• Structural Engineering and Mechanics
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• v.75 no.4
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• pp.435-444
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• 2020

Ultrasonic guided wave testing is a very promising non-destructive testing method for rails, which is of great significance for ensuring the safe operation of railways. On the basis of the semi-analytical finite element (SAFE) method, a analytical model of 59R2 grooved rail was proposed, which is commonly used in the ballastless track of modern tram. The dispersion curves of ultrasonic guided waves in free rail and supported rail were obtained. Sensitivity analysis was then undertaken to evaluate the effect of rail elastic modulus on the phase velocity and group velocity dispersion curves of ultrasonic guided waves. The optimal guided wave mode, optimal excitation point and excitation direction suitable for detecting rail integrity were identified by analyzing the frequency, number of modes, and mode shapes. A sinusoidal signal modulated by a Hanning window with a center frequency of 25 kHz was used as the excitation source, and the propagation characteristics of high-frequency ultrasonic guided waves in the rail were obtained. The results show that the rail pad has a relatively little influence on the dispersion curves of ultrasonic guided waves in the high frequency band, and has a relatively large influence on the dispersion curves of ultrasonic guided waves in the low frequency band below 4 kHz. The rail elastic modulus has significant influence on the phase velocity in the high frequency band, while the group velocity is greatly affected by the rail elastic modulus in the low frequency band.

• Journal of the Korean Regional Science Association
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• v.35 no.4
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• pp.19-32
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• 2019

Since the 2000s, China has been trying to develop the mid- and western regions and reduce regional disparity between the eastern region and the others by construction of the eight HSR corridors known as 4+4. The high-speed railway is known to have a positive impact on regional economic development by improving accessibility between regions. However, some studies point out that the high-speed railways could worsen regional imbalances. The purpose of this study is to examine the impact of the high-speed railway on regional economic growth and balanced development in China, using the beta-convergence model. In particular, we focused on how the effects of high-speed trains on regional economic development varied depending on the level of development. The analysis was conducted centering on the Shanghai-Chengdu line which is connecting eastern, central and western regions with different levels of development.

• Journal of Satellite, Information and Communications
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• v.10 no.3
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• pp.68-72
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• 2015

The railway system has been recognized as one of the best eco-friendly advanced transportation systems. Furthermore, the improvement of the passenger transportation quality and the energy saving have been studied for being the most competitive transportation system. However, most of the studies have been mainly focused on the improvement of the transportation efficiency and energy saving because of the characteristics of the urban railway which serves the unspecified multiple passengers. In this paper, the 3-dimensional vibratory lateral acceleration has been measured in various environments for the automatic and manual operation modes of the general train and express train in the urban railway lines. In terms of the improvement of the passenger transportation quality, the comparison analysis of the ride quality is carried out based on the measured 3-dimensional vibratory lateral acceleration and the statistical techniques of UIC513R suggested by the International Union of Railways.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.609-617
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• 2017

Railways are one of the safest and most important transportation systems in the world. On the other hand, due to the increasing complexity of the railway system and the running distance of rail vehicles, railway accidents occur continuously every year. In particular, in the case of high-speed trains and freight trains, if the function of the axle bearing is lost due to abnormal overheating of the axle box bearing, the load on the axle becomes uneven. Therefore, abnormal overheating in the train axle box bearings can cause serious accidents or derailments. For this purpose, a Hot Box Detector (HBD) was installed in the track side of a high speed line to detect abnormal overheating. This paper proposes an EWMA technique-based axle temperature monitoring method to detect abnormal overheating quickly and efficiently. A statistical design of the proposed method was also performed. The proposed method has better performance compared to the current method in the case of abnormal overheating and the performance is improved by approximately 170% at the maximum.

• Journal of the Korean Society for Railway
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• v.17 no.1
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• pp.70-78
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• 2014

Recently, the Korean government is considering a policy of adopting competition in railway transportation, such as the establishment of a subsidiary company to Korail as a company to operate a part of the KTX line, the separation of deficit-running lines of local railways and the opening of railway transportation to private operators. The termination of local railway service, which is a major provider of public transportation, will not only deprive the public of a means of transportation but also lead to a decline in the quality of public transit in general. The termination of local railway service is being decisively affected by the national railway policy. The purpose of this thesis is to clarify local railway policy in Japan by studying the development and philosophy of the local railway policy of the Japanese National Railway (JNR).

