INDUSTRY ARTICLE
planned offshore wind turbine. Collision- friendly design is proved if the calculations demonstrate that an individual wind turbine is ‘weaker’ than the reference ship, i.e. that the turbine would fail first in the case of a collision. In concrete terms this means that the hull of a ship (or, in the case of double- hull ships, the inner hull) will not tear.
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DOES THE MODEL ADEQUATELY REFLECT REALITY? Given this, the BSH does not require collision analysis to supply exact quantification of the extent of damage, but to give qualitative answers to the following questions: (1) what will fail first, the ship or the turbine, and (2) will the possible damage caused by a collision be minor, moderate, major or catastrophic? Of course the assumptions on which a collision scenario is based and which are included in the calculation models significantly influence the analysis results and their informative value. These are: Which type of ship is selected as reference ship? At what speed will the vessel hit the turbine? While the BSH defines the key parameters, experts are given plenty of leeway in the preparation of the finite-element models (FE models) that are needed for the analysis and the simulations.
2 - Collision Ship vs Monopile 3
CONSERVATIVE ASSUMPTIONS FOR SIMPLIFICATION Simplifying the very complex models and analyses by using assumptions suggests itself and is acceptable and expedient, provided the experts use conservative data and values. When this is done, the results are always on the safe side because a wind turbine that fails in a collision with a ‘weaker’ reference ship in the calculation model will definitely fail in a collision with a ship that is more robust in reality.
3 - Collision Ships vs MP results plastic strain after 7.4sec
www.windenergynetwork.co.uk 05
The offshore wind industry has shown a tendency to adopt this approach, i.e. the ships modelled in calculations so far have been more ‘fragile’ than they are in reality. However, as the standard does not define comprehensive requirements as to which parameters must be taken into account and how; the various scenarios cannot be compared to each other.
Given this, we do not know the extent to which the individual models actually reflect reality. This shows that – in the medium term – the development of standardised models and procedures is necessary and that all stakeholders should work together to develop a safety-focused strategy.
BINDING STANDARDS
Within the framework of a harmonisation process, stakeholders would benefit considerably from binding standards and directives in terms of safety, sustainability and not least profitability.
Björn Kramer TÜV SÜD Industrie Service GmbH Click to view more info
ED’S NOTE This is an abridged version – please view the full article through the QR Code below or link online including…
• Further aspects at a glance • The reference ship • Where does the ship hull hit the turbine or platform?
• What forces are developed by the displaced water mass?
• Will the nacelle stay in position? • Are operating loads relevant? • Loads caused by service boats • Accepting challenges
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