It was hit by a container ship https://www.nytimes.com/2024/03/26/us/ship-hits-baltimore-ke... That's gonna be expensive.
And more importantly, distressing for the people who lost loved ones.
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Baltimore's Key Bridge struck by cargo ship, collapses
311–320 of 1001 posts
Re: Baltimore's Key Bridge struck by cargo ship, collapses
#312Somehow I find it surprising how completely the bridge collapsed after the damage. I understand that a container ship collision is serious, but you could imagine a scenarios where the bridge slumps or buckles but doesn’t just disintegrate like that. It’s surprising that ships capable of doing this damage were probably regularly driving past it, and its safety as a thoroughfare depended entirely on those collisions no…
I don’t drive boats or around water much but I’ve seen “bumpers” on bridge pylons before that make a collision more of a glancing blow and guide the boat to the side. I guess there wasn’t any installed on this bridge? Also, someone on Imgur pointed out that when this bridge was built boats that large weren’t a risk. That may or may not be true but sounds plausible.
Re: Baltimore's Key Bridge struck by cargo ship, collapses
#313Earlier quoted context omitted.
It certainly does not seem reasonable to design a bridge pillar to withstand a direct impact from a massive cargo ship. But I guess I thought that maybe there was... typically some kind of earthen buffer around the pillar to prevent such an impact? That's probably impractical too, I guess. I guess I just didn't realize ~$1bn bridges were one fluky ship accident away from total collapse at any given time. I think mayb…
>>But I guess I thought that maybe there was... typically some kind of earthen buffer around the pillar to prevent such an impact? It does look reasonable to have such a buffer. But any preventive measure will have limits as what and how serious an impact it can deal with. In this case the ship this massive is something that is carrying ridiculous inertia, and its highly unlikely even a buffer could stop such an impa…
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Re: Baltimore's Key Bridge struck by cargo ship, collapses
#314You can look back on the livestream here to see the collision and collapse. https://www.youtube.com/watch?v=83a7h3kkgPg
The lights on the ship were going off and on, and it appeared to be smoking before hitting the bridge. Does not look like they had much control at the time.
The dark smoke was most likely the diesel generator firing up to get some steering control back
Re: Baltimore's Key Bridge struck by cargo ship, collapses
#315Insane that the pylons wasn't protected by artificial islands.
I tend to agree, but also, what could one even do? I have seen videos of shipping containers going into the shore and they don't stop for a good hundred yards or more.
I don't know how they achieve it, but its best practise to protect bearing elements from collisions like this. There's like a whole subfield of bridge collision research.
Re: Baltimore's Key Bridge struck by cargo ship, collapses
#316Earlier quoted context omitted.
>>But I guess I thought that maybe there was... typically some kind of earthen buffer around the pillar to prevent such an impact? It does look reasonable to have such a buffer. But any preventive measure will have limits as what and how serious an impact it can deal with. In this case the ship this massive is something that is carrying ridiculous inertia, and its highly unlikely even a buffer could stop such an impa…
> 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…
The "berm" in this case happens to be the seabed of the earth. There's nothing bigger.
Re: Baltimore's Key Bridge struck by cargo ship, collapses
#317Earlier quoted context omitted.
At least in the links with the video now you can see that the container ship directly hits one of the two main (and in the central area only) pillars completely collapsing it. No matter(1) the engineering there is no pretty much way to not lose the whole large middle area and left area leading to the destroyed pillar in that situation. Such a collapse crates so much force (tension vibrations etc.) so that the collaps…
Just to put some numbers on this: The MV Dali (IMO#9697428) is a little over 95000 GT, or ballpark-ish probably around 114000 tons loaded (and it seems to have been loaded, which would make sense on departure). If it was going even 5kn (2.6 m/s) that'd be about 300 million newton-seconds, or about 3.3 times the momentum of a large jumbo jet like a 747 shortly at cruising speed (around 560 mph). It'd still have the sa…
> enormously massive objects moving very slowly messes with human perception and "common sense"
Yes, hence warnings to amateur boat users (e.g. on a canal boat) not to try to stop a collision with the bank using your arms or legs.
[Edit] Boats can also do things that are unintuitive if you are used to driving a car. E.g. turning round the centre of gravity when you steer rather than following the front wheels.
Re: Baltimore's Key Bridge struck by cargo ship, collapses
#318Earlier quoted context omitted.
Bridges only last for roughly 50 years. Considering such collisions are rare enough to make the news as a memorable event you can workout for yourself that the odds are quite low over a bridges lifespan. They are designed to withstand smaller boat impacts because they occur relatively frequently, but cost vs benefit on rare events that are difficult to mitigate is quite different.
> Bridges only last for roughly 50 years. The bridge projects I've been on spec 75 or 100 years. Main difference is better protection/sacrificial depth on ferrous members.
I remember one of my engineering lecturers giving a good rule of thumb as “your retirement date, plus 10 years”
Re: Baltimore's Key Bridge struck by cargo ship, collapses
#319Earlier quoted context omitted.
Interested in this claim, because it sounds about right, except that I can’t name a bridge constructed in the past 50 years. The bridges we can all name are pushing 100+ right?
New York City has had two major recent new bridge replacements that probably about 20M people can name: the Mario Cuomo (formerly Tappan Zee) and the Kosciuszko bridge. I’d argue the Bayonne Bridge raising kinda counts since it was almost a rebuild and more impressive in many ways since it stayed open the whole time. Meanwhile in the San Francisco Bay Area they replaced the Bay Bridge…
The eastern span of the Bay Bridge, which had previously been a cantilever bridge, which was damaged during the 1989 Loma Prieta Earthquake, and shown to have quite obvious seismic deficiencies.
Its replacement is a self-anchored suspension bridge.
The original western span, actually a double suspension bridge, remains standing, as constructed in 1933, 91 years ago.
Re: Baltimore's Key Bridge struck by cargo ship, collapses
#320Earlier quoted context omitted.
It's no surprise that the entire bridge collapses after a pylon collapses. What surprises me is that the pylon collapses. I'd expect those to be extremely solid, with tons of padding. But with ships getting bigger and bigger, I guess there's a limit to what you can account for.
Ships are hundreds of thousands of tons in weight and the momentum acts as a force multiplier. Plus it hit the pylon dead center, which is the worst case scenario. It’s not terribly surprising. I think there’s also an underlying expectation that any competent ship captain would at least be able to see that they’re on a collision course with the pylon well ahead of time and be able to compensate. Which obviously didn’…
The trajectory of the ship seemed near perfect right up until just before the bridge where I suspect it experience it's mechanical issue.