PSI - Issue 64

Antonio Bilotta et al. / Procedia Structural Integrity 64 (2024) 2109–2116 "Bilotta A. et al." / Structural Integrity Procedia 00 (2019) 000 – 000

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Figure 2 Examples of substructures belonging to the considered ramp viaducts (from Morandi 1980). Figure 3 shows the position of the viaducts considered in this study, by using tridimensional Google Earth view, named according to the nomenclature used by the current highway operator. Different viaducts have common piers (see for example the node in which the end of O13 and O14 are connected with the beginning of O15 and O17). The ramps have also high longitudinal slope to accommodate different vertical height needed to fit the urban context at the construction time. Figure 4a shows, in the case of O13, two half joints connect a deck realized with a box section with the cantilever ends of a deck made by two prestressed concrete (PC) beams supported on two pears. Figure 4b shows, in case of O19, simply supported decks made of two PC beams on the bridge piers with a large pier cap. In the latter case additional steel plates were added during a retrofitting intervention considering the substitution of the old neoprene bearings and introducing lateral constraints for seismic upgrading. Generally, for all the considered bridges, there are three different deck types: (i) PC beams with collaborating reinforced concrete (RC) slab; (ii) PC box beams; (iii) steel-concrete composite decks mad of steel I-shaped beams or box steel beams. The substructure is made by RC piers and pier caps with rectangular cross section. Anyway, sometimes prestressed caps were realized.

O24

O25

O17

O18

O15

O19

O14

Via Marina

(a)

O13

(b) Figure 4 Examples of superstructures in O13 (a) and O19 (b).

Figure 3 3D view of the ramp viaducts considered in this study

2.2. Main structural issues It is possible to identify some issues typical of concrete structures of that age. Concrete deterioration is common, in some cases, reinforcing bars are experiencing the starting of the corrosion process, thus leading to additional concrete cover spalling spreading in both superstructure and substructure elements. Moreover, those issues are usually dominated by non-performing behaviour of the expansion joints. For the metal bearings it appears the presence of preliminary corrosion process for base plates, along with additional teflon degradation. Due to the low expansion joint performance and the high concrete aging, some issues arose in the half joints, with the presence of exposed reinforcing bars arose from superficial concrete degradation due to natural water flow.