Minnesota Bridge Disaster a Warning for Widespread Bridge Infrastructure Problems

August 2, 2007

Yesterday’s highway bridge collapse in Minneapolis is a sign of America's widespread problem with its aging infrastructure, says Brent Phares, PhD, Chief Engineer of Material Technologies Inc., a developer of technology to monitor and measure metal fatigue.

Phares says it is too early to tell exactly what caused Minnesota DOT Bridge 9340, which carries Interstate 35 West over the Mississippi River just east of downtown Minneapolis, to collapse suddenly during rush hour. But he says the bridge was 40 years old and was built at a time when vehicular traffic and weights were much less than they are today and at a time when bridge steels and redundancy where not at today’s standards. At the time of the collapse, trucks, buses and passenger vehicles were bumper-to-bumper on the bridge. The bridge also had fatigue-susceptible details which were difficult to inspect.

"Our first thoughts after this horrific event must go toward the injured, the families of the victims and the heroic people who have worked to save lives at the disaster scene and at hospitals," Phares says. "As authorities analyze the collapse and determine its cause, however, they will have to come to terms with the fact that bridge failures are not isolated, rare events, and that the risk of new tragedies from unseen metal fatigue inevitably grows as steel bridges age. There is a growing, urgent needto inspect bridges with the most advanced technology in order to prevent more tragedies like today’s collapse."

Phares notes the following facts about bridges in the U.S.:

Visual inspection is the primary method of checking bridges for possible metal fatigue and potential catastrophic failure.
One study by the Federal Highway Administration (FHWA) found that over 90 percent of fatigue cracks were missed with visual inspection.
According to federal data, 39 percent of the bridges in the U.S. are structurally deficient or functionally obsolete
Federal law mandates that bridges longer than 20 feet be inspected every other year, but it does not require any particular method of inspection.

SAFETEA-LU, the federal transportation bill currently in effect, mandated that the FHWA carry out a program to identify technologies that detect growing fatigue cracks in bridges. Material Technologies’ EFS is part of that program and has been used in Pennsylvania, New Jersey, Massachusetts and Utah. Overseas, bridge owners in Australia, the United Kingdom and elsewhere have shown interest in deployment of the EFS in the near future.

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