Solano County, California Bridges: Suisun Valley Road Bridge across Suisun Creek

February 9, 2014, 9:00 am

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January 2014 (38.29852 Degrees, -122.12697 Degrees) Suisun Valley Road Bridge

After my disappointment at finding the Suisun Valley Road Bridge (23C0077) had been removed I was relieved to find the other historic Suisun Valley Road Bridge (to the south) still in place. However, it would be more accurate to say that they turned the existing structure (23C0076L) into the southbound bridge and built a northbound bridge (23C0076R) beside it.

Like the other F.A. Steiger bridges, this Suisun Valley Road Bridge has very distinctive details such as the cleanly articulated borders around the closed spandrel arch walls and dome shaped end posts on the barrier rails.

Apparently the team of F.A. Steiger as County Engineer and G.H. Gildersleeve as contractor resulted in some well designed bridges. Their Suisun Valley Road Bridge across Suisun Creek was built in 1909, its in service 105 years later, and it's also eligible for the National Register of Historic Places. The arch span is 84 ft long but the bridge is barely 18 ft wide, which was why they built a parallel span beside it. That's a better idea than demolishing an old narrow (but still functioning) bridge.

Solano County, California Bridges: Suisun Valley Road Bridge across Suisun Creek by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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Solano County, California Bridge: State Route 37 Bridge across the Napa River

February 10, 2014, 9:00 am

≫ Next: Solano County, California Bridges: Mare Island Causeway across the Napa River

≪ Previous: Solano County, California Bridges: Suisun Valley Road Bridge across Suisun Creek

January 2014 (38.1204 Degrees, -122.2803 Degrees) Napa River Bridge

We have been looking at most of the smaller bridges in Solano County. Some were presented as part of the series of blogs on Solano County Bridges while others were presented as part of the blogs on the counties surrounding Solano County. We are now near the southwest corner of Solano County, which is bounded by Suisun Bay, the Carquinez Straits, the Napa River, and San Pablo Bay. These bodies of water are all crossed by much bigger bridges.

The State Route 37 Bridge across the Napa River is a 33 span precast girder bridge built in 1963. There are several distinctive features of this bridge, at least from my perspective. This is a very convenient alternative route into and out of the Bay Area when other roads are congested. Also, this is a very tall bridge that can be seen from many miles away.

The bridge is made up of flexible two-column bents with occasional stiff four column bents in between that are meant to restrain the bridge from lateral movement.

During the 1989 Loma Prieta Earthquake, the State Route 37 Bridge was the farthest bridge from the epicenter that had severe damage. Most of the girders had expansion joints but at eight locations they were tied together through the end diaphragms. However, there was not enough reinforcement to hold them together and they were pulled apart and almost fell off the bents.

The girders at the expansion joints also had a great deal of movement (see photo below). After the earthquake, better continuity, better rebar splices, and better development lengths were required for seismic bridge design.

Use of precast girder bridges are being encouraged by the federal government as part of the emphasis on speeding up bridge construction. Caltrans is spending money on research to make these superstructures capacity-protected from the earthquake resistant system (usually column plastic hinges or isolators).

Solano County, California Bridge: State Route 37 Bridge across the Napa River by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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Solano County, California Bridges: Mare Island Causeway across the Napa River

February 11, 2014, 9:00 am

≫ Next: Solano County, California Bridges: I-80 Bridges across the Carquinez Straits

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January 2014 (38.11056 Degrees, -122.27472 Degrees) Mare Island Causeway

Just south of yesterday's State Route 37 Bridge is the lift bridge onto Mare Island (which is more like a peninsula) on the west side of the Napa River. People can get on and off the island using these two bridges. In this photo I'm standing atop the west tower of the new Carquinez Suspension Bridge looking up the Napa River, which empties into the Carquinez Straits.

The Mare Island Causeway was built in 1934. The bridge is 2008 ft long with a 165 ft long main span. It has long concrete trestle approach spans and a steel lift main span. It's only 30 ft wide.

