PSI - Issue 64

Marco Pirrò et al. / Procedia Structural Integrity 64 (2024) 669–676 Author name / Structural Integrity Procedia 00 (2019) 000–000

673

5

a)

b)

c)

Fig. 5. Time evolution of: (a) identified natural frequencies; (b) measured air temperature and (c) measured reservoir water level, from 01/12/2015 to 01/12/2017.

Table 2. Statistics of the modal parameters identified from 01/12/2015 to 01/12/2017.

f mean (Hz)

ξ mean (%) 1.41 1.31 1.67 1.33 1.93 1.84

σ f (Hz)

σ ξ (%) 0.23 0.24 0.38 0.23 0.37 0.55

Id. Rate (%)

Mode

1 2 3 4 5 6

2.527 2.668 3.497 4.116 5.001 5.911

0.060 0.068 0.104 0.109 0.112 0.129

86.5 93.1 86.1 94.8 89.9 74.2

4. Structural assessment based on natural frequencies

The inspection of Fig. 5 suggests that the identified natural frequencies of the dam are mostly subjected to thermal and water level changes. Therefore, in order to assess the structural integrity based on natural frequencies, it is necessary to filter out the effects due to EOV, before approaching any anomaly detection paradigm.