Monday, November 30, 2009

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.
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Sunday, November 29, 2009

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.
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Saturday, November 28, 2009

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.
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Friday, November 27, 2009

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.
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Thursday, November 26, 2009

Mexico's Bridges: Puente Acatas


Another three-span precast girder bridge on two column bents and seat-type abutments. This bridge is very similar to the previously studied Puente Pialla.

Considerable effort was made to retain the slopes above the road and along the abutments. I like these handmade stone masonry retaining walls. The bridge seems more impersonal.

The deck looks like it is continuous across the three spans. The bridge crosses one of the many creeks (Acatas Creek?) running down the side of the volcanos.

Route 54D is near the base of these volcanos and runs parallel to a large river ( the previously encountered Armeria River?).

It looks like a road veers to the west away from the highway at the end of the bridge. There is a small gully a little west of the bride that drains this road into the creek.

This bridge also has asphalt spread onto the deck. This practice used to be common in California, and was sometimes done by road crews without asking the bridge engineer's opinion. It's even possible that there were expansion joints at the ends of the spans that were covered by the asphalt.
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Wednesday, November 25, 2009

Mexico's Bridges: Puente El Platanar

I just remembered that we had actually left the state of Colima (at the city of Tonila) and we are now in the state of Jalisco, Mexico.

The next bridge on our trip northward (on Route 54D) is Puente El Planatar. It is a three span precast I-girder bridge on two-column bents and seat-type abutments. El Planatar (translated as the banana grove) is a beautiful colonial village a few miles southeast of the bridge.

This bridge crosses over another river canyon. Note how steep the canyon wall is and the white rock layer near the top.  I wonder if that layer is from a large pyroclastic flow that occurred some time in the region's past.

It's an odd looking and not terribly attractive structure. The concrete is badly stained and the columns were built outside of the thin bent caps.  Perhaps a more monolithic structure makes for a more attractive bridge. For instance, I think the recently viewed Beltran and Pialla bridges (with their sculptural forms) are more attractive structures.
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Tuesday, November 24, 2009

Mexico's Bridges: Puente Pialla (3)

A view of an abutment expansion joint at Puente Pialla, a segmentally constructed, two-span box girder bridge on Route 54D in Jalisco, Mexico.

The coefficient of thermal expansion for concrete is 0.000006 units per degree Fahrenheit. This bridge is 158 meters long but it has two expansion joints, so each joint only needs to handle expansion for half the structure. The maximum change in temperature is 100 degrees, so the maximum expansion is 0.05 m or about 2 inches.

This expansion joint looks like it can handle more than two inches of movement. It's made of three steel bars with rubber diaphragms that expand and contract as the bridge changes temperature.

Note that the steel railing is built to slide in and out of a larger diameter tube as the bridge expands and contracts.

The concrete barrier on each side of the expansion joint has been patched. Perhaps the barriers banged together during the 2003 earthquake. That is one of the most common types of earthquake damage.

The expansion joint looks to be in pretty good shape. I believe that the road/bridge crew has been doing a good job patching spalled concrete, keeping the expansion joint clean, and maintaining this bridge. Note that the material on each side of the joint is different than the asphalt father away from the joint. Perhaps the deck close to the joint is being kept free of asphalt? We've stopped putting asphalt on our bridge decks and we try to remove it from our decks whenever possible. There are much better materials currently available to protect bridge decks and that provide the deck with a longer life.
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Monday, November 23, 2009

Mexico's Bridges: Puente Pialla (2)

I'm standing by the south abutment looking north along the side of the box girder superstructure of Puente Pialla on Route 54D in Jalisco Mexico.

From yesterday's photo we know that the road has two lanes of traffic and two narrow shoulders. It looks like the superstructure is just a single box girder with very wide overhangs. The superstructure with its haunched girders has an almost sculptural quality.

I can see some concrete patches, perhaps where there were rock pockets caused by problems vibrating the concrete during the pour.

We've been fortunate to get some good comments from Norrin who knows a lot about Mexican bridges. He said that these long bridges were built as balanced cantilevers, perhaps with some additional support during construction.

I imagine that after the concrete cured, the post-tensioning cables were jacked from both ends of the superstructure, set, and then the abutment backwalls were poured.
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Sunday, November 22, 2009

Mexico's Bridges: Puente Pialla (1)

Continuing north on Route 54D we come to a sign announcing we are about to cross the two-span Pialla Bridge. The Highway Department is justly proud of this large structure. The sign says the bridge is 158 m (520 ft) long and 89 m (292 ft) tall. It looks like another segmentally constructed cantilever structure, similar to Viaduct Beltran. We'll take a closer look at it tomorrow.

By the way, you may have noticed the steep cuts on the sides of the road, which are covered in wire mesh to protect motorists from falling rocks. My experience is that this mesh is quite effective for anything less than a large rockslide.

