According to modern seismic codes, in concentrically braced frames the seismic input energy should be dissipated
by means of the hysteretic behaviour of braces while all the other members (i.e. beams and columns) have to remain
elastic. Accordingly, the design internal forces of braces are determined in these codes by elastic analysis of the structure
subjected to seismic forces obtained by the design spectrum. The internal forces of the non-dissipative members, instead,
are calculated by means of specified rules for the application of capacity design principles. According to some recent numerical
analyses, the yielding or buckling of columns may take place before braces achieve their axial deformation capacity.
This paper investigates the reasons of this unsatisfactory behaviour and proposes technological suggestions and a design
procedure to improve the seismic performance of columns of building structures with diagonal braces.