Sunday, November 19, 2017

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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Sunday, November 12, 2017

Mendocino County, California Bridges: Highway 1 Bridge across Ten Mile River

September 2017 (39.54917-123.76278) Ten Mile River Bridge
Ten Mile River Bridge (10 0274) is an eight span prestressed concrete box girder bridge that was built in 2009. It replaced a timber deck truss bridge that had been built at this site in 1954 (see photo below, courtesy of the Mendocino County Historical Society).
With the tight radius curve at the south end of the bridge along with it's streamlined appearance and the dramatic landscape of water, sky, and rugged hills, this bridge provides some visual excitement. Note the open barrier rail and sidewalk, which is appropriate for a bridge along the coast.
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Sunday, November 5, 2017

Mendocino County, California Bridges: Highway and Railway Bridges across Pudding Creek

September 2017 (39.4586, -123.8078) Pudding Creek Bridges
A highway bridge and a railway bridge (now converted to a pedestrian bridge) cross Pudding Creek a few hundred yards from each other. The Highway 1 Bridge (10 0158) is an eight span, precast concrete channel beam bridge that was built in 1959. The bridge was seismically retrofit in 1996. Large diameter piles were placed at the ends of enlarged bent caps. This is called a 'superbent' and is a commonly used seismic retrofit to more firmly anchor a bridge into the ground. The simply supported channel beams (upside down bathtub sections) were securely anchored to each other and to the bents. It looks like at some point a water line was attached to the west side of the superstructure.
At the end of the 19th century Union Lumber built a 10 mile long railway to bring redwood logs (that were being deposited into Ten Mile River) to their mill at Fort Bragg. More information on the bridge, the railroad, and the lumber company is available on the Mendocino Model Rail Website.
Pudding Creek Trestle is a 515 ft long wooden bridge that was built by the Union Lumber Company in 1915. The railroad bridge became a truck bridge when the railway was converted to a haul road in 1949. The logging operation ended in the 1970s and the truck bridge became a pedestrian bridge in 2007.
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Sunday, October 29, 2017

Mendocino County, California Bridges: Highway 1 Bridge across the Noyo River

September 2017 (39.42694-123.80667) Noyo River Bridge
Continuing north on Highway 1 we arrived at the Noyo River Bridge (10 0298). This is a three span continuous, prestressed concrete box girder bridge. It has a 325 ft long main span and it was built in 2005. It's an odd looking bridge with columns that are recessed below the soffit to imitate a bridge on bearings. The columns have a stout shape with extra concrete that (hopefully) will spall off to allow the ductile core to undergo large displacements without breaking during an earthquake.
There was a fight between Caltrans and the community about various aspects of the proposed design of the bridge.  The bridge was to be located extremely close to commercial buildings along the bank and it doesn't look like a typical coastal bridge. One resident, Vince Taylor, fought Caltrans on the solid barrier rail that was originally proposed for the bridge. He provides a history of his hard-fought victory on the internet.
Tony Phillips provides an excellent pictorial history of the six different bridges that crossed the Noyo River near its mouth during the last 150 years. The first structure was a drawbridge that was built in 1861. Subsequent bridges were truss bridges until the current haunched box girder bridge was built.
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Sunday, October 22, 2017

Mendocino County, California Bridges: Three Bridges on Highway 1

August 2017 (39.3767, -123.8161) Three Highway 1 Bridges
Continuing north on Highway 1 we moved away from the coastline and crossed over the Caspar Creek Bridge (10 0153), a seven span continuous prestressed concrete structure on single column bents. This bridge was built in 1966.
A little further north is the Jug Handle Creek Bridge (10 0154), a 388 ft long reinforced concrete bridge with a 210 ft long open spandrel arch span that was built in 1938. This bridge is farther from the headlands and consequently lower to the ground than last week's Russian Gulch Bridge.
Finally, we parked at College of the Redwoods and walked to the Hare Creek Bridge (10 0175), another 388 ft arch bridge (that was built in 1947). However, the Hare Creek Bridge has a full arch for the main span and two almost full arches for the side spans (see General Plan below).
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Sunday, October 15, 2017

Mendocino County, California Bridges: Highway 1 Bridge across Russian Gulch Creek

September 2017 (32.3289, -123.8044) Russian Gulch Bridge)
Continuing north on Highway 1 we arrived at the Russian Gulch Bridge (10 0151). This structure, built in 1940, is a well-regarded bridge with it's own Wikipedia page. Even more remarkably, it was renamed in 1974 after a Caltrans' bridge engineer (the Frederick W. Panhorst Bridge) although the bridge was actually designed by his subordinate Henry E. Kuphal.
I stood as far back as I could along the narrow beach to shoot the top two photos. Jason Hollinger got an even better photo by going out to the headlands and turning back towards the shore.
Caltrans bridge engineer Arthur Elliott (1911 - 2004), wrote that the bridge's appearance was improved by providing wider spaces between the taller spandrel columns and narrower spaces between the shorter columns (with a reference to ancient Greek architecture). That's too subtle a feature for me to appreciate. However, I do like the shape of the arch.
The Russian Gulch Bridge is a reinforced concrete open spandrel arch structure that is 527 ft long and has a 240 ft long arch span. There were hundreds of this type of arch bridge built in California during the first half of the 20th century, especially along the coast. They were the preferred method of stepping over a moderate obstacle. Today, this narrow beach might be crossed by a prestressed concrete box girder bridge or by a more streamlined arch structure.
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Sunday, October 8, 2017

