Sensitivity analysis for system design improvement

In order to help identifying suitable design modifications for complex systems, there is a need to I) determine the weakest elements of the system, 2) identify a better design alternative, and 3) evaluate the effect of the adopted solution on system safety / availability. This is a well-known procedure applied to a single system failure mode. In reality, several undesired system states have to be checked for. On the other side, systems grow in complexity, and components are often multifunctional so that they could affect several system states concurrently and even in conflicting terms. This paper presents the sensitivity analysis module of the ASTRA package, based on component importance analysis techniques to be applied to all system failure states concurrently. The technique employs fault-tree analysis and Markovian processes as basic probabilistic models.