Baltimore (AFP) - Baltimore's Francis Scott Key Bridge, named after the poet who penned the lyrics to the US national anthem, used to carry around 34,000 vehicles a day across one of the busiest harbors in the United States.

Its nighttime collapse, within seconds of being struck by a container ship, is likely to cause major economic damage for as long as it continues to block shipping in the Port of Baltimore.

The bridge's dramatic destruction shut the port for maritime traffic, which last year accounted for more than 52 million tons of foreign cargo, worth some $80 billion, according to a recent statement from Maryland Governor Wes Moore's office. 

Baltimore is the deepest harbor in Maryland's Chesapeake Bay, and handles the highest volume of autos and light trucks in the United States, as well as the largest quantities of imported sugar and gypsum.

"There is no question that this will be a major and protracted impact to supply chains," said US Secretary of Transportation Pete Buttigieg at a press briefing.

"It's too soon to offer estimates on what it will take to clear the channel and reopen the port," he added.

The Port of Baltimore is the ninth-busiest major US port in terms of both foreign cargo handled and foreign cargo value, and is directly responsible for more than 15,000 jobs while supporting almost 140,000 more.

"We're going to do everything we can to protect those jobs and help those workers," President Joe Biden told reporters in a brief address from the White House.

"I'm directing my team to move heaven and earth to reopen the port and rebuild the bridge as soon as humanly possible," he said, adding: "This is gonna take some time."

'Disrupt commercial activities'

The Port of Baltimore generates around $3.3 billion in total personal income each year, according to the Maryland State Archives, and brings in almost $400 million in annual tax revenues.

More than 50 ocean carriers use the port every year, making a total of almost 1,800 trips annually.

Alongside its use as a major port for so-called roll on/roll off container shipping, the Port of Baltimore also serves as a cruise terminal. 

Last year, more than 440,000 individuals cruised out of the port -- the most since 2012, according to the Governor's office.

The extended closure of the Francis Scott Key Bridge "will inevitably disrupt commercial activities and supply chains," the Maryland Chamber of Commerce said in a statement. 

'Inadequate' protection

Major bridges over shipping lanes like this one are supposed to be designed in such a way to minimize damage in the event of a collision, according to bridge designer Robert Benaim.

"Clearly the protection of the piers in this instance was inadequate," he said. 

"A pier or column of a bridge could never resist the impact of a large ship. They must be protected from collision," he added. 

Toby Mottram, structural engineering professor at the University of Warwick, voiced a similar view.

"It's evident that the pier couldn't withstand the impact energy, leading to its failure and subsequent collapse of the steel truss and reinforced concrete deck superstructure," he said.

"The extent of the damage to the bridge superstructure appears disproportionate to the cause, a matter for future investigation," he added.