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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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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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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