Cable-Stayed Bridges - North Arm Bridge (5)

A photo of Don Bergman from Buckland and Taylor standing in front of the North Arm Bridge. Although this extrados river crossing is an attractive structure I think the different supports and various transitions for the approach structures are a little awkward.

The designer was stuck with a 139 m side span in order to cross Mitchell Channel, the nearby airport restricted the height of the towers, and the shipping channel restricted the depth of the girders. This limited the length of the main span and made an extrados bridge the logical choice for this bridge site.

Cable-Stayed Bridges - North Arm Bridge (5) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Cable-Stayed Bridges - North Arm Bridge (4)

A view from under the soffit of North Arm Bridge. Each tower supports twelve cables. The cables are made up of 58 sheathed, galvanized, and waxed strands in a 9 inch HDPE pipe. The cables were installed strand by strand. Dampers were provided at the deck anchorages to reduce wind vibration and the pipes have double-helix ribs to reduce rain vibration.  A cost-benefit analysis was performed to determine if traditional tower anchors or continuous cables in saddles (like on the Maumee River Bridge) could be used, but the tradition anchorage was found to be less expensive.

Cable-Stayed Bridges - North Arm Bridge (4) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Cable-Stayed Bridges - North Arm Bridge (3)

A closer look at the towers of the North Arm Bridge. Note the steel walkway hanging from the side of the concrete box girder superstructure.

This is an extradosed bridge, which means some of the prestressing tendons have been replaced by shorter towers and cable-stays. It has a main span of 590 ft, side spans of 456 ft, and transition spans of 170 ft. The bridge is supported by two 143 ft tall towers and a pier on each side of the river (see Google Earth photo). The towers are a steel/ reinforced concrete composite structure that Buckland and Taylor seem to prefer. The bridge was completed in 2008.

Cable-Stayed Bridges - North Arm Bridge (3) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Cable-Stayed Bridges - North Arm Bridge (2)

I took this photograph from the back window of an automated train. By the time I realized I was looking at the North Arm Bridge it was already on the horizon. We'll take another look at this extradosed bridge tomorrow.

Cable-Stayed Bridges - North Arm Bridge (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Cable-Stayed Bridges - North Arm Bridge

The North Arm Bridge (across the north arm of the Frazier River) is another light rail bridge carrying the Sky Train between the airport and downtown Vancouver. This is an extradosed bridge with short towers and short spans. We'll take another look at this interesting bridge tomorrow.

Cable-Stayed Bridges - North Arm Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Cable-Stayed Bridges - Alex Fraser Bridge (3)

The Alex Fraser (Annacis) Bridge was the world's longest cable-stayed bridge when it was completed (with a main span of 1525 ft). Now its the 32nd longest cable-stayed bridge in the world.  There must be a flurry of big bridge building when a country's economy suddenly blossoms. Japan was building the longest bridges in the 1990s and China is in the early 21st century.

This is another composite steel and concrete bridge designed by Buckland and Taylor. They must feel they have a competitive edge on this kind of structure (it was completed in only 31 months). It was built as two balanced cantilevers in 30 ft increments until the two structures became one. The cables are distributed along the arms of the 'H' shaped towers and support the superstructure in a semi-fan arrangement. The cables support the 6.6 ft deep steel frame with precast deck slabs placed on the flanges and made continuous with a closure pour.

I heard that this bridge was having maintenance problems. I hope the deterioration is minor or that it can be repaired. It is a very elegant looking structure and you can see it for miles above the surrounding landscape.

Cable-Stayed Bridges - Alex Fraser Bridge (3) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Cable-Stayed Bridges - Skytrain Bridge (2)

We previously looked at the Skytrain Bridge on October 6th of 2009. It has the distinction of being the world's longest cable-stayed light-rail bridge, with a 1115 ft long main span and 2020 ft total length. The prestressed concrete superstructure carries two sets of light rail tracks across the Fraser River.

The bridge cables are in an unusual fan arrangement with five cables attached to special anchors at the ends of the back spans. Perhaps the extra cables are needed to balance the long main span? At the top of the towers the cables are attached to diaphragms between the pylons. The girders on the approaches look very deep (or the girders on the cable-stayed bridge look very small).

