Seismic performance of sliding gusset connections in buckling-restrained braced steel frame

Buckling-restrained braces (BRB) are metallic yielding dampers which utilize axial yielding to dissipate seismic energy without significant buckling under tension and compression. Due to their stable cyclic behavior, BRBs have been widely adopted to mitigate structural damage. However, seismic performance of buckling-restrained braced frames (BRBFs) is often limited by premature fracture of corner gusset connections and surrounding framing members due to significant frame-gusset interaction under severe earthquakes. In this paper, commonly used design methods and failure modes for corner gussets connection were first reviewed. A novel sliding gusset connection, which utilized bolted end plates between the gusset plate and the beam-column flanges but minimized shear interaction via employment of low-frictional material, was proposed to mitigate the frame-gusset interaction. Finite element models of two beam-column joints incorporating the new and traditional gusset connections were constructed to investigate the effect of different configuration on the structural behavior of the gusset plate, framing members and BRBs. A quasi-static test was conducted on a full-scale joint incorporating the new gusset connection to examine its seismic performance under cyclic loading. It is found that the new connection is effective in minimizing the frame-gusset shear interaction and in reducing plastic damages on the gusset connection. The gusset connection can still remains essentially elastic under severe earthquakes. It is also found to have a minor rigid-zone effect on the framing members and thus, the plastic hinge of the beam shifts back to the original beam-column section and shear forces and plastic damages on the framing members are reduced. All the key structural components exhibite full and stable cyclic performance even at 4% inter-story drift ratio, indicating that the performance of steel BRBF can be significantly improved by using such a sliding gusset connection. © 2019, Editorial Office of Journal of Building Structures. All right reserved.