Seismic performance-based design based on ductility of buckling-restrained braced steel frame

The Bucking-Restrained Braces (BRBs) can undergo fully- reversed axial yield cycles without loss of stiffness and strength, whose seismic energy dissipation ability is superior. The additive damping ratio that BRBs impart to the structure is large, which must be considered in seismic performance design. The conventional seismic performance design is based on elasto-plastic inter-story displacement angle, the structure will possibly be unsafe because the total equivalent damping ratio of the structure is usually overrated. Based on the elastic demand spectrum and elasto-plastic demand spectrum which were established with elastic response spectrum in Chinese code for seismic design of buildings (GB50011-2001), a seismic performance design method based on ductility was put forward. In the design method, to meet the seismic performance objective, the braces will be installed, the section area of braces will be rectified or the common steel braces will be replaced by buckling-restrained braces.