By this summer, motor-ists passing through Las Cruces on Interstate 10 should be driving over University Avenue on a newly installed bridge. While this bridge may look like any other highway bridge, it isn’t.

It is among the first interstate highway bridges in the nation to be fitted with “smart bridge” technology – a technology that will allow engineers to continually monitor the safety of the bridge using fiber-optic sensors within its structure. The monitoring system will show the performance of the bridge under load, and any damage or deterioration that may occur over time.

“Traditionally, bridge inspections have relied primarily on a visual inspection of the exterior of the bridge,” says Rola Idriss, a professor of civil engineering who is leading NMSU’s “smart bridge” research. “This monitoring system can provide information on the effects of stress long before signs of fatigue begin to show visibly, allowing engineers to address potential problems before they become serious and costly.”

NMSU researchers used this technology to develop the world’s first “smart bridge” in 2000. This smaller bridge was installed over the Rio Puerco west of Albuquerque. It was monitored for a year following construction, and the technology proved to be a success.

Depending on the research results of the I-10 bridge over University Avenue, Idriss says that “smart bridge” technology might become standard in the construction of bridges in the future.

Long history of bridge research

“Smart bridge” technology is just one of many areas of bridge research being conducted at NMSU.

For more than 25 years, students, faculty and staff at the College of Engineering have worked to solve technical problems with bridge systems through the college’s Bridge Research Program.

Ken White, department head of civil and geological engineering, says the college is involved in three areas of bridge research – bridge inspection, bridge testing and monitoring, and bridge security.

The different projects have received close to $2 million in funding from the Federal Highway Administration, the New Mexico Department of Transportation and federal initiatives.

“By federal law each state has to inspect every bridge at least once every two years,” White says. “We are the only university in the nation that does hands-on field inspections, and we do this through a contractual relationship with the New Mexico Department of Transportation.” NMSU faculty members provide training to students and practicing engineers who conduct the inspections.

NMSU also provides bridge inspection training courses twice a year for federal, state and local government agencies around the country.

Enhancing bridge inspection capabilities

In addition to the installation of “smart bridge” technology, NMSU researchers are testing several other new techniques to enhance bridge inspection capabilities. One is a multi-media technology known as quick-time virtual reality and the other is close-range photogrammetry software, a technique for measuring how much bridges move up and down under the weight of traffic.

With quick-time virtual reality, researchers use computers equipped with panoramic and movie-creation programs to document the physical condition of bridges. These programs allow bridge inspectors to take a large number of photographs at the inspection site, then combine them to create a panoramic presentation. The presentation can be supplemented with text, maps, design drawings, oral descriptions and Internet links.

In about a year, NMSU-trained inspectors will begin incorporating quick-time virtual reality technology when they do inspections for the New Mexico Department of Transportation.

Close-range photogrammetry is a method for obtaining three-dimensional measurements from photographs taken from as close as four inches to as far away as 330 feet.

“Right now we are working towards merging the two techniques so they work together,” says David Jáuregui, an assistant professor of civil and geological engineering.

Jáuregui and White have published several articles on virtual reality and photogrammetry in leading civil engineering journals such as the Journal of Bridge Engineering, the Journal of Infrastructure Systems and the Transportation Research Record. They were recently asked to contribute a chapter on virtual reality and photogrammetry in the textbook “Inspection and Monitoring Techniques for Bridges and Highways” that will be published later this year.

Other bridge testing and monitoring research includes non-linear ultrasonics, which provides early detection of microscopic cracks, and new concrete mix designs that will help control cracking in concrete bridges.

Securing bridges

Most recently, NMSU has become involved in bridge security.

“Nationally, bridges have been identified as the most vulnerable asset in our transportation system,” White says. “If a terrorist wants to cause havoc in our highway or rail system, bridges are what they are going to concentrate on because they are easier to destroy, and if you destroy them they can be closed down for long periods of time.”

White says bridge security can be enhanced by limiting access to critical parts of a bridge, applying closed-circuit security video techniques, creating stand-off distances to keep terrorists away from critical points of a bridge, and hardening the structures by putting on steel jackets or other devices to protect them from explosions.

New Mexico will be the lead state in developing a prototype system for bridge security and NMSU will be a partner in this program, White says.

In the future, White hopes NMSU’s Bridge Research Program and the Oklahoma Transportation Institute (which is comprised of the University of Oklahoma and Oklahoma State University) will be designated by Congress as the Southwest Bridge Research Center. This designation would give NMSU and New Mexico a greater national and international reputation in bridge research, and provide long-term funding that will lead to collaborative research projects with other institutions and agencies.

For more information: Ken White - krwhite@nmsu.edu