Seismic performance of retrofitted steel moment resisting frames

The present analytical work investigates the feasibility of special metals such as stainless steels for seismic retrofitting of steel moment resisting frames (MRFs). In so doing, SS has been used either at beam-to-column connections or spread along beams and columns. To quantify the benefits deriving from the use of this metal, several inelastic analyses (static pushovers) were conducted on a set of regular and irregular medium-rise MRFs. The seismic performance of these MRFs has been assessed by means of multi-level performance-based methodology as recently proposed by SEAOC. Therefore the inter-storey drift has been chosen as the damage index. Three response parameters were estimated: the global overstrength, the roof translation ductility and the force reduction factor (behaviour factor). It was found that when SS is spread within columns, the system overstrength increases by 30% with respect to the carbon-steel benchmark structure. Similarly the design overstrength, plastic redistribution and energy dissipation capacity increase by the same amount. However, the study also reveals that there is no significant benefit in spreading SS within beams.