N. Giordano¹, P. Crespi² and A. Franchi²
1)  Politecnico di Milano
Piazza Leonardo da Vinci 32, 20133, Milan, Italy
e-mail: nicola.giordano@polimi.it
2)  Politecnico di Milano
Piazza Leonardo da Vinci 32, 20133, Milan, Italy
e-mail: pietro.crespi@polimi.it
3)  Politecnico di Milano
Piazza Leonardo da Vinci 32, 20133, Milan, Italy
e-mail: alberto.franchi@polimi.it

Keywords: Unreinforced masonry; Seismic retrofitting; Performance-based assessment; Cost-benefit analysis.

Abstract. Seismic assessment and retrofit of unreinforced masonry (URM) structures is a relevant topic nowadays, especially in countries where the majority of the buildings were built before the introduction of seismic design codes. Recent earthquakes have demonstrated that the structural weakness of URMs is responsible of fatalities, injuries and large economical losses in terms of reconstruction costs and business interruption.
Due to the complex seismic response of URM and to the lack of exhaustive guidelines, engineers and practitioners experience difficulties when involved in rehabilitation design projects of masonry. Uncertainties in the analysis procedures are hardly quantified, resulting in conservative structural assessment and expensive retrofits.
In this paper, a possible retrofitting cost optimization process is discussed adopting the PEER Performance Based Earthquake Engineering (PEER-PBEE) methodology. Particularly, thanks to a schematic step-by-step procedure (i.e. hazard, structural, damage and loss analyses) the performance of the URM building is expressed in the form of potential earthquakeinduced economic losses. In this sense, the effectiveness of different retrofitting design scenarios is assessed on an analytical bases taking into account the initial costs (retrofit) and the related benefits (reduction of monetary losses).