PSI - Issue 78

Pasquale Bencivenga et al. / Procedia Structural Integrity 78 (2026) 1545–1552

1548

Table 1 - Steel classes provided by Ministerial Decree of 30/05/1972, 26/03/1980 and 09/01/1996

Code

Steel class Characteristic yield strength Characteristic ultimate strength Elongation f yk [N/mm 2 ] f tk [N/mm 2 ] A5 [%]

FeB 22 FeB 32

≥ 220 ≥ 320 ≥ 380 ≥ 410 ≥ 440 ≥ 215 ≥ 315 ≥ 375 ≥ 430

≥ 3 40 ≥ 500 ≥ 460 ≥ 500 ≥ 550 ≥ 335 ≥ 490 ≥ 450 ≥ 540

≥ 24 ≥ 23 ≥ 14 ≥ 14 ≥ 12 ≥ 24 ≥ 23 ≥ 14 ≥ 12

M.D. 30/05/1972

A38 A41

FeB 44

FeB 22 k FeB 32 k FeB 38 k FeB 44 k

M.D. 26/03/1980 M.D. 09/01/1996

In the structural analysis of r.c. structures, the code allowed the use of a compressive cube strength R ck in the range 15-55 N/mm². Moreover, a cylindric characteristic compressive strength for concrete (f ck ) ranging from 12 to 50 MPa was identified. Furthermore, by applying partial safety factors of γ c =1.5 for concrete and γ s =1.15 for steel, it was possible to evaluate the design strengths, consistently with current codes. 3. The parametric study 3.1. Definition of geometries In order to identify the influence of the design code on the structural capacity of existing r.c. elements, a parametric study was carried out. In particular, the analysis aimed to evaluate the bending capacity of reinforced concrete beam sections according to the assumptions stressed in the previous section. This was performed by randomly defining rectangular cross-sections with dimensions typical of Italian r.c. bridge structures. For each code, one thousand cases were analysed by randomly varying the section height (H), width (B), the tensile reinforcement ratio (ρ =As/(BH) ), and the ratio between compressed and tensile reinforcement (ρ’ / ρ ), assuming a concrete cover of 3 cm. Table 2 summarizes the assumptions used to define the cross-sections.

Table 2 – Considered geometric dimensions min

max 120

interval

H [cm] B [cm]

50 20

5 5

60

ρ [%]

1

5

0.5

ρ’/ ρ [ -]

0.3

0.5

0.05

3.2. Strength and calculation hypotheses According to the study on the historical evolution of technical codes in terms of structural capacity, the previously defined geometries were analyzed based on the design assumptions established by each specific code. In particular, based on the historical overview of Section 2, the assumptions reported in Table 3 on material strengths were adopted. It should be noted that the results of the 1996 code are not considered as this regulation provides a calculation methodology similar to that of 2018.