PSI - Issue 84

Gianluca Centofanti et al. / Procedia Structural Integrity 84 (2026) 1339–1346

1344

Table 2. Modal parameters identified for the Boccea Viaduct by means of COV-SSI algorithm for the 2 sub-groups.

Subgroup: Whole

Subgroup: Piers

# 1 2 3 4 5 6 7 8 9

# 1 2 3 4 5 6 7 8 9

Freq. [Hz]

Damping [%]

Cluster size

MPC [%]

Freq. [Hz]

Damping [%]

Cluster size

MPC [%]

1.849 2.044 2.312 2.65 2.939 3.334 3.695 4.022 4.335 5.215 5.797 5.981 6.322 6.326 6.500 7.453

1.68 1.37 1.23 1.29 3.11 1.97 2.05 2.05 3.33 3.10 1.03 1.17 1.05 1.05 1.11 1.96 3.01 1.81 1.97 1.42 1.69 1.88

56 56 56 56 20 45 56 56 53 45 31 31 25 31 56 51 26 26 25 37 24 22

99.8 99.7 99.7 99.6 97.5 95.4 96.8 99.3 86.9 97.0 93.5 90.1 86.5 98.6 99.0 92.7 88.8 87.2 84.2 85.3 85.2 84.0

1.836 1.852 2.041 2.309 2.661 2.87 2.881 3.339 4.023 5.878 5.984 6.224 6.227 6.502 6.928 7.31 7.439 5.8

4.26 1.70 1.37 1.21 1.04 1.71 0.62 1.73 1.94 1.07 0.95 1.31 1.46 1.23 1.08 2.68 2.65 2.00

61

93.2 99.6 99.3 97.6 92.7 65.2 59.9 77.5 93.9 76.2 74.2 84.5 95.0 92.6 81.9 68.2 91.0 91.4

131 131 112

62 45 81 97 85 83 71 58 61

109

10 11 12 13 14 15 16 17 18 19 20 21 22

10 11 12 13 14 15 16 17 18

131

42

10.101 11.598 11.936 12.35 13.339 13.34

107

73

- - - -

- - - -

- - - -

- - - -

- - -

- In the presented case study, the number of channels in the largest subgroup is approximately 60, which can be considered close to an upper practical limit, mainly due to the computational constraints of the edge PC. In other applications involving continuous structures with a high number of spans, the number of channels may exceed this threshold. In such cases, the subdivision of the structure into subgroups including a maximum of ten consecutive spans has been considered. To preserve diagonal MAC matrices under this approach, the last span of the previous subgroup was included within each subsequent subgroup. However, this strategy may become computationally demanding, particularly when the analyses are performed directly on the edge computing unit. Based on these considerations, the number of sensors shared among multiple subgroups can be limited to a restricted number of locations. If, in order to further reduce the computational burden, no shared measurement points with the previous subgroup are adopted, it must be taken into account that the MAC matrix will no longer exhibit a diagonal structure. 2.3. S. Onofrio Viaduct The structure forms part of the E45 motorway and is located in the municipality of Pizzo (VV), Italy. The viaduct consists of six spans, each composed of three prestressed reinforced concrete I-girders (see Figure 5). The spans have different lengths, ranging from a minimum of 24.48 m to a maximum of 34.46 m, with an average length of 33.50 m. The spans are structurally independent due to the presence of finger joints (see Figure 6). The monitoring system corresponds to the minimum ANAS standard configuration and includes six mono-axial accelerometers placed at the quarter points of the spans, as well as one triaxial sensor for each pier cap. A preliminary analysis revealed a dynamic coupling between spans 2–3 and 4–5. This coupling is fictitious, as it is not related to any structural continuity (given the presence of finger joints); instead, it can be attributed to piers 2 and 4, whose heights of 9.46 m and 9.88 m result in natural frequencies close to those of the supported spans, thereby triggering a dynamic coupling phenomenon.

Figure 5. The S. Onofrio Viaduct: a global view and a view of the superstructure.