet-cold-dry cycle test showed that plywood flooring appeared some cracks. In accelerated weathering test, color difference increased with increasing Xenon arc light irradiation

• 한국도로학회논문집
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• 제16권2호
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• pp.35-41
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• 2014

PURPOSES : Surface treatment is a favorable method in the pavement preventive maintenance. This study (Part I) aimed to develop the low viscosity filling material for waterproof characteristics and high penetrable and weather resistance, and a series of companion study (Part II) presents the coating characteristics and performance analysis using field and lab tests. METHODS : Hydrophobic characteristics of the advanced surface treatment material are observed and measured the filling depth and the permeability for sand and asphalt pavement specimen using the water absorption test and permeability test, X-RAY CT test. Color difference for the weather resistance using ultraviolet ray accelerated weathering test is compared with asphalt pavement specimens. RESULTS : The developed material shows the decreased water absorption and increased impermeable effect because of the hydrophobic characteristics. It is found that the filling depth is about 6mm and weather resistance is better than asphalt pavement specimen. CONCLUSIONS : The advanced hydrophobic - low viscosity filling treatment material is developed in this study (Part I) to improve the waterproof characteristics and high filling capacity and weather resistance for the pavement preventive maintenance.

• 한국도로학회논문집
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• 제15권5호
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• pp.75-79
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• 2013

PURPOSES : The objective of this study is to evaluate the environmental resistance of bio-polymer concrete for use of pavement materials developed for reducing the carbon-dioxide. METHODS : The compression, tension, and bending strength tests were conducted on the bio-polymer concrete specimens with and without environmental conditioning. The specimens were conditioned using the freezing-thaw and accelerated weathering process for long period of time. To assess the resistance against chloride, the chloride ion penetration resistance tests were carried out on the bio-polymer concrete specimens. RESULTS : Test results show that the maximum difference in strength between specimens with and without conditioning is about 2.6MPa indicating that the effect of environmental conditioning on specimen strength is negligible. Based on the chloride ion penetration resistance test, the penetration quantity of electric charge of the specimens is zero and there is no ion penetration within the bio-polymer concrete. CONCLUSIONS : It is found from this study that there is slight change in strength of bio-polymer concretes before and after environmental conditioning process and no chloride ion penetration observed in these specimens. Therefore, the developed bio-polymer concretes can be applied effectively as pavement materials due to the small change of physical properties with environment change.

• 한국지형학회지
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• 제28권1호
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• pp.1-12
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• 2021

This study tried to reveal relative surface denudation resistance and ranking by geologic types in the Southern Korean Peninsula using an 1:250,000 digital geologic map and ASTER GDEM. Among rock types such as igneous, sedimentary and metamorphic rocks, metamorphic rock showed the greatest resistance to surface denudation. The most resistant rock to surface denudation by geologic periods (e.g., the Precambrian, Paleozoic, Mesozoic and Cenozoic) was found from the Precambrian. Among the major tectonic settings in the Southern Korean Peninsula such as the Gyeonggi massif, Okcheon belt, Yeongnam massif, Gyeongsang basin and Pohang basin, the Okcheon belt indicated the greatest resistance. The most and least resistant rocks from the representative nine rocks in the Southern Korean Peninsula were Paleozoic limestone, and Cretaceous sedimentary rock and Cenozoic sedimentary rock, respectively. This study suggests that Paleozoic limestone, Cretaceous volcanic rock, Paleozoic sedimentary rock and Precambrian gneiss can be regarded as hard rocks with high elevation, steep slope and complicated relief, while soft rocks with low elevation, gentle slope and simple relief are Jurassic granite, Cretaceous sedimentary rock and Cenozoic sedimentary rock.