Francis Scott Key Bridge collapsed after ship hit it

Ian F (Forum Supporter) said:

In reply to NOHOME :

One issue mentioned is most of the structure is under stress, so they can't have folks just cutting steel willy-nilly lest something goes flying into other workers. Structural engineers are working like crazy to calculate what will (hopefully) happen when a part of the steel is cut. And then where the stresses will be focused after that cut is made.  I'm sure once they get a handle on it, they'll add more crews and work will go faster. 

Cutting up a ship is not the same. A static ship hasn't been torqued and bent into shapes it wasn't designed to be in.

Exactly.  One wrong cut and the falling structure takes out people and support vessels. 

 There is a large machine used in the de-commissioning of offshore oil platforms in Gulf of Mexico that could possibly pick up the pieces.  Doubtful the people in charge of this salvage operation even know about it though.

Versabar invention lifts submerged topsides in one piece | Offshore (offshore-mag.com)

In reply to jharry3 :

That looks a lot like the structure that was used to cut and lift the ship that rolled in the Port of Brunswick. Most of the salvage companies know what is out there. It's just a case of it being available. 

As to cutting, I'd use explosives for the majority of it. Rig it, back off and detonate it. Move back in and pick up the pieces. No one is in harm's way. Once the steel is up you can move in with clamshell dredges and cranes to get the concrete off the bottom of the harbor. 

In reply to jharry3 :

They are probably aware of that equipment, but scheduling rental is a different story. There aren't  many of these large and expensive pieces of specialty equipment and they are generally scheduled YEARS in advance.

I was involved in a bridge demo project where the very large barge mounted crane was reserved by a sizeable deposit 4 years in advance. Contractor originally wanted it in 3 years, but it wasn't available until 4 years. I'm pretty sure they said they made the deposit prior to even winning the bid for the job and there were only 5 or 6 total that were large enough for their plan. Otherwise they would have had to completely revise their demo plan and use multiple smaller cranes which would have cost more due to the longer time needed to do the work.

I wonder if there has been any though given to use debris from the bridge to build dolphins for the new bridge.

Not the steel of course, but there sure is a lot of rubble to move and why move it farther than you have too.

In reply to Noddaz :

240,000 tons of the demoed Charleston bridges were used to enhance 12 artificial reefs offshore of South Carolina. 

Had a friend in Seattle who was a marine salvage engineer.  Super interesting line of work. Wonder if he's involved here. 

In reply to Toyman! :

As far as I can see, the only way they use explosives is if they know 100% how it will fall and not break things in unknown ways.  Can't make the situation worse if you can help it.  So rigging up cranes to hold the bridge and then cut it apart may make a lot more sense.

The ground is just soft mud, and getting stuff out of that may be harder than blowing it up and letting it settle in.  For sure, they will not leave any debris of the bridge in the channel, as it's a risk to all shipping.  

In reply to alfadriver :

There is nothing left to break, it's pretty much as broken as it gets. It can only fall down and if all the workers are 1000' away, it won't matter where the pieces fall as long as they don't pierce the hull of the ship below the waterline. Cut the pieces small enough and the dangers are minimal. Cutting steel beams with explosives is a known process and every bit as exact as torches. It's just less dangerous to people and faster. 

They have a 1000-ton barge crane onsite. Cut the bridge into 100-ton chunks and lift them onto barges. At 10% of the load rating, their margin for error is huge and the crane won't have any issues moving the pieces. 4000+ tons landing on the bow didn't chop the nose off of the Dali. A few properly placed explosives can only make the ship's situation better. Once the ship is out of the way, there is nothing left to be concerned about. 

This^

Regarding getting the ship off the bottom.... It might float off if they got some of the weight off. Or is the hull torn open?

In reply to Toyman! :

I think we are all making assumptions of the condition and stresses on the structure.  As an engineer, I'm not really going to second guess how they are going to deal with it.  If they use explosives, great.  But I'm not going to say I know better than they do.

All I can suggest is making the span wider but keeping the channel the same width, which puts a grounding area between the ships and the bridge.

Toyman! said:

In reply to alfadriver :

There is nothing left to break, it's pretty much as broken as it gets.

That is not true at all.  There are large, heavy chunks of truss still intact, and probably stressed as hell.

In reply to Duke :

My point is that it doesn't matter if those chunks of truss get more broken. The more they break down the easier they will be to move. The only thing to worry about as far as clearing the shipping channel at the moment is poking holes in the bottom of the ship. 

The superstructure holding the front of the ship down is estimated to be 4000 tons. The weight of the steel and the buoyancy of the ship are working to maximize the amount of stress in that pile of wreckage. Unfortunately, a 1000-ton crane can not lift a 4000-ton structure to relieve stresses while it is cut. A stressed steel beam is not something you want to be standing next to when you cut it. You don't want to be anywhere near because the release of energy will be sudden and powerful. 

