Evaluation of the contact area of lorry tyres in Eurocode’s fatigue load model 4 (FLM4)

Fatigue considerations dominate the design of new, innovative steel bridge decks. Weighing bridge deck al- ternatives requires representative values for contact areas and contact stress distributions of the tyres of heavy vehicles. Fatigue load model 4 in the Eurocode EN 1991-2 (FLM4) provides tyre contact areas together with a set of axle loads. The literature survey presented herein shows that the length of the contact area in FLM4 is too large.The consequence of using a more realistic – i.e. shorter – tyre contact length together with a non-uniform contact stress distribution that is observed in practice, is that the contact stresses increase. As a result, the load effect and the fatigue life of some bridge deck details reduce, as is shown by the analyses presented in this paper. A method is proposed for determining an updated tyre contact area for the FLM4 Eurocode model, leading to a more realistic fatigue damage analyses.