Reconstructing beam bending strength of arctic second year ice from small disk bending tests

The flexural strength of ice is one of the most significant strength parameters for the design of ships and marine structures in ice. By an unwritten convention the flexural strength refers to beam bending tests in ice. For this engineering formulas are derived that support engineering design. However, both climate and engineering fields are changing and ice properties still need to be assessed by in-situ measurements. Beam bending tests in full-scale, i.e. nature, are laborious and require both significant time and equipment. In the light of this an alternative method based on thin disk bending tests gained from drilled standard ice cores is presented. The method of testing small disks is introduced in the late 1960ies and has gained little attention in the community. The method presented utilizes tested disk samples throughout the entire ice thickness in order to assess the distribution of properties, while using this information reconstructing the global behavior of an ice cantilever beam in flexure. A numerical model of a virtual cantilever ice beam experiment is built from which the reference flexural strength of a cantilever beam is derived. The determined flexural strength is reduced by a stress concentration factor accounting for the notch effect in the beam-root transition. This stress concentration factor is determined numerically for different ratios of radius and beam width. Finally, the obtained strength value is scaled accounting for the increase of flaws in larger ice specimens. The approach is compared with literature data and evaluated in terms of its validity and robustness. The method also indicates the problem of missing standards for flexural strength determination.

Subjects

flexural strength Arctic

ice

DDC Class

600: Technology

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Reconstructing beam bending strength of arctic second year ice from small disk bending tests