The Effect of Brace End Clearance on Ductility of Concentrically Braced Frames

The need for ductility in Concentrically Braced Frames (CBF) has driven researches to study the different parameters which influence the ductile performance of this kind of structure. Brace end clearance in gusset plates is one of the most important of these parameters, which is considered by seismic codes to improve the seismic behavior of these structures.
This study examines the effect of brace end clearance on the behavior of CBFs. Both rectangular andtapered gusset plates are considered in order to gain a deep insight into this issue. Nonlinear analyses using the detailed inelastic finite-element model (FEM) are employed to perform this research. The equivalent plastic strain concept is used to determine the limits of ductile behavior and to predict fracture and failure in these models. Results shows that while in tapered gusset observing 2tp clearance (which is recommended by codes) provides the optimum ductile behavior, in rectangular gusset plates, it is possible to reduce this distance and obtain a smaller gusset plate to maintain the ductile behavior of the frame.