Influence of semi‐rigid joints on the seismic performance of single‐storey steel frames

The design of joints of steel frames is often simplified, assuming that they have a fully rigid or ideally pinned behaviour. This wrong assumption is sometimes acquiesced by national technical codes, which mainly focus on the behaviour of simple connections and neglect the role of the joints in terms of global structural behaviour, particularly under lateral loads. In this paper, a numerical study about the evaluation of the influence of partial‐strength/semi‐rigid joints on the seismic performance of one‐storey steel buildings is presented. For this purpose, a population of real steel buildings has been considered, for which column bases and/or beam‐to‐column joints were originally designed as infinitely resistant/rigid restraints, but that, after the application of the component method, were found to be characterized by a partial‐strength/semi‐rigid behaviour. Finite element models of the examined buildings were developed, assuming both the theoretical and the actual joint behaviour. Fragility curves were constructed through nonlinear dynamic analyses, so to evaluate the seismic vulnerability of the structures and assess whether they need joint reinforcement, or, otherwise, if they already ensure adequate seismic safety.