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

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:

More articles from Studies and Analyses:

nachricht Diagnoses: When Are Several Opinions Better Than One?
19.07.2016 | Max-Planck-Institut für Bildungsforschung

nachricht High in calories and low in nutrients when adolescents share pictures of food online
07.04.2016 | University of Gothenburg

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: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

Im Focus: New Products - Highlights of COMPAMED 2016

COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.

In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...

Im Focus: Ultra-thin ferroelectric material for next-generation electronics

'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.

Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Resolving the mystery of preeclampsia

21.10.2016 | Health and Medicine

Stanford researchers create new special-purpose computer that may someday save us billions

21.10.2016 | Information Technology

From ancient fossils to future cars

21.10.2016 | Materials Sciences

More VideoLinks >>>