PSI - Issue 62

A. Lupoi et al. / Procedia Structural Integrity 62 (2024) 963–971 A. Lupoi, F. Romano / Structural Integrity Procedia 00 (2024) 000–000

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degrading effects of environmental conditions, such as rainwater dripping or seepage due to an inefficient water disposal system. Moreover, a suitable maintenance schedule and a structural health monitoring system in time was not envisaged. Furthermore, the magnitude and frequency of traffic load strongly increased with respect to the design loads adopted decades ago, reducing the current structural safety level (Bencivenga et al., 2022). Because of all these issues, the national infrastructures network presents nowadays a widespread condition of degradation (Bazzucchi et al., 2018). In order to plan the best intervention strategies for the great amount of road and railway bridges, an accurate performance assessment of single structures is crucial. In this direction, the Guideline approved by the Italian Transportation and Infrastructures Minister (MIMS, 2021) provide indications on how to assess the safety of existing bridges, relatively to different types of risks (Santarsiero et al., 2021). Within such evaluation of the overall construction performance, the assessment of the performance/capacity of degraded structural elements assumes primary importance. Once the main structural deficiencies are detected, cost-benefit analysis in time are necessary to figure out the best solution, e.g. replace the entire bridge or limit to some deficient elements, or address optimized in situ repair activities (Harries and Jarret Kasan Can, 2009; Ghaffary and Moustafa, 2020). The latter ones are the most economical solution in most of the cases, but they are also required to be easily implemented, effective and long lasting. This paper reports the results of an experimental test performed on an existing prestressed concrete bridge girder, taken off from an Italian highway bridge because of a full-depth crack close to the mid-span zone. A repair intervention was carried out on the damaged area by high-pressure injection of high-resistance mortar, with the goal to restore the girder integrity. Then, a three-point bending test was performed on the repaired girder to assess the effectiveness of the repair intervention. The prestressed concrete girder was part of a simply supported beam deck of an existing bridge located on the Italian A1 highway, in the Emilia-Romagna region, built in the 1959. The girder has a 32.6 m length, and the transversal section height is 142 cm. Before removal, the girder was connected to the rest of the bridge deck by a 35 cm thick reinforced concrete slab and five 118 cm high prestressed transverse beams. The girder is prestressed by five curved post-tensioned tendons, each tendon composed of 42 wires of 6 mm diameter. Three tendons are anchored in correspondence of the end section, the remaining two are anchored in the first quarter of the girder, under the deck slab. Fig. 1 reports the prestressing system configuration of the girder, as well as the transverse end and mid-span sections. 2. Case study girder

2.1. Damage description

The girder was taken off due to the presence of a full-depth crack along the connection between the girder web and the bottom bulb, as shown in Fig. 2. The full-depth crack extends horizontally for about 4.5 m starting from the girder mid-span section, and continues as a partial-depth crack for additional 1 m. The crack is probably due to rainwater seepage into the ducts of the post-tensioned system; in fact, semi-destructive tests reveal that the full-depth crack is in correspondence of tendon no. 5, which lacks the circular steel duct and presents corroded wires. Moreover, Fig. 2(c) shows cracking and spalling phenomena of the cover concrete in the web surface above the full-depth crack.