• Journal of the Korean Society for Railway
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• v.17 no.1
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• pp.43-51
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• 2014

In the earth structures of railways, large coarse granular materials are widely used as fill materials. However, experimental studies that consider the dynamic properties of these coarse granular materials have rarely been carried out in Korea due to the lack of a large scale test apparatus in this country. In this study, large scale cyclic triaxial tests were carried out for materials such as reinforced roadbed (subballast, graded crushed stone), transition zone gravel, and the upper subgrade of a railway. These specimens were prepared according to certain conditions (dry unit weight, grain size distribution, and so on) specified in the Korea railroad design standard. Based on these large triaxial test results, normalized shear modulus and damping ratio curves according to small strain level are suggested. A model and coefficients for each material are also proposed.

• Journal of the Korean Society for Railway
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• v.10 no.6
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• pp.766-771
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• 2007

In this research, we were going to make the function which can forecast the operating cost of metropolitan railroad that is performing a role of assistant highway within the city. In order to do this, based on service records of subway line 1st to 8th in Seoul, we extracted 23 variables which can affect to the operating cost, and we selected the final variable for estimate the function of operating cost from correlation among variables and influence analysis. Then, we performed regression analysis by stages using final variable. 6 independent variables are chosen for presuming the operating cost, and we obtained the final 3 variables (quantity of holding motor cars, peak quantity of possessed motor cars, and quantity of stations) as a result of regression analysis. Through this research, function of operating cost of metropolitan railroad has better applicability than existing preliminary validity, and it is used by further preliminary validity investigation and master plan or validity investigation which is accompanied by operation designing, thus we expect that it could make a great contribution to the priority order of investment for metropolitan railroad or process of policy decision.

• Journal of the Korean Society for Railway
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• v.16 no.1
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• pp.52-58
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• 2013

This study discusses how transportation to connect railway stations in Korea's small and medium-sized cities can be improved, based on analysis of a survey on the Joongang Line. The analysis considered current problems in connectivity between parts of the Korean transportation system and suggests how to encourage more passengers to shift from private cars to railways. It was found that railway users in small and medium-sized cities hope for better connection between different modes of public transportation, especially for urban buses. However, there is not enough connectivity currently available; therefore it is crucial to establish a system of such connections, mainly focusing on urban buses. Furthermore, in order to minimize transfer distances and connect various transfer modes, plans for improvements of facilities are needed and governmental support should be provided.

• Wind and Structures
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• v.20 no.2
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• pp.213-236
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• 2015

For high-speed railways (HSR) in wind prone regions, wind barriers are often installed on bridges to ensure the running safety of trains. This paper analyzes the effect of wind barriers on the running safety of a high-speed train to cross winds when it passes on a bridge. Two simply-supported (S-S) PC bridges in China, one with 32 m box beams and the other with 16 m trough beams, are selected to perform the dynamic analyses. The bridges are modeled by 3-D finite elements and each vehicle in a train by a multi-rigid-body system connected with suspension springs and dashpots. The wind excitations on the train vehicles and the bridges are numerically simulated, using the static tri-component coefficients obtained from a wind tunnel test, taking into account the effects of wind barriers, train speed and the spatial correlation with wind forces on the deck. The whole histories of a train passing over the two bridges under strong cross winds are simulated and compared, considering variations of wind velocities, train speeds and without or with wind barriers. The threshold curves of wind velocity for train running safety on the two bridges are compared, from which the windbreak effect of the wind barrier are evaluated, based on which a beam structure with better performance is recommended.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.25 no.5
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• pp.352-360
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• 2015

Squeal noise is a harsh, high-pitched sound that occurs when railways are running at sharp curve tracks. The cause of squeal noise is known to be the transient lateral traction force between wheel and rail. Field measurements are too difficult to control the parameters. Thus, the scaled test rig should have been made in order to investigate the generating mechanism of squeal noise. The unique feature of our test rig, HSTR(Hongik Squeal Testing Rig), is that DOFs of its wheelset are as close to as those of the real railway. The attack angle and running speed of the rail roller are controlled in real time for simulating a transient characteristic of driving curve. The environment conditions, such as given axle load, running speed, and wheel's yaw angle have been identified for generating squeal noise and the squeal noise itself has been measured. The relation between wheel creepage and creep force in lateral direction and the criteria for squeal noise have been investigated, which results has been verified by finite element method.