Influence of BRBs deformation capacity on the seismic performance of RC building frames

The deformation design requirements of buckling-restrained brace (BRB) are explicitly stipulated in design standards to ensure the safety of the building structures. However, BRBs still have the risk of failure when the building structures are subjected to an extremely rare earthquake event. This investigation gives an insight into the seismic and collapse performance of BRB braced reinforced concrete (RC) frame structures considering the ultimate deformation capacity of BRBs. Three case study buildings of 3-, 6-, and 9-story RC frames equipped with BRBs that possess various ultimate deformation capacities are designed in accordance with Chinese standards. First, the significance of considering BRB failure in seismic performance evaluation is illustrated through comparative analysis. Then, the static pushover analysis and incremental dynamic analysis are conducted on BRB frames to quantitatively evaluate the influence of BRB ultimate deformation capacity on the seismic and collapse performance. The results reveal that the BRB ultimate deformation capacity has a significant influence on seismic response and collapse mode, especially under extremely rare earthquake events, and shall be legitimately considered in numerical modeling for accurate seismic performance evaluation. The BRB with an ultimate deformation safety coefficient of 1.2 will provide sufficient redundancy to ensure the safety of the building structures from BRB failure and potential collapse risk.