Reliability based fatigue assessment of existing motorway bridge

This paper provides an original framework for the fatigue reliability analysis of a road bridge; the framework is applied to the Venoge bridge, a composite steel-concrete bridge within the A1 Swiss highway. Two critical details are selected by inspection: a longitudinal weld attachment and a cover plate welded attachment. Weigh in Motion (WIM) data from Denges station (1 km far from the bridge) and a refined three-dimensional Finite Element (FE) model of the bridge are used to get realistic time-stress response at two critical locations. The fatigue failure probability of the bridge at two selected locations under the long-term effect of highway traffic is calculated for a 100 year-design life. The original contribution consists in computing the failure probability as joint probability of two events: (1) the exceeding of the constant amplitude fatigue limit (CAFL); and (2) the critical fatigue damage accumulation. The results show that fatigue is not a concern both for the longitudinal attachment detail and for the cover plate detail.