Numerous wrought-iron bridges can be found in the French railway network. Since most of this architectural heritage was built during the second half of the nineteenth century, these old riveted structures have been in service for over 100 years and need an adapted maintenance policy. This paper, done in collaboration between the University of Brest (France) and the National Society of French Railways, presents the French railway network, its wrought-iron riveted bridges and the different scales used to analyse their mechanical behaviour. Once these are established, the paper presents an experimental strategy carried out to identify the behaviour of a riveted constructional detail under quasi-static and cyclic loadings through the manufacture and testing of double-shear hot-riveted specimens. The tested assemblies were fabricated from the recovered material from the demolished bridge over Adour River (France). The tests showed an important scatter on the mechanical behaviour of the riveted wrought-iron specimens (for both tensile and fatigue tests). This was mainly attributed to material and process parameters. A static loading scenario was proposed, and the fatigue tests were statistically analysed and the results compared to data found in the literature.

Among more than 25 000 bridges and viaducts in the French railway network, more than 2000 metallic bridges have been in service for over a century, and they need adapted measures for their maintenance. Due to the increase in rolling speed and axle load, the understanding of the behaviour of this type of connection becomes of utmost importance. In order to understand better how old bridges behave, a specific aggressiveness index has been defined, and it enables comparison of the effects of different rolling stocks on the mechanical behaviour of stringers. This index has been determined for different French historical standard trains. For these calculations, a set of real iron stringers has been considered, including different periods of construction, different spans and different inertias. Since fatigue is one of the main phenomena to take into account in order to extend the safe service life of metallic bridges, a fatigue design criterion has been considered. Regarding historical calculation methods, an allowable fatigue stress has been chosen using the Societé Suisse des Ingénieurs et des Architectes fatigue curve, assuming Δσ c = 80 MPa. The method for determining the allowable stress in stringers presented in this paper shows a good agreement with the National Society of French Railways historical inventory of repairs.