美国大桥因集装箱船撞击坍塌
2024-03-28 04:49阅读：
美国马里兰州巴尔的摩一桥梁当地时间26日凌晨因船舶撞击坍塌。已知至少7人在巴尔的摩桥梁坍塌事件中落水。
事发时，一艘新加坡籍集装箱船达利轮(DALI, IMO NO 9697428,
300x48x12.2米)撞上巴尔的摩“弗朗西斯·斯科特·基”桥，这座长约2.6公里的桥随后坍塌。视频画面显示，船撞桥时发生爆炸，事发时桥面上多辆车辆行驶。
社交媒体上的视频显示，有两个桥墩之间的桥梁结构完全坍塌，坠入水中。
How a cargo ship took down Baltimore's Key
Bridge
By Michael Laris, Jennifer Hassan and Joel Achenbach
To bridge experts, the collapse of Baltimore's Francis Scott Key
Bridge after being hit b
y a heavy cargo ship was as inevitable as it was devastating.
When a vessel as heavy as the Singapore-flagged Dali crashes with
such force into one of the span’s supercolumns, or piers, the
result is the type of catastrophic, and heartbreaking, chain
reaction that took place early Tuesday.
“If the column is destroyed, basically the structure will fall
down,” said Dan Frangopol, a bridge engineering and risk professor
at Lehigh University in Pennsylvania who is president of the
International Association for Bridge Maintenance and Safety. “It’s
not possible to redistribute the loads. It was not designed for
these things.”
No bridge pier could withstand being hit by a ship the size of the
Dali, said Benjamin W. Schafer, a professor of civil and systems
engineering at Johns Hopkins University.
“These container ships are so huge,” Schafer said. “That main span
has two supports. You can’t take one away.” He called the accident
“a huge infrastructure failure,” but not because of the bridge
collapse; he said the shipping industry needs systems to keep a
ship on track when it loses power, as the Dali did before the
collision.
The bridge itself, which carried more than 30,000 vehicles daily,
appeared to be structurally sound. Its condition was rated fair,
according to data in the 2023 National Bridge Inventory maintained
by the Federal Highway Administration. Maryland state officials
said they were focused on search-and-rescue operations and did not
provide later inspection data. National Transportation Safety Board
Chair Jennifer Homendy said excavating detailed inspection history
information — and what was done in response to any earlier findings
— will be a cumbersome and protracted part of the agency’s
investigation.
But bridge safety and engineering experts are emphasizing a
separate issue: protective barriers.
When the span opened to traffic in 1977, many ships were smaller
and the standards for protecting bridges against them were lower,
they said.
A few years later, a Liberian cargo ship crashed into a bridge in
Florida, sending a Greyhound bus, a pickup truck and six cars into
the Tampa Bay and killing 35 people, according to the NTSB. That
deadly 1980 collision helped lead to the adoption of stronger
national standards for bridges, including protection from errant
ships, in the years that followed, safety experts said.
Sherif El-Tawil, a professor of civil and environmental engineering
at University of Michigan with expertise in bridges, said if the
Key Bridge had been built after those updated standards from the
American Association of State Highway and Transportation Officials
were put in place, the span could still be standing.
“I believe it would have survived,” El-Tawil said.
Maryland officials did not answer questions Tuesday about what
protective devices were in place near the bridge and whether they
were sufficient to withstand this type of collision.
Two examples of protective measures that did not appear to have
been in place, El-Tawil said, were large fenders designed to direct
marine traffic away from the bridge supports and an island built
around the pier.
Some states are building these kinds of protection systems around
vital bridges. Last year, officials from a joint New Jersey and
Delaware bridge authority announced work on eight 80-foot-wide,
stone-filled cylinders designed to protect the Delaware Memorial
Bridge. The existing protection for the bridge tower piers dates to
1951. “Today’s tankers and ships are bigger and faster than those
of the 1950s and 1960s,” the officials said in announcing the
nearly $93 million project.
State departments of transportation “are aware of the shortcomings
of these bridges,” said Roberto T. Leon, a bridge and structural
engineering professor at Virginia Tech. “It’s not that they don’t
know. It’s a matter of prioritizing the repairs. It is a very
expensive proposition to protect a bridge.”
Ian Firth, a British structural engineer and bridge designer, said
he was “not surprised” at how quickly the bridge came down after it
was hit. He noted that the support structure that was struck, which
would have been made of reinforced concrete, was one of two main
supports responsible for doing “all the work” to hold up the
bridge.
He said the ship appeared to have strayed to one side before
striking the bridge.
The bridge collapse, like other calamities, is probably the result
of overlapping low-probability failures, said Edward Tenner, a
historian and expert on disasters — akin to what happens when, by
chance, the holes in a stack of Swiss cheese slices line up
perfectly.
“This might have been a case where there were just an unlikely
series of failures,” said Tenner, author of “Why Things Bite Back,”
a book about technology and its unanticipated consequences. But he
added, “I suspect there was something about the equipment of a huge
ship like that, given the potential for damage like this, there
should have been more redundancy. There shouldn’t have been one
point of failure that could lead to a catastrophe.”
Speaking Tuesday afternoon in Baltimore, U.S. Transportation
Secretary Pete Buttigieg called the accident “a unique
circumstance,” adding, “I do not know of a bridge that has been
constructed to withstand a direct impact from a vessel of this
size.”
The ship was towed into the Patapsco River initially, but the
tugboats did not accompany the ship all the way to the bridge, said
John Konrad, a retired ship captain who runs the gCaptain maritime
news website and co-authored a book on the Deepwater Horizon oil
spill.
“The safe thing to do is keep the tugs,” Konrad said. “Moving
forward, I think that’s going to happen. The Coast Guard is going
to say you’ve got to keep the tugs tied up until you pass the
bridge.”
In video imagery, the ship can be seen losing electrical power,
then briefly regaining it before going completely dark. The ship
then veers to the right, directly toward the bridge’s structural
support.
The rudder may have gotten stuck in a position that caused the ship
to turn, said a senior retired maritime official, who spoke on the
condition of anonymity while waiting for more details on the
incident. It’s also possible that an incoming tide could have been
a factor, he said.
“Obviously, they could not control the ship. They could not stop
the ship,” he said.
A deficiency in the Dali’s systems was discovered when the ship was
inspected in June, records show. Inspectors at the port of San
Antonio, Chile, discovered a problem categorized as relating to
“propulsion and auxiliary machinery,” according to the Tokyo MOU,
an intergovernmental shipping regulator in the Asia-Pacific region.
The issue was classified in the subcategory of “Gauges,
thermometers, etc,” but no additional details of the deficiency
were provided. The problem was not serious enough to warrant
detaining the ship, according to the records.
After a follow-up inspection later the same day, the Dali was found
to have no outstanding deficiencies, the records show, indicating
that the problem was addressed.
Maryland Gov. Wes Moore (D) said at a news conference Tuesday that
the Dali lost power and issued an emergency call for help shortly
before the freighter crashed into the bridge. The “mayday” distress
call allowed officials to halt vehicle traffic headed over the
bridge and saved lives, Moore said.
