Sensitivity analysis for setting up the investigation protocol and defining proper confidence factors for masonry buildings

At present, the codified procedures for the seismic assessment of existing structures do not consider explicitly the use of sensitivity analysis that, on the contrary, is an essential tool due to the intrinsic and epistemic un-certainties involved. In particular, results of a sensitivity analysis allow, on one hand, to optimize the plan of investigations and tests, limiting it to what is really useful, and, on the other hand, to be aware of the propaga-tion of uncertainties in the final outcome of the assessment. The paper proposes how to implement the sensi-tivity analysis in a systemic way, in order to define proper confidence factors, which are used within the semi-probabilistic approach of the performance-based assessment procedure. In relation to the procedures adopted by current standards, this method is aimed to overcome the following drawbacks: i) the a priori definition of values for the confidence factor; ii) the a priori selection of parameters to which confidence factor has to be applied; iii) the weak connection between investigation and assessment. Despite the generality of most as-pects of the proposed procedure, main attention is given in the paper to its application in the case of masonry existing buildings and, in particular, of those with a significant cultural value, where the minimization of in-vasiveness of investigations on the construction together with that of costs plays a crucial role for the aim of conservation.