NSTC

Challenged by the Sea

Monday 09 Dec 19
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The sea is a demanding opponent, constantly impacting and challenging offshore structures. It takes a robust design to ensure a long service life of, for example, offshore wind turbines or platforms, which needs to stay operational for many years. Therefore, DHRTC has developed a design for a near shore test center, which is now in tender in order to have the facilities in operation from autumn 2020. Everyone with an interest in offshore structures will have a unique opportunity to gain knowledge about the impact of the sea.

All over the world, structure are being build offshore to have energy sent ashore. It requires accurate design calculations based on knowledge of, among other things, waves, ocean currents and winds to construct structures meeting the high safety requirements throughout a long service life. At worst, just a single wave can cause structural failure to occur.

DHRTC is working to establish a test centre that will provide information on extreme wave events and the actual wave loading that offshore structures such as wind mill foundations and platforms is exposed to during their lifetime at sea. These parameters is today associated with significant uncertainty due to lack of knowledge of extreme events such as breaking waves and the impact forces they cause during the encounter with an offshore construction. Furthermore, the test centre will be able to reduce some of the uncertainty involved in scaling between wave basins and full scale constructions by acting as a validation point.

“We use the sea for a number of things, of which energy supply plays a big role. We must build with due consideration for the extreme forces that the sea can impose on offshore structures so that the safety of the structures' integrity is maintained, even when hit by unusually heavy storms after standing at sea for many years.” says Anders Bak-Jensen , Program Manager at DHRTC about the upcoming test centres. “We have a design ready for the centre and are now preparing a tender for the manufacturing and offshore installation of. At the same time, we finalising specifications for the initial instrumentation package to be installed on the test structures in order to provide critical data on waves, load impact and the structural response. "

During the first quarter of 2020, funding needs to be secured in order for the centre to be ready for installation and start delivering data for researchers and companies interested in constructions at sea. Thus, the intention is to record data from the winter of 2020/2021.

The test centre is established with a facility platform and a sensor platform. This construction ensures that the platforms are prepared for later upgrades and can handle expansion with additional sensor structures, which may prove relevant in the long run. The upcoming sensor platform is designed in such way that the dynamic response matches the response of the full-scale offshore structures, providing the best basis for comparison of data from the test centre with existing structures.

The test centre will be placed approx. 4 km west of Anholt, which is a location selected in collaboration with DHI. The location has been selected based on wave and wind modelling showing that the site provides unique conditions for recording scaled wave statistics giving the opportunity to annually record the extreme waves that are otherwise expected to occur at offshore structures with 10,000 to 100,000 year intervals.

 

Caption
LIC Engineering has designed the test site structures, while DHI has assisted in identifying suitable locations for the test site. Now the construction and installation of the structures is being brought into tender with the plan to have the test centre become operational in 2020.

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https://www.oilgas.dtu.dk/english/news/news-and-press/nyhedsbase/2019/12/with-the-sea-as-a-challenger?id=fd55fa88-c864-4eeb-b8d7-e94e8dd0596c
1 JUNE 2020