• Proceedings of the KSR Conference
• /
• 2008.06a
• /
• pp.31-38
• /
• 2008

This Study discussed the roll forming process analysis of levitation rail for urban Maglev vehicle. To verify validity of roll forming process, we analyzed roll forming process for track shoe which is similar to levitation rail. The analysis process was composed of 12 passes and was performed for only 8 passes except overlapping passes. In the variation of temperature with each pass, surface temperature of the structure was cooled from initial $1200^{\circ}C$ to $1010^{\circ}C$ during 30 second before first pass, and central temperature and surface temperature was cooled to $980^{\circ}C$ and $900^{\circ}C$ in final pass, respectively. A length of structure after final pass is about 5 times longer than that before roll forming process. A strain of structure had a higher value in the inner part of the track shoe and show from minimum 2.5 to maximum 6.5. A torque applying on roll appear high in 2, 3 and 4 passes and a maximum value was $27,000ton{\cdot}mm$. Also it was analyzed that a load to the normal direction needs maximum 300ton.

• Proceedings of the KSR Conference
• /
• 2008.06a
• /
• pp.1809-1815
• /
• 2008

This experiment simulated the fire driven flow of an underground station through parallel processing method. Fire analysis program FDS(Fire Dynamics Simulation), using LES(Large Eddy Simulation), has been used and a 6-node parallel cluster, each node with 3.0Ghz_2set installed, has been used for parallel computation. Simulation model was based on the Kwangju-geumnan subway station. Underground station, and the total time for simulation was set at 600s. First, the whole underground passage was divided to 1-Mesh and 8-Mesh in order to compare the parallel computation of a single CPU and Multi-CPU. With matrix numbers($15{\times}10^6$) more than what a single CPU can handle, fire driven flow from the center of the platform and the subway itself was analyzed. As a result, there seemed to be almost no difference between the single CPU's result and the Multi-CPU's ones. $3{\times}10^6$ grid point one employed to test the computing time with 2CPU and 7CPU computation were computable two times and fire times faster than 1CPU respectively. In this study it was confirmed that CPU could be overcome by using parallel computation.

• Proceedings of the KSR Conference
• /
• 2008.06a
• /
• pp.39-45
• /
• 2008

A levitation rail is placed on the top of track structure to operate Maglev vehicles and a part of track that link up with a sleeper is applied repeated load in Maglev vehicles operation. This paper aimed to verify validity of design for levitation rail, through the fatigue analysis about load which is applied to levitation rail in Maglev vehicles operation and impact load occurring in an emergency landing. Load conditions applied design load(23kN/m) in normal operation and skid drop load(24kN/m) in vehicle drop. And boundary conditions are consider bolt fixing and welding. Through static analysis, weak point and maximum stress of levitation rail could be obtained. S-N(stress-life) method was used in oder to predict fatigue life, and Goodman relationship was applied to consider a effect of mean stress. Also damage was calculated by using Miner's. As a result of fatigue analysis, levitation rail had a fatigue life which was more than requirement ($10^6$cycle) in all analysis conditions. Assumption that $10^8{\sim}10^9$cycles is infinite life, all analysis conditions had infinite life except a case under drop load and bolt fixing($1.21{\times}10^6$).

• Proceedings of the KSR Conference
• /
• 2009.05a
• /
• pp.1498-1508
• /
• 2009

Recently, the expansion of roads are necessary because the population and vehicles have rapidly increased, but those are restricted because of the limited site. JES(Jointed Element Structure) method is the method of the new cross-structure, which is element-traction method which draws and excavates elements under the existing structure with high accuracy within a short time. Also JES(Jointed Element Structure) method has a facility of the economical execution, a small effect on the train-service during construction period and no limit of the crossing length under the trade In this study, the tractive force and settlement are compared with the upper element, side wall element and the lower element respectively in the section which the JES method is applied In the case of element located at left side wall, the tractive force measured by a guage is double or more than the tractive force calculated by a formula. It is expected that many boulder contented in the ground contrary to the site investigation data cause high tractive force. For comparison of the settlement, the settlement as excavating the upper element is the largest in all steps. It is expected that this is the same as the cause of high tractive force. Also in this study, the practical use of the JES method when some under pass structures are extended in the future is studied.

• Proceedings of the KSR Conference
• /
• 2006.11b
• /
• pp.1240-1246
• /
• 2006

Generally, there are two types of main factors to affect output power quality of a auxiliary power supply an EMU(electric multiple unit). One is a voltage flicker by amplitude modulation of short time and air compressors. The other is repetitive motion of large capacity motor such as air compressors, HVAC unit etc. in main factors. This paper compared two kinds of fluorescent lamp, 32W (after remodeling interior) and 40W(before remodeling interior) and measured the light output varying input power(AC220V) for a flicker phenomenon related power supply of lamps in EMU. Also, we analyzed a flicker considering EMU operating time and density in order to grasp main factors of a load change to cause a voltage change. As a results of test, a 40W fluorescent lamp was more insensitive with 20.26% degree an eye recognition degree sides about changes of the input power and lower with 19.9% voltage side generating flicker compare with fluorescent lamp 32W. Also, we confirmed the fact which the fluorescent lamp flicker was generated by varying fluorescent lamp output voltage when the commercial EMU was in high driving density and at the busy time. Additionally, we confirmed the frequency band which an EMU passenger could feel sensitively blinking of a fluorescent lamp was visually $8Hz{\sim}15Hz$.

