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Baltimore's Key Bridge struck by cargo ship, collapses

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Re: Baltimore's Key Bridge struck by cargo ship, collapses

#581

Post by ClumsyPilot »

paddy_m wrote: post #554
myself248 wrote: post #488

Earlier quoted context omitted.

At least in small craft, bow thrusters are usually electric, with local batteries charged from the main engine room. I don't know what large craft are like, but it doesn't seem unreasonable that a bow thruster may remain operable even if the main engine fails. Clearly that's not required or they would've had it and used it, but it could be required if the regulations didn't suck. Furthermore, steering could absolutel…

The difference for a car and drive by wire system is that the failure mode of control systems on cars is normally catastrophic and dangerous. If a car loses steering or brakes, it will hit something within seconds 95% of the time. That ship spent 1 (4:30 to 5:30) hour of a presumably 10-20 day voyage in a critical control section. The tugs left the ship right around 5:08 (43 seconds into the video). A much better pol…

Damage is less likely, but much more destructive. Same as for a nuclear reactor.

It’s not clear why adding ~$100k to the cost of a billion dollar ship is unreasonable

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#582

Post by trilbyglens »

jordanb wrote: post #495
ianburrell wrote: post #482

Earlier quoted context omitted.

It wouldn't help with this accident, but you would think that the electronics would be on batteries. It wouldn't be too hard to have rack of batteries that would power the lights, instruments, radios, and sensors. Doesn't help if the propulsion or steering go out, but does make easier to know whats going on.

The problem is with steering. The rudder on a ship this big is going to be wall of steel several stories tall with gears as big as car. Warships have several independent backup steering options reducing finally to a worm gear at the top of the shaft with a winch handle big enough to put a gang of men on it. But ships like this will have none of that. They will have a small wheel or joystick on the bridge and if power…

Wouldn't a ship like this have bow thrusters? Seems like otherwise it would be impossible to get into port without a tug.

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#583

Post by KoftaBob »

btbuildem wrote: post #338
tokai wrote: post #285

Insane that the pylons wasn't protected by artificial islands.

If you think about this for a minute, you'll realize that what you're asking for is pretty much impossible. What would these artificial islands be made of? Sand, gravel, concrete rubble? This is a river, the constant current of the water erodes anything that resists it by staying in place. Piling up enough material to resist erosion and create a meaningful obstacle to 70000 tonnes in motion, that would significantly…

There are real world examples of what it would look like, they're called "dolphins": https://en.wikipedia.org/wiki/Dolphin_(structure)#/media/Fil...

"The new bridge is protected by 36 dolphins: four large dolphins protecting the two main pylons supporting the cable-stayed main span plus 32 smaller dolphins protecting bridge piers for 1⁄4 mi (1⁄2 km) to either side of the main span"

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#584

Post by KoftaBob »

btbuildem wrote: post #395
tokai wrote: post #377

Earlier quoted context omitted.

I have thought about it for hours by now, and read literature on the matter. It is definitely possible to build berms that protects a bridge from catastrophic failure in case of a ship collision, and it is widely done during modern bridge construction. Please be less sure of yourself when you clearly don't have any actual knowledge on the subject.

I'd love to see a few examples, since you're so versed on the subject. I'm not a civil engineer by any means, but I imagine the people who designed and built that bridge knew what they were doing. There are likely limitations imposed by the site bathymetry and other things we don't know about. You can get a good look at the aftermath here: https://www.youtube.com/watch?v=WssFXRzRVLU I'll be interesting to see how the…

There are real world examples of what it would look like, they're called "dolphins": https://en.wikipedia.org/wiki/Dolphin_(structure)#/media/Fil...

