Sunday, October 30, 2016

Bridges of Lyon, France: Passerelle du College across the Rhone River

September 2016 (45.7643, 4.8397) Passerelle du College
The Passerelle du College is a pedestrian bridge that was built to carry children to school. It was almost completed when a cable swage broke, sending workers into the Rhone where 8 people drowned. After the accident, the bridge was quickly completed (in 1845). During WWII, the bridge was determined to be a danger to the retreating German Army and one of the piers was destroyed. The bridge was carefully rebuilt after the war (in 1945).
The Passerelle du College is a three span bridge with suspension cables and stays supporting the main and back spans and additional cables without stays to help support the main span (see above photo).
Looking west across the Rhone, we can see that the piers are protected by tiny islands that have trees and perhaps a garden? The closer pier has an inscription on top commemorating its reconstruction after WWII.
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Sunday, October 23, 2016

Bridges of Lyon, France: Pont Morand across the Rhone River

September 2016 (45.7686, 4.8397) Pont Morand
We continued downstream along the Rhone a few hundred yards until we arrived at Pont Morand. Because many of the bridges across the Rhone were destroyed during WWII, the river now has many modern structures. Similar to the Pont Winston Churchill, the Pont Morand (named after the architect who designed an earlier bridge) has a functional shape that matches the moment diagram of the bridge.
The Pont Morand is a three span 187m (614 ft) long bridge that was built in 1976. Like the Pont Winston Churchill it is composed of two prestressed concrete boxes with steel braces between them to support the deck during construction. The piers have a large shear key on the north side that seems to only function as a support for the tall light posts.
The Pont Morand that was built after the war was replaced to accommodate construction of the Lyon Metro (subway) that goes under the Rhone at this location. You can see the stairway to the subway stop on the bridge aprons at each end of the bridge in the photo above. It's strange that so many of these bridges carry roads that stop at the ends of the bridge. All of these obstacles make traffic pretty awful in Lyon, which is why so many people use the Metro. I took a train during rush hour and it was as crowded as a Tokyo subway.
There are tall quay walls at each end of the bridge and so the abutments have narrow seats up against the subway vents. Note that at the abutments the Pont Morand is more like two separate bridges, Also note the runner going by (just as I snapped the picture). The east bank of the Rhone has more exercise fanatics than I've seen in most U.S. cities.
In the photo above we can see the Pont Morand superstructure resting on its haunches.The Pont Morand has a very simple appearance without the parabolic curves that we typically associate with haunched girder bridges. The roof of the Lyon Opera House can be seen above a building across the river.
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Sunday, October 16, 2016

Bridges of Lyon, France: Pont de Lattre de Tassigny across the Rhone River

September 2016 (45.7722, 4.4395) Pont de Lettre de Tassigny
Continuing downstream along the Rhone we arrived at the Pont de Lettre de Tassigny. This bridge was built in 1956 to provide access to and from the Croix-Rousse Tunnel across the Rhone.  Jean de Lattre de Tassigny was a famous French general who fought in WWII for both the Vichy and the Free French Government and he also fought and helped get the US involved in Vietnam.
The Pont de Lettre de Tassigny is 150m (500 ft) long and 25m (80 ft) wide. The superstructure is composed of precast I girders supported on two column bents. The bridge has a 'T' shape with ramps coming off the bridge along the west bank. When the tunnel was renovated in 2013 the bridge was modified to include bike lanes.

Sunday, October 9, 2016

Bridges of Lyon, France: The Pont Winston Churchill across the Rhone River

September 2016 (45.7786 degrees, 4.8426 degrees) Pont Winston Churchill
After looking at a railroad bridge and a pedestrian bridge we'll take a look at a car and truck bridge across the Rhone. The Pont Winston Churchill is a three span prestressed concrete box girder bridge that was built in 1982. It's the latest in a series of bridges built at this location, which included the Pont Marshal de Castellane that was built in 1862 by lashing boats together. You can still see the piles from the previous bridge in front of the pier in the photo above. Note how clear and blue the river is and also the uprooted tree that was carried by the river and is now against the far pier.
The current bridge has seven traffic lanes and broad sidewalks. The seventh lane is a turning lane that switches from the east end to the west end to accommodate the complicated intersections at the ends of the bridge (see photo below).

The Pont Winston Churchill is a continuous structure on simple supports. It acts as a long beam that is supported on bearings at two piers and at two seat-type abutments. We can see the large expansion joint devices that connect the ends of the bridge to the roadway in the photo above. Another interesting thing about the superstructure is that it is composed of two box girders with steel bracing between the boxes to support the deck (see top photo).
The Point Winston Churchill has a streamlined shape along the superstructure, along with attractive railings, light posts, piers, and abutments. The bridge was named after the English Prime Minister who was instrumental in bringing about the liberation of France during the Second World War (there's also a boulevard named after Franklin Roosevelt).
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Sunday, October 2, 2016

Bridges of Lyon, France: Passerelle de la Paix across the Rhone River

September 2016 (45.7868 degrees, 4.8545 degrees) Passerelle de la Paix
A few hundred yards downstream from the Viaduc SNCF is the Passerelle de la Paix (Footbridge of Peace). The bridge connects Cite Internationale (east of the Rhone) to Saint-Clair (west of the Rhone). The idea of a peace bridge was to bring intercultural harmony between the two communities since Cite Internationale is French and Saint Clair has a large immigrant population.

The bridge project was first proposed by the Metropolis of Lyon (Grand Lyon) in 1994. A design competition was held and eventually won in 2009 by Dietmar Feichtinger (Architects) and Schlaich, Bergermann, and Partner (Engineers). Construction began in 2012 and the bridge opened in 2014.
The 220 m (710 ft) long bridge is composed of two cantilever space truss sections. The bridge supports a timber deck on the top and another timber deck to the side with an asymmetric tubular steel structure. The two decks meet in the middle to form an 8 meter (26 ft) wide public space.
The foundations were constructed at each riverbank while the bridge was being assembled offsite. Then it was brought onsite by two barges and set in place (see photo below). Note the suspension structure that was used to support the bridge before it was placed on the foundations (photo below by Michael Zimmerman).
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