Steel bracing members are widely used in steel structures to reduce lateral
displacement and dissipate energy during earthquake motions. Concentric steel
bracing provide an excellent approach for strengthening and stiffening existing RC
buildings. Using these braces the designer can hardly adjust the stiffness together
with ductility as needed because of buckling of braces in compression. Encased
bracing (buckling-restrained bracing) can permit designer choosing required stiffness
and strength together with high ductility independent of susceptibility to buckling.
These braces are composed of steel core member enclosed in concrete-filled square
steel tube. In this study the use of steel bracing and buckling-restrained bracing
(BRB) for retrofitting an inadequate reinforced concrete building are investigated. The
effectivness of these two systems in rehabilitating a mid-rise nine-storey reinforced
concrete (RC) building were examined using performance-based design and
nonlinear static analysis according to FEMA-356 seismic rehabilitation guidelines.
Results show that both systems improve the strength and stiffness of the original
structure but due to excellent behavior of BRBs in nonlinear phase and under
compressive forces this system shows much better performance than the
rehabilitation system of concentric bracing.