[WP4] Integration for risk assessment

It is the goal of this WP to integrate the spatial description of scenario earthquakes developed in WP2 and the fragility functions developed in WP3 in the framework of risk assessment for an infrastructure network. To this end, a hypothetical yet realistic industrial site that is connected to utility systems such as electric power and road networks will be considered. Depending on the selected system performance indicators (e.g. functionality of the industrial site, utility serviceability to the built areas, road accessibility between various sites, etc.), annual exceedance probabilities of losses will be quantified. The meta-models developed in WP2 will be used in order to generate the ground-motion maps (Pseudo Spectral Acceleration PSA) while accounting for the epistemic uncertainties that have been previously introduced. The detailed fragility functions are developed in WP3. The impact of various assumptions (source event, hazard propagation) or damage configurations on loss metrics will be analysed.

Specification and modelling of the infrastructure systems
This task is dedicated to the definition and specification of the hypothetical case-study of interdependent infrastructure systems. Based on previous works that have designed hypothetical infrastructure systems for demonstration purposes, the following system of systems will be proposed:

  • an electric power transmission network that is assumed to go from the power generating facility to high/medium voltage transformation stations, which are in turn supposed to deliver electricity to the built areas in the vicinity.
  • a road network that is assumed to ensure the accessibility of the power generating facility and the built areas: the vulnerable elements will mostly be the bridges.
  • a set of spatially extended built areas dependent on utility systems and transportation accessibility and industrial facilities located inside the Grenoble basin
  • an industrial site located outside the Grenoble basin comprising several buildings, which is typical of power generating facilities.

This set of infrastructure systems will be arbitrarily around the Grenoble basin area, for which many data on the soil properties and topography are available.

Simulation of loss scenarios
A set of Monte Carlo simulations will be performed in order to quantify the performance losses of the systems. While such an approach has become quite common over the last few years, the main difference here consists in the use of meta-models obtained by physics-based simulations (WP2) for the generation of scenario-based ground-motion maps. We build the correlation matrix of the residuals of the ground-motion simulations, thus leaving the possibility to reproduce the correlation structure of the intra-event variability that is usually used with ground-motion prediction equations. Indirect impacts, such as utility losses or accessibility losses for the built areas, will then be quantified thanks to the sampled physical damage of the exposed components and to a subsequent systemic analysis (e.g. connectivity or serviceability analysis).

Integration of the probabilistic risk analysis chain into a decision support system
This task aims to exploit the previous Monte Carlo simulations in order to build a simplified Bayesian Network that will represent and quantify the logical relations between the various variables in the risk analysis chain (e.g. event magnitude, spatially-distributed ground-motion parameters at the vulnerable sites, damage states of the elements at risk, system performance indicators, etc.). This hybrid formulation, based on Monte Carlo simulations that are used to build approximate probabilistic relations between the variables, will prevent some of the computational issues that are inherent to Bayesian Networks. As a result, this simplified Bayesian Network will lay the ground for an integrated decision support system, in which risk managers and end-users will have the opportunity to set some assumptions and observer how the remaining variables are updated, through a Bayesian inference.

Dernière mise à jour le 28.02.2018