Bidirectional loading performance of gusset plates in buckling restrained braced frames

Abstract

A study is conducted to evaluate the performance of gusset plates (GPs) in buckling restrained braced frames (BRBFs) subjected to bidirectional loading. It involves an experimental test, a parametric numerical study and a comparison with Thornton, AISC, Takeuchi’s and Notional Load Yield Line (NLYL) methods. The experimental test was conducted on a one-storey BRBF with pinned beam connections under both unidirectional and bidirectional cyclic loading.It was found that bidirectional loading decreases the GP axial strength by up to 18%, but there is no clear correlation with GP thickness. The parametric study indicated that greater out-of-plane (OOP) drifts reduce the GP axial strength. The methods evaluated with respect to the parametric study generally provided conservative strength predictions. The AISC method with an effective length factor of 2.0, which does not explicitly account for out-of-plane loading, was the most conservative among all methods. The strength predicted ranged from 69% to 92% of the actual strength. Similarly, both Takeuchi’s and NLYL method under bidirectional loading are conservative when the GPs have a rotational stiffness within the likely range of practical applications. However, they are non-conservative for BRBF GPs with a very low rotational stiffness. The NLYL method is less conservative than Takeuchi’s method. The NLYL method is always conservative for the limited range of CBF GP configurations investigated.