Minneapolis Disaster Spawning New Concepts in Bridge Research, Testing and Safety

Civil engineers at Oregon State University have developed a new system to better analyze the connections that hold major bridge members together, which may improve public safety, help address a trillion-dollar concern about aging infrastructure around the world, and save lives.

When testing is complete and the technology implemented, the system might allow a technician working for a day to produce a better analysis of a bridge’s structural condition than a more expensive and highly-trained engineer could do in weeks.

Developed at OSU, the technology is being tested this fall by a simulated laboratory failure of the exact type of truss connecting plate that caused a bridge to collapse on Interstate 35W in Minneapolis in 2007, killing 13 people and injuring 145.

The work also brings focus to a little-understood aspect of bridge safety — that most failures are caused by connections, not the girders and beams they connect, as many people had assumed. The issues involved are a concern with thousands of bridges worth trillions of dollars in many nations.

The tragic collapse of the interstate bridge across the Mississippi River in 2007 brought a lot of attention to this issue,” said Chris Higgins, a professor in the School of Civil and Construction Engineering at OSU. “For decades in bridge rating and inspections, we’ve been concentrating mostly on the members, but in fact it’s the connectors where most failures occur. And the failure of a single critical connection can bring down an entire bridge, just like it did in Minneapolis.”

This is a growing concern, Higgins said, because thousands of bridges were built around the world in the 1950s and later that may be nearing the end of their anticipated lifespan, including many of those on the interstate highway system in the United States. Maintenance, repair and replacement of this infrastructure could cost trillions of dollars, he said, at local, state and federal levels.

But prioritizing which bridges are still safe and which most urgently need repair or replacement is not easy and has never been obvious, Higgins said.

“The failure of the bridge in Minneapolis was caused by a single connecting plate that inspectors saw repeatedly,” Higgins said. “They took pictures of it, actually had to touch it, because an access ladder was right next to it when they were doing inspections.