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K-State Today

May 24, 2011



The ties that bind: making high-speed rail tracks safer focus of research

By Julie Fosberg

High-speed rail is poised to rapidly expand across the U.S. and a trio of Kansas State University engineering professors intend to help riders arrive safely.

The professors have received more than $1.2 million from the Federal Railroad Administration and K-State Transportation Center to study prestressed concrete railroad ties. The professors are Bob Peterman, professor of civil engineering; Terry Beck, professor of mechanical and nuclear engineering; and John Wu, associate professor of industrial and manufacturing systems engineering, along with Pelle Duong, chief engineer at CXT Concrete Tie. The Federal Railroad Administration grant is for $899,270 and the additional funding is coming from CXT Concrete Ties and the K-State Transportation Center.

High-speed rail requires prestressed concrete railroad ties, as wooden cross ties are too flexible. For these ties to be effective, prestressing forces must be applied at a considerable distance before the rail load is applied. This is called the transfer length. To resist the heavy impacts the concrete ties utilize about 20 steel wires, each stressed to around 7,000 pounds. If the prestressed force is not properly transferred, failures can occur in the track.

Peterman has observed some of these crumbling ties in track.

"They cannot resist the load because they don't have all of that prestressed force applied," he said.

The project will focus on how to create an adequate bond between the steel wires and surrounding concrete. All factors will be examined, including the mixtures of concrete, wires and indents that allow for better bonding. The team will also develop a test that prestressed concrete producers can use to determine the bond capacity of specific types of wire.

The project will culminate in a trip to Tucson, Ariz., to conduct research at the CXT Concrete Ties' prestressed concrete plant. At the plant, ties with 12 different wires and three different strands that the team researches will be produced. The transfer length in those ties will then be measured. This is possible because of a device using laser-speckle imaging that was developed by the K-State research team along with Weixin Zhao, doctoral student in mechanical engineering. The laser-speckle device images the surface of the tie before and after detention and subsequently plots the strain profile.

"We can tell by the strain profile how far from the end of the tie the prestressed force is transferred with each of the different reinforcing types," Peterman said. "That's the culmination of the project."

The team will then make recommendations to the Federal Railroad Administration on the appropriate methods to ensure good-bonding reinforcing steel, the best concrete and similar considerations for creating durable prestressed concrete ties. As part of this project, a fully automated laser-speckle device will be developed to allow for determination of transfer length within five minutes after the concrete ties are de-tensioned. The project began recently and will conclude in two and half years.

The project is coming full circle based on a previous collaboration with K-State's Advanced Manufacturing Institute. Ten years ago the institute funded Peterman, Beck and Wu to determine if laser-speckle technology could be applied to the measurement of concrete surface strains. In the current project the research team will use the institute's expertise to create a fully automated laser-speckle imaging device.

"It's a neat story within K-State," Peterman said. "I'm looking forward to working with the entire team at AMI."

Despite many logistical issues with high-speed rail, Peterman is confident about its future.

"We will see higher-speed rail in this country," he said.