"The new bridge is protected by 36 dolphins: four large dolphins protecting the two main pylons supporting the cable-stayed main span plus 32 smaller dolphins protecting bridge piers for 1⁄4 mi (1⁄2 km) to either side of the main span"

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#586

Post by moritonal »

bastardoperator wrote: post #494
paddy_m wrote: post #438

Youtube tracking analysis from a knowledgeable mariner. He says that at about 1:24 AM the ship loses power (from video feed) while traveling 8.5 knots. at 1:25.30 power is restored. at 12:25.59 the ship shows smoke. The ship has already drifted in the channel. It is believed that at this time the ship applied full reverse power as evidenced by the black smoke. (My analysis: the ship drifted but hasn't turned in the c…

The video is surreal, it looks like it barely bumps the bridge and 2 seconds later the entire thing is gone. I don't know what I was expecting, the bridge just looked extremely fragile, makes me wonder what other bridges are at risk of an event like this.

When you play about with game engines long enough, you start to realise that momentum is the key metric to track rather than speed. Especially in water magnitude can be very deceiving but to give some quick math, this vessel had a momentum at impact of about 154,000,000kg⋅m/s. For a car to have equivalent momentum it'd have hit the bridge at 156,580 mph. Humans are just less adept at appreciating mass vs velocity.

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#587

Post by lotu »

araes wrote: post #541
paddy_m wrote: post #438

Youtube tracking analysis from a knowledgeable mariner. He says that at about 1:24 AM the ship loses power (from video feed) while traveling 8.5 knots. at 1:25.30 power is restored. at 12:25.59 the ship shows smoke. The ship has already drifted in the channel. It is believed that at this time the ship applied full reverse power as evidenced by the black smoke. (My analysis: the ship drifted but hasn't turned in the c…

Current personal suspicion after watching your linked video (excellent discussion by the wgowshipping author) is: Catastrophic engine failure (1:24) causing wide scale power loss. No rudder control, rudder drift, and ship alignment drift (1:24-1:25:30) Power restored and ship reengages prop with bad ship/ruddder alignment (1:25). However, ship is now pushing itself into a further bad turn. Pilot likely stomps the bra…

> How many pilots, trained or not, really have any experience with a 100,000 ton ship in a crash situation with responses where seconds matter?

I would expect anyone piloting such a ship in a harbor/under bridges. We requite airline pilots to train for many unlikely plane failures because the alternative is letting planes crash that we could have saved with better training.

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#588

Post by boringg »

paddy_m wrote: post #438

Youtube tracking analysis from a knowledgeable mariner. He says that at about 1:24 AM the ship loses power (from video feed) while traveling 8.5 knots. at 1:25.30 power is restored. at 12:25.59 the ship shows smoke. The ship has already drifted in the channel. It is believed that at this time the ship applied full reverse power as evidenced by the black smoke. (My analysis: the ship drifted but hasn't turned in the c…

How much of this is falls on the protocols of the shipping company? I.e. the same shipping companies that gouged the planet during covid - did they strip away safety protocols in order for profits/expediency?

Is this similar to Boeing for the shipping world? I realize it is early to come to any conclusions.

The question of this being a rare one off vs container companies deprioritizing safety protocols is what I am interested. The power failures make me go down this logic of thought.

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#589

Post by rtkwe »

trilbyglens wrote: post #577
dweymouth wrote: post #564

Earlier quoted context omitted.

But in this case with slow speed, it's the massive (literally) amount of mass of the cargo ship that gives it an un-intuitively large amount of energy.

8kn isn't super slow

It's 10 mph which is pretty slow as speeds go.

Re: Baltimore's Key Bridge struck by cargo ship, collapses

#590

Post by corobo »

card_zero wrote: post #139
corobo wrote: post #41

Earlier quoted context omitted.

"I can't do much else, may as well keep folks up to date" I guess. If they're sitting on the shore with a fully stocked rescue boat delaying help to post their edits, aye I'd be peeved too. Otherwise, might as well keep info updated as it becomes known. One of the beauties of the internet is that there's enough people willing to do the work to keep the rest of the world up to date with real-time information. Chances…

It was somebody on their phone, not signed in, and all they did was change "is" to "was" in two places, leaving the single word edit summary "was". But thank you for imagining Wikipedians are so professional.

Thank you for the clarification.

Not sure I understand the snarky turn at the end there but I imagine I'm just lacking whatever context you have! No problem :)

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