PSI - Issue 84

Stefano Bozza et al. / Procedia Structural Integrity 84 (2026) 852–858

853

1. Introduction In several western countries such as U.S.A (American Society of Civil Engineers (2025)), Germany (Marzah and Gunreben (2017)) and Italy (Pinto and Franchin (2010)), a large part of the road infrastructure was built in the second half of the 20 th century, therefore many existing road bridges are approaching or have already exceeded their nominal life. Bridges are critical elements of road network, and can be subjected to natural hazards (like earthquake or flooding) as well as ageing effects, e. g. chloride corrosion (Bozza et al. (2024)), often accentuated by lack of maintenance. Thus, bridge management involving periodic inspections, maintenance planning and retrofit interventions is a complex task. In Italy, concern to bridge management has grown in the last decade, following some bridge collapses (once upon all, the collapse of the Polcevera bridge in Genova in 2018 (Calvi et al. (2019)), which led to the issuing of the “Guidelines for risk classification and management, safety assessment and monitoring of existing bridges” (“Guidelines” hereafter) (MIMS and CSLLPP (2022)). The Guidelines proposed a multi-level approach to manage the large stock of bridges in the national territory, considering structural, seismic, hydraulic and landslide risks. The multi level approach starts from bridge census (Level 0), then visual inspection and defects evaluation (Level 1), evaluation of a “Class of Attention” (CoA) (Level 2), preliminary assessment (Level 3) up to accurate assessment of critical bridges (Level 4) or even network resilience (Level 5) for very important structures. After the assignment of the CoA, ranging from Low to High across five levels, bridges with Medium or Medium-High CoA have to be preliminary assessed, in order to prioritize further investigations. As mentioned, many bridges are approaching their nominal life and could have suffered from lack of maintenance, thus a lot of structures could have a Medium or higher CdA, therefore a rapid method for preliminary assessment of bridge decks can help the management of large portfolios of bridges. As already highlighted by previous studies (Buratti et al. (2019), Bencivenga et al. (2022), Bozza et al. (2023)), the Italian codes about traffic load models have undergone a continuous evolution throughout the last century, therefore most of existing bridges were designed with outdated codes and likely for lighter traffic loads. The preliminary analysis for structural risk proposed by the Guidelines consists in comparing the original design traffic load effects with the effects induced by the current technical code (NTC (2018)). Although the Guidelines allow to use simplified methods for the assessment of the traffic load effects, performing the preliminary analysis of a large portfolio of bridges could be time-consuming, thus a rapid preliminary assessment can improve the bridges management. In this paper, the results of a parametric study about the comparison of the effects induced by the loads provided by outdated codes and by the current technical code are used to calibrate simplified functions useful to perform a fast preliminary assessment of bridges. The study focuses on PC beam-and-slab bridges with simply supported spans, one of the most common typologies among bridges with medium-small span (Pinto and Franchin (2010), Borzi et al. (2015)). The comparison is performed in terms of maximum bending moment of the most stressed girder, accounting for the transverse load distribution via the methodology proposed by Guyon, Massonnet and Bareš (Massonnet and Bareš (1966)). First, the outdated codes and the geometries considered in the parametric study are described, then different functions are fitted to the data obtained from the parametric study. Finally, results are reported and discussed, while the main conclusions are reported in the last section. 2. Methodology 2.1. Bridge deck geometries Since the effects induced by traffic load models on a simply supported bridge span depend mostly by geometry parameters, a large set of deck geometries was initially defined, accounting for several parameters such as span length, deck width, carriageway width, slab thickness, number of main girders, number of transverse diaphragms, and girder section. In particular, span ranging between 10 m and 40 m (discretising every 1 m) and width ranging between 8 m and 16m (discretising every 2m) were considered. Three different kerbs or sidewalks width (equal to 0.5 m, 1.0m or 1.5 m), as well as two different slab thickness (equal to 0.20 m or 0.25 m) were taken into account. For each span length, three different number of transverse diaphragms were considered, in order to obtain diaphragm spacing as close as possible to 5m, 10m and 15m, with the exception of bridges with length less than 15m, for which only