PSI - Issue 84

Marco Civera et al. / Procedia Structural Integrity 84 (2026) 49–56

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Fig. 2. (a) Simplified static scheme of the Amedeo VIII bridge in the longitudinal direction. Left (West, Turin side) to right (East, Settimo side): SPS = spalla sinistra (left abutment), SPD = spalla destra (right abutment), and P = pila (pier); the five spans are named according to the supports (SPS–P1, P1–P2, P2–P3, P3–P4, and P4–SPD). (b) Example of one cross-sectional view (mid-length of the first span). (c) Detail view of the SPD abutment and piers’ foundations. (d) Detail view of one example of a half-joint; the bearings are fixed toward the lateral spans and movable toward the central span. The movable bearings are formed by a reinforced-concrete roller placed between two lead plates. (e) The external unbonded post-tensioning tendons as added during the 2009-2011 retrofitting works. All technical drawings are retrieved from the original structural design of the retrofitting works, in Italian. In this regard, Fig. 3 reports a sketch of the indicative geometry of the scour holes, as determined by a visual survey carried out in August 2024. It must be stated, however, that the limited accessibility of the piers and the high water level (between 1.5 m and 2.5 m) did not allow for an effective characterisation of foundation conditions by visual inspection. In any case, Pier P1 lies on shallow water and no variations in the riverbed are detected, thus, no scour is expected at that location. Piers P2 and P3 are on the sides of two main channels of the river, and some excavation can be seen from the top, especially on the upstream (i.e., Northwestern) side. Nevertheless, their foundations do not seem to be exposed. Pier P4 falls inside the river’s main channel, and some excavation seems to be visible, again on the upstream side. This is compatible with some evidence reported in 2007, although the scouring conditions were not analysed in detail at that time. However, despite several surveys, even during low flows (July/August 2024), it was never possible to see if the excavation exposed the foundation. Conversely, the seismic risk is relatively low, given the low seismicity of the area, with an expected peak ground acceleration a g =0.051 g, no topographic amplification (S t =1.00), and mild stratigraphic amplification S s =1.20 (soil type B, V s30 between 360–800 m/s).