PSI - Issue 64

Rubina Canesi et al. / Procedia Structural Integrity 64 (2024) 1712–1719 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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resulting in the Cost Impact (CI i ) associated with each Increase Level. In the penultimate column, the probability of occurrence (P i ) has been reported. This percentage is estimated based on the Risk Matrix suggested by ANAC and filled in the previous study (Canesi & Gallo, 2023). Finally, the Risk Value for each level (RV i ) was calculated in the last column as the multiplication between CI i and each corresponding P i .

Table 1. Risk value assessment table.

Increase Level ( i )

Increase in value (IV i )

Increased Cost (IC i )

Cost Impact (CI i )

Probability (P i )

Risk Value RV i =(CI i ) x (P i )

IV a = 0.0% IV b = 2.5% IV c = 8.0% IV d = 15.5% IV e = 50.0%

IC a

0

P a P b P c P d P e

RV a RV b RV c RV d RV e

a b c d e

IC b = IC a × (1+IV b ) IC c = IC a × (1+IV c ) IC d = IC a × (1+IV d ) IC e = IC a × (1+IV e )

IC b − IC a IC c − IC b IC d − IC c IC e − IC d

∑( ) =

Total

4. Results and Discussion This Risk value assessment table has been applied to the three recognized “High” Risks, which correspond to the Risk of inaccurate assessment of construction costs and project timelines, Risk of Eminent Domain, and Risk of interference, please refer to (Canesi & Gallo, 2023) for their description. Of these three risks, the only one that could potentially be highly affected by the increase in Construction Costs could be the Risk of inaccurate assessment of construction costs (RCC).

Fig. 2. Annual variation of ISTAT construction cost index for new residential buildings in Italy, base 100: 2023. Source Data: Istat, Elaboration: Authors.

In Figure 2, depicting the annual variation of the ISTAT (Italian National Statistics Institute) construction cost index for new residential buildings, it is evident that construction costs remained relatively consistent between 2012 and 2019, with an average annual increase of approximately 0.66%. From the pandemic event onwards, however, it can be noted that the increase in these costs has been exponential with an average annual variation from 2020 to 2023 of approximately 6.01%. How could the assessment of the Risk Value of this specific risk (RCC) vary in light of the change in costs witnessed in recent years? Considering that the SR51 project was presented in 2017 and that at that time the construction costs had been estimated, in the risk assessment model, we have previously assumed a relatively flat probability of cost increase, in line with historical inflation. In 2017, the average annual increase in costs of the