The lift span is normally in the closed position. It has 20 ft of vertical clearance on the deck and over 100 ft of vertical clearance across the channel when the lift span is opened.

Mare Island seems to be going through an economic depression. For over 100 years, it was the main Naval shipyard for the United States. In 1995 it was finally closed during the big round of base closures. Now there are many empty factories with broken windows. However, many entrepreneurs have bought the old factories for new ventures. For instance, Victor Zayas has a factory that builds friction pendulum bearings on the island.

Solano County, California Bridges: Mare Island Causeway across the Napa River by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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Solano County, California Bridges: I-80 Bridges across the Carquinez Straits

February 12, 2014, 9:00 am

≫ Next: Solano County, California Bridges: Benicia Martinez Bridges across Carquinez Strait

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January 2014 (38.064 Degrees, -122.225 Degrees) Carquinez Bridges

Yesterday we looked at the Napa River Bridge and the Mare Island Lift Bridge from the tower of the Carquinez Suspension Bridge. Today we are looking at the Carquinez Bridges from the deck of the Mare Island Lift Bridge.

The Carquinez Bridges include a 1950s era truss bridge and a new suspension bridge. We studied these bridges previously when they were building the suspension bridge, retrofitting the truss bridge, and removing the 1920s era riveted truss bridge.

The remaining truss bridge got an interesting seismic retrofit in the1990s that included shock absorbers at the expansion joints to prevent unseating at the ends of the cantilevers (above) and supports at the bottom of the towers to facilitate rocking (below).

The bridges carry westbound and eastbound I-80 traffic across the strait that connects San Pablo Bay (on the west) to Suisun Bay (on the east).

The photo shown below was taken before they completed the suspension bridge and before they removed the 1920s truss bridge. On the north (far) side of the bridges is the city of Vallejo and on the south (near) side is the town of Crockett that includes the big C and H (California and Hawaii) Sugar Refinery.

Solano County, California Bridges: I-80 Bridges across the Carquinez Straits by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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Solano County, California Bridges: Benicia Martinez Bridges across Carquinez Strait

February 13, 2014, 9:00 am

≫ Next: Solano County, California Bridges: Rio Vista Bridge across the Sacramento River

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January 2014 (38.0424 Degrees, -122.1225 Degrees) Benicia Martinez Bridges

At the east end of the Carquinez Strait are the three Benicia Martinez Bridges (carrying I-680 between the cities of Benicia and Martinez). The photo above shows the new northbound Benicia Martinez Toll Bridge, a segmentally constructed prestressed concrete box girder bridge. I'm standing on the north side of the Strait photographing this bridge with a telephoto lens that considerably foreshortens the bridge. In the background is an oil refinery that includes a terminal in the Strait for tankers to offload their oil.

Besides the new northbound bridge, there is an old steel truss bridge that was retrofit with giant friction pendulum bearings in the 1990s (see photo below). These bearings reduced the inertia load to the piers and foundations, saving Caltrans the expense of retrofitting the foundation. Both the northbound bridge and the southbound retrofit are part of just a handful of bridges designed to remain in service after a large earthquake.

I had forgotten that we had once practiced our rope climbing techniques on a reinforced concrete leg of the retrofitted bridge (before the new bridge was built). The columns were so tall that we had to tie two static lines together and got to practice climbing above and below the knot as well as how to move from side to side around the column.

Between the northbound and southbound bridges is an old (1930) railroad bridge that still gets plenty of use from the BNSF, UP, and Amtrak trains that cross it every day. The bridge includes a lift span over the shipping channel. In fact, there were so many trains, that it was a hassle while they were trying to work on the retrofit because they had to clear the tracks every time a train came by. The photo below shows the railroad bridge before the northbound Benicia Martinez Bridge was constructed. A better view of the railroad bridge was in the June 5, 2001 blog.

