PSI - Issue 44

Michele Frizzarin et al. / Procedia Structural Integrity 44 (2023) 745–749 Michele Frizzarin et al./ Structural Integrity Procedia 00 (2022) 000–000

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2.1. Comparison between standards in terms of total loads This chapter presents a comparison between the total loads deriving from the traffic loads defined by the above mentioned regulations. The work takes up what was done by C. Strassil et al. (2002), extended both with the most recent regulations and in the seismic aspects. The graph expresses the weight values as a function of the length of a simply supported deck, with the following characteristics: • Single span isostatic bridge; • Total deck width 9.5 m; • Road width 7.5 m; • Two sidewalks 1 m wide each; • 5 equally spaced beams with a transversal distance of 1.875 m and lateral cantilevers of 1 m; • Transversal distribution calculated with the Engesser-Courbon method. The highest possible load was considered for each standard. Furthermore, the NTC2008 and the 2020 Guidelines refer to the same loads as the NTC2018; therefore only the latter provision was reported.

Fig. 1. Total weight of traffic loads in the span

3. The adaptation of existing road bridges The issue of the state of health of Italian road bridges has now become public knowledge, unfortunately for sadly known reasons, and not only because of the tragedy of the Morandi bridge in Genoa. For some years now, other serious accidents have seen the collapse of at least 5 bridges in the last 10 years. The need to secure the existing road network, however, clashes with the enormous amount of works which, as already mentioned, mostly date back to about 50 years ago. The regulator, aware of these difficulties, since the first rules on existing structures, has provided for the obligation to adapt to the current standard only in some specific cases. Also with regard to bridges, reference is made to the rules for buildings, specifying however some characteristic aspects, as indicated in § C8.8.7 of the 2019 Circular. Referring