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The crews have the complicated work began of cleaning up the site of the fatal collapse of the Francis Scott Key Bridge on the Patapsco River. Central to this effort are barge-mounted cranes, which are used to pull steel and concrete from the depths.
Last week the US Navy launched underwater images of the collapsed section, which show the magnitude of the job recovery facing workers. First, a global assessment of the wreckage will be made, then the bridge will be cut and lifted section by section onto barges and transported away.
This type of operation involves complicated physics and coordination, according to Jeff Ellis, director of field operations for Crane Tech, a crane training and service provider based in Brandon, Florida.
“This is one of those cases where we have to take time to get it right the first time,” Ellis said. who is not involved in the Key Bridge effort, but has experience in water rescue operations. “It’s much easier, much less expensive, much safer to do it right.”
Jeff Ellis
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The USA The Army Corps of Engineers released an updated timeline Thursday to clear a 280-foot-wide, 35-foot-deep channel in late April and to reopen the 700-foot-wide, 50-foot-deep permanent channel in late May. Despite this, poor visibility in murky water has hampered diving efforts around the bridge structure, according to Maryland Gov. Wes Moore.
Helping with cleaning is The Chesapeake or “Chessy”, a tower barge with a lifting capacity of 1,000 tons and the largest crane on the East Coast that was once used by the CIA.
Also supporting the operation are the Ferrell, a 200-ton jib crane barge; the Oyster Bay, a crane barge with a lifting capacity of 150 tons; and another barge with a lifting capacity of 400 tons, according to a Navy statement, along with 12 additional cranes and support vessels, including tugs, survey, dive and crew vessels.
Here, Ellis talks with Construction Dive as he breaks down the process and challenges of recovering the remains of the Key Bridge.
Editor’s Note: This interview has been edited for clarity and brevity.
BUILD Immersion: Can you tell us what the recovery process will likely involve?
JEFF ELLIS: As they begin a rescue on the bridge, they must remove the pieces and parts that have collapsed into the water, without causing further damage. If part of the cantilever section is across the boat, where it is picked up or where it is cut can have an adverse effect and cause another part to go deeper into the water.
Someone has to be the supervising adult and say, “We’ve got to get this piece out first, this is going to weigh about,” and plan that pick and then go pick number two. It will be a process of reflection.
And while those pieces are being pulled out of the water and the waterway is being cleaned, they’re trying to minimize damage to the ship, which is already pretty damaged.
What are some of the challenges in removing pieces of the bridge from the water?
The weight of something in the water will change dramatically with the current pulling it up and to the sides, possibly wind and buoyancy. There could also be mud suction.
Therefore, they must know what it weighs, because they will not be able to measure it while raising it. They will have to be pretty accurate and put in whatever margin of error they think it will be, probably 10%.
They will make sure that the piece they are trying to pick up is well within the crane’s capacity when it comes out of the water, so that they don’t pull it out of the water and then be unable to handle it, which has happened in the past. It is truly an engineering nightmare.
How is the use of barge-mounted cranes different from land-mounted cranes?
Whenever you take a barge and add a crane to it, a marine engineer will make sure the center of gravity is well below the center of buoyancy, so that as you pick up a load, it won’t capsize the whole unit. Their capacity will vary with the angle, what they call the list and the cut of a barge.
It will tilt with the added weight, because your boom on this crane is actually like a Johnson bar lever when it is deflected in the water. And the more it’s out of level, the less you’ll be able to choose, the less ability you’ll have.
There will be a list and a cut indicator that tells them what the physics moment is, then you’ll have a graph corresponding to that physics moment that shows what the reduced capacity of the crane is.
Also, once it clears the water and you lose that buoyancy, your actual weight will take effect on the crane. The last thing you want to do is add to your problem by having an accident on top of this accident.
What are the security issues for this type of operation? How has crane safety changed over the years you’ve been a coach?
When there are people underwater around these things, there are a lot more safety issues. With divers in the water, we’re not just talking about getting someone from a parking lot to an ambulance, now we’re talking about how we’re going to get them out of the river, onto a boat, to some sort of triage where they can start getting help.
The idea behind elevator planning is to make sure we are aware of all the hazards, and then do something about each and every hazard to reduce, mitigate, eliminate, or face them that, whatever the case may be. They will then have to make sure it runs as planned.
There was a time when the person who did the most with the least amount was a hero, until there was an accident.
There was a time when it was acceptable to expand people and equipment in the name of doing so. This is no longer acceptable, because we know it is not profitable.
Being able to change a culture through education is a wonderful thing. We are all smarter today than yesterday, at least I hope so.
