Civil Engineering Works

Hyère River Road Bridge

Cognin, France

The Cognin Bridge 1 | The Cognin Bridge
Certified Bois des Alpes™ wood was used for the construction of the bridge. Small, local companies were commissioned with the processing of the wood, helping to overcome the bias against their qualifications and capacities.
Design: The bridge over the Hyère River in the city of Cognin is the longest wooden road bridge in France. The innovative structural system is based on trussed girders combined with reinforced concrete for the surface, a unique approach in France. In order to use the naturally gnarled wood of the regionally available Douglas spruce, a large diameter was required for the 40-meter-long girders.

Wood: The project is the result of a 2010 agreement between the Agglomeration Community of Chambéry Métropole and Bois des Alpes, aiming to emphasize environmental and social criteria in the procurement process of public bodies. Some 224 m³ of Alpine wood were used. The use of wood allowed for local companies to be commissioned with the ambitious project.

Traceability/Value Chain: Two local sawmills delivered the Alpine wood to the local glued laminated timber production company. It was then processed by a small company, assisted by Eiffage, one of the largest French construction companies. The project made a substantial contribution to the qualification and utilization of the local companies (new machines, experience with long girders).
Across the river 2 | Across the river
During construction 3 | During construction
Below shot 4 | Below shot
Geländer 5 | Geländer
Bearing 6 | Bearing
Across the river 7 | Across the river
Across the river 8 | Across the river
Below shot 9 | Below shot
9m
Basic information
Year of Completion |  2016
Investor |  Agglomeration Community of Chambéry Métropole (FR)
Architecture |  Les Pressés de la Citée (Jacques Blanc), Grenoble (FR)
Structural Engineering |  BG Ingénieurs Conseils, Aix-les-Bains (FR)
Construction Time |  7 months
Gross floor area |  520 m²
Construction Costs (netto) |  1 250 000 €
Awards |  Coup de cœur du public Prix régional de la construction Bois Auvergne-Rhône-Alpes (2017)
Photography |  Pictures 1-5: Bois des Alpes, Chambéry (FR)

Technical aspects
Concept |  Glued laminated timber (Douglas spruce) for supports (40 m | 1 m | 54 cm) and railings; reinforced concrete for surface; load capacity: 2 busses/trucks
Woodworking |  Pierrefeu, Vernoux-en-Vivarais (FR); construction company: Groupe Eiffage TP (FR)
Origin of Timber, Certification |  PEFC-certified alpine forests in Les Bauges (La Biolle, Savoie) and Vercors (Saint-Martin-d'Uriage, Isère) (FR)
Traceability of Timber |  Yes, guaranteed through the use of certified Bois des Alpes™ wood
Forestry Value Chain |  All companies named (see internet database)


Energy Efficiency


Cross section (railing) Cross section (railing) Cross section (bearing) Cross section (bearing)



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