Author(s): J. Kajaste-Rudnitski
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Abstract: The ice-structure system consists from the moving ice field with highly non-linear material properties and a structure usually linearly responded to the random in time and space ice crashing. If one had a power density spectrum of the ice crashing forces, then the structure response could be studied using the linear spectral analysis, the non-linear behaviour of ice being incorporated into the known ice force density spectrum. The problem is to get somehow this spectrum or, in other words, to extract the ice crashing part from the measured total ice-structure interaction density spectrum. This spectral separation has been done for a slender structure assuming that the total load exerted upon the structure is a superposition of the unknown ice crashing force f (£, t) at the point £ on the structure x-axis and the linear resistance to the ice movement propotional to the small displacement y (, t) and its first time derivative (£, t). That is. .. . The sign and magnitude of the proportionality coefficients k and c can be evaluated from the measured response density spectrum and from the measured and calculated eigenvalues. Found this way the pure ice force density spectrum reveals a dominant frequency of ice crashing against the structure. Location of this dominant peak on the frequency axis depends on the ice sheet velocity and when hitting the nearest resonance frequency it produces severe vibrations of the structure. Assuming certain correlation in space of the ice crashing forces the analysis can be expanded to the wide structures of the shell type.
Year: 1990