• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 춘계학술대회 논문집
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• pp.1056-1061
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• 2007

Railroad roadbed was consisted into structure types that earthwork, tunnel, bridge and joint sections. Joint section was affected a large factor confidence and safety of the train running by stiffness transition zone that track substructure stiffness change section as like between tunnel and earthwork from ballast track to concrete track. These problems are the results of increased dynamic wheel loads, which also lead to wear and tear on vehicle components and contribute to poor ride quality. The study presented in this paper was conducted on model test by using Wheel Moving Loading System.

• 한국철도학회논문집
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• 제11권3호
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• pp.311-316
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• 2008

일정한 크기의 응력이 반복적으로 작용할 때 매 사이클마다 변형이 증가하는 현상을 라체팅이라고 한다. 라체팅은 레일이나 차륜의 균열발생 기구의 하나이지만 실험적, 이론적 측면에서 아직 많은 연구를 필요로 하는 분야이다. 레일의 경우 접선력 방향으로 소성변형이 축적되는 것으로 알려져 있다. 본 연구에서는 차륜-레일의 구름 접촉에서 발생하는 응력의 이론해에 대해 살펴보고, 라체팅을 모델링 할 수 있는 비선형 이동 경화법칙을 사용하는 탄소성 구성방정식을 적용하여 라체팅 현상을 모델링 하였다. 일정 크기의 접촉력이 반복적으로 작용할 때 매 사이클마다 일정 크기의 소성변형이 발생하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 춘계학술대회 논문집
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• pp.1705-1711
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• 2008

Analysis of settlement of foundation under the cyclic loading is very important element in the field construction. The fatigue of construct is inflicted by wheel load of mobile unit with railroad and superhighway. The settlement behavior under the cyclic loading is investigated through Power Model by Li and Selig. However, the settlement tendency of foundation appears to be the settlement of general Europe cohesive soil. In this study, the Power Model was used to determine the plastic deformation for sandy soil. Based on the laboratory cyclic loading test a, m, b parameters, for using in the Power Model were presented.

• 한국공간구조학회논문집
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• 제16권4호
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• pp.29-36
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• 2016

The objective of this research is to development of a parametric design system for membrane structures. The parametric design platform for the spatial structures has been designed and implemented. Rhino3D is used as a 3D graphic kernel and Grasshopper is introduced as a parametric modeling engine. Modeling components such as structural members, loading conditions, and support conditions are developed for structural modeling of the spatial structures. The interface module with commercial structural analysis programs is implemented. An iterative generation algorithm for design alternatives is a part of the design platform. This paper also proposes a design approach for the parametric design of Spoke Wheel membrane structures. A parametric modeling component is designed and implemented. SOFiSTik is examined to interact with the design platform as the structural analysis module. The application of the developed interface is to design optimally Spoke Wheel Shaped Ductile Membrane Structure using parametric design. It is possible to obtain objective shape by controlling the parameter using a parametric modeling designed for shape finding of spoke wheel shaped ductile membrane structure. Recently, looking at the present Construction Trends, It has increased the demand of the large spatial structure. But, It requires a lot of time for Modeling design and the Structural analysis. Finally an optimization process for membrane structures is proposed.

• 한국정밀공학회지
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• 제27권8호
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• pp.35-41
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• 2010

White Etching Layer(WEL) is a phenomenon that occurs on the surface of rail due to wheel/rail interactions such as excessive braking and acceleration. Rolling Contact Fatigue(RCF) cracks on the surface of rail have been found to be associated with WEL. In this study, we have investigated RCF damages of white etching layer using twin disc testing and fatigue analysis. These tests consist of wheel flat tests and rolling contact fatigue tests. WEL has been simulated by wheel flat test. It has been founded that the WEL with a bright featureless contrast is formed on the surface of specimen by etching. Rolling contact fatigue test was conducted by using flat specimens with the WEL generated by the wheel flat test. It has been observed that two types of cracks occur within the specimen. The contact fatigue test was simulated in 2D elastic-plastic FE simulations. Based on loading cycles obtained from the finite element analysis, the fatigue life analysis according to the thickness variation of WEL was carried out. The longest fatigue life was observed from the thickness of 20um.

