Seismic performances of magnetorheological flag-shaped damping braced frame structures

This paper studies the seismic performances of buckling-restrained braced frame (BRBF), magnetorheological self-centering braced frame (MR-SCBF) and variable damping self-centering braced frame (VD-SCBF). The working principles of MR-SCB and VD-SCB are presented and validated by the cyclic testing. The MR-SCB and VD-SCB exhibit full flag-shaped and quasi-flag-shaped hysteretic responses, respectively. Based on the experimental results, a modified Bouc-Wen based model of the MR-SCB and VD-SCB is proposed to simplify the simulation. Two types of 15-story braced frames are simulated to analyze the displacement responses and residual deformations under five natural ground motions with different peak ground acceleration (PGA) levels. The interstory drift and residual deformation ratios of MR-SCBFs and VD-SCBFs are all less than those of BRBFs under mega ground motions. The maximum interstory drift ratios of BRBFs, MR-SCBFs and VD-SCBFs under the PGA = 0.588 g earthquakes are 4.65%, 4.03% and 4.09%, respectively, and the maximum residual deformation ratios under the PGA = 0.4 g earthquakes are 0.51%, 0.18% and 0.23%, respectively. For better response control, the VD-SCB is suitable for frame structures with non-moment-resisting beam-column connections, while the MR-SCB is recommended for all-rigidly connected frame.