What experiences does Washington State have with its floating structures? What characteristics do steel structures have compared to concrete? What experiences do consultants have with large contracts abroad? How far has the Korea Advanced Institute of Science and Technology (KAIST) come in the development of submerged floating tunnel? These were some of the topics for the conference held in Trondheim, Norway. 

Sharing knowledge is key

Professor Haeng-Ki Lee from KAIST presented how he manages three research groups working on the Submerged Floating Tunnel / Pipe Bridge (SFT). The three groups concentrate on design / analysis, materials / construction / anchoring and operation / maintenance.

– We do thorough research to ensure that the solutions we choose are safe, we estimate to test a pilot in 2021-2024, Lee said.

Arianna Minoretti (Norwegian Public Roads Administration) explained in her presentation of submerged floating tunnels, the research results so far.

– I believe that sharing knowledge is necessary in order to realize this kind of solution, she said. She said that Norway now has 40 years of experience from offshore technology, and that the experience can be utilised in order to optimize the SFT construction.

– Every step forward is a step for everyone, so it's important for everyone to gain access to the results, said Minoretti. She also emphasized that this new type of bridge is a great opportunity both for Norway and for other countries, as the technology will give new opportunities for industrial growth as well as an opportunity for industries to prefabricate the elements.

 Is a floating bridge safe?

Nicholas T. Rodda of the Washington State Department of Transport talked about the four floating structures in Seattle, Washington. The first floating bridge, Hood Canal opened in 1940. Rodda explained how they have a special system for maintenance of the floating pontoons, and a complex lock system to adjust the water level in the canal. He explained that the bridge has been through several changes, e.g. adjusting the ship passing canal.

The first floating bridge was 1957 meters long. It sank during a storm in 1973 and was thereafter rebuilt with a new type of pontoons (hydraulic). Washington also has the world's longest float bridge, the Second lake bridge (opened in 1963) with a length of 2130 km. Due to a lot of storms, it must often close, as it is very low over the water. Rodda said that the Third Lake Bridge is now expanding to carry light trains. This is the widest bridge, and is 32 meters wide.

– In 1990, we experienced another disaster when one of the floating constructions was undergoing improvement. We had an unexpected storm and water leaked into the maintenance shutters that were open. 13 anchoring lines were torn, and the bridge sank. These two accidents have led to the development of new methods for detecting leaks. In addition, we have changed the pontoons so that we can add more when needed, almost like bricks of Lego. Floating bridges are safe, but it is important to monitor cracks that can lead to leaks. Lifetime is one of the biggest challenges we face, but the future looks bright, we have developed a new type of anchor cables with a lifespan of 25-30 years, and it helps increase the life of our floating bridges, Rodda said.

The consultants shared their experiences

The Norwegian companies Kværner and Aas-Jakobsen shared their experiences with floating structures (both steel and concrete structures), the construction of large floating structures abroad, experiences with international regulations and about cooperation with international companies. Katrine Haldorsen (Kværner) and Svein Erik Jakobsen had many experiences to share with the participants. The Danish company Svend Ove Hansen ApS was represented by Kristoffer Hoffmann who told about innovations in the field of constructing suspension bridges able to withstand wind loads.

The participants were active, and asked questions about contract experience and technical solutions.

The NPRA’s own specialists spoke about progress in the Coastal Highway Route E39 project and how the project is working towards the next national transportation plan (NTP) in Norway. The technical status of floating suspension bridge (Simen Holtberget) and the development of a floating bridge over the Bjørnafjord (Bernardo Costa) were presented.

Three PhD / PostDoc researchers presented their research on ship collisions (Yanyan Sha, NTNU), the aerodynamic stability of long suspension bridges (Ibuki Kusano, University of Stavanger) and driving comfort for motorists on floating bridges (Dragan Sekulic, Chalmers Technical University).

A call for more collaboration

– In my opinion, we have showcased a wide breadth and solid academic work today, says Kjersti Kvalheim Dunham, Program Manager for The Coastal Highway Route E39 project (NPRA). We know that research produces results! It has been an absolute pleasure for me to introduce all the professionals and excellent researchers who have shared their knowledge and experiences on bridge engineering, she says.

Dunham says that research in the E39-project has already resulted in savings for the Norwegian Public Roads Administration, but has also benefited Møre Ocean Lab, Rolls Royce, Avinor, the fishing industry, the shipping industry and the Digital Ocean Space research center in Norway.

– We welcome other industries who would like to cooperate with us! Please contact us, she exclaims.