• Journal of the Korean Geotechnical Society
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• v.26 no.8
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• pp.27-37
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• 2010

Downdrag force develops when a pile is driven through a soil layer which will settle more than a pile. There is no obvious criterion for application of the current pile design method considering the negative skin friction. Therefore, in this study, numerical analyses were performed to investigate the behavior of a single pile subjected to negative skin friction and their results were used to determine the applicability of the current design method. Including three different sites in Song-do area and two different cases with friction pile and end bearing pile conditions, total six cases were considered. The load-settlement relationships and the neutral points were estimated for different end bearing conditions and the allowable bearing capacity of piles with negative skin friction was investigated through parametric studies. Based on the results showed that the negative skin friction made a major influence on the settlement of a pile and its stress. However the allowable bearing capacity may not be influenced by the negative skin friction. Compared with the allowable bearing capacity obtained from the ultimate bearing capacity with the safety factor of 3, the current design method with the safety factor of 3 underestimated the allowable bearing capacities regardless of the end bearing conditions. On the other hand, the current design method with the safety factor of 2 yielded reasonable results depending on the end bearing conditions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.6D
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• pp.951-960
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• 2006

Structural pavement analysis considering lateral loads of moving vehicle was carried out in order to simulate passing vehicle loads under various interface conditions. To verify of existing multi-layer elastic analysis of layer interface effect parameters, this study compared outputs by using ABAQUS, a three dimensional finite element program and KENLAYER, multi-layer elastic analysis as vertical load was applied to the surface of asphalt pavements. Pavement performance depending on interface conditions was quantitatively evaluated and fundamental study of layer interface effect parameters was performed in this study. As results of the study, if only vertical loads of moving vehicle is applied, subdivision of either fully bonded or fully unbonded is enough to indicate interface effect parameters. On the other hand, when lateral loads are applied with vertical loads, pavement behavior and performance are greatly changed with respect to layer interface conditions. The thinner thickness of the asphalt layer is and the smaller elastic moduli of the asphalt layer is, the more pavement behavior is influenced by interface conditions. In addition, regression analysis equation analytically computing tensile strain which was considered thicknesses and elastic moduli of the asphalt layer and layer interface effect parameters at the bottom of the asphalt layer was presented using database from numerical analyses on national pavement model sections.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.187.1-187.1
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• 2014

아연 가격의 상승과 경량합금개발의 중요성이 부각됨에 따라 아연을 대체할 새로운 강판용 내식소재의 개발이 중요하다. Al-Mg 합금 박막은 낮은 밀도를 가지면서 질량 대비 높은 강도, 좋은 내식성을 지녀 아연도금강판을 대체할 코팅소재로 그 가능성이 연구되고 있다. 이러한 Al-Mg 합금 박막의 실용화를 위해 국내외의 관련 연구그룹에서 연구를 진행하고 있으며, 그 결과 Al-Mg 합금 박막의 내식성 및 기계적 특성은 박막의 조성 및 미세구조와 상당한 관련성이 있음이 알려지고 있다. 본 연구에서는 sputtering법으로 냉연 강판에 Al-Mg 합금을 조성 및 열처리 여부 등을 조절하여 증착시킨 후 각 조건에 따른 박막의 미세구조와 기계적 특징을 조사하였다. 각 조건별 내마모도와 경도, 마찰계수, 밀착력을 분석하여 기계적 특성과 미세구조와의 상관관계를 도출하고자 하였다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.05a
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• pp.208-210
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• 2009

5성분계 Ti-Al-Si-C-N 코팅막은 하이브리드 코팅 시스템을 사용하여 실리콘 (Si) 웨이퍼와 SUS 304 기판위에 합성되었다. 본 연구에서는 Si 첨가에 의해 Ti-Al-Si-C-N 코팅막의 미세구조와 기계적 특성의 변화를 체계적으로 조사하였다. Si 함량이 증가됨에 따라 Ti-Al-Si-C-N 코팅막의 미세구조는 주상정에서 나노복합체를 가지는 미세구조로 변화하였다. 나노복합체의 고유한 특성에 의하여 미소경도는 약 56GPa로 증가하였고, Si가 증가함에 따라 평균 마찰계수도 크게 줄어들었다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2008.11a
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• pp.37-37
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• 2008

고온에서 안정적인 DLC막을 성막하기 위해 PECVD공정에서 실리콘을 첨가하여 제조하였다. 기존의 실리콘첨가 DLC막과는 다르게 고온에서 생성됨으로 마이크로 클러스터 형태의 DLC구조로서 disordered 영역이 넓게 존재하고 있어 I(D)/I(G)비에서의 변화가 있는 것이 관찰되었다. 실리콘 양이 증가할수록 값이 낮아지는 것이 관찰되는데 이는 실리콘량이 증가하면서 수소의 위치에 실리콘이 결합하면서 sp3 단일구조형태의 코팅 막을 만드는 것이 관찰된다. 고온 어닐링효과로 내부구조에서 다량의 sp2구조가 관찰되는 것으로서 DLC막이 어느 정도 흑연화되지만, 실리콘이 SiC에서 SiOx로 $SiO_2$와 SiOH막으로 바뀌는 면서 마찰계수가 낮은 DLC막을 유지할 것으로 기대되며, XPS와 FT-IR분석에 의해 이러한 상들의 존재를 관찰할 수 있었다. 특히 공정상 TMS이 증가하면 첨가된 Si에 의해 형성되는 막이 초기부터 OH기를 다량 포함하고 있는 것을 알 수 있었고, 온도 상승에 의해서 실리콘표층에 더욱 많은 SiOx계열의 물질이 생성되는 것이 명확하게 발견되었다.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.46 no.3
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• pp.295-305
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• 2020

