Mexico's Bridges: Puente Atenquique I (5)

One last look at Puente Atenquique I, the very active Volcán de Colima, and the older, taller, and inactive Nevado de Colima.

This is a very beautiful area. A cloud forest (Sierra de Manantlan) with an abundance of the world's flora and fauna is nearby. There are many quaint villages with cobblestone streets around ancient churches. And there are modern two-lane highways with 250 ft tall, incrementally launched bridges.

Mexico's Bridges: Puente Atenquique 1 (5) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Mexico's Bridges: Puente Atenquique I (4)

Another view of Puente Atenquique with the inactive Nevado de Colima in the background. More information on this volcano and the highly active Vulcon de Fuego de Colima is available on Wikipedia.

Bridge engineers now have a variety of construction tools for building long, tall structures.

Bridges can have both segmentally constructed substructures and superstructures. They can use prefabricated girders or the girders can be cast-in-place using advancing forms. Suspension bridges, cable-stayed bridges, and long prestressed girder bridges can all be built segmentally. Truss bridges can also be built segmentally, although fewer are being built today. Incrementally launched bridges can also use precast or cast-in-place segments.

I wonder if it's possible to build an incrementally launched arch bridge?

Mexico's Bridges: Puente Atenquique l (4) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Mexico's Bridges: Puente Atenquique I (3)

Another incrementally-launched post-tensioned box girder bridge built in 1989 by Mexpresa on Route 54D in Colima Mexico.

The bridge seems to be in pretty good shape, although I wonder why those tendons/rebars are sticking out of the side of the box?

I imagine that the columns were segmentally constructed. A certain length of column forms were put together, the concrete is poured and cured, and then the forms were raised and additional concrete poured above the cold joint. This process was repeated until the column was completed.

I wonder if the entire rebar cage is first assembled.  It may be difficult to assemble and support a 250 ft tall rebar cage while the concrete is poured, but it's certainly possible.

The box girder superstructure was assembled just like the superstructure on Puente Atenquique II. The concrete was poured in units between a quarter to a half of the span length and then pushed out from the abutment. A steel nose was attached at the end to provide support from the next pier. The hydraulic jack must be well anchored to be able to push a bridge all the way to the other abutment. I think the development of hydraulic jacks has 'revolutionized' the art and practice of bridge engineering.

Mexico's Bridges: Puente Atenquique I (3) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Mexico's Bridges: Puente Atenquique I (1)

Rio Atenquique is quite meandering, and so about a mile north of the Puente Atenquique II it crosses under Puente Atenquique I.

I don't know why the sign for Puente Atenquique I shows a segmentally-constructed bridge with haunched girders. Most likely, the sign painter wasn't that knowledgeable about bridges. However, it's actually another incrementally-launched bridge like Puente Atenquique II. It only has seven spans though. It's a 320 m (1050 ft) long bridge, 75 m (246 ft) above the river, and with a 10.5 m (34.5 ft) wide deck.

Note the enormous road cut at back of this photo. Puente Atenquique is just beyond the cut. We have seen that the engineers who designed Route 54D always cut the top of the rise and then build a bridge over the subsequent valley. This makes the highway a little easier to drive, especially for someone (like me) who drives a Prius.

Mexico's Bridges: Puente Atenquique I (1) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Mexico's Bridges: Puente Atenquique II (4)

A look at an abutment on Puente Atenquique II. I would guess that this is not the abutment from which the superstructure was launched, because the soffit looks like it rode over eight piers and the end looks like it carried the steel guide.

I would guess that the square blocks on the front of the abutment stem wall are decorative although its possible they could have supported some equipment while the bridge was being launched. The shear keys seem slightly ineffective since there's such a big space between the girder web and the keys. The long overhangs would be riding on the top of the keys before the box girder ever got near it. Still that might be sufficient to prevent the superstructure from moving very far transversely.

The back wall looks like it is right up against the superstructure which can't be right, unless this is an extremely warm day, which I'm pretty sure isn't true.

The superstructure is supported on special  bearings with a teflon or stainless steel top surface that allows the soffit to slide with a minimum of friction for the 1/4 mile over the piers. This type of bearing is specially designed for incrementally launched bridges. The nose attached to the end of the superstructure is long enough to prevent large cantilever moments when the span is hanging half-way between supports.

Mexico's Bridges: Puente Atenquique II (4) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Mexico's Bridges: Puente Atenquique II (3)

Another view of Puente Atenquique II. It looks like a lubricant was applied to the bridge soffit to help the superstructure slide. There's also stains on the side of the superstructure, perhaps from the bridge launching system. You can see that the bridge is very straight, which must make launching the bridge easier (although I understand that bridges with horizontal curves are also built using incremental launching).

Mexico has many incrementally-launched bridges. The company Mexpresa has a website showing some of the incrementally-launched bridges they've built, beginning in 1978 with Puente Rio Tula in Hidalgo.

It looks like the pier closest to the viewer is somewhat stouter than the others, although I'm not sure why. Also, it appears that the bridge was built over a rock quarry. Note that the end of the bridge is at a road cut. The bridges must be at the top of grades and the cut material must be put at the bottom.

Mexico's Bridges: Puente Atenquique II (3) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Mexico's Bridges: Puente Atenquique II (2)

A closer look at the superstructure of Puente Atenquique II on Route 54D in Jalisco, Mexico.

I found this bridge referenced in Structurae. It was built in 1989, it has a 10.5 m (34.5 ft) wide deck, and it was build by incremental launching. We saw this technique used to build the Pont Charles de Gaulle in my blog of April 11, 2009. Although that was a steel bridge, the technique is similar. Box girder segments were cast behind the abutment, cured, and then pushed out with hydraulic jacks. It seems incredible to me that this 1/4 mile long bridge could be pushed out from one abutment!  It must have had a very high camber to have been cantilevered out so far without deflecting below the top of the pier!

A short article on incremental launching of bridges provided by the University of California at Berkeley is available on the Internet.  It looks as though a special nose is put on the end of the superstructure to help it get over the piers.

Note the squat bearings between the top of the piers and the bridge soffit. The superstructure must be able to slide on these bearings as it is pushed out across the canyon. Also note the rebar sticking out of the side of the superstructure. There must be a vertical diaphragm, perhaps at the end of each segment. I imagine each precast segment was pushed out and then post-tensioning tendons were attached to the next piece, which was also pushed out, until a completely post-tensioned superstructure reaches the other side of the canyon.

Mexico's Bridges: Puente Atenquique II (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Mexico's Bridges: Puente Atenquique II (1)

I skipped past a single span bridge (Puente Los Hornos) and another space-truss structure (Puente El Nuevo) to arrive at the incrementally launched box girder bridge,  Puente Atenquique II. It has a continuous nine span superstructure on single column bents and seat-type abutments.

I looked up Atenquique and found that it is a town with a tragic history. Heavy rains in 1955 caused a flash flood that drowned many members of the community as they were attending Mass. It is also the name of the stream that runs under this structure.

The bridge is 83 m (272 ft) tall and 440 m  (1445 ft) long. Like the other continuous superstructure bridges spanning wide canyons on Route 54D, this structure is a single prestressed box girder with long, gull-wing overhangs. A 1445 ft continuous superstructure is extreme long not to have an intermediate expansion joint. The superstructure is supported on sliding bearings that allows it to expand and contract without flexing the very tall piers. The 17 inch thermal movement must be addressed by very large expansion joints at each abutment.

We'll take another look at this bridge tomorrow.

Mexico's Bridges: Puente Atenquique II (1) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.