Model-based force identification in experimental ice-structure interaction by means of Kalman filtering

The level-ice forces exerted on a scale model of a compliant bottom founded structure are identified from noncollocated strain and acceleration measurements by means of a joint input-state estimation algorithm. The identification is performed based on two different finite element models: one entirely based on the blueprints of the structure, and an updated one which predicts the first natural frequency more accurately. Results are presented for two different excitation scenarios characterized by the ice failure process and ice velocity, and known as the intermittent crushing and the continuous brittle crushing regimes. The accuracy of the identified forces is assessed by comparing them with those obtained by a frequency domain deconvolution on the basis of experimentally obtained frequency response functions. Results show a successful identification of the level-ice forces for both the intermittent and continuous brittle crushing regimes, even when significant modeling errors are present. The ice-induced displacements of the structure identified in conjunction with the forces are also compared to those measured during the experiment. These are found to be sensitive to the modelling errors in the blueprint model. By a simple tuning of the model, however, the estimated response is seen to match the measured one with high accuracy.