Sunday, December 31, 2017

Bridges of Mexico: Tlapan Viaduct in Mexico City

September 2017 (19.2389, -99.1468) Tlapan Viaducto
After leaving Coajomulco, we continued north on Highway 95D to the newly constructed Viaducto Tlapan in southern Mexico City. The government really must like these elevated expressways (maybe because of the tolls they collect) and almost every highway in Mexico City now has a viaduct in the median. I wrote about the construction of these viaducts and the documentary film they inspired in a previous blog.
When we stopped at the viaduct to take photos, the highway police came over to talk to us. They were very nice (as were all the police and soldiers that we met) and they allowed us to continue shooting.
 We asked the police if this long viaduct had been damaged during the recent earthquake. They said they did a complete inspection following the earthquake and didn't see any damage. The one thing they did notice was that water began leaking out of the expansion joints at the ends of the spans after the earthquake. I think the reason for this is that they never completed the drainage system on the viaducts for some reason. Water that had accumulated inside the box girder supertructure was finally able to escape due to shaking during the earthquake.
The viaduct is composed of spans that cantilever over single column bents with a seat for the next span at the end of the cantilever. In this way a 20 km long viaduct is created (see photo above). This simple pattern is modified as required due to a variety of structures crossing the highway (see photo below).
I also wanted to mention the beautiful views on the east side of the highway at this location. Mexico City is at an elevation of 7000 ft with volcanoes encircling the city such as Volcan Guadalupe shown in the photo below.
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Sunday, December 24, 2017

Bridges of Mexico: Highway 95D Overcrossing in Coajomulco

September 2017 (19.0323, -99.2057) Overcrossing in Coajomulco
Heading back to Mexico City we stopped to photograph an overcrossing on Highway 95D. Although there's nothing special about this bridge it has a handcrafted look that's different from the cookie cutter appearance of most expressway bridges in the United States.
This bridge is composed of precast slab elements for the superstructure and wall elements for the substructure. The walls at the abutments have stone masonry wingwalls and the pier wall has pegs at the top to act as catchers. The bridge is painted white to complete its handmade appearance.
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Sunday, December 17, 2017

Bridges of Mexico: Highway 438D Overcrossing near Santiago Atzitzihuacán

September 2017 (18.8268, -98.6038) Highway 438D Overcrossing
Driving west out of Puebla on Highway 438D we came upon an overcrossing near Santiago Atzitz Huacan. It's a 3 span precast girder bridge on tall single column bents. The bents are located in deep cuts on the highway shoulders. This is because the highway itself is deeply cut into the surrounding hills. The engineers must have carefully calculated the volume of cuts and fills needed to built this road.  Note the vegetation growing in the expansion joints between the spans. All of the rain and debris caught in the joints must make a fertile environment for any seeds that find a home there.
This seems to me like a very common type of bridge in Mexico, perhaps as a result of having to build highways through the many mountain ranges. I saw much taller bridges during a previous trip through Colima, Mexico. Note that part of the cut around the south bent has sloughed off, probably as a result of the September 19th earthquake. However, no damage or even signs of movement were seen on the columns or on the simply supported spans. 

In the photo below we can see they are excavating to make the roadway wider. I wonder if they will also have to lengthen the bridge to span wider shoulders or additional lanes?
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Sunday, December 10, 2017

Bridges of Mexico: Bike Path on Periférico Ecológico in Puebla City


September 2017 (18.9791, -98.2206) Ciclovía del Periférico Ecológico de Puebla Ciudad
Driving south on Calle Periférico Ecológico in Puebla City I noticed a bright blue bike path in the median. Instead of an elevated bikeway like the one in the median of Hermanosa Serdán Blvd. the Ciclovía del Periférico Ecológico is 'at grade' but with elevated structures about every half mile to get on and off of this limited access expressway (see photo below).
These elevated structures include a narrow 'T' shaped superstructure on single column bents (the overcrossing), a 'C' shaped superstructure on squat four-legged trusses (the main ramp), and on/off ramps that zig-zag along the sides of the expressway.
The median has to be wide enough to accommodate bicyclists continuing their ride on each side of these elevated structures (see above). Since the resulting median could have been used to provide two extra lanes of traffic one might wonder if it's really worthwhile. Perhaps it's because I'm an avid bicyclist that I think the answer is yes!
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Sunday, December 3, 2017

