PSI - Issue 84

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

1342

composed of five prestressed reinforced concrete (PRC) I-shaped girders, simply supported, and separated by a central frame pier with a height of 8.50 m. Figure 2a shows the Pagano Viaduct. The installed SHM system comprises eight accelerometers per span, three installed on the edge girders at the quarter-span locations, and two central sensors installed on girders 2 and 4. The monitoring system is completed by one sensor located on the pier cap and one sensor installed in a pit, acting as a seismic sentinel. Temperature sensors are installed on the central girder of each span. The OMA analyses carried out on the structure indicate a dynamic behaviour characterised by dynamically uncoupled spans, with a very low degree of interaction among the structural components. The presence of a finger joint between the spans confirms the reasonableness of the result (see Figure 2b). Based on this observation, it is convenient to subdivide the system into three independent subgroups, each representing a structural element exhibiting autonomous dynamic behaviour: i) Span 1, ii) Span2 and iii) Piers. This subdivision is further validated by modal analyses (see Table 1 and Figure 3), which show a high percentage of Modal Phase Collinearity (MPC), as well as by the structure of the Modal Assurance Criterion (MAC) matrix, which appears predominantly diagonal, thus confirming a clear mode separation among the identified subsystems.

a)

b)

Figure 2. The Pagano Viaduct: a) global view of the infrastructure and b) view of the finger joints.

Table 1. Modal parameters identified for the Pagano Viaduct by means of COV-SSI algorithm for the 3 sub-groups.

Subgroup: Span 1

Subgroup: Span 2

Subgroup: Span 3

#

#

#

Freq. [Hz]

Damping [%]

Cluster size

MPC [%] 81.4 99.9 100 87.3 97.9

Freq. [Hz]

Damping [%]

Cluster size

MPC [%] 96.1 100 100 99.5 97.5

Damping [%]

Cluster size

MPC [%] 97.9 96.6 97.9

Freq.[Hz]

1 3.450 2 3.606 3 3.874 4 9.833 5 16.888

2.44 1.55 1.60 3.54 2.88

21 21 21 13 20

1 3.554 2 3.736 3 4.002 4 9.830 5 17.582

1.70 1.57 1.22 3.17 3.27

21 21 21 17 18

1 3.454 2 3.614 3 3.663

4.53 2.04 0.23

52 22 32

- -

- -

- -

- -

- -

Figure 3. Sensor positions and definition of sub-groups. Geometric descriptions of the identified mode shapes, together with MAC coefficients.