Experimental and numerical study of Friction Damper Parallel Composite Buckling-Restrained Bracing

To enhance the energy dissipation capability of flexural restraint bracing under various seismic activity, this study introduces a novel second-order energy-dissipating system—referred to as the Friction Damper Parallel Composite Buckling-Restrained Brace (FDBRB)—which combines buckling-restrained brace (BRB) and friction dampers in parallel. This paper details the configuration, restoring force model, and constraint ratio formula of the FDBRB system. Experimental investigations, including quasi-static tests on two friction damper specimens, one BRB specimen, and one FDBRB specimen, were conducted to evaluate the FDBRB’s performance and assess the contributions of its friction damper and BRB components. Numerical simulations were conducted to investigate key parameters, including the core unit’s constraint state (width ratio) and the load distribution between the BRB section and friction damper section (load ratio). Results show that under minor seismic excitation, the friction damper section effectively dissipates energy. As seismic intensity increases, the BRB section core yields and continues to dissipate energy, thereby reducing overall seismic impact. The FDBRB design meets seismic requirements for minor earthquakes and exhibits enhanced energy dissipation performance compared to conventional BRB systems across all seismic stages. Furthermore, integrating friction damper section does not degrade the mechanical properties of the BRB section component within the FDBRB. The proposed constraint ratio formula effectively reduces the risk of global instability in the FDBRB, while optimized parameters—such as constraint width ratio and load ratio—ensure consistent energy dissipation throughout its service life. Compared to traditional BRBs, the FDBRB system offers notable advantages in energy dissipation across all seismic stages and serves as a reliable design solution for instability prevention. These findings provide important guidance for the optimized design and practical application of BRBs in future seismic engineering.