Bridges of Mexico: Xonacatepec OC across 150D in the State of Puebla

September 2017 (19.0674, -98.1181) Xonacatepec Road OC
Driving west on 150D we approached a very strange looking overcrossing carrying Xonacatepec Road across the expressway. Note the diagonal tower with cables on the east side of the bridge supporting the two northern spans. You can't see from the photo (shot while hanging out of the passenger window) but there is an identical tower on the west side supporting the two southern spans. The diagonal towers positioned asymmetrically from each other must provide torsional and bending moments. Perhaps the asymmetrically positioned cable towers are to compensate for the torsion due to the highly skewed bridge?
A year ago there were no service roads and the overcrossing had fewer spans (see above). Looking at a later photo shows the new overcrossing being built (shown below). Note the tower that will support the cables sitting on the north shoulder (in the photo below). There's another tower sitting on the south shoulder on the west side of the bridge.
Looking at a photo of the bridge deck (below), we can see that this wide bridge was able to handle traffic during construction by working on half the bridge while allowing traffic to ride on the other half. Once that half was rebuilt, traffic was moved onto it while the other half was rebuilt.
One last photo (below) of the overcrossing through the (dirty) rear window. You can clearly see the diagonal towers on opposite ends and opposite sides of the bridge. What I find particularly interesting is that the engineer was allowed to design such an unusual structure on an interstate highway. I think California's bridge engineers may be too cautious and conservative to design something so unusual.
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Sunday, November 26, 2017

Bridges of Mexico: 150D/190 Interchange in the State of Puebla

September 2017 (19.2556, -98.98.0862) 150D/190 Interchange
Bridge engineers in the State of Puebla have a much larger toolbox than engineers in the State of California. For instance, I can count the number of cable-stayed bridges in California on the fingers of one hand but in Puebla, cable-stayed bridges are even used as connectors on interchanges.
In the Google Earth photo above a six span cable-stayed connector with three sets of towers is on our left (carrying traffic to downtown Puebla) while a seven span cable-stayed connector with only two sets of towers is on our right (carrying traffic to Perote and Veracruz).
These are unusual cable-stayed bridges. The connector carrying traffic to downtown Puebla has towers on the sides of the piers supporting the 1st and 2nd and the 5th and 6th spans. The 4th and fifth spans are supported by towers on a multicolumn bent in the median of Highway 150D (shown in the Google Earth photo above). Even more unusual is the connector carrying traffic to Veracruz, which only has two tower bents and so the 1st, 4th, and 7th spans are not supported by cables (see Google Earth photo below). Also, the connector shown below has two big outrigger bents supporting the center span. The connector shown above has a fancy sign with colored balls near the abutment.
A stunning feature of this interchange is that it sits on the flank of La Malinche, an enormous volcano. in fact, on a clear day you can see volcanos all around the interchange; part of the Trans-Mexican Volcano Belt. On the two days we spent in Puebla it was overcast but you can see La Malinche clearly in the first Google Earth photo and also at the top of the Google Earth photo below (the interchange is identified with a yellow pin). Puebla's elevation is over 7000 ft above sea level.
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Sunday, November 19, 2017

