Timeline

Heritage classified

Key figures

Origin and history

The test arch Freyssinet, built in 1909 in Moulins (Allier), is an experimental structure in unarmed concrete designed by engineer Eugene Freyssinet. It was designed to test the behaviour of flat arches (range 1/25) and long-range arches (range 50 m), and was designed to validate a method of compression stripping before the construction of three bridges on the Allier: the Veurdre bridge, the Boutiron bridge and the Châtel-de-Neuvre bridge. The major innovation was the use of a prestressed concrete draught (1,200 steel wires stretched to 2,000 tonnes) to contain the lateral thrusts of the arch, a world first.

The technique developed here allowed Freyssinet to overcome the boundaries of traditional reinforced concrete, subject to cracks under tensile tension. By compressing the bow before removing the hanger (temporary support), it avoided the risk of collapse during the decintration. Although the arch was buried during World War I and then forgotten, its rediscovery in 1993 revealed a remarkable state of conservation. It was listed at the Historic Monuments in 2021, alongside the Boutiron Bridge, only of the three original bridges still standing.

The arch, partially visible today (only the upper part emerges), is located on the former site of a secondary railway station, near the crossing of the streets of Narvik and Lyon to Moulins. Its prestressed shot, buried since 1909, remains inaccessible. This prototype marked a turning point in the history of bridges, foreshadowing the industrial applications of prestressed concrete (patented by Freyssinet in 1928). Later deformations observed on Allier bridges (fluage, withdrawal) also enabled the engineer to refine his methods, such as Freyssinet joints.

The local context was that of a rural department undergoing infrastructural modernization in the early twentieth century. The Allier bridges, commissioned by the General Council, were to link isolated areas while reducing costs compared to stone or cast iron bridges. The collaboration between Freyssinet and the mill entrepreneur François Mercier was decisive in achieving these bold projects. The test arch, though discreet, thus symbolizes the alliance between technical innovation and territorial issues.

Today owned by Moulins Communauté, the monument is the subject of a development project. Its recent listing among the Historic Monuments underscores its heritage importance, both as a material witness to the early prestressed concrete and as a milestone in the career of Freyssinet, the future pioneer of the great works of the twentieth century.

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