• Proceedings of the KSR Conference
• /
• 2006.11b
• /
• pp.1017-1028
• /
• 2006

Japanese railroad companies continued growing by developing diversification based on a railroad enterprise. However, after entering in the 1990s, the diversification model of a railroad company reached the management limit. Under economic depression, A decrease in the birthrate and aging progressed and passenger transport changed to the downward tendency. Nevertheless, since railroad investment was expanded, railroad achievements got worse and price competitiveness with JR East Japan became weak. But the achievements of a diversification section got worse compared with the railroad enterprise. Therefore, group management was thought as important and enterprise reorganization was developed.

• Proceedings of the KSR Conference
• /
• 2006.11b
• /
• pp.802-810
• /
• 2006

For a thorough train control, the precise train position detection is necessarily required. The widely used current way for train position detection is the one of using track circuits. The track circuit has a simple structure, and has a high level of reliability. However trains can be detected only on track circuits, which have to be installed on all ground sections, and much amount of cost for its installation and maintenance is needed. In addition, for the track circuit, only discontinuous position detection is possible because of the features of the closed circuit loop configuration. As the recent advances in telecommunication technologies and high-tech vehicle-based control equipments, for the train position detection, the method to detect positions directly from on trains is being studied. Vehicle-based position detection method is to estimate train positions, speed, timing data continuously, and to use them as the control information. In this paper, the features of GPS navigation and DR navigation are analyzed, and the navigation filters are designed by constructing vehicle-based train position detection method by combining GPS navigation and DR navigation for their complementary cooperation, and by using kalman filter. The position estimation performance of the proposed method is also confirmed by simulations.

• Proceedings of the KSR Conference
• /
• 2008.11b
• /
• pp.436-440
• /
• 2008

Monorail is a type of LRT that a train, made with $2{\sim}4$ cars runs on single track. Monorail can be divided into two types - straddled type, running on track beam and suspended type, running suspended from track beam. After Wuppertal, world's first monorail in German, many monorails are currently operated in Australia, U.S.A, Japan etc. In macountry, it was decided to introduce monorail to 3rd line of Daegue. Daegue's 3rd line is public financial project and supported about 60% of total project cost by central government. The central government announced a standard for rubber-wheel type LRT and steel-wheel type LRT. It becomes a guide to local government willing to introduce this type of LRT. The standard for monorail hasn't announced yet although the necessity of research has grown. Korea Railroad Research Institute which has been asked to research by Ministry of Land Transport and Maritime Affairs has carried out research on standard of monorail considering domestic condition. The on-going research is described in this paper. We wish that it becomes national standard and a good guide for local government.

• Proceedings of the KSR Conference
• /
• 2008.11b
• /
• pp.993-999
• /
• 2008

A girder height limitation is the critical parameter for rapid construction of bridge deck and construction space limitation especially in urban area such as high population area and high density habitats. A standard post-tensioned I-shaped concrete girder usually demands relatively higher girder height in order to retain sufficient moment arm between compression force and tensile force. To elaborate this issue, a small U-shaped section with wide flanges can be used as a possible replacement of I-shaped standard girder. This prestressed concrete box girder allows more flexible girder height adjustment rather than standard I-shaped post-tensioned girder plus additional torsion resistance benefits of closed section. A 30m-long, 1.7m-high and 3.63m-wide actual small prestressed concrete box girder is designed and a laboratory test for its static behaviors by applying 6,200kN amount of load in the form of 4-point bending test was performed. The load-deflection curve and crack patterns at different loading stage are recorded. In addition, to extracting the dynamic characteristics such as natural frequency and damping ratio of this girder, several excitation tests with artificial mechanical exciter with un-symmetric mass are carried out using operational frequency sweep-up. Nonlinear finite element analysis of this 4 point bending test under monotonic static load is investigated and discussed with aids of concrete damaged plasticity formulation using ABAQUS program.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.41 no.5
• /
• pp.533-541
• /
• 2021

Retaining walls have been used to prevent slope failure through resistance of earth pressure in railway, road, nuclear power plant, dam, and river infrastructure. To calculate dynamic earth pressure and determine the characteristics for seismic behavior, many researchers have analyzed the nonlinear response of ground and structure based on various numerical analyses (FLAC, PLAXIS, ABAQUS etc). In addition, seismic fragility evaluation is performed to ensure safety against earthquakes for structures. In this study, we used the FLAC2D program to understand the seismic response of the inverted T-type wall with a backfill slope, and evaluated seismic fragility based on relative horizontal displacements of the wall. Nonlinear site response analysis was performed for each site (S2 and S4) using the seven ground motions to calculate various seismic loadings reflecting site characteristics. The numerical model was validated based on other numerical models, experiment results, and generalized formula for dynamic active earth pressure. We also determined the damage state and damage index based on the height of retaining wall, and developed the seismic fragility curves. The damage probabilities of the retaining wall for the S4 site were computed to be larger than those for the S2 site.