My research project is about the assessment of critical infrastructure's safety and it is based on risk analysis, which includes evaluation of the demand on the most critical bridge components and of the capacity of these components. The main objectives are the development of a robust probabilistic framework for assessing structural degradation under repeated shocks (earthquakes) and the implementation of graphical models (Bayesian Network) to facilitate the understanding of the state of the infrastructure and the reasoning procedure to non-technical experts.