PSI - Issue 84

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Pasquale Bencivenga et al. / Procedia Structural Integrity 84 (2026) 264–271

267

0 0.2 0.4 0.6 0.8 1 1.2 1.4

w=8m

w=6m

NTC2018

M Ed /M Ed 2018

l=5m l=10m l=20m l=40m

1920

1940

1960

1980

2000

2020

1920

1940

1960

1980

2000

2020

Construction year

(b)

(a)

0 0.2 0.4 0.6 0.8 1 1.2 1.4

w=6m

w=8m

NTC2018

V Ed /V Ed 2018

l=5m l=10m l=20m l=40m

1920

1940

1960

1980

2000

2020

1920

1940

1960

1980

2000

2020

Construction year

(c)

(d)

Fig. 1. Results of parametric study: positive bending moments (a,b) and shear forces (c,d)

It is important to note that the 1945 regulations, issued in the immediate post-war period, introduced lower design loads compared to the previous 1933 standards, resulting in various structural vulnerabilities. To address these deficiencies, an internal circular issued by ANAS (Azienda Nazionale Autonoma delle Strade, 1952) effectively supplemented the 1945 regulations by providing updated guidance on design loads. The study reported in Bencivenga et al. (2022) highlighted that the lowest safety indices within the analyzed inventory were predominantly associated with bridges designed according to the 1945 regulations. It should be noted that the demand ratios defined in this study do not strictly follow the Level 3 guidelines, but adopt a simplified approach that neglects certain aspects, such as the transverse distribution of loads across the deck section. Nevertheless, these ratios provide a preliminary indication of the potential structural vulnerability of the bridges, relying on a few easily obtainable parameters, including the deck dimensions and the construction period. For each bridge, the minimum of the ratios for bending moment ( M Ed,code /M Ed,2018 ) and shear ( V Ed,code /V Ed,2018 ) , determined from the graphs of Figure 1, was taken as the I C parameter according to Equation (1). This parameter was then combined with the structural defect level to establish a priority scale for conducting detailed Level 4 assessments across a large sample of bridges. =min( , ,2018 , , ,2018 ) (1) In this respect, the obtained ratios appear generally consistent regardless of the internal force considered (i.e., shear or bending moment). Nonetheless, significant differences between the two ratios (approximately 15–20%) are observed only for codes issued before 1980. This discrepancy arises because load schemes derived from real vehicles tend to produce higher shear forces compared to the conventional distributed loads introduced in the 1980 code.

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