A general model of resistance partial factors for seismic assessment and retrofit

This paper presents a general model for computing partial factors on the resistance or capacity-side, to be used in codified limit-state design, accounting for epistemic uncertainty in the resistance model, aleatoric uncertainty on variables input to the model, statistical uncertainty on these variables stemming from limited available data, and target safety. The choice of resistance-side factors cannot be made independently of the demand-side ones, if a target safety is aimed at. The issue is only briefly discussed herein and derivations are carried out independently for the sake of illustration. The partial factor values can be obtained to replicate pre-existing (implicit, uncontrolled) safety from a former code, or to obtain a new consistent safety level, as desired. The format has been proposed in the framework of the ongoing Eurocodes’ revision work and the discussion makes reference to Part 3 of Eurocode 8, which deals with seismic assessment and retrofit of existing structures.