FBG-based dynamic characterization of a scaled offshore wind turbine foundation model under impact and recorded seismic excitations
Journal
Ocean Engineering
Journal Volume
363
Journal Issue
P4
Start Page
126846
ISSN
00298018
Date Issued
2026-08-15
Author(s)
Lin, Jui-Chi
Liao, Yi-Lun
Chen, Bor-Yann
Chiu, I-Hsin
Xu, Wan-Yu
Liao, You-Chen
Yang, Yi-Heng
Abstract
This study experimentally investigates the fiber Bragg grating (FBG)-based dynamic characterization of a 1:30-scale offshore wind turbine foundation model under impact and seismic excitations. The objective is to evaluate multi-sensor measurements for identifying representative structural frequencies of the tested scaled model and examining impact-based spectral indicators of connection-condition changes. Under floor-supported impact excitation, the intact structure exhibited a dominant frequency of approximately 6.40 Hz. When bolt loosening was introduced under the same impact-test configuration, the frequency response developed a distinct double-peak pattern near 5.00 Hz and 6.40 Hz, indicating FBG sensitivity to connection-related stiffness changes. When the rigid mounted on a triaxial seismic simulator, the dominant frequency shifted to approximately 7.57 Hz, reflecting the influence of boundary conditions. Under single-axis, biaxial, and triaxial Chi-Chi and Kobe seismic excitations, FBG sensors consistently identified a stable frequency near 7.6 Hz. Accelerometers, a Subsea Vibration Monitor, and Digital Image Correlation provided complementary validation. These results demonstrate that FBG-based multi-sensor measurements can support structural frequency identification, bolt-loosening assessment, and dynamic characterization of scaled models under laboratory conditions. The proposed approach serves as an FBG-based dynamic characterization workflow rather than a direct frequency-scaling method for full-scale foundations.
Subjects
Bolt loosening
Dynamic characterization
Fiber Bragg grating
Offshore wind turbine foundation model
Seismic excitation
Triaxial seismic simulator
Publisher
Elsevier Ltd
Type
journal article