FEM-based spectral matching to obtain specific surface spectra

The dynamic interaction between a civil infrastructure and the soil beneath is crucial for seismic risk assessment. Due to the increased computational capacity, more frequently, this problem is starting to be addressed by 3D modelling based on the finite element method (FEM). However, because of the interaction between the stresses and strains in the orthogonal directions of the soil volume, i.e. the Poisson effect, it is not trivial to achieve specific spectral ordinates at the surface of the FEM model, after propagation from the bedrock. This study introduces a novel method aimed at obtaining surface-level ground motions with specific spectral intensities by using 3D FEM models. This method integrates spectral matching, filters, deconvolution using 1D models, and frequency modulation techniques, to address misalignments between the outcomes of 1D and 3D models, particularly focusing on high-frequency spectral amplification in soil response. It has been tested by analysing two seismic scenarios, which have been characterized from a probabilistic perspective. The proposed approach ensures the development of ground motion records accurately producing specific spectral intensities at the surface, enhancing seismic risk assessments and structural analysis. The study emphasizes the importance of accurate seismic hazard characterization, providing valuable insights for earthquake engineering practices. • Method developed to spectrally match signals at the surface of 3D FEM soil models. • Integrates filters, deconvolution in 1D models and frequency modulation techniques. • Allows considering uncertainties in the seismic ground motions and soil properties. • Enables compliance with nuclear regulation standards such as RG 1.208 • Ensures accurate spectral matching over a wide frequency range.