Seismic Performance of Brace-Beam-Column Connections in Concentrically Braced Frames

Abstract

In typical brace-beam-column connections of concentrically braced frames (CBFs) with tubular braces, a gusset plate is used to connect the brace to the beam and column. The slotted tubular brace is welded to the gusset plate and subsequently the gusset plate is also welded to the beam and column. The beam-to-column connection at the gusset plate is either welded or bolted at the face of the column flange. Even though a bolted connection is provided at the face of the column flange, stiff gusset plates connected to beam and column could still provide a fully restrained beam-to-column connection as in the case of welded connection. Such a fully restrained beam-to-column connections in CBFs are such that plastic hinges will form in the column upon continued lateral deformation under severe shaking: hence, higher drift concentrations can be expected in the bottom storey when the partially restrained or pin-ended column-to-base connections are provided. For these reasons, this study investigates the local and global seismic performances of fully restrained brace-to-beam/column connections through numerical analyses. The global performance is examined using a 4, 8 and 12 storey concentrically braced prototype frames modelled in OpenSees, while the local performances are examined through the detailed finite element model of a single storey single bay frame located at the ground floor of the four storey brace frame using the finite element program MIDAS. Furthermore, this study introduces a partially restrained bolted connection at the corner of the gusset plate rather than providing it at the face of column flange in order to facilitate beam rotation at the bolted connection upon continued lateral deformation; this is expected to prevent the formation of plastic hinges in the columns and to distribute the