Seismic risk analysis of wind turbine support structures

Probabilistic models are developed to predict deformation, shear, and moment demands on wind turbine support structures subject to seismic excitations, and environmental (wind, wave, and current) and operational loadings. The probabilistic models are formulated starting from existing deterministic models and developing correction terms that capture the inherent bias. The correction terms and a model error are assessed using data obtained from detailed three-dimensional nonlinear finite element analyses of a set of wind turbine systems that consider different design parameters and account for the dynamic soil-structure interaction. The proposed probabilistic seismic demand models provide unbiased predictions of the seismic demand on support structures and properly account for the underlying uncertainties. The developed demand models are used to compute fragility estimates of an example support structure defined as the conditional probability of not meeting specified capacity levels.