On a simple oscillator problem describing ice-induced vibrations of an offshore structure
A. Abramian (Institute for Problems of Mechanical Engineering of the Russian Academy of Sciences, St. Petersburg)
SA Vakulenko (Institute for Problems of Mechanical Engineering of the Russian Academy of Sciences, St. Petersburg)
WT van Horssen (TU Delft - Mathematical Physics)
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Abstract
In this paper, a new simple oscillator model is considered describing ice-induced vibrations of upstanding, water-surrounded, and bottom-founded offshore structures. Existing models are extended by taking into account deformations of an ice floe and a moving contact interaction between an ice rod, which is cut out from the floe, and the oscillator which represents the offshore structure. Special attention is paid to a type of ice-induced vibrations of structures, known as frequency lock-in, and characterized by having the dominant frequency of the ice forces near a natural frequency of the structure. A new asymptotical approach is proposed that allows one to include ice floe deformations and to obtain a nonlinear equation for the simple oscillator vibrations. The instability onset, induced by resonance effects for the oscillator and generated by the ice rod structure interaction, is studied in detail.
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