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

September 2017 (19.0635, -98.1063) 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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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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