On the Buckland and Taylor Website, they mentioned that they were underbid by 0.5% on the project but later came in to evaluate whether the bridge was capable of carrying heavier trains. Information on this bridge is limited but I noticed that some websites say the bridge was completed in 1986 (in time for Expo86) while others say the bridge wasn't completed until 1990. Also I saw a couple of reports stating that chunks of concrete were falling from the bridge but that the bridge owner (Translink) assured reporters that there was no cause for alarm.

Cable-Stayed Bridges - Skytrain Bridge (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Cable-Stayed Bridges - New Port Mann Bridge (3)

One last look at the Port Mann Bridge (through the front window of our bus). I wonder why tied arches have so much cross-bracing? Maybe its for transport to the bridge site?

The new bridge will be supported by towers between the decks with big blocks on top with anchors for four planes of cables.

The government is attempting to make the new bridge more palatable to environmentalists by including bicycle and HOV lanes.

The Fraser is an odd sort of river. Freshly cut timber is still transported downstream through the city. Bridges on the Fraser must be well-protected to handle constant collisions with log booms and other river debris. An odd aspect of Vancouver is that virgin forests are just outside an expanding metropolis of about 3 million people.

There is a four mile gap between the Port Mann Bridge to the west and the Skytrain Cable-Stayed Bridge to the east across the Fraser River (see below). The river widens appreciably just before bending to the south. Perhaps the river is too wide to cross at this location with another cable-stayed bridge?

Cable-Stayed Bridges - New Port Mann Bridge (3) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Cable-Stayed Bridges - New Port Mann Bridge (2)

Another less than perfect photo from inside a bus, but at least we can see the towers going up beside the longest arch bridge in Canada, the soon to be demolished old Port Mann Bridge. This is one of those tied arch bridges with half arches for side spans. I wonder if the main span was carried to the site and set onto the side spans?

The new Port Mann Bridge will be 7200 ft long, 10 lanes wide, and with the same vertical clearance as the existing bridge. The main span will be 1540 ft long, making it only 6 ft shorter than the longest cable-stayed bridge in North America (the previously studied Arthur Ravenel (Cooper River) Bridge). The side spans will be 620 ft long. The bridge costs about $3 billion and replaces a 46 year old bridge. Is that a good thing or a bad thing?

Cable-Stayed Bridges - New Port Mann Bridge (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Cable-Stayed Bridges - New Port Mann Bridge

The British Columbia Ministry of Transportation is set to replace an existing through arch bridge that carries Highway 1 across the Fraser River with a new eight lane cable-stayed bridge. Bridge projects in Vancouver are a cause of considerable controversy, and there has been opposition to building another highway bridge that brings more cars into Vancouver.However, the New Port Mann Bridge is set for completion by the end of 2012.

Currently 327 precast concrete box girder segments are being moved from Coquitlam to the south side of the bridge (in Surrey) where they're launched by this huge truss system for the assembly of the south approach to the bridge. After the south approach is completed, they'll reassemble the launching system on the north side of the bridge. Meanwhile the towers are almost at deck level and will top out at 500 ft, taller than the nearby Alex Fraser Bridge.
We'll take another look at this project tomorrow.

Cable-Stayed Bridges - New Port Mann Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Cable-Stayed Bridges - Golden Ears Bridge (3)

I was going to provide a photo of a pedestrian on-ramp for the Golden Ears Bridge today, but then I realized I had already shown it in Saturday's photo. In that photo, the ramp (with a circle of columns all of the same height) provides a well-balanced seismic design. Also, the short piers for the bridge approaches are protected from the larger seismic demands of the taller river crossing with expansion joints.

For today's photo, I provided a view of the bridge deck of the Golden Ears Bridge, You can see eagles flying next to the pylons on the first tower. I'm not sure what the golden cylinders on the sides are meant to be (perhaps golden ears of corn?). Also, I'm surprised there are no cross-braces at the tops of the towers to improve the bridge's seismic behavior.

The pylons were quickly assembled out of steel boxes stacked together with a crane. The boxes alternate with anchor sections. Stay-in-place forms allowed the exterior concrete to be quickly poured. After each anchor section went up and the concrete was poured, the next steel girder and floor beam section could be hung from the towers.

