Critical analysis of the empirical relations for the evaluation of the ultimate plastic rotation of R.C. columns under cyclic loadings

Performance-based earthquake engineering relies on the availability of analysis models that can be used to predict structural performance, including collapse. Current code prescriptions allow to evaluate the ultimate rotational capacity from hybrid (mechanical-empirical) or empirical formulations, for R.C. members both seismically and not-seismically detailed. This work aim is a critical analysis of the empirical relationship proposed by Eurocode 8 Part 3 and Italian Seismic Code (NTC 2008). These relationships formerly similar, have been compared with the original formulation introduced by Biskinis and Fardis. A databank of cyclic tests on rectangular column sections, collapsing only in flexure, have been selected from available database and research reports. Their ultimate chord rotation corresponding to an ultimate strength of 80% have been compared with the results provided by the aforementioned empirical relationships in order to check the accuracy and the reliability of code proposal.