Impact of calibrated soil-monopile-interaction model on resonance frequencies

Jurado, C. Sastre; Stuyts, Bruno; Weijtjens, Wout; Devriendt, Christof

doi:10.1088/1742-6596/2265/3/032098

Cited by 4 publications

(9 citation statements)

References 16 publications

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“…To include Scour protection, two methods are proposed to model its effects. The first approach includes the scour protection as an additional layer of dense sand on top of the original soil profile, which is a common simplification and for example also used in [6]. Here, the scour protection itself is assumed to provide some lateral support to the monopile foundation.…”

Section: Modeling Approaches To Include Spmentioning

confidence: 99%

“…Both times the result of the lab test was an increased stiffness of the soil lateral response curves after scour protection installation. Recently, attempts to incorporate scour protection contribution in numerical models were bench-marked against full-scale measurements from monitored OWTs in [5,6], concluding that simulations agree better with measurements if the scour protection system is considered in the model.…”

Section: Introductionmentioning

confidence: 99%

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Quantifying the effect of rock armour scour protection on eigenfrequencies of a monopile supported OHVS

Winkler,

Weil,

Sastre Jurado

et al. 2023

J. Phys.: Conf. Ser.

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It is common practice to install scour protection systems during the construction of offshore wind farms. This is because the guidelines allow for a more optimal structural design, as the potential effects of scouring may be ignored. However, multiple sources, as well as measurements, suggest that there is an additional gain in stiffness which is not being taken into account by current guidelines. Scour protection has the ability to provide extra foundational stiffness to the monopile, which results in higher natural eigenfrequencies and mode shapes. In this paper the focus will be on an offshore high voltage station (OHVS) located in the North Sea and the impact of a rubble riprap scour protection on the foundational stiffness of the structure. Furthermore, a proposal is made on how to take these effects into account when calculating for design. This site was equipped with a mobile measurement system containing a multi-axial accelerometer, which was active in a period both before and after installation of the scour protection rock armour layer. In case of similar environmental circumstances, the eigenfrequencies of the OHVS were noticeably higher after the scour protection was installed, thus substantiating the claim of increased foundational stiffness. To perform numerical studies on the impact of the scour protection system on structural dynamics, an OHVS support structure finite element model was built. As no formally agreed upon formulation to include scour protection exists, two possible methods are proposed. One is adding a global accretion layer to model the scour protection as an additional soil layer. The other calculates an overburden pressure due to the scour protection weight, which translates to the stiffening of the upper soil layers of the foundation. Both methods have their own strengths and weaknesses, but more research on different locations and offshore structures is needed to formalize the definitive description for modelling scour protection.

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Section: Modeling Approaches To Include Spmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Quantifying the effect of rock armour scour protection on eigenfrequencies of a monopile supported OHVS

Winkler,

Weil,

Sastre Jurado

et al. 2023

J. Phys.: Conf. Ser.

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“…If the resonance frequency drops below this threshold, an alarm is triggered, signalling a potential issue in the OWT. But the as-design resonance frequency is often lower than the actual, measured resonance frequency, and significant scouring can occur well before the alarm is triggered [6,7]. To address this issue, a data-driven alarm threshold, typically expressed in relation to the variability of the observed resonance frequency, can be set.…”

Section: Introductionmentioning

confidence: 99%

“…The digital twin model developed at OWI-LAB, VUB [6] can be used to represent the changes in the dynamic response of the structure due to damage. The model accounts for the actual data and a state-of-the-art soil-structure interaction model (PISA [12]) and is used to compute the modal frequency reduction due to different scouring depths in this research.…”

Section: Introductionmentioning

confidence: 99%

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Quantifiable Scour Detection for Offshore Wind Turbines Using Resonance Frequency Monitoring and a Digital Twin

WEIL,

JURADO,

CHAAR

et al. 2023

Proceedings of the 14th International Workshop on Structural Health Monitoring

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This paper presents a methodology for enhancing frequency-based Structural Health Monitoring (SHM) of Offshore Wind Turbines (OWTs) by incorporating digital twin models. The proposed methodology utilizes an automated operational modal analysis to extract modal frequencies from acceleration measurements. The environmental and operational variability is removed through tree-based regression models, which can adequately recognize the different operational states of the OWT. The proposed data-driven approach relies on the detection of the modal frequency changes caused by a damaging scenario in the OWT (e.g. scouring). The digital twin model accounts for the actual properties of the substructure, considering the specific foundation geometry and soil conditions at the monitored OWT location. A statistical control chart is used to identify the possible scour depth by comparing the changes in the normalized modal frequency and the digital-twin calculations. The methodology is demonstrated on 4 months of measurements from a full-scale monitored OWT. The proposed methodology advances the SHM capabilities from damage detection to damage quantification, enabling improved operations & maintenance strategies for OWTs.

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On the influence of rotor nacelle assembly modelling on the computed eigenfrequencies of offshore wind turbines

Reinhardt,

Sastre Jurado,

Weijtjens

et al. 2024

J. Phys.: Conf. Ser.

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Motivated by the mismatch of measured and computed eigenfrequencies for the second tower mode of offshore wind turbines as well as previous studies examining the influence of including flexible blades in structural models, the need to extend the current integrated model to include flexible blades became apparent. A basic modelling approach which takes the blades as beam elements was implemented in an in-house finite element model of offshore wind turbines and benchmarked for the NREL 5 MW reference turbine with OpenFast. Moreover, the modelling approach was benchmarked with measurements that were obtained during the installation of a Belgian offshore wind turbine. The inclusion of flexible blades is shown to have a significant influence on the second tower mode and is able to reduce the mismatch between measurements and computations. Furthermore, the capability of the inclusion of flexible blades to model the effects of additional parameters is presented. Overall, the need to extend the rotor nacelle modelling in structural models of offshore wind turbines beyond a lumped mass approach is demonstrated.

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Impact of calibrated soil-monopile-interaction model on resonance frequencies

Cited by 4 publications

References 16 publications

Quantifying the effect of rock armour scour protection on eigenfrequencies of a monopile supported OHVS

Quantifying the effect of rock armour scour protection on eigenfrequencies of a monopile supported OHVS

Quantifiable Scour Detection for Offshore Wind Turbines Using Resonance Frequency Monitoring and a Digital Twin

On the influence of rotor nacelle assembly modelling on the computed eigenfrequencies of offshore wind turbines

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