Evaluation of seismic behaviour of strongback brace system with buckling restrained brace

In recent years, researchers have extensively studied various theories to evaluate the behaviour of braced frame systems. One such system is the strongback braced frame (SBF), which integrates buckling-restrained braces (BRBs) to achieve superior seismic performance. This hybrid system not only significantly reduces residual roof displacements but also enhances the behaviour coefficient (e.g. ductility and energy dissipation) while maintaining resistance to applied forces. The proposed system effectively mitigates storey drift, with its efficiency depending on brace height and load intensity. To validate its performance, six-, ten- and 20-storey building models were analysed. Given the novelty of the system, the study first established its fundamental design principles. Subsequently, non-linear time-history analysis and pushover analysis were conducted using seven near-fault and seven far-fault earthquake accelerograms. Key findings include: (a) under near-fault ground motions, the SBF with BRBs reduced maximum displacement by approximately 25% and interstorey drift ratio by 10%; (b) the behaviour coefficient of the SBF + BRB system improved by 4.5% compared to a conventional strongback system.