Fatigue vulnerability analysis of a historical railway steel bridge

Damage accumulation deriving from load cycles is one of the most important features in the fatigue vulnerability assessment of historical steel bridge structures. Starting from Wohler curves and referring to Eurocodes (Eurocode 3, 1993) and some current normatives (Italian Ministry of Infrastructure, 2008) a vulnerability analysis has been performed for estimating the structure probability to be damaged over time. Steel strength and corrosion depth probabilistic distributions have been discretized in finite intervals, combining them in order to represent all the possible bridge conditions. The performance levels considered in the analyses have been defined as submultiples of the maximum steel strength value for different specific number of cycles that will cause fatigue failure, assessing the produced damage. The adopted procedure has allowed to identify a combined fatigue-corrosion failure probability for each specific train-load and relative number of cycles considered, configuring it as a valuable tool for the assessment, prevention and management of the existing historical steel bridges.