Fatigue assessment of fillet weld in steel bridge towers considering corrosion effects

Field inspection shows that the fillet weld in steel bridge towers may be subjected to corrosion and fatigue loading simultaneously. To ensure the structural safety in the service life, corrosion effects on the fatigue life of the fillet weld in steel towers were investigated in this study. A prediction procedure of the fatigue life of the weld was firstly proposed based on the fracture mechanics method and verified by the test results. Three types of corrosion effects, pitting corrosion at the initial crack, pitting corrosion near the initial crack, and the corrosion fatigue crack growth were considered. Three corrosion levels were also defined under different corrosive environments. By taking the Third Nanjing Yangtze River Bridge as an example, a modified finite element (FE) model integrated with the local shell model was established to analyze the stress variation of the fillet weld in steel towers. Based on the stress influence lines, the maximum stress range was obtained under the vehicle load. Fatigue assessment of the fillet weld was finally performed considering the corrosion effects. The result shows that the remaining fatigue life of the fillet weld was greatly reduced by the corrosion pits at the initial crack or the interactions of corrosion and fatigue. However, since the tensile stress range was small in the steel bridge towers, the fatigue performance of the fillet weld considering the corrosion effects can still meet the requirements of the code specification.