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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

#141

Post by jack_riminton »

lukan wrote: post #105
jack_riminton wrote: post #99

Earlier quoted context omitted.

I like this quote. We have a medieval bridge near to our house (1000 years old perhaps), it's incredibly solidly built, but could you call it well-engineered? It's a subtle distinction that I don't think many in the digital realm quite grasp either i.e. far too many over-engineered technical solutions for features and products that aren't even desired

"but could you call it well-engineered" If it is still standing after 1000 years, I would say yes. You cannot build a bridge out of stones with bad engineering - it would collapse under its own weight. edit: does "well engineered" now means over engineered to some?

"If it is still standing after 1000 years, I would say yes" but what if they included far more material in areas where it wasn't needed, skimped on other areas and it fell down tomorrow? It's almost a philosophical question, and it's true that the bridge builders happened across a solid design by accident.

But I think the true definition of engineering has to encompass a level of efficiency through design, calculation and rationalization. In other words, echoing what the original commenter said, including only what is barely necessary.

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

#142

Post by dist-epoch »

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…

People love bridges which look sleek, thin and like air. They are also cheaper (less materials). But this means there is no redundancy left.

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

#143

Post by Symbiote »

yieldcrv wrote: post #122
jillesvangurp wrote: post #110

Earlier quoted context omitted.

I just watched the footage. It's pretty horrifying. The whole bridge collapsed in a few seconds. It's a pretty long drop down to the water. Anyone on that bridge ended up in the water with little/no warning. That drop alone would injure/kill many. And immediately after people would be in cold water still locked in their vehicles. The water there was deep enough to be able to deal with loaded container ships. So, tens…

from what I can tell it didn't look like vehicles, it looked like road maintenance, so people outside and maybe a vehicle. only difference is not trapped in vehicle, everything else still dire

There's a slight benefit that a road crew will be dressed for nighttime outside weather, with reflective clothing, are all adults, and probably have some level of physical fitness.

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

#144

Post by dredmorbius »

testfoobar wrote: post #10

You can look back on the livestream here to see the collision and collapse. https://www.youtube.com/watch?v=83a7h3kkgPg

Clip here, beginning at 1m23s, shows a (sped-up) edit of the ship approaching the bridge, with lights going out, on, and out again immediately prior to impact:

https://yewtu.be/watch?v=Cs6PrRiIHEw&t=1m23s>

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

#145

Post by lukan »

jack_riminton wrote: post #141
lukan wrote: post #105

Earlier quoted context omitted.

"but could you call it well-engineered" If it is still standing after 1000 years, I would say yes. You cannot build a bridge out of stones with bad engineering - it would collapse under its own weight. edit: does "well engineered" now means over engineered to some?

"If it is still standing after 1000 years, I would say yes" but what if they included far more material in areas where it wasn't needed, skimped on other areas and it fell down tomorrow? It's almost a philosophical question, and it's true that the bridge builders happened across a solid design by accident. But I think the true definition of engineering has to encompass a level of efficiency through design, calculatio…

"and it's true that the bridge builders happened across a solid design by accident"

Or by experience and learning from other sucessful bridges? Stone bridges were not new in the year 1000.

There is a roman bridge that was allmost completely surviving all this time, till it was blown up in WW2:

https://en.m.wikipedia.org/wiki/Ponte_Pietra_(Verona)

If they wanted a cheap solution, they would have used wood. But wood does not last a 1000 years.

Personally I salute anyone, who can build something that lasts that long.

"including only what is barely necessary."

And "barely necessary" in solid engineering includes lots of safety margins. Not barely standing.

And yes, that includes not using more than you need, because the more material you use, the heavier your bridge is -> the greater are the forces on the structure itself even with no one passing over it.

There are some fun games out there on various plattforms, google "bridge builder"

Not a scientific simulation of course, but they do show the concept.

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

#146

Post by cafard »

ohyes wrote: post #22

Apparently there were two different key bridges, one across the Potomac, another across the Patapsco. This was the Patapsco one.

The Potomac River is pretty shallow where the Key Bridge crosses between the Georgetown neighborhood of Washington, DC, and Rosslyn neighborhood of Arlington County, Virginia. The largest facilities upstream of it are boathouses, where one may put in a canoe or perhaps a racing shell.

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

#147

Post by mvdtnz »

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…

Not unlikely? Can you point us to all the other times this has happened? You must know of several given your knowledge of how obviously likely this is.

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

#148

Post by hiddencost »

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.

I don't think that's quite right. People in Dundalk will suffer a fair bit, as will folks in Glen Burnie and Annapolis, but most people are going from DC to Delaware, and go north rather than over the Key bridge.

I think this is most harmful for commuters.

Blocking the Baltimore harbor is brutal although I suspect the passage will be cleared as quickly as possible.

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

#149

Post by vertis »

gonzo41 wrote: post #125
mkl wrote: post #82

Earlier quoted context omitted.

Not all bridges are this vulnerable to a single impact. This one, opened 12 years earlier, has a different style and mostly survived a cargo ship impact: https://en.wikipedia.org/wiki/Tasman_Bridge_disaster

Hobart learned its lesson. You can't drive over the bridge when heavy ships sail under it.

I fell down reading about all the ships that have hit bridges, and this is probably the most practical solution for a lot of scenarios.
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