Sunday, April 30, 2017

San Luis Obispo County, California Bridges: Salinas and Estrella River Bridges

July 2016 (35.7532, -120.6893) Salinas and Estrella River Bridges
We studied several Salinas River Bridges in our survey of Monterey County. We drove past another Salinas River bridge just south of the border in San Luis Obispo County (on our way to the coast). The River Road Bridge (49C0444) across the Salinas River is an eight span prestressed box girder bridge on single column bents that was built in 2005. The bridge is composed of 145 ft long spans for an 1150 ft long bridge without any skew or curve.

The Salinas River is usually a narrow channel surrounded by a broad floodplain and so the River Road Bridge was designed to be long enough to span the floodplain. This bridge carries traffic from the east into the town of San Miguel just north of Paso Robles.
Continuing south we followed the Estrella River (a tributary of the Salinas River) until we reached two bridges that carry State Route 46 traffic just west of Paso Robles. These are prestressed, 6-span, box girder bridges that were built in 2012. Note that the Estrella River Bridges have stone decorations on the wing walls, the railing, and on the column flares.
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Sunday, April 23, 2017

Monterey County, California Bridges: Bridges Near the Town of Bradley

July 2016 (35.80806, -120.85556) Nacimiento Lake Drive Bridge
I wanted to acknowledge a few bridges that we missed in our survey of Monterey County. The Nacimiento Lake Drive Bridge (44C0009) over the San Antonio River is a single lane Pratt truss bridge (with a steel deck) that was built by the Jones and Laughlin Steel Company in 1921. Note the guides on the deck to keep vehicles from banging into the truss members. Photos of details and modifications to the truss provided by Craig Philpott are on the Bridgehunter Website.

State Highway 101 is carried over a county road on the Jolon Road Bridges (44 0009R/L) in Bradley. The parallel bridges have three span haunched T beam superstructures and were built in 1936.
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Sunday, April 16, 2017

Monterey County, California Bridges: Pfeiffer Canyon Bridge South of Big Sur

February 2017 (36.239, -121.775) Pfeiffer Canyon Bridge (44-0060)
Readers may recall my mentioning that Highway 1 is slowly sliding into the sea. I've shown several examples of roads that have been turned into bridges to step over these slides. However, in February a bridge (the Pfeiffer Canyon Bridge (44 0060) on Highway 1) began sliding downhill and this part of Highway 1 is now closed.
The Pfeiffer Canyon Bridge was a three span, reinforced concrete, continuous box girder bridge on single column bents.
The bridge was built in 1968 and it got a seismic retrofit in 1996. However, what was done to protect this bridge from earthquakes wasn't enough to prevent it from moving once the ground that supported it started to slide downhill.
The trouble and expense of keeping Highway 1 open is perfectly illustrated by this bridge damage. The heavy rains caused accelerated sliding of the fragile slopes. There are several locations of road closure due to slides on Highway 1 on both sides of this bridge.
The California Conservation Corp completed a trail for residents to get around the damaged bridge which was removed in March (see photo below).
A new 300 ft long, single span, steel girder bridge has already be selected as a replacement. The long span will allow the bridge to step over the slide. The girders are already being fabricated and the new bridge will be completed by the end of September. Photos and videos of the damage and the bridge demolition are available from Caltrans and also on YouTube.
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Sunday, April 9, 2017

Bridges of Lyon, France: Ponts de la Gare Lyon/Saint Exupéry

September 2016 (45.722, 5.073) Gare Saint Exupéry
I couldn't leave Lyon without taking some photos of Calatrava's beautiful Aeroport Gare de Lyon/Saint Exupéry. This station allows people to take a train to and from the airport. The airport was named after the children's book author and aviation pioneer who was born in Lyon.
In Calatrava's conceptual sketches for this project he imitates a human eye as well as the head and the flight of a raptor. The station has such a large vertical space that Calatrava even drew the air currents that travel through his structure.
He uses steel for the soaring main structure and concrete for the train platforms on each side. Perhaps it's the bizarre nature of the modern world that there is a barefoot pianist as well as machine gun carrying soldiers inside, both of whom are largely ignored by the public.
Caltrava's use of concrete reminds me of the factories and stadiums of Pier Nervi.
Since this is a blog about bridges, I also took some photos of the pedestrian bridge that carries people from the train station to the airport.
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Sunday, April 2, 2017

Bridges of Lyon, France: Aqueducts of Ancient Lyon (Lugdunum)

September 2016 (45.7270, 4.7813) Aqueducts of Ancient Lyon
The Roman Empire was adept at bringing water into their cities. Two thousand years ago Lyon was Lugdunum and the city is still surrounded with ancient Roman artifacts for transporting water into the city (and for removing sewage). In the map below, we can see how the aqueduct descends from the Massif Central into Lyon.
The aqueduct is surprisingly decorative. A layer of red brick is placed at every meter of elevation perhaps as a way of determining the height. Not only are there arches longitudinally along the aqueduct but also transversely on every pier. Some of these transverse arches are filled in and some remain open. The aqueducts must have been very attractive when they were first built with stones arranged as diamond shapes on the surface. This arrangement is called opus reticulatum (network) according to my copy of 'Guide to the Aqueducts of Ancient Rome.' These diamonds were actually pyramid in shape when they were new. According to the Guide 'aqueduct' is an English word without a Latin counterpart (the Romans referred to them as arcuationes or arcades).
Besides the arches, an aqueduct includes walls for the lower portions as well as tunnels through the hills. In fact, the aqueduct at Lyon is famous for having several well-preserved syphons, with pipes that allow the water to descend and then rise again close to its original elevation.
The Roman Aqueducts vary greatly in style across Europe and the Middle East. Readers can compare the aqueduct in Lyon with a photo of the aqueduct at Caesarea in Israel from my blog of January 27, 2009. The people of Lyon seem to have learned how to live beside all of the history that surrounds them. Where the aqueduct blocks a road it is removed while the rest of the aqueduct remains intact. Lyon is surrounded by so much Roman history that it has been designated a world heritage site by UNESCO.
Still, these ancient structures appear to be quickly disintegrating and probably won't last another 2000 years. Readers interested in learning more about the aqueducts of Lyon can find many well-written articles on the Internet.
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