Dynamic Analysis Of Floating Bridges

The main objective of this paper is to analyze the dynamic response of floating bridges with transverse pontoons, when subjected to harmonic regular wave loads. As a result, a simplified beam model of the Bergsoysund floating bridge is established in the FEM software Abaqus. Additional "synthetic" floating bridge structures are subsequently built and analyzed in a similar manner. The pontoon model constructed in Genie is analyzed in HydroD to obtain the pontoon's structural model and hydrodynamic parameters.In addition to these parameters, by implementing the calculated data of mass and sectional properties of the bridge truss-work components, the simplified beam model of the bridge is built in Abaqus. Taking the Bergsoysundfloating bridge model as the basis, "synthetic" bridge models are similarly assembled and studied. The effect of sideway mooring is also considered for the elongated bridge models. For each of the bridge models, eigenfrequency analysis is carried out in Abaqus in order to determine the natural frequency of the sway (lateral) and heave modes.For anatural frequencyof a bridge model obtained from Abaqus, the updated added mass of each pontoon is obtained from HydroD by directing waves of the same frequency at the pontoon model. The eigenfrequency analysis is performed again with the updated added mass and this process is repeated until the natural frequency of the mode and the subsequent added mass are concurrent.The wave loadamplitude on the pontoon model corresponding to the updated natural frequency of the modeis acquired from the hydrodynamic analysis in HydroD. The dynamic analysis is then carried out in Abaqus by applying the harmonic regular wave load on each pontoon of the bridge model. Efficient techniques are presented to calculate the phase difference at each pontoon. This arises due to the combined effect of changing wave direction and shapes of the models. A simplified method is employed to gauge the critical angle of wave heading. Limitations with regard to the non-application of full matrices of the pontoon's structural model and hydrodynamic parameters are highlighted. Negativelydamped sway motions are controlled by the application of external lateraldampers. Mixed results are obtained at the estimated critical angles. Better result is obtained by iteration of the responses for growing angles of wave heading. (C) 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of the 10th International Conference on Marine Technology.