Intitulé du poste :
An integrated methodology for source-to-structure seismic safety assessment including uncertainty propagation by surrogate modeling

Description de la mission :

The seismic safety assessment of structures and components of nuclear power plants is based on a well-established methodology consisting in the (i) establishment of the site-specific seismic hazard, the (ii) computation of the dynamic response of structures interacting with the surrounding soil to compute seismic demand, the iii) evaluation of the seismic fragility of structures and components and iv) the convolution of hazard and fragility for safety assessment.

The development of best-estimate approaches together with comprehensive consideration of uncertainties as well as the development of integrated approaches from hazard to structural response allow for more accurate risk estimates (e.g. SINAPS@ and METIS research projects). Recently, an integrated methodology was proposed by Korres et al. accounting for the seismic wave propagation, from the source, through the complex geological medium in the regional and local scale of the site under consideration, and up to the structure’s foundation and its transmission to the sensitive equipment of interest (e.g., electro-mechanical devices, piping systems, etc.). However, the link between physics-based simulation and regulatory approaches where seismic load is defined by response spectra still needs to be fully established. On the other hand, source-to-structure 3D simulation remain computationally expensive and requires the development of surrogate models in particular in the light of uncertainty propagation and sensitivity analysis.

In this context, the main objective of this work is to develop a global methodology for seismic assessment of structures integrating: (i) a source-to-structure wave propagation modeling conditioned on the site-specific seismic hazard defined on the outcropping rock, and (ii) uncertainties at the different scales, while propagating them through the different steps of the procedure.

The proposed strategy for this PhD work is based on ideas synthesized in the following :

·       Source-to-structure 3D physics-based simulations (PBS):
In order to appropriately model the seismic wave propagation at the different scales of analysis (regional scale ~km, site/structure scale ~m), a spectral element (SEM) - finite element method (FEM) coupling based on the domain reduction method already implemented in Korres et al. is used as a basis for the numerical simulations. In this context, important components of the source-to-structure wave propagation can be explicitly taken into account.
More precisely, such numerical approach requires : i) the definition of a realistic 3D geology (regional/local scale) and the mechanical properties of the structure, ii) the characterization and modeling of the excitation source on the regional scale, iii) the definition of the ground motion on the s

A successful candidate shall dispose strong knowledge in the following fields:

·       Structural dynamics and numerical methods (finite elements)

·       Parallel computing and programming

·       Statistics and probabilities, uncertainty modelling

·       Engineering seismology

A first experience in finite element modeling and parallel computing is appreciated.

Modalités : Starting date autumn 2024 for a duration of 3 years