Bridges of Mexico: The Hermanos Serdán Blvd. Bicycle Viaduct in Puebla City

September 2017 (19.09170, -98.2296) Viaducto de Bicicleta de Puebla Ciudad
On September 24th I went with the Geotechnical Extreme Events Reconnaissance (GEER) Team to investigate the September 19th Mexico Earthquake. The group was mostly interested in looking at landslides and soil settlement but I did manage to photograph a few bridges.
Puebla is a modern city and a showcase for Mexican culture. Among its many attractions is an elevated viaduct for bicyclists (and pedestrians) in the median of Hermanos Serdan Blvd. This structure is 7.6 km long and just one of several bike paths in the city. The photos above show the elevated bicycle roundabout at Hermanos Serdan Blvd and Avenue Francisco Villa in Sanctorum.
What's particularly nice about the viaduct is the diversity of structures. The roundabout is a steel truss on steel truss piers but there are also cable-stayed structures (shown above), long stretches of steel stringers on oddly crossed steel piers (shown below), as well as arches (see bottom photo). The one unifying feature is that all the structures are steel and they're all painted white. 
In the next couple of months we'll look at new and old bridge structures in Puebla, Morales, and Mexico City that I photographed between stops to study earthquake damage. Interested readers can also see a similar set of photos that I took following the 2003 Colima, Mexico Earthquake.
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Sunday, November 12, 2017

Mendocino County, California Bridges: Highway 1 Bridge across Ten Mile River

September 2017 (39.54917-123.76278) Ten Mile River Bridge
Ten Mile River Bridge (10 0274) is an eight span prestressed concrete box girder bridge that was built in 2009. It replaced a timber deck truss bridge that had been built at this site in 1954 (see photo below, courtesy of the Mendocino County Historical Society).
With the tight radius curve at the south end of the bridge along with it's streamlined appearance and the dramatic landscape of water, sky, and rugged hills, this bridge provides some visual excitement. Note the open barrier rail and sidewalk, which is appropriate for a bridge along the coast.
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Sunday, November 5, 2017

Mendocino County, California Bridges: Highway and Railway Bridges across Pudding Creek

September 2017 (39.4586, -123.8078) Pudding Creek Bridges
A highway bridge and a railway bridge (now converted to a pedestrian bridge) cross Pudding Creek a few hundred yards from each other. The Highway 1 Bridge (10 0158) is an eight span, precast concrete channel beam bridge that was built in 1959. The bridge was seismically retrofit in 1996. Large diameter piles were placed at the ends of enlarged bent caps. This is called a 'superbent' and is a commonly used seismic retrofit to more firmly anchor a bridge into the ground. The simply supported channel beams (upside down bathtub sections) were securely anchored to each other and to the bents. It looks like at some point a water line was attached to the west side of the superstructure.
At the end of the 19th century Union Lumber built a 10 mile long railway to bring redwood logs (that were being deposited into Ten Mile River) to their mill at Fort Bragg. More information on the bridge, the railroad, and the lumber company is available on the Mendocino Model Rail Website.
Pudding Creek Trestle is a 515 ft long wooden bridge that was built by the Union Lumber Company in 1915. The railroad bridge became a truck bridge when the railway was converted to a haul road in 1949. The logging operation ended in the 1970s and the truck bridge became a pedestrian bridge in 2007.
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Sunday, October 29, 2017

Mendocino County, California Bridges: Highway 1 Bridge across the Noyo River

September 2017 (39.42694-123.80667) Noyo River Bridge
Continuing north on Highway 1 we arrived at the Noyo River Bridge (10 0298). This is a three span continuous, prestressed concrete box girder bridge. It has a 325 ft long main span and it was built in 2005. It's an odd looking bridge with columns that are recessed below the soffit to imitate a bridge on bearings. The columns have a stout shape with extra concrete that (hopefully) will spall off to allow the ductile core to undergo large displacements without breaking during an earthquake.
There was a fight between Caltrans and the community about various aspects of the proposed design of the bridge.  The bridge was to be located extremely close to commercial buildings along the bank and it doesn't look like a typical coastal bridge. One resident, Vince Taylor, fought Caltrans on the solid barrier rail that was originally proposed for the bridge. He provides a history of his hard-fought victory on the internet.
Tony Phillips provides an excellent pictorial history of the six different bridges that crossed the Noyo River near its mouth during the last 150 years. The first structure was a drawbridge that was built in 1861. Subsequent bridges were truss bridges until the current haunched box girder bridge was built.
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