Sensitivity analysis of steel frames with buckling-restrained braces

Buckling-restrained braces (BRBs) represent a significant improvement compared to conventional braces in terms of cyclic inelastic deformation capacity. However, beside their benefits, multi-storey frames with BRBs may experience soft storey formation due to the low post-elastic stiffness of the braces. This critical aspect deserves particular attention, especially in steel frames with pinned beam-to-column connections where the frame global ductility is strongly dependent on the distribution of BRB strength and stiffness at each storey level. This work focuses on a procedure for seismic response sensitivity analysis of steel frame structures equipped with BRBs in order to explicate the relationship between BRB strength distribution and the relevant seismic performance as measured by selected engineering demand parameters (EDPs). Realistic steel frames equipped with buckling-restrained V-bracings systems are used as case studies for response and response sensitivity analysis. Response sensitivity analysis results for selected EDPs related to the damage of non structural element as well as to the damage of the braces are shown for quantifying the effect and importance of BRB strength distribution.