Baltimore's Francis Scott Key Bridge Collapses after Ship Strike

[gleem]

The Commander in Chief of the Army Corps of Engineers discusses the cleanup of the channel.

https://www.msn.com/en-us/news/us/a...n&cvid=858f8e5af11f462a8faf3a69b05087cf&ei=16

 

[phinds]

Interesting screen shot from politico.com

 

[Borg]

Is this the game?
http://forum.shipsim.com/index.php?topic=4478.0

No. World of Warships. I frequently turn while in reverse. The effect continues with engines stopped as long as the rudder is turned.

Speaking of the rudder, it would be interesting to know the dynamics of what happens to it when power is lost on the ship. It seems odd that the ship turned to the right at one point either before or after power was lost. I understand that they couldn't move it once they had no power but how/why did it turn the ship to starboard when they had been going perfectly straight? I wouldn't think that a power loss would cause it to suddenly turn unless there was a significant underwater cross-current.

 

[Baluncore]

I wouldn't think that a power loss would cause it to suddenly turn unless there was a significant underwater cross-current.

The propeller couples to, and moves water backwards. The moving water couples to, and is deflected by the rudder, so the rudder post pushes the stern of the boat sideways.

While maintaining steady engine RPM, small bursts of higher rudder deflection are used to correct the course, and so maintain alignment within the channel.

A failure of the rudder control, would require the main engines to be cut and then reversed, to counteract a jammed offset rudder, and to stop the vessel before it departs the channel.

 

[Borg]

My assumption with my post was that they appeared to be lined up properly such that the rudder would have been pointed directly aft. It seems like a pretty bad design to have to twist the rudder to one side in order to continue in a straight direction (minus any outside effects like current). The fuel impacts alone are mind-boggling.

I'm also not clear on the rudder dynamics when power is lost. Assuming that it is using hydraulics, it would just remain in position when power is lost.

 

[russ_watters]

Speaking of the rudder, it would be interesting to know the dynamics of what happens to it when power is lost on the ship. It seems odd that the ship turned to the right at one point either before or after power was lost. I understand that they couldn't move it once they had no power but how/why did it turn the ship to starboard when they had been going perfectly straight? I wouldn't think that a power loss would cause it to suddenly turn unless there was a significant underwater cross-current.

Possibly loss of prop walk:

https://ab-marine.com/knowledge-base-propeller-basics/what-is-prop-walk

Prop walk occurs when a turning propeller pushes a boat’s stern sideways. A single right-handed fixed propeller will tend to push the stern of a vessel to starboard when going forward and to port when going in reverse.

Prop walk affects most single-engine vessels

If prop walk pushes the bow to the left and is countered by right rudder, loss of engine and rudder control simultaneously will cause a turn to the right.

@Baluncore could also be right that random timing of the power failure and rudder movements happened to coincide with a touch of right rudder.

Edit: of course rudder authority and directional stability both increase with speed so rudder input required to counteract prop walk decreases. And loss of power causes immediate loss of rudder authority. So I don't know how these effects all shake out.

 

[sophiecentaur]

Wouldn't the flow just be reversed?

The effect continues with engines stopped as long as the rudder is turned.

When a ship is moving, the rudder will operate, with or without the propellor turning. But the steering when going forward is much greater. The prop will give you forward steerage from stationary (ignoring initilal prop-kick). Astern the rudder will only provide steerage when actually moving astern through the water. Very little directional control when 'slowing down' with reverse thrust and the sense of steering can also change. A lot of skill needed to go astern accurately in resitriced space (in a marina); lots of engine stop start plus confidence that the rudder will actually kick in eventually. (I'm re-living it in my memory as I write)

However, big ships have bow thrusters to take care of that problem. I dunno what supplies the power for big ship bow thrusters; auxilliary generators?

The speed was reported as 8kts so plenty of steerage initially without prop power. But the details are impoortant. What was the state of tidal flow through the bridge? The orientation of the ship can be at least as important as the course when manouvering past obstacles (just as in car parks).

I have been confused by the various videos on line. The ship seems to be moving to the right yet it appears to be in front of the bridge in some and behind in others. If the videos were from different sides of the bridge then the motion would be mirrored.

That warning to clear the bridge was well given. Someone was on their toes!

 

[Borg]

I do appreciate the responses because I assume that my understanding of the thrust dynamics is lacking. I wasn't aware of prop-walk before but it makes sense. In any case, the NTSB has the data recorders and it will be very interesting to see what comes out of that analysis.

 

[Baluncore]

It seems like a pretty bad design to have to twist the rudder to one side in order to continue in a straight direction (minus any outside effects like current).

Like riding a bicycle on an uneven path, you will have to make many small reversed corrections to remain both upright, and on the path. To move right, you must fall right, then catch that fall at an appropriate time. That requires you first steer left, to begin the fall to the right.

