Features
Bridge to somewhere
Innovative I-35W span could influence how the U.S. views bridge replacement

By David Tanner
staff writer

 

Aug. 1 marked the second anniversary of an American transportation tragedy – the collapse of the I-35W bridge in Minneapolis during rush hour. The collapse left 13 people dead, including a truck driver, and injured 145.

In an instant, the nation’s aging and overburdened infrastructure became mainstream news as people learned that 150,000 bridges on the national system are either structurally deficient or functionally obsolete.

All of a sudden, everyone could relate.

Congress and state governments unveiled new inspection protocols and began stepping up programs to repair, rehabilitate and replace bridges, starting with the worst.

The spotlight was on Minnesota and on the federal government for promising to rebuild the I-35W in record time and in impressive fashion. By all accounts, they succeeded.

Just 11 months after winning the contract to design and build the new I-35W bridge, Figg Engineering Group cut the ribbon on a new era in technology, innovation and design life, which is sure to influence the way lawmakers at all levels think about bridges.

“When the old bridge failed and collapsed, it certainly brought a huge focus to the nation on the condition of America’s infrastructure,” Linda Figg, company president and CEO, told Land Line.

“It was important, with all eyes of the world watching, that this new bridge set an example for what can be accomplished for the future, a modern concrete bridge that would encapsulate safety, quality and innovation.”

The $234 million bridge is a partnership of the Minnesota Department of Transportation, Federal Highway Administration, Flatiron-Manson, Figg Engineering and a number of subcontractors and suppliers who used local labor and materials whenever possible.

The quick turnaround time, three months ahead of schedule, could be attributed to smooth sailing through the usual red tape, but the designer also credits the decision to fabricate the bridge segments on-site.

“We had a precasting farm that was on one side of the unused portion of the I-35W roadway,” Figg said. “We precast the elements for the main span, which was a 504-foot main span. So, 120 precast segments that weighed up to 200 tons each were installed to create that main span in 47 days.”

The bridge that eats smog
An intriguing innovation employed in the bridge construction is found in the concrete itself. Figg describes a wonder material called photo-catalytic titanium dioxide, which accelerates the decomposition of organic material. In other words, it eats pollution.

“The cement has a nanotechnology in it such that when UV light hits the surface of the concrete, it creates a photo-catalytic reaction that cleans pollution out of the air,” Figg said. “It is a pollution-eating kind of concrete and it is also self-cleaning.”

The new I-35W is the only bridge in the U.S. to employ the pollution-eating technology to date.

Concrete used on the I-35W is considered high-performance, containing silica fume and fly ash for low permeability and a longer life span.

Figg said the bridge is designed to last at least 100 years – or 100 Minnesota winters to be precise. Most bridges in the U.S. are designed to last 50 years, and the average age of U.S. bridges is currently 43 according to the U.S. Department of Transportation.

Bridge-inspection technology has come a long way in recent years, says Figg, whose father founded Figg Engineering in 1978. She joined the team in 1981 after graduating from Auburn University.

The I-35W bridge is equipped with a structural-health monitoring system and sensors to alert officials to deck corrosion. These elements are branded as “Smart Bridge” technology. The I-35W incorporates 320 sensors exemplified by wire gauges embedded in the foundation, piers and superstructure. Data from the sensors are transmitted by fiber-optic cable to the University of Minnesota for monitoring as part of a partnership with the state and the FHWA.

When the weather turns cold – and it will – the bridge will be able to handle it with temperature sensors that trigger a de-icing feature. De-icing technology protects structural integrity by suppressing the need for salt and sand.

Don’t count on the I-35W bridge being restricted to truck weight anytime soon. Figg said the bridge is rated considerably higher than current traffic levels and will meet the traffic levels of tomorrow.

“It is already designed for a rail or a mass transit to be placed on the structure in the future,” she said.

The numerous innovations, artistic appearance and a project delivery time of three months ahead of schedule earned Figg Engineering the title of finalist for the 2009 Outstanding Civil Engineering Achievement award presented by the American Society of Civil Engineers.

“One of the things noted most there is how quickly they were able to get it done,” ASCE Spokeswoman Joan Buhrman told Land Line.

Buhrman credits the various federal, state and local officials and politicians who cleared the red tape to get the project on a fast track.

“That shows that the ability is there when the support is behind it,” she said.

The American Society of Civil Engineers estimates that the U.S. must spend $930 billion to bring its structurally deficient and obsolete bridges up to snuff.

This isn’t something that will happen overnight. Congress and the states must deal with the funding aspects and clear political hurdles to solve the nation’s bridge crisis.

Technology and innovation will figure prominently in the future, according to U.S Transportation Secretary Ray LaHood.

LaHood announced in late June that $5.2 million in grants would be awarded to 14 states to implement innovative technologies for bridges. Grants may be used for on-site fabrication that accelerates turnaround times.

“Advanced bridge construction and repair techniques cut construction time and repair costs, and ultimately reduce traffic delays,” LaHood said in a statement. “These funds will be spent on improvements that ultimately offer a better experience for our nation’s drivers.”

Truckers who make their living on the highways and pay their fair share in taxes would like nothing more than to see their contributions spent wisely on projects that hold up over time.

Give highway users a say in the matter, and they may demand state-of-the-art bridges like the I-35W – delivered early, paid for without tolls, and designed to last 100 years … all while cleaning the air.

“The 100-year design life, the pollution-eating nanotechnology, the de-icing sensors … the Minnesota project certainly presents a model that the Congress, state legislators, local officials, planners and stakeholders should use to address our infrastructure needs,” said Mike Joyce, director of legislative affairs for the Owner-Operator Independent Drivers Association.

Joyce followed the compliment with a reality check, saying that replicating the new I-35W bridge around the country would be cost-prohibitive. He does say that innovations and technologies like those employed in Minnesota will influence how lawmakers and engineers view the issue.

One thing the tragedy showed is that the writing is on the wall, and America needs to address the urgent needs of its infrastructure.

“The bridge collapse was a national tragedy and embarrassment,” Joyce said. “Our infrastructure is aging and decaying. We need to pay special attention to the connectivity of our nation as it relates to moving people and goods.”

While it’s too late to bring back the lives lost in Minnesota, the new I-35W bridge is an example of what can be accomplished when people come together to respond to a crisis. LL

 

david_tanner@landlinemag.com

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