PSI - Issue 44

Franco Braga et al. / Procedia Structural Integrity 44 (2023) 331–338

336

Franco Braga et al. / Structural Integrity Procedia 00 (2022) 000–000

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Based on the results shown on the graph in Fig. 3, the almost constant damage trend on constructions with ineffective storey connections, which is about 0.5, suggests that the damage is caused by the lack of connections, thus related to the activation of mode I collapse since it is not significantly affected as the other vulnerability parameters that have been gradually unified in the assumed configurations change. A greater variability, from 0.24 to 0.33, is seen instead on buildings with effective connections, whose damage is more sensitive to variations due to the other parameters. The most obvious differences are found in the transition from configuration 1 to 2, from 2 to 3 and from 5 to 6 thus due to the quality of masonry and connections at masonry intersections. The red broken line represents the difference in the damage of the two case histories described and is between 0.19 and 0.26: these values constitute the benefits given by the presence of effective floor connections and correspond to a reduction in damage between 37% (configuration 3) and 52% (configuration 6). 4. Connections at wall intersections On the same sample of buildings, elaborations were repeated to estimate the correlation between damage and the quality of connections at masonry intersections, the effectiveness of which is defined according to item No. 2 of the vulnerability model, which provides: • V1 (low vulnerability): masonry well connected to each other at angles and hammers; • V2 (medium vulnerability): the masonry partly connected to each other; • V3 (high vulnerability): the masonries not connected to each other.

Table 5. Average damage Dm assessed due to the effectiveness of connections at masonry intersections. (*) change in damage from the low vulnerability condition V1 (effective connections).

vulnerability due to connections at masonry intersections

Dm Damage (average)

Dev. standard Dm

vulnerabilità altre voci (average)

No floors (average)

D Dm (*) (%)

No.

D Dm (*)

V1 V2 V3

92

0.201 0.427 0.497

-

-

0.223 0.243 0.284

26.370 35.315 37.637

2.28 2.96 2.57

286 487

0.226 0.296

112.2% 147.1%

Using the same criterion as described in the previous paragraph, the damage sensitivity is estimated as the sample changes according to the following configurations: 1. initial sample (local seismic amplification S<=1.2 and seismic amplification by stratigraphic effects S T =1, a

condition common to all configurations); 2. buildings with poor or average masonry; 3. poor or average masonry and with masonry not encumbering false floors;

4. poor or medium masonry, with masonry not bearing in false on floors and without staggered decks; 5. poor or medium masonry, with masonry not bearing in false on slabs, without staggered decks, and with poor inter-floor and roof connections. The graph in Fig. 4 shows the average damage assessed for structural units with effective (V1) and ineffective (V3) connections for each configuration: the red-colored broken line represents, for each configuration, the benefit produced by effective connections producing a damage reduction between 0.22 and 0.29, corresponding to 45% and 60%, respectively. The trend of the broken shows a variability similar to that found in the case of storey connections but values, hence benefits, higher: however, the monotonic decreasing trend suggests a greater dependence on the other vulnerability parameters. Unlike the elaborations for storey connections, however, it was not possible to predict a configuration limited to poor masonry alone because there is no statistically significant sample of buildings that have simultaneously poor masonry and effective connections because, as might be expected, the quality of the connections is related to the quality of the masonry.