## 7 Comparison of Retrofitting Interventions  
In this section, a comparison of the retrofitting interventions is provided in terms of structural performance and financial and environmental costs. The four interventions are labeled as follows: \"I1-1\" and \"I1-2\" in the case of increasing the thickness of concrete walls for \(\zeta_{E}\geq 0.60\) and \(\zeta_{E}\geq 1.00\), respectively; \"I2-1\" and \"I2-2\" in the case of steel jacketing the RC cores for \(\zeta_{E}\geq 0.60\) and \(\zeta_{E}\geq 1.00\), respectively. From the structural point of view, the performance indices obtained by the different interventions are summarized in Table 16. According to the dominating failure modes identified by the vulnerability assessment presented in Section 6, attention was focused on the shear failure of the concrete walls (SF_w) and the flexural failure of the whole RC cores (FF). For each intervention, the performance index is provided as the minimum value between the FF criterion and SF_w failure mode. It is evident that in all the interventions, except the last one, the dominant collapse mechanism is always related to the shear failure of the cores' concrete walls. Figure 16: Construction detail of the connection to the foundation. (**1**) Existing RC wall; (**2**) Steel plates; (**3**) M16 bolts; (**4**) Stiffening plate with height of 120 mm; (**5**) Anchor bolts (M20 or M24); (**6**) Existing foundation. \begin{table}
\begin{tabular}{c c c c} \hline
**RC Core** & **Diameter-Class** & **Length [mm]** & **Spacing [mm]** \\ \hline T1 (T’1) & M24-8.8 & 980 & 140 \\ T3 (T’3) & M20-8.8 & 640 & 140 \\ T4 (T’4) & M20-8.8 & 640 & 140 \\ T5 & M24-8.8 & 980 & 140 \\ T6 (T’6) & M20-8.8 & 640 & 140 \\ \hline \end{tabular}
\end{table} 
Table 15: Main properties of anchor bolts. The cost estimations were based on the price list of the Campania region. The costs for the structural design and finishes are not included. Table 17 reports a summary of the costs for each retrofitting intervention. The costs for intervention 2 (\(\zeta_{E}\geq 1.00\)) are higher than those for intervention 1 (\(\zeta_{E}\geq 0.60\)). The cost of intervention I2-1 is approximately 14% higher than that of I1-1, while the cost of intervention I2-2 is about 18% higher than that of I1-2. Regarding the environmental impact of these structural interventions, an assessment was carried out in terms of CO\({}_{2}\) emissions. According to the life cycle impact assessment (LCA) [32], only the production stage (named \"cradle to gate\") were considered. Three sources of CO\({}_{2}\) emissions were considered: raw material supply (A1), transport (A2) and manufacturing (A3). For the production stage, the global warming potential parameter (GWP) was derived from environmental product declarations (EPDs). This parameter expresses the amount of CO\({}_{2}\) emitted per ton of material. The values of the GWP parameter considered in this work are reported in Table 18. The manufacturers that provided the EPDs are indicated in [33; 34; 35; 36]. The total values of CO\({}_{2}\) emissions for each intervention are reported in Table 18. It is interesting to observe that the interventions based on the use of steel plates (I2-1, I2-2) provide a reduction in the CO\({}_{2}\) emissions of about 70% more compared to the interventions using reinforced concrete (I1-1, I1-2). Figure 17 shows a summary of the results for our comparison of the proposed retrofitting interventions in terms of structural performance, financial costs and environmental impact. When comparing the interventions I1-1 and I2-1, no significant differences are expected for CO\({}_{2}\) emissions, whose values are very high, especially in the case of intervention I1-1. Meanwhile, in the case of safety level \(\zeta_{E}\geq 1.00\), intervention I1-2 is economically more advantageous than intervention I2-2, but it is less environmentally sound.