Fatigue Life Assessment of Suspenders in Tied-Arch Bridges Under Random Traffic Loads and Environmental Corrosion

This study proposes a method for evaluating the fatigue life of tied-arch bridge suspenders by considering the effects of random cyclic traffic loads and environmental erosion. To obtain cumulative fatigue load effects under traffic loadings, a multi-axle single-cell cellular automaton (MSCA) was used to analyze random traffic–bridge-coupled dynamics. Changes in stress amplitude caused by suspender sectional corrosion damage and degradation of suspender S–N curves owing to environmental corrosion were then used to update the relationship between load effect and resistance to obtain the fatigue limit states of the suspenders. To evaluate the dynamic performance and fatigue lives of typical suspenders, a case study involving a basket-type tied-arch bridge was conducted. The results indicated that, under the loading of a typical truck, structural vibration displacement was insignificant but suspender stress was very prominent, especially on the short suspenders. Parametric analysis of the vehicle–bridge interaction revealed that road surface roughness, vehicle weight, and traffic volume significantly affected the dynamic response of the bridge. Under random traffic loads, the shortest suspender experienced the most damage and had a fatigue life significantly shorter than those of the other suspenders. Ignoring corrosion, the shortest suspender fatigue life was 57.8 years; with fatigue corrosion accounted for, however, the shortest suspender experienced fatigue failure owing to cumulative damage after 30 years of service.