• Title, Summary, Keyword: Rail Stability

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Development of High Strength Lattice Girder and Evaluation of Its Performance (고강도 격자지보재의 개발 및 그 성능 평가)

  • Lee, Jae-Won;Min, Kyong-Nam;Jeong, Ji-Wook;Roh, Byoung-Kuk;Lee, Sang-Jin;Ahn, Tae-Bong;Kang, Seong-Seung
    • The Journal of Engineering Geology
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    • v.30 no.1
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    • pp.43-57
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    • 2020
  • The objective of this study was to evaluate the performance of high-strength lattice girders as a possible superior alternative to conventional steel arch ribs. For this purpose, the structural characteristics of supports were analyzed using numerical analysis, and their performance was evaluated using maximum bending load tests and tensile tests of the welded joint. According to the results of structural analysis, the optimum size of the upper and lower members and plates is 50 mm × 31.8 mm × 25.4 mm, demonstrating excellent functionality and economic efficiency. High-strength lattice girders of dimensions 55 mm × 30 mm × 20 mm and 85 mm × 30 mm × 20 mm, determined from bending load tests, are found to meet both the reference values and the target values of H-profiles 100 and 125. A review of the ratio of theoretical deflection to actual deflection shows that the high-strength lattice girder developed during this study meets fewer than five of the evaluation criteria for lattice girder deflections proposed by the Federal Railway Department of Germany. Finally, tensile test results reveal that the welded joint of the high-strength lattice girder at the main steel bar-auxiliary steel bar-plate junction exceeds the target value, indicating that the welded joint has sufficient stability.

A study on the estimation of rock mass classes using the information off a tunnel center line (터널 중심선으로부터 이격된 자료를 활용한 미시추구간의 암반등급 산정에 관한 연구)

  • You, Kwang-Ho;Lee, Sang-Ho;Choo, Suk-Yeon;Jue, Kwang-Sue
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.6 no.2
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    • pp.101-111
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    • 2004
  • In order to guarantee the stability of a tunnel and its optimum design, it is very important to obtain enough ground investigation data. In realty, however, it is not the case due to the limitation of measuring spatially distributed data and economical reasons. Especially, there are regions where drilling is impossible due to civil appeal and mountainous topology, and it is also difficult to estimate rock mass classes quantitatively with only geophysical exploration data. In this study, therefore, 3 dimensional multiple indicator kriging (3D-MI kriging), which can incorporate geophysical exploration data and drill core data off a tunnel center line, is proposed to cope with such problems. To this end, two dimensional mutiple indicator kriging, which is one of the geostatistical techniques, is extended for three dimensional analysis. Also, the proposed 3D-MI kriging was applied to determine the rock mass classes by RMR system for the design of a Kyungbu express rail way tunnel.

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Analysis of Aerodynamic Characteristics for determination of tunnel cross section in Honam high speed railway (호남고속철도 터널 단면선정을 위한 공기역학적 특성 분석)

  • Kim, Seon-Hong;Moon, Yeon-Oh;Seok, Jin-Ho;Jo, Hyeong-Jae;Yoo, Ho-Sik;Choi, Jeong-Hwan;Rim, Hyoung-Gyu
    • Proceedings of the KSR Conference
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    • pp.313-336
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    • 2007
  • Unlike a conventional railway system, a high-speed rail system experiences various aerodynamic problems in tunnel sections. Trains running at a high speed in a small tunnel, when compared with the open field, face significant air pressure, resulting in reduced operating stability and fast change in pressure inside the tunnel. These phenomena further cause some unexpected problems such as the passengers onboard feeling an aural discomfort and an impulsive noise at the tunnel exit. To solve these problems, this paper introduces analysis of aerodynamic characteristics for determination of tunnel cross section. The optimum cross-section that satisfies the criteria of aural discomfort was reviewed through lots of numerical simulation analysis. Also, the pressure inside the passenger car of a train operating on Kyungbu HSR line was measured, and the pressure inside the tunnel and the micro-pressure waves at tunnel exit were measured at Hwashin 5 Tunnel. At the same time, a test of train operation model was performed and then the measurement results and test results were compared to verify that various parameters used as input conditions for the numerical simulations were appropriate.

