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The massive cargo ship that lost control and slammed into a major Baltimore bridge on Tuesday was not the first to do so. The same bridge was also hit by a wayward cargo vessel in 1980.
On Aug. 29 of that year, a container ship named the Blue Nagoya drifted into a pier that supported the structure, the Francis Scott Key Bridge, after losing control about 1,800 feet away, according to a 1983 report by the U.S. National Research Council.
But when the Blue Nagoya hit the Key Bridge, it destroyed some protective concrete, yet did not topple the structure. So what was different this time?
The two vessels were traveling at roughly the same speed. The Blue Nagoya was moving at about six knots, or nearly seven miles per hour, when it made impact. The ship that hit the Key Bridge early Tuesday morning, the Dali, had been clocked at just under seven knots, the National Transportation Safety Board said on Wednesday.
The full story of how and why the 1.6-mile-long bridge collapsed could be years away. Investigators were still collecting evidence at the site on Wednesday.
For now, structural engineers have said that no bridge would have been able to withstand that kind of direct hit from a cargo ship weighing 95,000 tons, as the Dali did. But they have also noted that the bridge had no obvious protective barriers that might have redirected or prevented a ship from crashing into its piers in the first place.
So-called impact protection devices have been common in the industry ever since a freighter hit a support column of the Sunshine Skyway Bridge in Tampa Bay, Fla., in 1980, collapsing the structure and killing 35 people. But the Key Bridge opened in 1977.
Other experts say that because the size and weight of cargo vessels have significantly increased since the 1970s, vessels like the Dali are generally more dangerous to bridges than the Blue Nagoya would have been.
The National Research Council report did not specify how heavy the Blue Nagoya was when it hit the Key Bridge in 1980. Amar Khennane, a researcher at the School of Engineering and Technology at the University of New South Wales in Canberra, Australia, said in an email that the Dali appeared to be “notably larger and heavier than the one involved in the 1980 incident, with proportions three times greater.”
Vessels weighing up to 100,000 tons “can have a catastrophic effect on piers if there is a lack of protection against impact,” Raffaele De Risi, a civil engineer at the University of Bristol in England, said in a statement.
Benjamin W. Schafer, a professor of civil and systems engineering at Johns Hopkins University in Baltimore, told Scientific American this week that the accident would most likely hold lessons for protecting bridge support structures from shipping traffic.
“If you look at the size of the ships from the 1970s, when the bridge was built, to now, it’s radically changed,” Professor Schafer told the magazine.
Andrés R. Martínez contributed reporting.
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