Evaluation of seismic hazard for the assessment of historical elements at risk : description of input and selection of intensity measures

The assessment of historical elements at risk from earthquake loading presents a number of differences from the seismic evaluation of modern structures, for design or retrofitting purposes, which is covered by existing building codes, and for the development of fragility curves, procedures for which have been extensively developed in the past decade. This article briefly discusses: the hazard framework for historical assets, including a consideration of the appropriate return period to be used for such elements at risk; the intensity measures that could be used to describe earthquake shaking for the analysis of historical assets; and available approaches for their assessment. We then discuss various unique aspects of historical assets that mean the characterisation of earthquake loading must be different from that for modern structures. For example, historical buildings are often composed of heterogeneous materials (e.g., old masonry) and they are sometimes located where strong local site effects occur due to: steep topography (e.g., hilltops), basin effects or foundations built on the remains of previous structures. Standard seismic hazard assessment undertaken for modern structures and the majority of sites is generally not appropriate. Within the PERPETUATE project performance-based assessments, using nonlinear static and dynamic analyses for the evaluation of structural response of historical assets, were undertaken. The steps outlined in this article are important for input to these assessments

PRENOLIN project. Results of the validation phase at sendai site

One of the objectives of the PRENOLIN project is the assessment of uncertainties associated with non-linear simulation of 1D site effects. An international benchmark is underway to test several numerical codes, including various non-linear soil constitutive models, to compute the non-linear seismic site response. The preliminary verification phase (i.e. comparison between numerical codes on simple, idealistic cases) is now followed by the validation phase, which compares predictions of such numerical estimations with actual strong motion data recorded from well-known sites. The benchmark presently involves 21 teams and 21 different non-linear computations. Extensive site characterization was performed at three sites of the Japanese KiK-net and PARI networks. This paper focuses on SENDAI site. The first results indicate that a careful analysis of the data for the lab measurement is required. The linear site response is overestimated while the non-linear effects are underestimated in the first iteration. According to these observations, a first set of recommendations for defining the non-linear soil parameters from lab measurements is proposed. PRENOLIN is part of two larger projects: SINAPS@, funded by the ANR (French National Research Agency) and SIGMA, funded by a consortium of nuclear operators (EDF, CEA, AREVA, ENL)

Évaluation des Méthodes Meshfree pour les Simulations Géomécaniques en Transformations Finies

This work first presents a synthesis of the main available Galerkin-type meshfree methods (DEM, EFGM, h-p Clouds, SPH, RKPM, RKI, MLS/RK, PIM, RPIM, MLS/RBF, etc.), providing a unified formalism for all methods and thus enhancing at once specific features for building shape functions. Several techniques dedicated to the numerical implementation of meshfree methods are presented and discussed as well. Numerical performances of the various methods and techniques are then compared on standard mechanical applications. This work also presents the nonlinear dynamic model used for saturated porous media at finite strains, as well as the approaches usually adopted for the constitutive model of the solid phase. This model is finally evaluated on some geomechanical applications, by comparing results obtained with various numerical methods (i.e. meshfree and finite elements).Ce travail propose tout d'abord une synthèse des principales méthodes sans maillage (i.e. meshfree) existant actuellement (DEM, EFGM, h-p Clouds, SPH, RKPM, RKI, MLS/RK, PIM, RPIM, MLS/RBF, etc.), en fournissant une écriture commune à toutes les méthodes et en mettant ainsi directement en évidence les spécificités de chacune vis-à-vis de la construction des fonctions de forme. Plusieurs techniques spécifiques à la mise en œuvre numérique des méthodes meshfree sont également présentées et discutées. Les performances des différentes méthodes et techniques sont enfin comparées pour des tests mécaniques standards. Ce travail présente par ailleurs le modèle dynamique non linéaire utilisé pour modéliser les milieux poreux saturés en transformations finies, ainsi que les approches classiques pour établir la loi de comportement de la phase solide. Ce modèle est évalué sur diverses applications géomécaniques, en comparant les résultats obtenus pour différentes méthodes avec et sans maillage

Parametric studies and quantitative assessment of the vulnerability of a RC frame building exposed to differential settlements

International audienceThe aim of this paper is to propose a simplified methodology to evaluate the mechanical performances of buildings exposed to landslide hazard, by using procedures inspired from the seismic risk analysis, such as the Capacity Spectrum Method (ATC 40, 1996). Landslide hazard involves so many aspects, that quantitative vulnerability assessment requires to consider one basic scenario at a time, i.e. one typology for the landslide hazard and one for the structural element considered. In this paper, we propose to assess vulnerability for simple one bay-one storey reinforced concrete (RC) frame structures subjected to differential settlements, using 2-D parametric nonlinear static time-history analyses. After a short review of methods used in practice to estimate building deformations induced by ground movements (e.g. differential settlements), we present the parametric studies carried out to identify the most relevant parameters, in order to predict the structural damage, as well as the methodology to develop analytical fragility curves, that can be used to quantitatively evaluate the structural vulnerability in landslide risk analyses. Different types of parameters that could influence structural behaviour have been examined in this analysis: foundation type (i.e. different combinations of links), cross-section geometry, section reinforcement degree, displacement magnitudes and displacement inclination angles. We show that the magnitude and inclination angle of displacements can be used as two relevant parameters for this type of landslide scenario. Based on these results, some simulations are conducted using the software SeismoStruct (SeismoSoft, 2003), and the proposed structural damage levels consider the local strain limits of steel and concrete constitutive materials. Some preliminary fragility curves are proposed with respect to the magnitude of differential ground displacement. It can be seen that the curves corresponding to limit states LS2 (moderate damage) and LS4 (complete damage) in the present study, correspond respectively to the "tolerable settlements" "observed intolerable settlements" curves proposed by Zhang and Ng (2005)

