how about floating roads instead of bridges?

Discussion in 'Boat Design' started by Squidly-Diddly, Oct 20, 2019.

  1. Squidly-Diddly
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    Squidly-Diddly Senior Member

    People that know about such things ran the numbers after the Golden Gate 50th, and say the event exceeded the spec max live load buy about 2x, which is about what I get. Bridge management never gave a straight answer about anything. A few chains and anchors is all thats needed. Thats how they swing that floater in Greece, and that is how they move 40K ton freighters around at the docks when loading. Maybe a couple small tugboats to drag a large pre-assembled section during construction.
     
  2. gonzo
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    gonzo Senior Member

  3. Squidly-Diddly
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    Squidly-Diddly Senior Member

    They are making several typical Govt errors, starting with saying the old bridge was closed due to storms 6 times since 1996, which I assume they mean is too often. I'm not believing that closing a bridge every few years due to extreme weather, in an area noted for bad weather, created any public outcry needing billions of dollars. That probably led them to current design that should be able to stay open in higher winds, but at the cost of several billion dollars. Most people are gonna not travel during extreme weather, so a bridge that needs to close a couple times a year VS a couple times a decade is worth considering. Bay Bridge will close for several days at a time over 3 day weekends for construction and its not that big a deal. That in turn led to a few dozen massive pontoons, each of which may be a Single Point of failure. Just eyeballing it (pic shows less than 20% freeboard) it appears that if one or two adjacent pontoons flood, they might cause chain reaction similar to how Titanic succumbed to progressive flooding. The Space Shuttle's booster O-rings each had a small chance of failure, but there were many of them and one failure would be catastrophic, so it turned out the thing blew up more or less 'on schedule'. I'm guessing the reason for the many (and expensive) anchors is because the pontoons butt each other not allowing wind and waves pass through. If it means saving a few billion dollars, I'd be OK with mere 7000ft long Floater that had reduced speed limit of 45mph. Good luck if something does go wrong with one of the massive pontoons that can't be repaired in place. Pics show no compartments in pontoons. Maybe they could pump it full of ping-pong balls.

    My design would use something similar to my modular cat in my gallery, except bigger and spaced about 50/50 pontoon/open to allow easy replacement if needed and for redundancy, and to allow weather to pass through. Instead of pre-cast concrete, use open steel grating.
     
  4. gonzo
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    gonzo Senior Member

    You contradict yourself by first quoting government data and then claiming government data is unreliable. Your "design" is nonsense, and would never get built. There is a lengthy process, which the links I posted explain, which has no way around. Your "guessing" is only a show of complete lack of understanding of the engineering concepts behind the design of a bridge. Further, the building of a bridge is another exercise in engineering planning. People travel in mass during a bad weather evacuation. If the main bridge is closed, it would lead to countless deaths. Your whole argument is infantile. Spend some time reading and educating yourself, so that the arguments are in touch with reality. At the very least, post a diagram with an explanation of the magnitude of the stresses on your "revolutionary" design.
     
  5. Squidly-Diddly
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    Squidly-Diddly Senior Member

    We don't evac during bad weather in SF Bay Area, except for a few odd-ball spots, and we don't cross any bridge to evac. No deaths ever happen when we close bridges because it keeps people from traveling, deaths happened when Bay Bridge fell, THEN it was closed. No one in SF Bay needs to cross a bridge to get to world class hospital, just to get to work M-F.

