Reliability-based service-life assessment of aging concrete structures

Concrete structures may be affected by aging or changes in strength and stiffness beyond the baseline conditions assumed for design. These changes may impair the safety and serviceability of the structure, and should be considered as part of the process by which a structure is evaluated for continued future service. Methods are being developed using structural reliability principles to evaluate time-dependent reliability of reinforced or prestressed concrete structures. These methods enable the impact on safety and serviceability of uncertainties in loading conditions, structural strength, and strength degradation due to aggressive environmental stressors to be assessed qualitatively. Parametric analyses show that the reliability is sensitive to the choice of initial component strength and strength degradation models. Less sensitivity is found to correlate component strengths within a system. Identification of the critical components before performing system reliability analysis is important in reducing the size of the analysis. The role of periodic inspection and maintenance in enabling a target reliability level to be met over a period of continued service also is considered.