PSI - Issue 44

Elena Speranza et al. / Procedia Structural Integrity 44 (2023) 1784–1791 Elena Speranza et al../ Structural Integrity Procedia 00 (2022) 000–000

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(a) Reinforced concrete

(b) Masonry

(c) Mixed, steel or other

Fig. 7. Number of interventions vs. marginal cost (MC) of reinforced concrete (a), masonry (b) and mixed, steel or other structure.

W hen varying Δα SLV , the trend is well represented by the exponential equations reported on the graphs in Fig. 8. It turns out that MC ratios are higher for reinforced concrete buildings than for the other two structural types when the safety increment achieved is between 20%-30%. This should imply that small safety increments are more expensive for reinforced concrete buildings than for the other two structural types, while this difference tends to decrease for higher safety increments. Comparing the diagrams of Fig. 8 with the similar ones presented in Dolce et al. (2021), one can note that the increase in the building sample (passed from 1.034 to 1.207 items) brings about some improvements in the relationships previously found. For reinforced concrete, the number of interventions processed (passed to 111 from 63 items) produce more robust regression analyses and more reliable equations than those previously obtained by the authors. This is confirmed by an increase in R 2 values, which rise from 0.2 to 0.43. The resulting trend emphasizes the exponential shape of the r.c. regression curve, showing that by increasing ∆ α SLV , MC tends to lessen very sharply, to become smoother for values of ∆ α SLV higher than 80%. Some improvements in R 2 can also be noted for masonry, whose values pass from 0.24 to 0.29. A similar adjustment to the trends could be also expected for masonry and mixed (steel and other) structures, following similar enlargements of the relevant samples. The formulations found, further calibrated with larger datasets as above described, can be used as predictive tools, according to the method defined by Dolce et al 2021, to decide among different risk mitigation strategies for a given portfolio of buildings (e.g., schools in a given Region), as a function of the budget available and of the safety level to be performed.

(a) Reinforced concrete

(b) Masonry

(c) Mixed, steel or other

Fig. 8. Scattergrams of the MC ratio vs. the seismic safety index increment for the reduced sample of reinforced concrete (a), masonry buildings (b), and mixed, steel, or other structure (c). 6. Conclusion The paper deals with the analysis of seismic retrofit interventions on public strategic and relevant buildings funded by the NSPP, amounting to 1,207 interventions (88 local strengthening interventions, 999 seismic upgrading interventions, and 120 demolitions and reconstruction), with a total cost of 808 million euros). The increase in the