• Structural Engineering and Mechanics
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• v.77 no.2
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• pp.231-243
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• 2021

In this paper, a dynamic response mapping model of the wheel-rail system is established by using the support vector regression (SVR) method, and the hierarchical safety thresholds of the subgrade void are proposed based on the reliability theory. Firstly, the vehicle-track coupling dynamic model considering the subgrade void is constructed. Secondly, the subgrade void area, the subgrade compaction index K30 and the fastener stiffness are selected as random variables, and the mapping model between these three random parameters and the dynamic response of the wheel-rail system is built by using the orthogonal test and the SVR. The sensitivity analysis is carried out by the range analysis method. Finally, the hierarchical safety thresholds for the subgrade void are proposed. The results show that the subgrade void has the most significant influence on the carbody vertical acceleration, the rail vertical displacement, the vertical displacement and the slab tensile stress. From the range analysis, the subgrade void area has the largest effect on the dynamic response of the wheel-rail system, followed by the fastener stiffness and the subgrade compaction index K30. The recommended safety thresholds for the subgrade void of level I, II and III are 4.01㎡, 6.81㎡ and 9.79㎡, respectively.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.412-417
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• 2007

The energy efficiency and environment-friendly aspect of the railway system would be superior to other on-land transportation systems. In a preliminary feasibility study stage, the energy efficiency and problems related with environment are usually not considered. Selection of optimal railway line is taken into consideration include of the purpose of railway, geographical features and facility of management. The railway Alignment which could be reasons of environmental problems are focused and studied in this paper. This study performed opinions of specialists, checking of industrial environment, analysis of bid guideline to select the optimal line and executed AHP method to make quality model and choose weight factors. The investment for railway systems could be encouraged by the considering of main environmental elements evaluated with the modified noise and vibration standard for environment-friendly railway construction.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.93-99
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• 2008

The SeoulMerto, operating subway line No.$1{\sim}4$, was constructed in the metropolitan Seoul with the highest population. When it was built, the design was challenged to sharp curved tracks considering the protection of buildings, cultural assets, the connection to ground roads and rivers as well as to elevated railway in some parts. Lots of residential apartments and business complex have gradually increased in the area around subway stations and railway lines according to the urban development. Consequently, Requirements of better quality of life and comfortable environment caused the citizen complain for the noise. It has become one of serious social issues. In this paper, Noise level was analyzed using noise map measured in the running train of all routes. The analysis on the noise level was conducted according to railway type, track components type, seasonal type, retirement degree of the vehicle and subway station. Especially, Noise characteristics were analyzed by noise level data measured in the inside and outside of the train with geometry types of the concrete track. This study will contribute fundamental data for the "The Development of Sound-Absorbing Block on Concrete Track" promoted on The National R&D Project.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.357.1-357
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• 2002

The purpose of this study is to propose indoor noise level in residential buildings affected by transportation noise (road traffic, railway and air-craft noise) based on subjective evaluations. 30 subjects participated in the experiment to evaluate the noise. Experimental environment reproduced real living and office environment, and in asking subjects' annoyance to the noise. (omitted)

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1465-1468
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• 2006

Railway is superior to the other land transportation systems in aspects of environmental problems. Environmental problems are not considered during a preliminary feasibility study. Investment for railway is low because of low B/C(benefit/cost)ratio in the economical efficiency analysis during the preliminary feasibility study. The body of this paper studies the railway noise which can reflect environmental problems an assessment of environmental impact. The body of this paper studies the presumption of The Benefit Cost of railroad noise arresting it will be able to reflect the evaluation environmental matter of the effect which it gives to an environment.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2860-2865
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• 2011

