PSI - Issue 62

Elena Elettore et al. / Procedia Structural Integrity 62 (2024) 113–120 Elettore et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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correspondence between the defects has been analysed and checked. Figure 7 identifies the comparison of the catalogues of defects between MIT and ASPI classified by material, highlighting the presence of many items of the MIT defect sheets and not included in the ASPI catalogue and vice versa.

Figure 7. Comparison of the catalogues of defects between MIT and ASPI classified by material.

By comparing the defect sheets of MIT and ASPI, some differences in the approaches can be observed, in particular MIT identifies certain critical elements ( e.g., Gerber saddles, prestressing cables, bearings) and whatever damage there is, regardless of intensity, is considered high level; instead ASPI presents a catalogue of defects and for each defect identifies the structural elements that could be affected. It can be highlighted that in the ASPI defect sheets, there are many possible defects in the ASPI sheets related to the Gerber Saddles, and the level of defect is not always considered to affect the structural safety of the viaduct. 4. Methodologies for the defect level calculation The defect rating calculated according to ASPI is expressed through a logarithmic-based Total Work Degradation Index ( ) that takes into account the number of all defects on the work, to have an average defect rating of the work this index is averaged over the number of spans ( ,nc ): = ∑ =1 , = ( ) (1) where is the number of defects in the work and is a coefficient equal to 10 8 to be calibrated according to the results and placed, indicates the measure of the grades of a given class that are equivalent to a single defect the immediately higher class. is the degradation index associated with the class of the i -th defect. The defect level defined by LG20 in Section 4.2.2 " Estimation of the level of structural and foundational vulnerability ." The defect level is classified into 5 classes (low to high) according to the severity, intensity and extent of the defects detected, as well as the element affected by these defects and its significance on the overall structural behavior of the bridge. ASPI proposes the following correspondence between overall average defect rating and level of defectiveness of LG20, functional for the assignment of the attention class, as shown in Figure 7. The presence of critical defects or defects on critical parts or components of the work will result in an immediate transition to the medium-high and high defect level as specified in LG20.

I LOG,nc (n=1-nc=1)

Defect level (LG20)

Class

A1 A2 B1 B2 B3 B4 C1 C2

8 7 6 5 4 3 2 1

High

Medium-high

Medium

Medium-low

low

Figure 8. Correspondence between overall average defect rating and level of defectiveness (LG20) proposed by ASPI