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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

#171

Post by ThrustVectoring »

mcv wrote: post #164
317070 wrote: post #155

Earlier quoted context omitted.

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 eas…

You don't even need to run it as a tunnel the entire way through - Chesapeake Bay has vehicular traffic routed through a combination bridge/tunnel, using tunnels to span the two major shipping channels crossed by the complex.

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

#173

Post by Tanoc »

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.

The '70s were also a transitional period in bridge design where truss bridges were being phased out in favour of newer types of hybrid suspension bridge. Many of the iron and steel bridges of the 1890s through the 1970s were later replaced with suspension bridges or arch span bridges because they used less material and could be architecturally adapted to the area better. So some truss bridges were made as much for appearance as function in order to compete with the futuristic hybrid suspension bridges like the 1967 Ponte Morandi or the 1987 replacement Sunshine Skyway.

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

#174

Post by xienze »

mcv wrote: post #156
roenxi wrote: post #134

Earlier quoted context omitted.

It is worth observing that this bridge seems to have 2 pylons and one of them collapsed. The failure seems comprehensible after that - you can see in the video how the balances came apart, there is nothing to hold the left side up so it falls and then remainder of the bridge tried to rotate around the remaining pylon and failed.

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’t happen in this case.

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

#175

Post by jrwiegand »

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.

That was my exact thought. Thankfully, I woke up to messages that my family members were safe and sound. I hope they find everyone but at this point it seems unlikely.

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

#177

Post by adestefan »

mcv wrote: post #165
rpeden wrote: post #153

Earlier quoted context omitted.

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.

There already are two tunnels for I-95 and I-895 under the port.

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

#178

Post by jrwiegand »

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.

It is shocking and that does not sound like an inappropriate response.

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

#179

Post by keenmaster »

mcv wrote: post #167
bombcar wrote: post #138

Earlier quoted context omitted.

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.

Often in America the government waits for something to fail miserably before engaging in a high effort high cost activity that requires a lot of coordination and public buy-in.

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

#180

Post by ithkuil »

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…

“Any idiot can build a bridge that stands, but it takes an engineer to build a bridge that barely stands.”

And in practice only bridges that "barely" stand are economically viable

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