5 ms·

One word - Cost! Advances in Post-tensioning methods and technologies make cable stayed bridges the most economical type to span such long distances. So unless

One word - Cost! Advances in Post-tensioning methods and technologies make cable stayed bridges the most economical type to span such long distances. So unless it is a very long gap that needs to be spanned like Golden Gate Strait or the Strait of Messina, which would require a suspension bridge , the cable stayed type will be the "go to bridge" Source: personal experience. I have built 2 such bridges before. Led the planning and installation of the actual stay cables. I know all about it :-). Had to make a lot of the jigs ourselves. Lots of room for innovation and automation ;-)

L_Rahman 9y ago
Hey Arjun - I'm fascinated by the human processes that underly big projects like building bridges. Any chance we can talk about your work, and perhaps specifically about the room for innovation and automation?
- arjunvpaul 9y ago
  ok. my email is <username>@GMAIL
tropo 9y ago
You forgot trains. Suspension bridges can't handle trains well. What about buckling though? With all that force from the cables pulling the bridge deck toward the towers, it seems like a bit of unexpected bending or weakness (breeze, earthquake, minor damage) could cause the deck to travel inward to the tower while being crushed. I do have to agree that I am tired of cable-stay bridges. They are a distant third for looks, behind suspension and obviously the stone arch. More stone arches please! Do a big one, a mile or two in height.
- arjunvpaul 9y ago
  Good point about trains. But I know one of the first suspension bridges did carry trains. https://en.m.wikipedia.org/wiki/Niagara_Falls_Suspension_Bridge https://en.m.wikipedia.org/wiki/Niagara_Falls_Suspension_Bri... .When we bid for the Tappan Zee bridge, the community wanted us to design it to take trains in the future. (Our team did not get the project) . Not sure how the executed design turned out. Actually there is very little stress on the cables. The cables are stressed just enough to take the sag out of em. i.e. All the cables are actually supporting is their self weight! All you need is a hand-held jack and a lot of clever math, to install them :-). The deck on one side of the tower is held in place by counter weight of the deck on the other side. About earthquakes, it's designed for those 100 year quakes, hurricanes and floods. When we were building the Audubon Bridge across the Mississippi River, we were in fact hit by a 100-year flood and 2 hurricanes. Other than some stored material floating away and having to watch out for alligators in odd places. We got through fine :-) The bridge type is rarely chosen for beauty :-) especially when contractors have to bid competitively for tonget a chance to build them. Governing factors are technical feasibility (design and constructability) and cost.
  - icebraining 9y ago
    You mentioned the Golden Gate - in Lisbon, we actually have a very similar suspension bridge, but ours does have a train running underneath it, added years later after construction. Supposedly, it was the first aerial spinning of additional main cables on a loaded, fully operational suspension bridge. https://static.noticiasaominuto.com/stockimages/1370x587/naom_57a05e2bb3faa.jpg https://static.noticiasaominuto.com/stockimages/1370x587/nao...
    - arjunvpaul 9y ago
      Very cool! Now I know it may be possible to add trains to existing bridges :-). Thanks for the link.
      - icebraining 9y ago
        Found a video of the company adding the extra cables: https://vimeo.com/45236687 https://vimeo.com/45236687
        Fifer82 9y ago
        I can't believe how much I am enjoying seeing engineers speaking in regular chat about such large projects. I thoroughly enjoyed this thread. Appreciate the sharing.

L_Rahman 9y ago

Hey Arjun - I'm fascinated by the human processes that underly big projects like building bridges. Any chance we can talk about your work, and perhaps specifically about the room for innovation and automation?

arjunvpaul 9y ago
ok. my email is <username>@GMAIL

tropo 9y ago

You forgot trains. Suspension bridges can't handle trains well. What about buckling though? With all that force from the cables pulling the bridge deck toward the towers, it seems like a bit of unexpected bending or weakness (breeze, earthquake, minor damage) could cause the deck to travel inward to the tower while being crushed. I do have to agree that I am tired of cable-stay bridges. They are a distant third for looks, behind suspension and obviously the stone arch. More stone arches please! Do a big one, a mile or two in height.

arjunvpaul 9y ago
Good point about trains. But I know one of the first suspension bridges did carry trains. https://en.m.wikipedia.org/wiki/Niagara_Falls_Suspension_Bridge https://en.m.wikipedia.org/wiki/Niagara_Falls_Suspension_Bri... .When we bid for the Tappan Zee bridge, the community wanted us to design it to take trains in the future. (Our team did not get the project) . Not sure how the executed design turned out. Actually there is very little stress on the cables. The cables are stressed just enough to take the sag out of em. i.e. All the cables are actually supporting is their self weight! All you need is a hand-held jack and a lot of clever math, to install them :-). The deck on one side of the tower is held in place by counter weight of the deck on the other side. About earthquakes, it's designed for those 100 year quakes, hurricanes and floods. When we were building the Audubon Bridge across the Mississippi River, we were in fact hit by a 100-year flood and 2 hurricanes. Other than some stored material floating away and having to watch out for alligators in odd places. We got through fine :-) The bridge type is rarely chosen for beauty :-) especially when contractors have to bid competitively for tonget a chance to build them. Governing factors are technical feasibility (design and constructability) and cost.
- icebraining 9y ago
  You mentioned the Golden Gate - in Lisbon, we actually have a very similar suspension bridge, but ours does have a train running underneath it, added years later after construction. Supposedly, it was the first aerial spinning of additional main cables on a loaded, fully operational suspension bridge. https://static.noticiasaominuto.com/stockimages/1370x587/naom_57a05e2bb3faa.jpg https://static.noticiasaominuto.com/stockimages/1370x587/nao...
  - arjunvpaul 9y ago
    Very cool! Now I know it may be possible to add trains to existing bridges :-). Thanks for the link.
    - icebraining 9y ago
      Found a video of the company adding the extra cables: https://vimeo.com/45236687 https://vimeo.com/45236687
      - Fifer82 9y ago
        I can't believe how much I am enjoying seeing engineers speaking in regular chat about such large projects. I thoroughly enjoyed this thread. Appreciate the sharing.