A methodology for the calibration of partial safety factors accounting for knowledge level, in pushover-based seismic assessment of URM buildings according to the new draft of Eurocode 8

The current draft of the revised version of Eurocode 8 introduces significant modifications regarding the global seismic assessment of existing masonry buildings via nonlinear static analysis, particularly when dealing with building knowledge. The approach is still based on the selection of discrete knowledge levels, although partial safety factors are now consistently applied to global displacement capacity. This paper firstly describes the main new aspects introduced by the considered code revision. Among these, new strength criteria for the single masonry elements are introduced, together with a Bayesian approach to update the knowledge on material properties, exploiting the availability of experimental results. To better explore the code approach, the seismic assessment procedure is applied to a case study building, made of clay bricks, considering different knowledge levels. In particular, a distribution of displacement capacities is obtained for each knowledge level by considering residual uncertainties and properly sampling material properties and local drift capacities of masonry structural members. A statistical procedure for defining partial safety factors reducing the global displacement capacity resulting from the analysis is then presented.