Modeling The Seismic Resilience Of Electric Power Supply Systems
The modern community is an organically assembled system of people, organizations, and infrastructures, as well as patterned interdependences and interactions. Functioning of modern communities relies on the continuous production and distribution of the essential goods and services, accomplished by large-scale, man-made, networked systems, called infrastructures. Such infrastructures are termed critical if their incapacity or malfunction could have a devastating impact on the health, security, and social well-being of community inhabitants. As exemplified by many recent occurrences, critical infrastructure systems in diverse communities across the spectrum of wealth have not been sufficiently robust and have not recovered quickly enough after severe natural disasters, with long-lasting physical damage and technical failures causing significant hardships and economic losses. Against this backdrop, it is imperative to comprehensively investigate, understand and model the disaster resilience of critical community infrastructure systems. Among such critical infrastructure systems, the Electric Power Supply System (EPSS) stands at the core of a modern community. Among many natural hazards, the earthquake hazard stands out as potentially the most devastating and the most difficult to predict. Therefore, this thesis is focused on modeling and assessment of seismic resilience of EPSS and the community it serves. The study begins with a review and an examination of the merits and drawbacks of the resilience modeling and assessment of current civil infrastructure system seismic resilience modeling frameworks. An important common shortcoming is the focus solely on the supply capacity of the infrastructure systems. To overcome this shortcoming, a measure of EPSS-Community system functionality and seismic resilience is formulated by comparing the service supply provided by the EPSS to the Community and the service demand generate by the Community. The supply/demand approach to quantify the seismic resilience of an EPSS-Community system is demonstrated using a virtual EPSS-Community system. A direct measure of the seismic resilience of the EPSS-Community system, the gap between the electric power supply and demand, is proposed in this thesis. This measure is tracked from the time an earthquake occurs until the EPSS-Community system has recovered to yield instantaneous and cumulative measures of resilience. One such instantaneous seismic resilience measure, the percentage of people without power (PPwoP) at any time after an earthquake, can serve as a societal measure of EPSS-Community system systemic resilience. While the robustness of the EPSS-Community system is crucial for reducing the impact of an earthquake, the post-earthquake recovery process is critical to the seismic resilience of EPSS-Community system. This post-earthquake recovery process is case-specific, given their unique characteristics of EPSS and Community physical vulnerability, and dynamic, given the interactions among different infrastructure systems, community sectors, and the political and economic governance structures put in place after the disaster. An Agent-Based model is developed in this thesis to capture the unique dynamic characteristics of the EPSS-Community system seismic recovery process. Two individual agents, the EPSS Operator and the Administrator, are specified using a set of parameters to define their individual behavior and interactions. The effect of agent parameters and their interactions is identified in simulations of the seismic recovery process of a virtual EPSS-Community using the supply/demand approach. The post-earthquake restoration of a modern EPSS is contingent upon the post-earthquake serviceability of other critical infrastructure systems, in particular upon the serviceability of the transportation systems (TS) of the community. To investigate this interdependency among the community infrastructure systems, the virtual EPSS-Community system is expanded to include a transportation system, and a third agent, the TS Operator, is added to the model. The conducted case studies demonstrate that the interplay among different agents, as well as the interdependency between the civil infrastructure systems, determine the recovery path for the integrated EPSS-TS-Community system. The community resources available for post-earthquake recovery are finite. A network-theoretical model is used to gauge the impact of the quantity of the disposable repair resources and work crews on the seismic recovery for EPSS-TS system. The case study simulation results clearly indicate the rate of EPSS-TS system recovery is affected by the amount of available resources, but, importantly, that an optimal distribution of the available resources between the EPSS and the TS can significantly reduce the system recovery time and, thus, increase its seismic resilience. The presented scientific findings lay the foundation for a comprehensive and integrated resilience assessment on the EPSS-Community system based on the proposed agent-based network-theoretical supply/demand framework. Further work on generalizing the model by including all community infrastructure systems and refining their interactions in the model can be done using the proposed framework to investigate the interdependencies among the infrastructure systems and optimize community governance actions. Inclusion of dynamic models of community and infrastructure system post-disaster behavior, such as movement of the population, restructuring of the infrastructure and the effects on the production and consumption of goods and services, would make it possible to examine how disaster resilience of the integrated critical infrastructure systems shapes the long-term socio-economic development of the communities.