Dynamic Vehicle Model for Accommodating Fatigue Based on Axle Load Effects in Orthotropic Steel Bridge Decks

Vehicle-induced fatigue is a primary contributor to the formation of cracks on orthotropic steel bridge decks (OSDs). Currently, simplified fatigue vehicle models are often employed in bridge design specification to estimate fatigue damage. However, these models are constructed based on specific spatial and temporal traffic statistics. This specificity limits the development of a standardized fatigue vehicle model that can be applied in different regions and does not accommodate the varying nature of traffic flow. In addition, the stress characteristics of the OSDs under vehicle loading are not adequately reflected in current models. In this study, an innovative method of fatigue vehicle model generalization is proposed, enabling dynamic adaptation to varying traffic conditions. By analyzing the influence surfaces of four typical segments, traffic loads are subdivided into load spectra for three types of axle groups, with equivalent weights determined by damage contribution. In this way, a comprehensive 1 + 2 + 3-axle fatigue vehicle model with three types of equivalent axle groups is constructed. Using a 2,000-m-class suspension bridge as a case study, the robustness of the model is confirmed by analyzing four sets of simulated traffic flow and influence surfaces. The generalizability of the model is verified, and the consistency of the fatigue models is achieved in different traffic conditions.