Nowadays, the increased weight and volume of traffic on highway bridges have accelerated deterioration processes, with fatigue induced by dynamic loads standing out as a critical challenge. In this scenario, the emergence of fatigue cracks, resulting from vehicle dynamic impacts, represents a major concern for engineers, necessitating reliable methods to assess the service life and support intervention decisions. This way, this research work proposes an analysis methodology to assess the fatigue performance of steel-concrete composite highway bridges, integrating traffic dynamic effects and the progressive pavement degradation in the dynamic structural response. The methodology develops a computational tool called VBI (Vehicle-Bridge Interaction) implemented in MATLAB and comprising an interface with the finite element program ANSYS, enabling the incorporation of complex finite element models for both the bridge and the vehicles. In this context, different scenarios based on the standard vehicle traffic prescribed by EN 1991-2: 2023 (FLM 4: Fatigue Load Model 4) are generated and adapted to statistical models of Brazilian vehicle classes. This approach allows for diverse truck configurations and weight distributions, reflecting real traffic patterns. The proposed analysis methodology was applied to a 40m span steel-concrete composite highway bridge, where a critical structural detail, mainly subjected to distortion-induced fatigue, is investigated through sub modelling techniques. The results highlight the influence of the dynamic effects and pavement degradation on the service life of the bridge structural components.
