A Macro‐Model for Simulating Gusset Plate Buckling in Buckling‐Restrained Braced Frame Buildings

ABSTRACT 2D models, which are conventionally employed for the seismic performance assessment of buckling‐restrained braced frame (BRBF) buildings, are incapable of simulating the out‐of‐plane buckling of gusset plates. This study presents a novel 3D macro‐modelling approach capable of capturing the out‐of‐plane buckling of gusset plates in BRBFs. This modelling approach is used to gain new insight into the dynamic behaviour of BRBFs by analysing a case study four‐storey steel BRBF with a super‐X configuration, designed using the provisions of the New Zealand seismic design standards along with guidance from practising engineers. Numerical models of the building are subjected to static pushover analysis and dynamic analyses under bidirectional hazard‐consistent ground motions. The structural performance is observed to remain unaffected by gusset plate buckling up to the 2500‐year return period intensity level, beyond which buckling is observed. Consideration of gusset plate buckling is found to decrease the building's deformation capacity and increase its mean annual frequency of collapse by 170%, indicating that the current NZS 3404 design procedure for gusset plates is unconservative in nature. Bidirectional loading is found to have little to no impact on the performance of the gusset plates.