<p>In October 1944, a 20.9m span footbridge was built in Brussels (Belgium) across the Canal Charleroi-Brussels: it was the first applications of prestressing by post-tensioning to a concrete bridge-type structure in Belgium, and one of the earliest worldwide. The tendons consisted of high strength steel wires 5mm in diameter anchored in so-called « Sandwich » anchorages, a system of post-tensioning developed in Belgium from 1942 onwards by Professor Gustave Magnel with the Blaton-Aubert Company. This system will be extensively used in Belgium during the next 20 years, and was also applied to build the first prestressed concrete bridge in the US in 1949 (Walnut Lane, Philadelphia). The dead weight of the footbridge is 60 tons. Some years ago, the local Authority had decided that this footbridge had to be replaced. This 1944 prestressed concrete footbridge was obviously an engineering heritage structure, but preserving it in use somewhere else raised many problems in terms of reliability. The authors therefore proposed to the Authority to study in depth this historical structure in order to collect information that could be useful to assess the durability and actual carrying capacity of concrete structures built with the same prestressing technology in the period 1945-1965, many of them still standing. The paper presents the main findings from the load testing of this footbridge, that took place in October 2018, and the results from the characterization of its materials.</p>
Old riveted railway bridges are part of the cultural and technological heritage in many countries. The assessment of the actual behaviour and the remaining life of these structures is a key economical factor in the management of these bridges. This evaluation should take into account the evolution of the traffic loads, which have constantly increased since their construction, and a realistic estimation of the fatigue life derived from representative experimental tests. This study deals with the fatigue behaviour of riveted assemblies with specimens prepared from materials sampled in two old bridges: a railway bridge over the Adour river (France) built in 1862-1864 and the Stahringer bridge (Germany), constructed in 1895. Because all assemblies are not subjected to the same loads, this research concentrates on the influence of the stress ratio R on the fatigue behaviour. In order to quantify this influence, a comparison between the Basquin linear model and the Weibull model is performed. It is shown that a formula proposed in a recent study to determine the fatigue strength for an arbitrary value of R is not suitable in the high-cycle fatigue regime.
The paper will illustrate the contribution of research into Construction History in condition assessment or residual carrying capacity situations for three old types of concrete constructions. We will address: -the problem of assessing the actual carrying capacity of "Hennebique" reinforced concrete type beams with their characteristic reinforcement system, widespread in many countries before the First World War.-the replacement of the external post-tensioning tendons within a hollow box girder railway bridge built in the early 1960s with the "Blaton-Magnel" anchorage system developed in Belgium from 1941 onwards, and used until the early 1960s, in Belgium and abroad.-the structural assessment of thin concrete hyperbolic paraboloid shells, which were highly popular with architects and engineers in 1950s-1960s.
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