Wind turbine foundations - loading, dynamics and design

Horizontal axis wind turbines are dynamic structures. The foundations available to support these machines are varied, and the choice of foundation type has several influencing factors. The loading transmitted to the foundation is dependant on the power regulation philosophy of the turbine, the wind climate of the region where the turbine is to be installed, and the physical characteristics of the machine. The relationship between the frequently occurring loads and the extreme loads is discussed, with an explanation of how this bears on foundation design. Foundation design may also be impacted by additional factors such as no uplift criteria, ground sensitivity to cyclic loading and foundation stiffness requirements. The stiffness of deep water offshore foundations is investigated, with reference to study data. The paper concludes by comparing ULS and ALS load factors recommended by design codes.

Danny Bonnett MA, CEng, MICE
Design Civil Engineer, RES Group, Beaufort Court, Egg Farm Lane, Kings Langley, Hertfordshire. WD4 8LR