PSI - Issue 62

R. Martini et al. / Procedia Structural Integrity 62 (2024) 392–399

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Martini R. et al. / Structural Integrity Procedia 00 (2019) 000 – 000

1. Introduction Bridges play a critical role in connecting communities and facilitating the seamless flow of people, goods, and services. Among the various structural typologies, pre-stressed concrete bridges stand out for their structural efficiency and rapidity of construction. For these reasons, this bridge typology was the most used in the last decades to built the majority of bridges in Italy that today are almost at the end of their service life (Principi et al., 2023, Quqa et al., 2022). To address issues related to the classification of risks, safety assessment, and monitoring of existing bridges, the Italian Government recently decided to adopt specific regulations for the multi-risk evaluation of existing bridges and viaducts. These regulations were firstly published by the Italian Higher Council of Public Works as “Guidelines 2020” (MIMS), and later updated in 2022 (Guidelines 2022) when operational instructions were also published by ANSFISA (ANSFISA). The regulations address the multi-risk evaluation and classification for bridges and viaducts through a multilevel approach, starting from a comprehensive inventory of the infrastructures on a large scale, to the safety assessment and monitoring procedures of individual bridges (Matos et al., 2023, Natali et al., 2023, Nicoletti et al. 2023a, b). Importantly, this approach considers various types of risks arising from structural vulnerabilities and the surrounding environment, encompassing structural and foundational risks, seismic risk, landslide risk, and hydraulic risk, all of which are comprehensively evaluated. This paper presents an in depth investigation of an existing paired pre-stressed box-girder half-joint concrete bridge in the spirit of the Italian guidelines. The two bridges showed age-related degradation phenomena some years ago and they were carefully controlled during the last 2 years through investigations performed by a FABRE team, involving members of Università Politecnica delle Marche (UnivPM) and University of Camerino (UniCAM), in conjunction with an ANAS team, collaborating within the framework of a research agreement between the parties focusing on the first applications of the Italian Guidelines 2022. Issue related to the bridge health are presented, as well as the outcomes of the visual inspections, performed in the framework of the "Guidelines 2022 ” . Furthermore, preliminary safety verifications on bridges following the Italian code prescriptions are discussed as well. Finally, the monitoring activities and the test campaigns carried out to deepen the knowledge of old pre-stressed concrete bridges and to control the structure loss of performance, are presented. 2. The case study 2.1. Description of the bridges The two bridges are located in Marche Region (Central Italy) and belong to the same route, each hosting one of the 2-lane carriageway. They were designed around 70s and built between 70s and 80s. The bridges, crossing the Candigliano River, are identical and built adjacent to each other; both structures, on the upstream (UB) and downstream sides (DB) are composed by 8 spans and are slightly curved. Some pictures relevant to the bridges are reported in Figure 1, together with the static scheme and the adopted nomenclature. Spans 1, 2, 6, 7 and 8 are simply supported, whereas spans 3, 4 and 5 adopts a Gerber scheme with two half-joints located at span 4, sustaining a simply supported span The deck of each bridge consists of post-tensioned 3-cell concrete box-girders having constant height for the simply supported decks and variable height for the Gerber scheme at piers 3 and 4. The cast in place deck has a width of about 9 m. The reinforced concrete piers are characterized by a hollow cross-section and different heights ranging from about 5 m to about 9 m (over the river). 2.2. Bridges investigation according to the Italian guidelines The bridge is selected as case study for the first applications of the recently released Italian Guidelines 2022 in the framework of a research agreement between the FABRE Consortium and ANAS S.p.A. The guidelines are based on a multilevel approach that can be divided into three main parts, as reported in Figure 2. Part I discusses about actions relevant to the preliminary identification of the bridge (census and geo-localization, Level 0), the visual inspection (Level 1), and the definition of the Class of Attention (CoA, Level 2).