Assessment of a thin-web girder bridge subjected to distortion-induced fatigue utilising a vehicle-bridge dynamic interaction methodology based on the Eurocode FLM 4

Nowadays, many welded bridges are approaching their design operation life, with various fatigue-related damages becoming increasingly evident. On the other hand, the extensive inventory of highway bridges often necessitates the assessment of the remaining service life of aging or defective structures, to support the decision about whether to replace or reinforce them. In this context, there is a growing need for reliable methods to predict the fatigue life of welded components and accurately assess their long-term performance under fatigue loading. Thus, a computational tool called VBI (Vehicle-Bridge Interaction) was developed in MATLAB and comprising an interface with the finite element program ANSYS. It is important to emphasize that, while current design codes evaluate welded joints for fatigue life using primarily the Nominal Stress Method (NSM), this research utilises the Hot-spot Stress Method (HSM) for a more accurate definition of stress. In order to illustrate the application of the proposed analysis methodology, the details of a Finite Element (FE) global numerical model of a typical simply supported steel-concrete composite highway bridge are presented. Different damage scenarios based on the standard vehicle traffic prescribed by EN 1991-2: 2021 (Fatigue Load Model 4) are simulated with the proposed methodology considering the sub modelling technique combined with coarse FE models. An interesting and important structural detail mainly subjected to distortion-induced fatigue is investigated through sub modelling, thus allowing a more realistic approach to evaluate fatigue issues on thin-web girder bridges with typical web-gap details.