14 ms·

If you think about this for a minute, you'll realize that what you're asking for is pretty much impossible. What would these artificial islands be made of? San

If you think about this for a minute, you'll realize that what you're asking for is pretty much impossible. What would these artificial islands be made of? Sand, gravel, concrete rubble? This is a river, the constant current of the water erodes anything that resists it by staying in place. Piling up enough material to resist erosion and create a meaningful obstacle to 70000 tonnes in motion, that would significantly narrow and make shallow the navigable waterway. The only way to do this is to build giant underwater concrete towers -- basically the structures pylons typically rest on, the piers. Look up the process required to build these, it's quite an undertaking. They are engineered to withstand the pressure of ice floes every spring, they're not flimsy by any measure.

deleted 3y ago
[deleted]
tokai 3y ago
I have thought about it for hours by now, and read literature on the matter. It is definitely possible to build berms that protects a bridge from catastrophic failure in case of a ship collision, and it is widely done during modern bridge construction. Please be less sure of yourself when you clearly don't have any actual knowledge on the subject.
- btbuildem 3y ago
  I'd love to see a few examples, since you're so versed on the subject. I'm not a civil engineer by any means, but I imagine the people who designed and built that bridge knew what they were doing. There are likely limitations imposed by the site bathymetry and other things we don't know about. You can get a good look at the aftermath here: https://www.youtube.com/watch?v=WssFXRzRVLU https://www.youtube.com/watch?v=WssFXRzRVLU I'll be interesting to see how they choose to rebuild it.
  - KoftaBob 3y ago
    There are real world examples of what it would look like, they're called "dolphins": https://en.wikipedia.org/wiki/Dolphin_(structure)#/media/Fil https://en.wikipedia.org/wiki/Dolphin_(structure)#/media/Fil... "The new bridge is protected by 36 dolphins: four large dolphins protecting the two main pylons supporting the cable-stayed main span plus 32 smaller dolphins protecting bridge piers for 1⁄4 mi (1⁄2 km) to either side of the main span"
    - btbuildem 3y ago
      See my response to the other copy of your comment above
- low_common 3y ago
  "I have thought about it for hours by now, and read literature on the matter." Ah, the classic, pompous Hacker News user. The Baltimore Port Authority should've hired you to prevent this disaster - you're a genius!
  - pgwhalen 3y ago
    Seriously, this comment has to be satire.
KoftaBob 3y ago
There are real world examples of what it would look like, they're called "dolphins": https://en.wikipedia.org/wiki/Dolphin_(structure)#/media/File:Skyway_Bridge_old_and_new.jpg https://en.wikipedia.org/wiki/Dolphin_(structure)#/media/Fil... "The new bridge is protected by 36 dolphins: four large dolphins protecting the two main pylons supporting the cable-stayed main span plus 32 smaller dolphins protecting bridge piers for 1⁄4 mi (1⁄2 km) to either side of the main span"
- btbuildem 3y ago
  Dolphins seem to be just pilings tied together.. how could those withstand the impact of a loaded container ship? For something a bit more sturdy, look at the main pylons of the Jacques Cartier bridge in Montreal [1] - these are meant to withstand annual ice rush, hundreds of tons of ice floe moving with the current of the river. Interestingly, while the Saint Lawrence is a very active shipping channel, most shipping near the city moves through the seaway canal [2], which has solid earthen berms reinforced with concrete wherever it crosses a bridge span [3], [4] making it next to impossible for this type of accident to occur. If memory serves right, the seaway was built to avoid the strong currents and wild rapids of the river; there are a set of locks [5] upriver, and the engineering around bridge crossings [6] seems consistent as you trace its path 1: https://www.google.com/maps/@45.5198582,-73.5385996,94a,35y,312.25h,73.94t/data=!3m1!1e3?entry=ttu https://www.google.com/maps/@45.5198582,-73.5385996,94a,35y,... 2: https://www.google.com/maps/@45.5237446,-73.5262812,90a,35y,173.25h,71.54t/data=!3m1!1e3?entry=ttu https://www.google.com/maps/@45.5237446,-73.5262812,90a,35y,... 3: https://www.google.com/maps/@45.4986758,-73.5188312,123a,35y,173.25h,71.48t/data=!3m1!1e3?entry=ttu https://www.google.com/maps/@45.4986758,-73.5188312,123a,35y... 4: https://www.google.com/maps/@45.4717554,-73.5051917,148a,35y,173.25h,71.46t/data=!3m1!1e3?entry=ttu https://www.google.com/maps/@45.4717554,-73.5051917,148a,35y... 5: https://www.google.com/maps/@45.4080264,-73.5557603,298a,35y,262.25h,59.46t/data=!3m1!1e3?entry=ttu https://www.google.com/maps/@45.4080264,-73.5557603,298a,35y... 6: https://www.google.com/maps/@45.4082771,-73.6528304,266a,35y,288.25h,67.56t/data=!3m1!1e3?entry=ttu https://www.google.com/maps/@45.4082771,-73.6528304,266a,35y...

