PSI - Issue 84

Federica Di Criscio et al. / Procedia Structural Integrity 84 (2026) 1023–1030

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2. Framework The proposed framework establishes a practical and quantitative pathway from defect-based inspection data to a mechanically-based time-dependent safety assessment of corroded RC and PSC bridges. A schematic representation of the methodology is shown in Fig. 1; the following subsections describe each component in detail. 2.1. Data collection and defect indices assessment The first step (Step 1) of the framework consists of collecting all relevant information from bridge census forms, including structural typology, static scheme, construction materials, year of construction, and location. Specifically, the latter information is essential to define both the seismic demand and the environmental exposure conditions, which are required to model the corrosion-induced degradation process. In parallel, defect survey forms are examined to extract qualitative information on the deterioration observed during visual inspection. These defect indicators are translated into quantitative mechanical parameters representative of the underlying corrosion mechanisms. For RC members, the adopted defect index is the percentage loss of steel cross-section,  % , which provides a direct measure of reduction in mechanical capacity. For PSC elements, the maximum pitting depth, p max is used, which can be reliably measured in situ, once/when exposing/accessing the reinforcing bar. These parameters represent the input for both the degradation and capacity models adopted in the subsequent steps of the framework.

Fig. 1. Schematic illustration of the simplified procedure for evaluating the time-dependent structural safety of corroded bridges.

2.2. Corrosion rate model In Step 2, the corrosion phenomenon is described through a model involving the initiation, propagation, and structural deterioration phases (Tuutti, 1997). Its time evolution is obtained by adopting established mechanistic models for each phase (e.g., Fick’s law for chloride ingress, Faraday’s law for propagation, and statistical models for pitting; DuraCrete, 2000; Pugliese et al., 2022; Cui et al., 2018; Vidal et al., 2004). This task has two complementary objectives: (i) convert inspection-derived qualitative defect indices into consistent quantitative descriptors of degradation; and (ii) enable a predictive assessment of future deterioration to support the definition of time-dependent safety curves and their possible update after subsequent inspections. Once a corrosion level corresponding to an observed defect state is identified, mechanical material properties are modified by degrading the relevant stress–strain relationships according to experimentally and numerically calibrated models. For RC members, the equivalent reduction of steel constitutive law properties – in terms of strength, stiffness, and ductility capacity – is evaluated