Paul Royet

Probability-based assessment of dam safety using combined risk analysis and reliability methods – application to hazards studies

Dam safety assessment is a major challenge for engineers specialising in hydraulic works. It is now standardised in regulations providing for hazards studies using probability-based risk analysis procedures. Dam safety probability-based assessment includes two key scientific issues: the modelling of complex mechanisms that occur within the works, and a probability-based assessment of structural safety. This paper introduces a combined application of risk analysis and dam reliability methodologies. This combination required the completion of our work on the adaptation of risk analysis methods to dams, and on the probability-based modelling of strength and loading input data for a reliability-based analysis. These methodologies are then implemented as part of a hazards study on a roller-compacted-concrete gravity dam.

French recommendations for limit-state analytical review of gravity dam stability

ABSTRACT This article presents the recent French recommendations drawn up by FRCOLD for the design of gravity dams. Recognising the disparities in the approaches of the various dam engineering bodies, the recommendations aim at harmonising practices to arrive at a standard approach. They adopt the same limit state design method as already used in the Eurocodes, with particular emphasis on cracking and shear strength limit states. They define a series of new parameters which were not introduced in earlier methods such as characteristic strength of materials, partial factors of safety and inclusion of new design situations. The background to the new format is the probabilistic concept of the acceptable design requirements. These recommendations are applied to an existing concrete gravity dam and the results are compared with other international guidelines.

Approches de l'analyse de risques en génie civil Exemple des barrages

ABSTRACT Considering risk analysis in the industrial context we first present the main concepts dealing with risk and its analysis. Secondly we build up a synthesis of the different existing approaches: internal methods including physical and functional modelling, external methods including statistical approach and expertise. For each of them, we list the main applications in civil engineering and we develop their use in the peculiar case of dams.

Development of a Scenario-based DSS for Dam Ageing Diagnosis

This paper presents the Cemagref work in the field of diagnosis aid applied to dam ageing. The context is a portfolio of 250 dams under the supervisory of the environment ministry and involving public safety. These dams are characterised by a relative heterogeneity in their conception, age and management modes. First, the paper presents this dam portfolio. Our approach proposes to capitalise on feedback and expert knowledge, in order to improve dam diagnosis. Our work has started with computer researches, in order to model expert’s process of reasoning by dam ageing scenarios. We have produced a decision making aid system for dam ageing diagnosis. This system is able to manage historic and ageing scenario databases. Then, we have developed with LERMES/CUST a dam degradation model in order to build up the scenarios. Our methodology is based on functional modelling and FMEA method. Our main goal is to build up a dam ageing scenario database and to manage this database with the decision making tools.

Study on a semi-probabilistic method for embankment hydraulic works: Application to sliding mechanism

ABSTRACT Both in France and at the global level, hydraulic works have remained excluded from semi-probabilistic regulations. As far as embankment hydraulic works are more specifically concerned, there are no formal rules for their design. In this context, the French Commitee on Large Dams initiated a research project to define a semi-probabilistic limit-state method for the design of embankment hydraulic works. This paper accounts for the work done over two years. It determines the position of embankment hydraulic works in relation to Eurocode 7. It briefly outlines the suggested semi-probabilistic limit-state method and focuses on the sliding limit-state. Applying the method to a pseudo-homogenous dam helps comparing the standard deterministic practice, the Eurocode 7-based approach and the developed semi-probabilistic method.

Assessment of hydraulic load acting on dams including filling variability and stochastic simulations

ABSTRACT Standard practice in dam engineering is to consider only the maximum reservoir level governing the maximum hydraulic loading. This article presents a probability method for modelling reservoir level and the corresponding load on the dam. It uses multiple randomly-generated flood hydrographs to investigate the effect of reservoir level variability. The method was tried on three operational dams to assess its utility as an operational dam safety analysis method.

Vers l'adaptation aux Eurocodes de la justification des barrages-poids

ABSTRACT In France as in others countries, design of dams is not considered into probabilistic format and is deterministic. In addition, there are no formal rules for the design of dams that remains based on guidelines, leading to strong heterogeneities in French practice. In this context, the French Committee of Dams and Reservoirs produced a work which aims at examining the feasibility of a limit states method for the design of gravity dams. This article synthesises the study leaded over two years by a group of experts representing French engineering and dam public organizations. It establishes a synthesis of the current practices, develops a limit state methodology and examines the feasibility of its calibration. The medium-term prospects for this work are to build up guidelines to design gravity dams in a limit state format.

Etude de la sûreté de fonctionnement d'un aménagement hydraulique de génie civil : Application à des ouvrages de protection contre les inondations de la ville de Nîmes

ABSTRACT Cemagref and ISL consulting engineers produced for Nîmes city (France) a reliability study concerning a hydraulic works system, composed of several dams, singular civil works, canals and collectors networks, and intended to ensure protection against floods. This study constitutes one of the first quantitative reliability studies of a hydraulic works system realized in France. This article presents the step and the methodologies used in a reliability quantitative analysis. The methodological developments are illustrated all along the text through this remarkable application.