This paper describes the basic structural design for a Submerged Floating Tube Bridge (from now on SFTB) across the Digernessund in Norway. The SFTB is proposed as part of a scheme for a new and improved fixed link along the E39 route, across the Bømlafjord in Norway. The existing fixed link consists of a 7.8 km long subsea rock tunnel below the main part of the Bømlafjord, and a 677 m long suspension bridge spanning across the Digernessund, which was too deep for a subsea rock tunnel. The two parts of the link meet at a small island named Føyno. The existing tunnel does not comply with new EU regulations for tunnels due to the high gradient, but an improved tunnel with a SFTB through the Digernessund will solve the problem.
The paper will discuss different structural solutions for the SFTB. A possible construction method will also be evaluated.