Recently, the number of passengers using urban railway has been increased by reasons of the reductions of car use due to high fuel prices and the enlightenment about the environment. Above all, the noise and the vibration coming from the friction between the wheel and the rail of trains in operation which is not only a factor that hinders riding comforts but causes civil complaints. Furthermore, the noise has become social issues from tightening the relevant regulations by the government since January 2010. Although ballasted tracks were constructed on urban railways at the time of opening, they have been changed into slab tracks because slab tracks require much less maintenance. However, in view of sound absorptivity of track, slab tracks have 10 times less capability than ballasted tracks(ballasted track : 0.5~0.6/slab tracks : 0.06) results more noise than that of ballasted tracks as much as 3dB(A) since slab tracks emit more reflection noise. Therefore, in order to minimize reflection noise on slab tracks, noise abatement system has been developed as a national R&D program to apply on-site test. It is assumed that the construction technology developed in this study can be used not only as basic data for the on-site test for the noise reduction in urban railway but as an efficient construction method.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.1342-1351
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• 2011

Nowadays rolling stock has become a fast and convenient transportation and increased in its demands. But the improvement of speed has result in increase of aerodynamic noise and therefore residential districts near by the railroad are now constantly suffering from the racket. Thus the study regarding rolling stock's environmental noise measurement and appraisal has become important. The case of environmental noise, there are no changes of tone so prediction can be made by reducing areas around the railway. This is part of the study which estimates the noise around the railway using scaled model, and the source of the noise has been researched on. The scaled model of rolling stock will have to be able to make high frequency and it needs to be spread out in a short amount of time. When popping a balloon or firing a gun fits its condition and this study analyzed the characteristics of these two different noises. Measurement was held on a wide vacant lot and the reflection effect of the ground is additionally examined. It is judged to be used in the future when predicting the environmental noise of railway vehicles.

• 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.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.324-329
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• 2010

The surroundings around subway are becoming more lively for project of CBD (an redevelopment project), however vibrations which are made through passing train cold spread buildings around. The structure-borne noise could be generated at the same time that makes people including developers and th citizens have negative viewpoint on railway. Especially, Seoul Metro 1-4 lines ar built alongside the road nearby houses and business district. That could make plenty of public resentments because of the structure-borne noise. Seoul Metro should make active alternative plans for their future urban environment projects which will be conducted. The case was Railway Facility which were conducted to minimize structure-borne noise from sharp curved track section (4 line, Sinyongsan~Ichon, R 250m). The section is adjacent to house district as near as 6.6m related with pusing international city project, the 4th urban environment project around international building, near Yongsan station. The interval of sleepers would be downsized in half with breaking existing case, and pad stiffness is reduced 4 ton from 10 ton. That makes structure-borne noise minimized because of vibrations are lowered about 19.1-23.0db. The structure above has remained for a year and a half from October, 2008, and had not any trouble to perform excellence with 80million ton rail accumulated tonnage.

• Structural Engineering and Mechanics
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• v.75 no.4
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• pp.507-518
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• 2020

With the rapid development of rail transit, rail transit noise needs to be paid more and more attention. In order to accurately and effectively analyze the characteristics of low-frequency noise, a prediction model of vibration of box girder was established based on the hybrid FE-SEA method. When the train speed is 140 km/h, 200 km/h and 250 km/h, the vibration and noise of the box girder induced by the vertical wheel-rail interaction in the frequency range of 20-500 Hz are analyzed. Detailed analysis of the energy level, sound pressure contribution, modal analysis and vibration loss power of each slab at the operating speed of 140 km /h. The results show that: (1) When the train runs at a speed of 140km/h, the roof contributes more to the sound pressure at the far sound field point. Analyzing the frequency range from 20 to 500 Hz: The top plate plays a very important role in controlling sound pressure, contributing up to 70% of the sound pressure at peak frequencies. (2) When the train is traveling at various speeds, the maximum amplitude of structural vibration and noise generated by the viaduct occurs at 50 Hz. The vibration acceleration of the box beam at the far field point and near field point is mainly concentrated in the frequency range of 31.5-100 Hz, which is consistent with the dominant frequency band of wheel-rail force. Therefore, the main frequency of reducing the vibration and noise of the box beam is 31.5-100 Hz. (3) The vibration energy level and sound pressure level of the box bridge at different speeds are basically the same. The laws of vibration energy and sound pressure follow the rules below: web