Improvements in the fatigue design of support structures for offshore wind turbines

Schaumann, Peter; Böhm, Manuela; Schürmann, Karsten

doi:10.1002/stco.202000060

Cited by 14 publications

(4 citation statements)

References 15 publications

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“…As described in Section 3.1 some bending in the fastener has to be assumed due to the inclination of the fastener with regard to the force direction. Niebuhr and Sieder (2021) showed that the performance of the examined fastener is superior if the axial fastener stresses are caused by bending rather than an axial force as is known for other threaded fasteners such as steel bolts (cf., e.g., Agatonovic, 1973;Schaumann and Marten, 2009). Hence, a safe side approximation of the behaviour under bending or combined loading is possible with S-N-curves determined with pure axial loading if the actual fastener stresses with consideration of bending are utilised.…”

Section: Involved Fatigue Phenomenamentioning

confidence: 99%

Estimation of the high-cycle fatigue behaviour of timber connections with inclined screws under tension

Niebuhr,

Sieder

2024

Preprint

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Based on 31 quasistatic tests and 27 constant-amplitudefatigue tests the withdrawal behaviour of a self-tapping timber screw under cyclic loading is examined in two configurations with regard to the penetration length. Together with similar results from earlier withdrawal tests on threaded rods, indications of a dependence of the bearable load cycles on the penetration length are found where a larger penetration length yields inferior performance under cyclic loads. Further, in conjunction with results from earlier axial tensile tests on the examined screw, insights into the transition point between steel tensile failure and withdrawal are gained. The obtained results on the withdrawal failure mode are combined with results from earlier studies to develop a proposal for a holistic verification concept for the high-cycle fatigue design of connections with inclined self-tapping screws. After a discussion of the state of knowledge regarding the relevant failure modes, the verification is reduced to the dominant failure modes withdrawal and steel tensile failure, while subsidiary effects such as bending in the fastener are inherentlyconsidered.

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Section: Involved Fatigue Phenomenamentioning

confidence: 99%

Estimation of the high-cycle fatigue behaviour of timber connections with inclined screws under tension

Niebuhr,

Sieder

2024

Preprint

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“…As a synergy effect, an application of the digital image correlation (DIC) technique to cyclically loaded welded joints was developed to identify and analyse the transition from crack initiation to crack propagation [21]. By doing so, initial macroscopic cracks with lengths of about 1-1.5 mm could be detected [22], [23]. Owing to the chronological storage of the 3D digital images during the fatigue test, the DIC method used also includes the option of reviewing the history of the fatigue test and the 3D surface of the specimen to analyse, for example, the occurrence of outliers due to undercuts or sharp notches afterwards.…”

Section: Articlementioning

confidence: 99%

Improvements in the fatigue design of support structures for offshore wind turbines

2021

Stahlbau

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This article provides an overview of the various support structures for offshore wind turbines and addresses the challenges that arise for the different design variants. First of all, the existing types of support structures are explained and their benefits and shortcomings discussed. Following that, the focus is on material fatigue and its analysis, which is of great importance due to the cyclic loading on the structures. A central topic of this article is the experimental evaluation of fatigue strength using large-scale test setups and state-of-the-art measurement methods. Critical and complex design details such as welds for extremely thick plates, tubular joints, grouted connections, large HV bolts and ring flanges are investigated to improve methods of analysis. Further, the new series of German standards (DIN 18088) for support structures for wind energy turbines and platforms is addressed. Finally, these topics are summarized and the importance of offshore wind energy for the transition to cleaner energy is emphasized.

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“…The tower has always played an important role in the total cost of a wind turbine, about 20 -30% of the total. Therefore, optimized and lightweight tower structures are important [1][2][3][4]. For wind energy branch, tubular steel towers are still the dominant tower concept.…”

Section: Introductionmentioning

confidence: 99%

Further development of detail categories for bolt‐assemblies subjected to normal stress in steel constructions

Glienke,

Schwarz,

Meyer

et al. 2023

ce papers

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The fatigue strength of bolts is determined not only by the geometric design but also by production‐related influences such as rolled before heat treatment, rolled after heat treatment or even hot‐dip galvanising. For the bolts of steel constructions considered in this paper, these production‐related influencing factors are considered very differently in the evaluation of the fatigue resistance, depending on the used respective standards. This is for example done according to the still valid version of EN 1993‐1‐9 in the unified form of detail category 50, taking into account the size effect, but independent of the other influencing factors mentioned before. This is not least due to the very limited available experimental database and test documentation. The authors address this topic in this paper, especially for large‐size bolts used in large quantities in wind turbines. This article presents an evaluation of results from 22 fatigue test series (n = 411 tests) on 3 different high‐strength bolt assembly systems with varying manufacturing conditions. The data base is covering a diameter range between M12 and M72 and focusses on test series with high mean stress in a representative order of magnitude for practical application of the bolts. For their further evaluation, the findings described in the technical literature are considered in relation to the different tested manufacturing conditions. The additional comparison of the test results with the current design codes serves to a better classification of the results. The authors give a proposal for the adjustment of detail categories of bolt assemblies subjected to normal stress.

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Improvements in the fatigue design of support structures for offshore wind turbines

Cited by 14 publications

References 15 publications

Estimation of the high-cycle fatigue behaviour of timber connections with inclined screws under tension

Estimation of the high-cycle fatigue behaviour of timber connections with inclined screws under tension

Improvements in the fatigue design of support structures for offshore wind turbines

Further development of detail categories for bolt‐assemblies subjected to normal stress in steel constructions

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