Solano County, California Bridges: Benicia Martinez Bridges across Carquinez Strait by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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Solano County, California Bridges: Rio Vista Bridge across the Sacramento River

February 14, 2014, 9:00 am

≫ Next: Contra Costa County, California Bridges: State Route 160 (Antioch) Bridge across the San Joaquin River (1)

≪ Previous: Solano County, California Bridges: Benicia Martinez Bridges across Carquinez Strait

January 2014 (38.15899 Degrees, -121.68393 Degrees) Rio Vista Bridge

Continuing to the east of the Benicia Martinez Bridges is the Rio Vista Bridge across the Sacramento River (previously visited in May of 2010). This is the last bridge in our survey of Solano County bridges. It's a 2890 ft long vertical lift bridge that was built in 1944. It includes a 306 ft long Warren truss lift span across the river channel.

The Rio Vista Bridge is on State Route 12 (in the town of Rio Vista) and the bridge gets raised and lowered a lot, which can back up traffic for miles. The bridge tender was nice enough to let us into the bridge house so we could watch him raise and lower the lift span.

This bridge got an extensive seismic retrofit in the 1990s that included lead-rubber isolation bearings supporting the approach spans (see photo above) and viscous dampers that were placed transversely to allow the tower to rock if the anchor bolts were to break (see photo below).

Sacrificial expansion joints were used to accommodate large longitudinal movements. Also cable restrainers were placed in front of the counterweights to prevent them from swinging into the towers (see photo below). Thus, the retrofit allows movement and damage while preventing a collapse for the maximum credible earthquake. For a more moderate event, the retrofit may allow the structure to remain in service.

Solano County, California Bridges: Rio Vista Bridge across the Sacramento River by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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Contra Costa County, California Bridges: State Route 160 (Antioch) Bridge across the San Joaquin River (1)

February 15, 2014, 2:59 pm

≫ Next: Contra Costa County, California Bridges: State Route 160 (Antioch) Bridge across the San Joaquin River (2)

≪ Previous: Solano County, California Bridges: Rio Vista Bridge across the Sacramento River

February 2014 (38.0240, -121.7516) Antioch Bridge

We are leaving Solano County today to look at the bridges to the south in Contra Costa County (see map below). Many of the biggest bridges cross county lines. For instance, today's Antioch Bridge (28 0009) crosses the San Joaquin River between Sacramento and Contra Costa Counties.

The Antioch Bridge is a toll bridge that was built in the 1970s and so it wasn't originally a part of the state legislative mandated retrofit program. Eventually Caltrans decided to analyze it, and like many other 1970 era bridges we found it was designed for too low a seismic load.

The retrofit included isolation bearings between the superstructure and the substructure and cross-bracing between the columns. We'll take a closer look at this interesting bridge tomorrow.

Contra Costa County, California Bridges: State Route 160 (Antioch) Bridge across the San Joaquin River (1) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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Contra Costa County, California Bridges: State Route 160 (Antioch) Bridge across the San Joaquin River (2)

February 16, 2014, 9:00 am

≫ Next: Contra Costa County, California Bridges: Indian Slough Bridges

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February 2014 (38.02400, -121.75162) Antioch Bridge

The Antioch Bridge (28 0009) is a narrow, two lane toll bridge that carries State Route 160 across the San Joaquin River. It was built in 1978 with continuous steel girders. It's a 40 span, 9440 ft long steel girder bridge with a 460 ft span across the shipping channel. In the photo above we can see how steeply the bridge rises to provide 140 ft of vertical clearance over the river. The bridge includes gates to stop traffic when the wind starts blowing. The toll plaza is on the opposite (west) side but one can avoid the toll altogether by driving across the river a little downstream on State Route 4.

This Caltrans bridge was designed by my boss Chuck Yakabe in the 1970s and the retrofit was completed last year by Kim Yong-Pil. It includes friction pendulum bearings just slightly higher than the existing bearings that can move 0.6 meters for the design earthquake. More information on the retrofit is available on the Internet.

