- Engineering experts tried to explain how the Francis Scott Key Bridge in Baltimore collapsed.
- They focused on one factor: the sheer size of the cargo ship that collided with it.
- In the face of such momentum, complete collapse is inevitable, they said.
Baltimore's Francis Scott Key Bridge was unable to withstand a major impact from a cargo ship Tuesday morning, engineering experts told Business Insider.
The bridge was destroyed early Tuesday morning, collapsing violently after the large cargo ship Dali collided with one of the bridge's supports.
This video shows the impact.
Understanding why and how bridges collapse can have a major impact on safety in both the freight transportation industry and civil engineering.
Leroy Gardner, professor of structural engineering at Imperial College London, said the physics of the impact was “pretty clear”.
“The cargo ship had a big impact on one of the piers,” he said in a phone call with BI. “Once the bridge collapsed, the rest of the bridge collapsed shortly after.”
Experts told BI that structural defects in the bridge were unlikely to be related to the collapse, given the magnitude of the impact.
Perhaps the engineers could not have protected themselves from such a huge impact. According to the website “vesselfinder.com,'' the Dali is a large ship with a total length of 300 meters and a weight of approximately 95,000 tons.
Its size and weight are comparable to the U.S. Navy's Nimitz-class aircraft carriers. The Dali was almost as high as the bridge she was passing under.
“All piers are going to be designed to withstand impacts from ships, and I think this is definitely no different,” Gardner said.
“I think it's the magnitude of the force in this case that caused the problem for this bridge, which I think is highly unusual,” he said.
The Francis Scott Key Bridge opened in 1977. Its design is a steel truss bridge. Based on footage shared online, experts said the bridge was resting on concrete piers before the crash.
Ian Firth, a British structural engineer and bridge consultant, told the BBC: “At first glance, this column is a very, relatively flimsy structure. It's a kind of trestle structure with independent legs.” “So the bridge simply collapsed as a result of this very large impact force.”
Gardner told BI that the impact from the Dali appears to have destroyed one of the concrete piers, which is a “significant and critical part of the bridge.”
“Structures are generally designed to have some degree of rigidity, so if one part is damaged, the rest of the structure remains intact,” Gardner said.
“If you lose such a critical element, you would expect the whole bridge to collapse, and that's what happens,” he said.
The cause of the crash was not immediately clear. Experts said it was not clear from the footage how fast the Dali was moving. It had just recently left port.
Barbara Rossi, associate professor of engineering at the University of Oxford, told BI in an email: “It takes an impact force for these huge (concrete) structures to collapse, leaving the superstructure without one of its supports. It must have been immeasurable.” ”
Mark Richards, director of NESTA Consulting Engineers, said a lengthy investigation was likely to follow.
“It's inevitable that the engineering community will take note of this and look very carefully at what happened and take lessons from it,” he told BI by phone.
“Bridges are designed for events that are considered appropriate or likely by the broader engineering community unit. Perhaps this event just goes beyond that.” He said.
“Those events may not have been foreseen, so we cannot forget them,” he said.
A Danish engineering and architectural consultancy called COWI said in an emailed statement to BI that bridges are typically not designed to withstand direct impacts from ships.
Instead, engineers create structures near the bridge supports where the ship first hits to absorb the impact.
That way, “the failure would be about the bridge, not the bridge itself,” said Lorna Wharton, COWI's director of media and public affairs.
Experts said it was not immediately clear what defenses the Francis Scott Key Bridge had. COWI and Richards said something may have been there.
Experts say engineers are likely to consider not just the protection of the bridge itself, but also the broader dynamics of how ships navigated under and around the bridge. is said to be high.
