The effect of retrofit intervention on empirical vulnerability curves of Italian masonry buildings

In this study, empirical vulnerability curves for Italian masonry buildings are derived taking advantage of the post-earthquake damage data recently released by the Italian Department of Civil Protection through the online platform Da.D.O. Thus, a comprehensive analysis of data for L'Aquila 2009 seismic event has performed in order to determine only the most reliable and unbiased datasets. Macro-seismic intensity values for each Municipality are evaluated from Macro-seismic database relative to each event [1]. Census data relative to locations with Macro-seismic intensities less than 4, resulting undamaged according to the European Macro-seismic Scale EMS-98 [2] classification, are used in combination with post-earthquake data in order to avoid any bias in fitting procedures. In addition, the ShakeMaps in terms of peak parameters released by National Institute of Geophysics and Volcanology (Istituto Nazionale di Geofisica e Vulcanologia) are also considered to characterize ground motion shaking at each building’s location. Empirical Vulnerability curves, considering both Macro-seismic intensity values and peak ground parameters, are derived using lognormal cumulative functions to fit observational data through the least squared error technique. Vulnerability curves are firstly derived considering 8 classes defined as a function of different vertical (bad or good quality layouts) and horizontal structures (vaults, flexible-, semi-rigid, rigid-slabs). Then, a further subdivision has considered as a function of design typology, i.e. buildings designed to sustain only gravity loads or also seismic loads, determined through a complex procedure which compares the construction age of buildings with the seismic classification codes enforced in that location through the years. Lastly, the effectiveness of retrofit interventions as a function of different horizontal and vertical structures, together with the different design typology, has been broadly investigated