GNGTS 2022 - Atti del 40° Convegno Nazionale

GNGTS 2022 Sessione 2.2 297 SEISMIC LOSS ASSESSMENT FOR THE CITY OF AJDOVŠČINA (SLO) L. Hofer, M.A. Zanini Dipartimento di Ingegneria Civile, Edile e Ambientale, Università degli Studi di Padova, Padova, Italia Introduction. Nowadays, seismic risk is matter of concern for public authorities and private entities since numerous fatalities and significant economic losses can be caused by a seismic event. This is mainly due to urbanization, growing population and the increase of Gross Domestic Product (GDP). These three factors imply a concentration of people and goods, thus increasing their exposure to natural hazards more than in the past. In addition, the vulnerability of many structures and infrastructures is still high, since retrofitting and re- building are time and money consuming processes (Zanini et al., 2019; Hofer et al., 2020). This study, developed within the framework of the INTERREG Project CROSSIT-SAFER (Project Interreg V-A Italy-Slovenia), aims to assess the susceptibility to earthquake-induced losses for the city of Ajdovščina (SLO). To this aim, an in-depth vulnerability and exposure assessment of the residential building stock of the city of Ajdovščina has been performed and then 864 seismic scenarios have been simulated. Results consist in a chart showing the expected losses as a function of magnitude and the epicentral distance from the city center. Furthermore, the effect of different uncertainty sources is considered in the development of such loss analysis chart for a proper risk management. Residential buildings portfolio. The exposure of the city of Ajdovščina is modelled at building level. This means that the expected losses are computed for each single building and are aggregated only at the end of the computation stage to obtain the expected losses at municipality level. For each of the 5583 considered buildings, the information made available were the construction year, the construction material, the number of floors and the total built area. Starting from these data, the seismic vulnerability of the analyzed asset has been characterized by setting a building taxonomy consisting of 8 taxonomy class ( TCs ), and for each of them finding a suitable set of fragility curves related to 4 Damage States DSs (i.e. DS 1 – slight, DS 2 – moderate, DS 3 – extensive and DS 4 – collapse). Fig.1a shows the percentage of each building taxonomy class, together with the construction year (Fig.1b) and number of floors distributions (Fig.1c). Masonry buildings represent the 35% of the building portfolio of Ajdovščina. They were constructed mostly between 1970 and 2000 and the 70% of them has less than 2 floors. As regards reinforced concrete structures, they were subdivided in two class depending on the number of storeys (1-2 storeys and 3+). They were considered seismically designed since most of them were built after 1964, year in which first building code explicitly addressing seismic action and design came into force in Slovenia (Babič et al., 2021). Then, the 35% of the buildings of Ajdovščina is represented by old stone structures, built between 1600 and 1920. A small percentage (4%) is represented by wood structures, some old and others relatively new. Also, a small quantity of precast buildings (1%) is present in Ajdovščina, all built after 1970. Finally, remaining 20% of structures have been considered representative of other mixed structural types, i.e., combined stone-masonry and RC-masonry structures. For each TC a suitable set of fragility functions with PGA as reference intensity measure has been assumed between those proposed in literature: Tab. 2 lists all the adopted fragility curves parameters. Shaking scenarios. Shake fields associated to each simulated seismic scenario, are computed assuming Peak Ground Acceleration (PGA) as reference intensity measure and adopting the GroundMotion Prediction Equation (GMPE) proposed by Bindi et al., 2011. Losses are computed for each building as expected values of the reconstruction cost associated to each damage level, according to the procedure reported in HAZUS-MH, assuming a unitary