• Structural Engineering and Mechanics
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• 제44권1호
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• pp.51-60
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• 2012

Concrete sleepers are essential components of the conventional railway. As support elements, sleepers are always subjective to a variety of time-dependent loads attributable to the train operations, either wheel or rail abnormalities. It has been observed that the sleepers may deteriorate due to these loads, inducing the formation of hairline cracks. There are two areas along the sleepers that are more prone to crack: the central and the rail seat sections. Several non-destructive methods have been developed to identify failures in structures. Health monitoring techniques are based on vibration responses measurements, which help engineers to identify the vibration-based damage or remotely monitor the sleeper health. In the present paper, the dynamic effects of the cracks in the vibration signatures of the railway pre-stressed concrete sleepers are investigated. The experimental modal analysis has been used to evaluate the modal bending changes in the vibration characteristics of the sleepers, differentiating between the central and the rail seat locations of the cracks. Modal parameters changes of the 'healthy' and cracked sleepers have been highlighted in terms of natural frequencies and modal damping. The paper concludes with a discussion of the most suitable failure indicator and it defines the vibration signatures of intact, central cracked and rail seat cracked sleepers.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.332-336
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• 2011

IN THIS STUDY, BASED ON THE TYPE OF HIGH SPEED RAILWAY TRACK VIBRATION CHARACTERISTICS WERE MEASURED AT KTX VEHICLE. KTX ROUTE BALLASTED TRACK HAS BEEN INSTALLED TOGETHER WITH THE CONCRETE TRACK. CONCRETE MUST BE TRACK IRREGULARITY THAN BALLASTED TRACK, VEHICLES VIBRATION VALUES THAT ARE SMALLER. ALSO, IN TERMS OF MAINTENANCE, CONCRETE TRACK IS KNOWN TO BE MORE FAVORABLE THAN THE BALLASTED TRACK. PHASE 2 IS THE KTX, DAEGU - BUSAN IS A SECTION OF CONCRETE TRACK. IN THIS STUDY, "KUUNG-BU HIGH-SPEED RAILWAY LINES" INSTALLED ON THE CONCRETE TRACK AND BALLASTED TRACK KTX FROM THE VEHICLE WHEN INSTALLED BETWEEN RAILS, SLEEPER AND BALLAST ON THE TRACK WAS MEASURED VIBRATIONS.

• International Journal of Railway
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• 제7권3호
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• pp.85-89
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• 2014

The use of pozzolanic materials in concrete mixtures can enhance the mechanical properties and durability of concrete. By reactions with pozzolanic materials and calcium hydroxide in cement matrix, calcium-silicate-hydrate (C-S-H) increases and calcium hydroxide decreases in cement matrix of concrete. Consequently, the volume of solid materials increases. The pozzolanic particles also fill spaces between clinker grains, thereby resulting in a denser cement matrix and interfacial transition zone between cement matrix and aggregates; this lowers the permeability and increases the compressive strength of concrete. Moreover, the total contents of alkali in concrete are reduced by replacing cements with pozzolanic materials; this prevents cracks due to alkali-aggregate reaction (AAR). In this study, nanosilica is incorporated in cement pastes. The differences of microstructural compositions between the hydrated cements with and without nanosilica are examined using nanoindentation, XRDA and $^{29}Si$ MAS NMR. The results can be used for a basic research to enhance durability of concrete slab tracks and concrete railway sleepers.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 추계학술대회 논문집(II)
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• pp.111-116
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• 2003

The Permanent Way consisting of rails and sleeper laid on ballast is a technically and economically viable solution. After two decades of targeted research and development activities Slab Track turned out to be a reasonable option on special fields. Slab Track proves that especially under extreme condition and loads - they reliably help stability and a long service life of track. Technical and experimental solution of slab track are particularly underlined. This paper presents a few Results of the experiments of SFRC slab tracks under fatigue load.

• 한국안전학회지
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• 제25권1호
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• pp.57-61
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• 2010

Formwork is a temporary structure that supports its weight and that of fresh concrete as well as construction live loads. Scaffoling is a temporary frame used to support people and material in the construction or repair of buildings and other large structures. It is usually a modular system of metal pipes, although it can be made out of other materials. Bamboo is still used in some Asian countries like China. The purpose of a working scaffold is to provide a safe place of work with safe access suitable for the work being done. In construction site, steel pipes are usually used as scaffolds. In this study, scaffolding systems which is changed according to sleeper and joist space were measured by buckling test. Buckling load of respective scaffolding system was analyzed by structural analysis program(MIDAS). Buckling load of scaffold with/without wall connection and footboard was got by test and structural analysis. According to these results，we know that scaffolding system of case 3 is suitable. Buckling load of scaffold with wall connection is higher than without wall connection. So wall connection is important in scaffoling systems. Footboard in the scaffolding systems is not effective against promotion of buckling load. Finally, the present study results will be used to design scaffolding systems safely in the construction sites.

