The conventional energy-based seismic design procedure based on the energy-balance concept was revised for performance-based design of buckling-restrained braced frames. The errors associated with the energy-balance concept were identified and were corrected by implementing proper correction factors. The design process began with the computation of the input energy from a response spectrum. Then the plastic energy computed based on the modified energy-balance concept was distributed to each story and the cross-sectional area of each brace was computed in such a way that all the plastic energy was dissipated by the brace. The proposed procedure was applied to the design of three-, six-, and eight-story steel frames with buckling-restrained braces for three different performance targets. According to the time-history analysis results, the mean values of the top story displacements of the model structures, designed in accordance with the proposed procedure, corresponded well with the given target displacements. Key words: energy-balance concept, buckling-restrained braces, hysteretic energy, performance-based seismic design.
On the European Norms of Design of Buckling Restrained Braced Frames
