This paper deals with a critical analysis of the current seismic design criteria provided by Eurocode 8 for Moment Resisting Frames. This approach is based on the capacity design principle, in which the design is governed by the strength and stability of the structural elements and by hierarchy of strength, this in order to allows development of high dissipative collapse mechanism. The drawbacks of this approach is that the maximum required inter-storey drifts, at service limit states, are not directly satisfied. This leads to an enlargement of geometrical dimensions of the elements, producing significant over-strength and nullifying the use of high behaviour factors.
In this paper, an alternative design criterion is proposed. According to this the design is governed by maximum inter-storey drift at service limit state, whereas the satisfaction of capacity design rules is contextually verified. This means to design the structure with seismic actions corresponding to service earthquakes (i.e. unitary q-factor). Linear and non-linear static analyses on 3, 6 and 9-storey steel frames were performed to compare the design methodologies in terms of push-over curves (i.e. over-strength), inter-storey-drifts and collapse mechanisms. Furthermore, the effect of panel zone on the global seismic response of frames was taken into account in the performed analyses. It has been properly modelled using one of the most diffused literature model, the so called Krawinkler’s ‘frame model’, accounting both its elastic and plastic behaviour.
