PSI - Issue 62

Francesco Mariani et al. / Procedia Structural Integrity 62 (2024) 955–962 Mariani et al / Structural Integrity Procedia 00 (2019) 000 – 000

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positive bending moments during the casting of closure segments. Visual inspections revealed an anomalous deformed shape along the viaduct, as shown in Figure 2, attributable to viscous effects. Specifically, spans with joints shifted downward, while others exhibited upward displacements, with maximum vertical displacements observed near the vertically prestressed joints. Moreover, the horizontal displacements of the rollers within the joints exceeded the maximum allowable stroke limit and some of the lower supports are decompressed or detached. All mentioned issues prompt a thorough investigation of the viaduct’s behavior using a calibrated FE model based on experimental test results.

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Fig. 1. (a) Global view of the viaduct; (b) Detailed view of a vertically prestressed internal joint.

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Fig. 2. (a) Schematic representation of the case study viaduct; (b) Schematic deformed shape observed in-situ.

3. Experimental tests After the acceptance load test performed at the end of the construction, other experimental campaigns have been conducted, aiming both to understand the service conditions of the structure, and to fine tune the numerical FE model. The subsequent sections detail the various tests conducted on the viaduct. 3.1. Concrete cores compression test In 2022, two concrete specimens were taken from the box girder for strength assessment, one extracted from the top slab (C0) and the other from the web (C1). These cores were subjected to an axial compression test in the laboratory to ascertain the concrete’s compressive strength and Young’s modulus. The properties and outcomes from each core are presented in Table 1. The average experimental elastic modulus is established at 24500 MPa and allows to refine the input concrete properties defined in the Finite Element (FE) model. Despite the limited number of cores, which precludes a statistically significant characterization of the concrete properties, the results provided by this campaign offer a valuable estimate, forming the basis for the preliminary numerical model updating.

Table 1 . Specimens’ properties and compression test results. Specimen ID Diameter [mm] Height [mm] Density [kg/mm 3 ]

Compressive strength [MPa]

Ec [MPa]

C0 C1

114.31 114.53

229.12 230.31

2240 2190

39.23 26.03

27353 21891