• Proceedings of the KSR Conference
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• 2000.05a
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• pp.471-478
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• 2000

For many decades, the railway was constructed using tracks with jointed rails of relatively short lengths. The joints cause many drawbacks in the track and lead to signeficant maintenance cost. so, railroad engineers became interested in eliminating joints. Continuous welded rail(CWR) track has many advantages over the conventional jointed-rail track. but, in the case of the elimination of rail joints, it may cause the track to be suddenly buckled laterally by thermal loads. In this paper, firstly, 3-D CWR track model and CWRB program exactly considering the influence of tie are developed far linear static and buckling analysis using finite element method. Characteristics of CWR track model are using 7-dofs beam element as rail, Offset technic exactly considering centroid axies difference of track components(rail, rail-pad-fastener, tie), and Thermal gradient considering thermal difference of top flange and bottom flange in rail section.. second,, Through the static and linear buckling analysis by CWRB, Influences of various track components (rail, ballast, fastener, tie and so on..) on CWR track behavior and stability was characterized.

• Journal of the Korean Society for Railway
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• v.17 no.5
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• pp.373-380
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• 2014

With a view to the commercialization of the Korean automatic variable-gauge bogie in the Eurasia railway system, the aim of this research was to perform an economic analysis concerning the possible introduction and operation of this bogie at the present time. For this purpose, we compared the possible types of freight connection service for container transportation, transshipment and the gauge-adjustable system, estimating the total life-cycle cost (LCC) incurred by each system, depending on type and quantity, over the whole process of acquisition, operation, maintenance and disposal. Based on this, we presented a case-by case analysis. Furthermore, in estimating economic feasibility, we analyzed the cost-benefit ratio taking into account not only the objective LCC, but also the reduced time required for the gauge-change and customer convenience. After estimating the LCC and analyzing the cost-benefit ratio of the respective systems, we demonstrated the economic superiority of view of the gauge adjustable system.

• Journal of the Korean Geotechnical Society
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• v.37 no.9
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• pp.13-24
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• 2021

Recently, attempts have been made to detect fouling patterns in the ground using Ground Penetrating Radar (GPR) during the maintenance of gravel ballast railway tracks. However, dealing with GPR signal data obtained with a large amount of noise in a site where complex ground conditions are mixed, often depends on the experience of experts, and there are many difficulties in precise analysis. Therefore, in this study, a numerical modeling technique that can quantitatively simulate the GPR signal characteristics according to the degree of fouling of the gravel ballast material was proposed using python-based open-source code gprMax and RSA (Random sequential Absorption) algorithm. To confirm the accuracy of the simulation model, model tests were manufactured and the results were compared to each other. In addition, the identification of the fouling layer in the model test and analysis by various test conditions was evaluated and the results were analyzed.

• Journal of the Korean Geotechnical Society
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• v.24 no.11
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• pp.25-34
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• 2008

An application of concrete track is being actively processed for the construction of Korean high speed railway. The concrete track has an advantage in decreasing the maintenance cost, whereas it has much difficulty controlling the long term settlement after settlement occurred. Therefore, the management and control of settlement are very important for the successful construction of concrete track. The purpose of this paper is to verify the allowable settlement between concrete track and ballast track, and piled raft foundation installation effects as settlement reducers for concrete track. Therefore, a series of 3D finite element analyses that take into account the allowable settlement were performed for major parameters such as soil condition, pile installation and loading type. Based on the analysis, it is shown that concrete track causes much smaller settlement than ballast track, and the effect of installation is necessary to effectively reduce the settlement of concrete track.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.6D
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• pp.905-913
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• 2008

Recently, concrete tracks are introduced into high-speed railroads as an alternative to ballast tracks. Concrete tracks are superior to ballast tracks in the aspect of durability, maintenance and safety. However, deteriorated stiffness of railroad bed and settlement of soft ground induced by trapped or seepage water lead to problems in safety of train operation. In this research, flexural rigidity of concrete tracks was employed as an index of track displacement and a new seismic technique called FRACTAL (Flexural-Rigidity Assessment of Concrete Tracks by Antisymmetric Lamb Waves) method was proposed to delineate flexural rigidity of concrete tracks in a 2-D image. In this paper, to establish theoretical background, parametric research was performed using numerical simulations of stress-wave tests at concrete tracks. Feasibility of the FRACTAL technique was proved at a real concrete track for Korean high-speed trains. Validity of the FRACTAL technique was also verified by comparing the results of impulse-response tests performed at the same measurement array and the results of DC resistivity survey performed at a shoulder nearby the track.

