ABSTRACT
Fatigue cracks in steel bridges can lead to catastrophic failure and cause significant risks to public safety. These cracks can grow, propagate, reduce the structure maximum design capacity, and ultimately lead to a sudden failure. Fatigue cracks in steel bridges are primarily induced by the cyclic loading from constant traffic loads over time. Therefore, monitoring fatigue on steel bridges is essential to ensure structural safety. Operational modal analysis (OMA) is a non-destructive testing technique that can be used to monitor fatigue-induced damage through changes in modal parameters. When the fatigue crack grows the stiffness of the beam will reduce. This study implements OMA on a simply supported steel beam with changing stiffness. The natural frequencies and mode shapes of the beam are obtained through OMA, and combined with a model to predict the stress/strains at any point of the structure. The case study shows how maximum stresses and the natural frequencies that are affected by the crack growth are varying due to changes in stiffness. The result demonstrates that by combining OMA with fatigue assessment, the risk of fatigue failure in steel bridges can be significantly reduced.
