Time-dependent reliability of a prestressed concrete bridge incorporating residual prestress and material properties updates for service limit state assessment

This paper presents a time-dependent reliability assessment that integrates experimental data with Bayesian updates and is applied to a 66-year-old prestressed concrete box-girder bridge. Non-destructive and destructive tests were performed to evaluate its actual serviceability condition. The tests included on-site prestress measurements, material evaluations, a serviceability-proof load test, and refining structural response and boundary conditions using monitoring system data. These tests offered crucial updates to assumptions based on the as-built drawings. The bridge’s structural reliability for serviceability is studied by comparing two approaches: (1) a prior reliability analysis based on traditional Eurocode methods to estimate prestress losses; and (2) a posterior reliability analysis incorporating on-site measurement for residual prestress and material properties. A Bayesian update was performed to refine the estimates of concrete strength and prestress losses and improve the accuracy of the reliability assessment. The results showed that updating material properties doubled the reliability index relative to the initial analysis. Similarly, updating residual prestress measurements via strand cutting and saw cut methods increased the reliability index from 1.75 to 2.84 and 2.35, respectively. These findings highlight the need for on-site prestress measurements and time-dependent reliability analyses to accurately assess the serviceability performance of ageing bridges accounting for long-term degradation.