Fatigue reliability analysis considering corrosion effects and integrating SHM information

Abstract

Fatigue cracking is a common problem facing steel bridges. S-N curves have been adopted in design specifications to offer guidance on fatigue design of these bridges. Structural health monitoring (SHM) techniques can provide reliable information on stress states at fatigue-prone details using strain sensors, thereby circumventing complex theoretical analyses. When corrosion is present, simply relying on SHM information obtained through the monitoring period may not be sufficient to reliably estimate the damage incurred by corrosion-enhanced fatigue as corrosion is a long-term process and the time-variant effect of corrosion on fatigue needs to be determined. In this paper, time-variant analysis is used to estimate the reliability of fatigue-prone details at the coped region of a transverse diaphragm in a tied-arch bridge. Stress histograms obtained based on SHM information associated with this case study are utilized to establish the distribution of the original effective stress. Finite element analysis is conducted for (a) determining the spatial adjustment factor (SAF) to adjust the stress range obtained at the location of strain sensors, and (b) assessing the effect of corrosion on the effective stress range. The reliability analysis results show that for the fatigue details investigated in this case study, corrosion has a significant effect on the fatigue reliability and, therefore, should be considered in the life-cycle management of fatigue-prone details.