3 ms·

You can also look at the problem from the perspective of the bridge. Why was it possible that a ship took it down? Motors can fail ...

richardwhiuk 1y ago
It’s not realistically plausible to build bridges that won’t be brought down by that size of ship
- capyba 1y ago
  This, 100%. I forget the specific numbers but regardless, the kinetic energy of a thing with that much mass, even moving at a very slow speed, is off the charts. Designing a bridge or protections for a bridge to survive that would at a minimum be cost prohibitive, if even possible with today’s materials and construction technologies.
  - sitkack 1y ago
    Doesn't mean that nothing can be done. https://www.ntsb.gov/news/press-releases/Pages/nr20250320.aspx https://www.ntsb.gov/news/press-releases/Pages/nr20250320.as... > The NTSB found that the Key Bridge, which collapsed after being struck by the containership Dali on March 26, 2024, was almost 30 times above the acceptable risk threshold for critical or essential bridges, according to guidance established by the American Association of State Highway and Transportation Officials, or AASHTO. > Over the last year, the NTSB identified 68 bridges that were designed before the AASHTO guidance was established — like the Key Bridge — that do not have a current vulnerability assessment. The recommendations are issued to bridge owners to calculate the annual frequency of collapse for their bridges using AASHTO’s Method II calculation. Letters to the 30 bridge owners and their responses https://data.ntsb.gov/carol-main-public/sr-details/H-25-003 https://data.ntsb.gov/carol-main-public/sr-details/H-25-003
    - deleted 1y ago
      [deleted]
    - throwaway173738 1y ago
      This is essentially the same thing that happened with Fukushima Daiichi. The organization running it failed to respond to new information.
  - potato3732842 1y ago
    Energy doesn't mean squat without a time component over which it's dissipated. Stopping a car normally vs crashing a car. Skydiving with a parachute vs skydiving without a parachute. For something like ship vs bridge you have to account for the crunch factor. USS Iowa going the same speed probably would've hit way harder despite having ~1/3 the tonnage.
- potato3732842 1y ago
  Nah, we definitely can. Plan the bridge so any ship big enough to hurt it grounds before it gets that close. Don't put pilings in the channel. It's just money. But it's a lot of money so sometimes it's better to just have shipping not suck. Alternatively, the Chunnel will almost certainly never get hit with a ship.
  - jacquesm 1y ago
    > Plan the bridge so any ship big enough to hurt it grounds before it gets that close. Have a look at the trajectory chart that I posted upthread and tell me how in this particular case you would have arranged that.
    - amelius 1y ago
      Yet another idea: if a ship's motors fail, have a ship ready that can push it in the right direction, in time. Probably need 2x the amount of horsepowers to make up for lost time, but it's not impossible.
      - jacquesm 1y ago
        Yes, that's called a tug and in plenty of harbors a vessel of this size would not be permitted to do close quarters maneuvers without the mandatory assistance of one, or in this case more likely two, tug boats of a certain minimum size relative to the size of the vessel.
jacquesm 1y ago
Yes, but if you think of a ship once underway when the engine fails as an unguided ballistic missile with a mass that is absolutely mind boggling (the Dali masses 100,000 tonnes) there isn't much that you could build that would stop it. The best suggestion I've seen is to let the ship run aground but that ignores the situation around the area where the accident happened. This ship wasn't towed by a tug, it was underway under its own power and in order for the ship to have any control authority at all it needs water flowing over the rudder. Without that forward speed you're next to helpless and these things don't exactly turn on a dime. So even if there had been a place where it could have run aground it would never have been able to reach it because it was still in the water directly in front of the passage way under the bridge. 100,000 tonnes doing 7 Kph is a tremendous amount of kinetic energy. The exact moment the systems aboard the Dali failed could not have come at a worse time, it had - as far as I'm aware of the whole saga - just made a slight course correction to better line up with the bridge and the helm had not yet been brought back to neutral. After that it was just Newton taking over, without control I don't think there is much that would have stopped it. This is a good plot of the trajectory of the vessel from the moment it went under way until the moment it impacted the bridge: https://www.pilotonline.com/wp-content/uploads/2024/03/5HVqi-pathway-of-the-cargo-ship-dali-copy-.png?w=1200&resize=1200,900 https://www.pilotonline.com/wp-content/uploads/2024/03/5HVqi... You can clearly see the kink in the trajectory a few hundred meters before it hit the bridge.
- amelius 1y ago
  Perhaps, but you can also build redundancy into the bridge.
  - ninju 1y ago
    Too build "a redundancy into the bridge" to survive such a overwhelming force would be a very expensive endeavor. Better to spend the effort in fleet education
  - jacquesm 1y ago
    You can, if you're prepared to pay for it. You could halt shipping while people are working on the bridge. You could make tunnels instead of bridges. The question is simple: who will pay for it? Apparently we are ok with this kind of risk, if we weren't we would not be doing this at all. There is a similar thing going on in my country with respect to railway crossings. Every year people die on railway crossings. But it took for a carriage full of toddlers to be hit by a train before the sentiment switched from 'well, they had it coming' to 'hm, maybe we should do something about this'. People don't like to pay for risks they see as small or that they perceive as that they're never going to affect them. This never was about technology, it always was about financing. Financing for proper regulatory tech oversight (which is vastly understaffed) on the merchant marine fleet, funding for better infrastructure, funding for (mandatory) tug assistance for vessels of this size near sensitive structures, funding for better educated and more capable crew and so on. The loose wire is just a consequence of a whole raft of failures that have nothing to do with a label shroud preventing a wire from making proper contact. The 'root cause' here isn't really the true root cause, it is just the point at which technology begins and administration ends.

