Fatigue Life Assessment of Existing Motorway Bridge

The aim of this paper is to provide a fatigue-life assessment of an existing composite steel-concrete bridge within Switzerland. The Venoge bridge is a 219 meters length, four spans, four girder composite bridge, situ-ated on the Geneva-Lausanne Swiss motorway. Stress response influence lines at fatigue critical details are characterized with a refined three-dimensional (3-D) finite element (FE) model that takes into account the ef-fective transverse load repartition and the cracking of the concrete slab; the model is further validated using strain gauge measurements. Real traffic simulations are run to get the effective traffic histograms on the bridge. Weigh in Motion (WIM) data from the Denges station (1km from the bridge) are used as input for the simulations. The effective slow lane position over the bridge section is taken in account and future traffic in-crease is considered. The fatigue failure probability of the bridge at a critical location under the long-term ef-fect of highway traffic is calculated by defining a limit state function for fatigue reliability analysis. The re-sults show that fatigue is not a concern for the Venoge bridge, even though particular attention has to be paid to future change in traffic lane configurations which could require re-consideration of the fatigue critical de-tails.