Influence of construction age on seismic vulnerability of masonry buildings damaged after 2009 L'Aquila earthquake

The aim of this study is to describe the evolution of vulnerability over the years for masonry buildings characterized by a good quality layout and/or a regular texture. To this aim, data collected shortly afterwards the L'Aquila 2009 earthquake are considered, recently released by the Italian Department of Civil Protection (DPC) through the Da.D.O. (Database di Danno Osservato, Database of Observed Damage) platform (Dolce et al., 2019) [1]. The taxonomy has been defined reflecting the need to consider all the parameters available from post-earthquake inspections and the obtainment of reliable and homogeneous sample. A time-consuming data processing has been performed to obtain a generalized version of the original database, which has been integrated with census data to avoid bias in vulnerability analysis. Then, damage analysis has been done considering 5 + 1 damage grades defined for the whole building based on the conversion of damage for vertical structures in sight of the classification of European Macroseismic Scale. The analysis of mean damage values reveals the general trends as a function of the main influential parameters, i.e. construction age and horizontal structural types, having fixed the vertical structural type and the quality layout. Vulnerability curves were derived assuming a lognormal statistical model and peak ground acceleration as intensity measure, through a minimization procedure of the distance between predicted and observed mean damage. In addition, the general criteria established to define the taxonomy had allowed to accomplish a direct comparison also between vertical structures, namely buildings with good quality and regular texture analysed herein and those with bad quality and irregular layout thoroughly analysed in Del Gaudio et al. (2021) [2]; fully characterizing the behaviour of masonry buildings under lateral loads.