Studio teorico e sperimentale sul comportamento ciclico di controventi concentrici a X

The paper describes the theoretical and experimental study on the slenderness of diagonal members in frames with concentric bracings. In accordance with the Eurocode 8 and Italian Standards,the non-dimensional slenderness of the diagonal members should be contained within an upper limit to ensure sufficient hysteretic energy dissipation and a lower limit to avoid column overloading in the pre-buckling stage. This seismic design provision requires the realistic evaluation of diagonal member slenderness. A reduced scale testing bench has been designed to study concentrically braced frames with geometrical diagonal member and restraint characteristics as close as possible to the theoretical ones. The results confirm the theoretical prediction of the effective length factor of the diagonal members and the good hysteretic behaviour of X bracings. The low effective length factor values suggest that steel plates should be used to construct the diagonal member, rather than the classical L shaped sections, as shown in the design example.