Development of a hierarchical approach to analyse interdependent infrastructure system failures

Infrastructure systems underpin our modern communities, providing a platform for social and economic growth. Increasing urbanisation coupled with an increasing population means that these systems are continually expanding, becoming increasingly complex and interconnected. Therefore, a single infrastructure system now relies on other systems to maintain normal functionality. Whilst analysis methods exist to determine the impact of failures in single infrastructure systems, methods to analyse the impact of interdependence of infrastructure systems can be found lacking. Percolation theory is often used to assess failures in one system due to an initial failure in another connected systems. However, whilst this method has many mathematical applications, we show that it can give erroneous results when applied to model failure in infrastructure systems. In this paper, we propose a new method for the analysis of interdependent infrastructure systems which also accounts for their hierarchical structure.