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CATEGORIES:Isaac Newton Institute Seminar Series
SUMMARY:Design and Assessment Methods for Ships in Ice - C
laude Daley (Memorial University of Newfoundland)
DTSTART;TZID=Europe/London:20171107T100000
DTEND;TZID=Europe/London:20171107T110000
UID:TALK94570AThttp://talks.cam.ac.uk
URL:http://talks.cam.ac.uk/talk/index/94570
DESCRIPTION:Design and assessment of ships in ice is a topic t
hat concerns a wide range of people\, from owners\
, to designers\, builders\, regulators and the ins
urance industry\, with the public\, the environmen
t and the economy being impacted by arctic shippin
g risks. The methods that are being used to design
and evaluate ice class ships have evolved over ma
ny decades and are currently continuing to change.
In this discussion\, the focus is on the steel st
ructure of ice-going ships\, including structurall
y important ice loads and the nature of the struct
ural response. \;
As we seek to better
understand the nature of the interaction between
ships and ice\, we are increasingly focusing on co
mplex multi-body interactions and non-linear behav
iours. In such situations\, general solutions are
not only not currently available\, but may not be
achievable at all. While we can assemble specific
solutions\, we must ask whether a general understa
nding of complex nonlinear systems is possible\, a
nd if so\, what mathematics can we use to develop
them?
Concern for structural ice loads has\
, until now\, mainly focused on a single situation
\; the &ldquo\;design condition&rdquo\;. For that
condition\, the structure behaves linearly or pseu
do-linearly. The &ldquo\;design&rdquo\; loads have
been largely developed empirically\, from a combi
nation of measurement data and loads inferred from
past successful practice.
While much of th
e current industrial and regulatory practice still
employs relatively simple models of load and resp
onse\, new sets of tools and approaches are taking
shape and are being applied by the most sophistic
ated ship owners\, builders and operators. These n
ew approaches seek to directly model a growing set
of complex issues and scenarios\, with consequent
improvements in the fidelity of ice loads and str
uctural response. The growing computational power
and improving simulation tools are enabling these
developments. To illustrate these approaches\, som
e of the author&rsquo\;s own efforts will be descr
ibed.
One recent and developing technique
is called safe speed analysis. This method involve
s modeling a wide variety of discrete ship-ice int
eraction cases\, modelling the load and overload c
apacity of the vessel and then combining these res
ults to produce a multi-parameter map of acceptabl
e operations (speed\, ice size\, etc). The method
makes use of available tools and solutions\, inclu
ding &ldquo\;Popov&rdquo\; type collision models (
algebraic solutions of two-body collisions)\, and
explicit dynamic finite element models (LS-Dyna) t
o capture interaction kinematics\, contact and a f
ull range of structural responses (ductility\, dyn
amics\, stability).
A second\, but related
technique is a model called GEM\, which uses simpl
e event solutions and simple equations of motion t
o model large scale operations of vessels in ice.
GEM\, while seeking a reasonable level of accuracy
\, focuses on high simulation speeds and practical
decision support rather than on fidelity and univ
ersality.
After presenting these two method
s\, the presentation raises three mathematical cha
llenges. The first challenge relates to the proble
m of interacting chaotic systems and wonders wheth
er a calculus for such systems is possible. The se
cond challenge questions the application of probab
ilistic design to ice class ships. The third chall
enge relates to the simulation of multi-body syste
ms. Such systems are highly nonlinear and computat
ionally costly to model. Could an asynchronous or
quasi-synchronous timestep algorithm yield improve
ments in overall speed?
LOCATION:Seminar Room 1\, Newton Institute
CONTACT:INI IT
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