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How vulnerable are America's bridges? Engineers aim to find out in landmark research after Key Bridge collapse

Johns Hopkins expert discusses vulnerable bridges in America
Johns Hopkins expert discusses vulnerable bridges in America 03:20

BALTIMORE - In the wake of the Key Bridge collapse, Baltimore's worst maritime disaster, engineers and students at Johns Hopkins University quickly got to work, aiming to find out which bridges nationwide are at risk of a catastrophic collapse. 

"What are the chances that these vessels are going to go off course that they're going to potentially collide with a bridge? What is the real risk to the major bridges across the country?" asked Johns Hopkins associate professor Michael Shields, who is helping lead the investigation, fueled by a rapid response grant from the National Science Foundation.

"We have a team of seven students and three investigators who will be pouring over global shipping data that looks at the frequency of vessel traffic under American bridges, so we're specifically looking at major American ports—East Coast, West Coast, Gulf of Mexico—and looking at the major bridges, the large bridges that these huge vessels are traveling underneath," Shields told WJZ Investigator Mike Hellgren. 

The Francis Scott Key Bridge, built in 1977, passed all recent inspections including one less than a year before its collapse with a "fair" rating.

NTSB concerns 

The National Transportation Safety Board has long warned ships, many now weighing tens of thousands of tons, are getting bigger and posing greater risks to bridges across the country. 

"You have a bridge that was opened in 1977, and over time, it's not the bridge that's getting larger. It's not the waterway that's getting larger. It's the vessels that are getting larger," National Transportation Safety Board chair Jennifer Homendy told Congress earlier this month.

The Chesapeake Bay Bridge, like the Key Bridge, is considered "fracture critical." That means if one major support fails, the whole structure could fall.

And it is not alone in being vulnerable.

CBS News' Innovation Lab recently reported on whether the majority of U.S. bridges lack impact protection.

"One of the major factors that we're looking at is ship traffic of these enormous vessels. When the Key Bridge was built in the 1970s, the largest vessels weren't anywhere near what they are today, and the volume of traffic was much, much less, and so the risk to bridges at that time was much lower than it is now," Shields said. "But the real impetus for this study is we don't really have a good assessment. We don't have a good understanding of what the risk to the current bridges is, and we need to put a good assessment in place so that we can make infrastructure decisions so policymakers can put investments where they're really needed."

According to Johns Hopkins, there were 17 major bridge collapses between 1960 and 2011, averaging one every three years. 

"Our hypothesis is the probability of these events occurring is higher than it is intended to be," Shields said. "These types of events are intended to be very rare in fact the American Association of State Highway and Transportation Officials aims to have the annual probability of one in 10,000, and anecdotally, were not seeing anything close to that."

Study timeline

A preliminary report on the research should be finished by the end of this summer with the full report released by the end of the year.

The findings will help lawmakers prioritize infrastructure improvement spending.

"The team's findings will be crucial in reassessing and potentially redefining the safety standards for transportation infrastructure," said Johns Hopkins professor and structural engineer Ben Schafer. "Given the estimated $1.7 billion to $1.9 billion cost to rebuild the Key Bridge and the potential billions needed to retrofit existing bridges, accurate risk assessment is vital to ensure the sustainability of society's critical infrastructure."

New satellite images 

  satellite images credit: Maxar

New before-and-after satellite images from Maxar show the swift progress clearing the Key Bridge wreckage from the Patapsco River.

President, governor meet at White House

More than 50 days since President Biden's Baltimore visit, he met privately with Governor Moore in Washington this week. 

The White House summed it up, writing, "During the meeting, the President underscored his Administration's commitment to standing with Baltimore every step of the way in this recovery." 

The White House noted, "The meeting also focused on continued support for impacted workers, small business owners, and families of the victims of the bridge collapse. The group also discussed how Baltimore is open for business, and the President reiterated his support for bringing commerce and tourism back to the city." 

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