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

The seismic performance of steel braced frames with elastoplastic devices is related to global and local damages, typically measured by the inter-storey drifts and by the brace plastic strains, respectively. The relationship between these two deformation measures depends on the brace configuration and on the yielding length of the devices. In this paper a displacement-based design (DBD) procedure, which permits to control both the inter-storey drifts and the brace plastic strains, is used to obtain design solutions involving different levels of local and global damage. Numerical results refer to a benchmark structure with V-bracing systems equipped with buckling-restrained braces (BRBs). Different design values of the inter-storey drift and of the BRB plastic strain, obtained by varying the length Ly of the BRB yielding segment, are adopted in the design. The influence of the design damage parameters on the structural ductility, the vibration period, the sensitivity to P- effects and the dimension of braces and columns are discussed. Among the admissible solutions, attention is focused to the set of solutions having the same dimensions of the bracing system components, in order to show that the local and global damages can be efficacy controlled by means of the BRB yielding length only.