Cyclic Testing of Chevron Braced Steel Frames with IPE Shear Panels

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Cyclic Testing of Chevron Braced Steel Frames with IPE Shear Panels
Seyed Mehdi Zahrai, School Civil Engineering, the University of Tehran and Research Associate at the University of Ottawa, mzahrai@ut.ac.ir
(Received , Revised , Accepted )
Abstract. Despite considerable life casualty and financial loss resulting from past earthquakes, many existing steel buildings are still seismically vulnerable as they have no lateral resistance or at least need some sort of retrofitting. Passive control methods with decreasing seismic demand and increasing ductility reduce rate of vulnerability of structures against earthquakes. One of the most effective and practical passive control methods is to use shear panel system working as a ductile fuse in the structure. Shear Panel System, SPS, is located vertically between apex of two chevron braces and flange of floor beam. Seismic energy is highly dissipated through shear yielding of shear panel web while other elements of structure remain almost elastic. In this paper, lateral behavior and related benefits of this system with narrow-flange link beams is experimentally investigated in chevron braced simple steel frames. For this purpose, five specimens with IPE (narrow-flange I section) shear panels were examined. All of the specimens showed high ductility and dissipated almost all input energy imposed to the structure. For example, maximum SPS shear distortion of 0.128-0.156 rad, overall ductility of 5.3-7.2, response modification factor of 7.1-11.2, and finally maximum equivalent viscous damping ratio of 35.5-40.2% in the last loading cycle corresponding to an average damping ratio of 26.7-30.6% were obtained. It was also shown that the beam, columns and braces remained elastic as expected. Considering this fact, by just changing the probably damaged shear panel pieces after earthquake, the structure can still be continuously used as another benefit of this proposed retrofitting system without the need to change the floor beam.
Keywords: IPE shear panel, vertical link beam, chevron braced simple frame, cyclic testing, ductility ratio, energy dissipation, response modification factor.

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