"Triple R" - a quantitative model for critical infrastructures to withstand extreme events

Modern societies are increasingly dependent on the successful provision of critical services delivered through Critical Infrastructures (CI). A Critical Infrastructure consists of systems that, if disrupted or destroyed, have a serious impact on the health, safety, security, and wellbeing of society or the effective performance of governments. Terrorism and physical attack on CI have continued to increase and the safety of Critical Infrastructures concerns nation's stability and economic wellbeing. This research proposes a quantitative risk analysis model named "Triple R Analysis" (TRA) to determine the most effective
protective Strategy (Resilience, Robustness or Redundancy) to mitigate hazards and risks to Critical Infrastructures under the scenario of man-made extreme events. TRA model consists of four main phases: Initialization (site characteristics), Risk Analysis (Probabilistic Risk Assessment and Fault-Tree-Analyses), Cost of Protective Effectiveness (CPE) of alternative protective strategies, and Total Cost of Protective Effectiveness (TCPE) that sums up the costs of risk and risk mitigation. The proposed model provides distinctive alternative protective strategies: Redundancy, Robustness and Resilience, it
quantifies the risk and risk mitigation costs along the C.I. life cycle and proposes a layout for protective policy making and investment in C.I.s. A case study on electric power supply sub-station was carried out to demonstrate the model; three alternative strategies were analyzed and compared. Redundancy was found to be the least effective solution in terms of cost effectiveness whereas resilience was found to be a preferred solution for Protective Effectiveness (the effectiveness of the protective system to prevent the event) of between 0.50 and 0.90. The costs of all strategies diverge as the Protective Effectiveness is greater than 0.95.