Thursday, December 31, 2009

Ecuador's Bridges: Puente Rio Cupa (2)


The Rio Cupa bridge gets a surprising number of visitors in the course of a day. The heavy traffic explains why they first tried to build a vehicular bridge at this site.

The towers are 9.2 meters high and the deck is 1.3 meters wide. I'm standing at the west anchorage.  It's 23.9 meters to the west tower, 85.1 meters to the east tower, and 19.8 meters to the east anchorage. The east anchorage is 2 meters higher than the west anchorage.

The site was surveyed and a preliminary design was proposed by Walter in July of 2004. The design was checked by Toni Ruttimann and the bridge was built by Walter and the community of 5 de Agosto, Union Manabi later that year.
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Wednesday, December 30, 2009

Ecuador's Bridges: Puente Rio Cupa (1)

Equestrian loads are not usually addressed for pedestrian bridges.  The load from a cantering horse can be several times larger than a pedestrian load. Still, this bridge (across the Cupa River) regularly carries horses without undo fatigue or displacement.

The Puente Rio Cupa is another bridge designed and built by Walter Yánez. Originally, the village (Union Manabi) was hoping to build a vehicular bridge across the river. You can still see one of the abutments behind the bridge in this photo. Either they ran out of money or they had trouble building such a long span across the river.

Walter's bridge is an 85 meter long suspension bridge supported on pinned base towers. We'll take another look at this interesting bridge tomorrow.
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Tuesday, December 29, 2009

Ecuador's Bridges: Puente Rio Baba (6)

This photo shows one of the anchorages for Puente Rio Baba. Walter (the designer and builder) is standing with one foot on the suspension cable and Zoe (from Bridges to Prosperity) is sitting next to him.

A metal frame made from pipes is embedded in the concrete of the anchorage and a length of cable is wrapped around the metal frame and extends outside the concrete. Walter weaves this cable into the suspension cable (he showed me how to do it, but now I can't remember).

Walter took me deep into the jungle to see how he surveyed the riverbanks near a village to see if he could build a bridge at the site. We traveled up and down the river in a dugout canoe with campesinos using machetes who clear a path for us.

Everyone was very grateful for Walter's work. Sometimes farmers would cut down bunches of bananas and other fruit and throw them into the back of Walter's truck. Once, we spent several hours surveying, and then Walter had to tell the villagers that the river was too wide for one of his bridges.
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Monday, December 28, 2009

Ecuador's Bridges: Puente Rio Baba (5)

A view of the bottom of one of the towers for Puente Rio Baba. The pins for each tower (and a metal frame for each anchorage) are placed in the concrete before it is cured. Then the towers can be raised (usually with the help of a truck) and the suspension cables are attached to the top of the tower saddles and to the anchorages. Two or three struts provide lateral stability to the towers.

As I previously mentioned, the suspension cable has the same angle on each side of the tower so that the longitudinal force on each side of the tower is equal.  Also note that the hangers are made from a single cable that descends from one suspension cable, goes through a hole in one side of the floor beam, back up through a hole in the other side, and back up to the other suspension cable.
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Sunday, December 27, 2009

Ecuador's Bridges: Puente Rio Baba (4)

I've mentioned that a bridge looks very different from under the deck. Some bridges are more attractive from below, but they are usually not suspension bridges. However, the underside provides a lot of information on how the bridge works.

The floor beams for Puente Rio Baba are steel pipes hanging from the suspension cables. Timber stringers are staggered from side to side so that both ends of the stringers can be supported on the floor beams.

I believe that the villagers were responsible for supplying the timber used on Walter's bridge. After he completes his survey, he provides the villagers with a list of what he needs and if it's not there when he returns, he just drives on to the next village and the next bridge project.