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An Electrochemical Study on the Corrosion Resistance Improvement of Galvanizing Steel by Dipping to Solution with Inhibitor (인히비터 첨가용액의 침지에 의한 용융아연도금 강판의 내식성 개선에 관한 전기화학적 연구)

  • Moon, Kyung-Man;Cho, Hwang-Rae;Kang, Tae-Young;Lee, Myung-Hoon;Kim, Yun-Hae
    • Journal of Advanced Marine Engineering and Technology
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    • v.31 no.2
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    • pp.173-181
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    • 2007
  • Recently, galvanizing method is predominantly being used not only a economical point of view but also due to it s stability and long life. For example, guard rail of high way, all kinds of structures for ship etc. were protected with galvanizing and demand of galvanized structural materials was being increased with more and more. However, galvanized structures were inevitably being deteriorated with time eventually because they were corroded with solution of galvanizing film and exfoliation of it s film in the present severe corrosive environment. Therefore, it is necessary to improve the corrosion resistance of the galvanizing film through various methods such as variation of chemical composition of galvanizing bath, chromate treatment and coating treatment. In this study, three test specimens such as pure galvanizing, galvarium, and chromate treatment were submerged at tap water with inhibitor addition. And the effect of their corrosion resistance improvement was comparatively investigated with electrochemical method. Corrosion current density of the galvanized steel was the largest among three specimens, however, the galvarium steel showed the lowest corrosion current density. Futhermore, these three kinds of test specimens indicated considerably excellent corrosion resistance by dipped at tap water with inhibitor addition. Especially, the galvanized steel showed the best effect of corrosion resistance improvement than other test specimens.

The Displacement Limit at the End of an Approach Slab for a Railway Bridge with Ballastless Track (콘크리트궤도 부설 교량의 접속슬래브 단부 처짐한도에 관한 연구)

  • Choi, Jin-Yu;Yang, Shin-Chu
    • Journal of the Korean Society for Railway
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    • v.11 no.2
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    • pp.195-202
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    • 2008
  • The transition area between a bridge and an earthwork is one of the weakest area of track because of the track geometry deterioration caused unequal settlement of backfill of abutment. In case of a ballastless track, the approach slab could be installed to prevent such a phenomenon. But, if there is occurred the inclined displacement on the approach slab by a settlement of the foundation or formation, the track is also under the inclined displacement. And this defect causes reducing the running stability of a vehicle, the riding comfort of passengers, and increasing the track deteriorations by excessive impact force acting on the track. In this study, parametric studies were performed to investigate the displacement limit on the approach slab to avoid such problems. The length and the amount of unequal settlement of approach slab were adopted as parameter for numerical analysis considering vehicle-track interaction. Car body accelerations, variations of wheel force, stresses in rail, and uplift forces induced on fastener clip were investigated. From the result, resonable settlement limit on the end of an approach slab according to slab length was suggested.

Effect of Lateral Deformations of Guideway on Guidance Characteristics of Maglev Train (가이드웨이 횡변형의 자기부상열차 안내특성에의 영향 분석)

  • Kim, Ki-Jung;Lee, Jae-Kyoung;Han, Hyung-Suk;Yang, Seok-Jo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.39 no.11
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    • pp.1161-1167
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    • 2015
  • A slender guideway is essential in improving aesthetically and reducing its construction cost which accounts for about 70% of overall investment for maglev system. As the slender guideway, however, may increase its deformation, its effect on levitation stability and guidance performance needs to be analyzed. The purpose of this study is to analyze the effect on guidance characteristics of maglev due to the lateral deformation of the guideway girder and lateral irregularity of guiderail. For doing this, 3D model considering lateral deformation of girder and irregularity of rail of the guideway is developed. Using the dynamic interaction model integrated with the proposed guideway and maglev vehicle including electromagnetics and its controller, guidance characteristics of maglev are analyzed. It is analyzed that the effect on lateral deformation of girder is relatively small compared to deformation on the lateral irregularities of guiderail.

A Suggestion of Blasting Patterns of a Mine closed to Railway Line for Securing Safety of High Speed Train (고속철도 안전확보를 위한 노선 인접 광산의 발파패턴 제안)

  • Kim, Hyun-Ki;Lee, Sung-Hyeok;Lee, Jin-Wook;Choi, Chan-Yong
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.19 no.5
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    • pp.1-9
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    • 2015
  • Recently Honam high-speed railroad line is constructed in southern part of Korea. This line is for next generation HST named HEMU-430X. But there is a limestone mine near this line and this mine will make a process to dig a passageway under the railway line. In this case, safety of railroad system and stability of mine are crucial problems on both sides. By measuring mine blasting vibration and calculating regression equation, effect of mine blasting to train running is investigated quantitatively. 0.5 kine (cm/sec) is applied as a management specification of vibration based on field measurement. In this study, changes of blasting patterns are suggested to control vibration of mine blasting. And the effect of train vibration to mine is also invesitigated by numerical analysis.

