Damage and failure of heterogeneous materials and structures under complex loading

Darius Seyedi (1)

1 SEMT - Service d'Etudes Mécaniques et Thermiques

This manuscript presents a synthesis of my research activities, submitted in partial fulfillment of the French HDR degree (Habilitation à Diriger des Recherches), on the subject of damage and failure of heterogeneous materials and structures under complex loading. The work presented here was performed essentially during my time at BRGM (French Geological Survey) from 2004 to 2012, and at Andra (French national agency for radioactive waste management) from 2012 to 2018. Three application domains have been addressed in the present document. Each one is presented in a separate chapter. First, thermo-hydromechanical behavior of Callovo-Oxfordian claystone is discussed as a potential host formation for an industrial radioactive waste repository. A synthesis of research conducted essentially within \textit{Mechanical behavior of repository components and materials Group of Labs (GL Mouv)} at Andra is presented. Second application concerns damage and fracturing of heterogeneous quasi-brittle materials. The main motivation for these developments has been the study of the integrity of geological storage of $CO_2$. A non-local damage model accounting for the rock heterogeneities was developed. The model was then extended to account for hydromechanical couplings. Seismic fragility of structures is addressed in the third chapter. Standard fragility functions represent the conditional probability for a structure to reach a certain damage level for a given earthquake represented by a single intensity measure. This standard procedure introduces epistemic uncertainties in the risk evaluation as such approach cannot fully represent the effect of an earthquake on the response of structures. A concept of vector-valued fragility functions (or fragility surfaces) is proposed enabling to represent earthquake shaking by two intensity measures. It will be shown that an increase from one to two IMs leads to a significant reduction in the scatter in fragility functions. Moreover, the proposed methodology can be extended to multi-hazard risk assessment, and accounting for initial damage of structures. My resume and a short synthesis of my research activities in French are presented at the beginning of this manuscript. The document is concluded by some research perspectives.

Mots clés: Damage; Fracture; heterogeneous materials

Mots clés: Endommagement; Rupture; Hétérogénéités

Domaines: Sciences de l'ingénieur [physics]

Darius Seyedi. Damage and failure of heterogeneous materials and structures under complex loading. Engineering Sciences [physics]. Université Paris-Saclay, 2021. ⟨tel-04560033⟩