DYNAMIC SOIL-STRUCTURE INTERACTIONOF MODERN WIND TURBINES

This paper assesses the way soil-structure interaction phenomena affect the seismic response of modern wind turbines. To this end, a novel element for three-dimensional finite element analysis of rigid rectangular foundations is proposed and implemented using the computational platform OpenSees. It is worthy of note that the proposed model is capable of capturing the effect of soil nonlinearity. Afterward, using the NREL 1.5-MW baseline turbine, some interaction models are introduced and the effects of three types of cohesionless soils, including soft, medium and stiff soils are investigated. Modal analyses show a decrease in natural frequencies when SSI is considered; and higher modes especially undergo bigger changes. The effect of viscous damping on the predicted turbine response is evaluated as well. Finally, several nonlinear dynamic time-history analyses are performed using three earthquakes with different peak ground accelerations to evaluate the effect of SSI on the maximum internal forces of the tower. Results reveal that SSI influence on the value and distribution of the maximum moment and shear demand will be significant. The alterations in the response of the tower are likely to require redesign of the turbine to account for SSI.