ABSTRACT
Within the framework of performance based earthquake-resistant design of buildings, the authors have recently proposed a simple approach for evaluating the performance levels of seismic-resistant steel frames. With reference to global moment-resisting steel frames (GMRFs), i.e. frames designed to assure a collapse mechanism of global type, this paper presents a refinement of the proposed approach.
The frame structural response is modelled by means of an equivalent SDOF system exhibiting a trilinear force-displacement behaviour. The force-displacement relationship is derived by the coupling of a simple frame elastic analysis with a second order rigid-plastic analysis. Therefore, the main feature of the approach is its ability in providing the designer with a quick evaluation of the performance objectives of moment resisting steel frames. In fact, neither push over inelastic analyses nor dynamic inelastic analyses are required.
The refinement presented in this paper regards the characterization of the state of damage, for global moment-resisting frames, corresponding to different performance levels which have to be guaranteed as far as the return period of the expected ground motion increases.