• 한국철도학회논문집
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• 제17권4호
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• pp.270-280
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• 2014

이 연구에서는 연속철근 콘크리트궤도에서의 균열의 원인과 균열 발생에 미치는 주요 영향인자를 파악해 보고자 경부고속철도 콘크리트궤도 구간에서 균열 발생 현황과 발생 패턴을 조사하고, 연속철근 콘크리트궤도의 구조를 감안한 2차원 비선형 유한요소해석모델을 이용하여 슬래브 상부와 기층 하부의 온도차와 콘크리트 수축에 의한 연속철근 콘크리트궤도(CRCT)에서의 균열 발생 패턴을 예측하였다. 연구 결과에 따르면 온도차와 콘크리트 건조수축에 의해 침목과 슬래브(TCL) 경계부 및 침목하부에서 균열이 발달할 것으로 예상되고, 이는 현장 조사에서 발생한 균열의 발생 위치와 일치한다. 또한 온도차에 대해서는 열팽창계수가, 콘크리트 수축에 대해서는 건조수축 변형율이 상대적으로 큰 영향을 미치는 것으로 나타났고, 침목이 TCL에 매립되어 있어서 균열 간격이 반드시 철근비에 비례하지 않을 수 있으므로 이러한 CRCT의 구조적 특성을 감안하여 철근비를 정할 필요가 있다.

• 한국안전학회지
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• 제21권2호
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• pp.80-88
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• 2006

In the present study damage behavior of resilient sleepers on concrete ballasts is analyzed. Cracks of resilient sleepers in a railway track system are concentrated on inside of blocks to which the tie bars are connected. Finite element analysis is performed by dividing a block into the straight section and the curved section according to the load condition of the resilient sleeper, and limited the interpretation within the range of resilience. In addition, the value of stress obtained from the interpretation was compared with the allowable stress of concrete to determine the safety. According to the result of numerical analysis, compared with the stress before unequal settlement, the tensile stress of the inside of the block increased significantly after the settlement considering the entire block, and the tensile stress of this part exceeded the allowable stress of concrete, so was undesirable in terms of safety. In reality, the arrangement of tensile stiffeners inside blocks connected to tie bars is improper in the design of resilient sleepers, and when unequal settlement occurs, tensile stress increases on this part and consequently causes cracking damage. It is necessary to arrange wire meshes or tensile reinforcing bars in a structurally safe way to reinforce the inside of blocks on which cracks are concentrated.

• 한국철도학회논문집
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• 제14권3호
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• pp.248-255
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• 2011

현재 한국에서 궤도설계 시 사용하고 있는 궤도충격계수는 미국철도기술협회(AREA)의 식(1+0.513V/100)을 사용하고 있다. 이 식은 자갈 및 콘크리트궤도 모두 동일하게 적용되고 있으며 이러한 단일수치로서의 충격계수는 다양한 궤도구조의 역학적 거동특성을 반영하지 못하여 경우에 따라 과다설계가 될 소지가 있다. 또한 자갈궤도의 경우 도상자갈의 상태변화에 따라, 콘크리트궤도는 궤도탄성층의 구성과 탄성범위에 따라 궤도에 작용하는 동적윤하중의 효과, 즉 충격의 효과가 상이하게 발생된다. 이에 본 연구에서는 자갈궤도(도상 상태 양호 및 불량개소)와 콘크리트궤도(일반적인 침목매입식 궤도, 레일플로팅궤도, 침목플로팅궤도)에서의 현장측정을 통해 도상별, 궤도구조별 열차 주행시 발생하는 윤중의 동적효과를 분석하여 궤도의 상태 및 구조적 특성과 궤도 충격의 효과와의 상관관계 및 영향을 비교, 분석하였다. 연구결과 궤도구조의 특성을 감안하여 궤도충격의 영향을 합리적으로 산정 할 수 있는 제안식을 제시하였다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 춘계학술대회 논문집
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• pp.1002-1008
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• 2011

Turnout is a mechanical installation enabling railway trains to be guided from one track to another at a railway junction. there are classified variously according to rail type, sleeper type, fastening system, track type. Construction of concrete track are on the increase recently to secure the safety of track structure as well as to reduce the maintenance cost. SFC fastening system used the plain track a lot and for those reasons, The fast clip turnout demand growing to improving efficiency of the maintenance cost by unification of fastening clip on whole line. in this study is about development of the fastening system for new turnout using fast clip. this fastening system assembled elasticity pad underneath a base plate. its can change stiffness how to adjust contact surface area of elasticity pad Developed fastening system have passed test according to rule of KRS-TR0014-09R (rail fastening system) and Performance Certification by KR.

• Geomechanics and Engineering
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• 제11권6호
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• pp.757-769
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• 2016

Rail support modulus is an important parameter for analysis and design of ballasted railway tracks. One of the challenges in track stiffness assessment is its dynamic nature under the moving trains which differs it from the case of standing trains. So the present study is allocated to establish a relation between the dynamic and static stiffness of ballasted tracks via field measurements. In this regard, two different sites of ballasted tracks with wooden and concrete sleepers were selected and the static and dynamic stiffness were measured based on Talbot - Wasiutynski method. In this matter, the selected tracks were loaded by two heavy and light car bodies for standing and moving conditions and consequently the deflection basins were evaluated in both sites. Knowing the deflection basins respect to light and heavy loading conditions, both of static and dynamic stiffness values were extracted. Finally two definite relations were obtained for ballasted tracks with wooded and concrete sleepers.