Authors: Serena Cattari, Jamil Haddad, Sergio Lagomarsino
Department of Civil, Chemical and Environmental Engineering - University of Genoa.

The procedures for seismic assessment of existing buildings adopted in national and international standards (NTC 2008, Eurocode 8-3 2005, ASCE 41-13 2014) are based on the use of the Confidence Factor (CF), which, as part of a semi-probabilistic approach, is intended to take into account incomplete residual knowledge.

The current approach is "rigid" in that it does not allow for the specificities of the buildings under consideration from time to time and also "conventional" in that it does not allow for differentiation in the outcome of the safety assessment when the insights performed are diverse but such as to produce the same FC value.

In this regard, the article proposes, first, thestandardized use of sensitivity analysis to direct the investigation plan and a more effective calibration of the FC value and, second, a differentiation and extension of the use of the FC concept to take into account the different sources of uncertainty inherent in safety assessment (random, epistemic and model type), only the random ones being explicitly included to date.

In order to validate the proposed changes, an application example is illustrated in the article on an existing masonry building for which the level of safety achieved through the semi-probabilistic approach is compared with that achievable through the probabilistic approach.

Incomplete knowledge in the seismic evaluation of existing buildings: defining the confidence factor through sensitivity analysis