Improved design of tubular wind tower foundations using steel micropiles

Matos, Rui; Pinto, Paula; Rebelo, Carlos; Gervásio, Helena; Veljković, Milan

doi:10.1080/15732479.2015.1076853

Cited by 4 publications

(4 citation statements)

References 8 publications

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“…Moreover, the existence of micro piles will make the foundation stiffer, reducing the vibrations of the wind turbine. Finally, this foundation configuration leads to a more sustainable solution compared with the traditional shallow foundation since a reduction of 15-54% and 30-53% is achieved for concrete and steel, respectively [46].…”

Section: Onshore Foundationsmentioning

confidence: 96%

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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: Onshore Foundationsmentioning

confidence: 96%

“…Onshore foundations contribute to around 30% of the total cost of the tower [46], contributing 24% of the total global warming emissions of material components for a typical 2 MW [47]. In general, two main categories can be considered for wind turbine foundations, namely spread foundations and piled foundations (Figure 7) [48].…”

Section: Onshore Foundationsmentioning

confidence: 99%

Recent Advances in Vibration Control Methods for Wind Turbine Towers

2021

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“…5,6 Especially referring to wind turbines with steel mast, their foundation system has to sustain cyclically applied large horizontal forces and overturning moments induced by wind load with contemporary moderate vertical load. Two types of foundation systems are mostly employed for onshore towers 7,8 : truncated-conical shallow foundations, 9,10 eventually combined with piles, 11 or deep monopiles, 12 being the former one the most common solution. The connection of the steel mast of tubular towers with the reinforced concrete foundation is usually bolted, where either large steel rings or stud bolt adapters are alternatively employed.…”

Section: Introductionmentioning

confidence: 99%

Experimental tests on shallow foundations of onshore wind turbine towers

Lago

Flessati

Marveggio

et al. 2022

Structural Concrete

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The current effort towards the progressive switch from carbon‐based to renewable energy production is leading to a relevant spreading of both on‐ and off‐shore wind turbine towers. Regarding reinforced concrete shallow foundations of onshore wind turbine steel towers, possible reductions of reinforcement may increase their sustainability, speed of erection, and competitiveness. The article presents the results of an experimental program carried out at Politecnico di Milano concerning both cyclic and monotonic loading, simulating extreme wind conditions on 1:15 scaled models of wind turbine steel towers connected by stud bolt adapters to reinforced concrete shallow foundations embedded in a sandy soil. Three couples of foundation specimens were tested with different reinforcement layouts: (a) similar to current praxis, (b) without shear reinforcement, and (c) without shear reinforcement and with 50% of ordinary steel rebars replaced by steel fibers. Additional vertical loads were added to the small‐scale models in order to ensure similarity in terms of stresses. The test results allowed to (i) characterize the mechanical behavior of the foundation element considering soil‐structure interaction under both service and ultimate load conditions, (ii) assess the foundation failure mode, (iii) highlight the role of each typology of reinforcing bars forming the cage, and (iv) provide hints for the optimization of these latter.

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“…This solution will be more effective on foundations with higher force eccentricity, such as steel wind towers, where the vertical force is low compared to the bending moment. Concrete towers in areas of high seismicity may also benefit from this hybrid solution as concluded by Matos et al (2016).…”

Section: Introductionmentioning

confidence: 99%

Axial Monotonic and Cyclic Testing of Micropiles in Loose Sand

Matos

Pinto

Rebelo

et al. 2018

Geotechnical Testing Journal

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Micropiles, which are small-diameter deep foundation solutions with diameters that can measure up to 300 mm, are often used to reinforce new and existing foundations. Their use in the foundations of structures with high eccentricity, such as wind towers when subjected to wind loads, may lead to more efficient and economical solutions. As the new generation of wind towers will reach more than 150 m tall, very large and uneconomical gravity foundations are required. In regions of high seismicity this problem is aggravated. To evaluate the behavior of micropiles under variable loading and predict the improvement of the reinforced solution, load tests were performed on steel micropiles under controlled laboratory conditions. A total of 36 tests were conducted on 3-m-long pipe micropiles, both while isolated and in 2 by 2 groups, with three different spacings. The micropiles were installed in a cylindrical container filled with calibrated sand and tested under monotonic and cyclic loading, first without grout, then when low-pressure grouted and retested, with the aim to evaluate the improvement caused by the grout injection, the micropile spacing, and application of cyclic loading both in terms of resistance and stiffness. An improvement both in stiffness and resistance due to the grouting was obtained and, for the applied cyclic loading, there was no clear reduction in micropile cyclic stiffness. The presented results provide a tool for the calibration of numerical models to estimate the behavior of real-scale micropiles installed in higher density sand.

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Improved design of tubular wind tower foundations using steel micropiles

Cited by 4 publications

References 8 publications

Recent Advances in Vibration Control Methods for Wind Turbine Towers

Recent Advances in Vibration Control Methods for Wind Turbine Towers

Experimental tests on shallow foundations of onshore wind turbine towers

Axial Monotonic and Cyclic Testing of Micropiles in Loose Sand

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