PSI - Issue 84

Michele D’Amato et al. / Procedia Structural Integrity 84 (2026) 536–543

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The number of bridges affected by scour phenomena is equal to 48 (50% of the sub-sample considered), distributed within the Hydraulic CoA as follows (Fig. 4, on the left): 21 in the H class, 13 in the MH class, 11 in the M class, and 3 in the ML class. Fig. 4 shows, on the right, also the distribution of scoured bridges in the Overall CoAs for each Hydraulic CoA. It should be noted that within the 6 bridges having both H Hydraulic and Overall CoAs, 3 report evident pier foundation scour, 1 evident abutment foundation scour, while 2 show other significant structural defects (vertical cracks at the piers and lateral abutment wall out-of-plane overturning). This means that, as expected, the H Structural CoA directly influences the Overall CoA, but also that the foundations scour in 3 bridges is due to hydraulic phenomena (landslides phenomena are not present here). Similarly, in 2 of 5 bridges resulting from combining MH Hydraulic CoA and H Overall CoA significant pier foundations scour phenomena are observed.

Fig. 4. Hydraulic CoA distribution of the sample of bridges affected by scour and its weight on the Overall CoA.

The parameters considered in this study for the typological analysis are: piers shape and material, riverbed typology, non-zero flow attack angle, contraction factor, and basin extension. Statistical analyses are conducted on the selected factors, both individually or in combination. Then, the relative frequencies of the scour-affected bridges is assessed through the following ratios: the within-sub-sample scour rate ( f c - Eq.1), the relative frequency of each sub-sample in the scoured sample ( f s - Eq.2) and the relative frequency of each sub-sample in the total sample ( f t -Eq. 3): = ℎ ℎ − ℎ ℎ − (1) = ℎ ℎ − (2) = ℎ ℎ − (3) where each sub-sample includes bridges sharing the same pier or river-flow characteristics. In this study, a bridge is considered affected by erosion or scour if at least one pier/abutment or river bed exhibits this phenomenon. 4. Results and discussion The available sub-samples consisted of RC , M , and CC material bridge piers. Based on the information collected within the database, the RC results the predominant construction pier material (33 bridges), subjected to varying