Railroad bridge fatigue life estimation using the probabilistic method and new fatigue resistance for riveted details

Existing fatigue life evaluation procedures are often over-simplified and do not account accurately for the uncertainty in applied load and fatigue resistance of steel railway bridges. Simplified calculations and conservative assumptions often lead to significant reductions in estimated life that indicate older structures ceased to be functional decades ago. Fitness for service assessments that utilise probabilistic methods and that are informed by and consistent with detailed physical inspections of the structures provide a more accurate assessment of the expected life of bridges and can be used to establish improved bridge inspection programmes. This paper focuses on development of probabilistic, risk-based methods and models for assessing steel bridge Fitness for Service (FFS) and remaining life. The fatigue resistance models developed in this project are calibrated, validated, and verified against all available and relevant fatigue test results. For some bridge types, these models provide remaining fatigue life estimates that are double and sometimes even triple those obtained by using existing simplified methods. In this paper, a probabilistic method is demonstrated on two, riveted deck plate girder spans that exceed 100 years of service and are currently located at the Facility for Accelerated Service Testing (FAST) near Pueblo, CO.