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Recent damaging earthquakes in Iran and around the world have induced great death and damage providing serious reminders of seismic vulnerability of existing structures. It is more crucial in Iran, where many structures have been built when seismic codes were not effective enough, specially considering the fact that construction is not perfectly consistent with design specifications and drawings Many of existing building, therefore, have inadequate strength when subjected to earthquake. To prevent such damage and tragic event, efficient ways are necessary for retrofitting these buildings. One of useful extensively used methods is passive control. By reducing seismic demand and increasing ductility, these control ways can reduce rate of seismic damage. Seismic resisting structures are expected to maintain adequate stiffness during frequent but moderate excitations on one hand, and to dissipate a large amount of energy under damaging earthquake on the other hand. The conventional framing systems, i.e., concentrically braced frames, and moment frames are not able to satisfy two aforementioned requirements instantaneously. The concentrically braced frames usually possess high stiffness, but poor ductility owing to the buckling of the compression diagonal braces. On the contrary, the steel moment frames can show acceptable ductility and energy dissipation capacity through flexural yielding in beams, while their stiffness is limited. A combination of these two systems can make a balance between requirements concerning stiffness and energy dissipation capacity. One of the most effective mechanisms available for dissipating seismic energy through inelastic deformations of metallic substances is use of shear panels. Use of yielding dampers has been increased recently for their high capability in energy dissipation. Due to recent advances in passive control methods specifically significant improvements in earthquake energy dissipation and prevention of damage in the main parts of the structures, this paper provides a new hysteretic damping system, especially beneficial to retrofitting steel structures having Eccentrically Braced Frames, EBFs. Despite eccentrically braced frames, EBFs, these pieces are not embedded in floor and can be exchanged easily with little cost after earthquakes. The basic role of shear panel system is to absorb a major portion of input seismic energy, thus reducing energy dissipation demand on structural members and minimizing probable structural damage. This research studies the seismic performance of EBFs with double shear panels. Five specimens have been evaluated using nonlinear finite element analysis under cyclic and monotonic loading. The findings present the proper performance of proposed revision for EBFs, the rise in energy dissipation and the elimination of damage to the main parts of structure (column, bracing, main beam) and its concentration in shear panels reducing displacement of horizontal link (main beam) of EBFs. The analytical results showed the shear panel shear distortion capacity of 0.08 - 0.15rad (displacement of horizontal link of 0.5 - 1.25cm). The response modification factor of this system was also obtained in the range of 8.7-9.8.

Keywords: Seismic control, passive control, Energy Dissipation, eccentrically braced frames, double shear panel

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