Overstrength and rotation capacity for EBF links made of European IPE sections

Abstract

Overstrength factor and inelastic rotation capacity are the key parameters in eccentrically braced frames (EBFs) design which may affect significantly the design economy or safety. The overstrength factor given in the 2005 AISC Seismic Provisions is based on the previous tests on wide-flange link beams commonly used in the united states. Despite the extensive research conducted on EBFs link beams, it is not known whether the overstrength factor given by the Provisions can be used for the design of EBFs having IPE link beams. In this paper a three dimensional finite-element model using ABAQUS is developed for the inelastic nonlinear analysis of IPE link beams. The model is used to investigate the applicability of the overstrength factor and inelastic rotation capacity given by the Provisions to design of EBFs with IPE link beams. It was found that the strain hardening overstrength factor of short link beams made of European IPE sections with closely spaced stiffeners is greater than the Provisions' factor. Therefore, using the Provisions' overstrength factor may lead to unconservatie design of EBFs having such links. However, the overstrength factor given by the Provisions can be used conservatively to design EBFs with intermediate and long IPE links. Also, it was shown that links made of IPE sections can sustain much larger rotations than the rotations required by the Provisions.