PSI - Issue 44

Maria Polese et al. / Procedia Structural Integrity 44 (2023) 123–130

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Maria Polese et al. / Structural Integrity Procedia 00 (2022) 000–000

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2.4. Consequence model

Different consequence functions that convert structural damage into impacts were defined. First, the consequence functions used in previous national studies of seismic risk were compared. It was found that there are not many differences between the procedures used in Italy and Slovenia. In terms of the number of fatalities, the consequence function was defined as a ratio of the occupants in buildings that reached the two most severe damage states. For the D4 damage state, the number of fatalities was considered equal to 1 % of occupants, while for the D5 damage state, this percentage was increased to 10 %. A similar consequence function was defined for the number of injured people. In this case, the percentages of building occupants to obtain injuries in the event of D4 and D5 damage states were considered equal to 5 % and 30 %, respectively. Consequence functions were also defined for the evaluation of the numbers of long-term and short-term unusable buildings, which directly affect the number of displaced people. All five damage states (from D1 to D5) were considered potentially problematic in this case. Lastly, a consequence function was defined for the (direct) economic losses, where it was considered that each damage state results in a different cost of repair or replacement. The cost corresponding to damage states D1–D5 was assumed equal to 0.02, 0.1, 0.3, 0.6 and 1 of the replacement cost, respectively. 3. Application for the case study of Gorizia and N ova Gorica The proposed methodology for transboundary seismic risk assessment is applied herein for two cross-border municipalities, Gorizia and Nova Gorica. Seismic input in terms of PGA values is derived by ESHM2020 that provides hazard maps for 5 different return periods (i.e., 50, 475, 975, 2500 and 5000 years) on a uniform rock site condition (Vs,30>800m/s). For the return period of 475, a PGA value of 0.148g is obtained for the city of Gorizia and a PGA value of 0.162g in Nova Gorica. Building inventory is compiled at the municipal level considering building classes defined by the combination of construction material, age of construction and number of storeys, as described in paragraph 2.2. From the inventories it can be noted that the number of masonry buildings in Nova Gorica is more than twice as those estimated in Gorizia (9060 against 3810), of which 47% were built before 1965 and 99% with 1-3 storeys. Also in Gorizia, most of the masonry buildings are 1 to 3 storeys buildings (88%), but the percentage of building built before 1965 is significantly higher (77%). Concerning RC buildings, this typology is not so widespread in Nova Gorica (12% of residential buildings), while in Gorizia they represent 43% of the residential building stock.

(a)

(b)

Fig. 1. Comparison of the fragility curves adopted for Italy, Slovenia and the combined model for the Italian cross-border area (continuous lines) for masonry buildings built before 1965 with 1-3 storeys (a) and for RC buildings built after 1982 with 1-3 storeys (b).

As already mentioned, for each building class, the vulnerability models of the two countries are combined according to a heuristic approach to obtain specific sets of fragility curves for the considered cross-border area. As in