Recent Developments in Wind Turbine Foundation Design: Post Tensioned Single Pier-Paper

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The paper reviews post-tensioned single-pier foundations as an alternative to conventional shallow spread foundations for increasingly large wind turbines. The foundation is a large-diameter, cast-in-place annular concrete pier formed between two corrugated metal pipes. Tower anchor bolts extend through the pier and are post-tensioned so the concrete remains in compression, reducing fatigue damage and potentially enabling foundations to be reused when turbines are repowered.<br /><br />Design addresses geotechnical stability and stiffness, structural strength, serviceability, and fatigue. Conventional calculations assess ultimate capacity, including resistance from passive soil pressure, side friction, and base bearing. Numerical modeling—particularly three-dimensional finite element analysis—can additionally represent soil–structure behavior, site stratigraphy, construction stages, post-tensioning, and loading, helping estimate movements, stiffness, and stresses more realistically.<br /><br />Two Texas projects illustrate the approach. At Sweetwater, a 28-foot-deep pier supporting a 1.7 MW turbine met required stiffness and movement limits; analysis found adequate overturning stability and no tensile stress in the pier. At Cochran County, 30- to 32-foot piers supported 2.3 MW turbines, with calculated results within the specified design criteria. In both cases, finite element analysis supplemented rather than replaced conventional geotechnical calculations for ultimate capacity.<br /><br />The authors conclude that post-tensioned single piers can offer economic, durability, and fatigue-life advantages over large spread foundations, particularly for higher turbine loads. Numerical modeling supports optimized design and a better understanding of foundation behavior.

Keywords

post-tensioned single-pier foundation

wind turbine foundations

annular concrete pier

finite element analysis

geotechnical stability

fatigue resistance

tower anchor bolts

soil-structure interaction

repowering reuse

Texas wind projects