Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Importance of short-wavelength excitation in environmental vibrations due to urban rail traffic

27.04.2012
Environmental vibrations induced by urban railway traffic are mainly generated from uneven wheel–rail contact in the short wavelength range, according to a study in the 4th issue of SCIENCE CHINA Technological Sciences, 2012.

The introduction of urban railways is one of the most effective ways to deal with traffic problems in large cities. However, in the vicinity of railways, day-by-day vibrations from trains may cause discomfort to people, the malfunctioning of sensitive equipment, and even damage to old buildings, and railways therefore have serious environmental problems. The development of urban railways is now limited by such environmental vibrations.

Effective vibration-reduction technologies rely on a good understanding of the excitation source that generates the vibrations. "In recent years, substantial progress has been made in modeling the train–track–ground interaction, and consensus has been reached that the excitation source is the moving of constant loads and uneven contact between wheels and rails," according to background information in the article. "Nevertheless, the contact can hardly be measured directively, so its amplitude and frequency contents are not completely understood, and its quantitative expression remains a problem for further research to address.

Recently, a research group led by Prof. Tao Xiaxin at Harbin Institute of Technology, China, has made a breakthrough in revealing the excitation mechanism. Based on an inversion study in the frequency and wave-number domain, Dr. Wang Futong, a key research member in the group, has found that high-frequency contents are predominant in the excitation. A power spectral density function (PSD) of uneven wheel–rail contact, rather than the track PSD, was suggested to describe the random characteristics of the excitation source. An inversion strategy was then established to obtain the source function from vibration data recorded by an observation array at the ground surface. The wheel–rail unevenness PSD, being the source function for the No. 13 Beijing urban railway, was obtained by the inversion strategy. The result indicated that the source function properly described the track unevenness in the range of wavelengths over 1.2 m, and showed wheel irregularities in the range of wavelengths shorter than 1.2 m.

The researchers found that, in the range of short wavelengths under 1.2 m, the wheel–rail PSD maintained a value higher than the 6th class of the track PSD suggested by the Federal Railway Administration. As urban trains do not travel particularly quickly, this short wavelength range exactly corresponds to the main frequency band of environmental vibrations; i.e., the frequency components of the vibrations stem mainly from that range of uneven excitation. Taking account of only moving constant loads and track unevenness could result in a severe underestimation of the environmental vibrations.

"Whereas the track spectrum reflects only the evenness of the track, the wheel–rail spectrum expresses both the track unevenness and the irregularities of wheels, and it is therefore more suitable to be used as the source function of urban railway traffic," the researchers write. "It is also shown that inversion of the exciting source according to observed ground vibrations is an effective way to detect quantitatively the combined wheel–rail unevenness."

The research has been supported by the National Natural Scientific Foundation of China, under contract No. 50538030.

For more information, please see the original article.

Wang Futong, Tao Xiaxin, Zheng Xin. Inversion of Excitation Source in Ground Vibration from Urban Railway Traffic. Sci China Tech Sci, 55: 950-959, doi: 10.1007/s11431-011-4665-9

WANG Futong | EurekAlert!
Further information:
http://zh.scichina.com/english/

More articles from Studies and Analyses:

nachricht Real-time feedback helps save energy and water
08.02.2017 | Otto-Friedrich-Universität Bamberg

nachricht The Great Unknown: Risk-Taking Behavior in Adolescents
19.01.2017 | Max-Planck-Institut für Bildungsforschung

All articles from Studies and Analyses >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Stingless bees have their nests protected by soldiers

24.02.2017 | Life Sciences

New risk factors for anxiety disorders

24.02.2017 | Life Sciences

MWC 2017: 5G Capital Berlin

24.02.2017 | Trade Fair News

VideoLinks
B2B-VideoLinks
More VideoLinks >>>