• Journal of Korean Society of Transportation
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• v.24 no.2 s.88
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• pp.65-78
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• 2006

This paper investigates the cost structure ot the Korea and Japan railroad industry with respect to density, scale and scope economies as well as productivity growth rate using a generalized trans)og multiproduct cost function model. The paper then assumes that the Korea and Japan railway companies pi·educe three outputs (incumbent railway passenger-kilometers. Shinkansen passenger-kilometers, ton-kilometers of freight) using four input factors (labor, fuel, maintenance, rolling stock and capital). The specified cost function includes foul other independent variables: track lengths to reflect network effects, two dummies to reflect nation and ownership effects, and time trend as a proxy for technical change. The simultaneous equation system consisting of a cost function and three input share equations is estimated with the Zellner's iterative seemingly unrelated regression. The unbalanced panel data used in the paper, a total of 154 observations. are collected from the annual records of the Korea National Railroad (KNR) for the yews $1977{\sim}2003$, Japan National Railways (JNR) for the years $1977{\sim}1984$. seven Japan Railways (JR's) for the years $1987{\sim}2003$. The findings show that the Korean and Japanese railways exhibit product-specific and overall economies of density but product-specific diseconomies of scale with respect to incumbent railway passenger-kilometers, Shinkansen-kilometers and ton-kilometers. However, the railways experience mild overall economies of scale which result from economies of scope associated with the joint production of incumbent railway/Shinkansen and feight, freight/incumbent railway and Shinkansen except Shinkansen/incumbent railway and freight. In addition, the economies of density and scale in the KNR, JR east, JR central, and JR west companies at the point of the years $1990{\sim}2003$ average is generally analogous to the above results at the point of sample average. There also appear to be economies of ssope associated with the joint Production of the incumbent railway and Shinkansen in JR central but diseconomies of scope in JR East and JR West. The findings also indicate that the productivity growth rate of the privately-owned JR's is larger than that of the government-owned KNR.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2007.11a
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• pp.396-400
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• 2007

Various ways of automated guideway transit construction are being planned recently owing to the policies of the national government and local municipalities as well as increasing investment from the private sector. Particularly, the increase in the private investment is increasing greatly in SOC (Social Overhead Cost). This trend of promoting private sector investment must be conducted on the basis of a thorough analysis of the economic feasibility of the project from the government and construction companies in the private sector. In other words, an accurate cost analysis of initial investment cost (Construction cost), maintenance/repair cost, profit making through the operation of the concerned facilities, cost of dissolution, etc. in terms of the life cycle is very much in need. Nevertheless, the analysis of uncertainty factors and its probabilistic theory are in need of development so that they can be used in the analysis of the economic feasibility of a construction project. First of all, the actual studies on maintenance/repair cost of automated guideway transit are scarce as of yet, prohibiting an accurate computation of the cost and its economic analysis. Accordingly, this study focused on the uncertainty analysis of the economic feasibility for civil engineering structures among automated guideway transit construction projects based on the rapidly increasing investment on such structures from the private sector. For this research purpose, a cost classification system for the automated guideway transit is proposed, first of all, and the data On the cost cycle of the civil structure facilities and their unit cost are collected and analyzed. Then, the uncertainty in the cost is analyzed from the perspective of LCC. In consideration of the current status with almost no. studies on maintenance/repair of such facilities, it is expected that the cost classification system and the uncertainty analysis technique proposed in this study will greatly enhance LCC analysis and economic feasibility studies for automated guideway transit projects in the future.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.23 no.6
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• pp.449-469
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• 2011