A Study on the Spray-atomization Characteristics of Diesel-ethanol Blended Fuels in a High Pressure Diesel Injection System (디젤 고압 분사 시스템에서 디젤-에탄올 혼합연료의 분무 및 미립화 특성에 관한 연구)

  • Kim, Se-Hun;Park, Su-Han;Lee, Chang-Sik
    • Transactions of the Korean Society of Automotive Engineers
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    • v.18 no.3
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    • pp.80-87
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    • 2010
  • The purpose of this paper is to analyze the effects of ethanol blending ratio and fuel temperature in diesel-ethanol blended fuel on the spray-atomization characteristics in a high pressure common-rail injection system. In this work, a diesel fuel and three blended fuels were used as test fuels. Blended fuels were made by blending ethanol with a purity 99.9% to diesel fuel, from 0% to 30%. In order to keep diesel-ethanol blending stability, 5% of biodiesel fuel as volumetric ratio was added into test fuels. The fuel temperature was controled in steps with 40K, from 290K to 370K. Macroscopic spray characteristics were investigated by analyzing the spray tip penetration and spray cone angle through spray images obtained from visualization system. In addition, in order to study microscopic spray characteristics of ethanol blended fuels, the droplet diameter, was analyzed using the droplet measuring system. It is revealed that the spray tip penetration is similar regardless of ethanol blending ratio. As ethanol blending ratio is increased, the spray cone angle becomes wider. It is shown that the spray cone angle is affected by low viscosity and density of ethanol. As the fuel temperature increases, the spray tip penetration and spray cone angle become shorter and narrower respectively. The SMD of ethanol blending fuels is smaller than that of diesel fuel because of low viscosity and surface tension of ethanol.

A Study on the Behavior of Concrete floors with Over-break in Railroad Tunnel (여굴깊이에 따른 철도터널 바닥 콘크리트의 거동에 관한 연구)

  • Yang, Joo-Kyoung;Kim, Hyo-Jung
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.21 no.5
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    • pp.101-107
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    • 2017
  • Over-break, which is excavated larger than planned line at tunnel excavation, is inevitable due to the nature of blasting. But regarding the bottom of the foundation, most of the domestic ordering organizations pay only 10 cm thick filled concrete when pouring concrete due to over-break. In accordance, the construction cost will increase greatly if all the depths of the designed over-break are filled only with concrete. When tunnel excavation occurs, concrete filling of 18 MPa(T = 100 mm) and 150 mm~237 mm auxiliary concrete layer and 240 mm concrete track(TCL) are applied to the upper part. The concrete is installed in an excessive amount of about 600 mm between the lower part of the rail and the tunnel rock bed. Therefore, in this study, it is necessary to analyze the concrete crack structure according to the depth of the existing tunnel and the modified tunnel section, and to evaluate the adequacy of the required thickness of the tunnel floor concrete for securing the crack stability of the concrete.

A numerical study of the influence of rock mass classes boundary on tunnel stability (암반 등급 경계가 터널 안정성에 미치는 영향에 관한 수치해석적 연구)

  • Kim, Gyeomyeon;Jung, Chanmook;Lee, Yongjun
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.21 no.6
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    • pp.825-835
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    • 2019
  • When the tunnel is designed, the ground is classified into several grades and the corresponding support system is applied according to the support pattern table. However, a simple pattern application based on rock grade does not take into account the longitudinal stress transitions occurring at rock grade boundaries. In this study, three-dimensional numerical analysis was performed to estimate the stress change in the longitudinal rock grade change of NATM tunnel, and the influence zone of load transfer was investigated using the influence line and trend line. As a result, the downward change of rock grade in the direction of tunnel excavation occurs in the range of 0.35~0.7D from low-strength rock to high-strength rock around the grade change boundary. It is necessary to apply a downward pattern of about 1.0D to the safety direction in consideration of the influence range of 0.35D to 0.7D.