Influence of attacker’s prior knowledge on the performance of redundant systems

The main objectives of civil engineering structures are to provide functional spaces for societal activities and shelter from the environment.To ensure the safety of such structures, design standards employ methods derived from structural reliability to achieve a target safety level throughout the operational life of structures for expected loading.However, disruptions may occur to a system that involve the initial damage to one or more components.To manage the consequences of system disruptions, robustness strategies can be used to enhance the robustness of a system.Previous research has shown that targeted risk-reducing measures are the most efficient.Therefore, knowledge on the system disruptions is crucial for informing decision-making on appropriate counter-measures.In this paper, initial damage scenarios to redundant systems with a mix of brittle and ductile components are investigated and the effect of prior knowledge of an attacker are quantified using probabilistic and combinatorial analysis.The results are presented in - diagrams, which compare the reliability and robustness of systems in a visual medium.The results show that for the same component reliabilities, brittle systems are less robust than ductile systems.In mixed systems, the initial damage that leads to the lowest robustness is not always the loss of only ductile components, but often a combination of damage to ductile and brittle components.In a deliberate attack on a system, there is a large reduction in the robustness and reliability, depending on the prior knowledge of the attacker and the severity of the attack.This analysis shows the importance of considering the prior knowledge of an attacker on the system performance, and facilitates the development of targeted counter-measures and design strategies.