Operational Modal Analysis and Finite-Element Model Updating of Pilot Concrete Wind Turbine Tower

Camargo, Edilson A.; Ulfkjær, J. P.; Brincker, Rune; Nøergaard, Jens; Gadegaard, Simon Steen

doi:10.1061/(asce)st.1943-541x.0002242

Cited by 7 publications

(3 citation statements)

References 22 publications

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“…Since accelerometers are considered very robust, an estimation of the displacement by using of acceleration measurement data has been a topic of research for a long time (Berg and Housner, 1961). For example, Camargo et al (2019) applied time integration to measured data of a prototype concrete wind turbine tower. Park et al (2005) estimated the displacement of a bridge using acceleration sensors.…”

Section: Introductionmentioning

confidence: 99%

Dynamic displacement measurement of a wind turbine tower using accelerometers: tilt error compensation and validation

Jonscher,

Helming,

Märtins

et al. 2023

Preprint

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Abstract. For vibration-based structural health monitoring (SHM) of wind turbine support structures, accelerometers are often used. Besides the structural acceleration, the measured quantity also contains the acceleration component due to gravity, which is known as tilt error. This tilt error must be quantified and taken into account, otherwise it can lead to incorrect evaluations, especially in the fatigue estimation or the dynamic displacement estimation using accelerometers. The standard solution is to explicitly measure the tilt angle, which requires an additional sensor for each measurement point and is not applicable for already recorded measurements without tilt information. Therefore, a novel tilt error compensation method is presented by using the static bending line. As a result the influence of the tilt error can be estimated in advance and no additional sensors for tilt measurement are needed. The compensation method is applied to accelerometer measurements of an onshore wind turbine tower and validated with contactless absolute distance measurements from a terrestrial laser scanning (TLS) system. The position and frequency-dependent tilt error of the investigated tower has a significant influence on the quasi static motion below 0.2 Hz with a minimum amplitude error of 9 %, whereas the normalised bending mode shapes around 0.3Hz are only slightly affected.

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Section: Introductionmentioning

confidence: 99%

Dynamic displacement measurement of a wind turbine tower using accelerometers: tilt error compensation and validation

Jonscher,

Helming,

Märtins

et al. 2023

Preprint

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show abstract

“…FE model updating has the potential of identifying the structural damage occurrence, damage locations, and its severities from the variation of identified structural mechanical parameters 42 . Examples of FE model updating used for OWT monitoring can be found in previous studies 43–47 . The target of model updating in these studies is either a numerical model of a certain OWT compoent (blade in Baldassarre et al 43 and Luczak et al, 46 tower in Camargo et al, 44 and support in Xu et al 47 ) or a simlified OWT model 45 without considering the operational conditions.…”

Section: Introductionmentioning

confidence: 99%

“…42 Examples of FE model updating used for OWT monitoring can be found in previous studies. [43][44][45][46][47] The target of model updating in these studies is either a numerical model of a certain OWT compoent (blade in Baldassarre et al 43 and Luczak et al, 46 tower in Camargo et al, 44 and support in Xu et al 47 ) or a simlified OWT model 45 without considering the operational conditions.…”

Section: Introductionmentioning

confidence: 99%

Structural damage identification of offshore wind turbines: A two‐step strategy via FE model updating

Zhang

Sun

Jahangiri

2021

Structural Contr & Hlth

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This study proposes a two-step strategy for damage identification of offshore wind turbines via Finite Element (FE) model updating. In this methodology, the first step identifies the damaged component(s) using a verified global mathematical model of the offshore wind turbine under operational wind and wave loading. Damaged components can be the tower, a certain blade, or the foundation. Natural frequencies and mode shapes obtained from operational modal analysis are used to formulate the objective function for deterministic model updating. With the identified damaged component(s) in the first step, the second step of the strategy focuses on exact damage localization and quantification of the damaged component(s). To this end, an FE model of a baseline 5 MW monopile offshore wind turbine is established using ANSYS. Wind and wave loading are applied to simulate the structural responses under different damage scenarios. In additional to natural frequencies and mode shapes, mode shape curvatures obtained in the second step are included in the objective function. Results indicate that the proposed methodology can correctly identify most structural damage on the offshore wind turbines using operational data.The proposed two-step damage identification strategy can circumvent the requirement of intensive computation due to full model updating of offshore wind turbine models and thus greatly improve the efficiency in real application.

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Influence of system changes on closely spaced modes of a large-scale concrete tower for the application to structural health monitoring

Jonscher

Liesecke

Penner

et al. 2023

J Civil Struct Health Monit

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Concrete steel towers are increasingly being used for onshore wind turbines. The lower part consists of separated segmented concrete rings connected with dry joints. Due to slight deviations from the axisymmetric cross-section, closely spaced modes occur. Therefore, the influences of small system changes on closely spaced modes, particularly the mode shapes, should be investigated to enable reliable vibration-based monitoring. In this context, the influence of imperfections due to the waviness of the dry joints requires attention. As no acceleration measurements on concrete towers considering small system changes have been performed so far, this has not yet been investigated. Therefore, an experiment is carried out using a large-scale laboratory model of a prestressed concrete segment tower. The system modifications are introduced by changing the preload. This changes the influence of imperfections of the surfaces of the horizontal dry joints, estimated by measuring strain and displacement at the lowest joint. An increasing preload causes the first two pairs of bending modes to move closer together. This enables to study the effect of the closeness of natural frequencies on the related mode shapes based on the same structure. Thus, the known effects of increasing uncertainty of the alignment and a rotation of the mode shape in the mode subspace with closer natural frequencies can be shown experimentally. In this work, the operational modal analysis (OMA) methods Bayesian-OMA (BAYOMA) and Stochastic Subspace Identification (SSI) are used. Local imperfections can significantly affect modal parameters, so these should be considered for vibration-based monitoring.

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Operational Modal Analysis and Finite-Element Model Updating of Pilot Concrete Wind Turbine Tower

Cited by 7 publications

References 22 publications

Dynamic displacement measurement of a wind turbine tower using accelerometers: tilt error compensation and validation

Dynamic displacement measurement of a wind turbine tower using accelerometers: tilt error compensation and validation

Structural damage identification of offshore wind turbines: A two‐step strategy via FE model updating

Influence of system changes on closely spaced modes of a large-scale concrete tower for the application to structural health monitoring

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