richardwhiuk 1y ago

It’s not realistically plausible to build bridges that won’t be brought down by that size of ship

capyba 1y ago
This, 100%. I forget the specific numbers but regardless, the kinetic energy of a thing with that much mass, even moving at a very slow speed, is off the charts. Designing a bridge or protections for a bridge to survive that would at a minimum be cost prohibitive, if even possible with today’s materials and construction technologies.
- sitkack 1y ago
  Doesn't mean that nothing can be done. https://www.ntsb.gov/news/press-releases/Pages/nr20250320.aspx https://www.ntsb.gov/news/press-releases/Pages/nr20250320.as... > The NTSB found that the Key Bridge, which collapsed after being struck by the containership Dali on March 26, 2024, was almost 30 times above the acceptable risk threshold for critical or essential bridges, according to guidance established by the American Association of State Highway and Transportation Officials, or AASHTO. > Over the last year, the NTSB identified 68 bridges that were designed before the AASHTO guidance was established — like the Key Bridge — that do not have a current vulnerability assessment. The recommendations are issued to bridge owners to calculate the annual frequency of collapse for their bridges using AASHTO’s Method II calculation. Letters to the 30 bridge owners and their responses https://data.ntsb.gov/carol-main-public/sr-details/H-25-003 https://data.ntsb.gov/carol-main-public/sr-details/H-25-003
  - deleted 1y ago
    [deleted]
  - throwaway173738 1y ago
    This is essentially the same thing that happened with Fukushima Daiichi. The organization running it failed to respond to new information.
- potato3732842 1y ago
  Energy doesn't mean squat without a time component over which it's dissipated. Stopping a car normally vs crashing a car. Skydiving with a parachute vs skydiving without a parachute. For something like ship vs bridge you have to account for the crunch factor. USS Iowa going the same speed probably would've hit way harder despite having ~1/3 the tonnage.
potato3732842 1y ago
Nah, we definitely can. Plan the bridge so any ship big enough to hurt it grounds before it gets that close. Don't put pilings in the channel. It's just money. But it's a lot of money so sometimes it's better to just have shipping not suck. Alternatively, the Chunnel will almost certainly never get hit with a ship.
- jacquesm 1y ago
  > Plan the bridge so any ship big enough to hurt it grounds before it gets that close. Have a look at the trajectory chart that I posted upthread and tell me how in this particular case you would have arranged that.
  - amelius 1y ago
    Yet another idea: if a ship's motors fail, have a ship ready that can push it in the right direction, in time. Probably need 2x the amount of horsepowers to make up for lost time, but it's not impossible.
    - jacquesm 1y ago
      Yes, that's called a tug and in plenty of harbors a vessel of this size would not be permitted to do close quarters maneuvers without the mandatory assistance of one, or in this case more likely two, tug boats of a certain minimum size relative to the size of the vessel.

jacquesm 1y ago

Yes, but if you think of a ship once underway when the engine fails as an unguided ballistic missile with a mass that is absolutely mind boggling (the Dali masses 100,000 tonnes) there isn't much that you could build that would stop it. The best suggestion I've seen is to let the ship run aground but that ignores the situation around the area where the accident happened. This ship wasn't towed by a tug, it was underway under its own power and in order for the ship to have any control authority at all it needs water flowing over the rudder. Without that forward speed you're next to helpless and these things don't exactly turn on a dime. So even if there had been a place where it could have run aground it would never have been able to reach it because it was still in the water directly in front of the passage way under the bridge. 100,000 tonnes doing 7 Kph is a tremendous amount of kinetic energy. The exact moment the systems aboard the Dali failed could not have come at a worse time, it had - as far as I'm aware of the whole saga - just made a slight course correction to better line up with the bridge and the helm had not yet been brought back to neutral. After that it was just Newton taking over, without control I don't think there is much that would have stopped it. This is a good plot of the trajectory of the vessel from the moment it went under way until the moment it impacted the bridge: https://www.pilotonline.com/wp-content/uploads/2024/03/5HVqi-pathway-of-the-cargo-ship-dali-copy-.png?w=1200&resize=1200,900 https://www.pilotonline.com/wp-content/uploads/2024/03/5HVqi... You can clearly see the kink in the trajectory a few hundred meters before it hit the bridge.

amelius 1y ago
Perhaps, but you can also build redundancy into the bridge.
- ninju 1y ago
  Too build "a redundancy into the bridge" to survive such a overwhelming force would be a very expensive endeavor. Better to spend the effort in fleet education
- jacquesm 1y ago
  You can, if you're prepared to pay for it. You could halt shipping while people are working on the bridge. You could make tunnels instead of bridges. The question is simple: who will pay for it? Apparently we are ok with this kind of risk, if we weren't we would not be doing this at all. There is a similar thing going on in my country with respect to railway crossings. Every year people die on railway crossings. But it took for a carriage full of toddlers to be hit by a train before the sentiment switched from 'well, they had it coming' to 'hm, maybe we should do something about this'. People don't like to pay for risks they see as small or that they perceive as that they're never going to affect them. This never was about technology, it always was about financing. Financing for proper regulatory tech oversight (which is vastly understaffed) on the merchant marine fleet, funding for better infrastructure, funding for (mandatory) tug assistance for vessels of this size near sensitive structures, funding for better educated and more capable crew and so on. The loose wire is just a consequence of a whole raft of failures that have nothing to do with a label shroud preventing a wire from making proper contact. The 'root cause' here isn't really the true root cause, it is just the point at which technology begins and administration ends.