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigerating Engineering during 2010. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) Research trends of thermal and fluid engineering have been surveyed as groups of general thermal and fluid flow, fluid machinery, and new and renewable energy. Various topics were presented in the field of general thermal and fluid flow. Research issues mainly focused on the thermal reliability of axial fan and compressor in the field of fluid machinery. Studies on the design of ground source heat pump systems and solar chemical reactors were executed in the field of new and renewable energy. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics and industrial heat exchangers. Researches on heat transfer characteristics included heat transfer in thermoelectric cooling/power generation systems, combined heat and power systems, carbon nano fluid with PVP, channel filled with metal foam and smoke ventilation in a rescue station of a railroad tunnel. Also the studies on flow boiling of R123/oil mixture in a plain tube bundle and R410A charge amount in an air cooled mini-channel condenser were reported. In the area of industrial heat exchangers, researches on plate heat exchanger, shell and tube heat exchanger, enthalpy exchanger, micro channel PCHE were performed. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics and industrial heat exchangers. Researches on heat transfer characteristics included heat transfer in thermoelectric cooling/power generation systems, combined heat and power systems, carbon nano fluid with PVP, channel filled with metal foam and smoke ventilation in a rescue station of a railroad tunnel. Also the studies on flow boiling of R123/oil mixture in a plain tube bundle and R410A charge amount in an air cooled mini-channel condenser were reported. In the area of industrial heat exchangers, researches on plate heat exchanger, shell and tube heat exchanger, enthalpy exchanger, micro channel PCHE were performed. (3) Refrigeration systems with alternative refrigerants such as hydrocarbons, mixed refrigerants, and CO2 were studied. Performance improvement of refrigeration systems are tried applying various ideas of refrigerant subcooling, dual evaporator with hot gas bypass control and feedforward control. The hybrid solar systems combining the solar collection devices with absorption chillers or compression heat pumps are simulated and studied experimentally as well to improve the understanding and the feasibility for actual applications. (4) Research trend in the field of mechanical building facilities has been found to be mainly focused on field applications rather than performance improvements. Various studies on heating and cooling systems, HVAC facilities, indoor air environments and energy resources were carried to improve the maintenance and management of building service equipments. In the field of heating and cooling systems, papers on a transformer cooling system, a combined heat and power, a slab thermal storage and a heat pump were reported. In the field of HVAC facilities, papers on a cooling load, an ondol and a drying were presented. Also, studies on HVAC systems using unutilized indoor air environments and energy resources such as air curtains, bioviolence, cleanrooms, ventilation, district heating, landfill gas were studied. (5) In the field of architectural environment and energy, studies of various purposes were conducted such as indoor environment, building energy, renewable energy and green building. In particular, renewable energy and building energy-related researches have mainly been studied reflecting the global interest. In addition, many researches which related the domestic green building certification of school building were performed to improve the indoor environment of school.

• Journal of the Korean Society for Railway
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• v.17 no.3
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• pp.193-200
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• 2014

In this study, fatigue tests on existing continuous welded rail (CWR) on a concrete track were carried out. Based on the test results, a S-N curve expressing the remaining life of the CWR at a fracture probability of 50% was obtained using weighted probit analysis suitable for small-sample fatigue data sets. As rails had different histories in terms of accumulated passing tonnage, the test data were corrected to average out the accumulated passing tonnage. The remaining service life for the CWR on the concrete track in an urban railway was estimated using the prediction equation for the bending stress of rail developed in the past to estimate rail base bending stress and taking the surface irregularities into consideration. Estimating the remaining service life of the CWR in an urban railway showed that the rail replacement period could be extended over 200MGT. In addition, comparing the concrete track to the ballast track, the fatigue life of rail was analyzed as approximately 300MGT higher than. Therefore, the rail replacement criteria needs to distinguish between the ballast track and the concrete track, and not the criteria needs to be changed as a target for the maintenance, although it is necessary to remove longitudinal rail surface irregularities at welds by grinding.

• Journal of the Korean GEO-environmental Society
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• v.16 no.2
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• pp.45-52
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• 2015

To minimize the cost of maintenance, repair and over-design of track substructure, an accurate evaluation of strength and stiffness of the track substructure is necessary. In this study, a cone penetrometer with impact penetration rod (CPI) is developed for the evaluation of track substructure. For applicability test, the chamber and field tests were performed. As the experimental results of the CPI, dynamic cone penetration endex (DCPI), cone tip resistance ($q_c$), friction resistance ($f_s$) and friction ratio (Fr) were obtained. In the chamber test, the experimental results show reasonable values for the simulated track substructure. In the field test, the CPI clearly detects the interface between the ballast and the subgrade. Also, discontinuous layers are detected in the subgrade. It is expected that the developed CPI may be an effective tool for the evaluation of track substructure by evaluating the ballast layer by dynamic penetration and the subgrade by static penetration of the inner rod.