The bridge of the future is coming soon to the St. Louis area, but first it will be tested at the University of Missouri at Rolla. The high-tech bridge will have no concrete or steel - just so-called composite materials of glass and carbon fibers. These lightweight, stronger-than steel materials are used in the aerospace industry, including in advanced fighter jets.

Researchers liken the coming change in bridge technology to the shift from the typewriter to the computer word processor. "This technology has lots of benefits," said Steve E. Watkins, an electrical engineering professor at Rolla who leads the project. "It's not a complete replacement, but it will be a major tool, particularly in areas that have corrosion problems."

A prototype of the bridge will be built this spring as a footbridge on the Rolla campus, Watkins said in an interview last week. If that succeeds, engineers propose to build two similar bridges to carry vehicular traffic over culverts in Wellston.

The two new Wellston bridges would replace bridges on Etzel and Plymouth avenues over Engelholm Creek.

These and other "full-composite" bridges cost more to build than a traditional bridge. But they cost less over their lifespan than traditional bridges, Watkins and other experts said.

That's partly because corrosion from water and salt spread on roads in winter gradually eats away at the steel and concrete in many area bridges. The estimated life of a composite bridge is about 75 years, while that of a traditional bridge is about 50 years.

Because composite materials are light, much of the bridge can be constructed off-site. That could lead to further savings over a traditional bridge.

"It's modular," said John Unser, an engineer and president of Composite Products Inc. of St. Louis, a partner on the project. "You have your railings in place, your road surface in place, and so on. Then you just drop it in, and you're done. You won't disturb traffic as much."

Switching to composite materials " is a nationwide trend in the transportation industry, especially in bridges," said Ray Purvis, an engineer with the Missouri Department of Transportation, in Jefferson City. Purvis works in the agency's Division of Research, Development and Technology.

"We're monitoring how it performs before we take it to the next level," Purvis said. "The aerospace industry has long used this material in spacecraft and aircraft. It's lightweight and long-lasting. We're looking to see where can we take advantage of similar benefits.

"If researchers don't find problems, "We'll be using these products quite extensively in the future," Purvis said.

A few bridges in the region have some parts made of composite materials. But the Wellston bridges would be the first to be constructed all from the materials.

The Rolla and Wellston bridges are simple compared with the long bridges across the Mississippi River.

The new bridges are short, shaped like a box and don't have structural components that extend above the road's surface. They are constructed by assembling tubes made from composite materials.

The tubes come in different lengths and are arranged in a way that best fits the site and the requirements for carrying certain loads. That's the term engineers use to describe the weight of trucks, cars, people and other objects crossing the bridge.

Partners on the project with UM-Rolla and Composite Products include the Lemay Center for Composites Technology, the state Transportation Department and the Navy.

The Rolla research is supported by $400,000 from the National Science Foundation and $149,000 from the university.

A team of researchers at Rolla has been testing the bridge components and ironing out design issues. They include Watkins and professors Abdeldjelil Belarbi, Antonio Nanni, K. Chandrashekhara and Richard Hall.

Construction of the footbridge over a campus creek will begin in March as part of a student project, Watkins said. The bridge should be completed, with the sidewalks leading up to it, by the end of April.

The Rolla bridge will be about 30 feet long and 14 feet wide at its widest point. The Wellston bridges, over Engelholm Creek, will be about 24 feet long and 55 feet wide - enough for two lanes of traffic.

Cost of the Wellston bridges won't be known until after the Rolla bridge is tested. A traditional bridge for one of the Wellston sites cost about $130,000.

Sensors embedded in the tubes at key stress points can tell engineers how the structure is performing and whether weak spots are developing - even deep inside the bridge where such information hasn't been available before. Some of the sensors use electric impulses, while others detect changes using light signals.

The bridge can be any color, Watkins said. Its deck can be covered with any surface now put on bridges, including asphalt.

Building a better bridge

Bridges may soon be built with lightweight composite "building blocks" that can be cheaply mass-produced and used to create virtually any kind of structure.

The new method of building, which also uses computer-generated models to predict how various forces will affect the structure, was developed by researchers at the University of Missouri at Rolla.

With these computer models, engineers can not only design their bridges with greater precision but can also tailor the strength of the bridge to fit its use. A prototype footbridge on the Rolla campus aims to demonstrate the unique capabilities of these new materials.

Reprinted with permission from St. Louis Post-Dispatch.
copyright 1999 St. Louis Post-Dispatch

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