New York's Tappan Zee Bridge is among 18,000 bridges deemed fracture-critical in the U.S. and is subject to a higher level of scrutiny to ensure its safety. “These bridges have an amazing safety record to this point, but they are getting old and have to be watched,” said Andrew Herrmann, president of the ASCE. "Their fracture-critical nature means they don’t give any warning at the point of collapse. It is sudden and catastrophic," said Thomas Fisher, dean of the College of Design at the University of Minnesota.
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