. The experience feedback on a crisis that hit a city is frequently used as a "recollection" tool. However, it may not be held in itself as a tool for analyzing a city's performance. The city, considered as a complex system, was modeled using a functional analysis method. Based on such modeling, two risk analysis methods (Failure Mode and Effect Analysis and Event Tree Method) were deployed and adjusted. Lastly, a qualitative reasoning model had been used for get the scenario modeling of the urban crisis. Such functional model was deployed on a case study.
No abstract is provided for this article.
No abstract is provided for this article.
Mountain reservoirs are hydraulic structures in mountains, used in ski resorts to store water, generally for producing artificial snow; there are about 120 of them in France. Despite their modest volumes (5000–400,000m3) and dam heights of between 5 and 20m, these structures do induce potentially high risks, due to their location in mountain at altitudes of between 1200 and 3000m. These reservoirs are very often made watertight artificially by geomembrane. A survey conducted on about 70 of these reservoirs provided considerable information on their pathologies, incidents and even accidents and served as a basis for writing a set of guidelines for studying, designing, constructing, monitoring and rehabilitating. The paper is divided into two parts; the first based on an analysis of the 32 best documented structures is a feedback of water-tightness quality of Geosynthetic Liner Systems (GLS) at high altitudes; the second based on the guidelines above-mentioned, concerns the construction choices and behaviour of GLS at high altitudes. In particular, the guide advises using a cover layer in most cases to protect the geomembrane, and paying particular attention to the support layers and to drainage under the geomembrane.
Hydro-Québec and Cemagref have implemented condition evaluation methods for water retaining structures: the condition index (CI) method for embankment dams in Quebec, and SIRS Digue for fluvial dykes in France. These methods were developed from similar approaches, including functional analysis, gathering and formalization of knowledge about failure mechanisms, and definition of performance indicators. Development of both methods was done within a group of experts and lead to technical guides that explain the application limits. The main objective is to prioritize maintenance tasks within a large inventory of dams for Hydro-Quebec, and for fluvial dykes, in France. The use of these methods reaches also other goals at the same time: aid to safety review and dam diagnosis, and experience transfer among the technical staff.
No abstract is provided for this article.
No abstract is provided for this article.
A probabilistic method of modeling the floodwater level in a dam reservoir is described the purpose of this paper is to add a probability dimension to hydraulic loading computations. Unlike the standard engineering approach, the method presented here incorporates two innovative aspects. First, the method uses a probabilistic hydrological method (simulated hydrographs for flood probability estimation method) based on simulation techniques, for generating multiple hydrological scenarios. Second, it can address the variability in reservoir level at the time of the occurrence of the flood event. The method generates a random set of floodwater levels from a random selection of flood hydrographs and headwater levels. Statistical analysis of the sample of reservoir levels obtained over a given period allows one to assess a probability distribution for floodwater levels. The method was tested on three applications representing dams having different operating rules and hydromorphological properties. The lessons learned with the present method as compared with the standard engineering approach are discussed from the viewpoint of inclusion in the modeling of the hydraulic loading on the dam and the assessment of the hydraulic safety of the dams.
Le diagnostic et l`analyse de risques sont des missions essentielles pour la securite des barrages en service. Pour ces tâches, des methodes puissantes existent : modeles physiques, calculs numeriques, statistiques, fiabilite~ Toutefois, face a des ouvrages complexes et uniques, dans des contextes presentant des donnees insuffisantes, lors de diagnostics preliminaires ou en synthese d`analyses approfondies, il est necessaire de recourir au jugement des experts. A partir de leurs connaissances et de leur experience, ils vont fournir alors un avis ou une recommandation au probleme pose. Les auteurs proposent des methodes d`aide a l`expertise pour le diagnostic et a l`analyse de risques des barrages. L`objectif est de capitaliser la connaissance et le retour d`experience des experts sous forme de base de donnees relatives, d`une part, a la pathologie generale des barrages, d`autre part, aux etudes de cas de barrages ayant connu des deteriorations sous l`effet de mecanismes de vieillissement. La recherche met en oeuvre des methodes de la surete de fonctionnement issues de l`industrie et des methodes du raisonnement qualitatif. Dans un cadre plus applicatif, une base de connaissances sur les mecanismes de vieillissement des barrages a ete constituee et une base de donnees de barrages ayant connu des incidents est progressivement renseignee au fil des missions des experts. Par ailleurs, des outils informatiques d`aide a l`expertise sont en cours de developpement. / Diagnosis and risk analysis are essential to insure safety of dams in operation. In this field, powerful methods have been produced and provide useful aids in modelling, simulation, statistical