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Historical earthquake catalogs are one of the building blocks for the assessment of seismic hazard. Despite many years of research in the archives, many earthquakes remain poorly known. New sources of informationare hence required.Among these, historical buildings are witnesses of natural catastrophes recorded in their walls as structural disorders, repairs, and restorations. Our project aims to study past earthquakes using buildings as “stone seismometers”, analyzing the seismic ground motions required to explain building repairs/disorders, or their absence. The goal is to demonstrate that archaeological characterization of post-seismic repairs on buildings can be successfully used to infer key ground motion and earthquake source characteristics of historical earthquakes.An interdisciplinary connecting “ArChaeology, inventory of RecOnstruction, Seismology and Structural engineering” (ACROSS) is introduced to gain such knowledge. Based on innovative techniques to inventory repairs in the building archaeology; seismic input signals consistent with the seismotectonic context; digital building models implementing realistic geometry and construction materials as well as robust modelling of masonry behaviour, the ACROSS method is declined in five steps, 1. Collecting the data produced by the archaeology of the buildings and the study of historical sources.2. Identification of damage mechanisms. 3. Definition of the digital building model used for seismic dynamic analysis.4. Comparison of the numerical analysis results, based on previous steps, with repairs and damage mechanisms.The method is applied to six bell towers located in the Mugello basin (Tuscany, Italy). They were affected by many historical earthquakes at least from the middle of the 16th century., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

The Eikonal non-local damage (ENL) approach models damage as a space-deforming phenomenon that affects the interaction distance between material points. As damage increases, interactions between points decrease, ultimately resulting in no interaction. In the integral version of such an approach, non-local interaction distances between material points are computed by solving a stationary Hamilton-Jacobi equation with a damage-dependent Riemannian metric. In the implicit gradient version of ENL models, the Riemannian metric figures in the Helmholtz equation to be solved for computing the non-local field controlling damage evolution. However, one of the main criticisms of such formulation is the lack of thermodynamics basis in its derivation. This paper presents a thermodynamics derivation of the Eikonal implicit gradient formulation based on differential geometry concepts to overcome this issue. A free-energy potential is defined considering the non-local strain as a morphological descriptor belonging to the abstract differentiable manifold (where the Riemannian metric is defined). Following a micromorphic media framework, the balance equations of the model are obtained. It is shown that the stress tensor and thermodynamic force associated with damage are the sum of standard and additional non-local contributions. It is also shown that the resulting energy dissipation is always positive, thus verifying the Clausium-Duhem inequality. After presenting all development considering second-order anisotropic continuum damage, the isotropic formulation is obtained as a particular case. Finally, a two-dimensional numerical implementation of an isotropic implicit Eikonal non-local gradient damage model is illustrated. Test cases are simulated to show the relocalization features of the considered formulation and its natural capability of naturally representing damage-to-fracture transition for high damage levels.

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International audience; The quantification of historical earthquakes is a key element in seismic hazard assessment.Historical buildings recorded in their walls disorders induced by ancient earthquakes as "stone seismometers".We developped an innovative methodology to infer key ground motion characteristics of historical earthquakes by connecting building archaeology, seismology and earthquake engineering through the case study of the medieval church of Sant'Agata del Mugello (Central Apennines, Italy) for which many historical sources described the damage induced by past earthquakes, and their post seismic repair. The largest known events occurred in 1542 (Mw 6) and 1919 (Mw 6.3).The church's history is described by combining stratigraphic analysis of walls with an in-depth study of archives. Ambient vibration measurements provide a structural identification of the church in its present state. A preliminary model of the church is updated through a Vibration-Based model updating process. Strategies to compute the seismic response of the church are discussed. Preliminary results using a continuum damage model to identify the limit of the updated model is discussed.

International audience

International audience; This work proposes a framework for the reevaluation of the intensity based on probabilistic method and structural analysis. The method developed in this work allows for an update of the magnitude of historical earthquakes based on structural fragility functions and comparison to the damage observed in situ. The goal of this work is to assess the feasibility of the approach initially proposed by (Ryu, Kim, & Baker, 2009) to characterize fragile structures. The Bayesian updating procedure allows for accounting for uncertainty related to the structural response, ground motion and site parameters. In order to assess the vulnerability of a large set of existing buildings a global methodology has been developed in the present work. After defining class of typology, a method used to analyze the nonlinear response of old masonry structures, in the context of low to moderate seismicity, is proposed. For the Bayesian updating, a modeling strategy tailored on the non linear analysis of large scale masonry building has been developed for the study within a probabilistic frame. MOTS-CLÉS : archéoseismicité, maçonnerie, endommagement; Ce travail propose un cadre pour la réévaluation de l'intensité basée sur des méthodes probabilistes et l'analyse structurelle. La méthode développée dans ce travail permet de mettre à jour la magnitude des séismes historiques. L'objectif de ces travaux est d'évaluer la faisabilité de l'approche initialement proposée par (Ryu, Kim, & Baker, 2009) pour l'actualisation de magnitude de séismes historiques. La procédure bayésienne de mise à jour permet de tenir compte de l'incertitude liée à la réponse structurale, au mouvement du sol et aux paramètres du site. Afin d'évaluer la vulnérabilité d'un grand nombre de bâtiments existants, une méthodologie globale a été mise au point dans le travail présenté. Après avoir défini une classe de typologie, une méthode d'analyse de la réponse non linéaire des structures de maçonnerie anciennes, dans un contexte de sismicité faible à modérée, est proposée. Pour la mise à jour bayésienne, une stratégie de modélisation adaptée à l'analyse non linéaire des bâtiments de maçonnerie à grande échelle a été développée pour l'étude dans un cadre probabiliste