deleted 3y ago

[deleted]

tokai 3y ago

I have thought about it for hours by now, and read literature on the matter. It is definitely possible to build berms that protects a bridge from catastrophic failure in case of a ship collision, and it is widely done during modern bridge construction. Please be less sure of yourself when you clearly don't have any actual knowledge on the subject.

btbuildem 3y ago
I'd love to see a few examples, since you're so versed on the subject. I'm not a civil engineer by any means, but I imagine the people who designed and built that bridge knew what they were doing. There are likely limitations imposed by the site bathymetry and other things we don't know about. You can get a good look at the aftermath here: https://www.youtube.com/watch?v=WssFXRzRVLU https://www.youtube.com/watch?v=WssFXRzRVLU I'll be interesting to see how they choose to rebuild it.
- KoftaBob 3y ago
  There are real world examples of what it would look like, they're called "dolphins": https://en.wikipedia.org/wiki/Dolphin_(structure)#/media/Fil https://en.wikipedia.org/wiki/Dolphin_(structure)#/media/Fil... "The new bridge is protected by 36 dolphins: four large dolphins protecting the two main pylons supporting the cable-stayed main span plus 32 smaller dolphins protecting bridge piers for 1⁄4 mi (1⁄2 km) to either side of the main span"
  - btbuildem 3y ago
    See my response to the other copy of your comment above
low_common 3y ago
"I have thought about it for hours by now, and read literature on the matter." Ah, the classic, pompous Hacker News user. The Baltimore Port Authority should've hired you to prevent this disaster - you're a genius!
- pgwhalen 3y ago
  Seriously, this comment has to be satire.

KoftaBob 3y ago

There are real world examples of what it would look like, they're called "dolphins": https://en.wikipedia.org/wiki/Dolphin_(structure)#/media/File:Skyway_Bridge_old_and_new.jpg https://en.wikipedia.org/wiki/Dolphin_(structure)#/media/Fil... "The new bridge is protected by 36 dolphins: four large dolphins protecting the two main pylons supporting the cable-stayed main span plus 32 smaller dolphins protecting bridge piers for 1⁄4 mi (1⁄2 km) to either side of the main span"

btbuildem 3y ago
Dolphins seem to be just pilings tied together.. how could those withstand the impact of a loaded container ship? For something a bit more sturdy, look at the main pylons of the Jacques Cartier bridge in Montreal [1] - these are meant to withstand annual ice rush, hundreds of tons of ice floe moving with the current of the river. Interestingly, while the Saint Lawrence is a very active shipping channel, most shipping near the city moves through the seaway canal [2], which has solid earthen berms reinforced with concrete wherever it crosses a bridge span [3], [4] making it next to impossible for this type of accident to occur. If memory serves right, the seaway was built to avoid the strong currents and wild rapids of the river; there are a set of locks [5] upriver, and the engineering around bridge crossings [6] seems consistent as you trace its path 1: https://www.google.com/maps/@45.5198582,-73.5385996,94a,35y,312.25h,73.94t/data=!3m1!1e3?entry=ttu https://www.google.com/maps/@45.5198582,-73.5385996,94a,35y,... 2: https://www.google.com/maps/@45.5237446,-73.5262812,90a,35y,173.25h,71.54t/data=!3m1!1e3?entry=ttu https://www.google.com/maps/@45.5237446,-73.5262812,90a,35y,... 3: https://www.google.com/maps/@45.4986758,-73.5188312,123a,35y,173.25h,71.48t/data=!3m1!1e3?entry=ttu https://www.google.com/maps/@45.4986758,-73.5188312,123a,35y... 4: https://www.google.com/maps/@45.4717554,-73.5051917,148a,35y,173.25h,71.46t/data=!3m1!1e3?entry=ttu https://www.google.com/maps/@45.4717554,-73.5051917,148a,35y... 5: https://www.google.com/maps/@45.4080264,-73.5557603,298a,35y,262.25h,59.46t/data=!3m1!1e3?entry=ttu https://www.google.com/maps/@45.4080264,-73.5557603,298a,35y... 6: https://www.google.com/maps/@45.4082771,-73.6528304,266a,35y,288.25h,67.56t/data=!3m1!1e3?entry=ttu https://www.google.com/maps/@45.4082771,-73.6528304,266a,35y...