Baltimore's Francis Scott Key Bridge Collapses after Ship Strike

[Baluncore]

As I understand it, this is a fairly common and well-known option for collision protection on (newer) bridges, so do anyone know the specific reason why that protection was not selected for this bridge?

The two main supports of the Baltimore's Francis Scott Key Bridge, could have been retrofitted with collision protection, to bring it up to date. All other supports are in shallow water.

It was only in the mid-seventies that ships started to knock down big bridges.

These are the dates of collisions resulting in collapse.
1942 https://en.wikipedia.org/wiki/Chesapeake_City_Bridge
1946 https://en.wikipedia.org/wiki/Cooper_River_Bridges_(1929–2005)#History
1960 https://en.wikipedia.org/wiki/Severn_Railway_Bridge
1964 https://en.wikipedia.org/wiki/General_Rafael_Urdaneta_Bridge
1964 https://en.wikipedia.org/wiki/Lake_Pontchartrain_Causeway
1972 https://en.wikipedia.org/wiki/Sidney_Lanier_Bridge
1975 https://en.wikipedia.org/wiki/Tasman_Bridge_disaster
1977 https://en.wikipedia.org/wiki/Benjamin_Harrison_Memorial_Bridge#Disaster_in_1977
1980 https://en.wikipedia.org/wiki/Sunshine_Skyway_Bridge#1980_collapse
1980 https://en.wikipedia.org/wiki/Almö_Bridge
1980 https://en.wikipedia.org/wiki/Sunshine_Skyway_Bridge#1980_collapse
1983 https://en.wikipedia.org/wiki/Aleksandr_Suvorov_(ship)#1983_accident
1993 https://en.wikipedia.org/wiki/Big_Bayou_Canot_rail_accident
2001 https://en.wikipedia.org/wiki/Queen_Isabella_Causeway
2002 https://en.wikipedia.org/wiki/I-40_bridge_disaster
2007 https://en.wikipedia.org/wiki/Collapse_of_Jiujiang_Bridge
2008 https://en.wikipedia.org/wiki/Jintang_Bridge
2009 https://en.wikipedia.org/wiki/Popp's_Ferry_Bridge
2024 https://en.wikipedia.org/wiki/Francis_Scott_Key_Bridge_collapse

 

[Rive]

I foresee this question quickly becoming relevant

Agree. One thing is the malfunction of the ship (I'm still considering it likely related to human factor - not necessarily from the crew, though), other is the environment being unable to mitigate it.
A major reevaluation and overhaul of safety for harbors and bridges indeed seems likely.

 

[russ_watters]

By my calculations, the impact energy was roughly 1.25 terajoules or 300 tons of TNT or 8 fully loaded B-52 bomber's-worth.

 

[Borg]

During last evening's news, there already was a large, floating crane at the site. NTSB still has to approve any removal once they've done their initial investigation but they clearly aren't going to waste any time with the removal process once they're cleared to do so.

However, this morning I don't see anything other than small patrol boats on the current Real Time Ship Tracking. Hmmm, maybe I saw one of the gantry cranes in the background. I could have sworn there was one in the water though.

 

[Borg]

Live stream of the harbor on YouTube..

 

[russ_watters]

Agree. One thing is the malfunction of the ship (I'm still considering it likely related to human factor - not necessarily from the crew, though), other is the environment being unable to mitigate it.
A major reevaluation and overhaul of safety for harbors and bridges indeed seems likely.

It's a human made machine so ultimately human factor will be at play, even in a mechanical/electrical failure. But I tend to doubt it was an immediate cause, other than maybe procedural.

The Wikipedia article on the ship implies (in an ambiguously written sentence) that the two main generators are driven by the main engine and it has two auxiliary diesel generators. The smoke is consistent with a diesel lighting-off, but which one? The (single) main engine re-starting or an auxiliary generator? Why not keep an auxiliary generator running in standby during critical operations? Or maybe the multiple power failures indicate main switchgear problems that turning on a[nother] generator can't fix?

 

[Baluncore]

The smoke is consistent with a diesel lighting-off, but which one? The (single) main engine re-starting or an auxiliary generator?

I know it does not seem rational, but the volume of black smoke looked to me like a main engine restart, not one of the much smaller diesel generators being started.

When they lost steering, did they ring "Full astern" to reverse the main engine, and so slow the ship. That would explain the volume of black smoke.

 

[gleem]

When you put the pedal to the metal on a diesel you get a lot of black exhaust. So a full astern would do that. Also, I do not think the ship hit the bridge at 8 kts. If russ-wattes' calcs are correct I think it would have produced much more damage to the ship

 

[sophiecentaur]

Please don't do that; it's very inappropriate.

Are you saying that it's not a money problem? (Or that there's no parallel.) It would have been quite possible (albeit expensive) to avoid collisions with the bridge piers. OR, the decision could have been made to site a bridge elsewhere. That tragedy will go down in history and affect every subsequent major bridge installation. Those few seconds of video will play in the minds of all designers and investors and may /should change the culture. Normally, Investors Rule. (And the mayor of Amity)
Air travel is the highest profile but. even there, the cost / risk calculations sometimes get it wrong. Who cares about the the idea of a bridge collapsing until they see it actually happen. The whole view of risk is based on experience; certainly, in UK, a road junction is not considered to be dangerous until someone dies.

