Estimation of natural frequencies and damping using dynamic field data from an offshore wind turbine

Norén-Cosgriff, Karin; Kaynia, Amir M.

doi:10.1016/j.marstruc.2020.102915

Cited by 29 publications

(13 citation statements)

References 12 publications

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“…45 Rayleigh damping was adopted based on the first two lateral vibration modes of the system. It should be noted that recent studies have implied that the instantaneous damping of the OWT can be highly dependent on its operational state, such as the nacelle-yaw position, the rotor azimuth, or the real-time inflow wind speed, 46,47 and that the damping values associated with each natural vibration mode can be significantly different. 48 Nevertheless, for simplicity, OWT is often considered as an overall lightly damped structure.…”

Section: 12mentioning

confidence: 99%

Multi‐hazard fragility assessment of monopile offshore wind turbines under earthquake, wind and wave loads

Zhang

Risi

Sextos

2023

Earthq Engng Struct Dyn

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This study establishes a multi‐hazard probabilistic assessment framework for assessing the integrity of monopile offshore wind turbines (OWT) under the stochastic coupled effect of wind, wave and earthquake loading. The procedure deals with the entire operational range of inflow wind speed (i.e., 3–25 m/s), for which the probability of failure under multi‐hazard excitations is found to be non‐negligible. Numerical analysis is performed by implementing nonlinear finite‐element models of the OWT developed in OpenSees. The dynamic response of the OWT system under wind‐ and wave‐load combinations is individually validated against those obtained from the aero‐hydro‐servo‐elastic simulator OpenFAST. Following the Latin‐hypercube approach, a cloud‐based assessment procedure is then performed with an ensemble of 300 earthquake ground motions, from which the multi‐hazard performance of the OWT regarding the serviceability limit state (SLS) and the ultimate limit state (ULS) can be evaluated. The epistemic uncertainty associated with various loads, structural properties, and soil conditions is also accounted for. Based on this probabilistic assessment framework, the sensitivity of the resulting OWT fragility surfaces to different statistical regression methods and wind—ground motion intensity measure pairs (IM‐pairs) is further scrutinised. Regression methods are comparatively evaluated. The efficiency, practicality, proficiency and sufficiency of various IM‐pairs are examined for the purpose of assessing operating OWT multi‐hazard fragility functions. The optimum IM‐pair is then employed in a trained Gaussian Process Regression (GPR) scheme for cloud data regression to assess the multi‐hazard fragility of the system. The derived multi‐hazard fragility function shows that the contribution of seismic forces in structural demand for a design‐level earthquake is comparable to those caused by operational‐level wind and wave loads.

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Section: 12mentioning

confidence: 99%

Multi‐hazard fragility assessment of monopile offshore wind turbines under earthquake, wind and wave loads

Zhang

Risi

Sextos

2023

Earthq Engng Struct Dyn

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“…However, two properties could introduce a significant dependence with respect to the magnitude of excitation. First, amplitude-dependent dynamics of buildings under wind loading have been reported extensively in the literature, see, for example, previous works, [50][51][52] and the references therein. Generally, this is exhibited by an increase in damping and a decrease in natural frequencies.…”

Section: Linearity and Nonlinearitymentioning

confidence: 99%

A new open‐database benchmark structure for vibration‐based Structural Health Monitoring

Wernitz

Hofmeister

Jonscher

et al. 2022

Structural Contr & Hlth

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Vibration-based Structural Health Monitoring is an ongoing field of research in many engineering disciplines. As for civil engineering, plenty of experimental structures have been erected in the past decades, both under laboratory and real-life conditions. Some of these facilities became a benchmark for different kinds of methods associated with Structural Health Monitoring such as damage analysis and Operational Modal Analysis, which led to fruitful developments in the global research community. When it comes to the continuous monitoring and assessment of the structural integrity of mechanical systems exposed to environmental and operational variability, the robustness and adaptability of the applied methods is of utmost importance. Such properties cannot be fully evaluated under laboratory conditions, which highlights the necessity of outdoor measurement campaigns. To this end, we introduce a test facility for Structural Health Monitoring comprising a lattice tower exposed to realistic conditions and featuring multiple reversible damage mechanisms. The structure located near Hanover in Northern Germany is densely equipped with sensors to capture the structural dynamics. The environmental conditions are monitored in parallel. The obtained continuous measurement data can be accessed online in an open repository. That is the foundation for benchmarks, consisting of a growing data set that enables the development, evaluation, and comparison of Structural Health Monitoring strategies and methods. In this article, we offer a documentation of the test facility and the data acquisition system. Lastly, we characterize the structural dynamics with the help of a finite element model and by analyzing several month of data.

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“…The mentioned method requires a significant amount of time for a large number of samples [ 10 ]. Another approach is modal analysis with mechanical excitation and strain gauge [ 11 ], difference from the previous method is only in the sensor where mentioned strain gauge instead of acoustic sensor is used [ 12 , 13 ]. In the article, Natural Vibration Frequency Definition of Turbine Blades, the principle of modal analysis is nicely described [ 14 ].…”

Section: Introductionmentioning

confidence: 99%

A novel method for the natural frequency estimation of the jet engine turbine blades based on its dimensions

Spodniak,

Hovanec,

Korba

2024

Heliyon

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Estimation of natural frequencies and damping using dynamic field data from an offshore wind turbine

Cited by 29 publications

References 12 publications

Multi‐hazard fragility assessment of monopile offshore wind turbines under earthquake, wind and wave loads

Multi‐hazard fragility assessment of monopile offshore wind turbines under earthquake, wind and wave loads

A new open‐database benchmark structure for vibration‐based Structural Health Monitoring

A novel method for the natural frequency estimation of the jet engine turbine blades based on its dimensions

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