Seismic Retrofitting of Steel Frames with Buckling Restrained Braces

Buckling-restrained braced frames (BRBFs) are used as primary lateral load resisting systems for buildings in high seismic areas. The main characteristics of buckling-restrained braces (BRBs) are enhancedenergy dissipation potential, excellent ductility and nearly symmetrical hysteretic response in tension andcompression. This paper presents an analytical study aimed to assess the feasibility of using BRBs as a retrofitscheme for existing steel frames. For that purpose, the seismic response of four two-dimensional frame models representative of typical steel frames was analyzed prior to and after including BRBs as a retrofit strategy. Comprehensive nonlinear static and time-history analysis were carried out for analyzing the frames. A set ofseven code-compliant natural earthquake records was selected and employed to perform nonlinear time-historyanalysis. Frames were analyzed and designed based on 2800 Iranian Seismic Code. The evaluation was based on comparing seismic displacement demands such as target roof displacements, maximum displacements and inter-storey drifts. The results showed that the effectiveness of braced frames can vary significantly withground motions, frame rises and retrofitting systems. It perceived that the seismic response of frames coincides well with the given design objectives