Building these bridges is a communal process. It is quite common for villagers to have heated debates about the pros and cons of building a bridge. A firm commitment from the villagers is needed before Walter will begin a project. Because, the river can become dangerous or impassable during the rainy season, the standard of living for most people in the village will improve once they are able to safely cross the river.
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Saturday, December 26, 2009

Ecuador's Bridges: Puente Rio Baba (3)


After the anchorages and tower foundations have been poured and cured for one of Walter's bridges, then it can be assembled in a couple of days. The suspension cables are draped over the towers and attached to the anchorages. Then one or two people sit up on the suspension cables and attach precut stays every two meters. Floor beams are connected to each pair of stays and timber stringers are supported on the floor beams. Finally, wooden planks are laid on top of the timber stringers, hand railing and fencing is attached to the stays, and the bridge is complete.

For Puente Rio Baba, the deck also had to be anchored to the side of the cliff and steps were laid to help people get to the top. This isn't a bad solution when one bank is 40 meters higher than the other.

The deck is 102 meters long but the towers are 130 meters apart. The lower tower is 6.8 meters tall and the upper tower is only 3.9 meters tall. The anchorage is 23 meters behind the lower tower but only 9 meters behind the upper tower.

Toni wrote some software that Walter uses to determine the sizes of the towers and the lengths of the cables so he can cut everything out before construction begins.

We'll take another look at this interesting bridge tomorrow.
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Friday, December 25, 2009

Ecuador's Bridges: Puente Rio Baba (2)


This bridge is a somewhat unusual design for Walter because it has one tower 40 meters above the other on a cliff on the other side of the river.

Walter began building bridges with Toni Ruttimann who had a strong desire to help the poor. Because neither Walter nor Toni were engineers, they came up with a very safe bridge design. As long as they maintained some simple geometric relationships and kept the span length below about 100 meters, they knew their bridges would be very safe. The towers were pinned and the force on each side of the tower was kept equal by making the angle of the cable the same on each side of each tower.

I called this bridge Puente Rio Baba but looking at my notes, I found that Walter called it Puente Santa Marianita, which is the name of the community that helped build the bridge. This bridge is in the country of Ecuador, the province of Pichincha, the canton of Santo Domingo, the parish of El Esfuerzo, and the community of Santa Marianita.

The Catholic Church plays a large role in rural life in Ecuador. We were sometimes accompanied by a priest to visit a bridge and then we would drive slowly because so many people would run out of their house to say hello or ask something from the priest.

We'll take another look at this bridge tomorrow.
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Thursday, December 24, 2009

Ecuador's Bridges: Puente Rio Baba (1)


I thought we might continue traveling south to look at some interesting bridges that I photographed in Ecuador.


In September The Happy Pontist devoted several blogs to voluntary organizations that provide bridges to help the rural poor. Coincidentally, I had recently spent some time in Ecuador for Bridges to Prosperity studying inexpensive bridges constructed (from used oil-drilling pipe and cable) by Walter Yánez. 


If a village wants a bridge, they can write to the provincial government. A vehicular bridge is preferred, but if that's not possible, Walter will come and perform a survey with an EDM and hand level to see if he can build a footbridge.  


He gives the villagers instructions on where to dig the holes and returns in about a month to pour the foundations and anchorages for the bridge. Then he'll return with the pipe and cable and work with the village to construct a suspension bridge up to 100 meters in length.


We'll take a closer look at Walter's bridge tomorrow.
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Wednesday, December 23, 2009

Mexico's Bridges: Puente cerca de La Lima (2)


A closer view of one of the piers supporting Puente cerca de La Lima. I like the trapezoidal shape, the color of the stones, and the thick bentcap and slab. The sides of the pier seem the right shape to deflect fast-moving water and flood debris.

There is something very human and almost comforting about this bridge. The pier looks like it was shaped by a human hand. It reminds me of the Roman aqueducts that I sometimes come upon in Europe and the Middle East.. It has the same timeless quality.

Was this bridge built ten years or a hundred years ago?
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Tuesday, December 22, 2009

Mexico's Bridges: Puente cerca de La Lima (1)

The Street of Roses (Calle de la Rosas) turns into a county road north of Manzanillo. Driving along this road towards La Lima I came across an eight span slab bridge.


