Hyère River Road Bridge

Cognin, France

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).

2 | Across the river

3 | During construction

4 | Below shot

5 | Geländer

6 | Bearing

7 | Across the river

8 | Across the river

9 | Below shot

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)