Sub-soil strain measurements on an operational wind turbine for design validation and fatigue assessment

Henkel, Maximilian; Noppe, Nymfa; Weijtjens, Wout; Devriendt, Christof

doi:10.1088/1742-6596/1037/5/052032

Cited by 4 publications

(8 citation statements)

References 7 publications

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“…Finally, stress time histories σðtÞ (7) are calculated using εðtÞ and the stress-strain relationship. This technique has been validated through experimental tests on lab-scaled structures (Fern andez et al, 2009;Hjelm et al, 2005;L opez-Aenlle et al, 2013;Tarpø et al, 2020) and real structures (Christensen, 2020;Dascotte et al, 2013;Henkel et al, 2019Henkel et al, , 2020Hjelm et al, 2005;Iliopoulos et al, 2017;Nabuco et al, 2020;Noppe et al, 2018).…”

Section: Fatigue Monitoring Of Structuresmentioning

confidence: 99%

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A review on fatigue monitoring of structures

García-Fernández

Aenlle

Álvarez-Vázquez

et al. 2023

IJSI

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PurposeThe purpose of this study is to review the existing fatigue and vibration-based structural health monitoring techniques and highlight the advantages of combining both approaches.Design/methodology/approachFatigue monitoring requires a fatigue model of the material, the stresses at specific points of the structure, a cycle counting technique and a fatigue damage criterion. Firstly, this paper reviews existing structural health monitoring (SHM) techniques, addresses their principal classifications and presents the main characteristics of each technique, with a particular emphasis on modal-based methodologies. Automated modal analysis, damage detection and localisation techniques are also reviewed. Fatigue monitoring is an SHM technique which evaluate the structural fatigue damage in real time. Stress estimation techniques and damage accumulation models based on the S-N field and the Miner rule are also reviewed in this paper.FindingsA vast amount of research has been carried out in the field of SHM. The literature about fatigue calculation, fatigue testing, fatigue modelling and remaining fatigue life is also extensive. However, the number of publications related to monitor the fatigue process is scarce. A methodology to perform real-time structural fatigue monitoring, in both time and frequency domains, is presented.Originality/valueFatigue monitoring can be combined (applied simultaneously) with other vibration-based SHM techniques, which might significantly increase the reliability of the monitoring techniques.

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Section: Fatigue Monitoring Of Structuresmentioning

confidence: 99%

“…, 2020) and real structures (Christensen, 2020; Dascotte et al. , 2013; Henkel et al. , 2019, 2020; Hjelm et al.…”

Section: Fatigue Monitoringmentioning

confidence: 99%

A review on fatigue monitoring of structures

García-Fernández

Aenlle

Álvarez-Vázquez

et al. 2023

IJSI

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“…While not all fiber lines survived pile-driving, the majority of sensors recorded strains over a time of three years. For more details see [8]. The measurement data is complemented by environmental/operational data, e.g., wind speed, yaw angle, so-called SCADA data once every 10 min.…”

Section: Measurements Of the Nobelwind Campaignmentioning

confidence: 99%

Fatigue Stress Estimation for Submerged and Sub-Soil Welds of Offshore Wind Turbines on Monopiles Using Modal Expansion

2021

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The design of monopile foundations for offshore wind turbines is most often driven by fatigue. With the foundation price contributing to the total price of a turbine structure by more than 30%, wind farm operators seek to gain knowledge about the amount of consumed fatigue. Monitoring concepts are developed to uncover structural reserves coming from conservative designs in order to prolong the lifetime of a turbine. Amongst promising concepts is a wide array of methods using in-situ measurement data and extrapolating these results to desired locations below water surface and even seabed using models. The modal decomposition algorithm is used for this purpose. The algorithm obtains modal amplitudes from acceleration and strain measurements. In the subsequent expansion step these amplitudes are expanded to virtual measurements at arbitrary locations. The algorithm uses a reduced order model that can be obtained from either a FE model or measurements. In this work, operational modal analysis is applied to obtain the required stress and deflection shapes for optimal validation of the method. Furthermore, the measurements that are used as input for the algorithms are constrained to measurements from the dry part of the substructure. However, with subsoil measurement data available from a dedicated campaign, even validation for locations below mud-line is possible. After reconstructing strain history in arbitrary locations on the substructure, fatigue assessment over various environmental and operational conditions is carried out. The technique is found capable of estimating fatigue with high precision for locations above and below seabed.

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“…The process model was validated on a suspension test rig in the laboratory. Henkel et al [65] applied modal expansion with multiple frequency bands to estimate the strain response of the subsoil part of an offshore wind turbine in the Belgian North Sea with good accuracy for wind velocities of 4-9 m/s. In 2019, Pedersen et al [66] compared the modal expansion with two adaptive filter algorithms -the Kalman filter and the joint input-state estimation algorithm -where they studied the effect of the number of sensors.…”

Section: Smentioning

confidence: 99%

Stress Estimation of Offshore Structures

Tarpø¹

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Offshore structures are subjected to a harsh environment where the fluctuating waves continuously strain the structures and these forces cause the initiation and propagation of cracks in the structures. In other words, the structures accumulate fatigue damage, which eventually leads to structural failure. To avoid fatigue failure, the operational lifetime of a structure is limited to a design lifetime in which the structure is safe for operation. This design process is based on precautious stochastic assessments, norms, and industry standards that simplify the actual structure and environment in such a manner that it involves little risk of structural failure. As many structures in the North Sea approach the end of their design lifetime, the owners are faced with a dilemma: either abandon the field or replace the structures. Another option is the lifetime extension of the existing structures. This requires a reduction of the uncertainties in the design process - such as the stress history in fatigue-critical location. Unfortunately, these locations are often inaccessible or directly harmful to the sensors due to the hostile environment of the ocean. This thesis focuses on virtual sensing to estimate the stress/strain response of offshore structures by indirect measurements. The thesis addresses the state of the art and maps some essential issues within stress/strain estimation. In this thesis, stress/strain estimation is applied to different test specimens to address certain scientific issues. Parts of the thesis relate to the calibration of the system model for virtual sensing by operational modal analysis.

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Sub-soil strain measurements on an operational wind turbine for design validation and fatigue assessment

Cited by 4 publications

References 7 publications

A review on fatigue monitoring of structures

A review on fatigue monitoring of structures

Fatigue Stress Estimation for Submerged and Sub-Soil Welds of Offshore Wind Turbines on Monopiles Using Modal Expansion

Stress Estimation of Offshore Structures

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