عنوان مقاله [English]
Seismic isolation is an outstanding achievement in earthquake engineering, leading to the design of important structures and life lines, with operational to immediate occupancy levels of performance, after strong ground motions. However, taking into account technological advances in the design and manufacturing process of different kinds of isolators, base-isolation will no longer be a design strategy applicable only to very important structures; with a decline in cost, it will be used in ordinary buildings. In the latter category, there is no need to prevent the structure from nonlinear behavior under every kind of ground motion, and the designer can take advantage of both isolation technology, in order to reduce the seismic demand, and a performance-based design approach, using the inelastic capacity of the structural members, which will lead to a more economical structure with lighter frames. In this research, taking into account the nonlinear behavior of two 5 and 8 story base-isolated buildings with special moment steel frames and designed in accordance with ASCE 7-05 and AISC 360-05 seismic and structural regulations for base-isolated structures under near-field earthquakes compatible with BSE-1 and BSE-2 seismic hazard levels, the performance levels of the structures under very strong near-field motion (BSE-2) are changed from immediate occupancy to life safety, with respect to the acceptance criteria of FEMA 356 guidelines.