Goal Tree Success Tree–Dynamic Master Logic Diagram and Monte Carlo simulation for the safety and resilience assessment of a multistate system of systems

We extend a system-of-systems framework previously proposed by the authors to evaluate the safety and physical resilience of a critical plant exposed to risk of external events. The extension is based on a multistate representation of the different degrees of damage of the individual components and the different degrees of safety of the critical plant. We resort to a hierarchical model representation by Goal Tree Success Tree–Dynamic Master Logic Diagram (GTST–DMLD), adapting it to the framework of analysis proposed. We perform the quantitative evaluation of the model by Monte Carlo simulation. To the best of the author’s knowledge this is the first time that a multistate framework of combined safety and resilience analysis relating the structural and functional behaviour of the components to the system function in a GTST–DMLD logic modelling of a system of systems is adopted in Seismic Probabilistic Risk Assessment. To illustrate the approach, we adopt a case study that considers the impacts produced by an earthquake and its aftershocks (the external events) on a nuclear power plant (the critical plant) embedded in the connected power and water distribution, and transportation networks which support its operation.