Rocking foundations offer a potential mechanism for improving seismic performance by allowing controlled uplift and settlement, but uncertainties in soil-foundation interactions limit their widespread use. Current models require complex numerical simulations, which lack accurate representation of the soil-foundation interface.
The main objective of this thesis is to model the transition from local effects (friction, uplift) to the global response of the structure (rocking, sliding, and settlement) under seismic loads, using a combined experimental and numerical approach. Hence, ensure reliable numerical modeling of rocking structures. Key goals include:
• Investigating sensitivity of physical parameters in seismic response of rocking soil-structure systems using machine learning and numerical analysis.
• Developing and conducting both monotonic and dynamic experimental tests to measure the soil-foundation-structure responses in rocking condition.
• Implementing numerical simulations to account for local interaction effects and validate results with experimental results.
Finally, this research aims to propose a reliable experimental and numerical framework for enhancing seismic resilience in engineering design. This thesis will provide the student with practical engineering, along with expertise in laboratory tests and numerical modeling. The results will be published in international and national journals and presented at conferences, advancing research in the soil and structure dynamics field.

The containment building is the third safety barrier in nuclear power plants. Its role is to protect the environment in the event of a hypothetical accident by limiting releases to the environment. Its function is therefore closely linked to its tightness, which it must maintain throughout its operating life. Traditionally, the estimation of the leakage rate is based on a good knowledge of the hydric state and potential mechanical disorders, associated with transfer laws (such as permeability) in a chained (thermo-)hygro-mechanical simulation approach. While the mechanical behaviour of the structure is now generally well known, using advanced simulation tools, progress is still needed to improve the understanding and quantification of flows. This is particularly the case in the presence of heterogeneities (cracks, honeycombs, reinforcement, cables, etc.), all of which can locally disrupt permeability. This is the context of the proposed thesis topic. The aim is to improve the understanding and representation of flows through a reinforced concrete structure using an approach that combines experimental tests and modelling. An initial analysis will be used to define an optimised experimental design based on several configurations (leak paths, type of flow, temperature, saturation, etc.), which will then be implemented during the thesis. The results will be analysed in order to characterise empirically the influence of the leakage path on the macroscopic laws classically used (Darcy's law). A more refined simulation approach will then be developed, based on the finite element method. The aim will be to reproduce the experimental results and extend them to the behaviour of containment vessels, thereby improving the modelling tools currently available.

In nuclear power plants, the concrete biological shield (CBS) is designed to be very close of the reactor vessel. It is expected to absorb radiation and acts as a load-bearing structure. It is thus exposed during the lifetime of the plant to high level of radiations that can have consequences on the long term. These radiations may result especially in a decrease of the material and structural mechanical properties. Given its key role, it is thus necessary to develop tools and models, to predict the behaviors of such structures at the macroscopic scale.
Based on the results obtained at a lower scale - mesoscopic simulations, from which a better understanding of the irradiation effect can be achieved and experimental results which are expected to feed the simulation (material properties especially), it is thus proposed to develop a macroscopic methodology to be applied to the concrete biological shield. This approach will include different phenomena, among which radiation-induced volumetric expansion, induced creep, thermal defromations and Mechanical loading.
These physical phenomena will be developed within the frame of continuum damage mechanics to evaluate the mechanical degradation at the macroscopic scale in terms of displacements and damage especially. The main challenges of the numerical developments will be the proposition of adapted evolution laws, and particularly the coupling between microstructural damage and damage at the structural level due to the stresses applied on the structure.

Fluid-structure interaction (FSI) phenomena are omnipresent in industrial installations where structures are in contact with a flowing fluid that exerts a mechanical load. In the case of slender flexible structures, IFS can induce vibratory phenomena and mechanical instabilities, resulting in large displacement amplitudes. The nuclear industry is confronted with this problem, particularly concerning piping, fuel assemblies, and steam generators. Computation codes are an essential tool that, based on several input parameters, provide access to quantities of interest (output variables) that are often inaccessible experimentally for the prevention and control of vibrations. However, knowledge of input parameters is sometimes limited by a lack of characterization (measurement error or lack of data) or simply by the intrinsically random nature of these parameters.

In this context, this thesis aims to analyze the vibratory response of a thin structure with uncertain geometric characteristics (structure with a curvature defect, localized or global). In particular, we aim to understand how geometric uncertainties affect the stability of the flexible structure.
This characterization will be carried out both theoretically and numerically. As the work progresses, the effect of different uncertainties (linked, for example, to the material characteristics of the structure or the properties of the incident flow) may be considered. Ultimately, the work carried out as part of this thesis will enable us to improve the prediction and control of vibrations of thin structures under axial flow.

Fluid-structure interactions and associated instabilities are present in many fields, whether in aeronautics with the phenomena of wing flutter, in nuclear power with the vibrations of components under flow, in biology for the understanding of underwater animal locomotion, in botany for the understanding of plant growth, in sport for performance optimization, in energy recovery from fluid-excited flexible structures. The thesis will enable the student to acquire a wide range of skills in mathematics, numerical simulation, fluid mechanics and solid mechanics, and to train for research in the field of fluid and solid mechanics, leading ultimately to a career in this field, whether in academia or in applied research and development in numerous fields of interest to scientists and society in general. A 6-month internship subject is also offered as a preamble to the thesis (optional).

Education level: Master 2 / Final year of engineering school.
Required training: continuum mechanics, strength of materials (beam theory)
fluid mechanics, fluid-structure interaction, numerical simulation (finite elements).