Fatigue Assessment of Slender Long-Span Bridges: Reliability Approach

Abstract

It is well known that wind loads result in wind-induced buffeting of slender long-span bridges. Traffic also frequently exists on a slender long-span bridge simultaneously throughout its service life, which can affect the dynamic behavior of the slender structural systems. The nature of the vibration of a slender long-span bridge is further complicated by the dynamic coupling effects among the bridge, wind, and traffic. Fatigue damage is an important consideration in the serviceability performance of slender long-span bridges that typically experience cyclic or repetitive loads, such as those induced by wind and traffic. Stochastic wind and traffic loads, dynamic interaction, and fatigue accumulation for a slender long-span bridge essentially vary over time, with uncertainty contributions from each. Therefore, a reliability-based fatigue assessment model, which can rationally consider the combined load effects from wind and traffic as well as the associated uncertainties, is needed to provide an accurate estimate of reliability for fatigue. Initially, a scenario-based deterministic fatigue analysis model is developed. A typical year is categorized into several representative scenarios of traffic and wind conditions. After identifying the duration for each representative scenario in a typical year, a cumulative yearly fatigue damage factor can be predicted by superposing the cumulative hourly damage factors for all representative scenarios. On the basis of the scenario-based deterministic analytical model, the framework of the reliability-based fatigue damage assessment for a slender long-span bridge is further developed. Finally, an illustrative example for a prototype bridge is conducted.