Evaluation of Strength and Stiffness of Steel Concentrically Braced Frame Gusset Plates Under Seismic Loads
Steel Concentrically Braced Frames (CBFs) are conventionally used as Seismic Force-Resisting Systems (SFRS) in North American building structures. Under seismic loadings, braces are designed to yield under tension and buckle under compression. The flexural buckling of the compression brace imposes large rotations and bending at the end gusset plates. This can lead to significant plastic deformations in the gussets. Therefore, the stiffness and strength of the gusset plates affect the brace seismic response, which in turn affects the seismic response of the CBFs. This makes the strength/stiffness factor of a gusset plate an important parameter to study in structural design.
The goal of this project was to use analytical and numerical methods to evaluate the stiffness/strength of the brace gusset plates. A finite element (FE) model of a gusset plate and brace connection was produced using SAP2000 analysis software. The bending and rotation caused by seismic forces on the gusset plate were reproduced using distributed loading couples to emulate bending moment and torque at the end of the brace connection to the gusset plate. The degree of rotation obtained from the deformed gusset model is used to obtain strength/stiffness factors.