Sliding corner gusset connections in concentrically braced frames using BRBs: Numerical analysis and practical design

Abstract

In braced frames, the frame action, i.e. beam-column joint opening and closing, may cause premature rupture of the welded corner gusset connection and/or its adjacent framing members. To mitigate the detrimental frame action effect, a novel sliding gusset connection, in which the gusset plate is bolt connected to beam and column flanges through slotted end plates and sliding at the gusset-to-frame interfaces is permitted, has been proposed and experimentally studied for buckling-restrained braced frames (BRBFs) in previous research. To extend the findings of the experimental tests and develop a practical design procedure, high-fidelity finite element models for the sliding gusset connections were constructed, and their accuracy was validated against the experimental results. A series of numerical parametric studies were subsequently conducted. Firstly, the effect of different beam-to-column connection configurations was studied. With the strengthened beam end, the beam plastic hinge developed outside the gusset connection region, which reduced the plasticity in the gusset plate and the force demands on the bolts, due to the mitigated normal interaction at the gusset-to-frame interfaces. Secondly, for the design of bolts in the sliding gusset connection, the equivalent tensile force method was proposed. The acting position of the equivalent forces under brace tension action was quantified, considering different bracing angles and frame member sections. Thirdly, the behavior of the sliding gusset connection under the combined brace-frame action was studied. Based on the results, the design method for the gusset plate was validated, and recommended bolt design criterion was proposed. Lastly, based on all the results and discussion, a practical design procedure was proposed for the sliding gusset connection in BRBFs, which can be immediately used by engineers.