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Discussion Starter #1 (Edited)
These are proposals for a bridge crossing Norways largest and longest Fjord, from Oppedal to Lavik. The crossing is 3 700 meters long, and so far there have been several proposals. Building a bridge crossing this fjord is one of the main goals of Norways infrastructure program. It is one of the key holes in getting a ferry free road all the way from Kristiansand to Trondheim through cities like Stavanger, Bergen and Ålesund.

Reinertsen's proposal:


This proposal wants to create an artificial bedding that strengthens the floating bridge and the tunnel.

Aas-Jakobsen's proposal:


3x1240 meter suspension bridges on top of floating pontoons. The pontoons have each a diameter of 75 meters, and a depths of 175 meters.

LMG Marin's proposal:


Floating bridge with a viaduct at its center.

Multiconsult's proposal:


Double tube bridge in two layers held up by pontoon's.

Norconsult's proposal:


Floatingbridge held up by 300m or 400m diameter pontoon's.

Sweco's proposal:


Floating bridge with a tunnel held up by grounded pillars. The tunnel will be 4000 meters long.


The most interesting proposal (engineer not assigned):


One suspension span at 3 700 meters (nearly twice that of the Akashi-Kaikyo bridge in Japan at 1991 meters). In order to build this, a new type of steel will need to be made. But the norwegian infrastructure authority is in discussion with scientists in Korea who is making this new type of steel.
It will also have 455 meters tall towers, and the diameter of the steel cabels if they were to built by ordinary steel used today would have to be 1.3 meters thick. This new type of steel is supposedly 20-30% stronger. So 1 meter in diameter is a good guess.

The main benefits of building a suspension bridge over the other proposals are cited to be the much lower maintainance cost of suspension bridges.

We probably won't see the start of construction for this bridge before in 4-6 knowing how long these projects normally takes. But something will get built, and it is high on the agenda.

Links:
http://e24.no/naeringsliv/monsterbro-med-nytt-superstaal/20322922
http://e24.no/naeringsliv/disse-gigantbruene-skal-gjoere-fjordene-fergefrie/20306081
 

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These are proposals for a bridge crossing Norways largest and longest Fjord, from Oppedal to Lavik. The crossing is 3 700 meters long, and so far there have been several proposals. Building a bridge crossing this fjord is one of the main goals of Norways infrastructure program. It is one of the key holes in getting a ferry free road all the way from Kristiansand to Trondheim through cities like Stavanger, Bergen and Ålesund.

Reinertsen's proposal:


This proposal wants to create an artificial bedding that strengthens the floating bridge and the tunnel.

Aas-Jakobsen's proposal:


3x1240 meter suspension bridges on top of floating pontoons. The pontoons have each a diameter of 75 meters, and a depths of 175 meters.

LMG Marin's proposal:


Floating bridge with a viaduct at its center.

Multiconsult's proposal:


Double tube bridge in two layers held up by pontoon's.

Norconsult's proposal:


Floatingbridge held up by 300m or 400m diameter pontoon's.

Sweco's proposal:


Floating bridge with a tunnel held up by grounded pillars. The tunnel will be 4000 meters long.


The most interesting proposal (engineer not assigned):


One suspension span at 3 700 meters (nearly twice that of the Akashi-Kaikyo bridge in Japan at 1991 meters). In order to build this, a new type of steel will need to be made. But the norwegian infrastructure authority is in discussion with scientists in Korea who is making this new type of steel.
It will also have 455 meters tall towers, and the diameter of the steel cabels if they were to built by ordinary steel used today would have to be 1.3 meters thick. This new type of steel is supposedly 20-30% stronger. So 1 meter in diameter is a good guess.

The main benefits of building a suspension bridge over the other proposals are cited to be the much lower maintainance cost of suspension bridges.

We probably won't see the start of construction for this bridge before in 4-6 knowing how long these projects normally takes. But something will get built, and it is high on the agenda.

