PSI - Issue 78

Matteo Tatangelo et al. / Procedia Structural Integrity 78 (2026) 404–411

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provided by EN 1992-1-1 (2004) are adopted, which may eventually be combined. These consist of model a (Fig. 4.b), with vertical suspension reinforcement, and model b (Fig. 4.c), with inclined reinforcement. Both trusses schematize the half-joint, each one providing a resisting mechanism. Note that all rebars nearby the nib belong to one model or to the other, and all the stress paths are not repeated more than once. Therefore, overall resisting force will be equal to the sum of the two models resistance. 4.1. Reliability assessment over time The reliability of RC half-joint is assessed at its 100 th year, considering =0 year known (i.e. year 1972) and as year of first assessment =53 year, and consequently =47 years. This evaluation is then compared with assessments where no monitoring data exists adopting the conservative constant capacity assumption, and also with cases where initial conditions are unknown and therefore = (Fig. 1.c). Once , and are defined then, consequently, is also obtained. The targets reliability indexes referred to the 100 th year of the RC half-joint resulting be equal to 2.8 and 3.8, respectively for ̅ 0 ( ) and ̅ ( ) , which are evaluated in accordance with fib Bulletin n. 80 (2016) for CC3 and = 10.38 m. During construction, materials conformed to C.S.LL.PP 1472/1957, 1547/1965, and 180/1972, with Rck 350 concrete and Fe 38k a.m. steel. On-site checks (Ponzo et al., 2013), however, indicated a concrete compressive strength of 31.15 N/mm² (with a of 25.85 N/mm²). Steel showed a tensile strength ( ) of 375 N/mm² (Verderame, Stella, & Cosenza, 2001), with its characteristic value derived from design documents and experimental studies on period-typical reinforcing bars. Permanent loads on the structure include a 1 of 176.86 kN/m and a 2 of 31.18 kN/m. Additionally, variable traffic loads, incorporating dynamic effects, are calculated based on the load patterns outlined in NTC-18 (2018). These traffic loads are applied over a 15.65 m wide roadway, divided into five conventional traffic lanes with a width of 3.00 m. Moreover, the steel corrosion effect over time is modeled as, resulting in a bar section reduction ( ), expressed as follows (Li & Ye, 2018) = 0.0366 ∙ ∙ ∙ ( − ) (8) where represents the corrosion rate, denotes the corrosion initiation year, while represents the bar diameter. In order to determine the demand and capacity PDFs, according to the basic variables assumed, Monte Carlo simulations is conducted. Note that, in accordance with a time-integrated approach, the basic variables of all the applied loads are assumed constant year-by-year for calculating the demand PDFs. On the contrary, basic variables defining the steel corrosion vary with the time as previously described, for the capacity PDFs. Fig. 5 illustrates the reliability assessment via the Level 2 method for the chosen case study, utilizing the detailed procedure from this research.

a)

b)

c)

CC3 S=10.38m

CC3 S=10.38m

CC3 S=10.38m

Fig. 5. Reliability analysis of RC half-joint. a) =0 ; b) =0 with constant past-capacity; c) =