• Journal of the Korean Geotechnical Society
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• v.16 no.6
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• pp.161-172
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• 2000

자연암석절리 및 인공 절리에 대하여 일정수직응력제어, 일정 수직하중제어 그리고 무한 강성제어가 가능한 암석 절리면 전단기 시험기를 개발하였다. 이 시험기는 전단변위에 의한 첩촉면적의 변화량을 계산하여 하중변화량을 조절하여 일정수직응력상태를 유지한다. 수직하중에 따른 시험기 강성에 의한 변화향이 제어 프로그램 내에서 제어되어 순수한 시편의 변위량을 출력하도록 하였다. 전단하중에 따른 시험기 강성에 의한 변위량은 상, 하부 전단상자의 상대변위 측정으로 최소화하였다. 전단거동 중의 자유도는 전당방향에 대하여 수평이도, 연직이동, 피칭, 롤링이 가능하도록 하였다. 자연절리면을 모사한 석고시편에 대하여 일정 수직응력 제어, 일정수직하중제어 그리고 무한 강성제어 조건으로 시험하여 제어상태 검증 및 비교를 하였다. 또한 경사각이 16.7˚와 22.6˚인 톱니형 시편에 대하여 시험한 결과 경사각 16.7˚와 22.6˚는 JRC로 10과 15를 나타내었으며, 첨두팽창각이 첨두전단강도에서 발생되며, Barton의 모델과 잘 일치함을 보였다.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.5
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• pp.345-352
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• 2017

In this study, squeal noise with respect to pressure variation is measured by a lab-scaled brake dynamometer and estimated by a complex finite element (FE) eigenvalue analysis. From the FE eigenvalue sensitivity analysis, unstable frequencies occur due to a mode-coupling mechanism and are found to change with variation in contact stiffness. In the experiment, squeal frequencies near 1 kHz, 2.5 kHz, 3.5 kHz, and 4 kHz are increased with pressure variation. The sensitivity of squeal modes to contact stiffness variation obtained from the FE analysis is shown to approximate the variation of squeal frequencies under pressure variation in the experiment.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2009.05a
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• pp.228-229
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• 2009

탐침현미경(Atomic Force Microscope)을 이용하여 탐침과 표면사이에 나노스케일의 접촉 반경을 가지는 접촉보를 만든 후 접촉 강성(contact stiffness) 을 관찰하였다. 다양한 습도 조건하에서 접촉 강성의 변화를 측정한 결과, 습도에 의해 접촉부의 인장 거동이 달라짐을 확인할 수 있었으며, 습도 변화에 따라 인장 거동의 천이점이 존재함을 확인할 수 있었다.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.870-873
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• 2008

레일패드는 궤도전체의 탄성확보 뿐만 아니라 열차하중에 의해 침목으로 전달되는 충격을 완화시켜 침목과 도상의 파손을 방지하는 역할을 하는데, 통과톤수의 증가와 기후적 요인에 의하여 패드가 열화되면 패드의 강성이 증가하게 된다. 패드의 강성이 증가하게 되면 레일을 통해 침목으로 전달되는 충격하중이 증가하게 되어 침목의 파손을 유발할 수 있을 뿐만 아니라 침목하면의 도상에도 과도한 충격하중을 전달하여 도상의 손상을 가속화시킬 수 있다. 또한 레일패드의 강성변화는 궤도의 소음과 레일의 파상마모의 진전에도 영향을 미치게 된다. 따라서 레일패드의 공용기간 중에 적정한 강성을 유지할 필요가 있으며, 통과톤수의 증가에 따른 레일패드의 경화도를 산정하는 방법과 레일패드의 경화가 궤도에 미치는 영향을 정량적으로 분석하여 레일패드의 교체주기에 관한 기준을 마련할 필요가 있다. 본 연구에서는 슬래브의 질량과 일정속도대역에서의 패드강성의 민감도분석을 하여 그 결과를 비교하고 레일패드경화에 따른 대상궤도의 동적거동을 수치해석을 통하여 패드강성과 차량주행속도에 따른 윤중의 변동량과 레일의 변위, 가속도 그리고 침목의 변위, 가속도의 변화정도를 분석해 보았다. 궤도시스템의 동적해석을 위한 해석 프로그램으로는 네덜란드 델프트 공과대학에서 개발된 궤도시스템 전용 해석 프로그램인 DARTS(The dynamic analysis of a rail track structure)를 사용하였다. 대상궤도는 국내 1단계 경부고속철도에서 사용되고 있는 3중보 무도상궤도를 사용하였다.

