Durchrutschende Grout‐Verbindungen in OWEA – Tragverhalten, Instandsetzung und Optimierung

Schaumann, Peter; Lochte-Holtgreven, Stephan; Lohaus, Ludger; Lindschulte, Nick

doi:10.1002/stab.201001357

Cited by 28 publications

(8 citation statements)

References 6 publications

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“…There is also the possible risk of water flow providing a transportation medium for fragmented or ground grout or cyclic moisture movement, which in turn would affect the fatigue capacity through microcraking, as demonstrated by Berndt (2010). The effects of slenderness of the transition piece and pile walls on the containment of grout, due to ovalisation and shape deformation under loading, have been also mentioned in the recent papers (Schaumann, 2007 andSchaumann et al, 2010). Veludo et al (2012) have experimentally demonstrated that the initial bond strength between grout and steel has a very strong positive correlation to the radial confinement for axially loaded micro-piles.…”

Section: Position Of the Problemmentioning

confidence: 94%

“…Once this initial 'bond' is broken, the axial capacity becomes a function of stiffness, material properties, surface irregularities, coefficient of friction and horizontal compressive load and so these properties become important. Recent studies have also paid attention to the severe environmental conditions in operation, e.g the reduction of the groutsteel coefficient of friction due to the ingress of sea water (Schaumann et al 2010), which is likely to reduce the post-bond axial capacity of the connection (Det Norske Veritas, 2010). There is also the possible risk of water flow providing a transportation medium for fragmented or ground grout or cyclic moisture movement, which in turn would affect the fatigue capacity through microcraking, as demonstrated by Berndt (2010).…”

Section: Position Of the Problemmentioning

confidence: 99%

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Wear in Large Diameter Grouted Connections for Offshore Wind Energy Converters

Dallyn¹,

El-Hamalawi²,

Palmeri³

2012

Proceedings of the 10th International Conference on Advances in Steel Concrete Composite and Hybrid Structures

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The paper provides a critical appraisal of the events surrounding the unexpected settlement of large-diameter monopile foundations for offshore wind energy converters, and will detail experimentation that is to be undertaken to determine the extent of the wear failure mode in such structures. The potential for wear deterioration at the grout-steel interface has been caused by the lack of axial load transfer of the grout and steel and so relative movement between the grout and steel is occurring. Hence, a better understanding of this phenomenon is of key importance to determine the long term integrity of the structure. The remedial solution currently favoured within industry consists of the installation of elastomeric bearings, which however may further exasperate the wear due to its lower stiffness than steel contact currently occurring, also because of the presence of water in the grouted connection. The aim of the testing is therefore to identify the risk to offshore foundation integrity due to grout wear under conditions typically observed during life-time operation of offshore wind turbines. The main factors influencing the wear rate of grout will be identified, and the possibility to define indicators for the integrity of the grout that could be used for offshore inspection will be also considered.

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Section: Position Of the Problemmentioning

confidence: 94%

Section: Position Of the Problemmentioning

confidence: 99%

Wear in Large Diameter Grouted Connections for Offshore Wind Energy Converters

Dallyn¹,

El-Hamalawi²,

Palmeri³

2012

Proceedings of the 10th International Conference on Advances in Steel Concrete Composite and Hybrid Structures

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“…Diese Verbindung ist technisch wie auch aus Sicht der erforderlichen Installations-und Aushärtezeiten aufwändig. Zudem wurden in den letzten Jahren wiederholt Schadensfälle dokumentiert [1].…”

Section: ) Innerer Flanschdurchmesser B) äUßerer Flanschdurchmesser Cunclassified

“…Als Ergänzung zu den Beiträgen in [1] und [13] werden im Rahmen dieses Aufsatzes die Schwerpunkte auf die Beanspruchungsermittlung und Nachweisführung gelegt. Die hierfür zur Anwendung kommenden ingenieurmäßigen Berechnungsmodelle, normative bzw.…”

Section: ) Innerer Flanschdurchmesser B) äUßerer Flanschdurchmesser Cunclassified

Monopfahlgründungen – Besonderheiten der stahlbaulichen Nachweisführung von gerammten Ringflanschen

