The use of a credibility index in the life-cycle assessment of structures

The behaviour of structural systems can change during their service lives due to unexpected loadings, environmental effects and deterioration processes. In order to optimise maintenance interventions, the life cycle of a structure has to be properly assessed. Structural health monitoring (SHM) using collected experimental data provides a method for assessing structural behaviour over time. As the cost related to SHM is substantial, sometimes that monitoring is limited in space and time. However, the modelling of the structural behaviour using experimental data-sets is characterised by increased uncertainty both in the choice of the appropriate model (epistemic uncertainty) and in parameters estimation (aleatory uncertainty). This paper provides an original procedure to support decisions in the presence of epistemic uncertainty. The procedure provides the development of a credibility index able to catch, between two possible models, which is the most reliable to describe the evolution of parameters of interest. Considering as a case study the occurrence of a foundation settlement in an arch bridge, the efficacy of the model proposed is assessed. The approach can be applied to investigate the behaviour of other aspects of the life-cycle assessment: the evolution of structural resistance, the failure time of an element or of the whole system.