PSI - Issue 78

Marco Nale et al. / Procedia Structural Integrity 78 (2026) 1095–1102

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indicates the CL1 inspection area, and a green circle shows the CL2 zone. From the comparison, it is evident that the radius specified in the 2002 guideline is significantly larger than the CL2 inspection radius defined in 2017, indicating a much more conservative approach. Indeed, the 2002 protocol was more cautious than several international standards (ICOLD,2008). Table 2 presents the expected PGA values for the first earthquake, extrapolated from average attenuation curves. Based on available records, no significant structural damage was observed at any of the sites investigated. Only minor effects were reported at Opera Reno, where temporary gates in storage were slightly displaced at their supports.

HI6

HI5

HI4

HI2

HI7

HI1

HI3

Control required by IMIT guideline:

CL1

CL2

IMIT 2002

Hydraulic Infrastructure

(a)

0.300

a g1 (Nale et al., 2025) a g2 (Nale et al., 2025)

0.250

a g1 (IMIT,2017) a g2 (IMIT,2017)

0.200

0.150

a g

0.100

0.050

0.000

Tieni

Fiscaglia

Opera a Po

Valle Lepri

Valpagliaro

Opera Reno

Pontelagoscuro

(b)

Fig. 3. (a) Shake map of the first 2012 Emilia earthquake event (May 20) showing activation control radii according to IMIT (2002;2017). (b) Bar plot of the acceleration activation thresholds for control levels (red and blue bars) at the hydraulic structures, as defined by the proposed procedure (Nale et al., 2025). Activation thresholds established by the Italian guideline for large dams (IMIT, 2017) are reported as magenta and green lines.