Abstract
Ice-induced vibrations have to be considered in the design of vertically sided offshore structures which may encounter drifting sea or lake ice during their lifetime. One particular aspect is the contribution of ice-induced vibrations to the fatigue of such structures. Estimation of the duration of events is often difficult, due to limited available data on ice drift, leading to conservative assumptions.
In this paper, the approach followed for assessing the fatigue resulting from frequency lock-in vibrations in the design stage of a recent offshore wind project is presented. The project concerned offshore wind turbines with jacket support structures consisting partly of vertical structural members.
The severity of ice-induced vibrations for the structures is first assessed using a simulation model. Following this, ice drift is included in the assessment to obtain an estimate of the number of cycles of frequency lock-in over the lifetime of the structure. Results show that sitespecific combinations of ice floe size and driving forces significantly influence the expected number of cycles of frequency lock-in. It is concluded that for this project limited conditions exist in which sustained vibrations can develop and that the contribution of frequency lock-in to structural fatigue is therefore limited as well.
In this paper, the approach followed for assessing the fatigue resulting from frequency lock-in vibrations in the design stage of a recent offshore wind project is presented. The project concerned offshore wind turbines with jacket support structures consisting partly of vertical structural members.
The severity of ice-induced vibrations for the structures is first assessed using a simulation model. Following this, ice drift is included in the assessment to obtain an estimate of the number of cycles of frequency lock-in over the lifetime of the structure. Results show that sitespecific combinations of ice floe size and driving forces significantly influence the expected number of cycles of frequency lock-in. It is concluded that for this project limited conditions exist in which sustained vibrations can develop and that the contribution of frequency lock-in to structural fatigue is therefore limited as well.
| Original language | English |
|---|---|
| Title of host publication | Proceedings of the 25th International Conference on Port and Ocean Engineering under Arctic Conditions |
| Subtitle of host publication | June 9-13, 2019, Delft, The Netherlands |
| Publisher | Lulea University of Technology |
| Number of pages | 14 |
| Volume | 2019-June |
| ISBN (Print) | 9780000000002 |
| Publication status | Published - 2019 |
| Event | 25th International Conference on Port and Ocean engineering under Arctic Conditions - Delft University of Technology, Delft, Netherlands Duration: 9 Jun 2019 → 13 Jun 2019 https://www.poac2019.nl |
Conference
| Conference | 25th International Conference on Port and Ocean engineering under Arctic Conditions |
|---|---|
| Abbreviated title | POAC19 |
| Country/Territory | Netherlands |
| City | Delft |
| Period | 9/06/19 → 13/06/19 |
| Internet address |
Bibliographical note
Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-careOtherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.
Keywords
- Ice crushing
- offshore wind
- frequency lock-in
- ice floe