Mendocino County, California Bridges: Highway 1 Bridge across Big River

September 2017 (39.3017, -123.7921)Big River Bridge
Continuing north on Highway 1 we arrived at Big River and the bridge that carries the highway across it. Walking along the river we saw people with their dogs along with joggers and hikers. The bridge is just south of the town of Mendocino and so a large community of people use the trail under the bridge to get their exercise.
The history of Big River is about entrepreneurs who built sawmills, railroads, and bridges along the river to harvest and sell the forest of redwoods that once covered this region. All of that activity has disappeared without a trace.
The Big River Bridge (10 0146) is a three span box girder structure on single column bents (built in 1962) with a 190 ft long center span. In 1994 the bridge columns were wrapped in steel casings to protect them from earthquakes. Unfortunately these casings soon began to rust due to the marine environment.
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Sunday, October 1, 2017

Mendocino County, California Bridges: Highway 1 Bridge across Albion Creek

August 2017 (39.2264, -123.7660) Albion River Bridge
I wrote a year ago about the Albion community's reluctance to replace the aged Albion River Bridge. It's amazing all of the issues raised by a community of 200 people over this bridge replacement. Each individual has their own unique concerns about this project. How will the replacement affect the use of the harbor? Will fishing operations be affected? Will the influx of workers to build the replacement displace residents? What are the costs of repair versus replacement?
Whether the old bridge is rehabilitated or a new bridge is built, it will have a big impact on the community. I wonder how one could take this old bridge and repair/seismically retrofit it without replacing most of the members? This is an issue that is being addressed all over the world. How to preserve our past while preparing for the future? In the old days the government would just come in and do what it wanted but I think it's a good thing that the community gets a voice in these decisions.
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Sunday, September 24, 2017

Mendocino County, California Bridges: Highway 1 Bridge across Salmon Creek

August 2017 (39.21528-123.76806) Salmon Creek Bridge
A couple of miles north of the Navarro River is Salmon Creek and the deck truss bridge that crosses over it. The Salmon Creek Bridge is a 5-span, 685 ft long bridge with a 26 ft wide deck. The superstructure sits on two and four legged reinforced concrete towers. This bridge was built in 1950, improved in 1985, and now Caltrans is planning to replace it.
Among the reasons why Caltrans is considering replacing this bridge are:
  • Functionally Obsolete - the deck geometry only provides for one foot shoulders.
  • Fracture Critical - lack of redundancy in the deck truss and floor beam members, which could result in collapse.
  • Structurally Deficient – the bridge deck is in poor condition.
  • Low Load Rating – larger permit trucks are not allowed on the bridge.
  • Deficient Rail – the existing bridge rail does not meet current design standards.
  • Costly Maintenance – Painting is required every 4 to 5 years to protect the steel at a cost of $2.5 million. Spalls and delamination of concrete also need to be repaired.
  • Seismically Deficient – the bridge needs to be retrofitted to prevent collapse during a large earthquake. 
Caltrans builds very few steel bridges today. Part of this is due to the high maintenance costs of steel, but it is also because cast-in-place and precast bridges have become less expensive to build. Only when there is a good reason (usually related to quickly building over an obstacle) that steel is used. Also, Caltrans ductility-based seismic design philosophy favors reinforced concrete. Perhaps with the federal push for accelerated bridge construction steel may become more popular again.
Caltrans performed a value analysis for replacing Salmon Creek (and the adjacent Albion River Bridge), held meetings with the community, and created designs for box arch (shown below), spandrel arch, and box girder bridges as options for bridge replacement.
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Sunday, September 17, 2017

Mendocino County, California Bridges: Highway 1 Bridge across the Navarro River

August 2017 (39.197, -123.747) Navarro River Bridge
In Southern Mendocino County there are creeks and rivers emptying into the Pacific every few miles. I recently took a trip to photograph the bridges that carry Highway 1 over the mouths of these rivers.
The Navarro River Bridge (10 0130) is the southernmost of these river crossings. It is a two span continuous steel girder bridge (with short approach spans) on concrete piers (and pile extensions). It was built in 1949 and rehabilitated in 1985. It looks like the rehabilitation included a seismic retrofit to anchor the girders to the piers.
The Navarro River Bridge is where State Route 128 intersects and becomes part of Highway 1 about one mile from the coast (see photo below).
One hundred years ago, the town of Wendling was located at the mouth of the Navarro River. There was a port, a railroad siding, a lumber mill, and a hotel for the sailors who anchored at the river's mouth to load their schooners with redwood cut from the surrounding forest. A truss bridge was built near the mouth of the river to support the community (see photo below).
Today, there isn't anything left from the bridge or the town, just a sandy beach.
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