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Ice
crushing
Ice
crushing
Rigid (or elastic)
structural responce
permanent structural deforma-
tions (damage)
Ultimate Limit State approach
Accidental Limit State approach
Rigid (or elastic)
structural responce
Ice
crushing
Figure 8. Difference between Ultimate Limit State and Accidental Limit State approaches for an ice-structure collision
scenario.
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• ANNUAL REPORT 2013
photos and aircraft patrols, accidents involving ships
and offshore structures continue to occur.
The concept of structural analysis in which the structure
is allowed to deform inelastically due to rare, extreme
ice actions (e.g., a collision with an ice mass) is there-
fore of crucial importance in engineering. In the litera-
ture, this concept is often referred to as Accidental Limit
State (ALS) design (Figure 8). With an ALS approach,
adequate precautions against scenarios outside of the
ice class requirements can be established for both ships
and offshore structures.
During the last five decades, scientists and engineers
have searched for understanding the nature of local
loads generatedduring ice impact. The analysis of impact
phenomena has been restricted due to the complex ice
behaviour under conditions of rapidly applied stress and
the complex geometries of the bodies in contact.
The size-effect problem is quintessential and particu-
larly important to engineers and scientists, who must
inevitably extrapolate ice behaviour from reduced-scale
model tests to real structures. Knowledge of the scale
transition of ice parameters is important because the
tests are often conducted on miniature ice specimens.
The study carried out was a re-examination of the
experimental data obtained for freshwater and iceberg
ice on different scales. The specific energy absorption of
laboratory-grown freshwater ice during crushing on a
small scale is compared with that of lake ice and iceberg
ice during crushing on a medium scale. The main objec-
tive of this study was to assess the specific energy
(energy per unit mass of crushed ice) necessary to turn
solid ice into crushed ice. The specific energy of the ice
crushing process depends on the geometry, the size of
the problem and the ice temperature. If the ice grains
are sufficiently small compared with the indenter size
and the penetration depth and the sample size (width
and thickness) is sufficiently large compared with the
indenter size and the penetration depth, the specific
energy is a size- and scale-independent characteristic.
However, if the grain size is sufficiently large compared
with the indenter (and sample) size and the penetration
depth, the specific energy has a multi-scale character.
The findings of this study were used to further develop
a numerical model of the ice crushing process using
the finite element method and smooth particle
hydrodynamics.
This work considers the ice material model, which was
primarily developed by Dr. Liu to simulate ship-iceberg
impacts and is an isotropic, elastic-plastic model with
failure. This physical interpretation of the input material
parameters and evaluation of the ice material model has
been performed by a potential end user of this model.
The aim of the study was to provide an understanding
of the input parameters and determine recommenda-
tions for the appropriate choice of values in engineering
applications. The results of the calculations were used,