Assessment of heritage value and resistance of a 1935 Vierendeel steel railway bridge

From 1923 to 1960, a significant number of “Vierendeel” steel railway bridges have been built in Katanga and Belgium. In the town of Mechelen, three railway lines cross the Mechelen-Leuven canal, offering a distinctive illustration of this type of application. Two of these are 1953-built bridges; suffering severe deterioration, they were refurbished in 2021–2022. The third and oldest bridge (L25), erected in 1935, was found to have numerous cracks in the vertical members and to exhibit significant corrosion damage in auxiliary parts. As a result, doubts about this bridge capacity to carry the required loads developed. The authority responsible for the care of monuments encourages the conservation of these historic structures. An extensive experimental and numerical examination was used to analyze the material characteristics, load carrying capacity and fatigue strength. An independent committee provided guidance on the heritage value of the bridge, reviewed critically the results of the analyses, issued an opinion on the origins of cracks and proposed the refurbishment of the bridge. This paper summarizes the findings of this committee.