Evaluation de stratégies pour la gestion du risque sismique du bâtiment

This document presents the results of a research on seismic risk management. It echoes the worldwide trend of increasing awareness of the importance of this risk and represents a contribution to the effort of research. In order to manage risk in a rational way, it is necessary to quantify it. The first part of this research consists in evaluating the seismic risk of a portfolio of buildings. The selected portfolio is the city of Aigle located in the center of the Swiss Alps. The evaluation was based on a seismic inventory of the city, enabling, through a global approach, to consider the behavior of the buildings. Different losses (life, building, furniture) could be estimated for several scenarii of seismic hazards intensities. Knowing the probability of occurency of these intensities, as well as the uncertainties of the constitutive parameters, it was then possible to quantify the risk affecting the selected portfolio of buildings. The maximum potential loss for the studied area was also estimated. As a result, a reproducible risk estimation model was developed with its constitutive parameters. The obtained results provide information on potential losses, on the level of insurance premium as well as on elements of reinsurance. Seismic risk management, because of its complexity and the extent of the consequences ensuing from major events, requires a different approach from other natural risks. In the second part of this research, management tools are therefore developed in order for decision makers to face these particularities. A comprehensive management framework is elaborated. This framework makes it possible to deal with the complexity of seismic risk, which not only stems from its inherent specificities but also from the multiplicity of decision criteria as well as the variety of actors within the system. The definition of protection objectives receives special attention in this research. Construction codes usually fix safety levels for new constructions. For existing buildings on the other hand, there are no such provisions. The present research proposes a method for fixing this protection level. This method also considers the often contradictory principles of precaution and proportionality. An innovative catalogue of mitigation measures are then proposed, classified according to their influence on the components of risk. These measures can be focused on prevention, protection or intervention. They have an impact on the hazard, the vulnerability or on the exposed value at the considered risk. Consequently, different strategies are built to be later evaluated and compared. For this work, a strategy is considered to be a panel of measures that have an impact on the constitutive elements of risk. The decision-making process is regarded as a systemic approach considering the multiplicity of decision criteria and actors. A multicriteria analysis method based on an outranking philosophy is adopted for the comparison. Criteria are proposed for individual buildings as well for a portfolio of buildings. Applications of the decision-making process on pilot projects illustrate the methodology and provide practical recommendations. The pilot project of the city of Aigle was the guideline for the presented research, which aimed to deal with the complexity of seismic risk management in the most comprehensive way possible.