Seismic evaluation of all-steel buckling restrained braces using finite element analysis

• Ten specimens were modeled and subjected to cyclic analysis to identify the hysteretic behavior of all-steel BRBs.
• A special cyclic loading protocol was used according to AISC Seismic Provisions prescription.
• Bilinear FE-derived back-bone curves were used to introduce the modeling parameters used in retrofitting of X-braced frames.
• The effect of gap size and cross sectional area was examined to determine an optimum configuration.
• The axial forces imposed to the first story columns of the three spans retrofitted structure experienced reduction.
• The static pushover curves of the frames approved the large ductility of BRBs.
• The inter-story drifts computed for near-fault records were higher than those obtained for the far-field records.
• The response modification factor, R, of all-steel BRBs was about 50% larger than that of the X-braced frames.

All-steel buckling restrained braces (BRBs) are a newly developed variation of ordinary BRBs with enhanced characteristics in terms of weight and curing of the mortar core. Finite element (FE) models of all-steel BRBs with varied geometries were subjected to cyclic analyses in this study. The satisfactory brace geometries that minimized instability of the core section while maximizing energy dissipation capacity were then identified. Bilinear FE-derived back-bone curves of the selected BRBs were subsequently used in the representative truss elements to retrofit three 4-, 8-, and 12-story frames. The advantages of these braces were highlighted by drawing performance comparisons against ordinary braces. Nonlinear static and dynamic responses of the frames with all-steel BRBs were also assessed in terms of parameters such as maximum inelastic deformation demand.