A hybrid buckling-restrained brace for enhancing the seismic performance of steel moment resisting frames

Abstract

Buckling-restrained braces (BRBs) are effective and widely used devices to enhance the seismic performance of steel moment resisting frames (SMRF), but they might fail to prevent significant structural damage or structural collapse under unexpectedly high seismic loads. To address this issue, a novel hybrid BRB (HBRB) composed of a conventional BRB and a friction damper in series is proposed, where the activated force/displacement of the friction damper could be adjusted to protect the HBRB from failure. The paper begins by providing a detailed explanation of the configuration and working principle of the proposed HBRB. The cyclic behavior of the HBRB is thoroughly analyzed both theoretically and numerically. Building on this, a performance-based design approach is developed, focusing on enhancing the seismic response of SMRF using the HBRB. To assess the effectiveness of the proposed HBRB and design method, two typical SMRFs, one with 9 stories and the other with 20 stories, are enhanced with the HBRB. Comprehensive numerical models are established, considering the bare SMRFs, HBRB-enhanced SMRFs, and conventionally BRB-enhanced SMRFs. Nonlinear static and dynamic analyses are conducted to evaluate the seismic performance of these steel frames. Special attention is given to the performance comparison between HBRB-enhanced SMRFs and conventionally BRB-enhanced SMRFs, specifically under the extremely rare earthquake (ERE) scenario. The results highlight that the HBRB can achieve comparable energy dissipation capacity to conventional BRB while displaying superior energy dissipation efficiency. Moreover, the proposed design method achieves the predefined seismic performance objectives for the enhanced SMRFs in a straightforward and time-efficient manner. Furthermore, the HBRB proves effective in eliminating the failure risk associated with conventional BRB under ERE conditions, effectively mitigating structural damage and preventing collapse.