Service-life prediction of deteriorating concrete bridges

Experience has demonstrated that highway bridges are vulnerable to damage from environmental attack, such as alkali-silica reaction, corrosion, and freeze-thaw. To make rational decisions in a life-cycle cost perspective, reliable prediction of the service life of deteriorating highway bridges is necessary. To obtain an accurate insight into this problem, time-variant reliability methods have to be used. The application of these methods in the performance and safety assessment of deteriorating structures is relatively new. In this study, the reliability of reinforced concrete highway girder bridges under aggressive conditions is investigated using a time-variant series system reliability approach in which both load and resistance are time-dependent. Monte Carlo simulation is used to find the cumulative-time system failure probability. An existing reinforced-concrete T-beam bridge located near Pueblo, Colo., is investigated. The effects of various parameters such as variabilities in dead and live loads, live load occurrence rate, strength loss rate, degradation initiation time, resistance correlation, and number of girders under attack on the time-variant bridge reliability are studied. The results can be used to better predict the service life of deteriorating reinforced concrete bridges, and to develop optimal lifetime reliability-based maintenance strategies for these bridges.