Risk and Vulnerability Analysis of Interdependent Technical Infrastructures: Addressing Socio-Technical Systems

The society of today is highly dependent on technical infrastructures. Several incidents around the world the last decades have clearly highlighted the major effects technical infrastructure breakdowns have on life, health and economy of society. The vulnerabilities inherent in our technical infrastructures must be addressed in a proactive manner; it is not feasible to wait for major incidents to highlight them. What further exaggerates the complexities of technical infrastructures is that they are highly interconnected and mutually dependent of each other. Disturbances in one infrastructure can thus easily spread and influence the function of several other infrastructures, leading to widespread consequences for society. In order to proactively and properly manage technical infrastructures, different types of risk and vulnerability analyses give valuable input. The aim of thesis is to develop a modelling approach and methods for such analyses, with focus on identifying technical infrastructure vulnerabilities.The presented modelling approach is based on dividing the model of the technical infrastructure into one structural and one functional part, enabling the analysis of interdependent technical infrastructures for both structural and functional strains. The methods for vulnerability analysis have three perspectives, in order to comprehensively address the complexities of vulnerabilities from different viewpoints: global vulnerability analysis, critical component analysis and geographical vulnerability analysis. As the resilience of technical infrastructures depends critically on the restoration capacities of supporting actors, a method addressing this is also presented. The focus of the presented methods is on vulnerability analysis of technical infrastructures, but their use in wider context of risk and vulnerability management is also addressed.Empirical studies of electrical distribution systems and a railway system, consisting of seven interdependent subsystems, have been carried out to demonstrate the proposed modelling approach and the applicability and validity of the methods to address the complexities associated with identifying vulnerabilities of interdependent socio-technical infrastructures. It is concluded that the proposed research gives a valuable foundation for input to proactive policy- and decision-making of technical infrastructure risks and vulnerabilities