• Proceeding of Spring/Autumn Annual Conference of KHA
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• 2008.04a
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• pp.291-296
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• 2008

This paper reports on the results of a questionnaire survey on actual conditions of sleep environment, sleep problems and sleep patterns in bedroom of house. The objectives of survey are: 1) classifying Korean people into several groups by sleep environment condition, sleep problem and life pattern, 2) describing the characteristics of user groups, and 3) searching needs of support for each user group. Despite of several studies about sleep condition that researched in advance, they weren't considered about user's respective characters. So it seems necessary for more studies about users' needs, and segment users to grasp their each detail needs. Therefore, this study conducted questionnaire survey gathering relevant information to classify user groups and to investigate the current bedroom condition. In the result, 702 respondents were divided into six clusters by extracted eight factors. Four clusters of them had some problems for sleep, so it could be seen that they need environmental solution for their good sleep. As the further objective, it will be connected to develop the good sleep system.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.1359-1370
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• 2008

In the track geometry such as rails, sleepers, ballasts and fastener, track deterioration occurs by repetitive train weight and the high-speed railway takes a trend faster than normal. Track deterioration of over threshold value harms ride comfort and furthermore affect in trains safety seriously. An organic and systematic track maintenance system is very important because a trend of the track deterioration effects on track life-cycle and running safety. Also costs of the railway track permanent way and its maintenance are extremely large, forming a significant part of the total infrastructure expenditure. Therefor reasonable and efficient track maintenance has to be planed on a budget. It is required to carry out not only corrective maintenance but preventive maintenance for the track maintenance. In order to perform maintenance jobs in the boundary of the machines and resources given regarding the type and amount jobs, it is necessary to determine feasible or optimal scheduling considering the priority. In this study, the system organization and required functions for the development of track maintenance system supported track deterioration prediction and optimal scheduling are proposed.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.195-196
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• 2014

Unlike general construction works, bridge construction is mostly done in a high place. The conventional deck form of bridge is installed between precast concrete girders using sleepers, bridging joints and plywoods, and after concrete is poured to the deck, the form materials are removed at high altitudes. When removing the form, it may be dropped on ground, damaging the materials and resulting in economic loss. In addition, safety accidents are likely as the works are performed in a high place, and as the manpower increases, the cost increases. Also, it is difficult to install and remove temporary equipment. Therefore, it is required to develop a system form that allows easier and quicker installation and removal by unskilled workers and ensures safety of workers. In this regard, the study is intended to analyze requirements for the system form for pouring concrete to bridge decks, which can be easily installed and removed. The study result will be used as basic information for development of the system form for pouring concrete to bridge decks.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.6
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• pp.4185-4191
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• 2015

The demand for improved rail transportation safety is growing due to the increased speeds of current railways. In addition, freight trains with heavier axle loads are required to run on conventional railways. In order to meet these requirements, increased rail weights and the application of a CWR system have been introduced on conventional railways. The H type sleeper, which has higher lateral resistance than the existing mono sleepers, has been recently developed to increase track stiffness and reduce track irregularities. In this paper, the effects of a H-type sleeper on track behavior were investigated by 3-Dimensional F.E. analysis.

• Journal of the Korean Society for Railway
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• v.10 no.5
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• pp.463-472
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• 2007

In this paper, the correlation between the vibration characteristics of the track components and the parameters affecting the vibration is analysed. To do it, the accelerations of each track component such as rails, sleepers and ballast are measured in Kyong-Bu high-speed line. The RMS values of the measured data are calculated and the pad stiffness, the longitudinal irregularity, running velocity and the corrugation, are considered as the parameters in the viewpoint of track. By using the linear regression, the correlation coefficient is calculated to analyse the relationship. Also, the 1/3 Octave analysis is calculated to analyse the dominant frequency band of tile vibrations of the track components.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.1454-1462
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• 2008

This paper is focused on the analysis of the noise and vibration measured near the wheelset of the high-speed trains using a time-varying frequency transform as a preliminary research of running monitoring. Due to the non-stationary characteristics, it is necessary to examine noise and vibration of the train with time-varying frequency transforms. In this paper, the short-time Fourier transform method is utilized - the stored data is localized by modulating with a window function, and Fourier transform is taken to each localized data. For the examination, the non-stationary noise and vibration of the high-speed train's wheelset are measured by using some microphones and accelerometers, and those signals are stored in a on-board data acquisition system. The non-stationary random signal analyses with the short-time Fourier transform are performed, and the result are classified as follows; auto-spectral density, cross-spectral density, frequency response, and coherence functions. From those functions, it is possible to observe the frequency characteristics of sleepers, switchers, tunnels, and steel bridges. Also, some distinct peaks, which are not dependent upon the train's speed, are identified from the results.

• International Journal of Railway
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• v.7 no.3
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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.

• Structural Monitoring and Maintenance
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• v.9 no.1
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• pp.1-27
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• 2022

Extensive laboratory tests were conducted to investigate the effect of load amplitude, geogrid position, and number of geogrid layers, thickness of ballast layer and clay stiffness on behavior of reinforced ballast layer and induced strains in geogrid. A half full-scale railway was constructed for carrying out the tests, the model consists of two rails 800 mm in length with three wooden sleepers (900 mm × 10 mm × 10 mm). The ballast was overlying 500 mm thickness clay in two states, soft and stiff state. Laboratory tests were conducted to investigate the response of the ballast and the clay layers where the ballast was reinforced by a geogrid. Settlement in ballast and clay, soil pressure and pore water pressure induced in the clay were measured in reinforced and unreinforced ballast cases. It was concluded that the effect of frequency on the settlement ratio is almost constant after 500 cycles. This is due to that the total settlement after 500 cycles, almost reached its peak value, which means that the ballast particles become very close to each other, so the frequency is less effective for high contact particles forces. The average maximum vertical stress and pore water pressure increased with frequency.

• Journal of the Korean Society for Railway
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• v.19 no.6
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• pp.744-754
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• 2016

Asphalt concrete track (ACT) is a track system connecting wide sleepers and concrete panels on top of an asphalt concrete layer; such a system requires adequate resistance force against various longitudinal and lateral external loads. In this study, a series of experiments were carried out to assess the longitudinal and lateral resistance force of a wide sleeper and concrete panel type ACT. The required shear resistance force of the horizontal displacement restraint device (HDRD) was evaluated. Furthermore, a concrete block type anchor and a steel pipe type anchor were developed as HDRDs. The shear resistance force was decided based on the experimental results of horizontal shear tests for each anchor system. In addition, proper numbers and arrangement design guidelines for the HDRDs were suggested considering the shear resisting capacity and economics for HDRDs applied to ACT.

• The Journal of the Convergence on Culture Technology
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• v.4 no.3
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• pp.213-220
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• 2018

The objective of this study was to estimate the optimum spacing of rail joint for a personal rapid transit(PRT) track system, and to compare the results with the normal rail and rail joint by performing the finite element analysis(FEA) and field measurements using actual vehicles. Based on the FEA and field measurement results compared, the optimum spacing of the rail joints was calculated to be maximum of 1.20m based on the rail displacement. The vertical displacement of the normal rail was higher than that of the rail joint at a spacing of 1.0m, but it was considered that the vehicle riding performance and serviceability of track would be improved in terms of the stability of the train due to similar to rail defection between normal rail and rail joint. Also, because of the proposed rail joint spacing in this study was longer than the current rail joint spacing, the economic effect would be expected by decreasing the amount of sleepers.