Life-cycle based optimal design of seismic retrofit interventions through dissipative bracing systems

Renovation of the existing building stock is one of the most important task in support sustainable development. Life-Cycle based design methods, either newly developed or adapted from existing ones, are thus needed to consider economic, environmental and social sustainability impact of retrofit interventions. These methods should use new performance criteria based on concepts and metrics consistent with a sustainability-based approach. This paper presents one such method, an optimal design procedure for seismic retrofit interventions through dissipative bracing. Life-cycle economic and environmental optimization is carried out by converting environmental impact into its economic equivalent by using the Carbon Tax approach. Original parametric functions are proposed to model the initial cost and impact of intervention. Earthquake related losses are assessed by adopting a SAC-FEMA closed form, adapted for loss assessment. Social impact is treated as a constraint to the optimization, in terms of safety, also assessed with a SAC-FEMA closed form for the structural collapse exceedance. The entire procedure is based on an effective response evaluation at a few hazard levels, employing linearized models, and it is implemented for use with a commercial FEM software, thereby extending its applicability beyond the research domain. The retrofit of an existing low code RC structure is used to illustrate the procedure and draw more general conclusions.