Abstract
This chapter presents recent research and developments on floating bridges, with a particular focus on the analysis of environmental load effects for ULS design checks and analyses for risk-based design against ship impacts of the Bjørnafjord floating bridge in Norway. Both numerical and experimental methods are used in addressing challenging features associated with handling inhomogeneity in environmental conditions, wave interaction between pontoons, wave-current interaction and viscous damping, parametric excitation generating horizontal motion of the bridge as well as proper and efficient account of the long-term variability in environmental conditions. A risk analysis procedure to deal with the major accidental load for floating bridges, namely ship impacts, is presented. It involves an estimate of the frequency of impact scenarios, the immediate structural damage and possible flooding, the expected time for repair and ultimate consequences in terms of fatalities and road traffic downtime. To reduce the relatively high road traffic disruption rate estimated, it is proposed that the impact frequency for relatively frequent low energy events (in addition to the initial focus on 10–4 events relevant for the ALS criterion) be scrutinized. Additionally, consider introducing extended ship traffic control measures, as well as to possibly introduce a limit state in addition to the ALS to address the risk associated with frequent impacts.