A Study of the Damping Provided by Buckling-Restrained Braces (BRBs) within Their Linear-Elastic Response

This paper presents an experimental investigation aimed at measuring the increases of damping produced by buckling-restrained braces (BRBs) working within their linear-elastic range. For that purpose, five one-storey one-bay steel frames, working in parallel, were tested on a shaking table. First, the frames were tested without BRBs and then BRBs were provided to form dual systems. A test with a conventional brace was also included for comparison purposes. The values of the damping ratio were calculated for each case. The results show that the BRBs increase the damping ratio on structures significantly. This happens even under linear-elastic behaviour. The contribution of each BRB to the damping is quantified and presented in this paper. The findings of this study are significant because they show that BRBs start dissipating energy at very small displacement levels, and this energy dissipation must be taken into account in the context of performance-based seismic design, in order to estimate the behaviour of BRB-equipped structures reliably.