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Independent Analyses of OON Floating Bridge BJF 2019
This report documents the independent analyses for OON concept K12 alternative for Bjørnafjorden crossing. The independent analyses are focused on the capacity of the bridge girder and the mooring lines. Independent analyses are based on a coupled time domain analysis model in SIMO/RIFLEX. Each simulation has an effective duration of 3 hours, and each ULS/ALS simulation has been repeated with 30 different realizations of wind and waves. The geometry of the bridge has been received from the designer. Cross-section properties of the steel girder has been based on latest drawings while designer’s cross section data has been used for tower, columns, cables and concrete sections. Hydrodynamic loads on the pontoons are based on WADAM. Analysis cases are based on DNV GL interpretation of the Metocean design basis. The designer has used quasi-static stiffness for the mooring lines, while DNV GL has used dynamic stiffness, which is more appropriate. This results in larger dynamic line tensions than the designer. Apart from the small effect on the eigen periods, the use of quasi-static stiffness is probably slightly conservative with respect to the response in the girder. Otherwise, the analysis results are generally in line with designer’s results.