Cable-Stayed Bridges - Golden Ears Bridge (3) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Cable-Stayed Bridges - Golden Ears Bridge (2)

A closer look at the Golden Ears Bridge. Don Bergman from Buckland and Taylor kindly took me on a tour of this bridge on Thursday.

Don said the bridge owner was concerned about excessive settlement and so they provided openings in the pedestals for jacking the towers (the pile caps are supported by 12 - 8 ft diameter pile shafts). Above the pedestals at stiff Pier M2 (in the foreground) are steel plates that can form plastic hinges and give the bridge a more balanced response during earthquakes.

Note the complicated connection where the steel girders, towers, and tower struts meet. Also note the steel fairings on the outside of the main spans to control wind vibrations. The bridge has six lanes supported by two steel girders connected to long floor beams and a composite concrete deck. The deck is made of precast concrete segments laid on the floor beams and made composite with closure pours. Pedestrian/bike lanes are on the overhangs outside of the cable-stays.

The cables are parallel, at an extremely flat angle, and are distributed from the top to the bottom of the short towers. Don said the cables are composed of 7 galvanized wires per strand. Each strand is sheathed in polyethylene and placed parallel to the other strands. The interstices between the strands are filled with corrosion resistant material and the cable is wrapped in a polyethylene. Dampers control vibrations at the bottom of the stays.

This long bridge with its short towers is a very economical design. The superstructure is light and requires a minimum of support from towers and cables. Its not a very dramatic structure, but not every bridge needs to be dramatic. Its about 8000 ft long and 100 ft wide and cost $800 million CAD, which gives a unit cost of about $1000 per square ft.

We'll take one more look at the bridge (at one of its approaches) tomorrow.

Cable-Stayed Bridges - Golden Ears Bridge (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Cable-Stayed Bridges - Golden Ears Bridge

The City of Vancouver is laced with waterways and so there is a need to connect the bodies of land between them. Consequently, Vancouver has a lot of bridges and probably more cable-stayed bridges than any other city.


The Golden Ears Bridge is a five span hybrid cable-stayed structure. Some have called it an extradosed bridge, but a true extradosed bridge carries dead load with its cables and live load with deeper girders. 


This bridge was designed by Buckland and Taylor and completed in 2009. It has a continuous, 2370 ft long composite steel girder superstructure. There are three equal main spans of 800 ft and two side spans of 400 ft. It crosses the Fraser River just east of Barnston Island. It's name is taken from the twin peaks of Mount Blanshard (seen in the background) which apparently has a golden glow at sunset. It also comes from 'Golden Eyries' and so the bridge towers are decorated with eagles. 


We'll take a closer look at this interesting bridge tomorrow.

Cable-Stayed Bridges - Golden Ears Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.Publish Post

Vancouver's Bridges: Patullo Bridge (2)

One last photo of the Patullo Bridge and then I'll have to find another city's bridges to put in my blog. There are so many new and interesting bridges in Vancouver that I'd like to come back one day. In particular, I'd like to study the extradosed bridges that were recently built.

An extradosed bridge is a cable-stayed bridge with short towers. Since the cables have a smaller vertical component, they are much less effective and it's more like a prestressed girder bridge.

Just 72 years ago, the Patullo Bridge was a brand new structure and considered the height of modernity. Now, with its 10 ft traffic lanes and aging structural members, it's considered antiquated and will shortly be replaced. In 1937, it cost $4 million to build and was named after the premier of British Columbia. I wonder if the works of Calatrava will prove to be equally short lived? Most bridges have about a 75 year life-span, unless the public is willing to make a special effort to preserve them.

In 2009, the Burnaby Village Museum celebrated the bridge's 1937 grand opening with a special show and luncheon. Information from the museum's show is available online.

Vancouver's Bridges: Patullo Bridge (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Vancouver's Bridges: Skytrain, Patullo, and New Westminster Bridges

We looked at the Skytrain Bridge yesterday. It's a cable-stayed bridge (built in 1990) that carries automated trains over the Fraser River.

A few hundred meters to the east is the Patullo Bridge that we looked at back in March 2, 2009. It is a suspended deck truss arch bridge that was built in 1937. Because of the narrow lanes and the lack of a median barrier, there are frequent accidents on the bridge and it's expected to be replaced in a few years with a toll bridge. In 2009 vandals set fire to the wooden trestle on the south end of the bridge but it was quickly repaired.

