In this paper, a new design methodology for concentrically braced frames is presented aiming at the control of the failure mode by means of a rigorous application of the capacity design principles. The design goal is the prevention of the out-of-plan buckling of columns. In fact, the use of the recommendations provided by Eurocode 8 /1/, which have been substantially adopted by OPCM 3431 /2/, leads to the design of structures which are not able to exploit all the possible dissipative zones due to the premature out-of-plan buckling of columns. Whith reference to three bay concentrically braced frames having only one brace element for each braced bay, the proposed design methodology is applied both including and without including the local weakening strategy (Reduced Section Solution or RSS). The behaviour of concentrically braced frames designed according to above methodologies is compared with the one resulting from application of Eurocode 8 design rules. To this scope, the Jalayer and Cornell approach leading to the evaluation of the mean annual frequency of exceeding a given limit state is applied, so that the obtained results accounts for the record-to-record variability.