Contra Costa County, California Bridges: State Route 160 (Antioch) Bridge across the San Joaquin River (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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Contra Costa County, California Bridges: Indian Slough Bridges

February 17, 2014, 9:00 am

≫ Next: Contra Costa County, California Bridges, State Route 4 Bridge across the Old River

≪ Previous: Contra Costa County, California Bridges: State Route 160 (Antioch) Bridge across the San Joaquin River (2)

February 2014 (37.93889 Degrees, -121.61000 Degrees) Indian Slough Bridges

Around the Antioch Bridge is the California Delta, a maze of sloughs and swampy islands. California's Delta has similar problems to the ones that plague the Mississippi Delta. It's below sea level and protected by gates and levees. The state government wants to divert some of the water into tunnels for farmers and wildlife habitats, but this plan is fiercely opposed by the people who live in the Delta.

We'll spend the next few days studying a few of the bridges that cross the Delta in Contra Costa County.

Indian Slough is crossed by several bridges at Orwood Road a little north of the waterfront community of Discovery Bay. A squat concrete trestle bridge carries Amtrak and BNSF trains across the slough (top photo). Three large diameter utility bridges cross the slough to bring fresh water to communities in the Bay (see photo above). The utility bridge to the north has a seismic retrofit with lead rubber bearings supporting a steel eccentrically braced frame that will act as a fuse for transverse displacement (see photo below).

Just south of the utility bridges, the Orwood Road Bridge (28C0024) crosses Indian Slough. It's a twelve span timber trestle bridge with a reinforced concrete deck (see photo below). This road bridge is 230 ft long, 22 ft wide, and it was built in 1947.

Contra Costa County, California Bridges: Indian Slough Bridges by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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Contra Costa County, California Bridges, State Route 4 Bridge across the Old River

February 18, 2014, 9:00 am

≫ Next: Contra Costa County, California Bridges: Washington Island RR Bridge across the Old River

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February 2014 (37.89072 Degrees, -121.57039 Degrees) Old River Bridge

The California Delta has many movable bridges. This swing bridge carries State Route 4 across the Old River between Contra Costa and San Joaquin Counties. The Old River Bridge (29 0045) was built in 1917 but it was considerably renovated in 1978 and it looks almost new.

A closer inspection shows that the bridge was put together with rivets and laced cross members. In fact, the bridge is in poor shape and has a sufficiency rating for the superstructure of only 22 and is rated structurally deficient.

The Old River Bridge has Howe truss swing spans and Pratt truss approach spans. The bridge is 528 ft long with a 20 ft wide deck. It provides 15.5 ft of vertical clearance below the cross beam and 13 ft vertical clearance above the river in the closed position. The highway makes a sharp 'S' to cross the river at a right angle. Broad levees on each bank protect the surrounding farmland from flooding.

Contra Costa County, California Bridges, State Route 4 Bridge across the Old River by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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Contra Costa County, California Bridges: Washington Island RR Bridge across the Old River

February 19, 2014, 9:00 am

≫ Next: Contra Costa County, California Bridges: Pacheco Slough Bridges in Martinez

≪ Previous: Contra Costa County, California Bridges, State Route 4 Bridge across the Old River

February 2014 (37.94127 Degrees, -121.55907 Degrees) Washington Island Railroad Bridge

We are continuing our study of movable bridges in Contra Costa County. Just downstream from yesterday's State Route 4 Bridge is the Washington Island Railroad Bridge across the Old River. Like the previously studied Indian Slough Railroad Bridge, this bridge carries the BNSF Railroad and Amtrak between Stockton and Martinez.

The Washington Island RR Bridge has concrete trestle approaches and plate girder/through truss bascule spans. According to the Bridgehunter, this is one of only 8 remaining bridges that use Hugo A.F. Abt's patented design. In this design the counterweight swings under the tall truss while lifting the plate girder span. This allows the approach to remain open under the counterweight. This odd design allows a replacement Abt bridge to be built on the same alignment in the open position facing the other bridge. Terry Koglin describes this solution for movable bridge replacement in his book, "Movable Bridge Engineering." I would imagine that the deck of the replacement bridge must wait until after the old bridge is removed.

