New nonlinear model for ice induced vibrations

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 (IIV) 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. We propose a new asymptotical method that allows us to exclude ice floe deformations and obtain a nonlinear equation for structure vibrations. We investigate instability onset, and resonance effects for these vibrations.