Seismic fragility analysis of near-fault mountainous wind turbines considering source-path-site effects

With the increasing demand for renewable energy, the deployment of wind turbines (WTs) in mountainous areas has surged, raising concerns about the associated seismic risk. The seismic fragility of these turbines is governed by a combination of factors, including the characteristics of the seismic source, the propagation paths, and the site-specific conditions. However, there is limited understanding of how these coupled source-path-site effects impact WT fragility, creating a critical knowledge gap that impedes the development of reliable seismic design guidelines for wind farms in mountainous areas. To address this issue, a physics-based method for fragility assessment is proposed, combining scenario-specific ground motion simulations with a hybrid semi-analytical-numerical modeling approach. This methodology integrates three computational components: (i) the frequency-wavenumber (FK) technique to compute the semi-analytical Green's function for a semi-infinite crustal space, (ii) the spectral element method (SEM) for efficient wavefield simulations in heterogeneous terrains, and (iii) the finite element method (FEM) for detailed nonlinear modeling of WT structural responses. The FK-SEM-FEM framework enables end-to-end simulation of seismic wave propagation from fault rupture to the nonlinear structural response of the WTs. The study analyzes the effects of key parameters on the seismic performance of WTs in mountainous regions, and introduces, for the first time, a fragility model for WTs considering diverse mountain geometries. The results indicate that the seismic response of WTs on mountaintops can be amplified by 1.16–3.02 times compared to those at the base. The combined effect of fault rupture mode and local site effects leads to spatially variable damage patterns, making WTs on mountaintops more susceptible to failure. The findings reveal that current seismic design codes for WTs in mountainous areas are inadequate, highlighting the need for immediate updates to address these risks.