Parametric Study and Fatigue Life Evaluation Using Effective Notch Stress Approach for Rib-to-Deck Welded Joints in Orthotropic Steel Decks

Abstract

Fatigue cracking of orthotropic steel decks is a long-standing problem in bridge structures. The notch stress approach has been applied to the fatigue evaluation of steel structures. Parameters of the notch stress approach in this study include the notch type, notch radius, and level and slope of the fatigue design curve. First, a finite-element model (FEM) for the rib-to-deck welded joint using the notch stress approach is built and influences of notch types and notch radii on the notch stress are analyzed. Then, based on the fatigue test results of rib-to-deck welded joints, notch stress fatigue classification levels under different notch types and notch radii are studied. The notch stress fatigue design curves for the rib-to-deck welded joints are recommended. Finally, a multiscale model of Jiangyin Bridge is built. Based on the recommended notch type, notch radius, and notch stress fatigue design curves, the fatigue life of rib-to-deck welded joints of Jiangyin Bridge is evaluated using the notch stress approach and compared with that using the nominal stress approach and the hot-spot stress approach. The results show that the intersecting notch stress is higher than the tangent notch stress, and the notch stress decreases with the increase of the notch radius. For a weld toe tangent notch with a radius of 1 mm (0.04 in.), the fatigue class 206 (FAT206) fatigue design curve with a slope of 3.5 is recommended to be used. The fatigue class 225 (FAT225) fatigue design curve should be applied to a weld toe tangent notch with a radius of 0.75 mm (0.03 in.). A comparison of Jiangyin Bridge fatigue life evaluation results show that the bridge fatigue life calculated by the notch stress approach is lower than that calculated by the nominal stress approach and the hot-spot stress approach. When the vehicle load is 50% heavier than the fatigue standard vehicle load, the bridge fatigue life calculated by the notch stress approach is only about 5 years.