Welded Connections of Wind Turbine Towers under Fatigue Loading: Finite Element Analysis and Comparative Study

Stavridou, Nafsika; Efthymiou, Evangelos; Baniotopoulos, Charalampos

doi:10.3844/ajeassp.2015.489.503

Cited by 15 publications

(9 citation statements)

References 14 publications

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“…The weld connecting the shell part and the flange presents a high normal stress concentration. A comparative study of welds connecting tube sections and welds connecting the shell and the flange of a wind turbine verified the above assumption [62]. Alonso-Martinez et al, using finite element and experimental analysis, stated that the pretension of bolts resulted in a high stress concentration of the flange neck, which led to a collapse in Spain [63] (Figure 10).…”

Section: Connectionsmentioning

confidence: 83%

Recent Advances in Vibration Control Methods for Wind Turbine Towers

2021

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Wind power is a substantial resource to assist global efforts on the decarbonization of energy. The drive to increase capacity has led to ever-increasing blade tip heights and lightweight, slender towers. These structures are subject to a variety of environmental loads that give rise to vibrations with potentially catastrophic consequences, making the mitigation of the tower’s structural vibrations an important factor for low maintenance requirements and reduced damage risk. Recent advances in the most important vibration control methods for wind turbine towers are presented in this paper, exploring the impact of the installation environment harshness on the performance of state-of-the-art devices. An overview of the typical structural characteristics of a modern wind turbine tower is followed by a discussion of typical damages and their link to known collapse cases. Furthermore, the vibration properties of towers in harsh multi-hazard environments are presented and the typical design options are discussed. A comprehensive review of the most promising passive, active, and semi-active vibration control methods is conducted, focusing on recent advances around novel concepts and analyses of their performance under multiple environmental loads, including wind, waves, currents, and seismic excitations. The review highlights the benefits of installing structural systems in reducing the vibrational load of towers and therefore increasing their structural reliability and resilience to extreme events. It is also found that the stochastic nature of the typical tower loads remains a key issue for the design and the performance of the state-of-the-art vibration control methods.

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Section: Connectionsmentioning

confidence: 83%

Recent Advances in Vibration Control Methods for Wind Turbine Towers

2021

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“…After implementation (Figure 2), the turbine was tested and connected to the electrical grid. The current approaches for designing the main load frame rely on fully welded [31][32][33][34], fully cast [35][36][37], and hybrid structures [30]. Literature on the fatigue life of wind turbine components indicates that the focus is on the casting parts of the turbine [38][39][40].…”

Section: Introductionmentioning

confidence: 99%

Fatigue Analysis Design Approach, Manufacturing and Implementation of a 500 kW Wind Turbine Main Load Frame

2021

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The main load frame of a wind turbine is the primary mount for all nacelle equipment and is used as the principal load transmitter. This frame should have a reliable fatigue safety rating because it is a load-bearing component. In this work, the fatigue life design, manufacturing and implementation process for the main load frame of a 500 kW wind turbine are studied. The weight of the main load frame and static safety factors are preserved while the cyclic life of the bedplate is kept infinite. Modified Goodman theory is applied to achieve an effective fatigue design using a commercial finite element software package. Analytical calculations are carried out to obtain the safety factors of the bedplate and dynamic strength of the materials. A finite element approach is employed to perform stress analysis. Stress oscillations are established for both welded and cast parts of the hybrid bedplate, and the maximum and minimum stress values are established. Fatigue safety factors are calculated via fatigue analysis iterations. The obtained safety factors are adequate from the perspective of commonly accepted fatigue safety standards. Welding and casting techniques are applied together for manufacturing of the frame. On-site testing indicates that the wind turbine does not show any signs of fatigue. Rupture, cracks, and abrupt accelerometer reading variations are not observed.

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“…The time-history loading data necessary for the calculation of the towers' fatigue life are artificial wind time-histories produced by National Renewable Energy Laboratory (NREL, 2015) and National Wind Technology Center (NWTC, 2015) software. The same software is used for the production of loading time histories that are employed for the fatigue assessment of bolted connections in the work of Thanasoulas et al (2014) and welded connections in the work of Stavridou et al (2015). Comparative results of the tower models are discussed and useful conclusions are derived on the effect of bottom diameter and anchor bolt number on the capacity of the tower bottom joint.…”

Section: Introductionmentioning

confidence: 99%

Verification of Anchoring in Foundations of Wind Turbine Towers

Stavridou¹,

Efthymiou²,

Baniotopoulos³

2015

American Journal of Engineering and Applied Sciences

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Tubular steel towers are the most common supporting structure of wind converters. The towers' foundation covers an important part of the initial cost and its configuration depends heavily on the type of subsoil. Onshore structures are founded on spread footing foundations or pile foundations with the first being the commonest. In these spread footing foundations, the tower is either embedded in the concrete foundation slab or the tower bottom flange is anchored to the concrete by means of pretensioned bolts. This anchoring of the steel tower on the concrete foundation is very rarely analyzed separately and recent failures due to inadequate design have alerted the wind industry towards the solution of the problem. For the purposes of the analytical and numerical approaches, two alternative types of foundation dimensioning are investigated. The tower properties of the two configurations are the same, providing the same loading and material data. The analytical study of the foundation anchoring is performed with the use of the equivalent ring method and the numerical verification of the two foundation solutions is performed with the use of a detailed micro model. The same micro model is used for the calculation of the fatigue life of the tower bottom joint following the damage accumulation method. In both foundation solutions, the total cross sectional area of the anchor bolts is proved to be the decisive factor for the selection of bolt size and number. The size of the tower bottom diameter plays also an important role on the maximum number and size of bolts used. Both analytical and numerical results are in good agreement and valuable outcomes are emerging from the comparative study on the foundation dimensioning of contemporary structures.

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Welded Connections of Wind Turbine Towers under Fatigue Loading: Finite Element Analysis and Comparative Study

Cited by 15 publications

References 14 publications

Recent Advances in Vibration Control Methods for Wind Turbine Towers

Recent Advances in Vibration Control Methods for Wind Turbine Towers

Fatigue Analysis Design Approach, Manufacturing and Implementation of a 500 kW Wind Turbine Main Load Frame

Verification of Anchoring in Foundations of Wind Turbine Towers

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