Seismic Analysis of Concentrically Braced Frame Systems with Self-Centering Friction Damping Braces

This paper presents a special type of bracing element termed self-centering friction damping brace (SFDB) for use in seismic-resistant concentrically braced frame (CBF) systems. The SFDB is a passive energy dissipation device with its core recentering component made of stranded superelastic Nitinol wires while enhanced energy dissipation mechanism of the SFDB is achieved through friction. Compared with conventional braces for steel frame buildings, SFDB has a few desirable performance characteristics such as minimized residual drifts of the CBF system and its ability to withstand several design level earthquakes without the need for replacement. The mechanical configuration of the SFDB is first described. A comparative study of SFDB frame and buckling restrained braced (BRB) frame was carried out, which is based on nonlinear dynamic analysis of two prototype CBF buildings—a three- and a six-story steel frame. Two suites of earthquake ground motions, which represent the frequent and design basis earthquakes for Los Angeles, were considered in the nonlinear time-history analysis. The results of the nonlinear time-history and pushover analysis show that the SFDB frame can achieve a seismic response level comparable to that of the BRB frame while having significantly reduced residual drifts. The SFDB thus has a potential to establish a new type of CBF system with self-centering capability.