Time dependent reliability of structural systems subject to deterioration

A probabilistic procedure for the analysis of the current and future reliability of existing structural components and systems is developed: they are assumed subject to deterioration over time, due to the effects of ageing and of accidental events, such as thermal shocks or earthquakes. In particular, the following aspects are dealt with: the identification of probabilistic models for forecasting structural deterioration by ageing as a function of the initial and operating conditions and of the presence and nature of aggressive agents; the formulation of a probabilistic method for the assessment of the reliability of structural components subject to deterioration, that can be updated should maintenance or repair operations be carried out. The adopted approach involves the solution of a stochastic differential equation, which provides the time evolution of the reliability of a deteriorating structural component. Once the reliability of each structural element is defined, it is possible to evaluate the decreasing reliability of the structural system composed by these elements as a whole, taking into account its operating and behavioral logic.