PSI - Issue 64

Marco di Prisco et al. / Procedia Structural Integrity 64 (2024) 2133–2140 M. di Prisco, L. Radice, M. Colombo / Structural Integrity Procedia 00 (2019) 000 – 000

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to be made in a reference time frame for periodic (repair or restoration) and urgent maintenance, by using prognostic deterioration models or numerical indicators of the condition state (Biondini, 2019; Scalbi et al., 2022). Despite the ageing of the Italian infrastructures (di Prisco, 2019), in the past years the asset owners and managers mostly allocated economic resources on ordinary maintenance of the road surface and urgent maintenance of the structural parts, leaving aside life-cycle based models which have been proved beneficial in the rational planning and implementation of maintenance activities over time. The paper describes the assessment of the bearing capacity of a three-span overpass, built in the sixties, located on the east shore of Maggiore Lake, intersecting a provincial road. The main aim is to check the serviceability and the ultimate limit states of the bridge, when variable loads are applied. The bridge is a second category bridge, that means that no trucks with a total load exceeding 44t could freely cross the bridge. The bridge is a girder bridge 21.1 m long: the central span is 0.92m deep and 10m long, while the external spans are 0.32 m deep and 5.4 m long. In 2013 a significant restoration was carried out due to the bad conditions of the infrastructure. The restoration was not originally planned by a specific plan, because the maintenance plan was introduced as a requirement only in 2010 (D.P.R. 207/2010), even if the need of this requirement is well known since the first eighties (De Sitter 1984); its lack was clearly denounced by Helmerich (2008) and its late introduction is the main reason of the critical situation highlighted In 2013 a significant restoration was carried out due to the bad conditions of the infrastructure. The eleven P/C beams, 0.8 m deep, were retrofitted by means of carbon fibre reinforced polymer (CFRP) strips and the top slabs over the two internal piers were also strengthened by additional reinforcement (Figure 1 and 2). The CFRP system includes the placement, on the bottom face of the beams, of a 100 x 1.4 mm 2 longitudinal layer. In addition, 14 U-shaped strips 400 mm wide were placed along each beam, 4+4 located side by side closed to each support and the 6-remaining distributed with a spacing equal to 2.10 m or 3.00 m. On the existing slab, an additional R/C layer 10 cm thick was cast; this new slab is connected to the existing one through Ø12/25 shear connectors and is reinforced with Ø8/15 upper and lower longitudinal bars and Ø20/15 transversal bars. When the new slab intersects the existing structural joint on the pile, an additional longitudinal reinforcement consisting in 1Ø12/30 is added. The latter intervention substantially modifies the structural behaviour of the bridge, as it inserts a bending continuity between the central and the lateral spans. by European Commission (2018). 2. The retrofitting intervention

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Fig. 1. Views of precast beams before the retrofitting: a) Lateral and b) bottom view.