A Submerged Floating Tube Bridge Concept for the Bjørnafjord Crossing: Marine Operations

Abstract

A submerged floating tube bridge (SFTB) concept is one of the three alternatives for the Bjørnafjord crossing in Norway. Two SFTB designs have been developed: one pontoon-stabilized and one tether-stabilized. There are no submerged floating tube bridges yet built and installed. Consequently there is no direct practical experience with assembly and installation of such massive string-like structures. The purpose of this article is to describe possible means of fabrication, assembling, jointing and installation of SFTB elements and the tube-bridge itself. All major project activities have been divided into stages. Further, these stages have been subdivided into factual steps to demonstrate feasibility based on various criteria. The major construction challenge is to assembly fabricated SFTB elements into one 4580 m string in a floating condition and then to tow and install it in the fjord. The focus was to utilize existing technologies and experiences available from offshore industry to the fullest extent, so that conventional tools and methods could be applied to this new application. Possible solutions both for the tether-stabilized and pontoon-stabilized alternatives — with differences in the foundation/tether and pontoon installations and associated SFTB interfaces — have been developed.

Experimental Study on 2D Motion Characteristics of Submerged Floating Tunnel in Waves

“…However, most of them are still in the concept design stage and have not yet been seen in engineering applications [5]. Recently, the Norwegian Public Road Administration has been considering the first construction of the SFT crossing 'fjords' in Norway and initial research has been carried out [6,7]. In China, the concept of the SFT has also been selected as one of the potential 60 future-oriented scientific and engineering technical challenges by the China Association for Science and Technology (CAST) in 2018.…”

Time-Domain Hydro-Elastic Analysis of a SFT (Submerged Floating Tunnel) with Mooring Lines under Extreme Wave and Seismic Excitations

“…Considering that wave/current/wind effects are greatly reduced, the cost is almost constant along the length [5], and ship passage is not obstructed by the structure, the SFT has been regarded as a competitive alternative to floating bridges and immersed tunnels. In this regard, since Norway's first patent in 1923 [6], many proposals and case studies have been published worldwide, which includes Høgsfjord/Bjørnafjord in Norway [7][8][9], the Strait of Messina in Italy [10], Funka Bay in Japan [11,12], Qiandao Lake in China [13,14], and the Mokpo-Jeju SFT in Korea [15]. Even though there is no actually installed structure in the world despite extensive research [16], the first construction of the SFT is being considered by Norwegian Public Road Administration (NPRA) with global interest [17].…”