Fatigue reliability evaluation of existing railway steel bridges based on the structural health monitoring

In this paper, the structural health monitoring (SHM) system of the Nanjing Yangtze River Bridge (NYRB) is briefly presented first. The system comprises a total of approximately 150 sensors, including accelerometers, strain gauges, displacement transducers, temperature sensors, weigh-in-motion sensors, anemometer and seismograph etc, installed permanently on the bridge. Since the fatigue damage contains a considerable amount of uncertainty, reliability-based method is a more reasonable than deterministic for existing bridges. The development of a probabilistic model to evaluate fatigue damage of existing bridges is the objective of this paper. The limit-state equation is derived and uncertainty associated with all the basic random variables is quantified. Using the advanced first-order second-moment (ASM) and Monte Carlo methods, the reliability index and corresponding probability of failure calculated with the stress-time history data recorded by the SHM system.