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

Case study: The Bergsøysund Bridge

The Bergsøysund Bridge is a unique type of floating bridge, located on the northwestern coast of Norway. Its floating span of 840 m is supported by pontoons with no mooring to the seabed. This fact makes it a very interesting case study. Our extensive research on floating bridges requires knowledge from several engineering fields; such as hydrodynamics, finite element analysis, and control theory.

A comprehensive structural monitoring campaign has been conducted on the Bergsøysund Bridge in order to improve the current understanding of the dynamic behaviour of floating bridges and their interaction with waves. We have also published the long-term measurements of acceleration responses and waves as an open data set.

System identification and modal analysis

Using the data from the monitoring system, the modal vibration parameters of the bridge such as natural frequencies, damping ratios, and mode shapes can be found. The results are a highly valuable asset for several applications:

• Studying the dynamic behaviour of the bridge

• Updating a numerical finite element model, such that it better describes the real behaviour of the bridge

• Verifying and improving 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 system 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.