analysis, reliability, etc. However it is necessary to use the expert`s judgement when the works are complex and unique, when data is imprecise or insufficient, and when a preliminary diagnosis or detailed analysis is being made. Using their experience and knowledge, experts are able to provide answers and recommendations to a specific problem. The authors propose methods to support expert diagnosis and risk analysis. The main goal is to capitalise on the expert`s knowledge and feedback and to build up database of dam pathologies and database of ageing case histories. This work uses reliability techniques and qualitative reasoning models. In terms of practical applications, the research produced a knowledge database on dam pathologies, and an ageing history database was compiled from dams having experienced deterioration. Computer aids to assist experts in the diagnostic and risk analysis tasks are under development. DIAGNOSTIC, VIEILLISSEMENT, BARRAGE, METHODE, AIDE, EXPERTISE, SECURITE, OUVRAGE HYDRAULIQUE, SECURITE HYDRAULIQUE
Depuis 1994, les colloques JFMS - Journées de la Fiabilité des Matériaux et des Structures rassemblent tous les deux ans, chercheurs et doctorants, consultants ou ingénieurs, familiers de l’analyse de fiabilité ou de risques appliquée aux matériaux et aux structures et privilégient les développements méthodologiques de traitement de l’incertain (probabilistes, possibilistes ou autres).Les JFMS2014 ont été organisées à Aix-en-Provence par Irstea les 9 et 10 avril 2014. Cette édition a porté plus particulièrement sur le thème de l’interaction systèmes-aléas, les systèmes considérés pouvant être des matériaux, des structures ou des ouvrages. En effet, dans la plupart des cas réels, les incertitudes sur les sollicitations et sur l’environnement mécanique, naturel et anthropique conditionnent l’évaluation de la fiabilité des structures et des ouvrages.Cet ouvrage est le recueil de l’ensemble de ces communications.
No abstract is provided for this article.
Diagnosis and risk analysis are essential to insure safety of dams in operation. In this field, powerful methods have been produced and provide useful aid support : modelling, simulation, statistical analysis, reliability.\nHowever it is necessary to use expert's judgement when the works are complex and unique, when data is imprecise or insufficient, and when preview diagnosis or detailed analysis synthesis are made. Using their experiences and their knowledge, experts are able to provide answers and recommendations to a specific problem.\nThis work proposes methods to support diagnosis and risk analysis tasks, within an expertise approach. It is used for specialised engineers during preview diagnosis or studies synthesis.\nOur approach is based on capitalising on expert's knowledge and feedback. It is composed of three parts:\n- an ageing functional model, built up with FMEA method, adapted to dam context and using a Causal Graph representation. This modelling represents ageing scenarios leading to loss of functions,\n- a qualitative method to write dam ageing history and to represent evolution laws of performance loss,\n- qualitative methods to assess the criticality of performance loss of dams and their components.\nThe first part of a knowledge database about dam ageing has been produced, concerning gravity dam mechanisms.\nAfter applying these methods to specific ageing mechanisms (alkali-aggregate reaction on concrete gravity dam and internal erosion on embankment dams) and to example of dams concerned by these mechanisms, we propose various developments and prospects to this work. / Le diagnostic et l'analyse de risques sont des missions essentielles pour assurer la sécurité des barrages en service. Pour réaliser ces tâches, des méthodes puissantes ont été développées et apportent une aide précieuse aux ingénieurs spécialisés : modèles physiques, calculs numériques, statistiques, fiabilité. Toutefois, face à des ouvrages complexes et uniques, dans des contextes présentant des données insuffisantes, lors de diagnostics préliminaires ou en synthèse d'analyses approfondies, il est nécessaire de recourir au jugement des experts. A partir de leurs connaissances et de leur expérience, ces derniers vont fournir alors une interprétation, un avis ou une recommandation à la question posée. Cette recherche propose des méthodes d'aide au diagnostic et à l'analyse de risques dans le cadre d'une approche par expertise. Elle vise à assister les ingénieurs spécialisés lors d'analyses préliminaires et rapides ou en synthèse d'études approfondies. La démarche adoptée met à profit les connaissances et le retour d'expérience des experts. Elle comporte trois étapes :\n- un modèle fonctionnel de vieillissement, bâti à partir de l'Analyse des Modes de Défaillance et de leurs Effets (méthode AMDE) adaptée au domaine des barrages, et utilisant une représentation sous forme de graphes orientés. Il permet de construire des scénarios de vieillissement en enchaînant des séquences successives de défaillances ;\n- une méthode qualitative pour constituer des historiques de vieillissement et pour représenter les lois d'évolution des pertes de performance ;\n- des méthodes qualitatives pour évaluer la criticité des pertes de performance des barrages et de leurs composants.\nLa première partie d'une base de connaissances relative à la pathologie des barrages est réalisée et concerne les scénarios de vieillissement des ouvrages poids.\nAprès la présentation de différentes applications sur des mécanismes de vieillissement (alcaliréaction des barrages en béton et suffusion interne des remblais) et sur des ouvrages représentatifs de ces mécanismes, nous proposons divers développements et perspectives à cette recherche.
