PSI - Issue 44

A. Sandoli et al. / Procedia Structural Integrity 44 (2023) 1332–1339 / Structural Integrity Procedia 00 (2022) 000 – 000

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representative for likelihood damage scenarios at ULS, has been obtained. This represents a way of taking into account uncertainties for recognizing the building classes and for predicting their structural behavior. Furthermore, the average values of capacity (PGA/g) C relative to a 50% of exceedance probability are indicated over the curves. Such values can be compared with the average seismic demand represented by the values of a g /g recorded during the 1980 earthquake (case pre-1980) or expected for Balvano (case post-1980), which are representative for the anchorage peak-ground acceleration of an average response spectrum at ULS. Note that the peak-ground acceleration estimated for Balvano due to 1980 earthquake was a g =0.295 g , calculated by the authors with the following I MCS -a g correlation formula: where the coefficients c 1 and c 2 have been assumed equal to c 1 = -1.33 and c 2 =0.20, according to Faccioli and Cauzzi (2006) proposal. The value a g =0.295 g is referred to bed rock (i.e., soil A) and is valid for the compartment C_01. Instead, for the compartment C_02, located on a sloping land, such value has been increased by the topographic factor equal to 1.20, thus resulting a g = 0.354 g . Instead, the current seismic hazard map (Italian Building Code 2018) provides for Balvano a value of a g =0.255 g at ULS (on soil-type A). Regarding the case pre-1980 (Fig. 3), the fragility curves show that the average seismic capacity of the compartments resulted equal to 0.07 g and 0.067 g for C_01 and C_02, respectively. As a consequence, for an earthquake having a ground-motion intensity equal to that recorded during the Irpinia earthquake (i.e. 0.295 g for C_01 and 0.354 g for C_02), the almost totality of buildings attains the damage level DS4 (i.e., ULS). This result is plausible and quite representative for the actual damage scenario observed in Balvano in the aftermath of 1980 earthquake, where almost the totality of buildings was highly damaged or partially/totally collapsed (especially for the compartment C_02). The same comparisons are reported for the case post-1980 in Fig.4. In this case, the fragility curves shifted forwards with respect to the case pre-1980, denoting a significant seismic vulnerability reduction. The average seismic capacity of the compartment passes from 0.07 g to 0.210 g , the latter is very close to the expected acceleration a g =0.255 g . This reduction of vulnerability is the result of the introduction of the first seismic rules introduced by the Italian Government in the middle of 1970s and in 1980s (for the zones hit by an earthquake) to design new buildings or for retrofitting the existing ones, where the effect of the horizontal seismic actions was mandatory to be considered. MCS g a c c I 1 2 ) log(   (3)

1,0

1,0

C_01

C_02

Mean Min Max

0,8

0,8

Mean Min Max

0,6

0,6

(PGA/g) C 0,070 0,041 0,097

(PGA/g) C 0,067 0,039 0,092

0,4

0,4

a g /g=0,295

0,2

0,2

P(ds>DS4|PGA/g)

P(ds>DS4|PGA/g)

a g /g=0,354

0,0

0,0

0,00 0,05 0,10 0,15 0,20 0,25 0,30 0,35 0,40

0,00 0,05 0,10 0,15 0,20 0,25 0,30 0,35 0,40

PGA/g

PGA/g

Fig. 3. Fragility curves for Balvano pre-1980

Fig. 4. Fragility curves for Balvano post-1980 0,0 0,2 0,4 0,6 0,8 1,0 0 0,05 0,1 0,15 0,2 0,25 0,3 0,35 0,4 0,45 0,5 P(ds>DS4|PGA/g) PGA/g C_01 Mean Min Max a g /g=0,255 (PGA/g) C 0,210 0,164 0,250