    Nothing revolutionary, the PLA does it for practice. PLA builds 600m pontoon bridge in 22 minutes (1/6) - Headlines, stories and photos from ecns.cn http://www.ecns.cn/visual/hd/2011/10-24/1923.shtml For a more permanent version that can carry more weight and traffic, add some freeboard and covers on the pontoons, and some real guard rails. Oh, and if those boats are made out of wood or bamboo, make them out of steel. IIRC when the Yangtze is only 600 meters across its a reasonable fast flowing river, so good enough match for fairly fast tides in SF Bay. Note the long slender aspect of the pontoons to reduce cross load on span from water flow. Note the ratio of freeboard and shallow draft of pontoons VS Lake W, due to use of steel matrix VS concrete. Light weight steel might not be as good for heavy truck traffic, but on SF Bay we just need more regular auto traffic lanes (and already restrict certain types of trucks and hours for various bridges and tunnels). Shallow draft be good for placing in mostly very shallow SF Bay. I'd bet the guy in PLA who did this used only basic rule of thumb engineering and pre-1949 second hand knowledge of trusses from copying old photos, because that is all thats needed.

    My understanding of the Lake W pontoons and their low 20% freeboard is that each one could flood at no more than 20% before going Neg Buoyancy. Even more troubling is that if one loses even 80% (like if it flooded only to the design waterlevel) it would have more than enough NB to pull both its neighbors under water. That would no doubt create great stress on those concrete shells and could start a chain reaction. While concrete pontoons have been around for a while, defects still happen in both even high dollar concrete construction and of course fully inspected and certified bridge engineering. The Lake W pontoons are a very special project, with virtually all involved doing it for the very first time, and I very much doubt any pontoons are being torture tested, much less tested to point of failure. Such testing would be doable with PLA type bridge, or even units 4X larger.

    There is no magic engineering needed for pontoon bridge such as demonstrated by the PLA, any more than is needed when illiterates successfully build and operate fairly large boats, and those boats on the high seas are a much greater risk than a pontoon bridge, because you always be able to be on dry land in 10 minutes max if the weather starts to change.

    How did Uber and Lyft completely ignore not just one city's Taxi Commission, but apparently EVERY SINGLE TC, even those in foreign nations? NYC Taxi "medallions" were worth $250K at one point (SF about same), and even the Mafia in its heyday of freely operating illegal gambling, loansharking, drugs and worse, never got too far into the illegal taxi biz due to massive fines the TC was known to levy with little to no legal recourse. That is something that needs study to understand, and I think it has something to do with how Uber/Lyft were addressing a very common need that existing Govt processes had been failing to fix for decades.

    Step 1) Don't call it an Illegal, Uninsured Taxi Service, and don't call it a "bridge". World’s Longest Piers https://www.geographyrealm.com/worlds-longest-pier/ Pier would be fine for shallow parts anyways, to keep everything under the radar. Start from both sides. Then switch to a "pier" of pontoons that ride on poles, then finally to pontoons held by anchors and cables. Finally, add the center connecting swing section. Charge folks $5 to enter, and just don't care if they don't go out same way they came in.

    Step 2) Tell govt locals that unlike "bridges", their pet projects get some of the "pier entrance fee" funds (there will be plenty to go around).

    "But a bridge/pier is an actual structure in a known location, not just "an app" in "the cloud (actually Lyft/Uber very much have offices, corp "agent of service" for lawsuits, execs in office for arrest, etc) so the authorities will just show up and shut everything down". This operation is violating too many laws and codes to even start counting, yet otherwise draconian LA city govt hasn't even knocked, much less fined them or asked for taxes. This bunk bed is $1,200 a month, privacy not included - CNN https://www.cnn.com/2019/07/05/success/podshare-co-living/index.html
     

  6. gonzo
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    gonzo Senior Member

    I tried to follow the rant, but it is very unfocused and has a myriad of random unrelated claims. I will address your steps 1 & 2.
    1- It doesn't matter what you call it. When you submit the building permit application, the environmental impact, structural details, load calculations, etc. will be the same. Comparing a permanent structure to a service is nonsense. If you start building your proposed pier, without the proper permits, you will probably end up in jail. Further, the fines and other penalties will be also huge.
    2- More infantile nonsense. You are going to tell the government that the bridge is a pier and nobody will notice. You are smoking too much of the newly legal weed buddy.
     
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