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Terenez bridge Pont de Térénez
File:Terenez Bridge 02.jpg
Coordinates	48.271211°N 4.262836°W / 48.271211; -4.262836
Locale	Crozon
Characteristics
Design	Cable-stayed bridge
Total length	515m
Height	100m
Longest span	285m
Location

Terenez Bridge is a 515 meters long road bridge that is located between Landévennec and Rosnoen, Finistère, France, connecting the Brittany mainland in the northwest of France with the Crozon peninsula. The steel cable-stay supported superstructure is curved in plan and the unique geometry of the two pylons each forms the Greek letter λ (Lambda). The main span of the Terenez Bridge is 285 m and the the two pylons each reach a height of around 100 m. As an aesthetically innovative structure that plays a decisive role in public transportation, Terenez Bridge is a work of structural art.

Design and Construction Process

The bridge was designed by architect Charles Lavigne and consulting engineer Michel Virlogeux. The project was commissioned by Centre Expérimental de Recherches et d'Etudes du Bâtiment et des Travaux Publics (CEBTP) and co-contracted by VINCI Construction France, Campenon Bernard TP, GTM Génie Civil et Services, and Sogea Bretagne. Wind analysis of the structure was performed by Centre Scientifique et Technique du Bâtiment. The total cost of the construction was estimated to be €35,000,000.

Structural Analysis

Main article: Cable-stayed bridges

Somewhat similar to suspension bridges like Golden Gate Bridge and Brooklyn Bridge, cable-stayed bridges like Terenez Bridge use steel cables to transfer loads from the bridge deck to the towers. However, cable-stayed bridges actually are very different from suspension bridges in principles and method of construction. In a suspension bridge, the long cables are the primary load-bearing structures that are mainly responsible for the function of the bridge; for a cable-stayed bridge, the pylons form the primary load-bearing structures. For a bridge span of medium length, like that of Terenez Bridge, a cable-stayed design is optimal from both structural and economic perspectives. Since the cables of Terenez Bridge will not be exerting large horizontal tensile forces on the anchorages, construction of the bridge does not require excellent soil conditions. The deck of a cable-stayed bridge will also be stiffer than that of a suspension bridge, and therefore deformations of the deck under live loads are generally smaller. In addition, construction of a cable-stayed bridge will be simpler since the structure can be built by cantilevering out from the pylons.

• Difference between types of bridges
• 
  Suspension bridge
• 
  Cable-stayed bridge, fan design
• 
  Cable-stayed bridge, harp design

Although Terenez is designed with an asymmetric form, observation of its cross section shows that tensile loads in cables are transferred to the top of the towers in a rather symmetric manner. The top of each pylon is, in fact, located above the center of the deck’s cross section, and cables are evenly distributed on both sides of the tower. Each pylon seems like a giant man standing inside the Aulne River with his legs spread out and steel cable arms holding the deck of the bridge. The “giant man” also directly supports vertical loads flowing down from the deck onto his “lap”. With both of the towers located on the same side of the bridge deck, it actually is reasonable to create a curved deck to stabilize the overall structure in the horizontal direction.

Qualification as Structural Art

Main article: Structural Art

Works of structural art are typically defined in terms of the 'Three S's': the science, social and symbolic meanings of the structures. Terenez Bridge satisfies the three criteria.

The conservative nature of structural engineering restricts designers from experimenting with bizarre forms, and thus it is uncommon for a civil engineering structural designs to experiment with special artistic features like those of Terenez Bridge. With curved deck spans and asymmetric cross sections, this cable-stayed bridge seems completely different from bridges commonly seen. Successful collaboration between architects, engineers, and contractors have made it possible for Terenez Bridge to perform outstandingly from both engineering and artistic aspects. The steel cables and concrete pylon structures safely transmit gravity loads and wind loads to the ground. Unlike stable yet inefficient structure such as the Forth Bridge located in the Firth of Forth, the simple structure of Terenez Bridge displays an economically optimized use of construction materials.

The total construction cost of Terenez Bridge was €35,000,000. The installation of this road bridge across Aulne has provided convenient transportation and promoted economic and cultural exchanges between Brittany and Crozon. It is also noted that the structure also helps preserve and enhance natural environment and wildlife species in the Valley of the Alder.

Further reading

• De Miranda F., et al., (1979), "Basic problems in long span cable stayed bridges", Rep. n. 25, Dipartimento di Strutture - Università di Calabria - Arcavacata (CS) Italy, (242 pagg.) September 1979.

• Walther, Rene (1999). Cable Stayed Bridges (2nd ed.). Thomas Telford. ISBN 0727727737. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)