Modelling the stochastic dynamic behaviour of a pontoon bridge: A case study

•Case study on existing floating pontoon bridge.•Study is based on finite element method and linearized potential theory.•Investigation of damping contribution from fluid–structure interaction.•Correlation of wave excitation interpreted with respect to geometry.•Response effects due to changes in sea state are studied.

Herein, a study on the hydrodynamic modelling of pontoon bridges is presented, with the Bergsøysund Bridge as a representative example. The model relies on the finite element method and linearized potential theory. The primary emphasis is placed on the stochastic response analysis within the framework of the power spectral density method. The quadratic eigenvalue problem is solved using a state-space representation and an iterative algorithm. The contribution of the fluid–structure interaction to the overall modal damping is investigated. Response effects due to changes in the sea state are studied. A frequency-independent approximation of the hydrodynamic coefficients is presented and discussed.