Reliability, redundancy and risk as performance indicators of structural systems during their life-cycle

Structural reliability, redundancy and risk as performance indicators are expected to change over time due to structural deterioration and time-variant loadings. The objective of this paper is to investigate the effects of (a) the deterioration in structural resistance, (b) the type of system modeling, and (c) the correlations among the failure modes of components on the time-dependent reliability, redundancy and risk of structural systems. A representative three-component system is used to demonstrate a general approach for studying these effects. This approach is then applied to an existing highway bridge in Colorado. The bridge is modeled using different types of systems with the consideration of two extreme correlation cases among the failure modes of the girders. An event-tree model is used to assess the direct, indirect, and total risk associated with the failure of component/system due to corrosion and traffic loads. The results reveal the importance of realistic system modeling and time effects in the quantification of reliability, redundancy and risk.