Local and global damage control in steel frames with elastoplastic dissipative bracing systems

Displacement-Based Design (DBD) procedures have been developed for different structural systems. Since damages are directly related to displacements and deformations, DBD procedures permit the design of structures according to an assigned level of damage, thus becoming one of the most effective design tool in modern Performance-Based Design (PBD). Unlike other kinds of structures, e.g., reinforced concrete frames and moment resistant steel frames, where damages of structural and non structural element can be both efficiently controlled by one deformation measure only (usually the inter-storey drift), in steel frames with elastoplastic dissipative braces the damage of non structural elements is controlled by the inter-storey drift whereas the damage of dissipative devices is controlled by the local strain. A compatibility relation, depending on brace geometry and device configuration, relates this two quantities at each storey level. The aim of this paper is to investigate the implications of this compatibility relation on the seismic performance of steel frames with BRBs, by using a DBD procedure previously developed by the authors for frames with bracing systems based on elastoplastic devices. Specifically, the DBD procedure is applied to a benchmark frame with V-bracing systems equipped with BRBs, assuming different design inter-storey drifts and different BRB design strains for each inter-storey drift assumed. The obtained design solutions are illustrated and critically discussed.