Deriving an ice strength coefficient from mean crushing loads and observations on low-speed ice–structure interaction

The design of flexible vertical offshore structures exposed to ice, like offshore wind turbines, can become governed by ice loads and structural responses at low relative ice speeds. This study attempts to quantify the low-speed ice loads based on a hypothesized interaction mechanism linking the velocity dependence of global loads to specific states of the ice supported by model- and full-scale observations. The quantified velocity effect is applied to estimate potential global pressures at low speeds from high-speed crushing events from the full-scale measurement campaign at the Norströmsgrund lighthouse. It is estimated that the velocity effect may produce global pressures equivalent to applying an ice strength coefficient of 0.9 MPa to 1.6 MPa. These results substantiate an alternative physics-informed approach to account for the velocity effect for ice loads and provide an interpretation of the interaction scenario captured by the 1.8 MPa value in the ISO19906 design standard.