ABSTRACT
ABSTRACT For the assessment of existing structures, reliability analyses or the adjustment of partial safety factors can be very helpful if a conventional verification of structural safety according to design codes is not possible anymore. However, if probabilistic methods are applied, it is crucial to quantify all uncertainties realistically. This paper deals with the assessment of existing masonry structures and aims to categorise the occurring uncertainties. Compared to the uncertainties in the design phase of new structures, additional types of uncertainty arise in the assessment of existing structures. This is mainly due to the fact that the material of an existing structure can be tested or has to be tested because of e.g. missing construction documents and, therefore, a lack of information. In general, uncertainties can be either aleatory or epistemic. A further subdivision can be made to differentiate between the natural scatter of material properties and their spatial variability as well as statistical, testing and model uncertainties. The differences between the types of uncertainties are pointed out. Furthermore, proposals are made towards a consistent treatment of these uncertainties in a probabilistic assessment of existing masonry structures.