I was thinking more how could a massive cargo ship collide with a bridge?

Going too damn fast and without tugs (apparently). Money money money.

 

[phinds]

Going too damn fast and without tugs (apparently).

It is absolutely standard practice that once a ship leaving harbor is clear of the docks and under its own power in a clear channel, tugs leave the ship. That may change as part of the fallout of this investigation but nothing was done improperly in this case.

 

[Bystander]

https://en.wikipedia.org/wiki/List_of_bridge_failures
Statistically inevitable; rate(s) of collapse(s)/catastrophe(s) vs. global population/trade/economy look to be down? Up? Same?

 

[sophiecentaur]

but nothing was done improperly in this case.

That's probably right. However, this experience should perhaps be taken as a lesson - as with the Space Shuttle. It took a long time for people to come clean about causes of those accidents.

 

[russ_watters]

I know it does not seem rational, but the volume of black smoke looked to me like a main engine restart, not one of the much smaller diesel generators being started.

For reference the main engine is 10x the size of the generators. Agree, it did seem like a lot of smoke.

When they lost steering, did they ring "Full astern" to reverse the main engine, and so slow the ship. That would explain the volume of black smoke.

Maybe but I doubt it unless they had engine but not (electronic) steering control. In reverse you lose steering control (due to loss of flow over the propeller).

 

[Borg]

Maybe but I doubt it unless they had engine but not (electronic) steering control. In reverse you lose steering control (due to loss of flow over the propeller).

Wouldn't the flow just be reversed? If not, my online games are messed up when I back up.

 

[Baluncore]

In reverse you lose steering control (due to loss of flow over the propeller).

Did you mean loss of flow over the rudder?

 

[Bystander]

For reference the main engine is 10x the size of the generators. Agree, it did seem like a lot of smoke.

Maybe but I doubt it unless they had engine but not (electronic) steering control. In reverse you lose steering control (due to loss of flow over the propeller).

Wouldn't the flow just be reversed? If not, my online games are messed up when I back up.

Did you mean loss of flow over the rudder?

Free-wheeling, or not free-wheeling?

 

[gmax137]

tugs

Just curious, can tugboats alter the course of a ship this massive once it's moving at 8 to 10 knots?

 

[russ_watters]

Wouldn't the flow just be reversed? If not, my online games are messed up when I back up.

Did you mean loss of flow over the rudrudder

Yes, the issue is loss of flow over the rudder due to the propeller being in front of it and also pushing the water opposite the motion of the ship. I'm not sure the numbers exactly but say the ship is moving 10kts and adds 10kts to the water, for 20kts over the rudder.

In reverse it would be 10-10=0.....with a lot of extra complications.

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

My one big bug bare with SS06 & 08 is the fact that the ships steer astern. This is totally unrealistic and does not happen in real life and big ships.

For a rudder to be effective it needs a flow of water over it. The prop is positioned infront of the rudder for this reason. When going astern there is minimal direct flow over the rudder which means a vessel would not readily steer.

 

[russ_watters]

Free-wheeling, or not free-wheeling?

What do you mean by free-wheeling?

 

[russ_watters]

Just curious, can tugboats alter the course of a ship this massive once it's moving at 8 to 10 knots?

Unsure. Tugboats are designed to provide a large propulsive force at very low speed. How they would do at for them relatively high speed is tough to know. I suspect no.

It's been a while so I'm not sure if I'm remembering correctly but if memory serves some ports require a tug to be alongside even if not hooked up, for a certain amount distance away from the dock.

 

[russ_watters]

The other thing about reverse thrust is that a single screw fixed pitch prop ship like this one won't go instantly from forward to reverse. It's kind of like a car in that you have to stop the prop/wheels and then change gears to go into reverse. I'm not sure how long that takes. The warship I helmed had two variable pitch screws and could instantly go from full ahead to full astern. It is like a helicopter versus a cargo plane.

 

[phinds]

I'm not sure how long that takes.

I remember reading that for the biggest cargo ships it takes about a mile to go from cruising speed to full stop. Don't recall what it was in minutes, but I'm sure it's a few at least.

EDIT: and I note that it is an assumption on my part that this means a powered stop, not just cruising to a stop.

 

[russ_watters]

I remember reading that for the biggest cargo ships it takes about a mile to go from cruising speed to full stop. Don't recall what it was in minutes, but I'm sure it's a few at least.

I'm talking about ahead thrust to reverse thrust.

 

[gleem]

Container ships cruise at about 20 to 25 kts. If they stop in one nautical mile it would take about 70 seconds at 25 kts. The DALI was supposedly traveling at 8 kts. If it has a single rt hand propeller is full reverse the bow would turn to starboard which seems to be the case in the video.

 

[Bystander]

What do you mean by free-wheeling?

Spinning as a result of water movement, a la, helicopter auto-rotation following power/engine loss.

 

[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.