Baltimore bridge collapse was a failure, engineers say — but likely not with the bridge
Francis Scott Key Bridge was up to code, Maryland governor says
It's "extremely unusual" for a bridge collapse to be caused by a ship impact, says an engineering specialist reacting to the collapse of a major bridge in Baltimore after a container ship rammed into one of its support beams early Tuesday.
The failure isn't necessarily related to the bridge itself, but could have more to do with why the ship hit it in the first place, other engineers noted.
Six people are still unaccounted for and presumed dead after the collapse of the Francis Scott Key Bridge. The Singapore-flagged vessel, the Dali, which was on its way to Sri Lanka, reported losing power just before it struck a column on the bridge, authorities said. Federal officials say it wasn't intentional.
Maryland Gov. Wes Moore said in a news conference that the bridge was up to code. The 300-metre-long ship appeared to hit a main concrete pier, which rests on soil underwater and is part of the foundation.
Benjamin Schafer, a professor of civil and systems engineering at Johns Hopkins University in Baltimore, told CBC News Network that the bridge was supported at two points, and when one of those supports is compromised, it's inevitable the bridge will collapse.
"There's nothing any of us can do about that," he said. "Unfortunately, there's not a huge structure story to tell when you have something as simple as two ways to keep it up in there, and you take one away."
But that doesn't mean there isn't a larger failure at play, Schafer said. It's just not necessarily with the bridge itself.
"There's still a failure here, obviously," he said. "It's just probably not one about the physics of the steel that was particularly used in that bridge."
Other engineers on Tuesday raised questions about the bridge construction, including the lack of adequate protective fenders around its supporting columns that might have lessened the ship's impact.
What investigators will need to understand is why the ship couldn't avoid the pier when there were no other vessels around, Marina Bock, a lecturer in structural engineering at Aston University in the U.K, said in a statement on the Science Media Centre.
"Maybe if the vessel had hit a small section of the suspended deck, the bridge would have been able to survive the collision, but not a main pier," she said.
Not the first bridge collapse due to ship impact
This is the first major collapse due to a ship impact in decades, U.K. engineering specialist David Knight told CBC News Network Tuesday morning.
"It's extremely unusual to have a bridge collapse caused by a ship impact," Knight said.
"We do get instances of ship impact on piers, but normally, piers are designed to accommodate ... a certain level of impact from ships and from shipping that's expected in that area."
From 1960 to 2015, there have been 35 major bridge collapses worldwide due to ship or barge collisions, with a total of 342 people killed, according to a 2018 report from the World Association for Waterborne Transport Infrastructure.
Eighteen of those collapses happened in the United States. One of them, in 1993, caused 47 deaths when a barge tow became lost in dense fog and struck a low-level railroad bridge near Mobile, Ala.
"There are numerous vessel collision accidents with bridges which cause damage that varies from minor to significant but does not necessarily result in collapse of the structure or loss of life," the report states.
There were, for example, six separate barge collisions with highway and rail bridges crossing the Mississippi River during a two-week period in January 2016 alone because of floodwater conditions, the report said.
ABOUT THE AUTHOR
With files from the Associated Press