We are driving along the side of two large active volcanoes, and so the rock is probably cemented tuff or other pyroclastic material. Mexico's Pacific Coast is along a large subduction zone that causes many earthquakes and creates enough pressure underground to melt the underlying rock and cause active volcanoes.
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Saturday, November 21, 2009

Mexico's Bridges: Puente El Tapon

Continuing north from Viaduct Beltran on Route 54D across a narrow ravine on the one span El Tapon Bridge. This is another of those reinforced concrete slabs supported on a metal understructure like we saw on my blog of November 16th. That blog received an interesting comment from Norrin, who said that these truss-like structures haven't performed too well and have even failed.

This bridge reminds me of a prefabricated bridge system like the old Bailey Bridges that could be easily transported and set up in the field. At Caltrans we often use the undercarriages of old railroad cars as temporary bridges. Maybe this system is similar. It looks like it could be used as falsework to support bridge forms when pouring concrete superstructures.

Note the PVC pipe sticking out of the concrete barrier rail. This must be the deck drainage system to prevent the bridge from carrying too much water and possibly hydroplaning vehicles. Usually, we drain the deck with ducts that carry the water through the columns, which is a pain since the columns are already stuffed with reinforcement. Also, the ducts are always getting filled with debris and are hard to clean.

The truck that we see crossing the bridge has a tandem trailer (illegal in California) and it's carrying what looks like an heavy load of bags of cement and rebar cages. This suggests that at least this single-span bridge with its odd understructure was well-designed.
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Friday, November 20, 2009

Mexico's Bridges: Viaduct Beltran (4)


Looking north at the Viaduct Beltran. There appears to be a short pier in front of the abutment.

The superstructure is a single continuous, segmentally constructed box girder, with two long center spans and two short end spans. The superstructure sits on the supports without transferring moment into the piers, which suggests that it was perfectly balanced during construction. That must be why it was built with two piers under the center of the bridge.

I wonder if this long bridge has prestressing tendons? I'm not sure what the longest reinforced concrete box girder bridge is, but this looks past the limit. The haunched girders undoubtedly helps.

I couldn't find any information on this bridge or on the other long bridges on Route 54D. It seems that the many amazing engineering achievements in Mexico get little publicity outside their borders.
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Thursday, November 19, 2009

Mexico's Bridges: Viaduct Beltran (3)

A closer look at the pier walls under the middle of the Viaduct Beltran. Yesterday's photo was taken on a hill that hid the bottom of these piers, but in this photo we can see their full height and also that they are flared at the bottom.

The abutments are socketed into the canyon walls and there is a very tall pier in front of the south abutment. The bottom of this tall pier is hidden in a ravine. 

In this photo, we get a good view of the haunched and foreshortened superstructure and of the shear key at the top of the pier. This is the first of several long, tall bridges as we travel north on Route 54D through southwestern Mexico.


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Wednesday, November 18, 2009

Mexico's Bridges: Viaduct Beltran (2)

Another view of Viaduct Beltran. There's a parking lot along Route 54D with a path and a viewing platform under the bridge.

Note how the superstructure rests on two short piers near the middle of the bridge. The haunched girders must have been carefully shaped to ensure the superstructure is balanced on these two central piers. I imagine that the bridge was constructed by cantilevering outward in both directions from this fulcrum.

Also note the key at the top of the piers, which was meant to provide transverse stability to the superstructure. It seems more likely that the tiny key would break, or that the superstructure would topple. However, the fact that the bridge has survived several earthquakes suggests that these keys are effective at preventing transverse movement.
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Tuesday, November 17, 2009

Mexico's Bridges: Viaduct Beltran (1)

A few miles further north on Route 54D (between Colima and Guadalajara) are a series of extremely long bridges supported on extremely tall piers.

Viaduct Beltran is an odd four-span bridge. The first pier is supported at the bottom of a ravine, making it many times taller than if it had been moved farther or closer to the first abutment. The second pier is actually two bents placed twenty feet apart. My feeling is that the superstructure is balanced on the two bents, but the first abutment was too far away so they had to support it on the long first pier.

I imagine the superstructure was segmentally constructed. It's a haunched, prestressed concrete, box girder bridge. The superstructure is continuous, but it just sits on the piers (with a downward projecting element between transverse shear keys).

We'll take another look at this interesting bridge tomorrow and I welcome your thoughts or any information you may have on it. I wonder how long the spans are and how tall the first pier is?
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Monday, November 16, 2009

Mexico's Bridges: Overcrossing near Tonila

Continuing north on Route 54D toward Guadalajara, the road goes through a series of cuts in the mountains. Driving through one of these cuts, I got my first glimpse of a kind of bridge I've never seen before.