• 한국도로학회논문집
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• 제5권2호
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• pp.15-24
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• 2003

방수시스템(WPS)의 성능은 재료 인자들의 복잡한 상호작용, 설계상세, 그리고 시공의 질에 따라 영향을 받고, 주로 인장접착강도(TAS)로 측정되는 교면과의 접착성에 의해 결정되는 것으로 알려져 있다. 따라서 본 연구는 현재 국내에 유통되고 있는 교면방수재 8종의 WPS의 성능을 아스팔트 포장층 혼합물의 종류, 시공시 혼합물의 온도, 포장층의 두께, 반복주행시험에 따른 접착특성을 중심으로 인장접착특성을 비교하였다. 또한 TAS 시험 후 계면에서의 탈리상태를 조사하였다. WPS에 대한 TAS 시험결과 SMA 혼합물이 밀입도 혼합물 보다 TAS가 크게 나타나 아스팔트 혼합물 종류에 따라서 차이가 났다. 시트식 방수재는 아스팔트 혼합물의 종류에 상관없이 시공온도가 높은 것이 접착력이 더 크게 나타났으나 도막식에서는 방수재 계열별로 다소 차이가 있고 시트식과 같지 않은 것으로 나타났다. 포장층 두께에 따른 영향은 방수재 종류에 상관없이 대동소이한 것으로 나타났다. 반복주행시험에 따라서 시트식에서의 접착력은 하중 재하지점>하중재하 않은 곳>하중 재하지점 옆 부근의 순서로 나타났고, 도막식에서는 방수재 종류에 따라 다르게 나타났다. 또한 방수재의 종류 및 특성에 따라 방수시스템 계면에서의 탈리상태가 다르다는 것을 알 수 있었다.

• 한국정밀공학회지
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• 제18권9호
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• pp.18-24
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• 2001

• 한국도로학회논문집
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• 제20권3호
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• pp.1-9
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• 2018

PURPOSES : In order to evaluate a crack resistance at cold joint, sealing tape was adopted to apply at cold joint instead of typical tack coat material(RSC-4). The sealing tape was made by hot sealing material. The crack resistance as function of environmental and traffic loading was measured with visual observation. METHODS : In this study, the crack resistance was evaluated as function of environmental and traffic loading. The freeze-thaw method was adopted for environmental loading of asphalt pavement. condition. The damage of cold joint under freeze-thaw action is initiated by ice expansion load and accelerated by the interfacial damage between new and old asphalt pavement. The traffic loading was applied with wheel tracking machine on the cold joint area of the asphalt pavement for 3 hours at $25^{\circ}C$. The evaluation of crack resistance was measured with visual observation. The freeze-thaw results shows that the sealing tape was significantly increased the crack resistance based on. RESULTS : To estimate the crack resistance at cold joint area due to the environmental loading, the Freeze-thaw test was conducted by exposing the product to freezing temperature(approximately $-18^{\circ}C$) for 24 hours, and then allowing it to thaw at $60^{\circ}C$ for 24 hours. The tack coat material(RSC-4) was debonded after 21 cycles of the Freeze-thaw test. The first crack was observed after 14 freeze-thaw cycle with RSC-4 material. But, the sealing tape was not debonded after 24 cycle test. Also, the sealing tape shows the better performance of the crack resistance under the traffic loading with wheel track test. The crack was generated the under traffic loading with RSC-4(tack coating), however, the crack was not shown with sealing tape. It indicates that the sealing tape has a strong resistance of tensile stress due to traffic loading. CONCLUSIONS :Based on limited laboratory test result, a performance of crack resistance using the sealing tape is better than that of general tack coat material(RSC-4). It means that the sealing tape is possible to extend a pavement service life because the crack, one of the main pavement distresses, will be delayed.

• 한국자동차공학회논문집
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• 제11권3호
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• pp.124-130
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• 2003

Many structural evaluation procedures of road and airfield pavements use the Falling Weight Deflectometer (FWD) as a critical element of non-destructive deflection testing. FWD is a trailer mounted device that provides accurate data on pavement response to dynamic wheel loads. A dynamic load is generated by dropping a mass from a variable height onto a loading plate. The magnitude of the load and the pavement deflection are measured by a load celt and geophones. And database concerning pavement damage should be enhanced to analyze loss of thickness asphalt layer caused from the plastic deformation of pavement structure, such as cracking or rutting. The prototype FWD is developed, which consists of chassis system, hydraulic loading system, data acquisition and analysis system. This system subsequently merged to from automation management system and is then validated and updated to produce a working FWD which can actually be used in the field.

• Geomechanics and Engineering
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• 제12권4호
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• pp.579-593
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• 2017

Geosynthetic reinforced soil retaining walls can be employed as railway embankments to carry large static and dynamic train loads, but very few studies can be found in the literature that investigate their dynamic behavior under simulated wheel loading. A large-scale dynamic test on a reinforced soil railway embankment was therefore carried out. The model embankment was 1.65 meter high and designed to have a soilbag facing. It was reinforced with HDPE geogrid layers at a vertical spacing of 0.3 m and a length of 2 m. The dynamic test consisted of 1.2 million cycles of harmonic dynamic loading with three different load levels and four different exciting frequencies. Before the dynamic loading test, a static test was also carried out to understand the general behavior of the embankment behavior. The study indicated the importance of loading frequency on the dynamic response of reinforced soil railway embankment. It also showed that toe resistance played a significant role in the dynamic behavior of the embankment. Some limitations of the test were also discussed.