Vibration improvement of offshore wind turbines under multiple hazards

authored by

Said Elias

Abstract

The slenderness ratio, particularly pronounced in offshore wind turbines (OWTs) with values exceeding five, renders them highly susceptible to dynamic sensitivity when exposed to lateral loads, setting them apart from conventional structures. The simultaneous interaction of wind and wave forces often results in the generation of extreme vibrations, ultimately jeopardizing the structural integrity of offshore wind turbines. This study is dedicated to assessing the effectiveness of distributed tuned mass dampers (d-TMDs) in mitigating responses in OWTs when subjected to the concurrent action of wind and wave forces. The finite element model (FEM) for the OWT, accounting for its multi-degree of freedom (MDOF) nature, is meticulously constructed using ANSYS software. The analysis encompasses uncontrolled offshore wind turbines (NC), those equipped with single tuned mass dampers (STMD), and variants featuring d-TMDs. These structures are exposed to random wind and wave loading conditions, mirroring real-world scenarios and necessitating the deployment of control schemes to counteract the adverse vibrations induced. Consequently, wind and wave spectra are generated using the Kaimal spectrum and Pierson and Moskowitz spectrum, respectively, with drag wave forces calculated through Morison's equation. Moreover, the study takes into account the impact of soil-structure interaction (SSI), incorporating both rotational and lateral springs. The results, comprising displacement and acceleration responses at the pinnacle of the OWT, facilitate a comprehensive comparison between the responses of the NC, STMD, and d-TMD configurations. In single hazard analysis, it is evident that TMDs exhibit greater efficacy in mitigating wind-induced responses in offshore wind turbines compared to wave-induced responses. Furthermore, d-TMD schemes demonstrate superior performance in enhancing the response of flexible base offshore wind turbines as opposed to their fixed base counterparts.

Organisation(s)

Institute for Risk and Reliability

Type

Article

Journal

Structures

Volume

59

No. of pages

13

ISSN

2352-0124

Publication date

01.2024

Publication status

Published

Peer reviewed

Yes

ASJC Scopus subject areas

Civil and Structural Engineering, Architecture, Building and Construction, Safety, Risk, Reliability and Quality

Electronic version(s)

https://doi.org/10.1016/j.istruc.2023.105800 (Access: Closed)