In a narrow and shallow channel, there will be bank suction effects, prop-walk, wind and tide. The sum of those deviations must be controlled with small, quick side thrusts, that change the alignment of the vessel, and so move it back towards the centre of the channel. The rudder impulse required, to rotate the long vessel onto a slightly different course, is significant.

 

[sophiecentaur]

The sum of those deviations must be controlled with small, quick side thrusts,

Actually, I'd imagine the autopilot would use a very long time constant in the loop. Minimal deviation about a long term mean rudder position would be the most efficient. At a very noddy level, I remember my tiller pilot would be very good at finding a steady setting (with small deviations) when sailing diagonally over regular lines of waves in a variable wind.. That was a very cheap and cheerful bolt on to the tiller of a 26ft Westerly. Whatever happened, it would resist the temptation to make a rapid course correction, based on experience of the last few minutes of what it had already done. It usually got it right; better than I could do, mostly - except when I could foresee the oncoming sea changes.

 

[Gheed]

My assumption with my post was that they appeared to be lined up properly such that the rudder would have been pointed directly aft. It seems like a pretty bad design to have to twist the rudder to one side in order to continue in a straight direction (minus any outside effects like current). The fuel impacts alone are mind-boggling.

I'm also not clear on the rudder dynamics when power is lost. Assuming that it is using hydraulics, it would just remain in position when power is lost.
View attachment 342463

What I can see from this image, and previous "marinetraffic" AIS data, is that there seem to be very few GPS datapoints after the ship made the turn into the straight. Unfortunately I can't download the historical data as there is a paywall...

 

[DaveE]

A really good commentary. Much more than just a time line.

 

[gleem]

This is a Jeff Ostroff video commenting on the inspection of DALI after the collision and the revealing electrical problem before the ship left the dock at time 9:55 of the video

 

[gmax137]

This is a Jeff Ostroff video ...

Thanks @gleem .

Anyone else notice the NTSB inspectors are all wearing shiny new white hardhats? I hope this is not their first trip to the field.

I know they are hard to pack, but I always took mine.

 

[DaveC426913]

Has there been any report on what crew were aboard? The first article I read, just hours after the incident, seemed to say there was no crew on board. Obviously there must have been the pilots, but still, why would there be no crew?

 

[gmax137]

Has there been any report on what crew were aboard? The first article I read, just hours after the incident, seemed to say there was no crew on board. Obviously there must have been the pilots, but still, why would there be no crew?

Here's one report:
https://www.msn.com/en-us/news/us/c...rancis-scott-key-bridge-collision/ar-BB1kIaa5

The crew of the Dali, the ill-fated vessel that slammed into the Francis Scott Key Bridge in Baltimore, are still onboard the cargo ship — and they could be stuck there even longer as authorities continue to assess the situation.

Two pilots and 21 crewmembers were manning the Dali on Tuesday when it rammed into one of the bridge’s support pillars, causing the 1.6-mile span to crumble and plunge into the Patapsco River.

 

[PeterDonis]

Moderator's note: A subthread about removing hyperlinks from cut & paste text has been moved to a separate thread in the Feedback forum:

https://www.physicsforums.com/threads/how-to-remove-hyperlinks-from-cut-paste-text.1061361/

 

[Borg]

Multiple cranes being positioned this morning. Some cutting of the steel has already begun.

 

[Vanadium 50]

Is the plan to try and float the ship away? Or to cart it away in pieces?

If removed, is that enough to reopen the channel? Or is there too much bridge debris?

 

[Frabjous]

Is the plan to try and float the ship away? Or to cart it away in pieces?

If removed, is that enough to reopen the channel? Or is there too much bridge debris?

The plan is to float the ship away. Tearing it apart would create too much waste.

There is too much bridge debris. Somewhere I read that there is only 12 to 18 inches of clearance for large ships. Admittedly smaller ships, might be allowed earlier.

 

[Vanadium 50]

There is too much bridge debris. Somewhere I read that there is only 12 to 18 inches of clearance for large ships.

My neighbor learned that lesson when trying to park his giant Hum-V in his garage. It didn't fit. Not the first time, anyway.

The more I think about the cleanup, the more of a mess this looks like it will be. And the Port of Baltimore is not exactly tiny. Not only do you have ship debris and bridge debris, you have cargo and fuel. And the competing goals of cleaning up quickly and preserving evidence.

 

[Borg]

Is the plan to try and float the ship away? Or to cart it away in pieces?

If removed, is that enough to reopen the channel? Or is there too much bridge debris?

