The document introduces a tubular rivet foundation as an alternative to traditional gravity foundations for wind turbines. Key points: - Tubular rivet foundations consist of an inner and outer tube connected by structural members like arm beams and a circular grade beam, anchored deep into the ground like a fastener. - They are constructed by excavating a hollow tube using long-reach equipment. Reinforced concrete is then cast to form a rigid connection between members. - Analysis shows they can reduce engineering quantities of concrete and steel by 20-45% compared to gravity foundations, with savings increasing in difficult soil conditions. Construction is also faster with less environmental impact. - The foundation acts as both an anchor and

1. Tubular Rivet Foundation
for Wind Turbines
Introduction for Civil Engineers and Developers of Wind Energy
Apposite Engineering Systems, LLC
https:aescorpllc.com
April 2023

2. Overview
• Background
• Tubular Rivet Foundation
• Structural Members of the Foundation
• Construction
• Design and Analysis
• Engineering Quantities
2

3. Background
Cost reductions of 17-35% by 2035 are anticipated due to advancements in
technology and lower capital and operating costs.
3
Source: https://www.renewableenergyworld.com/wind-power/wind-power-experts-expect-wind-energy-costs-to-decline-up-to-35-by-2035/

4. Background
Gravity foundation diameters have increased over 55% as a result of
the increase in turbine size.
4

5. Background
• Larger spread foundations have higher costs and a greater
environmental impact.
• A deeper and stronger foundation is the solution.
5

6. Tubular Rivet Foundation
Rivets are known for their strength and are commonly used in
structures that are subject to high loads or vibrations where secure and
reliable fasteners are required.
6

7. Tubular Rivet Foundation
Tubular Rivet Foundation acts as a fastener between the wind
turbines/towers and the ground.
7

8. Structural Members of the Foundation
8
Tubular Rivet Foundations typically consist of:
• Inner/outer tube diameters that match the dimension of the tower flange base
and satisfy the steel reinforcement requirements.
• Tube wall thicknesses of 3.0 ft.
• Tube depths of approximately 50 to 60 feet for 4MW turbines in medium stiff
soils. However, depths of 65 feet or more may be required depending on
soil/loading condition.
It ANCHORS the turbine to the ground

9. Structural Members of the Foundation
• The arm beams, the circular grade beam, and the tube in the center of the system work
together. All members are rigidly connected with reinforcement extruded into each other and
all are cast in place.
• The radius of the circular beam varies, typically in the range of 15 to 20 feet. Arm beams
with a rectangular section are built between the tube and the circular beam. The arm beams
and the circular grade beam can be combined forming a solid cap.
• Larger cap diameter or deeper burial circular grade beams can be used to enhance the
stiffness of the foundations for larger turbines. The design will be finalized based on
optimization.
• The features will enhance the resistance greatly and eliminate the risk of gapping between
the tube structure and the surrounding soils under cyclic loading. It is not only capable as
acting like an anchor, but it also provides the stiffness that is required to maximize the
turbine’s output.
9

10. Tubular Rivet Foundation Construction
Clamshell basket with long reach or
telescopic arms
10
Construction methods, procedures, and equipment are dependent on geologic
conditions. The following equipment may be used to excavate the hollow tube:
Long reach excavator Long reach trencher (e.g. hydro-mill trench cutter)
Or other equipment suitable to accommodate the shape of the excavation.

11. Design and Analysis
• All geotechnical and structural analyses
are FEA- based
• Our copyrighted analysis platform –iFED
© make the analysis enjoyable
• All requirements for gravity foundation
are checked and satisfied
11

12. Design and Analysis
• 3-D drawings have been successfully developed
• Reinforcement is easy to cast, and assembly bundles of rebars
12

13. Engineering Quantities
• Savings of about 20% to 45% on engineering quantities compared to
a gravity foundation.
• Savings increase further when unfavorable site conditions are
present e.g., high groundwater level, voids (Karst geologic sites), soft
soils or hard rocks.
• Faster construction and less impact to the environment compared to
gravity foundations.
13

14. Engineering Quantities
Comparison of engineering quantities between
Tubular Rivet Foundation and a gravity
foundation.
Conc. 353 cy vs 674 Cy
Steel: 86 k vs 107 k

15. Cooperation is the Key to Success
Apposite Engineering Systems LLC is a research/consulting
combined institute, always happy to use our expertise to help you to
succeed.
We look forward to your cooperation so we can make a more beautiful
tomorrow in this world.
For any inquiries or collaboration interests, please contact
info@aescorpllc.com
15