Floating bridges

Floating bridges

The Bergsøysund Bridge. Photograph by NTNU/Knut Andreas Kvåle.

Case study: The Bergsøysund Bridge

The Bergsøysund Bridge is a 931 meters long floating bridge, located on the northwestern coast of Norway. It relies on a pontoon-based design with no mooring to the seabed; and it is the second longest in the world of its kind. This fact makes it a very interesting case study. Our research in the field of floating bridges requires knowledge from several engineering fields; such as hydrodynamics, finite element analysis, and control theory.

Experimental surveys

A comprehensive measurement system is operating on the Bergsøysund Bridge to improve our current understanding of the dynamic behaviour of floating bridges and their interaction with waves. This includes sensors for measurement of both response and environmental excitation. The system is described in detail under Structural monitoring (Structural monitoring - The Bergsøysund Bridge).

System identification and modal analysis

Based on recordings established by the monitoring system, parameters characterizing the system behaviour; typically represented by natural frequencies, damping ratios, and mode shapes; are estimated (system identification). The results are a highly valuable asset for these applications:

  • Studying the dynamic behaviour of the bridge
  • Updating the numerical model, such that it better describes the real behaviour of the bridge
  • Verification and possible improvement of the current state-of-the-art methods used for numerical modelling

The application of system identification on floating bridges is a relatively unexplored problem, and it will put the current state-of-the-art identification methods to the test. 

Animation of second vertical mode (f=0.16 Hz). Model and animation by NTNU/Øyvind Wiig Petersen and Knut Andreas Kvåle.

Load modelling

Floating bridges represent a new phase of pushing the boundaries of civil engineering structures. Since we want to construct longer bridges, at more exposed locations, with novel structural concepts, it is important to ensure the structural safety is satisfactory. A good understanding of the loads the structure is exposed to, as well as the corresponding structural response is required. A range of research topics is relevant to the wave excitation, which is the governing load on floating bridges:

  • Extreme loads such as annual or 100 year storms
  • Investigation of the structural response to different sea states
  • Identification of hydrodynamic loading using measured dynamic response
  • Uncertainties in the load models and how these transfer to the predicted dynamic response


Postdocs and PhD candidates working with floating bridges:

Contact bridge


Professor Ole Øiseth

Phone: +47 735 91 493

E-mail: ole.oiseth@ntnu.no