Baltimore's Key Bridge struck by cargo ship, collapses • Hacker News Board

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

#161

Post by _giorgio_ » Tue, Mar 26, 2024, 10:37 AM UTC

4gotunameagain wrote: post #100

_giorgio_ wrote: post #81

Earlier quoted context omitted.

The problem is the static scheme of the bridge. Most modern bridges are hyperstatic: if you remove one support, it still stands. Or at least isostatic: you remove one support or one span, and nothing happens to the nearest ones. This bridge was ill conceived: you remove one support or span, and it brings down everything like a chain that pulls down everything it's linked to. It's bad because the "engineer" just wante…

You cannot put the entire weight of the 70's safety culture to an engineer "showing off" I bet there was a much more complex and nuanced analysis which included crossing ship dimensions, budget, time to completion, available technology, composition of the local seabed etc.. Designing a bridge is proper engineering and not that easy.

Believe me, an engineering student that sees that, immediately understands the problems after taking the first science of construction lessons.

You do need need the truss at all. If the truss fails (in any of the three spans), it brings down two adjacents spans.

It's just a show off.

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

#162

Post by fl7305 » Tue, Mar 26, 2024, 10:40 AM UTC

whizzter wrote: post #118

mkl wrote: post #103

Earlier quoted context omitted.

Parts of the Francis Scott Key Bridge not connected to the hit pylon went down too. The beam structure above the road that supports the whole thing collapsed and took down other spans.

And that structure probably existed because the bridge has fewer longer spans, probably since the seabed below the bridge is deeper (and needs to be deeper to support container ships passing below). The Öresundsbron (connecting Sweden and Denmark) features both short segments but also with an overhand section in the middle for larger ships to pass through. (1) The great belt bridge (inside Denmark) is slightly higher…

Öresundsbron is claimed to be designed to be resistant against ships hitting it. They have placed artificial underwater reefs around the pylons. The pylons themselves can also take quite a beating.

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

#163

Post by CaptainBanger » Tue, Mar 26, 2024, 10:40 AM UTC

millzlane wrote: post #158

jxdxbx wrote: post #136

Not that it matters to anyone else, but having driven across that bridge dozens of times with my kids, this is just shocking. It’s one of the main corridors in the area. Thank god it happened in the middle of the night, though that’ll be no consolation to the families of those who may have died.

Local to the area. This was devastating news to wake up to. I don't know what's wrong with me but seeing this and knowing there were casualties made me cry. Edit: Maybe I'm just tired and need more sleep.

No shame in feeling human friend

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

#164

Post by mcv » Tue, Mar 26, 2024, 10:41 AM UTC

317070 wrote: post #155

armchairdweller wrote: post #133

Earlier quoted context omitted.

Thanks! So why are huge—ass container ships allowed to navigate underneath fragile public bridges with single points of failure? The not unlikely worst case is that the ship is out of control for some reason…

If bridges and container ships indeed do not go together (something I don't necessarily agree with), you probably want to take away the public bridge and continue to let ships go by. This is economically speaking for the area. Car traffic is just not very efficient in the comparison between the two. Edit: of course there are a ton of other solutions here as well. I am disagreeing with the parent that it is the cars w…

You can have smaller container ships. Or have the port outside the bridge. Or indeed replace the bridge with a tunnel, or a better bridge.

Amsterdam has no bridges at all crossing the IJ on the west side (where sea-going ships come from) and only a single bridge on the east side (though there's often talk of adding another). Everything is tunnels.

Rotterdam has bridges (including the famous Erasmusbrug), but only east of the port area. To the west, everything is tunnels. And the largest ships don't even come close to the city center, but dock at the Maasvlakte out at sea.

For both cities, ports have constantly moved closer to the sea.

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

#165

Post by mcv » Tue, Mar 26, 2024, 10:44 AM UTC

rpeden wrote: post #153

armchairdweller wrote: post #133

Earlier quoted context omitted.

Thanks! So why are huge—ass container ships allowed to navigate underneath fragile public bridges with single points of failure? The not unlikely worst case is that the ship is out of control for some reason…

Because the Port of Baltimore is a very major port, and not allowing ships under it really isn't an option. Vertical clearance for ship traffic might have been the reason this kind of bridge was built in the first place. Otherwise, something lower and more causeway-like might have been sufficient.

If it's a very major port, they can afford to make it a tunnel.

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

#166

Post by cool_dude85 » Tue, Mar 26, 2024, 10:44 AM UTC

TaylorAlexander wrote: post #66

Somehow 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…

The Mathews Bridge in Jacksonville was clipped by a container ship a few years back and did not collapse. Despite being almost 75 years old, they fixed it up and it opened back up after a year or two. The difference is that the boat did not hit a pylon.

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

#167

Post by mcv » Tue, Mar 26, 2024, 10:45 AM UTC

bombcar wrote: post #138

armchairdweller wrote: post #133

Earlier quoted context omitted.

Thanks! So why are huge—ass container ships allowed to navigate underneath fragile public bridges with single points of failure? The not unlikely worst case is that the ship is out of control for some reason…

Because bridges over harbors are quite common an incidents like this are rare.

The Dutch ports of both Amsterdam and Rotterdam have no bridges at all. It's all tunnels. I think that's the best way to go; the least chance of conflict between road and water traffic.

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

#168

Post by rpeden » Tue, Mar 26, 2024, 10:46 AM UTC

dvh wrote: post #116

Could this be cyber attack? On the video the ship goes normally straight under the bridge, then does sharp turn right and for 20s or so goes directly into the pier.

Anything's possible, but a ship losing steering control is not that uncommon.

This just happened at a particularly bad time and place.

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

#169

Post by LargoLasskhyfv » Tue, Mar 26, 2024, 10:46 AM UTC

armchairdweller wrote: post #133

onetimeuse92304 wrote: post #124

Earlier quoted context omitted.

Most bridges nowadays (say last century) depend on a careful balance of forces that are transferred through a chain of members in tension and compression. When any piece in the chain of those forces breaks, the entire structure loses ability to transfer forces and breaks. This arrangement is what allows us to build these structures in the first place. There is careful calculations of forces and risks and allowance fo…

Thanks! So why are huge—ass container ships allowed to navigate underneath fragile public bridges with single points of failure? The not unlikely worst case is that the ship is out of control for some reason…

> out of control for some reason...

I think the whole ship went dark for a moment. That may have had an impact on the rudder, and then some strong current and/or wind, pushing it sideways.

Couldn't see tug-boats.

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

#170

Post by HlessClaudesman » Tue, Mar 26, 2024, 10:49 AM UTC

onetimeuse92304 wrote: post #124

TaylorAlexander wrote: post #66

Somehow 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…

Most bridges nowadays (say last century) depend on a careful balance of forces that are transferred through a chain of members in tension and compression. When any piece in the chain of those forces breaks, the entire structure loses ability to transfer forces and breaks. This arrangement is what allows us to build these structures in the first place. There is careful calculations of forces and risks and allowance fo…

On a long enough timeline we all get rammed by a container ship.

I would be interested to know some calculations with factors like: expected bridge lifetime, chance of being rammed per year, cost of making supports strong enough plus an extra safety margin to survive maximum ramming force, cost of having major commercial shipping route unusable for an extended period.