Today's bridge was built by the American Bridge Company in 1929. It has a 177 ft long bascule section with a 90 ft long span over the channel with 11 ft of vertical clearance in the closed position.

Contra Costa County, California Bridges: Washington Island RR Bridge across the Old River by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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Contra Costa County, California Bridges: Pacheco Slough Bridges in Martinez

February 20, 2014, 9:00 am

≫ Next: Contra Costa County, California Bridges: Benicia Martinez Bridges across the Carquinez Strait

≪ Previous: Contra Costa County, California Bridges: Washington Island RR Bridge across the Old River

February 2014 (38.03142 Degrees, -122.08008 Degrees) Pacheco Slough Bridges

Another movable railroad bridge in Contra Costa County carries trains across Pacheco Slough in Martinez. It's a long timber trestle bridge with pony truss swing spans at the east end. This bridge was built in 1901 by the Southern Pacific Railroad.

On the north side of the railroad bridge is another swing bridge built in 1946 to carry Waterfront Road. This Pacheco Slough Bridge (28C0006) was improved in 1965 with precast girder approach spans and steel girder swing spans. There is also a utility truss bridge just north of the roadway bridge that carries pipelines to a nearby refinery (see photo below).

Contra Costa County, California Bridges: Pacheco Slough Bridges in Martinez by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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Contra Costa County, California Bridges: Benicia Martinez Bridges across the Carquinez Strait

February 21, 2014, 9:00 am

≫ Next: Contra Costa County, California Bridges: El Curtola Overcrossing over State Route 24

≪ Previous: Contra Costa County, California Bridges: Pacheco Slough Bridges in Martinez

February 2014 (38.0415 Degrees, -122.12330 Degrees) Benicia Martinez Bridges

Some bridges that we recently viewed from Solano County make another appearance in Contra Costa County. The Benicia Martinez Bridges include a new segmentally constructed prestressed concrete box girder bridge that carries northbound I-680. Just behind it is the Southern Pacific Railroad Bridge composed of camelback Warren trusses, a lift span over the channel, and a deck truss approach. Behind the much lower railroad bridge is a tall deck truss bridge that carries southbound I-680.

Contra Costa County, California Bridges: Benicia Martinez Bridges across the Carquinez Strait by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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Contra Costa County, California Bridges: El Curtola Overcrossing over State Route 24

February 22, 2014, 9:00 am

≫ Next: Contra Costa County, California Bridges: 680/24 Interchange in Walnut Creek

≪ Previous: Contra Costa County, California Bridges: Benicia Martinez Bridges across the Carquinez Strait

February 2014 (37.89803 Degrees, -122.085002 Degrees) El Curtola OC

The El Curtola Bridge (28 0125) across State Route 24 is supported by an unusual upside-down 'V shaped bent. The bent splits in two to step over the Bay Area Rapid Transit (BART) tracks in the middle of the expressway. The tracks are in a trench that becomes a tunnel just east of the bridge.

I previously wrote about this bridge in April of 2010 and mentioned that the bridge had later been retrofitted with steel column casings. However, when I returned this week there were still no column casings! The bridge was constructed in 1971 and improved in 1996, but the improvements apparently didn't include a column casing (it could have been a concrete casing). It will be interesting to see how this oddly-shaped bent performs during the next big earthquake. This area of Contra Costa County is crossed with many faults, including the Franklin Fault that crosses under the adjacent 24/680 Interchange that we will be studying tomorrow.

The El Curtola OC is a cast-in-place prestressed concrete, box girder bridge with two 194 ft long spans and a single very unusual bent. It seems like they could have built this bridge more traditionally with a bent on either side of the BART tracks, but maybe they wanted the columns sloping away from traffic.

