Proceedings of the

The 33rd European Safety and Reliability Conference (ESREL 2023)
3 – 8 September 2023, Southampton, UK

Ship Allision Risk Analysis for the 28-Year-Old Nordhordland Bridge in Norway

Mathias Egeland Eidem1,a, Yanyan Sha1,b, Ida Moen1,c and Roger Flage2

1Department of Mechanical and Structural Engineering and Materials Science, University of Stavanger, Norway.

2Department of Safety, Economics and Planning, University of Stavanger, Norway.


The Nordhordland bridge is a 1246 m long floating bridge in Norway, completed in 1994. Since its opening, the bridge has suffered two ship allisions leading to minor damage. With new and improved tools and knowledge about ship allision risk, ship impact analysis, and changes in maritime ship traffic, the original design requirements of the bridge are revisited to investigate if the structure meets the original and current design code requirements. A simplified frequency analysis for ship allisions against the bridge is performed based on past events as well as by using the software IWRAP to determine the design impact load for the bridge. Furthermore, a structural impact analysis is performed using the software LS-DYNA to investigate if the bridge can survive the previously determined impact load level. It is found that the pontoons are the weak spot when it comes to ship impacts and do not have sufficient capacity to meet today's requirements.

Keywords: Ship collision risk, Ship allision risk, Floating bridge, Frequency analysis, Impact analysis.

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