Analytical investigation on cyclic response of buckling-restrained braces with short yielding core segments

Buckling-restrained braced frames (BRBFs) are considered to be one of the efficient lateral force-resisting systems used in buildings located in the seismically active regions. Nearly symmetric hysteretic response of buckling-restrained braces (BRBs) in tension and compression due to the yielding of steel core plates helps the BRBFs to withstand the seismic excitations without causing any extensive damage to the primary frame members. However, BRBFs may exhibit the excessive post-earthquake residual drift response due to the low axial stiffness of BRBs under the strong ground motions. A reduction in the yielding core segments of BRBs results in the improved elastic and post-elastic axial stiffness of BRBs which may help in controlling the excessive residual drift response. This study is focussed on the analytical evaluation of hysteretic response of BRBs of varying lengths using finite element (FE) software. The results of FE study are further used to evaluate the inter-story and residual drift response of a 3-story braced frame fitted with BRBs of short core lengths (referred as SBRBF). Nonlinear dynamic analysis results of SBRBF are compared with the conventional BRBF and concentrically braced frame (CBF). It is concluded that the optimum reduction in yielding core lengths of BRBs can improve the overall seismic response of BRBFs with a reduction in the residual drift response.