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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

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 maybe I prefer my previous state of ignorance, to be quite honest....

hgomersall 3y ago
An earth buffer is just a bigger pier.
kamaal 3y ago
>>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 impact. I think at some point you are better off solving these issues with more regulation(smaller ships)? Instead of treating this as a engineering problem.
- unsupp0rted 3y ago
  It wouldn't take as much of a buffer to redirect the ship at an angle away from the pillar, would it?
  - kergonath 3y ago
    I think this would be even harder. Whilst the ship has a lot of kinetic energy that needs to get dissipated, it also has a huge momentum that needs to be partly overcome to redirect it. You’d also need a material with enough structural strength to turn the ship. Materials that can crumple or deform (like huge concrete blocks or earthworks) are great at dissipating energy, but they aren’t great at deflecting things.
- mannykannot 3y ago
  > 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 frequent enough that this should not have been dismissed as a low-probability event.) https://www.cnn.com/2022/03/16/business/evergreen-container-ship-grounded/index.html https://www.cnn.com/2022/03/16/business/evergreen-container-... In this case, the nearby towers supporting transmission lines across the channel seem to be better-protected against ship collisions than the piers of the bridge. https://images.app.goo.gl/J6vTeDW5xjysbdjr9 https://images.app.goo.gl/J6vTeDW5xjysbdjr9
  - rkagerer 3y ago
    What's needed is the will to do something about low-probability but catastrophic events In general I share your sentiment society could do more to insure itself against lower-probability catastrophes. But overbuilding every bridge would probably cost more than rebuilding the occasional one that's taken out when an unusual event like this occurs. Maybe in a different environment that would make sense, like a warzone (although I think even then there's more tendency to rely on redundant infrastructure and mobile, power-at-a-point defense).
  - deleted 3y ago
    [deleted]
  - throwaway48476 3y ago
    The "berm" in this case happens to be the seabed of the earth. There's nothing bigger.
    - mannykannot 3y ago
      Of course - but it doesn't take all of it...
  - bmelton 3y ago
- deleted 3y ago
  [deleted]
Reason077 3y ago
When Florida's Sunshine Skyway bridge was partly collapsed by a similar incident in 1980, the replacement bridge was built with a series of "structural dolphins" and concrete barriers to protect against ship strikes. You can see them in the image linked below: https://en.wikipedia.org/wiki/Sunshine_Skyway_Bridge#/media/File:Skyway_Bridge_old_and_new.jpg https://en.wikipedia.org/wiki/Sunshine_Skyway_Bridge#/media/...
- WarOnPrivacy 3y ago
  > the replacement bridge was built with a series of "structural dolphins" and concrete barriers to protect against ship strikes. Given how the Skyway collapse is burned into the local consciousness, I suspect some of the benefit comes from their visibility. I truly don't know how the dolphins would fair against a massive ship strike but I can imagine them doing their job. (ship passing): https://pbs.twimg.com/media/FPgQhy2X0AE8yw1.jpg https://pbs.twimg.com/media/FPgQhy2X0AE8yw1.jpg
  - tomatotomato37 3y ago
    I would also add those barriers seem to depend on the ship staying intact during collision. Given the immense inertia involved on the bigger ships I could just as easily see a scenario where the barrier ends up ripping through the lower hull while the rest of the ship continues forward.
    - krisoft 3y ago
      > easily see a scenario where the barrier ends up ripping through the lower hull while the rest of the ship continues forward I don’t think that is likely? My intuition is that in order to stay seaworthy ships are constructed with more integrity than that. I don’t have any hard evidence though, just that I have looked at many ship collision/allision aftermath photos and what you describe is not a failure mode I have seen so far.
      - semireg 3y ago
dathinab 3y ago
In smaller channels and similar it's not that uncommon to have crash barriers. For example in many Berlin channels and rivers. And while I'm not quite sure what it is for the bridge had concrete pillars orthogonal in front of the pillars (this picture shows them well, to be clear I do NOT mean the power line isles: https://www.upi.com/News_Photos/view/upi/7191ba50f17c5a683077417c69ff53c7/Francis-Scott-Key-Bridge-collapses-in-Baltimore/ https://www.upi.com/News_Photos/view/upi/7191ba50f17c5a68307...). They would have stopped the ship if it would have went orthogonal to the bridge (i.e. if they mistook where the pillar where in a otherwise normal situation). Through not sure if that was the purpose of them.