• Journal of Korean Association for Spatial Structures
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• v.4 no.1 s.11
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• pp.69-75
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• 2004

In the construction of row-rise steel buildings, double angle connection can be considered as one of most effective connection types. Its connection flexibility depends mainly on several parameters such as angle thickness, bolt gage distance, and number of bolts. To establish the effect of the variation of the number of bolts on the moment-rotation relationship, three experimental tests have been conducted in this research. Based on the results of each experimental test, the rotational stiffness of each angle specimen can be calculated by performing regression analysis. Considering the results of regression analysis, we concluded that the more the number of bolts used in double angle connection, the higher the rotational stiffness as one can expected.

• International Journal of Highway Engineering
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• v.10 no.2
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• pp.69-79
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• 2008

This study presents the test results on the performance and the moisture retaining ability of semi rigid pavement using the moisture retaining grouting. The two kinds of the grouting materials were used for the Laboratory tests. The method of the tests includes the compression(3 hours and 7 days) and flexural strength(7 days) varying the P lot flow values. The test results show that the variation of the P lot value has no great effects on the strength, however, the different strength was found as the different grouting materials were used. The performance of the semi rigid pavement was evaluated varying the air void ration of the base asphalt pavement. The test results show that the flexural strength of the semi rigid pavement increases with increasing the air void of the base asphalt pavement so that the flexural strength of the semi rigid asphalt pavement can be effected by the air void of the base asphalt pavement. The moisture retaining tests were conducted and compared in the field the comparisons were made with the dense grade asphalt pavement and the semi rigid asphalt pavement with and without spraying the water. The difference of the temperature of the semi rigid pavement with the spraying water has recorded $11^{\circ}C$ when it compared with the dense grade asphalt pavement and $4^{\circ}C$, when it compared with the semi rigid pavement without the spraying the water. It can be seen that decrease the temperature of the pavement by the moisture retaining ability from the semi rigid pavement.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2A
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• pp.179-186
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• 2008

To analyzing the validity for using the stiffness ratio in evaluating edge stiffness effect of the composite girder bridges, modification factors are analyzed with changing girder spacing. The relation between stiffness ratio, loading type, girder spacing and modification factors is analyzed. From the results of comparing modification factors analyzed from the field loading test and the established design method with the modification factor analyzed from this study, it was concluded that evaluating the edge stiffness effect using stiffness ratio is possible.

• Journal of the Korean Geotechnical Society
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• v.31 no.4
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• pp.31-43
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• 2015

A numerical analysis on the effect of increasing tensile stiffness of the geosynthetics on the soil displacement and pile efficiency was conducted. Parametric studies by changing the stiffness of soft soil, internal friction and dilatancy angles of the embankment material, and flexual stiffness of the composite layer including the geosynthetics were carried out. In general, increasing stiffness of the geosynthetics improves the pile efficiency, whereas the amount of its improvement depends on the condition of parameters. In case of the sufficiently low stiffness of the soft soil or high flexual stiffness of the composite layer including the geosynthetics, a noticeable increase in the pile efficiency can be observed. When the stiffness of the soft soil is very low, the increase in the stiffness of the geosynthetics can significantly reduce the vertical displacement in the piled embankment. When the flexual stiffness of the composite layer is sufficiently high, increasing stiffness of the geosynthetics can greatly improve the pile efficiency.

• The Journal of the Convergence on Culture Technology
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• v.6 no.3
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• pp.347-352
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• 2020

In this study, the variation of track impact factor according to the spring stiffness change rate of sleeper resilience pad was analyzed based on field measurements. In addition, the correlation between field measurement results and 7 million fatigue test results was verified. The fatigue effect diagram of the sleeper resilience pads was presented considering the nonlinear deterioration characteristics of the sleeper resilience pads used for the STEDEF track. Based on the field measurement results, the nonlinear characteristics of the track impact factor for the spring stiffness change rate over 30% of sleeper resilience pad on the track impact factor-track support stiffness diagram were analyzed to be consistent with the fatigue test results.

• Journal of Korean Association for Spatial Structures
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• v.9 no.2
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• pp.83-90
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• 2009

The previous studies for dynamic behavior of spatial structure have been zoomed in on roof structure by numerical analytic method. But the roof structure of real spatial structures is supported by lower structure as column and wall. So, when earthquake is occurred, it is predicted that dynamic behavior of roof structure is affected by lower structure. Therefore, on this study, natural period characteristics of arch structures are analyzed according to section, length and the modulus of elasticity of brass column and polycarbonate column and additional mass of roof structure by the scale-down model of arch structure as the most simple structure of spatial structures. The changes of natural periods are generally alike. But, when Polycarbonate column is connected to roof structure, the change of natural period for change of section is relatively large. That means that change of section and section and length of column and additional mass of roof structure have less influence on change of stiffness because the modulus of elasticity of brass is relatively large.