Intensity and location of corrosion on the reliability of a steel bridge

Visual inspections generally represent the initial step of the safety assessment of bridges. In particular, steel railway bridges are particularly prone to corrosion phenomena. Therefore, visual inspections provide the geometric characterization of the conservation state of each structural member, in particular, the size reduction originating from the progress of corrosion. Nonetheless, the geometric definition of corrosion is not directly related to structural safety, depending on the damage location. The paper quantifies and discusses the uncertainties in the safety assessment of trussed bridges associated with the unknown effect of damage location on the stress distribution, given initial knowledge of the number and intensity of damaged members. Is it possible to preliminary assess the structural safety for typological structures without knowing the effect of damage location on the stress re-distribution? This paper discusses these aspects by randomly simulating damage scenarios in a finite element model of a historic steel bridge. The model, validated against the experimental modal parameters and measured deflection under train transit, is used for estimating bidimensional fragility curves as a function of the damage intensity and the number of damaged members. Finally, a safety domain can support the preliminary safety assessment of typological steel railway bridges.