PSI - Issue 84

Vincenzo Mario Di Mucci et al. / Procedia Structural Integrity 84 (2026) 521–528

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inherent uncertainties according to Section 3.1. The reinforcement layout consists of 55 longitudinal bars of ϕ 20 mm and 16 stirrups spaced at 100 mm. A deterministic lumped mass of 500 tons, representing the superstructure, was applied at the top of the pier. For illustrative purpose, only the seismic response in the transverse direction is considered for the presented case study. 4.2. Results and discussion: Time-dependent seismic risk and residual life assessment The temporal evolution of seismic risk was quantified through MAFE for the four Damage States (DS1–DS4) defined by Cardone (2014) and benchmarked against the target annual exceedance probabilities ( P t,,LS ) for Consequence Class CC2: Near Collapse (NC) - 5.0×10 -4 , Significant Damage (SD) - 1.5×10 -3 , Damage Limitation (DL) -5.25×10 -3 (Steenbergen et al., 2018). Due to the Poissonian nature of seismic events, for low risk levels typical of structural reliability (10 -3 to 10 -5 ), P t,,LS =1-e -MAFE ≈ MAFE , allowing for a consistent point-in-time performance assessment. The pier’s seismic response was evaluated over six future scenarios ( t=+5,+10,+15,+20,+25, and +30 years), incrementing Q corr for each face in stochastic samples and updating mechanical properties to reflect corrosion-induced section loss, reinforcement reduction, and confinement degradation. Fragility functions and the intensity measure corresponding to 50% probability of DS exceedance S a (T 1 ) 50% are shown in Fig. 3.

Fig. 3. (a) Fragility functions; (b) Sa(T 1 ) 50% .

The risk metric was computed by integrating scenario-specific fragility functions with the site-specific seismic hazard of the case study bridge located in Southern Italy, yielding the MAFE values in Table 1. The time evolution of seismic risk is shown in Fig. 4 (log scale) alongside the target thresholds, enabling a time-dependent reliability assessment. Near-Collapse (DS4) govern s structural safety: at t₀, DS4 -MAFE is below the prescribed limit, confirming compliance with existing-asset criteria, but corrosion drives a rapid increase in collapse probability. Interpolation of MAFE indicates the DS4 threshold will be exceeded in roughly 23 years from now, defining a critical intervention deadline and the end of the remaining service life. In contrast, the seismic risk for Moderate (DS2) and Significant (DS3) damage remains below target levels throughout the 30-year horizon. This behaviour reflects corrosion-induced reductions in steel and concrete ductility, with minimal effect on Young’s modulus; global stif fness is largely preserved, while ultimate displacement capacity decreases. Consequently, corrosion mainly affects ductility controlled collapse mechanisms, making DS4 the governing limit state.