Treatment for beauty using oxidizing agents damages hair with inducing structural alteration in cuticle layer, degradation of protein, and loss of lipid. This study connects a frictional coefficient upon the damaged hair by an instrumental test to the texture test by human being, and considered a moisture as a factor of the damage. A friction coefficient has been measured upon the hair with successive treatment of dye, perm, and bleach. The friction coefficient from the hair dye-treated three times was defined with 0.60, where 58% of answerer indicated an initial damage point as the hairs of iteration of dye-treatment increased. Even bleach treated three times results in 0.84 of friction coefficient corresponding to 88% of answerer attributed the hair to an initially damaged hair. In order to figure out a lipid loss in hair for human being to respond damage, a friction coefficient of the hair was controlled by removing 18-methyleicosanoic acid (18-MEA). The initial damage has been recognized by 0.60 of the friction coefficient for the 68% of answerer. Since moisture is the largest portion of the components in hair, moisture analysis has been performed to study a relationship between texture of damage and the friction coefficient from an instrumental evaluation. As an iteration of dye increases, the hair became hydrophilic with smaller contact angle. It is found that a damaged hair by dyeing possessed more than 0.42% of moisture compared to a healthy hair. Finally, it is elucidated that an increase of moisture in hair induced higher adhesive force corresponding to the friction coefficient, and the friction coefficient above 0.6 is attributed to the preception of hair damage.

• Journal of the Korean Geotechnical Society
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• v.15 no.4
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• pp.235-246
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• 1999

Some of the underground structures such as subway tunnels are constructed by open cut method, in which the ground is excavated, a structure installed, and after that the excavated space is backfilled. In this case, because of their narrow and constrained boundary conditions, the earth pressure induced by self-weight of the backfilled soil acting on the underground structures is different from that of the classical theory. The vertical and horizontal earth pressures acting on upper slab and side wall of the underground structures constructed by open cut method are affected by the backfill geometry. The laboratory model tests were performed in the conditions of a variety of the shapes of backfill geometry and wall friction. And their results were compared with those from theories. As a result, it was observed that the distribution of the earth pressure acting on the underground structure is affected by the shapes of backfill geometry, the width of backfill, the angle of excavation and the wall friction.

• Journal of the Korean Society for Railway
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• v.19 no.3
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• pp.341-350
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• 2016

Concrete track on railway bridges should be designed to effectively respond to the movement of the superstructure of the bridge. In the design procedure, shear keys are generally placed on the protection concrete layer (PCL) before casting the concrete track so the shear force due to slip between the concrete track and the bridge super-structure can be transferred. In this paper, a nonlinear structural analysis procedure that considers the construction joint has been developed to predict the shear behavior of a shear key. With the developed analysis procedure, it was possible to predict the shear force-shear slip response at the construction joint in a shear key by considering the friction of concrete surface and the dowel action of the rebars. The analysis results showed good agreement with the test results for 4 specimens.

• Journal of the Society of Disaster Information
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• v.7 no.3
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• pp.171-180
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• 2011

As a great earthquake hit east Japan recently, the interests for the necessity of earthquake resistant design and earthquake resistance ability of existent structures are much increased. The damage or collapse of a bridge, as a social overhead capital structure affects socially and economically. Thus the evaluation of earthquake resistance ability of these structures is very important. The reviewing methods for earthquake resistance ability are mostly deterministic. Although the deterministic methods are fit for the evaluation of safety of each member, they are not practical for the whole structure. For the evaluation of structural safety for earthquake, the method for the evaluation of fragility or damage is needed for some stages of damage. In this paper, fragility curves of steel box bridge using RFPB bearing for PGA, PGV, SA, SV, SI are constructed, and these are compared with the cases of FPB.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.27 no.6
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• pp.581-588
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• 2014

The PSC bridges have recently been widely used in Korea. The PSC bridge is a structure whose performance is improved through the use of tendons and steel bars in deflection and cracking characteristics of the concrete. Therefore, measurement or estimation of the load acting on tendon is important in order to maintain the PSC bridges efficiently and safely. This paper deals with a numerical study on the deformation of a multi-tendon anchor head in order to verify the relationship between the load acting on tendon and the deformation of anchor head. All kinematics, material properties and contact nonlinearity are included for the precise analysis and numerical studies are performed by Abaqus. From the numerical results, it is verified that the hoop strain is most useful in the estimation of the load acting on tendon and strains are affected by various parameters such as friction coefficient, boundary conditions, and arrangement.