The Opportunity of Failing Bridges

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There are obvious reasons for the U.S. to update its roads and bridges: stimulating the economy, creating middle-class jobs, improving commercial efficiency. Another equally appealing and less obvious reason for upgrading our infrastructure is the opportunity to develop the products and materials needed around the world for the next generation of bridge design.

The collapse of the bridge over the Skagit River in northwest Washington state last week was blamed on its "fracture-critical" design, meaning that when one part of the bridge fails, the rest of the structure is compromised and will probably fail as well. This is what happened in Washington when a truck with a tall load struck the top of the bridge, causing it to collapse. Two vehicles plunged into the Skagit River below, leaving three people with minor injuries.

The Interstate 35 bridge in Minneapolis, which collapsed and killed 13 people in 2007, also had a fracture-critical design. In that case, an undersized gusset plate -- a steel plate used to connect the sections within a truss -- failed, setting off a chain reaction that brought the entire bridge down.

Fracture-critical design was all the rage during the development of the U.S. highway and interstate system: Between the mid-1950s and late 1970s, about 18,000 bridges were built using such methods. The design allowed engineers to create efficient, interconnected and aesthetically pleasing shapes. But because redundancy is inherently inefficient, every piece is dependent on the others.

These bridges are not necessarily destined to fail but the nature of their design necessitates careful inspection and maintenance. At the end of last year, the Federal Highway Administration categorized 151,497 bridgesas either structurally deficient or functionally obsolete. Many of these bridges are fracture-critical. In some cases, the lack of redundancy can be addressed simply by adding additional support to existing structures. Other bridges need to be removed and rebuilt.

Where bridges must be replaced, the U.S. has an opportunity to innovate and design long-lasting, durable structures using next-generation materials and techniques. For example, incorporating advances in material engineering -- like non-coated corrosion resistant reinforcing in concrete -- could produce bridges with a lifespan of 100 years, twice that of older designs.

Furthermore, though bridge designs are not proprietary, the materials used to build them are. So once American companies develop next-generation materials and incorporate them domestically, they can export them, especially to the developing world. Nations like Brazil, Russia, India and China are all behind the U.S. in the development of their infrastructure. As these markets grow, demand for advanced materials will follow.

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Alex Bruns at