Contra Costa County, California Bridges: El Curtola Overcrossing over State Route 24 by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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Contra Costa County, California Bridges: 680/24 Interchange in Walnut Creek

February 23, 2014, 9:00 am

≫ Next: Contra Costa County, California Bridges: Iron Horse (and Contra Costa Canal) Footbridges

≪ Previous: Contra Costa County, California Bridges: El Curtola Overcrossing over State Route 24

February 2014 (37.8963 Degrees, -122.0734 Degrees) 680/24 Interchange

Just east of EL Curtola OC is the 680/24 Interchange with connectors, separators, overcrossings, and undercrossings all climbing over each other. Many of my friends worked on this interchange in the 1990s as part of Caltrans engineer rotation program.

These photos hardly do justice to the many soaring bridges in this interchange (I was too nervous to stop in the middle of the expressway to take a photo). Most of the bridges are cast in place prestressed concrete structures, but there was a temporary steel girder bridge that sat on isolation bearings for several years and then was picked up at the end of the project and placed on its new substructure.

The interchange (and El Curtola OC) can be seen in the Google earth photo shown above (the blue lines are a few of the many earthquake faults in the area. The urban area east of the Interchange is the affluent city of Walnut Creek which we will be exploring over the next few days.

Contra Costa County, California Bridges: 680/24 Interchange in Walnut Creek by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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Contra Costa County, California Bridges: Iron Horse (and Contra Costa Canal) Footbridges

February 24, 2014, 9:00 am

≫ Next: Contra Costa County, California Bridges: Robert I. Schroder Pedestrian Overcrossing across Treat Blvd

≪ Previous: Contra Costa County, California Bridges: 680/24 Interchange in Walnut Creek

February 2014 (37.9217 Degrees, -122.0606 Degrees) Iron Horse (and Contra Costa Canal) Trails

The Iron Horse Trail extends from Dublin all the way to Martinez (a distance of about 55 miles). The trail was part of the Southern Pacific Railroad right of way from 1891 until it was abandoned in 1977. We've seen several other counties (El Dorado County, Yolo County, etc.) that have turned their abandoned railroad tracks into parks and trails. This part of Contra Costa County is called the 'East Bay' and is an idyllic area to go for a walk or a ride.

I spent some time hiking the Iron Horse Trail and the adjacent Contra Costa Canal Trail (see photo) in Walnut Creek. However, these trails were narrow and without any markings to separate bicyclists from pedestrians. It became nerve wracking as the bicyclists were constantly interrupting my reverie with calls of "On your left!" There are several old and new footbridges on the trail, which we will be studying over the next few days.

Contra Costa County, California Bridges: Iron Horse (and Contra Costa Canal) Footbridges by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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Contra Costa County, California Bridges: Robert I. Schroder Pedestrian Overcrossing across Treat Blvd

February 25, 2014, 9:00 am

≫ Next: Contra Costa County, California Bridges: Iron Horse Trail POC across Ygnacio Valley Road

≪ Previous: Contra Costa County, California Bridges: Iron Horse (and Contra Costa Canal) Footbridges

February 2014 (37.92655 Degrees, -122.0546 Degrees) Iron Horse Trail Bridge

One of the nicest bridges on the Iron Horse Hiking Trail is the Robert I. Schroder Pedestrian Overcrossing in Pleasant Hill. This tied arch bridge was designed by Arup of San Francisco, it cost $6.8 million, and it was completed in October of 2010. It's an 800 ft long steel structure with a concrete substructure and a 10 ft wide deck. The bridge has a steel box girder superstructure supported by outward-inclining steel arches that rise 42 ft above Treat Blvd.

Each arch rib is composed of three steel pipes bolted to wedge-shaped steel diaphragms. The ends of the steel arch ribs are connected with a steel cross brace and anchored into cylindrical reinforced concrete legs that are part of a single large foundation. The main span is 240 ft long and supported by pairs of crossed cables (40 ft apart) hanging from the wedge-shaped steel diaphragms.

This is an efficiently designed structure. A cylindrical concrete column is placed squarely between the concrete legs of the arch ribs. The steel diaphragms brace the pipe elements of the arch ribs and also carry the weight of the deck. In the past arch ribs were parallel or inclined together into a basket-handle shape but now outward inclining arch ribs seem to be popular.