7th ECCOMAS Thematic Conference on Computational Methods in Structural Dynamics and Earthquake Engineering (COMPDYN), HERSONISSOS, GRECE, 24-/06/2019 - 26/06/2019; The homogenization technique consists in describ-ing the global behavior of the structure with an 'equivalent beam' model according to the following process : (i) Static analysis of only a story for the determination of the mechanical properties of the global model, (ii) Dynamic analysis of the equivalent beam, which is a 1D analytical model, (iii) Application of the macroscopic deformation on the model of a story in order to compute the internal forces of the structural elements.

International audience; The embedding of anchoring systems in the retrofitting of Reinforced Concrete (RC) structures by means of Fiber Reinforced Polymers (FRP) often implies local failure modes associated to high stress concentrations. In order to account for such mechanical behaviours in standard finite element computations, an explicit representation of interfaces is required. This strategy presents, however , several limitations in terms of computational cost and mesh-related issues. On the other hand, implicit models may not be sufficiently accurate in order to reproduce the aforementioned localized phenomena. Specific finite elements for the simulation of pull-out mechanisms are here presented. The presence of interfaces is taken into account by enriching the displacement approximation by means of additional unknowns defined at the element level. Static-condensation, therefore, allows preserving the structure of the finite element procedure and limiting the computational effort.

International audience

International audience

International audience; The analysis and prediction of the degradation process and cracking of concrete structures with numerical models is an important issue in the field of civil engineering. In order to describe the global behavior of a structure composed of quasi-brittle material as well as local fields, a continuous approach using nonlinear constitutive law (e.g. damage, plasticity,…) remains the most efficient one regarding the computational time. However, one has to consider additional tools to extract discrete information about cracks like spacing and openings from these computations. The objective of this research is to propose tools capable of extracting local information such as cracking using two post-treatment methods of a global finite element analysis. First, in the proposed method, a global non-linear finite element analysis of the whole structure is performed. This analysis reveals the zones of degradation that are to be reanalyzed via a local analysis using two post-treatment methods. The first method combines a topological search method used to locate cracks developed by Bottoni et al. [1] and a continuous/discontinuous approach used to compute the crack opening initially proposed by Dufour et al. [2].. It consists in comparing the computed strain fields, with the analytical one derived from the displacement profile described as a strong disconti-nuity. Both strain fields are regularized using a Gaussian function. The crack opening can then be adjusted so as to reduce the gap between the regularized strain field and the regular-ized strong discontinuity strain field. Furthermore, a general formulation of these tools for 2D and 3D problem is proposed in this work. The direction of the mode I crack at a point is determined as the one which maximizes the crack opening along the associated 1D profile. The second method is a non-intrusive reanalysis at the local scale performed with a discrete model in order to extract fine information about crack opening. A region of interest (ROI) corresponding to the damaged area obtained from the global analysis is defined. Then, the loading steps corresponding to the steps of reanalysis are determined, where boundary conditions are extracted from the continuous displacement field and applied on the non-free surfaces of the ROI. The material is described with a discrete element approach based on an assembly of polyhedral particles linked by Euler-Bernoulli beams with brittle behaviour. Further details concerning the discrete model used at the local scale can be found in [3]. The displacement fields obtained from the FE analysis are compared to the experimental data provided from the post-processing of the actual test in order to analyze the concordance of the results on the global scale.

International audience; Le processus de fissuration d’une poutre entaillée en béton fibré soumise à une sollicitation de flexion 1-point dynamique a été étudié. L’analyse est faite à partir de la réponse globale issue d’un calcul élément fini afin d’extraire localement de l’information fine concernant la fissure. Deux approches pour le post-traitement de l’analyse globale sont comparées : une méthode continue/discontinue ainsi qu’une analyse globale/locale. Les estimations d’ouverture de fissure obtenues numériquement sont alors comparées aux résultats expérimentaux.

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International audience; This work aims to develop and identify a new model for reinforced concrete joint element subject to cyclic loadings. Based on experiments and 3D numerical modeling, a simplified model of RC beam-column joint is introduced (within the framework of macro-element). In a first experimental study, this joint will be tested under reverse cyclic loading applied at the beam tip to identify its behavior under this kind of loading in terms of strength, stiffness and ductility. In parallel of experiments, a finite elements model of the joint based on 3D finite elements is presented to highlight and define the nonlinear mechanisms involved in the ruin of the assembly. This step will confirm the experimentally observed phenomena: damage, friction, plasticity. Secondly, a simplified macro-element model for beam-column joint, associated to a nonlinear behavior, is introduced to reflect the response of the joint under cyclic loading loads. Model parameters will be identified from experimental results and analysis on a local scale via 3D finite element calculation. Finally, numerical analyses will be performed to validate the proposed approach in comparison with the experimental tests.