EVALUATION OF CONCENTRIC BRACED FRAME MODELING METHODS

Special concentrically braced frames (SCBFs) are one of the structural systems resisting against lateral loads in seismic regions. Evaluating the performance of these systems requires accurate modelling of the braces. Various models have been developed to simulate the behaviour of the braces. Some of these methods are more accurate and sophisticated but some are simpler. All the methods attempt to implement buckling, tension yielding, and inelastic post-buckling response in the braces.This paper focuses on different models to find out which methods are appropriate and practical to use in nonlinear analyses. These models use fiber section with imperfection as the physical model to define the behaviour of the braces. Out-of-plane buckling, low-cycle fatigue, and rigid end zone are also considered in the model. In addition to these specific parameters, gusset plates deformation could impact the out-of-plane buckling behavior of the brace. Hence, three methods are evaluated to simulate the out-of-plane behavior for gusset plates in OPENSEES. The pinned joint, fixed joint (Uriz et al., 2008), and nonlinear spring (Hsiao et al., 2013) models are shown in Figures 1 to 3. In the fixed joint model, the gusset plate between the rigid offset and the brace (the 2tp length) is modeled by fiber element.

Keywords:

Braced frame , Gusset plate , Modeling , Fatigue , Initial imperfection