(Note: This would be Vancouver Island – Georgia Straight type crossing design. Howe Sound is a much simpler, shorter and shallower crossing)
SOGNEFJORDEN: Reintertsen og Dr.Tehcn. Olav Olsen vant konkurransen om det beste alternativet for en rørbro for kryssing av Sognefjorden.
Superbridge of Norway’s deepest fjord shall withstand a ship collision.
Drunk sailors and engine failure are taken into account.
PER- IVAR NIKOLAISEN – TECHNICAL Magazine
24:34 – 01/05/2014
The probability of a ship’s collision with disastrous consequences are negligible , said two risk analyzes that TU has disclosed in.
The plans for ferry-free E39 along west coast opens for floating bridges in some fjord crossings . This is submerged bridges located under the water surface. The risk analysis shows that a concrete pipe average being struck by a vessel every nine years .
This includes , however, cases where vessels are barely touched or where very small ship hit the bridge .
The probability of a collision which causes the bridge collapse is so small that it will not happen in a hundred year period , according to estimates from Ramboll .
A fixed connection over the Sognefjord is the major technological test whether it is realistic that the E39 between Stavanger and Trondheim once can be quite ferry-free , so the majority in Parliament has been calling for .
If successful, the engineering masterpiece to cross it up to 1,309 meters deep and 203 km long fjord , most of the remaining fjordkryssingene for trifles to rain.
– Sognefjord crossing is considered one of the most difficult , especially because of the depth . So it is essential to go for a complete ferry-free E39 , says Mathias Kjerstad Eidem who led the subproject for fjord crossings in the project ” Ferry free E39 ” in the Norwegian Public Roads Administration .
One of the challenges is shipping traffic through the fjord . Therefore, the Norwegian Public Roads asked Ramboll consider whether this might pose a danger to the bridge elller of vessels exposed to unacceptable risk. These vessels are mainly industrial sites Årdalstangen and Hoyanger , but also a hub Sogndal . Express boats leave from Bergen and into the Sognefjord. Through the fjord sailing also a number of large cruise ships to places like Flam, Gudvangen , Vik and Subdivision . A total of 3,300 vessels passing it past the place where the bridge might be .
SOGNEFJORD : < / b > Reinertsen and Dr.Tehcn . Olav Olsen won the competition for the best option for a pipe bridge for crossing the Sognefjord.
SOGNEFJORD : Reinertsen and Dr.Tehcn . Olav Olsen won the competition for the best option for a pipe bridge for crossing the Sognefjord. PHOTO: REINERTSEN TECHNICAL Magazine
Model of the Øresund
Floating tunnel in the analysis consists of 16 floats , called pontoons , which keeps tunnel under surface. The bridge is about 4100 meters long and the longest is the 400 feet between the tubes .
Risk analysts in Ramboll has used a model that was originally developed for the Øresund Bridge 15 years ago , to see the risk of ship collision .
After this , the model has been refined , most recently in connection with the proposed bridge between Lolland in Denmark and Fehmarn in Germany.
The model is based on the likelihood that a ship is on a collision course , and the likelihood that it is not controlled at the right hire again . It also looks at how much energy it will be the different types of collisions .
The more traffic that goes through the fjord , the higher the accident rate .
Also read : Will build floating bridges with the middle of the fjord ship passage
The idea is that the bridge is equipped with a so-called ” weak link ” that acts as a fuse if a larger ship would front colliding with one of the tubes .
This weak link between the floater and the pipe where the cars will run , will break when a ship impact of a certain size. Pontoon will loosen and drive away, while the rest of the bridge is intact .
– We thought this was an elegant way to solve it , and it increases the safety of the bridge , says Mathias Kjerstad Eidem the Norwegian Public Roads Administration .
In the project , a number of engineering companies challenged to show how it was possible to cross the Sognefjord with floating bridge and floating tunnel or suspension bridge ( bridge-sections in Roads looked at hengebroalternativene ) Suspensionbridges. Dr. techn . Olav Olsen and Reinertsen won the concept of pipe bridge with this design with pontoons .
– It is difficult to anchor in the mountain slopes of avalange. It was submitted proposals anchored to the bottom, where it is okay to dock. But it is deeply significant , and therefore the concept of pontoons favored in this game , says Eidem .
Weak link must not be weak link
Ramboll emphasizes that it is “very important” that the fuse is functioning properly , and encourage NPRA to follow this closely.
– We have been very aware of yourself. If it gets built one pipe bridge with such a weak link , it will be carefully analyzed , and we will also conduct full-scale tests , said Eidem .
Risk analysts have also looked at the likelihood that a large ship will drift sideways, and go with him two tubes at once . The probability for that to happen something like this is very small , and thus do not control how the bridge will be constructed.
– Any pipe bridge will be built as neutrally as possible. In an emergency situation shall withstand two pontoons also disappears . It will have ballast tanks that can be pumped out if it gets too heavy, and it will be able to pump the water if it gets too easy , says Eidem .
See also: Oil Technology will provide anchoring new mega bridges
The tubes for vehicle traffic will be so deep that it is never any danger of the ship going down to the keel.
But one of the questions analysts have looked at the risk that an anchor in tow to destroy the bridge.
This part of the analysis is based on experience from a power cable out of Bornholm in the Baltic Sea and from a Dutch survey .
Bornholm cable has been damaged by anchors twice in 30 years. Based on this, such “uncontrolled drop anchor ” at a frequency of 1.15 * 10-2 per year per ship .
The Dutch study has looked at the sailing of 474 large ships between 1969 and 1978 . Based on how many times these ships have lost anchor , losing a ship anchors in 0,002 years , that is quite a bit rarer . For Sognefjord analysts have placed midway between the two cases.
Further analysis says that 90 percent of these cases, the anchors being dragged up again within two kilometers sailing. In ten percent of cases will continue to be the anchor dragged by the ship, an average of 192 km .
Sognefjord analysts have settled at an average of 21 km with trailing anchor. Considering that an average ship sails 105,000 kilometers a year, the likelihood that a ship should have the anchor out when they pass any pipe bridge as little as 9.6 * 10-7 .
It is considered unlikely that an anchor will hook up to the bridge and take it with him. But the report notes that the anchor chain can act as a saw and destroy pipes.
– The likelihood of a dragging anchor is so small that you can ignore it in the design. Either one will then be able to go for a reasonable protection solution with steel on top of the concrete pipes , points Eidem .
See also: ferry free E39 generates huge gains for society
In the second report, Ramboll specifically on how the new bridge will increase the risk of shipping itself . Although the risk of an accident is somewhat larger , with floating elements in the bay , it is not that much bigger than that it will have a major impact . It is pointed out that the ships already collide with shores in the narrow fjords.
The report also covers its costs by closing the connection as a result of an accident . In a severe collision, the pontoon could be repaired. The repairs will take 4.5 months and cost 45 million Nok
It is ten percent probability that one will lose the pontoon . The repairs will take 16.5 months and cost 145 million Nok
The so-called feasibility study for crossing the Sognefjord is closed . Ministry has now ordered a final concept study of a crossing . This work will soon get underway.