Performance-based seismic design of multi-story CBFs equipped with SMA-friction damping braces

Abstract

This paper focuses on the performance-based seismic design (PBSD) methodology of multi-story concentrically braced frames (CBFs) equipped with a novel brace, i.e., the shape memory alloy (SMA)-friction damping brace (SMAFDB). The fundamental response characteristics of the framing structure are first understood through nonlinear response history analysis on the equivalent single-degree-of-freedom (SDOF) systems. The parameters varied in the SDOF analyses are the period of vibration (T), the strength reduction factor (R), and the normalized friction slip displacement (μf). The seismic response indexes of interest are the peak displacement, the ductility, the residual displacement and the peak acceleration. Relationships are built between the seismic response indexes and parameters of T, R and μf. Then, the SDOF-based results are explored to develop the PBSD methodology, which defines the peak interstory drift, the peak floor acceleration and the residual interstory drift as the performance targets. To demonstrate and validate the proposed design methodology, the six-story prototype CBFs equipped with SMAFDBs are designed and then subjected to ground motions associated with hazard levels of design basis earthquakes (DBE) and maximum considered earthquakes (MCE). The performance evaluation results indicate that the frames can be effectively designed to meet the targeted performance objectives at the DBE level. It also indicates that the frames maintain seismic-resisting capacity at the MCE level.