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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

#561

Post by deltarholamda »

danpalmer wrote: post #501
bastardoperator wrote: post #494

Earlier quoted context omitted.

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.

It's somewhat counterintuitive how much energy can be in something moving so slowly. I say somewhat, because when you're up close it's much more obvious, but you're right that on a video it doesn't look like much.

This disconnect happens with boats quite a lot. For example, I can, by myself, pull a 45 foot grand banks trawler in shallow water. I know because I've done so.

But at even very low speeds, I cannot stop it from hitting a pier. I have not tried to do this, but every harbor master has a bunch of stories about people trying to do so and getting a leg or an arm or something squished and pulverized.

People who are not boat people rarely recognize these sorts of dangers, which is why so many get hurt on boats. "I can push us off the dock, so I can definitely keep us from hitting it." Nope, Sir Isaac Newton says you're wrong.

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

#562

Post by yourapostasy »

spenczar5 wrote: post #475
secstate wrote: post #442

Earlier quoted context omitted.

Does that mean this was effectively captain error? Like in response to a power outage the decision was made to try to reverse and rather than arrest forward momentum it just pushed their forward vector into the piling?

Captain, or pilot? In Baltimore, as in most harbors, a local pilot comes on board to guide the ship. Is this their responsibility?

This news report [1] confirms there were two pilots at the time of the accident. Baltimore Port runs a dock pilot from the Key Bridge to the port itself, and after the Key Bridge, a harbor pilot who takes the ship (I believe the rule is any vessel > 100 tons, and all non-domestic ships of any tonnage must by Maryland state law be piloted in this manner) out to the mouth of the bay.

The after-accident report and insurer and re-insurer wranglings will be a fascinating read, I'm sure. It will be a miracle if the taxpayers escape unscathed for the rebuilding of the transit spanning the harbor, and it falls entirely upon the insurers and re-insurers.

As dramatic as this accident was though, and the many parallels I can draw from its lessons to software engineering, IT operations, cybersecurity and so on, I'm not as sanguine believing it will really drive home to organization leaderships the evergreen advice to pay down your tech debt, maintenance matters, organizational culture/esprit de corps counts, the operational teams are just as important as the engineering teams, etc.

[1] https://fox59.com/news/national-world/cargo-ship-hits-baltim...

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

#563

Post by michaelt »

bmelton wrote: post #396
mannykannot wrote: post #283

Earlier quoted context omitted.

> But any preventive measure will have limits as what and how serious an impact it can deal with. The recent grounding of a large container ship in Baltimore's harbor channel demonstrates that a sufficiently massive berm will stop any ship. What's needed is the will to do something about low-probability but catastrophic events (though large-ship collisions, groundings and fortuitously harmless steering failures are f…

Starting from xoa's calculations above, assuming you can pack a berm with well-compacted soil enough that it can absorb 1,000 joules per cubic meter, you'd need a buffer of something like 10 meters surrounding each piling with 3 meters of depth to keep it safe from this kind of impact. That's 10 meters in every direction from the center of the support -- let's assume the support has a thickness of 0 meters for the sa…

> acknowledging that the gaps between structural supports on the bridge is approximately 30 meters

Measuring a satellite image in Google Maps [1] tells me the bridge's central span is more than 300 meters.

[1] https://maps.app.goo.gl/SzAzuzQRUwW7s2gN8

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

#564

Post by dweymouth »

throw0101b wrote: post #551
danpalmer wrote: post #501

Earlier quoted context omitted.

It's somewhat counterintuitive how much energy can be in something moving so slowly. I say somewhat, because when you're up close it's much more obvious, but you're right that on a video it doesn't look like much.

> It's somewhat counterintuitive how much energy can be in something moving so slowly. Reminder: Kinetic Energy = ½mv^2 Squaring numbers can make them big in a hurry.

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.

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

#565

Post by bobthepanda »

throw0101b wrote: post #550
bastardoperator wrote: post #494

Earlier quoted context omitted.

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.

> 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. The bridge style in question > Conversely, continuous truss bridges rely on rigid truss connections throughout the structure for stability. Severing a continuous truss mid-span endangers the structure. However, continuous truss bridges do not experience the tipping force…

cable stays are also generally more popular these days because of the differences in material. All other things being equal, concrete is generally a lot cheaper than a steel truss bridge these days

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

#566

Post by culebron21 »

jcgrillo wrote: post #555
araes wrote: post #541

Earlier quoted context omitted.

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…

I'm not sure what configuration of props a ship like this has, but in my experience with a 40ft sailboat with a single propeller you have absolutely no rudder authority while reversing. I've read that some large ships also are direct drive--there's no transmission between the engine and the propeller, so "reversing" (if it's even possible) entails shutting down the engine and restarting it in reverse. This can be don…

This reminded me of an old physics book I read where author claimed that Titanic also lost rudder control and yawed because of full reverse.

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

#567

Post by [deleted] »

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.

[deleted]

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

#568

Post by paddy_m »

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…

On ships like this the propulsion is separate from the steering. There is a separate rudder that is close to, but not attached to the prop and propshaft. The propshaft is fixed. The rudder doesn't just "restart in a random position" it would remain in the previous position unless there was a physical piece that broke in the rudder gear.

The fact that ship was able to reverse hard ( as evidenced by the slowdown), indicates to me that the prop was most likely still attached to the propshaft and hadn't flown off to mangle the rudder.

We still don't know exactly what happened on board, but it is interesting to work through possible scenarios.

Pilots certainly have experience with ship handling of 100,000 ton ships, that's their job. Pilots coordinate the moves of multiple tugs to assist with docking regularly.

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

#569

Post by rayiner »

throwanem wrote: post #436
mikeyouse wrote: post #414

Earlier quoted context omitted.

In Philly, they sacrificed some of the road underneath it and narrowed the traffic lanes over the bridge to enable a very quick, albeit temporary repair. There’s no such option for a span of this length over a river — this is a decade long project that could potentially be sped up to be a years long one.

Sure, 5-10 years makes sense especially considering it took 5 years to build last time. But GP's formulation seemed to suggest a considerably longer expectation, and that's more what I was wondering about.

I would be shocked if it was rebuilt in less than a decade. The Frederick Douglass bridge that opened recently in DC took 15 years. That’s a long time for Baltimore to be without a key piece of infrastructure.

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

#570

Post by supportengineer »

jcgrillo wrote: post #555
araes wrote: post #541

Earlier quoted context omitted.

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…

I'm not sure what configuration of props a ship like this has, but in my experience with a 40ft sailboat with a single propeller you have absolutely no rudder authority while reversing. I've read that some large ships also are direct drive--there's no transmission between the engine and the propeller, so "reversing" (if it's even possible) entails shutting down the engine and restarting it in reverse. This can be don…

No variable-pitch propeller?
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