Predicting yielding of gusset plates in seismic frames using finite element modelling

Abstract

Gusset plates connect lateral bracing to a building by fixing two perpendicular edges into the corners of a frame. This results in a gusset plate having a non-uniform cross-sectional area and generally, each gusset plate design is bespoke. For these reasons, stress distribution through a gusset plate is complex and difficult to predict. The Whitmore width method (1952) approximates this stress distribution by defining an effective yield area used to size a gusset plate. This method originates from a small sample of experimental observations. This paper investigates the accuracy of the Whitmore width method by using finite element modelling to study the development of yielding in gusset plates with bolted connections. Seismic frames such as buckling-restrained-braced frames require accurate strength and stiffness properties of each member to ensure stability and that energy is dissipated effectively. Of interest is how different design parameters such as the size of the connection area, shape of the gusset plate and angle of inclination effect yielding behaviour. In total 184 variations of gusset plate geometries were modelled in Abaqus®. The simulated testing was under ideal conditions, applying a monotonic uniaxial load. Results show that the Whitmore width does not accurately represent the initial yielding area of gusset plate designs and is generally un-conservative for larger gusset plate designs. Subsequently a modification to the Whitmore method is proposed.