Links:
http://e24.no/naeringsliv/monsterbro-med-nytt-superstaal/20322922
http://e24.no/naeringsliv/disse-gigantbruene-skal-gjoere-fjordene-fergefrie/20306081
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NWO Henchman
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Could someone please explain the concept of floating pontoons when it comes to the tremendous weight of a suspension bridge.
Short answer: Use a big enough pontoon.

Long answer: The OP forgot to mention the main reason it's considered a challenge to bridge the fjord: it is 1300 m deep. That means you don't get any support along the way unless it floats, but it also means you can build the pontoons as big as you want. Further; the Norwegian Maritime Authority demands a sailing channel at least 400 meters wide and 70 meters tall with at least 20 m of clearance underwater. Lifting a float bridge that high up creates stability problems, so using a few very large pontoons is preferable to many smaller ones because they need to be so big and wide for stability anyway. Further; larger pontoons means a smaller cross section exposed to winds and currents for the same amount of buoyancy, so you might get away with a little less tethering to the bottom.

Here's a video created by Statens vegvesen about this crossing. It was made before the contractors submitted their proposals, so you'll notice some of the designs are a little bit different.


Here is the same video in original Norwegian version or with Chinese text.
 

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I'm just having a difficult time imagining the towers of a suspension bridge being supported by pontoons, if thats what is meant by this proposed project. Does anyone know if a suspension bridge has ever been built using this technique.
 

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NWO Henchman
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I'm just having a difficult time imagining the towers of a suspension bridge being supported by pontoons, if thats what is meant by this preposed project. Does anyone know if a suspension bridge has ever been built using this technique.
Not to my knowledge, no. But there's a first for everything, right? :D
 

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I'm guessing they'll use a similar technique which they used for the Troll drill platforms that are floating and anchored to some great precision and stability.
 

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NWO Henchman
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I'm guessing they'll use a similar technique which they used for the Troll drill platforms that are floating and anchored to some great precision and stability.
Troll is actually fixed to the bottom, these would not be; it's much too deep. But if you're talking about the way they moved it out there, you might be right.

I'm still hoping they won't have to move anything though ;)
 

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Ah yes, that's right, my bad :) It's still amazing to see how they moved a structure on water at the height of an Eiffel tower and not tipping over.
 

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The Railroad Anomily
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Oddly about the underwater tunnel idea with it sitting under the water like a under water bridge held up on pillars that go to the bottom of the bay. I once had a few drawings about building a clear model railroad tunnel that went though a giant fish tank. The idea was that in order for the train tracks to cross though the giant fish tank at the level of the train tables around it. They would cross the fish tank though a underwater tube that would be held up with several tall underwater acrylic supports that rested on the bottom of the fish tank like a underwater bridge.

The underwater tunnel idea sounds like a giant version of this fish tank idea. I hope they put viewing windows in the roof and on the sides along with a bike path to look at this odd underwater crossing.
 

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The two last proposals in the video was selected for further investigation, the Y-solution floating tunnel+bridge (starting at 5:40) and the floating cable-stayed (starting 6:30).
 

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NWO Henchman
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Statens vegvesen have updated their video to show the new concepts that are now being considered. Although this video is nice, keep in mind that this project is still a long way ahead, and now occupies the vague intersection between vision, proposed and approved. The new content starts at around 3:30.
 

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Flying HigH
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WooW. This is an interesting project. I wish that this is not a bom penger project. So I can just simply cross the fjord when I traveled to Bergen from Sogn.

I like the single span but it might pose a lot of challenge.
 

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For future engineering considerations that is the only one not (that) interesting. There are a number of ambitious-to-crazy-ambitious bridge/tunnel projects, e.g. a bridge connecting Japan and Korea, the island in Indonesia, Europe and Africa and so on. What many have in common is a ocean trough that cannot be crossed with conventional means, much like the fjord for this bridge. Those would be way beyond a suspension bridge, but could be done with a floating bridge or submerged tunnel.
 
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