Seismic Collapse Resistance Capacity of Buckling-Restrained Braced Steel Frame with Ductility-Enhanced Joints

Under the actions of earthquakes, the damage distribution of Buckling-Restrained Braced Steel Frames (BRBFs) is usually not uniform. Once the beam-column joints or other components of BRBFs are destroyed, the high ductility of the buckling-restrained braces cannot be fully achieved. The local failure and the weak stories of BRBFs would cause the structures to collapse. Therefore, this paper proposed the scheme of two improved ductile beam-column joints and applied it in the BRBFs to achieve the high ductility by coordinating the global ductility of the structure and the local ductility of the ductile joints and members. Firstly, the finite element models of the BRBFs with ductility-enhanced joints were established, and the accuracy of the numerical model was verified. Secondly, the incremental dynamic analysis method was used to analyze the influence of the global ductility on the seismic collapse capacity resistance of the structural systems. Finally, the seismic collapse capacity of the structural system was evaluated based on the Collapse Margin Ratio (CMR). The results show that, compared to the BRBFs with rigid connections, the global ductility of BRBFs with the Reduced Beam Section (RBS) connections and the Top-Flange Beam Splice (TFBS) connections increase gradually. The CMR and the seismic collapse resistance capacity of BRBFs are improved with the increment of structural global ductility.