DYNAMIC SOIL-STRUCTURE INTERACTIONOF MODERN WIND TURBINES

This paper assesses the wa y 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, includi ng soft, medium and stiff soils are investigated. Modal analyses show a decrease in natural frequencies when SSI is considered; and higher modes es pecially undergo bigger changes. The effect of viscous da mping on the predicted turbine response is eva luated as well. Finally, several nonlinear dynamic time-his tory analyses are performed using three earthquakes with different peak ground accelerations to evaluate th e effect of SSI on the maximum internal forc es of the tower. Results reveal that SSI influence on the vallue and distribution of the maximum moment annd shear demand will be significant. The alterations in the ressponse of the tower are likely to require redesign of the turbine to account for SSI.