I thought that this was an attractive little bridge. Although many of the posts were broken, I liked the handmade stone masonry piers sitting between green river banks.
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Monday, December 21, 2009

Mexico's Bridges: Puente Rio Armeria (2)


Its surprising how different a bridge looks from the deck. One would hardly notice  crossing a bridge over a river from the road. I guess a bridge always has two aspects, one from above the deck and another from below the deck.

For some reason, this bridge has two sidewalks although they don't continue onto the adjacent roadway. Maybe the sidewalk allowed the designer to use a vertical barrier rail instead of the New Jersey barrier used on US bridges.  These barriers are shaped to push errant vehicles back onto the road.

The sidewalk and rail have expansion joints to allow each span to expand and contract. Note the end of the rail has black and white stripes and the sidewalk curb is painted yellow. Apparently the Mexican Highway Department uses paint rather than protective devices to prevent injuries to distracted drivers.
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Sunday, December 20, 2009

Mexico's Bridges: Puente Rio Armeria (1)


Highway 8 connects the City of Colima to the City of Minatitlan. This road crosses over the ubiquitous Rio Armeria on a four span precast I-girder bridge with stone masonry pier walls and abutments. The deck is supported by five I-girders and has expansion joints at the end of each span, despite being covered in asphalt. Tiny shear keys sit on the inside of the exterior girders. A diaphragm holds the girders together and the little shear keys are meant to prevent the superstructure from moving off the wall during earthquakes. It looks like the girders sit directly on the wall although there might be a thin sill plate between them.
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Saturday, December 19, 2009

Mexico's Bridges: Puente de la Ciudad de Coquimatlan (4)

A last look at the little slab bridge built by the City of Coquimatlan. What's most noticeable in this photo is how high the bridge is above the existing roadway. Perhaps the bridge was built so the soffit would be above the hundred year flood. This idea is borne out by the wingwalls on the upstream side of river that protect the roadway from being washed out during floods. It looks like the riverbed was raised along the downstream side of the bridge to allow vehicles to ford the river during construction.

A special concrete crossing that allows people to ford a river (with wet wheels) may have been originally built at this site. We will look at several of these types of crossings when we study the bridges of India.
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Friday, December 18, 2009

Mexico's Bridges: Puente de la Ciudad de Coquimatlan (3)

Another view of the Puente de la Ciudad de Coquimatlan. The abutments were built in the river due to the short span length of the slab superstructure.

My feeling is that there is no fixity at the ends of the span. Considerable reinforcement would have to be developed from the slab into the abutment to carry moments at the span ends. This would have allowed a longer span and the abutments could have been built on land.

A coffer dam was placed to dewater the area where the abutments were built. Note that the slab is slightly raised over the abutment to allow room for the falsework and forms to support the reinforcement and wet concrete.

Slab bridges make inefficient use of concrete but provide a good riding surface.
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Thursday, December 17, 2009

Mexico's Bridges: Puente de la Ciudad de Coquimatlan (2)

Another view of a bridge across a branch of Rio Armeria near Coquimatlan in Colima, Mexico. It's the opposite of many of the bridges shown by the Happy Pontist, which are often state-of-the-art structures.

Should bridge aesthetics be the art of designing the cheapest bridge that fulfills its function? When we remove all the unneeded expense, is this the type of structure that emerges?
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Wednesday, December 16, 2009

Mexico's Bridges: Puente de la Ciudad de Coquimatlan (1)

Near the City of Coquimatlan I came upon a bridge being built. There was a sign at the site that said, 'Excuse the annoyance. Coquimatlan City Hall is building this bridge with funds from SEDESOL (the Social Programs Ministry) and the municipality with a $284,518 investment.'

The apology was warranted because drivers had to go around the bridge and ford the river. The cost (in Mexican Pesos) is surprisingly cheap, about $22,000 US which is about $25 US per square foot of deck!

