Behavior of a Structured Piled Beam–Slab Foundation for a Wind Turbine under Multidirectional Loads in Sand
Publication: International Journal of Geomechanics
Volume 21, Issue 3
Abstract
With wind farm development, a new type of foundation, the piled beam–slab foundation, was invented to support wind turbines on land. Although this foundation enables a lower-cost investment, its structure is complex. Wind turbine foundations are usually subject to combined vertical, horizontal, and moment loads. To investigate the coupled effects on the piled beam–slab foundation, scaled model tests were conducted. The results show that the presence of a vertical load increases the horizontal bearing capacity of the piled beam–slab foundation. The axial forces of the piles are mostly caused by the vertical load and moment acting on the foundation. The vertical load carried by the piles increases when the horizontal load acting on the foundation increases or the moment acting on the foundation decreases. Several equations are proposed to calculate the responses of the foundation under a combined load based on the responses of the foundation under a pure horizontal or moment load, which can be calculated by the traditional design method. Finite-element analysis on a prototype piled beam–slab foundation is performed to prove that the proposed equations are reasonable for actual foundations.
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Acknowledgments
The authors would like to acknowledge the financial support provided by the National Science Fund of China (41572260, 41877252 and 51208378) and the Fundamental Research Funds for the Central Universities.
Notation
The following symbols are used in this paper:
- Ap
- effective section area of the pile;
- D
- slab diameter;
- Eb
- elastic modulus of the beam;
- Ep
- elastic modulus of the pile;
- F
- axial force of the pile;
- H
- horizontal load acting on the foundation;
- Hult
- ultimate horizontal load of the foundation under both vertical and horizontal loads;
- Hult,0
- ultimate horizontal load of the foundation under a pure horizontal load;
- Ib
- moment of inertia of the beam;
- Ip
- moment of inertia of the pile;
- M
- moment acting on the foundation;
- Mb
- moment on the beam when the foundation is subject to a combined load;
- Mb,0
- moment on the beam when the foundation is subject to a pure horizontal load or moment;
- Mp
- moment on the pile top;
- Mult
- ultimate moment of the foundation under both vertical and moment loads;
- Mult,0
- ultimate moment of the foundation under a pure moment;
- u
- perimeter of the pile;
- V
- vertical load acting on the foundation;
- α1, α2, α3, α4, α5, α6, c1, c2, and c3
- factors;
- β
- percentage of the moment carried by all the piles;
- ɛ
- measured strain;
- ɛ+
- strains measured along the pile or the beam at the compression side;
- ɛ−
- strains measured along the pile or the beam at the extension side;
- ρ
- percentage of the vertical load carried by one pile; and
- ρt
- percentage of the vertical load carried by all the piles.
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Published In
International Journal of Geomechanics
Volume 21 • Issue 3 • March 2021
Copyright
© 2020 American Society of Civil Engineers.
History
Received: Feb 20, 2020
Accepted: Oct 1, 2020
Published online: Dec 23, 2020
Published in print: Mar 1, 2021
Discussion open until: May 23, 2021
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