ABSTRACT
Abstract The performance at the serviceability and the ultimate limit states of fixed-base and base isolated unbraced steel structures is compared. The inelastic behaviour of low-to-medium rise steel frames, designed according to UBC 91 requirements, is evaluated in order to assess the improvement of performance in base isolated structures. Moderate and severe earthquakes are considered in the analyses for checking the serviceability and the ultimate conditions while the response of the frames, computed in terms of drift ratios and energy dissipation, evidences the benefits obtained through the adoption of base isolation systems. Keywords: Base Isolation System, Steel Frames, Serviceability and Ultimate States, Seismic performance.
