Model tests in ice are well-established to assess ice loads acting on ship-shaped structures. Model basins worldwide have elaborated different types of model ice over the past decades and gained confidence in e.g. predicting ship’s resistance which is validated by full scale data. Driven by industrial needs, the model ice was invented and modified with emphasis on the failure observed on ship hulls: Mostly flexural failure with only limited influence of crushing, i.e. against a vertical stem contour. Nowadays, the same model ice is occasionally used for structures exposed to ice action which are far from being ship-shaped, such as vertical sided monopiles or artificial islands. This approach is often questioned as the currently used model ice is usually insufficiently brittle, overstates out-of-plane deformation and flexural failure of the ice sheet, and transfers most of the ice load by a hard top layer rather than creating a wedge-shaped ice edge with a line-like contact approximately at middle height of the ice thickness as observed in full scale indentation tests. Therefore, results from tests with vertical structures in model ice have to be treated cautiously and not all observations are directly scalable. In an attempt to overcome the most severe issues with HSVA’s model ice in tests with vertically sided structures, a new way of initiating the formation of a model ice sheet was tested as a part of the IVOS project. Instead of spraying a top layer, the water in the basin was kept in motion by a wave maker while crystals formed. When the waves were stopped, an ice sheet with larger crystals in the top layer grew. A compliant vertical structure was pushed through this ice sheet and global and local loads were measured. The measurements were compared to tests with the same structure in conventional columnar model ice. Various ice properties were measured throughout the tests.
This paper introduces an alternative way to create a model ice sheet for tests with vertically sided structures utilizing a wavemaker, and discusses the findings from first model tests.
