Enhanced Seismic Response Prediction of Critical Structures via 3D Regional Scale Physics-Based Earthquake Simulation

Realistic physics-based 3D earthquake simulation for source-to-structure wave propagation consists of a powerful numerical tool for seismic response prediction of critical structures submitted to high safety standards. Structural response considering soil-structure interaction (SSI) is usually estimated by Finite Element Method (FEM) approach, as it is considered as the most flexible numerical approach for nonlinear structural dynamics. However, current engineering practice considers seismic input motion as vertically incident plane waves, despite the fact that this assumption excludes wave passage effects for large infrastructures and surface waves appearing from possible local basin effects. In this framework, a realistic input excitation needs to be defined as an input excitation of the FEM model, accounting for (i) a realistic dynamic excitation, (ii) wave propagation path in the regional scale, and (iii) local site-effects. The Domain Reduction Method (DRM), which allows for the imposition of a 3D complex incident wave field as an input to the SSI model, is adapted and examined here in a Spectral Element Method (SEM) - FEM weak coupling approach. The weak coupling is verified at first for a canonical case-study and for an increasing complexity of the dynamic excitation: (i) double-couple point-source and (ii) extended fault. An optimization approach, based on the decimation of SEM output signal, is then examined in order to decrease the computational burden by maintaining the same accuracy of the final solution. The SEM-FEM weak coupling is then used to study the SSI problem, where the impact of the reduced domain size on structural response is examined at first. The current study shows that a reduced domain of dimension greater than 4 x lambda(s), where lambda(s) is the maximum wavelength, is sufficient for a proper representation of structural response. For a fixed size model, structural and soil responses are then examined for a hypothetical case-study.