Under the deck of a reinforced concrete single span overcrossing (a bridge over the highway) is what I would call a structural steel space truss. It's made up of eight-legged elements connecting the concrete slab to longitudinal and transverse steel elements. Apparently, these thin elements are strong enough to increase the bending resistance of this structure.

This type of structure is apparently very popular in Colima. There is a water main supported by a similar structure 140 ft away, and single span and two span bridge undercrossings (a bridge carrying the highway) a few miles to the north.
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Sunday, November 15, 2009

Mexico's Bridges: Puentes Los Lobos

Traveling north from the City of Colima on Route 54D, we enter into mountains and cross over tall bridges. A second bridge (on the left) was just beginning to be built parallel to the first bridge when I came by in 2003.

The existing bridge is a four span reinforced concrete I-girder bridge on cruciform-shaped two column bents. There are vertical stiffeners or perhaps diaphragms providing stability for the girders.

It is a four span bridge on bents at different heights with struts at different levels.

Route 54D is carried by a series of tall bridges across the many streams running down the flanks of two enormous volcanoes just west of the highway. You can see this part of the highway is in a steep cut at both ends of the bridge.
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Saturday, November 14, 2009

Mexico's Bridges: PSV Ent. Jiquilpan

Eventually I arrived in the City of Colima, which is a nice region, but without many unusual bridges. However, I did see a variety of innovative interchanges in Colima as well as throughout Mexico.

I'm particularly fond of this interchange. It includes a traffic circle under a freeway undercrossing with on-ramps and off-ramps on the approach embankments.  The bridge is a six-span precast I girder superstructure on multicolumn bents and seat-type abutments.

I think this is a simple and effective means for getting people on and off expressways without traffic signals or expensive connectors.

Traffic circles are seldom used to get people on and off expressways in California. The offramp I take to get home from work (the Watt Avenue exit on US-50) is just after the expressway onramp causing everyone to stop to avoid plowing into each other as they try to get on and off the expressway.
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Friday, November 13, 2009

Mexico's Bridges: Nuevo Puente Armeria (2)

Another view of the New Armeria Bridge. Maybe bridge owners should avoid calling their bridges 'new,' since they so rapidly become old. However, this bridge appears to still be in pretty good shape.

I see some cables near the bottom flange. Perhaps it was strengthened with prestressed tendons to carry heavier trucks. This was popular in California twenty years ago as a way to allow permit vehicles onto more roads. However, it may have been wiser to keep heavy vehicles off most roads since they tear up the pavement so quickly.

I also see some cables hanging from the barrier rail, but those look like electrical wiring, maybe to power a nearby ranch.

The wingwalls stick straight out from the sides of the stemwall because the bridge is in a small canyon that was carved by the river. There are concrete corbels under the steel girders. Perhaps they are used as jacking platforms for the girders in case the bearings need to be replaced.

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Thursday, November 12, 2009

Mexico's Bridges: Nuevo Puente Armeria (1)

North of the Armeria Highway Bridge and the Armeria Railway Bridge is the New Armeria Bridge. It carries Route 110 from Ciudad de Armeria northward to Cofradia de Juarez before returning to Route 200 at the Colima Armeria Overcrossing.

Nuevo Puente Armeria is a four span steel girder bridge on single column bents and seat-type abutments. As can be seen on the placard, the bridge was completed in 1963 at a cost of 3.3 million Mexican Pesos.

Placards are mounted on important bridges. Not only do they provide basic information about the bridge, but also some information about the government that financed the bridge construction.

Note that the end of the concrete bridge barrier had been struck by oncoming vehicles. Because such accidents can cause terrible injuries, guardrails should be mounted at the approaches to bridges to deflect drivers away from the ends of concrete barriers.
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Wednesday, November 11, 2009

Mexico's Bridges: Nuevo Caxitlan POC

The road from Manzanillo to Colima includes many pedestrian overcrossings (POCs) that carry people (and especially children) over the busy highway.

The Nuevo Caxitlan POC connects the town of Nuevo Caxitlan to an orchard (and farmer's markets) to the south. With its metal roof and railing, it makes a pleasant place to stand and watch the passing traffic. Apparently, it also makes a convenient place to mount advertisements and political posters.

This POC includes two spans over the highway and long zigzagging ramps along the sides of the highway. Note that the spans over the highway are made out of two precast girders laid side by side. Also note that the bent cap has big shear keys.
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Tuesday, November 10, 2009

Mexico's Bridges: Tecoman Overcrossings

Continuing northeast along the Colima - Manzanillo Highway (Route 200) is an interchange to the nearby town of Tecoman, which includes a two span and and a three span overcrossing.

