NONLINEAR FINITE ELEMENT ANALYSIS OF ALL-STEEL BUCKLING RESTRAINED BRACES

Abstract

Buckling restrained braces are gaining popularity in earthquake-resistant designs these days. These braces give stable hysteretic behaviour with a non-buckling steel core encased in a steel tube, that is filled with concrete or mortar. However, in the last few years, researchers have observed that these braces do not need any filler material and can be all-steel. This study aims to carry out a parametric study on All-Steel Buckling Restrained Braces (ASBRBs) by varying the restraining mechanism, the amount of gap between the core and the restrainer, and loading protocols. This paper presents a parametric study conducted on 12 proposed ASBRBs through non-linear finite element analysis. The proposed models have identical inner steel core cross-sections, but the restraining mechanism differs in each case. This paper also includes an experimental study on two small-scale ASBRB specimens. In addition, a finite element study on the effect of variation in stiffness of the transition portion of the core on different performance parameters is carried out. The parameters investigated include hysteretic response, energy dissipation, compression adjustment factor, and strain hardening adjustment factor. The results indicated that the global buckling behaviour of ASBRBs is significantly influenced by the restraining mechanism. In addition, this study also revealed that the global buckling behaviour does not significantly depend on the spacing of the restrainers. It was also observed that BRBs with unstiffened cores show stable hysteretic behaviour up to 2% strain, which deteriorates with further increase in the strain.