A couple hundred meters further to the east is the New Westminster (or CNR) Bridge. It is a long truss bridge that was built in 1904 with a swing span in the middle of the Fraser River. Like the Patullo Bridge, it is frequently the target of vandals and they have stopped using open car vehicle transporters on this bridge.

Six kilometers further to the east along the Fraser River is the Port Mann Bridge (completed in 1964) that closely resembles the Patullo Bridge. I never had time to photograph this bridge, but photos are available at Wikipedia. The bridge carries an amazing 126,000 vehicles a day. Although the bridge is only 45 years old, there are plans to build another bridge with a larger capacity and to tear the Port Mann Bridge down. As can be expected in a politically active city like Vancouver, there have been protests to improve mass transit instead of building more ways for people to drive cars into the city. Perhaps the Golden Ears Bridge was built to carry some of the excess traffic?

With its broad rivers and growing population, I guess Vancouver is a good city for bridge engineers.

Vancouver's Bridges: Skytrain, Patullo, and New Westminster Bridges by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Vancouver's Bridges: Skytrain Bridge

Skytrain is a fully-automated elevated train system that runs through metropolitan Vancouver.

Continuing east along the Fraser River we come to the Skytrain Bridge. It has a 350 m (1115 ft) long main span, a total length of 616 m (2020 ft), the tower height is 117 m (384 ft), and it carries two pairs of light rail tracks. Like yesterday's Alex Fraser Bridge, it has a semi-fan arrangement of cables, but it has a very thin prestressed concrete superstructure, and reinforced concrete A-shaped towers.

The Alex Fraser Bridge has a 465 m span across the Fraser River and so the Skytrain Bridge with a 350 m span has both towers in the river. I guess it must have been cheaper to build a shorter span in the water than a longer span on dry land.

The bridge owner is Translink and the bridge was completed in 1990. You can see a train going over the bridge in the accompanying photo, but it looks like a toy next to the huge tower.

Vancouver's Bridges: Skytrain Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Vancouver's Bridges: Alex Fraser Bridge (2)

The Alex Fraser Bridge has a composite superstructure made up of a reinforced concrete deck securely attached to longitudinal girders that act together in bending. This was the first use of a composite superstructure for a cable-stayed bridge and it was how such a long span (at that time) was achieved. Soon, much longer spans were achieved using composite and steel superstructures.

The cables are in a semi-fan arrangement with the longest cables attached to the top of the tower legs and the shortest cables at the cross-support on the tower legs. It looks like the superstructure is suspended above the bottom crossbeam of the towers. This would be helpful during an earthquake since the towers could move out-of-phase (longitudinally) with the superstructure. However, the superstructure looks like it is up against the legs of the towers, which means they will move together transversely (putting a lot more load on the towers).

The bridge owner is the British Columbia Ministry of Transportation. The designers were CBA-Buckland & Taylor Ltd. who also provided support during construction. The main contractor was Paschen Pike with Canron in charge of steel construction and PCL handling cable installation (the cables were provided by Bridon International). Construction took 27 months (from 1983 to 1986) and set the record for the lowest cost per square foot of a cable-stayed structure (at that time).

The bridge has a width of 32 m (105 ft) and carries six traffic lanes as well as pedestrians and cyclists. The bridge has a total length of 2602 m (8540 ft) and carries Highway 91 over the Fraser River from Annacis Island south into the North Delta Region.

Vancouver's Bridges: Alex Fraser Bridge (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Vancouver's Bridges: Alex Fraser Bridge

The Fraser River begins in the Rocky Mountains and flows for 1375 km (870 mi) before reaching the City of Vancouver. Then it splits into several arms and forms large islands before flowing through a delta into the Strait of Georgia.

The Alex Fraser Bridge crosses the Fraser River about 20 km (16 miles) east of the Strait of Georgia. Although the bridge and river share the same name, the river was named after the early 19th century explorer Simon Fraser while the bridge was named after a Canadian politician named Alex Fraser.