It will be interesting to see how they proceed. 

In reply to Toyman! :

It does matter- smaller pieces are harder to find in the mud.  And they can't leave anything behind.

But we will see how they progress.  

Toyman! said:

In reply to Duke :

My point is that it doesn't matter if those chunks of truss get more broken.

And my point is that it DOES matter if people, equipment, and surroundings get broken trying to demolish the rest of the bridge.  That stuff contains A LOT of pent up potential energy.

No one is Bob Costasfooting around to protect the parts of the fallen bridge.  No one but Elon Musk thinks they can be reused in any way that doesn't involve a recycling smelter.

But they ARE trying to avoid making a hard job even harder and more dangerous, and trying to avoid damaging the surroundings even more than they are.

From what I understand, the disposal of the steel part of the bridge is already taken care of.  There's a local place/firm that is more than capable of dealing with the steel.  Even in really large chunks.

In reply to Duke :

The nearest surroundings are two power poles at 600+ feet distance, the Fort Carrol Landing Dock at just under 3000' away and one slightly damaged ship that they certainly don't want to sink in place. 

Anything else is going to be a mobile platform that can be moved before the demolition. The only thing they really need to not destroy is the ship.

Edit: Compare that to the explosive demo of the Charleston bridges. The brand new bridge was only 360' from the old one. They stopped traffic at 1000' for 10 minutes, made the shot, and turned traffic loose. 

In reply to Toyman! :

How long did it take to plan and engineer the bridge you talk about before it was blown?  Takes a lot of planning and models to be sure that you break it apart in a way that is fast AND easy to recover.  And it's not about debris hitting anyone- it's about the debris making clean up harder.  The draft is quite shallow in the channel, so they have to make sure they get everything.  

In reply to alfadriver :

2 years to remove 4 miles of bridge, all the associated interchanges, build 1250' pier and park. $61 million. 

https://www.jaycashman.com/uploads/2018/07/CooperRiverBridges.pdf

The only part of the Baltimore bridge that needs to be removed quickly is the main span which is a paltry 1100' long. Once it's out of the way and the harbor channel is clear, there is time to slow down and remove the rest of it. 

With that, I think I've exceeded my 5 responses so I'll stop now. 

Thanks for the conversation. 

In reply to Toyman! :

The Charleston bridge was a controlled demolition.  It was standing normally and you could safely walk or drive vehicles on it right up until until they pulled the trigger to drop it.

This is NOT a controlled demolition.  This is more like a failed explosive demolition, with a partially-collapsed building that they now have to go back into in order to finish the job.  There is a huge amount of mass left in a probably unstable, definitely overstressed attitude.

I've worked with large-scale demolition firms.  Having to finish off a partially demolished structure is every one's nightmare scenario.

I know you think this is easy.  It is not.

In reply to Toyman! :

That's kind of the point here.  They don't have two years to understand the current status of the structure to know how it will come apart when using demolition.  So that when they take it out of the channel, they know the size and location, as well as it all being there.

Again, it's not about the danger to people or stuff during the explosion.  It's about how to make it manageable to clean up in just about 7 weeks.  And even after the structure is dealt with, they have to get all of the former road bed out of the channel.  

Very interesting video of a very educated guess on what happened on the ship- https://www.youtube.com/watch?v=jxeKXjDVqMA&ab_channel=ChiefMAKOi

This is a Engineering Chief on a ship, who is very familiar with all of the systems and how they are supposed to work.  He does say many times that he's not sure, and that there are other possibilities- as the investigation has not taken place.  But based on his experience, a strong possibility of what happened.  Probably a fuel system problem of some type, since all of the generators have a common fuel supply.  And I find that very interesting that there's a single source of fuel for systems that are redundant for each other- a single point failure possibility.

There was an interview with someone from the corps of engineers earlier this week on the radio. He said  they were going over the options to quickly and safely release the energy in the damaged steel, and once that was done and the necessary equipment was on scene it should progress relatively quickly. There isn't a lot of heavy demolition equipment sitting around so it sounded like they were coming up with some ways around that as well. 

M/V APL Qingdao, an 89,000 ton container ship, lost complete power and propulsion while underway near NYC's Verrazzano bridge 

It had three Ford Econobox tugs at time of power loss, but required three more to bring under complete control

Mr_Asa said:

M/V APL Qingdao, an 89,000 ton container ship, lost complete power and propulsion while underway near NYC's Verrazzano bridge 

It had three Ford Econobox tugs at time of power loss, but required three more to bring under complete control

If I was a conspiracy theorist...

I'd blame the eclipse 🫤, but I'm not so it's just coincidence until proven different. 

In reply to No Time :

Not enough virgins.  Maybe they needed a Virgin cruise ship.