ABSTRACT
When the degradation of reliability over time is taken into account, the lifetime of a structure is a random variable (Lawless 1982) and reliability can be characterised in relation to the so-called ‘‘hazard function’’ (the damage rate in the infinitesimal time interval), which assumes various forms depending on the distribution model adopted (Weibull, Gamma. etc.). In this connection, a monitoring-oriented approach (Natke & Cempel 1997, Ceravolo et al. 2007) is of great interest, as the monitoring process is able to supply useful data both to plot the reliability curves, defined as a function of the symptom, and to interpret the diagrams obtained.