These bridges are interesting because the abutments, including the stem walls, are constructed from mechanically stabilized earth (MSE) panels. I don't think we have ever used an MSE wall to support a bridge superstructure in California. It seems to be doing a good job though, especially when you consider the bridges were about 15 km from the epicenter of the 2003 M8 Colima Earthquake.

Also, I like how the area around the interchange has been landscaped with palm trees, bougainvillea, and shrubbery. The State of Colima does a nice job of maintaining their highways.

However, I wonder how effective the sign on the outside of the bridgerail 'SI TOMA NO MANEJE' (don't drink and drive) is at preventing drunk driving? It may be too late to stop someone who is already driving, but it may possibly give them pause from continuing to drink while they drive.
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Monday, November 9, 2009

Mexico's Bridges: Colima Armeria Overcrossing

The next bridge along Route 200 is a two-span overcrossing (part of a trumpet interchange) that takes eastbound drivers around a ramp and onto the northbound lanes of the Colima-Armeria Highway.

It seems to me that bridges in Mexico have a lot of character. This bridge has a precast I-girder superstructure, but it also has a beautiful hand-mortared abutment stem-wall. I like the little sidewalls (below the wingwalls) that hold back the embankment and the slope paving under the abutments. And the entire abutment structure was freshly hand painted. You can see that the highway bridges are well maintained.

Perhaps it reflects a less litigious society that there are no crash cushions or guardrails to stop an errant driver from crashing into the center pier. Instead, the pier is painted with black and white stripes to warn drivers to avoid it.

I also like the little pedestals that were poured to support each girder, the big shear keys at the ends of the bent cap, and the bright yellow barrier rails on the bridge. We'l see a lot more of these little touches on Mexican highways that make even a humble overcrossing into something special.
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Sunday, November 8, 2009

Mexico's Bridges: Antiguo Puente Ferroviario de Armeria


Just upstream from the highway bridge we studied yesterday is an old railroad bridge. It is a six span through truss bridge with five short Pratt trusses and a longer Parker truss over the Armeria River. The superstructure is supported on hexagonal-shaped masonry pier walls. The abutments include long wingwalls.

There was a truck on the embankment (and a couple of workers on the bridge) when I took this photo, but I didn't have a chance to go and see if the bridge was damaged by the earthquake. Since the bridge is close to the epicenter, I would imagine the trusses sit on tall bearings that might have gotten damaged or fallen over.
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Saturday, November 7, 2009

Mexico's Bridges: Rio Armeria Puentes

We've travelled from the State of California in the U.S. to the State of Colima in Mexico. This is a trip I took in 2003 to look at bridge damage following a large earthquake that occurred near the coast.

The State of Colima is a pretty region. I drove north from the coastal plain up into steep mountains with quaint villages and a cloud forest with very diverse flora and fauna. The region's economy seemed healthy and the earthquake damage was quickly repaired.

I was driving on Route 200, the highway from Manzanillo on the coast to Colima in the foothills. One of the first bridges I came to was the Rio Armeria Puentes, which are two 14 span precast I-girder bridges supported on tall, thin piers with hammerhead caps and on seat-type abutments.

I like the texture of the concrete, which looks like it was formed with something other than 4' x 8' sheets of plywood. This bridge was close to the earthquake epicenter, but the only damage was to the shear keys at the abutments and to tiny keys at the tops of the pier caps.
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Friday, November 6, 2009

American River Bridges: Jibboom Street (Richard's Blvd) Bridge

Over the last few weeks we've looked at every bridge crossing the American River between it's confluence with the North and Middle Forks (in the Sierra Foothills) to its confluence with the Sacramento River (at the Jibboom Street Bridge). You can see the Sacramento River just beyond the bridge (in the photo) where all the speedboats congregate.

Many of the rivers coming out of the northern Sierra Mountain Range empty into the Sacramento as it flows south from Mt Shasta (for 450 miles) to Suisun Bay. Perhaps I can provide photos of all the bridges crossing the Sacramento River after I photograph a few of the bridges I'm still missing.

According to Historic Highway Bridges of California (published by Caltrans in 1990), the Jibboom Street Bridge is a cantilever swing bridge. The main span is a 351 ft long swing through span (on the left). The side spans are through Parker trusses. The bridge was built in 1931.

The swing span hasn't worked in many years, which is just as well since large vessels shouldn't be going up or down the American River. Its far too shallow and there are too many rapids. I wonder where the name Jibboom came from? It sounds like somebody's last name. Maybe a business person from the days of the Gold Rush.

I mentioned a few days ago that cyclists are encouraged to take the SNRR Bridge across the American River during the winter because the Jibboom Street Bridge can be under water due to flooding. Perhaps the swing span no longer works because the bridge is periodically under water? I remember flooding damaged the swing and lift mechanisms on most of the movable bridges along the Gulf Coast after Hurricane Katrina.
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