Floating Bridge / Fixed high Bridge Flakk – Rørvik
The technical solution in Rambøll’s work was based on a low floating bridge over most of the fjord, with a 70-meter fixed high bridge for ship traffic on the Flakk side. The cost in 2013 were estimated at around NOK 11.5 billion.
The solution is not considered sufficient to cover the need for passengers for ships and tugs, and large deviations from natural sailing guides are considered to entail a greater risk of both ship impacts on construction and other accidents. It may be relevant to have a solution that takes most ships and vessels at normal sailing height, and that rare needs are covered by special solutions when need arises.
Especially the need that Kvaerner Verdal has for towing could be decisive for a passage that has no restrictions on height nor depth. In principle, the Hood Canal Bridge floating bridge in Washington State in the USA has such a solution, although it can technically be done differently today.
Crossings along the E39 (Statens Vegvesen)
Directed by the Norwegian Public Roads Administration, a great deal of work is underway for some of the crossings along the E39. The work is continued with the previous main concepts of floating bridges, pipe tunnels, suspension bridges with larger spans than before and hybrid solutions where more than one technical concept is included. In general, the technical processing provides an increasingly better basis for the technical design of fiord crossings.
In particular, the solution for crossing the Bjørnafjord between Stord and Os in Hordaland has come a long way, see presentation from the Fosenbru conference 2020 and E39 Stord-Os (Statens vegvesen). For the crossings of the Halsafjord, the Sulafiord and the Vartdalsfiord in Møre and Romsdal, ongoing preliminary projects for three main technical concepts are expected to clarify the technical solution, cf. presentation from the Halsafjord Conference 2020 at www.halsafjordsambandet.no.
In the private sector, the development of bridge technology is also taking place outside the work that takes place under directions of the E39 projects, and there are some interesting development features in this work that can reduce costs in relation to what has been the prevailing perception of the cost level so far.
Low floating bridge solutions
Current suppliers believe that low floating bridge solutions for relatively sheltered waters such as here, will have a construction cost ex. VAT. of 0.7 – 1.0 million kroner per meter. The Trondheimsfiord has a width of just under seven kilometers between Flakk and Rørvik, while the crossing of the Stjørnfiord is around three kilometers. We have assumed the highest meter price as an average, but the solutions for passengers for ships and towing mean considerable uncertainty for the Trondheim Fiord. It is the suppliers who in our case will offer solutions based on functional requirements for the crossing of both fiords.
The prices depend to a relatively small extent on the steel price on the world market. The costs related to transport, processing, logistics at the production site, and marine installation represent 80-90% of the costs per. kg pre-installed steel. These costs are strongly influenced by how the constructions are designed and adapted to automated production lines. The lines in Norway are still considered to be relatively poorly automated, but the first is pr. September 2020 under establishment.
Below are several examples of technical solutions. All crossings will be special with their sets of loads from wind, current, waves, bottom conditions, etc., and technical solutions must therefore be tailored to each individual location.
Other solutions can be found in the presentations from the Fosenbru conference 2020, as well as the Halsafjord conference 2020.