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SAMC
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• ANNUAL REPORT 2013
Ice-induced vibration, analysis of
measurements
Torodd Nord works with ice-induced vibration and
specifically addresses the analysis of measurements.
He worked together with Dr. Eliz-Mari Lourens from
TU Delft on Force identification throughout 2013, and
will continue in 2014. State-of-the-Art methods to
identify crushing forces on a bottom-founded struc-
tures forces have been implemented and applied on
experimental data. The recently developed Kalman
filter-based algorithm is compared with the traditional
force identification method by means of frequency
response functions (see Nord et al., 2013). Since the
latter approach is difficult to apply on large structures,
the new one overcomes that difficulty. No assumptions
have to be made on the forces we identify, it needs no
regularization, thus it can be implemented to render
forces directly from the response-measurements. In
addition, the method allows the unmeasured extrac-
tion of responses (acceleration, velocity, displace-
ment, strain) at any location. The results will first be
presented in the Eurodyn conference in Portugal 2014
and at the SAMCoT PhD workshop in May 2014. A journal
article will be submitted in early 2014. Nord has also
been working on describing the interaction process by
analysing forces, responses and tactile sensor data. The
results will be part of a second journal paper in 2014. In
autumn 2013, it was agreed to cancel laboratory testing
of ice-induced vibration experiments, which had been
evaluated through several rounds with different designs.
Nord embedded that task into Øyvind Wiig Pettersen’s
project, intended for use in the Aalto University mechan-
ical laboratory. A new proposal for full-scale monitoring
of the Hanko-1 channel marker was raised in November,
and Nord started the process of designing protection
for the sensors deployed close to the water level. The
weather forecast will decide if the instrumentation will
be deployed in January 2014 or in 2015.
Nord has been teaching at UNIS in the spring and
autumn, and also doing fieldwork involving in situ uniax-
ial compression tests, temperature profiling, beam
tests and indentation tests.
Ice-induced vibrations, modelling and
prediction
PhD candidate Hayo Hendrikse addresses ice-induced
vibrations but works with the modelling and predic-
tion of ice-induced vibrations. The work on modelling
and prediction of ice-induced vibrations (IIV) reached a
phase of consolidation of knowledge and tying up loose
ends in 2013. Through cooperation and discussion with
international experts in the field, answers were sought
to key questions identified in earlier phases. Part of
the result of these discussions was presented at the
POAC’13 conference in Helsinki. Considerable effort has
been put into defining a test campaign that could fill the
knowledge and data gaps. It was decided to postpone
the actual execution of such a campaign until the first
results are reported upon. As a result of this decision
the work on modelling and prediction of ice-induced
vibrations entered the reporting phase at the end of
2013.
A series of discussions organized in Trondheim with
Professor E.M. Schulson (USA), Dr. K. Kolari (Finland)
and Dr. D.S. Sodhi (USA) has led to an increase in both
understanding of the physics of ice failure as well as
the generation of new concepts for the explanation of
ice-induced vibrations. The sessions proved invalu-
able for PhD studies and the interest, patience and
open-minded approach of all participants were greatly
appreciated.
The first model for the prediction of ice-induced vibra-
tions is currently being reported upon and will be
made available to the partners of SAMCoT at the start
of the second quarter in 2014. The model implements
PhD candidate Nord installing a load cell before indentation
tests at UNIS.
Photo: Marina Verbeckaya