Dual System for Enhanced Seismic Performance of Friction-Sliding Braced Frames

Pall friction dampers (PFD) installed in braced frames have been shown to exhibit large energy dissipation. Nevertheless, in high-risk seismic zones, the Friction-Sliding Braced Frame (FSBF) is prone to large residual interstorey drifts (RISD) and weak-storey mechanism formation. To solve this drawback, a backup moment resisting frame (MRF) was added in parallel to the FSBF and the system is analysed as dual (D-FSBF). Considering a force-based design approach, the dual system was evaluated for the assumptions that the backup MRF's columns have fixed-bases and the damper's stroke length allows interstorey drifts within the code limit. In this paper, the failure hierarchy criteria is defined and the parameters analysed are the MRF's base fixity condition and the PFD's stroke length, as well as, their effects on the global seismic response. Results from nonlinear response history analyses using OpenSees demonstrated that the D-FSBF with a fixed-base MRF encountered undesirable MRF column failure caused by increased moment demand at the bottom floor. Conversely, when pinned-base MRF is employed, the D-FSBF system subjected to earthquake loads is able to achieve the failure hierarchy. However, the seismic response of D-FSBF at design level is unaffected by the MRF base connection flexibility.