In the local news conferences, they've stated generally the following phases:

• Clear enough debris from the channel for one-way traffic
• Remove the debris from the ship, float it away and clear remaining debris from center of channel for two-way traffic.
• Clear the remaining bridge debris outside of the channel
• Rebuild the bridge (many years of course)

The haven't give a timeline for recovering the remaining bodies. They're saying it's just too dangerous for the divers right now but they do want to recover them as soon as they can. There haven't been any timelines but I'm guessing from the way that it's being discussed that phase one might be completed within two months or less. The local news last night had a large list of 8+cranes, more than a dozen tugs, barges and support ships all on site or arriving soon. They have stressed over and over that getting the harbor open and doing it safely are the top priorities. When it comes to the logistics, it looks to be full speed ahead.

 

[Borg]

Carnival Cruises has moved their Baltimore operations to Norfolk VA until further notice.

 

[Baluncore]

I would expect the main channel to be cleared quickly. Bridge truss sections can be cut apart, using shaped charges placed by divers, then lifted by the cranes onto barges for removal. Bureaucracy and environmental impact permits can delay that process.

The vessel hull appears to be functional, so the insurance company will want to tow the DALI back to the container terminal ASAP to be unloaded.

 

[Vanadium 50]

Anyone else notice the NTSB inspectors are all wearing shiny new white hardhats

Are you surprised? This is an election year, this will get a lot of coverage, and it doesn't hurt that the Secretary has aspirations. I'm sure everyone within range of a camera has a brand new hard hat.

As far as alternative routes, the next best options are tunnels, which means no hazardous materials. That includes things like gasoline.

I am wondering if they might set up a ferry. It won't handle the 30,000 cars per day, but it could mitigate the need to drive all the way around. The Boston MBTA operates two, and up until recently there was a ferry across the Potomac in north suburban DC.

 

[ChemAir]

Are you surprised? This is an election year, this will get a lot of coverage, and it doesn't hurt that the Secretary has aspirations. I'm sure everyone within range of a camera has a brand new hard hat.

As far as alternative routes, the next best options are tunnels, which means no hazardous materials. That includes things like gasoline.

I am wondering if they might set up a ferry. It won't handle the 30,000 cars per day, but it could mitigate the need to drive all the way around. The Boston MBTA operates two, and up until recently there was a ferry across the Potomac in north suburban DC.

Gotta be honest. New hard hats don't give me the confidence level that well used hard hats would.

 

[ChemAir]

Gotta be honest. New hard hats don't give me the confidence level that well used hard hats would.

I have a pretty hard hat for pictures. I have a well used one for, well everything else.

 

[DaveE]

Gotta be honest. New hard hats don't give me the confidence level that well used hard hats would.

What would you bet that those guys work for many different customers, consulting and such. I bet their favorite hard hat is in their back of their truck and doesn't have a NTSB sticker on it. I don't imagine that would go over well with developers on normal job sites.

 

[gmax137]

The ones I hated to wear the most were the orange ones that say "VISITOR."

 

[Astronuc]

Abi Aghayere, a professor of structural engineering at Drexel University, said his first reaction to seeing footage of the disaster was to wonder whether the bridge was designed to resist the massive force that would be generated by impact from a container ship, even traveling at low speeds.

Given that the four-lane bridge was constructed half a century ago, Aghayere questioned whether the original design took into account that the ships, which have grown considerably in size since then, would be maneuvering so close to the piers.

https://www.thebaltimorebanner.com/...esign-engineering-MZ6H4HUQOJGKRES3AYKGJZEXNI/

Legitimate concerns. At what point should a bridge (or its design) be evaluated for protection - besides routine inspection? Every 5 years? Every decade?

Edit/update: Titanic Law Helps Ship Owner Limit Bridge Collapse Liability (3)
https://news.bloomberglaw.com/insur...ship-owner-limit-liability-in-bridge-collapse

Companies file claim under 'Titanic' law that could drastically limit bridge collapse payout
https://www.wbaltv.com/article/brid...pany-petition-limit-payout-liability/60359628

As for Boring, Inc.

Recent investigations into The Boring Company, a tunnel construction startup founded by Elon Musk, have raised significant concerns over worker safety at its project sites. A recent investigation by Fortune found a widespread lack of accountability, dangerous working conditions, and a series of injuries that surfaced, casting a shadow over the company’s ambitious mission to revolutionize transportation through underground tunneling.

In May, an alarming email from an employee at the Bastrop, Texas, site to the company's then–safety manager, Wayne Merideth, revealed the dire situation: “I feel that the company as a whole has been very fortunate these past few months that there hasn't been a fatality,” the employee wrote. This message was just one of many warnings that Merideth received during his tenure, indicating a consistent disregard for employee safety under the pressure to meet high expectations and tight deadlines.

https://finance.yahoo.com/news/refuse-first-fatality-elon-musks-161507318.html

That is concerning.