Evaluation des méthodes meshfree pour les simulations géomécaniques en transformations finies

Ce travail propose tout d'abord une synthèse des principales méthodes sans maillage (i.e. meshfree) existant actuellement (DEM, EFGM, h-p Clouds, SPH, RKPM, RKI, MLS/RK, PIM, RPIM, MLS/RBF, etc.), en fournissant une écriture commune à toutes les méthodes et en mettant ainsi directement en évidence les spécificités de chacune vis-à-vis de la construction des fonctions de forme. Plusieurs techniques spécifiques à la mise en œuvre numérique des méthodes meshfree sont également présentées et discutées. Les performances des différentes méthodes et techniques sont enfin comparées pour des tests mécaniques standards. Ce travail présente par ailleurs le modèle dynamique non linéaire utilisé pour modéliser les milieux poreux saturés en transformations finies, ainsi que les approches classiques pour établir la loi de comportement de la phase solide. Ce modèle est évalué sur diverses applications géomécaniques, en comparant les résultats obtenus pour différentes méthodes avec et sans maillage.CHATENAY MALABRY-Ecole centrale (920192301) / SudocSudocFranceF

Simulation numérique des essais de liquéfaction sur table vibrante

International audienceCet article traite de la représentativité des simulations numériques pour les études de liquéfaction des sols. Tout d'abord, les essais sur table vibrante menés dans le cadre du projet ANR ISOLATE et visant à liquéfier un massif de sable homogène, sont brièvement présentés. Ensuite, deux solveurs éléments finis basés sur des modèles constitutifs différents sont utilisés pour comparer les résultats expérimentaux et numériques et montrer la capacité des modèles constitutifs à capturer les principales caractéristiques du comportement des sols saturés pendant la liquéfaction

Probabilistic Safety Assessment for internal and external events on nuclear power plants and on mitigation strategies/H2020 European projects NARSIS, R2CA and BESEP

International audienceThe NARSIS project aimed at improving assessment methodologies to be integrated into “extended Probabilistic Safety Assessment” (PSA) procedures for nuclear plants in case of single, cascade and combined external natural events. An open-access framework tool has been released to build multi-hazard scenarios, and various risk integration approaches (e.g., Bayesian Networks) have been implemented and compared, identifying their advantages and limits for further collaborative research activities. The R2CA project aims at harmonizing the safety analysis methods for best estimate evaluations of the radiological consequences, in case of Design Basis Accidents and Design Extension Conditions without significant fuel melting. It is planned to improve models and upgrade existing simulation tools and calculation chains used in safety studies. Finally, the BESEP project is to support safety margin determination, by developing best practices for safety requirement verification against external hazards, using efficient and integrated set of Safety Engineering practices and PSA. The project is carried out in a benchmark exercise based on case studies previously performed by the consortium participants. All three projects aim to improve nuclear safety within the European research and development framework. The research objectives are achieved by the development and improvement of proven and justified safety assessment methodologies for the verification of stringent safety requirements of nuclear industry

Probabilistic Safety Assessment for internal and external events on nuclear power plants and on mitigation strategies/H2020 European projects NARSIS, R2CA and BESEP

International audienceThe NARSIS project aimed at improving assessment methodologies to be integrated into “extended Probabilistic Safety Assessment” (PSA) procedures for nuclear plants in case of single, cascade and combined external natural events. An open-access framework tool has been released to build multi-hazard scenarios, and various risk integration approaches (e.g., Bayesian Networks) have been implemented and compared, identifying their advantages and limits for further collaborative research activities. The R2CA project aims at harmonizing the safety analysis methods for best estimate evaluations of the radiological consequences, in case of Design Basis Accidents and Design Extension Conditions without significant fuel melting. It is planned to improve models and upgrade existing simulation tools and calculation chains used in safety studies. Finally, the BESEP project is to support safety margin determination, by developing best practices for safety requirement verification against external hazards, using efficient and integrated set of Safety Engineering practices and PSA. The project is carried out in a benchmark exercise based on case studies previously performed by the consortium participants. All three projects aim to improve nuclear safety within the European research and development framework. The research objectives are achieved by the development and improvement of proven and justified safety assessment methodologies for the verification of stringent safety requirements of nuclear industry

Probabilistic Safety Assessment for internal and external events on nuclear power plants and on mitigation strategies/H2020 European projects NARSIS, R2CA and BESEP

The NARSIS project aimed at improving assessment methodologies to be integrated into “extended Probabilistic Safety Assessment” (PSA) procedures for nuclear plants in case of single, cascade and combined external natural events. An open-access framework tool has been released to build multi-hazard scenarios, and various risk integration approaches (e.g., Bayesian Networks) have been implemented and compared, identifying their advantages and limits for further collaborative research activities. The R2CA project aims at harmonizing the safety analysis methods for best estimate evaluations of the radiological consequences, in case of Design Basis Accidents and Design Extension Conditions without significant fuel melting. It is planned to improve models and upgrade existing simulation tools and calculation chains used in safety studies. Finally, the BESEP project is to support safety margin determination, by developing best practices for safety requirement verification against external hazards, using efficient and integrated set of Safety Engineering practices and PSA. The project is carried out in a benchmark exercise based on case studies previously performed by the consortium participants. All three projects aim to improve nuclear safety within the European research and development framework. The research objectives are achieved by the development and improvement of proven and justified safety assessment methodologies for the verification of stringent safety requirements of nuclear industry