PSI - Issue 44

E. Renzi et al. / Procedia Structural Integrity 44 (2023) 355–362 E. Renzi et al./ Structural Integrity Procedia 00 (2022) 000 – 000

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One of the most important and challenging aspects upon which the road networks safety depends is represented by the stability of bridges. For the assessment of the stability of bridges, the road infrastructure managers so far have utilized mandatory and also optional regulations (Government Regulation n. 6736/61A1, 1967, etc.). However, the main Italian rule for structural evaluation (Legislative Decree of New Italian Construction Standard, 2018), for bridges, has been upgraded (in 2018) focusing just on new structures, but, due to the obsolescence of the existing road network it is now necessary to work on a specific section of the main rule oriented towards the existing bridges, as already done for the existing buildings. In order to provide the various road managers with a standard procedure focused on the creation of a uniform classification system and the maintenance of the managed bridges, the Italian Government recently adopted the “Guidelines for the risk Management of Existing Bridges” (GMEB). The GMEB have been developed by the Italian “Superior Council of Public Works” and have been adopted by the Italian Ministry of Sustainable Infrastructures and Mobility (Ministerial Decree n. 578, 2020). The large number of bridges requires that the GMEB procedure uses a “multi - Level” philosophy to work with increasing levels of complexity, ranging from an inventory to an enhanced evaluation of every single structure. The procedure is based on six Levels: the first three levels must be applied on a country-wide scale (for all the bridges) while the next three levels (more accurate and demanding) are only applied for the bridges which are characterized by a higher priority (i.e. to the bridges with higher risks). The first five Levels of the GMEB procedure are reported in Fig. 1. The GMEB procedure also requires a multi- risk analysis for the evaluation of the “Overall Attention Classification” (OAC) related to each element that constitutes the so called “domain” of bridges, in order to manage the safety and the maintenance of the domain. A “Multiple Criteria Decision Method” (MCDM)” has been considered by the GMEB, in order to define the Attention Classification (AC) of every bridge for the different considered risks, i.e. “Structural/Operational”, “Seismic”, “Landslide” and “Flood”. The same methodology is also used to determine the OAC for every single bridge, which is derived from the different ACs of the bridge. The ACs and the derived OAC can assume five different ratings, ranging f rom “low” to “high” priority. In particular (see Fig. 1), the GMEB procedure starts with the activities of the first two Levels, which determines the characteristics (in terms of age, geometry, structural elements, traffic, etc.) and the defects (cracks, bar corrosion, concrete carbonation, water penetration, etc.) of the considered bridge.

Fig. 1. Schematization of the Levels of the GMEB procedure

These status characteristics - basically corresponding to maintenance defects -, recognized through the first two Levels of analysis (and where appropriate, slightly processed), represent the parameters (primary or secondary, depending on their importance) which are consequently used to define the priority ratings. The subsequent Level of the proced ure (“Level 2”) indeed determines the four ACs (related to the specific Risks) using the aforesaid parameters (primary and secondary) in order to define the Vulnerability, the Hazard, and the Exposure priority rating. In other words, by starting with the results of the first two Levels of the procedure and applying a MCDM, the classifications (in terms of Vulnerability, Hazard, and Exposure) are evaluated for every single structure and every single risk. The combination of these three classifications defines the single ACs of every bridge (related to the different Risks). The last step of “Level 2” consists of the definition of the OAC for the single bridge; the OAC can refer to five different conditions (or priority levels): Low (better condition), Low/medium, Medium, High/medium, and High