My friend Richard Hartzell mentioned that the bridge is on a horizontal curve and so each arch rib has a different slope to accommodate the curve, which must have been difficult to analyze and design. More information about this bridge can be found on the Arup website.

Contra Costa County, California Bridges: Robert I. Schroder Pedestrian Overcrossing across Treat Blvd by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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Contra Costa County, California Bridges: Iron Horse Trail POC across Ygnacio Valley Road

February 26, 2014, 9:40 am

≫ Next: Contra Costa County, California Bridges: Iron Horse Trail Bridge across Walnut Creek

≪ Previous: Contra Costa County, California Bridges: Robert I. Schroder Pedestrian Overcrossing across Treat Blvd

February 2014 (37.90707 Degrees, -122.05778 Degrees) Ygnacio Valley Road POC

The next bridge on the Iron Horse Hiking Trail is a more traditional steel arch. The Ygnacio Valley Road Pedestrian Overcrossing is a 550 ft long viaduct with a 136 ft long tied arch main span and with truncated deck arches for the side spans.

This bridge was built in 1998 by C. A. Rasmussen and designed by Santina and Thompson. However, unlike yesterday's Treat Blvd OC, there are few postings on the internet other than the always reliable Bridgehunter Website with photos by Craig Philpott.

Today's bridge is more utilitarian than the Treat Blvd POC. The arch ribs are parallel steel box girders with lots of tubular steel cross-braces between the ribs. The deck is wider but it's hanging from steel rods with turnbuckles. The dark fence imparts a feeling of claustrophobia while crossing over the bridge.

Contra Costa County, California Bridges: Iron Horse Trail POC across Ygnacio Valley Road by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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Contra Costa County, California Bridges: Iron Horse Trail Bridge across Walnut Creek

February 27, 2014, 10:36 am

≫ Next: Conta Costa County, California Bridges: Richmond-San Rafael Bridge across San Francisco Bay

≪ Previous: Contra Costa County, California Bridges: Iron Horse Trail POC across Ygnacio Valley Road

February 2014 (37.90560 Degrees, -122.05736 Degrees) Walnut Creek Bridge

The Iron Horse Trail has a number of older bridges from when the trail was a railroad line. Today's bridge is a four panel Pratt truss with diagonal members sloping towards the center in tension. The bridge crosses over Walnut Creek, which is a concrete-lined channel covered with warning signs due to the danger of flash floods and drownings.

This bridge was built in 1929 and has the date stamped on the portal frames at the ends of the bridge. It's 102 ft long, 18 ft wide, and made up of wide flange compression members and laced tension members. The Ygnacio Valley Road POC is just north of the Walnut Creek Bridge and a little to the side to allow people to continue on or off the trail as shown in the photo below.

Contra Costa County, California Bridges: Iron Horse Trail Bridge across Walnut Creek by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.

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Conta Costa County, California Bridges: Richmond-San Rafael Bridge across San Francisco Bay

February 28, 2014, 9:00 am

≫ Next: Santa Cruz County, California Bridges: Southern Pacific Railroad Bridge across San Lorenzo River

≪ Previous: Contra Costa County, California Bridges: Iron Horse Trail Bridge across Walnut Creek

February 1999 (37.93405 Degrees, -122.42.955 Degrees) Richmond-San Rafael Bridge

Like the other San Francisco Bay toll bridges the Richmond-San Rafael Bridge is named after the two cities it connects. It's the northernmost of the bay toll bridges and when it was built in 1956 it was the world's longest bridge at 5.5 miles. I took the photo above (and for a previous blog) many years ago with a film camera. The bridge looks slightly different today because it was retrofit in 2001.

The Richmond-San Rafael Bridge is composed of two cantilever truss bridges with an odd sway-backed truss frame between them. It's similar to the old East Bay Bridge Crossing that was replaced last year, but the Richmond-San Rafael Bridge isn't a lifeline structure and so it was easier to retrofit to prevent collapse.