The Metropolitan Vancouver region seems to have an insatiable need for bridges. In the couple of years since I last visited Vancouver, they've built the Golden Ears Bridge and the North Arm Bridge (two extradosed bridges) over the Fraser River. Both were designed by Buckland and Taylor, who have become experts in cable-stayed and extradosed bridges. Last year, I took a two day class on cable-stayed bridges, which was just some engineers from Buckland and Taylor discussing their past projects, including the Alex Fraser Bridge.

When the Alex Fraser Bridge was completed in 1986, it was the longest cable-stayed bridge in the world with a main span of 465 m (1526 ft). Twenty-three years later, it has dropped to the 32nd longest cable-stayed bridge (the Sutong Bridge in China is currently the longest cable-stayed bridge with a main span length of 1088 m (3570 ft)).

The Alex Fraser Bridge has two reinforced concrete H-shaped towers that are 154.3 m (506 ft) tall. Usually, there are obstructions like trees, buildings, or mountains that make it hard to photograph a bridge, but the Alex Fraser Bridge is hard to miss. Its by far the biggest thing in the landscape. Both the tower legs are on the river banks, which makes this part of the river (south of Annacis Island) about the same width as the Huangpu River in Shanghai and much narrower than the Hudson River in New York. Although the approach spans look normal in depth, the cable spans are very thin. The precast deck panels are 220 mm or 8.7 inches thick and are supported on two-meter deep steel girders. The bridge was built as two balanced cantilevers with each 9 m (30 ft) deck segment built on both sides of each tower before being attached to the tower with cables. The side spans are only 183 m (600 ft) long so they must have anchored the side spans to the back piers before they finished putting down the deck for the center of the main span.

We'll take a closer look at the Alex Fraser Bridge tomorrow.

Vancouver's Bridges: Alex Fraser Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Vancouver's Bridges: Queensborough Bridge

All of the bridges we've looked at crossing the North Arm of the Fraser River have haunched girders. The engineers must have been after every inch of vertical clearance they could get to avoid collisions. However, I believe there's a few highway bridges near the airport without haunches.

The Queensborough Bridge is the easternmost bridge crossing the North Arm of the Fraser River. In the accompanying photo we are standing up on the north bank looking south across the river and at Lulu Island. There's so much timber floating down the river, that there's barely room for vessels through the shipping channel. I wonder how many of the great forests of the Pacific Northwest still remain?

In the photo you can see the haunched steel girders over the river, the timber fenders protecting the piers, and the very long approach at a steep grade south of the river. The river crossing looks flat, like they didn't maintain a smooth vertical curve over the river. The river spans are supported on pier walls while the approach spans are supported on two column bents.

The Queensborough Bridge was built in 1960 for the City of New Westminster at a cost of $4 million Canadian. It replaced an earlier bridge that was built in 1909. The entire structure including the approach spans is 924 m (3034 ft) long. It was built to provide access to and from the City of Queensborough on Lulu Island.  It was purchased by the provincial government in 1966 and became a connector between Highway 91A and Highway 91 to the south. Like most bridges around Vancouver, it provides vehicle lanes as well as access for pedestrians and cyclists.

I'm surprised that I could find no information on whether the bridge had been retrofitted for earthquakes. Also, I couldn't find out how much vertical clearance it has over the water, although I would guess it's at least 20 m. There is a book Richmond and its bridges: Fifteen crossings of the Fraser River by Alan Dawe (published in 1996) for those wishing more information about this bridge.

Vancouver's Bridges: Queensborough Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Arch Bridges: The Pattullo Bridge

The four-lane, Pattullo Bridge (named after a British Columbia premier) is a heavily travelled through arch bridge over the Fraser River southeast of Vancouver.   It's similar to the Grand Island Bridges on the Niagara River: a truss bridge that changes to a suspended-deck arch over the shipping channel. However, instead of being supported by concrete caissons, the Pattullo Bridge is supported on two-column bents.

It was built in 1937, has a number of problems, and is expected to be replaced in a few years. Its narrow lanes, lack of a median barrier, and large daily traffic (80,000 vehicles) has contributed to a number of head-on collisions.  It was closed due to arson in January, but was reopened a week later by reusing some bridge falsework (Buckland and Taylor found a steel-concrete composite structure in a construction yard) to fill the 60 ft (18 m) gap.

These old truss arch bridges will most likely disappear from the landscape in another 20 years.

Arch Bridges: Pattullo Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution 3.0 United States License.