Proposed design procedure for gusset plate dimensions and force distribution at its interfaces to beam and column

Abstract

Concentrically braced frames (CBFs) are stiff systems of the minimized drift that are widely used in seismic regions. In CBFs, the brace force is transferred to the beam and column through a gusset plate. Researchers have proposed several methods to determine the forces at gusset plate-to-beam and column interfaces. AISC in 1991 presented the Uniform Force Method (UFM) in the Manual of Steel Construction as the preferred method to obtain the forces at gusset plate interfaces. In the UFM, the dimensions of gusset plates depend on each other and this dependence occasionally leads to disproportionately large gusset plates with awkward look. So far, no numerical studies have been conducted to confirm the validity and correctness of these methods. Also, the UFM is the only available method that obtains the dimensions of a gusset plate.In this paper, a new procedure is proposed to determine the dimensions of a gusset plate and also a new method is proposed to calculate the force distribution at the gusset plate-to-beam and column interfaces. For this purpose, fifteen one-bay, one-story braced frames with the brace angles of 31, 37, 45, 59 and 72° and one one-bay, two-story braced frame with the brace angle of 37° are subjected to monotonic loading. The gusset plates of specimens are designed according to the proposed procedure and then are modeled in ABAQUS. The extracted forces from ABAQUS at the gusset plate-to-beam and column interfaces are compared with those calculated according to the proposed procedure and previous methods. The results revealed that the proposed procedure presents more accurate distribution of forces at gusset plate interfaces than other methods.