Seismic Performance and Design of Strongback Truss–Buckling Restrained Brace Steel Frame Using Performance-Based Plastic Design (PBPD)

Aiming at the problem that the traditional center-braced frame structure has a single seismic protection mechanism under earthquake, which is prone to damage the weak layer and trigger the collapse of the structure. This paper proposes a hybrid steel frame system (Strongback Truss–Buckling Restrained Brace Steel Frame, ST-BRBSF). The structural system adopts a three-stage cooperative working mechanism, which can fully consider the yield energy dissipation of the BRB and the nonlinear deformation of the frame, and utilize strongback trusses to realize the damage uniform distribution. The performance-based plastic design concept is adopted to design and build 12 SAP2000 analytical models with different BRB shear ratios and structural heights. The seismic performance of the structures is studied and a sensitivity analysis is performed by combining the Pushover analysis with the dynamic time history analysis. The findings indicate that structures employing this design method can realize the ideal damage mode of BRB, fully energy dissipating action and a full beam-hinge type (plastic hinges form at beam ends and the base of ground-floor columns). The damage distribution of the structure is uniform and conforms to the concept of multiple seismic resistance and damage control. Meanwhile, a reasonable range of values for the shear ratio parameter is suggested.