Implications of code provisions in the seismic design of concentric braced frames

Concentric braced frame (CBF) typology is widely used in steel structures to increase lateral stiffness and consequently reduce drifts under wind and earthquake loads. During a strong motion, bracing members are subjected cyclically to large inelastic deformations in tension beyond yield and compression in the post-buckling range. This kind of behavior imposes a considerable attention to be paid in the selection and detailing of bracing members and connections. Specif ic design provisions have recently been introduced in seismic codes in order to guarantee a ductile ultimate behaviour of CBFs, by implementing strength hierarchy between frame members. In this paper, after an extensive examination of the CBFs design provisions proposed in the different seismic codes, some case studies are presented and discussed.