The Puente de la Ciudad de Coquimatlan is a single span reinforced concrete slab bridge on stone masonry abutments. There are several interesting aspects to this simple bridge. There are no bearings, just a cold joint between the slab and the abutments. Rubble was placed at the embankments behind the abutments rather than well-compacted backfill. The stones for the abutments look like they were placed by hand (there are no obvious signs that the stones and concrete were poured into forms). Note the plastic tubing that goes through the deck. Perhaps those are for the optical and electrical cables the bridge will carry.
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Tuesday, December 15, 2009

Mexico's Bridge: Puente Los Amiales #2

This is one bridge I'm not interested in crossing. I've seen scarier bridges (thousands of feet up in the mountains of Spain, but this one just doesn't look very stable. Based on his bridge, I don't think I'd be interested in buying one of the owner's tables (mesas 15 pesos).

I'm guessing it's supposed to be a suspended span bridge, but it doesn't look well-anchored, it doesn't look securely supported on the piers, and the piers look flimsy. Fortunately, its only a fall of five or six feet.
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Monday, December 14, 2009

Mexico's Bridges: Puente Armeria

Another bridge over the Rio Armeria.


I admit that I was a little nervous driving over this bridge. I don't like a bridge that rocks back and forth as I drive over it. Moreover, it has stone abutments and a stone center pier.


I guess this shows the variety of bridge construction in Mexico: from state-of-the-art incrementally launched structures, to two-span bridges on stone supports.
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Sunday, December 13, 2009

Mexico's Bridges: Puente Los Amiales #1

As I traveled deeper into the interior of Colima, the bridges became simpler, but they still seemed quite effective. This little single span steel girder bridge is missing a railing and I'm not sure if there's any reinforcement in the abutments. Also, you have to wait to cross if someone is driving from the other direction.

Maybe this is a local agency bridge or maybe it's owned by a campansino. I like the thick concrete deck that looks like cream cheese on a bagel.

I first became familiar with the State of Colima through the writing of Ken Kesey who moved to Manzanillo for a couple of years to escape harassment from US drug enforcement officials. Apparently, his experience in Colima wasn't much better.

I finally got a chance to visit Colima after an M8 earthquake struck the coast in 2003 and the ASCE wanted a report on infrastructure damage. I inventoried 100 bridges in Colima and Jalisco, but the damage was very minor.
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Saturday, December 12, 2009

Mexico's Bridges: Puente Rojo del Ferrocarril (2)

Another view of the railroad bridge near Coquimatlan. This through steel truss is carried by big rocker bearings. Note the man under the bridge throwing a fishing net into the river.

Today I watched the film In the Pit by Juan Carlos Rulfo, which was recommended by Norrin in a comment to this blog. The film follows laborers and ironworkers building the elevated portion (the Second Deck) of Mexico City's Periferico Freeway.

The film referred to a Mexican legend that the devil requires a human life during the construction of every bridge to keep it standing.  Rulfo had a nice shot at the end of the film from a helicopter of mile after mile of freeway. It really gave a sense of how much work was required to build about 20 km of elevated expressway. The movie had lots of moments of humor, sweetness, frustration, and anger expressed by the construction workers that made the film engrossing. I think we're fortunate that the owners gave Rulfo access to the construction site.

You can rent the movie (it's available on Netflix) or you can look at photos of the freeway at skyscrapercity on the Internet.
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Friday, December 11, 2009

Mexico's Bridges: Puente Rojo del Ferrocarril (1)

This is a classic single-span Warren truss bridge on stone masonry abutments. All the main truss members are wide flange girders. It's a couple miles south of Puente Juarez and west of Coquimatlan.

This bridge supports railroad tracks without ballast. The wooden ties rest on steel channels supported on the floor beams, which in turn are supported by the vertical hangers.

The abutments were cleanly mortared with extruded joints and built with three steps. The lowest step is under the bottom chord and may be used for jacking up the truss. The second step supports the truss and the tracks run across the top.

