PSI - Issue 78

Giuseppe Santarsiero et al. / Procedia Structural Integrity 78 (2026) 560–567

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(a)

(b)

Fig. 4. Overall degradation indices of bridge averaged by both spans (a) and beams (b).

Table 2. Rankings based on the degradation index values and comparison with the class of attention result.

CoA_sf (structure-foundation)

CoA (overall)

Bridge

IDeg_p,c IDeg_p,t Rank (IDeg_p,c) Rank (IDeg_p,t)

1

22.75

7.58

1°

1°

M-H

M

5

12.34

3.09

2°

2°

M-H

M-H

4

5.07

1.69

3°

3°

H

H

6

4.32

1.44

4°

4°

H

H

2

2.54

0.85

6°

5°

M-H

M-H

3

3.20

0.74

5°

6°

M-H

M

The comparison between the degradation indices and the assigned Class of Attention related to the structure and foundation risk (CoA_sf) reveals a significant discrepancy that deserves careful consideration. As shown in the graphs of Fig. 4, Bridges 1 and 5 exhibit the highest values of degradation indices — both in terms of spans (IDeg_p,c) and beams (IDeg_p,t) — clearly standing out from the rest. However, when looking at the CoA_sf related to the structural and foundation system, these bridges are classified as M-H (Medium-High), rather than H (High), as it could be expected. On the contrary, Bridges 4 and 6, which show significantly lower degradation indices, are classified as High CoA and CoA_sf. This contrast becomes even more evident when considering the overall CoA, where again Bridges 1 and 5 have respectively M (medium) and M-H values, despite presenting a far more critical condition based on measured deterioration. This mismatch may suggest that current CoA assignments based on the worst element degradation may not be representative of the intervention urgency among a group of bridges. 5. Conclusions This study analysed the degradation of post-tensioned prestressed concrete beams in six existing bridges through the definition and application of two complementary degradation indices. After the definition of a degradation index, the methodology enabled both span-based and beam-based comparisons, highlighting variations in degradation distribution and severity across different structural components. First of all, the analysis method allows for easy