Development of an experimental setup to investigate the impact of higher structural modes on dynamic ice-structure interaction
Dynamic ice-structure interaction is a major issue for bottom founded offshore structures subjected to drifting sea ice.The interaction can magnify the ice loads the structure has to withstand, and severe vibrations may occur which can lead to fatigue damage. However, today’s understanding of dynamic ice-structure interaction is still insufficient, and available predictiontools and methods suffer from several uncertainties. One reason is the lack of data of sufficient quality which could be used for model validation. Full-scale data typically suffer from missing ice parameters and insufficiently defined ice conditions. Model scale data are usually obtained from tests with a single degree of freedom (SDOF) structure, thus neglecting the influence of higher structural modes on the interaction, although it was already pointed out in the 1970s that the second mode may have a considerable impact. In order to fill this gap, a new experimental setup was developed at HSVA as part of the FATICE project. This setup enables testing with a structure whose configuration could be changed from SDOF to multi-degree of freedom (MDOF, 2 natural frequencies) to compare the developing dynamic ice-structure interaction modes.The paper describes the development of the experimental setup, its practical implementation, and its applicability and limitations for ice model tests. Basic results from the comparison of SDOF and MDOF conditionsare discussed.