The bridge appears to be in good condition. It crosses over a little stream that may be a branch of Rio Armeria. It seems like a rather light structure to carry heavy trains, but that's what makes truss bridges so effective.
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Thursday, December 10, 2009

Mexico's Bridges: Puente sobre el Río (2)


Another view of a four span steel girder bridge on stone masonry pierwalls on Route 115 in the State of Colima. I've seen the use of stone bridge supports in India and other places where economics require the minimum use of concrete and the maximum use of filler material.

It looks like this dry river bed is periodically flooded (note the debris collecting against the side of the pier). Perhaps cutwaters could be designed at the upstream end of the piers to deflect the water and debris downstream.

I wonder how this bridge would perform during a large earthquake? The pierwalls are very short and stiff and would attract large forces, and they may not have much reinforcements. Still, the bridge bearings may fail first, lowering the forces on the bridge, and the resulting displacement may not be large enough to cause unseating. Probably flooding is a bigger hazard. My impression is that the engineers did a good job of building the girders above the 100 year (500 year?) flood.

I like the deck overhangs that look like they were formed with thin strips of wood. I also like the bright red color of the girders and the bright yellow of the railing. That reminds me of the Accelerated Bridge Construction blog where he shows a video of how great New Jersey barrier is at keeping vehicles on the road. I haven't seen much New Jersey barrier in Mexico.

The steel girders look well designed with plenty of vertical stiffeners and cross-bracing. I don't see any signs of fatigue or any maintenance problems, but the bridge looks fairly new.
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Wednesday, December 9, 2009

Mexico's Bridges: Puente sobre el Río (1)

What I like about Mexican bridges (and about many other things made in Mexico) is they show a technical understanding as well as an understanding of the surroundings, of the culture, and of art.

Continuing past Route 56 I took a little detour onto Route 115 and to a village (whose name escapes me). I soon crossed a dry river bed onto a four span steel girder bridge with stone masonry pierwalls and abutments.

I like the handmade look of the bridge. The wingwalls, abutments, and piers look like they were built by a craftsperson. I like the appearance of the concrete pier caps and deck, which were formed with long, thin boards instead of plywood. However, the steel girder superstructure is quite conventional with lots of web stiffeners and cross-braces.

We'll take a closer look at this bridge tomorrow.
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Tuesday, December 8, 2009

Mexico's Bridges: Puente Juarez

Returning to Colima, I took Route 56 southwest, back towards Manzanillo. I soon crossed the ubiquitous Rio Armeria (near the town of Coquimatlan) on the Puente Juarez, a seven span I-girder bridge on reinforced concrete pierwalls and odd, two-column abutments.

This bridge has a handsome plaque giving relevant bridge data. It is 251 m (824 ft) long with a 7.5 m (24.6 ft) wide traveled way and a 9.1 m (30 ft) wide deck. This is a very green, fertile area with many orchards. Note the tall palm trees at the other end of the bridge.

Unfortunately we've too often seen the end of the concrete barrier damaged from drivers smashing into it. Steel rails or crash cushions at the ends of bridges might save some lives.

I like the flared elements connecting the girder webs to the deck, which give the bridge a modern appearance. The Rio Armeria must have a tendency to flood. The plaque gives the volume of water that can pass under the bridge. The rounded ends to the pierwalls can deflect debris downstream instead of collecting against the bridge and possibly causing scour or bridge damage.
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Monday, December 7, 2009

Mexico's Bridges: Puente Cuatro Caminos (2)


This bridge is near the intersection of roads going to Tuxpan, Ciudad Guzman, Tecalitlan, and Colima, hence the name Cuatro Caminos.

Puente Cuatro Caminos has three precast I-girder spans and short slab end spans. I wonder why they needed the little end spans?

It looks like the girders and the deck are simple spans, but they covered the deck (including the expansion joints) with asphalt so the bridge looks continuous from the road.

The I-girders are supported by large two column bents. Note that the top of the bents have wide platforms, perhaps for jacking up the spans and replacing the bearings.

Route 54D continues another 80 miles to Guadalajara, but I turned around at this point and returned to Colima.
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