PSI - Issue 84

Vittorio Palma et al. / Procedia Structural Integrity 84 (2026) 1318–1325

1325

performance method and 26 tendons (about 65%) with the intermediate-performance method, indicating that robust risk-based decisions can be supported by partial but targeted information. More generally, inspection planning for post-tensioned systems should explicitly account for diagnostic performance, expected defect severity, inspection costs, and failure consequences within a structural reliability-based Bayesian decision framework. For larger tendon populations, the optimal inspected fraction is expected to decrease as the informational benefit saturates under sampling without replacement. 5. Conclusion This study presents a Bayesian decision-analytic approach for planning special inspections of post-tensioned bridge tendons, aimed at quantifying and reducing epistemic uncertainty in the tendon condition while supporting risk efficient inspection decisions. Tendon defectiveness is modelled as a discrete system state in a finite population and updated through Bayesian inference using a hypergeometric-binomial formulation that accounts for imperfect detection via sensitivity and specificity. The updated system-state probabilities are then incorporated into flexural reliability assessment by Monte Carlo simulation. Inspection planning is formulated as a pre-posterior decision problem, in which the inspection sample size is selected by maximizing the value of predicted information relative to the prior decision baseline. The results show that the benefit of inspections typically exhibits an initial regime, where a limited number of inspections yields substantial informational gains, followed by a saturation regime with diminishing marginal returns. Accordingly, the optimal inspection effort depends on diagnostic performance, inspection costs, and failure consequences, rather than on prescriptive rules or fixed sampling ratios. Overall, the proposed framework provides a quantitative basis for cost-effective and reliability-consistent inspection strategies for post-tensioned bridge systems. Future work will extend the approach to multiple failure modes and system-level reliability, incorporate spatial heterogeneity and clustering of defectiveness, and investigate defect-severity models informed by explicit degradation modelling and operational constraints. Parametric studies on tendon population size and span length will further support transferability and the development of guidance for practical applications. References BDI, Arezoo Imani, BDI, et al. 2025. «Advancing Condition Assessment of Post-Tensioned Ducts Using Ultrasonic and Impact Echo Data». E Journal of Nondestructive Testing 30 (5). https://doi.org/10.58286/31106. 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