Devoid of its marble veneer the book is naked and vulnerable

Characterized by his immense stage wall, the ancient theatre of Orange is the only of the West to have retained its original through two millennia configuration. Classified world heritage of Unesco, the monument is today alive, allowing each summer 45,000 spectators at the famous "Chorégies" and 200,000 visitors in the year, but it is a monument at risk. Devoid of its marble veneer, the book is naked and vulnerable. Violent winds (mistral), weather, thermal amplitudes (75 C) are stretched Roman masonry built under Augustus, thirty-five years before our era. The admirable façade of 112 metres long, which Louis XIV was told that it was the most beautiful wall of his Kingdom, short inexorably to ruin. "Under the giboulées of March 1995, it was raining stones on all sides, the streets and on the stage," said Xavier Magnin, Director of Office of the Mayor.

To the risk, the municipality becomes aware of the urgency of intervention. Mission is given to the Chief Architect of historic monuments Didier Repellin find the parade. "How to protect the great wall yesterday dressed in marble, now in the State of ruin" How to stop disorders that are growing ", questioned the man of art.

First step, the campaign of purge launched in 1996 balance by 30 tonnes of debris removed by hand, some reaching approximately 20,000 modénature and décor elements stored. "The work has been protected until the middle of the 19th century by the small houses backed on the wall of scene from the middle ages, said Didier Repellin, and their demolition between 1828 and 1852 revealed dangerously thinned lower portions.". As the Roman Theatre was a medieval village before being promoted monument by the emergence of heritage thinking and return to the scene to the modern era.

Undermined the basis by the occupation, gnawed at the top by erosion, the expensive wall to Louis XIV place therefore his salvation in the restitution of a cover of scene, "only possible solution for effective protection in the time after little convincing tests of mineralization of the stone and repointing of all kind, concludes architect, except to undermine the authenticity of the monument by reconstructions". In addition to the analysis of the State of the wall, it is requested a summary study of historical data in the event of a restoration of the roof scene, under the system of origin and in the light of the proposals advanced in the 19th century. Many traces, empochements and bloodletting, attest to the presence of this roof which burned in the fourth century, with the adjacent stones.

If its configuration and its constitution remain a mystery, his return appears as the best way to protect the wall, including side scene, where ornate face is particularly degraded and vulnerable. Incidentally, the roof has the advantage to accommodate theatrical equipment by sparing the ancient and to improve the acoustics of this place to its first destination.

In support of it, Didier Repellin excavated different sketches of its predecessors, the first contained a roof caissons (Caristie, 1856), other tense structures of a Velar. Restoration campaigns by Daumet (1873-1891) then Formigé father and son (1920-1960) leave the question of the outstanding roof. Too many unknowns remain leading Didier Repellin towards "a contemporary solution keeping the former and the mind", without claim to historical reenactment.

The contribution of technology

On this working hypothesis in 1999, the Office Happold established a typology of profiles of roof varied materials, up to carbon fiber, with, for guidance, "sticking to the old templates and protect to the maximum the ancient elements". Finally, heritage and technical constraints have dictated the choice of a solution of steel, with a main beam anchored in the upper part of the parascenia (sidewalls) relieved in the 19th century, therefore no impact on the ancient stones. The definition of the metal work was then somehow failing in the Office of studies associated with SRN adventure in January 2005. This specialist of the stained-glass Windows, including rail, has drawn a girder of triangular section consisting of tubes welded and intersected 18 transverse beams arranged in ridges, welded partly low and relieved by draughts in part high. The truss support system combines the suspension girder sealed boxes of support slipping (stainless steel/Teflon) in end of the frames to an optimal allocation of efforts on these heterogeneous masonry and the two walls. Roof plan defined by this structure fits precisely between walls whose arase it receives a couvertine lead. It consists partly skylight, an intercalary acoustic canvas and a Velar stainless steel mesh, only visible from the stands to the Saint-Eutrope Hill. Materials used and the book contemporary resolution remove any ambiguity on the identity of this reflector forming roof. "Without contradicting the quest for lightness, everything has been sized with coefficients of safety increased by 50," commented Nicolas Cheval, architect engineer in charge of the project in SRN, and tested in a wind tunnel at Nantes by the CSTB maquette and prototype.

Market structure in June 2005, the company awarded Eiffel (Eiffage group) is currently in a calendar tight five months between the manufacture of the main beam in five sections in Maizières-lès-Metz and the delivery of the work June 21 three days first repetition of the "Chorégies" 2006. Highlight of the site, lifting by two cranes of the beam Assembly ground intervened on April 19. Subsequent editing of the plagues and other elements of frame and cover required the establishment of a general decking under the beam, 32 metres in height. A point of view available to the participants in the professional visit week last technique for the use of steel (Otua), tomorrow reserved only the theatre technicians who will operate on two gateways innervating the roof to deploy theatrical equipment by the Office. Technology and heritage mix to keep alive the ancient monument.