hgomersall 3y ago

An earth buffer is just a bigger pier.

kamaal 3y ago

>>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 impact. I think at some point you are better off solving these issues with more regulation(smaller ships)? Instead of treating this as a engineering problem.

unsupp0rted 3y ago
It wouldn't take as much of a buffer to redirect the ship at an angle away from the pillar, would it?
- kergonath 3y ago
  I think this would be even harder. Whilst the ship has a lot of kinetic energy that needs to get dissipated, it also has a huge momentum that needs to be partly overcome to redirect it. You’d also need a material with enough structural strength to turn the ship. Materials that can crumple or deform (like huge concrete blocks or earthworks) are great at dissipating energy, but they aren’t great at deflecting things.
mannykannot 3y ago
> 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 frequent enough that this should not have been dismissed as a low-probability event.) https://www.cnn.com/2022/03/16/business/evergreen-container-ship-grounded/index.html https://www.cnn.com/2022/03/16/business/evergreen-container-... In this case, the nearby towers supporting transmission lines across the channel seem to be better-protected against ship collisions than the piers of the bridge. https://images.app.goo.gl/J6vTeDW5xjysbdjr9 https://images.app.goo.gl/J6vTeDW5xjysbdjr9
- rkagerer 3y ago
  What's needed is the will to do something about low-probability but catastrophic events In general I share your sentiment society could do more to insure itself against lower-probability catastrophes. But overbuilding every bridge would probably cost more than rebuilding the occasional one that's taken out when an unusual event like this occurs. Maybe in a different environment that would make sense, like a warzone (although I think even then there's more tendency to rely on redundant infrastructure and mobile, power-at-a-point defense).
- deleted 3y ago
  [deleted]
- throwaway48476 3y ago
  The "berm" in this case happens to be the seabed of the earth. There's nothing bigger.
  - mannykannot 3y ago
    Of course - but it doesn't take all of it...
- bmelton 3y ago
deleted 3y ago
[deleted]

Reason077 3y ago

When Florida's Sunshine Skyway bridge was partly collapsed by a similar incident in 1980, the replacement bridge was built with a series of "structural dolphins" and concrete barriers to protect against ship strikes. You can see them in the image linked below: https://en.wikipedia.org/wiki/Sunshine_Skyway_Bridge#/media/File:Skyway_Bridge_old_and_new.jpg https://en.wikipedia.org/wiki/Sunshine_Skyway_Bridge#/media/...

WarOnPrivacy 3y ago
> the replacement bridge was built with a series of "structural dolphins" and concrete barriers to protect against ship strikes. Given how the Skyway collapse is burned into the local consciousness, I suspect some of the benefit comes from their visibility. I truly don't know how the dolphins would fair against a massive ship strike but I can imagine them doing their job. (ship passing): https://pbs.twimg.com/media/FPgQhy2X0AE8yw1.jpg https://pbs.twimg.com/media/FPgQhy2X0AE8yw1.jpg
- tomatotomato37 3y ago
  I would also add those barriers seem to depend on the ship staying intact during collision. Given the immense inertia involved on the bigger ships I could just as easily see a scenario where the barrier ends up ripping through the lower hull while the rest of the ship continues forward.
  - krisoft 3y ago
    > easily see a scenario where the barrier ends up ripping through the lower hull while the rest of the ship continues forward I don’t think that is likely? My intuition is that in order to stay seaworthy ships are constructed with more integrity than that. I don’t have any hard evidence though, just that I have looked at many ship collision/allision aftermath photos and what you describe is not a failure mode I have seen so far.
    - semireg 3y ago

dathinab 3y ago

In smaller channels and similar it's not that uncommon to have crash barriers. For example in many Berlin channels and rivers. And while I'm not quite sure what it is for the bridge had concrete pillars orthogonal in front of the pillars (this picture shows them well, to be clear I do NOT mean the power line isles: https://www.upi.com/News_Photos/view/upi/7191ba50f17c5a683077417c69ff53c7/Francis-Scott-Key-Bridge-collapses-in-Baltimore/ https://www.upi.com/News_Photos/view/upi/7191ba50f17c5a68307...). They would have stopped the ship if it would have went orthogonal to the bridge (i.e. if they mistook where the pillar where in a otherwise normal situation). Through not sure if that was the purpose of them.