Lawrence Reaveley, a professor in the University of Utah's department of civil and environmental engineering, said Thursday that he and a colleague reviewed video of the Minneapolis accident. He said the 1,900-foot-long steel truss bridge is of a design where any one "weak link" in the structure could cause it to fail.

Most Utah bridges are built so that multiple beams or structural systems can carry a load if something fails. These are known as "redundant" structures, whereas the Minneapolis bridge was a "non-redundant" structure.

Non-redundant structures are "kind of like that chain that only requires one link to break and the load to fall," Reaveley said. "We call that a lack or redundancy, and a desirable property for the building of a bridge is to have some redundancy in its structural makeup to give the road a bit of an alternative path."

Reaveley, who has studied structures and roads damaged by earthquakes and other events, said the nation is lucky that more bridges don't collapse, given the age of our transportation systems.

The average age of most Utah bridges is about 35 to 40 years old. The average age for the nation's bridges is 42 years, according to the Associated Press.

The Minneapolis bridge was 40 years old.

Reaveley said more money should be spent to maintain and rebuild the nation's bridges, but he believes UDOT is vigilant in tracking structures for safety.

"Not to be screaming wolf, but I think what this should tell us is that we need to continue to support the cities, counties and state folks who have responsibility to make sure our public facilities are maintained," he said. "If they don't, something could happen."

Eixenberger wouldn't predict how much money it would cost to fix Utah's structurally deficient bridges. This year, the agency received roughly $45 million for bridge repairs, and it costs about $150 a square foot to replace a bridge, he said.

A few Utah bridges with low rankings in terms of safety are in Salt Lake County along the stretch of I-80 from State Street to Highland Drive. During the past two years, chunks of concrete reportedly fell from some bridges. In one case, the fallen concrete left a hole through the entire bridge deck.

Beck Street, which brings I-215 over I-15 in Davis County, is another bridge that ranks low for safety. The Beck Street bridge, in addition to I-80 from State Street to Highland Drive, is slated for reconstruction in the coming years.

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Contributing: New York Times

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E-mail: nwarburton@desnews.com