Wirth¹,

Lüddecke²,

Otaibi³

et al. 2015

Stahlbau

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Derzeit ist bei Monopfahlgründungen von Offshore-Windenergieanlagen ein Trend hin zu geschraubten Ringflansch-Verbindungen zwischen Monopfahl und dem Übergangsstück (Transition Piece) zu erkennen, analog zu den herkömmlichen Verbindungen im Bereich des Turmbaus von Windenergieanlagen. Das Einbringen der Monopfähle erfolgt weiterhin zumeist mittels Impuls-Rammung, wobei der Lasteintrag zwischen dem Hydraulik-Hammer und dem Pfahl durch direkten Kontakt bzw. Formschluss an der Flanschoberseite erfolgt. Für diesen temporären Bauzustand kommt der Nachweisführung des monopfahlseitigen Flansches und dessen Anschlusses an den Pfahl eine besondere Bedeutung zu. Im Rahmen dieses Aufsatzes werden Berechnungsannahmen, die Beanspruchungsermittlung, die zu berücksichtigenden Bauteilwiderstände und schließlich die Nachweisführung dargelegt. Normative bzw. Richtlinien-spezifische Unterschiede bei der Ermittlung der Bauteilwiderstände, insbesondere für den Ermüdungs-nachweis, werden ebenso aufgezeigt wie die Besonderheiten zur Ermittlung bzw. Wahl der zu berücksichtigenden Imperfektionen der am Schlag-Kontakt beteiligten Partner. Die Beanspruchungshöhen an einem perfekten System werden verglichen mit einem System, bei dem die baulichen Toleranzen einbeschrieben sind. Besonderheiten bei der Nachweisführung im Grenzzustand der Tragfähigkeit, beim Ermüdungsnachweis und die Abgrenzung zwischen beiden werden diskutiert. Abschließend werden Hinweise für die Beanspruchungsermittlung und die Bemessung zusammengestellt. Driven Monopiles -Specifics for structural verification of flanges. The current trend in monopile foundations for offshore wind turbines is to use a flanged connection between the monopile and the transition piece. This trend is analogous to the conventional installation of different tower sections for the wind turbines. The monopile installation continues to be done using impact driving, in which the load transfer between the hydraulic hammer and the pile is achieved by direct contact on the top

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“…More recent investigations on lateral loading of grouted connections under conditions relevant to their current use in the wind industry have been undertaken [12][13][14][15][16][17][18], taking into account the influence of water and relative stiffness of the MP and TP, however the influence of abrasive wear has not been considered. Experimental testing of wear has been investigated in relation to low strength concretes and non-confined systems [19][20][21][22][23], but the mechanisms used are not representative if the conditions experienced in offshore WTG grouted connections.…”

Section: Introductionmentioning

confidence: 99%

Prediction of Wear in Grouted Connections for Offshore Wind Turbine Generators

et al. 2017

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Insufficient axial capacity of large-diameter plain-pipe grouted connections has recently been observed in offshore wind turbine substructures across Europe. Aimed at understanding the implications of this phenomenon, a campaign of structural condition monitoring was undertaken. The measurements showed significant axial displacements occurring between the transition piece and the monopile, which in turn resulted in a considerable amount of wear. Given the existing lack of technical data on the implications that this relative movement has on the wear of grouted connections, a methodology was developed to quantify the likely risk to the foundation integrity of the wear failure mode. The proposed approach consists of a numerical model which applies the wear rate derived from previous experimental testing to the conditions experienced by typical offshore grouted connections, as indicated by the wind turbine generators' supervisory control and data acquisition systems. The output of this model showed that, for a representative sample of the wind farm substructures analysed as a case study, the accumulated lifetime wear would be minimal in the majority of the grouted connection, i.e. less than 0.4 mm over 75% of the connection, but a much greater loss in thickness, of the order of 4 mm, was predicted at the very top and bottom of the connection. This assessment is based on the assumptions that no significant changes occur in the surrounding environmental conditions and that the degradation in the grouted connection does not significantly affect the dynamic response of the foundation structure over its life span. Importantly, these assumptions may affect the model's predictions in terms of cumulated wear over time, not in terms of identifying the individual connections to be prioritised when performing remedial work, which is indeed the main intended use of the model.

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Durchrutschende Grout‐Verbindungen in OWEA – Tragverhalten, Instandsetzung und Optimierung

Cited by 28 publications

References 6 publications

Wear in Large Diameter Grouted Connections for Offshore Wind Energy Converters

Wear in Large Diameter Grouted Connections for Offshore Wind Energy Converters

Monopfahlgründungen – Besonderheiten der stahlbaulichen Nachweisführung von gerammten Ringflanschen

Prediction of Wear in Grouted Connections for Offshore Wind Turbine Generators

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