Contracting Authority
Inter-municipal Syndicate of Boundary Developers
Paula Castro, Céline Cerisier, Vincent Dominguez, Toma Dryjski, Bertrand Potel, Louis Ratajczak, Daniel Vaniche
Carlota Guillen
Segex
Metallic carpentry
Text description provided by the architects. At the con uence of the Loing and the Seine, the overpass constructed by the DVVD architecture, design and engineering agency blends perfectly with its remarkable setting in the heart of Seine-et-Marne, a favourite site for walkers in the Ile-de-France. This panorama inspired numerous studies, sketches and paintings by the famous impressionist artist Alfred Sisley in the late 19th century. !00 years later, the spirit of creativity is still at large here, as evinced by the clean- cut metal arch, 67 metres in length, which connects the municipalities of Saint-Mammès and Veneux-les- Sablons.
First conceived early in the 20th century, the installation of an overpass has been much discussed since, with a fear in many quarters of the consequent spoiling of the site. It was by the particular consideration of this mandatory respect for the existing setting that the DVVD agency was able to win the competition organized in 2010 by the Inter-municipal Syndicate of Boundary Developers [Syndicat Intercommunal des Maisons du Bornage]. Given a free choice of location, the architects sited their project at the margins of the Seine, at a location where the Loing is relatively broad, and where the banks are free of road tra c and urban development. This siting also allows the lines of force delivered by the landscape to be exploited, and to enjoy the fruits of reciprocal enhancement.
Caressing both banks, the overpass unfurls freely, on the left bank towards the Veneux-les-Sablons tow path, and on the right bank towards the car park of the Saint-Mammès market. Its arched form is more clearly suggestive of a water crossing than a girder or trellis structure, while establishing a strong visual link between the two towns. The structure is supported on foundations which are independent of the banks, which themselves are reinforced over a length of 10 – 15 metres: on the Saint-Mammès side, the existing quayside, of cement construction but a ected by cracks, has been consolidated by the installation of a beam; on the Veneux-les-Sablons side, a bundled structure of willows and timber piles, combined with geotextiles, improves the mechanical strength of the bank, hitherto comprised of back ll covered with herbaceous vegetation and a few woody plants. The symmetrical design of this structure is comprised of two slender load-bearing arches, with a deck suspended from reinforcements which are supported by the arches. Manufactured and painted at the Viry workshops in Remiremont (Vosges), the latter were transported in three sections respectively and welded in situ. The curvature in elevation is matched by the curvature of the decking plane: the decking is expanded in the central section to form a panoramic viewpoint over the river. Over and above its function as a crossing, the overpass serves as a landmark, a destination for walkers and an exceptional observation point.
The overpass is distinguished by the restraint and elegance of its geometry, which render it virtually transparent in the landscape, without impairing the impression of freedom and exposure to the sky which are symbolic of the con uence of the Loing and the Seine. This sensation is attributable to the lightweight pro le of its superstructure, constructed of high- performance steel, for the optimization of structural behaviour. The arches are designed in rectangular sections, reconstituted by welding, constant in the area above the decking and of variable inertia in the lower sections, aring to form a bedding structure at ground level. The reinforcements which support the decking are also reconstituted by welding in a variable inertia arrangement, and are suspended from the arches.
The overall form of the structure is resistant to bending, but also to torsional loading associated with winds or the application of imbalanced dynamic loads to the decking. Dictated by the proximity of the naval shipyard, the air draft has been extended up to 6 metres, reducing the visual impact of the structure while enhancing the dynamism of its design. Broadly-spaced cradles (at intervals of 5.40 metres) are suspended below the arches, and carry H-section girders for the formation of the decking structure. In the interests of convenience, natural water drainage and anti-slip properties, the latter is formed of rot-proof timber planks in a crosswise arrangement. The architects from DVVD summarize the design as follows: “In spirit, the project as a whole is distinguished by details, which we have endeavoured to keep clean and simple, allowing the intent of the project to take precedence ”.