Concentrically Braced Frames: European vs. North American Seismic Design Provisions

A critical review of seismic design provisions for concentrically braced frames (CBFs) in both European and North American (i.e. US and Canadian) codes is presented in this paper. Indeed, even though those codes are based on capacity design philosophy, different requirements and different approaches are used to guarantee the hierarchy of resistances between dissipative and non-dissipative elements, thus leading different overall seismic performance. In detail, the main issues critically discussed are (i) the ductility classes and the correlated force-reduction factors; (ii) the structural analysis methods permitted by different codes; (iii) the modelling aspects of braces; (iv) the detailing rules for both dissipative (bracing members) and non-dissipative elements. Synoptic tables summarizing the corresponding assumptions and requirements in different codes are provided.